Laser processing apparatus, method for laser processing a workpiece, and related configurations

Abstract

This invention relates to a laser processing apparatus and a method for laser processing a workpiece. [Solution] One embodiment relates to processing a workpiece in a manner that improves accuracy and throughput. Another embodiment relates to real-time Z-direction height measurement and, where appropriate, compensation for a certain Z-direction height displacement. Yet another embodiment relates to modulating scan patterns, beam characteristics, etc., to facilitate feature formation, avoid undesirable heat accumulation, or increase processing throughput. Numerous other embodiments and configuration details are also described.

Description

Related applications

[0001] This application claims the interests of U.S. Provisional Patent Application No. 62 / 216,102 filed on September 9, 2015, U.S. Provisional Patent Application No. 62 / 241,624 filed on October 14, 2015, U.S. Provisional Patent Application No. 62 / 271,446 filed on December 28, 2015, U.S. Provisional Patent Application No. 62 / 294,991 filed on February 12, 2016, and U.S. Provisional Patent Application No. 62 / 366,984 filed on July 26, 2016, each of which is incorporated in whole by reference. Background

[0002] I.Technical field The embodiments disclosed herein generally relate to laser processing apparatuses and methods for laser processing workpieces.

[0003] II. Description of Related Technologies Since the invention of the laser, material ablation using pulsed light sources has been studied. A 1982 report on polymers etched by ultraviolet (UV) excimer laser radiation spurred a broader investigation into microfabrication processes. Since then, scientific and industrial research in this field has flourished, primarily driven by the use of lasers for drilling, milling, marking, and replicable, extremely small features. A variety of potential applications for lasers in high-tech manufacturing have been developed and realized, and continue to be developed and realized. For example, lasers are useful tools for milling and drilling holes, such as forming trenches, and for forming other features in a wide range of materials. The combination of high resolution, precision, speed, and flexibility has made laser processing acceptable in many industries, including the manufacturing of workpieces such as integrated circuits, hard disks, printing devices, displays, and wiring. However, trends in many industries are increasingly demanding the creation of more features, smaller features, and denser features, pushing existing laser processing technologies to their limits in processing workpieces within acceptable levels of precision, quality, throughput, and flexibility.

[0004] In one embodiment, a method for forming vias in a workpiece includes raster scanning of the workpiece with respect to the beam axis (which is capable of irradiating the workpiece with laser pulses along it) and irradiating a plurality of laser pulses at a plurality of spot positions on the workpiece.

[0005] In other embodiments, a method for forming vias in a workpiece includes irradiating the workpiece with laser pulses along a beam path forming a beam axis, and moving the beam axis relative to the workpiece using a positioner including an AOD to form vias having a diameter less than or equal to the scanning range associated with the AOD.

[0006] In other embodiments, a method for forming a feature on a workpiece includes irradiating the workpiece with a group of laser pulses along several scan lines, and moving the beam axis relative to the workpiece such that, for each scan line, the last laser pulse is irradiated at a position closer to the boundary of the feature to be formed than the position where the first laser pulse was irradiated.

[0007] In yet another embodiment, the method for processing a workpiece includes moving the beam axis relative to the workpiece within a scanning range, wherein the range of the first scanning range in the first direction is smaller than the range of the first scanning range in the second direction.

[0008] In yet another embodiment, a device for processing a workpiece using multiple laser energy beams may include first to fourth scan heads, a first stage configured to cause a first movement of the first scan head and the third scan head, and a second stage configured to cause a second movement of the first scan head and the second scan head.

[0009] In yet another embodiment, the apparatus may include multiple distributors for directing the laser energy beam between multiple beam paths.

[0010] In other embodiments, an optical component assembly used in an apparatus for laser processing a workpiece may include a housing having an optical input port and an optical output port, the housing comprising at least one alignment feature configured to facilitate optical alignment of a beam path within the apparatus using at least one selected from the group consisting of the optical input port and the optical output port. The optical component assembly may further include at least two optical elements mounted within the housing and optically aligned with respect to the optical input port and the optical output port.

[0011] In one embodiment, the acousto-optical (AO) device may include an AO cell, an ultrasonic transducer, an absorber, and a cooling plate that is in thermal contact with the surface of the AO cell extending between the ultrasonic transducer and the absorber. The heat transfer characteristics of the cooling plate may vary along the direction extending from the connector end and the absorber end so that the cooling plate removes less heat from the central region of the AO cell located relatively far from at least one selected from the group consisting of the connector end and the absorber end, and b) removes a relatively large amount of heat from the peripheral region of the AO cell relatively close to at least one selected from the group consisting of the connector end and the absorber end.

[0012] In other embodiments, the method includes driving an AOD system to modulate the received laser pulse, and the modulated laser pulse is M 2 The type of factor and / or spatial intensity profile differs from that of the received laser pulse.

[0013] In yet another embodiment, the method includes generating a laser pulse having a wavelength in the range of 9 μm to 11 μm and deflecting the beam path through which the pulse propagates using an acousto-optic deflector (AOD) system including a germanium-containing AO cell.

[0014] In yet another embodiment, a method for forming a feature on a workpiece including a conductive structure arranged to be in thermal contact with a dielectric structure may include indirectly ablating the conductive structure using a laser pulse having a wavelength shorter than 1 μm. Another method for forming a feature on a workpiece may involve deflecting a laser pulse beam to irradiate multiple spot locations and indirectly ablating the material layer.

[0015] In yet other embodiments, a method for processing a workpiece may include irradiating a first laser energy beam and a second laser energy beam along a common beam axis to ablate the workpiece. The first laser energy beam has a wavelength at which at least a portion of the workpiece is transparent and is characterized by a plurality of laser pulses having a first pulse duration that is short enough to induce non-linear absorption of light within the portion of the workpiece, and the timing at which the laser pulses within the first laser energy beam are generated is independent of the operation of generating the second laser energy beam.

[0016] As will become apparent, this specification identifies numerous problems (relating to, for example, accuracy, quality, throughput, etc. that were difficult to solve with conventional laser processing apparatuses or conventional laser processing techniques), and details numerous embodiments, examples, combinations, etc. that solve such problems and provide new or improved performance, etc.

Brief Description of the Drawings

[0017] [Figure 1] FIG. 1 schematically shows an apparatus for processing a workpiece in one embodiment. [Figure 2] FIG. 2 schematically shows a second positioner of the apparatus shown in FIG. 1 in one embodiment. [Figure 3] FIG. 3 schematically shows a second scanning range associated with the second positioner shown in FIG. 2 in one embodiment. [Figure 4] FIGS. 4 to 6 schematically show the spatial relationship between a detection range and a second scanning range in one embodiment. [Figure 5] FIGS. 4 to 6 schematically show the spatial relationship between a detection range and a second scanning range in one embodiment. [Figure 6]Figures 4 to 6 schematically show the spatial relationship between the detection range and the second scanning range in one embodiment. [Figure 7] Figure 7 schematically shows a multi-head device for processing a workpiece in one embodiment. [Figure 8] Figures 8 and 9 schematically show a top view and a side view of a workpiece handling system for use in the apparatus shown in Figures 1 and 7 in one embodiment. [Figure 9] Figures 8 and 9 schematically show a top view and a side view of a workpiece handling system for use in the apparatus shown in Figures 1 and 7 in one embodiment. [Figure 10] Figure 10 schematically shows the process flow associated with the multi-head device shown in Figure 7 in one embodiment. [Figure 11] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 12] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 13] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 14] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 15] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 16] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 17]Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 18] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 19] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 20] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 21] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 22] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 23] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 24] Figures 11 to 24 schematically show a method for scanning a detection range and a second scanning range in one embodiment. [Figure 25] Figures 25 to 28 schematically illustrate a method for scanning processing spots in one embodiment. [Figure 26] Figures 25 to 28 schematically illustrate a method for scanning processing spots in one embodiment. [Figure 27] Figures 25 to 28 schematically illustrate a method for scanning processing spots in one embodiment. [Figure 28] Figures 25 to 28 schematically illustrate a method for scanning processing spots in one embodiment. [Figure 29]Figures 29, 29A, and 29B schematically illustrate a scanning method that facilitates the removal of anisotropic material in one embodiment. Specifically, Figure 29 shows a scan pattern superimposed on a top view of the workpiece to be processed. [Figure 29A] Figures 29, 29A, and 29B schematically illustrate a scanning method that facilitates the removal of anisotropic material in one embodiment. Specifically, Figures 29A and 29B schematically show cross-sectional views along the lines XXIXA-XXIXA and XXIXB-XXIXB', respectively, of a feature formed using the scan pattern shown in Figure 29. [Figure 29B] Figures 29, 29A, and 29B schematically illustrate a scanning method that facilitates the removal of anisotropic material in one embodiment. Specifically, Figures 29A and 29B schematically show cross-sectional views along the lines XXIXA-XXIXA and XXIXB-XXIXB', respectively, of a feature formed using the scan pattern shown in Figure 29. [Figure 30] Figures 30 to 32 schematically show a multi-source device in one embodiment. [Figure 31] Figures 30 to 32 schematically show a multi-source device in one embodiment. [Figure 32] Figures 30 to 32 schematically show a multi-source device in one embodiment. [Figure 33] Figure 33 schematically illustrates a method for coupling laser energy beams in a multi-source device according to one embodiment. [Figure 34] Figures 34 to 37 schematically illustrate a method for managing the thermal load within an AO cell in one embodiment. [Figure 35] Figures 34 to 37 schematically illustrate a method for managing the thermal load within an AO cell in one embodiment. [Figure 36] Figures 34 to 37 schematically illustrate a method for managing the thermal load within an AO cell in one embodiment. [Figure 37]Figures 34 to 37 schematically illustrate a method for managing the thermal load within an AO cell in one embodiment. [Figure 38] Figure 38 schematically shows a by-product removal system in one embodiment. Detailed description of preferred embodiments

[0018] The following describes examples of embodiments with reference to the attached drawings. Unless explicitly stated, the sizes, positions, and distances between components, features, and elements in the drawings are not necessarily to scale and are exaggerated for ease of understanding. Similar numbers throughout the drawings represent similar elements. Therefore, identical or similar numbers may be mentioned by reference to other drawings even if they are not mentioned or described in the corresponding drawings. Furthermore, elements without reference numbers may also be mentioned by reference to other drawings.

[0019] The terms used in this specification are for the sole purpose of describing specific exemplary embodiments and are not intended to be limiting. Unless otherwise specifically defined, all terms used herein (including technical and scientific terms) have the same meaning as generally understood by those skilled in the art. Where used herein, singular nouns are intended to include plural nouns unless the context explicitly indicates otherwise. Furthermore, the terms “equipped with” and / or “equipped with” should be understood to identify the presence of a described feature, integer, step, operation, element, and / or component, but not to exclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Unless otherwise specifically indicated, where a range of values ​​is given, that range includes the upper and lower limits, as well as the sub-range between the upper and lower limits of that range. Unless otherwise specifically indicated, terms such as “first” and “second” are used solely to distinguish elements from one another. For example, one node may be called the “first node,” and similarly another node may be called the “second node,” or vice versa.

[0020] Unless otherwise specified, “approximately” or “around” means that quantities, sizes, proportions, parameters, and other quantities and characteristics are not, and do not need to be, exact, and may be approximate, and may be larger or smaller, as needed, or to reflect tolerances, conversion factors, rounding, measurement errors, and other factors known to those skilled in the art. In this specification, spatially relative terms such as “below,” “down,” “below,” “up,” and “above” may be used to facilitate explanation when describing the relationship between one element or feature and another element or feature, as shown in the figures. It should be understood that spatially relative terms are intended to include different orientations in addition to the orientations shown in the figures. For example, an element described as being “below” or “below” another element or feature would, if the object in the figure were inverted, face “above” the other element or feature. Thus, the exemplary term “below” may include both upward and downward orientations. If the object is facing a different direction (for example, if it is rotated 90 degrees or is in a different direction), the spatially relative descriptors used herein may be interpreted accordingly.

[0021] Section headings used herein are for organizational purposes only, unless otherwise specified, and should not be construed as limiting the subject matter discussed. It will be understood that many different forms, embodiments, and combinations are conceivable without departing from the spirit and teachings of this disclosure, and that this disclosure should not be construed as limiting to the examples of embodiments described herein. Rather, these examples and embodiments are provided to fully convey the scope of this disclosure to those skilled in the art, as it is complete and all-encompassing.

[0022] I. Overview The embodiments described herein generally relate to methods and apparatus for laser processing (or more simply, “processing”) a workpiece. Generally, the processing is carried out entirely or partially by irradiating the workpiece with laser radiation to heat, melt, evaporate, ablate, scratch, decolorize, polish, roughen, carbonize, foam, or modify one or more properties or characteristics (e.g., chemical composition, atomic structure, ionic structure, molecular structure, electronic structure, microstructure, nanostructure, density, viscosity, refractive index, permeability, relative permittivity, texture, color, hardness, transmittance to electromagnetic radiation, or any combination thereof) of one or more materials forming the workpiece. The material to be processed may be located outside the workpiece before or during processing, or it may be located entirely inside the workpiece before or during processing (i.e., not outside the workpiece).

[0023] Specific examples of processes that can be performed by the disclosed laser processing apparatus include via drilling or other hole formation, cutting, punching, welding, scribing, engraving, marking (e.g., surface marking, sub-surface marking), laser-induced forward transfer, cleaning, bleaching, repair of high-luminance pixels (e.g., color filter darkening, modification of OLED materials), film removal, surface texturing (e.g., roughening, smoothing), or similar, or any combination thereof. Thus, one or more features that may be formed on or within a workpiece as a result of processing may include openings, slots, vias or other holes, grooves, trenches, scribe lines, grooves, recesses, conductive traces, ohmic contacts, resistance patterns, human-readable or machine-readable marks (e.g., comprising one or more areas within or on a workpiece having one or more distinguishable characteristics visually or tactilely), or similar, or any combination thereof. Features such as openings, slots, vias, and holes may have any preferred or desirable shape in a top view (e.g., circular, elliptical, square, rectangular, triangular, tubular, or similar, or any combination thereof). Furthermore, features such as openings, slots, vias, and holes may extend completely through the workpiece (e.g., to form a so-called "through via" or "through hole") or may extend only partially within the workpiece (e.g., to form a so-called "non-through via" or "non-through hole").

[0024] The workpieces that can be processed are comprehensively characterized as being formed from one or more metals, polymers, ceramics, composites, or any arbitrary combination thereof (regardless of whether it is an alloy, compound, mixture, solution, composite, etc.). Specific examples of workpieces that can be processed include panels of printed circuit boards (PCBs) (also referred to as "PCB panels" in this specification), PCBs, flexible printed wiring boards (FPCs), integrated circuits (ICs), IC packages (ICPs), light-emitting diodes (LEDs), LED packages, semiconductor wafers, substrates for electronic or optical devices (e.g., Al2O3, AlN, BeO, Cu, GaAS, GaN, Ge, InP, Si, SiO2, SiC, Si 1-x Ge x (0.0001 < x < 0.9999), etc., or substrates formed from any arbitrary combination or alloy thereof), lead frames, lead frame blanks, plastics, non-reinforced glass, heat-strengthened glass, chemically strengthened glass (e.g., via an ion exchange process), quartz, sapphire, plastics, silicon, etc., components of electronic displays (e.g., substrates on which TFTs, color filters, organic LED (OLED) arrays, quantum dot LED arrays, etc., or any arbitrary combination thereof are formed on the surface), lenses, mirrors, screen projectors, turbine blades, powders, films, foils, plates, molds (e.g., wax molds, molds for injection molding processes, investment casting processes, etc.), fabrics (weaves, felts, etc.), surgical instruments, medical implants, packaged household appliances, shoes, bicycles, automobiles, automotive parts or aircraft parts (e.g., frames, body panels, etc.), appliances (e.g., microwave ovens, ovens, refrigerators, etc.), housings for devices (e.g., for watches, computers, smartphones, tablet computers, wearable electronic devices, etc., or any arbitrary combination thereof).

[0025] Therefore, the materials that can be processed include one or more metals such as Al, Ag, Au, Cu, Fe, In, Mg, Pt, Sn, Ti, or any combination thereof (whether alloy or composite, for example), conductive metal oxides (e.g., ITO), transparent conductive polymers, ceramics, waxes, resins, inorganic dielectric materials (used as interlayer dielectric structures, such as silicon dioxide, silicon nitride, silicon oxynitride, or any combination thereof), low-k dielectric materials (e.g., methylsilsesquioxane (MSQ), hydrogen silsesquioxane (HSQ), tetraethyl orthosilicate fluoride (FTEOS), or any combination thereof), organic dielectric materials (e.g., SILK, benzocyclobutene, Nautilus (all manufactured by Dow), polyfluorotetraethylene (manufactured by DuPont), FLARE (Allied This includes fiberglass, polymer materials (such as those manufactured by Chemical Co., Ltd., or any combination thereof), polyamides, polyimides, polyesters, polyacetals, polycarbonates, modified polyphenylene ethers, polybutylene terephthalates, polyphenylene sulfides, polyethersulfones, polyetherimides, polyetheretherketones, liquid crystal polymers, acrylonitrile butadiene styrene, and any compounds, composites, or admixtures thereof), leather, paper, assemblies (e.g., Ajinomoto Build-Up Film, also known as "ABF"), glass fiber reinforced epoxy laminates (e.g., FR4), prepregs, solder resists, or any composites, laminates, or other combinations thereof).

[0026] II. System Overview Figure 1 schematically shows an apparatus for processing a workpiece according to one embodiment of the present invention.

[0027] Referring to the embodiment shown in Figure 1, the apparatus 100 for processing a workpiece includes a laser source 104 for generating laser pulses, a first positioner 106, a second positioner 108, a third positioner 110, a scan lens 112, and a controller 114. Considering the following description, it should be understood that if the apparatus 100 includes the second positioner 108 or the third positioner 110, then including the first positioner 106 is optional (i.e., the apparatus 100 does not need to include the first positioner 106). Similarly, if the apparatus 100 includes the first positioner 106 or the third positioner 110, then including the second positioner 108 is optional (i.e., the apparatus 100 does not need to include the second positioner 108). Finally, it should be understood that if the device 100 includes a first positioner 106 or a second positioner 108, then including a third positioner 110 is optional (i.e., the device 100 does not need to include a third positioner 110).

[0028] Although not shown in the figures, the apparatus 100 also includes one or more optical elements (e.g., beam expander, beam shaper, aperture, filter, collimator, lens, mirror, polarizer, waveplate, diffractive optical element, refractive optical element, or any combination thereof) for focusing, expanding, collimating, shaping, polarizing, filtering, splitting, combining, cropping, modifying, adjusting, directing, monitoring, or measuring the laser pulses generated by the laser source 104 along one or more beam paths (e.g., beam path 116) leading to the scan lens 112. U.S. Patent Nos. 4,912,487, 5,633,747, 5,638,267, 5,751,585, 5,847,960, 5,917,300, 6,314,473, 6,430,465, 6,700,600, 6,706,998, 6,706,999, 6,816,294, 6,947,454, 7,019,89 No. 1, No. 7,027,199, No. 7,133,182, No. 7,133,186, No. 7,133,187, No. 7,133,188, No. 7,245,412, No. 7,259,35 No. 4, No. 7,611,745, No. 7,834,293, No. 8,026,158, No. 8,076,605, No. 8,158,493, No. 8,288,679, No. 8,404,998 U.S. Patent Application Publications No. 8,497,450, 8,648,277, 8,680,430, 8,847,113, 8,896,909, 8,928,853, 9,259,802 or the aforementioned U.S. Patent Application Publications No. 2014 / 0026351, 2014 / 0197140, 2014 / 0263201, 2014 / 0263212, 2014 / 02632 It will also be understood that one or more of the above components may be provided, or that the apparatus 100 may include one or more additional components, as disclosed in Patent No. 23, No. 2014 / 0312013, or German Federal Patent No. DE102013201968B4, or International Patent Publication No. WO2009 / 087392, or any combination thereof. Each of these publications is incorporated herein by reference in its entirety.

[0029] The laser pulse that has passed through the scan lens 112 propagates along the beam axis so as to irradiate the workpiece 102. The laser pulse irradiating the workpiece 102 may be characterized as having a Gaussian spatial intensity profile or a non-Gaussian (i.e., “shaped”) spatial intensity profile (e.g., a “top-hat” spatial intensity profile). Regardless of the type of spatial intensity profile, the spatial intensity profile may also be characterized as the cross-sectional shape of the laser pulse propagating along the beam axis (or beam path 116) (which may be circular, elliptical, rectangular, triangular, hexagonal, ring-shaped, or any other shape). The irradiated laser pulse may be characterized as striking the workpiece 102 with a spot size ranging from 2 μm to 200 μm. As used herein, the term “spot size” means the diameter or maximum spatial width of the irradiated laser pulse at a location (also called the “processing spot,” “spot location,” or more simply the “spot”) that spans a region of the workpiece 102 that is at least partially processed by the irradiated laser pulse.

[0030] For the purposes of this specification, the size is defined as the optical intensity being 1 / e of the optical intensity at the beam axis, relative to the beam axis. 2It is measured as the radial or transverse distance to the point where it drops down to a certain point. Generally, the spot size of a laser pulse is smallest at the beam waist. However, it can be understood that the spot size can be smaller than 2 μm or larger than 200 μm. Thus, at least one laser pulse irradiated onto the workpiece 102 can have a spot size greater than or equal to 2 μm, 3 μm, 5 μm, 7 μm, 10 μm, 15 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 80 μm, 100 μm, 150 μm, 200 μm, or a spot size between any of these values. Similarly, at least one laser pulse irradiated can have a spot size smaller than 200 μm, 150 μm, 100 μm, 80 μm, 55 μm, 50 μm, 45 μm, 40 μm, 35 μm, 30 μm, 15 μm, 10 μm, 7 μm, 5 μm, 3 μm, 2 μm, or a spot size between any of these values. In one embodiment, the laser pulse irradiated onto the workpiece 102 can have a spot size in the range of 25 μm to 60 μm. In another embodiment, the laser pulse irradiated onto the workpiece 102 can have a spot size in the range of 35 μm to 50 μm.

[0031] A. Laser source Generally, the laser source 104 can generate laser pulses. Therefore, the laser source 104 may include pulsed laser sources, CW laser sources, QCW laser sources, burst-mode lasers, or any combination thereof. If the laser source 104 includes a QCW laser source or a CW laser source, the laser source 104 may further include a pulse gating unit (e.g., an acousto-optic (AO) modulator (AOM), a beam chopper, etc.) that temporally modulates the beam of laser radiation output from the QCW laser source or CW laser source. Although not shown, the apparatus 100 may optionally include one or more harmonic generating crystals (also known as "wavelength conversion crystals") configured to convert the wavelength of light output by the laser source 104. Therefore, the laser pulse ultimately irradiated onto the workpiece 102 may be characterized by having one or more wavelengths in one or more of the following electromagnetic spectra: ultraviolet (UV), visible light (e.g., violet, blue, green, red, etc.), or infrared (IR) (e.g., near-infrared (NIR) in the wavelength range of 750 nm to 1.4 μm, short-wavelength infrared (SWIR) in the wavelength range of 1.4 μm to 3 μm, mid-wavelength infrared (MWIR) in the wavelength range of 3 μm to 8 μm, or long-wavelength infrared (LWIR) in the wavelength range of 8 μm to 15 μm), or any combination thereof.

[0032] In other embodiments, the laser source 104 may be provided as a QCW laser source or a CW laser source and may not include a pulse gating unit. In such embodiments, the laser source 104 may generate a continuous (non-pulsed) laser beam for subsequent propagation along the beam path 116. Thus, the laser source 104 can be broadly characterized as capable of generating a beam of laser energy. The laser energy can then be represented as a series of laser pulses or as a continuous laser beam, which can then propagate along the beam path 116. While many embodiments described herein refer to laser pulses, it should be understood that, where appropriate, a continuous beam can be used instead, or in addition to, laser pulses.

[0033] The laser pulse output by the laser source 104 can have a pulse width or pulse duration (i.e., based on the full width at half maximum (FWHM) of the optical power of the pulse as a function of time) in the range of 10 fs to 900 ms. However, it can be understood that the pulse duration may be shorter than 30 fs or longer than 900 ms. Thus, at least one laser pulse output by the laser source 104 can have durations of 10 fs, 15 fs, 30 fs, 50 fs, 100 fs, 150 fs, 200 fs, 300 fs, 500 fs, 700 fs, 750 fs, 850 fs, 900 fs, 1 ps, 2 ps, 3 ps, 4 ps, 5 ps, 7 ps, 10 ps, ​​15 ps, 25 ps, 50 ps, ​​75 ps, 100 ps, ​​200 ps, ​​500 ps, ​​1 ns, 1.5 ns, 2 ns, and 5 ns. The pulse duration may be longer than or equal to 10ns, 20ns, 50ns, 100ns, 200ns, 400ns, 800ns, 1000ns, 2μs, 5μs, 10μs, 50μs, 100μs, 300μs, 500μs, 900μs, 1ms, 2ms, 5ms, 10ms, 20ms, 50ms, 100ms, 300ms, 500ms, 900ms, 1s, etc., or between any of these values. Similarly, at least one laser pulse output by the laser source 104 is 1 s, 900 ms, 500 ms, 300 ms, 100 ms, 50 ms, 20 ms, 10 ms, 5 ms, 2 ms, 1 ms, 300 ms, 900 μs, 500 μs, 300 μs, 100 μs, 50 μs, 10 μs, 5 μs, 1 μs, 800 ns, 400 ns, 200 ns, 100 ns, 50 ns, 20 ns, 10 ns, 5 ns, 2 ns, 1.5 ns, 1 ns The pulse duration can be shorter than s, 500ps, 200ps, 100ps, 75ps, 50ps, 25ps, 15ps, 10ps, 7ps, 5ps, 4ps, 3ps, 2ps, 1ps, 900fs, 850fs, 750fs, 700fs, 500fs, 300fs, 200fs, 150fs, 100fs, 50fs, 30fs, 15fs, 10fs, etc., or between any of these values. In one embodiment, the laser pulse output by the laser source 104 has a pulse duration in the range of 3ps to 15ps.In other embodiments, the laser pulses output by the laser source 104 have a pulse duration in the range of 5 ps to 7 ps.

[0034] The laser pulses output by the laser source 104 can have an average power in the range of 100mW to 50kW. However, it can be understood that the average power may be less than 100mW or greater than 50kW. Thus, the laser pulses output by the laser source 104 can have an average power greater than or equal to 100mW, 300mW, 500mW, 800mW, 1W, 2W, 3W, 4W, 5W, 6W, 7W, 10W, 15W, 18W, 25W, 30W, 50W, 60W, 100W, 150W, 200W, 250W, 500W, 2kW, 3kW, 20kW, 50kW, or an average power between any of these values. Similarly, the laser pulses output by the laser source 104 can have an average power less than 50kW, 20kW, 3kW, 2kW, 500W, 250W, 200W, 150W, 100W, 60W, 50W, 30W, 25W, 18W, 15W, 10W, 7W, 6W, 5W, 4W, 3W, 2W, 1W, 800mW, 500mW, 300mW, 100mW, or an average power between any of these values.

[0035] The laser source 104 can output laser pulses at pulse repetition rates in the range of 5 kHz to 1 GHz. However, it can be understood that the pulse repetition rate may be lower than 5 kHz or higher than 1 GHz. Thus, the laser source 104 can output laser pulses at pulse repetition rates higher than or equal to 5 kHz, 50 kHz, 100 kHz, 175 kHz, 225 kHz, 250 kHz, 275 kHz, 500 kHz, 800 kHz, 900 kHz, 1 MHz, 1.5 MHz, 1.8 MHz, 1.9 MHz, 2 MHz, 2.5 MHz, 3 MHz, 4 MHz, 5 MHz, 10 MHz, 20 MHz, 50 MHz, 70 MHz, 100 MHz, 150 MHz, 200 MHz, 250 MHz, 300 MHz, 350 MHz, 500 MHz, 550 MHz, 700 MHz, 900 MHz, 2 GHz, 10 GHz, or any of these values. Similarly, the laser source 104 can output laser pulses at pulse repetition rates lower than 10 GHz, 2 GHz, 1 GHz, 900 MHz, 700 MHz, 550 MHz, 500 MHz, 350 MHz, 300 MHz, 250 MHz, 200 MHz, 150 MHz, 100 MHz, 90 MHz, 70 MHz, 50 MHz, 20 MHz, 10 MHz, 5 MHz, 4 MHz, 3 MHz, 2.5 MHz, 2 MHz, 1.9 MHz, 1.8 MHz, 1.5 MHz, 1 MHz, 900 kHz, 800 kHz, 500 kHz, 275 kHz, 250 kHz, 225 kHz, 175 kHz, 100 kHz, 50 kHz, 5 kHz, or at pulse repetition rates between any of these values.

[0036] In addition to wavelength, pulse duration, average power, and pulse repetition rate, the laser pulses irradiated onto the workpiece 102 can be characterized by one or more other properties such as pulse energy and peak power. These one or more other properties are sufficient to process the workpiece 102 (W / cm²) (for example, to form one or more features having one or more desired properties, or to prevent the workpiece 102 from suffering undesirable damage during feature formation, or similar, or a combination thereof). 2 Light intensity (measured at), (J / cm²) 2 The fluence (measured by) can be used to irradiate the workpiece 102 at the processing spot (for example, based on one or more other characteristics such as wavelength, pulse duration, average power, and pulse repetition rate as needed).

[0037] Examples of laser types that may characterize the laser source 104 include gas lasers (e.g., carbon dioxide lasers, carbon monoxide lasers, excimer lasers, etc.), solid-state lasers (e.g., Nd:YAG lasers, etc.), rod lasers, fiber lasers, photonic crystal rod / fiber lasers, passive mode-locked solid bulk or fiber lasers, dye lasers, mode-locked diode lasers, pulsed lasers (e.g., ms pulsed lasers, ns pulsed lasers, ps pulsed lasers, fs pulsed lasers), CW lasers, QCW lasers, etc., or any combination thereof. Depending on the configuration, a gas laser (e.g., a carbon dioxide laser, etc.) may be configured to operate in one or more modes (e.g., CW mode, QCW mode, pulsed mode, or any combination thereof). Specific examples of laser sources that may be provided as laser source 104 include: BOREAS, HEGOA, SIROCCO, or CHINOOK series lasers manufactured by EOLITE; PYROFLEX series lasers manufactured by PYROPHOTONICS; PALADIN Advanced 355 or DIAMOND series lasers (e.g., DIAMOND E series, G series, J-2 series, J-3 series, J-5 series) manufactured by COHERENT; PULSTAR series or FIRESTAR series lasers manufactured by SYNRAD; TRUFLOW series lasers (e.g., TRUFLOW 2000, 2700, 3000, 3200, 3600, 4000, 5000, 6000, 7000, 8000, 10000, 12000, 15000, 20000) manufactured by TRUMPF; and TRUCOAX series lasers (e.g., TRUCOAX 1000) or TRUDISK series, TRUPULSE series, TRUDIODE series, TRUFIBER series, or TRUMICRO series lasers, FCPAμJEWEL or FEMTOLITE series lasers manufactured by IMRA AMERICA, TANGERINE and SATSUMA series lasers (and MIKAN and T-PULSE series oscillators) manufactured by AMPLITUDE SYSTEMES, IPGOne or more laser sources include lasers from the CL series, CLPF series, CLPN series, CLPNT series, CLT series, ELM series, ELPF series, ELPN series, ELPP series, ELR series, ELS series, FLPN series, FLPNT series, FLT series, GLPF series, GLPN series, GLR series, HLPN series, HLPP series, RFL series, TLM series, TLPN series, TLR series, ULPN series, ULR series, VLM series, VLPN series, YLM series, YLPF series, YLPN series, YLPP series, YLR series, YLS series, FLPM series, FLPMT series, DLM series, BLM series, or DLR series (including, for example, GPLN-100-M, GPLN-500-QCW, GPLN-500-M, GPLN-500-R, GPLN-2000-S, etc.) manufactured by PHOTONICS, or similar lasers, or any combination thereof.

[0038] B. First positioner The first positioner 106 is positioned, located, or installed in the beam path 116 and can operate to diffract, reflect, refract, or similarly deflect (i.e., "deflect") the laser pulses generated by the laser source 104, thereby moving the beam path 116 (for example, relative to the scan lens 112) and consequently moving the beam axis relative to the workpiece 102. Generally, the first positioner 106 is configured to move the beam axis relative to the workpiece 102 along the X-axis (or X direction) and the Y-axis (or Y direction). Although not shown, the X-axis (or X direction) can be understood to mean an axis (or direction) perpendicular to the shown Y-axis (or Y direction) and Z-axis (or Z direction).

[0039] The movement of the beam axis relative to the workpiece 102 by the first positioner 106 is generally limited to scanning, moving, or positioning the processing spot within a first scan field or "first scanning range" extending from 0.01 mm to 4.0 mm in the X and Y directions. However, it can be understood that the first scanning range may extend to less than 0.01 mm in either the X or Y direction, or to more than 4.0 mm, depending on one or more factors such as the configuration of the first positioner 106, the position of the first positioner 106 along the beam path 116, the beam size of the laser pulse incident on the first positioner 106, and the spot size. Thus, the first scanning range may extend in either the X or Y direction by a distance longer than or equal to 0.04 mm, 0.1 mm, 0.5 mm, 1.0 mm, 1.4 mm, 1.5 mm, 1.8 mm, 2 mm, 2.5 mm, 3.0 mm, 3.5 mm, 4.0 mm, 4.2 mm, or a distance between any of these values. Similarly, the first scanning range may extend in either the X or Y direction by a distance shorter than 5 mm, 4.2 mm, 4.0 mm, 3.5 mm, 3.0 mm, 2.5 mm, 2.0 mm, 1.8 mm, 1.5 mm, 1.4 mm, 1.0 mm, 0.5 mm, 0.1 mm, 0.04 mm, 0.01 mm, or a distance between any of these values. As used herein, the term “beam size” means the diameter or width of a laser pulse, where the optical intensity is 1 / e of the optical intensity along the propagation axis along the beam path 116. 2 It can be measured as a radial or transverse distance down to a certain point. Thus, in one embodiment, the maximum dimension of the first scanning range (for example, in the X or Y direction, or in other directions) may be greater than or equal to the corresponding maximum dimension (measured in the XY plane) of a feature (e.g., an opening, recess, via, trench, etc.) formed on the workpiece 102. However, in another embodiment, the maximum dimension of the first scanning range may be less than the maximum dimension of the feature to be formed.

[0040] Generally, the speed at which the first positioner 106 can position (and thereby move the beam axis) a processing spot at any position within the first scanning range (also called the "positioning speed") is in the range of 50 kHz (or around) to 10 MHz (or around). This range is also referred to herein as the first positioning bandwidth. The reciprocal of the positioning speed is referred to herein as the "positioning time" and represents the shortest time required to change the position of the processing spot from one position within the first scanning range to any other position within the first scanning range. Thus, the first positioner 106 can be characterized by a positioning time in the range of 20 μs (or around) to 0.1 μs (or around). In one embodiment, the first positioning bandwidth is in the range of 100 kHz (or around) to 2 MHz (or around). For example, the first positioning bandwidth is 1 MHz (or around).

[0041] The first positioner 106 may be a first steering mirror (FSM) element incorporating a microelectromechanical system (MEMS) mirror or mirror array, an AO deflector (AOD) system, an electro-optical deflector (EOD) system, a piezoelectric actuator, an electrostrictive actuator, a voice coil actuator, etc., or similar, or any combination thereof. In one embodiment, the first positioner 106 is an AOD system including at least one (e.g., one, two, etc.) single-element AOD system, at least one (e.g., one, two, etc.) phased array AOD system, or any combination thereof. Both AOD systems include an AO cell formed from a material such as crystalline Ge, PbMoO4, or TeO2, glassy SiO2, quartz, or As2S3. As used herein, a “single-element” AOD system means an AOD system having only one ultrasonic transducer acoustically coupled to an AO cell, while a “phased array” AOD system includes a phased array consisting of at least two ultrasonic transducers acoustically coupled to a common AO cell.

[0042] As those skilled in the art will understand, acousto-optics (AO) techniques (e.g., AOD, AOM, etc.) utilize the diffraction effect caused by sound waves propagating through an AO cell to modulate one or more properties of a light wave (i.e., a beam of laser energy in the context of this application) simultaneously propagating through the AO cell. Typically, an AO cell can maintain both sound and light waves in the same region. The sound wave perturbs the refractive index within the AO cell. The sound wave is typically delivered to the AO cell by driving an ultrasonic transducer element at one or more RF frequencies. By controlling the properties of the sound wave (e.g., amplitude, frequency, phase, etc.), one or more properties of the propagating light wave can be controllably modulated (e.g., relative to the scan lens 112) to move the beam path 116. It should also be understood that the properties of the sound wave delivered to the AO cell can be controlled using known techniques for attenuating the energy in the laser energy beam as it passes through the AO cell. Therefore, the AOD system can also be activated to modulate the pulse energy (and accordingly the fluence, peak power, light intensity, average power, etc.) of the laser pulse that is ultimately irradiated onto the workpiece 102.

[0043] It is understandable that the material from which the AO cell is formed depends on the wavelength of the laser pulse that propagates along the beam path 116 and is incident on the AO cell. For example, if the wavelength of the deflected laser pulse is in the range of 2 μm (or around) to 12 μm (or around), a material such as crystalline Ge can be used. If the wavelength of the deflected laser pulse is in the range of 200 nm (or around) to 5 μm (or around), materials such as quartz and TeO2 can be used.

[0044] It should be understood that AOD systems are dispersive elements and, as a result, preferably deflect laser pulses having a preferably narrow spectral linewidth (based, for example, on the full width at half maximum (FWHM) of the optical power spectral density in the pulse). Typically, a laser source 104 configured to generate laser pulses having one or more wavelengths in one or more of the ultraviolet, visible, or NIR ranges generates laser pulses with a preferably narrow spectral linewidth. Laser sources 104 such as high-power CW gas lasers (e.g., carbon dioxide or carbon monoxide CW lasers with an average power higher than about 300 W) and other low-power CW or pulsed gas lasers (e.g., with an average power of less than about 300 W) can similarly generate laser pulses with a preferably narrow spectral linewidth in the SWIR, MWIR, or LWIR range. Conventionally, high-power pulsed gas lasers capable of generating laser pulses (e.g., carbon dioxide or carbon monoxide pulsed lasers with an average power higher than about 300 W) are based on a main oscillator power amplifier (MOPA) laser system architecture.

[0045] Any of the AOD systems may be provided as a single-axis AOD system (for example, configured to move the beam axis along a single direction) or as a multi-axis AOD system (for example, configured to move the beam axis along multiple directions, e.g., the X and Y directions) by deflecting the beam path 116. Generally, a multi-axis AOD system can be a multi-cell system or a single-cell system. A multi-cell multi-axis system typically includes multiple AOD systems, each configured to move the beam axis along a different axis. For example, a multi-cell multi-axis system may include a first AOD system (e.g., "X-axis AOD system") (e.g., a single-element or phased-array AOD system) configured to move the beam axis along the X direction, and a second AOD system (e.g., "Y-axis AOD system") (e.g., a single-element or phased-array AOD system) configured to move the beam axis along the Y direction. A single-cell multi-axis system (e.g., "X / Y-axis AOD system") typically includes a single AOD system configured to move the beam axis along the X and Y directions. For example, a single-cell system may include at least two ultrasonic transducer elements acoustically coupled to different planes, facets, or sides of a common AO cell.

[0046] C. Second position Similar to the first positioner 106, the second positioner 108 is positioned in the beam path 116 and can diffract, reflect, refract, or similarly diffract, reflect, or similarly refract, or any combination thereof, the laser pulse generated by the laser source 104 and passing through the first positioner 106, thereby moving the beam axis relative to the workpiece 102 (e.g., along the X and Y directions) via the movement of the beam path 116 relative to the scan lens 112. The movement of the beam axis relative to the workpiece 102 performed by the second positioner 108 is generally limited to scanning, moving, or positioning the processing spot within a second scan field or “scanning range” that extends in the X and / or Y directions over a larger area than the first scanning range. It should be understood that in the configurations described herein, the beam axis movement performed by the first positioner 106 can be superimposed on the beam axis movement performed by the second positioner 108. Thus, the second positioner 108 is capable of operating to scan the first scanning range within the second scanning range.

[0047] In one embodiment, the second scanning range extends from 1 mm to 50 mm in the X and / or Y directions. In another embodiment, the second scanning range extends from 15 mm to 30 mm in the X and / or Y directions. However, it can be understood that the second positioner 108 may be configured such that the second scanning range extends less than 1 mm or longer than 50 mm in either the X and / or Y direction. Thus, in one embodiment, the maximum dimension of the second scanning range (e.g., in the X and / or Y directions, or in other directions) may be greater than or equal to the corresponding maximum dimension (measured in the XY plane) of a feature (e.g., a via, trench, scribe line, recess, conductive trace, etc.) formed on the workpiece 102. However, in another embodiment, the maximum dimension of the second scanning range may be less than the maximum dimension of the feature to be formed.

[0048] Generally, the positioning speed at which the second positioner 108 can position the processing spot at any position within the second scanning range (thus moving the beam axis within the second scanning range and / or scanning the first scanning range within the second scanning range) is narrower than the first positioning bandwidth (also referred to herein as the "second positioning bandwidth"). In one embodiment, the second positioning bandwidth is in the range of 900 Hz to 5 kHz. In other embodiments, the first positioning bandwidth is in the range of 2 kHz to 3 kHz (e.g., about 2.5 kHz).

[0049] The second positioner 108 may be provided as a galvanometer mirror system comprising two galvanometer mirror components. One galvanometer mirror component is configured to move the beam axis along the X direction relative to the workpiece 102, and the other galvanometer mirror component is configured to move the beam axis along the Y direction relative to the workpiece 102. However, in other embodiments, the second positioner 108 may be provided as a rotating polyhedron mirror system, etc. Thus, it will be understood that, depending on the specific configuration of the second positioner 108 and the first positioner 106, the second positioning bandwidth may be greater than or equal to the first positioning bandwidth.

[0050] D. Third position The third positioner 110 can move the workpiece 102 relative to the scan lens 112, thereby moving the workpiece 102 relative to the beam axis. The movement of the workpiece 102 relative to the beam axis is generally limited to scanning, moving, or positioning the processing spot within a third scan field or "scanning range" that extends in the X and / or Y directions over a larger area than the second scanning range. In one embodiment, the third scanning range extends from 25 mm to 2 m in the X and / or Y directions. In other embodiments, the third scanning range extends from 0.5 m to 1.5 m in the X and / or Y directions. Generally, the maximum dimension of the third scanning range (e.g., in the X or Y direction, or in other directions) is greater than or equal to the corresponding maximum dimension (measured in the XY plane) of the features formed on the workpiece 102. If necessary, the third positioner 110 may be configured to move the workpiece 102 relative to the beam axis within a scanning range that extends in the Z direction (for example, over a range of 1 mm to 50 mm). For this reason, the third scanning range may extend along the X, Y, and / or Z directions.

[0051] In the configurations described herein, it should be understood that the movement of the beam axis performed by the first positioner 106 and / or the second positioner 108 can be superimposed on the movement of the workpiece 102 performed by the third positioner 110. Thus, the third positioner 110 is operable to scan the first scanning range and / or the second scanning range within the third scanning range. Generally, the positioning speed at which the third positioner 110 can position the processing spot at any position within the third scanning range (thus moving the workpiece 102, scanning the first scanning range within the third scanning range, and / or scanning the second scanning range within the third scanning range) is narrower than the second positioning bandwidth (also referred to herein as the "third positioning bandwidth"). In one embodiment, the third positioning bandwidth is in the range of 10 Hz (or around that range) or narrower.

[0052] In one embodiment, the third positioner 110 is provided as one or more linear stages (for example, capable of translating the workpiece 102 along the X, Y, and / or Z directions, respectively), one or more rotary stages (for example, capable of providing rotational movement of the workpiece 102 about axes parallel to the X, Y, and / or Z directions, respectively), similar arrangements, or any combination thereof. In one embodiment, the third positioner 110 includes an X-axis stage for moving the workpiece 102 along the X direction, and a Y-axis stage supported by the X-axis stage (and thus movable along the X direction by the X-axis stage) for moving the workpiece 102 along the Y direction. Although not shown, the apparatus 100 may include an optional base (e.g., a granite block) for supporting the third positioner 110.

[0053] Although not shown in the figures, the apparatus 100 may include an optional chuck connected to a third positioner 110, to which the workpiece 102 can be mechanically clamped, fixed, held, secured, or supported. In one embodiment, the workpiece 102 can be clamped, fixed, held, secured, or supported so as to be in direct contact with the typically flat main support surface of the chuck. In another embodiment, the workpiece 102 can be clamped, fixed, held, secured, or supported so as to be spaced away from the support surface of the chuck. In yet another embodiment, the workpiece 102 can be fixed, held, or secured by forces applied to the workpiece 102 from the chuck or by forces present between the workpiece 102 and the chuck.

[0054] As described above, the apparatus 100 utilizes a so-called "stacked" positioning system in which the positions of components such as the first positioner 106, the second positioner 108, and the scan lens 112 are stationary within the apparatus 100 (for example, via one or more supports, frames, etc., as is well known) relative to the workpiece 102 which is moved via the third positioner 110. In other embodiments, the third positioner 110 may be positioned and configured to move one or more components such as the first positioner 106, the second positioner 108, and the scan lens 112, and the workpiece 102 may remain stationary. In yet another embodiment, the apparatus 100 can use a segmented axis positioning system in which one or more components such as the first positioner 106, the second positioner 108, and the scan lens 112 are transported by one or more linear or rotary stages. In such embodiments, the third positioner 110 includes one or more linear or rotary stages positioned and configured to move one or more components such as the first positioner 106, the second positioner 108, and the scan lens 112, and one or more linear or rotary stages positioned and configured to move the workpiece 102. Thus, the third positioner 110 moves the workpiece 102 of the scan lens 112 (or scans the head associated with the scan lens 112 as described later). Examples of split-axis positioning systems that can be usefully or advantageously used in the apparatus 100 include any of those disclosed in U.S. Patents 5,751,585, 5,798,927, 5,847,960, 6,706,999, 7,605,343, 8,680,430, 8,847,113, or U.S. Patent Application Publication 2014 / 0083983, or any combination thereof. Each of these publications is incorporated herein by reference in its entirety.

[0055] In other embodiments, one or more components, such as the first positioner 106, the second positioner 108, and the scan lens 112, may be transported by a multi-axis articulated robot arm (e.g., a 2-axis, 3-axis, 4-axis, 5-axis, or 6-axis arm). In such embodiments, the second positioner 108 and / or the scan lens 112 may be transported by the end effector of the robot arm, if necessary. In yet another embodiment, the workpiece 102 may be transported directly on the end effector of the multi-axis articulated robot arm (i.e., without the third positioner 110). In yet another embodiment, the third positioner 110 may be transported on the end effector of the multi-axis articulated robot arm.

[0056] D. Scan Lens Generally, the scan lens 112 (for example, provided as either a simple lens or a composite lens) is typically configured to focus a laser pulse directed along the beam path to generate a beam waist that can be located at a desired processing spot. The scan lens 112 may be provided as an f-theta lens, a telecentric lens, an axicon lens (in which case a series of beam waists are generated, resulting in multiple processing spots offset from each other along the beam axis), or any combination thereof. In one embodiment, the scan lens 112 is provided as a fixed focal length lens and is coupled to a lens actuator (not shown) configured to move the scan lens 112 (for example, to change the position of the beam waist along the beam axis). For example, the lens actuator may be provided as a voice coil configured to linearly translate the scan lens 112 along the Z direction. In other embodiments, the scan lens 112 is provided as a variable focal length lens (e.g., a zoom lens, or a so-called "liquid lens" incorporating technology currently offered by COGNEX, VARIOPTIC, etc.) that can be operated (e.g., via a lens actuator) to change the position of the beam waist along the beam axis.

[0057] In one embodiment, the scan lens 112 and the second positioner 108 are integrated into a common housing or a “scan head” 118. In such embodiments, where the device 100 includes a lens actuator, the lens actuator may be connected to the scan lens 112 (for example, so that the scan lens 112 is movable relative to the second positioner 108 within the scan head 118). Alternatively, the lens actuator may be connected to the scan head 118 (for example, so that the scan head 118 itself is movable (in which case the scan lens 112 and the second positioner 108 move together)). In other embodiments, the scan lens 112 and the second positioner 108 are integrated into different housings (for example, so that the housing into which the scan lens 112 is integrated is movable relative to the housing into which the second positioner 108 is integrated). The components of the scan head 118 or the scan head 118 as a whole may be a modular assembly such that components of the scan head 118 can be simply removed and replaced with other components, or one scan head 118 can be simply removed and replaced with another scan head.

[0058] E. Controller Generally, the controller 114 is communicatively connected to one or more components of the device 100, such as the laser source 104, the first positioner 106, the second positioner 108, the third positioner 110, and the lens actuator (via one or more wired or wireless communication links, such as USB, Ethernet, Firewire, Wi-Fi, RFID, NFC, Bluetooth, Li-Fi, or any combination thereof). One or more of these components of the device 100 are capable of operating in response to one or more control signals output by the controller 114.

[0059] For example, the controller 114 may control the operation of the first positioner 106, second positioner 108, or third positioner 110 to perform relative movement between the beam axis and the workpiece, and to generate relative motion between the processing spot and the workpiece 102 along a path or trajectory (also referred to herein as the “process trajectory”) within the workpiece 102. It can be understood that any two or all of these positioners may be controlled to cause two positioners (e.g., the first positioner 106 and the second positioner 108, the first positioner 106 and the third positioner 110, the second positioner 108 and the third positioner 110) or three positioners to simultaneously generate relative movement between the processing spot and the workpiece 102 (thus generating a “composite relative movement” between the beam axis and the workpiece). Of course, it is also possible to control only one positioner (e.g., a first positioner 106, a second positioner 108, or a third positioner 110) to cause a relative movement between the processing spot and the workpiece 102 at any given time (thus causing a "non-compound relative movement" between the beam axis and the workpiece).

[0060] Control signals instructing combined or uncombined relative movement may be calculated in advance or determined in real time. In other examples, the controller 114 may control the operation of the first positioner 106 to change the spot shape or spot size of the laser pulses irradiated onto the processing spot (for example, by chirpening the RF signal supplied to one or more ultrasonic transducer elements of one or more AOD systems in the first positioner 106, or by supplying spectrally shaped RF signals to one or more ultrasonic transducer elements of one or more AOD systems in the first positioner 106, or similar, or by any combination thereof).

[0061] Examples of actions that can be controlled to perform on one or more of the above-mentioned components include the above-mentioned U.S. Patents No. 4,912,487, No. 5,633,747, No. 5,638,267, No. 5,751,585, No. 5,847,960, No. 5,917,300, No. 6,314,473, No. 6,430,465, No. 6,700,600, No. 6,706,998, No. 6,706, No. 999, No. 6,816,294, No. 6,947,454, No. 7,019,891, No. 7,027,199, No. 7,133,182, No. 7,133,186, No. 7,133,18 No. 7, No. 7,133,188, No. 7,245,412, No. 7,259,354, No. 7,611,745, No. 7,834,293, No. 8,026,158, No. 8,076,605 , in U.S. Patent Publications No. 8,288,679, No. 8,404,998, No. 8,497,450, No. 8,648,277, No. 8,680,430, No. 8,847,113, No. 8,896,909, No. 8,928,853, and No. 9,259,802, or in the aforementioned U.S. Patent Publications No. 2014 / 0026351, No. 2014 / 0197140, and No. 2014 / 0263201 Examples include operations, functions, processes, and methods disclosed in patents No. 2014 / 0263212, No. 2014 / 0263223, No. 2014 / 0312013, or in German Federal Patent No. DE102013201968B4, or in International Patent Publication No. WO2009 / 087392, or any combination thereof.

[0062] Generally, the controller 114 includes one or more processors configured to generate the aforementioned control signals when executing instructions. The processors, once configured to execute instructions, may be provided as programmable processors (e.g., one or more general-purpose computer processors, microprocessors, digital signal processors, or any combination thereof). Instructions executable by the processors may be implemented as software, firmware, or in any preferred form of circuitry, including programmable logic devices (PLDs), field-programmable gate arrays (FPGAs), field-programmable object arrays (FPOAs), application-specific integrated circuits (ASICs) (including digital circuits, analog circuits, and mixed analog / digital circuits), or any combination thereof. Instruction execution may occur on a single processor, distributed across multiple processors, in parallel across multiple processors within a single device or across a network of devices, or in similar manner, or in any combination thereof.

[0063] In one embodiment, the controller 114 includes a tangible medium such as computer memory accessible by the processor (for example, via one or more wired or wireless communication links). As used herein, “computer memory” includes magnetic media (e.g., magnetic tape, hard disk drives, etc.), optical disks, volatile or non-volatile semiconductor memory (e.g., RAM, ROM, NAND flash memory, NOR flash memory, SONOS memory, etc.), and may be locally accessible, remotely accessible (e.g., via a network), or a combination thereof. Generally, instructions may be stored as computer software (e.g., executable code, files, instructions, library files, etc.). Such computer software can be written in, for example, C, C++, Visual Basic, Java, Python, Tel, Perl, Scheme, Ruby, etc., and can be easily created by those skilled in the art from the descriptions provided herein. Computer software is typically stored in one or more data structures transmitted by computer memory.

[0064] Although not shown in the diagram, one or more drivers (e.g., RF drivers, servo drivers, line drivers, power supplies, etc.) may be communicatively connected to the inputs of one or more components, such as the laser source 104, the first positioner 106, the second positioner 108, the third positioner 110, the lens actuator, and a mechanism for performing Z-direction height compensation (see below). In one embodiment, each driver typically includes an input to which a controller 114 is communicatively connected, thereby enabling the controller 114 to generate one or more control signals (e.g., trigger signals). These control signals may be transmitted to the inputs of one or more drivers associated with one or more components of the device 100. Thus, components such as the laser source 104, the first positioner 106, the second positioner 108, the third positioner 110, and the lens actuator are configured to respond to the control signals generated by the controller 114.

[0065] In other embodiments, although not shown, one or more additional controllers (e.g., component-specific controllers) may be communicatively connected to the inputs of drivers communicatively connected to (and associated with) components such as the laser source 104, the first positioner 106, the second positioner 108, the third positioner 110, the lens actuator, and the mechanism for performing Z-direction height compensation, as needed. In this embodiment, each component-specific controller may be communicatively connected to controller 114 and capable of generating one or more control signals (e.g., trigger signals) in response to one or more control signals received from controller 114. These one or more control signals may then be transmitted to the inputs of drivers communicatively connected to it. In this embodiment, the component-specific controllers may be configured in the same manner as described with respect to controller 114.

[0066] In other embodiments where one or more component-specific controllers are provided, a component-specific controller associated with a component (e.g., a laser source 104) may be communicatively connected to a component-specific controller associated with another component (e.g., a first positioner 106). In this embodiment, one or more of the component-specific controllers may generate one or more control signals (e.g., trigger signals) in response to one or more control signals received from one or more other component-specific controllers.

[0067] III. Embodiments relating to the second positioner While specific embodiments of the second positioner 108 described in this section are related to apparatus 100, it will be understood that any one of these embodiments, or any combination thereof, can be implemented for any laser processing apparatus other than apparatus 100. In one embodiment, the second positioner 108 is provided as a galvanometer mirror system including a plurality of galvanometer mirror components (each including a mirror, for example) arranged in the beam path.

[0068] For example, referring to Figure 2, the galvanometer mirror system is provided as a galvanometer mirror system 200, which includes a first galvanometer mirror component 202a and a second galvanometer mirror component 202b. The first galvanometer mirror component 202a includes a first mirror 204a connected to a first mount 206a, a first motor 208a for rotating the first mirror 204a via the first mount 206a, and a position detector (not shown) which may be used as needed, configured to generate a position signal corresponding to the rotation of the first mount 206a about a first rotation axis 210a to enable closed-loop servo control of the first motor 208a. Similarly, the second galvanometer mirror component 202b includes a second mirror 204b, a second mount 206b, and a second motor 208b, each of which is configured in the same manner as described above with respect to the first galvanometer mirror component 202a. The second galvanometer mirror component 202b optionally includes a position detector (not shown) configured to generate a position signal corresponding to the rotation of the second mount 206b around a second rotation axis 210b, for example, to enable closed-loop servo control of the second motor 208b.

[0069] As illustrated, the first mirror 204a is positioned at a first position in the beam path 116 (for example, at a distance relatively far from the scan lens 112), and the second mirror 204b is positioned at a second position in the beam path 116 (for example, at a distance relatively close to the scan lens 112). The first mirror 204a is rotatable about a first axis of rotation 210a (e.g., the Y-axis), and reflects laser pulses to move the beam path 116 (thus moving the beam axis within a second scanning range extending, for example, a distance d(x) along the X-direction). Similarly, the second mirror 204b is rotatable about a second axis of rotation 210b (e.g., the X-axis), and reflects laser pulses to move the beam path 116 (thus moving the beam axis within a second scanning range extending, for example, a distance d(y) along the Y-direction). In one embodiment, distances d(x) and d(y) can be within the range of 1 mm to 200 mm, as described above. However, it can be understood that distances d(x) and d(y) can be within a range smaller than 1 mm or larger than 200 mm. Thus, distances d(x) and d(y) can be greater than or equal to 1 mm, 2 mm, 5 mm, 10 mm, 25 mm, 50 mm, 100 mm, 150 mm, 160 mm, 170 mm, 200 mm, etc. Similarly, distances d(x) and d(y) can be less than or equal to 200 mm, 170 mm, 160 mm, 150 mm, 100 mm, 50 mm, 25 mm, 10 mm, 5 mm, 2 mm, 1 mm, etc., or between any of these values.

[0070] A. Telecentric error In one embodiment, the galvanometer mirror system 200 is configured such that, as the beam axis moves within the second scanning range, the beam path is first deflected by the first mirror 204a and then deflected by the second mirror 204b, and the resulting beam path intersects with the pupil of the scan lens 112 (or intersects at a position of the scan lens 112 near the pupil). However, depending on the configuration of the galvanometer mirror system 200, the beam path deflected first by the first mirror 204a and then deflected by the second mirror 204b intersects at a position offset from the pupil of the scan lens 112 (or intersects at a position outside the vicinity of the pupil of the scan lens 112 as described above), resulting in a telecentric error, and it has been found that the laser pulse is irradiated at a position offset from the desired processing spot. For example, the inventors have discovered that, depending on the Z-direction height of the workpiece surface, a position offset of ±0.8 μm (in the X and Y directions) is observed for each 1° deflection angle at the first mirror 204a. Much smaller positional offsets were observed for each deflection angle at the second mirror 204b. While we do not wish to be constrained by any particular theory, it is thought that the distance from the first mirror 204a to the scan lens 112 (which is greater than the distance between the second mirror 204b and the scan lens 112) primarily contributes to the generation of the observed telecentric error and positional offsets. These positional offsets can ultimately degrade the positional accuracy and precision of drilling via-like features.

[0071] To facilitate maintaining positional accuracy and precision in drilling features such as vias, the first galvanometer mirror component 202a can be driven (for example, in response to one or more control signals output by the controller 114, or in response to a current output by a servo driver connected to the first galvanometer mirror component 202a) to rotate the first mirror 204a around the first rotation axis 210a, thereby moving the beam path 116 so that the beam axis moves within a second scanning range that extends, for example, along the X direction by a distance d'(x) smaller than d(x). When limiting the size of the second scanning range in the X direction, the size of the second scanning range can be increased to a distance d'(y) which can be larger than the distance d(y), as illustrated above. For example, see Figure 3, which shows a second scanning range according to two embodiments of the present invention. The second scanning range 302a represents a typical scanning range where distances d(x) and d(y) are equal to each other. The second scanning range 302b represents other scanning ranges where distances d'(x) and d'(y) are not equal (i.e., distance d'(x) is smaller than distance d'(y)). In a process such as via drilling, distance d'(x) can be in the range of 0.04 mm to 200 mm. However, it can be understood that distance d'(x) can be smaller than 0.04 mm or larger than 200 mm. For example, distance d'(x) may remain smaller than distance d'(y) but be larger than or between any of the following values: 0.04 mm, 0.1 mm, 0.5 mm, 1 mm, 2 mm, 5 mm, 10 mm, 15 mm, 20 mm, 25 mm, 40 mm, 70 mm, 100 mm, 150 mm, etc. Similarly, the distance d'(x) can be less than or between any of the following values: 30mm, 25mm, 20mm, 15mm, 10mm, 5mm, 2mm, 1mm, 0.5mm, etc.

[0072] The second galvanometer mirror component 202b is similarly driven to rotate the second mirror 204b around the second rotation axis 210b to such an extent that an undesirable positional offset caused by a telecentric error occurring when the second mirror 204b is rotated is detected, thereby moving the beam path 116 so as to move the beam axis within a second scanning range that extends, for example, along the Y direction by a correction distance smaller than d(y) (such a correction distance is greater than d'(x)).

[0073] Notwithstanding the foregoing, it can be understood that telecentric errors can be reduced or eliminated by replacing the galvanometer mirror system 200 with a positioner such as a two-axis FSM element (capable of deflecting the beam path along the X and Y directions) incorporating a piezoelectric actuator, electrostrictive actuator, voice coil actuator, or similar, or any combination thereof.

[0074] IV. Embodiments relating to height measurement and compensation in the Z direction In many cases, the length of the portion of the beam path extending from the output of the device 100 (e.g., the scanning lens 112 in the illustrated embodiment) to the desired processing spot location (i.e., the distance the laser pulse travels from leaving the device 100 until it irradiates the processing spot on the workpiece) is called the "Z-direction height". For many processes utilizing lasers, the laser pulse typically produces the best processing spot quality and best fluence (e.g., in terms of size, shape, and uniformity) at the beam waist (i.e., when the spot size of the laser pulse irradiating the processing spot is equal to (or at least substantially equal to) the spot size at the beam waist. However, other processes utilizing lasers do not require the spot size of the laser pulse irradiating the processing spot to be equal to (or substantially equal to) the spot size at the beam waist. Nevertheless, deviations in the spot size of the laser pulse irradiating the desired processing spot can result in undesirable low fluence levels and alter the dimensional and intensity distribution of the laser pulse irradiating the desired processing spot. These deviations can affect the quality and / or throughput of the laser process.

[0075] To ensure that the laser pulses irradiated onto the desired processing spot have the desired spot size, the apparatus 100 may optionally include a Z-direction height sensor 124 configured to measure the distance (or characteristic indicating the distance between them) between the scan lens 112 and a region of the work surface 102a (also referred to as the “detection range” of the work surface 102a). As used herein, this measured distance (or characteristic indicating the measured distance) is also referred to as the “measured work surface Z-direction height.” In addition, if the Z-direction height sensor 124 is configured to measure the distance (or characteristic thereof) between a particular scan lens 112 and a region of the work surface 102a, the Z-direction height sensor 124 may also be referred to as a Z-direction height sensor associated with a particular scan lens 112 (or a particular scan head incorporating the scan lens), or more simply as the “associated Z-direction height sensor.” The Z-direction height sensor 124 may be provided as any suitable or advantageous displacement sensor, distance sensor, position sensor, etc., or any combination thereof. Examples of sensors that can be used as the Z-direction height sensor 124 include laser triangulation sensors, laser profile sensors, scanning confocal laser sensors, confocal interference displacement sensors, barometer sensors, or any combination thereof.

[0076] In one embodiment, the Z-direction height sensor 124 is fixed in position relative to the associated scan lens 112 (for example, the Z-direction height sensor 124 is connected to the scan head 118, the scan lens housing, etc., or to a frame to which the scan head 118 is connected). In this case, the position of the detection range relative to the second scanning range (for example, measured in the XY plane) is fixed. In another embodiment, the device 100 is configured such that the Z-direction height sensor 124 and the scan lens 112 are movable relative to each other. For example, the Z-direction height sensor may be movable relative to the scan lens 112 (for example, in the X, Y, or Z directions, or in any combination thereof) (for example, the Z-direction height sensor 124 is connected to a linear or rotary stage, which is then connected to the scan head 118, or to other frames, brackets, rails, etc. associated with the device 100). In other embodiments, the Z-direction height sensor 124 may be fixed in position within the device 100, and the scan lens 112 may be movable relative to the Z-direction height sensor 124 (for example, in the X, Y, or Z directions, or any combination thereof).

[0077] The Z-direction height sensor 124 can generate one or more signals (e.g., "Z-direction height signals"), data (e.g., Z-direction height data), or any combination thereof (collectively referred to as "Z-direction height information") indicating the measured Z-direction height of the workpiece surface, and output this to the controller 114. In its raw form, the Z-direction height information generated or output from the Z-direction height sensor 124 may contain noise. Sometimes, this noise is too great to form a reliable basis for determining whether the Z-direction height of the workpiece surface is outside a predetermined nominal Z-direction height process window (e.g., ±60 μm, ±70 μm, ±80 μm, ±90 μm, ±100 μm, etc.) relative to the reference Z-direction height of the workpiece surface. If the "raw" Z-direction height information is too noisy, the raw Z-direction height information can be processed by the Z-direction height sensor 124, or the controller 114, or similarly, or by any combination thereof (for example, by filtering, smoothing, similar processing, or any combination thereof) to obtain the "processed" work surface Z-direction height. The "processed" work surface Z-direction height can form the basis for determining whether the work surface Z-direction height is outside a predetermined nominal Z-direction height process window.

[0078] In one embodiment, raw or processed Z-direction height information items are stored (for example, in a data structure transmitted by computer memory such as a buffer or cache of the controller 114). When a Z-direction height measurement is obtained associated with a Z-direction height information item, each Z-direction height information item may be stored in association with a corresponding item of information indicating the position of the detection range relative to the third scanning range (also referred to herein as the "detection position"). The information indicating the detection position can be obtained or derived (for example, by the controller 114) from one or more signals (e.g., encoder signals) generated by the third positioner 110 and output to the controller 114, and is given as a position along the X, Y, or Z directions, or any combination thereof.

[0079] Generally, the spacing between detection positions may depend on one or more factors, such as the workpiece 102 being processed, the type of processing performed, the location where features are formed on or within the workpiece 102, the desired precision or accuracy when features are formed on or within the workpiece 102, or any combination thereof. In some embodiments, the spacing between detection positions is in the range of 0.1 mm to 6 mm (e.g., 0.2 mm to 5 mm). In other embodiments (e.g., the workpiece 102 is a PCB and the processing involves via drilling), the spacing between detection positions is in the range of 0.5 mm to 1.5 mm (e.g., 1 mm or slightly above). However, it can be understood that the spacing between detection positions may be less than 0.1 mm or greater than 6 mm. The spacing between two pairs of adjacent detection positions may be constant or variable. In one embodiment, the measurement of the height in the Z direction can be triggered in response to a control signal received from the controller 114 (which is generated and output when one or more encoder signals output by a third positioner 110 are received, for example), or in response to one or more encoder signals received from the third positioner 110, in response to something similar, or in any combination thereof.

[0080] In other embodiments, an item of Z-direction height information (and its associated position information) is saved only if it indicates that the work surface Z-direction height is outside a predetermined nominal Z-direction height process window. In this embodiment, the controller 114 may be configured to process Z-direction height information to determine whether the (e.g., measured or processed) work surface Z-direction height at a particular position is outside a predetermined nominal Z-direction height process window (and save the Z-direction height information and position information if the determination is positive). In other embodiments, the Z-direction height sensor 124 may be configured to process Z-direction height information to determine whether the (e.g., measured or processed) work surface Z-direction height is outside a predetermined nominal Z-direction height process window (and output the Z-direction height information to the controller 114 if the determination is positive).

[0081] If the Z-direction height of the workpiece surface (for example, measured or processed) is determined to be outside a predetermined nominal Z-direction height process window (for example, by the controller 114 or the Z-direction height sensor 124), the controller 114 generates one or more control signals to compensate for the detected change or displacement outside the predetermined nominal Z-direction height process window (for example, so that the irradiated laser pulse has a desired spot size at the desired processing spot) and outputs them to a lens actuator, a third positioner 110, or any combination thereof. Z-direction height compensation can be achieved by outputting one or more control signals that activate one or more mechanisms for performing Z-direction height compensation so that the irradiated laser pulse has a desired spot size at the desired processing spot. Examples of mechanisms for performing Z-direction height compensation that can be used in the embodiments provided herein are described in more detail below.

[0082] When the Z-direction height of the workpiece surface is known, the straightforward approach is to perform real-time Z-direction height compensation. However, the Z-direction height of the workpiece surface may not be known (or may not be known with the required accuracy) before the workpiece 102 is processed. In one embodiment, the Z-direction height of the workpiece surface at all positions where the workpiece 102 is processed is measured before the laser processing of the workpiece 102 begins. However, such "offline" measurement of the Z-direction height of the workpiece surface can be time-consuming and expensive, especially when the workpiece 102 is large. This is particularly true when the expected time required to complete the laser processing is relatively short, or when the detection range for the Z-direction height sensor is small relative to the size of the workpiece 102. Furthermore, the change in the Z-direction height of the workpiece surface may become so large that the intended laser processing fails to meet certain quality requirements. Therefore, it may be preferable to measure the Z-direction height of the workpiece surface in real time during workpiece processing, rather than before.

[0083] To facilitate real-time measurement of the Z-direction height of the work surface, the Z-direction height sensor 124 may be positioned and configured such that its detection range is located within the second scanning range 302b (for example, partially or completely within the second scanning range 302b such that the centroid or other central region of the detection range is located inside or outside the second scanning range 302b). Thus, in one embodiment, compensation for the detected change or displacement of the work surface Z-direction height can be performed as soon as it is determined that the detected change or displacement is outside the nominal Z-direction height process window. However, the response time associated with the mechanism for performing Z-direction height compensation is considered to be too long, and as a result, this must be compensated for (for example, by delaying the laser processing sequence until the detected change or displacement of the work surface Z-direction height is compensated). The delay due to the response time of the mechanism for performing Z-direction height compensation will be referred to below as the "response time delay". Furthermore, processing raw Z-direction height information (for example, to obtain the Z-direction height of the "processed" work surface) can also cause delays that may require compensation (this is also called "processing delay"). However, if the response time delay and processing delay are relatively small compared to the speed at which the second scanning range moves relative to the workpiece (or vice versa), such delays do not need to be compensated for.

[0084] In some cases, as described above, it may be difficult to obtain accurate Z-direction height measurements of the work surface when the detection range is located within the second scanning range 302b. Therefore, in other embodiments, the Z-direction height sensor 124 can be positioned and configured such that the detection range is located completely outside the second scanning range 302b. For example, referring to Figures 4 to 6, the Z-direction height sensor 124 is positioned and configured such that the detection range 402 is offset from the second scanning range 302b along the Y direction (for example, as shown in Figure 4), along the X direction (for example, as shown in Figure 5), or along both the X and Y directions (for example, as shown in Figure 6). Figures 4 to 6 show a state in which the detection range 402 is offset from the second scanning range 302b in the -X direction, the -Y direction, or both the -X and -Y directions. However, it can be understood that the detection range 402 may be offset from the second scanning range 302b in any of the -X direction, the +X direction, the -Y direction, or the +Y direction, or in any combination thereof. In the embodiments shown in Figures 4 and 6, the distance or pitch p(y) along the Y direction between the second scanning range 302b and the detection range 402 (i.e., measured from the center of each of these regions along the Y direction) is equal to the distance d'(y) of the second scanning range 302b. Similarly, in the embodiments shown in Figures 5 and 6, the distance or pitch p(x) along the X direction between the second scanning range 302b and the detection range 402 (i.e., measured from the center of each of these regions along the X direction) is equal to the distance d'(x) of the second scanning range 302b. However, in other embodiments, the distances p(y) and p(x) may be greater than or less than the corresponding distances d'(y) and d'(x), respectively.

[0085] In the examples described with respect to Figures 4 to 6, the detection range 402 is generally a circle with a diameter in the range of 1 mm to 3 mm; in one embodiment, the detection range 402 has a diameter in the range of 1.5 mm to 2 mm. However, it can be understood that the detection range 402 may have a diameter smaller than 1 mm or larger than 3 mm. For example, the detection range 402 may have a diameter equal to or larger than any of the distances d(x), d'(x), d(y), or d'(y) described above. However, in examples of other embodiments, instead of having a circular shape, the shape of the detection range 402 may generally be a triangle, square, rectangle, ellipse, etc. In examples of yet another embodiment, the shape and size of the detection range 402 may generally be the same as the shape and size of the second scanning range 302b. In one embodiment, the Z-direction height sensor 124 is configured to generate Z-direction height information indicating the average or arithmetic mean Z-direction height of the work surface measured within the detection range 402. In other embodiments, the Z-direction height sensor 124 is configured to generate Z-direction height information indicating the actual, average or arithmetic mean Z-direction height of the work surface measured at multiple points within the detection range 402.

[0086] From the above perspective, the arrangement of the detection range 402 relative to the second scanning range 302b (for example, this can be characterized by a direction in which the detection range 402 is offset from the second scanning range 302b by a pitch between the detection range 402 and the second scanning range 302b, or by any combination thereof) can be made flexible. For example, the arrangement of the detection range 402 relative to the second scanning range 302b can correspond to the relative motion between the second scanning range 302b and the workpiece 102 during laser processing. Such relative motion can be characterized by parameters such as the speed of movement and the direction of movement, and can proceed along the X direction or the Y direction, one or more directions other than the X and Y directions, or any combination thereof.

[0087] Thus, in one embodiment, the detection range 402 may be offset from the second scanning range 302b in a direction different from the direction in which the second scanning range 302b is moved relative to the workpiece 102 (for example, when the scan lens 112, workpiece 102, or a combination thereof is moved by operating the third positioner 110). For example, if the second scanning range 302b is moved in the +Y or -Y direction relative to the workpiece 102 during the intended laser processing, the detection range 402 may be offset from the second scanning range 302b in the -X or +X direction (for example, as shown in Figure 5 or Figure 6). By offsetting the detection range 402 in this way, real-time height measurement in the Z direction of the work surface becomes possible, but the same response time delay and processing delay described above also occur. Furthermore, as described above, offsetting the detection range 402 can be problematic if laser processing is performed on the edge of the workpiece 102 and the detection range 402 is not located on the workpiece 102, or is only partially located on the workpiece 102. However, these problems (or the likelihood of these problems occurring) can be improved or avoided by implementing a scanning method according to one or more embodiments described below when processing the workpiece 102.

[0088] In other embodiments, the detection range 402 may be offset from the second scanning range 302b in the same direction as the second scanning range 302b is moved relative to the workpiece 102 (for example, when moving the scan lens 112, workpiece 102, or a combination thereof by operating the third positioner 110). For example, if the second scanning range 302b is moved in the -Y direction relative to the workpiece 102 during the intended laser processing, the detection range 402 may be offset from the second scanning range 302b in the -Y direction (for example, as shown in Figure 4 or Figure 6). Offsetting the detection range 402 in this way enables real-time measurement of the workpiece surface height in the Z direction, but also introduces the same delay as described above. Furthermore, depending on the workpiece 102 being processed, the offset of the detection range 402 described above is often effective only when the detection range 402 is offset in the same direction as moving the second scanning range 302b relative to the workpiece 102 (though not always). However, this problem can be mitigated by providing multiple Z-direction height sensors (for example, configured and positioned so that multiple detection ranges are each located on the opposite side of the second scanning range 302b). This problem can also be mitigated by implementing a scanning method according to one or more embodiments described below when processing the workpiece 102.

[0089] In embodiments where the centroid or other central region of the detection range 402 is located entirely outside the second scanning range 302b, the controller 114 compensates for the detected change or detected displacement indicated by the item in the Z-direction height information when the processing position is the same as the detected position associated with that item in the Z-direction height information. In other embodiments, compensation for the detected change or detected displacement is performed when the processing position is within a specific distance from the detected position (e.g., within a distance of 400 μm, 200 μm, 100 μm, 80 μm, 60 μm, 50 μm, 30 μm, 15 μm, or similar values). This specific distance may be fixed or may vary depending on factors such as the speed at which the second scanning range 302b is scanned, the response time associated with the mechanism for performing Z-direction height compensation, or any combination thereof. Such compensation can also be performed in embodiments where the centroid or other central region of the detection range 402 is located within the second scanning range 302b, or in embodiments where the detection range 402 is partially located within the second scanning range 302b, but the centroid or other central region of the detection range 402 is located outside the second scanning range 302b.

[0090] The processing position may be the position where the current laser pulse irradiates the processing spot during workpiece processing (for example, determined with respect to a third scanning range), the centroid position corresponding to the position where a series of laser pulses sequentially irradiate multiple spatially distributed processing spots during workpiece processing, a part of the second scanning range 302b (for example, its edge, centroid, or other internal region), a part of the first scanning range (for example, its edge, centroid, or other internal region), or any combination thereof. Information indicating the processing position can be obtained or derived (for example, by the controller 114) from one or more signals (e.g., encoder signals) generated by the first positioner 106, the second positioner 108, the third positioner 110, or any combination thereof and output to the controller 114, or from information describing the process trajectory, or similar information, or any combination thereof.

[0091] While specific embodiments of the arrangement of the detection range 402 in this section are described in relation to the second scanning range 302b, it will be understood that in other embodiments, the Z-direction height sensor 124 may be arranged and configured such that the detection range 402 is similarly offset from other scanning ranges, such as the second scanning range 302a. Furthermore, while specific embodiments of the Z-direction height in this section are described in relation to the apparatus 100, it will be understood that any one of these embodiments or any combination thereof may be implemented in relation to any laser processing apparatus other than the apparatus 100. Furthermore, while specific embodiments of the Z-direction height measurement and Z-direction height compensation in this section are described in relation to the laser processing apparatus and laser-based processes, it will be understood that any one of these embodiments or any combination thereof may be implemented in relation to any other suitable apparatus configured to process workpieces, such as a mechanical drill, a water jet cutting apparatus or a water jet drilling apparatus, an electron beam cutting machine, or a spraying machine.

[0092] Example of an embodiment of a mechanism for performing height compensation in the AZ direction i. Lens Actuator In one embodiment, the mechanism for performing Z-direction height compensation may include the lens actuator described above. For example, the lens actuator can be operated to adjust the position of the beam waist along the beam axis (also referred to herein as "focusing the Z-direction height," measured from the exit pupil of the scan lens 112), so that the irradiated laser pulse has a desired spot size at the desired processing spot.

[0093] ii. First positioner In one embodiment, the first positioner 106 may include a MEMS mirror or mirror array, as illustrated above, and can be operated to perform Z-direction height compensation by changing the spot shape or spot size of the laser pulse irradiated onto the workpiece 102. In other embodiments, the first positioner 106 may include one or more AOD systems, as illustrated above, and can be driven to perform Z-direction height compensation (for example, when one or more RF signals are applied to one or more ultrasonic transducer elements acoustically coupled to one or more AO cells, each). Examples of embodiments for driving the AOD systems are described in more detail below. Although these examples of embodiments are described in relation to AOD systems incorporated inside a device such as device 100 or 700, it will be understood that these examples of embodiments can be suitably implemented with any device using a laser incorporating an AOD system, regardless of whether the device using the laser is a laser processing device or not.

[0094] a. Chirpened RF signal In one embodiment, if the first positioner 106 includes an AOD system (e.g., a multi-axis AOD system), the AOD system can be driven by chirpening the RF signal applied to one or more ultrasonic transducer elements of the AOD system as the laser pulse passes through an AO cell acoustically coupled to the ultrasonic transducer element. Chirpening the applied RF signal has the effect of causing a change in the focal length of the laser pulse beam emitted from the AOD system. When the focal length is changed, the effective spot size of the laser pulse irradiated onto the workpiece 102 changes accordingly. The degree to which the focal length changes can be characterized by the following formula.

number

[0095] Generally, chirpening an applied RF signal is effective for laser pulses shorter than the travel time of sound waves through the aperture irradiated by the laser pulse beam. Essentially, QCW lasers can be difficult to effectively change the focal length of the laser pulse beam generated by a laser source 104, such as a QCW laser, because there is no (effective) laser off time between pulses during which the chirp frequency can be reset to its starting value. Therefore, it is easier to implement the chirp technique with discrete pulse lasers, and as a result, the chirp sweep (around the central AOD frequency required for spot positioning) can be properly set as the laser pulse passes through the AOD. However, if a pulse gating unit is provided, the chirp technique can be used with CW or QCW lasers.

[0096] The range over which the AOD system can move the beam axis is proportional to the frequency of the applied RF signal. If the applied RF frequency is chirp, the sound wave frequency changes over the width of the laser pulse passing through the AO cell (i.e., measured across the beam path 116), and the deflection of the beam path 116 is proportional to the average frequency over the passing laser pulse. The average frequency can be appropriately set or calibrated to achieve the desired movement of the beam axis. However, changes in the timing of the laser pulse and / or the AOD control signal can cause deviations in this average frequency, which can result in spot position errors (i.e., the laser pulse will irradiate a position on the workpiece 102 different from the desired spot position). For example, the AOD system has a first scanning range of 150 μm (e.g., beyond a 30 MHz bandwidth). Therefore, the beam path deflection per MHz is 150 μm / 30 MHz, or 5 μm / MHz. If the desired char rate is 30 MHz / μs, a 10 ns timing change will result in a beam path deflection error of 1.5 μm (i.e., (5 μm / MHz) * (30 MHz / μs) * (10 ns)).

[0097] Variations in the timing of laser pulses and / or AOD control signals typically arise from circuitry or operation within the controller 114 (which can be embodied in various forms), changes in the driver, and the generation of laser pulses from the laser source 104. In some laser sources (such as diode pulsed fiber lasers), the jitter between the input laser trigger signal and the corresponding laser pulse ultimately generated can be relatively low (<10 ns). In other laser sources (e.g., Q-switched diode-pumped lasers), the variation can be larger (e.g., due to random synchronization of internal Q-switch activity and laser resonator dynamics). For example, in a typical UV Q-switched laser, the timing uncertainty between the input laser trigger signal and the corresponding laser pulse ultimately generated can be approximately ±15 ns. Furthermore, a typical FPGA may have a fundamental clock operating with a clock period of 20 ns. Therefore, a controller 114 containing such an FPGA introduces an additional ±10 ns of timing uncertainty. These timing uncertainties can result in positioning errors for the laser pulse ultimately irradiating the workpiece 102 (i.e., changes or displacements in the actual position where the laser pulse ultimately irradiates away from the desired processing spot). Depending on the specific features formed during processing, this positioning error may or may not be significant.

[0098] When performing Z-direction height compensation, the above-described positioning error may become significant. In such a situation, synchronization can be improved among the output of a trigger signal to the laser source 104 (for example, for generating laser pulses), the output of a trigger signal to the AOD system (for example, for applying one or more chirped RF signals), and the generation of laser pulses by the laser source 104. For example, in an embodiment where the laser source 104 depends on an internal clock to trigger the output of laser pulses, the internal clock can be synchronized (for example, via a PLL, logic gates, etc.) to the internal clock of the controller 114 that starts the trigger signal to the AOD system. Further, the clock used when generating the chirp sequence itself (for example, the clock used by a direct digital synthesizer (DDS) circuit, etc.) may be synchronized as well. This synchronization can reduce the timing uncertainty to only the timing uncertainty due to the random laser resonator effect.

[0099] b. Spectralized RF signal In one embodiment, when the first positioner 106 includes an AOD system (for example, a multi-axis AOD system), the AOD system can be driven by applying an RF signal whose spectrum is shaped to one or more ultrasonic transducer elements when a laser pulse passes through an AO cell acoustically coupled to the ultrasonic transducer elements. In this embodiment, the shape of the spectrum in the applied RF signal is selected to change the M 2 factor (also known in the art as the "beam quality factor" or "beam propagation factor"). Changing the M 2 factor causes a corresponding change in the effective spot size of the laser pulses irradiated on the workpiece 102. The range within which the M 2 factor can be changed corresponds to the width of the spectrum in the applied RF signal (for example, a relatively wide spectrum has a stronger effect than a relatively narrow spectrum on M 2(Applies to the factor). Generally, shaping the spectral components of the applied RF signal (as described herein) is effective for laser pulses that are longer than the travel time of sound waves through the aperture irradiated by the laser pulse beam.

[0100] In embodiments where a laser pulse having a radially symmetric Gaussian spatial intensity profile is irradiated onto the workpiece 102 (assuming the laser pulse output by the laser source 104 has a Gaussian spatial intensity profile), the spectrum of the applied RF signal may also have a Gaussian shape. Therefore, in one embodiment, the first type of RF signal that can be applied is characterized as a relatively narrow signal spike in the time domain (i.e., suggesting a constant or substantially constant phase at all frequencies in the applied signal spectrum). This type of signal can adversely affect the overall diffraction efficiency of the AOD cell. Therefore, in other embodiments, the second type of RF signal that can be applied is characterized as a relatively smooth signal, almost like a single-frequency oscillation (e.g., the amplitude of one oscillation peak is approximately equal to the amplitude of the oscillation peak with one oscillation peak placed between them). Such RF signals may include quasi-periodic signals. Unlike RF signals with spikes, these spectrally shaped RF signals can be configured to have less impact on the diffraction efficiency of the AO cell.

[0101] A spectrally shaped RF signal can be generated using any preferred method. In one embodiment, the spectrally shaped RF signal has a desired center frequency ω to set the centroid position of the modulation beam. o Select the desired spectral width σ to set the effective laser pulse spot size on workpiece 102. ω Select the desired frequency resolution r to set the interval of the discrete frequencies to be used. ω Select the center frequency ω o , spectral width σ ω and frequency resolution r ωThis can be generated by inputting the desired spectral characteristics for the applied RF signal into an algorithm such as the Gercberg-Saxton algorithm, which approximates the desired spectral characteristics for each frequency by determining the required phase. In this embodiment, the AOD system can be designed so that the laser pulse beam incident on the AO cell irradiates a relatively large number of grating periods of the AO cell (for example, so that a 6 mm beam size incident on a quartz AO cell with a pulse repetition rate of 100 MHz irradiates more than 100 periods), thereby achieving a good approximation to a Gaussian spectrum for many practical examples. This approximation can then be applied (for example, in the controller 114) to generate one or more suitable spectrally shaped RF signals applied to the AOD system. The spectral width σ input to the approximation algorithm ω By changing the center frequency ω input to the approximation algorithm, the spectrum of the applied RF signal can be changed, thereby altering the spectral width of the applied RF signal. o By changing the spectral width σ, the beam path 116 can be deflected. ω , center frequency ω o , and frequency resolution r ω It can be understood that these can be arbitrarily combined and modified together or separately.

[0102] iii. The third positioner In other embodiments, the mechanism for performing Z-direction height compensation may include a third positioner 110. For example, the third positioner 110 can be activated to move the workpiece 102 so that the Z-direction height of the workpiece surface falls within a predetermined nominal Z-direction height process window (so that the beam waist of the irradiated laser pulse is positioned at a desired processing spot).

[0103] iv. Examples of other embodiments of the mechanism for performing height compensation in the Z direction In one embodiment, the mechanism for Z-direction height compensation may include components such as a lens, a MEMS mirror, or a mirror array, or any combination thereof. In this embodiment, such a mechanism may be provided (for example, in addition to the first positioner 106, the third positioner 110, the scan lens 112, or any combination thereof) and positioned at any location in the beam path 116, either optically "upstream" or "downstream" of the first positioner 106, the second positioner 108, the third positioner 110, the scan lens 112, or any combination thereof. If provided as a lens, the lens may be provided as a fixed focal length lens connected to a lens actuator (e.g., a voice coil) configured to translate the lens along the beam path 116 and change the position of the beam waist along the beam axis. In other embodiments, the lens may be provided as a variable focal length lens (e.g., a zoom lens, or a so-called "liquid lens" incorporating technology currently offered by COGNEX, VARIOPTIC, etc.) that can be operated (e.g., via a lens actuator) to change the position of the beam waist along the beam axis.

[0104] V. Embodiments relating to the configuration of the scanhead In the embodiment shown in Figure 1, the apparatus 100 includes a single scan head 118. However, in other embodiments, the apparatus 100 may have multiple scan heads (e.g., two, three, four, five, six, eight, etc.), each of which may or may not be provided with respect to the scan head 118 in the manner described. Providing the apparatus 100 with multiple scan heads (i.e., a “multi-head apparatus”) can improve the throughput of the laser process performed by the apparatus 100. Different scan heads in such a multi-head apparatus can be installed, configured, driven, operated, etc., in the same or different manner, or they can be combined as desired.

[0105] For example, in one embodiment, one or more characteristics of the scan lenses of different scan heads may be the same or different. Examples of scan lens characteristics include type (e.g., f-theta, telecentric, axicon, etc.), focal length, numerical aperture, material composition, presence or absence of coating, and coating composition.

[0106] In other examples, a positioner (e.g., the second positioner 108 described above) may be incorporated into the scan head, and other scan heads may or may not have internally incorporated or associated positioners. Furthermore, one or more characteristics of the positioners of different scan heads may be identical or different. Examples of positioner characteristics include the number of positioners in the scan head 702 (e.g., one, two, three, etc.), the type of positioner for each scan head (e.g., mechanical positioners such as galvanometer mirrors, MEMS mirrors or mirror arrays, piezoelectric actuators, electrostrictive actuators, voice coil actuators, fixed positioners such as AODs and EODs, etc.), positioning bandwidth, scanning range size, scanning range shape, manufacturer, and software control. Similarly, the positioner of one scan head 702 may be driven by the same control signal as the positioners of one or more other scan heads 702. Alternatively, the positioner of one scan head 702 can be driven by a different control signal than the positioners of one or more other scan heads 702.

[0107] In one embodiment, different scan heads can be installed in the device in the same or different ways. For example, at least one (or all) scan heads can be fixed in a stationary position within the device (e.g., on a frame incorporated within the device). In another example, at least one (or all) scan heads can be made movable within the device. If movable, at least two (or all) scan heads may be made movable in the same direction or along the same direction, in different directions or along different directions, or in similar directions, or in any combination thereof (e.g., linear translation, rotation). If configured to be movable in the same direction, the at least two (or all) scan heads may be made movable at the same speed (e.g., so that no relative movement occurs between these scan heads), or at different speeds (e.g., so that relative movement occurs between these scan heads). To facilitate movement, the device may include one or more gantry, linear stage, rotary stage, articulated robot arm, or any combination thereof, which are beneficially coupled to one or more of the scan heads. Such a stage may be part of the third positioner 110 described above (and therefore driven by one or more control signals intended to cause relative movement between the beam axis and the workpiece 102, as described above), or it may be separate from the third positioner 110 (and therefore driven by one or more control signals intended to ensure alignment adjustment between each scan head and one or more workpieces processed by the multi-head device, for purposes other than causing relative movement between the beam axis and the workpiece 102).

[0108] In one embodiment, the multi-head device may include a single Z-direction height sensor, such as the Z-direction height sensor 124 described above, or it may include multiple such Z-direction height sensors. In one embodiment, the Z-direction height sensor may be associated with a single scan head, or it may be associated with multiple scan heads (e.g., two, three, four, five, six, eight, etc.). In one embodiment, the number of Z-direction height sensors included is the same as the number of scan heads in the multi-head device, and each Z-direction height sensor is associated with a single scan head.

[0109] The above describes some features of a multi-head device. A configuration associated with a multi-head device according to a certain embodiment will be described in more detail with reference to Figure 7.

[0110] When configured as a multi-head device, the device 100 (referred to as the multi-head device 700 in Figure 7) may include four scan heads, such as a first scan head 702a, a second scan head 702b, a third scan head 702c, and a fourth scan head 702d (each collectively referred to as scan head 702, or more broadly as multiple scan heads 702). A group of scan heads 702 can be supported by a common rail. For example, the first scan head 702a and the third scan head 702c can be commonly supported by a first rail 704a, and the second scan head 702b and the fourth scan head 702d can be commonly supported by a second rail 704b. As used herein, the first rail 704a and the second rail 704b are collectively referred to as rail 704, or more broadly as multiple rails 704.

[0111] Generally, each rail 704 can be fixed to remain stationary within the device 100 or to be movable (for example, linearly translated along the X direction, along the Y direction, or along another direction, or rotated about an axis parallel to the X or Y direction, or similar movement, or any combination thereof). For example, in the illustrated embodiment, the first rail 704a may be connected to a stage (not shown) configured to move the first rail 704a along the X direction (for example, as indicated by arrow 706), and the second rail 704b may be fixed to remain stationary within the multi-head device 700.

[0112] Generally, the scan head 702, which is transported by the rail 704, can be connected to the rail 704 in a manner that allows it to remain stationary or move (for example, by being linearly translated along the X direction, along the Y direction, or along another direction, or by being rotated around an axis parallel to the X or Y direction, or by a similar movement, or any combination thereof). For example, in the illustrated embodiment, a third scan head 702c and a fourth scan head 702d are fixed to a stationary position relative to a first rail 704a and a second rail 704b, respectively. The first scan head 702a is connected to a first Y-axis stage 708a (which can be transported by the first rail 704a) so as to be movable along the Y direction (as shown, for example, by arrow 710). The second scan head 702b is connected to a second Y-axis stage 708b (which can be transported by the second rail 704b) so as to be movable along the Y direction (independently of or in coordination with the first scan head 702a). Alternatively, the first scan head 702a and the second scan head 702b may be connected to a common Y-axis stage (not shown) that is movably connected to the first rail 704a and / or the second rail 704b (for example, via any suitable or advantageous mechanical linkage across the first rail 704a and the second rail 704b). With the configuration described above, the first scan head 702a is movable along the X and Y directions, the second scan head 702b is movable along the Y direction (for example, in coordination with the first scan head 702a), the third scan head 702c is movable along the X direction (for example, in coordination with the first scan head 702a), and the fourth scan head 702d is fixed to remain stationary.

[0113] Generally, each scan head 702 is adapted to receive laser pulses propagating from one or more laser sources, such as the laser source 104 described above, along one or more beam paths, such as the beam path 116 described above. For example, in the illustrated embodiment, the laser pulse is generated from a single laser source 104 and modified (e.g., by focusing, expanding, collimating, shaping, polarizing, filtering, or modifying, adjusting, or directing) by an optional optical system 712. The optical system 712 may include one or more optical elements, including beam expanders, beam shapers, apertures, harmonic generating crystals, filters, collimators, lenses, mirrors, polarizers, diffractive optical elements, refractive optical elements, or any combination thereof. In one embodiment, the optional optical system 712 may include any configuration of optical elements, such as those described exemplary as a modular image optical rail in U.S. Patent No. 6,433,301, which is incorporated herein by reference in its entirety.

[0114] In the illustrated embodiment, laser pulses generated by the laser source 104 (and optionally passing through the optical system 712) pass through the primary beam distributor 714 to simultaneously and / or alternately direct the laser pulses along a first primary beam path 116a1 and a second primary beam path 116a2 (each collectively referred to as primary beam paths 116a, or more broadly as multiple primary beam paths 116a). In one embodiment, the primary beam distributor 714 is provided as an AOM, and the primary beam paths 116a are provided as zero-order and primary beam paths associated with the AOM (for example, as illustrated in U.S. Patent No. 7,133,187 above). Generally, the diffraction efficiency of the AOM is not 100%. Therefore, even when the AOM is driven to select a primary beam path, at least some energy is always transferred along the primary beam paths 116a. Therefore, in an optional embodiment, the energy transmitted along the zero-order beam path can be blocked or prevented from reaching the workpiece surface 102a by suitably operating the first positioner 106, the second positioner 108, or any combination thereof. However, in another embodiment, one of the primary beam paths 116a may be provided as a positive primary beam path associated with the AOM, and the other primary beam path 116a may be provided as a negative primary beam path associated with the AOM. In this embodiment, a beam dump (not shown) may be provided to receive the energy transmitted along the zero-order beam of the AOM.

[0115] When provided as an AOM, the primary beam distributor 714 may be operated as needed (for example, in response to one or more control signals output by the controller 114, or other controllers, or any combination thereof) to temporally cut or slice the laser pulses generated by the laser source 104 (and passing through the optical system 712 as needed), or to block, dump or attenuate one or more laser pulses (or all of them) generated by the laser source 104 (and passing through the optical system 712 as needed), or in any combination thereof. For example, the AOM may be operated to block, dump or attenuate at least a portion of one or more (or all) laser pulses generated by the laser source 104 (and passing through the optical system 712 as needed). One or more portions of laser pulses may be blocked, dumped or attenuated to generate one or more laser pulses having a relatively short pulse duration, a short or long rise time, a short or long fall time, or similar characteristics, or any combination thereof.

[0116] Blocking or dumping one or more laser pulses in a sequentially generated series of laser pulses is also known as "pulse selection." Pulse selection can be performed whenever it is appropriate or necessary. For example, if the processing trajectory required to form multiple features (e.g., vias) specifies that at least a portion of the movement between features traversed by the processing spot requires the same time Tm, then the laser source 104 can generate laser pulses at a pulse repetition rate of 1 / Tm. Then, for movement between features traversed by the processing spot over a time of an integer k multiple of Tm (e.g., k*Tm), the primary beam distributor 714 (if provided as an AOM) can be operated to block pulses generated during the k*Tm period.

[0117] In some cases, changes in the pulse repetition rate of the laser pulses generated by the laser source 104 result in changes in the measurable temporal intensity profile of the generated laser pulses. Such changes can be characterized (e.g., by a pre-processing calibration step), and the primary beam distributor 714 (if provided as an AOM) can be operated to compensate for these pre-characterized changes (e.g., by blocking, dumping, or attenuating at least one portion of one or more (or all) laser pulses generated by the laser source 104). As a result, the laser pulses propagating along the primary beam path 116a can have a uniform (or at least substantially uniform) temporal intensity profile regardless of changes in the pulse repetition rate of the generated laser pulses.

[0118] In other embodiments, the primary beam distributor 714 may be provided as one or more polarizers, beam splitters, spinning chopper mirrors, rotating polyhedron mirrors, resonant galvanometer mirror systems, electro-optic modulators (EOMs), or any combination thereof. The use of EOMs to control other beam paths and / or to combine beam paths is described in detail in U.S. Patent No. 8,374,206, which is incorporated herein by reference in its entirety. It will be understood that optional optical systems 712 may be commonly located along the primary beam path 116a downstream of the primary beam distributor 714, rather than upstream of the primary beam distributor 714 as illustrated. In other embodiments, multiple optional optical systems 712 may be located downstream of the primary beam distributor 714, and each optional optical system 712 may be positioned along a different primary beam path 116a.

[0119] Laser pulses directed along the primary beam path 116a are further distributed by a first secondary beam splitter 716a and a second secondary beam splitter 716b (each collectively referred to as a secondary beam splitter 716, or comprehensively referred to as a secondary beam splitter 716). The first secondary beam splitter 716a is configured to simultaneously and / or alternately direct laser pulses propagating along the first secondary beam path 116a1 to the first secondary beam path 116b1 and the second secondary beam path 116b2. Similarly, the second secondary beam splitter 716b is configured to simultaneously and / or alternately direct laser pulses propagating along the second secondary beam path 116a2 to the third secondary beam path 116b3 and the fourth secondary beam path 116b4. In the illustrated embodiment, each secondary beam splitter 716 is provided as a system comprising a beam splitter and mirrors. For example, the first secondary beam divider 716a includes a beam splitter 718 and a mirror 720. However, in other embodiments, any secondary beam divider 716 can be provided as an AOM, one or more polarizers, a beam splitter, a spinning chopper mirror, a rotating polyhedron mirror, an electro-optic modulator (EOM), or any combination thereof.

[0120] The first secondary beam path 116b1, the second secondary beam path 116b2, the third secondary beam path 116b3, and the fourth secondary beam path 116b4 (collectively referred to as secondary beam paths 116b, or more broadly as multiple secondary beam paths 116b) each propagate through different scan heads 702. For example, in the illustrated embodiment, the first primary optical path 116a1 is split by the beam splitter 718 of the first secondary beam distributor 716a to form the first secondary beam path 116b1 and the third secondary beam path 116b3, and the second primary optical path 116a2 is split by the beam splitter 718 of the first secondary beam distributor 716b to form the second secondary beam path 116b2 and the fourth secondary beam path 116b4. The first secondary beam path 116b1 is directed to the first scan head 702a, the second secondary beam path 116b2 is directed to the second scan head 702b, the third secondary beam path 116b3 is directed to the third scan head 702c, and the fourth secondary beam path 116b4 is directed to the fourth scan head 702d. In the illustrated embodiment, each secondary beam path 116b acts on a pair of scan heads 702 on only one rail 704. However, it can be seen that the primary beam path 116a may be divided so that the associated secondary beam paths 116b can reach scan heads 702 on different rails 704.

[0121] In the illustrated embodiment, optical component assemblies such as the first optical component assembly 722a, the second optical component assembly 722b, the third optical component assembly 722c, and the fourth optical component assembly 722d (each collectively referred to as optical component assembly 722, or more broadly as multiple optical components 722) are arranged in the secondary beam path 116b such that the optical component assemblies 722 are located in the secondary beam path 116b at an upstream position of the scan head 702 located in the same secondary beam path 116b. Therefore, in the illustrated embodiment, the first secondary beam path 116b1 goes through the first optical component assembly 722a to the first scan head 702a, the second secondary beam path 116b2 goes through the second optical component assembly 722b to the second scan head 702b, the third secondary beam path 116b3 goes through the third optical component assembly 722c to the third scan head 702c, and the fourth secondary beam path 116b4 goes through the fourth optical component assembly 722d to the fourth scan head 702d. However, it can be understood that there may be fewer optical component assemblies 722 than scan heads 702.

[0122] Although not shown, an optical bypass system (for example, comprising one or more mirrors, AOMs, positioners (e.g., a galvanometer mirror system, a fast steering mirror, etc.), beam splitters, optical switches, etc., or any combination thereof) may be placed in any of the secondary beam paths 116b to bypass the corresponding optical component assembly 722. In this way, if an optical bypass system is placed in any particular secondary beam path 116b, the optical component assembly 722 can be functionally removed from that particular secondary beam path 116b. Alternatively, one or more (or all) of the optical component assemblies 722 can be omitted from the apparatus 700.

[0123] Each optical component assembly 722 may include one or more positioners, such as the first positioner 106 described above, and, if necessary, one or more half-wave plates, apertures, relay lenses, mirrors, etc., or any combination thereof (for example, all of these may be located inside a common housing, or any combination thereof, having optical input and output ports fixed to a common frame). Different optical component assemblies 722 may be configured, driven, operated, etc., in the same or different ways, or in any combination thereof. For this reason, the positioners of one optical component assembly 722 may be of the same type or different type (or the same type but with different characteristics) as those of one or more other optical component assemblies 722. Examples of positioner characteristics include the number of positioners in the optical component assembly 722 (e.g., one, two, three, etc.), the type of each positioner in the optical assembly 722, the positioning bandwidth, the size of the scanning range, the shape of the scanning range, the manufacturer, and software control. Similarly, the positioner of one optical component assembly 722 can be driven by the same control signal as the positioner of one or more other optical component assemblies 722. Alternatively, the positioner of one optical component assembly 722 can be driven by a different control signal than the positioner of one or more other optical component assemblies 722. The positioners of different optical component assemblies 722 can be driven simultaneously, sequentially, randomly, in a similar manner, or in any combination thereof. Each optical component assembly 722 can be individually packaged as a modular assembly, thereby allowing for selective removal or replacement of other optical component assemblies 722.

[0124] Although not shown in the figures, the housings, frames, etc., of one or more optical component assemblies 722 may include alignment features configured to facilitate the optical alignment of the corresponding secondary beam path 116b within the multi-head device 700 for at least one component of the optical component assembly 722 (e.g., a positioner, aperture, relay lens, mirror, optical input port, optical output port, etc., or any combination thereof). For this reason, the multi-head device 700 may further include frames, latches, etc., configured to engage with the alignment features of the optical component assemblies 722.

[0125] As illustrated in Figure 7, the primary beam distributor 714 distributes the incident train of laser pulses across a set of primary beam paths 116 (e.g., two primary beam paths 116a), and the secondary beam distributor 716 distributes the incident train of laser pulses across a set of secondary beam paths 116b (e.g., four secondary beam paths 116b). However, in other embodiments, one of the secondary beam distributors 716 positioned along the selected primary beam path 116a may be omitted (e.g., along with a corresponding optical component assembly 722 positioned along the downstream secondary beam path 116b), and the laser pulses propagating along the selected primary beam path 116a may be directed to the scan head 702 (e.g., with the aid of one or more mirrors).

[0126] Generally, the configuration described above allows one or more components of the multi-head device 700 (e.g., a first beam distributor 714, a second beam distributor 716, a first positioner 106, a second positioner 108 in the optical component assembly 722, etc.) to be operated (for example, in response to one or more control signals output by the controller 114 (see Figure 1) so that laser pulses (or bursts of laser pulses) are transmitted from a scan head 702 to a workpiece (not shown) simultaneously with laser pulses (or bursts of laser pulses) from at least one other scan head 702 (or all other scan heads 702) to a workpiece. In one embodiment, the operation of the multi-head device 700 is controlled so that laser pulses (or bursts of laser pulses) are transmitted from one scan head 702 supported by rail 704 to a workpiece simultaneously with laser pulses (or bursts of laser pulses) emitted from another scan head 702 (or all other scan heads 702) supported by the same rail 704. In other embodiments, laser pulses (or bursts of laser pulses) are irradiated at different time points from different scan heads 702 supported by a common rail 704 (for example, commonly supported by a first rail 704a or a second rail 704b).

[0127] It will be understood that the overall design of the multi-head device 700, including the desired optical distances between components, may affect the relative positioning of the optional optical system 712 and / or its components, the primary beam distributor 714, the secondary beam distributor 716, the optical component assembly 722 and its components, and the scan head 702 and / or its components. For example, to avoid obstacles, provide a desired segment length, improve alignment, or to combine these, numerous folding mirrors 724 can be used to facilitate the folding of various beam paths through which the laser pulse propagates (e.g., primary beam path 116a, secondary beam path 116b, etc., collectively referred to as beam paths 116, or more broadly as multiple beam paths 116). Some of these folding mirrors 724, such as the first folding mirror 724a and the second folding mirror 724b, may be supported by the first rail 704a and the second rail 704b, respectively. Alternatively, or in addition to the above, one or both of the first folding mirror 724a and the second folding mirror 724b may be directly or indirectly supported by one or more linear or rotary stages on which the rail 704 is supported.

[0128] As configured as described above, the multiple scan heads 702 of the multi-head device 700 may be used to process multiple separate workpieces simultaneously and / or sequentially, or to process a single workpiece simultaneously and / or sequentially. When multiple scan heads 702 are used to process multiple workpieces (for example, simultaneously), the device 100 may include multiple third positioners 110. Each of the third positioners 110 may be capable of moving its respective workpiece relative to the scan head. In this case, the third positioners may be operated to move the workpieces together relative to each other (i.e., no relative movement occurs between workpieces), or in a similar manner, or in any combination thereof.

[0129] VI. Embodiments relating to a workpiece handling system To facilitate loading and unloading workpieces onto and from a device such as the device 100 or the multi-head device 700 (each collectively referred to as the device), a workpiece handling system may be provided that can transfer workpieces onto and from the third positioner 110 (for example, in response to one or more control signals output by the controller 114, or other controllers, or any combination thereof).

[0130] In one embodiment, referring to Figures 8 and 9, the workpiece handling system may be a workpiece handling system 800 including a storage bay configured to hold one or more workpieces. These one or more workpieces may not have been processed by the apparatus, may have been partially processed by the apparatus, may have been fully processed by the apparatus, or may be any combination thereof. To facilitate the transfer of workpieces, the workpiece handling system 800 may be located next to the apparatus. For example, as shown in Figure 9, the workpiece handling system 800 may be located next to the aforementioned base (e.g., base 802) that supports the third positioner 110 (and may optionally support the chuck 902). The workpiece handling system 800 may include a first transfer mechanism 900 that can transfer a workpiece 102 from a first handling area 804 of the workpiece handling system 800 to the apparatus. The workpiece handling system 800 may also include a second transfer mechanism (not shown) capable of transferring the workpiece 102 from the device to a second handling area 806 of the workpiece handling system 800. The first transfer mechanism 900 and the second transfer mechanism may be a robotic arm (for example, equipped with an end effector for engaging with a workpiece at its end), a roll-to-roll handling system such as the ROLL MASTER system manufactured by NORTHFIELD AUTOMATION SYSTEMS, or any combination thereof.

[0131] In one embodiment, the workpiece to be transported by the first transport mechanism 900 is pre-positioned in the first handling area 804 so that the workpiece is positioned on or above the third positioner 110 when the first transport mechanism 900 transports the workpiece from the first handling area 804 to the apparatus. In other embodiments, the workpiece to be transported by the first transport mechanism 900 is not pre-positioned in the first handling area 804, and as a result, the first transport mechanism 900 may position the workpiece on or above the third positioner 110 in any preferred or advantageous manner (for example, as illustrated in U.S. Patent No. 7,834,293 above).

[0132] In one embodiment, the apparatus may be configured to facilitate the transfer of workpieces to or from the workpiece handling system 800. For example, referring to Figure 10, the multi-head apparatus 700 may include a third positioner (not shown) configured to move a workpiece 102 (which may be supported by a chuck 902 as needed) within a workpiece moving area 1000. As shown in Figure 10, the workpiece moving area 1000 includes a workpiece loading area 1002, a workpiece unloading area 1004, and a workpiece processing area 1006. The workpiece loading area 1002 is aligned with the first transfer mechanism 900 of the workpiece handling system 800, the workpiece unloading area 1004 is aligned with the second transfer mechanism of the workpiece handling system 800, and the workpiece processing area 1006 is aligned with the scan head 702 of the multi-head apparatus 700.

[0133] As described above, an example sequence for processing a workpiece using the multi-head device 700 may be as follows: If the chuck 902 is not already located in the workpiece loading area 1002, the third positioner is first activated to move the chuck 902 into the workpiece loading area 1002, and the first robot is activated to transfer the workpiece 102 from the first handling area 804 onto the chuck 902. Next, the third positioner is activated to move the chuck 902 on which the transferred workpiece 102 is currently supported from the workpiece loading area 1002 to the workpiece processing area 1006 (for example, in the X direction, the Y direction, or a combination of these directions such as along arrow 1008) (for example, so as to be aligned with one or more of the scan heads 702). One or more laser pulses are irradiated onto the workpiece 102 through one or more of the scan heads 702 to process the workpiece 102. After processing is complete, the third positioner is activated to move the chuck 902 from the workpiece processing area 1006 to the workpiece unloading area 1004 (for example, in the X direction, the Y direction, or a combination of these directions such as along arrow 1010), and the second transfer mechanism is activated to transfer the processed workpiece 102 from the chuck 902 to the second handling area 806. Subsequently, the third positioner can be activated to move the chuck 902 from the workpiece unloading area 1004 to the workpiece loading area 1002 (for example, only in the Y direction, such as along arrow 1012), and the sequence described above may be repeated as needed.

[0134] In one embodiment, the third positioner 110 can be operated to move the chuck 902 in one direction faster than in another. For example, the third positioner 110 can be operated to move the chuck 902 in the Y direction faster than in the X direction. In a particular embodiment, the third positioner 110 includes an X-axis stage and a Y-axis stage (e.g., stacked). The X-axis stage is configured to move the chuck in the X direction at a first speed, and the Y-axis stage is configured to move the chuck in the Y direction at a second speed faster than the first speed.

[0135] As shown in Figure 10, the workpiece 102 can be conceptually divided into four regions (e.g., a first region I, a second region II, a third region III, and a fourth region IV) corresponding to the positions of the scan heads 702 within the multi-head device 700. Therefore, when the workpiece 102 is located within the workpiece processing region 1006, the multi-head device 700 may be operated to create relative movement between the workpiece 102 and the scan heads 702 from which laser pulses are emitted during processing (i.e., applied to the workpiece 102). As a result, the first region I may be processed with laser pulses emitted from the first scan head 702a, the second region II with laser pulses emitted from the second scan head 702b, the third region III with laser pulses emitted from the third scan head 702c, and the fourth region IV with laser pulses emitted from the fourth scan head 702d. It can also be understood that the multi-head device 700 may be operated to generate the relative movement described above so that multiple areas of the workpiece 102 can be processed (for example, sequentially or alternately) with laser pulses emitted from a common scan head 702.

[0136] In one embodiment, the relative position of the scan head 702 in the multi-head device 700 may be adjusted in a manner similar to, or in any combination thereof, to correspond to the dimensions of a particular unprocessed workpiece 102, or to correspond to the dimensions of a region within a particular unprocessed workpiece 102, or in any combination thereof.

[0137] While specific embodiments of the workpiece handling system 800 described in this section are presented in relation to the multi-head device 700, it will be understood that any one of these embodiments, or any combination thereof, can be implemented with respect to the device 100, or to any laser processing device other than the device 100, or to other devices advantageously or suitably configured to process the workpiece 102 (e.g., mechanical drills, water jet cutting devices or water jet drilling devices, electron beam cutting machines, spraying machines, etc.).

[0138] VII. Embodiments relating to scanning methods As used herein, the term “scanning method” can mean a method by which a processing spot is scanned with respect to the workpiece 102 (e.g., within a first scanning range, a second scanning range, a third scanning range, or any combination thereof), a method by which the first scanning range is scanned within the second scanning range, a method by which either the first or second scanning range is scanned within the third scanning range, or any combination thereof. Generally, a scanning method can be characterized by one or more parameters such as the process trajectory in which the processing spot is scanned, the direction (i.e., the direction in which the processing spot, the first scanning range, the second scanning range, or any combination thereof is scanned), the scanning speed (i.e., the speed at which the processing spot, the first scanning range, the second scanning range, or any combination thereof is scanned), or any combination thereof.

[0139] Facilitating height measurement and compensation in the AZ direction. In the embodiments described in this section, the apparatus 100 includes a Z-direction height sensor, such as a Z-direction height sensor 124, which is positionally fixed relative to the scan lens 112. As a result, whenever relative movement occurs between the second scanning range 302b and the workpiece 102 (i.e., whenever the second scanning range is "scanned" (which can be done by operating the third positioner 110)), the detection range 402 is also scanned together with the second scanning range 302b (for example, in the same direction and at the same speed). The second scanning range 302b (and thus the detection range 402) can be scanned at a scan speed ranging from 25 mm / second to 200 mm / second. In one embodiment, the scan speed is in the range of 50 mm / second to 100 mm / second. Depending on factors such as processing speed, the speed and / or accuracy of Z-axis height measurement, and changes in the surface topology of the workpiece surface 102a, the scan speed may be slower than 25 mm / second or faster than 200 mm / second.

[0140] As described above, and with respect to Figures 4 to 6 above, offsetting the detection range 402 relative to the second scanning range 320b may cause problems during processing of the workpiece 102. However, these problems (or susceptibility to them) can be mitigated or avoided by raster scanning the second scanning range 302b (and thus the detection range 402) along a process trajectory that defines a scan pattern including multiple strips or segments that are parallel or non-parallel to each other (e.g., straight, curved, or a combination thereof). Raster scanning can be performed using one-way scanning techniques, two-way raster scanning techniques, or any combination thereof. Each example is described in more detail below. In addition to (or instead of) raster scanning, it is also possible to vector scan and position the scanning range 302b (and thus the detection range 402) using step-and-repeat techniques, or any combination thereof.

[0141] To simplify the discussion of the raster scanning techniques described herein, each portion of a workpiece that matches a segment of a raster scan pattern is referred herein as a “segment” of the workpiece, or more simply, a “workpiece segment.” Generally, each workpiece segment contains a portion of the workpiece that is processed by the apparatus 100 (for example, to form one or more features). However, in one embodiment, at least one workpiece segment does not contain a portion of the workpiece that is processed by the apparatus 100.

[0142] Any two workpiece segments may overlap, be adjacent to each other, or be spaced apart from each other. As used herein, two parallel workpiece segments are considered "adjacent" if there are no intervening workpiece segments (either parallel or non-parallel) between them. Thus, two workpiece segments can be adjacent even if they are adjacent or spaced apart from each other. In embodiments where there are multiple pairs of parallel and spaced-apart workpiece segments, the distances between at least two pairs of workpiece segments may be the same or different. Furthermore, the distance between any pair of adjacent workpiece segments may be set manually (e.g., by the user), automatically (e.g., by the controller 114), in a similar manner, or a combination of these. When set automatically, the distance between any pair of adjacent workpiece segments can be determined by the length (or width) of the second scanning range 302b (for example, measured along a direction perpendicular to the scanning direction), the arrangement of the detection range 402 relative to the second scanning range 302b, the size and / or shape of the detection range 402, by optimizing a cost function that represents the total time required to process all of the workpiece segments, or by any combination thereof.

[0143] As used herein, the direction in which the second scanning range 302b is raster-scanned while irradiating the workpiece with laser pulses (thus forming a processing spot) is referred to as the “scan direction.” Similarly, the scan direction also means the direction in which the detection range 402 is scanned while acquiring Z-direction height measurements. In the embodiments described below, the width of the workpiece segment (measured, for example, along a direction perpendicular to the scan direction) is equal to the length (or width) of the second scanning range 302b (measured, for example, along a direction perpendicular to the scan direction). However, in other embodiments, the width of the workpiece segment is either less than or greater than the length (or width) of the second scanning range 302b (measured, for example, along a direction perpendicular to the scan direction). Also, in the embodiments described below, all workpiece segments of the same workpiece may have the same width (for example, when measured along a direction perpendicular to the scan direction). In other embodiments, at least two of the workpiece segments may have different widths (for example, at least one width may be less than, equal to, or greater than the length (or width) of the second scanning range 302b when measured along a direction perpendicular to the scanning direction). Furthermore, the width of any of the workpiece segments may be set manually (e.g., by the user), automatically (e.g., by the controller 114), set in a similar manner, or a combination thereof. When set automatically, the width of the workpiece segments may be set by the length (or width) of the second scanning range 302b (e.g., measured along a direction perpendicular to the scanning direction), by the arrangement of the detection range 402 relative to the second scanning range 302b, by the size and / or shape of the detection range 402, by optimizing a cost function that represents the total time required to process all of the workpiece segments, or by any combination thereof.

[0144] While specific embodiments relating to scanning techniques, Z-direction height measurement, and Z-direction height compensation in this section are described in relation to apparatus 100, it will be understood that any one of these embodiments or any combination thereof can be implemented with respect to the multi-head apparatus 700. Furthermore, it will be understood that embodiments described in this section may be implemented using other suitably equipped single-head or multi-head laser processing apparatuses or other devices advantageously or suitably configured to process the workpiece 102 (e.g., mechanical drills, water jet cutting apparatuses or water jet drilling apparatuses, electron beam cutting machines, spraying machines, etc.).

[0145] i. One-way scanning In the unidirectional rastus scanning method, the detection range 402 and the second scanning range 302b are sequentially scanned in a single scanning direction along a common workpiece segment. In addition, the detection range 402 and the second scanning range 302b are scanned in a single scanning direction along adjacent workpiece segments.

[0146] To facilitate unidirectional rastus scanning, the device 100 may include a Z-direction height sensor positioned and configured to project a detection range 402 offset from the second scanning range 302b in the same direction as the scan direction. For example, referring to Figure 4 or 6, if the scan direction is the -Y direction, the detection range 402 may be offset from the second scanning range 302b in the -Y direction. In another example, referring to Figure 5 or 6, if the scan direction is the -X direction, the detection range 402 may be offset from the second scanning range 302b in the -X direction.

[0147] Before processing, the relative position between the workpiece and the detection range 402 is initially set so that the detection range 402 is aligned with or near the edge of the workpiece segment of the unprocessed workpiece. For example, as shown in Figure 11, the detection range 402 (offset from the second scanning range as described in Figure 4) is aligned with the edge of the current workpiece segment 1102 to be processed. Similarly, as shown in Figure 15, the detection range 402 (offset from the second scanning range as described in Figure 5) is aligned with the edge of the current workpiece segment 1502 to be processed.

[0148] After the detection range 402 is aligned with the current workpiece segment, the second scanning range 302b and the detection range 402 are scanned together along the segment in the scanning direction (for example, in the -Y direction or -X direction as shown in Figures 12 and 16, respectively). Thus, prior to the second scanning range 302b, the detection range 402 is scanned along the current workpiece segment to be processed. During the scanning of the detection range 402, Z-direction height measurements at various detection positions are acquired and saved as necessary (and further processed as described above as necessary).

[0149] During scanning of the second scanning range 302b, a laser pulse may be irradiated onto the portion of the current workpiece segment being processed. If it is determined that the Z-direction height of the workpiece surface at a particular detection position (e.g., previously detected or processed and stored) is outside a predetermined nominal Z-direction height process window, Z-direction height compensation can be performed (e.g., as described above) when the processing position is the same as (or within a certain distance from) the particular detection position.

[0150] After processing the current workpiece segment (for example, when the second scanning range 302b is at or near the end of the current workpiece segment, as shown in Figure 13 or Figure 17), the relative position between the workpiece and the detection range 402 may be indexed so that the detection range 402 is aligned with or near the end of the next unprocessed workpiece segment (for example, segment 1104 or segment 1504, as shown in Figures 14 and 18, respectively), and the process described above may be repeated.

[0151] ii. Bidirectional scanning In the bidirectional rastus scanning method, the detection range 402 and the second scanning range 302b are sequentially scanned in opposite scanning directions along a common workpiece segment. In addition, each of the detection range 402 and the second scanning range 302b is scanned in opposite scanning directions along an adjacent workpiece segment.

[0152] To facilitate bidirectional rastus scanning, the device 100 may include a Z-direction height sensor positioned and configured to project a detection range 402 offset from the second scanning range 302b in a direction different from the scanning direction. For example, referring to Figures 4 and 6, if the scanning direction is the +X or -X direction, the detection range 402 may be offset from the second scanning range 302b in the +Y or -Y direction. In another example, referring to Figure 5 or 6, if the scanning direction is the +Y or -Y direction, the detection range 402 may be offset from the second scanning range 302b in the +X or -X direction.

[0153] Before processing, the relative position between the workpiece and the detection range 402 is initially set so that the detection range 402 is aligned with or near the edge of the unprocessed workpiece segment. For example, as shown in Figure 19, the detection range 402 (offset from the second scanning range as described in Figure 5) is aligned with the edge of the workpiece segment 1100a1 described above. Similarly, as shown in Figure 22, the detection range 402 (offset from the second scanning range as described in Figure 4) is aligned with the edge of the workpiece segment 1502 described above.

[0154] After the detection range 402 is aligned with the unprocessed workpiece segment, the second scanning range 302b and the detection range 402 are scanned together so that the detection range 402 is scanned along the unprocessed workpiece segment (e.g., segment 1100a1 or segment 1502 as shown in Figures 21 and 24, respectively) in a first scanning direction (e.g., the -Y direction or -X direction as indicated by the arrows in Figure 20 or Figure 23, respectively). During scanning of the detection range 402 in the first scanning direction, Z-direction height measurements at various detection positions along the workpiece segment are acquired and saved as necessary (and further processed as described above as necessary).

[0155] After measuring an unprocessed workpiece segment using the Z-direction height sensor 124 (for example, when the detection range 402 is at or near the end of an unprocessed workpiece segment 1100a1 or 1502 as shown in Figure 20 or Figure 23), the relative position between the workpiece and the detection range 402 is indexed so that the detection range 402 is aligned with or near the end of another unprocessed workpiece segment (for example, segment 1104 or segment 1504 as shown in Figures 21 and 24, respectively). In the embodiments described herein, since the Z-direction height sensor 124 is positionally fixed with respect to the scan lens 112, the second scanning range 302b will also be aligned with or near the end of a workpiece segment previously measured by the Z-direction height sensor 124 (for example, the previously measured 1100a1 or segment 1502 as shown in Figures 21 and 24, respectively).

[0156] As described above, after indexing the detection range 402 and the second scanning range 302b, the second scanning range 302b and the detection range 402 are scanned together in the second scanning direction opposite to the first scanning direction (for example, in the +Y direction or +X direction as indicated by the arrows in Figure 21 or Figure 24, respectively). As a result, the second scanning range 302b is scanned along the previously measured workpiece segment (i.e., along segment 1100a1 or segment 1502 as shown in Figures 21 and 24, respectively), while the detection range 402 is scanned along other unprocessed workpiece segments (for example, along segment 1104 or segment 1504 as shown in Figures 21 and 24, respectively).

[0157] During scanning of the detection range 402 in the second scanning direction, Z-direction height measurements at various detection positions are acquired and stored as necessary (and further processed as described above as necessary). During scanning of the second scanning range 302b in the second scanning direction, a laser pulse may be irradiated onto a previously measured portion of the workpiece segment (i.e., segment segment 1100a1 or segment 1502 as shown in Figures 21 and 24, respectively). If it is determined that the Z-direction height of the workpiece surface (e.g., measured or processed) at a particular detection position is outside a predetermined nominal Z-direction height process window, Z-direction height compensation can be performed (e.g., as described above) when the processing position is the same as (or within a certain distance from) the particular detection position.

[0158] After a previously measured workpiece segment (e.g., workpiece segment 1100a1 or 1502) has been processed and another (e.g., unprocessed) workpiece segment (e.g., workpiece segment 1104 or 1504) has been measured, indexing may be performed again to align the detection range 402 with the end or vicinity of the other unmeasured workpiece segment (not shown) and to align the second scanning range 302b with the end or vicinity of the previously measured workpiece segment (e.g., segment 1104 or segment 1504). After alignment, the detection range 402 and the second scanning range 302b may be scanned together in the first scanning direction, and the process involving measurement, processing, Z-direction height compensation, etc., described above may be repeated.

[0159] B. Facilitating feature generation As described above, the first positioner 106 has a first positioning bandwidth in the range of 50 kHz to 10 MHz, and can therefore be used to rapidly scan a processing spot within the first scanning range to form one or more features (e.g., one or more openings, vias, trenches, slots, scribe lines, recesses, etc.) on the workpiece 102. As also mentioned above, the maximum dimension of the feature formed on the workpiece 102 (e.g., measured in the XY plane) may be less than or equal to the maximum dimension of the first scanning range (e.g., in the X or Y direction). However, in other embodiments, the maximum dimension of the feature may be greater than the maximum dimension of the first scanning range.

[0160] Generally, the first positioner 106 can be operated to scan a processing spot along the X direction (e.g., +X direction or -X direction) and / or along the Y direction (e.g., +Y direction or -Y direction) while the second positioner 108 scans the first scanning range along the Y direction (e.g., +Y direction or -Y direction), while the second positioner 108 scans the first scanning range along the Y direction (e.g., +X direction or -X direction), while the third positioner 110 scans the first and / or second scanning range along the X direction (e.g., +X direction or -X direction), or in any combination thereof. However, it should be understood that when the second positioner 108 is not scanning the first scanning range, or when the third positioner 110 is not scanning the first or second scanning range, or in any combination thereof, the first positioner 106 can be operated to scan the processing spot along the X direction (e.g., in the +X or -X direction) and / or along the Y direction (e.g., in the +Y or -Y direction). It should also be understood that the direction in which the processing spot is scanned by the first positioner 106 at any given time may be the same as, or different from, the direction in which the first scanning range is scanned by the second positioner 108 within the second scanning range, or the direction in which the first scanning range is scanned by the third positioner 110 within the third scanning range, or in any combination thereof.

[0161] In one embodiment, the workpiece 102 is provided as a PCB panel, PCB, FPC, IC, ICP, semiconductor device, etc. Thus, the workpiece 102 may include one or more constituent structures such as conductive structures (e.g., films, foils, etc. that can be formed from copper, copper alloys, etc., wiring or conductive wire structures containing one or more metals such as copper, titanium, titanium nitride, tantalum, etc., or any combination thereof), dielectric structures (e.g., build-up films, glass fiber reinforced epoxy laminates, interlayer dielectric materials, low-k dielectric materials, solder resists, etc.), or any combination thereof. When provided as a PCB panel or PCB, the workpiece 102 may include a dielectric structure (e.g., a glass fiber reinforced epoxy laminate) which is fixed on a first side to a first conductor (e.g., a copper foil or copper alloy foil that may have darkened or un-darkened exposed surfaces (e.g., by a chemical reaction or a laser darkening process)) and optionally fixed on a second conductor (e.g., a pad, trace, foil, etc. made of copper or a copper alloy) on a second side opposite to the first side. One or more features (e.g., one or more openings, slots, grooves, non-through vias, through vias, slot vias, etc.) may be formed in or on one or more components of the workpiece 102 by removing material by ablation of the material (e.g., during a cutting process, drilling process, engraving process, routing process, etc., or any combination thereof). As used herein, the term “feature region” means a region of the workpiece 102 that is processed to form a feature.

[0162] Generally, unless explicitly stated, the term “ablation” can mean “direct ablation,” “indirect ablation,” or any combination thereof. Direct ablation of the material in workpiece 102 occurs when the primary cause of ablation is the decomposition of the material due to absorption of energy in the irradiated laser energy beam by the material (e.g., linear absorption, nonlinear absorption, or any combination thereof). Indirect ablation of the material in workpiece 102 (also known as “lift-off”) occurs when the primary cause of ablation is melting and evaporation due to heat transferred from adjacent material that absorbs energy in the irradiated laser energy beam.

[0163] In one embodiment, the feature may be formed to completely or partially penetrate one or more components of the workpiece 102 (e.g., one or more conductive structures, one or more dielectric structures, or any combination thereof). In one embodiment, the conductive structure or dielectric structure may have a thickness in the range of 5 μm to 500 μm. However, it can be understood that the conductive structure or dielectric structure may have a thickness less than 5 μm or a thickness greater than 500 μm. Thus, the thickness of the conductive or dielectric structure may be greater than or equal to 1 μm, 3 μm, 5 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 70 μm, 80 μm, 100 μm, 110 μm, 120 μm, 250 μm, 300 μm, 350 μm, 400 μm, 450 μm, 550 μm, 600 μm, etc., or may be any of these values. Similarly, this thickness may be less than or between any of the following values: 550 μm, 450 μm, 400 μm, 350 μm, 300 μm, 250 μm, 120 μm, 110 μm, 100 μm, 80 μm, 70 μm, 50 μm, 40 μm, 35 μm, 25 μm, 20 μm, 18 μm, 15 μm, 10 μm, 5 μm, 3 μm, 1 μm, 0.5 μm, 0.1 μm, etc.

[0164] Generally, the top of a feature may have a diameter (i.e., "top diameter") ranging from 5 μm to 300 μm. However, it is understandable that the top diameter may be less than 5 μm or greater than 300 μm. Thus, the top diameter may be greater than or equal to 5 μm, 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 80 μm, 100 μm, 120 μm, 150 μm, 200 μm, 250 μm, 150 μm, 200 μm, 250 μm, 300 μm, 320 μm, etc., or may be between any of these values. Similarly, the upper diameter may be smaller than or between any of the following values: 350 μm, 300 μm, 250 μm, 200 μm, 150 μm, 120 μm, 100 μm, 80 μm, 50 μm, 40 μm, 30 μm, 20 μm, 10 μm, 5 μm, etc.

[0165] Generally, the bottom of a feature may have a diameter less than or equal to the top diameter (i.e., the “bottom diameter”). The difference between the top diameter and the bottom diameter is referred to herein as the “taper” of the feature or simply the “feature taper.” The feature taper indicates the inclination of the sidewall of the feature within the workpiece 102. It is often desirable to form features with a relatively small taper (for example, to facilitate the formation of a large number of features within a relatively small area of ​​the workpiece 102). If the feature is a via, a relatively small taper facilitates reliable plating or filling. One factor that affects the taper is the depth of the feature being formed. Relatively shallow features tend to have zero taper or a smaller taper than relatively deep features. In this example, the taper of the features formed on the workpiece 102 may be 20 μm or less. For example, the taper may be less than or equal to 18 μm, 15 μm, 12 μm, 10 μm, 9 μm, 8 μm, 7.5 μm, 7 μm, 6 μm, 5 μm, 4 μm, 3 μm, 2 μm, 1 μm, 0.5 μm, or any of these values.

[0166] Generally, the depth of a feature is measured along an axis (also referred to herein as the “feature axis”) that penetrates the top and bottom of the feature. In one embodiment, the depth of the feature corresponds to the thickness of one or more structures on which the feature is formed (in this case, the feature completely penetrates one or more structures). In other embodiments, the depth of the feature does not correspond to the thickness of the structure on which the feature is formed (in this case, the feature only partially penetrates the structure). Thus, a feature may have a depth in the range of 5 μm to 250 μm (or less than 5 μm or greater than 250 μm). For example, a feature may have a depth greater than or equal to 1 μm, 3 μm, 5 μm, 10 μm, 15 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 50 μm, 70 μm, 80 μm, 100 μm, 110 μm, 120 μm, 250 μm, 300 μm, etc., or a depth between any of these values. Similarly, this depth may be smaller than or between any of the following values: 300 μm, 250 μm, 120 μm, 110 μm, 100 μm, 80 μm, 70 μm, 50 μm, 40 μm, 35 μm, 25 μm, 20 μm, 18 μm, 15 μm, 10 μm, 5 μm, 3 μm, 1 μm, 0.5 μm, 0.1 μm, etc.

[0167] Generally, features can be formed by scanning a processing spot along a process trajectory that defines one or more scan patterns (for example, by controlling the first positioner 106 to scan the processing spot with one or more corresponding scan patterns within a first scanning range). Depending on one or more factors, such as the desired depth of the feature to be formed, the material to be removed during feature formation, one or more parameters of the laser pulse beam irradiated during feature formation, or any combination thereof, a feature can be formed by scanning the processing spot along a scan pattern (also called the “feature formation” scan pattern) once or multiple times. If the processing spot is scanned multiple times along a scan pattern, the processing spot can be repeatedly scanned along the same scan pattern (i.e., the same scan pattern can be repeatedly used). In other embodiments, at least two different scan patterns can be used during feature formation. If the same scan pattern is repeatedly used, the subsequent scan pattern may have the same direction as the previously used scan pattern (e.g., measured relative to the feature axis), or it may have a different direction than the previously used scan pattern.

[0168] While specific embodiments of the scanning techniques described in this section are presented in relation to apparatus 100, it will be understood that any one of these embodiments, or any combination thereof, can be implemented with respect to the multi-head apparatus 700. It will also be understood that the embodiments described in this section can be implemented with respect to any suitably equipped single-head or multi-head laser processing apparatus other than those described herein, or any other suitable apparatus advantageously or suitably configured to process the workpiece 102 (e.g., a mechanical drill, a water jet cutting apparatus or a water jet drilling apparatus, an electron beam cutting machine, a spraying machine, etc.).

[0169] i. Example of a scan pattern embodiment Examples of scan patterns for forming features such as vias and other holes, openings, recesses, and trenches include scan patterns 2500, 2600, 2700, and 2800, as shown in Figures 25, 26, 27, and 28, respectively, or any combination thereof. Generally, scan patterns may resemble or depict raster patterns (e.g., as shown in Figure 25), star polygons or stellated polygons (e.g., as shown in Figure 26), helices or sets of arcs or multiple circles (e.g., arranged concentrically or as shown in Figure 27), a single circle, a set of circles, or one or more shapes (e.g., ellipses, triangles, squares, rectangles, or other regular or irregular shapes) (e.g., as shown in Figure 28), or any combination thereof. In one embodiment, one or more scan patterns (for example, one or more scan patterns 2500, 2600, 2700, or 2800, or any combination thereof) can be used to remove material from one or more conductive structures, one or more dielectric structures, or any combination thereof (for example, by direct ablation, indirect ablation, or any combination thereof) during the formation of features such as circular openings and vias.

[0170] In Figures 25 to 28, the dotted line 2502 represents the desired boundary on the work surface 102a for a feature (e.g., a circular opening or via in this example) formed in the conductive or dielectric structure of the workpiece 102. For the sake of illustrating this example, once a feature is formed in the workpiece 102, the feature can be characterized as including an "upper" formed on the work surface 102 and extending axially into the workpiece 102 (e.g., either terminating within the workpiece 102 or penetrating the workpiece 102 completely). The portion of the feature that thus terminates within the workpiece 102 or exists on the other face of the workpiece 102 may be referred to herein as the "bottom" of the feature.

[0171] Figures 25 to 28 illustrate the formation of a feature boundary 2502 (also referred to herein as the “feature boundary”) as being circular, but it will be understood that this boundary may have any preferred or desirable shape (e.g., ellipse, square, rectangle, triangle, hexagon, irregular shape, or any combination thereof). In the embodiments described herein, the shape of the boundary 2502 at the top and bottom of the feature is the same or similar (e.g., circular). In other embodiments (e.g., embodiments in which material removal occurs by direct ablation and multiple scan patterns are scanned during material processing), the boundary 2502 at the top of the feature may differ in shape from the boundary 2502 at the bottom of the feature. For example, the top of the feature may have a circular boundary 2502, or it may have an elliptical, rectangular, or other shape boundary 2502.

[0172] The centers of the processing spots within the scan pattern (each collectively referred to as a "spot location," or more broadly as multiple "spot locations") are indicated by diamonds 2504. While scan patterns 2500, 2600, 2700, and 2800 are illustrated as having a specific arrangement of the illustrated spot locations 2504, it will be understood that any scan pattern may contain more or fewer spot locations in any preferred or desired arrangement. The arrangement of spot locations 2504 within a scan pattern or along a common scan line (i.e., characterized by the number of spot locations, the location of the spot locations, the pitch between adjacent spot locations, or any combination thereof) can vary depending on factors such as the thermal conductivity, thermal diffusivity, specific heat capacity, and absorbance of the material at or near the spot location; the viscosity of the material at or near the spot location during feature formation; the absorbance of the material at or near the spot location (relative to the irradiated laser energy beam); the presence or absence of conductive or dielectric structures near the spot location; the geometric arrangement of conductive or dielectric structures near the spot location; the spot size; the type and shape of the spatial intensity profile; the pulse duration, fluence, pulse repetition rate; the scan speed; the size and shape of the formed feature, or any combination thereof. Generally, the arrangement of spot locations commonly along a particular scan line in a given scan pattern may be the same as or different from the arrangement of spot locations commonly along other scan lines in that given scan pattern.

[0173] Of the spot positions 2504, spot position 2504a represents the first spot position in the scan pattern to which a laser pulse is irradiated, and spot position 2504b represents the last spot in the scan pattern to which a laser pulse is irradiated. Therefore, the solid lines connecting the spot positions 2504 indicate the sequence in which the spot positions 2504 are processed (for example, by one or more laser pulses being irradiated). However, it should be understood that spot positions 2504 in one scan pattern may be processed in other desired sequences (which may change the configuration of the solid lines), or they may be processed randomly. At any point in the processing, a spot position 2540 in a scan pattern can be characterized as a previously processed spot position (i.e., a spot position to which a laser pulse was irradiated), a spot position currently being processed (i.e., a spot position to which a laser pulse is being irradiated), and a spot position to be processed (i.e., a spot position to which a laser pulse will be irradiated).

[0174] In one embodiment, the placement of spot locations 2504 and the sequence in which spot locations 2504 are processed are selected, if necessary, to reduce or avoid undesirable heat accumulation within the workpiece 102 during feature formation (e.g., this may result in undesirable cracking, melting, evaporation, ablation, crystallization, annealing, carbonization, oxidation, etc.). In other embodiments, (as described in more detail below) the placement of spot locations 2504 and the sequence in which spot locations 2504 are processed are selected, if necessary, to affect (e.g., reduce) the taper of the final formed feature. In other embodiments, the placement of spot locations 2504 and the sequence in which spot locations 2504 are processed are selected, if necessary, to facilitate heating of the workpiece 102 to promote the efficient formation of one or more features on or within the workpiece 102.

[0175] Depending on one or more factors such as pulse repetition rate, first positioning bandwidth, and scan pattern being scanned, at least two temporally consecutive laser pulses (e.g., 2, 3, 5, 8, 10, or 20 laser pulses) may be irradiated onto the same spot position 2504 or onto different spot positions 2504. In this case, the pulse repetition rate can generally be characterized as being greater than the first positioning bandwidth. However, in other embodiments, the pulse repetition rate may be less than or equal to the first positioning bandwidth. The period during which temporally consecutive laser pulses irradiate the same spot position 2504 (or a local vicinity of a common spot position 2504) is referred to herein as the “dwell time” associated with the spot position 2504. For illustrative purposes, if a laser pulse irradiates within a 1 μm range of the spot position 2504, it can be considered that the laser pulse irradiated a local vicinity of the spot position 2504. In one embodiment, if a laser pulse is irradiated within the range of 10.0 μm, 8.0 μm, 7.0 μm, 6.0 μm, 5.0 μm, 4.0 μm, 3.5 μm, 3.0 μm, 2.5 μm, 2.0 μm, 1.5 μm, 1.0 μm, 0.9 μm, 0.8 μm, 0.75 μm, 0.7 μm, 0.65 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.25 μm, 0.2 μm, 0.15 μm, 0.1 μm, 0.08 μm, 0.05 μm, or 0.01 μm of the spot position 2504, or within a range smaller than 0.01 μm of the spot position 2504, then the laser pulse can be considered to have irradiated a local vicinity of the spot position 2504.

[0176] In the illustrated embodiments, the scan pattern can be characterized as comprising one or more rows of sequentially processed spot positions 2504. Each of these row of spot positions 2504 can generally be characterized as being located along a common scan line. Generally, sequentially processed spot positions located on a common scan line are closer to each other than sequentially processed spot positions located on different scan lines. The scan lines may be straight (as shown, for example, in Figure 25 or 26), curved (as shown, for example, in Figure 27 or 28), similar to these, or any combination thereof. For example, the scan pattern 2500 shown in Figure 25 includes a plurality of straight, parallel scan lines, and the scan pattern 2600 shown in Figure 26 includes a plurality of straight scan lines that are oblique to each other. In scan pattern 2600, the scanlines extend along axes that radiate (or nearly radiate) toward the feature boundary 2502 from its center (or from a central region surrounding the center of the feature boundary 2502). The scan pattern 2700 shown in Figure 27 includes multiple concentrically arranged arc-shaped scanlines (the outermost radial scanlines extend along the desired feature boundary 2502). The scan pattern 2800 shown in Figure 28 includes a single arc-shaped scanline (for example, extending along the desired feature boundary 2502).

[0177] At least one laser pulse is directed at each spot position 2504. In one embodiment, multiple laser pulses are directed at one or more spot positions 2504 (or at a local vicinity of a common spot position 2504). Generally, the same number of laser pulses may be directed at at least two spot positions 2504 in the scan pattern, or different numbers of laser pulses may be directed at at least two spot positions 2504 in the scan pattern.

[0178] Generally, the pitch between adjacent spot locations 2504 is considered to be greater than the distance included in the local neighborhood of the spot location 2504. In one embodiment, the pitch between adjacent spot locations within a scan pattern can range from 0.1 μm to 50 μm. Similarly, the pitch between adjacent spot locations 2504 located along a common scan line can range from 0.1 μm to 50 μm. Thus, the pitch between adjacent spot locations 2504 (generally located within a scan pattern or along a common scan line) can be greater than or equal to 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4.5 μm, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 55 μm, 60 μm, 80 μm, etc. The pitch between spot locations is measured as the distance between the centers of two adjacent spot locations. Two spot locations are considered adjacent to each other if there are no intervening spot locations between them.

[0179] The pitch between pairs of adjacent spot positions 2504 (generally located within a scan pattern or along a common scan line) can be constant, variable, or an arbitrary combination thereof. In one embodiment, the pitch between adjacent spot positions located along a common scan line can increase or decrease in the direction extending from a spot position to which one laser pulse is irradiated to another spot position to which the laser pulse subsequently irradiates. Therefore, the pitch between pairs of adjacent spot positions 2504 located along a common scan line may be constant, increase, decrease, or an arbitrary combination thereof as they move along the scan line. Generally, the spot size of the irradiated laser pulses and the pitch between pairs of adjacent spot positions 2504 can be selected or set so that the spot areas irradiated by the laser pulses on the pair of adjacent spot positions 2504 overlap or do not overlap.

[0180] In one embodiment, the arrangement of scan lines within a scan pattern (i.e., characterized by the number of scan lines, the direction of scan lines relative to other scan lines, the direction of scan lines relative to the boundary 2502, the length of scan lines, the pitch between adjacent scan lines, etc.) is not limited to the arrangement shown in Figures 25 to 28, and can vary according to one or more factors as described above regarding the arrangement of spot positions 2504. Thus, a scan pattern may have an odd or even number of scan lines. In one embodiment, the number of scan lines in a scan pattern can range from 1 to 64. For example, the number of scan lines in a scan pattern may be more than or equal to 2, 4, 8, 16, 32, 50, 60, etc., or less than 64, 32, 16, 8, 4, 2. It should also be understood that a scan pattern may have more than 64 scan lines. Within a given scan pattern, at least some of the scan lines may be arranged symmetrically (or at least substantially symmetrically), or asymmetrically. Examples of symmetric arrangements include rotational symmetry (i.e., rotationally symmetric n times with n being an integer greater than 1, such as 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 20, 50, etc.) and reflectional symmetry.

[0181] ii. Considerations regarding the removal of anisotropic materials a. Theory Through experiments and multiphysics modeling, the inventors irradiated a workpiece 102 (a dielectric structure such as ABF, solder resist, or glass fiber reinforced epoxy laminate) with laser pulses along a scanline (extending in the +X direction as shown in Figure 29, for example) (with minimal or no change in the incident angle of the beam axis at the workpiece surface 102a), directly ablating the workpiece 102 with such laser pulses to form multiple trenches, such as the trench 2900 schematically shown in Figures 29, 29A, and 29B. In Figure 29, the scan line along which the scanned laser pulse beam follows includes multiple spot locations (i.e., "n" spot locations where n is 2, 3, 4, 5, etc.), with the spot region irradiated by one or more laser pulses at the first spot location being indicated by 2906a, the spot region irradiated by one or more laser pulses at the second spot location being indicated by 2906b, and so on, until the spot region irradiated by one or more laser pulses at the final spot location (also referred to herein as the "terminal spot location") is indicated by 2906n. During the experiment, trenches with lengths ranging from tens of micrometers to several millimeters were formed. Figures 29A and 29B are cross-sectional views of the trench shown in Figure 29, and are cross-sectional views along the lines XXIXA-XXIXA and XXIXB-XXIXB' in Figure 29, respectively. As used herein, the scan line along which these spot locations are arranged is called the "anisotropic material removal scan line." When formed as described above, we found that the end 2902 of the trench 2900 has a smaller taper than the beginning 2904 of the trench 2900 (see Figure 29B) when the laser pulse is irradiated at a sufficiently high pulse repetition rate and characterized by other parameters such as spot size and average power sufficient to directly ablate the workpiece 102. Thus, the trench formation process described above appears to exhibit anisotropic material removal characteristics. While we do not necessarily wish to be bound by a particular theory, the simulations appear to indicate that this anisotropic material removal phenomenon is at least partially attributable to one of two factors.

[0182] One of the factors mentioned above relates to the temperature of the area of ​​the workpiece 102 before it is irradiated by the laser pulse. Initially, when the laser pulse is irradiated to a first spot position along the scan line, the workpiece 102 is relatively cold, and as a result, the material removal mechanism at the first spot position is relatively inefficient. Consequently, after being irradiated with numerous laser pulses, the resulting taper of the sidewall formed in the workpiece 102 at the first spot position is relatively large. However, after being irradiated with several laser pulses, heat begins to accumulate around the irradiated spot position within the workpiece 102 as a result of thermal diffusion within the workpiece 102. Thus, by the time the final spot position on the scan line is irradiated with one or more laser pulses, a significant amount of heat has accumulated at the final spot position. This thermal energy is thought to increase the efficiency of removing material from the workpiece 102. Consequently, after being irradiated with numerous laser pulses along the scan line, the resulting taper of the sidewall formed in the workpiece 102 at the final spot position on the scan line is relatively small.

[0183] Other factors among those mentioned above relate to the temperature and pressure associated with the vapor plume generated at the processing spot when the material is ablated directly from the workpiece 102. As the laser pulse beam scans along the scan line, the high temperature and pressure within the vapor plume can act to vaporize, melt, or erode the material in the workpiece around the irradiated processing spot. This erosion is likely to be more severe if heat has already accumulated in the material around the irradiated processing spot (for example, generated by one or more previously irradiated laser pulses). The high pressure generated by the resulting vapor plume induces hydrodynamic motion in the eroded material, moving it out of the area within and around the irradiated processing spot, thereby creating sidewalls with a relatively small taper within the workpiece 102. Furthermore, as the laser pulse is irradiated to one or more other spot locations that are subsequently irradiated along the scan line, the eroded material located in the trench is advection or transported toward the previously irradiated spot locations, likely increasing the taper of the sidewalls formed in the workpiece 102 at the previously irradiated spot locations. In Figure 29B, the side wall 2902, which has a relatively small taper, can be characterized as being inclined at an angle Φ3 (smaller than angle Φ2) with respect to the bottom surface of the trench 2900. The side wall 2904 (which has a relatively large taper) can be characterized as being inclined at an angle Φ2 with respect to the bottom surface of the trench 2900. The taper of the intermediate side wall of the trench 2900 (shown in cross-section in Figure 29A, for example) can vary from the start end to the end of the trench 2900 depending on the position where the taper measurement moves from the start end to the end. Thus, angle Φ1 can be less than or equal to angle Φ2. In some embodiments, angle Φ1 may be greater than angle Φ2.

[0184] b. Sidewall taper The anisotropic material removal properties associated with the trench formation process described above can be adapted to be selected to affect (e.g., reduce) the sidewall taper of features (e.g., openings or vias as described above) or trenches, scribe lines, recessed areas, etc. For example, feature formation may be performed by scanning a processing spot along one or more scan patterns as described above. However, in this embodiment, the scan pattern includes one or more anisotropic material removal scan lines. As a result, for a given spot size, depending on one or more factors such as the depth of the feature to be formed and the structure of the feature to be formed, the sidewall taper of a feature (e.g., vias, trenches, scribe lines, recessed areas, etc.) formed by scanning a processing spot according to a scan pattern having one or more anisotropic material removal scan lines (e.g., as described with respect to scan pattern 2600) can be reduced compared to the sidewall taper of a feature formed simply by scanning a laser pulse beam along a scan line extending along a desired feature boundary (e.g., as described with respect to scan patterns 2700 and 2800).

[0185] Conversely, depending on one or more factors such as the depth of the feature being formed and the structure of the feature being formed, the same sidewall taper obtained by scanning a laser pulse beam with a relatively small spot size along a scan line extending along the desired feature boundary (for example, as described with respect to scan patterns 2700 and 2800) can be obtained by scanning a laser pulse beam with a relatively large spot size according to a scan pattern having one or more anisotropic material removal scan lines. Where possible, it may be desirable to form features using a relatively large spot size if a) it is easier to form a relatively large spot size than a relatively small spot size, b) a relatively large spot is more tolerant of changes or displacements of the work surface Z-direction height outside the Z-direction height process window (for example, by a relatively large Rayleigh range), and c) a relatively large spot size allows for a larger deflection range of a positioner such as an AOD system (since the AOD deflection for a given update rate and positioning bandwidth is proportional to the spot size of the laser pulse irradiated onto the workpiece 102).

[0186] As used herein, an anisotropic material removal scanline is a scanline having an axis that intersects the desired feature boundary at an angle ranging from 60° to 120° when measured in the scanning plane (i.e., a scanline extending in the scanning plane, which is the XY plane in the embodiment shown in Figure 29). It should be understood that the angle at which the axis of the anisotropic material removal scanline intersects the desired feature boundary may depend on factors such as the spot size, the type and shape of the spatial intensity profile, the thermal conductivity, thermal diffusivity, and specific heat capacity of the workpiece material at or near the spot where the irradiated laser pulse strikes, the viscosity of the workpiece material at or near the spot where the irradiated laser pulse strikes, the pulse duration, fluence, pulse repetition rate, the speed at which the processing spot moves along the process trajectory defining the scan pattern, or any combination thereof. Thus, the angle at which the axis of the anisotropic material removal scanline can intersect the desired feature boundary may be less than 60° or greater than 120°. For example, the axes of the scanline may intersect the desired boundary at angles greater than or equal to 50°, 60°, 65°, 70°, 75°, 80°, 85°, 87°, 88.5°, 90°, 91.5°, 93°, 95°, 100°, 105°, 110°, 115°, 120°, or between any of these values. Similarly, the axes of the scanline may intersect the desired boundary at angles less than 130°, 120°, 115°, 110°, 105°, 100°, 95°, 93°, 91.5°, 90°, 88.5°, 87°, 85°, 80°, 75°, 70°, 65°, 60°, or between any of these values.

[0187] In one embodiment, the pitch between adjacent terminal spot positions of a pair of scan lines in the scan pattern may be in the range of 0.5 μm to 50 μm, or it may be less than 0.5 μm, or it may be greater than 50 μm. Thus, the pitch between adjacent spot positions 2504 (generally located within the scan pattern or along a common scan line) may be greater than or equal to 0.5 μm, 1 μm, 1.5 μm, 2 μm, 3 μm, 3.5 μm, 4.5 μm, 5 μm, 10 μm, 15 μm, 20 μm, 30 μm, 40 μm, 55 μm, etc., or between any of these values, or less than 60 μm, 55 μm, 40 μm, 30 μm, 20 μm, 15 μm, 10 μm, 5 μm, 4.5 μm, 3.5 μm, 3 μm, 2 μm, 1.5 μm, 1 μm, 0.5 μm, 0.1 μm, etc., or between any of these values. If there is no intervening scan line between two scan lines, those two scan lines are considered adjacent to each other.

[0188] The scan pattern 2600 shown in Figure 26 is an example of a scan pattern that includes multiple anisotropic material removal scan lines. In scan pattern 2600, the scan lines within region 2602 are examples of anisotropic material removal scan lines, and the spot position 2504c is the terminal spot position of the anisotropic material removal scan line. Although Figure 26 illustrates scan pattern 2600 as containing 27 anisotropic material removal scan lines, it should be understood that a scan pattern like scan pattern 2600 may have more or fewer anisotropic material removal scan lines than 27, depending on one or more factors such as the shape of the desired boundary, the relative size difference between the desired boundary and the spot size, the type and shape of the spatial intensity profile of the irradiated laser pulse, or any combination thereof.

[0189] Figure 26 illustrates that each anisotropic material removal scanline contains the same arrangement of spot positions; however, it should be understood that the arrangement of spot positions for one or more (or all) of the anisotropic material removal scanlines may differ from that of the illustrated embodiment. Furthermore, the arrangement of spot positions for one or more anisotropic material removal scanlines in a scan pattern may be the same as, or different from, the arrangement of spot positions for at least one other anisotropic material removal scanline in the scan pattern. Thus, although Figure 26 illustrates that each anisotropic material removal scanline contains four spot positions, it should be understood that any anisotropic material removal scanline may have more or fewer spot positions than four. For example, the number of spot positions that a single anisotropic material removal scanline (such as the anisotropic material removal scanline shown in region 2602) may contain may be 2, 3, 5, 6, 7, 8, 9, 10, or more.

[0190] iii. Considerations regarding localized heat accumulation Depending on one or more factors such as the wavelength, pulse duration, pulse repetition rate, and average power of the laser pulse irradiated onto the workpiece 102; the linear absorption of the material at the spot location (for example, with respect to the wavelength of the laser pulse irradiated onto the spot location); the thermal conductivity, thermal diffusivity, and specific heat capacity of the material at or near the spot location; the scan pattern along which the processing spot is scanned; or any combination thereof, the heat generated as a result of irradiating one or more spot locations with a laser pulse may diffuse from the irradiated spot location and accumulate in the region of the workpiece 102 outside the processing spot, causing the temperature of the workpiece 102 in the region outside the processing spot to rise.

[0191] The accumulated heat will raise the temperature of the area of ​​the workpiece 102 located at or near the processing spot to be processed next. If this temperature rise exceeds a threshold temperature (i.e., the "processing threshold temperature"), it can have a positive effect on the efficiency of subsequent processing of the workpiece 102 (e.g., by direct ablation, indirect ablation, or any combination thereof). Generally, the processing threshold temperature associated with the material being processed is equal to or greater than the melting point or glass transition temperature of the material being processed. However, in other embodiments, the processing threshold temperature may be lower than the melting point or glass transition temperature of the material being processed (e.g., 98%, 95%, 93%, 90%, 89%, 87%, 85%, 80%, 75%, 70%, 65%, or 50%).

[0192] In some cases, accumulated heat may raise the temperature in areas of workpiece 102 that are not intended to be processed (each of which is also referred to herein as a “non-feature area” of workpiece 102). If the temperature is sufficiently high, the non-feature areas of workpiece 102 may be susceptible to undesirable damage (e.g., undesirable scratching, melting, delamination, or annealing). Thus, it may be preferable to process workpiece 102 in a way that avoids the accumulation of undesirable heat in its non-feature areas. As used herein, the temperature at which an area of ​​workpiece 102 is susceptible to undesirable damage is referred to as the “damage threshold temperature.” It should be understood that the damage threshold temperature of any non-feature area of ​​workpiece 102 may depend on one or more factors, such as the thickness, thermal conductivity, thermal diffusivity, specific heat capacity, and absorbance (to the irradiated laser energy beam) of the material at or near the spot location or in the non-feature area, as well as the thermal conductivity, thermal diffusivity, specific heat capacity, size, and dimensions of structures located near the non-feature area, or any combination thereof.

[0193] a. Affects localized heat accumulation: Indirect ablation Considerations regarding heat accumulation can generally be problematic depending on the properties of the workpiece 102 and the method by which the workpiece 102 is processed, but such considerations can be particularly problematic when the workpiece 102 is processed by indirect ablation. For example, if the workpiece 102 is a PCB containing a dielectric structure (e.g., a glass fiber reinforced epoxy laminate) attached to a first conductor (e.g., copper or copper alloy foil) on its first side and optionally to a second conductor (e.g., a pad, trace, foil, etc. formed of copper or copper alloy foil) on a second side opposite to the first side, the workpiece 102 can be processed to indirectly ablate the first conductor (e.g., by directing a laser pulse beam along the beam axis to irradiate the workpiece 102 with a laser pulse), thereby forming an opening that exposes the dielectric structure.

[0194] In this embodiment, the first conductor may have a thickness ranging from approximately 5 μm (or around that) to approximately 50 μm (or around that). For example, the first conductor may have a thickness equal to (or approximately equal to) a value between 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 15 μm, 17 μm, 18 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, etc. The dielectric structure may have a thickness ranging from approximately 30 μm (or around that) to approximately 200 μm (or around that). For example, the dielectric structure may have a thickness equal to (or approximately equal to) a value between 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 140 μm, 180 μm, etc. The openings formed by indirect ablation may have an upper or lower diameter in the range of 30 μm (or around that) to 350 μm (or around that). For example, the upper or lower diameter of the opening may be equal to (or approximately equal to) a value between 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 150 μm, 200 μm, etc.

[0195] According to one embodiment, the laser pulse beam irradiated onto the workpiece surface 102a (i.e., the first conductor) has a wavelength in the visible green light region of the electromagnetic spectrum, a Gaussian or non-Gaussian spatial intensity profile, a pulse duration of 1 ns or more (e.g., 1 ns, 1.5 ns, 2 ns, 2.5 ns, 5 ns, 7 ns, 10 ns, etc., or a value between any of these values), and a spot size smaller than the upper or lower diameter of the aperture formed (e.g., 30 μm, 25 μm, 20 μm, 15 μm, 12 μm, 10 μm, 9 μm, 8 μm, 5 μm, etc.). The laser has a spot size of 100W or less (or a value between any of these values) and an average power of 100W or more (e.g., 120W, 150W, 180W, 200W, 225W, 250W, 275W, 300W, 350W, 500W, etc., or a value between any of these values), and is irradiated onto the work surface 102a with a pulse repetition rate of 100MHz or more (e.g., 125MHz, 150MHz, 175MHz, 200MHz, 250MHz, 300MHz, 350MHz, 500MHz, etc., or a value between any of these values). Laser pulses having the above characteristics can typically be generated by or obtained from laser sources such as CW laser sources and QCW laser sources. Materials typically used to form the first conductor (i.e., copper or copper alloys) tend to absorb green light fairly efficiently. Therefore, in the above example, the process of darkening the exposed surface of the first conductor (i.e., the surface of the first conductor not facing the dielectric structure) (a process typically used when indirectly ablating the first conductor using laser pulses with wavelengths in the LWIR range of the electromagnetic spectrum) can be omitted if necessary.

[0196] (For example, when operating the first positioner 106) the beam axis can be moved to scan the processing spot along a scan pattern such as scan pattern 2800 at a scan speed of 10 m / s or more (e.g., 12 m / s, 13 m / s, 14 m / s, 15 m / s, 16 m / s, 18 m / s, 20 m / s, etc., or any value between these values). In one embodiment, scan pattern 2800 fits over the entire first scanning range of the first positioner 106, although it can be understood that scan pattern 2800 may be larger than the first scanning range. In this example, the pitch between adjacent spot positions 2504 in the scan pattern is constant, and the dwell time associated with each spot position 2504 is the same as the dwell time associated with other spot positions 2504 (e.g., 1 μm or more).

[0197] In the example described above, given the parameters, the first conductor can be indirectly ablated to form an opening in the first conductor. During indirect ablation, the spot positions 2504 of the scan pattern 2800 are processed sequentially (i.e., by irradiating them with one or more laser pulses), generating and accumulating heat within the first conductor. This heat is emitted or transferred from the regions of the first conductor 102 at the previously processed spot positions 2504 and the currently processed spot position 2504, and accumulates within the regions of the first conductor at one or more unprocessed spot positions 2504. The heat accumulated within the regions of the first conductor at the unprocessed spots acts to raise the temperature of the first conductor in those regions and is also transferred to the regions of the dielectric structure beneath. Heat can also accumulate in other regions of the first conductor, such as at previously processed spot positions 2504 (for example, if the regions of the first conductor have not yet been indirectly ablated at the previously processed spot positions 2504). During processing, the heat transferred to the dielectric structure accumulates and acts to evaporate the region of the dielectric structure below and adjacent to the region of the first conductor. If the region of the first conductor does not reach a temperature above its processing threshold temperature before the region of the dielectric structure below it evaporates, the evaporation of the region of the dielectric structure acts to create a pocket or space below the first conductor (for example, a high-pressure region containing pressurized heating gas, particles, etc., generated during the evaporation of the dielectric structure). Then, when the region of the first conductor above the pocket reaches a temperature above its processing threshold temperature, the pressure generated within the pocket acts to push or eject the region of the first conductor from the workpiece 102, exposing the dielectric structure below it.

[0198] The region of the first conductor above the pocket may be an untreated spot location. In this case, when such a region is ultimately irradiated with one or more laser pulses, it may reach a temperature above the processing threshold temperature of the first conductor. In some cases, during processing, the region of the first conductor above the pocket at an untreated spot location may reach a temperature above the processing threshold temperature of the first conductor after accumulating heat emitted from other previously processed or currently processed spot locations. In other cases, during processing, the region of the first conductor above the pocket may become a previously processed spot location. In this case, such a region may reach a temperature above the processing threshold temperature of the first conductor after accumulating heat emitted from other previously processed spot locations, or from the currently processed spot location, or any combination thereof. For example, a pocket may be formed below a region of the first conductor at the first spot position 2504a of the scan pattern 2800, but such a region of the first conductor may not exceed its processing threshold temperature until one or more spot positions, such as spot positions 2504e, 2504f, etc., are subsequently processed.

[0199] When developing a process for indirectly ablating a first conductor by scanning processing spots along a scan pattern 2800, it should be understood that the minimum and maximum achievable diameters of the aperture (either at the top or bottom of the first conductor) depend on one or more factors, such as the scanning speed, the thickness of the first conductor, the thermal properties of the first conductor and dielectric structure, and the arrangement of spot positions within the scan pattern 2800, including the spot size, pulse duration, pulse repetition rate, and average power of the irradiated laser pulse. For example, the minimum achievable diameter of an aperture formed using an irradiated laser pulse of a particular spot size is typically limited to a range of 1.5 times (or around) to 2 times (or around) the particular spot size. The maximum achievable diameter of an aperture formed using an irradiated laser pulse of a particular spot size typically corresponds to the maximum diameter obtainable before any region within the feature boundary 2502 (e.g., its central region) can no longer accumulate enough heat during processing to enable indirect ablation. Thus, depending on one or more of the factors described above, by scanning an irradiation laser pulse beam with a spot size of 15 μm (or around that) along the scan pattern 2800, an aperture having a diameter in the range of 25 μm (or around that) to 80 μm (or around that) can be formed within the first conductor. Similarly, when using a spot size of 30 μm (or around that), an aperture having a diameter in the range of 60 μm (or around that) to 200 μm (or around that) can be formed. It should be understood that an aperture of any diameter can be formed by adding one or more additional spot positions to the scan pattern 2800 (for example, in its central region) to ensure that all areas enclosed by the desired feature boundary 2502 accumulate enough heat during processing to enable indirect ablation.

[0200] In the embodiment described above, the first conductor is processed by scanning the processing spots along the scan pattern 2800 such that the pitch between adjacent spot positions 2504 is constant and the dwell time associated with each spot position 2504 is the same as the dwell time associated with other spot positions 2504. However, in other embodiments, parameters such as dwell time, pitch, or any combination thereof may be adjusted to control how heat is accumulated within the first conductor. It should be understood that the selection of such parameters (such as dwell time and pitch) in any scan pattern (including, but not limited to, the scan pattern 2800) may depend on one or more factors, such as the diameter of the desired feature boundary 2502, the thickness of the first conductor, the thickness of the dielectric structure, the geometric configuration of the second conductor, the desired throughput of the process for forming an aperture in the first conductor, the pulse duration of the laser pulse irradiated onto the first conductor, the spot size, the average power, or any combination thereof. Embodiments relating to the adjustment of scanning method parameters are described in more detail below. It should be understood that, regardless of the type of workpiece 102 being processed or the type of features formed during processing, these examples of embodiments may be implemented to control how heat accumulates within the workpiece 102.

[0201] b. Controlling localized heat storage: Residence time In one embodiment, the dwell time associated with each spot position within a scan pattern (e.g., scan patterns 2500, 2600, 2700, 2800, etc.) is the same. However, in other embodiments, the dwell time associated with at least one spot position within a scan pattern is different from the dwell time associated with at least one spot position within the same scan pattern. The dwell time can be controlled by controlling the operation of the first positioner 106 (e.g., to scan the processing spot within a first scanning range), or by controlling the operation of the second positioner 108 (e.g., to scan the processing spot or the first scanning range within a second scanning range), or by delaying the irradiation of laser pulses onto the workpiece 102 (e.g., using a pulse gating unit not shown), or by similar methods, or by any combination thereof.

[0202] The difference in residence times between different spot locations within a common scan pattern or along a common scan line can be selected, modulated, or set so that the temperature of the workpiece 102 at one or more (or all) processing spots of the scan pattern is ensured to reach or exceed the processing threshold temperature during processing. For example, the residence time associated with the first spot location of the irradiated scan pattern may be longer than the residence times associated with one or more (or all) other spot locations of the same scan pattern. In another example, the residence time associated with the first spot location along the irradiated scan line (such a spot location is not the first spot location in the irradiated scan pattern) may be equal to or longer than the residence times associated with one or more (or all) other spot locations located along the same scan line. In yet another example, the residence time associated with any spot location along the irradiated scan line (such a spot location is not the first spot location in the irradiated scan pattern) may be equal to or longer than the residence times associated with adjacent spot locations (or other spot locations) located along the same scan line that are subsequently irradiated. In yet another example, the dwell time associated with the first spot location along a particular scanline being illuminated (such a spot location is not the first spot location in the illuminated scan pattern) may be equal to or longer than the dwell time associated with the first spot location along other scanlines being subsequently illuminated (which may or may not be adjacent to the first spot location of a particular scanline).

[0203] The difference in dwell time between different spot locations within a common scan pattern or along a common scan line can be selected, modulated, or set so that the temperature of the non-feature regions of workpiece 102 is reliably below the damage threshold temperature during processing of workpiece 102. For example, the dwell time associated with the last spot location in the irradiated scan pattern may be shorter than the dwell time associated with one or more (or all) other spot locations in the same scan pattern. In another example, the dwell time associated with the last spot location along the irradiated scan line (such a spot location is not the last spot location in the irradiated scan pattern) may be equal to or shorter than the dwell time associated with one or more (or all) other spot locations located along the same scan line. In yet another example, the dwell time associated with any unprocessed spot location along a scan line (such a spot location is not the first spot location in the scan pattern) may be equal to or shorter than the dwell time associated with other previously processed spot locations located along the same scan line. In yet another example, the dwell time associated with the first spot location along one scan line being illuminated (such a spot location is not the first spot location in the illuminated scan pattern) may be equal to or longer than the dwell time associated with the first spot location along any other scan lines subsequently illuminated.

[0204] By increasing the dwell time associated with one spot location relative to one or more other spot locations within a scan pattern (or arranged along a common scan line), the way in which regions of the workpiece (e.g., previously processed spot locations, currently processed spot locations, spot locations to be processed, or any combination thereof) accumulate heat (e.g., as a result of irradiating one or more previously processed spot locations with laser pulses, or as a result of irradiating the currently processed spot location with laser pulses, or any combination thereof) can be controlled to enable efficient ablation or other processing while avoiding undesirable damage to non-feature regions of the workpiece 102.

[0205] With the above in mind, continuing with the example of the embodiment described above (i.e., an opening is formed in the first conductor of the PCB by indirect ablation), it should be understood that the dwell time associated with one or more spot positions 2504 of the scan pattern 2800 may differ from that of any of the other spot positions 2504 of the scan pattern 2800. For example, the processing spots can be scanned along the scan pattern 2800 such that the dwell time associated with the first spot position 2504a of the first scan pattern 2800 is longer than the dwell time associated with all the other spot positions 2504 of the scan pattern 2800. Generally, the dwell time associated with the first spot position 2504a is set to be long enough to ensure that the portion of the first conductor at one or more spot positions 2504 to be processed after the first spot position 2504a (e.g., one or more of the second spot position 2504e, third spot position 2504f, etc. in the scan pattern 2800) can be indirectly ablated when one or more of those spot positions 2504 to be processed are finally processed. If necessary, the residence time associated with the first spot position 2504a can be set such that the region of the first conductor at the first spot position 2504a is indirectly ablated when the first spot position 2504a is processed. However, generally, the residence time associated with each of the spot positions 2504 can be set such that the temperature of non-feature regions of the workpiece 102 (e.g., regions in the dielectric structure adjacent to or near the second conductor) is below the damage threshold temperature during processing of the first conductor. In one embodiment, the residence time associated with the first spot position 2504a or any other spot position 2504 in the scan pattern 2800 may be longer than or equal to the positioning time of the first positioner 106 described above.In one embodiment, the residence time associated with the first spot position 2504a may be in the range of 2 μs (or around that) to 9 μs (or around that) (for example, the residence time associated with the first spot position 2504a may be equal to (or approximately equal to) a value between 2 μs, 3 μs, 4 μs, 5 μs, 6 μs, 7 μs, 8 μs, 9 μs, etc.). In another embodiment, the residence time associated with a spot position 2504 other than the first spot position 2504a may be equal to 1 μs (or around that).

[0206] c. Controlling localized heat storage: pitch In one embodiment, the pitch between adjacent spot positions within a scan pattern, the pitch between adjacent spot positions along a common scan line, or any combination thereof is the same. However, in other embodiments, the pitch between one pair of adjacent spot positions and another pair of adjacent spot positions (i.e., within the same scan pattern, along a common scan line, or any combination thereof) may be different. The pitch can be controlled by controlling the operation of the first positioner 106 (for example, to scan the processing spot within a first scanning range), or the operation of the second positioner 108 (for example, to scan the processing spot or the first scanning range within a second scanning range), or the operation of the third positioner 110 (for example, to scan the first scanning range or the second scanning range within a third scanning range), or similar operations, or any combination thereof.

[0207] The pitch difference between different spot locations in a common scan pattern or along a common scan line can be selected, modulated, or set so that the temperature of the workpiece 102 at one or more (or all) processing spots in the scan pattern is reliably at or above the processing threshold temperature during processing. For example, the pitch between the first pair of adjacent spot locations in the irradiated scan pattern may be smaller than the pitch between one or more (or all) other pairs of adjacent spot locations in the same scan pattern. In another example, the pitch between the first pair of adjacent spot locations along the irradiated scan line (such a pair of adjacent spot locations is not the first pair of adjacent spot locations in the irradiated scan pattern) may be equal to or shorter than the pitch between one or more (or all) other pairs of adjacent spot locations arranged along the same scan line. In yet another example, the pitch between any pair of adjacent spot locations along the irradiated scan line (such a pair of adjacent spot locations is not the first pair of adjacent spot locations in the irradiated scan pattern) may be equal to or smaller than the pitch between other pairs of adjacent spot locations arranged along the same scan line that are subsequently irradiated. In yet another example, the pitch between the first pair of adjacent spot locations along a particular scanline being illuminated (such a pair of adjacent spot locations is not the first pair of adjacent spot locations in the illuminated scan pattern) may be equal to or shorter than the pitch between the first pair of adjacent spot locations along other scanlines being subsequently illuminated (which may or may not be adjacent to the first spot locations of a particular scanline).

[0208] The pitch difference between different pairs of adjacent spot positions in a common scan pattern or along a common scan line can be selected, modulated, or set so that the temperature of workpiece 102 at one or more (or all) processing spots in the scan pattern is reliably at or above the processing threshold temperature during processing, so that the temperature of workpiece 102 at one or more (or all) processing spots in the scan pattern is reliably at or above the processing threshold temperature during processing, so that the temperature of workpiece 102 at one or more (or all) processing spots in the scan pattern is reliably at or above the processing threshold temperature during processing. For example, the pitch between the last pair of adjacent spot positions in the irradiated scan pattern may be longer than the pitch between one or more (or all) other pairs of adjacent spot positions in the same scan pattern. In another example, the pitch between the last pair of adjacent spot positions along the irradiated scan line (such a pair of adjacent spot positions is not the last pair of spot positions in the irradiated scan pattern) may be equal to or longer than the dwell time associated with one or more (or all) other spot positions arranged along the same scan line. In yet another example, the pitch between any pair of adjacent spot locations along the illuminated scanline (such a pair of adjacent spot locations is not the first spot location in the scan pattern) may be equal to or longer than the pitch between any pair of previously processed adjacent spot locations located along the same scanline. In yet another example, the pitch between the first pair of adjacent spot locations along one illuminated scanline (such a pair of adjacent spot locations is not the first pair of adjacent spot locations in the scan pattern) may be equal to or shorter than the pitch between the first pair of adjacent spot locations along the other scanline of the scan pattern that is subsequently illuminated.

[0209] By shortening the pitch between any pair of adjacent spot locations relative to one or more other pairs of adjacent spot locations in the scan pattern (or arranged along a common scan line), the way in which regions of the workpiece (e.g., previously processed spot locations, currently processed spot locations, spot locations to be processed, or any combination thereof) accumulate heat (e.g., as a result of irradiating one or more previously processed spot locations with laser pulses, or as a result of irradiating the currently processed spot location with laser pulses, or any combination thereof) can be controlled to enable efficient ablation or other processing while avoiding undesirable damage to non-feature regions of the workpiece 102.

[0210] In consideration of the above, continuing with the example of the embodiment described above (i.e., an opening is formed in the first conductor of the PCB by indirect ablation), it should be understood that the pitch between one or more pairs of adjacent spot positions 2504 in the scan pattern 2800 may be different from or the same as the pitch between any other pair of adjacent spot positions 2504 in the scan pattern 2800. For example, in one embodiment, the pitch between pairs of adjacent spot positions in the scan pattern 2800 may increase from the first spot position 2504a to the last spot position 2504b (e.g., linearly or non-linearly, uniformly or non-uniformly, continuously or discontinuously, etc.). In another embodiment, the pitch between pairs of adjacent spot positions in one group of sequentially processable spot positions in the scan pattern 2800 may be different from the pitch between pairs of adjacent spot positions in other groups of sequentially processable spot positions in the scan pattern 2800. For example, the pitch between each pair of adjacent spot positions in the first group of sequentially processable spot positions in the scan pattern 2800 may be smaller than the pitch between each pair of adjacent spot positions in the second group of sequentially processable spot positions in the scan pattern 2800. Generally, spot positions in the first group of sequentially processable spot positions are processed before spot positions in the second group of spot positions. Thus, the first group of sequentially processable spot positions includes at least spot positions 2504a, 2504e, and 2504f, and the second group of sequentially processable spot positions includes at least spot positions 2504b, 2504g, and 2504h. In one embodiment, the number of spot positions in the first group of sequentially processable spot positions ranges from 1% to 95% of the total number of spot positions in the scan pattern 2800, and spot positions not included in the first group of sequentially processable spot positions are included in the second group of sequentially processable spot positions.

[0211] In one embodiment, the pitch between each pair of adjacent spot positions in the first group of sequentially processable spot positions is constant, and the number of spot positions in the first group of sequentially processable spot positions is in the range of 1% to 95% of the total number of spot positions in the scan pattern 2800. In this embodiment, the number of spot positions in the first group of sequentially processable spot positions is equal to (or approximately equal to) a value between 3%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc.

[0212] iv. Other considerations regarding scan patterns a. Single-spot location scan pattern In the embodiments described above, the scan pattern is described as including a plurality of sequentially processed spot locations, and the workpiece 102 may be processed to form features by scanning the processing spots along the scan pattern that irradiates various spot locations. However, in other embodiments, the scan pattern may consist of only a single spot location, and the workpiece 102 may be processed (e.g., ablated, marked, or melted) simply by irradiating the single spot location (or a spot location irradiated in the local vicinity of the single spot location) with one or more laser pulses. Such a scan pattern is referred to herein as a “single-spot location scan pattern”. For example, a single spot location in the scan pattern may be repeatedly irradiated with multiple laser pulses to directly ablate the workpiece 102 (e.g., to form non-penetrating vias, through vias, or other recesses, holes, or openings in the workpiece 102). This type of direct ablation process is often referred to as a “punching” process.

[0213] In other examples, if the workpiece 102 is a PCB, as described in the section “Affecting Localized Thermal Accumulation: Indirect Ablation” above, the workpiece 102 can be processed to directly or indirectly ablate the first conductor, thereby forming an opening that exposes a region of the dielectric structure. In one embodiment, the laser pulse irradiated to a single spot location may have wavelengths in the UV region of the electromagnetic spectrum and may have one or more other properties suitable for directly ablating the first conductor. In another embodiment, the laser pulse irradiated to a single spot location may have wavelengths in the long-wavelength IR (LWIR) region of the electromagnetic spectrum (i.e., such a laser pulse is typically generated from a carbon dioxide laser as the laser source 104) and may have one or more other properties suitable for indirectly ablating the first conductor. In yet another embodiment, the laser pulse irradiated to a single spot location may have wavelengths in the visible-green region of the electromagnetic spectrum and may have one or more other properties suitable for indirectly ablating the first conductor.

[0214] Laser pulses with wavelengths in the visible-green region of the electromagnetic spectrum can often be generated with much higher average power than corresponding laser pulses with wavelengths in the UV region of the electromagnetic spectrum, enabling high-throughput processing of the workpiece 102. Furthermore, laser pulses with wavelengths in the visible-green region of the electromagnetic spectrum can be focused to much smaller spot sizes than laser pulses with wavelengths in the LWIR region of the electromagnetic spectrum, allowing for the formation of smaller features within the workpiece 102. Moreover, as mentioned above, the materials typically used to form the first conductor (i.e., copper or copper alloy) tend to absorb green light very efficiently. Therefore, darkening the exposed surfaces of the first conductor (i.e., surfaces of the first conductor not facing the dielectric structure) (a process typically used when indirectly ablating the first conductor using laser pulses with wavelengths in the LWIR range of the electromagnetic spectrum) can be omitted if necessary.

[0215] Generally, a laser pulse beam irradiated onto the work surface 102a (i.e., the first conductor) has a wavelength in the visible green region of the electromagnetic spectrum, a Gaussian or non-Gaussian spatial intensity profile, a pulse duration of 1 ns or more (e.g., longer than or equal to 1 ns, 1.5 ns, 2 ns, 2.5 ns, 5 ns, 7 ns, 10 ns, etc., or a value between any of these values), a spot size smaller than the upper or lower diameter of the aperture formed (e.g., smaller than or equal to 30 μm, 25 μm, 20 μm, 15 μm, 12 μm, 10 μm, 9 μm, 8 μm, 5 μm, etc., or a spot size between any of these values), and an average power of 100 W or more (e.g., greater than or equal to 120 W, 150 W, 180 W, 200 W, 225 W, 250 W, 275 W, 300 W, 350 W, 500 W, etc., or a value between any of these values).

[0216] In one embodiment, the above-described green wavelength laser pulse is irradiated onto the workpiece surface 102a (i.e., the first conductor) at a pulse repetition rate of 100 MHz or higher (e.g., greater than or equal to, or between, values ​​such as 125 MHz, 150 MHz, 175 MHz, 200 MHz, 250 MHz, 300 MHz, 350 MHz, 500 MHz, etc.). Laser pulses having the above-described characteristics can typically be generated by, or obtained from, a laser source such as a CW laser source or a QCW laser source. However, in other embodiments, other laser sources can also be used that can generate green wavelength laser pulses having pulse energies in the range of 100 μJ (or around) to 50 mJ (or around) on a timescale of 1 microsecond or longer (e.g., a burst mode of ns or ps pulses over 2 microseconds or longer, or a burst mode in which bursts are repeated every microsecond or less).

[0217] It should be understood that the residence time associated with a single spot location can range from 1 μs (or around) to 30 μs (or around) depending on one or more factors such as the thickness of the first conductor, surface absorption characteristics, and certain laser parameters (e.g., pulse energy, pulse duration, pulse repetition rate, spot size, and spot shape).

[0218] b. Sequential feature generation and parallel feature generation In one embodiment, multiple features can be sequentially formed within or on the workpiece 102 using an irradiated laser pulse beam. That is, the beam axis of multiple laser pulses irradiated onto the workpiece 102 is moved, and the resulting processing spot is scanned along a first scan pattern, such as one of the scan patterns described above or other scan patterns (or a first set of such scan patterns), until a first feature is formed. After the first feature is formed, the beam axis is moved to another area of ​​the workpiece 102, and the resulting processing spot is scanned along a second scan, such as one of the scan patterns described above or other scan patterns (or a second set of such scan patterns), until a second feature is formed. Thereafter, one or more additional features can be sequentially formed in a similar manner.

[0219] In other embodiments, multiple features can be formed in parallel within or on the workpiece 102 using the irradiated laser pulse beam. That is, the beam axis of multiple laser pulses irradiated onto the workpiece 102 is moved, and the resulting processing spots are alternately scanned along multiple scan patterns. For example, the beam axis can be moved so that one or more laser pulses are irradiated to one or more spot positions (but not all) of a first scan pattern, and then the beam axis can be scanned so that one or more laser pulses are irradiated to one or more spot positions (but not all) of a second scan pattern. Then, the beam axis can be moved so that one or more laser pulses are irradiated to one or more spot positions (but not all) of the first scan pattern (or a first set of scan patterns) to be processed, or to one or more spot positions (but not all) of a third scan pattern (or a third set of scan patterns), etc. The process of moving the beam axis and alternately irradiating one or more spot locations of various scan patterns with laser pulses may be repeated until all spot locations of a first scan pattern (or a first set of scan patterns) are processed (i.e., a first feature is formed), or until all spot locations of a second scan pattern (or a second set of scan patterns) are processed (i.e., a second feature is formed). Forming multiple features in parallel helps prevent undesirable damage to non-feature areas of the workpiece 102 due to heat that may have accumulated during the formation of a single feature or the sequential formation of multiple features.

[0220] As described in the above embodiments, the sequentially or parallelly formed features may be the same as or different from each other. At least some of the sequentially or parallelly formed features may be spatially relative to each other within or on the workpiece 102 so that they can be simultaneously placed within a first scanning range, a second scanning range, or any combination thereof. For this reason, depending on the size of the final formed features and the distance between such features, the first or second scanning range may surround at least two sequentially or parallelly formed features.

[0221] In one embodiment (for example, when the workpiece 102 is a PCB, as described in the section "Affecting Local Heat Accumulation: Indirect Ablation"), the workpiece 102 can be processed to sequentially or in parallel form multiple features, such as apertures, on the first conductor by scanning the irradiated laser pulses (for example, having the characteristics described in the section "Single Spot Location Scan Patterns" or having one or more other characteristics suitable for facilitating indirect ablation of the first conductor) within different single-spot location scan patterns. In other embodiments (for example, when the workpiece 102 is a dielectric structure such as a build-up film, a glass fiber reinforced epoxy laminate, an interlayer dielectric material, a low-k dielectric material, a solder resist, or any combination thereof), the workpiece 102 can be processed to sequentially or in parallel to form multiple features such as one or more vias (e.g., one or more non-penetrating or through vias), recesses, holes, openings, or any combination thereof, by scanning an irradiated laser pulse beam (having, for example, one or more other properties suitable for facilitating direct ablation of the dielectric structure) within different single-spot position scan patterns. Generally, laser pulses generated by a burst-mode laser (or other laser operating in burst mode) are typically generated at pulse repetition rates lower than 100 MHz (often 10 kHz or less). Therefore, if the laser pulse in any of the embodiments described above is irradiated onto the work surface 102a at a pulse repetition rate of 100 MHz or more (or less), multiple features may be formed (i.e., on the first conductor or dielectric structure) by operating the first positioner 106 to scan the irradiated laser pulse into different single-spot position scan patterns that are simultaneously surrounded by the first scanning range.When a laser pulse is irradiated onto the work surface 102a at a pulse repetition rate of less than 10 kHz, multiple features may be formed by operating the second positioner 108 to scan the irradiated laser pulse into different single-spot position scan patterns that are simultaneously surrounded by the second scanning range.

[0222] VIII. Embodiments relating to beam characteristic modulation As described above, the laser energy beam (whether continuous or pulsed) irradiated onto the workpiece 102 during processing of the workpiece 102 has wavelength, average power, spatial intensity profile type, and M 2 A laser energy beam can be characterized by one or more properties, such as factor, spatial intensity profile shape, spot size, light intensity, and fluence. If the laser energy beam contains one or more laser pulses, the beam can also be characterized by one or more properties, such as pulse repetition rate, pulse duration, pulse energy, and peak power. All of these properties of a laser energy beam (whether continuous or pulsed) are collectively and comprehensively referred to herein as the "properties" or simply "beam properties" of the laser energy beam. The beam properties of laser pulses irradiated to (or near) a common spot location may be the same or different. For example, one or more properties, such as spot size, pulse energy, and pulse repetition rate, of sequentially irradiated laser pulses irradiated to (or near) a common spot location may be constant, increasing, decreasing, or any combination thereof. Similarly, the beam properties of laser pulses irradiated to different spot locations in a common scan pattern may be the same or different.

[0223] The characteristics such as spot size can be adjusted by activating one or more of the mechanisms that perform Z-direction height compensation as described above. 2Characteristics such as the factor and spatial intensity profile shape can be adjusted by operating one or more AOD systems (for example, the first positioner 106 or others) using the method described above. Furthermore, M 2 The methods described above for operating the AOD system to change the factor can be modified to adjust the type of spatial intensity profile of the laser pulse beam in the manner described above. For example, the spectrum of an RF signal applied to one or more transducers of the AOD system (e.g., the first positioner 106 or others) can be shaped to have a non-Gaussian spectral profile (e.g., a rectangular or "top-hat" spatial profile). When such an RF signal is applied to one or more transducers of the AOD system (e.g., the first positioner 106 or others), the laser pulses leaving the AOD system can be modified in such a way that they generate laser pulses of a non-Gaussian spatial intensity profile type (e.g., a rectangular or "top-hat" spatial intensity profile). In one embodiment, the spectrally shaped RF signal is not chirp. In other embodiments, the spectrally shaped RF signal may be chirp. Thus, depending on how the AOD system is driven (i.e., in response to one or more applied RF signals), the laser pulses leaving the AOD system can be shaped to M 2 The beam characteristics and other beam characteristics may differ from those of the incident laser pulse in one or more characteristics, such as the factor, type of spatial intensity profile, spatial intensity profile shape, and spot size. Furthermore, these beam characteristics and other beam characteristics may be altered in other suitable or desirable ways known in the art or disclosed herein (in this section or elsewhere).

[0224] Generally, during processing of the workpiece 102, one or more (or all) beam characteristics may be kept constant (or at least substantially constant), modulated (for example, to be substantially non-constant), or any combination thereof. Examples of embodiments in which one or more beam characteristics can be changed during feature processing are described below. While the specific embodiments relating to beam characteristic modulation in this section are described in relation to apparatus 100, it will be understood that any one of these embodiments or any combination thereof can be implemented with respect to the multi-head apparatus 700. Furthermore, it will be understood that the embodiments described in this section may be implemented using a preferredly equipped single-head or multi-head laser processing apparatus other than those described herein.

[0225] i. Feature generation in multilayer workpieces A multilayer workpiece can be processed to form one or more features that penetrate multiple layers of the workpiece. In one embodiment, a multilayer workpiece 102 can be processed to form features such as openings, slots, vias, or other holes, grooves, trenches, scribe lines, cut grooves, or recessed regions that penetrate at least partially two different layers of the multilayer workpiece 102. The different layers of the multilayer workpiece 102 may be formed from different materials, have different optical absorption properties (for example, with respect to an irradiated laser energy beam), or be an arbitrary combination thereof. Therefore, for example, a feature may be formed in the multilayer workpiece 102 by ablating the first layer of the workpiece 102 using an irradiated laser energy beam characterized by a first set of beam characteristics in order to expose the second layer of the workpiece 102. The first set of beam characteristics is then defined by (for example, wavelength, average power, spatial intensity profile type, M 2The second layer of the workpiece 102 may be ablated using an irradiation laser energy beam characterized by a second set of different beam characteristics (such as factor, spatial intensity profile shape, spot size, light intensity, fluence, pulse repetition rate, pulse duration, peak power, or any combination thereof). The characteristics in the second set of beam characteristics may be identical to the corresponding characteristics in the first set of beam characteristics, insofar as at least one characteristic is greater than, less than, or different from the corresponding characteristic in the first set of beam characteristics.

[0226] For example, the multilayer workpiece 102 may be a PCB panel or PCB including a dielectric structure (e.g., a glass fiber reinforced epoxy laminate) which is fixed on a first side to a first conductor (e.g., a copper foil or copper alloy foil which may have a darkened exposed surface or an undarkened exposed surface (e.g., by a chemical reaction or a laser darkening process)) and optionally fixed on a second conductor (e.g., a pad, trace, foil, etc. made of copper or a copper alloy) on a second side opposite to the first side. The multilayer workpiece 102 may be processed to form vias that completely penetrate the first conductor and at least partially penetrate the dielectric structure. The vias may be terminated in the second conductor (in which case the vias are non-through vias) or may completely penetrate the second conductor (in which case the vias are through vias).

[0227] In the above example, a laser energy beam characterized by a first set of beam characteristics may be irradiated onto a first conductor in a first processing step of directly or indirectly ablating the first conductor to form an aperture that exposes the dielectric structure (and may also be scanned, for example, by the scanning technique described exemplary above, if necessary). Subsequently, in a second processing step, a laser energy beam characterized by a second set of beam characteristics may be irradiated onto the dielectric structure through the aperture to directly ablate the dielectric structure to form a hole extending into the dielectric structure (and may also be scanned, for example, by the scanning technique described exemplary above, if necessary).

[0228] In one embodiment, the first and second sets of beam characteristics may be the same in wavelength (for example, the irradiated laser energy beam may have wavelengths in the UV, visible, and IR regions of the electromagnetic spectrum), but may differ in fluence, light intensity, or any combination thereof. For example, the fluence may be higher during the first processing step than during the second processing step. Between the first and second processing steps, the fluence may be adjusted by reducing the pulse energy of the irradiated laser pulse beam, increasing the spot size of the irradiated laser pulse beam, or any combination thereof. For example, to reduce the fluence at the processing spot without reducing the average power (for example, to a threshold fluence that can directly ablate the materials of the first and second conductors), the spot size of the laser pulse beam irradiated during the second processing step (i.e., the "second spot size") may be increased relative to the spot size of the laser pulse beam irradiated during the first processing step (i.e., the "first spot size"). As a result, the number of pulses required to form holes in the dielectric structure can be kept relatively low, thus avoiding damage to adjacent conductive structures. In one embodiment, the first spot size may be in the range of 2 μm (or around) to 35 μm (or around), and the second spot size, which is larger than the first spot size, may be in the range of 40 μm (or around) to 150 μm (or around). For example, the first spot size may be equal to (or approximately equal to) 2 μm, 3 μm, 5 μm, 7 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, etc., or a value between any of these values, and the second spot size may be equal to (or approximately equal to) 40 μm, 50 μm, 60 μm, 80 μm, 100 μm, 125 μm, 140 μm, 155 μm, etc.

[0229] ii. Considerations regarding localized heat accumulation In one embodiment, one or more beam characteristics (e.g., pulse energy, pulse repetition rate, pulse duration, average power, or any combination thereof) may be selected, modulated, or set such that the temperature of the non-feature regions of the workpiece 102 is at or below the damage threshold temperature during processing of the workpiece 102 (e.g., over the period during which one or more features are formed on the workpiece 102). The modulation of one or more beam characteristics may be performed independently of the parameters associated with any scanning technique used to form the features, or it may be performed in relation to the modulation of one or more scanning technique parameters (e.g., residence time, pitch, or any combination thereof).

[0230] For example, continuing with the above embodiment in which an aperture is formed in the first conductor of the PCB by indirect ablation (for example, by scanning processing spots along the scan pattern 2800), the pulse energy of the laser pulses irradiated onto the work surface 102a (i.e., the exposed surface of the first conductor) can be modulated such that the pulse energy of one or more laser pulses irradiated onto the last spot position 2504b of the scan pattern 2800 is lower than the pulse energy of one or more laser pulses irradiated onto the first spot position 2504a of the scan pattern 2800. For example, one or more laser pulses irradiated at the last spot position 2504b may have a pulse energy in the range of 75% (or around) to 20% (or around) of the pulse energy of one or more pulses irradiated at the first spot position 2504a (e.g., equal to or approximately equal to 80%, 75%, 70%, 65%, 60%, 55%, 50%, 45%, 40%, 35%, 30%, 25%, 20%, 15%, etc., or any value between these values). In one embodiment, the pulse energy of the laser pulses irradiated at the spot positions of the scan pattern 2800 may decrease from the first spot position 2504a to the last spot position 2504b (e.g., linearly or nonlinearly, uniformly or non-uniformly, continuously or discontinuously, etc.).

[0231] In other embodiments, the pulse energy of the laser pulses irradiated to the spot positions within one group of the sequentially processable spot positions within the scan pattern 2800 may be different from the pulse energy of the laser pulses irradiated to the spot positions within other groups of the sequentially processable spot positions within the scan pattern 2800. For example, the pulse energy of the laser pulses irradiated to the spot positions within the first group of the sequentially processable spot positions within the scan pattern 2800 may be higher than the pulse energy of the laser pulses irradiated to the spot positions within the second group of the sequentially processable spot positions within the scan pattern 2800. Generally, the spot positions within the first group of the sequentially processable spot positions are processed earlier than the spot positions within the second group of the sequentially processable spot positions. For this reason, the first group of the sequentially processable spot positions includes at least the spot positions 2504a, 2504e, and 2504f, and the second group of the sequentially processable spot positions includes at least the spot positions 2504b, 2504g, and 2504h. In one embodiment, the number of the spot positions within the first group of the sequentially processable spot positions is in the range of 1% to 95% of the total number of the spot positions of the scan pattern 2800, and the spot positions not included in the first group of the sequentially processable spot positions are included in the second group of the sequentially processable spot positions.

[0232] In one embodiment, the pulse energy of the laser pulses irradiated to the spot positions within the first group of the sequentially processable spot positions is constant, and the number of the spot positions within the first group of the sequentially processable spot positions is in the range of 1% to 95% of the total number of the spot positions of the scan pattern 2800. In this embodiment, the number of the spot positions within the first group of the sequentially processable spot positions is equal to (or approximately equal to) 3%, 5%, 10%, 15%, 20%, 30%, 40%, 50%, 60%, 70%, 80%, 90%, etc., or a value between any of these values.

[0233] IX. Post-processing Sometimes, additional processing may be performed after a feature has been formed (for example, by scanning the processing spot along one or more feature formation scan patterns as described above, or along one or more other scan patterns, or any combination thereof). Additional processing may be performed (for example, in the presence of ambient air, an oxidizing gas or oxidizing solution, a reducing gas or reducing solution, an inert gas or inert solution, a vacuum, etc.) to remove material from the bottom surface of the side wall region of the etcher (for example, residual material generated during feature formation or residual material remaining on or within the feature after the feature has been formed), or to further remove one or more portions of the workpiece 102 at the feature boundary (for example, to obtain a feature boundary that more closely matches a desired feature boundary), or to alter or process the one or more materials that define the feature (for example, by using a photoactive reagent, etc.), or any combination thereof. Therefore, one or more post-processing techniques can be performed by scanning processing spots along one or more post-processing scan patterns that may be identical to or different from any of the feature formation patterns described above.

[0234] Generally, one or more characteristics of the post - processing scan pattern (such as, for example, the placement of spot positions, the proximity of spot positions to feature boundaries, etc.), one or more beam characteristics selected or used during post - processing, or any arbitrary combination thereof, may be the same as the corresponding characteristics of the feature - forming scan pattern, or may be different therefrom. Further, the corresponding characteristics of the beam characteristics selected or used during feature formation may be the same as, or different from, those during post - processing. In one embodiment, for a feature being formed, one or more post - processing techniques can be performed before forming other features. However, in other embodiments, one or more post - processing techniques can be performed on a plurality of features only after all of the plurality of features have been formed.

[0235] Here, examples of embodiments of post - processing techniques will be described in more detail. Specific embodiments regarding modulation of beam characteristics in this section are described in relation to apparatus 100, but it will be understood that any one of these embodiments, or any arbitrary combination thereof, can be realized in relation to multi - head apparatus 700. Further, it will be understood that the embodiments described in this section may be realized using a single - head or multi - head laser processing apparatus suitably equipped other than those described herein.

[0236] i. Via cleaning Features such as non-penetrating vias may be formed on a workpiece by directly ablating a dielectric structure (e.g., a glass fiber reinforced epoxy laminate) to create holes that expose a conductor (e.g., a pad, trace, foil, etc., made of copper or a copper alloy) at its bottom. Generally, holes can be formed using an irradiation laser energy beam characterized by a first set of beam characteristics. Residual material (e.g., including resin material) may remain in the non-penetrating via (e.g., on the exposed conductor), which can prevent the subsequent metal film formed in the non-penetrating via from adhering properly and reduce the effective area for electrical contact with the exposed copper layer, etc., at the bottom of the non-penetrating via. Therefore, it may be beneficial to remove the residual material (partially or completely). In one embodiment, the first set of beam characteristics is (e.g., wavelength, average power, type of spatial intensity profile, M 2 Residual material may be removed using an irradiation laser energy beam characterized by a second set of different beam characteristics (such as factor, spatial intensity profile shape, spot size, optical intensity, fluence, pulse repetition rate, pulse duration, peak power, or any combination thereof). The characteristics in the second set of beam characteristics may be the same as the corresponding characteristics in the first set of beam characteristics, insofar as at least one characteristic is greater than, less than, or different from the corresponding characteristics in the first set of beam characteristics. The laser energy beam characterized by the second set of beam characteristics may be irradiated onto a conductor exposed in an aperture formed within a dielectric structure and residual material located thereon. Such a laser energy beam may be scanned (for example, by the scanning techniques described exemplified above) to ablate the residual material on the exposed conductor directly or indirectly without ablating the exposed conductor, if necessary.

[0237] In one embodiment, the first set and the second set of beam characteristics may be the same in terms of wavelength (for example, the irradiated laser energy beam may have wavelengths in the UV, visible, or IR range of the electromagnetic spectrum), type of spatial intensity profile (for example, Gaussian spatial intensity profile), but the spot size, M 2 Factors, or any combination thereof, may differ. For example, the spot size of the irradiation laser energy beam during the second processing step may be larger than the spot size of the irradiation laser energy beam during the first processing step. Similarly, the M of the irradiation laser energy beam may be adjusted to produce an irradiation laser energy beam having a larger effective spot size during the second processing step than during the first processing step. 2 The factor may be adjusted using any preferred or desired method (for example, as described in the section "Embodiments relating to beam characteristic modulation" above) to change the spot size or M 2 The factor may be adjusted. During the second processing step, the processing spot may be scanned as needed (for example, to process multiple spot locations along the scan pattern). If the spot size (or effective spot size) at the processing spot during the second processing step is sufficiently large, the number of spot locations processed at the processing spot may be reduced (to one or two spot locations).

[0238] In other embodiments, the first and second sets of beam characteristics may be identical in wavelength (for example, the irradiated laser energy beam may have wavelengths in the UV, visible, and IR regions of the electromagnetic spectrum), but may differ in the type of spatial intensity profile, the shape of the spatial intensity profile, the spot size, or any combination thereof. The irradiated laser energy beam during the first processing step may have a Gaussian spatial intensity profile with a substantially circular shape and a relatively small spot size. However, the irradiated laser energy beam during the second processing step may have a non-Gaussian spatial intensity profile with a circular or non-circular (e.g., square) shape (e.g., a "top-hat" spatial intensity profile) and a relatively large spot size. The type of spatial intensity profile, the shape of the spatial intensity profile, and the spot size may be adjusted using any preferred or desired method (e.g., as described in the "Embodiments relating to beam characteristic modulation" section above). During the second processing step, the processing spot may be scanned as needed (e.g., to process multiple spot positions along a scan pattern). If the spot size (or effective spot size) at the processing spot during the second processing step is sufficiently large, the number of spot locations processed at the processing spot may be reduced (to one or two spot locations).

[0239] a. Cleaning of non-penetrating vias - central region When forming features such as non-penetrating vias (for example, those that penetrate a dielectric structure and expose a copper layer at their bottom), residual material (e.g., dielectric material) may be present in the central region at the bottom of the non-penetrating via (e.g., on the conductor exposed at the bottom of the non-penetrating via). This is often observed when using feature formation scan patterns characterized by a relatively small number (or no) of spot locations located within the central region of the desired feature boundary (similar to scan pattern 2600 shown in Figure 26).

[0240] To remove such residual material (partially or completely), a post-processing scan pattern (also referred to herein as a “central region cleanup scan pattern”) may be scanned. Generally, a central region cleanup scan pattern includes one or more spot locations located in the central region of the feature boundary at the bottom of the feature. Figure 26 shows an example of an embodiment of a central region cleanup scan pattern. The central region cleanup scan pattern includes one or more spot locations located within the central region of the feature boundary (e.g., inside the central region of boundary 2502 surrounded within region 2602) (e.g., as shown in Figure 26, the central region cleanup scan pattern includes multiple spot locations 2504'). Of the spot locations 2504', spot location 2504a' represents the first spot location to be irradiated with a laser pulse during central region cleanup, and spot location 2504b' represents the last spot location to be irradiated with a laser pulse during central region cleanup. Therefore, the solid line connecting the spot positions 2504' indicates the order in which the spot positions 2504 are processed (for example, by one or more irradiation laser pulses). However, it should be understood that the spot positions 2504' may be processed in any other desired order (which may change the configuration of the solid line), or they may be processed randomly.

[0241] Generally, laser pulses irradiated onto the spot position while scanning the central region clean scan pattern do not irradiate areas of workpiece 102 at the feature boundary. However, depending on one or more factors such as the spot size of the irradiated laser pulse, the spatial intensity distribution, the size and shape of the feature boundary at the top of the feature, the size and shape of the feature boundary at the bottom of the feature, the depth of the feature, or any combination thereof, one or more areas of workpiece 102 at the feature boundary (for example, at or near the top of the feature) may be irradiated by at least a portion of one or more irradiated laser pulses.

[0242] b. Cleaning of non-penetrating vias - peripheral region When forming features such as non-penetrating vias using scan patterns as described above with respect to Figures 25 to 28 (for example, penetrating a dielectric structure and exposing a copper layer at its bottom), residual material (e.g., dielectric material) may be present in the peripheral region of the bottom of the non-penetrating via (for example, in the region where the sidewall of the non-penetrating via is in contact with or near the conductor exposed at the bottom of the non-penetrating via).

[0243] To remove such residual material (partially or completely), a post-processing scan pattern (also referred to herein as a “peripheral cleanup scan pattern”) may be scanned. A peripheral cleanup scan pattern may include one or more spot locations located in the peripheral region of the feature boundary at the bottom of the feature. In one embodiment, spot locations such as spot locations 2504a, 2504b, and 2504d of scan pattern 2500, spot location 2504c of scan pattern 2600, spot locations 2504b and 2504d of scan pattern 2700, and spot location 2504 of scan pattern 2800 are considered to be located in the peripheral region of the feature boundary at the bottom of the feature (if such scan patterns 2500, 2600, 2700, or 2800 were actually scanned when the bottom of the feature was formed). In other embodiments, the spot locations of the peripheral cleanup scan pattern may be located within a local vicinity of the aforementioned spot locations. For illustrative purposes, if a spot in the peripheral region cleaning scan pattern is located within 1 μm of one of the aforementioned spot locations (for example, within 0.8 μm, 0.75 μm, 0.7 μm, 0.65 μm, 0.6 μm, 0.5 μm, 0.4 μm, 0.3 μm, 0.25 μm, 0.2 μm, 0.15 μm, 0.1 μm, 0.08 μm, 0.05 μm, 0.01 μm, or less than 0.01 μm of one of the aforementioned spot locations), it is considered to be located within the local vicinity of one of the aforementioned spot locations. When cleaning both the central and peripheral regions of a non-penetrating via, the peripheral region can be cleaned before or after cleaning the central region.

[0244] Generally, the laser pulses irradiated onto the spot position while scanning the peripheral region cleanup scan pattern irradiate one or more areas of the workpiece 102 at the feature boundary (for example, at or near the top of the feature). However, depending on one or more factors such as the spot size of the irradiated laser pulse, the spatial intensity distribution, the size and shape of the feature boundary at the top of the feature, the size and shape of the feature boundary at the bottom of the feature, the depth of the feature, or similar factors, or any combination thereof, the laser pulses can be irradiated onto the spot position of the central region cleanup scan pattern in such a way that they do not hit areas of the workpiece 102 at the feature boundary.

[0245] ii. Fine-tuning feature boundaries In one embodiment, the spot locations of the scan patterns described above adjacent to the desired feature boundary 2502 (e.g., spot locations 2504a, 2504b, and 2504d of scan pattern 2500, spot location 2504c of scan pattern 2600, spot locations 2504b and 2504d of scan pattern 2700, and spot location 2504 of scan pattern 2800) are positioned close enough to the desired feature boundary so that when one or more laser pulses are irradiated, material is removed from the workpiece 102 to form at least a portion of the desired feature boundary 2502. In other embodiments, the material removed from the workpiece 102 at such spot locations does not need to form a portion of the desired feature boundary. In any embodiment, a post-processing scan pattern (also referred to herein as a “boundary improvement scan pattern”) may be scanned, which includes one or more scan lines extending along at least a portion of the desired feature boundary (e.g., to improve the smoothness of the sidewalls, to improve the accuracy of the actually obtained feature boundary with respect to the shape of the desired feature boundary, or any combination thereof).

[0246] iii. Timing of post-processing In one embodiment, the post-processing method described above may be performed immediately after the feature is formed. That is, immediately after the last laser pulse is irradiated onto the spot location in the feature formation scan pattern, the first laser pulse may be irradiated onto the spot location in the post-processing scan pattern. For example, a boundary fine-tuning process or a central or peripheral region cleaning process may be performed immediately after the formation of a feature such as a non-penetrating via. In another embodiment, another processing method (e.g., a peripheral region cleaning process) may be performed immediately after the completion of a certain post-processing method (e.g., a central region cleaning process). Here, "immediately after" means that the time elapsed between the completion of the feature formation process (or the previously performed post-processing process) and the subsequent post-processing process is equal to (or at least substantially equal to) the shortest or longest positioning time (of the first positioner 106 during the feature formation process or the previously performed post-processing process) or the median or average value. In one embodiment, the positioning time of the first positioner 106 is shorter than 20 μs (or around that). For example, the positioning time of the first positioner 106 may be shorter than or equal to 15 μs, 10 μs, 5 μs, 3 μs, 2 μs, 1 μs, 0.8 μs, 0.5 μs, 0.3 μs, 0.1 μs, etc.

[0247] During feature formation, heat can accumulate in the area of ​​the workpiece 102 surrounding the feature being formed (for example, due to the absorption of energy from the irradiation laser pulse by one or more materials in the workpiece 102, or due to heat transfer through one or more materials in the workpiece 102). Therefore, the temperature of the area of ​​the workpiece 102 surrounding the feature being formed can rise significantly during feature formation. If it is desired to remove material (e.g., dielectric material) from one or more areas of the workpiece 102 at the feature boundary (for example, when post-processing to fine-tune the feature boundary), the accumulated thermal energy present in this removed material advantageously increases the efficiency of the post-processing.

[0248] However, if we want to remove material (e.g., residual material) at the bottom of a feature (for example, post-processing to clean the central or peripheral region at the bottom of a feature), the accumulated thermal energy present in one or more regions of the workpiece 102 (e.g., at or near the top of the feature) makes it easier to remove portions of the workpiece 102 at or near the top of the feature if the laser pulse irradiated onto the spot position during central or peripheral region cleaning irradiates such portions of the workpiece 102. As a result, the feature boundary at the top of the feature may be undesirably widened while scanning a post-processing scan pattern, such as a central region cleaning scan pattern or a peripheral region cleaning scan pattern.

[0249] To overcome the problems described above, a delay time may be inserted between the completion of the feature formation process (or a previously performed post-processing process) and a subsequent post-processing process, such as a central region cleaning process or a peripheral region cleaning process. The duration of the delay time is selected or set to allow thermal energy to be released within the workpiece 102 (e.g., above or near the feature) so that areas of the workpiece 102 above or near the feature are not removed when irradiated by laser pulses during central or peripheral region cleaning (i.e., so that areas of the workpiece 102 above or near the feature are cooled). Generally, the delay time is longer than the shortest or longest positioning time (e.g., the median or average value of the first positioner 106 during the feature formation process or a previously performed post-processing process). In one embodiment, if the positioning time is less than 20 μs (or around that), the delay time is longer than 20 μs (or around that). For example, the delay time may be longer than or equal to 22 μs, 25 μs, 30 μs, 35 μs, 40 μs, 45 μs, 50 μs, 55 μs, 60 μs, etc. It should be understood that the delay time can be selected or set depending on one or more factors, such as the thermal conductivity, thermal diffusivity, specific heat capacity, viscosity of the material of the workpiece 102 above or near the features, the pulse duration, fluence, pulse repetition rate of the laser pulses irradiated during post-processing, the desired throughput when processing the workpiece 102 (including forming and post-processing multiple features), or any combination thereof.

[0250] X. Embodiments relating to the removal of by-products When one or more features such as openings, slots, vias, holes, grooves, trenches, scribe lines, kerfs, recesses, etc. are formed in the workpiece 102 as a result of laser processing, by-products such as vapor (including particles having a maximum cross-sectional dimension ranging from about 0.01 μm to about 4 μm), dust (including particles having a maximum cross-sectional dimension ranging from about 0.1 μm to about 0.7 mm), workpiece fragments or other debris (having a maximum cross-sectional dimension greater than about 0.7 μm) can be generated. In some cases (e.g., during a drilling process or a cutting process), such by-product materials are ejected from the workpiece 102 and reattach to the workpiece surface 102a of the workpiece 102. In other cases (e.g., during a cutting process for forming a through hole or other feature that penetrates the workpiece 102), one or more fragments or other debris do not eject from the workpiece 102 but rather remain simply attached to the workpiece 102 (e.g., in a kerf formed in the workpiece 102 during the cutting process). Depending on the size of the through hole or other feature that penetrates the workpiece 102, the workpiece fragments or other debris of the workpiece 102 can have a maximum dimension significantly larger (e.g., at least one order of magnitude) than the spot size of the laser energy irradiated during processing. In order to facilitate the removal of such by-products, a by-product removal system may be provided.

[0251] In one embodiment, referring to FIG. 38, a by-product removal system 3800 can be provided that includes a frame 3802 for supporting the workpiece 102, an air knife 3804 disposed on the frame 3802, and a collection bin 3806 disposed below the frame 3802.

[0252] When the workpiece 102 is supported by the frame 3802, the workpiece 102 (e.g., PCB, FPC, lead frame blank, etc.) will have been processed and may contain vapors and dust that have fallen onto the work surface 102a. When the workpiece 102 has been processed to form through-holes or other features, one or more fragments or other pieces may remain in the through-holes or adhere to the workpiece 102 (e.g., in grooves formed in the workpiece 102 during the cutting process). The workpiece 102 can be transferred from the laser processing apparatus onto the frame 3802 by a transfer mechanism such as a robotic arm (e.g., equipped with end effectors for engaging the workpiece at its ends), a roll-to-roll handling system, or any combination thereof. In this case, the transfer mechanism may be controlled in response to one or more control signals output by the controller 114, or by other controllers, or any combination thereof.

[0253] In one embodiment, the air knife 3804 is connected to an actuator (not shown) and one or more linear stages or other mechanical linkages (e.g., guide rails) that allow the air knife 3804 to move on the workpiece 102 (for example, along the X-axis, or along the Y-axis, or along any combination thereof, as indicated by arrow 3808) while keeping the workpiece 102 stationary. In another embodiment, the frame 3802 is connected to an actuator (not shown) and one or more linear stages or other mechanical linkages (e.g., guide rails) that allow the frame 3802 (and thus the workpiece 102) to move (for example, along the X-axis, or along the Y-axis, or along any combination thereof, as indicated by arrow 3808) below the air knife 3804. In any embodiment, the actuator may be controlled in response to one or more control signals output by the controller 114, or by other controllers, or by any combination thereof.

[0254] The air knife 3804 may be provided as a compressed air-driven air knife, a blower-driven air knife, or any combination thereof, and includes a nozzle 3804a configured to generate a high-pressure airflow or gasflow on the workpiece surface 102a with sufficient force to blow away dust or vapor particles that have fallen on the workpiece surface 102a, or to remove debris or fragments adhering to the workpiece 102. The removed debris or other fragments (generally indicated as 3810) fall into the collection 3806 (for example, due to gravity, or the high-pressure flow generated by the air knife 3804, or any combination thereof). In one embodiment, an automated optical inspection (AOI) system (not shown) may be provided to verify that the by-products have been removed as desired. The air knife 3804 and the optional AOI system may be controlled in response to one or more control signals output by the controller 114, or by other controllers, or any combination thereof.

[0255] After the processed workpiece 102 is exposed to the high-pressure flow generated by the air knife 3804, the workpiece 102 may be transferred (for example, to a storage bay of a material handling device such as the material handling device 800, or to a similar location to return it to the laser processing device for further processing).

[0256] XI. Embodiments relating to the use of multiple laser sources Some workpieces can be characterized as having a heterogeneous composition or as being composite materials. Examples of such workpieces include PCB panels, PCBs, glass fiber reinforced epoxy laminates, prepregs, build-up materials, FPCs, ICs, ICPs, LEDs, and LED packages. Sometimes, such heterogeneous or composite workpieces (collectively referred to herein as “composite workpieces”) are formed from components that are not transparent to the wavelength of the laser pulse irradiated onto the workpiece 102 (i.e., referred herein as “opaque workpiece components”), in addition to one or more components that are transparent to the wavelength of the laser pulse irradiated onto the workpiece 102 (i.e., referred herein as “transparent workpiece components”). In this sense, components of the workpiece 102 can be considered transparent workpiece components if they are formed from a material having a linear absorption spectrum of a specific bandwidth of the irradiated laser pulse and a thickness such that the percentage of light transmitted through the material (e.g., along the beam axis) is greater than 10%, greater than 25%, greater than 50%, greater than 75%, greater than 80%, greater than 85%, greater than 90%, greater than 95%, greater than 98%, or greater than 99%.

[0257] As can be understood, it can be difficult to efficiently process composite workpieces having components formed from materials transparent to the wavelength of the irradiating laser pulse, especially when the pulse duration of the irradiating laser pulse is longer than several tens of picoseconds. While transparent workpiece components can be effectively processed via nonlinear absorption by using "ultrashort" laser pulses (i.e., laser pulses with pulse durations of less than several tens of picoseconds, often in the femtosecond range), using ultrashort laser pulses to process composite workpieces is not satisfactory because the amount of material removed by each ultrashort laser pulse is relatively small. Considering these problems, one embodiment of the present invention provides an apparatus having multiple laser sources (referred to herein as a "multi-source apparatus") for processing composite workpieces (composed of both transparent and opaque workpiece components).

[0258] For example, referring to Figure 30, one embodiment of a multi-source apparatus such as apparatus 3000 may include a first laser source 3002a and a second laser source 3002b. Generally, each of the first laser source 3002a and the second laser source 3002b is capable of generating sufficient laser energy to process the opaque workpiece components of the composite workpiece. In addition, the first laser source 3002a is also generally capable of generating sufficient laser energy to process the transparent workpiece components of the composite workpiece.

[0259] Generally, each of the first laser source 3002a and the second laser source 3002b may be provided as exemplified above with respect to the laser source 104. Thus, each of the first laser source 3002a and the second laser source 3002b may include pulsed laser sources, CW laser sources, QCW laser sources, burst-mode laser sources, or any combination thereof. If either the first laser source 3002a or the second laser source 3002b includes a QCW laser source or a CW laser source, such a laser source may optionally include a pulse gating unit (e.g., an acousto-optic (AO) modulator (AOM), a beam chopper, etc.) that temporally modulates the beam of laser radiation output from the QCW laser source or CW laser source. In one embodiment, each of the first laser source 3002a and the second laser source 3002b is provided as a pulsed laser source. In other embodiments, the first laser source 3002a is provided as a pulsed laser source, and the second laser source 3002b is provided as a QCW laser source or a CW laser source, and includes a pulse gating unit that temporally modulates the beam of laser radiation output from the QCW laser source or CW laser source.

[0260] Furthermore, depending on the properties and composition of the various components of the synthetic workpiece, the second laser source 3002b may be capable of generating sufficient laser energy to process the transparent workpiece components of the synthetic workpiece. For example, during processing of a synthetic workpiece (e.g., a glass fiber reinforced epoxy laminate) having transparent workpiece components (e.g., glass fibers) embedded in (or in contact with) opaque workpiece components (e.g., a resin material), the opaque workpiece components may be directly processed (e.g., melted, evaporated, ablated, carbonized, etc.) when exposed to laser energy generated by the first laser source 3002a or the second laser source 3002b. During or as a result of the direct processing of the opaque workpiece components, the transparent workpiece components may be indirectly processed (e.g., via photo-induced or thermally induced chemical reactions between the transparent and opaque workpiece components). For example, the transparent workpiece components may be scratched, heated, or decolorized, or coated (e.g., with opaque workpiece components or residues of opaque workpiece components). Indirect processing of such transparent workpiece components can facilitate subsequent processing under the direct influence of laser energy generated by the second laser source 3002b. Depending on the properties and composition of the various components of the composite workpiece, such subsequent direct processing may be important.

[0261] Generally, the first laser source 3002a can output a laser pulse having a first pulse duration, and the second laser source 3002b can output a laser pulse having a second pulse duration longer than the first pulse duration. For example, the first pulse duration may be shorter than 500 ps (for example, shorter than 450 ps, ​​25 ps, 15 ps, 10 ps, ​​7 ps, 5 ps, 4 ps, 3 ps, 2 ps, 1 ps, 900 fs, 850 fs, 750 fs, 700 fs, 500 fs, 400 fs, 300 fs, 200 fs, 150 fs, 100 fs, 50 fs, 30 fs, 15 fs, 10 fs, etc., or a value between any of these values). In one embodiment, the second pulse duration may be longer than or equal to 500 ps (for example, longer than or equal to 600 ps, ​​700 ps, ​​800 ps, ​​900 ps, ​​1 ns, 1.5 ns, 2 ns, 5 ns, 10 ns, 20 ns, 50 ns, 100 ns, 200 ns, 400 ns, 800 ns, 1000 ns, 2 μs, 5 μs, 10 μs, 50 μs, 100 μs, 200 μs, 300 μs, 500 μs, 900 μs, 1 ms, 2 ms, 5 ms, 10 ms, 20 ms, 50 ms, 100 ms, 300 ms, 500 ms, 900 ms, 1 s, etc., or a value between any of these values). In other embodiments, the second laser source 3002b is provided as a QCW laser source or a CW laser source and does not include a pulse gating unit (for example, so that the second laser source 3002b can generate a QCW laser energy beam or a CW laser energy beam).

[0262] Generally, the first laser source 3002a is capable of outputting laser pulses at a first pulse repetition rate, and the second laser source 3002b is capable of outputting laser pulses at a first pulse repetition rate higher than the first pulse repetition rate. For example, the second pulse repetition rate may be higher than or equal to 100 kHz (e.g., higher than or equal to 150 kHz, 250 kHz, 500 kHz, 800 kHz, 900 kHz, 1 MHz, 2 MHz, 10 MHz, 20 MHz, 50 MHz, 70 MHz, 100 MHz, 150 MHz, 200 MHz, etc., or any of these values). In one embodiment, the second pulse repetition rate is equal to 150 MHz (or around that), and the first pulse repetition rate is equal to 1 MHz (or around that). Alternatively, the first laser source 3002a and the second laser 3002b may be capable of outputting laser pulses at the same (or at least substantially the same) pulse repetition rate.

[0263] In one embodiment, the first laser source 3002a and the second laser source 3002b are capable of generating laser energy beams having at least substantially the same wavelength and at least substantially the same spectral bandwidth (when measured by FWHM). For example, the first laser source 3002a and the second laser source 3002b are capable of generating laser energy beams having one or more wavelengths in the visible light (e.g., green) region of the electromagnetic spectrum. In other embodiments, at least one of the wavelength and spectral bandwidth of the laser energy generated by the first laser source 3002a may differ from that of the laser energy generated by the second laser source 3002b (for example, it may be greater, less, or any combination thereof).

[0264] Although not shown in the figures, the apparatus 3000 also includes one or more optical elements (e.g., beam expanders, beam shapers, apertures, harmonic generating crystals, filters, collimators, lenses, mirrors, polarizers, waveplates, diffractive optical elements, refractive optical elements, or any combination thereof) that focus, expand, collimate, shape, polarize, filter, split, combine, crop, or modify, adjust, or direct the laser energy generated by the first laser source 3002a and propagating along the first pre-beam path 3004a. Similarly, the apparatus 3000 may include one or more optical elements that focus, expand, collimate, shape, polarize, filter, split, combine, crop, or modify, adjust, or direct the laser energy generated by the second laser source 3002b and propagating along the second pre-beam path 3004b.

[0265] The laser energy propagating along the first pre-beam path 3004a and the second pre-beam path 3004b may be spatially coupled in any preferred manner. For example, a return mirror 3006 may be provided to direct the second pre-beam path 3004b toward a beam combiner 3008 located on the first pre-beam path 3004a. Upon exiting the beam combiner 3008, the laser energy may propagate along beam path 116c (corresponding, for example, to beam path 116 shown in Figure 1) to a beam propagation system such as the first beam propagation system 3010.

[0266] Generally, the first beam propagation system 3010 may include one or more positioners provided as exemplary above, such as the first positioner 106, the second positioner 108, or any combination thereof. However, in some embodiments, the beam combiner 3008 may change the polarization state of the laser energy propagating along the first preliminary beam path 3004a or the second preliminary beam path 3004b. As a result, the laser energy propagating along the beam path 116c can be characterized by a plurality of polarization states (e.g., p-polarization state, s-polarization state, or states between any of these values). In such embodiments, the first beam propagation system 3010 does not include components that are relatively responsive to the polarization state of the incident laser energy (e.g., an AOD system that is generally responsive in operation to laser energy exhibiting linear polarization at a particular orientation). Rather, the first beam propagation system 3010 includes one or more components that are relatively unresponsive to polarization, such as a galvanometer mirror system, a MEM mirror or mirror array, an FSM, or any combination thereof.

[0267] Although not shown in the illustration, the apparatus 3000 may additionally include the third positioner 110 described above, a scanning lens (e.g., the scanning lens 112 described above), a controller (e.g., the controller 114 described above), or other components previously mentioned with respect to the apparatus 100 or 700, or any combination thereof.

[0268] In one embodiment, the controller 114 controls the operation of the first laser source 3002a and the second laser source 3002b to enable setting or adjustment of a temporal offset (or temporal overlap) between one or more laser pulses generated by the first laser source 3002a and one or more laser pulses generated by the second laser source 3002b. To facilitate such setting or adjustment, in one embodiment, the apparatus 3000 may further include one or more synchronization devices, oscillators, etc., as described in International Patent Application Publication No. WO2015 / 108991. This publication is incorporated herein by reference in its entirety.

[0269] In other embodiments, the controller 114 does not control the operation of the first laser source 3002a and the second laser source 3002b to enable setting or adjustment of the temporal offset (or temporal overlap) between the laser pulses generated by the first laser source 3002a and the laser pulses generated by the second laser source 3002b. In this case, the apparatus 3000 does not include a synchronization device, oscillator, etc., as described in International Patent Application Publication WO2015 / 108991. Rather, the relative operation control of the first laser source 3002a and the second laser source 3002b is performed regardless of the temporal relationship between the laser pulses generated by the first laser source 3002a and the generation of laser energy (which may be pulsed or continuous) by the second laser source 3002b. Therefore, the first laser source 3002a may be operated to generate laser energy regardless of whether the second laser source 3002b is operated to generate laser energy or not. The trigger signals transmitted to the first laser source 3002a and the second laser source 3002b may be synchronized with each other by any preferred or desirable method, or they may not be synchronized at all.

[0270] As described above, the laser energy propagating along the beam path 116c may include multiple polarization states. Instead of limiting the components in the first beam propagation system 3010 to those that are relatively unresponsive to polarization, a multi-source device can be provided to modify the polarization state of the laser energy transmitted by the beam combiner 3008. For example, referring to Figure 31, one embodiment of a multi-source device, such as device 3100, may be provided as described above with respect to device 3000, but may further include a waveplate 3102 (e.g., a half-waveplate) positioned in the beam path 116c to change the polarization state of the laser energy transmitted by the beam combiner 3008, and a polarizer 3104 for filtering a portion of the laser energy propagated by the waveplate 3102. The laser energy transmitted by the polarizer 3104 can then propagate along the beam path 116d (e.g., corresponding to the beam path 116 shown in Figure 1) to the first beam propagation system 3010. In one embodiment, one or both of the waveplate 3102 and polarizer 3104 can be adjusted (for example, rotated around the axis of the beampath 116c) to adjust the ratio of the amount of power in the laser energy beam propagating along the beampath 116d originating from the second laser source 3002b to the amount of power in the laser energy beam propagating along the beampath 116d originating from the first laser source 3002a. Thus, the laser energy propagating along the beampath 116d may include powers originating from the first and second laser sources in a 50:50 mixture ratio, or other suitable or desirable ratios (e.g., 60:40, 70:30, 80:20, 90:10, 10:90, 20:80, 30:70, 40:60, or any of these values). In this embodiment, the first beam propagation system 3010 may be provided as described above with respect to the apparatus 3000, or the first beam propagation system 3010 may be provided to include one or more components with good polarization response, such as the AOD system described exemplified above.

[0271] In other embodiments, referring to Figure 32, one embodiment of a multi-source apparatus such as apparatus 3200 may be provided as described above with respect to apparatus 3100, but may further include a second beam propagation system 3202 optically coupled to the polarizer 3104 (e.g., via beam path 116d2), and the first beam propagation system 3010 is optically coupled to the polarizer 3104 via beam path 116d1. The second beam propagation system 3202 may be configured in the same way as (or differently from) the first beam propagation system 3010. In the embodiment shown in Figure 32, beam paths 116d1 and 116d2 each correspond to different examples of beam path 116 shown in Figure 1. In this embodiment, the waveplate 3102 and polarizer 3104 (referred to here as a polarizing beam splitter cube) are configured such that each of the beam paths 116d1 and 116d2 includes half (or at least approximately half) of the optical power originating from the first laser source 3002a and half (or at least approximately half) of the optical power originating from the second laser source 3002b. An additional waveplate 3204 (e.g., a half-waveplate) is placed in beam path 116d1 to change the polarization state of the laser energy transmitted by the polarizing beam splitter cube 3104.

[0272] In other embodiments, within the apparatus 3200, the half-wave plate 3102, polarizer 3104, and half-wave plate 3204 may be omitted and replaced with a spinning chopper mirror, rotating polyhedron mirror, resonant galvanometer mirror system, or any combination thereof, to distribute the laser energy along the beam paths 116d1 and 116d2. In this case, the first beam propagation system 3010 and the second beam propagation system 3202 do not include any components that are highly sensitive to polarization.

[0273] In other embodiments, referring to Figure 33, one embodiment of a multi-source device such as device 3300 may include a beam distributor 3302 configured to direct laser pulses output by a first laser source 3002a and a second laser source 3002b in various directions to a first beam propagation system 3010, a second beam propagation system 3202, or any combination thereof. In this case, the beam distributor 3302 may include an AO cell 3304, an ultrasonic transducer element 3306 acoustically coupled to one side of the AO cell 3304, and an absorber 3308 acoustically coupled to the other side of the AO cell 3304 opposite the ultrasonic transducer element 3306.

[0274] As shown in the figure, the first laser source 3002a and the second laser source 3002b may be aligned (or one or more optical elements may be provided) so that the laser pulses propagating along the first pre-beam path 3004a and the second pre-beam path 3004b can completely (or at least substantially completely) overlap each other in a region (e.g., shown as black dots) within the AO cell 3304. Furthermore, the light in the laser pulses propagating along the first pre-beam path 3004a and the second pre-beam path 3004b can be generated or tuned in any preferred way to have the polarization state necessary for favorably diffracted within the AO cell 3304 or favorably diffracted by the first beam propagation system 3010 or the second beam propagation system 3202.

[0275] When driven by an applied RF signal, the ultrasonic transducer element 3306 generates sound waves within the AO cell 3304, where the power of the applied RF signal is modulated (while maintaining a constant RF frequency) to control the power of the deflected laser pulse within the AO cell 3304. If no RF signal is applied, no sound waves are generated by the ultrasonic transducer element 3306 within the AO cell 3304, and the laser pulses generated by the first laser source 3002a and the first laser source 3002b are incident on the AO cell 3304, pass through the AO cell 3304, and reach the first beam propagation system 3010 and the second beam propagation system 3202, respectively. For example, if there is no RF signal laser applied to the ultrasonic transducer element 3306, the laser pulse propagating along the first preliminary beam path 3004a passes through the AO cell 3304 and propagates along beam path 116d1 to the first beam propagation system 3010. Similarly, the laser pulse propagating along the second preliminary beam path 3004b passes through the AO cell 3304 and propagates along beam path 116d2 to the second beam propagation system 3202. In this way, beam path 116d1 constitutes the zero-order beam path for the first laser source 3002a, and beam path 116d2 constitutes the zero-order beam path for the second laser source 3002b.

[0276] When an RF signal having a first power level (e.g., "full power level") is applied to the ultrasonic transducer element 3306, most of the power of the laser pulse propagating along the first preliminary beampath 3004a (e.g., about 90%) is deflected by the AO cell 3304 and propagates along the beampath 116d2 to the second beam propagation system 3202. Similarly, most of the power of the laser pulse propagating along the second preliminary beampath 3004b (e.g., about 90%) is deflected by the AO cell 3304 and propagates along the beampath 116d1 to the first beam propagation system 3010. In this case, the residual power (e.g., about 10%) of the laser pulse propagating along the first preliminary beam path 3004a passes through the AO cell 3304 and propagates along the beam path 116d1 to the first beam propagation system 3010, and similarly, the residual power (e.g., about 10%) of the laser pulse propagating along the second preliminary beam path 3004b passes through the AO cell 3304 and propagates along the beam path 116d2 to the first second propagation system 3202.

[0277] Considering the above, it can be understood that when the ultrasonic transducer element 3306 is driven at full power, approximately 90% of the power of the laser pulse generated by the first laser source 3002a and approximately 10% of the power of the laser pulse generated by the second laser source 3002b are propagated to the second beam propagation system 3202, and approximately 90% of the laser pulse generated by the second laser source 3002b and approximately 10% of the power of the laser pulse generated by the first laser source 3002a are propagated to the first beam propagation system 3010. The amount of power of the laser pulse generated by any single laser source and ultimately propagated to the first beam propagation system 3010 and the second beam propagation system 3202 can be further modulated by changing the power of the RF signal applied to the ultrasonic transducer element 3306. For example, when an RF signal having a second power level of 50% of the first power level is applied to the ultrasonic transducer element 3306, approximately 50% of the power of the laser pulses generated by the first laser source 3002a and the second laser source 3002b is propagated to the first beam propagation system 3010 and the second beam propagation system 3202. The power level of the applied RF signal can be kept constant while processing the workpiece 102 to form features, or the power level of the applied RF signal can be varied during the formation of individual features.

[0278] Although the multi-source device 3300 is described as including both the first beam propagation system 3010 and the second beam propagation system 3202, it can be understood that the multi-source device 3300 may include only the first beam propagation system 3010 or only the second beam propagation system 3202. In such cases, the omitted beam propagation system can be replaced with a beam dump.

[0279] Generally, the rate at which the power of the applied RF signal can be changed to modulate the power of the laser pulses propagated from the first laser source 3002a or the second laser source 3002b to the first beam propagation system 3010 or the second beam propagation system 3202 (also called the "modulation speed") is in the range of 50 kHz (or around) to 10 MHz (or around). In one embodiment, the modulation speed is in the range of 100 kHz (or around) to 2 MHz (or around). In other embodiments, the modulation speed is 1 MHz (or around). In this way, the relative power levels of the laser pulses generated by the first laser source 3002a and the second laser source 3002b and ultimately propagated to either the first beam propagation system 3010 or the second beam propagation system 3202 can be rapidly changed during processing of the workpiece 102 simply by modulating the power level of the RF signal applied to the ultrasonic transducer element 3306.

[0280] For e...

Claims

1. A device for laser processing a workpiece, A laser source that operates to generate a laser energy beam, A scanning lens is positioned in a beam path along which the laser energy beam can propagate to the workpiece, A first positioner positioned in the beam path between the laser source and the scanning lens, the first positioner being positioned and operating to deflect the beam path along a first direction, A second positioner positioned in the beam path between the first positioner and the scan lens, the second positioner being positioned and operating to deflect the beam path along a second direction, A controller that is communicatively connected to the first positioner and the second positioner, and is configured to control the operation of the first positioner and the second positioner so as to deflect the beam path within a two-dimensional scanning range. Equipped with, The maximum range of the two-dimensional scanning range along the first direction is smaller than the maximum range of the two-dimensional scanning range along the second direction. Device.

2. The apparatus according to claim 1, wherein the laser source operates to generate a laser energy beam represented as a series of laser pulses.

3. The apparatus according to claim 1, wherein the laser source operates to generate a laser energy beam that can be expressed as a continuous wave (CW) or quasi-continuous wave (QCW) laser energy beam.

4. The apparatus according to claim 1, wherein the first direction is perpendicular to the second direction.

5. The apparatus according to claim 1, wherein the first positioner is a galvanometer mirror system.

6. The apparatus according to claim 1, wherein the second positioner is a galvanometer mirror system.

7. The apparatus according to claim 1, further comprising a third positioner that operates to move the workpiece relative to the scanning lens, the third positioner that operates to move the workpiece within a scanning range larger than the two-dimensional scanning range in at least one of the first and second directions.

8. A non-transient computer-readable medium used in conjunction with the controller described in claim 1, A non-transient computer-readable medium storing a command that, when executed by the controller, causes the controller to operate the first positioner such that the maximum range of the two-dimensional scanning range along the first direction is smaller than the maximum range of the two-dimensional scanning range along the second direction.

9. A device for laser processing a workpiece, A laser source that operates to generate a laser energy beam, A first positioner positioned in a beam path along which the laser energy beam can propagate to the workpiece, the first positioner being positioned and operating to deflect the beam path relative to the workpiece within a two-dimensional scanning range, A second positioner is positioned and operates to variably position the workpiece within the two-dimensional scanning range, causing relative movement between the workpiece and the two-dimensional scanning range. A controller, which is communicatively connected to the first positioner and the second positioner, is configured to control the operation of the first positioner so as to deflect the laser energy beam within the two-dimensional scanning range such that the maximum range of the two-dimensional scanning range along the first direction is smaller than the maximum range of the two-dimensional scanning range along the second direction. A device equipped with the following features.

10. The apparatus according to claim 9, wherein the controller is further configured to cause a relative movement between the workpiece and the two-dimensional scanning range along a first direction, while operating the first positioner to deflect the laser energy beam within the two-dimensional scanning range.

11. The apparatus according to claim 9, wherein the controller is further configured to cause a relative movement between the workpiece and the two-dimensional scanning range along the second direction, while operating the first positioner to deflect the laser energy beam within the two-dimensional scanning range.

12. The apparatus according to claim 9, wherein the laser source operates to generate a laser energy beam represented as a series of laser pulses.

13. The apparatus according to claim 9, wherein the laser source operates to generate a laser energy beam that can be expressed as a continuous wave (CW) or quasi-continuous wave (QCW) laser energy beam.

14. The apparatus according to claim 9, wherein the first positioner includes a galvanometer mirror system.

15. The apparatus according to claim 9, further comprising a third positioner positioned in the beam path between the laser source and the first positioner, the third positioner operating to deflect the beam path within a scanning range smaller than the two-dimensional scanning range in both the first and second directions.

16. A non-transient computer-readable medium used in conjunction with the controller described in claim 9, A non-transient computer-readable medium storing a command that, when executed by the controller, causes the controller to operate the first positioner such that the maximum range of the two-dimensional scanning range along the first direction is smaller than the maximum range of the two-dimensional scanning range along the second direction.

17. A device for laser processing a workpiece, A laser source that operates to generate a laser energy beam, A first positioner positioned in a beam path along which the laser energy beam can propagate to the workpiece, the first positioner being positioned and operating to deflect the beam path relative to the workpiece within a two-dimensional scanning range, A second positioner is positioned and operates to variably position the first positioner relative to the workpiece so as to cause relative movement between the workpiece and the two-dimensional scanning range. A controller, which is communicatively connected to the first positioner and the second positioner, is configured to control the operation of the first positioner so as to deflect the laser energy beam within the two-dimensional scanning range such that the maximum range of the two-dimensional scanning range along the first direction is smaller than the maximum range of the two-dimensional scanning range along the second direction. A device equipped with the following features.

18. The apparatus according to claim 17, wherein the controller is further configured to cause a relative movement between the workpiece and the two-dimensional scanning range along the first direction, while operating the first positioner to deflect the laser energy beam within the two-dimensional scanning range.

19. The apparatus according to claim 17, wherein the controller is further configured to cause relative movement along the second direction between the workpiece and the two-dimensional scanning range, while operating the first positioner to deflect the laser energy beam within the two-dimensional scanning range.

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