Laser processing apparatus using ultrafast laser and methods of operating the same

Abstract

A laser drilling system includes a laser source configured to generate a pulsed laser beam, a beam steering system configured to direct the pulsed laser beam at a first surface of a substrate, and a controller. The substrate comprises a conductive layer at a second surface opposite the first surface and a dielectric structure positioned between the conductive layer and the first surface. The controller is configured to control the pulsed laser source and beam steering system to remove material from the dielectric structure to form a via, vaporize a first region of the dielectric structure at the conductive layer to generate a high-pressure region, and heat a third region such that a second region is ejectable when pressure of the vaporized first region exceeds the strength of the heated third region.

Description

Docket Number: 00809-WOLASER PROCESSING APPARATUS USING ULTRAFAST LASER AND METHODS OF OPERATING THE SAMEFIELD OF INVENTION

[0001] Embodiments of the present disclosure relate to apparatus and techniques for laser-processing workpieces.BACKGROUND

[0002] Laser processing is often used in various industries, including electronics manufacturing, materials processing, and precision engineering. This versatile technique utilizes focused laser energy to modify, cut, or shape materials with high precision and efficiency. As the demand for miniaturization and complex designs in electronic devices continues to grow, laser processing has emerged as a tool for creating intricate features and structures at micro and nanoscales.

[0003] Ultrafast lasers have the ability to deliver extremely short pulses of light. These lasers, operating in the femtosecond to picosecond range, offer advantages such as reduced heat-affected zones, improved precision, and the ability to process a wide range of materials, including those traditionally considered difficult to machine. As a result, ultrafast laser processing has found applications in diverse areas, from semiconductor manufacturing to biomedical device fabrication, opening new possibilities for advanced material processing and manufacturing techniques.SUMMARY

[0004] The summary is a high-level overview of various aspects of the invention and introduces some of the concepts that are further detailed in the Detailed Description section below. This summary is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used in isolation to determine the scope of the claimed subject matter. The subject matter should be understood by reference to the appropriate portions of the entire specification, any or all drawings, and each claim.

[0005] The present disclosure provides a laser drilling system, including: a laser source configured to generate a pulsed laser beam; a beam steering system configured to direct the pulsed laser beam at a first surface of a substrate, where the substrate includes: a conductive layer at a second surface of the substrate opposite the first surface, and a dielectric structure positioned between the conductive layer and the first surface of the substrate; a controllerDocket Number: 00809-WOconfigured to control the pulsed laser source and the beam steering system to: remove material from the dielectric structure to form a via extending from the surface towards the second surface; vaporize a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure, heat a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the workpiece due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure, where the third region of the dielectric structure includes a plurality of irregularly distributed fibers.

[0006] In some embodiments, the second region of the dielectric structure is adjacent to the first region of the dielectric structure.

[0007] In some embodiments, the pulsed laser beam has a wavelength in the green range of the electromagnetic spectrum.

[0008] In some embodiments, the pulsed laser beam has a pulse width of 100 fs to 100 ps.

[0009] In some embodiments, the pulsed laser beam has a pulse width of 300 fs to 15 ps.

[0010] In some embodiments, the pulsed laser beam has a repetition rate of 2 MHz to 50 MHz.

[0011] In some embodiments, the pulsed laser beam has a repetition rate of 5 MHz to 25 MHz.

[0012] In some embodiments, the pulsed laser beam has a fluence of 0.1 J / cm2to 25 J / cm2.

[0013] In some embodiments, the pulsed laser beam has a fluence of 3 J / cm2to 10 J / cm2.

[0014] In some embodiments, the controller is further configured to heat the third region of the dielectric structure to a melting point before the pressure of the vaporized first region exceeds an adhesion strength of the first region of the dielectric structure to the conductive layer.

[0015] In some embodiments, the via has a diameter of 5 pm to 250 pm.

[0016] In some embodiments, the via has a diameter of 20 pm to 80 pm.Docket Number: 00809-WO

[0017] In some embodiments, the controller may be further configured to: control the laser source to generate a first set of laser pulses to vaporize the first region of the dielectric structure; and control the laser source to generate a second set of laser pulses to heat the second region of the dielectric structure.

[0018] In some embodiments, the first set of laser pulses may have a different pulse energy, pulse duration, or repetition rate than the second set of laser pulses.

[0019] In some embodiments, the beam steering system includes a galvanometer.

[0020] In some embodiments, the beam steering system includes at least one acoustooptic deflector system operative to deflect the beam path.

[0021] In some embodiments, the laser source may include an ultrafast laser capable of generating pulses with durations in the femtosecond to picosecond range.

[0022] In some embodiments, the dielectric structure may include a glass-reinforced epoxy laminate material.

[0023] The present disclosure provides a method of laser drilling, including: directing a pulsed laser beam at a first surface of a substrate, where the substrate includes a conductive layer at a second surface opposite the first surface and a dielectric structure positioned between the conductive layer and the first surface; removing material from the dielectric structure to form a via extending from the first surface towards the second surface; vaporizing a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure; and heating a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the substrate due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure.

[0024] In some embodiments, the third region of the dielectric structure includes a plurality of irregularly distributed fibers.

[0025] In some embodiments, the pulsed laser beam has a wavelength in the green range of the electromagnetic spectrum.

[0026] In some embodiments, the pulsed laser beam has a pulse width of 100 fs to 100 ps.

[0027] In some embodiments, the pulsed laser beam has a repetition rate of 2 MHz to 50 MHz.Docket Number: 00809-WO

[0028] In some embodiments, the pulsed laser beam has a fluence of 0.1 J / cm2to 25 J / cm2.

[0029] In some embodiments, the method further includes heating the third region of the dielectric structure to a melting point before the pressure of the vaporized first region exceeds an adhesion strength of the first region of the dielectric structure to the conductive layer.

[0030] In some embodiments, the via has a diameter of 5 pm to 250 pm.

[0031] In some embodiments, the method further includes: generating a first set of laser pulses to vaporize the first region of the dielectric structure; and generating a second set of laser pulses to heat the second region of the dielectric structure.

[0032] In some embodiments, the first set of laser pulses has a different pulse energy, pulse duration, or repetition rate than the second set of laser pulses.

[0033] In some embodiments, the method further includes steering the pulsed laser beam using a galvanometer.

[0034] In some embodiments, the method further includes steering the pulsed laser beam using at least one acousto-optic deflector system.

[0035] In some embodiments, the method further includes employing a layer-by-layer drilling approach for multi-layer substrates with alternating conductive and dielectric layers.

[0036] In some embodiments, the method further includes performing automated quality checks upon completion of a drilling program.

[0037] In some embodiments, the dielectric structure includes a glass-reinforced epoxy laminate material.

[0038] The present disclosure further provides a method of laser drilling, including: generating a first pulsed laser beam from a first laser source; generating a second pulsed laser beam from a second laser source; directing the first and second pulsed laser beams at a first surface of a substrate, where the substrate includes: a first conductive layer at the first surface, a second conductive layer at a second surface of the substrate opposite the first surface, and a dielectric structure positioned between the first conductive layer and the second conductive layer; controlling the first laser source to generate the first pulsed laser beam at a first repetition rate to remove material from the conductive layer; dynamically switching from the first laser source to the second laser source; controlling the second laser source to generate the second pulsed laser beam at a second repetition rate to remove materialDocket Number: 00809-WOfrom the dielectric structure, where the second repetition rate is different from the first repetition rate; and vaporizing a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure; and heating a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the substrate due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure.BRIEF DESCRIPTION OF FIGURES

[0039] The accompanying drawings are included to provide a further understanding of the disclosure and are incorporated in and constitute a part of this specification, illustrate embodiments, and together with the description serve to explain the principles of the present disclosure.

[0040] FIG. l is a schematic illustrating a laser processing apparatus according to embodiments of the present disclosure.

[0041] FIG. 2 is a graph showing copper ablation efficiency vs. repetition rate and fluence for a green laser at 500 fs pulses according to embodiments of the present disclosure.

[0042] FIG. 3 is a cross-sectional view of a workpiece according to embodiments of the present disclosure.

[0043] FIG. 4 is a cross-sectional view of a workpiece including a feature formed therein using the laser processing apparatus according to embodiments of the present disclosure.

[0044] FIG. 5 is a cross-sectional view of a workpiece according to embodiments of the present disclosure.

[0045] FIG. 6 is a cross-sectional view of a workpiece including a feature formed therein using the laser processing apparatus according to embodiments of the present disclosure.

[0046] FIG. 7 is a cross-sectional view of a workpiece undergoing the laser drilling process according to embodiments of the present disclosure.

[0047] FIG. 8 is a cross-sectional view of a workpiece undergoing the laser drilling process according to embodiments of the present disclosure.

[0048] FIG. 9 is a cross-sectional view of a workpiece undergoing the laser drilling process according to embodiments of the present disclosure.Docket Number: 00809-WO

[0049] FIG. 10 is a cross-sectional view of a workpiece undergoing the laser drilling process according to embodiments of the present disclosure.

[0050] FIG. 11 is a top view of a via in a workpiece after a first circle repetition according to embodiments of the present disclosure.

[0051] FIG. 12 is a top view of a via array in a workpiece after a first circle repetition according to embodiments of the present disclosure.

[0052] FIG. 13 is a top view of a via in a workpiece after a second circle repetition according to embodiments of the present disclosure.

[0053] FIG. 14 is a top view of a via array in a workpiece after a second circle repetition according to embodiments of the present disclosure.

[0054] FIG. 15 is a top view of a via in a workpiece after a third circle repetition according to embodiments of the present disclosure.

[0055] FIG. 16 is a top view of a via array in a workpiece after a third circle repetition according to embodiments of the present disclosure.

[0056] FIG. 17 is a top view of a via in a workpiece after a fourth circle repetition according to embodiments of the present disclosure.

[0057] FIG. 18 is a top view of a via array in a workpiece after a fourth circle repetition according to embodiments of the present disclosure.

[0058] FIG. 19 is a cross-sectional view of a via formed by the laser processing apparatus according to embodiments of the present disclosure.

[0059] FIG. 20 is a graph showing the absorption of three constituent materials for via drilling vs. various typical laser wavelengths according to embodiments of the present disclosure.

[0060] FIG. 21 is a cross-sectional heat absorption map of a via formed at 30 MHz by the laser processing apparatus according to embodiments of the present disclosure.

[0061] FIG. 22 is a cross-sectional heat absorption map of a via formed at 5 MHz by the laser processing apparatus according to embodiments of the present disclosure.

[0062] FIG. 23 is a cross-sectional heat absorption map of a via formed at 1 MHz by the laser processing apparatus according to embodiments of the present disclosure.Docket Number: 00809-WO

[0063] FIG. 24 is a cross-sectional view of a via formed at 30 MHz according to embodiments of the present disclosure.

[0064] FIG. 25 is a cross-sectional view of a via formed at 5 MHz according to embodiments of the present disclosure.

[0065] FIG. 26 is a cross-sectional view of a via formed at 2 MHz according to embodiments of the present disclosure.DETAILED DESCRIPTION

[0066] Example embodiments are described herein with reference to the accompanying drawings. Unless otherwise expressly stated, in the drawings the sizes, positions, etc., of components, features, elements, etc., as well as any distances therebetween, are not necessarily to scale, but are exaggerated for clarity. In the drawings, like numbers refer to like elements throughout. Thus, the same or similar numbers may be described with reference to other drawings even if they are neither mentioned nor described in the corresponding drawing. Also, even elements that are not denoted by reference numbers may be described with reference to other drawings.

[0067] The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It should be recognized that the terms “includes” and / or “including,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range, as well as any sub-ranges therebetween. Unless indicated otherwise, terms such as “first,” “second,” etc., are only used to distinguish one element from another. For example, one node could be termed a “first node” and similarly, another node could be termed a “second node”, or vice versa.

[0068] Unless indicated otherwise, the term “about,” “thereabout,” etc., means that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and / or larger or smaller, as desired, reflectingDocket Number: 00809-WOtolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art. Spatially relative terms, such as “below,” “beneath,” “lower,” “above,” and “upper,” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element or feature, as illustrated in the FIGS. It should be recognized that the spatially relative terms are intended to encompass different orientations in addition to the orientation depicted in the FIGS. For example, if an object in the FIGS, is turned over, elements described as “below”, or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the exemplary term “below” can encompass both an orientation of above and below. An object may be otherwise oriented (e.g., rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may be interpreted accordingly.

[0069] The section headings used herein are for organizational purposes only and, unless explicitly stated otherwise, are not to be construed as limiting the subject matter described. It will be appreciated that many different forms, embodiments and combinations are possible without deviating from the spirit and teachings of this disclosure and so this disclosure should not be construed as limited to the example embodiments set forth herein. Rather, these examples and embodiments are provided so that this disclosure will be thorough and complete, and will convey the scope of the disclosure to those skilled in the art.

[0070] I, Overview

[0071] Embodiments described herein relate generally to methods and systems for laserprocessing ("processing") a workpiece. In some embodiments, the processing is accomplished, either in whole or in part, by irradiating the workpiece with laser radiation, to heat, melt, evaporate, ablate, crack, discolor, polish, roughen, carbonize, foam, or otherwise modify one or more properties or characteristics of one or more materials from which the workpiece is formed (e.g., in terms of chemical composition, atomic structure, ionic structure, molecular structure, electronic structure, microstructure, nanostructure, density, viscosity, index of refraction, magnetic permeability, relative permittivity, texture, color, hardness, transmissivity to electromagnetic radiation, or the like or any combination thereof). Materials to be processed may be present at an exterior of the workpiece prior to or during processing or may be located completely within the workpiece (i.e., not present at an exterior of the workpiece) prior to or during processing.Docket Number: 00809-WO

[0072] Specific examples of processes that may be carried out by the disclosed apparatus for laser processing include via drilling or other hole formation, cutting, perforating, welding, scribing, engraving, marking (e.g., surface marking, sub-surface marking, etc.), laser-induced forward transfer, cleaning, bleaching, bright pixel repair (e.g., color filter darkening, modification of OLED material, etc.), decoating, surface texturing (e.g., roughening, smoothing, etc.), or the like or any combination thereof. Thus, in some embodiments, one or more features on that may be formed on or within a workpiece, as a result of the processing, may include openings, slots, vias or other holes, grooves, trenches, scribe lines, kerfs, recessed regions, conductive traces, ohmic contacts, resist patterns, human- or machine-readable indicia (e.g., including one or more regions in or on the workpiece having one or more visually or texturally distinguishing characteristics), or the like or any combination thereof. Features such as openings, slots, vias, holes, etc., can have any suitable or desirable shape (e.g., circular, elliptical, square, rectangular, triangular, annular, or the like or any combination thereof) when viewed from a top plan view. Further, features such as openings, slots, vias, holes, etc., can extend completely through the workpiece (e.g., so as to form so-called “through vias,” “through holes,” etc.) or only partially through the workpiece (e.g., so as to form so-called “blind vias,” “blind holes,” etc.).

[0073] Workpieces that may be processed can be generically characterized as being formed of one or more metals, polymers, ceramics, composites, or any combination thereof (e.g., whether as an alloy, compound, mixture, solution, composite, etc.). Examples of workpieces that are specifically described herein include panels of printed circuit boards (PCBs) (also referred to herein as “PCB panels”), PCBs, flexible printed circuits (FPCs), integrated circuits (ICs), and IC packages (ICPs). However, it will be appreciated that other types of workpieces may also be beneficially processed, such as light-emitting diodes (LEDs), LED packages, semiconductor wafers, electronic or optical device substrates (e.g., substrates formed of A12O3, AN, BeO, Cu, GaAS, GaN, Ge, InP, Si, SiO2, SiC, Sil-xGex, or the like, or any combination or alloy thereof), lead frames, lead frame blanks, articles formed of plastic, unstrengthened glass, thermally-strengthened glass, chemically-strengthened glass (e.g., via an ion-exchange process), quartz, sapphire, plastic, silicon, etc., components of electronic displays (e.g., substrates having formed thereon, TFTs, color filters, organic LED (OLED) arrays, quantum dot LED arrays, or the like or any combination thereof), lenses, mirrors, screen protectors, turbine blades, powders, films, foils, plates, molds (e.g., wax molds, molds for injection-molding processes, investment-casting processes, etc.), fabricsDocket Number: 00809-WO(woven, felted, etc.), surgical instruments, medical implants, consumer packaged goods, shoes, bicycles, automobiles, automotive or aerospace parts (e.g., frames, body panels, etc.), appliances (e.g., microwaves, ovens, refrigerators, etc.), device housings (e.g., for watches, computers, smartphones, tablet computers, wearable electronic devices, or the like or any combination thereof).

[0074] Accordingly, materials that may be processed include one or more metals such as Al, Ag, Au, Cu, Fe, In, Mg, Pt, Sn, Ti, or the like, or any combination thereof (e.g., whether as an alloy, composite, etc.), conductive metal oxides (e.g., ITO, etc.), transparent conductive polymers, ceramics, waxes, resins, inorganic dielectric materials (e.g., used as interlayer dielectric structures, such as silicon oxide, silicon nitride, silicon oxynitride, or the like or any combination thereof), low-k dielectric materials (e.g., methyl silsesquioxane (MSQ), hydrogen silsesquioxane (HSQ), fluorinated tetraethyl orthosilicate (FTEOS), or the like or any combination thereof), organic dielectric materials (e.g., SILK, benzocyclobutene, Nautilus, (all manufactured by Dow), polyfluorotetraethylene, (manufactured by DuPont), FLARE, (manufactured by Allied Chemical), or the like or any combination thereof), glass fibers, polymeric materials (polyamides, polyimides, polyesters, polyacetals, polycarbonates, modified polyphenylene ethers, polybutylene terephthalates, polyphenylene sulfides, polyether sulfones, polyether imides, polyether ether ketones, liquid crystal polymers, acrylonitrile butadiene styrene, and any compound, composite, or alloy thereof), leather, paper, build-up materials (e.g., ANJINOMOTO Build-up Film, also known as “ABF”, etc.), glass-reinforced epoxy laminate (e.g., FR4), prepregs, solder resist, or the like or any composite, laminate, or other combination thereof.

[0075] In some embodiments, the present disclosure relates to a laser drilling system for creating vias in inhomogeneous substrates. The laser drilling system may utilize pulsed laser energy to form vias through heterogeneous dielectric materials containing, for example, glass fibers and epoxy. In some embodiments, the dielectric structure may include a glass-reinforced epoxy laminate material. In some cases, the glass-reinforced epoxy laminate material may be FR-4. In some embodiments, the glass fibers may provide mechanical strength and electrical insulation, while the epoxy resin may bind the glass fibers together and provide additional insulation properties. In some embodiments, the laser drilling process may be controlled to homogenize via results across regions in a workpiece with varying glass fiber density. Thus, exemplary methods of the present disclosure may allow for more consistent and reliable via formation compared to conventional drilling techniques.Docket Number: 00809-WO

[0076] In some embodiments, the glass fibers in the dielectric structure may be arranged in a woven pattern. In some cases, the weave pattern and density of the glass fibers may affect the mechanical and electrical properties of the substrate. For example, in some embodiments, a tighter weave may provide improved mechanical strength and better control of the dielectric constant.

[0077] In some embodiments, the laser drilling system may address challenges associated with drilling through inhomogeneous materials like glass-reinforced epoxy laminates commonly used in PCB substrates. The system may enable drilling of smaller via sizes while maintaining quality and reliability across the substrate. In some cases, the laser drilling process may be optimized to avoid issues like excessive bottom copper damage or delamination that can occur with other drilling methods.

[0078] In some embodiments, the laser drilling system may provide advantages in terms of drilling speed, via quality, and process flexibility compared to traditional CO2 laser or mechanical drilling approaches. In some embodiments, the laser drilling system may also provide advantages over other ultrafast drilling techniques such as Han’s, MSOLV, and Schmoll’s green picosecond systems. The system may allow for precise control over laser parameters to tailor the drilling process for different material stacks and via requirements. This may enable the fabrication of next-generation HDI boards with higher interconnect densities to support advanced electronics applications.

[0079] In some embodiments, the substrate may include multiple alternating layers of conductive material and dielectric material. In some cases, this multilayer structure may allow for complex routing of electrical signals in printed circuit board applications.

[0080] II, System Overview

[0081] FIG. 1 depicts a laser-processing system in accordance with embodiments of the present disclosure. As depicted in FIG. 1, in some embodiments, a laser-processing system 100 (also referred to herein simply as an “system”) for processing a workpiece 102 may include a laser source 104 for generating a beam of laser energy, and a beam steering system 103. In some embodiments, the beam steering system may include various optical components to enable precise control and positioning of the laser beam. In some embodiments, the beam steering system 103 may include at least one positioner (e.g., a first positioner 106, a second positioner 108, a third positioner 110, or any combination thereof)Docket Number: 00809-WOand at least one scan lens 112. In some embodiments, the scan lens 112 and the second positioner 108 may be integrated into a scan head 120, described in further detail below.

[0082] In some embodiments, laser energy transmitted along a beam path 114, through the scan lens 112, propagates along a beam axis 118 so as to be delivered to the workpiece 102. In some embodiments, laser energy propagating along the beam axis 118 may be characterized as having a Gaussian-type spatial intensity profile or a non-Gaussian-type (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 a shape (i.e., a cross-sectional shape, also referred to herein as a “spot shape”) of the beam of laser energy propagating along the beam axis 118 (or beam path 114), which may be circular, elliptical, square, rectangular, triangular, hexagonal, ring-shaped, etc., or arbitrarily shaped. As used herein, the term “spot size” refers to the diameter or maximum spatial width of the beam of laser energy delivered at a location (also referred to as a “process spot,” “spot location” or, more simply, a “spot”) where the beam axis 118 intersects a region of the workpiece 102 that is to be, at least partially, processed by the delivered beam of laser energy. For purposes of discussion herein, spot size is measured as a radial or transverse distance from the beam axis 118 to where the optical intensity drops to, at least, 1 / e2of the optical intensity at the beam axis 118. Generally, the spot size of the beam of laser energy will be at a minimum at the beam waist.

[0083] In some embodiments, the at least one positioner (e.g., the first positioner 106, the second positioner 108 and the third positioner 110) is configured to change the relative position between the spot and the workpiece 102. In view of the description that follows, in some embodiments, inclusion of the second positioner 108 is optional, provided that the apparatus 100 includes the first positioner 106 and, in some embodiments, the third positioner 110. In some embodiments, inclusion of the third positioner 110 is optional, provided that the apparatus 100 includes the first positioner 106 and, in some embodiments, the second positioner 108.

[0084] A, Laser Source

[0085] In some embodiments, the laser source 104 is operative to generate laser pulses. In some embodiments, the laser source 104 may be, for example, a pulsed laser source, a QCW laser source, a burst mode laser, or the like or any combination thereof. In some embodiments where the laser source 104 includes a QCW or CW laser source, the laserDocket Number: 00809-WOsource 104 may be operated in a pulsed mode, or may be operated in a non-pulsed mode but further include a pulse gating unit (e.g., an acousto-optic (AO) modulator (AOM), a beam chopper, etc.) to temporally modulate the laser radiation output from the QCW or CW laser source. In some embodiments, the laser source 104 may be operated a “burst-mode” where multiple individual pulses may be grouped within a burst envelope. Within the burst envelope, power of each pulse and the time between each pulse may be tailored to specific laser-processing requirements. Thus, the laser source 104 may be broadly characterized as operative to generate a beam of laser energy, which may be manifested as a series of laser pulses or as a continuous or quasi-continuous laser beam, which can thereafter be propagated along the beam path 114. Although some embodiments discussed herein refer to laser pulses, it should be recognized that continuous or quasi-continuous beams may alternatively, or additionally, be employed whenever appropriate or desired.

[0086] In addition to wavelength, average power and, when the beam of laser energy is manifested as a series of laser pulses, pulse duration and pulse repetition rate, the beam of laser energy delivered to the workpiece 102 can be characterized by one or more other characteristics such as pulse energy, peak power, etc., which can be selected (e.g., optionally based on one or more other characteristics such as wavelength, pulse duration, average power and pulse repetition rate, etc.) to irradiate the workpiece 102 at the process spot at an optical intensity (measured in W / cm2), fluence (measured in J / cm2), etc., sufficient to process the workpiece 102 (e.g., to form one or more features).

[0087] In some embodiments, the laser source 104 may be an ultrafast laser capable of producing pulse durations in the femtosecond to picosecond range. In some embodiments, the laser source may be a green picosecond laser. In some embodiments, the operating parameters of the laser source 104 may be determined based on various considerations such as, for example, via size requirement, composition and configuration of the workpiece, optical system structure and components, cost effectiveness of the laser source, etc.Accordingly, parameter regimes choices are not independent of one other but, rather, depend on these considerations.

[0088] In some embodiments, the laser source 104 may operate at a repetition rate of 2 MHz and 50 MHz; or at a repetition rate of 5 MHz to 50 MHz; or at a repetition rate of 10 MHz to 50 MHz; or at a repetition rate of 15 MHz to 50 MHz; or at a repetition rate of 20 MHz to 50 MHz; or at a repetition rate of 25 MHz to 50 MHz; or at a repetition rate of 30Docket Number: 00809-WOMHz to 50 MHz; or at a repetition rate of 35 MHz to 50 MHz; or at a repetition rate of 40 MHz to 50 MHz; or at a repetition rate of 45 MHz to 50 MHz.

[0089] In some embodiments, the laser source 104 may operate at a repetition rate of 2 MHz and 45 MHz; or at a repetition rate of 2 MHz to 40 MHz; or at a repetition rate of 2 MHz to 35 MHz; or at a repetition rate of 2 MHz to 30 MHz; or at a repetition rate of 2 MHz to 25 MHz; or at a repetition rate of 2 MHz to 20 MHz; or at a repetition rate of 2 MHz to 15 MHz; or at a repetition rate of 2 MHz to 10 MHz; or at a repetition rate of 2 MHz to 5 MHz.

[0090] In some embodiments, the laser source 104 may operate at a repetition rate of 5 MHz and 25 MHz; or at a repetition rate of 5 MHz to 10 MHz; or at a repetition rate of 10 MHz to 25 MHz; or at a repetition rate of 15 MHz to 30 MHz; or at a repetition rate of 2 MHz to 15 MHz; or at a repetition rate of 25 MHz to 45 MHz; or at a repetition rate of 30 MHz to 40 MHz; or at a repetition rate of 25 MHz to 35 MHz; or at a repetition rate of 5 MHz to 30 MHz; or at a repetition rate of 10 MHz to 30 MHz.

[0091] In some embodiments, a pulse width generated by the laser source 104 may be from 100 fs to 100 ps; or from 200 ps to 100 ps; or from 300 fs to 100 ps; or from 400 fs to 100 ps; or from 500 fs to 100 ps; or from 600 fs to 100 ps; or from 700 fs to 100 ps; or from 800 fs to 100 ps; or from 900 fs to 100 ps; or from 1 ps to 100 ps; or from 15 ps to 100 ps; or from 50 ps to 100 ps.

[0092] In some embodiments, a pulse width generated by the laser source 104 may be from 100 fs to 50 ps; or from 100 fs to 15 ps; or from 100 ps to 1 ps; or from 100 fs to 900 fs; or from 100 fs to 800 fs; or from 100 fs to 800 fs; or from 100 fs to 700 fs; or from 100 fs to 600 fs; or from 100 fs to 500 fs; or from 100 fs to 400 fs; or from 100 fs to 300 fs; or from 100 fs to 200 fs.

[0093] In some embodiments, a pulse width generated by the laser source 104 may be from 300 fs to 15 ps; or from 400 fs to 10 ps; or from 500 ps to 1 ps; or from 600 fs to 900 fs; or from 900 fs to 1 ps; or from 400 fs to 600 fs; or from 1 ps to 15 ps; or from 100 fs to 100 ps; or from 100 fs to 100 ps; or from 100 fs to 100 ps; or from 100 fs to 100 ps; or from 100 fs to 100 ps; or from 100 fs to 100 ps.

[0094] In some embodiments, the laser source may operate at a power of 0.05 W to 750 W; 0.1 W to 750 W; or 5 W to 750 W; or 7 W to 750 W; or 10 W to 750 W; or 15 W to 750 W; or 20 W to 750 W; or 25 W to 750 W; or 30 W to 750 W; or 35 W to 750 W; or 40 W to 750 W; or 45 W to 750 W; or 50 W to 750 W; or 55 W to 750 W; or 60 W to 750 W; or 65 WDocket Number: 00809-WOto 750 W; or 70 W to 750 W; or 75 W to 750 W; or 80 W to 750 W; or 85 W to 750 W; or 90 W to 750 W; or 95 W to 750 W; or 100 W to 750 W; or 105 W to 750 W; or 110 W to 750 W; or 120 W to 750 W; or 125 W to 750 W; or 130 W to 750 W; or 135 W to 750 W; or 140 W to 750 W; or 145 W to 750 W; or 150 W to 750 W; or 160 W to 750 W; or 175 W to 750 W; or 200 W to 750 W; or 225 W to 750 W; or 250 W to 750 W; or 275 W to 750 W; or 300 W to 750 W; or 375 W to 750 W; or 400 W to 750 W; or 425 W to 750 W; or 450 W to 750 W; or 475 W to 750 W; or 500 W to 750 W; or 525 W to 750 W; or 550 W to 750 W; or 575 W to 750 W; or 600 W to 750 W; or 625 W to 750 W; or 650 W to 750 W; or 675 W to 750 W; or 700 W to 750 W; or 725 W to 750 W.

[0095] In some embodiments, the laser source may operate at a power of 0.05 W to 725 W; 0.05 W to 700 W; or 0.05 W to 675 W; or 0.05 W to 650 W; or 0.05 W to 624 W; or 0.05 W to 600 W; or 0.05 W to 575 W; or 0.05 W to 550 W; or 0.05 W to 525 W; or 0.05 W to 500 W; or 0.05 W to 475 W; or 0.05 W to 425 W; or 0.05 W to 400 W; or 0.05 W to 375 W; or 0.05 W to 350 W; or 0.05 W to 325 W; or 0.05 W to 300 W; or 0.05 W to 275 W; or 0.05 W to 250 W; or 0.05 W to 225 W; or 0.05 W to 200 W; or 0.05 W to 175 W; or 0.05 W to 160 W; or 0.05 W to 150 W; or 0.05 W to 145 W; or 0.05 W to 140 W; or 0.05 W to 135 W; or 0.05 W to 130 W; or 0.05 W to 125 W; or 0.05 W to 120 W; or 0.05 W to 115 W; or 0.05 W to 110 W; or 0.05 W to 105 W; or 0.05 W to 100 W; or 0.05 W to 95 W; or 0.05 W to 90 W; or 0.05 W to 85 W; or 0.05 W to 80 W; or 0.05 W to 75 W; or 0.05 W to 70 W; or 0.05 W to 65 W; or 0.05 W to 60 W; or 0.05 W to 55 W; or 0.05 W to 50 W; or 0.05 W to 45 W; or 0.05 W to 40 W; or 0.05 W to 35 W; or 0.05 W to 30 W; or 0.05 W to 25 W; or 0.05 W to 20 W; or 0.05 W to 15 W; or 0.05 W to 10 W; or 0.05 W to 7 W; or 0.05 W to 5 W; or 0.05 W to 1 W; or 0.05 W to 0.5 W; or 0.05 W to 0.1 W.

[0096] In some embodiments, the laser source may operate at a power of 0.1 W to 150 W; 0.1 W to 25 W; or 5 W to 50 W; or 7 W to 74 W; or 10 W to 75 W; or 5 W to 37 W; or 0.1 W to 7.3 W; or 25 W to 50 W; or 30 W to 50 W; or 7 W to 50 W; or 27 W to 75 W; or 15 W to 69 W; or 69 W to 74 W; or 60 W to 75 W; or 0.1 W to 150 W; or 1 W to 69 W; or 0.1 W to 1 W; or 1 W to 5 W; or 0.1 W to 0.5 W; or 85 W to 150 W; or 90 W to 150 W; or 15 W to 150 W; or 100 W to 250 W; or 105 W to 350 W; or 110 W to 450 W; or 120 W to 550 W; or 25 W to 100 W; or 130 W to 150 W; or 135 W to 250 W; or 140 W to 450 W.

[0097] In some embodiments, the laser fluence may be chosen to optimize efficiency of the via drilling process. In some embodiments, different laser fluences may be chosen for different parts of the workpiece 102 to optimize quality delivered by the laser source 104. ForDocket Number: 00809-WOexample, the ablation efficiency of copper for an ultrafast green laser pulse peaks around 1 J7cm2to 3 J / cm2up to a laser pulse repition rate of 25 MHz. However, ablation efficiency of the dielectric material, FR4, tends to peak between 0.1 J / cm2and 1 J / cm2. Thus, different fluences may be chosen for the different parts to make the via drilling as fast as possible. In some embodiments, the laser fluence produced by the laser source 104 may be from 0.1 J / cm2to 50 J / cm2; or from 1 J / cm2to 50 J / cm2; or from 3 J / cm2to 50 J / cm2; or from 5 J / cm2to 50 J / cm2; or from 10 J / cm2to 50 J / cm2; or from 15 J / cm2to 50 J / cm2; or from 20 J / cm2to 50 J / cm2; or from 25 J / cm2to 50 J / cm2; or from 30 J / cm2to 50 J / cm2; or from 35 J / cm2to 50 J / cm2; or from 40 J / cm2to 50 J / cm2; or from 45 J / cm2to 50 J / cm2.

[0098] In some embodiments, the laser fluence produced by the laser source 104 may be from 0.1 J / cm2to 50 J / cm2; or from 0.1 J / cm2to 45 J / cm2; or from 0.1 J / cm2to 40 J / cm2; or from 0.1 J / cm2to 35 J / cm2; or from 0.1 J / cm2to 30 J / cm2; or from 0.1 J / cm2to 25 J / cm2; or from 0.1 J / cm2to 20 J / cm2; or from 0.1 J / cm2to 15 J / cm2; or from 0.1 J / cm2to 10 J / cm2; or from 0.1 J / cm2to 5 J / cm2; or from 0.1 J / cm2to 3 J / cm2; or from 0.1 J / cm2to 1 J / cm2.

[0099] In some embodiments, the laser fluence produced by the laser source 104 may be from 3 J / cm2to 10 J / cm2; or from 7 J / cm2to 15 J / cm2; or from 5 J / cm2to 12 J / cm2; or from 3 J / cm2to 8 J / cm2; or from 8 J / cm2to 20 J / cm2; or from 1 J / cm2to 5 J / cm2.

[0100] In some embodiments, a spot size of the laser source 104 may depend on the via sizes to be drilled, as well as the limits of the system 100 and the stability of the system 100 against depth of focus changes. In some embodiments, a larger spot size (e.g., up to the fluence limit the system can provide) may be preferable for maximum throughput, while a smaller spot size enables smaller vias and better tapers for larger vias. In some embodiments, the laser source 104 may produce a spot size of 3 pm to 50 pm; or 6 pm to 50 pm; or 8.5 pm to 50 pm; or 10 pm to 50 pm; or 11.3 pm to 50 pm; or 12 pm to 50 pm; or 15 pm to 50 pm; or 18 pm to 50 pm; or 20 pm to 50 pm; or 25 pm to 50 pm; or 30 pm to 50 pm; or 40 pm to 50 pm . In some cases, a preferred spot size range may be 5-20 pm.

[0101] In some embodiments, the laser source 104 may produce a spot size of 3 pm to 40 pm; or 3 pm to 25 pm; or 3 pm to 20 pm; or 3 pm to 18 pm; or 3 pm to 15 pm; or 3 pm to 12 pm; or 3 pm to 11.3 pm; or 3 pm to 10 pm; or 3 pm to 8.5 pm; or 3 pm to 6 pm.

[0102] In some embodiments, the laser source 104 may produce a spot size of 5 pm to 20 pm; or 11 pm to 18 pm; or 7 pm to 11 pm; or 5 pm to 18 pm; or 7 pm to 11 pm; or 20 pm to 35 pm; or 11 pm to 45 pm; or 18 pm to 35 pm.Docket Number: 00809-WO

[0103] In some embodiments, the laser source 104 may be configured to switch between different repetition rates for processing different materials. For example, the laser source 104 may operate at a higher repetition rate (e.g. 50 MHz) for removing electrical conductor material and switch to a lower repetition rate (e.g. 10 MHz) for removing dielectric material.

[0104] FIG. 2 illustrates how the laser source parameters may affect material removal efficiency. The graph shows copper ablation efficiency versus pulse fluence for different repetition rates. In some embodiments, operating the laser source at higher repetition rates, such as 50 MHz, may achieve notably higher ablation efficiencies compared to lower repetition rates.

[0105] B, First Positioner

[0106] Referring back to FIG. 1, in some embodiments, the first positioner 106 may be arranged, located or otherwise disposed in the beam path 114 and is operated to diffract, reflect, refract, or the like, or any combination thereof, laser pulses that are generated by the laser source 104 so as to deflect or impart movement of the beam path 114 (e.g., relative to the scan lens 112) and, consequently, deflect or impart movement of the beam axis 118 relative to the workpiece 102. In some embodiments, the first positioner 106 is operated to impart movement of the beam axis 118 relative to the workpiece 102 along the X-axis (or direction), the Y-axis (or direction), or a combination thereof. Although not illustrated, the X-axis (or X-direction) will be understood to refer to an axis (or direction) that is orthogonal to the illustrated Y- and Z-axes (or directions).

[0107] In some embodiments, the first positioner 106 is provided as one or more AO deflector (AOD) systems, configured to deflect the beam path 114 by diffracting an incident laser beam. Diffracting an incident laser beam produces a diffraction pattern that typically includes zeroth- and first-order diffraction peaks, and may also include higher-order diffraction peaks (e.g., second-order, third-order, etc.). Within the art, it is common to refer to the portion of the diffracted laser beam in the zeroth-order diffraction peak as a "zeroth-order" beam, to refer to the portion of the diffracted laser beam in the first-order diffraction peak as a "first-order" beam, and so on. Generally, the zeroth-order beam and other diffracted-order beams (e.g., the first-order beam, etc.) propagate along different beam paths upon exiting the AOD system. Laser energy in the zeroth-order beam (and any other high-order beams other than the first-order beam) can be absorbed at one or more beam dumps (not shown) in any suitable or desired manner, while laser energy in the first-order beam isDocket Number: 00809-WOallowed to propagate along the beam path 114. In some embodiments, AODs of AOD systems may include an AOD crystal formed of a material including, but not limited to, crystalline germanium (Ge), gallium arsenide (GaAs), wulfenite (PbMoO4), tellurium dioxide (TeO?), crystalline quartz, glassy SiO2, arsenic trisulfide (AS2S3), lithium niobate (LiNbOs), or the like or any combination thereof.

[0108] C. Second Positioner

[0109] In some embodiments, the second positioner 108 is configured to impart movement of the beam axis relative to the workpiece 102 along the X-axis (or direction), the Y-axis (or direction), or a combination thereof (e.g., by deflecting the beam path 114 within the first secondary angular range 118a or within the second secondary angular range 118 >).

[0110] In some embodiments, movement of the beam axis relative to the workpiece 102, as imparted by the second positioner 108, may be limited such that the process spot can be scanned, moved or otherwise positioned within a second scan field projected by a scan lens 112. In some embodiments, depending upon one or more factors such as the configuration of the second positioner 108, the location of the second positioner 108 along the beam path 114, the beam size of the beam of laser energy incident upon the second positioner 108, the spot size, etc., the second scan field may extend, in any of the X- or Y-directions to a distance that is greater than a corresponding distance of the first scan field. In view of the above, the second scan field may extend, in any of the X- or Y-directions, to a distance that is less than, greater than or equal to 1 mm, 25 mm, 50 mm, 75 mm, 100 mm, 250 mm, 500 mm, 750 mm, 1 cm, 25 cm, 50 cm, 75 cm, 1 m, 1.25 m, 1.5 m, etc., or between any of these values. A maximum dimension of the second scan field (e.g., in the X-Y plane) may be greater than, equal to or less than a maximum dimension (as measured in the X-Y plane) of a feature (e.g., an opening, a recess, a via, a trench, a scribe line, a conductive trace, etc.) to be formed in the workpiece 102.

[0111] In view of the configuration described herein, movement of the beam axis imparted by the first positioner 106 may be superimposed by movement of the beam axis imparted by the second positioner 108. Thus, the second positioner 108 is operative to scan the first scan field within the second scan field.

[0112] In some embodiments, the positioning rate with which the second positioner 108 is capable of positioning the process spot at any location within the second scan field (thus moving the beam axis within the second scan field and / or scanning the first scan field withinDocket Number: 00809-WOthe second scan field) spans a range (also referred to herein as the “second positioning bandwidth”) that is less than the first positioning bandwidth. In one embodiment, the second positioning bandwidth is in a range from 500 Hz (or thereabout) to 8 kHz (or thereabout). For example, the second positioning bandwidth can be greater than, equal to or less than 500 Hz, 750 Hz, 1 kHz, 1.25 kHz, 1.5 kHz, 1.75 kHz, 2 kHz, 2.5 kHz, 3 kHz, 3.5 kHz, 4 kHz, 4.5 kHz, 5 kHz, 5.5 kHz, 6 kHz, 6.5 kHz, 7 kHz, 7.5 kHz, 8 kHz, etc., or between any of these values.

[0113] In some embodiments, the second positioner 108 may be a galvanometer mirror system. In some embodiments, the galvanometer mirror system may include two galvanometer mirror components, i.e., a first galvanometer mirror component (e.g., an X-axis galvanometer mirror component) arranged to impart movement of the beam axis relative to the workpiece 102 along the X-axis and a second galvanometer mirror component (e.g., a Y-axis galvanometer mirror component) arranged to impart movement of the beam axis relative to the workpiece 102 along the Y-axis. In other embodiments, the second positioner 108 may be a galvanometer mirror system having a single galvanometer mirror component arranged to impart movement of the beam axis relative to the workpiece 102 along the X- and Y-axes. In other embodiments, the second positioner 108 may be a rotating polygon mirror system, etc. In some embodiments, 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.

[0114] D, Third Positioner

[0115] Referring again to FIG. 1, in some embodiments, the third positioner 110 may include one or more linear stages (e.g., each capable of imparting translational movement to the workpiece 102 along the X-, Y- and / or Z-directions), one or more rotational stages (e.g., each capable of imparting rotational movement to the workpiece 102 about an axis parallel to the X-, Y- and / or Z-directions), or the like or any combination thereof arranged and configured to impart relative movement between the workpiece 102 and the scan lens 112, and, consequently, to impart relative movement between the workpiece 102 and the beam axis 118. According to embodiments described herein, and although not illustrated, the third positioner 110 may include one or more stages configured and adapted to impart relative movement between the scan lens 112 and the first positioner 106.Docket Number: 00809-WO

[0116] In view of the configurations described herein, in some embodiments, movement of the process spot relative to the workpiece 102 (e.g., as imparted by the first positioner 106 and / or the second positioner 108) may be superimposed by any movement of the workpiece 102 or scan lens 112 as imparted by the third positioner 110.

[0117] In the illustrated embodiment, the third positioner 110 is operated to move the workpiece 102. In some embodiments, however, the third positioner 110 may be arranged and configured to move the scan head 120. In some embodiments, one or more components such as the first positioner 106 and the workpiece 102 may be kept stationary.

[0118] In some embodiments in which the third positioner 110 includes a Z-stage, the Z-stage may be arranged and configured to move the workpiece 102 along the Z-direction. In these embodiments, the Z-stage may be carried by one or more of the other aforementioned stages for moving or positioning the workpiece 102, may carry one or more of the other aforementioned stages for moving or positioning the workpiece 102, or any combination thereof. In some embodiments in which the third positioner 110 includes a Z-stage, the Z-stage may be arranged and configured to move the scan head along the Z-direction. In some embodiments, moving the workpiece 102 or the scan head along the Z-direction may result in a change in spot size at the workpiece 102.

[0119] E, Scan Lens

[0120] In some embodiments, the scan lens 112 may be configured to focus the beam of laser energy directed along the beam path so as to produce a beam waist that can be positioned at or near the desired process spot. In some embodiments, the scan lens 112 may be either a simple lens, or a compound lens. In some embodiments, the scan lens 112 may be a non-telecentric f-theta lens (as shown), a telecentric f-theta lens, an axicon lens (in which case, a series of beam waists are produced, yielding a plurality of process spots displaced from one another along the beam axis 118), or the like or any combination thereof.

[0121] In some embodiments, the scan lens 112 may be a fixed-focal length lens. In some embodiments, a fixed-focal length lens may be coupled to a scan lens positioner (e.g., a lens actuator, not shown) configure to move the scan lens 112 (e.g., so as to change the position of the beam waist along the beam axis 118). For example, in some embodiments, the lens actuator may be a voice coil configured to linearly translate the scan lens 112 along the Z-direction. In this case, the lens actuator may be a component of the aforementioned thirdDocket Number: 00809-WOpositioner 110. In some embodiments, changing the position of the beam waist along the beam axis 118 may result in a change in spot size at the workpiece 102.

[0122] As described above, in some embodiments, the scan lens 112 and the second positioner 108 may be integrated into a common scan head 120. Thus, in some embodiments in which the apparatus 100 includes a lens actuator, the lens actuator may be coupled to the scan lens 112 (e.g., so as to enable movement of the scan lens 112 within the scan head 120, relative to the second positioner 108). Alternatively, in some embodiments, the lens actuator may be coupled to the scan head 120 and be configured to enable movement of the scan head itself, in which case the scan lens 112 and the second positioner 108 would move together). In either case, in some embodiments, the lens actuator may be a component of the aforementioned third positioner 110. In some embodiments, the scan lens 112 and the second positioner 108 may be integrated into different housings (e.g., such that the housing in which the scan lens 112 is integrated is movable relative to the housing in which the second positioner 108 is integrated).

[0123] F, Controller

[0124] In some embodiments, the apparatus 100 includes one or more controllers, such as controller 122, to control, or facilitate control of, the operation of the apparatus 100. In some embodiments, the controller 122 is communicatively coupled (e.g., over one or more wired or wireless communications links) to one or more components of the apparatus 100, such as the laser source 104, the first positioner 106, the second positioner 108, third positioner 110, the lens actuator, the scan lens 112 (when provided as a variable-focal length lens), the fixture, etc., which are thus operative in response to one or more control signals output by the controller 122.

[0125] For example, in some embodiments, the controller 122 may control an operation of the first positioner 106, the second positioner 108, or the third positioner 110, or any combination thereof, to impart relative movement between the beam axis 118 and the workpiece 102 so as to cause relative movement between the process spot and the workpiece 102 along a path or trajectory (also referred to herein as a “process trajectory”) within the workpiece 102. In some embodiments, any two of these positioners, or all three of these positioners, may be controlled such that two positioners (e.g., the first positioner 106 and the second positioner 108, the first positioner 106 and the third positioner 110, or the second positioner 108 and the third positioner 110), or all three positioners simultaneously impartDocket Number: 00809-WOrelative movement between the process spot and the workpiece 102 (thereby imparting a “compound relative movement” between the beam axis and the workpiece).

[0126] In some embodiments, the controller 122 may manage scanning patterns of the beam steering system 103 to control the spatial distribution of laser energy during the via drilling process. In some embodiments, the scanning pattern may be tailored to optimize material removal efficiency and via quality for different via sizes and substrate compositions. In some embodiments, for smaller vias, the controller 122 may implement tighter, more focused scanning patterns to achieve precise material removal within a confined area. In contrast, for larger vias, in some embodiments, the controller 122 may utilize wider, spiral or concentric circle patterns to efficiently remove material over a larger area. In some embodiments, the scanning pattern may also be dynamically adjusted during the drilling process to account for variations in material properties at different depths within the substrate. In some embodiments, the controller 122 may employ a combination of scanning patterns, such as an initial spiral pattern followed by a series of concentric circles, to achieve desired via characteristics. The flexibility in scanning pattern control may allow the laser drilling system 100 to adapt to a wide range of via specifications and substrate materials, potentially improving overall process versatility and throughput.

[0127] III, Feature Formation

[0128] In some embodiments, the laser drilling system 100 may be configured to form vias in a workpiece 102 through a controlled process of material removal. In some embodiments, the controller 122 may be configured to control the laser source and component(s) of the beam steering system 103 to remove material from the workpiece 102 to form a feature (e.g., an opening, via, trench, slot, scribe line, recessed region, etc.) in a workpiece. In some embodiments, the feature may be a via extending from a first surface of the workpiece 102 towards a second surface of the workpiece 102. In some embodiments, the controller may manage various process parameters to optimize the via formation process for different material compositions and via size requirements.

[0129] In some embodiments, the first positioner 106 may be configured to rapidly scan or otherwise place a process spot within the first scanning range (e.g., as discussed above) to form the feature in the workpiece 102. In some embodiments, as discussed above, the workpiece 102 may be provided as a PCB panel, a PCB, an FPC, an IC, an ICP, a semiconductor device, etc. In some embodiments, the workpiece 102 may thus include one orDocket Number: 00809-WOmore constituent structures such as an electrical conductor structure (e.g., such as a film, foil, etc., which may be formed of copper, a copper alloy, an interconnect or wiring structure including one or more metals such as copper, titanium, titanium nitride, tantalum, etc., or the like or any combination thereof), a dielectric structure (e.g., a build-up film, a glass-reinforced epoxy laminate, an interlayer dielectric material, a low-k dielectric material, solder resist, a polymeric material, or the like or any combination thereof), or the like or any combination thereof.

[0130] In some embodiments, any electrical conductor structure or dielectric structure of the workpiece 102 can have a thickness in a range of from 0.1 pm to 600 pm; or from 0.5 pm to 600 pm, or from 1 pm to 600 pm, or from 3 pm to 600 pm, or from 5 pm to 600 pm, or from 10 pm to 600 pm, or from 15 pm to 600 pm, or from 18 pm to 600 pm, or from 20 pm to 600 pm, or from 25 pm to 600 pm, or from 30 pm to 600 pm, or from 35 pm to 600 pm, or from 40 pm to 600 pm, or from 50 pm to 600 pm, or from 70 pm to 600 pm, or from 80 pm to 600 pm, or from 100 pm to 600 pm, or from 110 pm to 600 pm, or from 120 pm to 600 pm, or from 250 pm to 600 pm, or from 300 pm to 600 pm, or from 350 pm to 600 pm, or from 400 pm to 600 pm, or from 450 pmto 600 pm, or from 550 pm to 600 pm.

[0131] In some embodiments, any electrical conductor structure or dielectric structure of the workpiece 102 can have a thickness in a range of from 0.1 pm to 550 pm; or from 0.1 pm to 500 pm, or from 0.1 pm to 450 pm, or from 0.1 pm to 400 pm, or from 0.1 pm to 350 pm, or from 0.1 pm to 300 pm, or from 0.1 pm to 250 pm, or from 0.1 pm to 120 pm, or from 0.1 pm to 110 pm, or from 0.1 pm to 100 pm, or from 0.1 pm to 80 pm, or from 0.1 pm to 70 pm, or from 0.1 pm to 50 pm, or from 0.1 pm to 40 pm, or from 0.1 pm to 35 pm, or from 0.1 pm to 30 pm, or from 0.1 pm to 25 pm, or from 0.1 pm to 20 pm, or from 0.1 pm to 18 pm, or from 0.1 pm to 15 pm, or from 0.1 pm to 10 pm, or from 0.1 pm to 5 pm, or from 0.1 pm to 3 pm, or from 0.1 pmto 1 pm, or from 0.1 pm to 0.5 pm.

[0132] In some embodiments, any electrical conductor structure or dielectric structure of the workpiece 102 can have a thickness in a range of from 1 pm to 50 pm; or from 50 pm to 150 pm, or from 150 pm to 450 pm, or from 25 pm to 400 pm, or from 100 pm to 350 pm, or from 100 pm to 300 pm, or from 300 pm to 425 pm, or from 10 pm to 120 pm, or from 120 pm to 150 pm, or from 150 pm to 225 pm, or from 225 pm to 375 pm, or from 2 pm to 70 pm, or from 70 pm to 120 pm, or from 120 pm to 175 pm, or from 175 pm to 330 pm, or from 25 pm to 80 pm, or from 80 pm to 350 pm, or from 350 pm to 475 pm, or from 70 pm to 250 pm.Docket Number: 00809-WO

[0133] In some embodiments, as depicted in FIGS. 3-6, the workpiece 102 (or substrate) may include a first surface 10, an electrical conductor structure 12 at a second surface 14 opposite the first surface 10, and a dielectric structure 16 that is positioned between the electrical conductor structure 12 and the first surface 10. In some embodiments, the electrical conductor structure 12 is contacted by, or otherwise adhered to, the dielectric structure 16. In some embodiments, the dielectric structure 16 may be a material having a heterogenous composition. In some embodiments, the dielectric structure 16 may be formed of a glass-reinforced epoxy laminate material such as, for example, FR4. In some embodiments, the dielectric structure 16 may be formed from other materials including, but not limited to, a polyimide, a liquid crystal polymer, ABF, glass, etc. In some embodiments, as depicted in FIGS. 3-6, the dielectric structure 16 may include at least one epoxy region 18a, 18b and at least one glass fiber reinforcement region 20. In some embodiments, as depicted in FIGS. 5-6, the workpiece 102 may include a second, top electrical conductor structure 22.

[0134] In some embodiments, the electrical conductor structure 12 may be a pad, a trace, a foil, etc., formed of copper or a copper alloy, or the like. In some embodiments, the second electrical conductor structure 22 may be in contact with, or otherwise adhered to, a second side of the dielectric structure 16 that is opposite the first side. In some embodiments, the second electrical conductor structure 22 may be positioned at the first surface 10 of the workpiece 102. In some embodiments, the second electrical conductor structure 22 may have an exposed surface that is either treated, e.g., by a chemical reaction, by a laser-darkening process, etc., to increase absorption of laser energy, or that is not darkened. If present, in some embodiments, the second electrical conductor structure 22 may have a thickness that is less than, greater than or equal to the thickness of the first electrical conductor structure 12. In some embodiments, the workpiece 102 may include one or more additional structures, such as an additional dielectric structure, contacted by or otherwise adhered to the electrical conductor structure 12 (e.g., such that the second electrical conductor structure 12 is interposed between the dielectric structure 16 and the additional dielectric structure.

[0135] In some embodiments, the epoxy resin in the dielectric structure 16 may be formulated with various additives to enhance specific properties. In some cases, these additives may include flame retardants, thermal management materials, or materials to adjust the coefficient of thermal expansion.

[0136] In some embodiments, the surface of the dielectric structure 16 may be treated or modified to improve adhesion with the electrical conductive layers. In some cases, thisDocket Number: 00809-WOtreatment may involve chemical etching, plasma treatment, or the application of adhesion promotion layers.

[0137] In some embodiments, a feature 24 (e.g., an opening, via, trench, slot, scribe line, recessed region, etc.), depicted in FIGS. 4 and 6, may be formed in the workpiece 102 by removing material from one or more constituent structures of the workpiece 102 by way of ablation. Unless explicitly stated otherwise, the term “ablation” can refer to “direct ablation,” “indirect ablation” or any combination thereof. Direct ablation of a material in the workpiece 102 occurs when the dominant cause of ablation is decomposition of the material due to absorption (e.g., linear absorption, nonlinear absorption, or any combination thereof) of energy within the beam of delivered laser energy by the material. Indirect ablation (also known as “lift off’) of a target material in the workpiece 102 occurs when the dominant cause of ablation is melting and vaporization due to heat generated in, and transported from, an adjacent material which absorbs the energy within the beam of laser energy that is delivered to the workpiece 102. In some embodiments, removal of the target material occurs when the pressure within a pocket of vaporized material (e.g., formed upon vaporization of the adjacent material) between the target material and the adjacent material is sufficient to eject the target material from the workpiece 102.

[0138] In some embodiments, as ultrafast lasers are precise in the amount of material they remove per pulse for a given material, drilling through an inhomogeneous FR4 material where the ablation efficiency of glass is considerably lower than that of epoxy, and where the material includes fiber-dense regions, requires more energy. However, applying more energy may damage the bottom electrical conductor structure 12 in the fiber sparse regions that require less energy to process excessively. Yet, in some cases, if some light reaches the bottom interface 26 of the electrical conductor structure 12 and the dielectric structure 16 before the epoxy of the dielectric structure 16 is removed, the light may be partially absorbed by the electrical conductor structure 12. In some embodiments, the electrical conductor structure 12 may then conduct some of the heat to the epoxy 18a above such that the epoxy starts boiling / decomposing before the electrical conductor structure 12 begins to melt, creating a vapor bubble. In some embodiments, as the drilling process continues (e.g., cutting through top layers of the epoxy region 18b and glass fibers in the glass reinforcement region 20), the dielectric thickness above the interface 26 of the electrical conductor structure 12 and the dielectric structure 16 may continue to shrink. Additionally, in some embodiments, the vapor pressure at the interface 26 of the electrical conductor structure 12 and the dielectricDocket Number: 00809-WOstructure 16 increases as more and more light reaches the electrical conductor structure 12. In some embodiments, if the strength of the remaining epoxy in the to-be-formed via connected to the surrounding epoxy (e.g., the remaining epoxy in the epoxy region 18a justabove / adjacent to the vapor bubble) is exceeded by the underlying vapor bubble, the remaining epoxy will rupture and be ejected.

[0139] In some embodiments, this feature-drilling method is robust enough to compensate for dielectric material variation (e.g., glass fiber density variation) while reliably forming a via with sufficient taper, fiber protrusions and all other via quality parameters across a full workpiece without damaging the bottom electrical conductor structure 12 through direct, unattenuated laser pulse exposure. In some embodiments, because the glass fiber weave of the glass reinforcement region 20 provides a much greater mechanical strength than the epoxy regions 18a, 18b or the epoxy to electrical conductor structure peel strength, the laser drilling process is configured to cut through the glass fiber reinforcement region 20 before the bottom epoxy-electrical conductor structure adhesion strength is exceeded by the vapor bubble's pressure. Thus, in some embodiments, the glass fiber weave may be softened or molten before the vapor bubble reaches the point where it would force delamination of the electrical conductor structure 12. Accordingly, in some embodiments, the laser beam repetition rate cannot be too high such that leaked optical power will heat up the bottom electrical conductor structure 12 too rapidly. In some embodiments, if the laser beam repetition rate is above a certain threshold (such as, for example, 50 MHz), the bottom electrical conductor structure 12 may be damaged before the via 24 is fully formed such that the high-pressure vapor bubble may delaminate the bottom layers of the workpiece 102. Conversely, if the repetition rate is below a certain threshold (such as, for example, 2 MHz), the bottom electrical conductor structure 12 may conduct the absorbed heat efficiently, but with each pulse, the epoxy region 18a at the interface may boil / decompose without rupturing, adding to the buildup of vapor pressure because the pulse repetition rate is faster than the cool down time of the epoxy.

[0140] With reference to FIGS. 7-10, an example of the described drilling method according to embodiments of the present disclosure can be seen. In some embodiments, the controller 122 may be configured to control the laser source 104 and beam steering system 103 to vaporize a first region of the dielectric structure at an interface with the bottom electrical conductor structure. Specifically, as depicted in FIG. 7, during the feature drilling process, a laser beam 28 is directed to the first surface 10 of the workpiece 102. As a laserDocket Number: 00809-WObeam 28 cuts through top layers of the workpiece, light 30 extends through glass-sparse regions to the bottom electrical conductor structure 12, as depicted in FIG. 8. As depicted in FIG. 9, the light 30 causes the electrical conductor structure 12 to conduct energy to a first region 32 of the dielectric structure 16, causing the first region 32 to boil and vaporize. In some embodiments, this first region 32 of the dielectric structure is positioned within the first epoxy region 18a located between the bottom electrical conductor structure 12 and the glass fiber reinforcement region 20. In some embodiments, vaporization of the first region 32 may generate a high-pressure region (or vapor bubble) 34 between the electrical conductor structure 12 and a second region 36 of the dielectric structure 16. In some embodiments, the second region 36 of the dielectric structure 16 is also positioned within the first epoxy region 18a, between the first region 32 of the dielectric structure 16 and the at least one glass fiber reinforcement region 20 (i.e., a third region of the dielectric structure). In some embodiments, the controller 122 may heat the glass fiber reinforcement region 20 at least to as softening point before the pressure of the vaporized first region 34 exceeds the adhesion strength between the dielectric structure 16 and the bottom electrical conductor structure 12. This timing is critical to prevent delamination while ensuring complete via formation. In some embodiments, the controller 122 may be configured to heat the glass fiber reinforcement region 20 to a sufficient level that the pressure of the vaporized first region allows ejection of the second region 36, as depicted in FIG. 10, forming the via 24 (depicted in FIG. 4).

[0141] In some embodiments, the resultant via may have a diameter range of 5 pm to 250 pm; or 10 pm to 250 pm; or 15 pm to 250 pm; or 20 pm to 250 pm; or 50 pm to 250 pm; or 80 pm to 250 pm; or 100 pm to 250 pm; or 120 pm to 250 pm; or 150 pm to 250 pm; or 180 pm to 250 pm; or 200 pm to 250 pm; or 220 pm to 250 pm.

[0142] In some embodiments, the resultant via may have a diameter range of 5 pm to 220 pm; or 5 pm to 200 pm; or 5 pm to 180 pm; or 5 pm to 150 pm; or 5 pm to 120 pm; or 5 pm to 100 pm; or 5 pm to 80 pm; or 5 pm to 50 pm; or 5 pm to 20 pm; or 5 pm to 15 pm; or 5 pm to 10 pm.

[0143] In some embodiments, the resultant via may have a diameter range of 20 pm to 80 pm; or 80 pm to 160 pm; or 160 pm to 220 pm; or 10 pm to 80 pm; or 15 pm to 120 pm; or 60 pm to 240 pm; or 150 pm to 200 pm; or 10 pm to 170 pm; or 170 pm to 200 pm; or 100 pm to 140 pm; or 15 pm to 60 pm.Docket Number: 00809-WO

[0144] In some embodiments, a drill time may be less than 0.5 ps. In some embodiments the drill time may be greater than 100 ps. In some embodiments, the drill time may be 0.5 ps to 100 ps; or 1 ps to 100 ps; or 1.5 ps to 100 ps; or 1.8 ps to 100 ps; or 2 ps to 100 ps; or 3 ps to 100 ps; or 4 ps to 100 ps; or 5 ps to 100 ps; or 6 ps to 100 ps; or 8 ps to 100 ps; or 10 gs to 100 gs; or 12 gs to 100 gs; or 14 gs to 100 gs; or 16 gs to 100 gs; or 18 ps to 100 ps; or 20 gs to 100 gs; or 22 gs to 100 gs; or 24 gs to 100 gs; or 26 gs to 100 gs; or 28 ps to 100 ps; or 30 gs to 100 gs; or 32 gs to 100 gs; or 34 gs to 100 gs; or 36 gs to 100 ps; or 38 gs to 100 gs; or 40 gs to 100 gs; or 42 gs to 100 gs; or 44 gs to 100 gs; or 46 gs to 100 ps; or 48 gs to 100 gs; or 50 gs to 100 gs; or 55 gs to 100 gs; or 60 gs to 100 gs; or 65 ps to 100 ps; or 70 gs to 100 gs; or 75 gs to 100 gs; or 80 gs to 100 gs; or 85 gs to 100 gs; or 90 ps to 100 ps; or 95 gs to 100 gs.

[0145] In some embodiments, the drill time may be 0.5 gs to 95 gs; or 0.5 gs to 90 gs; or 0.5 ps to 85 ps; or 0.5 gs to 80 gs; or 0.5 gs to 75 gs; or 0.5 gs to 70 gs; or 0.5 gs to 65 gs; or 0.5 ps to 60 ps; or 0.5 gs to 55 gs; or 0.5 gs to 50 gs; or 0.5 gs to 48 gs; or 0.5 gs to 46 gs; or 0.5 ps to 44 ps; or 0.5 gs to 42 gs; or 0.5 gs to 40 gs; or 0.5 gs to 38 gs; or 0.5 gs to 36 gs; or 0.5 ps to 34 ps; or 0.5 gs to 32 gs; or 0.5 gs to 30 gs; or 0.5 gs to 28 gs; or 0.5 gs to 26 gs; or 0.5 ps to 24 ps; or 0.5 gs to 22 gs; or 0.5 gs to 20 gs; or 0.5 gs to 18 gs; or 0.5 gs to 16 gs; or 0.5 ps to 14 ps; or 0.5 gs to 12 gs; or 0.5 gs to 10 gs; or 0.5 gs to 8 gs; or 0.5 gs to 6 gs; or 0.5 ps to 5 ps; or 0.5 gs to 4 gs; or 0.5 gs to 3 gs; or 0.5 gs to 2 gs; or 0.5 gs to 1.8 gs; or 0.5 ps to 1.5 ps; or 0.5 gs to 1 gs; or 0.5 gs to 0.75 gs.

[0146] FIGS. 11-18 depict the laser via drilling process progression for an array of vias within a workpiece, according to exemplary embodiments of the present disclosure. The workpiece of FIGS. 11-18 includes a top copper layer, a middle inhomogeneous FR4 dielectric layer, and a bottom copper layer. As depicted in FIGS. 11-12, a first circle repetition removes the top copper layer. As depicted in FIGS. 13-14, a second circle repetition cuts into the glass fiber weave exposing the different drill progression rate across the drilled array due to the fiber weave density variation. As depicted in FIGS. 15-16, a third repetition continues to cut through the glass fiber weave, further exacerbating the via-to-via variation. As depicted in FIGS. 17-18, a fourth repetition leverages a novel aspect of the disclosed laser via drilling process: the final resin layer is ejected for all density variations in such a manner that the vias show a homogenous result and the copper damage is minimal across the entire array. In some embodiments, the laser via drilling process may include more or less repetitions than the above-describe progression.Docket Number: 00809-WO

[0147] FIG. 19 depicts a cross-sectional view of a 20 pm via 224 formed in a workpiece 202 using the above-described via drilling process using a 10 MHz repetition rate, 7 ps punching duration, 77 W power, and 7.7 J / cm2fluence. As depicted, distinct morphologies in the upper and lower portions of the via 224 demonstrate the precision achievable with the controlled ejection of material. The smooth upper portion of the via walls transitioning to a more textured lower region indicates the different material removal mechanisms at play during via formation. Specifically, from the top of the epoxy layer 218b to the bottom edge of the glass fiber reinforcement region 220, the epoxy has a smooth / molten look which can be attributed to a high repetition rate and therefore, thermal nature of the drilling process cutting through the workpiece 202. In contrast, the bottom epoxy region 218a, below the glass reinforcement region 220, shows a markedly different morphology: this is the layer that is broken off due to the underlying vapor pressure, rather than boiling off / decomposing from the top down. This breaking off part emphasizes the difference between the disclosed process from a top-down drilling process, which would have extended molten resin morphology all the way to the bottom electrical conductor structure.

[0148] As depicted in FIG. 20, the absorption spectra of different materials across various wavelength ranges from ultraviolet to infrared. The graph plots absorption on the y-axis versus wavelength in micrometers on the x-axis for three distinct materials - copper, resin, and glass - demonstrating how different materials in the workpiece absorb laser energy at various wavelengths. The wavelength range spans from deep ultraviolet (DUV) through ultraviolet (UV), visible light, near-infrared (NIR), and mid-infrared (MIR) regions. By understanding the absorption characteristics of each material, the laser parameters may be fine-tuned to achieve the desired balance between processing efficiency and quality. For instance, in some embodiments, the wavelength may be chosen to preferentially heat the glass fibers or the epoxy resin, depending on the specific requirements of the drilling process. As can be seen in FIG. 20, the green DPSS laser at 0.532 pm shows relatively high absorption for both resin and glass materials, while maintaining lower absorption for copper. This wavelength may allow for efficient processing of the dielectric structure while minimizing damage to the copper layers. In some embodiments, the absorption spectra may suggest potential benefits of using multiple laser wavelengths in the drilling process. For example, one wavelength may be used for initial material removal, while another may be employed for precision finishing or selective material processing.Docket Number: 00809-WO

[0149] In some embodiments, the controller 122 may optimize the repetition rate of the laser source based on the thermal properties of the materials being processed. Higher repetition rates may be used for materials with higher thermal conductivity to maintain sufficient heat accumulation, while lower rates may be used for thermally sensitive materials to prevent excessive heat buildup.

[0150] FIGS. 21-23 illustrate temperature and phase distributions during a model IR femtosecond laser drilling process at different power and frequency settings. FIG. 21 shows results at 30 MHz and 120 W, while FIG. 22 shows results at 5 MHz and 20 W and FIG. 23 shows results at 1 MHz and 4 W. As depicted in FIG. 21, if the repetition rate is too high (e.g., ~30 MHz), the leaked optical power will heat up the bottom copper rapidly, resulting in bottom copper damage before the via is fully formed and a high-pressure vapor bubble that easily delaminates the bottom layers. As depicted in FIG. 23, if the repetition rate is too low (e.g., ~1 MHz), the bottom copper conducts the absorbed heat efficiently, but with each pulse the resin at the interface boils / decomposes, adding to the buildup of vapor pressure as the pulse repetition rate is still fast compared to the cool down time of the resin. At the same time, not only does the copper cool down, but so does the fiber layer. As depicted in FIG. 22, an in-between repetition rate (e.g., ~5 MHz) balancing these two effects is preferable, resulting in minimized delamination.

[0151] FIGS. 24-26 further demonstrates the results of a model IR femtosecond laser drilling process at different processing parameters. FIG. 25, corresponding to a 5 MHz process, shows minimized delamination compared to a higher repetition rate of 30 MHz in FIG. 24 and a lower repetition rate of 2 MHz in FIG. 26.

[0152] In some embodiments, the laser drilling system 100 may drill a pilot hole before initiating the main via drilling process. In some embodiments, the pilot hole may be created using a shorter burst of laser pulses or a lower power setting compared to the main drilling process. In some embodiments, the initial hole may penetrate partially through the top layers of the workpiece, such as the upper copper layer and a portion of the dielectric material. By creating a pilot hole, the system may achieve improved control over the subsequent drilling process. Reducing the initial reflection may allow for more efficient energy coupling into the material from the start of the main drilling process, potentially leading to more consistent via formation across the workpiece. In some embodiments, the presence of a pilot hole may also influence the formation of the vapor channel during the main drilling process. For example, the pilot hole may provide an initial path for vapor and debris evacuation, potentially leadingDocket Number: 00809-WOto a more stable drilling process with reduced risk of material redeposition or via clogging. In some embodiments, the size and depth of the pilot hole may be adjusted based on the overall via specifications and material properties of the workpiece. In some cases, the pilot hole may be as small as 1pm to 5 pm in diameter, while in other cases it may be closer to the final desired via diameter. By incorporating a pilot hole step, the laser drilling system may achieve enhanced process stability, improved via quality, and potentially higher throughput in some applications. The specific benefits and parameters for pilot hole drilling may vary depending on the particular workpiece materials, via specifications, and overall process requirements.

[0153] In some embodiments, the laser system may include two lasers on a single laser tool. In some embodiments, the laser system may include two different laser tools. In some embodiments, the laser drilling system may be configured to dynamically adjust the repetition rate based on the specific material being processed. While a repetition rate below 50 MHz may be used for dielectric removal and ejection, different parameters may be advantageous when drilling through thicker top copper layers (e.g., >12 pm, >18 pm, or even as thick as 50 pm or more). Conventional laser drilling systems often cannot effectively drill treated copper thicker than 12 pm due to insufficient power density to fully melt the copper column and drive the ejection process. Such thick copper layers have traditionally required UV laser processing, necessitating either systems with multiple lasers on a single tool or separate laser tools for different processing stages.

[0154] In some embodiments, a hybrid laser drilling system may offer a significant advantage through its ability to dynamically switch operating parameters. In some embodiments, when encountering thick copper layers, the system may temporarily switch to a 50 MHz repetition rate while maintaining the same pulse energy. This temporary switch accomplished by operating in burst mode with a 20% duty cycle (e.g., 20 ps on, 80 ps off), which effectively delivers 5 times the average power (e.g., 750 W during the burst) while maintaining the same overall average power of 150 W. Testing has demonstrated that at 50 MHz, the hybrid laser drilling system can achieve approximately 4 times the ablation efficiency compared to operation at 25 MHz or below. This translates to a 20-fold increase in ablation rate during the 20 ps burst period, enabling the system to efficiently remove substantial amounts of copper without requiring a separate laser source or tool.

[0155] This capability represents a significant advancement in laser processing technology. While previous research has established that higher ablation efficiencies can be achieved with ultrafast IR lasers operating in the approximately 1 GHz repetition rate regime,Docket Number: 00809-WOthe present system demonstrates that these efficiency benefits extend down to the 50 MHz range. This finding enables practical implementation in industrial laser systems where GHz repetition rates may be challenging to achieve or maintain. The ability to dynamically switch between repetition rates optimized for different materials within a single process allows for more efficient processing of complex, multi-material substrates without compromising quality or requiring multiple processing steps on different equipment. As shown in FIG. 2, the ablation efficiency at 50 MHz significantly outperforms lower repetition rates across various pulse fluence levels, particularly when using the burst mode configuration.

[0156] In some embodiments, the laser drilling process may be further optimized to control the size of ejected resin fragments.

[0157] In some embodiments, the controller 122 may implement adaptive control algorithms that adjust process parameters in real-time based on optical or thermal feedback from the processing area. This may enable consistent via formation across substrates with varying material properties or thicknesses

[0158] In some embodiments, the control system may receive design data specifying the desired via locations, sizes, and patterns. Based on this information, the system may generate a drilling program to coordinate the laser firing and beam positioning.

[0159] In some embodiments, the laser source may be configured with appropriate parameters such as wavelength, pulse duration, repetition rate, and pulse energy to suit the specific workpiece materials. The beam steering system 103, which may include components like acousto-optic deflectors and galvanometer scanners, may be calibrated to ensure accurate beam placement.

[0160] In some embodiments, the system may utilize in-process monitoring techniques to assess drilling progress and quality. This may include optical sensors to detect when the beam has penetrated through the substrate layers or to measure via dimensions in real-time. The control system may use this feedback to dynamically adjust process parameters. In some embodiments, the laser drilling system may be capable of adapting to variations in workpiece designs and materials. The control software may allow for easy input of different substrate specifications, such as layer thicknesses and material properties. The system may then automatically optimize laser and motion parameters to achieve consistent via quality across varying board regions.Docket Number: 00809-WO

[0161] In some embodiments, for multi-layer workpieces with alternating conductive and dielectric layers, the system may employ a layer-by-layer drilling approach. The laser parameters and focus position may be adjusted for each layer to account for different material properties and ensure clean via walls without damage to underlying layers.

[0162] In some embodiments, the laser drilling system may incorporate features to manage thermal effects during processing. This may include implementing appropriate pulse strategies, such as bursts or pulse shaping, to control heat accumulation. The system may also utilize gas assist or debris removal mechanisms to maintain drilling efficiency and via quality.

[0163] In some embodiments, upon completion of the drilling program, the system may perform automated quality checks. This may involve optical inspection of via dimensions, circularity, and positioning accuracy. The results may be logged for traceability and process optimization.

[0164] In some embodiments, the laser drilling system 100 may be designed for flexibility and scalability. The modular architecture may allow for easy upgrades or reconfiguration to accommodate evolving PCB manufacturing requirements. The control software may provide interfaces for integration with broader PCB production lines and manufacturing execution systems.

[0165] At least some aspects of the present disclosure will now be described with reference to the following numbered clauses.

[0166] 1. A laser drilling system, including:a laser source configured to generate a pulsed laser beam;a beam steering system configured to direct the pulsed laser beam at a first surface of a substrate,where the substrate includes:a conductive layer at a second surface of the substrate opposite the first surface, anda dielectric structure positioned between the conductive layer and the first surface of the substrate;Docket Number: 00809-WOa controller configured to control the pulsed laser source and the beam steering system to:remove material from the dielectric structure to form a via extending from the surface towards the second surface:vaporize a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure,heat a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the workpiece due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure,where the third region of the dielectric structure includes a plurality of irregularly distributed fibers.

[0167] 2. The laser drilling system of clause 1, where the second region of the dielectric structure is adjacent to the first region of the dielectric structure.

[0168] 3. The laser drilling system of clause 1, where the pulsed laser beam has a wavelength in the green range of the electromagnetic spectrum.

[0169] 4. The laser drilling system of clause 1, where the pulsed laser beam has a pulse width of 100 fs to 100 ps.

[0170] 5. The laser drilling system of clause 1, where the pulsed laser beam has a pulse width of 300 fs to 15 ps.

[0171] 6. The laser drilling system of clause 1, where the pulsed laser beam has a repetition rate of 2 MHz to 50 MHz.

[0172] 7. The laser drilling system of clause 1, where the pulsed laser beam has a repetition rate of 5 MHz to 25 MHz.

[0173] 8. The laser drilling system of clause 1, where the pulsed laser beam has a fluence of 0.1 J / cm2to 25 J / cm2.

[0174] 9. The laser drilling system of clause 1, where the pulsed laser beam has a fluence of 3 J / cm2to 10 J / cm2.Docket Number: 00809-WO

[0175] 10. The laser drilling system of clause 1, where the controller is further configured to heat the third region of the dielectric structure to a melting point before the pressure of the vaporized first region exceeds an adhesion strength of the first region of the dielectric structure to the conductive layer.

[0176] 11. The laser drilling system of clause 1, where the via has a diameter of 5 pm to 250 pm.

[0177] 12. The laser drilling system of clause 1, where the via has a diameter of 20 pm to 80 pm.

[0178] 13. The laser drilling system of clause 1, where the controller may be further configured to:control the laser source to generate a first set of laser pulses to vaporize the first region of the dielectric structure; andcontrol the laser source to generate a second set of laser pulses to heat the second region of the dielectric structure.

[0179] 14. The laser drilling system of clause 13, where the first set of laser pulses may have a different pulse energy, pulse duration, or repetition rate than the second set of laser pulses.

[0180] 15. The laser drilling system of clause 1, where the beam steering system includes a galvanometer.

[0181] 16. The laser drilling system of clause 15, where the beam steering system includes at least one acousto-optic deflector system operative to deflect the beam path.

[0182] 17. The laser drilling system of clause 1, where the laser source may include an ultrafast laser capable of generating pulses with durations in the femtosecond to picosecond range.

[0183] 18. The laser drilling system of clause 1, where the dielectric structure may include a glass-reinforced epoxy laminate material.

[0184] 19. A method of laser drilling, including:directing a pulsed laser beam at a first surface of a substrate,where the substrate includes:Docket Number: 00809-WOa conductive layer at a second surface opposite the first surface; and a dielectric structure positioned between the conductive layer and the first surface;removing material from the dielectric structure to form a via extending from the first surface towards the second surface;vaporizing a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure; andheating a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the substrate due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure.

[0185] 20. The method of clause 19, where the third region of the dielectric structure includes a plurality of irregularly distributed fibers.

[0186] 21. The method of clause 19, where the pulsed laser beam has a wavelength in the green range of the electromagnetic spectrum.

[0187] 22. The method of clause 19, where the pulsed laser beam has a pulse width of 100 fs to 100 ps.

[0188] 23. The method of clause 19, where the pulsed laser beam has a repetition rate of 2 MHz to 50 MHz.

[0189] 24. The method of clause 19, where the pulsed laser beam has a fluence of 0.1 J / cm2to 25 J / cm2.

[0190] 25. The method of clause 19, further including heating the third region of the dielectric structure to a melting point before the pressure of the vaporized first region exceeds an adhesion strength of the first region of the dielectric structure to the conductive layer.

[0191] 26. The method of clause 19, where the via has a diameter of 5 pm to 250 pm.

[0192] 27. The method of clause 19, further including:generating a first set of laser pulses to vaporize the first region of the dielectric structure; andDocket Number: 00809-WOgenerating a second set of laser pulses to heat the second region of the dielectric structure.

[0193] 28. The method of clause 27, where the first set of laser pulses has a different pulse energy, pulse duration, or repetition rate than the second set of laser pulses.

[0194] 29. The method of clause 19, further including steering the pulsed laser beam using a galvanometer.

[0195] 30. The method of clause 19, further including steering the pulsed laser beam using at least one acousto-optic deflector system.

[0196] 31. The method of clause 19, further including employing a layer-by-layer drilling approach for multi-layer substrates with alternating conductive and dielectric layers.

[0197] 32. The method of clause 19, further including performing automated quality checks upon completion of a drilling program.

[0198] 33. The method of clause 19, where the dielectric structure includes a glass-reinforced epoxy laminate material.

[0199] 34. The method of clause 19, further including drilling a pilot hole.

[0200] 35. A method of laser drilling, including:generating a first pulsed laser beam from a first laser source;generating a second pulsed laser beam from a second laser source;directing the first and second pulsed laser beams at a first surface of a substrate, where the substrate includes:a first conductive layer at the first surface,a second conductive layer at a second surface of the substrate opposite the first surface, anda dielectric structure positioned between the first conductive layer and the second conductive layer;controlling the first laser source to generate the first pulsed laser beam at a first repetition rate to remove material from the conductive layer;dynamically switching from the first laser source to the second laser source;Docket Number: 00809-WOcontrolling the second laser source to generate the second pulsed laser beam at a second repetition rate to remove material from the dielectric structure, where the second repetition rate is different from the first repetition rate; andvaporizing a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure; andheating a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the substrate due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure.

[0201] XIII. Conclusion

[0202] The foregoing is illustrative of embodiments and examples of the disclosure, and is not to be construed as limiting thereof. Although a few specific embodiments and examples have been described with reference to the drawings, those skilled in the art will readily appreciate that many modifications to the disclosed embodiments and examples, as well as other embodiments, are possible without materially departing from the novel teachings and advantages of the disclosure. Accordingly, all such modifications are intended to be included within the scope of the disclosure as defined in the claims. For example, skilled persons will appreciate that the subject matter of any sentence, paragraph, example or embodiment can be combined with subject matter of some or all of the other sentences, paragraphs, examples or embodiments, except where such combinations are mutually exclusive. The scope of the present disclosure should, therefore, be determined by the following claims, with equivalents of the claims to be included therein.

Claims

1. Docket Number: 00809-WOWhat is claimed is:

1. A laser drilling system, comprising:a laser source configured to generate a pulsed laser beam;a beam steering system configured to direct the pulsed laser beam at a first surface of a substrate,wherein the substrate comprises:a conductive layer at a second surface of the substrate opposite the first surface, anda dielectric structure positioned between the conductive layer and the first surface of the substrate;a controller configured to control the pulsed laser source and the beam steering system to:remove material from the dielectric structure to form a via extending from the surface towards the second surface:vaporize a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure,heat a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the workpiece due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure,wherein the third region of the dielectric structure comprises a plurality of irregularly distributed fibers.

2. The laser drilling system of claim 1, wherein the second region of the dielectric structure is adjacent to the first region of the dielectric structure.

3. The laser drilling system of claim 1, wherein the pulsed laser beam has a wavelength in the green range of the electromagnetic spectrum.

4. The laser drilling system of claim 1, wherein the pulsed laser beam has a pulse width of 100 fs to 100 ps.Docket Number: 00809-WO5. The laser drilling system of claim 1, wherein the pulsed laser beam has a pulse width of 300 fs to 15 ps.

6. The laser drilling system of claim 1, wherein the pulsed laser beam has a repetition rate of 2 MHz to 50 MHz.

7. The laser drilling system of claim 1, wherein the pulsed laser beam has a repetition rate of 5 MHz to 25 MHz.

8. The laser drilling system of claim 1, wherein the pulsed laser beam has a fluence of 0.1 J / cm2to 25 J / cm2.

9. The laser drilling system of claim 1, wherein the pulsed laser beam has a fluence of 3 J / cm2to 10 J / cm2.

10. The laser drilling system of claim 1, wherein the controller is further configured to heat the third region of the dielectric structure to a melting point before the pressure of the vaporized first region exceeds an adhesion strength of the first region of the dielectric structure to the conductive layer.

11. The laser drilling system of claim 1, wherein the via has a diameter of 5 pm to 250 pm.

12. The laser drilling system of claim 1, wherein the via has a diameter of 20 pm to 80 pm.

13. The laser drilling system of claim 1, wherein the controller may be further configured to:control the laser source to generate a first set of laser pulses to vaporize the first region of the dielectric structure; andcontrol the laser source to generate a second set of laser pulses to heat the second region of the dielectric structure.

14. The laser drilling system of claim 13, wherein the first set of laser pulses may have a different pulse energy, pulse duration, or repetition rate than the second set of laser pulses.

15. The laser drilling system of claim 1, wherein the beam steering system comprises a galvanometer.

16. The laser drilling system of claim 15, wherein the beam steering system comprises at least one acousto-optic deflector system operative to deflect the beam path.

17. The laser drilling system of claim 1, wherein the laser source may comprise an ultrafast laser capable of generating pulses with durations in the femtosecond to picosecond range.Docket Number: 00809-WO18. The laser drilling system of claim 1, wherein the dielectric structure may comprise a glass-reinforced epoxy laminate material.

19. A method of laser drilling, comprising:directing a pulsed laser beam at a first surface of a substrate,wherein the substrate comprises:a conductive layer at a second surface opposite the first surface; and a dielectric structure positioned between the conductive layer and the first surface;removing material from the dielectric structure to form a via extending from the first surface towards the second surface;vaporizing a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure; andheating a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the substrate due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure.

20. The method of claim 19, wherein the third region of the dielectric structure comprises a plurality of irregularly distributed fibers.

21. The method of claim 19, wherein the pulsed laser beam has a wavelength in the green range of the electromagnetic spectrum.

22. The method of claim 19, wherein the pulsed laser beam has a pulse width of 100 fs to 100 ps.

23. The method of claim 19, wherein the pulsed laser beam has a repetition rate of 2 MHz to 50 MHz.

24. The method of claim 19, wherein the pulsed laser beam has a fluence of 0.1 J / cm2to 25 J / cm2.

25. The method of claim 19, further comprising heating the third region of the dielectric structure to a melting point before the pressure of the vaporized first region exceeds an adhesion strength of the first region of the dielectric structure to the conductive layer.Docket Number: 00809-WO26. The method of claim 19, wherein the via has a diameter of 5 m to 250 pm.

27. The method of claim 19, further comprising:generating a first set of laser pulses to vaporize the first region of the dielectric structure; andgenerating a second set of laser pulses to heat the second region of the dielectric structure.

28. The method of claim 27, wherein the first set of laser pulses has a different pulse energy, pulse duration, or repetition rate than the second set of laser pulses.

29. The method of claim 19, further comprising steering the pulsed laser beam using a galvanometer.

30. The method of claim 19, further comprising steering the pulsed laser beam using at least one acousto-optic deflector system.

31. The method of claim 19, further comprising employing a layer-by-layer drilling approach for multi-layer substrates with alternating conductive and dielectric layers.

32. The method of claim 19, further comprising performing automated quality checks upon completion of a drilling program.

33. The method of claim 19, wherein the dielectric structure comprises a glass-reinforced epoxy laminate material.

34. The method of claim 19, further comprising drilling a pilot hole.

35. A method of laser drilling, comprising:generating a first pulsed laser beam from a first laser source;generating a second pulsed laser beam from a second laser source;directing the first and second pulsed laser beams at a first surface of a substrate, wherein the substrate comprises:a first conductive layer at the first surface,a second conductive layer at a second surface of the substrate opposite the first surface, andDocket Number: 00809-WOa dielectric structure positioned between the first conductive layer and the second conductive layer;controlling the first laser source to generate the first pulsed laser beam at a first repetition rate to remove material from the conductive layer;dynamically switching from the first laser source to the second laser source; controlling the second laser source to generate the second pulsed laser beam at a second repetition rate to remove material from the dielectric structure, wherein the second repetition rate is different from the first repetition rate; andvaporizing a first region of the dielectric structure at the conductive layer, thereby generating a high-pressure region between the conductive layer and a second region of the dielectric structure; andheating a third region of the dielectric structure to a sufficient level that the second region of the dielectric structure is ejectable from the substrate due to pressure of the vaporized first region exceeding a strength of the heated third region of the dielectric structure.

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