Method and apparatus for laser drilling blind via

Abstract

To provide a method of forming a blind via in a substrate comprising a mask layer, a conductive layer, and a dielectric layer.SOLUTION: A method includes conveying a substrate to a scanning chamber; determining one or more properties of a blind via, the one or more properties comprising a top diameter, a bottom diameter, a volume, or a taper angle of about 80° or more; focusing a laser beam at the substrate to remove at least a portion of a mask layer; adjusting laser process parameters based on the one or more properties; and focusing the laser beam, under the adjusted laser process parameters, to remove at least a portion of a dielectric layer within the volume to form the blind via. In some embodiments, the mask layer can be pre-etched.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] Embodiments of this disclosure generally relate to methods and apparatus for drilling blind vias. [Background technology]

[0002] As the demand for miniaturized electronic devices and components increases, the need for faster processing power with higher circuit density is imposing demands on the materials, structures, and processes used in the manufacture of integrated circuit chips and printed circuit boards. Incorporating blind vias allows for more connections and higher circuit density. Laser drilling is an established method for forming blind vias.

[0003] While the trend toward smaller vias, such as those with diameters of 5 μm to 10 μm, for higher interconnection densities, the quality parameters of a particular blind via remain unchanged. These quality parameters include via top diameter and roundness, via bottom diameter and roundness, via taper angle (greater than 80°), and via pad cleanliness. However, conventional laser drilling techniques cannot produce high-quality blind vias with such small diameters for mass production.

[0004] Conventional approaches to laser drilling blind vias involve directly drilling blind vias into a panel using nanosecond pulsed 355 nm ultraviolet (UV) lasers or pulsed CO2 lasers. However, both of these approaches require complex beam shaping optics to convert the Gaussian laser beam profile emitted by the laser source into a top-hat shaped beam profile. Furthermore, top-hat shaped laser beam profiles generally have a very short depth of field, during which the laser beam profile remains constant in intensity. Moreover, such top-hat beam profiles cannot consistently drill vias with diameters smaller than 40 μm, particularly between 5 μm and 10 μm, in a cost-effective manner. Additionally, conventional laser drilling methods cannot achieve blind vias with a taper angle greater than 80°.

[0005] There is a need for new and improved methods and equipment for drilling large quantities of high-quality, small-diameter blind vias. [Overview of the project]

[0006] Embodiments of this disclosure generally relate to methods and apparatus for drilling blind vias. Embodiments provide a method for forming blind vias in a substrate, comprising transporting the substrate to a scan chamber, wherein the substrate comprises a conductive layer, a dielectric layer disposed on at least a portion of the conductive layer, and a mask layer disposed on at least a portion of the dielectric layer, the mask layer providing the substrate surface. The method further comprises one or more properties of the blind vias. decisionThis method includes, where one or more characteristics are the top diameter and bottom diameter of the blind via, the blind via having a height from the top diameter to the bottom diameter, and the top diameter being greater than the bottom diameter, the volume of the blind via corresponding to the top diameter, bottom diameter, and height, or a taper angle of about 80 degrees or more. This method further includes focusing a laser beam emitted from a laser source onto the substrate surface under laser process parameters to remove at least a portion of the mask layer, adjusting the laser process parameters based on one or more characteristics, and focusing the laser beam under the adjusted laser process parameters to remove at least a portion of the dielectric layer in the volume to form a blind via.

[0007] Another embodiment provides a method for forming blind vias on a substrate, comprising transporting the substrate to a scan chamber, wherein the substrate comprises a conductive layer having a height of about 2 μm or more, a dielectric layer disposed on at least a portion of the conductive layer, and a pre-etched mask layer disposed on at least a portion of the dielectric layer, the pre-etched mask layer having blind via openings for exposing at least a portion of the dielectric layer, and the dielectric layer providing the substrate surface. The method further comprises one or more properties of the blind vias decisionThe method includes, where one or more characteristics are the top diameter and bottom diameter of the blind via, the blind via having a height from the top diameter to the bottom diameter, the top diameter being greater than the bottom diameter, and the top diameter corresponding to the blind via opening, the volume of the blind via corresponding to the top diameter, bottom diameter, and height, or a taper angle of about 80 degrees or more. The method further includes, to remove a first portion of the dielectric layer in a volume from a pre-etched mask layer without causing damage of more than half the thickness of the mask layer, focusing a laser beam emitted from a laser source onto the substrate surface under laser process parameters, adjusting the laser process parameters based on one or more characteristics, and focusing the laser beam under the adjusted laser process parameters to remove a second portion of the dielectric layer in a volume to form a blind via.

[0008] In another embodiment, an apparatus for forming blind vias in a substrate is provided, comprising an optical device including a galvanometer scanner having a plurality of reflective facets and rotation axes, and a beam expander and a collimator. The apparatus further comprises a femtosecond laser beam source configured to direct electromagnetic radiation towards the beam expander, a transport assembly configured to position the substrate to receive electromagnetic radiation reflected from at least one of the reflective facets of the galvanometer scanner, a height sensor configured to detect the height of one or more layers of the substrate, and a controller configured to receive signals from the height sensor and to control the femtosecond beam laser source and the transport assembly based on the signals received from the height sensor.

[0009] To better understand the above features of the present disclosure, a more specific description of the present disclosure, briefly summarized above, can be made by referring to the embodiments illustrated in several of the accompanying drawings. However, it should be noted that the accompanying drawings only show exemplary embodiments and should not be regarded as limiting the scope thereof, and other equally effective embodiments may be recognized.

Brief Description of the Drawings

[0010] [Figure 1A] FIG. showing an exemplary substrate according to at least one embodiment of the present disclosure. [Figure 1B] FIG. showing an exemplary substrate according to at least one embodiment of the present disclosure. [Figure 1C] FIG. showing an exemplary substrate having a blank mask layer according to at least one embodiment of the present disclosure. [Figure 1D] FIG. showing an exemplary substrate having a pre-etched mask layer according to at least one embodiment of the present disclosure. [Figure 2A] FIG. showing an exemplary substrate after forming blind vias according to at least one embodiment of the present disclosure. [Figure 2B] FIG. showing an exemplary substrate after forming blind vias on a substrate having a blank mask layer according to at least one embodiment of the present disclosure. [Figure 2C] FIG. showing an exemplary substrate after forming blind vias on a substrate having a pre-etched mask layer according to at least one embodiment of the present disclosure. [Figure 3] FIG. showing an exemplary method of forming blind vias on a substrate according to at least one embodiment of the present disclosure. [Figure 4] FIG. showing an exemplary method of forming blind vias on a substrate according to at least one embodiment of the present disclosure. [Figure 5]This is a schematic plan view of an exemplary substrate having a plurality of blind vias formed by the apparatus and methods disclosed herein, according to at least one embodiment of the present disclosure. [Figure 6A] This is a schematic side view of an exemplary laser drilling system according to at least one embodiment of the present disclosure. [Figure 6B] This is an enlarged side view of an exemplary optical device of Figure 6A according to at least one embodiment of the present disclosure. [Figure 7] This is an isometric view of an exemplary laser drilling tool having an exemplary laser drilling system, as shown in Figure 6A, arranged within at least one embodiment of the present disclosure. [Figure 8] This is a side view of an exemplary embodiment of the optical alignment device shown in Figure 7, according to at least one embodiment of the present disclosure. [Figure 9] Figure 8 is an isometric view of an exemplary optical alignment device according to at least one embodiment of the present disclosure. [Modes for carrying out the invention]

[0011] For ease of understanding, the same reference numerals are used to indicate common and identical elements in the figures where possible. Elements and features of one embodiment are considered to be usefully incorporated into other embodiments without further detail.

[0012] Embodiments of this disclosure generally relate to methods and apparatus for drilling blind vias. The inventors have discovered methods and apparatus for laser drilling blind vias in panels including conductive and insulating layers. Unlike conventional laser drilling methods and apparatus, the methods and apparatus described herein can enable the formation of blind vias having a taper angle greater than about 80° and can enable the formation of blind vias having a diameter of less than about 40 μm, such as about 5 μm to about 10 μm. The methods and apparatus described herein enable the formation of high-quality blind vias for mass production.

[0013] While there is a trend toward smaller diameter blind vias, such as 5 μm to 10 μm in diameter, for higher interconnection density, the quality parameters of a particular blind via remain unchanged. These include via top diameter and roundness, via bottom diameter and roundness, via taper angle (greater than 80°), and via pad cleanliness. However, conventional laser drilling techniques cannot form high-quality blind vias with such small diameters for mass production.

[0014] Conventional approaches to laser drilling blind vias involve directly drilling blind vias into a panel using nanosecond pulsed 355 nm ultraviolet (UV) lasers or pulsed CO2 lasers. These approaches have certain limitations. Firstly, the Gaussian laser beam profile emitted by the laser source requires a complex beam shaping optical system to convert the beam into a top-hat shaped beam profile. Secondly, the applied beam shaping optical system results in approximately 40% optical energy loss. Thirdly, the intensity profile of a top-hat shaped beam has a very short depth of field (DOF), and within the DOF range, the laser beam profile remains of equal intensity. Here, the intensity profile of an output top-hat beam deforms / degrades rapidly from the image plane along the beam propagation axis due to a non-uniform phase distribution, limiting its application to imaging at large DOFs. The smaller the diameter of the top-hat image beam, the shorter the DOF, and because the DOF is shorter than the variation range of panel thickness / chuck flatness, it is difficult to ensure that the top-hat beam always intersects the panel surface at each via drilling location, thus resulting in inconsistent via quality, especially in mass production. The inability to achieve consistent via quality at higher throughput is not cost-effective. Another conventional method is to apply a deep ultraviolet (DUV) excimer laser with a wavelength of 193 to 308 nm. Mask projection converts the laser beam into a top-hat shaped beam profile. This method also has certain limitations. Firstly, equipment such as lasers and optics, and their maintenance, can be expensive. Secondly, the intensity profile of a top-hat shaped beam has a very short DOF, limiting its applications. Thirdly, masks are consumables. The methods and apparatus described herein can eliminate (or at least mitigate) the aforementioned drawbacks of conventional approaches for laser drilling blind vias.

[0015] substrate Figure 1A shows an exemplary substrate 100 according to at least one embodiment. The exemplary substrate 100 can be used for structural support and electrical interconnection of a semiconductor package. The exemplary substrate 100 generally includes a core structure 102, a conductive layer 104, and an insulating layer 106.

[0016] In at least one embodiment, the core structure 102 includes a patterned (e.g., structured) substrate formed of any suitable substrate material. For example, the core structure 102 may be made of a III-V compound semiconductor material, silicon, crystalline silicon (e.g., Si <100> or Si <111> The substrate may be formed from silicon oxide, silicon germanium, doped or undoped silicon, doped or undoped polysilicon, silicon nitride, quartz, glass (e.g., borosilicate glass), sapphire, alumina, and / or ceramic materials. In at least one embodiment, the core structure 102 includes a single-crystal p-type or n-type silicon substrate. In some embodiments, the core structure 102 includes a polycrystalline p-type or n-type silicon substrate. In another embodiment, the core structure 102 includes a p-type or n-type silicon solar substrate. The substrate used to form the core structure 102 may further have a polygonal or circular shape. For example, the core structure 102 may include a substantially square silicon substrate having a lateral dimension of about 120 to about 180 mm and having chamfered or unchamfered edges. In another example, the core structure 102 includes a circular silicon-containing wafer having a diameter of approximately 20 mm to approximately 700 mm, such as approximately 100 mm to approximately 50 mm, or approximately 300 mm.

[0017] The conductive layer 104 is formed on one or more surfaces of the core structure 102. The conductive layer 104 can be formed from a metallic material such as copper (Cu), tungsten (W), chromium (Cr), molybdenum (Mo), aluminum (Al), gold (Au), nickel (Ni), palladium (Pd), or a combination thereof. In at least one embodiment, the conductive layer includes a layer of tungsten on top of copper. In at least one embodiment, the conductive layer 104 has a height H0 of about 100 μm or less, such as about 50 μm or less, 25 μm or less, etc. For example, the conductive layer 104 can have a height H0 of about 5 μm to about 20 μm, such as a height H0 of about 7 μm to about 18 μm, or a height H0 of about 10 μm to about 15 μm, etc. In at least one embodiment, the height H0 is H 0a From H 0b It is within the range of H 0a From H 0b H 0a <H 0b As long as this is the case, they can be independently, for example, about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, about 15 μm, about 16 μm, about 17 μm, about 18 μm, about 19 μm, or about 20 μm.

[0018] The insulating layer 106 is formed on one or more surfaces of the conductive layer 104. In at least one embodiment, the insulating layer 106 is formed of a polymer-based dielectric material. For example, the insulating layer 106 is formed from a fluid build-up material, typically in the form of a dry film. Thus, although referred to as the “insulating layer” below, the insulating layer 106 can also be described as a dielectric layer. In some embodiments, the insulating layer 106 is formed from an epoxy resin material having ceramic fillers such as silica (SiO2) particles. Other examples of ceramic fillers that can be used to form the insulating layer 106 include aluminum nitride (AlN), aluminum oxide (Al2O3), silicon carbide (SiC), silicon nitride (Si3N4, Sr2Ce2Ti5O 16) Zirconium silicate (ZrSiO4), wollastonite (CaSiO3), beryllium oxide (BeO), cerium dioxide (CeO2), boron nitride (BN), calcium copper titanate (CaCu3Ti4O 12 ) includes magnesium oxide (MgO), titanium dioxide (TiO2), zinc oxide (ZnO), etc. In some examples, the ceramic filler used to form the insulating layer 106 has particles in a size range between about 40 nm and about 1.5 μm, such as between about 80 nm and about 1 μm. For example, the ceramic filler has particles in a size range between about 200 nm and about 800 nm, such as between about 300 nm and about 600 nm. In some embodiments, the insulating layer is a polymer with or without a particulate reinforcing agent. The insulating layer can be a dry dielectric film or a liquid dielectric film.

[0019] In at least one embodiment, the insulating layer 106 has a height H1 of about 100 μm or less, such as about 50 μm or less, about 25 μm or less. For example, the insulating layer 106 can have a height H1 between about 5 μm and about 20 μm, such as between about 7 μm and about 18 μm, between about 10 μm and about 15 μm. In at least one embodiment, the height H1 is in the range from H 1a to H 1b , and H 1a to H 1b are, as long as H 1a <H 1b , independently, for example, about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, about 15 μm, about 16 μm, about 17 μm, about 18 μm, about 19 μm, or about 20 μm.

[0020] Figure 1B shows an exemplary substrate 150 according to at least one embodiment. The exemplary substrate 150 can be used for structural support and electrical interconnection of semiconductor packages. The exemplary substrate 150 generally includes a core structure 152, conductive layers 154a, 154b formed on opposing surfaces of the core structure 152, an insulating layer 156a formed on the surface of the conductive layer 154a, and an insulating layer 156b formed on the surface of the conductive layer 154b. The exemplary properties and features of the core structure 152, the conductive layers 154a, 154b, and the insulating layers 156a, 156b are the same as those described above with respect to the core structure 102, the conductive layer 104, and the insulating layer 106, respectively.

[0021] Figure 1C shows an exemplary substrate 170 having a blank mask layer (e.g., not pre-etched) according to at least one embodiment. The exemplary substrate 170 can be used for structural support and electrical interconnection of semiconductor packages. The exemplary substrate 170 generally includes a core structure 172, a conductive layer 174 formed on the surface of the core structure 172, an insulating layer 176 formed on the surface of the conductive layer 174, and a mask layer 178 formed on the surface of the insulating layer 176. The exemplary properties and features of the core structure 172, the conductive layer 174, and the insulating layer 176 are the same as those described above with respect to the core structure 102, the conductive layer 104, and the insulating layer 106, respectively.

[0022] In at least one embodiment, the mask layer 178 comprises Al, Cu, W, Mo, Cr, or a combination thereof. In some embodiments, the mask layer (with or without openings) has a height H2 of about 2 μm or less, such as about 0.03 μm to about 2 μm, or about 0.05 μm to about 1 μm. In at least one embodiment, the height H2 is H 2a From H 2b It is within the range of H 2a From H 2b H 2a <H 2bAs long as this is the case, they can be independently, for example, about 0.1 μm, about 0.2 μm, about 0.3 μm, about 0.4 μm, about 0.5 μm, about 0.6 μm, about 0.7 μm, about 0.8 μm, about 0.9 μm, about 1 μm, about 1.1 μm, about 1.2 μm, about 1.3 μm, about 1.4 μm, about 1.5 μm, about 1.6 μm, about 1.7 μm, about 1.8 μm, about 1.9 μm, or about 2 μm.

[0023] The mask layer 178 can be formed, for example, by deposition, sputtering, or electroplating. In at least one embodiment, the mask layer is laser ablated. In some embodiments, the mask layer 178 is removed by an etching operation after blind vias have been formed by the processes described herein. In some embodiments, such as when the mask layer 178 is Mo and / or W, the mask is maintained after the blind vias have been formed and, in combination with a deposited conductive layer (e.g., Cu), functions as an interconnection layer.

[0024] In at least one embodiment, as again shown with reference to Figure 1B, the exemplary substrate includes a mask on the surface of insulating layer 156a and / or insulating layer 156b. The mask layer is blank or can be pre-etched to form via openings. The characteristics of each mask layer are similar to those described above with respect to mask layer 178.

[0025] Figure 1D shows an exemplary substrate 180 having a pre-etched (or pre-opened) mask layer according to at least one embodiment. Here, the exemplary substrate 180 is pre-etched to form via openings. The exemplary substrate 180 can be used for structural support and electrical interconnection of a semiconductor package. The exemplary substrate 180 generally includes a core structure 182, a conductive layer 184 formed on the surface of the core structure 182, an insulating layer 186 formed on the surface of the conductive layer 184, and a mask layer 188 formed on the surface of the insulating layer 186. The exemplary properties and features of the core structure 182, the conductive layer 184, and the insulating layer 186 are the same as those described above with respect to the core structure 102, the conductive layer 104, and the insulating layer 106, respectively. The exemplary properties and features of the mask layer 188 are the same as those of the mask layer 178 described above.

[0026] Figure 2A shows an exemplary substrate 200 after blind vias have been formed on an exemplary substrate 100 (shown in Figure 1A), according to at least one embodiment. The exemplary substrate 200 generally includes a core structure 202, a conductive layer 204, and an insulating layer 206. The blind via 208 extends from the surface of the insulating layer 206 to the conductive layer 204. The blind via 208 has a top diameter D1, a bottom diameter D2, a taper angle (A1), and a volume V1. In some embodiments, the blind via 208 penetrates the conductive layer 204 or penetrates it minimally. In some embodiments, the blind via does not penetrate the conductive layer 204 or does not penetrate it substantially.

[0027] The diameters of the top diameter D1 and bottom diameter D2 can be approximately 15 μm or less, approximately 5 μm to approximately 10 μm, and approximately 20 μm or less. In at least one embodiment, the top diameter D1 is D 1a From D 1b It is within the range of D 1a From D 1b D 1a <D 1bAs long as this is the case, independently they can be, for example, about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, about 15 μm, about 16 μm, about 17 μm, about 18 μm, about 19 μm, or about 20 μm. In at least one embodiment, the bottom diameter D2 is D 2a From D 2b It is within the range of D 2a From D 2b D 2a <D 2b As long as this is the case, they can be independently, for example, about 1 μm, about 2 μm, about 3 μm, about 4 μm, about 5 μm, about 6 μm, about 7 μm, about 8 μm, about 9 μm, about 10 μm, about 11 μm, about 12 μm, about 13 μm, about 14 μm, about 15 μm, about 16 μm, about 17 μm, about 18 μm, about 19 μm, or about 20 μm.

[0028] In some embodiments, the bottom diameter D2 is smaller than the top diameter D1 so that the blind via has a taper. The taper corresponds to the ratio of the bottom diameter D2 to the top diameter D1. In at least one embodiment, the ratio of the bottom diameter D2 to the top diameter D1 is about 0.353*H, such as about 0.4*H1 to about 1, about 0.5*H1 to about 1, and so on. IL (Here, H IL It is approximately 1 from the insulating layer (for example, the height of insulating layer 206).

[0029] In at least one embodiment, the blind via 208 has a taper angle A1 corresponding to the angle between the inner wall of the blind via 208 and the surface of the conductive layer 204. In at least one embodiment, the taper angle A1 is about 75° to 90°, such as about 80° to about 89°. In at least one embodiment, the taper angle A1 is A 1a From A 1b It is within the range of A 1a From A 1b is, A 1a 1b ​As long as this is the case, they can be independently, for example, approximately 71°, 72°, 73°, 74°, 75°, 76°, 77°, 78°, 79°, 80°, 81°, 82°, 83°, 84°, 85°, 86°, 87°, 88°, 89°, or 90°.

[0030] Figure 2B shows an exemplary substrate 250 after blind vias have been formed on an exemplary substrate 170 having a blank mask (shown in Figure 1C), according to at least one embodiment. The exemplary substrate 250 generally includes a core structure 252, a conductive layer 254, an insulating layer 256, and a mask layer 260. The blind vias are indicated by reference numeral 258. The characteristics of the core structure 252, conductive layer 254, insulating layer 256, height H0, height H1, diameter D1, diameter D2, and taper angle A1 are the same as those described above. Angle A2 can substantially correspond to and / or have similar characteristics to taper angle A1. In at least one embodiment, A2 is less than or equal to A1. In at least one embodiment, taper angle A2 is A 2a From A 2b It is within the range of A 2a From A 2b is, A 2a 2b As long as this is the case, independently, we can have, for example, approximately 71°, approximately 72°, approximately 73°, approximately 74°, approximately 75°, approximately 76°, approximately 77°, approximately 78°, approximately 79°, approximately 80°, approximately 81°, approximately 82°, approximately 83°, approximately 84°, approximately 85°, approximately 86°, approximately 87°, approximately 88°, approximately 89°, or approximately 90°.

[0031] ​In some embodiments, the diameter D3 of the mask layer 260 is approximately equal to or greater than the diameter D1, ranging from approximately D1 to approximately D1+5μm, for example, approximately D1+4μm, approximately D1+3μm, approximately D1+2μm, or approximately D1+1μm. In at least one embodiment, diameter D3 ≥ diameter D1 ≥ diameter D2. Blind vias can correspond to reference nominal 258 when the mask layer is removed from the substrate after the process, or to reference nominal 262 when the mask layer is retained on the substrate after the process.

[0032] Figure 2C shows an exemplary substrate 270 after blind vias have been formed on an exemplary substrate 180 having a pre-etched / pre-opened mask (shown in Figure 1D), according to at least one embodiment. The exemplary substrate 270 generally includes a core structure 272, a conductive layer 274, an insulating layer 276, and a mask layer 280. The blind vias are indicated by reference numeral 278. The characteristics of the core structure 272, conductive layer 274, insulating layer 276, height H0, height H1, diameter D1, diameter D2, taper angle A1, and taper angle A2 are similar to those described above. In at least one embodiment, taper angle A2 is substantially 90° or substantially corresponding to taper angle A1. In at least one embodiment, the taper angles A1 and A2 are independently, for example, about 71°, about 72°, about 73°, about 74°, about 75°, about 76°, about 77°, about 78°, about 79°, about 80°, about 81°, about 82°, about 83°, about 84°, about 85°, about 86°, about 87°, about 88°, about 89°, or about 90°. Taper angle A1 can be equal to, less than, or greater than taper angle A2. The diameter D3 (in μm) of the mask layer 280 can be about D1 to about (D1 + (1 / 4)H2), about D1 to about (D1 + (1 / 3)H2), about D1 to about (D1 + (1 / 2)H2), etc., and less than or equal to about (D1 + H2). In at least one embodiment, diameter D3 ≥ diameter D1.

[0033] In some embodiments, the allowable variation range of taper angle A2 is wider than the allowable variation range of taper angle A1, for example, 70°≦A2≦90° and 75°≦A1≦90°. In some examples, for vias with a diameter of 5 to 10 μm, 80°≦A1 is the limit, and for vias larger than 10 μm, 75°≦A1 is the limit.

[0034] In at least one embodiment, the mask layer (with or without openings) has a height of about 2 μm or less, such as about 0.03 μm to about 2 μm, or about 0.05 μm to about 1 μm.

[0035] The mask layers described herein can be opened by photolithography. In some embodiments, a photoresist layer is applied to the top of a metal mask. The photoresist layer can be patterned by photolithography to define the size and position of via openings on the metal mask layer. The openings on the metal mask layer can be formed by etching processes such as plasma etching and wet chemical etching. Lithographically defined openings allow for a relaxation of positional accuracy and improve laser throughput.

[0036] process Embodiments described herein also include a process for laser drilling blind vias. The laser source for laser drilling blind vias can be a femtosecond laser. A suitable femtosecond-based laser process can typically be characterized by a high peak intensity (irradiance) that results in nonlinear interactions between various materials.

[0037] Figure 3 shows an exemplary method 300 for forming blind vias on a substrate according to at least one embodiment. In at least one embodiment, exemplary method 300 is used on a substrate having a mask layer without openings (i.e., a blank). Exemplary method 300 includes transporting the substrate to a scan chamber in operation 302, where the substrate may include a conductive layer (e.g., a copper layer), a dielectric layer disposed on at least a portion of the conductive layer, and a mask layer disposed on at least a portion of the dielectric layer, the mask layer providing the substrate surface. Exemplary method 300 further includes, in operation 304, one or more properties of the blind vias decision This includes: One or more properties may include the top diameter of the blind via, the bottom diameter of the blind via, the height of the blind via, the volume of the blind via, and the taper angle of the blind via. In at least one embodiment, the taper angle is greater than 75° or greater than 80° as described above. In some embodiments, the top diameter is greater than the bottom diameter, and the top diameter corresponds to the blind via opening. The volume of the blind via corresponds to the top diameter, bottom diameter, and height. Exemplary method 300 further includes, in operation 306, focusing a laser beam emitted from a laser source onto the substrate surface under laser process parameters. This operation will remove a first portion of the dielectric layer in volume, but will cause only gentle melting and polishing on the surface of the conductive layer beneath the dielectric layer, and the ablation depth of the conductive layer will be, for example, only about 2 μm. In some embodiments, operation 306 will remove less than about half the thickness of the mask layer. Thus, in some embodiments, the conductive layer will have virtually no damage after operation 306.

[0038] An exemplary method 300 further includes adjusting laser process parameters based on one or more characteristics in operation 308. In some embodiments, the laser process parameters are laser power, laser energy in burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in burst, pulse frequency, burst frequency, beam spot size, M2 The value includes the beam focusing offset from the substrate surface (above and / or below the substrate surface), or a combination thereof. 2 This is a unitless spatial characteristic of the laser beam and measures the difference between the actual laser beam and the Gaussian beam. These and other laser process parameters are described below. Exemplary method 300 further includes focusing the laser beam under tuned laser process parameters to remove at least a portion of the dielectric layer in the volume to form blind vias in operation 310.

[0039] In some embodiments, further operations are performed, such as removing the mask layer from the substrate. In at least one embodiment, if the mask layer contains Mo and / or W, the further operation includes depositing a layer of copper on top of the mask layer.

[0040] Figure 4 shows an exemplary method 400 for forming blind vias on a substrate according to at least one embodiment. In at least one embodiment, exemplary method 400 is used to form blind vias on a substrate having a pre-etched mask layer. Exemplary method 400 includes transporting the substrate to a scan chamber in operation 402. Here, the substrate may include a conductive layer (e.g., a copper layer), a dielectric layer disposed on at least a portion of the conductive layer, and a pre-etched mask layer disposed on at least a portion of the dielectric layer, the pre-etched mask layer having blind via openings to expose at least a portion of the dielectric layer, and the dielectric layer providing the substrate surface. Exemplary method 400 further includes, in operation 404, one or more properties of the blind vias decisionThis includes: One or more properties may include the top diameter of the blind via, the bottom diameter of the blind via, the height of the blind via, the volume of the blind via, and the taper angle of the blind via. In at least one embodiment, the taper angle is greater than 75° or greater than 80° as described above. In some embodiments, the top diameter is greater than the bottom diameter, and the top diameter corresponds to the blind via opening. The volume of the blind via corresponds to the top diameter, bottom diameter, and height. Exemplary method 400 further includes, in operation 406, focusing a laser beam emitted from a laser source onto the substrate surface under laser process parameters. This operation removes a first portion of the dielectric layer in the volume and can be performed without substantially damaging the pre-etched mask layer and / or the conductive layer. "Without causing substantial damage to the pre-etched mask layer" means that the mask layer is slightly melted and the mask surface is "polished / buffed," but no material is removed from the mask surface by visible ablation that would cause changes in top via diameter or the formation of elliptical vias. The mask is a removable sacrificial layer. In at least one embodiment, the acceptable mask damage depends on the height of the mask. As a non-limiting example, if the height of the mask is about 0.3 μm, the depth of damage / ablation to the mask must be less than about 0.3 μm. As another non-limiting example, if the height of the mask is about 2 μm, the depth of damage / ablation to the mask must be less than about 2 μm.

[0041] An exemplary method 400 further includes adjusting laser process parameters based on one or more characteristics in operation 408. In some embodiments, the laser process parameters are laser power, laser energy in burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in burst, pulse frequency, burst frequency, beam spot size, M 2This includes values, beam focusing offset from the substrate surface, or combinations thereof. These and other laser process parameters are described below. Exemplary method 400 further includes focusing the laser beam under tuned laser process parameters in operation 410 to remove at least a portion of the dielectric layer in the volume to form blind vias.

[0042] In some embodiments, further operations are performed, such as removing the pre-etched mask layer from the substrate. In at least one embodiment, if the pre-etched mask layer contains Mo and / or W, the further operation includes depositing a layer of copper on the pre-etched mask layer.

[0043] The femtosecond laser sources (such as ultraviolet lasers) used in at least some embodiments of this specification have several tunable features (laser process parameters), as described below. In at least one embodiment, the laser process parameters include one or more of the following features:

[0044] (1) The femtosecond laser source has a pulse width or pulse width range of approximately 1 fs to approximately 1000 fs, such as approximately 100 femtoseconds (fs) to approximately 750 fs, approximately 200 fs to approximately 500 fs, etc.

[0045] (2) The femtosecond laser source has a wavelength or wavelength range of about 250 nm to about 2000 nm, such as about 266 nanometers (nm) to about 1500 nm or about 350 nm to about 540 nm. In at least one embodiment, the femtosecond laser source has a wavelength of about 400 nm or less.

[0046] (3) The femtosecond laser source and the corresponding optical system provide a focal point or focal range on the work surface in the range of approximately 1.5 μm to approximately 12 μm, such as approximately 3 microns (μm) to approximately 10 μm, approximately 4 μm to approximately 8 μm, etc. The spatial beam profile on the work surface can be a single-mode (Gaussian) profile.

[0047] (4) The femtosecond laser source outputs bursts of pulses. Within each burst, the pulse frequency or range of pulse frequencies is approximately 500 MHz or more, such as approximately 1 GHz or more, approximately 2 GHz or more, approximately 1 GHz to approximately 10 GHz, approximately 2 GHz to approximately 9 GHz, approximately 3 GHz to approximately 8 GHz, approximately 4 GHz to approximately 7 GHz, approximately 5 GHz to approximately 6 GHz, etc. In at least one embodiment, the pulse frequency or range of pulse frequencies within each burst is approximately 2 GHz to approximately 5 GHz.

[0048] (5) The number of pulses in each burst output from the femtosecond laser source can be adjusted. The number of pulses in each burst can be approximately 2 or more, or approximately 3 or more, such as approximately 5 to approximately 100, approximately 10 to approximately 100, approximately 20 to approximately 90, approximately 40 to approximately 80, approximately 50 to approximately 70, approximately 55 to approximately 65, etc. In at least one embodiment, the number of pulses in each burst is approximately 20 to approximately 100.

[0049] (6) The burst frequency is adjustable. The burst frequency of the femtosecond laser source can be about 100 kHz or higher, such as about 500 kHz or higher. In at least one embodiment, the burst frequency is about 200 kHz to about 5 MHz, or about 500 kHz to about 5 MHz, such as about 300 kHz to about 2 MHz, about 1 MHz to about 2 MHz, or about 500 kHz to about 1 MHz.

[0050] (7) The femtosecond laser source delivers bursts of laser energy ranging from approximately 1 μJ to approximately 100 μJ, such as from approximately 1 μJ to approximately 80 μJ, from approximately 3 μJ to approximately 50 μJ, and from approximately 5 μJ to approximately 20 μJ. In at least one embodiment, the laser and burst frequency are set to achieve bursts of laser energy ranging from approximately 5 μJ to approximately 50 μJ, such as from approximately 5 μJ to approximately 50 μJ, and from approximately 10 μJ to approximately 30 μJ.

[0051] (8) The laser output of the femtosecond laser source is approximately 1W or more, such as approximately 1W to approximately 100W, approximately 5W to approximately 80W, and approximately 10W to approximately 50W.

[0052] (9) M that characterizes the quality of the laser beam 2 The values ​​are approximately 1 to 1.3, 1.1 to 1.2, 1 to 1.15, or 1 to 1.1, etc., less than or equal to approximately 1.5 (M 2 (This is always ≥ 1.0).

[0053] (10) The focal beam diameter can be approximately 2 μm to approximately 10 μm, for example, approximately 3 μm to approximately 6 μm when drilling a via with a diameter of 5 μm. The focal beam diameter can be approximately 7 μm to approximately 12 μm, for example, approximately 8 μm to approximately 11 μm when drilling a via with a diameter of 10 μm. The focused beam diameter is the laser beam spot diameter on the processing surface, which is the result of the output laser beam passing through the beam expander and being focused by the focusing lens.

[0054] (11) The beam focusing offset from the substrate, also called the focal height, is approximately 0 μm to 100 μm, such as approximately 0 μm to 50 μm, approximately 0 μm to 30 μm, etc. The focal height is an adjustable parameter. In some embodiments, for example, the focus is set directly above the panel surface to cut out the mask and remove a portion of the insulating layer material, and then the focal height is adjusted so that the focal plane is above the panel surface. In other words, the laser beam that intersects the panel surface is defocused to remove only the insulating layer material and obtain a low fluence that does not damage the mask layer and conductive layer at the via bottom.

[0055] (12) The number of bursts is approximately 2 or more, ranging from about 5 to about 20.

[0056] (13) The focused beam spot size is approximately 80% to approximately 120% of the target entrance diameter of the hole on the dielectric surface (for example, the entrance diameter D1 of the hole to be drilled as defined in Figure 2C, or the diameter D1 of the hole to be drilled as defined in Figure 2B), for example, approximately 90% to approximately 110%, approximately 95% to approximately 100%, etc.

[0057] The focused beam diameter can be adjusted using a programmable beam expander to drill vias of different diameters.

[0058] A femtosecond laser source can be an electromagnetic radiation source such as a diode-pumped solid-state (DPSS) laser, or other similar radiation sources capable of providing and emitting a continuous or pulsed beam. Depending on the laser medium (crystal) configuration, in at least one embodiment, the DPSS laser can be a rod crystal laser, a fiber laser, a disk laser, a rod-type photonic crystal fiber laser, an InnoSlab laser, or a hybrid thereof. In some embodiments, the laser source comprises multiple laser diodes, each generating uniform, spatially coherent light at the same wavelength.

[0059] Device Embodiments of this disclosure also generally relate to apparatus for laser drilling blind vias. Figure 6A is a schematic side view of an exemplary laser drilling system 600 for performing a particular aspect of this disclosure, according to several embodiments.

[0060] The laser drilling system 600 includes a housing 602 having a substrate positioning system 605 inside. The substrate positioning system 605 can be a conveyor for supporting and transporting the substrate 510 by the laser drilling system 600. The laser drilling system 600 can be used to drill blind vias 501 (Figure 5) in one or more layers arranged on the substrate 510 according to embodiments of the present disclosure. Each substrate 510 can be an exemplary substrate as shown in Figures 1 and 2. In at least one embodiment, the mask of the substrate 510 can be faced upward for processing in the laser drilling system 600.

[0061] In at least one embodiment, the substrate positioning system 605 is a linear conveyor system including a continuous transfer belt 615 made of a material configured to support and transport a line of substrates 510 by a laser drilling system 600 in a flow path "A". The housing 602 is positioned between a loading station 617A for supplying substrates 510 and an unloading station 617B for receiving processed substrates 510. The loading station 617A and the unloading station 617B can be coupled to the housing 602 and may include robotic equipment and / or transfer mechanisms for supplying substrates 510 to the transfer belt 615. The substrate positioning system 605 includes support rollers 620 for supporting and / or driving the transfer belt 615. The support roller 620 is driven by a mechanical drive unit 625, such as a motor / chain drive unit, and is configured to transport the transport belt 615 at a linear speed of approximately 100 mm / s to approximately 2000 mm / s, such as approximately 500 mm / s to approximately 2000 mm / s, or approximately 500 mm / s to approximately 1500 mm / s, during operation. The mechanical drive unit 625 can be an electric motor, such as an AC or DC servo motor. The transport belt 615 can be made of, for example, stainless steel, polymer material, and / or aluminum. In at least one embodiment, the transport belt 615 includes two parallel belts that can be spaced apart in the X direction, and each of the two parallel belts has a width in the X direction that is smaller than the dimension in the X direction of the substrate 510. In this configuration, each substrate 510 in the laser drilling system 600 can be placed in part of both parallel belts.

[0062] The substrate positioning system 605 may be a transfer device configured to sequentially transfer a line of substrates 510 (for example, within flow path "A") toward and by a laser scanning device 630. The laser scanning device 630 includes an optical device 635A coupled to a support member 640 that supports the optical device 635A on a transfer belt 615 and substrates 510. The laser scanning device 630 also includes a scan chamber 635B fixed in place relative to the transfer belt 615 adjacent to the optical device 635A, allowing the substrates 510 to pass along the transfer belt 615.

[0063] Figure 6B is a side view of the exemplary optical device 635A shown in Figure 6A, where the optical device 635A is rotated 90 degrees from the standard position shown in Figure 6A for the purposes of discussion. Figure 5 is a schematic plan view of an exemplary substrate 510 having a plurality of blind vias 501 formed by the optical device 635A of Figures 6A and 6B. The optical device 635A includes a housing 641 that provides light or electromagnetic radiation directed to the surface of the substrate 510 as the substrate 510 passes through the scan chamber 635B on the transfer belt 615. In at least one embodiment, the optical device 635A is configured to, in combination with the movement of the transfer belt 615, to form a pattern (P) which may include a pattern of rows (R) and columns (C) of blind vias 501 formed on the substrate 510, as shown in Figure 5. In some embodiments, the optical device 635A forms a pattern (P) on the substrate 510 with a time period of about 0.5 ms or less, such as about 0.01 milliseconds (ms) to about 0.1 ms, or about 0.001 ms to about 0.005 ms, using an optical system capable of providing a pulsed beam that rapidly crosses the substrate 510 as the substrate 510 moves along the transport belt 615. The optical device 635A also includes a laser source 642, such as a femtosecond laser source, which emits light or electromagnetic radiation by an optical system that provides, for example, about 50,000 blind vias to the substrate 510 having desired features described herein, such as diameter and taper angle.

[0064] In laser processing, unlike typical plasma processing in semiconductor processes, the plasma is like a cloud or feather that can cover the entire wafer surface, and the laser beam is a tiny spot, especially when focused. Therefore, relative movement between the laser beam and the sample (e.g., wafer) is usually required to process the entire sample. Relative movement can be achieved in various ways. In the first method, in some embodiments, the laser beam remains stationary, and the substrate is moved by a linear stage with movement in the directions of X / Y / Z (height) / theta angle (on the XY plane for rotating the sample) / A tilt angle (on the XZ and YZ planes for tilting the sample). For microfabrication, X / Y / Z / theta movement is usually sufficient. In the second method, in some embodiments, the laser source and / or laser focusing head is mounted on the X / Y / Z / theta stage.

[0065] In a third method, in some embodiments, the substrate is held stationary on a chuck, and the laser beam is scanned across the substrate. An optical scanner is used to direct, position, and / or "scan" the laser beam over a desired area of ​​the substrate. In this case, the light beam is refracted, diffracted, and / or reflected by the optical scanner to achieve movement across the substrate surface. Generally, there are three types of optical scanners: acousto-optic scanners that use diffraction to deflect the beam, electro-optic scanners that use refraction to deflect the beam, and mechanical scanners (resonance, polygon, and galvanometer scan types) that utilize reflection to deflect the beam.

[0066] The fourth technique involves the combined movement of the laser beam and the sample. For example, the laser beam is scanned across the entire substrate while the substrate is moved simultaneously or sequentially on the chuck / stage. In addition to this, or instead, a scanner is mounted on a single-axis moving stage to move and scan the beam.

[0067] In some embodiments, optical scanning techniques such as mechanical scanners like polygon and / or Garbo scanners are used to move a laser beam from one position to another on the substrate surface, for example, to drill via arrays at specified locations on a substrate. These mechanical scanners achieve high optical throughput by rotating physical mirrors that can be coated to reflect any wavelength or combination of wavelengths from the rotating mirrors with very high reflectivity. The scan angle achievable with optical angles is twice the actual motor rotation angle. Using those physical mirrors, the beam can be scanned at a very wide angle with a polygon scanner, but there is a limitation that the same pattern will be scanned many times. Polygon scanners perform 1-axis scanning. To generate 2D patterns, other axial movement can be provided by adding a linear stage or Garbo mirror.

[0068] Mechanical galvanometer-based scanners (or galbos) typically include a physical mirror driven by a motor. In most cases, the mirror is mounted on the motor shaft, although some designs integrate the mirror and motor into a single unit. Galbo motors can rotate over a range of angles (typically around ±20°). High-precision position detectors can also be incorporated into the galbo motor, providing feedback to another controller and achieving positioning repeatability of 5 μrad (5 mm at a distance of 1 km). Two galvanometer scanners can be configured for 2-axis scanning.

[0069] In at least one embodiment, the speed of the transport belt 215 is controlled during operation from about 100 mm / s to about 5000 mm / s, such as from about 250 mm / s to about 2000 mm / s, and from about 0.5 m / s to about 1 m / s, in order to form a plurality of blind vias 501 on the substrate 510 in a substantially linear row in the X direction (Figure 6A) as the substrate 510 passes under the optical device 635A on the transport belt 615 in the Y direction.

[0070] In at least one embodiment, a Garbo scanner is used as an alternative to (or in addition to) the transfer belt 215 to change the drilling location from one via to the next via.

[0071] As shown again with reference to Figure 6B, the laser source 642 can emit light or electromagnetic radiation 655 by a process of optical amplification based on stimulated emission of photons. In at least one embodiment, the laser beam emitted by the laser source 642 is a Gaussian beam. In some embodiments, the emitted electromagnetic radiation 655 has a high degree of spatial and / or temporal coherence. In at least one embodiment, the laser source 642 emits continuous or pulsed light or electromagnetic radiation 655 directed towards an optical system including a beam expander 644, a beam collimator 646, and a galvanometer scanner 650.

[0072] The galvanometer scanner 650 may include a movable mirror for guiding the laser beam, and the beam guidance can be one-dimensional, two-dimensional, or three-dimensional. To position the laser beam in two dimensions, the galvanometer scanner 650 can rotate one mirror along two axes or reflect the laser beam off two closely spaced mirrors mounted on orthogonal axes. To position the laser beam focal point in three dimensions, a servo-controlled galvanometer scanner can be used. Features of the laser source 642, such as a femtosecond laser source, are described above.

[0073] In some embodiments, the pulse width and frequency of the electromagnetic radiation pulses 655 are controlled by providing an external trigger signal to the laser source 642, which is provided by the controller 690 at a desired frequency.

[0074] The pulses of electromagnetic radiation 655 emitted from the laser source 642 are received by a beam expander 644 having a first diameter, such as approximately 1 mm to 6 mm, approximately 2 mm to 5 mm, or approximately 3 mm to 4 mm. The beam expander 644 can increase the diameter of the electromagnetic radiation 655 to a second diameter by a preset magnification, such as approximately 2x, 5x, or 8x, or the beam expander 644 can have an adjustable magnification range, such as approximately 1x to 8x. Next, the pulses of electromagnetic radiation 655 are sent to a beam collimator 646 to narrow the beam.

[0075] In at least one embodiment, the beam collimation function is integrated into the beam expander 644. That is, in such an embodiment, the beam expander 644 is also a beam collimator. Here, the beam expander 644 has at least two functions: beam expansion to a specific magnification and beam parallelization. The beam expander can have a fixed magnification (for example, if it is 2x, the output beam diameter is equal to twice the input beam diameter) or an adjustable range of magnification (for example, from 3x to 8x). For example, a laser beam with a diameter of 2 mm can be incident on the input side of a 3x beam expander, and then a beam with a diameter of 6 mm is output at the output (exit) side of the beam expander. This 6 mm beam (because it propagates along the optical axis) can be a diverging or converging beam, but is not typically a fully collimated beam. A fully collimated beam neither diverges nor converges as it propagates along the optical axis. The "beam collimating" mechanism allows the beam to be adjusted to have very little divergence or convergence, so even when the travel distance is several meters or more, the beam diameter may change by only about 1% to about 2% or less.

[0076] A pulse of electromagnetic radiation 655 is sent from the beam collimator 646 to the galvanometer scanner 650, which guides the pulse of electromagnetic radiation 655 to the substrate 510 via the focusing lens 652. The focusing lens 652 can be a telecentric focusing lens. The focusing lens 652 may have one or more lenses.

[0077] The galvanometer scanner 650 induces pulses of electromagnetic radiation onto the surface of the substrate 510, which moves continuously in the Y direction on the transfer belt 615 in the scan chamber 635B, via a focusing lens 652, which is part of the optical system of the optical device 635A (Figure 6A). Therefore, the transfer belt 615 does not need to stop / start during the blind via formation process on the substrate 510, which can improve throughput. However, in some embodiments, the surface of the substrate moves periodically in the Y direction on the transfer belt 615 in the scan chamber 635B (Figure 6A). The galvanometer scanner 650 may include a mirror having multiple reflective facets, each of which is arranged so that it can generally be angled with respect to another reflective facet 653 of the reflective facet 653 in the direction of entering the page in the X direction with respect to the rotation axis 651 of the galvanometer scanner 650 (in the X direction in Figure 6B). The angle of each reflective facet 653 of the galvanometer scanner 650 allows the electromagnetic radiation 655 to scan across the surface of the substrate 510 in one direction (the X direction in Figure 6A) as the galvanometer scanner 650 rotates around the rotation axis 651 by the actuator 654. Using the actuator 654, the rotation speed of the galvanometer scanner 650 can be controlled to a desired linear speed, such as from about 0.5 m / s to about 10 m / s, from about 1 m / s to about 6 m / s, or from about 2 m / s to about 5 m / s. The scanning speed can be changed / fixed during the laser perforation process to create a pattern on the substrate 510. In at least one embodiment, the scanning speed is fixed so that all pulses are directed to a single spot when perforating individual vias. This is often called percussion perforation or punching. From via to via, the galvo mirror can scan to change the perforation position.

[0078] For example, the rotational speed of the galvanometer scanner 650 can be set to a first speed to create a first pattern on one or more first substrates, and this first speed can be maintained during the ablation of each of the one or more first substrates. If different patterns are desired on one or more second substrates, the rotational speed of the galvanometer scanner 650 can be set to a second speed different from the first speed, and this second speed can be maintained during the ablation of each of the one or more second substrates.

[0079] In some embodiments, when reflecting pulses of electromagnetic radiation 655 delivered from a laser source 642, the rotation of a single facet of the galvanometer scanner 650 creates a complete row (R) (e.g., a row in the X direction) of blind vias 501 in one or more layers formed on the substrate 510. The electromagnetic radiation 655 is scanned across the surface of the substrate 510 using the galvanometer scanner 650, while the substrate 510 is transferred in the Y direction oriented perpendicularly, resulting in a row (R) of blind vias 501 (e.g., in the X direction) along the length of the substrate 510 (e.g., in the Y direction). In another example, the Y direction is positioned at an angle with respect to the X direction. In yet another example, the Y direction is positioned at an angle of approximately 90 degrees ± several degrees with respect to the X direction.

[0080] In at least one embodiment, the optical system of the optical device 635A is configured to feed focused beam diameters from about 1.5 μm to about 7 μm, such as from about 2 μm to about 6 μm, and from about 3 μm to about 5 μm, for the formation of blind vias 501 having an entrance diameter D1 equal to about 5 μm, and to feed focused beam diameters from about 5 μm to about 14 μm, such as from about 7 μm to about 12 μm, and from about 8 μm to about 10 μm, for the formation of blind vias 501 having an entrance diameter D1 equal to about 10 μm (for example, D1 as defined in Figure 2B or Figure 2C). In some embodiments, the number of pulse bursts for drilling can be from about 1 burst to about 40 bursts per via, such as from about 3 bursts to about 30 bursts per via, and from about 5 bursts to about 20 bursts per via.

[0081] As shown again with reference to Figure 6A, the laser drilling system 600 also includes a substrate sensing system 660 which includes one or more substrate position sensors. The substrate sensing system 660 uses an optical sensor 662 to detect the leading edge 665 of the substrate 510 and transmit a corresponding signal to the controller 690. The controller 690 then transmits a signal to the optical device 635A to time the operation of the laser source 642 and the rotation of the galvanometer scanner 650, and starts the laser scanning operation when the leading edge 665 of the substrate 510 is under the focusing lens 652. The controller 690 further controls the rotation speed of the galvanometer scanner 650 so that each facet of the galvanometer scanner 650 rotates across the pulses of electromagnetic radiation 655 to scan a row (R) of blind vias 501 in one or more layers placed on the substrate 210. The controller 690 further controls the speed of the substrate positioning system 605 and the rotation of the galvanometer scanner 650 so that when the linear movement of the substrate 510 by the substrate positioning system 605 ends a first row (R) of blind vias 501 (e.g., aligned in the X direction), the next row (R) of blind vias 501 can begin at a desired interval from the first row (e.g., in direction A). Thus, in some embodiments, as the substrate 510 moves under the optical device 635A, a row (R) of blind vias 501 can be formed in one or more layers of the substrate 510 across the entire width and length of the substrate 510. The controller 690 further controls the timing of the optical device 635A so that when the trailing edge 670 of the substrate 510 passes under the focusing lens 652, the scanning operation stops after a desired period of time has elapsed until the leading edge of the next substrate 510 is positioned under the focusing lens 652. The controller 690 can be any controller having a suitable processor, software, and memory for the operation of the laser drilling system 600. The substrate sensing system 660 also includes a substrate alignment device 680 configured to align the substrate 510 before it enters the scan chamber 635B.

[0082] The controller 690 generally includes a central processing unit (CPU) (not shown), memory (not shown), and support circuitry (not shown). The CPU can be one of any form of computer processor used to control system hardware and processes in an industrial environment. The memory can be connected to the CPU and can be one or more of readily available memories, such as random access memory (RAM), read-only memory (ROM), floppy disks, hard disks, or any other form of digital storage, whether local or remote. Software instructions and data can be coded and stored in memory to instruct the CPU. Support circuitry can also be connected to the CPU to conventionally support the processor. Support circuitry may include caches, power supplies, clock circuits, input / output circuit configuration subsystems, etc. A program (e.g., instructions) readable by the controller 690 may include code for performing tasks related to monitoring, executing, and controlling the movement, support, and positioning of the substrate 510, along with various process recipe tasks performed in the laser drilling system 600. In at least one embodiment of the controller 690, the process of forming holes on the surface of the substrate includes at least one scan (to form a complete row (R) of blind vias 501 (as shown in Figure 2C)) which is interrupted at a desired time to further control the formation of blind vias 501 at desired locations on the surface of the substrate. This feature allows for short-term and / or selective stopping / starting of pulse trains, enabling advanced patterning capabilities.

[0083] The controller 690 further controls the height sensor 664. Although Figure 6A shows the height sensor 664 as part of the substrate sensing system 660, the height sensor 664 can be a separate unit. During use of the laser drilling system 600, the height sensor 664 adjusts the optical device 635A with respect to the Z direction before, during, or after ablation, as described in Figures 8 and 9. In at least one embodiment, the height sensor 664 accurately determines the surface of a mask placed on one or more layers of the substrate 510.

[0084] Figure 7 is an isometric view of an exemplary laser drilling tool 700 having an optical device 635A and a scan chamber 635B located therein. The laser drilling tool 700 includes a main frame 701 having a first side 702A that can be coupled to a loading station 617A (shown in Figure 6A) and a second side 702B that can be coupled to an unloading station 617B (shown in Figure 6A). The main frame 701 may include a panel 705 that can function as a door or a removable sheet, a portion of which is not shown to illustrate components within the laser drilling tool 700. The panel 705 includes an observation window 710 for providing visual access to the interior of the laser drilling tool 700. The observation window 710 may include laser safety glass and / or filters that allow viewing of electromagnetic radiation during the laser drilling process within the laser drilling tool 700 without the need for safety glasses. Power and control equipment, such as the laser power supply 715 (shown by a dashed line), are housed within the main frame 701. In addition, the optical alignment device 720 (Figures 7 and 8) is coupled to the main frame 701 within the laser drilling tool 700. The optical alignment device 720 can adjust the position of the optical device 635A with respect to the direction of movement of the substrate 510 on the substrate positioning system 605, thereby adjusting the beam path radiated onto the substrate.

[0085] As described above, the optical device 635A can be adjusted in the Z direction before, during, or after ablation using the height sensor 664, as shown in Figures 8 and 9.

[0086] Figure 8 is a side view of an exemplary embodiment of the optical alignment device 720. The optical alignment device can be coupled to a height sensor 664 (not shown). The optical alignment device 720 includes a base plate 800 coupled to one or more support members 805 of a main frame 701. The base plate 800 is movably coupled to a first support plate 810, having a second support plate 815 extending therefrom in a plane substantially orthogonal to the plane of the first support plate 810. The second support plate 815 generally supports the optical device 635A. The first support plate 810 is coupled to the base plate 800 by a plurality of adjustment devices 820, which may include fasteners, linear guides, or a combination thereof. The adjustment devices 820 can enable at least height adjustment (in the Z direction) of the optical device 635A and can enable theta adjustment in the XZ plane and / or YZ plane. Height adjustment can be used to adjust the focal length of the focusing lens 652 (Figures 6A and 6B) of the optical device 635A. The adjustment device 820 can also be used to horizontalize the second support plate 815 with respect to the plane of the transfer belt 615. An adjustable aperture device 840 is provided between the second support plate 815 and the scan chamber 635B. The adjustable aperture device 840 may be, for example, a telescopic housing with an aperture formed inside that is sized to accept the beam path provided by the optical device 635A. The telescopic housing can be adjusted upward or downward based on the height adjustment of the optical alignment device 720.

[0087] In some embodiments, the optical alignment device 720 also includes an adjustable mounting plate 825 positioned between a second support plate 815 and the underside of the optical device 635A. The adjustable mounting plate 825 is fixed to the underside of the optical device 635A and fastened to the second support plate 815 by fasteners 830. The adjustable mounting plate 825 can be adjusted not only to horizontal the optical device 635A but also to different angular orientations in order to adjust the scan plane 835 of the beam path emitted by the optical device 635A during processing. As described in more detail in Figure 9, the adjustable mounting plate 825 can be rotated about the scan plane axis 635, for example in the Z direction, to adjust the orientation of the scan plane of the output of the optical device 635A (for example, the plane aligned in the row (R) direction on the substrate in Figure 5). The adjustable mounting plate 825 can be adjusted to change the beam path in the scan plane of the optical device 635A in order to align the row (R) of blind vias 501 on the substrate 510 (Figure 5).

[0088] Figure 9 is an isometric view of the exemplary optical alignment device 720 of Figure 8. Optical device 635A is not shown in this figure, but the scan surface 835 of optical device 635A is shown. The adjustable mounting plate 825 includes a plurality of slots 900 for receiving the fasteners 830 shown in Figure 8. Each of the slots 900 can allow the adjustable mounting plate 825 to rotate with respect to the Z axis in order to adjust the scan surface of optical device 635A. For example, a first alignment position 905 of the adjustable mounting plate 825 may include a direction in which the scan surface is substantially parallel to the leading edge 665 of the substrate 510 (shown in Figure 2A). In at least one embodiment, the adjustable mounting plate 825 is adjusted to a second alignment position 910 corresponding to an angle 915. The angle 915 can be adjusted based, for example, on the speed of the substrate 510 on the transport belt 615 and / or the scan speed of the electromagnetic radiation 655. The scanning speed of the electromagnetic radiation 655 can be based at least partially on the pulse width of the electromagnetic radiation 655 and / or the movement of the galvanometer scanner 650 (shown in Figure 6B).

[0089] In at least one embodiment, the angle 915 is about -20 degrees to about +20 degrees from the normal axis of the mirror plane when the speed of the transport belt 615 is about 140 mm / s to about 180 mm / s, the pulse width is about 1 fs to about 1.5 ms, and the scan speed of the galvanometer scanner 650 is about 1,000 RPM, thereby obtaining a row (R) of blind vias 501 that is substantially linear and / or parallel to the leading edge 665 of the substrate 510.

[0090] Any of the operations described above can be included in a computer-readable medium as instructions for execution by a control unit (e.g., controller 690) or any other processing system. The computer-readable medium may include any suitable memory for storing instructions, such as read-only memory (ROM), random access memory (RAM), flash memory, electrically erasable programmable ROM (EEPROM), compact disk ROM (CD-ROM), or floppy disk.

[0091] For the sake of brevity, only specific ranges are expressly disclosed herein. However, ranges not explicitly enumerated can be enumerated by combining any lower bound with any upper bound, and similarly, ranges not explicitly enumerated can be enumerated by combining any lower bound with any other lower bound, and similarly, ranges not explicitly enumerated can be enumerated by combining any upper bound with any other upper bound. In addition, ranges include all points or individual values ​​between their endpoints, even if they are not explicitly enumerated. Thus, all points or individual values ​​may function as their own lower bound or upper bound in combination with any other point or individual value or any other lower or upper bound to enumerate ranges not explicitly enumerated.

[0092] For the purposes of this disclosure, unless otherwise specified, all numerical values ​​in the detailed descriptions and claims herein are modified by "approximately" or "about" the given values, taking into account experimental errors and variations expected by those skilled in the art.

[0093] All documents described herein, including priority documents and / or test procedures, are incorporated herein by reference to the extent that they do not conflict with this document. As is evident from the general statements and specific embodiments above, the forms of this disclosure are illustrative and described, but various modifications can be made without departing from the spirit and scope of this disclosure. Therefore, this disclosure is not intended to be limited thereto. Similarly, the term “composes” is to be considered synonymous with the term “includes.” Similarly, whenever the transition term “composes” precedes a configuration, element, or group of elements, it is understood that the same configuration or group of elements having the transition terms “substantially consists of,” “composed of,” “selected from a group consisting of,” or “is,” precedes the enumeration of the configuration, element, or multiple elements, and vice versa.

Claims

1. A method for forming blind vias on a substrate, Transporting a substrate into the scan chamber of a laser drilling system, wherein the substrate comprises a conductive layer, a dielectric layer disposed on at least a portion of the conductive layer, and a mask layer disposed on at least a portion of the dielectric layer and providing the substrate surface. The sensor of the laser drilling system detects the mask layer, Determining one or more characteristics of the blind via, wherein the one or more characteristics are The volume of the blind via, corresponding to the top diameter of the blind via, the bottom diameter of the blind via, and the height of the blind via, or To determine one or more characteristics, including a taper angle of approximately 70 degrees or more. Under the laser process parameters, the laser beam emitted from the laser source of the laser drilling system is focused onto the substrate surface to remove less than half the thickness of the mask layer, Adjusting the laser process parameters based on one or more of the above characteristics, Under the adjusted laser process parameters, the laser beam is focused onto the area where the mask layer has been removed to remove the dielectric layer and form the blind vias. Methods that include...

2. The method according to claim 1, wherein the laser process parameters include laser output, laser energy in burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in burst, pulse frequency, burst frequency, beam spot size, M2 value, beam focusing offset from the substrate surface, or a combination thereof.

3. The aforementioned laser process parameters are: Laser energy amount in bursts of approximately 5 μJ or more, A focal beam diameter of approximately 2 μm to approximately 10 μm is required to drill vias with a diameter of 5 μm. A focal beam diameter of approximately 7 μm to approximately 12 μm is required to drill vias with a diameter of 10 μm. Focal height from approximately 0 μm to approximately 50 μm, Pulse frequencies of approximately 500 MHz or higher, The number of pulses in a burst is approximately 2 or more. The number of bursts is approximately 2 or more. Burst frequencies of approximately 100 kHz or higher, or The method according to claim 1, including these combinations.

4. The method according to claim 1, wherein the top diameter is approximately 10 μm or less.

5. Under the adjusted laser process parameters, the laser beam is focused to remove the dielectric layer and form the blind vias. The method according to claim 1, comprising removing at least a portion of the dielectric layer in the volume to form the blind via.

6. The method according to claim 1, further comprising removing the mask layer from the substrate.

7. The mask layer contains Al, Cu, W, Mo, Cr, or a combination thereof. The mask layer has a height of approximately 2 μm or less, or The method according to claim 6, which is a combination of these.

8. The method according to claim 1, wherein the laser source is a femtosecond ultraviolet laser having a wavelength of approximately 400 nm or less.

9. A method for forming blind vias on a substrate, Transporting a substrate into a scan chamber of a laser drilling system, wherein the substrate comprises a conductive layer with a height of approximately 2 μm or more, a dielectric layer disposed on at least a portion of the conductive layer, and a pre-etched mask layer disposed on at least a portion of the dielectric layer, the pre-etched mask layer having blind via openings for exposing at least a portion of the dielectric layer, and the dielectric layer providing the substrate surface, and transporting the substrate. The sensor of the laser drilling system detects the blind via openings in the pre-etched mask layer, Determining one or more characteristics of the blind via, wherein the one or more characteristics are The volume of the blind via, corresponding to the top diameter of the blind via, the bottom diameter of the blind via, and the height of the blind via, or To determine one or more characteristics, including a taper angle of approximately 70 degrees or more. Under laser process parameters, the laser beam emitted from the laser source of the laser drilling system is focused onto the substrate surface to remove a first portion of the dielectric layer within the volume, Adjusting the laser process parameters based on one or more of the above characteristics, Under the adjusted laser process parameters, the laser beam is focused to remove the second portion of the dielectric layer within the volume and form the blind via. Methods that include...

10. The method according to claim 9, wherein the laser process parameters include laser output, laser energy in burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in burst, pulse frequency, burst frequency, beam spot size, M2 value, beam focusing offset from the substrate surface, or a combination thereof.

11. The aforementioned laser process parameters are: Laser energy amount in bursts of approximately 5 μJ or more, A focal beam diameter of approximately 2 μm to approximately 10 μm is required to drill vias with a diameter of 5 μm. A focal beam diameter of approximately 7 μm to approximately 12 μm is required to drill vias with a diameter of 10 μm. Focal height from approximately 0 μm to approximately 50 μm, Pulse frequencies of approximately 500 MHz or higher, The number of pulses in a burst is approximately 2 or more. Approximately 2 or more bursts, Burst frequencies of approximately 100 kHz or higher, or The method according to claim 9, including these combinations.

12. The method according to claim 9, wherein the top diameter is approximately 10 μm or less.

13. The method according to claim 9, further comprising removing the pre-etched mask layer from the substrate.

14. The pre-etched mask layer contains Al, Cu, W, Mo, Cr, or a combination thereof. The pre-etched mask layer has a height of 3 μm or less, or The method according to claim 9, which is a combination of these.

15. The method according to claim 14, wherein if the pre-etched mask layer contains Mo or W, the method further comprises depositing a layer of copper on the pre-etched mask layer.

16. The method according to claim 9, wherein the first portion of the dielectric layer in the volume is removed without causing substantial damage to the pre-etched mask layer.

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