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] SUMMARY OF THE DISCLOSURE Embodiments of the present 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 demand for faster processing power with higher circuit density imposes demands on the materials, structures, and processes used in the manufacture of integrated circuit chips and printed circuit boards. The incorporation of blind vias allows for more connections and higher circuit density. Laser drilling is an established method for forming blind vias.

[0003] Along with the trend toward smaller vias, e.g., diameters from 5 μm to 10 μm, for higher interconnect density, certain blind via quality parameters remain unchanged. The quality parameters include via top diameter and roundness, via bottom diameter and roundness, via taper angle (80° or more), and via pad cleanliness. However, conventional laser drilling techniques cannot form high-quality blind vias with such small diameters for mass production.

[0004] The traditional approach to laser drilling blind vias is to use nanosecond pulsed 355 nm ultraviolet (UV) lasers or pulsed CO 2Lasers are used to drill blind vias directly into panels. 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. Moreover, top-hat shaped laser beam profiles generally have a very short depth of field where the laser beam profiles remain equal in intensity. Moreover, such top-hat beam profiles cannot consistently and cost-effectively drill diameters below 40 μm, especially 5 μm to 10 μm. Moreover, conventional laser drilling methods cannot achieve blind vias with taper angles of 80° or more.

[0005] There is a need for new and improved methods and apparatus for drilling high quality, small diameter blind vias in large quantities. Summary of the Invention

[0006] The embodiments of the present disclosure generally relate to a method and apparatus for drilling blind vias. In an embodiment, a method for forming a blind via in a substrate is provided, comprising transporting the substrate to a scanning chamber, the substrate comprising 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 a substrate surface. The method further comprises determining one or more characteristics of the blind via, the one or more characteristics including a top diameter of the blind via and a 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, the top diameter of the blind via and the bottom diameter of the blind via, a volume of the blind via corresponding to the top diameter, the bottom diameter, and the height, or a taper angle of about 80 degrees or more. The method further includes focusing a laser beam emitted from the laser source at the substrate surface under laser process parameters to remove at least a portion of the mask layer, adjusting the laser process parameters based on the 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] In another embodiment, a method of forming a blind via in a substrate is provided that includes transporting the substrate to a scan chamber, the substrate comprising 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 a blind via opening to expose at least a portion of the dielectric layer, the dielectric layer providing a substrate surface, the method further includes determining one or more characteristics of the blind via, the one or more characteristics including a top diameter of the blind via and a 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, the top diameter corresponding to the blind via opening, a top diameter of the blind via and a bottom diameter of the blind via, a volume of the blind via corresponding to the top diameter, the bottom diameter, and the height, or a taper angle of about 80 degrees or more. The method further includes focusing a laser beam emitted from the laser source at the substrate surface under laser process parameters to remove a first portion of the dielectric layer within the volume without causing damage to the pre-etched mask layer by more than half a thickness of the mask layer, adjusting the laser process parameters based on the one or more characteristics, and focusing the laser beam under the adjusted laser process parameters to remove a second portion of the dielectric layer within the volume to form a blind via.

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

[0009] So that the above-mentioned features of the present disclosure can be understood in detail, a more particular description of the present disclosure briefly summarized above can be made by reference to embodiments, some of which are illustrated in the accompanying drawings, It should be noted, however, that the accompanying drawings depict only exemplary embodiments and therefore should not be considered as limiting its scope, as other equally effective embodiments may be recognized. [Brief description of the drawings]

[0010] [Figure 1A] FIG. 1 illustrates an exemplary substrate in accordance with at least one embodiment of the present disclosure. [Figure 1B] FIG. 1 illustrates an exemplary substrate in accordance with at least one embodiment of the present disclosure. [Figure 1C] FIG. 2 illustrates an exemplary substrate having a blank mask layer in accordance with at least one embodiment of the present disclosure. [Figure 1D] FIG. 2 illustrates an exemplary substrate having a pre-etched mask layer in accordance with at least one embodiment of the present disclosure. [Figure 2A] FIG. 2 illustrates an exemplary substrate after forming blind vias in accordance with at least one embodiment of the present disclosure. [Figure 2B]FIG. 2 illustrates an example substrate after forming blind vias into the substrate having a blank mask layer in accordance with at least one embodiment of the present disclosure. [Figure 2C] FIG. 2 illustrates an example substrate after forming a blind via in the substrate having a pre-etched mask layer in accordance with at least one embodiment of the present disclosure. [Diagram 3] 1A-1D illustrate an exemplary method of forming a blind via in a substrate in accordance with at least one embodiment of the present disclosure. [Figure 4] 1A-1D illustrate an exemplary method of forming a blind via in a substrate in accordance with at least one embodiment of the present disclosure. [Diagram 5] 1 is a schematic plan view of an exemplary substrate having a plurality of blind vias formed by the apparatus and methods disclosed herein, in accordance with at least one embodiment of the present disclosure. FIG. [Figure 6A] FIG. 1 is a schematic side view of an exemplary laser drilling system in accordance with at least one embodiment of the present disclosure. [Figure 6B] FIG. 6B is an enlarged side view of the example optical device of FIG. 6A in accordance with at least one embodiment of the present disclosure. [Figure 7] FIG. 6B is an isometric view of an example laser drilling tool having the example laser drilling system of FIG. 6A disposed therein, in accordance with at least one embodiment of the present disclosure. [Figure 8] 8 is a side view of an exemplary embodiment of the optical alignment device of FIG. 7 in accordance with at least one embodiment of the present disclosure. [Figure 9] 9 is an isometric view of the exemplary optical alignment device of FIG. 8 in accordance with at least one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] For ease of understanding, the same reference numerals have been used, where possible, to designate identical elements common to the figures. It is believed that elements and features of one embodiment may be beneficially incorporated in other embodiments without further detail.

[0012] The embodiments of the present disclosure generally relate to methods and apparatus for drilling blind vias. The inventors have discovered a method and apparatus for laser drilling blind vias in a panel including a conductive layer and an insulating layer. Unlike conventional laser drilling methods and apparatus, the methods and apparatus described herein can enable the formation of blind vias having a taper angle of 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] Along with the trend towards smaller diameter blind vias, for example 5 μm to 10 μm diameters for higher interconnect density, certain blind via quality parameters remain unchanged. These include via top diameter and roundness, via bottom diameter and roundness, via taper angle (80° or more), 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 for laser drilling blind vias use nanosecond-pulsed 355 nm ultraviolet (UV) lasers or pulsed CO2 lasers to drill blind vias directly in panels. These approaches have certain limitations. First, the Gaussian laser beam profile emitted by the laser source requires complex beam shaping optics to transform the beam into a top-hat shaped beam profile. Second, the applied beam shaping optics results in about 40% optical energy loss. Third, the intensity profile of the top-hat shaped beam has a very short depth of field (DOF), and within the range of the DOF, the laser beam profile remains equal in intensity. Here, the intensity profile of the output top-hat beam is rapidly deformed / degraded from the image plane along the beam propagation axis due to the non-uniform phase distribution, limiting its application to imaging with large DOF. The smaller the diameter of the top-hat image beam, the shorter the DOF, and since the DOF is shorter than the range of variation of the panel thickness / chuck flatness, it is difficult to make the top-hat beam always intersect the panel surface at each via drilling location, resulting in inconsistent via quality, especially for mass production. The inability to achieve consistent via quality at higher throughput is not cost-effective. Another conventional method applies a deep ultraviolet (DUV) light excimer laser with a wavelength of 193 to 308 nm. Mask projection transforms the laser beam into a top-hat shaped beam profile. This method also has certain limitations. First, the equipment, e.g., laser and optics, and their maintenance can be expensive. Second, the intensity profile of the top-hat shaped beam has a very short DOF, limiting its application. Third, the mask is a consumable item. The method and apparatus described herein can eliminate (or at least reduce) the aforementioned shortcomings of conventional approaches for laser drilling blind vias.

[0015] substrate 1A is an exemplary substrate 100 according to at least one embodiment. The exemplary substrate 100 may be utilized 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 a III-V compound semiconductor material, silicon, crystalline silicon (e.g., Si <100> or Si <111> ), silicon oxide, silicon germanium, doped or undoped silicon, doped or undoped polysilicon, silicon nitride, quartz, glass (e.g., borosilicate glass), sapphire, alumina, and / or a ceramic material. In at least one embodiment, the core structure 102 comprises a monocrystalline p-type or n-type silicon substrate. In some embodiments, the core structure 102 comprises a polycrystalline p-type or n-type silicon substrate. In another embodiment, the core structure 102 comprises a p-type or n-type silicon solar substrate. The substrate utilized to form the core structure 102 can further have a polygonal or circular shape. For example, the core structure 102 can comprise a substantially square silicon substrate having a lateral dimension of about 120 to about 180 mm and with chamfered or unchamfered edges. In another example, the core structure 102 includes a circular silicon-containing wafer having a diameter of about 100 mm to about 50 mm, such as about 20 mm to about 700 mm, such as about 300 mm.

[0017] A conductive layer 104 is formed on one or more surfaces of the core structure 102. The conductive layer 104 may be formed of a metallic material such as copper (Cu), tungsten (W), chromium (Cr), molybdenum (Mo), aluminum (Al), gold (Au), nickel (Ni), palladium (Pd), or the like, or combinations thereof. In at least one embodiment, the conductive layer comprises a layer of tungsten over copper. In at least one embodiment, the conductive layer 104 has a height H of about 100 μm or less, such as about 50 μm or less, 25 μm or less. 0 For example, the conductive layer 104 has a height H of about 7 μm to about 18 μm, such as about 10 μm to about 15 μm. 0 Such as, about 5 μm to about 20 μm high H 0 In at least one embodiment, the height H 0 is H 0a From H 0b H 0a From H 0b is H 0a <H 0b 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, so long as

[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 flowable build-up material, typically in the form of a dry film. Thus, although referred to hereinafter as an "insulating layer," the insulating layer 106 may also be described as a dielectric layer. In some embodiments, the insulating layer 106 is formed of a silica (SiO 2 The insulating layer 106 is formed from an epoxy resin material having ceramic fillers such as aluminum nitride (AlN), aluminum oxide (AlO), and the like. Other examples of ceramic fillers that can be utilized to form the insulating layer 106 include aluminum nitride (AlN), aluminum oxide (AlO), and the like. 2 O 3), silicon carbide (SiC), silicon nitride (Si 3 N 4 , Sr 2 Ce 2 Ti 5 O 16 ), zirconium silicate (ZrSiO 4 ), wollastonite (CaSiO 3 ), beryllium oxide (BeO), cerium dioxide (CeO 2 ), Boron nitride (BN), Calcium copper titanium oxide (CaCu 3 Ti 4 O 12 ), magnesium oxide (MgO), titanium dioxide (TiO 2 ), zinc oxide (ZnO), and the like. In some examples, the ceramic fillers utilized to form the insulating layer 106 have particles ranging in size between about 40 nm and about 1.5 μm, such as between about 80 nm and about 1 μm. For example, the ceramic fillers have particles ranging in size 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 particle reinforcement. 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 H of about 100 μm or less, such as about 50 μm or less, such as 25 μm or less. 1 For example, the insulating layer 106 has a height H of about 7 μm to about 18 μm, such as about 10 μm to about 15 μm. 1 As shown in Fig. 1, the height H of about 5 μm to about 20 μm 1 In at least one embodiment, the height H 1 is H 1a From H 1b H 1a From H 1b is H 1a <H 1bcan 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, so long as

[0020] 1B is an exemplary substrate 150 according to at least one embodiment. The exemplary substrate 150 can be utilized for structural support and electrical interconnection of a semiconductor package. 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. Exemplary properties and characteristics of the core structure 152, the conductive layers 154a, 154b, and the insulating layers 156a, 156b are similar to those described above with respect to the core structure 102, the conductive layer 104, and the insulating layer 106, respectively.

[0021] 1C is an exemplary substrate 170 having a blank mask layer (e.g., not pre-etched) according to at least one embodiment. The exemplary substrate 170 may be utilized for structural support and electrical interconnection of a semiconductor package. The exemplary substrate 170 generally includes a core structure 172, a conductive layer 174 formed on a surface of the core structure 172, an insulating layer 176 formed on a surface of the conductive layer 174, and a mask layer 178 formed on a surface of the insulating layer 176. Exemplary properties and characteristics of the core structure 172, the conductive layer 174, and the insulating layer 176 are similar to 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 H 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. 2 In at least one embodiment, the height H2 is H 2a From H 2b H 2a From H 2b is H 2a <H 2b can be, 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, so long as

[0023] The mask layer 178 may be formed by, for example, 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 the blind vias are formed by the processes described herein. In some embodiments, the mask is maintained after the blind vias are formed, such as when the mask layer 178 is Mo and / or W, and in combination with a deposited conductive layer (e.g., Cu), serves as an interconnect layer.

[0024] 1B, an exemplary substrate includes a mask on a surface of insulating layer 156a and / or a surface of insulating layer 156b. The mask layers can be blank or 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] 1D is an exemplary substrate 180 having a pre-etched (or pre-opened) mask layer according to at least one embodiment, where the exemplary substrate 180 is pre-etched to form via openings. The exemplary substrate 180 may be utilized 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 a surface of the core structure 182, an insulating layer 186 formed on a surface of the conductive layer 184, and a mask layer 188 formed on a surface of the insulating layer 186. Exemplary properties and characteristics of the core structure 182, the conductive layer 184, and the insulating layer 186 are similar to those described above with respect to the core structure 102, the conductive layer 104, and the insulating layer 106, respectively. Exemplary properties and characteristics of the mask layer 188 are similar to those of the mask layer 178 described above.

[0026] 2A is an exemplary substrate 200 after blind vias have been formed in the exemplary substrate 100 (shown in FIG. 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. A blind via 208 extends from a surface of the insulating layer 206 to the conductive layer 204. The blind via 208 has a top diameter D 1 , bottom diameter D 2 , taper angle (A 1 ), and volume V 1 In some embodiments, the blind vias 208 penetrate or minimally penetrate the conductive layer 204. In some embodiments, the blind vias do not penetrate or substantially do not penetrate the conductive layer 204.

[0027] Top diameter D 1 and bottom diameter D 2 can be about 20 μm or less, such as about 15 μm or less, such as about 5 μm to about 10 μm. In at least one embodiment, the top diameter D 1 D 1a From D 1b D 1a From D 1b D 1a <D1b 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, so long as the base diameter D 2 D 2a From D 2b D 2a From D 2b D 2a <D 2b 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, so long as

[0028] In some embodiments, the blind via has a bottom diameter D 2 is the top diameter D 1 The taper is smaller than the base diameter D 2 and top diameter D 1 In at least one embodiment, the bottom diameter D 2 and top diameter D 1 The ratio is about 0.4*H 1 From about 1, about 0.5*H 1 From about 1, for example, about 0.353*H IL (Here, H IL is about 1 from the height of the insulating layer, e.g., insulating layer 206).

[0029] In at least one embodiment, the blind via 208 has a taper angle A , which corresponds to the angle between the inner wall of the blind via 208 and the surface of the conductive layer 204. 1 In at least one embodiment, the taper angle A 1 is about 75° to 90°, such as about 80° to about 89°. In at least one embodiment, the taper angle A 1 A 1aFrom A 1b A is in the range 1a From A 1b A 1a 1b can be, 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°, independently.

[0030] 2B is an example substrate 250 after forming a blind via in the example substrate 170 with a blank mask (shown in FIG. 1C), according to at least one embodiment. The example substrate 250 generally includes a core structure 252, a conductive layer 254, an insulating layer 256, and a mask layer 260. The blind via is indicated by reference numeral 258. The core structure 252, the conductive layer 254, the insulating layer 256, the height H 0 , height H 1 , diameter D 1 , diameter D 2 , and taper angle A 1 The characteristics of angle A are the same as those described above. 2 is the taper angle A 1 and / or a taper angle A 1 In at least one embodiment, A 2 A 1 In at least one embodiment, the taper angle A 2 A 2a From A 2b A is in the range 2a From A 2b A 2a 2b For example, the angle can be 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°, independently.

[0031] In some embodiments, the diameter D of the mask layer 260​​3 For example, the diameter is about D 1 +4μm, diameter approximately D 1 +3μm, diameter approx. D 1 +2μm, or diameter approximately D 1 +1μm, etc., diameter approximately D 1 From diameter D 1 +5μm, such as diameter D 1 Approximately equal to or diameter D 1 In at least one embodiment, the diameter D 3 ≧Diameter D 1 ≧Diameter D 2 The blind via may correspond to reference numeral 258 when the mask layer is removed from the substrate after processing, or may correspond to reference numeral 262 when the mask layer is maintained on the substrate after processing.

[0032] 2C is an example substrate 270 after forming a blind via in the example substrate 180 with a pre-etched / pre-opened mask (shown in FIG. 1D ), according to at least one embodiment. The example substrate 270 generally includes a core structure 272, a conductive layer 274, an insulating layer 276, and a mask layer 280. The blind via is indicated by reference numeral 278. The core structure 272, the conductive layer 274, the insulating layer 276, the height H 0 , height H 1 , diameter D 1 , diameter D 2 , taper angle A 1 , and taper angle A 2 The characteristics of the taper angle A are similar to those described above. In at least one embodiment, 2 is substantially 90° or the taper angle A 1 In at least one embodiment, the taper angle A 1 , A 2 is 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°. 1 is the taper angle A2 The diameter D of the mask layer 280 can be equal to, smaller than, or larger than 3 (unit: μm) is approximately D 1 From about (D 1 +(1 / 4)H 2 ), about D 1 From about (D 1 +(1 / 3)H 2 ), about D 1 From about (D 1 +(1 / 2)H 2 ), etc., about (D 1 +H 2 In at least one embodiment, the diameter D 3 ≧Diameter D 1 It is.

[0033] In some embodiments, the taper angle A 2 The allowable variation range of taper angle A 1 For example, 70°≦A 2 ≦90°, 75°≦A 1 ≦90°. In some cases, for vias with diameters of 5 to 10 μm, 80°≦A 1 For vias larger than 10 μm, 75°≦A 1 It is.

[0034] In at least one embodiment, the mask layer (with or without openings) has a height of about 2 μm or less, such as from about 0.03 μm to about 2 μm, or from 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 on top of the metal mask. The photoresist layer can be patterned by photolithography to define the size and location of the via opening on the metal mask layer. The opening on the metal mask layer can be formed by an etching process such as plasma etching and wet chemical etching. The lithographically defined openings relax positional accuracy and improve laser throughput.

[0036] process The 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. Suitable femtosecond-based laser processes can be characterized by high peak intensity (irradiance), which typically results in non-linear interactions of various materials.

[0037] FIG. 3 illustrates an exemplary method 300 of forming a blind via in a substrate, according to at least one embodiment. In at least one embodiment, the exemplary method 300 is used on a substrate having a mask layer without an opening (i.e., blank). The exemplary method 300 includes, in operation 302, transferring the substrate to a scan chamber. 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 mask layer disposed on at least a portion of the dielectric layer, the mask layer providing a substrate surface. The exemplary method 300 further includes, in operation 304, determining one or more characteristics of the blind via. The one or more characteristics may include a top diameter of the blind via, a bottom diameter of the blind via, a height of the blind via, a volume of the blind via, and a 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, the bottom diameter, and the height. The exemplary method 300 further includes, in operation 306, focusing a laser beam emitted from a laser source under laser process parameters at the substrate surface. This operation will remove a first portion of the dielectric layer within the volume, but will cause only mild melting and abrasion to the surface of the conductive layer below the dielectric layer, with an ablation depth of the conductive layer being only about 2 μm, for example. In some embodiments, operation 306 will remove about half or less of the thickness of the mask layer. Thus, in some embodiments, the conductive layer is substantially undamaged after operation 306.

[0038] The exemplary method 300 further includes adjusting laser process parameters based on the one or more characteristics at operation 308. In some embodiments, the laser process parameters include laser power, laser energy in a burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in a burst, pulse frequency, burst frequency, beam spot size, M 2 value, the offset of the beam focus from the substrate surface (above and / or below the substrate surface), or a combination thereof. 2 is a unit-free spatial characteristic of the laser beam and measures the difference between the actual laser beam and a Gaussian beam. These and other laser process parameters are described below. The exemplary method 300 further includes, at operation 310, 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.

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

[0040] FIG. 4 illustrates an exemplary method 400 of forming a blind via in a substrate, according to at least one embodiment. In at least one embodiment, the exemplary method 400 is used to form a blind via on a substrate having a pre-etched mask layer. The exemplary method 400 includes, in operation 402, transferring a substrate to a scan chamber. 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 a blind via opening to expose at least a portion of the dielectric layer, and the dielectric layer providing a substrate surface. The exemplary method 400 further includes, in operation 404, determining one or more characteristics of the blind via. The one or more characteristics may include a top diameter of the blind via, a bottom diameter of the blind via, a height of the blind via, a volume of the blind via, and a 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, the bottom diameter, and the height. The exemplary method 400 further includes, in operation 406, focusing a laser beam emitted from a laser source on the substrate surface under laser process parameters. This operation will remove a first portion of the dielectric layer within the volume and can be performed without substantial damage to the pre-etched mask layer and / or without substantial damage to the conductive layer. "Without substantial damage to the pre-etched mask layer" means that the mask layer is slightly melted to "polish / grind" the mask surface, but no material is removed from the mask surface by visible ablation that would cause a change in the top via diameter or the formation of an elliptical via. The mask is a removable sacrificial layer. In at least one embodiment, the allowable mask damage depends on the height of the mask.As a non-limiting example, if the mask height is about 0.3 μm, the damage / ablation depth to the mask should be less than about 0.3 μm. As another non-limiting example, if the mask height is about 2 μm, the damage / ablation depth to the mask should be less than about 2 μm.

[0041] The exemplary method 400 further includes adjusting laser process parameters based on the one or more characteristics at operation 408. In some embodiments, the laser process parameters include laser power, laser energy in a burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in a burst, pulse frequency, burst frequency, beam spot size, M 2 The laser process parameters may include a value of the thickness of the dielectric layer, an offset of the beam focus from the substrate surface, or a combination thereof. These and other laser process parameters are described below. The exemplary method 400 further includes, at operation 410, 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.

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

[0043] The femtosecond laser source (such as an ultraviolet laser) used in at least some embodiments herein has several adjustable characteristics (laser process parameters), as described below. In at least one embodiment, the laser process parameters include one or more of the following characteristics:

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

[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, about 350 nm to about 540 nm, etc. 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 corresponding optical system provide a focus or focal range at the work surface in a range of about 1.5 μm to about 12 μm, such as about 3 microns (μm) to about 10 μm, about 4 μm to about 8 μm, etc. The spatial beam profile at 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 about 500 MHz or greater, such as about 1 GHz or greater, about 2 GHz or greater, about 1 GHz to about 10 GHz, about 2 GHz to about 9 GHz, about 3 GHz to about 8 GHz, about 4 GHz to about 7 GHz, about 5 GHz to about 6 GHz, etc. In at least one embodiment, the pulse frequency or range of pulse frequencies within each burst is about 2 GHz to about 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 about 2 or more, or about 3 or more, such as about 5 to about 100, about 10 to about 100, about 20 to about 90, about 40 to about 80, about 50 to about 70, about 55 to about 65, etc. In at least one embodiment, the number of pulses in each burst is about 20 to about 100.

[0049] (6) The burst frequency can be adjusted. The burst frequency of the femtosecond laser source can be about 100 kHz or more, such as about 500 kHz or more. 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 laser energy in a burst in an amount of about 1 μJ to about 100 μJ, such as about 1 μJ to about 80 μJ, about 3 μJ to about 50 μJ, about 5 μJ to about 20 μJ, etc. In at least one embodiment, the laser and burst frequency are set to achieve laser energy in a burst in an amount that can be about 5 μJ or more, such as about 5 μJ to about 50 μJ, about 10 μJ to about 30 μJ.

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

[0052] (9) Characterizing the laser beam quality M 2 The value is about 1.5 or less (M 2 is always ≥ 1.0).

[0053] (10) The focused beam diameter can be about 2 μm to about 10 μm, such as about 3 μm to about 6 μm when drilling a 5 μm diameter via. The focused beam diameter can be about 7 μm to about 12 μm, such as about 8 μm to about 11 μm when drilling a 10 μm diameter via. The focused beam diameter is the laser beam spot diameter at the work surface that is the result of the output laser beam passing through a beam expander and being focused by a focusing lens.

[0054] (11) The offset of the beam focus from the substrate, also referred to as the focal height, is from about 0 μm to about 100 μm, such as from about 0 μm to about 50 μm, from about 0 μm to about 30 μm. The focal height is an adjustable parameter. In some embodiments, for example, the focal point is set just above the panel surface to cut the mask and remove some of the insulating layer material, and then the focal height is adjusted so that the focal plane is above the panel surface. That is, the laser beam intersecting 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 the conductive layer at the bottom of the via.

[0055] (12) The number of bursts is greater than or equal to about 2, such as from about 5 to about 20.

[0056] (13) The focused beam spot size is determined by the target entrance diameter of the hole in the dielectric surface (e.g., the entrance diameter D of the hole to be drilled as defined in FIG. 2C). 1 , or the diameter D of the hole to be drilled as defined in FIG. 2B 1 ), such as about 80% to about 120%, for example, about 90% to about 110%, such as about 95% to about 100%.

[0057] The focused beam diameter is adjustable using a programmable beam expander to drill vias of different diameters.

[0058] The femtosecond laser source can be an electromagnetic radiation source, such as a diode-pumped solid-state (DPSS) laser, or other similar radiation emission source capable of providing and emitting a continuous or pulsed beam. According to 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 inoslab laser, or a hybrid thereof. In some embodiments, the laser source includes multiple laser diodes, each generating uniform and spatially coherent light at the same wavelength.

[0059] Device

[0023] Embodiments of the present disclosure also generally relate to an apparatus for laser drilling blind vias. Figure 6A is a schematic side view of an exemplary laser drilling system 600 for carrying out certain aspects of the present disclosure, according to some embodiments.

[0060] The laser drilling system 600 includes a housing 602 having a substrate positioning system 605 therein. The substrate positioning system 605 may be a conveyor for supporting and transporting the substrates 510 through the laser drilling system 600. The laser drilling system 600 may be used to drill blind vias 501 (FIG. 5) in one or more layers disposed on the substrates 510 in accordance with embodiments of the present disclosure. Each substrate 510 may be the exemplary substrate shown in FIGS. 1 and 2. In at least one embodiment, the mask of the substrates 510 may face 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 transfer belt 615, which may be continuous, made of a material configured to support and transport a line of substrates 510 through the laser drilling system 600 in flow path "A". The housing 602 is disposed between a loading station 617A for providing a substrate 510 and an unloading station 617B for receiving a processed substrate 510. The loading station 617A and the unloading station 617B may be coupled to the housing 602 and may include robotic equipment and / or transfer mechanisms for providing the substrate 510 to the transfer belt 615. The substrate positioning system 605 includes support rollers 620 that support and / or drive the transfer belt 615. The support rollers 620 are driven by a mechanical drive 625, such as a motor / chain drive, configured to transport the transport belt 615 at a linear speed of about 100 millimeters per second (mm / s) to about 2000 mm / s, such as about 500 mm / s to about 2000 mm / s, or about 500 mm / s to about 1500 mm / s, during operation. The mechanical drive 625 can be an electric motor, such as an alternating current (AC) or direct current (DC) servo motor. The transport belt 615 can be made of, for example, stainless steel, a polymeric 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, each of the two parallel belts having a width in the X-direction that is smaller than a dimension in the X-direction of the substrate 510X. In this configuration, each substrate 510 in the laser drilling system 600 can be positioned on a portion of both parallel belts.

[0062] The substrate positioning system 605 may be a transfer device configured to sequentially transport the line of substrates 510 (e.g., in flow path "A") towards and through the laser scanning apparatus 630. The laser scanning apparatus 630 includes an optical device 635A coupled to a support member 640 that supports the optical device 635A above the transport belt 615 and the substrates 510. The laser scanning apparatus 630 also includes a scan chamber 635B fixed in position relative to the transport belt 615 adjacent the optical device 635A that allows the substrates 510 to pass over the transport belt 615.

[0063] 6B is a side view of the exemplary optical device 635A of FIG. 6A, where the optical device 635A is rotated 90 degrees from the standard position shown in FIG. 6A for purposes of discussion. FIG. 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 FIGS. 6A and 6B. The optical device 635A includes a housing 641 that provides light or electromagnetic radiation that is directed to a surface of the substrate 510 as the substrate 510 passes through a scan chamber 635B on a transport belt 615. In at least one embodiment, the optical device 635A is configured to form a pattern (P) that can include a pattern of columns (R) and rows (C) of blind vias 501 formed in the substrate 510, as shown in FIG. 5, in combination with the movement of the transport belt 615. 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 traverses the substrate 510 as it moves on the transport belt 615. The optical device 635A also includes a laser source 642, such as a femtosecond laser source, that emits light or electromagnetic radiation via the optical system that provides, for example, about 50,000 blind vias in the substrate 510 having the desired characteristics described herein, such as diameter and taper angle.

[0064] In laser machining processes, unlike typical plasma processing in semiconductor processes, the plasma resembles a cloud or plume that can cover the entire wafer surface, and the laser beam, especially when focused, is only a small spot, so a relative movement between the laser beam and the sample (e.g., wafer) is usually required to process the entire sample. The relative movement can be achieved in various ways. In the first way, in some embodiments, the laser beam remains stationary and the substrate is moved by a linear stage with movements in the directions of X / Y / Z (height) / theta angle (on the XY plane to rotate the sample) / A tilt angle (in the XZ and YZ planes to tilt the sample). For micromachining, a movement of X / Y / Z / theta is usually sufficient. In the second way, in some embodiments, the laser source and / or the laser focusing head are mounted on an X / Y / Z / theta stage.

[0065] In a third approach, in some embodiments, the substrate is held stationary on a chuck and a 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 over the substrate surface. In general, there are three types of optical scanners: acousto-optical scanners, which use diffraction to deflect the beam; electro-optical scanners, which use refraction to deflect the beam; and mechanical scanners (resonant, polygon, and galvanometer scan types), which use reflection to deflect the beam.

[0066] A fourth approach is hybrid movement of the laser beam and sample. For example, the laser beam is scanned across the substrate while the substrate is moved simultaneously or sequentially on the chuck / stage. Additionally or alternatively, a scanner is mounted on a single-axis translation stage to move and scan the beam.

[0067] In some embodiments, optical scanning techniques such as mechanical scanners, such as polygons and / or galvos, are used to move the laser beam from one location to another on the substrate surface, for example to drill via arrays at specified locations on the substrate. These mechanical scanners work by rotating physical mirrors that can be coated to reflect any wavelength or combination of wavelengths off the rotating mirror with a very high reflectivity, thus achieving high optical throughput. The achievable scan angle in optical terms is twice the actual motor rotation angle. Using that physical mirror, polygon scanners can scan the beam over a very wide angle, but are limited to scanning the same pattern multiple times. Polygon scanners perform one-axis scanning. To generate two-dimensional patterns, the other axis of movement can be provided by adding linear stages or galvo mirrors.

[0068] Mechanical galvanometer-based scanners (or galvos) typically contain a physical mirror that is operated by a motor. In most cases, the mirror is attached to the shaft of the motor, but in some designs the mirror and motor may be an integrated unit. Galvo motors can rotate through a range of angles, typically around ±20°. Galvo motors can also incorporate a high-precision position detector that provides feedback to a separate controller, achieving positioning repeatability of 5 μrad (5 mm at a distance of 1 km). Two galvanometer scanners can be configured for two-axis scanning.

[0069] In at least one embodiment, the speed of the transport belt 215 is controlled from about 100 mm / s to about 5000 mm / s, such as from about 250 mm / s to about 2000 mm / s, from about 0.5 m / s to about 1 m / s, during operation to form a plurality of blind vias 501 in a substantially linear row in the X direction ( FIG. 6A ) on the substrate 510 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, as an alternative (or in addition to) the transport belt 215, a galvo scanner is used to change the punch location from one via to the next.

[0071] 6B, the laser source 642 can emit light or electromagnetic radiation 655 by a process of light 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 wave or pulsed wave light or electromagnetic radiation 655 that is directed to an optical system including a beam expander 644, a beam collimator 646, and a galvanometer scanner 650.

[0072] The galvanometer scanner 650 can include a movable mirror that steers the laser beam, and the steering of the beam can be in one, two, or three dimensions. To position the laser beam in two dimensions, the galvanometer scanner 650 can rotate a single mirror along two axes or reflect the laser beam off two closely spaced mirrors mounted on orthogonal axes. To position the focal point of the laser beam 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 pulses of electromagnetic radiation 655 are controlled by providing an external trigger signal to the laser source 642 provided at a desired frequency from the controller 690 .

[0074] The pulse of electromagnetic radiation 655 emitted from the laser source 642 is received by a beam expander 644 having a first diameter, such as about 1 mm to about 6 mm, about 2 mm to about 5 mm, about 3 mm to about 4 mm, etc. The beam expander 644 can increase the diameter of the electromagnetic radiation 655 to a second diameter by a preset factor, such as about 2x, about 5x, about 8x, or the beam expander 644 can have an adjustable range of magnification, such as about 1x to about 8x. The pulse of electromagnetic radiation 655 is then 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 in itself. Here, the beam expander 644 has at least two functions: expanding the beam size by a certain magnification and collimating the beam. The beam expander can have a fixed magnification (e.g., 2x, where the output beam diameter is equal to twice the input beam diameter) or an adjustable range of magnification (e.g., 3x to 8x). For example, a 2mm diameter laser beam can be incident on the input side of a 3x beam expander, and then at the output (exit) side of the beam expander, a 6mm diameter beam is output. This 6mm beam can be a diverging or converging beam (as it propagates along the optical axis), but is usually not a fully collimated beam. A perfectly collimated beam does not diverge or converge when propagating along the optical axis. Through the action of "beam collimating", the beam can be adjusted to have very little divergence or convergence, so that the beam diameter may vary by no more than about 1% to about 2%, or even less, over distances traveled of several meters or more.

[0076] From the beam collimator 646, the pulses of electromagnetic radiation 655 are sent to a galvanometer scanner 650, which directs the pulses of electromagnetic radiation 655 to the substrate 510 through a focusing lens 652. The focusing lens 652 can be a telecentric focusing lens. The focusing lens 652 can have one or more lenses.

[0077] The galvanometer scanner 650 directs pulses of electromagnetic radiation through a focusing lens 652, which is part of the optical system of the optical device 635A, onto the surface of the substrate 510, which moves continuously in the Y direction on a transport belt 615 in the scan chamber 635B (FIG. 6A). Thus, the transport 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 transport belt 615 in the scan chamber 635B (FIG. 6A). The galvanometer scanner 650 can include a mirror having multiple reflective facets arranged such that each of the reflective facets 653 can be generally angled with respect to another one of the reflective facets 653 in a direction relative to the rotation axis 651 of the galvanometer scanner 650 (into the page in the X direction in FIG. 6B). The angle of each of the reflective facets 653 of the galvanometer scanner 650 allows the electromagnetic radiation 655 to be scanned in one direction (X direction in FIG. 6A ) across the surface of the substrate 510 as the galvanometer scanner 650 is rotated about the axis of rotation 651 by the actuator 654. Using the actuator 654, the rotational speed of the galvanometer scanner 650 can be controlled to a desired linear speed, such as about 0.5 m / s to about 10 m / s, about 1 / s to about 6 m / s, about 2 m / s to about 5 m / s, etc. The speed of the scan can be changed / fixed during the laser drilling process to create a pattern on the substrate 510. In at least one embodiment, the scan speed is fixed so that all pulses are directed to one spot when drilling individual vias. This is often referred to as percussion drilling or punching. From via to via, the galvo mirror can scan to change the drilling 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 the first speed can be maintained during the ablation of each of the one or more first substrates. If a different pattern is 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 the second speed can be maintained during the ablation of each of the one or more second substrates.

[0079] In some embodiments, rotation of a single facet of the galvanometer scanner 650, when reflecting a pulse of electromagnetic radiation 655 sent from the laser source 642, 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 orthogonally oriented Y direction, resulting in a row (R) of blind vias 501 (e.g., in the X direction) that spans the length of the substrate 510 (e.g., in the Y direction). In another example, the Y direction is disposed at an angle relative to the X direction. In yet another example, the Y direction is disposed at an angle of about 90 degrees relative to the X direction, plus or minus a few degrees.

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

[0081] 6A, the laser drilling system 600 also includes a substrate sensing system 660 including one or more substrate position sensors. The substrate sensing system 660 uses an optical sensor 662 to detect a leading edge 665 of the substrate 510 and transmits a corresponding signal to a 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 to initiate a laser scanning operation when the leading edge 665 of the substrate 510 is under the focusing lens 652. The controller 690 further controls the rotational speed of the galvanometer scanner 650 to scan a row (R) of blind vias 501 in one or more layers disposed on the substrate 210 as each facet of the galvanometer scanner 650 rotates across a pulse of electromagnetic radiation 655. The controller 690 further controls the speed of the substrate positioning system 605 and the rotation of the galvanometer scanner 650 such that linear movement of the substrate 510 by the substrate positioning system 605 can end a first row (R) of blind vias 501 (e.g., aligned in the X direction) and start a next row (R) of blind vias 501 at a desired interval (e.g., in the direction A) from the first row. Thus, in some embodiments, as the substrate 510 moves under the optical device 635A, rows (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 such that as the trailing edge 670 of the substrate 510 passes under the focusing lens 652, the scanning motion is stopped 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 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 prior to entering the scan chamber 635B.

[0082] The controller 690 generally includes a central processing unit (CPU) (not shown), memory (not shown), and support circuits (not shown). The CPU can be one of any form of computer processor used in industrial environments to control system hardware and processes. The memory can be connected to the CPU and can be one or more of readily available memory such as random access memory (RAM), read only memory (ROM), floppy disk, hard disk, or any other form of digital storage, local or remote. Software instructions and data can be coded and stored in the memory for instructing the CPU. Support circuits can also be connected to the CPU for supporting the processor in a conventional manner. The support circuits can include cache, power supplies, clock circuits, input / output circuitry subsystems, and the like. Programs (e.g., instructions) readable by the controller 690 can include code for performing tasks associated with monitoring, executing, and controlling the movement, supporting, and positioning of the substrate 510 along with various process recipe tasks executed 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 (shown in FIG. 2C )) that is interrupted at desired times to further control the formation of blind vias 501 at desired locations on the surface of the substrate. This functionality allows for brief and / or selective stopping / starting of the train of pulses, enabling advanced patterning capabilities.

[0083] The controller 690 also controls the height sensor 664. Although FIG. 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 in the Z direction before, during, or after ablation, as described in FIGs. 8 and 9. In at least one embodiment, the height sensor 664 accurately determines the surface of a mask disposed on one or more layers of the substrate 510.

[0084] 7 is an isometric view of an exemplary laser drilling tool 700 having an optical device 635A and a scan chamber 635B disposed 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 FIG. 6A) and a second side 702B that can be coupled to an unloading station 617B (shown in FIG. 6A). The main frame 701 can include a panel 705 that can function as a door or a removable seat, a portion of which is not shown to illustrate the components within the laser drilling tool 700. The panel 705 includes an observation window 710 to provide visual access to the interior of the laser drilling tool 700. The observation window 710 can include laser safety glass and / or a filter that allows for viewing of electromagnetic radiation without the need for safety glasses during the laser drilling process within the laser drilling tool 700. Power and control equipment, such as a laser power supply 715 (shown in dashed lines), are housed within the mainframe 701. Additionally, an optical alignment device 720 (FIGS. 7 and 8) is coupled to the mainframe 701 within the laser drilling tool 700. The optical alignment device 720 can adjust the position of the optical device 635A relative to the direction of movement of the substrate 510 on the substrate positioning system 605, thereby adjusting the beam path emitted relative to the substrate.

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

[0086] FIG. 8 is a side view of an exemplary embodiment of an 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 the 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 perpendicular 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 number of adjustment devices 820, which can include fasteners, linear guides, or a combination thereof. The adjustment devices 820 can enable height adjustment (in the Z direction) of at least the optical device 635A and can enable theta adjustment in the XZ and / or YZ planes. The height adjustment can be used to adjust the focal length of the focusing lens 652 (FIGS. 6A and 6B) of the optical device 635A. The adjustment device 820 can also be used to level the second support plate 815 with respect to the plane of the transport 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 can be, for example, a telescopic housing having an aperture formed therein sized to accommodate the beam path provided by the optical device 635A. The telescopic housing can be adjusted upwards or downwards 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 disposed between the second support plate 815 and the lower surface of the optical device 635A. The adjustable mounting plate 825 is fixed to the lower surface of the optical device 635A and fastened to the second support plate 815 by fasteners 830. The adjustable mounting plate 825 can adjust the optical device 635A to different angular orientations as well as to level the optical device 635A to adjust the scan plane 835 of the beam path emitted by the optical device 635A during processing. As described in more detail in FIG. 9, the adjustable mounting plate 825 can rotate about the scan plane axis 635, e.g., the Z direction, to adjust the orientation of the scan plane (e.g., the plane aligned with the row (R) direction on the substrate in FIG. 5) of the output of the optical device 635A. Adjustments of the adjustable mounting plate 825 can be made to change the beam path in the scan plane of the optical device 635A to align the row (R) of the blind vias 501 on the substrate 510 (FIG. 5).

[0088] FIG. 9 is an isometric view of the exemplary optical alignment device 720 of FIG. 8. The optical device 635A is not shown in this view, but the scan plane 835 of the optical device 635A is shown. The adjustable mounting plate 825 includes a plurality of slots 900 that receive the fasteners 830 shown in FIG. 8. Each of the slots 900 can allow the adjustable mounting plate 825 to rotate relative to the Z axis to adjust the scan plane of the optical device 635A. For example, the first alignment position 905 of the adjustable mounting plate 825 can include an orientation in which the scan plane is substantially parallel to the leading edge 665 of the substrate 510 (shown in FIG. 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 on, for example, the speed of the substrate 510 on the transport belt 615 and / or the scan speed of the electromagnetic radiation 655. The scan speed of the electromagnetic radiation 655 can be based at least in part on the pulse width of the electromagnetic radiation 655 and / or the movement of the galvanometer scanner 650 (shown in FIG. 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 surface 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 scanning speed of the galvanometer scanner 650 is about 1,000 RPM, resulting in a row (R) of blind vias 501 that is substantially straight and / or parallel to the leading edge 665 of the substrate 510.

[0090] Any of the operations described above may be contained on 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 comprise any suitable memory for storing instructions, such as a read-only memory (ROM), a random-access memory (RAM), a flash memory, an electrically erasable programmable ROM (EEPROM), a compact disc ROM (CD-ROM), a floppy disk, etc.

[0091] For the sake of brevity, only certain ranges are explicitly disclosed herein. However, a range from any lower limit can be combined with any upper limit to enumerate a range that is not explicitly recited, and similarly, a range from any lower limit can be combined with any other lower limit to enumerate a range that is not explicitly recited, and similarly, a range from any upper limit can be combined with any other upper limit to enumerate a range that is not explicitly recited. In addition, a range includes all points or individual values ​​between its endpoints, even if not explicitly recited. Thus, every point or individual value can function as its own lower limit or upper limit in combination with any other point or individual value or any other lower limit or upper limit to enumerate a range that is not explicitly recited.

[0092] For purposes of this disclosure, unless otherwise indicated, all numerical values ​​in the detailed description and claims herein are modified by "about" or "approximately" the indicated value to account for experimental error and variations expected by those of ordinary skill in the art.

[0093] All documents described herein, including priority documents and / or testing procedures, are incorporated herein by reference to the extent not inconsistent therewith. As is apparent from the general description and specific embodiments above, forms of the disclosure have been illustrated and described, but various modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, no limitation of the disclosure is intended thereby. Similarly, the term "comprising" is considered synonymous with the term "including." Similarly, whenever the transition term "comprising" precedes a configuration, element, or group of elements, it is understood that the same configuration or group of elements with the transition term "consisting essentially of," "consisting of," "selected from the group consisting of," or "is" is considered to precede the enumeration of the configuration, element, or multiple elements, and vice versa.

Claims

1. 1. A method for forming a blind via in a substrate, comprising: transporting the substrate to a scan chamber, the substrate comprising 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 a substrate surface; determining one or more characteristics of the blind via, the one or more characteristics comprising: a top diameter of the blind via and a 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; a volume of the blind via corresponding to the top diameter, the bottom diameter, and the height; or Determining one or more characteristics, including a taper angle of about 80 degrees or greater; 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 the one or more characteristics; and and focusing the laser beam under the adjusted laser process parameters to remove at least a portion of the dielectric layer within the volume to form the blind via.

2. The laser process parameters include laser power, laser energy in a burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in a burst, pulse frequency, burst frequency, beam spot size, M ２ The method of claim 1 , further comprising: a value, an offset of the beam focus from the substrate surface, or a combination thereof.

3. The laser process parameters are: Amount of laser energy in a burst of about 5 μJ or more; A focused beam diameter of about 2 μm to about 10 μm for drilling a 5 μm diameter via; A focused beam diameter of about 7 μm to about 12 μm for drilling a 10 μm diameter via; A focal height of about 0 μm to about 50 μm; A pulse frequency of about 500 MHz or more, a number of pulses in a burst that is greater than or equal to about 2; a number of bursts greater than or equal to about 2; A burst frequency of approximately 100 kHz or more, or The method of claim 1 including combinations thereof.

4. The method of claim 1 , wherein the apex diameter is about 10 μm or less.

5. The method of claim 1 , further comprising removing the mask layer from the substrate.

6. The mask layer comprises Al, Cu, W, Mo, Cr or a combination thereof. the mask layer has a height of about 2 μm or less; or The method of claim 1 which is a combination thereof.

7. The method of claim 6 , wherein when the mask layer comprises Mo or W, the method further comprises depositing a layer of copper over the mask layer.

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

9. 1. A method for forming a blind via in a substrate, comprising: transporting the substrate to a scan chamber, the substrate comprising 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 a blind via opening to expose at least a portion of the dielectric layer, the dielectric layer providing a substrate surface; determining one or more characteristics of the blind via, the one or more characteristics comprising: a top diameter of the blind via and a 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, the top diameter corresponding to the blind via opening; a volume of the blind via corresponding to the top diameter, the bottom diameter, and the height; or Determining one or more characteristics, including a taper angle of about 80 degrees or greater; focusing a laser beam emitted from a laser source onto the substrate surface under laser process parameters to remove a first portion of the dielectric layer within the volume without causing damage to the pre-etched mask layer that is greater than or equal to half a thickness of the mask layer; adjusting the laser process parameters based on the one or more characteristics; and and focusing the laser beam under the adjusted laser process parameters to remove a second portion of the dielectric layer within the volume to form the blind via.

10. The laser process parameters include laser power, laser energy in a burst, focal beam diameter, focal height, burst energy, pulse energy, number of pulses in a burst, pulse frequency, burst frequency, beam spot size, M ２ 10. The method of claim 9, wherein the attenuation factor comprises a value, an offset of the beam focal plane from the substrate surface, or a combination thereof.

11. The laser process parameters are: Amount of laser energy in a burst of about 5 μJ or more; A focused beam diameter of about 2 μm to about 10 μm for drilling a 5 μm diameter via; A focused beam diameter of about 7 μm to about 12 μm for drilling a 10 μm diameter via; A focal height of about 0 μm to about 50 μm; A pulse frequency of about 500 MHz or more, a number of pulses in a burst that is greater than or equal to about 2; Approximately 2 or more bursts, A burst frequency of approximately 100 kHz or more, or The method of claim 9 including combinations thereof.

12. The method of claim 9 , wherein the apex diameter is about 10 μm or less.

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

14. the pre-etched mask layer comprises 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 of claim 9 which is a combination thereof.

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

16. The method of claim 9 , wherein the laser source is a femtosecond ultraviolet laser.

17. 1. An apparatus for forming blind vias in a substrate, comprising: a galvanometer scanner having a plurality of reflective facets and an axis of rotation; a beam expander and collimator; an optical device comprising: a femtosecond laser beam source configured to direct electromagnetic radiation to the beam expander; a transfer assembly configured to position the substrate to receive the electromagnetic radiation reflected from at least one of the reflective facets of the galvanometer scanner; a height sensor configured to detect a height of one or more layers of the substrate; receiving a signal from the height sensor; Controlling the femtosecond laser beam source and the transport assembly based on a signal received from the height sensor. A controller configured as follows: An apparatus comprising:

18. 20. The apparatus of claim 17, wherein the femtosecond laser is configured to emit a Gaussian laser beam profile.

19. The apparatus of claim 17 , further comprising a position sensor configured to detect a leading edge of the substrate.

20. The controller further comprises: receiving a signal from the position sensor; 20. The apparatus of claim 19, configured to control the femtosecond laser beam source and the transport assembly based on signals received from the positioning sensor.

21. The method of claim 1 , wherein the mask layer comprises Cr.

22. The method of claim 9 , wherein the mask layer comprises Cr.

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