Classifications

• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C23/00—Other surface treatment of glass not in the form of fibres or filaments
  • C03C23/0005—Other surface treatment of glass not in the form of fibres or filaments by irradiation
  • C03C23/0025—Other surface treatment of glass not in the form of fibres or filaments by irradiation by a laser beam
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C15/00—Surface treatment of glass, not in the form of fibres or filaments, by etching
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/089—Glass compositions containing silica with 40% to 90% silica, by weight containing boron
  • C03C3/091—Glass compositions containing silica with 40% to 90% silica, by weight containing boron containing aluminium
• • C—CHEMISTRY; METALLURGY
  • C03—GLASS; MINERAL OR SLAG WOOL
  • C03C—CHEMICAL COMPOSITION OF GLASSES, GLAZES OR VITREOUS ENAMELS; SURFACE TREATMENT OF GLASS; SURFACE TREATMENT OF FIBRES OR FILAMENTS MADE FROM GLASS, MINERALS OR SLAGS; JOINING GLASS TO GLASS OR OTHER MATERIALS
  • C03C3/00—Glass compositions
  • C03C3/04—Glass compositions containing silica
  • C03C3/076—Glass compositions containing silica with 40% to 90% silica, by weight
  • C03C3/097—Glass compositions containing silica with 40% to 90% silica, by weight containing phosphorus, niobium or tantalum

Definitions

• the disclosure relates generally to alkali -free glasses for glass via applications and articles comprising at least one via.
• Glass can be formed into thin, smooth, and large sheets without needing polishing, it has higher stiffness and greater dimensional stability than organic alternatives, it is a much better electrical insulator than silicon, it has better dimensional (thermal and rigidity) stability than organic options, and it can be tailored to different coefficients of thermal expansion to control stack warp in integrated circuits.
• This disclosure presents improved hole formation methods and glass compositions therefor for through glass via applications.
• a silicate-based composition comprises: 40-80 mol% S1O 2 , >0-25 mol% MO, >0-15 mol% AI 2 O 3 , >0-15 mol% B 2 O 3 , and >0-5 mol% Sn0 2 , wherein MO is a sum of BeO, MgO, CaO, SrO, and BaO.
• the silicate-based composition further comprises >0-5 mol% P 2 O 5. In one aspect, which is combinable with any of the other aspects or embodiments, the silicate-based composition comprises 5-15 mol% B 2 O 3. In one aspect, which is combinable with any of the other aspects or embodiments, the silicate-based composition comprises >6.5 mol% B 2 O 3. In one aspect, which is combinable with any of the other aspects or embodiments, the silicate-based composition comprises 4-9 mol% AI 2 O 3. In one aspect, which is combinable with any of the other aspects or embodiments, the silicate-based composition comprises ⁇ 10 mol% AI 2 O 3.
• the silicate- based composition comprises >0-10 mol% CaO; >0-10 mol% MgO; >0-10 mol% SrO; and >0-15 mol% BaO. In one aspect, which is combinable with any of the other aspects or embodiments, the silicate-based composition comprises >0-7 mol% CaO; >0-7 mol% MgO; >0-6 mol% SrO; and >0-11 mol% BaO. In one aspect, which is combinable with any of the other aspects or embodiments, the silicate-based composition comprises 60-75 mol% S1O 2.
• a silicate-based composition comprises: 40-80 mol% S1O 2 , >0-25 mol% MO, ⁇ 10 mol% AI 2 O 3 , >6.5 mol% B 2 O 3 , and >0-5 mol% Sn0 2 , wherein MO is a sum of BeO, MgO, CaO, SrO, and BaO.
• the silicate-based composition further comprises >0-5 mol% P2O5.
• the silicate-based composition comprises >0-10 mol% CaO; >0-10 mol% MgO; >0-10 mol% SrO; and >0-15 mol% BaO.
• the silicate-based composition comprises >0-7 mol% CaO; >0-7 mol% MgO; >0-6 mol% SrO; and >0-11 mol% BaO.
• the silicate-based composition comprises 60-75 mol% Si0 2.
• an article comprises: a top surface; a bottom surface; an intervening plane between the top surface and the bottom surface; a via extending from the top surface to the bottom surface, wherein the via has a diameter at the top surface and/or the bottom surface of Di; wherein the via has a diameter at the intervening place of D w ; and wherein a value of (D w /Di)xl00 is in a range of 4 to 85.
• the value of (D w /Di)x 100 is in a range of 4 to 35. In one aspect, which is combinable with any of the other aspects or embodiments, the value of (D w /Di)x 100 is in a range of 35 to 60. In one aspect, which is combinable with any of the other aspects or embodiments, the value of (D w /Di)x 100 is in a range of 60 to 85.
• the article comprises a silicate-based composition, including: 40-80 mol% Si0 2 , >0-25 mol% MO, >0-15 mol% A1 2 0 3 , >0-15 mol% B 2 0 3 , and >0-5 mol% Sn0 2 , wherein MO is a sum of BeO, MgO, CaO, SrO, and BaO.
• the silicate-based composition further comprises >0-5 mol% P 2 Os.
• FIG. 1 is a schematic illustration of one embodiment of an optical assembly for laser drilling.
• FIGS. 2A and 2B are illustrations of positioning of the laser beam focal line, i.e., the processing of a material transparent for the laser wavelength due to the induced absorption along the focal line.
• FIG. 3 A is an illustration of an optical assembly for laser processing according to one embodiment.
• FIG. 3B-1 through 3B-4 is an illustration of various possibilities to process the substrate by differently positioning the laser beam focal line relative to the substrate.
• FIG. 4 is an illustration of a second embodiment of an optical assembly for laser processing.
• FIGS. 5A and 5B are illustrations of a third embodiment of an optical assembly for laser processing.
• FIG. 6 is a graph of laser emission (intensity) as a function of time for exemplary picosecond lasers.
• FIGS. 7A and 7B are scanning electron micrographs of the features formed by laser drilling, as made in a piece of Eagle XG ® glass.
• FIG. 8 is a microscope image of typical damage tracks, perforations or defect lines (these three terms are used interchangeably herein), side view, no etching.
• the tracks made through the glass are generally not completely open - i.e., regions of material are removed, but complete through-holes are not necessarily formed.
• FIG. 9 is a microscope side view image at greater magnification than the micrograph shown in FIG. 8 of damage tracks or perforations, with no acid etching.
• FIG. 10 is a microscope image of typical damage tracks or holes, top view, no acid etching.
• FIG. 12 is a scanning electron micrograph of holes that do not penetrate the full thickness of the part, and which can be used to make blind vias.
• FIGS. 13A and 13B are scanning electron micrographs of entrance holes post etch (laser incident side) and exit holes - post acid etch (laser exit side), respectively.
• FIG. 14 is a post-etch image of the impact of microcracking.
• the microcracks have been acid etched out into elongated features.
• FIG. 15 is a photograph showing side views of holes - post acid etch. The sample has been diced to show a cross section. The bright areas are the glass; the dark areas are the holes.
• FIG. 16 is a photograph showing side views of holes - post acid etch, but with higher magnification than the photograph shown in FIG. 15.
• FIGS. 17A-17C are graphs of number of holes as a function of diameter at the top (FIG. 17A), bottom (FIG. 17B), and at the waists (FIG. 17C), showing hole diameter statistics made on about 10,000 holes, post-etch.
• FIGS. 19A-19C are photographs of radial cracks before etching (FIG. 19 A), and greater magnification of the entrance hole array (FIGS. 19B and 19C).
• FIGS. 20A-20C are photographs of holes before etching, showing a top view (FIG.
• FIG. 19 A bottom view (FIG. 19B), and side view (FIG. 19C).
• FIGS. 21 A-21E are photographs of top views of holes post acid etching at 55% laser power (FIG. 21 A), 65% laser power (FIG. 21B), 75% laser power (FIG. 21C), 85% laser power (FIG. 2 ID), and 100% laser power (FIG. 2 IE).
• FIGS. 22A-22E are photographs of bottom views of holes post acid etching at 55% laser power (FIG. 22A), 65% laser power (FIG. 22B), 75% laser power (FIG. 22C), 85% laser power (FIG. 22D), and 100% laser power (FIG. 22E).
• FIGS. 23A-23C are photographs of top views of holes post acid etch - FIG. 23 A: 100 micron holes at 200 micron pitch in a 150x150 array; FIGS. 23B and 23C: 50 micron holes at 100 micron pitch in a 300x300 array, showing (FIG. 23 C) some cracked and chipped holes.
• FIGS. 24A-24C are graphs of number of holes a function of diameter for a sample having 100x100 array of holes, showing results for a sample for the top (FIG. 24 A), bottom (FIG. 24B), and waists (FIG. 24C).
• FIGS. 25A-25C are graphs of number of holes a function of circularity for a sample having 100x100 array of holes, showing results for a sample for the top (FIG. 25 A), bottom (FIG. 25B), and waists (FIG. 25C).
• FIGS. 26A-26C are graphs of number of holes a function of diameter for a sample having 100x100 array of holes, showing results for a second sample for the top (FIG. 26 A), bottom (FIG. 26B), and waists (FIG. 26C).
• FIGS. 27A-27C are graphs of number of holes a function of circularity for a sample having 100x100 array of holes, showing results for a second sample for the top (FIG. 27 A), bottom (FIG. 27B), and waists (FIG. 27C).
• FIGS. 28A-28C and 29A-29C are post acid etch photographs of 30 micron and 50 micron holes, respectively, made using 100% laser power, showing top (FIGS. 28 A, 29 A), side (FIGS. 28B, 29B), and bottom (FIGS. 28C, 29C) views.
• FIGS. 30A-30C and 31A-31C are post acid etch photographs of 75 micron and 100 micron holes, respectively, made using 100% laser power, showing top (FIGS. 30A, 31 A), side (FIGS. 30B, 3 IB), and bottom (FIGS. 30C, 31C) views.
• FIGS. 32A-32C and 33A-33C are post acid etch photographs of 30 micron and 50 micron holes, respectively, made using 85% laser power, showing top (FIGS. 32A, 33 A), side (FIGS. 32B, 33B), and bottom (FIGS. 32C, 33C) views.
• FIGS. 34A-34C and 35A-35C are post acid etch photographs of 75 micron and 100 micron holes, respectively, made using 85% laser power, showing top (FIGS. 34A, 35A), side (FIGS. 34B, 35B), and bottom (FIGS. 34C, 35C) views.
• FIGS. 36A-36C and 37A-37C are post acid etch photographs of 30 micron and 50 micron holes, respectively, made using 75% laser power, showing top (FIGS. 36A, 37A), side (FIGS. 36B, 37B), and bottom (FIGS. 36C, 37C) views.
• FIGS. 38A-38C and 39A-39C are post acid etch photographs of 75 micron and 100 micron holes, respectively, made using 75% laser power, showing top (FIGS. 38 A, 39 A), side (FIGS. 38B, 39B), and bottom (FIGS. 38C, 39C) views.
• FIGS. 40A-40C and 41A-41C are post acid etch photographs of 30 microns and 50 micron holes, respectively, made using 65% laser power, showing top (FIGS. 40 A, 41 A), side (FIGS. 40B, 41B), and bottom (FIGS. 40C, 41C) views.
• FIGS. 42A-42C and 43A-43C are post acid etch photographs of 75 micron and 100 micron holes, respectively, made using 65% laser power, showing top (FIGS. 42A, 43 A), side (FIGS. 42B, 43B), and bottom (FIGS. 42C, 43C) views.
• FIGS. 44A-44C and 45A-45C are post acid etch photographs of 30 micron and 50 micron holes, respectively, made using 55% laser power, showing top (FIGS. 44 A, 45 A), side (FIGS. 44B, 45B), and bottom (FIGS. 44C, 45C) views.
• FIGS. 46A-46C and 47A-47C are post acid etch photographs of 75 micron and 100 micron holes, respectively, made using 55% laser power, showing top (FIGS. 46A, 47 A), side (FIGS. 46B, 47B), and bottom (FIGS. 46C, 47C) views.
• FIG. 48 illustrates a focal line extending through three stacked, 150 micron Eagle XG® glass sheets.
• FIG. 49 is a pre-acid etch photograph showing a side view a stack of two sheets of 300 micron thick EXG glass that have been drilled with damage tracks.
• FIG. 50 is a post-acid etch photograph showing a side view of the same stack from FIG. 49 after acid etch.
• FIG. 51 is a post-acid etch photograph showing a top view of the same stack from FIG. 49 after acid etch.
• FIGS. 52A and 52B illustrate a substrate 1000 after laser drilling and after acid etching, respectively.
• FIG. 53 illustrates the relationship between the Thiele modulus of the etching system and an expected percentage of the waist diameter with respect to the diameter of the top and bottom openings.
• FIG. 54 plots the Thiele modulus of the etching system as a function of the radius of the damage track.
• FIG. 55 plots the Thiele modulus of the etching system as a function of the half- thickness of a glass substrate.
• FIG. 56 plots the Thiele modulus of the etching system as a function of the effective diffusivity (D eff ).
• FIG. 57 plots the Thiele modulus of the etching system as a function of the acid concentration in volume % as well as the combined effect of modifying the effective diffusivity and acid concentration on the Thiele modulus.
• FIG. 58 is a post-acid etch photograph of a side view of the glass part.
• FIG. 59A illustrates a schematic drawing of laser damaged glass with pre-etching thickness Hi
• FIG. 59B illustrates a schematic drawing of via shape after etching.
• Di is top diameter of the via
• D w is the waist diameter of the via
• the final thickness is 3 ⁇ 4.
• FIG. 60A illustrates a microscopic image of laser damaged glass (followed by an acid etch) having a D w /Di ratio of 17% (laser: 20 burst, 90 pJ power; acid: 5 vol.% HF).
• 60B illustrates a microscopic image of laser damaged glass (followed by an acid etch) having a D w /Di ratio of 80% (laser: 15 burst, 85 pJ power; acid: 5 vol.% HF, 10 vol.% HNO3, 0.1 vol.% PE).
• FIGS. 61 A and 61B illustrate a comparison between 7607 glass and Coming Eagle® (EXG) glass after exposure to various acid etchants corresponding to their respective mean %openings (FIG. 61A) and waist standard deviation (FIG. 61B).
• EXG Coming Eagle®
• FIGS. 62Ai-62Jii illustrate a comparison between glasses having compositions of Table 1 and Corning Eagle® (EXG) glass after exposure to laser and acid etch processing.
• EXG Corning Eagle®
• compositions are expressed in terms of mol% amounts of particular components included therein on an oxide bases unless otherwise indicated. Any component having more than one oxidation state may be present in a composition in any oxidation state. However, concentrations of such component are expressed in terms of the oxide in which such component is at its lowest oxidation state unless otherwise indicated.
• the following embodiments utilize a short (e.g., from 10 10 to 10 15 second) pulsed laser with an optical system that creates a line focus system to form defect lines, damage tracks, or holes in a piece of material that is substantially transparent to the wavelength of the laser, such as a glass, fused silica, synthetic quartz, a glass ceramic, ceramic, a crystalline material such as sapphire, or laminated layers of such materials (for example, coated glass).
• the generation of a line focus may be performed by sending a Gaussian laser beam into an axicon lens, in which case a beam profile known as a Gauss-Bessel beam is created. Such a beam diffracts much more slowly (e.g.
• the material or article is substantially transparent to the laser wavelength when the absorption is less than about 10%, preferably less than about 1% per mm of material depth at this wavelength. In some embodiments, the material can also be transparent to at least one wavelength in a range from about 390 nm to about 700 nm.
• the material can also be transparent to at least one wavelength >1000 nm.
• Use of the intense laser and line focus allows each laser pulse to simultaneously damage, ablate, or otherwise modify a long (e.g. 100-1000 microns) track in the glass. This track can easily extend through the entire thickness of the glass part. Even a single pulse or burst of pulses thus creates the full “pilot hole” or intense damage track, and no percussion drilling is needed.
• the pilot holes/damage tracks are very small (single microns or less) in cross-sectional dimension, but are relatively long- i.e., they have a high aspect ratio.
• the parts are subsequently acid etched to reach final hole dimensions — for example diameter of about 30 microns to 100 microns, about 30 microns or less, about 25 microns or less, about 20 microns or less, about 15 microns or less, about 10 microns or less, in a range from about 5 to about 10 microns, about 5 to about 15 microns, about 5 to about 20 microns, about 5 to about 25 microns, about 5 to about 30 microns, or up to many tens of microns depending upon requirements for the intended use.
• the etching can be carried out so that the Thiele modulus of the etching process is about 3 or less, about 2.5 or less, about 2 or less, about 1.5 or less, about 1 or less, or about 0.5 or less.
• the surface of the glass may be slightly textured from imperfect uniformity in the etching process - the interior of the etched holes, while somewhat smooth, may also have some fine grain texture that is visible under a microscope or scanning electron microscope.
• the substrate can have a plurality of through-holes continuously extending from a first surface of the substrate to a second surface of the substrate, wherein the substrate is transparent to at least one wavelength in a range from 390 nm to 700 nm (or >1000 nm), the plurality of through-holes have a diameter of 20 pm or less, the plurality of through-holes comprise an opening in the first surface, an opening in the second surface, and a waist located between the opening in the first surface and the opening in the second surface, a diameter of the waist is at least 50% of the diameter of the opening in the first surface or the opening in the second surface, and a difference between a diameter of the opening in the first surface and a diameter of the opening in the second surface is 3 pm or less
• the holes may then be coated and/or filled with a conductive material, for example through metallization, in order to create an interposer part made of the transparent material.
• the metal or conductive material can be, for example copper, aluminum, gold, silver, lead, tin, indium tin oxide, or a combination or alloy thereof.
• the process used to metalize the interior of the holes can be, for example, electro- plating, electroless plating, physical vapor deposition, or other evaporative coating methods.
• the holes may also be coated with catalytic materials, such as platinum, palladium, titanium dioxide, or other materials that facilitate chemical reactions within the holes.
• the holes may be coated with other chemical functionalization, so as to change surface wetting properties or allow attachment of biomolecules and used for biochemical analysis.
• chemical functionalization could be silanization of the glass surface of the holes, and/or additional attachment of specific proteins, antibodies, or other biologically specific molecules, designed to promote attachment of biomolecules for desired applications.
• a method of laser drilling a material includes focusing a pulsed laser beam into a laser beam focal line oriented along the beam propagation direction and directed into the material, the laser beam having an average laser burst energy measured at the material greater than about 50 microJoules per mm thickness of material being processed, having burst energy density in a range from about 25 pJ/mm of line focus to about 125 pj/mm of line focus, having pulses having a duration less than about 100 picoseconds, and a repetition rate in a range of between about 1 kHz and about 4 MHz.
• the length of the line focus can be determined by the distance between the two points on the optical axis where the intensity is one half the maximum intensity.
• the laser beam focal line generates an induced absorption within the material, the induced absorption producing a hole along the laser beam focal line within the material.
• the method also includes translating the material and the laser beam relative to each other, thereby laser drilling a plurality of holes (or damage tracks) within the material at a rate greater than about 50 holes/second, greater than about 100 holes/second, greater than about 500 holes/second, greater than about 1,000 holes/second, greater than about 2,000 holes/second, greater than about 3,000 holes/second, greater than about 4,000 holes/second, greater than about 5,000 holes/second, greater than about 6,000 holes/second, greater than about 7,000 holes/second, greater than about 8,000 holes/second, greater than about 9,000 holes/second, greater than about 10,000 holes/second, greater than about 25,000 holes/second, greater than about 50,000 holes/second, greater than about 75,000 holes/second, or greater than about 100,000 holes/second, depending upon the desired pattern of holes/damage tracks.
• the method further includes etching the material in an acid solution at a rate
• the pulse duration can be in a range of between greater than about 5 picoseconds and less than about 100 picoseconds, and the repetition rate can be in a range of between about 1 kHz and 4 MHz.
• the pulses can be produced in bursts of at least two pulses separated by a duration in a range of between about 1 nsec and about 50 nsec, for example 10 to 30 nsec, such as about 20 nsec plus or minus 2 nsec, and the burst repetition frequency can be in a range of between about 1 kHz and about 4 MHz.
• the pulsed laser beam can have a wavelength selected such that the material is substantially transparent at this wavelength.
• the burst repetition frequency can be in a range between about 1 kHz and about 4MHz, in a range between about 10 kHz and about 650 kHz, about 10 kHz or greater, or about 100 kHz or greater.
• the laser beam focal line can have a length in a range of between about 0.1 mm and about 10 mm, or a length in a range of between about 0.1 mm and about 1 mm, and an average spot diameter in a range of between about 0.1 micron and about 5 microns.
• FIG. 1 gives a schematic of one version of the concept, where an axicon optical element 10 and other lenses 11 and 12 are used to focus light rays from a laser 3 (not shown) into a pattern 2b that will have a linear shape, parallel to the optical axis of the system.
• the substrate 1 is positioned so that it is within the line-focus. With a line-focus of about 1 mm extent, and a picosecond laser that produces output power greater than or equal to about 20 W at a repetition rate of 100 kHz (about 200 microJoules/burst measured at the material), then the optical intensities in the line region 2b can easily be high enough to create non-linear absorption in the material.
• the pulsed laser beam can have an average laser burst energy measured, at the material, greater than 40 microJoules per mm thickness of material.
• the average laser burst energy used can be as high as 2500 pJ per mm of thickness of material, for example 100-2000 pj/mm, with 200-1750 pj/mm being preferable, and 500-1500 pj/mm being more preferable.
• This “average laser energy” can also be referred to as an average, per- burst, linear energy density, or an average energy per laser burst per mm thickness of material.
• the burst energy density can be in a range from about 25 pj/mm of line focus to about 125 pj/mm of line focus, or in a range from about 75 pj/mm of line focus to about 125 pj/mm of line focus.
• a region of damaged, ablated, vaporized, or otherwise modified material is created that approximately follows the linear region of high intensity.
• a method of laser processing a material includes focusing a pulsed laser beam 2 into a laser beam focal line 2b oriented along the beam propagation direction.
• laser 3 (not shown) emits laser beam 2, which has a portion 2a incident to the optical assembly 6.
• the optical assembly 6 turns the incident laser beam into an extensive laser beam focal line 2b on the output side over a defined expansion range along the beam direction (length 1 of the focal line).
• the planar substrate 1 is positioned in the beam path to at least partially overlap the laser beam focal line 2b of laser beam 2. The laser beam focal line is thus directed into the substrate.
• Reference la designates the surface of the planar substrate facing the optical assembly 6 or the laser, respectively, and reference lb designates the reverse surface of substrate 1.
• the substrate or material thickness (in this embodiment measured perpendicularly to the planes la and lb, i.e., to the substrate plane) is labeled with d.
• the substrate or material can be a glass article that is substantially transparent to the wavelength of the laser beam 2, for example.
• substrate 1 (or material or glass article) is aligned perpendicular to the longitudinal beam axis and thus behind the same focal line 2b produced by the optical assembly 6 (the substrate is perpendicular to the plane of the drawing).
• the focal line being oriented or aligned along the beam direction, the substrate is positioned relative to the focal line 2b in such a way that the focal line 2b starts before the surface la of the substrate and stops before the surface lb of the substrate, i.e. still focal line 2b terminates within the substrate and does not extend beyond surface lb.
• the focal line 2b starts before the surface la of the substrate and stops before the surface lb of the substrate, i.e. still focal line 2b terminates within the substrate and does not extend beyond surface lb.
• the extensive laser beam focal line 2b generates (assuming suitable laser intensity along the laser beam focal line 2b, which intensity is ensured by the focusing of laser beam 2 on a section of length 1, i.e. a line focus of length 1) an extensive section 2c (aligned along the longitudinal beam direction) along which an induced absorption is generated in the substrate material.
• the induced absorption produces defect line formation in the substrate material along section 2c.
• the defect line is a microscopic (e.g., >100 nm and ⁇ 0.5 micron in diameter) elongated “hole” (also called a perforation, a damage track, or a defect line) in a substantially transparent material, substrate, or workpiece generated by using a single high energy burst pulse.
• Individual perforations can be created at rates of several hundred kilohertz (several hundred thousand perforations per second), for example. With relative motion between the source and the material, these perforations can be placed adjacent to one another (spatial separation varying from sub-micron to many microns as desired). This spatial separation (pitch) can be selected to facilitate separation of the material or workpiece.
• the defect line/damage track is a “through hole”, which is a hole or an open channel that extends from the top to the bottom of the substantially transparent material.
• the damage track is not a true “through hole” because there are particles of the material block the path of the damage track.
• the damage track can extend from the top surface to the bottom surface of material, in some embodiments it is not a continuous hole or channel because particles of the material are blocking the path.
• the defect line/damage track formation is not only local, but over the entire length of the extensive section 2c of the induced absorption.
• the length of section 2c (which corresponds to the length of the overlapping of laser beam focal line 2b with substrate 1) is labeled with reference L.
• the average diameter or extent of the section of the induced absorption 2c (or the sections in the material of substrate 1 undergoing the defect line formation) is labeled with reference D.
• This average extent D basically corresponds to the average diameter d of the laser beam focal line 2b, that is, an average spot diameter in a range of between about 0.1 micron and about 5 microns.
• a microscopic i.e., ⁇ 2 micron and >100 nm in diameter, and in some embodiments ⁇ 0.5 pm and >100 nm
• elongated “hole” also called a perforation, a damage track, or a defect line, as noted above
• These individual perforations can be created at rates of several hundred kilohertz (several hundred thousand perforations per second, for example).
• these perforations can be placed at any desired location within the workpiece.
• the defect line/damage track is a “through hole”, which is a hole or an open channel that extends from the top to the bottom of the transparent material.
• the defect line/damage track may not be a continuous channel and may be blocked or partially blocked by portions or sections of solid material (e.g., glass).
• the internal diameter of the defect line/damage track is the internal diameter of the open channel or the air hole.
• the internal diameter of the defect line/damage track is ⁇ 500 nm, for example ⁇ 400 nm, or ⁇ 300 nm.
• the disrupted or modified area (e.g, compacted, melted, or otherwise changed) of the material surrounding the holes in the embodiments disclosed herein preferably has diameter of ⁇ 50 microns (e.g,, ⁇ 10 micron).
• the substrate material (which is transparent to the wavelength l of laser beam 2) is heated due to the induced absorption along the focal line 2b arising from the nonlinear effects associated with the high intensity of the laser beam within focal line 2b.
• FIG. 2B illustrates that the heated substrate material will eventually expand so that a corresponding induced tension leads to micro-crack formation, with the tension being the highest at surface la.
• the selection of a laser source is predicated on the ability to create multi- photon absorption (MPA) in transparent materials.
• MPA is the simultaneous absorption of two or more photons of identical or different frequencies in order to excite a molecule from one state (usually the ground state) to a higher energy electronic state (possibly resulting in ionization).
• the energy difference between the involved lower and upper states of the molecule can be equal to the sum of the energies of the two or more photons.
• MPA also called induced absorption
• MPA can be a second-order, third-order, or higher-order process, for example, that is several orders of magnitude weaker than linear absorption.
• MPA differs from linear absorption in that the strength of induced absorption can be proportional to the square, or the cube, or other higher power, of the light intensity, for example, instead of being proportional to the light intensity itself.
• MPA is a nonlinear optical process.
• optical assemblies 6, which can be applied to generate the focal line 2b, as well as a representative optical setup, in which these optical assemblies can be applied, are described below. All assemblies or setups are based on the description above so that identical references are used for identical components or features or those which are equal in their function. Therefore only the differences are described below.
• the individual focal lines positioned on the substrate surface should be generated using the optical assembly described below (hereinafter, the optical assembly is alternatively also referred to as laser optics).
• the optical assembly is alternatively also referred to as laser optics.
• the optical assembly In order to achieve a small spot size of, for example, 0.5 micron to 2 microns in case of a given wavelength l of laser 3 (interaction with the material of substrate 1), certain requirements must usually be imposed on the numerical aperture of laser optics 6.
• the laser beam must illuminate the optics up to the required aperture, which is typically achieved by means of beam widening using widening telescopes between the laser and focusing optics.
• the spot size should not vary too strongly for the purpose of a uniform interaction along the focal line. This can, for example, be ensured (see the embodiment below) by illuminating the focusing optics only in a small, circular area so that the beam opening and thus the percentage of the numerical aperture only vary slightly.
• FIG. 3 A section perpendicular to the substrate plane at the level of the central beam in the laser beam bundle of laser radiation 2; here, too, laser beam 2 is perpendicularly incident to the substrate plane, i.e. incidence angle is 0° so that the focal line 2b or the extensive section of the induced absorption 2c is parallel to the substrate normal
• the laser radiation 2a emitted by laser 3 is first directed onto a circular aperture 8 which is completely opaque to the laser radiation used.
• Aperture 8 is oriented perpendicular to the longitudinal beam axis and is centered on the central beam of the depicted beam bundle 2a.
• the diameter of aperture 8 is selected in such a way that the beam bundles near the center of beam bundle 2a or the central beam (here labeled with 2aZ) hit the aperture and are completely absorbed by it. Only the beams in the outer perimeter range of beam bundle 2a (marginal rays, here labeled with 2aR) are not absorbed due to the reduced aperture size compared to the beam diameter, but pass aperture 8 laterally and hit the marginal areas of the focusing optic elements of the optical assembly 6, which, in this embodiment, is designed as a spherically cut, bi- convex lens 7.
• the laser beam focal line 2b is not only a single focal point for the laser beam, but rather a series of focal points for different rays in the laser beam.
• the series of focal points form an elongated focal line of a defined length, shown in FIG. 3 A as the length 1 of the laser beam focal line 2b.
• Lens 7 is centered on the central beam and is designed as a non-corrected, bi-convex focusing lens in the form of a common, spherically cut lens.
• the spherical aberration of such a lens may be advantageous.
• aspheres or multi-lens systems deviating from ideally corrected systems, which do not form an ideal focal point but a distinct, elongated focal line of a defined length can also be used (i.e., lenses or systems which do not have a single focal point).
• the zones of the lens thus focus along a focal line 2b, subject to the distance from the lens center.
• the diameter of aperture 8 across the beam direction is approximately 90% of the diameter of the beam bundle (defined by the distance required for the intensity of the beam to decrease to 1/e 2 of the peak intensity) and approximately 75% of the diameter of the lens of the optical assembly 6.
• FIG. 3 A shows the section in one plane through the central beam, and the complete three-dimensional bundle can be seen when the depicted beams are rotated around the focal line 2b.
• FIGS. 3B-1-4 show (not only for the optical assembly in FIG. 3 A, but basically also for any other applicable optical assembly 6) that the position of laser beam focal line 2b can be controlled by suitably positioning and/or aligning the optical assembly 6 relative to substrate 1 as well as by suitably selecting the parameters of the optical assembly 6.
• the length 1 of the focal line 2b can be adjusted in such a way that it exceeds the substrate thickness d (here by factor 2). If substrate 1 is placed (viewed in longitudinal beam direction) centrally to focal line 2b, an extensive section of induced absorption 2c is generated over the entire substrate thickness.
• the laser beam focal line 2b can have a length 1 in a range of between about 1.1 mm and about 100 mm or in a range of between about 0.1 mm and about 10 mm, for example.
• Various embodiments can be configured to have length 1 of about 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.7 mm, 1 mm, 2 mm, 3 mm or 5 mm, for example.
• a focal line 2b of length 1 is generated which corresponds more or less to the substrate thickness d.
• FIG. 3B-3 shows the case in which the substrate 1 (viewed along a direction perpendicular to the beam direction) is positioned above the starting point of focal line 2b so that, as in FIG. 3B-2, the length 1 of line 2b is greater than the length L of the section of induced absorption 2c in substrate 1.
• the focal line thus starts within the substrate and extends beyond the reverse surface lb.
• FIG. 4 depicts another applicable optical assembly 6.
• the basic construction follows the one described in FIG. 3 A so that only the differences are described below.
• the depicted optical assembly is based the use of optics with a non-spherical free surface in order to generate the focal line 2b, which is shaped in such a way that a focal line of defined length 1 is formed.
• aspheres can be used as optic elements of the optical assembly 6.
• a so-called conical prism also often referred to as axicon
• An axicon is a special, conically cut lens which forms a spot source on a line along the optical axis (or transforms a laser beam into a ring).
• the layout of such an axicon is generally known to one skilled in the art; the cone angle in the example is 10°.
• the apex of the axicon labeled here with reference 9 is directed towards the incidence direction and centered on the beam center. Since the focal line 2b produced by the axicon 9 starts within its interior, substrate 1 (here aligned perpendicularly to the main beam axis) can be positioned in the beam path directly behind axicon 9. As FIG. 4 shows, it is also possible to shift substrate 1 along the beam direction due to the optical characteristics of the axicon while remaining within the range of focal line 2b. The section of the induced absorption 2c in the material of substrate 1 therefore extends over the entire substrate depth d.
• the depicted layout is subject to the following restrictions: Since the region of focal line 2b formed by axicon 9 begins within axicon 9, a significant part of the laser energy is not focused into the section of induced absorption 2c of focal line 2b, which is located within the material, in the situation where there is a separation a between axicon 9 and the substrate or glass composite workpiece material. Furthermore, length 1 of focal line 2b is related to the beam diameter through the refractive indices and cone angles of axicon 9. This is why, in the case of relatively thin materials (several millimeters), the total focal line is much longer than the substrate or glass composite workpiece thickness, having the effect that much of the laser energy is not focused into the material.
• FIG. 5 A depicts such an optical assembly 6 in which a first optical element with a non-spherical free surface designed to form an extensive laser beam focal line 2b is positioned in the beam path of laser 3.
• this first optical element is an axicon 10 with a cone angle of 5°, which is positioned perpendicularly to the beam direction and centered on laser beam 3. The apex of the axicon is oriented towards the beam direction.
• a second, focusing optical element here the plano-convex lens 11 (the curvature of which is oriented towards the axicon), is positioned in the beam direction at a distance zl from the axicon 10.
• the distance zl in this case approximately 300 mm, is selected in such a way that the laser radiation formed by axicon 10 is circularly incident on the outer radial portion of lens 11.
• Lens 11 focuses the circular radiation on the output side at a distance z2, in this case approximately 20 mm from lens 11, on a focal line 2b of a defined length, in this case 1.5 mm.
• the effective focal length of lens 11 is 25 mm in this embodiment.
• the circular transformation of the laser beam by axicon 10 is labeled with the reference SR.
• FIG. 5B depicts the formation of the focal line 2b or the induced absorption 2c in the material of substrate 1 according to FIG. 5A in detail.
• the optical characteristics of both elements 10, 11 as well as the positioning of them is selected in such a way that the length 1 of the focal line 2b in beam direction is exactly identical with the thickness d of substrate 1. Consequently, an exact positioning of substrate 1 along the beam direction is required in order to position the focal line 2b exactly between the two surfaces la and lb of substrate 1, as shown in FIG. 5B.
• the focal line is formed at a certain distance from the laser optics, and if the greater part of the laser radiation is focused up to a desired end of the focal line.
• this can be achieved by illuminating a primarily focusing element 11 (lens) only circularly (annularly) over a particular outer radial region, which, on the one hand, serves to realize the required numerical aperture and thus the required spot size, and, on the other hand, however, the circle of diffusion diminishes in intensity after the required focal line 2b over a very short distance in the center of the spot, as a basically circular spot is formed. In this way, the defect line/damage track formation is stopped within a short distance in the required substrate depth.
• a combination of axicon 10 and focusing lens 11 meets this requirement.
• the axicon acts in two different ways: due to the axicon 10, a usually round laser spot is sent to the focusing lens 11 in the form of a ring, and the asphericity of axicon 10 has the effect that a focal line is formed beyond the focal plane of the lens instead of a focal point in the focal plane.
• the length 1 of focal line 2b can be adjusted via the beam diameter on the axicon.
• the numerical aperture along the focal line on the other hand, can be adjusted via the distance zl axicon-lens and via the cone angle of the axicon. In this way, the entire laser energy can be concentrated in the focal line.
• the circular (annular) illumination still has the advantage that (1) the laser power is used optimally in the sense that most of the laser light remains concentrated in the required length of the focal line and (2) it is possible to achieve a uniform spot size along the focal line - and thus a uniform separation of part from substrate along the focal line - due to the circularly illuminated zone in conjunction with the desired aberration set by means of the other optical functions.
• the focal length f of the collimating lens 12 is selected in such a way that the desired circle diameter dr results from distance zla from the axicon to the collimating lens 12, which is equal to f .
• the desired width br of the ring can be adjusted via the distance zlb (collimating lens 12 to focusing lens 11). As a matter of pure geometry, the small width of the circular illumination leads to a short focal line. A minimum can be achieved at distance f .
• the optical assembly 6 depicted in FIG. 5A is thus based on the one depicted in FIG. 1 so that only the differences are described below.
• the collimating lens 12, here also designed as a plano-convex lens (with its curvature towards the beam direction) is additionally placed centrally in the beam path between axicon 10 (with its apex towards the beam direction), on the one side, and the plano-convex lens 11, on the other side.
• the distance of collimating lens 12 from axicon 10 is referred to as zla, the distance of focusing lens 11 from collimating lens 12 as zlb, and the distance of the focal line 2b from the focusing lens 11 as z2 (always viewed in beam direction).
• the circular radiation SR formed by axicon 10 which is incident divergently and under the circle diameter dr on the collimating lens 12, is adjusted to the required circle width br along the distance zlb for an at least approximately constant circle diameter dr at the focusing lens 11.
• a very short focal line 2b is intended to be generated so that the circle width br of approximately 4 mm at lens 12 is reduced to approximately 0.5 mm at lens 11 due to the focusing properties of lens 12 (circle diameter dr is 22 mm in the example).
• burst is a type of laser operation where the emission of pulses is not in a uniform and steady stream but rather in tight clusters of pulses. This is depicted in FIG. 6.
• Each “burst” 610 may contain multiple pulses 620 (such as at least 2 pulses, at least 3 pulses, at least 4 pulses, at least 5 pulses, at least 10 pulses, at least 15 pulses, at least 20 pulses, or more) of very short duration .
• Pulses 610 can have a pulse duration T d in a range from about 0.1 psec to about 100 psec (for example, 0.1 psec, 5 psec, 10 psec, 15 psec, 18ps, 20 ps, 22 ps, 25 ps, 30 ps, 50 ps, 75 ps, or therebetween ).
• the pulse duration can be in a range from greater than about 1 picosecond and less than about 100 picoseconds or greater than about 5 picoseconds and less than about 20 picoseconds.
• These individual pulses 620 within a single burst 610 can also be termed “sub-pulses,” which simply denotes the fact that they occur within a single burst of pulses.
• the energy or intensity of each laser pulse 620 within the burst 610 may not be equal to that of other pulses within the bust, and the intensity distribution of the multiple pulses within a burst 610 often follows an exponential decay in time governed by the laser design.
• each pulse 620 within the burst 610 is separated in time by a duration T p in a range of between about 1 nsec and about 50 nsec, (e.g. 10-50 ns, or 10-50ns, or 10-30 nsec), with the time often governed by the laser cavity design.
• T p the time separation between each pulses (pulse -to- pulse separation) within a burst 610 is relatively uniform ( ⁇ 10% ).
• T p is approximately 20 nsec (50 MHz).
• the pulse to pulse separation T p within a burst is maintained within about ⁇ 10%, or is about ⁇ 2 nsec.
• the time between each “burst” 610 of pulses 620 i.e., time separation T b between bursts
• T b is about 10 microseconds, for a laser repetition rate of about 100 kHz.
• T b can be around 5 microseconds for a laser repetition rate or frequency of about 200 kHz.
• the time between each "burst" can also be around 5 microseconds, for a laser repetition rate of -200 kHz, for example.
• the laser repetition rate is also referred to as burst repetition frequency herein, and is defined as the time between the first pulse in a burst to the first pulse in the subsequent burst.
• the burst repetition frequency is in a range of between about 1 kHz and about 4 MHz. More preferably, the laser repetition rates can be in a range of between about 10 kHz and 650 kHz.
• the laser repetition rate can be about 10 kHz or greater or about 100 kHz or greater.
• the time T b between the first pulse in each burst to the first pulse in the subsequent burst may be 0.25 microsecond (4MHz repetition rate) to 1000 microseconds (1kHz repetition rate), for example 0.5 microseconds (2MHz repetition rate) to 40 microseconds (25kHz repetition rate), or 2 microseconds (500kHz repetition rate) to 20 microseconds (50kHz repetition rate).
• the exact timings, pulse durations, and repetition rates can vary depending on the laser design, but short pulses (T d ⁇ 20 psec and preferably T d ⁇ 15 psec) of high intensity have been shown to work particularly well. In some of the embodiments 5 psec ⁇ T d ⁇ 15 psec.
• the required energy to modify the material can be described in terms of the burst energy - the energy contained within a burst (each burst 610 contains a series of pulses 620), or in terms of the energy contained within a single laser pulse (many of which may comprise a burst).
• the energy per burst can be from 25pJ-750 pj, more preferably 40 pJ-750 pj, 50 pj -500 pj, 50-250 pj, or 100-250 pj.
• the energy of an individual pulse within the burst can be less, and the exact individual laser pulse energy will depend on the number of pulses within the burst and the rate of decay (e.g.
• each individual laser pulse will contain less energy than if the same burst had only 2 individual laser pulses.
• a laser capable of generating such bursts of pulses is advantageous for such processing.
• the use of a burst sequence that spreads the laser energy over a rapid sequence of sub-pulses (that comprise a burst) allows access to larger timescales of high intensity interaction with the material than is possible with single-pulse lasers.
• a single pulse can be expanded in time, as this is done the intensity within the pulse must drop as roughly one over the pulse width. Hence if a 10 psec pulse is expanded to a 10 nsec pulse, the intensity drop by roughly three orders of magnitude.
• the intensity during each sub-pulse can remain very high - for example three 10 psec pulses spaced apart in time by approximately 10 nsec still allows the intensity within each pulse to be approximately within a factor of three of a single 10 psec pulse, while the laser is allowed to interact with the material over a timescale that is now three orders of magnitude larger.
• This adjustment of multiple pulses within a burst thus allows manipulation of time-scale of the laser-material interaction in ways that can facilitate greater or lesser light interaction with a pre-existing plasma plume, greater or lesser light-material interaction with atoms and molecules that have been pre-excited by an initial or previous laser pulse.
• the damage track or hole is formed in the material when a single burst of pulses strikes substantially the same location on the material. That is, multiple laser pulses within a single burst correspond to a single defect line or a hole location in the material.
• the individual pulses within the burst cannot be at exactly the same spatial location on the material.
• the pulses are well within 1 micron of one another so that they strike the material at essentially the same location. For example, the pulses may strike the material at a spacing sp where 0 ⁇ sp ⁇ 500 nm from one another.
• the spacing sp is in a range from about 1 nm to about 250 nm or from about 1 nm to about 100 nm.
• the optical method of forming the line focus can take multiple forms, using donut shaped laser beams and spherical lenses, axicon lenses, diffractive elements, or other methods to form the linear region of high intensity as described above.
• the type of laser (picosecond, femtosecond, etc.) and wavelength (IR, green, UV, etc.) can also be varied, as long as sufficient optical intensities are reached to create breakdown of the substrate material.
• the damage tracks created by the aforementioned laser process generally take the form of holes with interior dimensions in the range of about 0.1 microns to 2 microns, for example 0.1 -1.5 microns.
• the holes formed by the laser are very small (single microns or less) in dimension-i.e., they are narrow. In some embodiments, these holes are 0.2 to 0.7 microns in diameter.
• the damage tracks are not continuous holes or channels.
• the diameter of the damage tracks can be 5 microns or less, 4 microns or less, 3 microns or less, 2 microns or less, or 1 micron or less.
• the diameter of the damage tracks can be in a range from greater than 100 nm to less than 2 microns, or from greater than 100 nm to less than 0.5 microns. Scanning electron micrograph images of such features are shown in FIGS. 7 A and 7B. These holes are un-etched holes (i.e., they have not been widened by the etching steps)
• the holes or defect lines/damage tracks can perforate the entire thickness of the material, and may or may not be a continuous opening throughout the depth of the material.
• FIG. 8 shows an example of such tracks or defect lines perforating the entire thickness of a workpiece of 150 micron thick Eagle XG ® glass substrate.
• the perforations or damage tracks are observed through the side of a cleaved edge.
• the tracks through the material are not necessarily through holes. There are often regions of glass that plug the holes, but they are generally small in size, on the order of microns, for example.
• FIG. 9 shows a greater magnification image of similar holes or damage tracks, where the diameter of the holes can be more clearly seen, and also the presence of regions where the hole is plugged by remaining glass.
• the tracks made through the glass are about 1 micron in diameter. They are not completely open - i.e., regions of material are removed, but complete through-holes are not necessarily formed.
• the focal line length needs to be longer than the stack height.
• the tests were performed with three stacked 150 micron sheets of Eagle XG ® glass, and full perforations were made through all three pieces with the perforations or defect lines/damage tracks (of approximately 1 micron internal diameter) extended from the top surface of the upper sheet all the way through the bottom surface of the bottom sheet.
• An example of a focal line configured for full perforation through a single substrate is shown in FIG. 3B-1, while a full perforation through three stacked sheets is described hereinafter in conjunction with FIG. 48.
• the internal diameter of a defect line or perforation is the internal diameter of the open channel or the air hole.
• the disrupted or modified area (e.g, compacted, melted, or otherwise changed) of the material surrounding the holes in the can have a diameter larger than the internal diameter of the open channel or air hole.
• the perforations in the stack can be acid etched to create a plurality of through holes that extend through all of the glass sheets comprising the stack, or alternatively the glass sheets can be separated and then the holes can be acid etched in each of the sheets separately.
• this process may result in glass with etched hole diameters of 1-100 microns, for example, 10-75 microns, 10-50 microns, 2-25 microns, 2-20 microns, 2-15 microns, 2-10 microns, and the holes may have, for example, spacing of 25- 1000 microns.
• This process may also be utilized to create holes in sheets of transparent materials other than glass. Since the optical system uses a line focus, it is possible to drill through transparent materials that have large (>1 micron, up to 4mm, for example 10-500 microns) air gaps or other filler materials (e.g. water, transparent polymers, transparent electrodes like indium tin oxide) between the substrate sheets.
• air gaps or other filler materials e.g. water, transparent polymers, transparent electrodes like indium tin oxide
• the ability to continue to drill through multiple glass sheets even when they are separated by a macroscopic (many microns, many tens of microns, or even many hundreds of microns) is to be noted as a particular advantage of this line focus method of drilling.
• the critical power to self-focus in air is ⁇ 20X as much as the critical power required in glass, making such an air gap very problematic.
• the beam will continue to form a high intensity core whether or not the glass material is there, or polymer, or an air gap, or even in the presence of a vacuum.
• the line focus beam will have no trouble continuing to drill the glass layer underneath regardless of the gap in material between it and the glass sheet above.
• the stack of substrate sheets may contain substrates of different glass compositions throughout the stack.
• one stack may contain both substrate sheets of Eagle XG glass and of Coming glass code 2320.
• the stack of transparent substrate sheets may contain non-glass transparent inorganic material such as sapphire.
• the substrates must be substantially transparent to the wavelength of the laser that is used to create the line focus, for example the laser wavelength being situated from 200nm to 2000nm, for example, 1064 nm, 532 nm, 355 nm, or 266 nm.
• the substrate can also be transparent to at least one wavelength in a range from about 390 nm to about 700 nm.
• the substrate can also be transparent to at least one wavelength >1000 nm.
• the substrate can transmit at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of at least one wavelength in a range from about 390 nm to about 700 nm.
• the substrate can transmit at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of at a wavelength of >1000 nm.
• Drilling holes/damage tracks in glass or other transparent materials can be used to create an article comprising a stack of substrates (spaced or in direct contact with one another) with a plurality of holes formed through said stack, where the holes extend through each of the substrates, the holes being, for example, between 1-100 microns in diameter, and, for example, having a spacing of 25-1000 microns. Accordingly, this process can be utilized to create a substantially transparent article comprising a multilayer stack, where the multilayer stack comprises multiple glass layers and at least one layer of polymer situated between the glass layers, or at least two glass layers of different compositions, or at least one glass layer and at least on non-glass inorganic layer.
• the lateral spacing (pitch) between the holes or defect lines/damage tracks is determined by the pulse or burst rate of the laser as the substrate is translated underneath the focused laser beam. Only a single picosecond laser pulse burst is usually necessary to form an entire hole, but multiple bursts may be used if desired.
• the laser can be triggered to fire at longer or shorter intervals. In some embodiments, the laser triggering generally can be synchronized with the stage driven motion of the workpiece beneath the beam, so laser bursts are triggered at a fixed interval, such as every 1 micron, every 5 microns, every 10 microns, or every 20 microns or greater.
• the distance, or periodicity, between adjacent damage tracks can depend upon the desired pattern of through-holes (i.e., the holes formed after the etching process).
• the desired pattern of damage tracks (and the resultant through-holes that are formed therefrom after etching) is an aperiodic pattern of irregular spacing. They need to be at locations where traces will be laid on the interposer or where specific electrical connections on the interposer to the chips are going to be placed. Therefore, a distinction between cutting and damage track drilling for interposers is that the through-holes for interposers is laid out in aperiodic patterns.
• the damage tracks are made at a specific periodic pitch where the pitch depends on the composition of the material being cut.
• the holes or defect lines can have a spacing between adjacent holes/defect lines/damage tracks of about 10 pm or greater, about 20 pm or greater, about 30 pm or greater, about 40 pm or greater, about 50 pm or greater.
• the spacing can be up to about 20 mm.
• the spacing can be from 50 microns to 500 microns or from 10 microns and 50 microns.
• FIG. 10 shows a similar sample, in this case 300 micron thick Corning Eagle XG ® glass, from a top view, with a periodic array of holes.
• the entrance points of the laser beam are clearly seen.
• the pitch or spacing between adjacent holes is 300 microns, and the approximate diameter of the holes is 2 microns, with a rim or modified or raised material around each hole of about 4 microns diameter.
• a variety of laser process parameters were explored to find conditions that produced holes that fully penetrated the material and had minimal micro-cracking of the glass.
• the laser power and lens focal length are particularly important parameters to ensure full penetration of the glass and low micro-cracking.
• FIG. 11 shows a result where significant micro cracking of the glass occurred.
• An example of laser formed blind holes is shown in FIG. 12.
• the damage tracks extend about 75% of the way through the glass. To accomplish this, the focus of the optics is raised up until the line focus only causes damage in the top section of the glass.
• Other blind hole depths may be realized, such as extending only 10% of the way through the glass, only 25%, only 50%, or any fractional value of the glass thickness.
• the laser triggering generally is synchronized with the stage driven motion of the part beneath the beam, and laser pulses are most often triggered at a fixed interval, such as every 1 micron, or every 5 microns.
• the exact spacing is determined by the material properties that facilitate crack propagation from perforated hole to perforated hole, given the stress level in the substrate.
• the holes are generally separated by much greater distance than required for cutting - instead of a pitch of about 10 microns or less, the spacing between holes can be hundreds of microns.
• the exact locations of the holes need not be at regular intervals (i.e., they are aperiodic) - the location simply is determined by when the laser is triggered to fire, and may be at any location within the part.
• the holes made in FIG. 9 are an example of spacing and pattern that are somewhat representative of interposer applications.
• the higher the available laser power the faster the material can be perforated and/or the fast damage tracks can be formed in the material with the above processes.
• process speed is generally not limited directly by laser power, but more by the ability to direct the already abundant laser pulses or bursts to the specific locations at which holes are needed.
• the desired pattern of damage tracks (and the resultant through-holes that are formed therefrom after etching) is an aperiodic pattern of irregular spacing. They need to be at locations where traces will be laid on the interposer or where specific electrical connections on the interposer to the chips are going to be placed.
• interposers a distinction between cutting and damage track drilling for interposers is that the through-holes for interposers is laid out in aperiodic patterns.
• burst mode psec lasers can readily produce laser bursts of -200 microJoules/burst at repetition rates - 100-200kHz. This corresponds to a time average laser power of about 20-40 Watts.
• to drill interposers most often the majority of these bursts will be unused, as even with very fast beam deflection methods the beam can only be placed at the desired hole locations at rates of kHz or possibly tens of kHz.
• a primary challenge for efficient drilling with the above line focus and psec pulsed laser process is how the beam is moved and directed across the substrate surface.
• the glass or beam can then be scanned in a “raster scan” mode where the laser beam travels in the x- direction, scanning across all of the desired hole locations that share common y-axis value. As the beam is scanned, that laser is triggered to fire a burst only at the desired hole locations.
• the substrate or laser beam are moved to a new y-location, the process is repeated for the new set of desired hole locations on this new y-line. This process is then continued until all of the desired holes on the substrate are made.
• Scanning of the glass or beam delivery optics can be combined with rapid beam deflection available from galvanometer mirrors (galvo) and f-theta lenses, or with piezo actuation of optics or the glass or small ranges, or electro-optic beam deflection (EOD) or acousto-optic beam deflection (AOD) , to allow the beam to be rapidly adjusted in a direction orthogonal to the linear “raster” scan direction described above.
• EOD electro-optic beam deflection
• AOD acousto-optic beam deflection
• the fast beam deflector that allow the pulses to be directed to any hole within a certain range of the linear stage (x,y) coordinate at a given time. So instead of being able to direct the laser beam holes to only given locations along a line, the system can now direct the laser beam to any holes within a swath of width dy of the raster scan line. This can greatly increase the number of accessible holes by the laser beam per unit time, and thus greatly increase the number of holes/sec that may be drilled.
• the fast beam deflector may be used not only in a direction perpendicular to the raster scan axis, but also parallel to the scan axis.
• the fast beam deflecting component e.g. galvo, AOD, EOD, piezo
• the fast beam deflecting component can be used to allow for holes within a dy swath that have identical scan axis locations (e.g. the x-axis in the above example) but different y-axis locations to be drilled, since the beam can be “moved” backwards relative to the stage scan to drill a second hole at a given x-location without stopping the linear stage motion.
• fast deflection along the scan axis also allows for more precision in the placement of holes, since it can be used to direct the beam to the desired x-axis location regardless of any small time delays in when the pulsed laser is available to fire a burst, and also compensate for velocity and acceleration artifacts in the linear stage motion.
• the above beam scanning methods may also be combined with beam splitting techniques, where a common laser source has its bursts distributed among multiple beam delivery heads above a single substrate or series of substrates.
• an acousto-optic or electro-optic elements may be used to deflect every N th pulse to a given optical path, and there may be N optical heads used. This may be accomplished by employing the angle-deflection properties of such beam steering elements, or by using the polarization altering properties of such elements to direct the beams through polarization dependent beam splitters.
• the damage tracks can be created at a speed greater than about 50 damage tracks/second, greater than about 100 damage tracks/second, greater than about 500 damage tracks/second, greater than about 1,000 damage tracks/second, greater than about 2,000 damage tracks/second, greater than about 3,000 damage tracks/second, greater than about 4,000 damage tracks/second, greater than about 5,000 damage tracks/second, greater than about 6,000 damage tracks/second, greater than about 7,000 damage tracks/second, greater than about 8,000 damage tracks/second, greater than about 9,000 damage tracks/second, greater than about 10,000 damage tracks/second, greater than about 25,000 damage tracks/second, greater than about 50,000 damage tracks/second, greater than about 75,000 damage tracks/second, or greater than about 100,000 damage tracks/second.
• acid etching changes the holes from a size (for example, about 1 micron) that is too small to practically metalize and use for interposers to more convenient size (for example, 5 microns or higher); 2) etching can take what may start as a non-contiguous hole or simply a damage track through the glass and etch it out to form a continuous though- hole via; 3) etching is a highly parallel process where all of the holes/damage tracks in a part are enlarged at the same time - which is much faster than what would happen if a laser had to re-visit the hole and drill out more material to enlarge it; and 4) etching helps blunt any edges or small checks within the part, increasing the overall strength and reliability of the material.
• FIGS. 52A and 52B illustrate a substrate 1000 after laser drilling and after acid etching, respectively.
• a substrate 1000 can be subjected to any of the laser drilling processes described above to form one or more damage tracks or pilot holes 1002 extending from a first or top surface 1004 to a second or bottom surface 1006.
• Damage track 1002 is illustrated as being a continuous hole for illustration purposes only. As described above, in some embodiments, damage track 1002 is a non-continuous hole wherein particles of the substrate are present in the damage track. As shown in FIG.
• the damage track is enlarged to a create a through- hole via 1008, having a top diameter Dt at a top opening in top surface 1004, a bottom diameter Db at a bottom opening in bottom surface 1006, and a waist diameter Dw.
• the waist refers to the narrowest portion of a hole located between the top and bottom openings. While the profile of through-hole via 1008 is shown as being hourglass shaped due to the waist, this is only exemplary. In some embodiments, the through-hole vias are substantially cylindrical.
• the etching process produces through-hole vias having a diameter greater than 1 micron, greater than about 2 microns, greater than about 3 microns, greater than about 4 microns, greater than about 5 microns, greater than about 10 microns, greater than about 15 microns, or greater than about 20 microns.
• the acid used was 10% HF / 15% HNO3 by volume.
• the parts were etched for 53 minutes at a temperature of 24-25 °C to remove about 100 microns of material.
• the parts were immersed in this acid bath, and ultrasonic agitation at a combination of 40 kHz and 80 kHz frequencies was used to facilitate penetration of fluid and fluid exchange in the holes/damage tracks.
• manual agitation e.g. mechanical agitation
• of the part within the ultrasonic field was made to prevent standing wave patterns from the ultrasonic field from creating “hot spots” or cavitation related damage on the part, and also to provide macroscopic fluid flow across the part.
• the acid composition and etch rate was intentionally designed to slowly etch the part - a material removal rate of only 1.9 microns/minute.
• An etch rate of less than, for example, about 2 microns/minute allows acid to fully penetrate the narrow holes/damage tracks and agitation to exchange fresh fluid and remove dissolved material from the holes/damage tracks which are initially very narrow. This allows the holes to expand during the etch at nearly the same rate throughout the thickness of the substrate (i.e. throughout the length of the hole or damage track).
• the etch rate can be a rate of less than about 10 microns/min, such as a rate of less than about 5 microns/min, or a rate of less than about 2 microns/min.
• FIGS. 13A and 13B show top and bottom views of a resulting part.
• the holes are about 95 microns in diameter, and are very circular, indicating that there was very little micro cracking of the material.
• the holes are at 300 micron pitch, and each hole is approximately 90-95 microns in diameter.
• the images in FIGS. 13A and 13B were taken with a back light, and the bright regions within each hole also indicate that the holes have been fully opened by the acid etching. The same samples were then diced, to look more closely at the interior profiles of the holes.
• FIGS. 15 and 16 show the results.
• the holes have an “hourglass” shape, i.e., they taper down toward the middle of the hole. Typically this shape is determined by the etching environment, rather than the pilot hole formation process.
• the bright areas are the glass; the dark areas are the holes.
• the top (laser incidence) diameter of the holes is about 89 micron diameter, the waist is about 71 microns, and the bottom
• FIG. 14 shows results of etching a sample that had significant micro cracking from the laser process - the holes etch out into elongated shapes instead of circular features.
• Micro-cracking can be reduced by lowering the laser burst energy, increasing the number of pulses per burst, or by increasing the length of the line focus, for example by using a longer focal length objective lens. These changes can lower the energy density contained within the substrate.
• care must be made to ensure optimal alignment of the optical system such that aberrations are not introduced to the line focus so that azimuthal asymmetries are created in the line focus. Such asymmetries can introduce high energy density locations within the substrate that can lead to microcracks.
• FIGS. 17A- 17C The results are shown as histograms in FIGS. 17A- 17C.
• the top and bottom diameters are both about 95 microns, very close in size, and the standard deviation of about 2.5 microns.
• the waists are about 70 microns, with a standard deviation of about 3 microns. Thus, the waists are about 30% narrower than the top and bottom diameters.
• Circularity is defined as the maximum diameter of the hole minus the minimum diameter of the same hole, and is given in units of microns.
• the distributions indicate that the holes are generally circular to less than about 5 microns. There are no significant tails to the distributions that would indicate micro-cracks or chips that have etched out to create non-round shapes.
• the acid etching conditions can be modified to adjust various attributes of the through-holes to make them useful as via through-holes for an interposer.
• the through-holes can have a top opening, a bottom opening, and a waist, and the ratio of the diameter of the waist to the diameter of the top or bottom opening can be controlled.
• the waist refers to the narrowest portion of a hole located between the top and bottom openings. Two factors that control the diameter of the waist, top opening, and bottom opening is the etching reaction rate and the diffusion rate.
• the acid In order to etch away material throughout the thickness of the substrate to enlarge the damage tracks into via through-holes, the acid needs to travel the entire length of the damage track. If the etching rate is too fast so that the acid does not have time to adequately diffuse and reach all portions of the damage track, then the acid will disproportionately etch more material away at the surface of the material than in the middle of the material.
• Manipulation of the Thiele modulus (cp) of an etching process as described in Thiele, E.W. Relation between catalytic activity and size of particle, Industrial and Engineering Chemistry, 31 (1939), pp. 916-920, can be utilized to control the ratio of the waist diameter to the diameter of the top or bottom opening.
• the Thiele modulus is a ratio of the diffusion time to the etching reaction time and is represented by the following equation:
• k r is the reaction rate constant for etching
• C is the bulk acid concentration
• g is a factor based on the kinetic reaction order
• r is the radius of the hole during the reaction
• D eff is the effective diffusivity of the acid through water down in the damage track or hole, which is an augmented natural diffusivity D enhanced by agitation and sonication
• L is 1 ⁇ 2 the thickness of the material.
• the Thiele modulus when the etching reaction time is greater than the diffusion time, the Thiele modulus will be greater than 1. This means that the acid will be depleted before it travels the entire length of the damage track or hole and can be replenished by diffusion in the center of the damage track or hole. As a result, etching will proceed faster at the top and bottom of the tracks or holes at a rate governed by k r and etching at the center will occur more slowly at a rate governed by diffusion leading to an hourglass-like shape for the via hole. However, if the diffusion time is equal to or greater than the etching reaction time, then the Thiele modulus will be less than or equal to 1. Under such conditions, the acid concentration will be uniform along the entire damage track or hole and the damage track or hole will be etched uniformly, yielding a substantially cylindrical via hole.
• the diffusion time and etching reaction time can be controlled to control the Thiele modulus of the etching system, and thereby the ratio of the waist diameter to the diameters of the top and bottom openings.
• FIG. 53 illustrates the relationship between the Thiele modulus of the etching system and an expected percentage of the waist diameter with respect to the diameter of the top and bottom openings.
• the Thiele modulus for the etching process can be less than or equal to about 5, less than or equal to about 4.5, less than or equal to about 4, less than or equal to about 3.5, less than or equal to about 3, less than or equal to about 2.5, less than or equal to about 2, less than or equal to about 1.5, or less than or equal to about 1.
• the diameter of the waist of the via hole is 50% to 100%, 50% to 95%, 50% to 90%, 50% to 85%, 50% to 80%, 50% to 75%, 50% to 70%, 55% to 100%, 55% to 95%, 55% to 90%, 55% to 85%, 55% to 80%, 55% to 75%, 55% to 70%, 60% to 100%, 60% to 95%, 60% to 60%, 60% to 85%, 60% to 80%, 60% to 75%, 60% to 70%, 65% to 100%, 65% to 95%, 65% to 90%, 65% to 85%, 65% to 80%, 65% to 75%, 65% to 70%, 70% to 100%, 70% to 95%, 70% to 90%, 70% to 85%, 70% to 80%, 70% to 75%, 75% to 100%, 75% to 95%, 75% to 90%, 75% to 85%, 75% to 80%, 80% to 100%, 80% to 95%, 80% to 90%, 80% to 85%, 70% to 80%, 70% to 75%, 75% to 100%, 75% to 95%, 75% to
• the diameter of the waist of the via hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of the diameter of the top and/or bottom opening of the via hole.
• the diameter of the waist of the via hole is 50% to 100%, 50% to 95%, 50% to 90%, 50% to 85%, 50% to 80%, 50% to 75%, 50% to 70%, 55% to 100%, 55% to 95%, 55% to 90%, 55% to 85%, 55% to 80%, 55% to 75%, 55% to 70%, 60% to 100%, 60% to 95%, 60% to 60%, 60% to 85%, 60% to 80%, 60% to 75%, 60% to 70%, 65% to 100%, 65% to 95%, 65% to 90%, 65% to 85%, 65% to 80%, 65% to 75%, 65% to 70%, 70% to 100%, 70% to 95%, 70% to 90%, 70% to 85%, 70% to 80%, 70% to 75%, 75% to 100%, 75% to 95%, 75% to 90%, 75% to 85%, 75% to 80%, 80% to 100%, 80% to 95%, 80% to 90%, 80% to 85%, 70% to 80%, 70% to 75%, 75% to 100%, 75% to 95%, 75% to
• the diameter of the waist of the via hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of average of the diameter of the top and bottom opening of the via hole.
• FIG. 54 illustrates how the Thiele modulus decreases with the initial radius of the damage track.
• FIG. 55 illustrates how the Thiele modulus increases with the half- thickness of the substrate.
• the thickness of the substrate and radius of the damage tracks are factors that in some instances cannot be changed if a certain thickness or radius of the damage track is needed. Thus other factors affecting the Thiele modulus can be adjusted in such instances.
• FIG. 56 illustrates how the Thiele modulus decreases as the effective diffusivity (D eff ) increases.
• the effective diffusivity can be increased by adding agitation and/or sonication to the etching conditions as described in more detail below.
• FIG. 57 illustrates how the Thiele modulus decreases as the acid concentration decreases, in this example the HF concentration.
• FIG. 57 also illustrates how a combination of increasing the effective diffusivity and decreasing the acid concentration decreases the Thiele modulus.
• the etching reaction time can be controlled by adjusting the acid concentration in the etching solution.
• the etching solution can be an aqueous solution including deionized water, a primary acid, and a secondary acid.
• the primary acid can be hydrofluoric acid and the secondary acid can be nitric acid, hydrochloric acid, or sulfuric acid.
• the etching solution can only include a primary acid.
• the etching solution can include a primary acid other than hydrofluoric acid and/or a second acid other than nitric acid, hydrochloric acid, or sulfuric acid.
• Exemplary etching solutions can include 10% by volume hydrofluoric acid/15% by volume nitric acid or 5% by volume hydrofluoric acid/7.5% by volume nitric acid, or 2.5% by volume hydrofluoric acid/3.75% by volume nitric acid.
• orientation of the substrate in the etching tank, mechanical agitation, and/or the addition of surfactant to the etching solution are other etching conditions that can be modified to adjust the attributes of the via holes.
• the etching solution is ultrasonically agitated and the substrate is oriented in the etching tank holding the etching solution so that the top and bottom openings of the damage tracks receive substantially uniform exposure to the ultrasonic waves in order for the damage tracks to be etched uniformly.
• the substrate can be oriented in the etching tank so that the surfaces of the substrate with the damage tracks are perpendicular to the bottom of the etching tank rather than parallel to the bottom of the etching tank.
• the etching tank can be mechanically agitated in the x, y, and z directions to improve uniform etching of the damage tracks.
• the mechanical agitation in the x, y, and z directions can be continuous.
• a surfactant can be added to the etching solution to increase the wettability of the damage tracks.
• the increased wettability lowers the diffusion time and can allow for increasing the ratio of the diameter of the via hole waist to the diameter of the via hole top and bottom openings.
• the surfactant can be any suitable surfactant that dissolves into the etching solution and that does not react with the acid(s) in the etching solution.
• the surfactant can be a fluorosurfactant such as Capstone® FS-50 or Capstone® FS-54.
• the concentration of the surfactant in terms of ml of surfactant/L of etching solution can be about 1, about 1.1, about 1.2, about 1.3, about 1.4, about 1.5, about 1.6, about 1.7, about 1.8, about 1.9, about 2 or greater.
• the hole formation rate was well in excess of 300 holes/sec. If the pattern was made larger in physical extent, so the stage would need to accelerate less often, the average hole formation rate would be faster.
• the laser used here can easily provide 100,000 pulses/sec at full pulse energy, it is possible to form holes at this rate.
• the limitation for hole formation rate is how fast the laser beam can be moved relative to the substrate. If the holes are spaced 10 microns apart, and the stage speed is 1 m/sec, then 100,000 holes/sec are formed. In fact, this is how cutting of substrates is often done. But for practical interposers the holes are often spaced by hundreds of microns, and at more random intervals (i.e., there is an aperiodic pattern). Hence the numbers stated above for the pattern shown are only about 300 holes/sec.
• the stage speed can be increased, for example, from 200 mm/sec to 1 m/sec, realizing another 5X increase in speed.
• the average hole pitch was less than 300 microns, the hole formation rate would increase commensurately.
• the damage tracks can be created at a speed greater than about 50 damage tracks/second, greater than about 100 damage tracks/second, greater than about 500 damage tracks/second, greater than about 1,000 damage tracks/second, greater than about 2,000 damage tracks/second, greater than about 3,000 damage tracks/second, greater than about 4,000 damage tracks/second, greater than about 5,000 damage tracks/second, greater than about 6,000 damage tracks/second, greater than about 7,000 damage tracks/second, greater than about 8,000 damage tracks/second, greater than about 9,000 damage tracks/second, greater than about 10,000 damage tracks/second, greater than about 25,000 damage tracks/second, greater than about 50,000 damage tracks/second, greater than about 75,000 damage tracks/second, or greater than about 100,000 damage tracks/second.
• subjecting a substrate to the above processes of damage track formation and acid etching can result in a substrate with a plurality of through-hole vias.
• the vias can have a diameter of about 30 microns or less, about 25 microns or less, about 20 microns or less, about 15 microns or less, about 10 microns or less, in a range from about 5 to about 10 microns, about 5 to about 15 microns, about 5 to about 20 microns, about 5 to about 25 microns, about 5 to about 30 microns, or up to many tens of microns depending upon requirements for the intended use.
• the vias can have a diameter of greater than about 20 pm.
• the substrate can have vias with varying diameter, for example the vias can have a difference of at least 5 pm in diameter.
• a difference in the diameter of the top opening and the bottom opening of the vias can be 3pm or less, 2.5 pm or less, 2 pm or less, 1.5 pm or less or 1 pm or less, which can be enabled by the use of a line focus beam to create damage tracks in the material. These damage tracks maintain a very small diameter over the entire depth of the substrate, which is what ultimately yields uniform top and bottom diameters after etching.
• the spacing (center to center distance) between adjacent the vias can be about 10 pm or greater, about 20 pm or greater, about 30 pm or greater, about 40 pm or greater, about 50 pm or greater.
• the spacing of adjacent vias can be up to about 20 mm.
• the density of the vias can about 0.01 vias/mm 2 or greater, about 0.1 vias/mm 2 or greater, about 1 via/mm 2 or greater, about 5 vias/mm 2 or greater, about 10 vias/mm 2 or greater, about 20 vias/mm 2 or greater, about 30 vias/mm 2 or greater, about 40 vias/mm 2 or greater, about 50 vias/mm 2 or greater, about 75 vias/mm 2 or greater, about 100 vias/mm 2 or greater, about 150 vias/mm 2 or greater, about 200 vias/mm 2 or greater, about 250 vias/mm 2 or greater, about 300 vias/mm 2 or greater, about 350 vias/mm 2 or greater, about 400 vias/mm 2 or greater, about 450 vias/mm 2 or greater, about 500 vias/mm 2 or greater, about 550 vias/mm 2 or greater, about 600 vias/mm 2 or greater, or about 650 vias/mm 2 or
• the diameter of the waist of the via hole is 50% to 100%, 50% to 95%, 50% to 90%, 50% to 85%, 50% to 80%, 50% to 75%, 50% to 70%, 55% to 100%, 55% to 95%, 55% to 90%, 55% to 85%, 55% to 80%, 55% to 75%, 55% to 70%, 60% to 100%, 60% to 95%, 60% to 60%, 60% to 85%, 60% to 80%, 60% to 75%, 60% to 70%, 65% to 100%, 65% to 95%, 65% to 90%, 65% to 85%, 65% to 80%, 65% to 75%, 65% to 70%, 70% to 100%, 70% to 95%, 70% to 90%, 70% to 85%, 70% to 80%, 70% to 75%, 75% to 100%, 75% to 95%, 75% to 90%, 75% to 85%, 75% to 80%, 80% to 100%, 80% to 95%, 80% to 100%, 80% to 95%, 80% to 90%, 80% to 85%, 85% to 100%, 85% to 95%, 80%
• the diameter of the waist of the via hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of the diameter of the top and/or bottom opening of the via hole.
• the diameter of the waist of the via hole is 50% to 100%, 50% to 95%, 50% to 90%, 50% to 85%, 50% to 80%, 50% to 75%, 50% to 70%, 55% to 100%, 55% to 95%, 55% to 90%, 55% to 85%, 55% to 80%, 55% to 75%, 55% to 70%, 60% to 100%, 60% to 95%, 60% to 60%, 60% to 85%, 60% to 80%, 60% to 75%, 60% to 70%, 65% to 100%, 65% to 95%, 65% to 90%, 65% to 85%, 65% to 80%, 65% to 75%, 65% to 70%, 70% to 100%, 70% to 95%, 70% to 90%, 70% to 85%, 70% to 80%, 70% to 75%, 75% to 100%, 75% to 95%, 75% to 90%, 75% to 85%, 75% to 80%, 80% to 100%, 80% to 95%, 80% to 90%, 80% to 85%, 70% to 80%, 70% to 75%, 75% to 100%, 75% to 95%, 75% to
• the diameter of the waist of the via hole is about 50% or greater, about 55% or greater, about 60% or greater, about 65% or greater, about 70% or greater, about 75% or greater, about 80% or greater, about 85% or greater, about 90% or greater, about 95% or greater, or about 100% of the average diameter of the top and bottom opening of the via hole.
• an aspect ratio (substrate thickness:via diameter) of the via holes can be about 1 : 1 or greater, about 2: 1 or greater, about 3 : 1 or greater, about 4: 1 or greater, about 5: 1 or greater, about 6: 1 or greater, about 7: 1 or greater, about 8: 1 or greater, about 9: 1 or greater, about 10: 1 or greater, about 11:1 or greater, about 12: 1 or greater, about 13:1 or greater, about 14:1 or greater, about 15:1 or greater, about 16:1 or greater, about 17:1 or greater, about 18:1 or greater, about 19: 1 or greater, about 20: 1 or greater, about 25: 1 or greater, about 30:1 or greater, or about 35: 1 or greater.
• the aspect ratio of the via holes can be in a range from about 5:1 to about 10:1, about 5:1 to 20:1, about 5:1 to 30:1, or about 10:1 to 20:1 about 10:1 to 30:1.
• the substrate has a thickness in a range from about 20 pm to about 3 mm, from about 20 mih to about 1 mm, or from about 50 mih to 300 mih, or from 100 mih to 750 mih, or from about 1 mm to about 3 mm.
• the substrate can be made of a transparent material, including, but not limited to, glass, fused silica, synthetic quartz, a glass ceramic, ceramic, and a crystalline material such as sapphire.
• the substrate can be glass and the glass can include alkali containing glass, alkali-free glass (for example an alkali-free alkaline aluminoborosilicate glass), or laminated glass pieces with layers containing different glass compositions.
• the glass can be chemically strengthened (e.g. ion exchanged) glass.
• the substrate can be transparent to at least one wavelength in a range from about 390 nm to about 700 nm.
• the substrate can transmit at least 70%, at least 75%, at least 80%, at least 85%, or at least 90% of at least one wavelength in a range from about 390 nm to about 700 nm.
• the through-hole vias can then be coated and/or filled with a conductive material and used for electrical interposer applications.
• the coating and/or filling can be done by metallization.
• Metallization can be done, for example, by vacuum deposition, electroless plating, filling with conductive paste, or a variety of other methods.
• electrical traces may be patterned on the surfaces of the parts, and a series of re-distribution layers and contact pads may be built up that allow routing of electrical signals from the holes to connections on microchips or other electrical circuitry.
• the parts can also be functionalized with coatings that allow control of the hydrophilic or hydrophobic nature of the surface.
• Other coatings can also be applied, that allow attachment of antibodies, proteins, or other biomolecules.
• substrates with very dense and regular arrays of holes are particularly useful - for example hexagonally close- packed patterns of holes at pitches of less than about 100 micron.
• the speed possible with the aforementioned laser process is particularly high, as the laser can be fired extremely often and effectively use the full repetition rate of the laser.
• hole formation rates in excess of 10,000 holes/sec may be achieved (1 m/sec stage speed with 100 micron spacing of holes).
• the hole forming may only utilize a small fraction of the laser pulses.
• the laser burst repetition rate can easily be hundreds of kHz, while it can be difficult to direct the beam to new hole locations at rates great enough to use all of these bursts.
• the actual hole forming rate may be 100 holes/sec, 500 holes/sec, 999 holes/sec, 3,000 holes/sec, 5,000 holes/sec, 10,000 holes/sec, while the laser repetition rate at the same time may be 100,000 bursts/sec, 200,000 bursts/sec. In these cases most of the burst pulse is redirected by a device such as an electro-optic modulator to enter a beam dump, rather than being directed out of the laser and to the substrate.
• Test samples of Coming Eagle XG® glass were prepared for making through holes in the samples, shown in FIGS. 19B and 19C. Small radial cracks inside the glass, about 10 microns in extent, were observed, as shown in FIG. 19 A, in all samples despite varying the burst energy and number of pulses per burst of the picosecond laser, and varying the pitch from 50 microns to 300 microns.
• FIGS. 25A-25C for the first sample
• the top shown in FIG. 24A for the first sample and FIG. 26A for the second sample
• bottom shown in FIG. 24B for the first sample and FIG. 26B for the second sample
• the waists shown in FIG. 24C for the first sample and FIG. 26C for the second sample
• FIGS. 29A-29C for 50 microns holes at 100% laser power, the waists on 30 microns holes appear narrowed (FIG. 28B), while the waists on 50 micron holes (FIG. 29B) are wide open.
• FIGS. 30A-30C for 75 microns holes and in FIGS. 31 A-31C for 100 micron holes at 100% laser power the waists (FIGS. 30B and 3 IB) on both sizes are wide open.
• FIGS. 32A-32C for 30 microns holes and in FIGS. 33 A-33C for 50 microns holes at 85% laser power the waists on 30 micron holes appear narrowed (FIG. 32B), while the waists on 50 micron holes (FIG. 33B) are very open.
• FIGS. 34A-34C for 75 micron holes and in FIGS. 35A-35C for 100 micron holes, at 85% laser power the waists (FIGS. 34B and 35B) on both sizes are wide open.
• FIGS. 36A-36C for 30 microns holes and in FIGS. 37A-37C for 50 micron holes, at 75% laser power the waists on 30 micron holes appear narrowed (FIG. 36B), while the waists on 50 micron holes (FIG. 37B) are wide open.
• FIGS. 38A-38C for 75 micron holes and in FIGS. 39A-39C for 100 micron holes, at 75% laser power the waists (FIGS.
• FIGS. 40A-40C for 30 micron holes and in FIGS. 41 A- 41C for 50 micron holes, at 65% laser power the holes are not fully formed inside the glass after etch, with the worst results on 30 micron holes (FIG. 41B), although even the 50 micron holes (FIG. 41 A) appear to have some lack of opening or clogging.
• FIGS. 42 A- 42C for 75 micron holes and in FIGS. 43A-43C for 100 micron holes, at 65% laser power there is evidence of poor opening and clogging from top (FIGS. 42A and 43 A) and bottom (FIGS. 42C and 43 C) views.
• FIGS. 47A and 47C even the 100 micron holes show evidence of lack of open waists or clogging in the top and bottom views, respectively.
• FIG. 48 illustrates a focal line 432 extending through three stacked, 150 micron Eagle XG® glass sheets 430. With the focal line 432 extending through all three stacked sheets, a full perforation or full defect line can be formed through all three layers simultaneously. To create a full perforation through a stack, the focal line length needs to be longer than the stack height. Once the parts are drilled, they can be separated and then etched, which allows for easier access of the aid into the holes of each sheet.
• a significant advantage of this line focus method for drilling is that the process is no sensitive to air gaps between the parts, unlike processes that rely upon self-focusing of the laser beam. For example, a focused Gaussian beam will diverge upon entering the first glass layer and will not drill to large depths, or if self-focusing occurs due to reflection along the side of the hole or waveguiding as the as the glass is drilled, the beam will emerge from the first glass layer and diffract and will not drill into the second glass layer.
• FIG. 49 shows an image of two sheets of 300 micron thick EXG glass that have been drilled with such a method.
• FIG. 50 shows the same parts after acid etch.
• the holes appear to be 150 microns in diameter from a side profile, but are actually about 70 microns in diameter, and only appear to be large form a side perspective because there are multiple rows of holes extending away from the focal plane of the camera, and each row is slightly offset laterally, giving the illusion of a large open hole than there actually is.
• the top view of the holes shows the diameter of the holes are indeed approximately 70 microns, and the light coming through the center of each hole indicates they are open through holes.
• a 150pm thick Coming Eagle XG® glass part having damage tracks was vertically placed in an acid etch bath having 5% HF / 7.5% HN03 by volume.
• the part was etched for 810 seconds at a temperature of 26 °C to remove about 13 microns of material at a rate of about 1 micron/min.
• Ultrasonic agitation at a combination of 40 kHz and 80 kHz frequencies was used to facilitate penetration of fluid and fluid exchange in the holes.
• continuous movement of the part in the x, y, and z directions within the ultrasonic field was made to prevent standing wave patterns from the ultrasonic field from creating “hot spots” or cavitation related damage on the part, and also to provide macroscopic fluid flow across the part.
• FIG. 58 is a post-acid etch photograph of a side view of the glass part.
• FIG. 59A illustrates a schematic drawing of laser damaged glass with pre-etching thickness Hi, while FIG.
• FIGS. 59A and 59B illustrates a schematic drawing of via shape after etching.
• Di is top diameter of the via
• D w is the waist diameter of the via
• the final thickness is 3 ⁇ 4.
• a via opening may be generated (see FIGS. 59A and 59B).
• the ratio of the waist opening to the top opening (D w /Di) may be selectively tuned from 17% (FIG. 60 A; taper-shaped) to 80% (FIG. 60B; cylindrical-shape) for the glass compositions disclosed herein (e.g., as in Table 1 below).
• 61A and 61B illustrates a comparison between the glasses of the present application (e.g., 7607 glass: 67.2% S1O2, 6.5% AI2O3, 20.1% B2O3, 0.89% Na 2 0, 0.4% MgO, 4.9% CaO, in mol%) and Corning Eagle® glass (EXG) after exposure to various acid etchants corresponding to their respective mean %openings (FIG. 61A) and waist standard deviation (FIG. 61B). From FIG. 61A, 7607 samples consistently has a higher % opening than EXG glass, regardless of etchant and from FIG. 6 IB, the standard deviation of the waist size for the 7607 glass is lower or roughly equivalent to the EXG glass in most etchants.
• EXG Corning Eagle® glass
• ultra-fast burst mode laser generates a damage trace along the vertical direction of a flat sheet of glass.
• the glass material along the damage trace either only shows refractive index (RI) change or shows RI change with very small bubbles (range in 50 nm to 1 um), or RI change with small cracks.
• the feature of the damage track can be tuned by laser parameters, such as laser wavelength, power level, pulse duration, number of laser pulse for each burst, and energy level of each pulse, etc.
• the laser damaged area usually etches faster than the undamaged area. Therefore, this process can generate a via through the glass thickness.
• the aspect ratio of via is a key parameter that influences the downstream step of via metallization and performance of the final product.
• Non-limiting examples of amounts of oxides for forming the embodied compositions are listed in Table 1, along with the properties of the resulting compositions.
• the composition comprises a combination of S1O 2 and alkaline earth oxides (MO, or the sum of BeO, MgO, CaO, SrO, BaO).
• the composition further comprises AI 2 O 3.
• the composition further comprises B 2 O 3.
• the composition further comprises Sn0 2 .
• the composition may further comprise P 2 O 5.
• the composition may comprise, in mol%: 40-80 S1O 2 and >0-25 MO.
• the composition further comprises, in mol%, >0-15 AI 2 O 3.
• the composition may further comprise, in mol%, >0- 15 B2O3.
• the composition may further comprise, in mol%, >0-5 Sn0 2.
• the composition may further comprise, in mol%, >0-5 P 2 0 5.
• the compositions disclosed herein are particularly suitable as thin glass substrates with precision- formed holes for electronics applications.
• Silicon dioxide which serves as the primary composition-forming oxide component of the embodiments, influences the mechanical strength, biocompatibility and degradation properties (e.g., temperature stability, chemical durability, etc.) of the glass compositions.
• Si0 2 functions to stabilize the networking structure of glass and glass-ceramics.
• the composition can comprise 40-80 mol% Si0 2.
• the composition can comprise 50-70 mol% Si0 2.
• the composition can comprise 40-80 mol%, or 40-60 mol%, or 45-65 mol%, or 50-70 mol%, or 55-75 mol%, or 60-80 mol% Si0 2 , or any value or range disclosed therein.
• the glass is essentially free of Si0 2 or comprises
• Divalent cation oxides are important for improvement of (1) melting behavior of the composition and (2) influencing the composition’s Young’s modulus and coefficient of thermal expansion.
• the composition can comprise, in mol%, >0-25 alkaline earth oxides (MO, or the sum of BeO, MgO, CaO, SrO, BaO).
• the composition can comprise, in mol%, 5-20 MO.
• the composition can comprise, in mol%, >0-25, or >0-20, or 2-20, or 2-15, or 5-15, or 5-10, or 10-25, or 10-20, or >0-15, or >0-10 MO, or any value or range disclosed therein.
• the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25 MO, or any value or range having endpoints disclosed herein.
• the composition can comprise, in mol%, >0-10 CaO. In some examples, the composition can comprise, in mol%, >0-7 CaO. In some examples, the composition can comprise, in mol%, >0-10, or >0-9, or 1-9, or 1-8, or 2-8, or 2-7, or 3-7, or >0-5, or >0-4 CaO, or any value or range disclosed therein. In some examples, the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 CaO, or any value or range having endpoints disclosed herein. In some examples, the composition can comprise, in mol%, >0-10 MgO. In some examples, the composition can comprise, in mol%, >0-7 MgO.
• the composition can comprise, in mol%, >0-10, or >0-9, or 1-9, or 1-8, or 2-8, or 2-7, or 3-7, or >0-5, or >0-4 MgO, or any value or range disclosed therein.
• the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 MgO, or any value or range having endpoints disclosed herein.
• the composition can comprise, in mol%, >0-10 SrO.
• the composition can comprise, in mol%, >0-6 SrO.
• the composition can comprise, in mol%, >0-10, or >0-9, or 1-9, or 1-8, or 2-8, or 2-7, or 3-7, or >0-5, or >0-4 SrO, or any value or range disclosed therein.
• the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 SrO, or any value or range having endpoints disclosed herein.
• the composition can comprise, in mol%, >0-15 BaO.
• the composition can comprise, in mol%, >0-11 BaO.
• the composition can comprise, in mol%, >0-15, or >0- 12, or 1-12, or 1-9, or 3-9, or >0-7, or 2-7, or 5-12 BaO, or any value or range disclosed therein. In some examples, the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5, 6, 7, 8,
• the composition further comprises network former alumina (AI2O3), which provides stabilization to the networking structure, as well as contributing to improved mechanical properties and chemical durability in silicate glasses while having no toxicity concerns. Additionally, alumina also helps lower liquidus temperature and coefficient of thermal expansion, or, enhance the strain point.
• AI2O3 network former alumina
• the composition can comprise, in mol%, >0-15 AI2O3. In some examples, the composition can comprise, in mol%, >0-13, or 1-13, or 1-12, or 2-12, or 2-11, or 3-11, or 3-10, or 4-10, or 4-9 AI2O3, or any value or range disclosed therein. In some examples, the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 AI2O3, or any value or range having endpoints disclosed herein.
• the composition further comprises network former boron oxide (B2O3), which is beneficial for glass melting, if present at low concentrations.
• B2O3 network former boron oxide
• the composition can comprise, in mol%, >0-15 B2O3.
• the composition can comprise, in mol%, 5-15 B2O3.
• the composition can comprise, in mol%, >0-15, or 2-15, or 2-14, or 3-14, or 3-13, or 5-13, or 5-10, or 10-15, or 7- 13 B2O3, or any value or range disclosed therein.
• the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15 B2O3, or any value or range having endpoints disclosed herein.
• the composition can comprise, in mol%, >0-5 SnCb. In some examples, the composition can comprise, in mol%, >0-1 SnCh. In some examples, the composition can comprise, in mol%, >0-5, or >0-4, or >0-3, or >0-2, or >0-1 SnCh, or any value or range disclosed therein. In some examples, the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5 SnC>2, or any value or range having endpoints disclosed herein.
• the composition further comprises network former phosphorus pentoxide (P2O5), which serves as a nucleating agent for bulk nucleation in glass compositions disclosed herein. Additionally, P2O5 increases glass viscosity, which expands the glass’s range of operating temperatures and is advantageous to its manufacture and formation. If P2O5 concentration is too low, the glass will not crystallize. If P2O5 concentration is too high, devitrification (occurring during cooling of the glass) can be difficult to control.
• the composition can comprise, in mol%, >0-5 P2O5. In some examples, the composition can comprise, in mol%, >0-5, or >0-4, or 1-4, or 1-3 P2O5, or any value or range disclosed therein. In some examples, the composition can comprise, in mol%, >0, 1, 2, 3, 4, 5 P2O5, or any value or range having endpoints disclosed herein.
• compositions can comprise one or more compounds useful as ultraviolet radiation absorbers.
• the composition can comprise 3 mol% or less ZnO, T1O 2 , CeO, MnO, Nb 2 0s, M0O3, Ta205, WO3, SnCh, Fe2C> 3 , AS2O 3 , St ⁇ Cb, Cl, Br, or combinations thereof.
• the composition can comprise, in mol%, 0-3, or 0-2, or 0-1, or 0-0.5, or 0-0.1, or 0- 0.05, or 0-0.01 ZnO, TiCb, CeO, MnO, Nb2C , M0O 3 , Ta2C , WO 3 , Sn02, Fe20 3 , AS2O 3 , Sb 2 0 3 , Cl, Br, or combinations thereof.
• the compositions can also include various contaminants associated with batch materials and/or introduced into the composition by the melting, fining, and/or forming equipment used to produce the composition.
• the glass can comprise, in mol%, 0-3, or 0- 2, or 0-1, or 0-0.5, or 0-0.1, or 0-0.05, or 0-0.01 SnCb, Fe 2 Cb, or combinations thereof.
• Etch conditions used to create these vias were taken from the standard Radio Frequency (RF) style TGV process, which calls for 100 pm top diameter vias which is closely a 1 : 1 ratio with the amount of etch removal required.
• the solution etches parts isotropically at the bulk surface 50 pm each side, however the damage track region has a faster, more preferential etch rate.
• Eagle XG® Eagle XG
• this preferential etch rate has been measured at 9: 1 of the bulk etch rate.
• the etch rate of the via and the bulk should be the same. EXG is used as the benchmark for comparing the final via shape.
• This process uses a 5 vol.% (1.45M) hydrofluoric acid (HF) solution held at 8°C.
• HF reacts with boron in the glass to form a gel layer, which cover the surface of glass and slows down the etching process significantly.
• 5 vol% (1.45M) HF and 5 vol% (0.8M) HNO3 was conducted at higher temperatures (20°C).
• wider open vias may be created by adding 1 wt.% of poly diallyldimethylammonium chloride (PDADMAC) in the etchant.
• PDADMAC poly diallyldimethylammonium chloride
• PDADMAC molecules can easily self-assemble and align on flat surfaces but may lack access to the laser damaged areas. Therefore, etch rates on glass surfaces may slow while etch rates around laser damaged areas proceed without being affected by PDADMAC.
• EXG, glass 1, 3, and 4 all indicate that adding PDADMAC causes wider via waists.
• FIGS. 62Ai-62Jii illustrate a comparison between glasses having compositions of Table 1 and Corning Eagle® (EXG) glass after exposure to laser and acid etch processing. Results for % opening are summarized in Tables 3 and 4.
• TGV glass substrates formed with the disclosed glass compositions may (1) be formed with more cylindrical via shape in comparison with traditional glasses and (2) have a tunable via diameter (i.e., and thereby, aspect ratios) with varied etchants.
• the term “and/or,” when used in a list of two or more items, means that any one of the listed items can be employed by itself, or any combination of two or more of the listed items can be employed.
• the composition can contain A alone; B alone; C alone; A and B in combination; A and C in combination; B and C in combination; or A, B, and C in combination.
• references herein to the positions of elements are merely used to describe the orientation of various elements in the FIGURES. It should be noted that the orientation of various elements may differ according to other exemplary embodiments, and that such variations are intended to be encompassed by the present disclosure. Moreover, these relational terms are used solely to distinguish one entity or action from another entity or action, without necessarily requiring or implying any actual such relationship or order between such entities or actions.
• the terms “about,” “approximately,” and the like mean that amounts, sizes, formulations, parameters, and other quantities and characteristics are not and need not be exact, but may be approximate and/or larger or smaller, as desired, reflecting tolerances, conversion factors, rounding off, measurement error and the like, and other factors known to those of skill in the art.
• composition that is “free” or “essentially free” of a component is one in which that component is not actively added or batched into the glass, but may be present in very small amounts as a contaminant (e.g., 500, 400, 300, 200, or 100 parts per million (ppm) or less).
• a contaminant e.g., 500, 400, 300, 200, or 100 parts per million (ppm) or less.
• compositions are expressed in terms of as-batched mole percent (mol%).
• melt constituents e.g., silicon, alkali- or alkaline-based, boron, etc.
• levels of volatilization e.g., as a function of vapor pressure, melt time and/or melt temperature
• the as-batched mole percent values used in relation to such constituents are intended to encompass values within ⁇ 0.5 mol% of these constituents in final, as-melted articles.
• substantial compositional equivalence between glass-ceramic compositions and as-batched glass compositions is expected.
• substantial compositional equivalence is expected between the glass and glass-ceramic after optional heat treatment steps.

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• 2021
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