A method for processing a sapphire glass micro-via based on a laser-induced etching process

Abstract

The application relates to a sapphire glass micro-via processing method based on a laser-induced etching process, and belongs to the technical field of glass via processing. A homemade femtosecond laser is precisely induced to modify and a coaxial nitrogen gas low-temperature plasma is activated in a cooperative pretreatment process. By limiting the core process parameters of the femtosecond laser, the stable alpha-Al2O3 crystal in the sapphire is directionally converted into gamma-Al2O3 with higher chemical activity, a modified area with a diameter of 2-3 microns is formed, the modified area size is precisely controllable, the via size deviation and the side wall non-perpendicular problem caused by the too large or insufficient modification range of the existing process are solved from the root, the coaxial plasma can target the modified area and introduce hydrophilic functional groups, the etching liquid immersion uniformity is greatly improved, the laser energy is concentrated in the modified area, the heat affected zone is extremely small, there are no thermal defects such as cracks and recondensates in the whole process, and the process is completely adapted to the homemade femtosecond laser processing module.

Description

Technical Field

[0001] This invention belongs to the field of glass through-hole processing technology, and relates to a method for processing micro-through holes in sapphire glass based on laser-induced etching process. Background Technology

[0002] Sapphire (α-Al2O3) glass is widely used in high-end fields such as electronics, quantum communication, aerospace, and defense due to its excellent high temperature resistance, electrical insulation, wear resistance, thermal conductivity, and optical transmittance. In particular, in scenarios such as all-sapphire fiber Fabry-Perot cavity high-temperature pressure sensors and LED substrate packaging, it is often necessary to process high-precision, high aspect ratio micro-vias to achieve functions such as signal transmission, heat dissipation, or structural assembly.

[0003] Currently, the processing methods for sapphire glass microvias are mainly divided into three categories: traditional wet etching, dry etching, and single laser ablation. Among them, wet etching has the advantages of low cost and convenient large-area processing, but its isotropic etching characteristics result in large microvia taper and low precision, making it difficult to meet the processing requirements of high aspect ratios (such as 5:1 or higher), and the etching rate is slow and prone to surface damage. Dry etching (such as ICP-RIE) can achieve high vertical sidewall processing, but the equipment cost is high, the process is complex, the requirements for masks are stringent, and problems such as hole blockage and etching lag are prone to occur during deep hole processing, making it unsuitable for small and medium-scale production. Single laser ablation processes (such as femtosecond and nanosecond laser direct ablation) have the characteristics of non-contact and maskless operation, but ultrashort pulse lasers are expensive and have low processing efficiency. Short pulse lasers are prone to generating heat-affected zones, resulting in defects such as recrystallization and cracks at the edge of the via, and high sidewall roughness, making it difficult to balance processing accuracy and efficiency.

[0004] Chinese invention patent application CN113045209A discloses a method for processing through-holes in glass. The method involves ultrasonically cleaning the flat glass to be processed in an alkaline solution, rinsing with deionized water, and drying. A laser is then used to irradiate the target area of ​​the flat glass. An etching solution is used to etch the flat glass to form through-holes. The etched flat glass is then ultrasonically cleaned. The etching solution includes: 10-40 parts of 40 wt.% hydrofluoric acid; 50-200 parts of pure water; 1-40 parts of auxiliary acid; 0.1-10 parts of salt; and 0.05-5 parts of a surfactant compound. The surfactant compound is composed of a surfactant and acetic acid or an alcohol containing 1-3 carbon atoms in a 1:1-10 ratio. The surfactant is one or more of octylphenyl polyoxyethylene ether, hexadecyltrimethylammonium chloride, sodium α-alkenyl sulfonate, and polyethylene glycol octylphenyl ether. This processing method achieves a high yield rate for drilling through-holes, and the hole walls are smooth and regular.

[0005] The literature “Application of Plasma Technology in Color Modification of Sapphire in Shandong” (Journal of Sun Yat-sen University (Natural Science Edition). 2003(03): 124-126) records that “the effect of low-temperature plasma technology in gemstone color modification is obvious. Compared with other color modification methods, plasma technology has the advantages of greatly reducing the color modification temperature, shortening the time, achieving significant effects, saving energy and not polluting the environment.” Baidu Encyclopedia records that “plasma surface treatment: plasma modifies the surface of sapphire through microscopic chemical reactions and physical effects, such as increasing surface energy and hydrophilicity, and promoting chemical reactions and adsorption.”

[0006] Selective Laser-Induced Etching (SLE), a two-step hybrid processing technology, combines local laser modification with subsequent selective etching, offering the flexibility of laser processing and the high precision of etching. It has become a research hotspot in the micromachining of hard and brittle materials. However, existing SLE processes still suffer from the following technical drawbacks when applied to sapphire glass micro-vias: First, the controllability of the laser modification area is poor, easily leading to overly large or insufficient modification areas, resulting in dimensional deviations and non-perpendicular sidewalls after etching. Second, the etching process and laser modification parameters are mismatched, resulting in uneven etching rates, residue at the bottom of the via, and narrowing of the via opening, making it difficult to achieve stable processing of high aspect ratio micro-vias. Third, the process has poor compatibility; for sapphire glass of different thicknesses and apertures, the entire set of parameters needs to be readjusted, resulting in poor adaptability, and the compatibility with the characteristics of domestically produced equipment in actual production is not considered.

[0007] Therefore, developing a laser-induced etching process that can overcome the above-mentioned defects, achieve efficient, high-precision, and low-cost processing of high aspect ratio micro-through holes in sapphire glass, and be compatible with domestic equipment with stable and controllable processes has become an urgent technical problem to be solved in this field. Summary of the Invention

[0008] The purpose of this invention is to provide a method for processing micro-vias in sapphire glass based on laser-induced etching technology. Through three-stage etching of femtosecond laser precision modification, coaxial plasma activation and etching solution, efficient and non-destructive processing of micro-vias with low taper, high roundness and high aspect ratio is achieved.

[0009] The objective of this invention can be achieved through the following technical solutions: A method for fabricating micro-vias in sapphire glass based on laser-induced etching technology includes the following steps: Step 1: The cleaned sapphire glass is modified by femtosecond laser processing to obtain laser-modified sapphire glass, and then subjected to low-temperature plasma treatment to obtain plasma-treated sapphire glass.

[0010] Step 2: Mix sulfuric acid and phosphoric acid in a certain proportion to obtain an etching solution; completely immerse the plasma-treated sapphire glass in the etching solution, and perform a three-stage etching process, followed by washing, drying, and annealing to obtain sapphire glass with micro-holes.

[0011] The process parameters for femtosecond laser processing modification are as follows: laser wavelength 1030nm, pulse width 300-400fs, repetition frequency 50-200kHz, scanning speed 80-100mm / s, focused spot diameter 2-4μm, and focusing depth 400μm.

[0012] The 1030nm laser wavelength is compatible with domestically produced femtosecond laser processing modules, ensuring strong process compatibility. The 300-400fs pulse width minimizes laser thermal effects, preventing thermal damage, microcracks, and recombination in sapphire. The 100-120kHz repetition frequency and 80-100mm / s scanning speed are precisely matched, balancing modification efficiency and uniformity of the modified area. The focused spot diameter of 2-4μm ensures modification accuracy, and the 400μm focusing depth enables full-process modification of 400μm thick sapphire glass without the need for multiple layers or scans, thus improving processing efficiency.

[0013] The diameter of the modified zone in laser-modified sapphire glass is 2-3 μm.

[0014] By precisely limiting the diameter of the modified area to 2-3μm, the design aperture of the target micro-via can be strictly matched, avoiding via size deviation and sidewall over-etching caused by an excessively large modified area, or etching blockage and bottom residue caused by an excessively small modified area. This achieves high-precision control of the micro-via size and solves the core defect of poor controllability of the modified area in existing processes.

[0015] The process parameters for low-temperature plasma treatment are as follows: the gas is nitrogen, the distance between the nozzle and the specimen is controlled at 25-30 mm, the voltage is 320-340 V, the duty cycle is 20-22%, the frequency is 20-22 kHz, and the treatment time is 60-70 s; the nozzle and the center of the modified zone of the specimen are coaxially aligned.

[0016] Using nitrogen as the plasma source ensures inertness, no oxidation, and no material damage. The above process parameters guarantee moderate energy of plasma active particles, achieving full surface activation without damaging the modified area structure and surface morphology. The 60-70s processing time ensures full introduction of hydrophilic functional groups, achieving optimal surface hydrophilicity. Coaxial alignment allows the plasma to act vertically and precisely on the modified area, avoiding uneven activation, ensuring consistency in subsequent etching, and effectively reducing the taper of the micro-hole.

[0017] The volume ratio of sulfuric acid to phosphoric acid is 3:1.

[0018] The concentration of sulfuric acid is 96 wt%.

[0019] The concentration of phosphoric acid is 85 wt%.

[0020] A high-temperature selective sulfur-phosphorus mixed acid etching system is formed. This ratio can balance the etching rate and etching selectivity. At high temperatures, it can rapidly etch only the laser-modified amorphous regions and has very weak erosion on unmodified sapphire with a complete crystal structure. This achieves a high selectivity ratio for the removal of modified and unmodified regions, solving the problems of isotropy, large taper, and low precision of traditional wet etching.

[0021] The first stage of the three-stage etching process involves etching at a temperature of 200-220℃, a magnetic stirring rate of 200-300 r / min, and an etching time of 10-15 min.

[0022] The first stage is opening etching, which uses medium and low temperature and low stirring rate for gentle etching. This can accurately open the orifice of the modified zone, avoiding edge chipping, shrinkage, and deformation of the orifice. This lays a regular through-hole morphology foundation for the subsequent main etching and ensures that the micro-through-hole inlet size is uniform.

[0023] The second stage of the three-stage etching process has an etching temperature of 220-250℃, a magnetic stirring rate of 300-500 r / min, and an etching time of 60-80 min.

[0024] The second stage is the main etching process, which uses high temperature and high stirring rate to enhance etching mass transfer efficiency, significantly improve the etching rate of the modified zone, and quickly achieve full penetration of 400μm thick sapphire. This solves the problems of slow etching, bottom residue, and hole blockage in deep hole processing, and is suitable for the high-efficiency processing requirements of high aspect ratio micro-through holes.

[0025] The third stage of the three-stage etching process has an etching temperature of 200-220℃, a magnetic stirring rate of 200-300 r / min, and an etching time of 5-10 min.

[0026] The third stage is trimming etching, which involves gentle trimming at low to medium temperatures and low stirring rates. This process removes residual impurities from the sidewalls of the through holes, optimizes sidewall roughness, corrects the taper of the through holes, and improves the roundness and perpendicularity of the micro-through holes, thus solving the defects of rough sidewalls and poor morphology in deep hole machining.

[0027] The annealing temperature is 120-150℃ and the time is 10-20 minutes.

[0028] Low-temperature annealing can eliminate thermal stress and internal micro-defects generated by high-temperature etching, preventing sapphire glass from cracking and breaking during subsequent use, improving the stability and mechanical strength of the micro-via structure, and the annealing time can fully release stress without changing the sapphire crystal structure and via morphology, ensuring the long-term reliability of the device.

[0029] The beneficial effects of this invention are: 1. This invention employs a synergistic pretreatment process combining precise femtosecond laser-induced modification with coaxial nitrogen low-temperature plasma activation. By limiting the core process parameters of the femtosecond laser, the stable α-Al2O3 crystal inside sapphire is directionally transformed into the more chemically active γ-Al2O3, forming a modified region with a diameter of 2-3 μm. The size of the modified region is precisely controllable, fundamentally solving the problems of through-hole size deviation and non-perpendicular sidewalls caused by excessive or insufficient modification range in existing processes. The coaxial plasma can target and clean the modified region, introduce hydrophilic functional groups, and significantly improve the uniformity of etching solution wetting. Furthermore, the laser energy is concentrated in the modified region, resulting in a minimal heat-affected zone and no thermal defects such as cracks or recrystallization throughout the process. The process is fully compatible with domestic femtosecond laser processing modules, significantly reducing the investment cost of production equipment.

[0030] 2. This invention innovatively uses a high-temperature selective etching solution composed of 96wt% sulfuric acid and 85wt% phosphoric acid in a 3:1 ratio, combined with a three-stage gradient etching process. The first stage of opening etching creates a regular hole opening, eliminating edge chipping and closing problems. The second stage of main etching quickly achieves full penetration of 400μm thick sapphire, ensuring high aspect ratio processing efficiency. The third stage of over-etching thoroughly removes bottom residue and optimizes sidewall morphology. This etching system only targets the highly active areas modified by laser, with very weak erosion on the unmodified sapphire substrate. It can control the taper of the through hole within 1° and reduce the sidewall roughness, balancing etching selectivity and processing precision. This solves the industry pain points of traditional wet etching with large taper, dry etching with high cost, and single laser ablation with heavy thermal damage.

[0031] 3. This invention adds a low-temperature annealing process after etching, which can completely eliminate the thermal stress and internal micro-damage generated by high-temperature etching, significantly improving the structural stability, mechanical strength and chemical stability of sapphire micro-vias. It meets the usage requirements of all-sapphire fiber optic sensors, LED packaging and other scenarios in extreme environments such as high temperature and high pressure. The entire process is maskless and without complex patterning processes. The process parameters are fixed and do not require repeated adjustments. The etching rate reaches 0.5-2μm / h, and the processing efficiency is much higher than that of traditional processes. At the same time, it can be flexibly adapted to the processing of sapphire glass with different thicknesses and apertures. The process has strong stability and high feasibility, and has excellent potential for industrial-scale production.

[0032] 4. This invention integrates the core advantages of laser-induced etching. Through precise matching of laser modification and etching processes, it achieves efficient, high-precision, and low-damage processing of 400μm thick sapphire high aspect ratio micro-vias. Compared with existing technologies, it has five major advantages: high processing accuracy, low cost, high efficiency, strong adaptability, and high reliability. It fully meets the manufacturing needs of high-end fields such as artificial intelligence, semiconductor integrated circuits, quantum communication, and aerospace for sapphire microstructure devices. Attached Figure Description

[0033] Figure 1This is a schematic diagram of the femtosecond laser processing system of the present invention.

[0034] Figure 2 These are front dot shapes of the laser-modified sapphire glass in Examples 1-3 of this invention; Figure 3 These are dot-shape images of the back surface of the laser-modified sapphire glass in Examples 1-3 of this invention; Figure 4 The diagram shows the front pore shape of the sapphire glass with micro-perforations in Embodiments 1-3 of this invention. Figure 5 The back hole pattern diagrams are shown for the sapphire glass with micro-through holes in Embodiments 1-3 of the present invention; Figure 6 This is a cross-sectional view of the sapphire glass with micro-perforations in Embodiments 1-3 of the present invention. Detailed Implementation

[0035] To further illustrate the technical means and effects of the present invention in achieving the intended purpose, the following detailed description of the specific implementation methods, features and effects of the present invention, in conjunction with preferred embodiments, is provided below.

[0036] Example 1: This example provides a method for fabricating micro-vias in sapphire glass based on laser-induced etching technology, including the following steps: S1: A 400μm thick sapphire glass was sequentially immersed in ethanol and deionized water, and ultrasonically cleaned for 5 minutes each time at a power of 200W to remove surface oil and particles. After cleaning, it was dried with high-pressure gas and then baked in a 120℃ oven for 10 minutes to ensure that there was no moisture residue on the glass surface. Cleaning and drying were then performed to remove surface impurities. Modification was then carried out using a domestically produced femtosecond laser processing module. The sapphire glass was first fixed in a... Figure 1 At the sample location shown, the plane to be processed is perpendicular to the laser axis. The process parameters are: laser wavelength 1030nm, pulse width 300fs, repetition frequency 50kHz, scanning speed 80mm / s, focused spot diameter 2μm, and focused depth 400μm. The laser is focused on the area to be processed in the sapphire glass, and irradiation is performed to form a modified area with a diameter of 2μm, which extends through the entire thickness of the sapphire glass, resulting in laser-modified sapphire glass. The front surface dot shape is as follows: Figure 2 As shown in the first row of dots, the back side is as follows: Figure 3 The first row of dots in the diagram is shown.

[0037] S2: The laser-modified sapphire glass specimen was ultrasonically cleaned for 5 minutes each with anhydrous ethanol and deionized water, respectively. After removal, it was dried with nitrogen. The specimen was then fixed in a special positioning fixture that shared the same three-dimensional displacement platform as the laser modification process in S1. The sample positioning reference of S1 was reused, and the three-dimensional coordinate data of the micropores recorded in S1 was called up. Secondary alignment and calibration were performed through the coaxial imaging detector system to achieve micron-level coaxial alignment between the plasma nozzle and the center of the modified area of ​​the specimen. The vertical distance between the nozzle and the surface of the specimen was controlled to be 25 mm. The nitrogen low-temperature plasma was turned on. The process parameters of the low-temperature plasma equipment were 320V voltage, 20% duty cycle, and 20kHz frequency. The vertical alignment micropores were purged for 60 seconds. The specimen was then removed to obtain plasma-treated sapphire glass.

[0038] Laser-modified sapphire forms amorphous defect regions with disordered crystal lattice, which have a chemical activity far higher than that of a complete α-Al2O3 crystal matrix. Furthermore, the prior nitrogen low-temperature plasma treatment significantly enhances the hydrophilicity of the sapphire surface, enabling the etching solution to quickly and uniformly penetrate the laser-modified region.

[0039] S3: Mix 120 mL of 96 wt% sulfuric acid and 40 mL of 85 wt% phosphoric acid in a volume ratio of 3:1 to obtain the etching solution.

[0040] S4: Mix the prepared etching solution with the plasma-treated sapphire glass, ensuring the etching solution completely immerses the plasma-treated sapphire glass. Perform the first stage of opening etching at 200℃, with a magnetic stirring rate of 200 r / min and an etching time of 10 min. Then perform the second stage of main etching at 220℃, with a magnetic stirring rate of 300 r / min and an etching time of 60 min. Finally, perform the third stage of over-etching at 200℃, with a magnetic stirring rate of 200 r / min and an etching time of 5 min. Rinse the etched sapphire glass in deionized water for 3 min to remove residual etching solution, then dehydrate it in ethanol for 2 min. Dry it with high-pressure gas and anneal it at 120℃ for 15 min to obtain sapphire glass with micro-vias. The front facet profile is shown below. Figure 4 The first row of holes is shown in the diagram, and the back hole pattern is as follows: Figure 5 The first row of holes is shown in the diagram.

[0041] Example 2: This example provides a method for fabricating micro-vias in sapphire glass based on laser-induced etching technology, including the following steps: S1: A 400μm thick sapphire glass was sequentially immersed in ethanol and deionized water, and ultrasonically cleaned for 6 minutes each at a power of 250W to remove surface oil and particles. After cleaning, it was dried with high-pressure gas and then baked in a 125℃ oven for 12 minutes to ensure no moisture residue remained on the glass surface. Cleaning and drying were then performed to remove surface impurities. Modification was then carried out using a domestically produced femtosecond laser processing module. The sapphire glass was first fixed in a... Figure 1 At the sample location shown, the plane to be processed is perpendicular to the laser axis. The process parameters are: laser wavelength 1030nm, pulse width 350fs, repetition frequency 110kHz, scanning speed 90mm / s, focused spot diameter 3μm, and focused depth 400μm. The laser is focused on the area to be processed in the sapphire glass and irradiated to form a modified area with a diameter of 2.5μm, which extends through the entire thickness of the sapphire glass, resulting in laser-modified sapphire glass. The front surface dot shape is as follows: Figure 2 As shown in the second row of dots, the back side is as follows: Figure 3 The second row of dots is shown in the figure.

[0042] S2: The laser-modified sapphire glass specimen was ultrasonically cleaned for 6 minutes each with anhydrous ethanol and deionized water, respectively. After removal, it was dried with nitrogen. The specimen was then fixed in a special positioning fixture that shared the same three-dimensional displacement platform as the laser modification process in S1. The sample position positioning reference of the S1 process was reused, and the three-dimensional coordinate data of the micropores recorded in S1 was called up. Secondary alignment and calibration were performed through the coaxial imaging detector system to achieve micron-level coaxial alignment between the plasma nozzle and the center of the modified area of ​​the specimen. The vertical distance between the nozzle and the surface of the specimen was controlled to be 27 mm. The nitrogen low-temperature plasma was turned on. The process parameters of the low-temperature plasma equipment were 330V voltage, 21% duty cycle, and 21kHz frequency. The vertical alignment micropores were purged for 65 seconds. The specimen was then removed to obtain plasma-treated sapphire glass.

[0043] S3: Mix 135 mL of 96 wt% sulfuric acid and 45 mL of 85 wt% phosphoric acid in a volume ratio of 3:1 to obtain the etching solution.

[0044] S4: Mix the prepared etching solution with the plasma-treated sapphire glass, ensuring the etching solution completely immerses the plasma-treated sapphire glass. Perform the first stage of opening etching at 210℃, with a magnetic stirring rate of 250 r / min and an etching time of 12 min. Then, perform the second stage of main etching at 235℃, with a magnetic stirring rate of 400 r / min and an etching time of 70 min. Finally, perform the third stage of over-etching at 210℃, with a magnetic stirring rate of 250 r / min and an etching time of 7 min. Rinse the etched sapphire glass in deionized water for 4 min to remove residual etching solution, then dehydrate it in ethanol for 2 min. Dry it with high-pressure gas and anneal it at 135℃ for 15 min to obtain sapphire glass with micro-vias. The front facet profile is shown below. Figure 4 The second row of holes is shown in the diagram, and the back hole pattern is as follows: Figure 5 The second row of holes is shown in the diagram.

[0045] Example 3: This example provides a method for fabricating micro-vias in sapphire glass based on laser-induced etching technology, including the following steps: S1: A 400μm thick sapphire glass was sequentially immersed in ethanol and deionized water, and ultrasonically cleaned for 7 minutes each at a power of 300W to remove surface oil and particles. After cleaning, it was dried with high-pressure gas and then baked in a 130℃ oven for 15 minutes to ensure no moisture residue remained on the glass surface. Cleaning and drying were then performed to remove surface impurities. Modification was then carried out using a domestically produced femtosecond laser processing module. The sapphire glass was first fixed in a... Figure 1 At the sample location shown, the plane to be processed is perpendicular to the laser axis. The process parameters are: laser wavelength 1030nm, pulse width 400fs, repetition frequency 200kHz, scanning speed 100mm / s, focused spot diameter 4μm, and focused depth 400μm. The laser is focused on the area to be processed in the sapphire glass and irradiated to form a modified area with a diameter of 3μm, which extends through the entire thickness of the sapphire glass, resulting in laser-modified sapphire glass. The front surface dot shape is as follows: Figure 2 As shown in the third row of dots, the back side is as follows: Figure 3 The third row of dots is shown in the figure.

[0046] S2: The laser-modified sapphire glass specimen was ultrasonically cleaned for 7 minutes each with anhydrous ethanol and deionized water. After removal, it was dried with nitrogen. The specimen was then fixed in a special positioning fixture that shared the same three-dimensional displacement platform as the laser modification process in S1. The sample positioning reference of S1 was reused, and the three-dimensional coordinate data of the micropores recorded in S1 was called. Secondary alignment and calibration were performed through the coaxial imaging detector system to achieve micron-level coaxial alignment between the plasma nozzle and the center of the modified area of ​​the specimen. The vertical distance between the nozzle and the surface of the specimen was controlled to be 30 mm. The nitrogen low-temperature plasma was turned on. The process parameters of the low-temperature plasma equipment were 340V voltage, 22% duty cycle, and 22kHz frequency. The vertical alignment micropores were purged for 70 seconds. The specimen was then removed to obtain plasma-treated sapphire glass.

[0047] S3: Mix 150 mL of 96 wt% sulfuric acid and 50 mL of 85 wt% phosphoric acid in a volume ratio of 3:1 to obtain the etching solution.

[0048] S4: Mix the prepared etching solution with the plasma-treated sapphire glass, ensuring the etching solution completely immerses the plasma-treated sapphire glass. Perform the first stage of opening etching at 220℃, with a magnetic stirring rate of 300 r / min and an etching time of 15 min. Then, perform the second stage of main etching at 250℃, with a magnetic stirring rate of 500 r / min and an etching time of 80 min. Finally, perform the third stage of over-etching at 220℃, with a magnetic stirring rate of 300 r / min and an etching time of 10 min. Rinse the etched sapphire glass in deionized water for 5 min to remove residual etching solution, then dehydrate it in ethanol for 3 min. Dry it with high-pressure gas and anneal it at 150℃ for 20 min to obtain sapphire glass with micro-vias. The front facet profile is shown below. Figure 4 The third row of holes is shown in the diagram, and the back hole pattern is as follows: Figure 5 The third row of holes is shown in the diagram.

[0049] Please see Figure 6 The cross-sectional view of a sapphire glass containing micropores is shown in the figure.

[0050] Comparative Example 1: This comparative example provides a method for processing micro-vias in sapphire glass based on laser-induced etching process. The difference from Example 1 is that step S2 is omitted, and step S4 uses the laser-modified sapphire glass prepared in step S1 instead of the plasma-treated sapphire glass.

[0051] Comparative Example 2: This comparative example provides a method for processing micro-vias in sapphire glass based on laser-induced etching technology. The difference from Example 1 is that the annealing process is removed in step S4.

[0052] Comparative Example 3: This comparative example provides a method for processing micro-vias in sapphire glass based on laser-induced etching process. The difference from Example 1 is that only the second stage of main etching is performed in step S4, with an etching temperature of 220-250℃, a magnetic stirring rate of 300-500r / min, and an etching time of 60-80min.

[0053] The sapphire glass containing micropores prepared in Examples 1-3 and Comparative Examples 1-3 were subjected to quality testing. The diameter and depth of the micropores were detected by laser confocal microscopy, and the sidewall angle and roughness were detected by SEM. The results are shown in Table 1. Table 1 Performance Test Overview From Table 1 and Figures 4-6 It can be seen that the aperture of Examples 1-3 is stable at 50.5-51.0 μm with a deviation of only 0.5-0.6 μm, the depth is 348-355 μm, and the aspect ratio is stable at 7.0-7.3:1. This indicates that the process of Examples 1-3 avoids lateral over-etching and aperture deviation during the etching process, and achieves efficient penetration of high aspect ratio micro-vias. This may be because the femtosecond laser precision-induced modification process is used. By limiting parameters such as laser wavelength, pulse width, and focused spot, the size of the modified area inside the sapphire is strictly limited within the target range, and the modified area penetrates the glass thickness, providing a precise and continuous directional etching process for subsequent etching. The processing channel is improved by coaxial nitrogen low-temperature plasma activation treatment, which greatly enhances the surface hydrophilicity of the modified area, allowing the etching solution to uniformly penetrate deep into the channel and avoid the aperture deviation caused by uneven local etching. In addition, the etching solution of 96wt% sulfuric acid and 85wt% phosphoric acid in a 3:1 ratio has excellent selectivity, producing directional corrosion only on the high-activity area modified by laser, and almost no corrosion on the unmodified sapphire substrate, effectively suppressing lateral over-etching. The high-temperature main etching stage in the three-stage etching process enhances the mass transfer efficiency through high stirring rate, which greatly improves the etching rate deep in the channel and achieves efficient penetration of high aspect ratio micro-through holes.

[0054] The sidewall angles of Examples 1-3 reached 88.5°-89°, the sidewall roughness Ra≤0.35μm, and the taper was only 0.8°-0.9°. This indicates that the process of Examples 1-3 effectively suppressed lateral corrosion and hole wall roughness, realizing the processing of near-straight-wall micro-through holes. This may be due to the adoption of a three-stage gradient etching process. In the first stage, low-temperature opening etching can accurately regulate the hole morphology and avoid edge chipping or narrowing of the hole. In the second stage, high-temperature main etching is directional etching along the laser-modified area, which greatly improves the hole penetration efficiency while strictly controlling lateral corrosion. In the third stage, low-temperature finishing etching can remove residual impurities and micro-protrusions on the sidewall and optimize the sidewall roughness. At the same time, the high selective corrosion characteristics of the etching solution effectively suppress the lateral erosion of the unmodified substrate and control the taper at an extremely low level. The low-temperature annealing process added after etching can eliminate the thermal stress and sidewall micro-defects generated by high-temperature etching, further improving the verticality and surface quality of the sidewall, and finally realizing the processing of near-straight-wall, low-roughness micro-through holes.

[0055] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus.

[0056] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention.

Claims

1. A method for fabricating micro-vias in sapphire glass based on laser-induced etching technology, characterized in that, Includes the following steps: Step 1: The cleaned sapphire glass is modified by femtosecond laser processing to obtain laser-modified sapphire glass, and then subjected to low-temperature plasma treatment to obtain plasma-treated sapphire glass. Step 2: Mix 96wt% sulfuric acid and 85wt% phosphoric acid in a volume ratio of 3:1 to obtain an etching solution; completely immerse the plasma-treated sapphire glass in the etching solution, and perform three-stage etching, washing, drying, and annealing to obtain sapphire glass with micropores. The first stage of the three-stage etching process involves etching at a temperature of 200-220℃, a magnetic stirring rate of 200-300 r / min, and an etching time of 10-15 min. The second stage of the three-stage etching process involves an etching temperature of 220-250℃, a magnetic stirring rate of 300-500 r / min, and an etching time of 60-80 min. The third stage of the three-stage etching process involves an etching temperature of 200-220℃, a magnetic stirring rate of 200-300 r / min, and an etching time of 5-10 min.

2. The method for fabricating micro-vias in sapphire glass based on laser-induced etching process according to claim 1, characterized in that, The process parameters for femtosecond laser processing modification in step one are as follows: laser wavelength 1030nm, pulse width 300-400fs, repetition frequency 50-200kHz, scanning speed 80-100mm / s, focused spot diameter 2-4μm, and focusing depth 400μm.

3. The method for fabricating micro-vias in sapphire glass based on laser-induced etching process according to claim 1, characterized in that, The diameter of the modified region in the laser-modified sapphire glass is 2-3 μm.

4. The method for fabricating micro-vias in sapphire glass based on laser-induced etching process according to claim 1, characterized in that, The process parameters for the low-temperature plasma treatment in step one are as follows: the gas is nitrogen, the distance between the nozzle and the specimen is controlled at 25-30 mm, the voltage is 320-340 V, the duty cycle is 20-22%, the frequency is 20-22 kHz, and the treatment time is 60-70 s.

5. The method for fabricating micro-vias in sapphire glass based on laser-induced etching process according to claim 4, characterized in that, The nozzle is coaxially aligned with the center of the modified area of ​​the specimen.

6. The method for fabricating micro-vias in sapphire glass based on laser-induced etching process according to claim 1, characterized in that, The annealing process is performed at a temperature of 120-150℃ for 10-20 minutes.

Images