A method of photoelectrocatalytic enhanced fixed abrasive polishing of monocrystalline silicon carbide

Abstract

This invention relates to a method for polishing single-crystal silicon carbide using photoelectrocatalytic enhanced bonded abrasives. First, diamond particles, a piezoelectric luminescent material, and a photocatalytic material are sintered to form a polymeric abrasive with piezoelectric, piezoelectric, and photocatalytic properties. Then, the polymeric abrasive is mixed with a polymer matrix and hot-pressed to form a bonded abrasive polishing pad. Finally, hydrogen peroxide containing an electrolyte is used as the polishing fluid, and the prepared bonded abrasive polishing pad is used to perform bonded abrasive processing on the single-crystal silicon carbide. Both the piezoelectric luminescent material and the photocatalytic material are semiconductor materials. The piezoelectric luminescent material emits red and blue visible light under stress, and the photocatalytic material absorbs this red and blue visible light. This method is applicable to the bonded abrasive polishing of single-crystal silicon carbide, ensuring high efficiency while forming a low-damage processed surface. It features high production efficiency, good processing stability, low damage, high yield, and low cost.

Description

Technical Field

[0001] This invention belongs to the field of ultra-precision surface planarization technology, and relates to a method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive. Background Technology

[0002] Single-crystal silicon carbide has a Mohs hardness exceeding 9, making it an ultra-hard and brittle semiconductor material. It possesses excellent mechanical properties, stable physicochemical properties, and superior optical properties, leading to its wide application in military and civilian fields such as machinery, optics, information technology, aerospace, and weaponry. However, due to the high hardness and brittleness of single-crystal silicon carbide, conventional polishing processes are extremely inefficient, or even if efficiency is improved, the surface quality is reduced, making it difficult to meet industrialization requirements.

[0003] Since the mid-20th century, researchers both domestically and internationally have begun studying polishing technology for single-crystal silicon carbide. Currently, polishing is mainly performed using free abrasives and bonded abrasive pads. When using free abrasives, the material removal mechanism is three-body wear, which has disadvantages such as low polishing efficiency, large subsurface damage layer, low abrasive utilization, high cost, and significant pollution. Polishing with bonded abrasive pads also suffers from poor self-sharpening properties of the abrasive, easy glazing of the abrasive pad surface in the later stages of polishing, and poor stability of polishing efficiency. This is because the abrasive penetrates only a small depth into the surface of single-crystal silicon carbide, resulting in fine abrasive debris, minimal wear on the abrasive pad substrate, inability to maintain the abrasive exposure height, and difficulty in removing and renewing the abrasive.

[0004] Nanjing University of Aeronautics and Astronautics proposed a grinding and polishing method for ultra-hard and brittle workpieces. This method uses aggregated abrasives to form abrasive pads or discs, and incorporates a free abrasive grinding and polishing slurry. Mechanical wear is used to improve the self-sharpening ability of the abrasive and the self-repairing ability of the abrasive pad / disc. However, the material removal rate is still below 200 nm / min, while the surface roughness exceeds 100 nm, falling short of polishing requirements (ZL201610857938.4). Furthermore, enhancing the processing performance of abrasives mainly employs two methods: 1) abrasive grain coating to improve wear resistance, such as a composite abrasive with a nickel oxide core-shell structure and its preparation method and application (ZL201210209689.X), a composite abrasive with an alumina core-shell structure and its preparation method and application (ZL201210210174.1), and coated abrasive products and methods for preparing coated abrasive products (CN202080085085.1); 2) abrasive grain agglomeration to improve wear resistance. Self-sharpening properties, such as a superhard aggregate abrasive with high micro-fragmentation characteristics and its preparation method (ZL201911335624.8), a grinding and polishing method for superhard and brittle workpieces (ZL201610857938.4), loose abrasive agglomerates and a method for grinding workpieces using them (CN202180012880.2), bonded abrasive products and manufacturing methods (CN202180010661.0), metal-bonded abrasive products and methods for preparing metal-bonded abrasive products (ZL 201880014168.4), and a long-life resin-bonded abrasive and its preparation method (ZL201811388108.7). While chemical mechanical polishing (CMP) has improved efficiency, the increase in removal rate for single-crystal silicon carbide is not significant, and the surface quality remains poor with severe scratches. (Existing methods have weak chemical catalysis; although the surface lattice structure of single-crystal silicon carbide is damaged by the scratching force of abrasive particles, and the chemical reagents in the polishing slurry enhance its corrosion or complexation effects, the reaction rate is still insufficient. The softening layer on the surface of single-crystal silicon carbide is thin, resulting in less material that can be removed by the mechanical action of abrasive particles.) Additionally, a visible light-assisted diamond CMP slurry and polishing method (ZL202111267345.X) utilizes hydrogen peroxide to remove Fe from ND / LDH. 3+ / Fe 2+ and Cu 2+ / Cu 1+ The oxidation-reduction cycle generates ·OH, thereby achieving chemical mechanical polishing of single-crystal diamond with a material removal rate of about 400 nm / h and a surface roughness of less than 1 nm. Summary of the Invention

[0005] The purpose of this invention is to solve the aforementioned problems in the prior art and provide a method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced bonded abrasives, ensuring high efficiency in single-crystal silicon carbide bonded abrasive polishing while forming a low-damage processed surface. Compared with the modified abrasives in the prior art, this invention utilizes the mechanical energy in the bonded abrasive polishing process. During polishing, the extrusion and frictional stress between the polymer abrasive and the wafer cause the piezoelectric luminescent material to emit light, and electrons on the surface of the photocatalytic material are excited by light. In addition, the piezoelectric luminescent material undergoes stress discharge, causing anodic oxidation on the surface of single-crystal silicon carbide and inhibiting the recombination of photogenerated holes (h+) and photogenerated electrons (e-) on the surface of the photocatalytic material. This intensifies the generation of highly oxidizing ·OH from hydrogen peroxide, softening the surface of single-crystal silicon carbide, thereby achieving a form- and property-integrated ultra-smooth surface polishing.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced bonded abrasive involves first sintering diamond particles, piezoelectric luminescent materials, and photocatalytic materials into a polymeric abrasive with piezoelectric, piezoelectric, and photocatalytic properties. Then, the polymeric abrasive is mixed with a polymer matrix and hot-pressed to form a bonded abrasive polishing pad. Finally, hydrogen peroxide containing electrolyte is used as the polishing fluid, and the prepared bonded abrasive polishing pad is used to perform bonded abrasive processing on the single-crystal silicon carbide.

[0008] Both piezoelectric luminescent materials and photocatalytic materials are semiconductor materials. Piezoelectric luminescent materials emit visible light under stress, while photocatalytic materials can absorb the visible light.

[0009] As a preferred technical solution:

[0010] As described above, in a method for photoelectrocatalytic enhancement of solidified abrasive polishing of single-crystal silicon carbide, the piezoelectric luminescent material is praseodymium-doped sodium niobate (NaNbO3:Pr). 3+ ), praseodymium-doped potassium sodium niobate (KxNa1-xNbO3:Pr 3+ ), manganese europium dysprosium doped magnesium silicate (MgSiO3:Mn 2+ Eu 2+ ,Dy 3+ Yttrium aluminum borate (YAl3(BO3)4) or europium-dysprosium-doped strontium aluminum oxide (SrAl2O4:Eu) 2+ ,Dy 3 + The photocatalyst material is nitrogen-doped zinc oxide (ZnO@N), bismuth oxybromide (BiOBr), or graphene carbon nitride (g-C3N4). When the piezoelectric luminescent material is praseodymium-doped sodium niobate (NaNbO3:Pr... 3+ ), praseodymium-doped potassium sodium niobate (KxNa1-xNbO3:Pr 3+) or manganese europium dysprosium doped magnesium silicate (MgSiO3:Mn 2+ Eu 2+ ,Dy 3+ When the piezoelectric luminescent material is yttrium aluminum tetraborate (YAl3(BO3)4) or europium-dysprosium-doped strontium aluminum oxide (SrAl2O4:Eu), it emits near-red light (635–650 nm) under stress. Nitrogen-doped zinc oxide (ZnO@N) is used as the photocatalyst material, which can absorb near-red light with wavelengths less than 650 nm. 2+ ,Dy 3+ When under stress, it emits blue light (445-473nm). The photocatalyst material selected is bismuth oxy bromide (BiOBr) or graphene carbon nitride (g-C3N4), which absorb blue light with wavelengths of 470nm and 440nm, respectively.

[0011] The method for polishing single-crystal silicon carbide using photoelectrocatalyst-enhanced consolidation abrasives, as described above, specifically includes the following steps:

[0012] (1) Diamond particles, piezoelectric luminescent materials and photocatalytic materials are mixed, molded and granulated to obtain polymer abrasive with a particle size of 5 to 150 μm;

[0013] (2) The polymer abrasive obtained in step (1) is stirred and mixed with the polymer matrix, and after foaming, it is poured into a mold and hot-pressed to obtain a solidified abrasive polishing pad.

[0014] (3) The solidified abrasive polishing pad obtained in step (2) is attached to the polishing disc of the polishing machine, a hydrogen peroxide polishing liquid containing electrolyte is prepared, the polishing circuit (i.e. the circuit between the substrate and the solidified abrasive pad) is connected, and the single crystal silicon carbide substrate is polished. In-situ photoelectrocatalytic enhanced polishing can efficiently and controllably remove single crystal silicon carbide material.

[0015] In the above-described method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive, the particle size of the diamond particles in step (1) is 0.5-10 μm, and their content is 25-75% of the total mass of diamond particles, piezoelectric luminescent material and photocatalytic material.

[0016] The particle size of the piezoelectric luminescent material is 0.1–2 μm, the particle size of the photocatalytic material is 0.1–2 μm, and the mass ratio of the piezoelectric luminescent material to the photocatalytic material is 1:3–3:1.

[0017] As described above, in the method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive as described above, the mixing process in step (1) adopts either wet ball milling or dry powder mixing, wherein the mixed powder obtained by wet ball milling needs to be dried.

[0018] As described above, in the method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive, the forming process in step (1) refers to adding a binder to the mixed powder and forming a blank by hot pressing.

[0019] The adhesive is one or more of polyvinyl acetate, polyvinyl alcohol, and polyvinyl acetal, and the adhesive content is 1 to 6% of the mass of the mixed powder.

[0020] As described above, in the method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive, the granulation process in step (1) refers to drying, degumming, sintering, crushing, and classifying the preform made by hot pressing to obtain polymerized abrasive;

[0021] The drying, degumming, and sintering processes are as follows:

[0022] Drying: Dry the mixture containing the binder in the range of 80 to 150°C;

[0023] De-adhesive: Remove the adhesive from the particles. The de-adhesive temperature is adjusted within the range of 400-550℃, and the time is 30-120 minutes.

[0024] Sintering: The degummed particles are sintered at high temperature to form diamond aggregates that can be cured or pressed into shape. The sintering temperature is 600-900℃ and the time is 30-120min.

[0025] In the above-described method for photoelectrocatalytic enhancement of bonded abrasive polishing of single-crystal silicon carbide, the polymer matrix in step (2) is one or more of epoxy resin, bismaleimide, thermosetting polyimide, cyanate ester, unsaturated polyester, polyvinyl acetal, polycarbonate, polyacrylate, polyethylene glycol, phenolic resin, urea-formaldehyde resin, melamine resin, silicone resin, polyurethane, ionized acrylic derivative resin, and polyacrylamide, and the content of the polymer matrix is ​​40-70% of the total mass of the bonded abrasive polishing pad.

[0026] The process parameters for hot pressing in step (2) of the above-mentioned photoelectrocatalytic enhanced solidified abrasive polishing method for single-crystal silicon carbide are: temperature 50-80℃ and pressure 3-6MPa.

[0027] In the above-described method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive, the electrolyte in step (3) is one or more of acetic acid, citric acid, oxalic acid, benzoic acid, sorbic acid and salicylic acid, and the mass content of the electrolyte in the hydrogen peroxide polishing solution containing the electrolyte is 5-30%.

[0028] The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive as described above, wherein the polishing process parameters in step (3) are: polishing pressure 5-25 kPa, rotation speed of polishing disc and single-crystal silicon carbide wafer 40-120 r / min, polishing fluid flow rate 20-100 ml / min, and polishing time 30-120 min.

[0029] The method described above for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasives results in a material removal rate (MRR) of 1.2–3.0 μm / min, a surface roughness (Sa) of 220–250 nm to 2–7 nm, and a subsurface damage layer thickness of 1–3 μm after polishing.

[0030] The principle of this invention is as follows:

[0031] The polymeric abrasive proposed in this invention differs from existing modified abrasives that only enhance wear resistance or self-sharpening properties to improve processing efficiency. Mechanical force not only causes micro-fracture of the polymeric abrasive particles, leading to the shedding of hard micro-powder from the surface, but also stimulates the piezoelectric luminescent material to emit light. When the photocatalyst material in the polymeric abrasive is irradiated, electrons in the valence band are excited and jump to the conduction band, forming free electrons. Simultaneously, positively charged holes (h+) are generated in the valence band. Electrons adsorbed on the surface of OH- and H2O2 fill these holes, causing OH- and H2O2 to lose electrons and transform into highly oxidizing hydroxyl radicals (·OH). Simultaneously, photogenerated electrons (e-) can also react with O2 to generate oxygen radicals (·O2). - Active free radicals, under the influence of frictional heat, undergo a redox reaction with silicon carbide, causing SiC to form a softening compound, SixCyOx(·O2). - +H₂O₂→·OH⁺OH - +O2, SiC+OH+O2→SixCyOx+H2O). Additionally, piezoelectric luminescent materials undergo force discharge, through methods such as... Figure 2 The conductive circuit shown forms anodization on single-crystal silicon carbide, and the polymer abrasive reacts with the solid phase of single-crystal silicon carbide to soften its surface.

[0032] This invention differs from existing ultraviolet photocatalytic assisted surface processing methods, such as those described in Reference 1 (Ultraviolet photocatalytic vibration composite polishing. Infrared and Laser Engineering, 2022, 51(11):361-367) and Reference 2 (Synergistic effect of long afterglow luminescent particles and photocatalytic materials in chemical mechanical polishing of SiC wafers. Surface Technology: 1-19 [2022-12-07]). These methods require external ultraviolet light source to irradiate polishing liquid containing photocatalytic materials, and the polishing liquid then flows into the surface of single-crystal silicon carbide to produce a photocatalytic assisted polishing effect. The active center of the chemical catalytic reaction is located on the surface of the photocatalytic material, but the catalyst cannot effectively delineate the surface of single-crystal silicon carbide to form mechanical removal. This invention integrates stress-induced luminescent discharge materials, photocatalytic materials, and hard particles. The combination of these three substances creates an in-situ photoelectrocatalytic polishing effect. In this invention, the polymerized abrasive emits light and discharges spontaneously under stress. Furthermore, because the luminescent and photocatalytic materials are integrated, photocatalysis is more easily achieved and less susceptible to obstruction. Simultaneous photocatalytic and oxidation reactions occur during the friction between the polymerized abrasive particles and the silicon carbide surface. This multi-energy field of force-heat-photon-electrochemical reaction is concentrated at the contact area between the polymerized abrasive and the single-crystal silicon carbide surface, significantly improving material removal efficiency. The polishing process is essentially a combination of mechanical friction and chemical reaction. This invention concentrates the mechanical action center and reactive center at the interface between the polymerized abrasive and the single-crystal silicon carbide, increasing the softening layer formation rate and the amount of material removed mechanically. Simultaneously, with a constant load and a constant depth of penetration into the silicon carbide surface, the increased softening layer thickness makes it less likely for the abrasive to cut the silicon carbide substrate, reducing scratches.

[0033] Beneficial effects:

[0034] The present invention discloses a method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive. This method is applicable to polishing single-crystal silicon carbide with solidified abrasive. It requires no external equipment and does not require changes to existing polishing equipment and process conditions. It features high production efficiency, good processing stability, minimal damage, high yield, and low cost. Attached Figure Description

[0035] Figure 1 This is a flowchart illustrating the preparation process of the polymer abrasive of the present invention.

[0036] Figure 2 This is a schematic diagram illustrating the principle and process of surface-bonded abrasive polishing of single-crystal silicon carbide according to the present invention. Detailed Implementation

[0037] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0038] The specific information of the substances used in the embodiments of the present invention is as follows:

[0039] (1) Praseodymium-doped sodium potassium niobate: sourced from Quanzhou Qijin New Material Technology Co., Ltd., brand name tb-675012682137;

[0040] (2) Manganese europium dysprosium doped magnesium silicate: sourced from Yousuo Chemical Technology Co., Ltd., brand name PT-XZ18;

[0041] (3) Yttrium aluminum tetraborate: sourced from Jinan Zeyang Chemical Co., Ltd., with trade name ZY-22062701;

[0042] (4) Europium-dysprosium doped aluminum strontium: sourced from Zhengzhou Yashen Chemical Products Co., Ltd., brand name ts-1633052;

[0043] (5) Nitrogen-doped zinc oxide: sourced from Foshan Jinghui Chemical Co., Ltd., brand name C30;

[0044] (6) Bismuth oxybromide: sourced from Shijiazhuang Kaiyu Chemical Co., Ltd., with trade name zo-20211005;

[0045] (7) Graphene carbon nitride: sourced from Shanghai Longquan Chemical Technology Co., Ltd., brand name is BS16;

[0046] (8) Polyvinyl alcohol: number average molecular weight is 200k;

[0047] (9) Polyvinyl acetal: Number average molecular weight is 30k;

[0048] (10) Polyvinyl acetate: Number average molecular weight is 20k;

[0049] (11) Phenolic resin: sourced from Shanghai Yunhe Materials Technology Co., Ltd., brand name BM-2;

[0050] (12) Organosilicon resin: sourced from Zongyang Sanjin Pigment Co., Ltd., brand name SJ-804;

[0051] (13) Urea-formaldehyde resin: sourced from Shandong Guangshen Electronic Technology Co., Ltd., brand name is GS98441;

[0052] (14) Polyacrylamide: Number average molecular weight is 1300k;

[0053] (15) Epoxy resin: number average molecular weight is 4k;

[0054] (16) Polyurethane: Number average molecular weight is 5k.

[0055] The drying, degumming, and sintering processes in this invention are as follows:

[0056] Drying: Dry the mixture containing the binder at a temperature of 115°C;

[0057] De-adhesive removal: Remove the adhesive from the particles. The de-adhesive removal temperature is adjusted within the range of 550℃, and the time is 75 minutes.

[0058] Sintering: The degummed particles are sintered at high temperature to form diamond aggregates that can be cured or pressed into shape. The sintering temperature is 750℃ and the time is 75min.

[0059] All embodiments of this invention were carried out on a single-sided polishing machine, such as... Figure 2 As shown, the specific polishing process is as follows: polishing pressure 25 kPa, polishing disk and single crystal silicon carbide wafer rotation speed 80 r / min, polishing fluid flow rate 60 ml / min, polishing time 50 min.

[0060] The testing method used in this invention is as follows:

[0061] (1) Material Removal Rate (MRR): The mass of the workpiece before and after processing was measured using a precision balance (accuracy 0.1 mg). The final material removal rate (MRR) (nm / min) of single-crystal silicon carbide was calculated using the following formula:

[0062]

[0063] In the formula: M0 and M represent the mass of single-crystal silicon carbide before and after processing, in grams; the polishing time t is 30 minutes, and the density ρ is 3.22 g / cm³. 3 The radius r is 25.4 mm;

[0064] (2) MRR change rate: Referring to the literature (Tribological effects of loose alumina abrasive assisted sapphire lapping by a fixed agglomerated diamond abrasive pad (FADAP), Materials Science in Semiconductor Processing, 2022, 143:106556.), the formula was used. The MRR change rate of single-crystal silicon carbide material was calculated, where MRRV is the MRR change rate, which is obtained by testing under five consecutive sets of equal-length short polishing periods under the same conditions. To ensure the accuracy of the reference point, the MRR2 of the second time period was selected as the starting value for the test. Therefore, the MRR of the i-th time period is... iThe percentage difference between the initial value MRR2 and the actual value is MRRV, and a value between -0.3 and 0.3 is considered to indicate that the polishing process is stable.

[0065] (3) Surface roughness Sa: The surface roughness Sa of single-crystal silicon carbide was directly read by observing with a white light interferometer and microscope;

[0066] (4) Damage layer thickness: The thickness of the subsurface damage layer of the processed single-crystal silicon carbide was measured by the angle polishing method.

[0067] Example 1

[0068] A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhancement of solidified abrasive, comprising the following specific steps:

[0069] (1) As Figure 1 As shown, diamond particles with a particle size of 0.5–1.5 μm, praseodymium-doped sodium potassium niobate with a particle size of 0.1–0.3 μm, and nitrogen-doped zinc oxide with a particle size of 0.1–0.3 μm are wet-milled. Then, polyvinyl alcohol is added to the mixed powder, and a preform is formed by hot pressing. The preform is then dried, degummed, sintered, crushed, and classified to obtain polymeric abrasive with a particle size of 5–40 μm.

[0070] The diamond particles comprise 40% of the total mass of the diamond particles, piezoelectric luminescent material, and photocatalytic material; the mass ratio of praseodymium-doped sodium potassium niobate to nitrogen-doped zinc oxide is 1:2; and the polyvinyl alcohol content is 1% of the mass of the mixed powder.

[0071] (2) The polymer abrasive obtained in step (1) is stirred and mixed with phenolic resin, and after foaming, it is poured into a mold and hot-pressed (temperature 50℃, pressure 3MPa) to obtain a solidified abrasive polishing pad.

[0072] The content of the polymer matrix is ​​60% of the total mass of the bonded abrasive polishing pad;

[0073] (3) The solidified abrasive polishing pad obtained in step (2) is attached to the polishing disc of the polishing machine. A hydrogen peroxide polishing liquid containing acetic acid is prepared. The mass content of acetic acid in the hydrogen peroxide polishing liquid containing acetic acid is 5%. The polishing circuit is connected to polish the single crystal silicon carbide substrate.

[0074] After five consecutive polishing tests, the minimum material removal rate (MRR) of single-crystal silicon carbide was 1.2 μm / min, and the maximum was 1.3 μm / min; the minimum MRR change rate (MRRV) was -0.05, and the maximum was 0.03; the minimum surface roughness of single-crystal silicon carbide (initial value 230 nm) was 2 nm, and the maximum was 3.5 nm; the minimum thickness of the subsurface damage layer of processed single-crystal silicon carbide was 1 μm, and the maximum was 1.5 μm.

[0075] Comparative Example 1

[0076] A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhancement of solidified abrasive, comprising the following specific steps:

[0077] (1) Diamond particles with a particle size of 5-40 μm are mixed with phenolic resin, foamed and then poured into a mold and hot-pressed (temperature 50℃, pressure 3MPa) to obtain a solidified abrasive polishing pad.

[0078] The content of the polymer matrix is ​​60% of the total mass of the bonded abrasive polishing pad;

[0079] (2) The bonded abrasive polishing pad obtained in step (1) is attached to the polishing disc of the polishing machine. A hydrogen peroxide polishing liquid containing acetic acid is prepared. The mass content of acetic acid in the hydrogen peroxide polishing liquid containing acetic acid is 5%. The polishing circuit is connected to polish the single crystal silicon carbide substrate.

[0080] After five consecutive polishing tests, the minimum material removal rate (MRR) of single-crystal silicon carbide was 0.1 μm / min, and the maximum was 0.5 μm / min; the minimum MRR change rate (MRRV) was -0.8, and the maximum was -0.5; the minimum surface roughness of single-crystal silicon carbide (initial value 230 nm) was 30 nm, and the maximum was 70 nm; the minimum thickness of the subsurface damage layer of processed single-crystal silicon carbide was 6 μm, and the maximum was 14 μm.

[0081] Example 2

[0082] A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhancement of solidified abrasive, comprising the following specific steps:

[0083] (1) Diamond particles with a particle size of 1.5-5 μm, potassium sodium niobate with a particle size of 0.3-1 μm and zinc oxide with a particle size of 0.3-1 μm were wet ball-milled, and then polyvinyl alcohol acetal was added to the mixed powder. The powder was then hot-pressed to form a preform. The preform was then dried, degummed, sintered, crushed and classified to obtain a polymer abrasive with a particle size of 40-80 μm.

[0084] The diamond particles comprise 40% of the total mass of the diamond particles, piezoelectric luminescent material, and photocatalytic material; the mass ratio of praseodymium-doped sodium potassium niobate to nitrogen-doped zinc oxide is 1:1; and the polyvinyl alcohol acetal content is 3% of the mass of the mixed powder.

[0085] (2) The polymer abrasive obtained in step (1) is mixed with a mixture of silicone resin and polyacrylamide in a mass ratio of 25:75. After foaming, it is poured into a mold and hot-pressed (temperature 60℃, pressure 4MPa) to obtain a solidified abrasive polishing pad.

[0086] The content of the polymer matrix is ​​50% of the total mass of the bonded abrasive polishing pad;

[0087] (3) The solidified abrasive polishing pad obtained in step (2) is attached to the polishing disc of the polishing machine. A hydrogen peroxide polishing liquid containing a mixture of citric acid and oxalic acid in a mass ratio of 1:1 is prepared. The mass content of the mixture of citric acid and oxalic acid in the polishing liquid is 20%. The polishing circuit is connected to polish the single crystal silicon carbide substrate.

[0088] After five consecutive polishing tests, the minimum material removal rate (MRR) of single-crystal silicon carbide was 1.5 μm / min, and the maximum was 1.8 μm / min; the minimum MRR change rate (MRRV) was -0.06, and the maximum was 0.13; the minimum surface roughness of single-crystal silicon carbide (initial value 230 nm) was 3 nm, and the maximum was 5 nm; the minimum thickness of the subsurface damage layer of processed single-crystal silicon carbide was 1.8 μm, and the maximum was 2.2 μm.

[0089] Example 3

[0090] A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhancement of solidified abrasive, comprising the following specific steps:

[0091] (1) Diamond particles with a particle size of 5-10 μm, magnesium silicate doped with manganese europium dysprosium with a particle size of 1-2 μm, and zinc oxide doped with nitrogen with a particle size of 1-2 μm are wet-milled, and then polyvinyl acetate is added to the mixed powder. The powder is then hot-pressed to form a preform, and the preform is dried, degummed, sintered, crushed, and classified to obtain a polymer abrasive with a particle size of 80-150 μm.

[0092] The diamond particles comprise 40% of the total mass of the diamond particles, piezoelectric luminescent material, and photocatalytic material; the mass ratio of manganese europium dysprosium-doped magnesium silicate to nitrogen-doped zinc oxide is 2:1; and the polyvinyl acetate content is 6% of the mass of the mixed powder.

[0093] (2) The polymer abrasive obtained in step (1) is mixed with a mixture of epoxy resin, urea-formaldehyde resin and polyurethane in a mass ratio of 25:35:40. After foaming, it is poured into a mold and hot-pressed (temperature 70℃, pressure 5MPa) to obtain a solidified abrasive polishing pad.

[0094] The content of the polymer matrix is ​​45% of the total mass of the bonded abrasive polishing pad;

[0095] (3) The solidified abrasive polishing pad obtained in step (2) is attached to the polishing disc of the polishing machine. A hydrogen peroxide polishing solution containing a mixture of sorbic acid and salicylic acid in a mass ratio of 1:1 is prepared. The mass content of the mixture of sorbic acid and salicylic acid in the polishing solution is 30%. The polishing circuit is connected to polish the single crystal silicon carbide substrate.

[0096] After five consecutive polishing tests, the minimum material removal rate (MRR) of single-crystal silicon carbide was 2.0 μm / min, and the maximum was 2.5 μm / min; the minimum MRR change rate (MRRV) was -0.04, and the maximum was 0.18; the minimum surface roughness of single-crystal silicon carbide (initial value 230 nm) was 3.8 nm, and the maximum was 5.7 nm; the minimum thickness of the subsurface damage layer of processed single-crystal silicon carbide was 2.1 μm, and the maximum was 2.5 μm.

[0097] Example 4

[0098] A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhancement of solidified abrasive, comprising the following specific steps:

[0099] (1) Diamond particles with a particle size of 5-7 μm, yttrium aluminum tetraborate with a particle size of 0.5-1.5 μm and bismuth oxybromide with a particle size of 0.5-1 μm are mixed in dry powder, and then polyvinyl alcohol is added to the mixed powder. The preform is formed by hot pressing, and then the preform is dried, degummed, sintered, crushed and classified to obtain polymer abrasive with a particle size of 50-100 μm.

[0100] The diamond particles comprise 25% of the total mass of the diamond particles, piezoelectric luminescent material, and photocatalytic material; the mass ratio of yttrium aluminum tetraborate to bismuth oxybromide is 1:3; and the polyvinyl alcohol content is 4% of the mass of the mixed powder.

[0101] (2) The polymer abrasive obtained in step (1) is stirred and mixed with phenolic resin, and after foaming, it is poured into a mold and hot-pressed (temperature 50℃, pressure 6MPa) to obtain a solidified abrasive polishing pad.

[0102] The content of the polymer matrix is ​​70% of the total mass of the bonded abrasive polishing pad;

[0103] (3) The solidified abrasive polishing pad obtained in step (2) is attached to the polishing disc of the polishing machine. A hydrogen peroxide polishing liquid containing benzoic acid is prepared. The mass content of benzoic acid in the polishing liquid is 10%. The polishing circuit is connected to polish the single crystal silicon carbide substrate.

[0104] After five consecutive polishing tests, the minimum material removal rate (MRR) of single-crystal silicon carbide was 1.6 μm / min, and the maximum was 1.8 μm / min; the minimum MRR change rate (MRRV) was 0.1, and the maximum was 0.125; the minimum surface roughness of single-crystal silicon carbide (initial value 230 nm) was 4 nm, and the maximum was 5 nm; the minimum thickness of the subsurface damage layer of processed single-crystal silicon carbide was 2 μm, and the maximum was 2.4 μm.

[0105] Example 5

[0106] A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhancement of solidified abrasive, comprising the following specific steps:

[0107] (1) Diamond particles with a particle size of 7-10 μm, europium-dysprosium-doped strontium alumina with a particle size of 1-2 μm, and graphene carbon nitride with a particle size of 1-2 μm are mixed in dry powder. Then, polyvinyl alcohol acetal is added to the mixed powder, and a preform is formed by hot pressing. The preform is then dried, degummed, sintered, crushed, and classified to obtain polymer abrasive with a particle size of 100-150 μm.

[0108] The diamond particles comprise 75% of the total mass of the diamond particles, piezoelectric luminescent material, and photocatalytic material; the mass ratio of europium-dysprosium-doped strontium alumina to graphene carbon nitride is 3:1; and the polyvinyl alcohol acetal content is 5% of the mass of the mixed powder.

[0109] (2) The polymer abrasive obtained in step (1) is mixed with epoxy resin, foamed and then poured into a mold and hot-pressed (temperature 80℃, pressure 3MPa) to obtain a solidified abrasive polishing pad.

[0110] The content of the polymer matrix is ​​40% of the total mass of the bonded abrasive polishing pad;

[0111] (3) The bonded abrasive polishing pad obtained in step (2) is attached to the polishing disc of the polishing machine. A hydrogen peroxide polishing slurry containing sorbic acid is prepared, with a sorbic acid mass content of 25%. The polishing circuit is connected to polish the single crystal silicon carbide substrate.

[0112] After five consecutive polishing tests, the minimum material removal rate (MRR) of single-crystal silicon carbide was 2.8 μm / min, and the maximum was 3.0 μm / min; the minimum MRR change rate (MRRV) was -0.05, and the maximum was 0.02; the minimum surface roughness of single-crystal silicon carbide (initial value 230 nm) was 5.5 nm, and the maximum was 7 nm; the minimum thickness of the subsurface damage layer of processed single-crystal silicon carbide was 2.6 μm, and the maximum was 3 μm.

Claims

1. A method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive, characterized in that: First, diamond particles, piezoelectric luminescent materials, and photocatalytic materials are sintered into a polymer abrasive with piezoelectricity, piezoelectricity, and photocatalyticity. Then, the polymer abrasive is mixed with a polymer matrix and hot-pressed to form a bonded abrasive polishing pad. Finally, hydrogen peroxide containing electrolyte is used as the polishing fluid, and the bonded abrasive polishing pad is used to perform bonded abrasive processing on single-crystal silicon carbide. Both piezoelectric luminescent materials and photocatalytic materials are semiconductor materials. Piezoelectric luminescent materials emit visible light under stress, while photocatalytic materials can absorb the visible light. The piezoelectric light-emitting materials are praseodymium-doped sodium niobate, praseodymium-doped potassium sodium niobate, manganese europium dysprosium-doped magnesium silicate, aluminum yttrium tetraborate, or europium dysprosium-doped strontium aluminum oxide, and the photocatalytic materials are nitrogen-doped zinc oxide, bismuth oxy bromide, or graphene carbon nitride. The diamond particles have a particle size of 0.5~10μm and their content is 25~75% of the total mass of diamond particles, piezoelectric luminescent materials and photocatalytic materials; The particle size of the piezoelectric luminescent material is 0.1~2μm, the particle size of the photocatalytic material is 0.1~2μm, and the mass ratio of the piezoelectric luminescent material to the photocatalytic material is 1:3~3:1; After polishing, the material removal rate (MRR) of single-crystal silicon carbide is 1.2~3.0 μm / min, the surface roughness (Sa) of single-crystal silicon carbide is reduced from 220~250 nm to 2~7 nm, and the thickness of the subsurface damage layer of processed single-crystal silicon carbide is 1~3 μm.

2. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive according to claim 1, characterized in that, Specifically, the steps include the following: (1) Diamond particles, piezoelectric luminescent materials and photocatalytic materials are mixed, molded and granulated to obtain polymer abrasive with a particle size of 5~150μm; (2) The polymer abrasive obtained in step (1) is stirred and mixed with the polymer matrix, and after foaming, it is poured into a mold and hot-pressed to obtain a solidified abrasive polishing pad. (3) The solidified abrasive polishing pad obtained in step (2) is attached to the polishing disc of the polishing machine, a hydrogen peroxide polishing liquid containing electrolyte is prepared, the polishing circuit is connected, and the single crystal silicon carbide substrate is polished.

3. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive according to claim 2, characterized in that, In step (1), the mixing process adopts either wet ball milling or dry powder mixing.

4. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced consolidation abrasive according to claim 2, characterized in that, The molding process in step (1) refers to adding a binder to the mixed powder and forming a blank by hot pressing. The adhesive is one or more of polyvinyl acetate, polyvinyl alcohol and polyvinyl acetal, and the adhesive content is 1 to 6% of the mass of the mixed powder.

5. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced consolidation abrasive according to claim 4, characterized in that, In step (1), the granulation process refers to drying, degumming, sintering, crushing, and grading the preform made by hot pressing to obtain polymer abrasive.

6. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive according to claim 2, characterized in that, In step (2), the polymer matrix is ​​one or more of epoxy resin, bismaleimide, thermosetting polyimide, cyanate ester, unsaturated polyester, polyvinyl acetal, polycarbonate, polyacrylate, polyethylene glycol, phenolic resin, urea-formaldehyde resin, melamine resin, silicone resin, polyurethane, ionized acrylic derivative resin and polyacrylamide, and the content of the polymer matrix is ​​40-70% of the total mass of the bonded abrasive polishing pad.

7. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced consolidation abrasive according to claim 2, characterized in that, The process parameters for hot pressing in step (2) are: temperature 50~80℃, pressure 3~6MPa.

8. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced consolidation abrasive according to claim 2, characterized in that, In step (3), the electrolyte is one or more of acetic acid, citric acid, oxalic acid, benzoic acid, sorbic acid and salicylic acid, and the mass content of the electrolyte in the hydrogen peroxide polishing solution containing the electrolyte is 5-30%.

9. The method for polishing single-crystal silicon carbide with photoelectrocatalytic enhanced solidified abrasive according to claim 2, characterized in that, The polishing process parameters in step (3) are: polishing pressure 5~25kPa, polishing disk and single crystal silicon carbide wafer rotation speed 40~120 r / min, polishing fluid flow rate 20~100 ml / min, and polishing time 30~120 min.

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