Method for eliminating wire marks of diamond wire cut silicon carbide wafer through double lapping

Abstract

The invention relates to a method for eliminating wire marks of diamond wire cut silicon carbide wafers through double lapping, which comprises the following steps of: sequentially carrying out double-sided coarse grinding and double-sided accurate grinding on two stacked silicon carbide wafers, and cleaning to finish the removal of the wire marks on the surfaces of the silicon carbide wafers; an oil-in-water type grinding fluid is used in the double-sided coarse grinding; a water-in-oil type grinding fluid is used in the two-sided accurate grinding. According to the method provided by the invention, through reasonable process design, the line marks can be efficiently removed after the silicon carbide wafer is cut, the surface quality of the wafer is remarkably improved, and meanwhile, the problem of surface damage possibly existing in a traditional method is avoided. Through the method provided by the invention, the surface defects can be reduced, the processing efficiency can be remarkably improved, the production cost is reduced, and the method is particularly suitable for large-scale production of the silicon carbide wafer.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor technology, and relates to a method for cutting silicon carbide wafers, in particular to a method for eliminating wire marks on silicon carbide wafers cut by a diamond wire through double grinding. Background Art

[0002] With the rapid development of the semiconductor industry, silicon carbide (SiC), as a material with excellent electronic properties, is widely used in high-power, high-frequency, high-temperature and other fields, especially in new energy vehicles, photovoltaic inverters, power electronics and other aspects, the applications are increasing day by day.

[0003] Silicon carbide has excellent physical and chemical properties such as high thermal conductivity, high breakdown voltage, and high temperature resistance, and is an important semiconductor material. However, there are many problems in the processing of silicon carbide. For example, surface defects are likely to occur during the cutting of silicon carbide.

[0004] At present, most of the cutting processes for silicon carbide ingots adopt diamond wire cutting technology. The diamond wire cutting process is widely used in the cutting of hard and brittle materials and can achieve high-precision cutting better. During the diamond wire cutting process, the diamond wire rotates and rubs at high speed on the surface of the silicon carbide ingot with cutting abrasive grains, thereby cutting the wafer into the required size. However, due to the cutting characteristics of the diamond wire itself, especially the minute fluctuations and frictional forces of diamond particles, obvious wire marks are often left on the wafer surface during the cutting process. These wire marks not only affect the appearance quality of the wafer, but also may affect subsequent processing technologies such as polishing and wafer thinning, and further affect the performance of the product.

[0005] The main reason for the wire marks generated by diamond wire cutting lies in the frictional force between the diamond wire and the silicon carbide ingot. Due to the high hardness of silicon carbide, during the cutting process, the contact between the surface of the diamond wire and the silicon carbide ingot will generate local pressure and heat, resulting in minute scratches, depressions or cracks on the crystal surface. Especially when parameters such as cutting speed, cutting pressure, and the use of coolant are inappropriate, the wire marks may be more serious. In addition, factors such as the wear of the diamond wire itself, the shedding of diamond particles, and the uneven size and distribution of abrasive grains will also exacerbate the generation of wire marks.

[0006] The methods for removing wire marks in the prior art include single grinding, chemical mechanical polishing (CMP), and laser deburring. However, the deburring effect of single grinding is limited and it cannot completely remove deeper wire marks, and new surface damages will also be generated; when treating high-hardness silicon carbide by CMP, it also requires a long treatment time; laser deburring has problems such as high energy consumption, complex technical operation and high equipment cost.

[0007] Therefore, in order to improve processing efficiency, reduce costs and ensure the deburring effect, a method for eliminating wire marks on silicon carbide wafers cut by a diamond wire through double grinding needs to be provided. Summary of the Invention

[0008] Aiming at the deficiencies of the existing technology, the purpose of the present invention is to provide a method for eliminating wire marks on silicon carbide wafers cut by diamond wire through double grinding. The method can efficiently remove wire marks after cutting silicon carbide wafers, significantly improve the surface quality of the wafers, and can also avoid the surface damage problems that may exist in traditional methods; moreover, the method provided by the present invention can significantly improve the processing efficiency and reduce the production cost, and is particularly suitable for the large-scale production of silicon carbide wafers.

[0009] To achieve the purpose of this invention, the following technical solutions are adopted:

[0010] The present invention provides a method for eliminating wire marks on silicon carbide wafers cut by diamond wire through double grinding. The method comprises the following steps:

[0011] Double-sided rough grinding and double-sided fine grinding are sequentially carried out on two stacked silicon carbide wafers, and then cleaning is performed to complete the removal of wire marks on the surface of the silicon carbide wafers;

[0012] The double-sided rough grinding uses an oil-in-water type grinding fluid;

[0013] The double-sided fine grinding uses a water-in-oil type grinding fluid.

[0014] Although the traditional diamond wire cutting process can efficiently complete the cutting of silicon carbide ingots, it will inevitably produce wire marks of different depths during the cutting process, resulting in the rough surface of silicon carbide wafers and affecting the effect of subsequent processing. Although the existing single grinding, CMP and laser scar removal can remove surface wire marks to a certain extent, there are problems such as incomplete scar removal, low processing efficiency, high cost and surface damage, which are difficult to meet the requirements of large-scale production.

[0015] The method provided by the present invention can effectively remove the wire marks left by the diamond wire after cutting through reasonable process design, ensuring the flatness and smoothness of the surface of the silicon carbide wafer; moreover, the scar removal process can be completed in a short time, thereby improving the production efficiency and saving production time; it can also make the silicon carbide wafer with a surface roughness Ra≤50nm and a subsurface damage layer thickness≤100nm.

[0016] Specifically, by processing two stacked silicon carbide wafers, the present invention improves the processing efficiency of the silicon carbide wafers on the one hand, and ensures the uniform stress of each silicon carbide wafer on the other hand, thereby improving the wire mark elimination effect.

[0017] Double-sided rough grinding is carried out using an oil-in-water grinding fluid. In the stage of double-sided rough grinding, the grinding particle size is relatively large, resulting in a relatively high surface temperature of the processed surface. Selecting an oil-in-water grinding fluid can utilize the outer water phase to achieve maximum heat dissipation (the thermal conductivity of silicon carbide is about 490 W / m·k, and active heat dissipation is required under high heat flux density). At the same time, the internally encapsulated oil phase can play a lubricating role (reducing from 0.8 of pure water phase to 0.3 - 0.5), thereby reducing the losses caused by double-sided rough grinding; through double-sided rough grinding, the present invention can remove the slicing line marks and unevenness on the surface of the silicon carbide wafer, reducing the surface roughness to below 200 nm.

[0018] The purpose of double-sided fine grinding is to reduce the processing damage layer on the surface of the silicon carbide wafer, control the thickness of the subsurface damage layer, and improve the surface flatness of the silicon carbide wafer; double-sided fine grinding is carried out using a water-in-oil grinding fluid. The outer oil phase plays a good lubricating role, reducing grinding damage; at the same time, the internal water phase can play a role in cooling, thereby obtaining a silicon carbide wafer with a surface roughness Ra≤50 nm and a subsurface damage layer thickness≤100 nm.

[0019] Preferably, the double-sided rough grinding includes first rough grinding, second rough grinding, and third rough grinding carried out in sequence.

[0020] The grinding pressure of the first rough grinding is 20 g / cm 2 ~50 g / cm 2 and the grinding rotation speed is 10 r / min~30 r / min.

[0021] The grinding pressure of the second rough grinding is 50 g / cm 2 ~150 g / cm 2 and the grinding rotation speed is 15 r / min~25 r / min.

[0022] The grinding pressure of the third rough grinding is 140 g / cm 2 ~160 g / cm 2 and the grinding rotation speed is 25 r / min~30 r / min.

[0023] The first rough grinding is used to eliminate the gap error and make the abrasives evenly distributed; the second rough grinding is used to increase the cutting force and avoid sudden stress changes; the third rough grinding can efficiently remove surface defects and control the temperature rise.

[0024] The present invention mechanically cuts the surface of silicon carbide through double-sided rough grinding, and finitely removes the wire marks and raised areas on the surface of the silicon carbide wafer. Within the pressure ranges of the first rough grinding, the second rough grinding, and the third rough grinding, the grinding efficiency and the risk of brittle fracture can be balanced; when the pressure of the rough grinding is too low, it is not conducive to the elimination of wire marks; while when the pressure of the rough grinding is too high, it will cause the expansion of lattice cracks and increase the subsurface damage; in addition, by controlling the grinding rotation speed during rough grinding, the action time of the abrasive is extended, and the surface roughness Ra ≤ 200 nm and the subsurface damage layer thickness ≤ 2 μm are achieved after double-sided rough grinding; moreover, the wire mark removal rate can reach 3 μm / min to 5 μm / min, and during the double-sided rough grinding process, the surface temperature is stabilized below 80°C.

[0025] Specifically, the grinding pressure of the first rough grinding is 20 g / cm 2 ~50 g / cm 2 , for example, it can be 20 g / cm 2 , 25 g / cm 2 , 30 g / cm 2 , 35 g / cm 2 , 40 g / cm 2 , 45 g / cm 2 or 50 g / cm 2 , but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0026] The grinding rotation speed of the first rough grinding is 10 r / min to 30 r / min, for example, it can be 10 r / min, 15 r / min, 20 r / min, 25 r / min or 30 r / min, but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0027] In the present invention, in order to achieve the purpose of the first rough grinding, the time of the first rough grinding is controlled ≤ 5 min, for example, it can be 1 min, 2 min, 3 min, 4 min or 5 min, but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0028] Specifically, the grinding pressure of the second rough grinding is 50 g / cm 2 ~150 g / cm 2 , for example, it can be 50 g / cm 2 , 60 g / cm 2 , 80 g / cm 2 , 100 g / cm 2 , 120 g / cm 2 or 150 g / cm 2 , but not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0029] The grinding speed of the second rough grinding is 15 r / min to 25 r / min. For example, it can be 15 r / min, 18 r / min, 20 r / min, 24 r / min or 25 r / min, but is not limited to the listed values. The other unlisted values within the numerical range are equally applicable.

[0030] In the present invention, in order to achieve the purpose of the second rough grinding, the time of the second rough grinding is controlled ≤ 10 min. For example, it can be 1 min, 3 min, 5 min, 6 min, 8 min or 10 min, but is not limited to the listed values. The other unlisted values within the numerical range are equally applicable.

[0031] Specifically, the grinding pressure of the third rough grinding is 140 g / cm 2 ~160 g / cm 2 , for example, it can be 140 g / cm 2 , 145 g / cm 2 , 150 g / cm 2 , 155 g / cm 2 or 160 g / cm 2 , but is not limited to the listed values. The other unlisted values within the numerical range are equally applicable.

[0032] The grinding speed of the third rough grinding is 25 r / min to 30 r / min. For example, it can be 25 r / min, 26 r / min, 27 r / min, 28 r / min or 30 r / min, but is not limited to the listed values. The other unlisted values within the numerical range are equally applicable.

[0033] In the present invention, in order to achieve the purpose of the third rough grinding, the time of the third rough grinding is controlled ≤ 15 min. For example, it can be 1 min, 3 min, 5 min, 8 min, 10 min, 12 min or 15 min, but is not limited to the listed values. The other unlisted values within the numerical range are equally applicable.

[0034] The double-sided fine grinding in the present invention promotes the plastic removal of the microcracks remaining after the double-sided rough grinding by the abrasive grains, makes the material undergo brittle-plastic transformation by increasing the normal stress, and reduces the subsurface dislocation density; the cooperation of its grinding pressure and grinding speed can make the material removal rate (MRR) reach 0.8 μm / min to 1.2 μm / min, and reduce the thickness of the subsurface damage layer to below 100 nm.

[0035] Preferably, the grinding pressure of the double-sided fine grinding is 100 g / cm 2 ~200 g / cm 2 , and the grinding speed is 10 r / min to 50 r / min.

[0036] In the present invention, the grinding pressure for double-sided fine grinding is 100 g / cm 2 ~200 g / cm 2 , for example, it can be 100 g / cm 2 , 120 g / cm 2 , 150 g / cm 2 , 160 g / cm 2 , 180 g / cm 2 or 200 g / cm 2 , but it is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0037] In the present invention, the grinding speed for double-sided fine grinding is 10 r / min to 50 r / min. For example, it can be 10 r / min, 20 r / min, 30 r / min, 40 r / min or 50 r / min, but it is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0038] Preferably, the raw materials for preparing the oil-in-water grinding fluid include mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickener and pH regulator.

[0039] Among them, the mineral oil plays a lubricating role; the diamond particles play an abrasive role; the use of the lipophilic dispersant is to improve the dispersibility of the diamond particles; the role of the alcohol-based solvent is to reduce the surface tension of the aqueous phase and assist in dispersing the mineral oil and diamond particles; the role of the deionized water is to provide cooling and chip flushing ability; the hydrophilic emulsifier is used to stabilize the oil-in-water structure; the thickener is used to increase the viscosity of the oil-in-water grinding fluid and prevent stratification; the role of the pH regulator is to enhance electrostatic stability.

[0040] Preferably, in the raw materials for preparing the oil-in-water grinding fluid, the mass ratio of the mineral oil, the diamond particles, the lipophilic dispersant, the alcohol-based solvent, the deionized water, the hydrophilic emulsifier, the thickener and the pH regulator is (15~25):(5~10):(2~5):(10~15):(40~50):(5~10):(1~3):(0.1~0.3).

[0041] Preferably, the mineral oil includes paraffin wax with a melting point of 50℃~55℃. For example, it can be 50℃, 51℃, 52℃, 53℃, 54℃ or 55℃, but it is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0042] Preferably, the median particle size D50 of the diamond particles is 5 μm to 10 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0043] Preferably, the lipophilic dispersant includes Span80 and / or a dispersant blend.

[0044] Preferably, the dispersant blend includes a combination of polyoxyethylene ether dispersants, oleic acid, and cetyl alcohol.

[0045] Preferably, the alcohol solvent includes ethanol and / or isopropanol.

[0046] Preferably, the hydrophilic emulsifier includes Tween 80 and / or sodium dodecyl sulfate.

[0047] Preferably, the thickener includes carboxymethyl cellulose and / or xanthan gum.

[0048] Preferably, the pH regulator includes ammonia water.

[0049] Preferably, the preparation method of the oil-in-water type grinding fluid includes the following steps:

[0050] (1) Mix the diamond particles with the lipophilic dispersant to obtain a premix; then uniformly mix the premix with the mineral oil to obtain an oil-phase material;

[0051] (2) Mix deionized water with the alcohol-based solvent to obtain a mixed solvent; then mix the hydrophilic emulsifier, pH regulator with the mixed solvent to obtain an aqueous-phase material;

[0052] (3) Under stirring conditions, drop the oil-phase material into the aqueous-phase material to obtain a crude oil-in-water emulsion; then homogenize the crude oil-in-water emulsion to form a stable oil-in-water emulsion; finally, mix it with the thickener to obtain the oil-in-water type grinding fluid;

[0053] Steps (1) and (2) are not in a sequential order.

[0054] Preferably, in step (1), the mineral oil is heated to 60 °C to 65 °C to completely liquefy the mineral oil, and then ultrasonic treatment is performed for 30 min to 60 min under the condition of a frequency of 20 kHz to 40 kHz to achieve uniform mixing of the premix and the mineral oil.

[0055] Preferably, the temperature of the mixed solvent in step (2) is 48 °C to 52 °C.

[0056] Preferably, the mixing conditions of the hydrophilic emulsifier are: stirring speed 780 rpm to 820 rpm, and time of more than 15 min.

[0057] Preferably, during the preparation of the oil-in-water coarse emulsion in step (3), the shear rate under the shearing condition is 12,000 rpm to 15,000 rpm.

[0058] Preferably, the pressure for homogenization in step (3) is 80 MPa to 100 MPa, and the number of cycles is 3 to 5 times.

[0059] By homogenization, the average particle size of the droplets in the oil-in-water emulsion of the present invention is 1 μm to 3 μm.

[0060] Preferably, the mixing temperature of the thickener in step (3) is ≤40°C, and the stirring speed is 150 rpm to 250 rpm.

[0061] The oil-in-water grinding fluid provided by the present invention has a relatively high proportion of the water phase compared with the traditional oil-based grinding fluid, and the heat dissipation efficiency is significantly improved. Moreover, the mineral oil in it reduces the cutting depth of the abrasive grains by 15% to 20%, and reduces the transverse crack density in the double-sided rough grinding stage.

[0062] Preferably, the raw materials for preparing the oil-in-water grinding fluid include mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickener and pH regulator.

[0063] Among them, the mineral oil plays a lubricating role; the diamond particles play an abrasive role; the use of the lipophilic dispersant improves the dispersibility of the diamond particles; the role of the alcohol-based solvent is to reduce the surface tension of the water phase and assist in dispersing the mineral oil and diamond particles; the role of the deionized water is to provide cooling and chip flushing capabilities; the hydrophilic emulsifier is used to stabilize the oil-in-water structure; the thickener is used to increase the viscosity of the oil-in-water grinding fluid and prevent stratification; the role of the pH regulator is to enhance electrostatic stability.

[0064] Preferably, in the raw materials for preparing the oil-in-water grinding fluid, the mass ratio of the mineral oil, the diamond particles, the lipophilic dispersant, the alcohol-based solvent, the deionized water, the hydrophilic emulsifier, the thickener and the pH regulator is (15 - 25):(5 - 10):(2 - 5):(10 - 15):(40 - 50):(5 - 10):(1 - 3):(0.1 - 0.3).

[0065] Preferably, the mineral oil includes paraffin with a melting point of 50°C to 55°C, for example, it can be 50°C, 51°C, 52°C, 53°C, 54°C or 55°C, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0066] Preferably, the median particle size D50 of the diamond particles is 5 μm to 10 μm, for example, it can be 5 μm, 6 μm, 7 μm, 8 μm, 9 μm or 10 μm, but is not limited to the listed values, and the other unlisted values within the numerical range are equally applicable.

[0067] Preferably, the lipophilic dispersant includes Span80 and / or a dispersant blend.

[0068] Preferably, the dispersant blend includes a combination of a polyoxyethylene ether dispersant, oleic acid, and cetyl alcohol.

[0069] Preferably, the alcohol solvent includes ethanol and / or isopropanol.

[0070] Preferably, the hydrophilic emulsifier includes Tween 80 and / or sodium dodecyl sulfate.

[0071] Preferably, the thickener includes carboxymethyl cellulose and / or xanthan gum.

[0072] Preferably, the pH regulator includes ammonia water.

[0073] Preferably, the method for preparing the water-in-oil grinding fluid includes the following steps:

[0074] (a) Mix the diamond particles with the lipophilic dispersant to obtain a premix; then uniformly mix the premix with the mineral oil to obtain an oil-phase material;

[0075] (b) Mix deionized water with the alcohol-based solvent to obtain a mixed solvent; then mix the hydrophilic emulsifier with the pH regulator to obtain an aqueous-phase material;

[0076] (c) Under stirring conditions, drop the aqueous-phase material into the oil-phase material to obtain a crude water-in-oil emulsion; then homogenize the crude water-in-oil emulsion to form a stable water-in-oil emulsion; finally, mix it with the thickener to obtain the water-in-oil grinding fluid;

[0077] Steps (a) and (b) are not in a sequential order.

[0078] Preferably, in step (a), the mineral oil is heated to 60 °C to 65 °C to completely liquefy the mineral oil, and then ultrasonically treated for 30 min to 60 min under the condition of a frequency of 20 kHz to 40 kHz to achieve uniform mixing of the premix and the mineral oil.

[0079] Preferably, the temperature of the mixed solvent in step (b) is 48 °C to 52 °C.

[0080] Preferably, the mixing conditions of the hydrophilic emulsifier are: a stirring speed of 780 rpm to 820 rpm and a time of more than 15 min.

[0081] Preferably, during the preparation of the water-in-oil coarse emulsion in step (c), the shear rate under the shearing condition is 12,000 rpm to 15,000 rpm.

[0082] Preferably, the pressure for homogenization in step (c) is 80 MPa to 100 MPa, and the number of cycles is 3 to 5 times.

[0083] By homogenization in the present invention, the average droplet size in the oil-in-water emulsion is 1 μm to 3 μm.

[0084] Preferably, the mixing temperature of the thickener in step (c) is ≤ 40 °C, and the stirring speed is 150 rpm to 250 rpm.

[0085] The water-in-oil grinding fluid used in the present invention has better lubrication stability than pure water-based fluid under high-pressure environment, the probability of abrasive embedding is reduced by 40% to 50%, and the evaporation of the aqueous phase can also reduce the temperature of the grinding interface to below 60 °C.

[0086] The method provided by the present invention uses an oil-in-water grinding fluid during double-sided rough grinding and a water-in-oil grinding fluid during double-sided fine grinding, and realizes the dynamic matching of thermo-mechanical coupling parameters through the inversion of the grinding liquid phase state; moreover, the grinding pressures for double-sided rough grinding and double-sided fine grinding in the present invention cover the critical pressure of the brittle-ductile transition of silicon carbide, and a smooth transition from brittle fracture to plastic removal is achieved through segmented loading, and the wafer edge integrity (BOW not exceeding 10 μm) is better than that of the constant pressure process.

[0087] Preferably, the surface roughness Ra of the silicon carbide wafer is ≥ 1 μm, and the thickness of the subsurface damage layer is ≥ 5 μm.

[0088] The numerical ranges described in the present invention not only include the point values exemplified above, but also any point values between the above numerical ranges not exemplified. Due to space limitations and for the sake of brevity, the specific point values included in the ranges are not exhaustively listed in the present invention.

[0089] Compared with the prior art, the present invention has the following beneficial effects:

[0090] (1) Through reasonable process design, the method provided by the present invention can effectively remove the wire marks left by the diamond wire after cutting, ensuring that the surface of the silicon carbide wafer is flat and smooth; moreover, the de-marking process can be completed in a short time, thereby improving production efficiency and saving production time; it can also obtain silicon carbide wafers with a surface roughness Ra ≤ 50 nm and a subsurface damage layer thickness ≤ 100 nm;

[0091] (2) The method provided by the present invention uses an oil-in-water grinding fluid during double-sided rough grinding and a water-in-oil grinding fluid during double-sided fine grinding, achieving dynamic matching of thermal-mechanical coupling parameters through the inversion of the grinding fluid phase state. Moreover, the grinding pressure during double-sided rough grinding and double-sided fine grinding of the present invention covers the critical pressure of the brittle-ductile transition of silicon carbide, and a smooth transition from brittle fracture to plastic removal is achieved through segmented loading. The wafer edge integrity (BOW not exceeding 10 μm) is better than that of the constant pressure process. Description of the Drawings

[0092] Figure 1 Atomic force microscopy image of the untreated silicon carbide wafer in Example 1

[0093] Figure 2 Atomic force microscopy image of the silicon carbide wafer treated by the method of Example 1. Detailed Description of the Invention

[0094] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention; unless otherwise specified, the drugs in the specific embodiments of the present invention are all commercially available conventional drugs.

[0095] Preparation Example 1-1

[0096] This preparation example provides an oil-in-water grinding fluid;

[0097] The raw materials for preparing the oil-in-water grinding fluid independently include mineral oil (paraffin with a melting point of 52 °C), diamond particles (median particle size D50 of 8 μm), lipophilic dispersant (Span80), alcohol-based solvent (ethanol), deionized water, hydrophilic emulsifier (Tween 80 and sodium dodecyl sulfate with a mass ratio of 1:1), thickener (carboxymethyl cellulose), and pH regulator (ammonia water with a concentration of 25 wt%).

[0098] The mass ratio of the mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickener, and pH regulator is 20:8:4:12:45:8:2:0.2.

[0099] The preparation method of the oil-in-water grinding fluid includes:

[0100] (1) Mix the diamond particles and the lipophilic dispersant to obtain a premix; then heat the mineral oil to 62 °C, mix it with the premix after the mineral oil is completely liquefied, and then perform ultrasonic treatment for 45 min under the condition of a frequency of 30 kHz to uniformly mix the premix and the mineral oil to obtain an oil phase material;

[0101] (2) Mix deionized water and an alcohol-based solvent to obtain a mixed solvent. Heat the mixed solvent to 50 °C, add a hydrophilic emulsifier, and stir for 15 min at 800 rpm to completely dissolve the hydrophilic emulsifier. Dropwise add a pH regulator to enhance the electrostatic repulsion of the hydrophilic emulsifier to obtain an aqueous phase material.

[0102] (3) Under high-speed shearing conditions of 14,000 rpm, drop the oil phase material into the aqueous phase material to obtain an oil-in-water coarse emulsion. Then homogenize the oil-in-water coarse emulsion (pressure 90 MPa, number of cycles 4 times) to form a stable oil-in-water emulsion. After cooling to 40 °C, mix it with a thickener at a stirring speed of 200 rpm to obtain the oil-in-water type grinding fluid.

[0103] Preparation Example 1-2

[0104] This preparation example provides an oil-in-water type grinding fluid.

[0105] The raw materials for preparing the oil-in-water type grinding fluid independently include mineral oil (paraffin with a melting point of 50 °C), diamond particles (median particle size D50 is 5 μm), lipophilic dispersant (Span80), alcohol-based solvent (isopropyl alcohol), deionized water, hydrophilic emulsifier (Tween 80 and sodium dodecyl sulfate with a mass ratio of 1:1), thickener (xanthan gum), and pH regulator (ammonia water with a concentration of 25 wt%).

[0106] The mass ratio of the mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickener, and pH regulator is 15:10:5:10:40:10:3:0.3.

[0107] The preparation method of the oil-in-water type grinding fluid includes:

[0108] (1) Mix diamond particles and a lipophilic dispersant to obtain a premix. Then heat the mineral oil to 60 °C, mix it with the premix after the mineral oil is completely liquefied, and then perform ultrasonic treatment for 60 min under the condition of a frequency of 20 kHz to uniformly mix the premix and the mineral oil to obtain an oil phase material.

[0109] (2) Mix deionized water and an alcohol-based solvent to obtain a mixed solvent. Heat the mixed solvent to 48 °C, add a hydrophilic emulsifier, and stir for 15 min at 780 rpm to completely dissolve the hydrophilic emulsifier. Dropwise add a pH regulator to enhance the electrostatic repulsion of the hydrophilic emulsifier to obtain an aqueous phase material.

[0110] (3) Under the condition of high-speed shearing at 12,000 rpm, the oil-phase droplets are dropped into the water-phase material to obtain a water-in-oil coarse emulsion; then the water-in-oil coarse emulsion is homogenized (pressure 80 MPa, number of cycles 5 times) to form a stable water-in-oil emulsion; after cooling to 40 °C, it is mixed with a thickening agent under the condition of a stirring speed of 200 rpm to obtain the water-in-oil type grinding fluid.

[0111] Preparation Examples 1-3

[0112] This preparation example provides a water-in-oil type grinding fluid;

[0113] The raw materials for preparing the water-in-oil type grinding fluid independently include mineral oil (paraffin with a melting point of 55 °C), diamond particles (median particle size D50 is 10 μm), lipophilic dispersant (Span80), alcohol-based solvent (ethanol), deionized water, hydrophilic emulsifier (Tween 80 and sodium dodecyl sulfate with a mass ratio of 1:1), thickening agent (xanthan gum) and pH regulator (ammonia water with a concentration of 25 wt%).

[0114] The mass ratio of the mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickening agent and pH regulator is 25:5:2:15:50:5:1:0.1.

[0115] The preparation method of the water-in-oil type grinding fluid includes:

[0116] (1) Mix the diamond particles and the lipophilic dispersant to obtain a premix; then heat the mineral oil to 65 °C, mix it with the premix after the mineral oil is completely liquefied, and then perform ultrasonic treatment for 30 min under the condition of a frequency of 40 kHz to uniformly mix the premix and the mineral oil to obtain an oil-phase material;

[0117] (2) Mix the deionized water and the alcohol-based solvent to obtain a mixed solvent; heat the mixed solvent to 52 °C, add the hydrophilic emulsifier, and stir for 15 min at 820 rpm to completely dissolve the hydrophilic emulsifier; dropwise add the pH regulator to enhance the electrostatic repulsion of the hydrophilic emulsifier to obtain a water-phase material;

[0118] (3) Under the condition of high-speed shearing at 15,000 rpm, the oil-phase material is dropped into the water-phase material to obtain a water-in-oil coarse emulsion; then the water-in-oil coarse emulsion is homogenized (pressure 100 MPa, number of cycles 3 times) to form a stable water-in-oil emulsion; after cooling to 40 °C, it is mixed with a thickening agent under the condition of a stirring speed of 200 rpm to obtain the water-in-oil type grinding fluid.

[0119] Preparation Example 2-1

[0120] This preparation example provides an oil-in-water type grinding fluid;

[0121] The raw materials for preparing the water-in-oil grinding fluid independently include mineral oil (paraffin with a melting point of 52 °C), diamond particles (median particle size D50 is 8 μm), lipophilic dispersant (Span80), alcohol-based solvent (ethanol), deionized water, hydrophilic emulsifier (Tween 80 and sodium dodecyl sulfate with a mass ratio of 1:1), thickening agent (carboxymethyl cellulose), and pH regulator (ammonia water with a concentration of 25 wt%).

[0122] The mass ratio of the mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickening agent, and pH regulator is 20:8:4:12:45:8:2:0.2.

[0123] The preparation method of the water-in-oil grinding fluid includes:

[0124] (a) Mix the diamond particles and the lipophilic dispersant to obtain a premix; then heat the mineral oil to 62 °C, mix the premix with the completely liquefied mineral oil, and then perform ultrasonic treatment for 45 min under the condition of a frequency of 30 kHz to uniformly mix the premix and the mineral oil to obtain an oil-phase material;

[0125] (b) Mix the deionized water and the alcohol-based solvent to obtain a mixed solvent; heat the mixed solvent to 50 °C, add the hydrophilic emulsifier, and stir at 800 rpm for 15 min to completely dissolve the hydrophilic emulsifier; dropwise add the pH regulator to enhance the electrostatic repulsion of the hydrophilic emulsifier to obtain a water-phase material;

[0126] (c) Under the condition of high-speed shearing at 14000 rpm, drop the water-phase material into the oil-phase material to obtain a water-in-oil coarse emulsion; then homogenize the water-in-oil coarse emulsion (pressure 90 MPa, number of cycles 4 times) to form a stable water-in-oil emulsion; cool down to 40 °C and mix with the thickening agent under the condition of a stirring speed of 200 rpm to obtain the water-in-oil grinding fluid.

[0127] Preparation Examples 1-2

[0128] This preparation example provides a water-in-oil grinding fluid;

[0129] The raw materials for preparing the water-in-oil grinding fluid independently include mineral oil (paraffin with a melting point of 50 °C), diamond particles (median particle size D50 is 5 μm), lipophilic dispersant (Span80), alcohol-based solvent (isopropanol), deionized water, hydrophilic emulsifier (Tween 80 and sodium dodecyl sulfate with a mass ratio of 1:1), thickening agent (xanthan gum), and pH regulator (ammonia water with a concentration of 25 wt%).

[0130] The mass ratio of the mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickener and pH regulator is 15:10:5:10:40:10:3:0.3.

[0131] The preparation method of the water-in-oil type grinding fluid comprises:

[0132] (1) Mix the diamond particles and the lipophilic dispersant to obtain a premix; then heat the mineral oil to 60 °C, mix the premix with the mineral oil after the mineral oil is completely liquefied, and then perform ultrasonic treatment for 60 min under the condition of a frequency of 20 kHz to uniformly mix the premix and the mineral oil, thereby obtaining an oil-phase material;

[0133] (2) Mix the deionized water and the alcohol-based solvent to obtain a mixed solvent; heat the mixed solvent to 48 °C, add the hydrophilic emulsifier, and stir for 15 min at 780 rpm to completely dissolve the hydrophilic emulsifier; dropwise add the pH regulator to enhance the electrostatic repulsion of the hydrophilic emulsifier, thereby obtaining a water-phase material;

[0134] (3) Under the condition of high-speed shearing at 12,000 rpm, drop the water-phase material into the oil-phase material to obtain a water-in-oil coarse emulsion; then homogenize the water-in-oil coarse emulsion (pressure 80 MPa, number of cycles 5 times) to form a stable water-in-oil emulsion; after cooling to 40 °C, mix with the thickener under the condition of a stirring speed of 200 rpm to obtain the water-in-oil type grinding fluid.

[0135] Preparation Examples 1-3

[0136] This preparation example provides a water-in-oil type grinding fluid;

[0137] The raw materials for preparing the water-in-oil type grinding fluid independently include a mineral oil (paraffin with a melting point of 55 °C), diamond particles (median particle size D50 is 10 μm), a lipophilic dispersant (Span80), an alcohol-based solvent (ethanol), deionized water, a hydrophilic emulsifier (Tween 80 and sodium dodecyl sulfate with a mass ratio of 1:1), a thickener (xanthan gum) and a pH regulator (ammonia water with a concentration of 25 wt%).

[0138] The mass ratio of the mineral oil, diamond particles, lipophilic dispersant, alcohol-based solvent, deionized water, hydrophilic emulsifier, thickener and pH regulator is 25:5:2:15:50:5:1:0.1.

[0139] The preparation method of the water-in-oil type grinding fluid comprises:

[0140] (1) Mix diamond particles with a lipophilic dispersant to obtain a premix; then heat the mineral oil to 65 °C until the mineral oil is completely liquefied, mix it with the premix, and then perform ultrasonic treatment for 30 min under the condition of a frequency of 40 kHz to uniformly mix the premix and the mineral oil to obtain an oil-phase material;

[0141] (2) Mix deionized water and an alcohol-based solvent to obtain a mixed solvent; heat the mixed solvent to 52 °C, add a hydrophilic emulsifier, and stir for 15 min at 820 rpm until the hydrophilic emulsifier is completely dissolved; dropwise add a pH regulator to enhance the electrostatic repulsion of the hydrophilic emulsifier to obtain an aqueous-phase material;

[0142] (3) Under the condition of high-speed shearing at 15000 rpm, drop the aqueous-phase material into the oil-phase material to obtain a water-in-oil coarse emulsion; then homogenize the water-in-oil coarse emulsion (pressure 100 MPa, number of cycles 3 times) to form a stable water-in-oil emulsion; after cooling to 40 °C, mix it with a thickener under the condition of a stirring speed of 200 rpm to obtain the water-in-oil type grinding fluid.

[0143] Example 1

[0144] This example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. The initial surface roughness Ra of the silicon carbide wafer (see Figure 1 , the vertical stripes are wire marks) is 3 μm, and the thickness of the subsurface damage layer is 24 μm. The method includes the following steps:

[0145] (1) Place 2 stacked silicon carbide wafers on a flat cast iron plate to ensure the flatness of the silicon carbide wafers during the grinding process, and then use the oil-in-water type grinding fluid in Preparation Example 1-1 for double-sided rough grinding. After double-sided rough grinding, perform washing;

[0146] The double-sided rough grinding includes the first rough grinding, the second rough grinding, and the third rough grinding performed in sequence; the grinding pressure of the first rough grinding is 35 g / cm 2 , the grinding speed is 20 r / min, and the time is 5 min; the grinding pressure of the second rough grinding is 100 g / cm 2 , the grinding speed is 20 r / min, and the time is 10 min; the grinding pressure of the third rough grinding is 150 g / cm 2 , the grinding speed is 28 r / min, and the time is 15 min.

[0147] (2) Then use the water-in-oil type grinding fluid in Preparation Example 2-1 for double-sided fine grinding. After double-sided fine grinding, perform cleaning to complete the removal of wire marks on the surface of the silicon carbide wafer;

[0148] The grinding pressure of the double-sided fine grinding is 150 g / cm 2, the grinding speed is 30 r / min.

[0149] The atomic force microscope image of the silicon carbide wafer processed by the method of this embodiment is as Figure 2 shown. It can be seen from Figure 2 that this embodiment can eliminate wire marks.

[0150] Example 2

[0151] This embodiment provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. The initial surface roughness Ra of the silicon carbide wafer to be processed is 4 μm, and the thickness of the subsurface damage layer is 35 μm. The method includes the following steps:

[0152] (1) Two stacked silicon carbide wafers are placed on a flat cast iron plate to ensure the flatness of the silicon carbide wafers during the grinding process. Then, the water-in-oil grinding fluid in Preparation Example 1-1 is used for double-sided rough grinding. After the double-sided rough grinding is completed, washing is carried out;

[0153] The double-sided rough grinding includes the first rough grinding, the second rough grinding, and the third rough grinding carried out in sequence; the grinding pressure of the first rough grinding is 20 g / cm 2 , the grinding speed is 10 r / min, and the time is 5 min; the grinding pressure of the second rough grinding is 50 g / cm 2 , the grinding speed is 15 r / min, and the time is 10 min; the grinding pressure of the third rough grinding is 140 g / cm 2 , the grinding speed is 25 r / min, and the time is 15 min.

[0154] (2) Then, the oil-in-water grinding fluid in Preparation Example 2-1 is used for double-sided fine grinding. After the double-sided fine grinding, cleaning is carried out to complete the removal of the wire marks on the surface of the silicon carbide wafer;

[0155] The grinding pressure of the double-sided fine grinding is 100 g / cm 2 , and the grinding speed is 10 r / min.

[0156] Example 3

[0157] This embodiment provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. The initial surface roughness Ra of the silicon carbide wafer to be processed is 4.9 μm, and the thickness of the subsurface damage layer is 42 μm. The method includes the following steps:

[0158] (1) Two stacked silicon carbide wafers are placed on a flat cast iron plate to ensure the flatness of the silicon carbide wafers during the grinding process. Then, the water-in-oil grinding fluid in Preparation Example 1-1 is used for double-sided rough grinding. After the double-sided rough grinding is completed, washing is carried out;

[0159] The double-sided rough grinding includes first rough grinding, second rough grinding, and third rough grinding performed in sequence; the grinding pressure for the first rough grinding is 50 g / cm 2 , the grinding rotation speed is 30 r / min, and the time is 5 min; the grinding pressure for the second rough grinding is 150 g / cm 2 , the grinding rotation speed is 25 r / min, and the time is 10 min; the grinding pressure for the third rough grinding is 160 g / cm 2 , the grinding rotation speed is 30 r / min, and the time is 15 min.

[0160] (2) Then, use the water-in-oil grinding fluid in Preparation Example 2-1 for double-sided fine grinding. After double-sided fine grinding, perform cleaning to complete the removal of the wire marks on the surface of the silicon carbide wafer;

[0161] The grinding pressure for the double-sided fine grinding is 200 g / cm 2 , and the grinding rotation speed is 50 r / min.

[0162] Example 4

[0163] This example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except that the water-in-oil grinding fluid in Preparation Example 1-2 is used for double-sided rough grinding and the water-in-oil grinding fluid in Preparation Example 2-2 is used for double-sided fine grinding, the rest are the same as in Example 1.

[0164] Example 5

[0165] This example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except that the water-in-oil grinding fluid in Preparation Example 1-3 is used for double-sided rough grinding and the water-in-oil grinding fluid in Preparation Example 2-3 is used for double-sided fine grinding, the rest are the same as in Example 1.

[0166] Example 6

[0167] This example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except that the first rough grinding is not performed and the time of the second rough grinding and the third rough grinding is increased proportionally to keep the total time of double-sided rough grinding unchanged, the rest are the same as in Example 1.

[0168] Example 7

[0169] This example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except that the second rough grinding is not performed and the time of the first rough grinding and the third rough grinding is increased proportionally to keep the total time of double-sided rough grinding unchanged, the rest are the same as in Example 1.

[0170] Example 8

[0171] This embodiment provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except for not performing the third rough grinding and increasing the time of the first rough grinding and the second rough grinding in equal proportion to keep the total time of double-sided rough grinding unchanged, the rest are the same as in Embodiment 1.

[0172] Comparative Example 1

[0173] This comparative example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except for using the water-in-oil grinding fluid provided in Preparation Example 1-1 for both double-sided rough grinding and double-sided fine grinding, the rest are the same as in Embodiment 1.

[0174] Comparative Example 2

[0175] This comparative example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except for using the oil-in-water grinding fluid provided in Preparation Example 2-1 for both double-sided rough grinding and double-sided fine grinding, the rest are the same as in Embodiment 1.

[0176] Comparative Example 3

[0177] This comparative example provides a method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding. Except for sequentially performing double-sided rough grinding and double-sided fine grinding on only 1 silicon carbide wafer, the rest are the same as in Embodiment 1.

[0178] Characterization

[0179] Characterize the effects of the methods provided in the above embodiments and comparative examples, measure the surface roughness and the thickness of the subsurface damage layer of the silicon carbide wafer, and the obtained results are shown in Table 1.

[0180] Among them, the surface roughness Ra is measured by an atomic force microscope (AFM); the thickness of the subsurface damage layer is measured by a transmission electron microscope (TEM).

[0181] Table 1

[0182]

[0183]

[0184]

[0185] In summary, through reasonable process design, the method provided by the present invention can effectively remove the wire marks left by the diamond wire after cutting, ensuring that the surface of the silicon carbide wafer is flat and smooth; moreover, the deburring process can be completed in a short time, thereby improving production efficiency and saving production time; it can also produce silicon carbide wafers with a surface roughness Ra≤50nm and a thickness of the subsurface damage layer≤100nm; in the method provided by the present invention, an oil-in-water type grinding fluid is used for double-sided rough grinding, and a water-in-oil type grinding fluid is used for double-sided fine grinding, realizing the dynamic matching of thermal-mechanical coupling parameters through the inversion of the grinding fluid phase state; moreover, the grinding pressure for double-sided rough grinding and double-sided fine grinding of the present invention covers the critical pressure of the brittle-ductile transition of silicon carbide, and a smooth transition from brittle fracture to plastic removal is achieved through segmented loading, and the wafer edge integrity (BOW not exceeding 10μm) is better than that of the constant pressure process.

[0186] The applicant declares that the above description is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily thought of by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for eliminating wire marks on a silicon carbide wafer cut by a diamond wire through double grinding, characterized in that, The method includes the following steps: Double-sided rough grinding and double-sided fine grinding are sequentially performed on two stacked silicon carbide wafers, followed by cleaning to remove surface scratches on the silicon carbide wafers. An oil-in-water grinding fluid is used for the double-sided rough grinding. A water-in-oil grinding fluid is used for the double-sided fine grinding.

2. The method according to claim 1, characterized in that, The double-sided rough grinding includes first rough grinding, second rough grinding, and third rough grinding performed in sequence. The grinding pressure for the first rough grinding is 20 g / cm 2 ~50 g / cm 2 , and the grinding speed is 10 r / min to 30 r / min; The grinding pressure for the second rough grinding is 50 g / cm 2 ~150 g / cm 2 , and the grinding speed is 15 r / min to 25 r / min; The grinding pressure of the third rough grinding is 140 g / cm 2 ~160 g / cm 2 , and the grinding speed is 25 r / min to 30 r / min.

3. The method according to claim 1 or 2, characterized in that, The grinding pressure for the double-sided fine grinding is 100 g / cm 2 ~200 g / cm 2 , and the grinding rotation speed is 10 r / min to 50 r / min.

4. The method according to claim 1, wherein The raw materials for preparing the oil-in-water grinding fluid include mineral oil, diamond particles, lipophilic dispersants, alcohol-based solvents, deionized water, hydrophilic emulsifiers, thickeners, and pH regulators. And / or, in the raw materials for preparing the oil-in-water grinding fluid, the mass ratio of the mineral oil, the diamond particles, the lipophilic dispersants, the alcohol-based solvents, the deionized water, the hydrophilic emulsifiers, the thickeners, and the pH regulators is (15 - 25):(5 - 10):(2 - 5):(10 - 15):(40 - 50):(5 - 10):(1 - 3):(0.1 - 0.3).

5. The method according to claim 4, wherein The mineral oil includes paraffin with a melting point of 50°C to 55°C. And / or, the median particle size D50 of the diamond particles is 5μm to 10μm. And / or, the lipophilic dispersant includes Span80 and / or a dispersant blend. And / or, the dispersant blend includes a combination of polyoxyethylene ether dispersants, oleic acid, and cetyl alcohol. And / or, the alcohol solvents include ethanol and / or isopropyl alcohol. And / or, the hydrophilic emulsifier includes Tween 80 and / or sodium dodecyl sulfate. And / or, the thickener includes carboxymethyl cellulose and / or xanthan gum. And / or, the pH regulator includes ammonia water.

6. The method according to claim 4 or 5, characterized in that, The method for preparing the oil-in-water grinding fluid includes the following steps: (1) Mix the diamond particles and the lipophilic dispersants to obtain a premix; then uniformly mix the premix with the mineral oil to obtain an oil phase material. (2) Mix the deionized water and the alcohol-based solvent to obtain a mixed solvent; then mix the hydrophilic emulsifier, the pH regulator, and the mixed solvent to obtain a water phase material. (3) Under shear conditions, drop the oil phase material into the water phase material to obtain a crude oil-in-water emulsion; then homogenize the crude oil-in-water emulsion to form a stable oil-in-water emulsion; finally, mix it with the thickener to obtain the oil-in-water grinding fluid. Steps (1) and (2) are not in a sequential order.

7. The method according to claim 1, characterized in that, The raw materials for preparing the water-in-oil grinding fluid include mineral oil, diamond particles, lipophilic dispersants, alcohol-based solvents, deionized water, hydrophilic emulsifiers, thickeners, and pH regulators. And / or, in the raw materials for preparing the water-in-oil grinding fluid, the mass ratio of the mineral oil, the diamond particles, the lipophilic dispersants, the alcohol-based solvents, the deionized water, the hydrophilic emulsifiers, the thickeners, and the pH regulators is (15 - 25):(5 - 10):(2 - 5):(10 - 15):(40 - 50):(5 - 10):(1 - 3):(0.1 - 0.3).

8. The method according to claim 7, characterized in that, The mineral oil includes paraffin with a melting point of 50°C to 55°C. And / or, the median particle size D50 of the diamond particles is 5μm to 10μm. And / or, the lipophilic dispersant includes Span80 and / or a dispersant blend; And / or, the dispersant blend includes a combination of a polyoxyethylene ether dispersant, oleic acid, and cetyl alcohol; And / or, the alcohol solvent includes ethanol and / or isopropyl alcohol; And / or, the hydrophilic emulsifier includes Tween 80 and / or sodium dodecyl sulfate; And / or, the thickener includes carboxymethyl cellulose and / or xanthan gum; And / or, the pH regulator includes ammonia water.

9. The method according to claim 7 or 8, characterized in that The method for preparing the water-in-oil grinding fluid includes the following steps: (a) Mix diamond particles with a lipophilic dispersant to obtain a premix; then uniformly mix the premix with mineral oil to obtain an oil-phase material; (b) Mix deionized water with an alcohol-based solvent to obtain a mixed solvent; then mix a hydrophilic emulsifier with a pH regulator to obtain an aqueous-phase material; (c) Under shear conditions, drop the aqueous-phase material into the oil-phase material to obtain a crude water-in-oil emulsion; then homogenize the crude water-in-oil emulsion to form a stable water-in-oil emulsion; finally, mix it with a thickener to obtain the water-in-oil grinding fluid; Steps (a) and (b) are not in a sequential order.

10. The method according to claim 1, characterized in that, The surface roughness Ra of the silicon carbide wafer is ≥1 μm, and the thickness of the subsurface damage layer is ≥5 μm.

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