Automatic processing method of silicon carbide substrate

Abstract

The invention relates to the technical field of silicon carbide, and particularly discloses an automatic processing method of a silicon carbide substrate. By controlling the removal amount of each process and accurately controlling the thickness of silicon carbide in each process, the matching degree of the previous and later processes is improved, the thickness deviation is reduced, the flatness and uniformity of the substrate are improved, and automatic and accurate control of substrate processing is realized; and by establishing a relational expression between the technological parameters of the laser lift-off process and the thickness and selecting proper laser irradiation parameters according to the target thickness, cracks and subsurface damage on the surface of the substrate are effectively reduced, the fragment rate is remarkably reduced, and the stability and repeatability of the machining process are improved. Through technical innovation, the problems of low efficiency, large damage and the like of the traditional process for processing silicon carbide are solved, the labor cost and the manufacturing cost are effectively reduced, large-scale industrial production is conveniently realized, a novel and efficient method is provided for high-quality processing of the silicon carbide substrate, and the method has important industrial application value.

Description

Technical Field

[0001] The present invention relates to the technical field of silicon carbide, and in particular to an automated processing method for a silicon carbide substrate. Background Art

[0002] With the rapid development of semiconductor technology, silicon carbide (SiC), as a third-generation semiconductor material, has become an ideal material for manufacturing high-temperature, high-frequency, and high-power electronic devices due to its excellent physical and chemical properties, such as high thermal conductivity, high electron saturation drift velocity, high critical breakdown electric field, and good chemical stability. These devices are widely used in new energy vehicles, 5G communications, photovoltaic power generation, aerospace, and other fields, which put forward higher requirements on the quality and performance of substrate materials.

[0003] However, traditional silicon carbide substrate processing technology has many limitations. For example, traditional cutting technology often causes cracks and damage on the surface and subsurface of silicon carbide substrates, increasing the substrate fragmentation rate and manufacturing cost. In addition, traditional grinding and polishing processes are inefficient, take a long time to process, and it is difficult to ensure the flatness and uniformity of the entire batch of substrates, which limits the performance and reliability of silicon carbide devices. Automated processing of silicon carbide substrates has the advantages of short process and high production efficiency, and has become the mainstream method pursued by silicon carbide substrate processing. However, the realization of automatic integrated processing of substrates has strict requirements on processing methods and is difficult to control the process. Therefore, there is an urgent need for a new processing method for silicon carbide substrates to improve the processing efficiency of silicon carbide substrates, ensure the quality and performance of processed substrates, and at the same time, reduce the substrate fragmentation rate and manufacturing cost. Summary of the invention

[0004] In view of the problems existing in the prior art of processing methods for silicon carbide substrates, such as low process efficiency, long processing time, high breakage rate, and difficulty in ensuring the flatness and uniformity of a whole batch of substrates, the present invention provides an automated processing method for silicon carbide substrates.

[0005] In order to solve the above technical problems, the technical solution provided by the present invention is:

[0006] An automated processing method for a silicon carbide substrate comprises the following steps:

[0007] S1, ultra-precision grinding the carbon surface of the silicon carbide ingot, with a thinning amount of 5 μm to 10 μm, to obtain a finely ground silicon carbide ingot;

[0008] S2, irradiating the silicon surface of the finely ground silicon carbide ingot with laser, peeling the wafer from the finely ground silicon carbide ingot, and obtaining a silicon carbide wafer; the number of laser peeling is 2≤K≤5;

[0009] If the target thickness of the silicon carbide substrate is 500 μm, the thickness d1 of the silicon carbide wafer is controlled to be 520 μm≤d1≤555 μm, d1=3.04L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5;

[0010] If the target thickness of the silicon carbide substrate is 350 μm, the thickness d2 of the silicon carbide wafer is controlled to be 370 μm ≤ d2 ≤ 405 μm, d2 = 2.34L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5; L is the cutting depth, P k is the cutting power of the Kth laser stripping, and 0.5≤P K+1 -P K ≤1.5;

[0011] S3, sequentially performing rough grinding and fine grinding on the silicon surface of the silicon carbide wafer to obtain a thinned wafer; wherein the removal amount of the rough grinding is 15 μm to 35 μm, and the removal amount of the fine grinding is 5 μm to 10 μm;

[0012] If the target thickness of the silicon carbide substrate is 500 μm, the thickness h1 after rough grinding and thinning is controlled to be 505 μm ≤ h1 ≤ 520 μm, and the thickness h2 after fine grinding and thinning is controlled to be 500 μm ≤ h2 ≤ 510 μm;

[0013] If the target thickness of the silicon carbide substrate is 350 μm, the thickness h3 after rough grinding and thinning is controlled to be 355 μm ≤ h3 ≤ 370 μm, and the thickness h4 after fine grinding and thinning is controlled to be 350 μm ≤ h4 ≤ 360 μm;

[0014] S4, double-sided polishing the thinned sheet, with a total removal amount of 3 μm to 6 μm, to obtain a polished sheet;

[0015] If the target thickness of the silicon carbide substrate is 500 μm, the thickness m1 of the polishing sheet is controlled to be 497 μm ≤ m1 ≤ 504 μm;

[0016] If the target thickness of the silicon carbide substrate is 350 μm, the thickness m2 of the polishing sheet is controlled to be 347 μm ≤ m2 ≤ 354 μm;

[0017] S5, chemically cleaning the polishing sheet to obtain a silicon carbide substrate.

[0018] It should be noted that the entire silicon carbide substrate processing process in the present invention adopts plug transmission. Plug transmission has the advantages of high efficiency, good substrate processing quality, and effective reduction of material loss, and is suitable for automated production processes. However, plug transmission has high requirements for the precision of the processing technology, the thickness deviation of the substrate, and the matching degree of the previous and next processes.

[0019] Compared with the prior art, the automated processing method for silicon carbide substrates provided by the present invention controls the removal amount of each process and accurately controls the thickness of silicon carbide in each process, thereby improving the matching degree between the previous and subsequent processes, reducing the thickness deviation, improving the flatness and uniformity of the substrate, and realizing automated and precise control of substrate processing; and by establishing a relationship between the process parameters and the thickness of the laser stripping process, appropriate laser irradiation parameters are selected according to the target thickness, which effectively reduces cracks and sub-surface damage on the substrate surface, significantly reduces the fragmentation rate, and improves the stability and repeatability of the processing process.

[0020] The improved processing method of silicon carbide substrates of the present invention solves the problems of low efficiency and large damage in the traditional processing of silicon carbide through technological innovation, effectively reduces labor costs and manufacturing costs, facilitates large-scale industrial production, and provides a new and efficient method for high-quality processing of silicon carbide substrates, which has important industrial application value and market prospects.

[0021] Furthermore, in S1, a wafer thinning machine is used to perform ultra-precision grinding on the silicon carbide ingot, the mesh size of the grinding wheel is 8000 to 30000, the spindle speed is 3100rpm to 3300rpm, the worktable speed is 200rpm to 280rpm, the feed speed in the starting stage is 0.2μm / s to 0.5μm / s, the feed speed in the processing stage is 0.1μm / s to 0.4μm / s, the feed speed in the deceleration stage is 0.05μm / s to 0.2μm / s, and the working time is 300s to 400s.

[0022] Furthermore, in S2, the wavelength of the laser irradiation is 800nm-1000nm, the cutting power is 14W-25W, the cutting depth is 190μm-200μm, the cutting speed is 400mm / s-700mm / s, and the laser stripping time is 15min / sheet-35min / sheet.

[0023] It should be noted that the cutting power of each stripping is selected according to the relationship in S2, and the power of each stripping is within the range of 14W to 25W and satisfies 0.5≤P K+1 -P K ≤1.5, that is, the requirement of increasing cutting power in a gradual manner is met.

[0024] The optimal laser irradiation parameters can reduce processing stress, reduce the fragmentation rate, and are conducive to obtaining a relatively smooth peeling surface, reducing the roughness of the peeling surface, thereby reducing material loss in subsequent grinding, while improving the silicon carbide peeling efficiency and reducing production costs.

[0025] Furthermore, in S3, the spindle speed of the rough grinding and thinning is 2500rpm~3500rpm, the spindle speed of the fine grinding and thinning is 2200rpm~3200rpm, the speed of the workbench is 150rpm~350rpm, and the total time of the rough grinding and thinning and the fine grinding and thinning is 600s~900s, wherein the time of the rough grinding and thinning is 350s~500s, and the time of the fine grinding and thinning is 250s~400s.

[0026] Furthermore, in S3, the mesh number of the rough grinding and thinning grinding wheel is 1500-2500 mesh, the feed speed in the initial stage is 0.3μm / s-0.6μm / s, the feed speed in the processing stage is 0.2μm / s-0.4μm / s, and the feed speed in the deceleration stage is 0.1μm / s-0.3μm / s; the mesh number of the fine grinding and thinning grinding wheel is 20000-30000 mesh, the feed speed in the initial stage is 0.2μm / s-0.5μm / s, the feed speed in the processing stage is 0.1μm / s-0.4μm / s, and the feed speed in the deceleration stage is 0.05μm / s-0.2μm / s.

[0027] By controlling the above-mentioned preferred thinning parameters, the damage on the surface of the silicon carbide substrate can be reduced, the overall quality of wafer processing can be improved, and the flatness of the wafer can be improved, while the loss of subsequent polishing materials can be reduced.

[0028] Further, in S4, the rotation speed of the grinding wheel for double-sided polishing is 100 rpm to 200 rpm, and the total polishing time is 1000 s to 1800 s.

[0029] Furthermore, in S5, the polishing sheet is transported by plugging for chemical cleaning.

[0030] The automated processing of silicon carbide substrates using plug transmission can eliminate the pre-cleaning process and the cleaning steps of paraffin residue in the traditional cleaning process of ceramic disc adhesion, effectively improving the processing efficiency of silicon carbide.

[0031] Further, in S5, the chemical cleaning specifically includes the following steps:

[0032] Step a, placing the polishing sheet into a plug, immersing it in an acidic oxidizing solution a, soaking and cleaning, and obtaining a first cleaning sheet; the acidic oxidizing solution a comprises concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3.5:1 to 4:1;

[0033] Step b, immersing the first cleaning sheet in an alkaline oxidizing solution for soaking and cleaning to obtain a second cleaning sheet; the alkaline oxidizing solution comprises ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:11 to 1:1:15;

[0034] Step c, immersing the second cleaning sheet in an acidic oxidizing solution b for soaking and cleaning to obtain a third cleaning sheet; the acidic oxidizing solution b comprises hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:11 to 1:1:15;

[0035] Step d, immersing the third cleaning sheet in a hydrofluoric acid solution, soaking and cleaning, rinsing with deionized water, and drying to obtain a silicon carbide substrate.

[0036] The above cleaning method can effectively remove the residue on the surface of the silicon carbide wafer, and at the same time, it can avoid damage to the silicon carbide wafer and ensure the quality of silicon carbide.

[0037] It should be noted that the above chemicals are all commercially available products, among which the mass concentration of concentrated sulfuric acid is 98%, the mass concentration of hydrogen peroxide is 30%, the mass concentration of ammonia water is 28%, the mass concentration of hydrochloric acid is 37%, and the mass concentration of hydrofluoric acid is 49%.

[0038] Furthermore, in step a, the immersion cleaning temperature is 110° C. to 120° C., and the immersion cleaning time is 900s to 1100s.

[0039] Furthermore, in step b, the immersion cleaning temperature is 60° C. to 70° C., and the immersion cleaning time is 700s to 800s.

[0040] Furthermore, in step c, the immersion cleaning temperature is 60° C. to 70° C., and the immersion cleaning time is 700s to 800s.

[0041] Furthermore, in step d, the immersion cleaning temperature is 30° C. to 40° C., and the immersion cleaning time is 700s to 800s.

[0042] It should be noted that after each step of the above-mentioned liquid cleaning is completed, it is rinsed with deionized water before being transferred to the next step of liquid cleaning.

[0043] Specifically, the hydrofluoric acid solution is prepared by mixing hydrofluoric acid and deionized water in a volume ratio of 1:13 to 1:15.

[0044] Compared with the prior art, the beneficial effect of the present technical solution is that the processing method of the silicon carbide substrate provided by the present invention realizes high-precision automated integrated processing of silicon carbide by controlling the processing process parameters and accurately determining the thickness and removal amount of silicon carbide at each stage, thereby reducing the fragmentation rate and material loss, increasing production efficiency by 5% to 10%, increasing the first-time processing pass rate by more than 5%, and reducing material loss by 8% to 10%. It can play a positive role in improving the production efficiency and reducing production costs of silicon carbide substrates, and has broad application prospects in the field of silicon carbide substrate production. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 Schematic diagram of the processing flow of a silicon carbide substrate in an embodiment of the present invention;

[0046] Figure 2 Schematic diagram of the processing flow of the silicon carbide substrate in Comparative Example 1 of the present invention;

[0047] Figure 3 This is a distribution diagram of small particles on the surface of the silicon carbide substrate prepared in Example 1 of the present invention;

[0048] Figure 4 This is a distribution diagram of small particles on the surface of a silicon carbide substrate prepared in Example 2 of the present invention;

[0049] Figure 5 This is a distribution diagram of small particles on the surface of a silicon carbide substrate prepared in Example 3 of the present invention;

[0050] Figure 6 This is a distribution diagram of small particles on the surface of a silicon carbide substrate prepared in Example 4 of the present invention;

[0051] Figure 7 This is a distribution diagram of small particles on the surface of a silicon carbide substrate prepared in Example 5 of the present invention;

[0052] Figure 8 This is a distribution diagram of small particles on the surface of a silicon carbide substrate prepared in Comparative Example 1 of the present invention;

[0053] Fig. 9 This is a distribution diagram of small particles on the surface of a silicon carbide substrate prepared in Comparative Example 2 of the present invention;

[0054] Fig.10 This is a distribution diagram of small particles on the surface of the silicon carbide substrate prepared in Comparative Example 3 of the present invention. DETAILED DESCRIPTION

[0055] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0056] In order to better illustrate the present invention, further examples are given below.

[0057] Unless otherwise specified, the reagents and equipment used in the following examples and comparative examples are all commercially available products, wherein the mass concentration of concentrated sulfuric acid is 98%, the mass concentration of hydrogen peroxide is 30%, the mass concentration of ammonia water is 28%, the mass concentration of hydrochloric acid is 37%, and the mass concentration of hydrofluoric acid is 49%.

[0058] Example 1

[0059] This embodiment provides an automated processing method for a 6-inch semi-insulating silicon carbide substrate with a target thickness of 500 μm, comprising the following steps:

[0060] S1, using a wafer thinning machine to ultra-precision grind the carbon surface of the silicon carbide ingot, the mesh number of the grinding wheel is 30000, the spindle speed is 3100rpm, the speed of the worktable is 200rpm, the feed speed in the initial stage is 0.2μm / s, the feed speed in the processing stage is 0.1μm / s, the feed speed in the deceleration stage is 0.05μm / s, the processing time is 300s, the thinning amount is 5μm, and the finely ground silicon carbide ingot is obtained;

[0061] S2, laser irradiation is performed on the silicon surface of the finely ground silicon carbide ingot, the laser stripping times are 3 times, the wavelength is 800nm, the cutting depth is 195μm, the cutting speed is 400mm / s, the laser cutting power is 16.5W, 17.5W, and 18.5W respectively, the laser stripping time is 20min / wafer, and the wafer is stripped from the finely ground silicon carbide ingot to obtain a silicon carbide wafer; the thickness of the wafer is d1=3.04L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5=3.04×195-1.001×16.5-0.999×17.5-0.995×18.5=540.39μm;

[0062] S3, the silicon surface of the silicon carbide wafer is subjected to rough grinding and thinning in sequence, the mesh number of the grinding wheel is 1500 mesh, the spindle speed is 3500rpm, the speed of the worktable is 350rpm, the feed speed in the initial stage is 0.6μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.3μm / s, the processing time is 450s, and the removal amount of rough thinning is 30μm; then fine grinding and thinning are performed, the mesh number of the grinding wheel is 30000 mesh, the spindle speed is 3200rpm, the speed of the worktable is 350rpm, the feed speed in the initial stage is 0.5μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.2μm / s, the processing time is 250s, the removal amount of fine thinning is 5μm, the total processing time is 700s, and the thickness of the substrate after thinning is 505.39μm;

[0063] S4, double-sided polishing of the thinned sheet, the polishing pad is a damping polishing pad, the polishing liquid is an aluminum oxide polishing liquid, the grinding wheel speed is 200 rpm, the total polishing time is 1200 s, the total removal amount of double-sided polishing is 4 μm, and a polished sheet with a thickness of 501.39 μm is obtained;

[0064] S5, chemically cleaning the polishing sheet:

[0065] SC3: Immerse the polishing sheet in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3.5:1, soak and clean at 110°C for 1100s, and rinse with deionized water to obtain the first cleaned sheet;

[0066] SC1: immerse the first cleaning sheet in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:15, soak and clean at 70°C for 800s, and rinse with deionized water to obtain a second cleaning sheet;

[0067] SC2: immerse the second cleaning sheet in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:15, soak and clean at 70°C for 800s, and rinse with deionized water to obtain a third cleaning sheet;

[0068] DHF: The third cleaning sheet was immersed in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:15, immersed at 40° C. for 800 seconds, rinsed with deionized water, and dried to obtain a silicon carbide substrate.

[0069] Example 2

[0070] This embodiment provides an automated processing method for a 6-inch semi-insulating silicon carbide substrate with a target thickness of 500 μm, comprising the following steps:

[0071] S1, using a wafer thinning machine to ultra-precision grind the carbon surface of the silicon carbide ingot, the mesh number of the grinding wheel is 10000, the spindle speed is 3300rpm, the speed of the worktable is 280rpm, the feed speed in the initial stage is 0.5μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.2μm / s, the processing time is 385s, the thinning amount is 8μm, and the finely ground silicon carbide ingot is obtained;

[0072] S2, laser irradiation is performed on the silicon surface of the finely ground silicon carbide ingot, the laser stripping times are 4 times, the wavelength is 1000nm, the cutting depth is 200μm, the cutting speed is 700mm / s, the laser cutting power is 14W, 15.5W, 16.5W, 18W, the laser stripping time is 28min / wafer, and the wafer is stripped from the finely ground silicon carbide ingot to obtain a silicon carbide wafer; the thickness of the wafer is d1=3.04L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5=3.04×200-1.001×14-0.999×15.5-0.995×16.5-1.05×18=543.18μm;

[0073] S3, the silicon surface of the silicon carbide wafer is subjected to rough grinding and thinning in sequence, the mesh number of the grinding wheel is 2500 mesh, the spindle speed is 2500rpm, the speed of the worktable is 200rpm, the feed speed in the initial stage is 0.3μm / s, the feed speed in the processing stage is 0.2μm / s, the feed speed in the deceleration stage is 0.1μm / s, the processing time is 430s, and the removal amount of rough thinning is 25μm; then fine grinding and thinning are performed, The mesh number of the grinding wheel is 20000, the spindle speed is 2200rpm, the speed of the worktable is 150rpm, the feed speed in the initial stage is 0.2μm / s, the feed speed in the processing stage is 0.1μm / s, the feed speed in the deceleration stage is 0.05μm / s, the processing time is 400s, the removal amount of fine thinning is 10μm, the total processing time is 830s, and the thickness of the substrate after thinning is 508.18μm;

[0074] S4, double-sided polishing of the thinned sheet, the polishing pad is a damping polishing pad, the polishing liquid is an aluminum oxide polishing liquid, the grinding wheel speed is 150rpm, the total polishing time is 1500s, the total removal amount of double-sided polishing is 5μm, and a polished sheet with a thickness of 503.18μm is obtained;

[0075] S5, chemically cleaning the polishing sheet:

[0076] SC3: Immerse the polishing sheet in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 4:1, soak and clean at 120°C for 900s, and rinse with deionized water to obtain the first cleaned sheet;

[0077] SC1: immerse the first cleaning sheet in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:11, soak and clean at 60°C for 700s, and rinse with deionized water to obtain a second cleaning sheet;

[0078] SC2: immerse the second cleaning sheet in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:11, soak and clean at 60°C for 700s, and rinse with deionized water to obtain a third cleaning sheet;

[0079] DHF: The third cleaning sheet was immersed in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:13, immersed at 30° C. for 700 seconds, rinsed with deionized water, and dried to obtain a silicon carbide substrate.

[0080] Example 3

[0081] This embodiment provides an automated processing method for a 6-inch semi-insulating silicon carbide substrate with a target thickness of 350 μm, comprising the following steps:

[0082] S1, using a wafer thinning machine to ultra-precision grind the carbon surface of the silicon carbide ingot, the mesh number of the grinding wheel is 10000, the spindle speed is 3300rpm, the speed of the worktable is 280rpm, the feed speed in the initial stage is 0.5μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.2μm / s, the processing time is 390s, the thinning amount is 9μm, and the finely ground silicon carbide ingot is obtained;

[0083] S2, laser irradiation is performed on the silicon surface of the finely ground silicon carbide ingot, and the laser stripping times are 3 times, the wavelength is 1000nm, the cutting depth is 195μm, the cutting speed is 400mm / s, the laser cutting power is 16.5W, 17.5W, and 18.5W respectively, and the laser stripping time is 30min / piece, and the wafer is stripped from the finely ground silicon carbide ingot to obtain a silicon carbide wafer; the thickness of the wafer is d1=2.34L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5=2.34×195-1.001×16.5-0.999×17.5-0.995×18.5=403.89μm;

[0084] S3, the silicon surface of the silicon carbide wafer is subjected to rough grinding and thinning in sequence, the mesh number of the grinding wheel is 1500 mesh, the spindle speed is 3500rpm, the speed of the worktable is 350rpm, the feed speed in the initial stage is 0.6μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.3μm / s, the processing time is 500s, and the removal amount of rough thinning is 35μm; then fine grinding and thinning are performed, the mesh number of the grinding wheel is 24000 mesh, the spindle speed is 3200rpm, the speed of the worktable is 350rpm, the feed speed in the initial stage is 0.5μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.2μm / s, the processing time is 390s, the removal amount of fine thinning is 9μm, the total processing time is 890s, and the thickness of the substrate after thinning is 359.89μm;

[0085] S4, double-sided polishing of the thinned sheet, the polishing pad is a damping polishing pad, the polishing liquid is an aluminum oxide polishing liquid, the grinding wheel speed is 170 rpm, the total polishing time is 1600 s, the total removal amount of double-sided polishing is 6 μm, and a polished sheet with a thickness of 353.89 μm is obtained;

[0086] S5, chemically cleaning the polishing sheet:

[0087] SC3: Immerse the polishing sheet in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 4:1, soak and clean at 120°C for 900s, and rinse with deionized water to obtain the first cleaned sheet;

[0088] SC1: immerse the first cleaning sheet in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:11, soak and clean at 60°C for 700s, and rinse with deionized water to obtain a second cleaning sheet;

[0089] SC2: immerse the second cleaning sheet in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:11, soak and clean at 60°C for 700s, and rinse with deionized water to obtain a third cleaning sheet;

[0090] DHF: The third cleaning sheet was immersed in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:13, immersed at 30° C. for 700 seconds, rinsed with deionized water, and dried to obtain a silicon carbide substrate.

[0091] Example 4

[0092] This embodiment provides an automated processing method for a 6-inch semi-insulating silicon carbide substrate with a target thickness of 350 μm, comprising the following steps:

[0093] S1, using a wafer thinning machine to ultra-precision grind the carbon surface of the silicon carbide ingot, the mesh number of the grinding wheel is 30000, the spindle speed is 3100rpm, the speed of the worktable is 200rpm, the feed speed in the initial stage is 0.2μm / s, the feed speed in the processing stage is 0.1μm / s, the feed speed in the deceleration stage is 0.05μm / s, the processing time is 300s, the thinning amount is 5μm, and the finely ground silicon carbide ingot is obtained;

[0094] S2, laser irradiation is performed on the silicon surface of the finely ground silicon carbide ingot, the laser stripping times are 4 times, the wavelength is 800nm, the cutting depth is 200μm, the cutting speed is 700mm / s, the laser cutting power is 16W, 17.5W, 18W, 19W, the laser stripping time is 28min / wafer, and the wafer is stripped from the finely ground silicon carbide ingot to obtain a silicon carbide wafer; the thickness of the wafer is d1=2.34L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5=2.34×200-1.001×16-0.999×17.5-0.995×18-1.05×19=396.64μm;

[0095] S3, the silicon surface of the silicon carbide wafer is subjected to rough grinding and thinning in sequence, the mesh number of the grinding wheel is 2200 mesh, the spindle speed is 2500rpm, the speed of the worktable is 200rpm, the feed speed in the initial stage is 0.3μm / s, the feed speed in the processing stage is 0.2μm / s, the feed speed in the deceleration stage is 0.1μm / s, the processing time is 480s, and the removal amount of rough thinning is 30μm; then fine grinding and thinning are performed, The mesh number of the grinding wheel is 22000 mesh, the spindle speed is 2200rpm, the table speed is 150rpm, the feed speed in the initial stage is 0.2μm / s, the feed speed in the processing stage is 0.1μm / s, the feed speed in the deceleration stage is 0.05μm / s, the total processing time is 380s, the removal amount of fine thinning is 8μm, the total processing time is 860s, and the thickness of the substrate after thinning is 358.64μm;

[0096] S4, double-sided polishing of the thinned sheet, the polishing pad is a damping polishing pad, the polishing liquid is an aluminum oxide polishing liquid, the grinding wheel speed is 200 rpm, the total polishing time is 1800 s, the total removal amount of double-sided polishing is 6 μm, and a polished sheet with a thickness of 352.64 μm is obtained;

[0097] S5, chemically cleaning the polishing sheet:

[0098] SC3: Immerse the polishing sheet in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3.5:1, soak and clean at 110°C for 1100s, and rinse with deionized water to obtain the first cleaned sheet;

[0099] SC1: immerse the first cleaning sheet in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:15, soak and clean at 70°C for 800s, and rinse with deionized water to obtain a second cleaning sheet;

[0100] SC2: immerse the second cleaning sheet in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:15, soak and clean at 70°C for 800s, and rinse with deionized water to obtain a third cleaning sheet;

[0101] DHF: The third cleaning sheet was immersed in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:15, immersed at 40° C. for 800 seconds, rinsed with deionized water, and dried to obtain a silicon carbide substrate.

[0102] Example 5

[0103] This embodiment provides an automated processing method for a 6-inch semi-insulating silicon carbide substrate with a target thickness of 500 μm, comprising the following steps:

[0104] S1, using a wafer thinning machine to ultra-precision grind the carbon surface of the silicon carbide ingot, the mesh number of the grinding wheel is 30000, the spindle speed is 3100rpm, the speed of the worktable is 200rpm, the feed speed in the initial stage is 0.2μm / s, the feed speed in the processing stage is 0.1μm / s, the feed speed in the deceleration stage is 0.05μm / s, the processing time is 300s, the thinning amount is 5μm, and the finely ground silicon carbide ingot is obtained;

[0105] S2, laser irradiation is performed on the silicon surface of the finely ground silicon carbide ingot, the laser stripping times are 3 times, the wavelength is 780nm, the cutting depth is 195μm, the cutting speed is 300mm / s, the laser cutting power is 16W, 17W, and 18W respectively, the laser stripping time is 30min / wafer, and the wafer is stripped from the finely ground silicon carbide ingot to obtain a silicon carbide wafer; the thickness of the wafer is d1=3.04L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5=3.04×195-1.001×16-0.999×17-0.995×18=541.89μm;

[0106] S3, the silicon surface of the silicon carbide wafer is subjected to rough grinding and thinning in sequence, the mesh number of the grinding wheel is 2500 mesh, the spindle speed is 2500rpm, the speed of the worktable is 200rpm, the feed speed in the initial stage is 0.3μm / s, the feed speed in the processing stage is 0.2μm / s, the feed speed in the deceleration stage is 0.1μm / s, the processing time is 420s, and the removal amount of rough thinning is 22μm; then fine grinding and thinning are performed, The mesh number of the grinding wheel is 20000, the spindle speed is 2200rpm, the table speed is 150rpm, the feed speed in the initial stage is 0.2μm / s, the feed speed in the processing stage is 0.1μm / s, the feed speed in the deceleration stage is 0.05μm / s, the processing time is 400s, the removal amount of fine thinning is 10μm, the total processing time is 820s, and the thickness of the substrate after thinning is 509.89μm;

[0107] S4, double-sided polishing of the thinned sheet, the polishing pad is a damping polishing pad, the polishing liquid is an aluminum oxide polishing liquid, the grinding wheel speed is 200 rpm, the total polishing time is 1800 s, the total removal amount of double-sided polishing is 6 μm, and a polished sheet with a thickness of 503.89 μm is obtained;

[0108] S5, pre-cleaning: adding the silicon carbide substrate into a mixed solution of hydrogen peroxide and deionized water in a volume ratio of 1:13, and immersing at 75°C for 1200s;

[0109] S6, RCA cleaning:

[0110] SC3: Immerse the silicon carbide substrate in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 4.1:1 at 110°C for 1500s and rinse with deionized water;

[0111] SC1-1: Immerse the silicon carbide substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:10 at 60°C for 900s, and rinse with deionized water;

[0112] SC1-2: Immerse the silicon carbide substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:10 at 60°C for 900s, and rinse with deionized water;

[0113] SC2: Immerse the silicon carbide substrate in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:10 at 60°C for 900s and rinse with deionized water;

[0114] DHF: Immerse the silicon carbide substrate in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:12 at 30°C for 900s, rinse with deionized water, and spin dry.

[0115] Comparative Example 1

[0116] This comparative example provides a method for processing a silicon carbide substrate, that is, a conventional method for processing a silicon carbide substrate, comprising the following steps:

[0117] S1, wire cutting the silicon carbide ingot, the single-piece wire length is 1800m, the wire tension is 40N, the wire speed is 800m / min, the processing temperature is 25°C, the processing time is 72min / piece, and the thickness of the obtained silicon carbide ingot is 600μm;

[0118] S2, mechanically polishing the cut silicon carbide ingot, with a lower plate speed of 30 rpm, a polishing head speed of 30 rpm, a processing temperature of 30°C, a pressure of 120 kg, a processing time of 30 min, and a thickness of the obtained silicon carbide ingot of 530 μm;

[0119] S3, polishing of surface A: the rotation speed of the lower plate is 30 rpm, the rotation speed of the polishing head is 40 rpm, the processing temperature is 30°C, the pressure is 90 KG, the processing time is 30 min, and the thickness of the obtained silicon carbide ingot is 525 μm;

[0120] S4, perform B-side polishing: the lower plate speed is 30 rpm, the polishing head speed is 40 rpm, the processing temperature is 30°C, the pressure is 60 KG, the processing time is 30 min, and the thickness of the obtained silicon carbide ingot is 520 μm;

[0121] S5, chemical mechanical polishing of silicon carbide: disk speed 50 rpm, polishing head speed 50 rpm, processing temperature 40°C, pressure 300KG, processing time 60min, silicon carbide thickness after processing is 518μm;

[0122] S6, pre-cleaning: adding the silicon carbide substrate into a mixed solution of hydrogen peroxide and deionized water in a volume ratio of 1:13, and immersing at 75°C for 1200s;

[0123] S7, RCA cleaning:

[0124] SC3: Immerse the silicon carbide substrate in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 4.1:1 at 110°C for 1500s and rinse with deionized water;

[0125] SC1-1: Immerse the silicon carbide substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:10 at 60°C for 900s, and rinse with deionized water;

[0126] SC1-2: Immerse the silicon carbide substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:10 at 60°C for 900s, and rinse with deionized water;

[0127] SC2: Immerse the silicon carbide substrate in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:10 at 60°C for 900s and rinse with deionized water;

[0128] DHF: Immerse the silicon carbide substrate in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:12 at 30°C for 900s, rinse with deionized water, and spin dry.

[0129] Comparative Example 2

[0130] This comparative example provides a method for processing a silicon carbide substrate, comprising the following steps:

[0131] S1, wire cutting the silicon carbide ingot, the single-piece wire length is 1800m, the wire tension is 40N, the wire speed is 1000m / min, the processing temperature is 25°C, the processing time is 60min / piece, and the thickness of the obtained silicon carbide ingot is 600μm;

[0132] S2, mechanically polishing the cut silicon carbide ingot, the lower plate speed is 30rpm, the polishing head speed is 30rpm, the processing temperature is 30°C, the pressure is 100KG, the processing time is 40min, and the thickness of the obtained silicon carbide ingot is 530μm;

[0133] S3, polishing of surface A: the rotation speed of the lower plate is 30 rpm, the rotation speed of the polishing head is 40 rpm, the processing temperature is 30°C, the pressure is 90 KG, the processing time is 40 min, and the thickness of the obtained silicon carbide ingot is 525 μm;

[0134] S4, perform B-side polishing: the lower plate speed is 40 rpm, the polishing head speed is 50 rpm, the processing temperature is 35°C, the pressure is 100 KG, the processing time is 20 min, and the thickness of the obtained silicon carbide ingot is 520 μm;

[0135] S5, chemical mechanical polishing of silicon carbide: disk speed 60rpm, polishing head speed 60rpm, processing temperature 45°C, pressure 320KG, processing time 50min, silicon carbide thickness after processing is 518μm;

[0136] S6, RCA cleaning:

[0137] SC3: Immerse the silicon carbide substrate in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3.5:1 at 110°C for 1200s and rinse with deionized water;

[0138] SC1: Immerse the silicon carbide substrate in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:15 at 70°C for 800s and rinse with deionized water;

[0139] SC2: Immerse the silicon carbide substrate in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:15 at 70°C for 800s and rinse with deionized water;

[0140] DHF: Immerse the silicon carbide substrate in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:15 at 40°C for 800s, rinse with deionized water, and spin dry.

[0141] Comparative Example 3

[0142] This comparative example provides a method for processing a silicon carbide substrate, comprising the following steps:

[0143] S1, using a wafer thinning machine to ultra-precision grind the carbon surface of the silicon carbide ingot, the mesh number of the grinding wheel is 30000, the spindle speed is 3100rpm, the speed of the worktable is 200rpm, the feed speed in the initial stage is 0.2μm / s, the feed speed in the processing stage is 0.1μm / s, the feed speed in the deceleration stage is 0.05μm / s, the processing time is 300s, the thinning amount is 5μm, and the finely ground silicon carbide ingot is obtained;

[0144] S2, laser irradiation is performed on the silicon surface of the silicon carbide ingot, and the laser stripping times are 4 times, the wavelength is 800nm, the cutting depth is 190μm, the cutting speed is 400mm / s, the laser cutting power is 16W, 17W, 18.5W, 19W, and the laser stripping time is 40min. The wafer is stripped from the finely ground silicon carbide ingot to obtain a silicon carbide wafer; the thickness of the wafer is 560μm;

[0145] S3, the silicon surface of the silicon carbide wafer is subjected to rough grinding and thinning in sequence, the mesh number of the grinding wheel is 1500 mesh, the spindle speed is 3500rpm, the speed of the worktable is 350rpm, the feed speed in the initial stage is 0.6μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.3μm / s, the processing time is 450s, and the removal amount of rough thinning is 30μm; then fine grinding and thinning are performed, the mesh number of the grinding wheel is 30000 mesh, the spindle speed is 3200rpm, the speed of the worktable is 350rpm, the feed speed in the initial stage is 0.5μm / s, the feed speed in the processing stage is 0.4μm / s, the feed speed in the deceleration stage is 0.2μm / s, the processing time is 250s, the removal amount of fine thinning is 5μm, the total processing time is 700s, and the thickness of the substrate after thinning is 525μm;

[0146] S4, double-sided polishing of the thinned sheet, the polishing pad is a damping polishing pad, the polishing liquid is an aluminum oxide polishing liquid, the grinding wheel speed is 200 rpm, the total polishing time is 1800 s, the total removal amount of double-sided polishing is 6 μm, and a polished sheet with a thickness of 519 μm is obtained;

[0147] S5, cleaning the substrate:

[0148] SC3: Immerse the polishing sheet in a mixed solution of concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3.5:1, soak and clean at 110°C for 1100s, and rinse with deionized water to obtain the first cleaned sheet;

[0149] SC1: immerse the first cleaning sheet in a mixed solution of ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:15, soak and clean at 70°C for 800s, and rinse with deionized water to obtain a second cleaning sheet;

[0150] SC2: immerse the second cleaning sheet in a mixed solution of hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:15, soak and clean at 70°C for 800s, and rinse with deionized water to obtain a third cleaning sheet;

[0151] DHF: The third cleaning sheet was immersed in a mixed solution of hydrofluoric acid and deionized water in a volume ratio of 1:15, immersed at 40° C. for 800 seconds, rinsed with deionized water, and dried to obtain a silicon carbide substrate.

[0152] The chamfering process in all the above embodiments and comparative examples adopts the same process, and the process duration is 300 seconds; the duration of each step of deionized water rinsing is 800 seconds, and the drying process is 500 seconds.

[0153] The sheet output rate, processing cycle and cleaning effect of the above embodiments and comparative examples are shown in Table 1.

[0154] Table 1

[0155]

[0156]

[0157] The distribution diagram of small particles on the surface of the silicon carbide substrate prepared in Examples 1 to 5 and Comparative Examples 1 to 3 is as follows: Figures 3 to 10 shown.

[0158] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modification, equivalent substitution or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. An automated processing method for a silicon carbide substrate, characterized in that: The steps include: S1, ultra-precision grinding the carbon surface of the silicon carbide ingot, with a thinning amount of 5 μm to 10 μm, to obtain a finely ground silicon carbide ingot; S2, irradiating the silicon surface of the finely ground silicon carbide ingot with laser, peeling the wafer from the finely ground silicon carbide ingot, and obtaining a silicon carbide wafer; the number of laser peeling is 2≤K≤5; If the target thickness of the silicon carbide substrate is 500 μm, the thickness d1 of the silicon carbide wafer is controlled to be 520 μm≤d1≤555 μm, d1=3.04L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5; If the target thickness of the silicon carbide substrate is 350 μm, the thickness d2 of the silicon carbide wafer is controlled to be 370 μm ≤ d2 ≤ 405 μm, d2 = 2.34L-1.001P1-0.999P2-0.995P3-1.05P4-0.532P5; L is the cutting depth, P k is the cutting power of the Kth laser stripping, and 0.5≤P K+1 -P K ≤1.5; S3, sequentially performing rough grinding and fine grinding on the silicon surface of the silicon carbide wafer to obtain a thinned wafer; wherein the removal amount of the rough grinding is 15 μm to 35 μm, and the removal amount of the fine grinding is 5 μm to 10 μm; If the target thickness of the silicon carbide substrate is 500 μm, the thickness h1 after rough grinding and thinning is controlled to be 505 μm ≤ h1 ≤ 520 μm, and the thickness h2 after fine grinding and thinning is controlled to be 500 μm ≤ h2 ≤ 510 μm; If the target thickness of the silicon carbide substrate is 350 μm, the thickness h3 after rough grinding and thinning is controlled to be 355 μm ≤ h3 ≤ 370 μm, and the thickness h4 after fine grinding and thinning is controlled to be 350 μm ≤ h4 ≤ 360 μm; S4, double-sided polishing the thinned sheet, with a total removal amount of 3 μm to 6 μm, to obtain a polished sheet; If the target thickness of the silicon carbide substrate is 500 μm, the thickness m1 of the polishing sheet is controlled to be 497 μm ≤ m1 ≤ 504 μm; If the target thickness of the silicon carbide substrate is 350 μm, the thickness m2 of the polishing sheet is controlled to be 347 μm ≤ m2 ≤ 354 μm; S5, chemically cleaning the polishing sheet to obtain a silicon carbide substrate.

2. The automated processing method for a silicon carbide substrate according to claim 1, wherein: In S1, a wafer thinning machine is used to perform ultra-precision grinding of silicon carbide ingots, the mesh size of the grinding wheel is 8000-30000 mesh, the spindle speed is 3100rpm-3300rpm, the speed of the worktable is 200rpm-280rpm, the feed speed in the starting stage is 0.2μm / s-0.5μm / s, the feed speed in the processing stage is 0.1μm / s-0.4μm / s, the feed speed in the deceleration stage is 0.05μm / s-0.2μm / s, and the processing time is 300s-400s.

3. The automated processing method for a silicon carbide substrate according to claim 1, wherein: In S2, the wavelength of the laser irradiation is 800nm-1000nm, the cutting power is 14W-25W, the cutting depth is 190μm-200μm, the cutting speed is 400mm / s-700mm / s, and the laser stripping time is 15min / sheet-35min / sheet.

4. The automated processing method for a silicon carbide substrate according to claim 1, wherein: In S3, the spindle speed of the rough grinding and thinning is 2500rpm~3500rpm, the spindle speed of the fine grinding and thinning is 2200rpm~3200rpm, the speed of the workbench is 150rpm~350rpm, the time of the rough grinding and thinning is 350s~500s, and the time of the fine grinding and thinning is 250s~400s.

5. The automated processing method for a silicon carbide substrate according to claim 1, wherein: In S4, the grinding wheel rotation speed of the double-sided polishing is 100 rpm to 200 rpm, and the total polishing time is 1000 s to 1800 s.

6. The automated processing method for a silicon carbide substrate according to claim 1, wherein: In S5, the polishing sheet is transported by plugging for chemical cleaning.

7. The automated processing method for a silicon carbide substrate according to claim 1 or 6, characterized in that: In S5, the chemical cleaning specifically includes the following steps: Step a, placing the polishing sheet into a plug, immersing it in an acidic oxidizing solution a, soaking and cleaning, and obtaining a first cleaning sheet; the acidic oxidizing solution a comprises concentrated sulfuric acid and hydrogen peroxide in a volume ratio of 3.5:1 to 4:1; Step b, immersing the first cleaning sheet in an alkaline oxidizing solution for soaking and cleaning to obtain a second cleaning sheet; the alkaline oxidizing solution comprises ammonia water, hydrogen peroxide and deionized water in a volume ratio of 1:1:11 to 1:1:15; Step c, immersing the second cleaning sheet in an acidic oxidizing solution b for soaking and cleaning to obtain a third cleaning sheet; the acidic oxidizing solution b comprises hydrochloric acid, hydrogen peroxide and deionized water in a volume ratio of 1:1:11 to 1:1:15; Step d, immersing the third cleaning sheet in a hydrofluoric acid solution, soaking and cleaning, rinsing with deionized water, and drying to obtain a silicon carbide substrate.

8. The automated processing method for a silicon carbide substrate according to claim 7, characterized in that: In step a, the immersion cleaning temperature is 110° C. to 120° C., and the immersion cleaning time is 900 s to 1100 s.

9. The automated processing method for a silicon carbide substrate according to claim 7, wherein: In step b, the immersion cleaning temperature is 60° C. to 70° C., and the immersion cleaning time is 700 s to 800 s; and / or In step c, the immersion cleaning temperature is 60° C. to 70° C., and the immersion cleaning time is 700 s to 800 s.

10. The automated processing method for a silicon carbide substrate according to claim 7, wherein: In step d, the immersion cleaning temperature is 30° C. to 40° C., and the immersion cleaning time is 700s to 800s.

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