Silicon carbide epitaxial wafer cleaning method

Abstract

The invention discloses a silicon carbide epitaxial wafer cleaning method. The silicon carbide epitaxial wafer cleaning method sequentially comprises the following steps: S1, pre-cleaning with ultrapure water and high-pressure N2 water-gas two-fluid; s2, transferring into an acid liquor tank filled with a mixed solution of hydrochloric acid, hydrofluoric acid and hydrogen peroxide for treatment; s3, transferring into No.1 alkali liquor filled with a mixed solution of ammonia water and hydrogen peroxide for treatment; s4, transferring into No.2 alkali liquor containing a mixed solution of ammonia water, hydrogen peroxide and an ampholytic surfactant for treatment, wherein the concentration of the ammonia water in the mixed solution in the step is lower than that of the ammonia water in the mixed solution in the step S3; s5, slowly pulling and drying with warm water; and S6, infrared heating and drying. Through cooperation of the steps, the cleaning effect of the silicon carbide epitaxial wafer is improved, and the number of residual metal ions and particles on the surface of the epitaxial wafer is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of epitaxial wafer cleaning technology, and more particularly to a method for cleaning silicon carbide epitaxial wafers. Background Technology

[0002] Silicon carbide (SiC) epitaxial wafers are made by epitaxially growing a high-quality SiC thin film layer on a silicon carbide single crystal substrate. As a wide bandgap semiconductor material, it is widely used in high-temperature, high-power and high-frequency electronic devices due to its high thermal conductivity, high breakdown electric field and high electron saturation drift velocity. Mercury probe capacitance-voltage (Hg-CV) testing is a commonly used method for testing electrical characteristics.

[0003] During Hg-CV testing, silicon carbide epitaxial wafers may become contaminated with residual mercury droplets and particles due to probe contact and environmental exposure. This can lead to problems such as increased leakage current, reduced breakdown voltage, and shortened lifespan, significantly affecting device performance and stability. Therefore, an effective cleaning process to remove residual mercury droplets and particle contamination from the surface is crucial.

[0004] Currently, silicon carbide epitaxial wafers undergoing Hg-CV testing are mostly cleaned using traditional RCA cleaning (a semiconductor cleaning benchmark process developed by RCA Corporation). This typically involves mechanical cleaning methods such as strong acid solutions (e.g., H2SO4 / H2O2) or brush cleaning. However, this method has many problems, including incomplete cleaning in a single cycle, environmental pollution, and damage to the silicon carbide epitaxial layer.

[0005] On the one hand, mercury is difficult to dissolve in conventional solvents; on the other hand, nanoscale particles are easily adsorbed by electrostatics, making conventional ultrasonic cleaning ineffective. Furthermore, strong oxidants easily corrode the surface of silicon carbide epitaxial wafers, affecting the performance of subsequent devices and causing environmental pollution. Therefore, even with repeated cleaning methods, it is difficult to remove tightly adsorbed submicron-level particles and trace metal impurities from the surface, and repeated cleaning is time-consuming, costly, and inefficient. Therefore, inventing a silicon carbide epitaxial wafer cleaning process that can achieve lower surface particle counts and metal residues is crucial. Summary of the Invention

[0006] Purpose of the invention: To address the shortcomings of existing cleaning methods that are not thorough, this invention provides a method for cleaning silicon carbide epitaxial wafers, which can achieve efficient cleaning and improve the removal of metal and particles from the surface of the epitaxial wafer.

[0007] Technical solution: To solve the above problems, the present invention employs a silicon carbide epitaxial wafer cleaning method, comprising the following steps:

[0008] S1. Pre-cleaning: Ultrapure water and high-pressure N2 are mixed and sprayed onto the surface of the silicon carbide epitaxial wafer for cleaning;

[0009] S2, Acid treatment; The silicon carbide epitaxial wafer is moved into a cleaning tank containing a mixture of hydrochloric acid, hydrofluoric acid and hydrogen peroxide for ultrasonic cleaning, and then rinsed in an ultrapure water tank.

[0010] S3 and No. 1 alkaline solution treatment: The silicon carbide epitaxial wafer is moved into a cleaning tank containing a mixture of ammonia and hydrogen peroxide for low-frequency megasonic cleaning, and then placed in an ultrapure water tank for rinsing.

[0011] S4, Alkali Solution Treatment: The silicon carbide epitaxial wafer is transferred into a cleaning tank containing a mixture of ammonia, hydrogen peroxide, and amphoteric surfactant for high-frequency megason cleaning, and then rinsed in an ultrapure water tank; the ammonia concentration in the mixture in this step is lower than the ammonia concentration in the mixture in step S3.

[0012] S5. Dry the silicon carbide epitaxial wafer using the warm water slow-lift drying method;

[0013] S6. Place the silicon carbide epitaxial wafer in an infrared heating bath to dry it.

[0014] Furthermore, in step S1, the flow ratio of ultrapure water to high-pressure N2 is (1:30) to (1:60), and the cleaning time is 20-30 seconds.

[0015] Furthermore, in step S2, the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of hydrofluoric acid is 49%, and the mass concentration of hydrogen peroxide is 30%; the volume ratio of hydrofluoric acid, hydrochloric acid, hydrogen peroxide, and water in the mixture is 1:25:25:(500-1000).

[0016] Furthermore, in step S2, the temperature of the mixture is 20-50℃, the ultrasonic frequency is 40kHz, the ultrasonic cleaning time is 100-300s, and the circulation flow rate of the mixture is 15-20L / min.

[0017] Furthermore, in step S3, the mass concentration of ammonia is 28%-30%, and the mass concentration of hydrogen peroxide is 30%; the volume ratio of ammonia, hydrogen peroxide, and water in the mixture is 1:1:(5-10).

[0018] Furthermore, in step S3, the concentration of the mixed solution is 50-60℃, the low-frequency megasonic frequency is 730kHz, the low-frequency megasonic cleaning time is 200-300s, and the mixed solution circulation flow rate is 15-20L / min.

[0019] Furthermore, in step S4, the mass concentration of ammonia is 28%-30%, and the mass concentration of hydrogen peroxide is 30%; the volume ratio of ammonia, hydrogen peroxide, and water in the mixture is 1:2:(10-20); the amphoteric surfactant is N,N,N-trimethylglycine, and the ratio of N,N,N-trimethylglycine to water is 0.3-0.5wt%.

[0020] Furthermore, in step S4, the concentration of the mixed solution is 60-70℃, the high-frequency megasonic frequency is 1000kHz, the high-frequency megasonic cleaning time is 200-300s, and the mixed solution circulation flow rate is 15-20L / min.

[0021] Further, step S5 specifically involves: placing the silicon carbide epitaxial wafer into a slow-pull tank containing ultrapure water and slowly pulling it up. The temperature of the ultrapure water is 30-45℃, and the pulling speed is 0.8-1.5mm / s.

[0022] Furthermore, in step S6, the temperature of the infrared heating bath is 60-80℃, and the drying time is 100-150s.

[0023] Beneficial effects: Compared with the prior art, the significant advantage of this invention is that by coordinating the steps of pre-cleaning, acid treatment, gradient alkaline treatment, warm water slow lifting drying, and infrared drying, the cleaning effect of silicon carbide epitaxial wafers is improved, and the number of residual metal ions and particles on the surface of the epitaxial wafers is effectively reduced. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the cleaning process of the silicon carbide epitaxial wafer cleaning method of the present invention;

[0025] Figure 2 This is a comparison chart of the surface particle test results of the epitaxial wafer before and after cleaning in Example 1;

[0026] Figure 3 This is a comparison chart of the surface particle test results of the epitaxial wafer before and after cleaning in Example 2;

[0027] Figure 4 This is a comparison chart of the surface particle test results of the epitaxial wafer before and after cleaning in Example 3;

[0028] Figure 5 This is a comparison chart showing the surface particle test results of an epitaxial wafer before and after cleaning, serving as a comparative example. Detailed Implementation

[0029] Example 1

[0030] like Figure 1 As shown, a silicon carbide epitaxial wafer cleaning method in this embodiment includes the following steps:

[0031] S1. Pre-cleaning. Take the silicon carbide epitaxial wafer after CV testing, and spray a mixture of pure water and high-pressure N2 onto the surface of the silicon carbide epitaxial wafer for cleaning. The flow ratio of ultrapure water to high-pressure N2 is 1:30, and the rinsing time is 20 seconds. This step uses a high-speed atomized fluid formed by water and air to pre-clean the surface of the epitaxial wafer, removing some particles and dirt. Compared with mechanical cleaning by brushing, the physical rinsing of water and air can avoid scratches and damage to the surface of the silicon carbide epitaxial wafer.

[0032] S2. Acid Treatment. The silicon carbide epitaxial wafer was transferred to a cleaning tank containing a mixture of hydrochloric acid, hydrofluoric acid, and hydrogen peroxide for ultrasonic cleaning. The hydrochloric acid concentration was 36%-38%, the hydrofluoric acid concentration was 49%, and the hydrogen peroxide concentration was 30%. All three solutions were UPS-grade (the highest purity level among electronic-grade chemical reagents). The volume ratio of hydrofluoric acid, hydrochloric acid, hydrogen peroxide, and water in the mixture was 1:25:25:1000. The temperature of the mixture was 30℃, the ultrasonic frequency was 40kHz, the ultrasonic cleaning time was 150s, and the circulation flow rate of the mixture was 15L / min. After acid cleaning, it was rinsed in an ultrapure water tank for 150s, with an ultrapure water circulation flow rate of 20L / min.

[0033] On the one hand, the mixed acid solution of hydrochloric acid and hydrofluoric acid causes metal ions such as Hg attached to the wafer surface to undergo a chemical reaction, forming soluble complexes that dissolve. On the other hand, hydrofluoric acid can remove the natural oxide layer (SiO2) on the surface and peel off particles attached to the epitaxial wafer surface. The alternating etching of the wafer surface oxide layer by hydrofluoric acid and oxidation by hydrogen peroxide is beneficial for removing surface metals and particles.

[0034] S3 and No. 1 alkaline solution treatment. The silicon carbide epitaxial wafer was transferred to a cleaning tank containing a mixture of ammonia and hydrogen peroxide for low-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:1:10. The temperature of the mixture was 60℃, the low-frequency megasonic frequency was 730kHz, the cleaning time was 200s, and the circulation flow rate of the mixture was 20L / min. After alkaline cleaning, it was rinsed in an ultrapure water tank for 200s, with a circulation flow rate of 25L / min.

[0035] Through repeated corrosion and oxidation of the surface silicon oxide layer by mixed alkaline solution, combined with the cavitation effect of megasonic waves, the surface micro-particles are continuously vibrated and peeled off, and react with some metal ions to form soluble complexes that dissolve.

[0036] S4 and No. 2 alkaline solutions were used for cleaning. The silicon carbide epitaxial wafers were transferred to a cleaning tank containing a mixture of ammonia, hydrogen peroxide, and an amphoteric surfactant for high-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS-grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:2:20. The amphoteric surfactant was N,N,N-trimethylglycine, with a water ratio of 0.3 wt%. The temperature of the mixture was 60°C, the megasonic frequency was 1000 kHz, the cleaning time was 200 s, and the circulation flow rate was 20 L / min. After alkaline cleaning, the wafers were rinsed in an ultrapure water tank for 200 s, with a circulation flow rate of 25 L / min.

[0037] High-frequency megasonic waves desorb submicron particles from the wafer surface, while amphoteric surfactants encapsulate the particles in the solution, preventing redeposition through electrostatic repulsion and steric hindrance. Amphoteric surfactants also enhance cleaning by reducing the surface tension of the solution. The combination of alkaline solution and amphoteric surfactants effectively removes the natural oxide layer and metal ion contamination, reducing surface defects.

[0038] S5. Dry the silicon carbide epitaxial wafer using a warm water slow-lift drying method. Specifically, place the silicon carbide epitaxial wafer into a slow-lift tank containing ultrapure water and slowly lift it. The ultrapure water temperature is 40℃, and the lifting speed is 1mm / s.

[0039] Conventional cleaning processes use spin-drying, which involves high-speed rotation of the cavity to dry the surface of the silicon carbide epitaxial wafer. However, the high-speed rotation of the cavity is driven by a rotating shaft, which requires a high degree of sealing between the rotating shaft and the cavity. Any sealing problems can lead to the introduction of particles, which can affect the surface metal. The warm water slow-lift drying method, on the other hand, involves slowly lifting the wafer from pure water, which avoids the introduction of other particles and prevents external particles from re-contaminating the epitaxial wafer.

[0040] S6. Place the silicon carbide epitaxial wafer in an infrared heating bath to dry it. The temperature of the infrared heating bath is 60℃ and the drying time is 120s. Finally, the cleaned epitaxial wafer is obtained.

[0041] Example 2

[0042] This embodiment of a silicon carbide epitaxial wafer cleaning method includes the following steps:

[0043] S1. Pre-cleaning. Take the silicon carbide epitaxial wafer after CV testing, mix pure water and high-pressure N2 and spray it onto the surface of the silicon carbide epitaxial wafer for cleaning. The flow ratio of ultrapure water to high-pressure N2 is 1:45, and the rinsing time is 25s.

[0044] S2. Acid Treatment. The silicon carbide epitaxial wafer was transferred to a cleaning tank containing a mixture of hydrochloric acid, hydrofluoric acid, and hydrogen peroxide for ultrasonic cleaning. The mass concentration of hydrochloric acid was 36%-38%, the mass concentration of hydrofluoric acid was 49%, and the mass concentration of hydrogen peroxide was 30%. All three solutions were UPS grade, and the volume ratio of hydrofluoric acid, hydrochloric acid, hydrogen peroxide, and water in the mixture was 1:25:25:500. The temperature of the mixture was 40℃, the ultrasonic frequency was 40kHz, the ultrasonic cleaning time was 200s, and the circulation flow rate of the mixture was 15L / min. After acid cleaning, it was rinsed in an ultrapure water tank for 200s, with an ultrapure water circulation flow rate of 20L / min.

[0045] S3 and No. 1 alkaline solution treatment. The silicon carbide epitaxial wafer was transferred to a cleaning tank containing a mixture of ammonia and hydrogen peroxide for low-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:1:5. The temperature of the mixture was 60℃, the low-frequency megasonic frequency was 730kHz, the cleaning time was 300s, and the circulation flow rate of the mixture was 20L / min. After alkaline cleaning, it was rinsed in an ultrapure water tank for 300s, with a circulation flow rate of 25L / min.

[0046] S4 and No. 2 alkaline solutions were used for cleaning. The silicon carbide epitaxial wafers were transferred to a cleaning tank containing a mixture of ammonia, hydrogen peroxide, and an amphoteric surfactant for high-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS-grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:2:10. The amphoteric surfactant was N,N,N-trimethylglycine, with a water ratio of 0.5 wt%. The temperature of the mixture was 70°C, the high-frequency megasonic cleaning frequency was 1000 kHz, the cleaning time was 300 s, and the circulation flow rate was 20 L / min. After alkaline cleaning, the wafers were rinsed in an ultrapure water tank for 300 s, with a circulation flow rate of 25 L / min.

[0047] S5. Dry the silicon carbide epitaxial wafer using a warm water slow-lift drying method. Specifically, place the silicon carbide epitaxial wafer into a slow-lift tank containing ultrapure water and slowly lift it. The ultrapure water temperature is 30℃, and the lifting speed is 0.8mm / s.

[0048] S6. Place the silicon carbide epitaxial wafer in an infrared heating bath to dry it. The temperature of the infrared heating bath is 70℃ and the drying time is 150s. Finally, the cleaned epitaxial wafer is obtained.

[0049] Example 3

[0050] This embodiment of a silicon carbide epitaxial wafer cleaning method includes the following steps:

[0051] S1. Pre-cleaning. Take the silicon carbide epitaxial wafer after CV testing, mix pure water and high-pressure N2 and spray it onto the surface of the silicon carbide epitaxial wafer for cleaning. The flow ratio of ultrapure water to high-pressure N2 is 1:60, and the rinsing time is 30s.

[0052] S2. Acid Treatment. The silicon carbide epitaxial wafer was transferred into a cleaning tank containing a mixture of hydrochloric acid, hydrofluoric acid, and hydrogen peroxide for ultrasonic cleaning. The mass concentration of hydrochloric acid was 36%-38%, the mass concentration of hydrofluoric acid was 49%, and the mass concentration of hydrogen peroxide was 30%. All three solutions were UPS grade, and the volume ratio of hydrofluoric acid, hydrochloric acid, hydrogen peroxide, and water in the mixture was 1:25:25:750. The temperature of the mixture was 50℃, the ultrasonic frequency was 40kHz, the ultrasonic cleaning time was 100s, and the circulation flow rate of the mixture was 15L / min. After acid cleaning, it was rinsed in an ultrapure water tank for 100s, with an ultrapure water circulation flow rate of 20L / min.

[0053] S3 and No. 1 alkaline solution treatment. The silicon carbide epitaxial wafer was transferred to a cleaning tank containing a mixture of ammonia and hydrogen peroxide for low-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:1:8. The temperature of the mixture was 60℃, the low-frequency megasonic frequency was 730kHz, the cleaning time was 250s, and the circulation flow rate of the mixture was 20L / min. After alkaline cleaning, it was rinsed in an ultrapure water tank for 250s, with a circulation flow rate of 25L / min.

[0054] S4 and No. 2 alkaline solutions were used for cleaning. The silicon carbide epitaxial wafers were transferred to a cleaning tank containing a mixture of ammonia, hydrogen peroxide, and an amphoteric surfactant for high-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS-grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:2:15. The amphoteric surfactant was N,N,N-trimethylglycine, with a water ratio of 0.4 wt%. The temperature of the mixture was 65°C, the megasonic frequency was 1000 kHz, the cleaning time was 250 s, and the circulation flow rate was 20 L / min. After alkaline cleaning, the wafers were rinsed in an ultrapure water tank for 250 s, with a circulation flow rate of 25 L / min.

[0055] S5. Dry the silicon carbide epitaxial wafer using a warm water slow-lift drying method. Specifically, place the silicon carbide epitaxial wafer into a slow-lift tank containing ultrapure water and slowly lift it. The ultrapure water temperature is 45℃, and the lifting speed is 1.5mm / s.

[0056] S6. Place the silicon carbide epitaxial wafer in an infrared heating bath to dry it. The temperature of the infrared heating bath is 80℃ and the drying time is 100s. Finally, the cleaned epitaxial wafer is obtained.

[0057] Comparative Example 1

[0058] This comparative example uses a conventional cleaning process, including the following steps:

[0059] S1 and No. 1 alkaline solution treatment. Silicon carbide epitaxial wafers after CV testing were transferred to a cleaning tank containing a mixture of ammonia and hydrogen peroxide for low-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:1:10. The temperature of the mixture was 60℃, the low-frequency megasonic frequency was 730kHz, the cleaning time was 300s, and the circulation flow rate of the mixture was 20L / min. After alkaline cleaning, the wafers were rinsed in an ultrapure water tank for 300s, with a circulation flow rate of 25L / min.

[0060] S2 and No. 2 alkaline solutions were used for cleaning. The silicon carbide epitaxial wafers were transferred to a cleaning tank containing a mixture of ammonia, hydrogen peroxide, and an amphoteric surfactant for high-frequency megasonic cleaning. The ammonia concentration was 28%-30%, and the hydrogen peroxide concentration was 30%. Both solutions were UPS-grade, and the volume ratio of ammonia, hydrogen peroxide, and water in the mixture was 1:2:20. The temperature of the mixture was 60℃, the high-frequency megasonic frequency was 1000kHz, the high-frequency megasonic cleaning time was 300s, and the circulation flow rate of the mixture was 20L / min. After alkaline cleaning, the wafers were rinsed in an ultrapure water tank for 300s, with a circulation flow rate of 25L / min.

[0061] S3. Acid Treatment. The silicon carbide epitaxial wafer is transferred to a cleaning tank containing a mixture of hydrochloric acid and hydrogen peroxide for cleaning. The hydrochloric acid concentration is 36%-38% by mass, and the hydrogen peroxide concentration is 30% by mass. Both solutions are UPS grade, and the volume ratio of hydrochloric acid, hydrogen peroxide, and water in the mixture is 1:1:20. The temperature of the mixture is 50℃, the cleaning time is 300s, and the circulation flow rate of the mixture is 20L / min. After acid cleaning, it is rinsed in an ultrapure water tank for 300s, with an ultrapure water circulation flow rate of 25L / min.

[0062] S4. Centrifugal drying: Set the centrifugal drying chamber speed to 800 rpm and the drying time to 300 s to obtain the cleaned silicon carbide epitaxial wafer.

[0063] The surface metal residue of the epitaxial wafers obtained after the final cleaning of each embodiment and comparative example was tested, and the results are shown in Table 1 below:

[0064]

[0065] Table 1

[0066] As can be seen from the data in the table above, compared with the conventional cleaning method in the comparative example, the cleaning method of the present invention has improved the removal effect of various metal ions on the surface, and the metal ion concentration on the epitaxial wafer surface is significantly reduced.

[0067] The surface particle residue of the epitaxial wafers obtained after final cleaning in each embodiment and comparative example was also tested using a defect tester 8520. The results are as follows: Figures 2 to 5 As shown in Table 2, the data results demonstrate that the cleaning method of the present invention is significantly better than traditional cleaning methods at removing surface particulate matter.

[0068] Table 2

[0069] This invention employs a two-fluid pre-cleaning process using pure water and N2, followed by sequential ultrasonic cleaning in an acid bath and concentration gradient and low- and high-frequency megasononic cleaning in an alkaline bath. Finally, a slow, warm water drying method is used to obtain clean, residue-free silicon carbide epitaxial wafers. This significantly reduces mercury residue and nanoparticle contamination issues after mercury CV testing of silicon carbide epitaxial wafers. It enables batch final cleaning of silicon carbide epitaxial wafers after testing, achieving cleaning results that meet the surface metal and particle cleanliness requirements of subsequent device manufacturing processes.

Claims

1. A method of cleaning a silicon carbide epitaxial wafer, comprising: The method comprises the following steps: S1, pre-cleaning; ultra-pure water is mixed with high-pressure N2 and sprayed to the surface of the silicon carbide wafer for cleaning; S2, acid treatment; the silicon carbide wafer is moved into a cleaning tank containing a mixed solution of hydrochloric acid, hydrofluoric acid and hydrogen peroxide for ultrasonic cleaning, and then is moved into an ultra-pure water tank for rinsing; S3, No. 1 alkali treatment; the silicon carbide wafer is moved into a cleaning tank containing a mixed solution of ammonia and hydrogen peroxide for low-frequency megasonic cleaning, and then is moved into an ultra-pure water tank for rinsing; S4, No. 2 alkali treatment; the silicon carbide wafer is moved into a cleaning tank containing a mixed solution of ammonia, hydrogen peroxide and amphoteric surfactant for high-frequency megasonic cleaning, and then is moved into an ultra-pure water tank for rinsing; the concentration of ammonia in the mixed solution in this step is lower than that in the mixed solution in step S3; S5, the silicon carbide wafer is dried by a warm water slow lifting and drying method; S6, the silicon carbide wafer is placed in an infrared heating tank for drying.

2. The silicon carbide epitaxial wafer cleaning method of claim 1 wherein, In step S1, the flow ratio of ultra-pure water to high-pressure N2 is (1:30)-(1:60), and the cleaning time is 20-30s.

3. The silicon carbide epitaxial wafer cleaning method of claim 1 wherein, In step S2, the mass concentration of hydrochloric acid is 36%-38%, the mass concentration of hydrofluoric acid is 49%, and the mass concentration of hydrogen peroxide is 30%; the volume ratio of hydrofluoric acid, hydrochloric acid, hydrogen peroxide and water in the mixed solution is 1:25:25:(500-1000).

4. The silicon carbide epitadyne wafer cleaning method of claim 1 wherein, In step S2, the temperature of the mixed solution is 20-50℃, the ultrasonic frequency is 40kHz, the ultrasonic cleaning time is 100-300s, and the circulating flow of the mixed solution is 15-20L / min.

5. The method of claim 1, wherein the cleaning solution is a mixture of 0.1% HF and 0.1% H2O2 in deionized water. In step S3, the mass concentration of ammonia is 28%-30%, and the mass concentration of hydrogen peroxide is 30%; the volume ratio of ammonia, hydrogen peroxide and water in the mixed solution is 1:1:(5-10).

6. The silicon carbide epitadyne wafer cleaning method of claim 1 wherein, In step S3, the temperature of the mixed solution is 50-60℃, the low-frequency megasonic frequency is 730kHz, the low-frequency megasonic cleaning time is 200-300s, and the circulating flow of the mixed solution is 15-20L / min.

7. The silicon carbide epitadyne wafer cleaning method of claim 1 wherein, In step S4, the mass concentration of ammonia is 28%-30%, and the mass concentration of hydrogen peroxide is 30%; the volume ratio of ammonia, hydrogen peroxide and water in the mixed solution is 1:2:(10-20); the amphoteric surfactant is N,N,N-trimethylglycine, and the ratio of N,N,N-trimethylglycine to water is 0.3-0.5wt%.

8. The method of claim 1, wherein the cleaning solution is a mixture of 0.1% HF and 0.1% H2O2 in deionized water. In step S4, the temperature of the mixed solution is 60-70℃, the high-frequency megasonic frequency is 1000kHz, the high-frequency megasonic cleaning time is 200-300s, and the circulating flow of the mixed solution is 15-20L / min.

9. The method of Claim 1 wherein, In step S5, the silicon carbide wafer is placed in a slow lifting tank containing ultra-pure water and is slowly lifted, the temperature of the ultra-pure water is 30-45℃, and the lifting speed is 0.8-1.5mm / s.

10. The method of claim 1, wherein the cleaning solution is a mixture of 0.1% HF and 0.1% H2O2 in deionized water. In step S6, the temperature of the infrared heating tank is 60-80℃, and the drying time is 100-150s.

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