Cleaning method for removing metal ion residues on surface of large-size silicon carbide substrate

Abstract

The invention relates to the technical field of semiconductor manufacturing, and particularly discloses a cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate. The method comprises the following steps: firstly, cleaning silicon carbide by adopting water-gas two-fluid jet, and rapidly stripping and taking away loose metal ions and impurity particles on the surface of a substrate by utilizing impact force of high-speed water flow and air flow; then, carrying out fluid cleaning on the silicon carbide by adopting an ammonia water solution which can promote solid particles to be separated from the surface of the silicon carbide substrate; after the silicon carbide is cleaned by the ammonia water solution, the brush is matched with ultrapure water for spraying, so that stubborn stains and small particles on the surface of the silicon carbide are effectively removed; cleaning the silicon carbide by adopting an ozone-containing hydrofluoric acid solution which can promote the dissolution of metal ions and remove metal impurities which are difficult to remove; and finally, carrying out deep cleaning by adopting a hydrofluoric acid solution, etching metal impurities oxidized by ozone and embedded in an oxide layer, and ensuring that the metal impurities which are difficult to remove are thoroughly eluted.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor manufacturing technology, and in particular to a cleaning method for removing metal ion residues on the surface of a large-sized silicon carbide substrate. Background Art

[0002] In the semiconductor field, silicon carbide (SiC) substrates have become ideal materials for making high-temperature, high-frequency, and high-power semiconductor devices due to their excellent properties such as high breakdown electric field, high electron saturation drift velocity, and high thermal conductivity. They have extremely broad application prospects in key fields such as new energy vehicles, 5G communications, and aerospace. With the rapid development of related industries, the demand for large-size silicon carbide substrates is growing. Large-size substrates can effectively reduce the manufacturing cost of devices and improve production efficiency, which is in line with the trend of large-scale development of the industry.

[0003] However, during the growth and processing of silicon carbide substrates, various contaminants, especially metal impurities, will inevitably be introduced onto their surfaces. These metal impurities will seriously affect the electrical properties of silicon carbide substrates and the reliability of devices. For example, metal residues may lead to increased leakage, reduced breakdown voltage, and shortened life of devices, which greatly limits the performance improvement and application expansion of silicon carbide devices.

[0004] The existing chemical mechanical polishing (CMP) cleaning process is mainly traditional RCA cleaning, which has many limitations for cleaning large-size silicon carbide substrates. On the one hand, traditional RCA cleaning is difficult to reduce metal residues to an extremely low level that meets the requirements of advanced device manufacturing, and cannot effectively remove trace metal impurities tightly adsorbed on the substrate surface. Even repeated RCA cleaning cannot further reduce the surface metal residues. Repeated RCA cleaning is time-consuming and costly, which is not conducive to rapid and high-quality output. On the other hand, as the size of the substrate increases, the uniformity of cleaning is difficult to ensure, and it is easy to have incomplete or over-cleaning of local cleaning, which in turn affects the overall quality and consistency of the substrate. In addition, during the APM cleaning process, Fe and Al will be redeposited, and the HPM solution will also cause particle redeposition and precious metal residues. Therefore, developing a large-size silicon carbide substrate cleaning method that can achieve lower surface metal residues is of vital significance to promote the development of the silicon carbide semiconductor industry. Summary of the invention

[0005] In view of the problem that the existing cleaning methods for large-sized silicon carbide substrates cannot effectively remove the trace metals remaining on the surface of the silicon carbide substrate, the present invention provides a cleaning method for removing the metal ion residues on the surface of the large-sized silicon carbide substrate. The present invention uses two-fluid jet cleaning, ammonia fluid cleaning, sponge brushing, O3-containing HF solution fluid cleaning, DHF solution cleaning, high-speed rotary drying and other steps to effectively remove the metal ions remaining on the surface of the large-sized silicon carbide substrate, and the metal ion residue can reach 5.0E+08atoms / cm 2 The following meets the manufacturing requirements of advanced devices and has high promotion and application value.

[0006] In order to solve the above technical problems, the technical solution provided by the present invention is: A cleaning method for removing metal ion residues on the surface of a large-sized silicon carbide substrate, wherein the silicon carbide substrate is a silicon carbide substrate that has been subjected to chemical mechanical polishing, dewaxing cleaning, and RCA cleaning, and the cleaning method comprises the following steps: S1, using water and gas two fluids to spray clean the rotating silicon carbide substrate to be cleaned, to obtain silicon carbide substrate I; S2, washing the rotating silicon carbide substrate I with an ammonia solution to obtain a silicon carbide substrate II; S3, scrubbing the rotating silicon carbide substrate II with a brush, and spraying with ultrapure water at the same time, to obtain silicon carbide substrate III; S4, washing the rotating silicon carbide substrate III with a hydrofluoric acid solution containing ozone to obtain a silicon carbide substrate IV; S5, washing the rotating silicon carbide substrate IV with a hydrofluoric acid solution and ultrapure water in turn, and drying by high-speed rotation to obtain a clean silicon carbide substrate.

[0007] Compared with the prior art, the cleaning method for removing metal ion residues on the surface of a large-sized silicon carbide substrate provided by the present invention first uses a water-gas two-fluid jet to clean the silicon carbide, and uses the impact force of high-speed water flow and air flow to quickly peel off and take away the loose metal ions and impurity particles on the surface of the substrate; then, an ammonia solution is used to perform fluid cleaning on the silicon carbide, and the ammonia solution can promote the solid particles to separate from the surface of the silicon carbide substrate, and chemically react with the metal ions to form a soluble complex, which is dissolved and removed from the substrate surface; after cleaning with the ammonia solution, a brush is used in combination with an ultrapure water spray to effectively remove the carbonized particles. Stubborn stains and tiny particles on the silicon surface; then use ozone-containing hydrofluoric acid solution to clean silicon carbide, which can promote the dissolution of metal ions and remove difficult-to-remove metal impurities; finally, use hydrofluoric acid solution for deep cleaning to etch away metal impurities oxidized by ozone and embedded in the oxide layer, ensuring that difficult-to-remove metal impurities are thoroughly washed away; in addition, during the entire cleaning process, silicon carbide always maintains a self-rotating state, and the superposition of the physical impact force brought by the fluid and self-rotation makes it easier to remove tiny particles and prevent particles from re-depositing, which is conducive to fully removing metal impurities wrapped in the particles.

[0008] The present invention realizes the efficient removal of metal ion residues on the surface of large-sized silicon carbide substrates through the close coordination of multiple cleaning processes. It is an efficient, green and environmentally friendly silicon carbide substrate cleaning method that can meet the strict requirements for silicon carbide substrate cleaning in different application scenarios and has wide applicability and promotion value.

[0009] It should be noted that the large-size silicon carbide substrate in the present invention refers to a silicon carbide wafer with a size of more than 8 inches.

[0010] It should be noted that before the above-mentioned cleaning process is performed using the present invention, the silicon carbide substrate has completed dewaxing cleaning and RCA cleaning. The present invention has no special requirements for dewaxing cleaning and RCA cleaning. The silicon carbide substrate after conventional existing dewaxing cleaning and RCA cleaning can also use the cleaning provided by the present invention to achieve the effect of effectively removing trace residual metal ions.

[0011] Furthermore, in S1, the flow rate of ultrapure water is 70 mL / min~120 mL / min, the flow rate of nitrogen is 9 L / min~14 L / min, the rotation speed of the silicon carbide substrate is 500 r / min~700 r / min, and the discharge time of the two fluids is 15 s~25 s.

[0012] Furthermore, in S1, the two-fluid nozzle reciprocates along the diameter direction of the silicon carbide substrate.

[0013] The process control of the above two-fluid jet cleaning can ensure that the entire large-size silicon carbide substrate surface is cleaned evenly and effectively, avoiding cleaning dead corners and ensuring that each location meets the required cleanliness standards.

[0014] Furthermore, in S2, the ammonia solution is a mixed solution of concentrated ammonia water and ultrapure water in a volume ratio of 1:6 to 1:3, wherein the mass concentration of the concentrated ammonia water is 25% to 28%.

[0015] The hydroxide ions dissociated from ammonia water can make the surface of the silicon carbide substrate negatively charged, change the zeta potential of the particles deposited on the surface of the silicon carbide substrate, and make the particles and the silicon carbide substrate repel each other. At the same time, the superposition of the physical impact force of the fluid and self-rotation makes it easier for the particles to detach from the silicon carbide surface and prevent the particles from re-depositing. In addition, it can also remove some small molecular organic matter and complex metal ions, thereby improving the cleanliness of the silicon carbide substrate.

[0016] Furthermore, in S2, the temperature of the aqueous ammonia solution is 35°C to 55°C.

[0017] Furthermore, in S2, the flow rate of the ammonia solution is 400 mL / min~500 mL / min, the spitting time is 20 s~60 s, and the rotation speed of the silicon carbide substrate 1 is 500 r / min~700 r / min.

[0018] The temperature and concentration of the ammonia solution are controlled within a specific range, which can not only ensure the cleaning effect but also minimize the corrosion to the silicon carbide substrate.

[0019] Further, in S2, the radial distance from the injection position of the ammonia solution on the surface of the silicon carbide substrate 1 to the center of the circle is 3 / 16 to 5 / 16 of the diameter.

[0020] The preferred injection position of the ammonia solution can allow the ammonia solution to quickly cover the entire surface of the silicon carbide substrate under the action of rotation, and timely update the cleaning liquid on the surface of the silicon carbide substrate, thereby improving the cleaning efficiency.

[0021] It should be noted that the ammonia solution is sprayed onto the surface of the silicon carbide substrate through a pipeline resistant to acid and alkali corrosion.

[0022] Furthermore, in S3, during brushing, the rotation speed of the brush is 100 r / min~150 r / min, and the rotation speed of the silicon carbide substrate II is 300 r / min~500 r / min.

[0023] Furthermore, in S3, the spray flow rate of the ultrapure water is 200 mL / min~300 mL / min.

[0024] Furthermore, in S3, the brush head of the brush and the spray head of ultrapure water reciprocate along the diameter direction of the silicon carbide substrate II.

[0025] Exemplarily, in S3, the brush is a PVA sponge brush, the brush head diameter is 20 mm to 30 mm, and the brush head directly contacts the upper surface of the silicon carbide substrate.

[0026] It should be noted that in S3, the brush head of the brush and the silicon carbide substrate rotate in the same direction, and both synchronously reciprocate along the diameter direction of the silicon carbide substrate under the control of the motor.

[0027] When using a brush in combination with ultrapure water spray for scrubbing, the brush speed, substrate speed and ultrapure water spray flow rate are controlled to minimize the damage caused by direct friction between the brush and the substrate while ensuring effective removal of stubborn stains and tiny particles on the surface of the silicon carbide substrate.

[0028] Furthermore, before step S4, an ultrapure water fluid cleaning step is also included: ultrapure water is used to rinse the scrubbed silicon carbide substrate III; wherein the flow rate of the ultrapure water is 200mL / min~400mL / min, the rotation speed of the silicon carbide substrate III is 500r / min~700r / min, and the radial distance from the injection position of the ultrapure water on the surface of the silicon carbide substrate III to the center of the circle is 1 / 3~1 / 4 of the diameter.

[0029] The ultrapure water fluid cleaning can fully remove the cleaning liquid of the previous step on the surface of the silicon carbide substrate, ensuring that the chemical liquid in the next step can fully exert its cleaning effect.

[0030] Furthermore, in S4, the concentration of O3 in the ozone-containing hydrofluoric acid solution is 10 ppb-30 ppb, and the concentration of HF is 7 wt%-15 wt%.

[0031] Furthermore, in S4, the flow rate of the ozone-containing hydrofluoric acid solution is 350 mL / min to 500 mL / min, the spitting time is 20 s to 60 s, and the rotation speed of the silicon carbide substrate III is 500 r / min to 700 r / min.

[0032] Furthermore, in S4, the radial distance from the spraying position of the ozone-containing hydrofluoric acid solution on the surface of the silicon carbide substrate III to the center of the circle is 1 / 3 to 1 / 4 of the diameter.

[0033] It should be noted that the hydrofluoric acid solution containing ozone is sprayed onto the surface of the silicon carbide substrate using a pipeline resistant to acid and alkali corrosion.

[0034] The ozone-containing hydrofluoric acid solution can oxidize some metal impurities that are difficult to be directly removed by hydrofluoric acid into high-valent oxides that are more easily reacted with hydrofluoric acid, so that hydrofluoric acid can effectively remove metal oxide impurities on the surface of the substrate. The synergy of HF and O3 significantly increases the effect of the cleaning solution in removing impurities, making the substrate surface purer. In addition, the oxygen produced by the decomposition of residual ozone also helps to form a protective oxide layer on the substrate surface, reducing the possibility of metal ions being adsorbed to the substrate surface again, so that the residual metal ions on the surface of the silicon carbide substrate reach an extremely low concentration level, meeting the stringent standards for ultra-high cleanliness of the substrate in high-end application fields such as semiconductor manufacturing and power device production.

[0035] Furthermore, before step S5, an ultrapure water fluid cleaning step is also included: the silicon carbide substrate IV is rinsed with ultrapure water; wherein the flow rate of the ultrapure water is 200mL / min~400mL / min, the rotation speed of the silicon carbide substrate IV is 500r / min~700r / min, and the radial distance from the injection position of the ultrapure water on the surface of the silicon carbide substrate IV to the center of the circle is 1 / 3~1 / 4 of the diameter.

[0036] Further, in S5, the concentration of the hydrofluoric acid solution is 5wt%~9wt%, the flow rate of the hydrofluoric acid solution is 400mL / min~500mL / min, the spitting time is 20s~60s, and the rotation speed of the silicon carbide substrate IV is 500r / min~700r / min.

[0037] The use of a relatively low concentration HF solution can further etch and remove the impurity oxides on the surface of the silicon carbide substrate completely, obtaining a clean and contaminant-free effect. The surface of the treated silicon carbide substrate is ultimately terminated with Si-OH and CO groups, showing a higher hydrophilicity and being less susceptible to contamination by particles and impurities.

[0038] Furthermore, in S5, the radial distance from the spraying position of the hydrofluoric acid solution on the surface of the silicon carbide substrate IV to the center of the circle is 1 / 3 to 1 / 4 of the diameter.

[0039] The preferred injection position of the hydrofluoric acid solution can allow the hydrofluoric acid solution to quickly cover the entire surface of the silicon carbide substrate under the action of rotation, and timely update the cleaning liquid on the surface of the silicon carbide substrate, thereby improving the cleaning efficiency.

[0040] It should be noted that the HF solution is sprayed onto the surface of the silicon carbide substrate using a pipeline resistant to acid and alkali corrosion.

[0041] Furthermore, in S5, the flow rate of the ultrapure water is 200 mL / min~400 mL / min, the rotation speed of the silicon carbide substrate IV is 500 r / min~700 r / min, and the radial distance from the injection position of the ultrapure water on the surface of the silicon carbide substrate IV to the center of the circle is 1 / 3~1 / 4 of the diameter.

[0042] Furthermore, in S5, in the spin drying step, the rotation speed of the silicon carbide substrate IV is 1800 r / min to 2200 r / min.

[0043] Through high-speed spin drying, the silicon carbide substrate can obtain a dry surface within 50 seconds, and there is almost no residual water film on the surface.

[0044] It should be noted that the process time of each of the above cleaning steps is controlled within 20 to 60 seconds, and can be adjusted within the above range according to the cleaning effect, and the present invention does not make any special limitation.

[0045] It should be noted that the rotations involved in the above steps are all horizontal rotations. The process steps without special temperature requirements are all carried out at room temperature (20-25°C).

[0046] The cleaning method of the large-size silicon carbide substrate provided by the present invention achieves the effect of reducing particle contamination and lower metal impurity residue on the surface of the silicon carbide substrate without the need for megasonic energy that may cause microstructural damage to the surface of the silicon carbide substrate. Each cleaning step can be completed within tens of seconds. At the same time, the amount of cleaning solution and purified water used is small, which is suitable for industrial production applications and has broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0047] Figure 1 FIG. 1 is a process flow chart of cleaning a silicon carbide substrate according to an embodiment. DETAILED DESCRIPTION

[0048] 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.

[0049] In order to better illustrate the present invention, further examples are given below.

[0050] The silicon carbide substrates cleaned in the following embodiments and comparative examples are silicon carbide wafers that have been treated with dewax water cleaning + tumbling cleaning (1800-2500s), RCA cleaning: SPM (110-120°C immersion cleaning for 1000-1500s) + APM (60-70°C ultrasonic cleaning for 500-1000s, 120-170kHz) + HPM (60-70°C ultrasonic cleaning for 500-1000s, 120-170kHz) + DHF (room temperature immersion for 300-500s), and QDR rinsing is performed after each liquid cleaning, and the wafers are dried in a spin dryer.

[0051] Among them, SPM is a mixed solution of sulfuric acid and hydrogen peroxide, APM is a mixed aqueous solution of ammonia and hydrogen peroxide, HPM is a mixed aqueous solution of hydrochloric acid and hydrogen peroxide, and DHF is a diluted hydrofluoric acid solution.

[0052] The resistivity of the ultrapure water used in the following examples and comparative examples is greater than 18.2 MΩ·cm. The ammonia water is 28 wt% UPS grade; and the HF is 40 wt% BV-III grade.

[0053] Ozone water is produced by using an ozone generator, with O2 and CO2 gases and ultrapure water as raw materials, under the action of radio frequency discharge, and the concentration is controllable. HF solution containing O3 is prepared by dissolving ozone water and HF in ultrapure water, and ozone water solution is prepared by dissolving O3 in ultrapure water.

[0054] Example 1 This embodiment provides a method for cleaning a silicon carbide substrate, comprising the following steps: S1, randomly select 12 silicon carbide wafers to be cleaned, and use water-gas two-fluid to spray clean the silicon carbide wafers, the flow rate of ultrapure water is controlled to 100mL / min, the flow rate of high-purity nitrogen is controlled to 12L / min, the wafer rotation speed is 600r / min, the two-fluid spitting time is 20s, the wafer always keeps self-rotation during the cleaning process, and the two-fluid nozzle reciprocates along the wafer diameter under the control of the motor; S2, using an ammonia solution to perform fluid cleaning on the silicon carbide wafer, wherein the ammonia solution is a mixed solution of concentrated ammonia water and ultrapure water in a volume ratio of 1:4, the temperature of the ammonia solution is 45°C, the flow rate of the ammonia solution is 400mL / min, the discharge time is 45s, the wafer rotation speed is 600r / min, the wafer always keeps self-rotating during the cleaning process, and the radial distance between the ammonia solution injection position and the wafer center is 1 / 4 of the diameter; S3, use a PVA sponge brush to scrub the silicon carbide wafer, and at the same time, use ultrapure water to rinse the wafer. The speed of the brush head is controlled to 120r / min, the diameter of the brush head is 20~30mm, the speed of the wafer is controlled to 400r / min, the two rotate in the same direction, the flow rate of ultrapure water is controlled to 250mL / min, and the brush head and ultrapure water nozzle are synchronously reciprocated along the diameter direction of the wafer under the control of the motor; S4, using ultrapure water to perform fluid cleaning on the silicon carbide wafer, the ultrapure water flow rate is controlled to be 300 mL / min, the wafer rotation speed is 600 r / min, and the radial distance between the ultrapure water spray position and the wafer center is 1 / 4 of the diameter; S5, using an ozone-containing hydrofluoric acid solution to perform fluid cleaning on the silicon carbide wafer, the concentration of O3 in the ozone-containing hydrofluoric acid solution is 25 ppb, the concentration of HF is 12 wt%, the flow rate of the ozone-containing hydrofluoric acid solution is controlled to be 450 mL / min, the spitting time is 60 s, the wafer rotation speed is 600 r / min, the wafer always keeps self-rotating during the cleaning process, and the radial distance between the injection position of the ozone-containing hydrofluoric acid solution and the center of the wafer is 1 / 4 of the diameter; S6, ultrapure water fluid cleaning, same as step S4; S7, using a dilute hydrofluoric acid solution with a concentration of 8wt% to perform fluid cleaning on the silicon carbide wafer, the flow rate of the dilute hydrofluoric acid solution is controlled to be 500mL / min, the spitting time is 60s, the wafer rotation speed is 600r / min, the wafer always keeps rotating during the cleaning process, and the radial distance between the injection position of the dilute hydrofluoric acid solution and the center of the wafer is 1 / 4 of the diameter; S8, ultrapure water fluid cleaning, same as step S4; S9, high-speed spin drying the silicon carbide wafer at a rotation speed of 2000 r / min to obtain a clean silicon carbide wafer. Two wafers are randomly selected, namely wafer a and wafer b, to detect the metal residue on the surface of the silicon carbide.

[0055] 12 silicon carbide wafers obtained by the same dewaxing water cleaning and RCA cleaning were used and cleaned according to the same process as above. The only difference was that the hydrofluoric acid solution containing ozone in S5 was replaced by an ozone aqueous solution. The concentration of O3 in the ozone aqueous solution was 25ppb, and the rest was exactly the same. Two wafers were randomly selected and recorded as wafer a' and wafer b' to detect the metal residue on the silicon carbide surface. The results are shown in Table 1.

[0056] Table 1 Metal ion residues

[0057] The residual Al, Fe, Cu, Ni, Au, Ag, and Pt on the surfaces of substrates a and b detected in Example 1 reached a level below 5.0E+08 atoms / cm². The metal elements of silicon carbide substrates a' and b' substrates cleaned with ozone aqueous solution had relatively higher residual values, especially Al, Fe, and Cu had obvious differences in order of magnitude, and the residual levels of Ca and Mg could not be fully maintained below 2.0E+10 atoms / cm².

[0058] Example 2 This embodiment provides a method for cleaning a silicon carbide substrate, comprising the following steps: S1, randomly select 25 silicon carbide wafers to be cleaned, and use water-gas two-fluid to spray clean the silicon carbide wafers, the flow rate of ultrapure water is controlled to 70mL / min, the flow rate of high-purity nitrogen is controlled to 9L / min, the wafer rotation speed is 500r / min, the two-fluid spitting time is 15s, the wafer always keeps self-rotation during the cleaning process, and the two-fluid nozzle reciprocates along the wafer diameter under the control of the motor; S2, using an ammonia solution to perform fluid cleaning on the silicon carbide wafer, wherein the ammonia solution is a mixed solution of concentrated ammonia water and ultrapure water in a volume ratio of 1:6, the temperature of the ammonia solution is 35°C, the flow rate of the ammonia solution is 450mL / min, the spitting time is 30s, the wafer rotation speed is 500r / min, the wafer always keeps rotating during the cleaning process, and the radial distance between the ammonia solution injection position and the wafer center is 3 / 16 of the diameter; S3, use a PVA sponge brush to scrub the silicon carbide wafer, and at the same time, use ultrapure water to rinse the wafer. The speed of the brush head is controlled to 100r / min, the diameter of the brush head is 20~30mm, the speed of the wafer is controlled to 500r / min, the two rotate in the same direction, the flow rate of ultrapure water is controlled to 300mL / min, and the brush head and the ultrapure water nozzle are synchronously reciprocated along the diameter direction of the wafer under the control of the motor; S4, using ultrapure water to perform fluid cleaning on the silicon carbide wafer, the ultrapure water flow rate is controlled to be 400 mL / min, the wafer rotation speed is 500 r / min, and the radial distance between the ultrapure water spray position and the wafer center is 1 / 3 of the diameter; S5, using an ozone-containing hydrofluoric acid solution to perform fluid cleaning on the silicon carbide wafer, the concentration of O3 in the ozone-containing hydrofluoric acid solution is 10 ppb, the concentration of HF is 15 wt%, the flow rate of the ozone-containing hydrofluoric acid solution is controlled to be 350 mL / min, the spitting time is 40 s, the wafer rotation speed is 500 r / min, the wafer always keeps self-rotating during the cleaning process, and the radial distance between the injection position of the ozone-containing hydrofluoric acid solution and the center of the wafer is 1 / 3 of the diameter; S6, ultrapure water fluid cleaning, same as step S4; S7, using a 9wt% dilute hydrofluoric acid solution to perform fluid cleaning on the silicon carbide wafer, the flow rate of the dilute hydrofluoric acid solution is controlled to be 400mL / min, the spitting time is 20s, the wafer rotation speed is 700r / min, the wafer always keeps rotating during the cleaning process, and the radial distance between the injection position of the dilute hydrofluoric acid solution and the center of the wafer is 1 / 3 of the diameter; S8, ultrapure water fluid cleaning, same as step S4; S9, the silicon carbide wafer is subjected to high-speed rotational drying at a rotation speed of 1800 r / min to obtain a clean silicon carbide wafer. Two wafers are randomly selected and respectively recorded as wafer c and wafer d to detect the metal residue on the surface of the silicon carbide. The results are shown in Table 2.

[0059] Table 2

[0060] The Al, Fe, Cu, Ni, Au, Ag, and Pt residues on the surfaces of substrates c and d detected in Example 2 reached a level below 5.0E+08atoms / cm².

[0061] Example 3 This embodiment provides a method for cleaning a silicon carbide substrate, comprising the following steps: S1, randomly select 15 silicon carbide wafers to be cleaned, and use water-gas two-fluid to spray clean the silicon carbide wafers, the flow rate of ultrapure water is controlled to 120mL / min, the flow rate of high-purity nitrogen is controlled to 14L / min, the wafer rotation speed is 700r / min, the two-fluid spitting time is 25s, the wafer always keeps self-rotation during the cleaning process, and the two-fluid nozzle reciprocates along the wafer diameter under the control of the motor; S2, using an ammonia solution to perform fluid cleaning on the silicon carbide wafer, wherein the ammonia solution is a mixed solution of concentrated ammonia water and ultrapure water in a volume ratio of 1:3, the temperature of the ammonia solution is 65°C, the flow rate of the ammonia solution is 500mL / min, the discharge time is 60s, the wafer rotation speed is 700r / min, the wafer always keeps rotating during the cleaning process, and the radial distance between the ammonia solution injection position and the wafer center is 5 / 16 of the diameter; S3, use a PVA sponge brush to scrub the silicon carbide wafer, and at the same time, use ultrapure water to rinse the wafer. The speed of the brush head is controlled to 150r / min, the diameter of the brush head is 20~30mm, the speed of the wafer is controlled to 300r / min, the two rotate in the same direction, the flow rate of ultrapure water is controlled to 200mL / min, and the brush head and the ultrapure water nozzle are synchronously reciprocated along the diameter direction of the wafer under the control of the motor; S4, using ultrapure water to perform fluid cleaning on the silicon carbide wafer, the ultrapure water flow rate is controlled to be 200 mL / min, the wafer rotation speed is 700 r / min, and the radial distance between the ultrapure water spray position and the wafer center is 1 / 4 of the diameter; S5, using an ozone-containing hydrofluoric acid solution to perform fluid cleaning on the silicon carbide wafer, the concentration of O3 in the ozone-containing hydrofluoric acid solution is 30 ppb, the concentration of HF is 7 wt%, the flow rate of the ozone-containing hydrofluoric acid solution is controlled to be 500 mL / min, the spitting time is 20 s, the wafer rotation speed is 700 r / min, the wafer always keeps rotating during the cleaning process, and the radial distance between the injection position of the ozone-containing hydrofluoric acid solution and the center of the wafer is 1 / 4 of the diameter; S6, ultrapure water fluid cleaning, same as step S4; S7, using a 5wt% dilute hydrofluoric acid solution to perform fluid cleaning on the silicon carbide wafer, the flow rate of the dilute hydrofluoric acid solution is controlled to be 450mL / min, the spitting time is 40s, the wafer rotation speed is 500r / min, the wafer always keeps rotating during the cleaning process, and the radial distance between the injection position of the dilute hydrofluoric acid solution and the center of the wafer is 1 / 4 of the diameter; S8, ultrapure water fluid cleaning, same as step S4; S9, the silicon carbide wafer is subjected to high-speed rotational drying at a rotation speed of 2200 r / min to obtain a clean silicon carbide wafer. Two wafers are randomly selected and respectively recorded as wafer e and wafer f to detect the metal residue on the surface of the silicon carbide. The results are shown in Table 3.

[0062] Table 3

[0063] The Al, Fe, Cu, Ni, Au, Ag, and Pt residues on the surfaces of substrates e and f detected in Example 3 reached a level below 5.0E+08atoms / cm².

[0064] 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. A cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate, characterized in that: The silicon carbide substrate is a silicon carbide substrate that has been subjected to chemical mechanical polishing, dewaxing cleaning and RCA cleaning, and the cleaning method comprises the following steps: S1, using water and gas two fluids to spray clean the rotating silicon carbide substrate to be cleaned, to obtain silicon carbide substrate I; S2, washing the rotating silicon carbide substrate I with an ammonia solution to obtain a silicon carbide substrate II; S3, scrubbing the rotating silicon carbide substrate II with a brush, and spraying with ultrapure water at the same time, to obtain silicon carbide substrate III; S4, washing the rotating silicon carbide substrate III with a hydrofluoric acid solution containing ozone to obtain a silicon carbide substrate IV; S5, washing the rotating silicon carbide substrate IV with a hydrofluoric acid solution and ultrapure water in turn, and drying by high-speed rotation to obtain a clean silicon carbide substrate.

2. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: In S1, the ultrapure water flow rate is 70 mL / min to 120 mL / min, the nitrogen flow rate is 9 L / min to 14 L / min, the rotation speed of the silicon carbide substrate is 500 r / min to 700 r / min, and the discharge time of the two fluids is 15 s to 25 s; and / or In S1, the two-fluid nozzle reciprocates along the diameter direction of the silicon carbide substrate.

3. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: In S2, the ammonia solution is a mixed solution of concentrated ammonia water and ultrapure water in a volume ratio of 1:6 to 1:3, wherein the mass concentration of the concentrated ammonia water is 25% to 28%; and / or In S2, the temperature of the ammonia solution is 35°C to 55°C; and / or In S2, the flow rate of the ammonia solution is 400 mL / min~500 mL / min, the discharge time is 20 s~60 s, and the rotation speed of the silicon carbide substrate 1 is 500 r / min~700 r / min; and / or In S2, the radial distance from the injection position of the ammonia solution on the surface of the silicon carbide substrate 1 to the center of the circle is 3 / 16 to 5 / 16 of the diameter.

4. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: In S3, during brushing, the rotation speed of the brush is 100 r / min to 150 r / min, and the rotation speed of the silicon carbide substrate II is 300 r / min to 500 r / min; and / or In S3, the spray flow rate of the ultrapure water is 200 mL / min to 300 mL / min; and / or In S3, the brush head of the brush and the spray head of ultrapure water reciprocate along the diameter direction of the silicon carbide substrate II.

5. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: Before step S4, an ultrapure water fluid cleaning step is also included: ultrapure water is used to rinse the scrubbed silicon carbide substrate III; wherein the flow rate of the ultrapure water is 200mL / min~400mL / min, the rotation speed of the silicon carbide substrate III is 500r / min~700r / min, and the radial distance from the injection position of the ultrapure water on the surface of the silicon carbide substrate III to the center of the circle is 1 / 3~1 / 4 of the diameter.

6. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: In S4, the concentration of O3 in the ozone-containing hydrofluoric acid solution is 10 ppb to 30 ppb, and the concentration of HF is 7 wt% to 15 wt%; and / or In S4, the flow rate of the ozone-containing hydrofluoric acid solution is 350 mL / min to 500 mL / min, the discharge time is 20 s to 60 s, and the rotation speed of the silicon carbide substrate III is 500 r / min to 700 r / min.

7. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: In S4, the radial distance between the spraying position of the ozone-containing hydrofluoric acid solution on the surface of the silicon carbide substrate III and the center of the circle is 1 / 3 to 1 / 4 of the diameter.

8. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: Before step S5, an ultrapure water fluid cleaning step is also included: the silicon carbide substrate IV is rinsed with ultrapure water; wherein the flow rate of the ultrapure water is 200mL / min~400mL / min, the rotation speed of the silicon carbide substrate IV is 500r / min~700r / min, and the radial distance from the injection position of the ultrapure water on the surface of the silicon carbide substrate IV to the center of the circle is 1 / 3~1 / 4 of the diameter.

9. The cleaning method for removing metal ion residues on the surface of a large-size silicon carbide substrate according to claim 1, characterized in that: In S5, the concentration of the hydrofluoric acid solution is 5wt%~9wt%, the flow rate of the hydrofluoric acid solution is 400mL / min~500mL / min, the discharge time is 20s~60s, and the rotation speed of the silicon carbide substrate IV is 500r / min~700r / min; and / or In S5, the radial distance between the spraying position of the hydrofluoric acid solution on the surface of the silicon carbide substrate IV and the center of the circle is 1 / 3 to 1 / 4 of the diameter.

10. The cleaning method for removing metal ion residues on the surface of a large-sized silicon carbide substrate according to claim 1, characterized in that: In S5, the flow rate of the ultrapure water is 200 mL / min to 400 mL / min, the rotation speed of the silicon carbide substrate IV is 500 r / min to 700 r / min, and the radial distance from the injection position of the ultrapure water on the surface of the silicon carbide substrate IV to the center of the circle is 1 / 3 to 1 / 4 of the diameter; and / or In S5, in the spin drying step, the rotation speed of the silicon carbide substrate IV is 1800 r / min to 2200 r / min.

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