A cleaning method for removing residual metal ions on the surface of large-size silicon carbide substrates

Abstract

The present invention relates to the field of semiconductor manufacturing technology, and specifically discloses a cleaning method for removing residual metal ions on the surface of a large-size silicon carbide substrate. First, the present invention uses a water-air two-fluid jet to clean the silicon carbide, and utilizes the impact force of high-speed water flow and air flow to quickly peel off and carry away loose metal ions and impurity particles on the surface of the substrate; then, an ammonia water solution is used to perform a fluid cleaning on the silicon carbide, and the ammonia water solution can promote the detachment of solid particles from the surface of the silicon carbide substrate; after the ammonia water solution cleaning, a brush is combined with ultra-pure water spraying to effectively remove stubborn stains and fine particles on the surface of the silicon carbide; then, a hydrofluoric acid solution containing ozone is used to clean the silicon carbide, and this solution can promote the dissolution of metal ions and remove difficult-to-remove metal impurities; finally, a hydrofluoric acid solution is used for deep cleaning to etch away the metal impurities oxidized by ozone and embedded in the oxide layer, ensuring that the difficult-to-remove metal impurities are completely 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] Aiming at the problem that the existing cleaning methods for large-size silicon carbide substrates cannot effectively remove the trace metals remaining on the surface of the silicon carbide substrates, the present invention provides a cleaning method for removing the residual metal ions on the surface of large-size silicon carbide substrates. The SiC substrates after chemical mechanical polishing and RCA cleaning are subjected to steps such as two-fluid jet cleaning, ammonia solution cleaning, sponge brushing, O3-containing HF solution cleaning, DHF solution cleaning, and high-speed rotation drying, effectively removing the residual metal ions on the surface of the large-size silicon carbide substrates, and the residual metal ions can reach 5.0E+08 atoms / cm 2 Thereafter, it meets the manufacturing requirements of advanced devices and has high popularization and application value.

[0006] To solve the above technical problems, the technical solution provided by the present invention is:

[0007] A cleaning method for removing the residual metal ions on the surface of a large-size silicon carbide substrate, wherein the silicon carbide substrate is a silicon carbide substrate after chemical mechanical polishing, dewaxing cleaning, and RCA cleaning, and the cleaning method includes the following steps:

[0008] S1, performing jet cleaning on the rotating silicon carbide substrate to be cleaned with water-vapor two-fluid to obtain silicon carbide substrate Ι;

[0009] S2, flushing the rotating silicon carbide substrate Ι with an ammonia water solution to obtain silicon carbide substrate Ⅱ;

[0010] S3, brushing the rotating silicon carbide substrate Ⅱ with a brush, and spraying ultrapure water while brushing to obtain silicon carbide substrate Ⅲ;

[0011] S4, flushing the rotating silicon carbide substrate Ⅲ with an ozone-containing hydrofluoric acid solution to obtain silicon carbide substrate Ⅳ;

[0012] S5, successively flushing the rotating silicon carbide substrate Ⅳ with a hydrofluoric acid solution and ultrapure water, and drying by high-speed rotation to obtain a clean silicon carbide substrate.

[0013] Compared with the prior art, the cleaning method for removing residual metal ions on the surface of a large-size silicon carbide substrate provided by the present invention first uses a two-fluid jet of water and gas to clean the silicon carbide, and utilizes the impact force of high-speed water flow and gas flow to quickly peel off and carry away loose metal ions and impurity particles on the substrate surface; then, an ammonia aqueous solution is used to perform a fluid cleaning on the silicon carbide. The ammonia aqueous solution can promote the detachment of solid particles from the silicon carbide substrate surface and react chemically with metal ions to form soluble complexes, which are dissolved and removed from the substrate surface; after the ammonia aqueous solution cleaning, a brush is combined with ultra-pure water spraying to effectively remove stubborn stains and fine particles on the silicon carbide surface; then, a hydrofluoric acid solution containing ozone is used to clean the silicon carbide. This solution can promote the dissolution of metal ions and remove difficult-to-remove metal impurities; finally, a hydrofluoric acid solution is used for in-depth cleaning to etch away the metal impurities oxidized by ozone and embedded in the oxide layer, ensuring that the difficult-to-remove metal impurities are completely eluted; in addition, during the entire cleaning process, the silicon carbide always maintains a self-rotating state, and the physical impact force brought by the superposition of the fluid and the self-rotation is more likely to remove fine particles and prevent particle redeposition, which is beneficial to fully removing the metal impurities wrapped in the particles.

[0014] Through the close cooperation of multiple cleaning processes, the present invention realizes the efficient removal of residual metal ions on the surface of a large-size silicon carbide substrate. It is an efficient, green and environmentally friendly cleaning method for silicon carbide substrates, which can meet the strict requirements for the cleaning of silicon carbide substrates in different application scenarios and has wide applicability and promotion value.

[0015] It should be noted that in the present invention, the large-size silicon carbide substrate refers to a silicon carbide wafer with a size of more than 8 inches.

[0016] It should be noted that before the above cleaning process is carried out 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 substrates after conventional dewaxing cleaning and RCA cleaning in the present invention can all be cleaned using the cleaning method provided by the present invention to achieve the effect of effectively removing trace residual metal ions.

[0017] Further, in S1, the flow rate of ultra-pure water is 70 mL / min to 120 mL / min, the flow rate of nitrogen 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 ejection time of the two-fluid is 15 s to 25 s.

[0018] Further, in S1, the two-fluid nozzle reciprocates along the diameter direction of the silicon carbide substrate.

[0019] The process control of the above two-fluid jet cleaning can ensure that the entire surface of the large-size silicon carbide substrate is uniformly and effectively cleaned, avoid the occurrence of cleaning dead corners, and ensure that each place can reach the required cleanliness standard.

[0020] Further, in S2, the ammonia aqueous solution is a mixed solution of concentrated ammonia water and ultrapure water with a volume ratio of 1:6 to 1:3, wherein the mass concentration of the concentrated ammonia water is 25% to 28%.

[0021] The hydroxide ions dissociated from ammonia can make the surface of the silicon carbide substrate negatively charged, change the zeta potential of the deposited particles on the surface of the silicon carbide substrate, cause the particles to repel each other from the silicon carbide substrate. At the same time, the superimposed physical impact force of the fluid and self-rotation makes the particles more likely to detach from the silicon carbide surface and prevents the particles from redepositing. In addition, it can also remove some small molecule organic substances and complex metal ions, thereby improving the cleanliness of the silicon carbide substrate.

[0022] Further, in S2, the temperature of the ammonia aqueous solution is 35°C to 55°C.

[0023] Further, in S2, the flow rate of the ammonia aqueous solution is 400 mL / min to 500 mL / min, the ejection time is 20 s to 60 s, and the rotation speed of the silicon carbide substrate Ι is 500 r / min to 700 r / min.

[0024] The temperature and concentration of the ammonia aqueous solution are controlled within a specific range, which can not only ensure the cleaning effect but also minimize the corrosion of the silicon carbide substrate.

[0025] Further, in S2, the radial distance of the ejection position of the ammonia aqueous solution on the surface of the silicon carbide substrate Ι from the center of the circle is 3 / 16 to 5 / 16 of the diameter.

[0026] The preferred ejection position of the ammonia aqueous solution can make the ammonia aqueous solution quickly cover the entire surface of the silicon carbide substrate under the rotation action and timely update the cleaning liquid on the surface of the silicon carbide substrate, improving the cleaning efficiency.

[0027] It should be noted that an acid and alkali resistant pipeline is used to spray the ammonia aqueous solution onto the surface of the silicon carbide substrate.

[0028] Further, 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.

[0029] Further, in S3, the spray flow rate of the ultrapure water is 200 mL / min to 300 mL / min.

[0030] Further, in S3, the brush head of the brush and the spray head of the ultrapure water move reciprocally along the diameter direction of the silicon carbide substrate Ⅱ.

[0031] Exemplarily, in S3, the brush is a PVA sponge brush with a brush head diameter of 20 mm to 30 mm, and the brush head directly contacts the upper surface of the silicon carbide substrate.

[0032] It should be noted that in S3, the rotation directions of the brush head of the brush and the silicon carbide substrate are the same, and the two synchronously perform reciprocating motion along the diameter direction of the silicon carbide substrate under the control of the motor.

[0033] When using the brush in combination with ultra-pure water spray cleaning, by controlling the rotation speed of the brush, the rotation speed of the substrate, and the flow rate of the ultra-pure water spray, it is possible to minimize the damage caused by direct friction between the brush and the substrate while ensuring the effective removal of stubborn stains and fine particles on the surface of the silicon carbide substrate.

[0034] Further, before step S4, there is also an ultra-pure water fluid cleaning step: rinsing the scrubbed silicon carbide substrate III with ultra-pure water; wherein, the flow rate of the ultra-pure water is 200 mL / min to 400 mL / min, the rotation speed of the silicon carbide substrate III is 500 r / min to 700 r / min, and the radial distance of the spraying position of the ultra-pure water on the surface of the silicon carbide substrate III from the center of the circle is 1 / 3 to 1 / 4 of the diameter.

[0035] Through the above ultra-pure water fluid cleaning, the cleaning liquid from the previous step on the surface of the silicon carbide substrate can be fully removed, ensuring that the chemical solution in the next step can fully play its cleaning role.

[0036] Further, in S4, the O3 concentration in the ozone-containing hydrofluoric acid solution is 10 ppb to 30 ppb, and the HF concentration is 7 wt% to 15 wt%.

[0037] Further, in S4, the flow rate of the ozone-containing hydrofluoric acid solution is 350 mL / min to 500 mL / min, the discharging 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.

[0038] Further, in S4, the radial distance of the spraying position of the ozone-containing hydrofluoric acid solution on the surface of the silicon carbide substrate III from the center of the circle is 1 / 3 to 1 / 4 of the diameter.

[0039] It should be noted that an acid and alkali resistant pipeline is used to spray the ozone-containing hydrofluoric acid solution onto the surface of the silicon carbide substrate.

[0040] The hydrofluoric acid solution containing ozone can oxidize some metal impurities that are difficult to be directly removed by hydrofluoric acid into higher-valent oxides that are more likely to react with hydrofluoric acid, so that hydrofluoric acid can effectively remove metal oxide impurities on the substrate surface. The synergy of HF and O3 significantly increases the effect of the cleaning solution in removing impurities, making the substrate surface cleaner. In addition, the oxygen generated by the decomposition of the residual ozone also helps to form a protective oxide layer on the substrate surface, reducing the possibility of metal ions being re-adsorbed onto the substrate surface, so that the metal ions remaining on the surface of the silicon carbide substrate reach an extremely low concentration level, meeting the strict standards for ultra-high cleanliness of the substrate in high-end application fields such as semiconductor manufacturing and power device production.

[0041] Further, before step S5, it also includes an ultra-pure water fluid cleaning step: rinsing the silicon carbide substrate Ⅳ with ultra-pure water; wherein, the flow rate of the ultra-pure 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 of the injection position of the ultra-pure water on the surface of the silicon carbide substrate Ⅳ from the center of the circle is 1 / 3 to 1 / 4 of the diameter.

[0042] Further, in S5, the concentration of the hydrofluoric acid solution is 5 wt% to 9 wt%, the flow rate of the hydrofluoric acid solution is 400 mL / min to 500 mL / min, the ejection time is 20 s to 60 s, and the rotation speed of the silicon carbide substrate Ⅳ is 500 r / min to 700 r / min.

[0043] Using an HF solution with a relatively low concentration can further etch and completely remove the impurity oxides on the surface of the silicon carbide substrate, achieving a clean and stain-free effect. Moreover, the surface of the treated silicon carbide substrate is finally terminated with Si-OH and C-O groups, showing high hydrophilicity and being less likely to be contaminated by particles and impurities.

[0044] Further, in S5, the radial distance of the injection position of the hydrofluoric acid solution on the surface of the silicon carbide substrate Ⅳ from the center of the circle is 1 / 3 to 1 / 4 of the diameter.

[0045] The preferred injection position of the hydrofluoric acid solution can make the hydrofluoric acid solution quickly cover the entire surface of the silicon carbide substrate under the action of rotation and timely update the cleaning solution on the surface of the silicon carbide substrate, improving the cleaning efficiency.

[0046] It should be noted that an acid and alkali resistant pipeline is used to spray the HF solution onto the surface of the silicon carbide substrate.

[0047] Further, 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 of the injection position of the ultrapure water on the surface of the silicon carbide substrate IV from the center of the circle is 1 / 3 to 1 / 4 of the diameter.

[0048] Further, in S5, in the rotary drying process, the rotation speed of the silicon carbide substrate IV is 1800 r / min to 2200 r / min.

[0049] Through high-speed rotary drying, the silicon carbide substrate can obtain a dry surface within 50 s, and there is almost no residual water film on the surface.

[0050] It should be noted that the process time of each of the above cleaning steps is controlled within 20 to 60 s and can be adjusted within the above range according to the cleaning effect. The present invention does not make special limitations.

[0051] It should be noted that all the rotations involved in the above steps are horizontal rotations. The process steps without special temperature requirements are carried out at room temperature (20 to 25 °C).

[0052] The cleaning method of the large-size silicon carbide substrate provided by the present invention achieves the effects of less particle contamination and lower metal impurity residue on the surface of the silicon carbide substrate without the megasonic energy that may cause microscopic structure damage to the surface of the silicon carbide substrate. Each cleaning step can complete the cleaning within dozens of seconds. At the same time, the amount of cleaning liquid and purified water used is small, which is suitable for industrial production applications and has broad application prospects. Description of the Drawings

[0053] Figure 1 It is a process flow chart of the silicon carbide substrate cleaning for the embodiment. Detailed Embodiments

[0054] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to 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.

[0055] To better illustrate the present invention, further examples will be given below through embodiments.

[0056] In the following examples and comparative examples, the silicon carbide substrates to be cleaned are silicon carbide wafers that have been cleaned with dewaxing water + agitation cleaning (1800 - 2500 s) and RCA cleaning: SPM (immersion cleaning at 110 - 120 °C for 1000 - 1500 s) + APM (ultrasonic cleaning at 60 - 70 °C for 500 - 1000 s, 120 - 170 kHz) + HPM (ultrasonic cleaning at 60 - 70 °C for 500 - 1000 s, 120 - 170 kHz) + DHF (immersion at room temperature for 300 - 500 s) in a tank cleaning process. After each chemical solution cleaning, QDR rinsing is carried out, and the wafers are dried and taken out by a spin dryer.

[0057] Among them, SPM is a mixed solution of sulfuric acid and hydrogen peroxide, APM is an aqueous mixed solution of ammonia water and hydrogen peroxide, HPM is an aqueous mixed solution of hydrochloric acid and hydrogen peroxide, and DHF is a diluted hydrofluoric acid solution.

[0058] 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 of UPS grade at 28 wt%; the HF is of BV-Ⅲ grade at 40 wt%.

[0059] Ozone water is generated by using an ozone generator with O2 and CO2 gases and ultrapure water as raw materials under the action of radio frequency discharge, and its concentration is controllable. The HF solution containing O3 is prepared by dissolving ozone water and HF in ultrapure water, and the ozone aqueous solution is prepared by dissolving O3 in ultrapure water.

[0060] Example 1

[0061] This example provides a cleaning method for silicon carbide substrates, including the following steps:

[0062] S1, Arbitrarily take 12 silicon carbide wafers to be cleaned, and perform spray cleaning on the silicon carbide wafers with a two-fluid of water and gas. The flow rate of ultrapure water is controlled at 100 mL / min, the flow rate of high-purity nitrogen is controlled at 12 L / min, the wafer rotation speed is 600 r / min, the ejection time of the two-fluid is 20 s. During the cleaning process, the wafer always maintains self-rotation, and the two-fluid nozzle reciprocates along the wafer diameter under the control of the motor;

[0063] S2, Perform fluid cleaning on the silicon carbide wafers with an ammonia aqueous solution. Among them, the ammonia aqueous solution is a mixed solution of concentrated ammonia water and ultrapure water with a volume ratio of 1:4. The temperature of the ammonia aqueous solution is 45 °C, the flow rate of the ammonia aqueous solution is 400 mL / min, the ejection time is 45 s, the wafer rotation speed is 600 r / min. During the cleaning process, the wafer always maintains self-rotation, and the radial distance from the ejection position of the ammonia aqueous solution to the center of the wafer is 1 / 4 of the diameter;

[0064] S3. Use a PVA sponge brush to scrub the silicon carbide wafer. Meanwhile, rinse the wafer with ultrapure water. Control the rotational speed of the brush head at 120 r / min, the diameter of the brush head at 20 - 30 mm, and the rotational speed of the wafer at 400 r / min. The rotational directions of both are the same. Control the flow rate of the ultrapure water at 250 mL / min. The brush head and the ultrapure water nozzle move reciprocally along the diameter direction of the wafer synchronously under the control of the motor;

[0065] S4. Conduct a fluid cleaning of the silicon carbide wafer with ultrapure water. Control the flow rate of the ultrapure water at 300 mL / min, the rotational speed of the wafer at 600 r / min, and the radial distance from the injection position of the ultrapure water to the center of the wafer to be 1 / 4 of the diameter;

[0066] S5. Conduct a fluid cleaning of the silicon carbide wafer with a hydrofluoric acid solution containing ozone. The concentration of O3 in the hydrofluoric acid solution containing ozone is 25 ppb, the concentration of HF is 12 wt%. Control the flow rate of the hydrofluoric acid solution containing ozone at 450 mL / min, the ejection time at 60 s, the rotational speed of the wafer at 600 r / min. The wafer always maintains self - rotation during the cleaning process. The radial distance from the injection position of the hydrofluoric acid solution containing ozone to the center of the wafer is 1 / 4 of the diameter;

[0067] S6. Conduct an ultrapure water fluid cleaning, the same as step S4;

[0068] S7. Conduct a fluid cleaning of the silicon carbide wafer with a dilute hydrofluoric acid solution with a concentration of 8 wt%. Control the flow rate of the dilute hydrofluoric acid solution at 500 mL / min, the ejection time at 60 s, the rotational speed of the wafer at 600 r / min. The wafer always maintains self - rotation during the cleaning process. The radial distance from the injection position of the dilute hydrofluoric acid solution to the center of the wafer is 1 / 4 of the diameter;

[0069] S8. Conduct an ultrapure water fluid cleaning, the same as step S4;

[0070] S9. Rotate - dry the silicon carbide wafer at a rotational speed of 2000 r / min to obtain a clean silicon carbide wafer. Randomly select 2 pieces, which are wafer a and wafer b respectively, to detect the metal residue on the surface of the silicon carbide.

[0071] Use 12 silicon carbide wafers obtained by completely the same dewaxing water cleaning and RCA cleaning, and conduct cleaning according to the process basically the same as above. The only difference is that the hydrofluoric acid solution containing ozone in S5 is replaced with an ozone aqueous solution. The concentration of O3 in the ozone aqueous solution is 25 ppb, and the rest is exactly the same. Randomly select 2 pieces, which are respectively recorded as wafer a' and wafer b' to detect the metal residue on the surface of the silicon carbide. The results are shown in Table 1.

[0072] Table 1 Metal Ion Residue

[0073]

[0074] For the substrates a and b detected in Example 1, the residues of Al, Fe, Cu, Ni, Au, Ag, and Pt on the surfaces are below the level of 5.0E+08 atoms / cm². For the silicon carbide substrates a' and b' cleaned with an aqueous ozone solution, the metal elements have relatively higher residue values. In particular, there are obvious differences in the order of magnitude for Al, Fe, and Cu, and the residue levels of Ca and Mg cannot be comprehensively maintained below 2.0E+10 atoms / cm².

[0075] Example 2

[0076] This example provides a cleaning method for silicon carbide substrates, including the following steps:

[0077] S1, Arbitrarily select 25 silicon carbide wafers to be cleaned, and perform spray cleaning on the silicon carbide wafers using a water-air two-fluid. The flow rate of ultrapure water is controlled at 70 mL / min, the flow rate of high-purity nitrogen is controlled at 9 L / min, the wafer rotation speed is 500 r / min, the ejection time of the two-fluid is 15 s, the wafer always maintains self-rotation during the cleaning process, and the two-fluid nozzle reciprocates along the wafer diameter under the control of a motor;

[0078] S2, Perform fluid cleaning on the silicon carbide wafers using an ammonia aqueous solution. Among them, the ammonia aqueous solution is a mixed solution of concentrated ammonia water and ultrapure water with a volume ratio of 1:6. The temperature of the ammonia aqueous solution is 35 °C, the flow rate of the ammonia aqueous solution is 450 mL / min, the ejection time is 30 s, the wafer rotation speed is 500 r / min, the wafer always maintains self-rotation during the cleaning process, and the radial distance from the ejection position of the ammonia aqueous solution to the wafer center is 3 / 16 of the diameter;

[0079] S3, Brush the silicon carbide wafers using a PVA sponge brush. At the same time, rinse the wafers with ultrapure water. The rotation speed of the brush head is controlled at 100 r / min, the diameter of the brush head is 20 - 30 mm, the rotation speed of the wafer is controlled at 500 r / min, and their rotation directions are the same. The flow rate of ultrapure water is controlled at 300 mL / min, and the brush head and the ultrapure water nozzle reciprocate synchronously along the wafer diameter direction under the control of a motor;

[0080] S4, Perform fluid cleaning on the silicon carbide wafers using ultrapure water. The flow rate of ultrapure water is controlled at 400 mL / min, the wafer rotation speed is 500 r / min, and the radial distance from the ejection position of the ultrapure water to the wafer center is 1 / 3 of the diameter;

[0081] S5. The silicon carbide wafer is cleaned by a fluid of hydrofluoric acid solution containing ozone. The concentration of O3 in the hydrofluoric acid solution containing ozone is 10 ppb, the concentration of HF is 15 wt%. Control the flow rate of the hydrofluoric acid solution containing ozone to be 350 mL / min, the ejection time to be 40 s, the wafer rotation speed to be 500 r / min. The wafer always keeps self-rotation during the cleaning process. The radial distance from the ejection position of the hydrofluoric acid solution containing ozone to the center of the wafer is 1 / 3 of the diameter;

[0082] S6. Ultra-pure water fluid cleaning, the same as step S4;

[0083] S7. The silicon carbide wafer is cleaned by a fluid of dilute hydrofluoric acid solution with a concentration of 9 wt%. Control the flow rate of the dilute hydrofluoric acid solution to be 400 mL / min, the ejection time to be 20 s, the wafer rotation speed to be 700 r / min. The wafer always keeps self-rotation during the cleaning process. The radial distance from the ejection position of the dilute hydrofluoric acid solution to the center of the wafer is 1 / 3 of the diameter;

[0084] S8. Ultra-pure water fluid cleaning, the same as step S4;

[0085] S9. The silicon carbide wafer is dried by high-speed rotation at a speed of 1800 r / min to obtain a clean silicon carbide wafer. Randomly select 2 wafers, denoted as wafer c and wafer d respectively, to detect the metal residue on the surface of silicon carbide. The results are shown in Table 2.

[0086] Table 2

[0087]

[0088] The Al, Fe, Cu, Ni, Au, Ag, Pt residues on the surfaces of the substrates c and d detected in Example 2 reach the level below 5.0E+08 atoms / cm².

[0089] Example 3

[0090] This example provides a cleaning method for a silicon carbide substrate, including the following steps:

[0091] S1. Randomly select 15 silicon carbide wafers to be cleaned, and spray-clean the silicon carbide wafers by a two-fluid of water and gas. Control the flow rate of ultra-pure water to be 120 mL / min, the flow rate of high-purity nitrogen to be 14 L / min, the wafer rotation speed to be 700 r / min, the ejection time of the two-fluid to be 25 s. The wafer always keeps self-rotation during the cleaning process. The two-fluid nozzle moves reciprocally along the diameter of the wafer under the control of the motor;

[0092] S2, perform fluid cleaning on the silicon carbide wafer with an ammonia water solution. Among them, the ammonia water solution is a mixed solution of concentrated ammonia water and ultrapure water with a volume ratio of 1:3. The temperature of the ammonia water solution is 65°C, the flow rate of the ammonia water solution is 500 mL / min, the ejection time is 60 s, the wafer rotation speed is 700 r / min, and the wafer always maintains self-rotation during the cleaning process. The radial distance from the ammonia water solution ejection position to the center of the wafer is 5 / 16 of the diameter;

[0093] S3, brush the silicon carbide wafer with a PVA sponge brush. At the same time, rinse the wafer with ultrapure water. The rotation speed of the brush head is controlled at 150 r / min, the diameter of the brush head is 20 - 30 mm, the rotation speed of the wafer is controlled at 300 r / min, and their rotation directions are the same. The flow rate of the ultrapure water is controlled at 200 mL / min. The brush head and the ultrapure water nozzle move reciprocally along the diameter direction of the wafer under the control of the motor synchronously;

[0094] S4, perform fluid cleaning on the silicon carbide wafer with ultrapure water. The flow rate of the ultrapure water is controlled at 200 mL / min, the wafer rotation speed is 700 r / min, and the radial distance from the ultrapure water ejection position to the center of the wafer is 1 / 4 of the diameter;

[0095] S5, perform fluid cleaning on the silicon carbide wafer with an ozone-containing hydrofluoric acid solution. The concentration of O3 in the ozone-containing hydrofluoric acid solution is 30 ppb, and the HF concentration is 7 wt%. Control the flow rate of the ozone-containing hydrofluoric acid solution at 500 mL / min, the ejection time is 20 s, the wafer rotation speed is 700 r / min, and the wafer always maintains self-rotation during the cleaning process. The radial distance from the ozone-containing hydrofluoric acid solution ejection position to the center of the wafer is 1 / 4 of the diameter;

[0096] S6, perform ultrapure water fluid cleaning, the same as step S4;

[0097] S7, perform fluid cleaning on the silicon carbide wafer with a dilute hydrofluoric acid solution with a concentration of 5 wt%. Control the flow rate of the dilute hydrofluoric acid solution at 450 mL / min, the ejection time is 40 s, the wafer rotation speed is 500 r / min, and the wafer always maintains self-rotation during the cleaning process. The radial distance from the dilute hydrofluoric acid solution ejection position to the center of the wafer is 1 / 4 of the diameter;

[0098] S8, perform ultrapure water fluid cleaning, the same as step S4;

[0099] S9, perform high-speed rotation drying on the silicon carbide wafer at a rotation speed of 2200 r / min to obtain a clean silicon carbide wafer. Randomly select 2 pieces, respectively recorded as wafer e and wafer f, and detect the metal residue situation on the surface of the silicon carbide. The results are shown in Table 3.

[0100] Table 3

[0101]

[0102] 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 of 5.0E+08 atoms / cm² or less.

[0103] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, or improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A cleaning method for removing residual metal ions on the surface of a large-size silicon carbide substrate, characterized in that, The silicon carbide substrate is a silicon carbide substrate after chemical mechanical polishing, dewaxing cleaning, and RCA cleaning. The cleaning method includes the following steps: S1. Spray-clean the rotating silicon carbide substrate to be cleaned with a water-air two-fluid to obtain silicon carbide substrate Ι; S2. Rinse the rotating silicon carbide substrate Ι with an ammonia water solution to obtain silicon carbide substrate Ⅱ; S3. Brush the rotating silicon carbide substrate Ⅱ with a brush, and spray ultrapure water while brushing to obtain silicon carbide substrate Ⅲ; S4. Rinse the rotating silicon carbide substrate Ⅲ with a hydrofluoric acid solution containing ozone to obtain silicon carbide substrate Ⅳ; S5. Rinse the rotating silicon carbide substrate Ⅳ with a hydrofluoric acid solution and ultrapure water in sequence, and dry it at high speed rotation to obtain a clean silicon carbide substrate.

2. The cleaning method for removing residual metal ions on the surface of a large-size silicon carbide substrate according to claim 1, wherein In S1, the flow rate of ultrapure water is 70 mL / min to 120 mL / min, the flow rate of nitrogen 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 ejection time of the two-fluid 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 residual metal ions on the surface of a large-sized silicon carbide substrate as described in claim 1, characterized in that, In S2, the ammonia water solution is a mixed solution of concentrated ammonia water and ultrapure water with 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 water solution is 35 °C to 55 °C; and / or In S2, the flow rate of the ammonia water solution is 400 mL / min to 500 mL / min, the ejection time is 20 s to 60 s, and the rotation speed of the silicon carbide substrate Ι is 500 r / min to 700 r / min; and / or In S2, the radial distance from the ejection position of the ammonia water solution on the surface of the silicon carbide substrate Ι to the center of the circle is 3 / 16 to 5 / 16 of the diameter.

4. The cleaning method for removing residual metal ions on the surface of a large-size silicon carbide substrate as described in claim 1, wherein, In S3, when 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 the ultrapure water reciprocate along the diameter direction of the silicon carbide substrate Ⅱ.

5. The cleaning method for removing residual metal ions on the surface of a large-sized silicon carbide substrate as described in claim 1, wherein, Before step S4, it further includes an ultrapure water fluid cleaning step: rinse the silicon carbide substrate Ⅲ after brushing with ultrapure water; wherein, the flow rate of the ultrapure water is 200 mL / min to 400 mL / min, the rotation speed of the silicon carbide substrate Ⅲ is 500 r / min to 700 r / min, and the radial distance from the ejection position of the ultrapure water on the surface of the silicon carbide substrate Ⅲ to the center of the circle is 1 / 3 to 1 / 4 of the diameter.

6. The cleaning method for removing residual metal ions on the surface of a large-sized silicon carbide substrate as described in claim 1, wherein In S4, the O3 concentration in the hydrofluoric acid solution containing ozone 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 hydrofluoric acid solution containing ozone is 350 mL / min to 500 mL / min, the ejection 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 residual metal ions on the surface of a large-size silicon carbide substrate according to claim 1, wherein In S4, the radial distance of the spraying position of the ozone-containing hydrofluoric acid solution on the surface of the silicon carbide substrate III from the center of the circle is 1 / 3 to 1 / 4 of the diameter.

8. The cleaning method for removing residual metal ions on the surface of a large-size silicon carbide substrate according to claim 1, wherein Before the step S5, there is also an ultra-pure water fluid cleaning step: the silicon carbide substrate IV is rinsed with ultra-pure water; wherein, the flow rate of the ultra-pure 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 of the spraying position of the ultra-pure water on the surface of the silicon carbide substrate IV from the center of the circle is 1 / 3 to 1 / 4 of the diameter.

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

10. The cleaning method for removing residual metal ions on the surface of a large-sized silicon carbide substrate according to claim 1, characterized in that, In S5, the flow rate of the ultra-pure 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 of the spraying position of the ultra-pure water on the surface of the silicon carbide substrate IV from the center of the circle is 1 / 3 to 1 / 4 of the diameter; and / or In S5, in the rotating drying process, the rotation speed of the silicon carbide substrate IV is 1800 r / min to 2200 r / min.

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