Silicon carbide substrate wafer cleaning method

Abstract

The present invention relates to wafer processing technology, and discloses a cleaning method for silicon carbide substrate wafers. The cleaning method comprises the following steps: step S1, immersing the silicon carbide substrate wafer in an organic solvent for a first ultrasonic cleaning, and then performing a first surface residual cleaning; step S2, immersing the silicon carbide substrate wafer processed in step S1 in a composite cleaning agent for a second ultrasonic cleaning, and then performing a second surface residual cleaning; step S3, immersing the silicon carbide substrate wafer processed in step S2 in an acid solution for a third ultrasonic cleaning, and then performing a third surface residual cleaning and drying treatment. The cleaning method provided by the present invention has a good cleaning effect on silicon carbide substrate wafers and a short cleaning time, which is beneficial to improving the yield of the wafer and extending the service life of the liquid medicine.

Description

Technical Field

[0001] The invention relates to a wafer processing technology, and in particular to a method for cleaning a silicon carbide substrate wafer. Background Art

[0002] The third generation of semiconductor materials are mainly wide bandgap semiconductor materials represented by silicon carbide (SiC), gallium nitride (GaN), and zinc oxide (ZnO). Silicon carbide (SiC) has attracted much attention due to its wide bandgap, high thermal conductivity, high carrier saturation drift velocity, small dielectric constant, strong radiation resistance, and good chemical stability. This material is widely used in new energy vehicles, 5G, lighting, photovoltaic components, intelligent robots, charging piles and other fields.

[0003] Due to the complex production process of silicon carbide wafers, many processes may introduce some organic matter, particles, metals and oxides and other impurities, which will seriously affect the performance and yield of silicon carbide devices. Therefore, it is very important to ensure the cleanliness of silicon carbide substrates. At present, most of the semiconductor substrate manufacturers at home and abroad use RCA wet chemical cleaning technology to remove impurities on the surface of silicon carbide substrates. Commonly used chemical cleaning agents are: SC-2: (HCl: H 2 O 2 :H 2 O), SC-1:(NH 4 OH:H 2 O 2 :H 2 O,DHF:(HF:H 2 O 2 :H 2 O), acetone (ACE), isopropyl alcohol (IPA) SC-3: (H 2 SO 4 :H 2 O 2 :H 2 O), etc. Different cleaning agents have different abilities and types of pollution removal. For example, SC-2 is mainly used to remove metal contamination; SC-1 can remove particles, some organic matter and some metals; DHF corrodes the surface oxide layer and removes metal contamination; acetone (ACE) can remove organic residues, organic particles and photoresist; SC-3 can oxidize metals and dissolve them in the solution, and can oxidize organic matter to generate CO 2 and water. In the cleaning process, the above cleaning agents can be used in combination. By adjusting the ratio of the cleaning solution, cleaning temperature, cleaning time and other process parameters, different cleaning effects can be achieved on the substrate surface. Although each semiconductor substrate manufacturer has its own cleaning process, there are often a small number of particles that cannot be removed. Some particles can be removed by re-cleaning after rework, but this will seriously affect production efficiency.

[0004] Therefore, it is very important to invent a cleaning process that can efficiently remove contamination from the substrate surface. Summary of the invention

[0005] The purpose of the present invention is to overcome the problems existing in the prior art and provide a method for cleaning a silicon carbide substrate wafer. The cleaning method has good cleaning effect and short cleaning time, which is beneficial to improving the yield of the wafer and extending the service life of the solution.

[0006] In order to achieve the above object, the present invention provides a method for cleaning a silicon carbide substrate wafer, comprising the following steps:

[0007] Step S1, immersing the silicon carbide substrate wafer in an organic solvent for a first ultrasonic cleaning, and then performing a first surface residual cleaning;

[0008] Step S2, immersing the silicon carbide substrate wafer processed in step S1 into a composite cleaning agent for a second ultrasonic cleaning, and then performing a second surface residue cleaning;

[0009] Step S3, immersing the silicon carbide substrate wafer processed in step S2 in an acid solution for a third ultrasonic cleaning, and then performing a third surface residual cleaning and drying treatment.

[0010] Preferably, the organic solvent in step S1 is a lower organic alcohol, preferably at least one of methanol, ethanol, n-propanol and isopropanol.

[0011] Preferably, the conditions for the first ultrasonic cleaning in step S1 include: ultrasonic frequency of 20-40 KHz, circulating filter element <0.5 μm, and immersion time of 15-35 s.

[0012] Preferably, the conditions for cleaning the residual on the first surface include: performing the cleaning in a fast-drain rinsing tank, with a rinsing time of 3-6 minutes and a drainage time of 2-5 seconds.

[0013] Preferably, the composite cleaning agent in step S2 contains alkali, oxidant and water.

[0014] Preferably, the base is aqueous ammonia.

[0015] Preferably, the oxidizing agent is hydrogen peroxide.

[0016] Preferably, the molar ratio of the alkali, the oxidant and the water in the composite cleaning agent in step S2 is 1:1-3.5:10-100.

[0017] Preferably, the conditions for the second ultrasonic cleaning in step S2 include: temperature of 7-12° C., ultrasonic frequency of 50-100 KHz, circulating filter element <0.5 μm, and immersion time of 30-60 s.

[0018] Preferably, the conditions for cleaning the residual on the second surface include: performing the cleaning in a fast-drain rinsing tank, with a rinsing time of 3-6 minutes and a drainage time of 2-5 seconds.

[0019] Preferably, the acid solution in step S3 is selected from at least one of hydrochloric acid solution, sulfuric acid solution and nitric acid solution, more preferably hydrochloric acid solution.

[0020] Preferably, the acid solution contains H + The concentration is 1.2-3mol / L.

[0021] Preferably, the conditions for the third ultrasonic cleaning in step S3 include: ultrasonic frequency of 50-100 KHz, circulating filter element <0.5 μm, and immersion time of 10-30 s.

[0022] Preferably, the conditions for cleaning the residual on the third surface include: performing the cleaning in a fast-drain rinsing tank, with a rinsing time of 3-6 minutes and a drainage time of 2-5 seconds.

[0023] Preferably, the drying process in step S3 includes: spinning the silicon carbide substrate wafer after the third surface residue cleaning under blowing conditions.

[0024] Preferably, the spin-drying conditions include: temperature of 35-65° C., rotation speed of 800-1200 rpm, and time of 200-300 s.

[0025] Through the above technical scheme, the beneficial effects of the present invention are as follows: the cleaning method of the silicon carbide substrate wafer provided by the present invention first uses an organic solvent for low-frequency ultrasonic pre-cleaning, and then uses a composite detergent and an acid solution for ultrasonic cleaning respectively, and each cleaning is coordinated with the surface residual cleaning, which can effectively remove particles, organic matter, metal impurities and other pollutants on the surface of the silicon carbide substrate wafer, and improve the yield of the wafer. By using the cleaning method provided by the present invention, the particle size of 0.08μm on the surface of the silicon carbide wafer is ≤300, the metal impurity concentration is low, and the qualified rate is above 96%, which has a significant improvement in the cleaning effect of the wafer;

[0026] Furthermore, the ultrasonic cleaning process in the cleaning method provided by the present invention has a low processing temperature and a short processing time, which can not only effectively extend the service life of the liquid medicine and save cleaning costs, but also save the time of the cleaning process and improve the cleaning efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a particle size detection diagram of 0.08 μm on the surface of the silicon carbide substrate wafer after cleaning in Example 1;

[0028] Figure 2This is a particle size detection diagram of 0.08 μm on the surface of the silicon carbide substrate wafer after cleaning in Example 5;

[0029] Figure 3 This is a grain size detection diagram of 0.08 μm on the surface of the silicon carbide substrate wafer after cleaning in Example 8. DETAILED DESCRIPTION

[0030] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0031] The present invention provides a method for cleaning a silicon carbide substrate wafer, comprising the following steps:

[0032] Step S1, immersing the silicon carbide substrate wafer in an organic solvent for a first ultrasonic cleaning, and then performing a first surface residual cleaning;

[0033] Step S2, immersing the silicon carbide substrate wafer processed in step S1 into a composite cleaning agent for a second ultrasonic cleaning, and then performing a second surface residue cleaning;

[0034] Step S3, immersing the silicon carbide substrate wafer processed in step S2 in an acid solution for a third ultrasonic cleaning, and then performing a third surface residual cleaning and drying treatment.

[0035] The inventors of the present invention discovered during the research and development and production process that the silicon carbide substrate wafer is first pre-cleaned with a low-frequency ultrasonic method using an organic solvent, and then ultrasonically cleaned using a composite cleaning agent and an acid solution respectively, and each cleaning is combined with a surface residual cleaning method. This can not only effectively improve the removal effect of pollutants such as particles, organic matter, and metal impurities on the surface of the silicon carbide substrate wafer, thereby improving the yield of the wafer, but can also further shorten the time of the cleaning process, improve the cleaning efficiency, and effectively extend the service life of the solution.

[0036] In the present invention, during the cleaning process, the silicon carbide substrate wafers are loaded using a wafer CASS (a conventional basket for loading wafers in the art) so that multiple wafers can be taken and placed at the same time, which facilitates the operation of each process and improves the cleaning efficiency. Preferably, the silicon carbide substrate wafers are inserted into the wafer CASS with spacers, and each CASS holds about 13 wafers.

[0037] According to the present invention, in order to further improve the removal effect of large particles of pollutants on the surface of the silicon carbide substrate wafer, so that the wafer surface has hydrophilicity, preferably, the organic solvent in step S1 is a low-grade organic alcohol. Further preferably, the organic solvent is at least one of methanol, ethanol, n-propanol and isopropanol. In the present invention, the organic solvent can be a pure organic solvent or an aqueous solution of an organic solvent, for example, anhydrous ethanol or an ethanol-water solution with a volume fraction of 70-99%.

[0038] According to the present invention, the first ultrasonic cleaning can be performed in an ultrasonic tank filled with an organic solvent, and a circulating filter element is provided in the ultrasonic tank to improve the cleaning effect on the surface of the silicon carbide substrate wafer.

[0039] According to the present invention, preferably, the conditions of the first ultrasonic cleaning in step S1 include: the ultrasonic frequency is 20-40KHz, specifically 20KHz, 25KHz, 30KHz, 35KHz, 40KHz or any value between the aforementioned values; the circulating filter element is less than 0.5μm, specifically 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm or any value between the aforementioned values; the immersion time is 15-35s, specifically 15s, 20s, 25s, 30s, 35s or any value between the aforementioned values. The inventors found that under this preferred embodiment, the use of a low-frequency cleaning procedure can not only effectively remove large particle contaminants on the surface of the silicon carbide substrate wafer using an organic solvent, but also the cleaning time is short, thereby improving the cleaning efficiency.

[0040] According to the present invention, preferably, the conditions for cleaning the first surface residue in step S1 include: being carried out in a quick drain rinsing tank (QDR tank), the drainage time is 2-5s, specifically 2s, 3s, 4s, 5s or any value between the aforementioned values; the rinsing time is 3-6min, specifically 3min, 4min, 5min, 6min or any value between the aforementioned values. Specifically, after the silicon carbide substrate wafer is taken out of the organic solvent, it is placed in a quick drain rinsing tank and the first surface residue is cleaned with water. The inventors have found that under this preferred embodiment, the residual liquid on the surface of the silicon carbide substrate wafer can be effectively removed.

[0041] According to the present invention, in order to further improve the removal effect of small particle pollutants, some organic matter and some metals on the surface of the silicon carbide substrate wafer, preferably, the composite cleaning agent in step S2 contains alkali, oxidant and water.

[0042] In the present invention, the water used can be conventional experimental water, such as distilled water, deionized water, reverse osmosis water or ultrapure water.

[0043] According to the present invention, the base is a weak alkaline substance, for example, ammonia water, sodium bicarbonate, etc. Preferably, the base is ammonia water.

[0044] According to the present invention, the oxidant is capable of oxidizing organic matter and metal impurities on the surface of the silicon carbide substrate wafer. Preferably, the oxidant is hydrogen peroxide.

[0045] According to the present invention, preferably, the molar ratio of alkali, oxidant and water in the composite cleaning agent in step S2 is 1: 1-3.5: 10-100. The inventors found that under this preferred embodiment, it is beneficial to improve the removal rate of small particle pollutants, some organic matter and some metals on the surface of the silicon carbide substrate wafer, and improve the yield of the wafer.

[0046] According to the present invention, the second ultrasonic cleaning can be performed in an ultrasonic tank filled with a composite cleaning agent, and a circulating filter element is provided in the ultrasonic tank to improve the cleaning effect on the surface of the silicon carbide substrate wafer.

[0047] According to the present invention, preferably, the conditions of the second ultrasonic cleaning in step S2 include: temperature of 7-12°C, specifically 7°C, 8°C, 9°C, 10°C, 11°C, 12°C or any value between the aforementioned values; ultrasonic frequency of 50-100KHz, specifically 50KHz, 60KHz, 70KHz, 80KHz, 90KHz, 100KHz or any value between the aforementioned values; circulating filter element <0.5μm, specifically 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm or any value between the aforementioned values; immersion time of 30-60s, specifically 30s, 40s, 50s, 60s or any value between the aforementioned values. The inventors found that under this preferred embodiment, the ultrasonic cleaning liquid is in a low temperature state, which can not only effectively remove organic matter and metal impurities on the surface of the silicon carbide substrate wafer, but also extend the service life of the liquid, effectively saving the cost of cleaning.

[0048] According to the present invention, preferably, the conditions for cleaning the second surface residue include: in a fast-drain rinsing tank, the drainage time is 2-5s, and the rinsing time is 3-6min. Specifically, after the silicon carbide substrate wafer is taken out of the composite cleaning agent, it is placed in a fast-drain rinsing tank and the second surface residue is cleaned with water. The inventors found that under this preferred embodiment, the residual liquid on the surface of the silicon carbide substrate wafer can be effectively removed.

[0049] According to the present invention, the third ultrasonic cleaning can be performed in an ultrasonic tank filled with acid solution, and a circulating filter element is provided in the ultrasonic tank to improve the cleaning effect on the surface of the silicon carbide substrate wafer.

[0050] According to the present invention, the acid solution can be a solution of an inorganic acid or an organic acid. In order to further effectively remove metal impurities on the surface of the silicon carbide substrate wafer, preferably, the acid solution in step S3 is selected from at least one of a hydrochloric acid solution, a sulfuric acid solution and a nitric acid solution, and more preferably a hydrochloric acid solution.

[0051] According to the present invention, preferably, H + The concentration of the acid is 1.2-3 mol / L, specifically 1.2 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L or any value in between. The inventors found that under this preferred embodiment, not only can the residual metal impurities on the surface of the wafer be effectively removed, but also the acid concentration is too high to damage the wafer.

[0052] According to the present invention, preferably, the conditions of the third ultrasonic cleaning in step S3 include: an ultrasonic frequency of 50-100KHz, specifically 50KHz, 60KHz, 70KHz, 80KHz, 90KHz, 100KHz or any value between the aforementioned values; a circulating filter element <0.5μm, specifically 0.05μm, 0.1μm, 0.2μm, 0.3μm, 0.4μm or any value between the aforementioned values; and a soaking time of 10-30s, specifically 10s, 15s, 20s, 25s, 30s or any value between the aforementioned values.

[0053] According to the present invention, preferably, the conditions for cleaning the third surface residue include: in a fast-drain rinsing tank, the drainage time is 2-5 seconds, and the rinsing time is 3-6 minutes. Specifically, after the silicon carbide substrate wafer is taken out of the acid solution, it is placed in a fast-drain rinsing tank and cleaned with water for the third surface residue.

[0054] According to the present invention, the drying in step S3 can be performed by a dryer or a spin dryer. Preferably, the drying process in step S3 includes: spin drying the silicon carbide substrate wafer after the third surface residue cleaning under blowing conditions, that is, drying the wafer by a spin dryer, and blowing nitrogen into the spin dryer. The inventors found that under this preferred embodiment, the drying rate is fast and is conducive to maintaining the cleanliness of the wafer surface.

[0055] According to the present invention, preferably, the spin-drying conditions include: a temperature of 35-65°C, specifically 35°C, 45°C, 55°C, 65°C or any value between the aforementioned values; a rotation speed of 800-1200rpm, specifically 800rpm, 900rpm, 1000rpm, 1100rpm, 1200rpm or any value between the aforementioned values; a time of 200-300s, specifically 200s, 220s, 240s, 260s, 280s, 300s or any value between the aforementioned values.

[0056] According to a particularly preferred embodiment of the present invention, a method for cleaning a silicon carbide substrate wafer comprises the following steps:

[0057] Step S1, immersing the silicon carbide substrate wafer in an organic solvent, performing a first ultrasonic cleaning for 15-35 seconds under the conditions of an ultrasonic frequency of 20-40KHz and a circulating filter element of less than 0.5μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a first surface residual cleaning (draining time is 2-5s, rinsing time is 3-6min), wherein the organic solvent is a low-grade organic alcohol;

[0058] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 30-60 seconds at a temperature of 7-12° C., an ultrasonic frequency of 50-100 KHz, and a circulating filter element of less than 0.5 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for a second surface residual cleaning (drainage time is 2-5 seconds, rinsing time is 3-6 minutes), wherein the composite cleaning agent contains an alkali, an oxidant, and water in a molar ratio of 1:1-3.5:10-100;

[0059] Step S3, immersing the silicon carbide substrate wafer treated in step S2 in an acid solution, performing a third ultrasonic cleaning for 10-30s under the conditions of an ultrasonic frequency of 50-100KHz and a circulating filter element of less than 0.5μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a third surface residual cleaning (drainage time is 2-5s, rinsing time is 3-6min), and finally placing the wafer in a spin dryer and spinning for 200-300s under the conditions of blowing, heating, and a rotation speed of 800-1200rpm.

[0060] In the above particularly preferred embodiment, the entire cleaning procedure does not require heating of the organic solvent, composite cleaning agent and acid solution, but maintains room temperature or low temperature, which can effectively extend the service life of the cleaning solution, and the ultrasonic cleaning steps are all controlled within 1 minute, which is short in time and is conducive to improving cleaning efficiency.

[0061] The present invention will be described in detail below through examples.

[0062] In the following examples, unless otherwise specified, the raw materials and reagents are conventional commercially available products, and the room temperature is 25±5°C.

[0063] Example 1

[0064] Step S1, placing the silicon carbide substrate wafer into the CASS, inserting the spacer (13 wafers per CASS), then immersing the CASS in ethanol, performing the first ultrasonic cleaning for 35 seconds under the conditions of an ultrasonic frequency of 20KHz and a circulating filter element of 0.3μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for the first surface residual cleaning (draining time is 2s, rinsing time is 3min);

[0065] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 60 seconds at a temperature of 7° C., an ultrasonic frequency of 80 KHz, and a circulating filter element of less than 0.1 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for a second surface residual cleaning (draining time is 2 seconds, rinsing time is 3 minutes), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide, and deionized water in a molar ratio of 1:1:97.5;

[0066] Step S3, immersing the silicon carbide substrate wafer treated in step S2 in a hydrochloric acid solution with a concentration of 5 weight%, performing a third ultrasonic cleaning for 30 seconds under the conditions of an ultrasonic frequency of 50 kHz and a circulating filter element of 0.1 μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a third surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), and finally placing the wafer in a spin dryer and spinning for 250 seconds under the conditions of blowing nitrogen, a temperature of 50°C, and a rotation speed of 1000 rpm.

[0067] After the cleaning of the silicon carbide substrate wafer in Example 1, the particle size of the wafer surface at 0.08 μm is 192 (as shown in FIG. Figure 1 As shown), the qualified rate is 98%. Compared with comparative example 1, the cleaning effect is significantly improved, and the service life of the composite cleaning agent is extended by about 35%.

[0068] Example 2

[0069] Step S1, placing the silicon carbide substrate wafer into the CASS, inserting the spacer (13 wafers per CASS), then immersing the CASS in ethanol, performing the first ultrasonic cleaning for 35 seconds under the conditions of an ultrasonic frequency of 20KHz and a circulating filter element of 0.3μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for the first surface residual cleaning (draining time is 2s, rinsing time is 3min);

[0070] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 60 seconds at a temperature of 7° C., an ultrasonic frequency of 80 KHz, and a circulating filter element of less than 0.1 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for a second surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide, and deionized water in a molar ratio of 1:3:15;

[0071] Step S3, immersing the silicon carbide substrate wafer treated in step S2 in a hydrochloric acid solution with a concentration of 5 weight%, performing a third ultrasonic cleaning for 30 seconds under the conditions of an ultrasonic frequency of 50 kHz and a circulating filter element of 0.1 μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a third surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), and finally placing the wafer in a spin dryer and spinning for 250 seconds under the conditions of blowing nitrogen, a temperature of 40°C, and a rotation speed of 1000 rpm.

[0072] After the silicon carbide substrate wafer was cleaned in Example 3, the particle size of the wafer surface at 0.08 μm was 172, and the qualified rate was 98%. Compared with Comparative Example 1, the cleaning effect was significantly improved, and the service life of the composite cleaning agent was extended by about 35%.

[0073] Example 3

[0074] Step S1, placing the silicon carbide substrate wafer into the CASS, inserting the spacer (13 wafers per CASS), then immersing the CASS in ethanol, performing the first ultrasonic cleaning for 35 seconds under the conditions of an ultrasonic frequency of 20KHz and a circulating filter element of 0.3μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for the first surface residual cleaning (draining time is 2s, rinsing time is 3min);

[0075] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 60 seconds at a temperature of 7° C., an ultrasonic frequency of 60 kHz, and a circulating filter element of less than 0.1 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for a second surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide, and deionized water in a molar ratio of 1:3:15;

[0076] Step S3, immersing the silicon carbide substrate wafer treated in step S2 in a hydrochloric acid solution with a concentration of 10 weight%, performing a third ultrasonic cleaning for 30 seconds under the conditions of an ultrasonic frequency of 50 kHz and a circulating filter element of 0.1 μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a third surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), and finally placing the wafer in a spin dryer and spinning for 250 seconds under the conditions of blowing nitrogen, a temperature of 65°C, and a rotation speed of 1000 rpm.

[0077] After the silicon carbide substrate wafer was cleaned in Example 3, the particle size of the wafer surface at 0.08 μm was 165, and the qualified rate was 98%. Compared with Comparative Example 1, the cleaning effect was significantly improved, and the service life of the composite cleaning agent was extended by about 35%.

[0078] Example 4

[0079] The silicon carbide substrate wafer is cleaned according to the cleaning method of Example 3, except that the time of the third ultrasonic cleaning in step S3 is adjusted to 25 seconds.

[0080] After the silicon carbide substrate wafer was cleaned in Example 4, the particle size of the wafer surface at 0.08 μm was 174, and the qualified rate was 98%. Compared with Comparative Example 1, the cleaning effect was significantly improved, and the service life of the composite cleaning agent was extended by about 35%.

[0081] Example 5

[0082] The silicon carbide substrate wafer is cleaned according to the cleaning method of Example 3, except that the time of the second ultrasonic cleaning in step S2 is adjusted to 30 seconds.

[0083] After the cleaning of the silicon carbide substrate wafer in Example 5, the particle size of the wafer surface at 0.08 μm is 212 (such as Figure 2 As shown), the qualified rate is 97%. Compared with comparative example 1, the cleaning effect is significantly improved, and the service life of the composite cleaning agent is extended by about 35%.

[0084] Example 6

[0085] The silicon carbide substrate wafer is cleaned according to the cleaning method of Example 2, except that step S2 is replaced by:

[0086] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 60 seconds at a temperature of 12°C, an ultrasonic frequency of 50KHz, and a circulating filter element of less than 0.1μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a second surface residual cleaning (drainage time is 2s, rinse time is 3min), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide and deionized water in a molar ratio of 1:3:15.

[0087] After the silicon carbide substrate wafer was cleaned in Example 6, the particle size of the wafer surface at 0.08 μm was 196, and the qualified rate was 97%. Compared with Comparative Example 1, the cleaning effect was significantly improved, and the service life of the composite cleaning agent was extended by about 30%.

[0088] Example 7

[0089] Step S1, placing the silicon carbide substrate wafer into the CASS, inserting the spacer (13 wafers per CASS), then immersing the CASS in ethanol, performing the first ultrasonic cleaning for 35 seconds under the conditions of an ultrasonic frequency of 20KHz and a circulating filter element of 0.3μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for the first surface residual cleaning (draining time is 2s, rinsing time is 3min);

[0090] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 60 seconds at a temperature of 7° C., an ultrasonic frequency of 50 KHz, and a circulating filter element of less than 0.1 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for a second surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide, and deionized water in a molar ratio of 1:3:15;

[0091] Step S3, immersing the silicon carbide substrate wafer treated in step S2 in a hydrochloric acid solution with a concentration of 10 weight%, performing a third ultrasonic cleaning for 20 seconds under the conditions of an ultrasonic frequency of 50 kHz and a circulating filter element of 0.1 μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a third surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), and finally placing the wafer in a spin dryer and spinning for 250 seconds under the conditions of blowing nitrogen, a temperature of 45°C, and a rotation speed of 1000 rpm.

[0092] After the silicon carbide substrate wafer was cleaned in Example 7, the particle size of the wafer surface at 0.08 μm was 193, and the qualified rate was 97%. Compared with Comparative Example 1, the cleaning effect was significantly improved, and the service life of the composite cleaning agent was extended by about 35%.

[0093] Example 8

[0094] Step S1, placing the silicon carbide substrate wafer into the CASS, inserting the spacer (13 wafers per CASS), then immersing the CASS in ethanol, performing the first ultrasonic cleaning for 15 seconds under the conditions of an ultrasonic frequency of 20 kHz and a circulating filter element of 0.3 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for the first surface residual cleaning (draining time is 2 seconds, rinsing time is 3 minutes);

[0095] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 30 seconds at a temperature of 7° C., an ultrasonic frequency of 50 KHz, and a circulating filter element of less than 0.1 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for a second surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide, and deionized water in a molar ratio of 1:1:97.5;

[0096] Step S3, immersing the silicon carbide substrate wafer treated in step S2 in a hydrochloric acid solution with a concentration of 5 weight%, performing a third ultrasonic cleaning for 20 seconds under the conditions of an ultrasonic frequency of 50 kHz and a circulating filter element of 0.1 μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a third surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), and finally placing the wafer in a spin dryer and spinning for 250 seconds under the conditions of blowing nitrogen, a temperature of 35°C, and a rotation speed of 1000 rpm.

[0097] After the cleaning of the silicon carbide substrate wafer in Example 8, the particle size of the wafer surface at 0.08 μm is 257 (as shown in FIG. Figure 3 As shown), the qualified rate is 96%. Compared with comparative example 1, the cleaning effect is significantly improved, and the service life of the composite cleaning agent is extended by about 35%.

[0098] Example 9

[0099] Step S1, placing the silicon carbide substrate wafer into the CASS, inserting the spacer (13 wafers per CASS), then immersing the CASS in ethanol, performing the first ultrasonic cleaning for 35 seconds under the conditions of an ultrasonic frequency of 20KHz and a circulating filter element of 0.3μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for the first surface residual cleaning (draining time is 2s, rinsing time is 3min);

[0100] Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent, performing a second ultrasonic cleaning for 60 seconds at a temperature of 7° C., an ultrasonic frequency of 50 KHz, and a circulating filter element of less than 0.1 μm, and then taking out the wafer and placing it in a fast-drain rinsing tank for a second surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide, and deionized water in a molar ratio of 1:3:15;

[0101] Step S3, immersing the silicon carbide substrate wafer treated in step S2 in a sulfuric acid solution with a concentration of 10 weight%, performing a third ultrasonic cleaning for 10 seconds under the conditions of an ultrasonic frequency of 50 kHz and a circulating filter element of 0.1 μm, and then taking out the wafer and placing it in a fast drain rinsing tank for a third surface residual cleaning (drainage time is 2 seconds, rinsing time is 3 minutes), and finally placing the wafer in a spin dryer and spinning for 250 seconds under the conditions of blowing nitrogen, a temperature of 55°C, and a rotation speed of 1000 rpm.

[0102] After the silicon carbide substrate wafer was cleaned in Example 8, the particle size of 0.08 μm on the wafer surface was 205, and the qualified rate was 96%. Compared with Comparative Example 1, the cleaning effect was significantly improved, and the service life of the composite cleaning agent was extended by about 35%.

[0103] Comparative Example 1

[0104] Step S1, immersing the silicon carbide substrate wafer in a composite cleaning agent at room temperature for 60 seconds, and then taking out the wafer and placing it in a fast-drain rinsing tank for first surface residual cleaning (draining time is 15 seconds, rinsing time is 3 minutes), wherein the composite cleaning agent contains ammonia water, hydrogen peroxide and deionized water in a molar ratio of 1:1:97.5;

[0105] Step S2, immersing the silicon carbide substrate wafer treated in step S1 in a 5 weight % hydrochloric acid solution for cleaning for 30 seconds, then taking out the wafer and placing it in a fast drain rinsing tank for a second surface residual cleaning (drainage time is 15 seconds, rinsing time is 3 minutes), and finally placing the wafer in a spin dryer under nitrogen blowing, heating, and a rotation speed of 1000 rpm for 250 seconds.

[0106] After cleaning in Comparative Example 1, the particle size of the silicon carbide substrate wafer at 0.08 μm on the wafer surface was 761, and the qualified rate was 83%.

[0107] Comparative Example 2

[0108] Step S1, immersing the silicon carbide substrate wafer in a heated mixed washing solution formed by mixing sulfuric acid and hydrogen peroxide, wherein the ratio of sulfuric acid to hydrogen peroxide is 3:1;

[0109] Step S2, rinsing the surface of the silicon carbide substrate wafer treated in step S1 with deionized water, and then placing it in acetone for ultrasonic cleaning;

[0110] Step S3, rinse the surface of the silicon carbide substrate wafer treated in step S2 with deionized water, and then soak it in a heated mixed washing solution formed by mixing ammonia water, hydrogen peroxide and deionized water, wherein the ratio of ammonia water, hydrogen peroxide and deionized water is 1:1:5.

[0111] Step S4: rinse the surface of the silicon carbide substrate wafer treated in step S3 with deionized water, and then soak it in a heated mixed solution of hydrochloric acid, hydrogen peroxide, and deionized water, wherein the ratio of hydrochloric acid, hydrogen peroxide, and deionized water is 1:1:5. Hydrochloric acid can quickly remove most metal contamination or residues.

[0112] Step S5, washing the surface of the silicon carbide substrate wafer treated in step S4 with ozone water, ammonia water, and high-purity nitrogen plus deionized water respectively. When washing with high-purity nitrogen plus deionized water, an upper and lower side-by-side inclined double channel is used, the high-purity nitrogen pressure value is about 80 psi, and the deionized water flow rate is about 2.5 L / min;

[0113] Step S6, washing the surface of the silicon carbide substrate wafer treated in step S5 with ozone water, hydrofluoric acid solution and ozone water respectively; wherein the concentration of the hydrofluoric acid solution is 0.1-2%.

[0114] Step S7, rinse the surface of the silicon carbide substrate wafer treated in step S6 with deionized water, and spin dry at high speed.

[0115] After cleaning in Comparative Example 2, the particle size of the silicon carbide substrate wafer at 0.08 μm on the wafer surface is 401, and the qualified rate is 90%.

[0116] Comparative Example 3

[0117] Step S1, rinsing the silicon carbide substrate wafer with deionized water and then soaking it in deionized water;

[0118] Step S2, prepare a metal cleaning solution with a volume concentration of 15% (produced by Beijing Dongyang Chemical Co., Ltd.), remove the wafer from the deionized water, place it in the metal cleaning solution, and immerse the entire wafer in the solution at a temperature of 80°C. Shake the wafer continuously for cleaning for 15 minutes. After cleaning, take it out, rinse it with deionized water, and immerse it in deionized water for 3 minutes.

[0119] Step S3, according to the volume ratio of 57%:43%, respectively measure the sodium hydroxide solution and hydrogen peroxide with a mass concentration of 2.5%, stir and mix them evenly to prepare an alkaline solution, remove the wafer that has been cleaned once from the deionized water, place it in the alkaline solution, and clean it for the second time at a temperature of 30°C for 30 seconds. After the cleaning is completed, rinse and soak it with deionized water for 3 minutes;

[0120] Step S4, measure 65% citric acid solution and 30% dilute sulfuric acid solution by volume ratio of 5:1 respectively, stir and mix them evenly to obtain an acid solution, place the wafer after the second cleaning in the acid solution, and perform the third cleaning at 28°C for 30s. After the cleaning is completed, rinse with deionized water and enter the next process.

[0121] After cleaning in Comparative Example 3, the particle size of the silicon carbide substrate wafer at 0.08 μm on the wafer surface was 375, and the qualified rate was 88%.

[0122] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A method for cleaning a silicon carbide substrate wafer, characterized in that: The following steps are involved: Step S1, immersing the silicon carbide substrate wafer in an organic solvent for a first ultrasonic cleaning, and then performing a first surface residual cleaning; the organic solvent is a low-grade organic alcohol, and the low-grade organic alcohol is at least one of methanol, ethanol, n-propanol and isopropanol, and the conditions for the first ultrasonic cleaning include: an ultrasonic frequency of 20-40KHz, a circulating filter element <0.5μm, and an immersion time of 15-35s, and the conditions for the first surface residual cleaning include: in a fast-drain rinsing tank, a rinsing time of 3-6min, and a drainage time of 2-5s; Step S2, immersing the silicon carbide substrate wafer treated in step S1 into a composite cleaning agent for a second ultrasonic cleaning, and then performing a second surface residual cleaning; the composite cleaning agent contains an alkali, an oxidant and water, the alkali is ammonia water, the oxidant is hydrogen peroxide, the molar ratio of the alkali, the oxidant and the water in the composite cleaning agent is 1:1-3.5:10-100, the conditions for the second ultrasonic cleaning include: a temperature of 7-12°C, an ultrasonic frequency of 50-100KHz, a circulating filter element <0.5μm, and an immersion time of 30-60s, and the conditions for the second surface residual cleaning include: being carried out in a fast-drain rinsing tank, the rinsing time is 3-6min, and the drainage time is 2-5s; Step S3, immersing the silicon carbide substrate wafer after the treatment in step S2 in an acid solution for a third ultrasonic cleaning, and then performing a third surface residual cleaning and drying treatment; the acid solution is selected from at least one of a hydrochloric acid solution, a sulfuric acid solution and a nitric acid solution, and the acid solution contains H + The concentration is 1.2-3 mol / L, the conditions of the third ultrasonic cleaning include: ultrasonic frequency is 50-100 KHz, circulating filter element is less than 0.5 μm, immersion time is 10-30 s, and the conditions of the third surface residual cleaning include: in a fast drain rinsing tank, the rinsing time is 3-6 min, and the drainage time is 2-5 s.

2. The cleaning method according to claim 1, characterized in that: The drying process in step S3 includes: drying the silicon carbide substrate wafer after the third surface residue cleaning under blowing conditions.

3. The cleaning method according to claim 2, characterized in that: The drying conditions include: temperature of 35-65° C., rotation speed of 800-1200 rpm, and time of 200-300 s.

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