A method for cleaning silicon carbide wafer

Abstract

The present invention provides a cleaning method for silicon carbide wafers. The cleaning method comprises: pre-cleaning the silicon carbide wafer to be cleaned; placing the pre-cleaned silicon carbide wafer in an ozone solution for a first main cleaning; placing the silicon carbide wafer after the first main cleaning in a composite acid solution for a second main cleaning; wherein the composite acid solution comprises an inorganic acid and an organic dispersant; and performing post-treatment. The present invention firstly uses an ozone solution for the first main cleaning to fully oxidize the surface of the wafer, which helps to remove metal ions on the surface of the wafer with the subsequent composite acid solution and reduces the risk of metal ion contamination on the surface of the wafer; secondly, the inorganic acid and the organic dispersant are used in synergistic cooperation to help accelerate the spreading at the hydrophilic interface or the hydrophobic interface of the wafer, improve the cleaning effect, shorten the cleaning process, and improve production efficiency. Silicon carbide wafers with atomically smooth surfaces and good structures can be obtained through the cleaning method.

Description

Technical Field

[0001] The invention belongs to the technical field of surface purification of semiconductor materials, and in particular relates to a method for cleaning a silicon carbide wafer. Background Art

[0002] Silicon carbide (SiC) is a third-generation semiconductor material with good performance. It has excellent properties such as high breakdown voltage, high migration speed, wide bandgap, strong radiation resistance and good chemical stability. It has good development prospects in the fields of energy conservation and emission reduction, new energy and electronic information. In addition, SiC semiconductors can be used in high power, power electronics, optoelectronic devices, etc., and are an important material for the new generation of wide bandgap semiconductor devices.

[0003] The cleanliness of the SiC wafer surface is one of the important indicators that affect the yield of subsequent processes and device performance. During the processing of SiC wafers, various metal impurities will be contaminated, which will lead to the failure of the function of the subsequent devices. Therefore, it is necessary to improve the cleaning yield and reduce the metal ion contamination on the wafer surface. The core of wafer cleaning is to effectively remove various pollutants on the wafer surface through physical, chemical and other methods to ensure that the wafer has a clean surface suitable for subsequent processing. In the cleaning of SiC wafers, wet cleaning process occupies the mainstream position. Wet cleaning mostly uses RCA cleaning, which is usually combined with physical methods such as ultrasound, megasonics, and bubbling to assist in removing pollutants on the wafer surface. The solutions used in this process include SPM, DHF, SC1 and SC2. Among them, DHF solution mainly removes the natural and chemical oxide layer and oxide on the wafer surface to reduce surface metal contamination. However, direct DHF cleaning cannot obtain an atomically smooth and well-structured surface, and will increase the risk of surface metal ion contamination. In addition, the surface of the wafer after SPM cleaning may be at risk of insufficient oxidation.

[0004] Therefore, there is an urgent need to provide a cleaning method for silicon carbide wafers to obtain an atomically smooth and well-structured wafer surface and reduce the risk of metal ion contamination on the wafer surface. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention aims to provide a method for cleaning silicon carbide wafers. The present invention first uses ozone solution for the first main cleaning to fully oxidize the wafer surface, which helps the subsequent composite acid solution to remove metal ions on the wafer surface and reduce the risk of metal ion contamination on the wafer surface; secondly, the use of inorganic acid and organic dispersant synergistically helps to accelerate the spreading on the hydrophilic interface or hydrophobic interface of the wafer, improve the cleaning effect, shorten the cleaning process, and improve production efficiency. The cleaning method can obtain a silicon carbide wafer with a smooth surface at the atomic level and a good structure, and its trace metal ion content is less than 1×10 10 atoms / cm 2 .

[0006] In order to achieve the purpose of the invention, the present invention adopts the following technical solutions:

[0007] In a first aspect, the present invention provides a method for cleaning a silicon carbide wafer, the cleaning method comprising the following steps:

[0008] The silicon carbide wafer to be cleaned is pre-cleaned.

[0009] The pre-cleaned silicon carbide wafer is placed in an ozone solution for a first main cleaning.

[0010] The silicon carbide wafer after the first main cleaning is placed in a composite acid solution for a second main cleaning; wherein the composite acid solution includes an inorganic acid and an organic dispersant.

[0011] Perform post-processing.

[0012] The present invention first uses an ozone solution to perform a first main cleaning on the pre-cleaned silicon carbide wafer, so that the wafer surface is fully oxidized, which is helpful for the subsequent removal of metal ions on the wafer surface by the composite acid solution, and reduces the risk of metal ion contamination on the wafer surface; secondly, the use of inorganic acid and organic dispersant synergistically helps to accelerate the spreading on the hydrophilic interface or hydrophobic interface of the wafer, improve the cleaning effect, shorten the cleaning process, and improve production efficiency. The cleaning method can obtain a silicon carbide wafer with a smooth surface at the atomic level and a good structure, and its trace metal ion content is less than 1×10 10 atoms / cm 2 .

[0013] Preferably, during the pre-cleaning process, the cleaning agents used include sulfuric acid, hydrogen peroxide and a wetting penetrant.

[0014] In the pre-cleaning process, the present invention introduces sulfuric acid, hydrogen peroxide and a wetting and penetrating agent for cleaning, wherein the wetting and penetrating agent has a highly efficient penetrating and wetting performance and can effectively improve the cleaning efficiency of oil stains and organic matter.

[0015] Preferably, the wetting and penetrating agent comprises polyether-modified acetylene glycol.

[0016] It should be noted that the present invention does not limit the source of the polyether-modified acetylene glycol. For example, it can be Dynol 604, Dynol 607 or Dynol 630 of Dow Chemical, or Tego Wet KL 245 or Tego Wet KL 265 of Evonik.

[0017] Preferably, the mass ratio of sulfuric acid, hydrogen peroxide and wetting penetrant is (2-5):1:(0.5-1), wherein the selection range of sulfuric acid "2-5" can be, for example, 2, 3, 4 or 5, etc., and the selection range of the wetting penetrant "0.5-1" can be, for example, 0.5, 0.6, 0.7, 0.8, 0.9 or 1, etc.

[0018] In the present invention, sulfuric acid, hydrogen peroxide and wetting penetrant in an appropriate mass ratio can further increase the contact area between the surface of the silicon carbide wafer and the solution, and improve the ability to remove organic matter on the surface of the wafer.

[0019] Preferably, the pre-cleaning temperature is 100-130°C, for example, 100°C, 110°C, 120°C or 130°C.

[0020] Preferably, the pre-cleaning time is 15-30 min, for example, 15 min, 20 min, 25 min or 30 min.

[0021] Preferably, the ozone concentration in the ozone solution is 20-30 ppm, for example, 20 ppm, 25 ppm or 30 ppm.

[0022] In the present invention, if the concentration of ozone in the ozone solution is too low, the cleaning effect will be insufficient; if the concentration of ozone in the ozone solution is too high, it will easily lead to excessive oxidation and cause surface defects of the wafer.

[0023] Preferably, the temperature of the first main cleaning is 25-35°C, for example, 25°C, 30°C or 35°C.

[0024] Preferably, the first main cleaning time is 5-15 minutes, for example, 5 minutes, 10 minutes or 15 minutes.

[0025] In the present invention, the ozone solution is used for cleaning under the above-mentioned time and temperature conditions, which can fully and appropriately oxidize the surface of the wafer and reduce the contact angle of the wafer surface, thereby facilitating the removal of organic pollutants and metal pollutants on the surface.

[0026] Preferably, the inorganic acid comprises any one of hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid or carbonic acid, or a combination of at least two thereof, preferably a combination of hydrofluoric acid and hydrochloric acid.

[0027] Preferably, the mass ratio of the hydrofluoric acid to the hydrochloric acid is 1:(1-2), for example, it can be 1:1, 1:1.5 or 1:2.

[0028] Preferably, the organic dispersant includes any one or a combination of at least two of polyether trisiloxane, alkyl aryl phosphate, alkyl benzene sulfonate, dialkyl sulfosuccinate, trimethyl stearamide chloride, polyoxyethylene alkylphenol ether or sorbitol alkylate. Exemplarily, the alkyl aryl phosphate is, for example, nonylphenol polyoxyethylene ether phosphate.

[0029] In the present invention, the polyether trisiloxane has efficient super diffusion performance and can be evenly spread on a hydrophilic interface or a hydrophobic interface. Compared with the traditional cleaning process, the cleaning effect of the cleaning agent is improved, the cleaning process is shortened, the production efficiency is improved, and the amount of hydrofluoric acid used in the cleaning process is reduced, which is conducive to obtaining a silicon carbide wafer with a smooth surface at the atomic level and a good structure.

[0030] Preferably, the chemical formula of the polyether trisiloxane is (CH3)3SiO-Si(CH3)[CH2CH2CH2-(OCH2CH2) n OH]-OSi(CH3)3, n=4-10, for example, it can be 4, 5, 6, 7, 8, 9 or 10, etc.

[0031] It should be noted that n represents the number of ethylene oxide units, which can be changed according to specific synthesis conditions and requirements, and is used to adjust the hydrophilicity and other properties of the polyether trisiloxane.

[0032] Preferably, the mass ratio of the inorganic acid to the organic dispersant is 1:(10-30), for example, it can be 1:10, 1:15, 1:20, 1:25 or 1:30, etc.

[0033] In the present invention, the inorganic acid and the organic dispersant in a suitable mass ratio are beneficial to reducing the etching of the solution on the wafer surface, improving the smoothness of the wafer surface, and increasing the surface tension of the solution, thereby reducing the contact angle of the wafer surface and improving the ability to remove metal ion contamination.

[0034] Preferably, the temperature of the second main cleaning is 40-50°C, for example, 40°C, 45°C or 50°C.

[0035] In the present invention, the second main cleaning process at a suitable temperature can improve the stability and wetting performance of the solution, is conducive to obtaining a suitable Zeta potential during the cleaning process, and is also conducive to the removal of stubborn pollutants.

[0036] Preferably, the second main cleaning time is 15-30 minutes, for example, it can be 15 minutes, 20 minutes, 25 minutes, 30 minutes, etc.

[0037] Preferably, the post-treatment includes alkali washing, water washing and drying.

[0038] Preferably, in the alkali washing process, the alkali solution used includes any one of ammonium hydroxide solution, ethylenediamine solution, tetramethylammonium hydroxide solution or silicate solution, or a combination of at least two of them.

[0039] Preferably, the silicate solution comprises any one of sodium silicate solution, sodium metasilicate solution, potassium silicate solution or lithium silicate solution, or a combination of at least two thereof.

[0040] Preferably, an active agent is also added during the alkali washing process.

[0041] Preferably, the active agent comprises hydrogen peroxide.

[0042] Preferably, the alkaline washing process is accompanied by ultrasound.

[0043] Preferably, the frequency of the ultrasound is 60-100 KHz, for example, 60 KHz, 70 KHz, 80 KHz, 90 KHz or 100 KHz.

[0044] Preferably, the power of the ultrasound is 350-450W, for example, 350W, 400W or 450W.

[0045] Preferably, the alkali washing temperature is 35-50°C, for example, 35°C, 40°C, 45°C or 50°C.

[0046] Preferably, the cleaning method comprises the following steps:

[0047] (1) placing the polished silicon carbide wafer in a quartz tank and pre-cleaning it at 100-130° C. for 15-30 min; wherein the cleaning agent used in the pre-cleaning comprises sulfuric acid, hydrogen peroxide and a wetting and penetrating agent in a mass ratio of (2-5):1:(0.5-1), and the wetting and penetrating agent comprises polyether-modified acetylene glycol.

[0048] (2) The pre-cleaned silicon carbide wafer is washed with water and then placed in an ozone solution with an ozone concentration of 20-30 ppm and subjected to a first main cleaning at 25-35° C. for 5-15 minutes.

[0049] (3) The silicon carbide wafer after the first main cleaning is washed with water, and then placed in a composite acid solution, and a second main cleaning is performed at 40-50° C. for 15-30 min; wherein the composite acid solution comprises an inorganic acid and an organic dispersant, the inorganic acid comprises hydrofluoric acid and hydrochloric acid in a mass ratio of 1:(1-2), the organic dispersant comprises polyether trisiloxane, and the mass ratio of the inorganic acid to the organic dispersant is 1:(10-30).

[0050] (4) The silicon carbide wafer after the second main cleaning is washed with water, and then placed in an alkaline solution with a concentration of 2-4wt.% (for example, 2wt.%, 2.5wt.%, 3wt.%, 3.5wt.% or 4wt.%) for ultrasonic heating cleaning, the ultrasonic frequency is 60-100KHz, the ultrasonic power is 350-450W, and the cleaning temperature is 35-50°C.

[0051] (5) The silicon carbide wafer after ultrasonic heating cleaning is washed with water and dried to complete the cleaning.

[0052] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0053] Compared with the prior art, the present invention has the following beneficial effects:

[0054] The present invention first uses ozone solution for the first main cleaning to fully oxidize the surface of the wafer, which is helpful for the subsequent removal of metal ions on the surface of the wafer by the composite acid solution, reducing the risk of metal ion contamination on the surface of the wafer; secondly, the use of inorganic acid and organic dispersant synergistically helps to accelerate the spreading on the hydrophilic interface or hydrophobic interface of the wafer, improve the cleaning effect, shorten the cleaning process, and improve production efficiency. The cleaning method can obtain a silicon carbide wafer with a smooth surface at the atomic level and good structure, and its trace metal ion content is less than 1×10 10 atoms / cm 2 . BRIEF DESCRIPTION OF THE DRAWINGS

[0055] Figure 1 This is a partial process flow chart of the cleaning method provided by the present invention. DETAILED DESCRIPTION

[0056] The technical solution of the present invention is further described below by specific implementation methods. It should be understood by those skilled in the art that the embodiments are only to help understand the present invention and should not be regarded as specific limitations of the present invention.

[0057] It should be noted that the polished silicon carbide wafers used in the following embodiments are all from the same batch.

[0058] Example 1

[0059] This embodiment provides a method for cleaning a silicon carbide wafer, and a partial process flow chart thereof is shown in FIG. Figure 1 As shown, the cleaning method comprises the following steps:

[0060] (1) The polished silicon carbide wafer is placed in a quartz tank and pre-cleaned at 115° C. for 25 minutes; wherein the cleaning agent used for the pre-cleaning includes sulfuric acid (with a concentration of 98 wt%), hydrogen peroxide and a wetting and penetrating agent, wherein the wetting and penetrating agent is a polyether-modified acetylene glycol, and the mass ratio of sulfuric acid, hydrogen peroxide and the wetting and penetrating agent is 3.5:1:0.75.

[0061] (2) The pre-cleaned silicon carbide wafer was placed in an HQDR tank for pure water rinsing, and then placed in an ozone aqueous solution with an ozone concentration of 25 ppm for a first main cleaning at 30° C. for 10 min.

[0062] (3) placing the silicon carbide wafer after the first main cleaning into an HQDR tank for pure water rinsing, and then placing it in a composite acid solution for a second main cleaning at 45° C. for 25 minutes; wherein the composite acid solution comprises an inorganic acid and an organic dispersant, wherein the inorganic acid comprises hydrofluoric acid (concentration of 49 wt%) and hydrochloric acid (concentration of 37 wt%) in a mass ratio of 1:1.5, and the organic dispersant is polyether trisiloxane with a chemical formula of (CH3)3SiO-Si(CH3)[CH2CH2CH2-(OCH2CH2) n OH]-OSi(CH3)3, n=7; the mass ratio of the inorganic acid to the organic dispersant is 1:20.

[0063] (4) The silicon carbide wafer after the second main cleaning is placed in an HQDR tank for pure water rinsing, and then placed in a 3.0wt.% ammonium hydroxide solution for ultrasonic heating cleaning. The ultrasonic frequency is 80KHz, the ultrasonic power is 400W, and the cleaning temperature is 45°C.

[0064] (5) The silicon carbide wafer after ultrasonic heating cleaning is placed in a QDR tank for pure water rinsing, and then the silicon carbide wafer is dried using a spin dryer to complete the cleaning.

[0065] Example 2

[0066] This embodiment provides a method for cleaning a silicon carbide wafer, the cleaning method comprising the following steps:

[0067] (1) The polished silicon carbide wafer is placed in a quartz tank and pre-cleaned at 100° C. for 15 minutes; wherein the cleaning agent used for pre-cleaning includes sulfuric acid (concentration of 98wt%), hydrogen peroxide and a wetting and penetrating agent in a mass ratio of 2:1:0.5, and the wetting and penetrating agent is a polyether-modified acetylene glycol.

[0068] (2) The pre-cleaned silicon carbide wafer was placed in an HQDR tank for pure water rinsing, and then placed in an ozone aqueous solution with an ozone concentration of 20 ppm for a first main cleaning at 25° C. for 15 minutes.

[0069] (3) Placing the silicon carbide wafer after the first main cleaning into an HQDR tank for pure water rinsing, and then placing it in a composite acid solution for a second main cleaning at 40° C. for 15 minutes; wherein the composite acid solution comprises an inorganic acid and an organic dispersant, wherein the inorganic acid comprises hydrochloric acid (concentration of 49wt%) and nonylphenol polyoxyethylene ether phosphate in a mass ratio of 1:1; and the mass ratio of the inorganic acid to the organic dispersant is 1:10.

[0070] (4) The silicon carbide wafer after the second main cleaning is placed in an HQDR tank for pure water rinsing, and then placed in a mixture of 2.0wt.% ethylenediamine solution and hydrogen peroxide for ultrasonic heating cleaning. The ultrasonic frequency is 60KHz, the ultrasonic power is 350W, and the cleaning temperature is 40°C.

[0071] (5) The silicon carbide wafer after ultrasonic heating cleaning is placed in a QDR tank for pure water rinsing, and then the silicon carbide wafer is dried using a spin dryer to complete the cleaning.

[0072] Example 3

[0073] This embodiment provides a method for cleaning a silicon carbide wafer, the cleaning method comprising the following steps:

[0074] (1) The polished silicon carbide wafer is placed in a quartz tank and pre-cleaned at 130° C. for 30 minutes; wherein the cleaning agent used for the pre-cleaning includes sulfuric acid (concentration of 98wt%), hydrogen peroxide and a wetting and penetrating agent in a mass ratio of 5:1:1, and the wetting and penetrating agent is a polyether-modified acetylene glycol.

[0075] (2) The pre-cleaned silicon carbide wafer was placed in an HQDR tank for pure water rinsing, and then placed in an ozone aqueous solution with an ozone concentration of 30 ppm for a first main cleaning at 35° C. for 15 minutes.

[0076] (3) Placing the silicon carbide wafer after the first main cleaning into an HQDR tank for pure water rinsing, and then placing it in a composite acid solution for a second main cleaning at 50° C. for 30 minutes; wherein the composite acid solution comprises an inorganic acid and an organic dispersant, wherein the inorganic acid comprises hydrochloric acid (concentration of 49wt%) and hydrochloric acid (concentration of 37wt%) in a mass ratio of 1:2, and the organic dispersant is polyoxyethylene alkylphenol ether; and the mass ratio of the inorganic acid to the organic dispersant is 1:30.

[0077] (4) The silicon carbide wafer after the second main cleaning is placed in an HQDR tank for pure water rinsing, and then placed in a mixture of 4.0wt.% tetramethylammonium hydroxide solution and hydrogen peroxide for ultrasonic heating cleaning. The ultrasonic frequency is 100KHz, the ultrasonic power is 450W, and the cleaning temperature is 50°C.

[0078] (5) The silicon carbide wafer after ultrasonic heating cleaning is placed in a QDR tank for pure water rinsing, and then the silicon carbide wafer is dried using a spin dryer to complete the cleaning.

[0079] Example 4

[0080] The difference between this embodiment and embodiment 1 is that no polyether-modified acetylene glycol is added in step (1).

[0081] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0082] Example 5

[0083] The difference between this embodiment and embodiment 1 is that the ozone concentration in the ozone aqueous solution in step (2) is 15 ppm.

[0084] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0085] Example 6

[0086] The difference between this embodiment and embodiment 1 is that the ozone concentration in the ozone aqueous solution in step (2) is 35 ppm.

[0087] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0088] Example 7

[0089] The difference between this embodiment and embodiment 1 is that the temperature of the first main cleaning in step (2) is 20°C.

[0090] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0091] Example 8

[0092] The difference between this embodiment and embodiment 1 is that the temperature of the first main cleaning in step (2) is 40°C.

[0093] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0094] Example 9

[0095] The difference between this embodiment and embodiment 1 is that the mass ratio of the inorganic acid to the organic dispersant in step (3) is 1:5.

[0096] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0097] Example 10

[0098] The difference between this embodiment and embodiment 1 is that the mass ratio of the inorganic acid to the organic dispersant in step (3) is 1:35.

[0099] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0100] Embodiment 11

[0101] The difference between this embodiment and embodiment 1 is that the temperature of the second main cleaning in step (3) is 30°C.

[0102] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0103] Example 12

[0104] The difference between this embodiment and embodiment 1 is that the temperature of the second main cleaning in step (3) is 60°C.

[0105] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0106] Comparative Example 1

[0107] The difference between this comparative example and Example 1 is that the first main cleaning is not performed.

[0108] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0109] Comparative Example 2

[0110] The difference between this comparative example and Example 1 is that no polyether trisiloxane is added to the composite acid solution.

[0111] The rest of the cleaning methods and parameters were the same as those in Example 1.

[0112] Performance Testing

[0113] The silicon carbide wafers cleaned by the cleaning methods provided in the above embodiments and comparative examples were subjected to surface roughness tests and surface trace metal ion content tests.

[0114] The surface roughness test uses Parker equipment to test the atomic force microscope to characterize the roughness change of the material. The surface trace metal ion content test uses inductively coupled plasma mass spectrometry to determine the metal ion content on the surface of the silicon carbide wafer.

[0115] The test results are shown in Table 1.

[0116] Table 1

[0117]

[0118]

[0119] analyze:

[0120] The present invention first uses ozone solution for the first main cleaning to fully oxidize the surface of the wafer, which is helpful for the subsequent removal of metal ions on the surface of the wafer by the composite acid solution, reducing the risk of metal ion contamination on the surface of the wafer; secondly, the use of inorganic acid and organic dispersant synergistically helps to accelerate the spreading on the hydrophilic interface or hydrophobic interface of the wafer, improve the cleaning effect, shorten the cleaning process, and improve production efficiency. The cleaning method can obtain a silicon carbide wafer with a smooth surface at the atomic level and good structure, and its trace metal ion content is less than 1×10 10 atoms / cm 2 .

[0121] From the comparison between Example 1 and Example 4, it can be seen that if the polyether-modified acetylene glycol is not added in step (1), it is not conducive to increasing the wettability of the wafer surface and reducing the contact angle of the wafer surface.

[0122] By comparing Example 1 with Examples 5-6, it can be seen that if the ozone concentration in the ozone aqueous solution is too low, impurities on the surface of the silicon carbide wafer may not be effectively removed; if the ozone concentration in the ozone aqueous solution is too high, the surface of the silicon carbide wafer may be damaged.

[0123] By comparing Example 1 with Examples 7-8, it can be seen that if the temperature of the first main cleaning is too low, ozone is not easily dissolved and the surface of the silicon carbide wafer cannot be fully oxidized; if the temperature of the first main cleaning is too high, the ozone stability is poor and the surface of the silicon carbide wafer is unevenly oxidized.

[0124] By comparing Example 1 with Examples 9-10, it can be seen that if the mass ratio of the inorganic acid to the organic dispersant is too low, the organic dispersant enriched on the surface of the silicon carbide wafer is insufficient, the surface wettability is poor, and it is not conducive to the removal of metal ions; if the mass ratio of the inorganic acid to the organic dispersant is too high, the surface adsorption reaches saturation, the organic dispersant cannot continue to be enriched on the surface, and it is easy to aggregate in the solution to form micelles.

[0125] By comparing Example 1 with Examples 11-12, it can be seen that if the temperature of the second main cleaning is too low, it is not conducive to softening and removing stubborn contamination, making the chip surface not smooth enough and the surface metal contaminants not cleaned thoroughly; if the temperature of the second main cleaning is too high, it leads to thermal motion energy between the solution molecules, the molecules are more likely to overcome the cohesive force, thereby reducing the surface tension of the solution, increasing the contact angle between the chip and the solution, and is not conducive to the removal of surface metal contaminants.

[0126] From the comparison between Example 1 and Comparative Example 1, it can be seen that if the first main cleaning is not performed, the surface of the wafer is not fully oxidized and the surface contact angle is large, which is not conducive to the removal of metal contaminants.

[0127] By comparing Example 1 with Comparative Example 2, it can be seen that if polyether trisiloxane is not added to the composite acid solution, the solution is unevenly mixed and dispersed, and the stability is poor. In addition, excessive etching may occur, resulting in an uneven wafer surface and insufficient removal of surface metal contaminants.

[0128] The applicant declares that the present invention illustrates the process method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned process steps, that is, it does not mean that the present invention must rely on the above-mentioned process steps to be implemented. Those skilled in the art should understand that any improvement of the present invention, equivalent replacement of the raw materials selected by the present invention, addition of auxiliary components, selection of specific methods, etc., all fall within the protection scope and disclosure scope of the present invention.

Claims

1. A method for cleaning a silicon carbide wafer, characterized in that: The cleaning method comprises the following steps: Pre-cleaning the silicon carbide wafer to be cleaned; placing the pre-cleaned silicon carbide wafer in an ozone solution for a first main cleaning; Placing the silicon carbide wafer after the first main cleaning in a composite acid solution for a second main cleaning; wherein the composite acid solution comprises an inorganic acid and an organic dispersant; Perform post-processing.

2. The cleaning method according to claim 1, characterized in that: During the pre-cleaning process, the cleaning agents used include sulfuric acid, hydrogen peroxide and a wetting penetrant; Preferably, the wetting and penetrating agent comprises polyether-modified acetylenic glycol; Preferably, the mass ratio of the sulfuric acid, hydrogen peroxide and wetting penetrant is (2-5):1:(0.5-1); Preferably, the pre-cleaning temperature is 100-130°C; Preferably, the pre-cleaning time is 15-30 minutes.

3. The cleaning method according to claim 1 or 2, characterized in that: In the ozone solution, the concentration of ozone is 20-30 ppm.

4. The cleaning method according to any one of claims 1 to 3, characterized in that: The temperature of the first main cleaning is 25-35°C; Preferably, the first main cleaning time is 5-15 minutes.

5. The cleaning method according to any one of claims 1 to 3, characterized in that: The inorganic acid comprises any one of hydrofluoric acid, hydrochloric acid, sulfuric acid, nitric acid or carbonic acid or a combination of at least two thereof, preferably a combination of hydrofluoric acid and hydrochloric acid; Preferably, the mass ratio of hydrofluoric acid to hydrochloric acid is 1:(1-2); Preferably, the organic dispersant comprises any one or a combination of at least two of polyether trisiloxane, alkyl aryl phosphate, alkyl benzene sulfonate, dialkyl sulfosuccinate, trimethyl stearamide chloride, polyoxyethylene alkylphenol ether or sorbitol alkylate; Preferably, the chemical formula of the polyether trisiloxane is (CH3)3SiO-Si(CH3)[CH2CH2CH2-(OCH2CH2) n OH]-OSi(CH3)3, n=7.

6. The cleaning method according to any one of claims 1 to 5, characterized in that: The mass ratio of the inorganic acid to the organic dispersant is 1:(10-30).

7. The cleaning method according to any one of claims 1 to 6, characterized in that: The temperature of the second main cleaning is 40-50°C; Preferably, the second main cleaning time is 15-30 minutes.

8. The cleaning method according to any one of claims 1 to 7, characterized in that: The post-treatment includes alkali washing, water washing and drying.

9. The cleaning method according to claim 8, characterized in that: During the alkali washing process, the alkali solution used includes any one of ammonium hydroxide solution, ethylenediamine solution, tetramethylammonium hydroxide solution or silicate solution, or a combination of at least two thereof; Preferably, during the alkali washing process, an active agent is also added; Preferably, the alkali washing process is accompanied by ultrasound; Preferably, the frequency of the ultrasound is 60-100 KHz; Preferably, the power of the ultrasound is 350-450W; Preferably, the temperature of the alkali washing is 35-50°C.

10. The cleaning method according to any one of claims 1 to 9, characterized in that: The cleaning method comprises the following steps: (1) placing the polished silicon carbide wafer in a quartz tank and pre-cleaning it at 100-130° C. for 15-30 min; wherein the cleaning agent used in the pre-cleaning comprises sulfuric acid, hydrogen peroxide and a wetting and penetrating agent in a mass ratio of (2-5):1:(0.5-1), and the wetting and penetrating agent comprises a polyether-modified acetylene glycol; (2) washing the pre-cleaned silicon carbide wafer with water, and then placing it in an ozone solution with an ozone concentration of 20-30 ppm, and performing a first main cleaning for 5-15 minutes at 25-35° C.; (3) washing the silicon carbide wafer after the first main cleaning with water, and then placing it in a composite acid solution, and performing a second main cleaning at 40-50° C. for 15-30 min; wherein the composite acid solution comprises an inorganic acid and an organic dispersant, the inorganic acid comprises hydrofluoric acid and hydrochloric acid in a mass ratio of 1:(1-2), the organic dispersant comprises polyether trisiloxane, and the mass ratio of the inorganic acid to the organic dispersant is 1:(10-30); (4) washing the silicon carbide wafer after the second main cleaning with water, and then placing it in an alkali solution with a concentration of 2-4wt% for ultrasonic heating cleaning, the ultrasonic frequency is 60-100KHz, the ultrasonic power is 350-450W, and the cleaning temperature is 35-50°C; (5) The silicon carbide wafer after ultrasonic heating cleaning is washed with water and dried to complete the cleaning.

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