CMP composition for obtaining high-quality SiC single crystal substrate surface and preparation method

Abstract

The invention relates to a CMP (chemical mechanical polishing) composition for obtaining a high-quality SiC single crystal substrate surface. The CMP composition is prepared from the following raw materials in percentage by weight: 20-50 wt% of a polishing abrasive, 3-5 wt% of an oxidizing agent, 0.1-0.5 wt% of a surfactant, 0.2-0.5 wt% of a hydrogen bond regulator, 0.2-1 wt% of a polishing accelerant, 0.01-0.05 wt% of a defoaming agent and the balance of water, the CMP composition is neutral. According to the CMP composition, silicon oxide is adopted as a grinding material, a hydrogen bond regulator, a polishing accelerant and an oxidizing agent are introduced, the CMP polishing rate of a silicon carbide wafer is increased, the surface roughness Ra of the cleaned silicon surface can reach 0.07 nm or below, the cleaned surface is free of large particles (larger than 0.2 micron), meanwhile, the silicon oxide raw material does not need to be treated, and the CMP composition has excellent long-term storage stability; and the system does not have particle aggregation and sedimentation phenomena along with the prolonging of the storage time, and excellent polishing surface quality can be obtained in the subsequent polishing process.

Description

Technical Field

[0001] The invention belongs to the technical field of CMP polishing of silicon carbide substrates, and in particular relates to a CMP composition for obtaining a high-quality SiC single crystal substrate surface and a preparation method thereof. Background Art

[0002] Chemical Mechanical Polishing (CMP) is a common process for achieving global planarization in integrated circuit manufacturing or other fields. This process is mainly used to obtain a smooth surface that is flat and free of scratches and impurities. This process is a process of removing and planarizing the surface material of the workpiece through the synergistic effect of chemical corrosion and mechanical wear.

[0003] Silicon carbide (SiC) is the most representative third-generation wide bandgap semiconductor material. It has the characteristics of wide bandgap, high critical breakdown electric field, high thermal conductivity, high carrier saturation migration velocity, low relative dielectric constant, high temperature resistance and radiation resistance. It can meet the needs of high-frequency, high-power, high-temperature, and radiation-resistant integrated electronic devices. It has broad application prospects in aerospace, new energy vehicles, 5G base stations and other scientific and technological fields. Traditional semiconductors cannot replace it. Therefore, the surface processing technology of SiC substrate materials has a great influence on the preparation quality of subsequent epitaxial layers and power devices. In addition, due to the high integration of electronic devices and the trend of feature size reduction, the surface quality of crystal materials is a direct factor restricting the development speed of large-scale integrated circuits. In the production process of silicon carbide wafers, the roughness of the surface after fine polishing is poor, and problems such as particles, pits, and cracks will affect the subsequent epitaxial growth or post-development process, and even seriously affect the performance and reliability of electronic equipment. Therefore, in order to improve the yield rate of post-processing of silicon carbide devices, the industry has increasingly stringent standards for evaluating the surface quality after the silicon carbide polishing process. Ordinary silica sol formula systems have a large number of residual particles, requiring that after the polishing process, the surface roughness of the SiC substrate Ra is less than 0.2nm, and the lower the better. At the same time, there are strict requirements on the number and length of large surface particle residues and scratches.

[0004] However, due to the high hardness and good chemical stability of SiC single crystal materials, and the fact that the compression strength of SiC single crystals is higher than their bending strength, the material exhibits great hardness and brittleness, making it extremely difficult to polish SiC single crystal substrates. At present, the formula of ordinary silicon carbide polishing liquid optimizes the system environment by introducing acid and alkali, which is not conducive to long-term storage, and there are many residual particles and particle agglomeration, which causes micro scratches and orange peel on the surface of silicon carbide wafers during the polishing process.

[0005] Many scholars have conducted relevant research on the polishing of silicon carbide crystals. Chinese patent CN117987015A discloses a CMP polishing liquid for fine polishing of single-crystal silicon carbide substrates and its preparation method. The key point of this patent is to simultaneously introduce a chelating agent, an oxidant and a dispersant through a composite abrasive to achieve a high removal rate of the SiC single crystal substrate. The defect of this patent is that although the polishing composition has a high removal rate, the roughness of the Si surface after polishing is still high (>0.2nm) and cannot meet the requirements of the subsequent epitaxial process in the actual industrial production process. At the same time, the mixed abrasive used in this patent contains abrasives with high hardness, which will cause micro scratches on the silicon surface during the polishing process and remain in the surface damage layer, which is difficult to remove. Moreover, this patent does not provide data on large particles remaining on the silicon surface after the fine polishing process is completed. Chinese patent CN117866536A discloses a method for preparing a CMP polishing liquid for silicon carbide substrates. This patent solves the problem that the SiC polishing process is prone to scratches, and the suspension stability and polishing stability of the slurry are weak by using rare earth oxide cerium oxide abrasives, proprietary formulas and environmentally friendly raw materials. However, the patent uses potassium permanganate oxidant for polishing under acidic conditions, which has an adverse effect on the stability of the polishing liquid system, and is prone to soft agglomeration and gelation. It is not suitable for the fine polishing process of silicon carbide single crystal substrates. At the same time, the cerium oxide abrasive used in the patent is difficult to clean in the subsequent cleaning process, and there is a problem of large particle residue. In addition, the patent does not provide the final Ra data and particle residue data. Chinese patent CN201010591103.1 discloses a method for preparing and using a polishing liquid for silicon carbide. The patent uses silicon oxide as an abrasive to fine polish the surface of silicon carbide. Since its hardness is smaller than that of silicon carbide, the polishing liquid of silicon oxide can effectively improve the surface scratches caused by the rough polishing process and reduce the surface roughness. The surface roughness Ra after polishing reaches 0.07nm. However, since the polishing liquid preparation process provided by the patent requires the addition of alkali as a pH regulator, it affects the stability of the silica sol itself, which is easy to cause problems such as poor solution stability.

[0006] Based on this, this application was developed. Summary of the invention

[0007] The purpose of the present invention is to overcome the defects of the prior art and provide a CMP composition for obtaining a high-quality SiC single crystal substrate surface. The CMP composition adopts silicon oxide as an abrasive, introduces a hydrogen bond regulator, a polishing accelerator and an oxidant, improves the CMP polishing rate of a silicon carbide wafer, and achieves a surface roughness Ra of the silicon surface after cleaning of less than 0.07 nm. There are no large particles (>0.2 um) on the surface after cleaning. At the same time, there is no need to process the abrasive used for polishing. The composition has excellent long-term storage stability, and the system will not have particle agglomeration and sedimentation as the storage time increases, so that excellent polishing surface quality can be obtained in the subsequent polishing process.

[0008] The present invention also provides a method for preparing the CMP composition for obtaining a high-quality SiC single crystal substrate surface.

[0009] To achieve the above object, the present invention adopts the following technical solution: A CMP composition for obtaining a high-quality SiC single crystal substrate surface, which is made of the following raw materials in weight percentage: Polishing abrasive 20-50 wt%, Oxidant 3-5 wt%, Surfactant 0.1-0.5 wt%, Hydrogen bond modifier 0.2-0.5 wt%, Polishing accelerator 0.2-1 wt%, Defoamer 0.01-0.05wt%, The balance is water; The CMP composition is neutral (pH between 7-8).

[0010] The abrasive slurry used in the present invention is alkaline. After adding a weakly acidic oxidant according to the formula ratio of the present application, the polishing liquid finally obtained can be made neutral.

[0011] Specifically, the abrasive can be silicon oxide (silicon dioxide) abrasive grains. The specific gravity (density) of the abrasive is preferably above 1.05, more preferably above 1.1, and further preferably above 1.2. Here, the specific gravity (density) of the abrasive refers to the specific gravity of the silicon dioxide particles in the abrasive grains composed of silicon dioxide particles.

[0012] Preferably, the pH of the abrasive slurry is alkaline, and the pH of the abrasive slurry is in the range of 7 to 12, more preferably in the range of 8 to 10, and most preferably in the range of 9 to 10.

[0013] Preferably, the shape (outer shape) of the abrasive grains can be spherical or non-spherical. The abrasive grains preferably used are mostly abrasive grains with a peanut shape or a cocoon shape. The abrasive grains contain at least 25wt% (weight percentage), more preferably at least 32wt%, and more preferably at least 37wt% of silicon oxide abrasive.

[0014] Preferably, the particle size of the abrasive is not particularly limited, and the particle size distribution of the abrasive is divided into two categories: unimodal and multimodal. Unimodal distribution means that there is only one peak on the particle size distribution curve, and there is only one mode particle size. Multimodal distribution means that there are two or more peaks on the particle size distribution curve, that is, there are two or more mode particle sizes. Preferably, the abrasive has only one peak. From the perspective of polishing efficiency and surface morphology control, it is preferably above 30nm, and more preferably above 50nm. In addition, from the perspective of the local pressure imposed by the abrasive on the surface of the polishing object, the particle size of the abrasive is preferably below 150nm, more preferably below 120nm, and further preferably below 110nm.

[0015] Specifically, the oxidant can be any oxidant suitable for one or more materials of the substrate to be polished by the polishing assembly. Preferably, the oxidant is selected from one or more of hydrogen peroxide, ketones, nitrates, ammonium nitrate salts, iodates, periodates, persulfates, and ozone. More preferably, the oxidant can be a mixture of one or more of hydrogen peroxide, periodates, and persulfates. Preferably, the oxidant contains at least 3wt% (weight percentage), more preferably at least 3.2wt%, and more preferably at least 3.5wt%.

[0016] Specifically, the surfactant can effectively reduce the large particle residues existing after surface polishing during the polishing process and improve the surface morphology. The surfactant can use one of the three types of anionic, cationic and nonionic surfactants. Preferably, anionic or nonionic surfactants can be used. More preferably, considering the foaming properties of the polishing process and the charge balance of the solvent, nonionic surfactants are more preferred; for example, nonionic surfactants such as polyvinyl alcohols (polyethylene glycol, polypropylene glycol, polybutylene glycol) and polyoxyalkylene copolymers (for example, diblock copolymers, triblock copolymers, random copolymers, and alternating copolymers). As the above-mentioned surfactant, it is preferred to include a surfactant having a polyvinyl alcohol structure.

[0017] Preferably, the molecular weight of the surfactant is at least higher than 5000, preferably higher than 7000, more preferably higher than 10000, more preferably higher than 15000. On the other hand, from the perspective of reducing surface particle residue, the molecular weight should be lower than 30000, more preferably lower than 25000, and most preferably lower than 20000. The molecular weight of the above-mentioned surfactant is the weight average molecular weight obtained by molecular gel chromatography. Preferably, the surfactant contains at least 0.1wt%, more preferably at least 0.15wt%, and more preferably at least 0.2wt%.

[0018] Specifically, the hydrogen bond regulator is to control the hydrogen bond rate formed between the silanol bond on the surface of the silica sol and the surfactant in the polishing liquid, so as to improve the bonding rate between the surface of the silicon carbide and the active group of the surfactant during the polishing process, thereby effectively reducing the number of large particles on the surface of the Si surface after polishing and cleaning, and improving the surface roughness. The hydrogen bond regulator used herein refers to a hydrogen bond regulating component present in any form in the composition, such as an additive that can reduce the bonding between the silica sol and the surfactant. Preferably, the hydrogen bond regulator can be an inorganic acid and alkali salt. The hydrogen bond inhibitor is preferably aminobenzamide, guanidine hydrochloride, aminoguanidine, phenylboric acid, urea and alkylboric acid and its derivatives, such as: p-aminobenzamide, o-aminobenzamide, p-dimethylaminobenzamide, 3.N-alkoxy o-aminobenzamide, guanidine hydrochloride, aminoguanidine, sodium phenylborate, potassium phenylborate, ammonium phenylborate, calcium phenylborate, aluminum phenylborate, urea, sodium alkyl borate, potassium alkyl borate, etc. One or more. More preferably, the hydrogen bond regulator is one or more of urea, guanidine hydrochloride and aminoguanidine. Preferably, the hydrogen bond modifier comprises at least 0.2 wt %, more preferably at least 0.3 wt %, and more preferably at least 0.35 wt %.

[0019] Specifically, the polishing accelerator is an inorganic salt that promotes the polishing process of silicon carbide. Preferably, the polishing accelerator can be one or more of nitrates, carbonates and sulfates, wherein the nitrates can be, for example, calcium nitrate, sodium nitrate, potassium nitrate, magnesium nitrate, aluminum nitrate, copper nitrate, etc.; the carbonates can be, for example, sodium carbonate, sodium bicarbonate, calcium carbonate, potassium carbonate, barium carbonate, magnesium carbonate, copper carbonate, ammonium carbonate, etc.; the sulfates can be, for example, sodium sulfate, magnesium sulfate, lithium sulfate, nickel sulfate, ammonium sulfate, zinc sulfate, etc. Preferably, the polishing accelerator is one of sodium nitrate, potassium nitrate, sodium sulfate and potassium sulfate. Preferably, the polishing accelerator contains at least 0.2wt%, more preferably contains at least 0.3wt%, and more preferably contains at least 0.5wt%.

[0020] Specifically, the defoamer may be a polysiloxane defoamer, containing at least 0.01wt%, more preferably at least 0.02wt%. Further, the polysiloxane defoamer includes but is not limited to BYK028 (BYK Chemical), DF689 (Guanzhi Chemical), AF9000 NE (Maitu), LY770 (Liqi Chemical), etc.

[0021] A method for preparing a CMP composition for obtaining a high-quality SiC single crystal substrate surface comprises the following steps: Step 1, weighing a surfactant, a polishing accelerator, a hydrogen bond regulator and a defoaming agent, adding them to a portion of water (the amount of water added here accounts for 1 / 3 to 2 / 3 of the total amount of water), mixing, and obtaining a polishing accelerator solution CS1; Step 2, weigh the oxidant, add the remaining amount of water, stir evenly, and obtain the oxidant solution CS2; Step 3, preparing the polishing abrasive into an abrasive slurry CS3 with a solid content of >25wt%; Step 4, adding the polishing accelerator CS1 solution prepared in the above step 1 to the abrasive slurry CS3 prepared in step 3, mixing, and preparing a mixed solution CS4; Step 5: Add the oxidant solution CS2 prepared in the above step 2 to the mixed solution CS4 prepared in step 4, mix well, and then filter through a 50-100 micron (preferably 50 micron) precision filter to finally obtain a CMP composition for obtaining a high-quality SiC single crystal substrate surface.

[0022] The present invention provides application of the above CMP composition in preparing a high-quality SiC single crystal substrate surface.

[0023] In view of the shortcomings of the prior art, the present invention has developed a CMP composition for obtaining a high-quality SiC single crystal substrate surface. The CMP composition adopts silicon oxide as an abrasive, introduces a hydrogen bond regulator, and adjusts the ratio of the surface groups of the silica sol and the bridging hydrogen bonds in the molecular structure of the surfactant to improve the bonding rate between the silicon carbide surface and the active groups of the surfactant during the polishing process, thereby effectively reducing the number of large particles remaining on the Si surface after polishing and cleaning, and achieving a surface roughness Ra (10um×10um) of the silicon surface below 0.07nm after polishing, and no large particles (>0.2um) on the surface after cleaning. At the same time, there is no need to process the silica sol raw material, and the composition has excellent long-term storage stability. In addition, the system will not experience particle agglomeration and sedimentation as the storage time increases, and excellent polishing surface quality can be obtained in the subsequent polishing process.

[0024] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention adopts silica sol raw materials as the main abrasive, and does not need to be grafted or modified on the surface of the silica sol. The silica sol's own structure is retained, and the dispersion stability during storage at room temperature can be effectively prolonged. At the same time, the prepared oxidant solution and polishing accelerator solution do not contain inorganic alkali, which can ensure the charge balance of the silica sol itself in the mixed solution, inhibit particle agglomeration, and prevent the abrasive particles in the polishing liquid from self-aggregating, causing precipitation and agglomeration, thereby enhancing the suspension stability of the polishing liquid.

[0025] 2. A hydrogen bond regulator is introduced into the formula of the present invention to adjust the ratio of bridging hydrogen bonds between the surface groups of the silica sol and the molecular structure of the surfactant, thereby improving the bonding rate between the silicon carbide surface and the active groups of the surfactant during the polishing process, thereby effectively reducing the number of large particles on the Si surface after polishing and cleaning, and improving the surface roughness.

[0026] 3. The polishing accelerator is introduced into the formula of the present invention, so that the polishing efficiency during the precision polishing of superhard silicon carbide materials is improved. At the same time, silica sol crystallization is not easy to occur during the efficient polishing process, and the machine is not corroded. The process has strong versatility and has good use effects in both single polishing process and double polishing cycle process.

[0027] 4. After polishing, the hydrogen bond regulator can improve the active sites of silanol bonds on the surface of silica sol particles, forming more hydrogen bond linking sites, so that the surfactant has a strong adsorption effect on the surface of silica sol, reducing the strong adsorption effect on the wafer surface. After polishing, an active layer of "surfactant-silica sol particles" can be formed on the SiC surface, which ultimately makes the residual particles after polishing easy to clean and remove, solving the problem of more large particles remaining after polishing and cleaning, and obtaining an ideal surface finish and lower surface roughness. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 The surface roughness test under an atomic force microscope of the polishing solution prepared in Example 2 before polishing (Ra=0.242); Figure 2 The surface roughness test under an atomic force microscope after polishing with the polishing solution prepared in Example 2 (Ra=0.063); Figure 3 The surface roughness test under atomic force microscope before polishing with the polishing solution used in Comparative Example 1 (Ra=0.215); Figure 4 The surface roughness test under atomic force microscope after polishing with the polishing solution used in Comparative Example 1 (Ra=0.105); Figure 5 This is a surface morphology image obtained by observing the polishing solution used in Comparative Example 1 under a white light interferometer after polishing; Figure 6 This is the surface morphology image obtained by observing under white light interferometer after polishing with the polishing solution used in Comparative Example 2. DETAILED DESCRIPTION

[0029] The following will be combined with the content of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0030] In the following examples, the raw materials used are all common commercial products that can be directly purchased in the art. The specific gravity of the polishing abrasive silica sol is above 1.05, and a common commercial product can be directly purchased. The molecular weight of the surfactant is at least higher than 5000 and lower than 30000. The defoamer is a polysiloxane defoamer, wherein BYK028 (BYK Chemical) is used in Examples 1 to 3 and Comparative Examples 8 and 9, DF689 (Guanzhi Chemical) is used in Examples 4 to 6 and Comparative Examples 10 and 11, AF9000 NE (Maitu) is used in Example 7 and Comparative Example 12, and LY770 (Lichi Chemical) is used in Example 8 and Comparative Example 13.

[0031] Example 1 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 37% of silica sol with a particle size of 100 nm as polishing abrasive, 3.5% of potassium periodate as an oxidant, 0.2% of polyethylene glycol as a surfactant, 0.35% of urea as a hydrogen bond regulator, 0.5% of sodium nitrate as a polishing accelerator, 0.02% of a polysiloxane defoaming agent, and the balance of water are selected. The pH of the CMP composition is 7.6.

[0032] The method for preparing the CMP composition for improving the surface quality of SiC single crystal substrates specifically comprises the following steps: Step 1, weighing a surfactant, a polishing accelerator, a hydrogen bond regulator and a defoaming agent, adding them to 1 / 3 to 2 / 3 of water, and mixing them to obtain a polishing accelerator solution CS1; Step 2, weigh the oxidant, add the remaining amount of water, stir evenly, and obtain the oxidant solution CS2; Step 3, preparing the polishing abrasive into an abrasive slurry CS3 with a solid content of >25wt%; Step 4, adding the polishing accelerator CS1 solution prepared in the above step 1 to the abrasive slurry CS3 prepared in step 3, mixing, and preparing a mixed solution CS4; Step 5: Add the oxidant solution CS2 prepared in the above step 2 to the mixed solution CS4 prepared in step 4, mix well, and then filter through a 50-micron precision filter to finally obtain a CMP composition for improving the surface quality of SiC single crystal substrates.

[0033] Example 2 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 40% silica sol with a particle size of 110 nm, 3% sodium periodate, 0.1% polyethylene glycol, 0.5% urea, 0.6% sodium nitrate, 0.02% polysiloxane defoaming agent, and the balance is water. The pH of the CMP composition is 7.9.

[0034] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0035] Figure 1 The surface roughness test of the polishing liquid prepared in Example 2 under an atomic force microscope before polishing is given; it can be seen from the figure that there are many residual particles on the surface of the SiC single crystal substrate before polishing, and the surface roughness is relatively large (Ra>0.2nm), and Ra is 0.242.

[0036] Figure 2 The surface roughness test under atomic force microscope after polishing with the polishing liquid prepared in Example 2 is given; after polishing the SiC single crystal substrate with the polishing liquid prepared in Example 2, there are no scratches, particles and corrosion marks on the surface under AFM, and Ra is less than 0.07nm (10×10um), and Ra is 0.063, indicating that the surface quality of the SiC surface is improved after polishing with the polishing composition prepared in Example 2.

[0037] Example 3 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 45% silica sol with a particle size of 80 nm, 5% potassium periodate, 0.5% polyethylene glycol, 0.3% urea, 1% sodium nitrate, 0.01% polysiloxane defoaming agent, and the balance is water. The pH of the CMP composition is 7.2.

[0038] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0039] Example 4 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 20% silica sol with a particle size of 80 nm, 3.5% potassium periodate, 0.5% polyethylene glycol, 0.4% urea, 0.6% sodium nitrate, 0.05% polysiloxane defoaming agent, and the balance is water. The pH of the CMP composition is 7.5.

[0040] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0041] Example 5 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 40% silica sol with a particle size of 120 nm, 4% potassium periodate, 0.5% polyethylene glycol, 0.35% urea, 0.6% sodium nitrate, 0.04% polysiloxane defoaming agent, and the balance is water. The pH of the CMP composition is 7.4.

[0042] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0043] Example 6 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 30% silica sol with a particle size of 90 nm, 3% potassium periodate, 0.5% polyethylene glycol, 0.35% urea, 0.2% sodium nitrate, 0.03% polysiloxane defoaming agent, and the balance is water. The pH of the CMP composition is 7.8.

[0044] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0045] Example 7 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 35% silica sol with a particle size of 110 nm, 3.5% potassium periodate, 0.1% polyethylene glycol, 0.3% urea, 1.0% sodium nitrate, 0.01% polysiloxane defoaming agent, and the balance is water. The pH of the CMP composition is 7.5.

[0046] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0047] Comparative Example 8 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 37% of silica sol with a particle size of 100 nm, 3.5% of potassium periodate, 0.2% of polyethylene glycol, 0.02% of polysiloxane defoaming agent, and the balance of water were selected. The pH of the CMP composition was 7.6.

[0048] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0049] Comparative Example 9 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: 37% silica sol with a particle size of 100 nm, 3.5% potassium periodate, 0.2% polyethylene glycol, 0.35% urea, 0.02% polysiloxane defoaming agent, and the balance is water. The pH of the CMP composition is 7.6.

[0050] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0051] Comparative Example 10 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: According to the corresponding mass fractions, 37% of silica sol with a particle size of 100 nm, 3.5% of potassium periodate, 0.2% of polyethylene glycol, 0.5% of sodium nitrate, 0.02% of polysiloxane defoaming agent are selected, and the balance is water. The pH of the CMP composition is 7.6.

[0052] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0053] Comparative Example 11 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: According to the corresponding mass fractions, 20% of silica sol with a particle size of 80 nm, 3.5% of potassium periodate, 0.5% of polyethylene glycol, 0.05% of polysiloxane defoaming agent are selected, and the balance is water. The pH of the CMP composition is 7.5.

[0054] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0055] Comparative Example 12 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: According to the corresponding mass fractions, 20% silica sol with a particle size of 80 nm, 3.5% potassium periodate, 0.5% polyethylene glycol, 0.4% urea, 0.05% polysiloxane defoaming agent are selected, and the balance is water. The pH of the CMP composition is 7.5.

[0056] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0057] Comparative Example 13 A CMP composition for improving the surface quality of a SiC single crystal substrate, which is made of the following raw materials in percentage by weight: According to the corresponding mass fractions, 20% of silica sol with a particle size of 80 nm, 3.5% of potassium periodate, 0.5% of polyethylene glycol, 0.6% of sodium nitrate, 0.05% of polysiloxane defoaming agent are selected, and the balance is water. The pH of the CMP composition is 7.5.

[0058] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates is based on the steps of Example 1.

[0059] Comparative Example 1 The mainstream silicon carbide CMP polishing liquid of Company A on the market was selected and mixed according to the proportions recommended by the seller to obtain Comparative Example 1.

[0060] Comparative Example 2 The mainstream silicon carbide CMP polishing liquid of Company B on the market was selected and mixed according to the proportions recommended by the seller to obtain Comparative Example 2.

[0061] Figure 3 The surface roughness test under atomic force microscope before polishing of the polishing liquid used in comparative example 1 is given; it can be seen from the figure that: before polishing, there are many residual particles on the surface of the SiC single crystal substrate, and the surface roughness is relatively large (Ra>0.2nm), Ra is 0.215.

[0062] Figure 4 The surface roughness test under atomic force microscope after polishing with the polishing liquid used in comparative example 1 is given; it can be seen from the figure that the surface Ra decreases after polishing with the currently commercially available SiC polishing liquid, but Ra is still greater than 0.1nm, Ra is 0.105, and the surface particles are not completely removed, which cannot meet the use requirements of high-power and high-precision devices in the actual production process.

[0063] Figure 5 The surface morphology image obtained by observing under a white light interferometer after polishing with the polishing liquid used in Comparative Example 1 is given; it can be seen from the figure that after polishing with the polishing liquid of Comparative Example 1, a small amount of particles still exist on the surface of the wafer.

[0064] Figure 6 The surface morphology image obtained by observing under a white light interferometer after polishing with the polishing liquid used in Comparative Example 2 is given; it can be seen from the figure that after polishing with the polishing liquid of Comparative Example 2, a small amount of particles still exist on the surface of the wafer.

[0065] Polishing test The prepared silicon carbide fine polishing CMP polishing liquid, all embodiments were compared and tested according to the following conditions and polishing parameters: Use a Chuangji single-sided polishing machine, the polishing pad is a black damping cloth pad, the polishing sheet is a 6-inch silicon carbide rough polishing sheet, and the pressure is 200~250g / cm 2 ; The relevant data testing methods are visual inspection with strong light, precision balance weight measurement, wafer surface particle size inspection system, microscope and atomic force microscope.

[0066] The polishing effects of the polishing solutions obtained in Examples 1 to 7 of the present invention, Comparative Examples 8-13, and Comparative Example 1 and Comparative Example 2 on silicon carbide wafers are shown in Table 1 below.

[0067] Table 1 Polishing performance of CMP polishing liquids obtained from different examples From the polishing results in Table 1 above, it can be seen that after adding hydrogen bond regulator to the formula system, the adsorption of silica sol particles on the surface of the substrate can be weakened. In the competitive adsorption process, it is shown that the adsorption rate of the active agent on the wafer surface increases, which is beneficial to the cleaning of particles on the surface of the material after polishing, and has a significant improvement effect on the particle residue on the surface after polishing. The surface Ra is less than 0.07nm, and there are no large particles on the surface after cleaning.

[0068] Polishing accelerator can catalyze and accelerate the chemical corrosion reaction process that occurs during the polishing process. Polishing accelerator can increase the ion strength in the chemical liquid during the CMP process and has the function of accelerating the dissolution of the oxide layer on the surface of the wafer. From the above results, the polishing efficiency is significantly improved after the addition of polishing accelerator.

[0069] From the polishing effect, in the embodiment formula, the addition of hydrogen bond regulator can effectively improve the number of large particles remaining on the silicon carbide surface after polishing, and at the same time improve the surface roughness. The addition of polishing accelerator has a significant effect on improving the polishing process rate.

Claims

1. A CMP composition for obtaining a high-quality SiC single crystal substrate surface, characterized in that: The invention is prepared from the following raw materials in weight percentage: 20-50 wt% of polishing abrasive, 3-5 wt% of oxidant, 0.1-0.5 wt% of surfactant, 0.2-0.5 wt% of hydrogen bond regulator, 0.2-1 wt% of polishing accelerator, 0.01-0.05 wt% of defoamer, and the balance is water; The CMP composition is neutral, with a pH between 7-8.

2. The CMP composition for obtaining a high-quality SiC single crystal substrate surface according to claim 1, characterized in that: The abrasive is silicon oxide abrasive grains, and the specific gravity of the abrasive is greater than 1.

05.

3. The CMP composition for obtaining a high-quality SiC single crystal substrate surface according to claim 1, characterized in that: The oxidant is selected from one or more of hydrogen peroxide, ketones, nitrates, ammonium nitrates, iodates, periodates, persulfates, and ozone.

4. The CMP composition for obtaining a high-quality SiC single crystal substrate surface according to claim 1, characterized in that: The surfactant is one of anionic, cationic and nonionic surfactants, and the nonionic surfactant includes polyvinyl alcohol and polyoxyalkylene copolymer nonionic surfactants; the molecular weight of the surfactant is at least higher than 5000 and lower than 30000.

5. The CMP composition for obtaining a high-quality SiC single crystal substrate surface according to claim 1, characterized in that: The hydrogen bond regulator is one or more of p-aminobenzamide, o-aminobenzamide, p-dimethylaminobenzamide, 3.N-alkoxy o-aminobenzamide, guanidine hydrochloride, aminoguanidine, sodium phenylborate, potassium phenylborate, ammonium phenylborate, calcium phenylborate, aluminum phenylborate, urea, sodium alkyl borate, and potassium alkyl borate.

6. The CMP composition for obtaining a high-quality SiC single crystal substrate surface according to claim 1, characterized in that: The polishing accelerator is one or more of nitrates, carbonates and sulfates.

7. The CMP composition for obtaining a high-quality SiC single crystal substrate surface according to claim 1, characterized in that: The defoaming agent is a polysiloxane defoaming agent.

8. The method for preparing a CMP composition for obtaining a high-quality SiC single crystal substrate surface according to any one of claims 1 to 7, characterized in that: The steps include: Step 1, weighing a surfactant, a polishing accelerator, a hydrogen bond regulator and a defoaming agent, adding them to part of the water, and mixing them to obtain a polishing accelerator solution CS1; Step 2, weigh the oxidant, add the remaining amount of water, stir evenly, and obtain the oxidant solution CS2; Step 3, preparing the polishing abrasive into an abrasive slurry CS3 with a solid content of >25wt%; Step 4, adding the polishing accelerator CS1 solution prepared in the above step 1 to the abrasive slurry CS3 prepared in step 3, mixing, and preparing a mixed solution CS4; Step 5: Add the oxidant solution CS2 prepared in the above step 2 to the mixed solution CS4 prepared in step 4, mix well, and then filter through a 50-100 micron precision filter to obtain.

9. Use of the CMP composition according to any one of claims 1 to 7 in preparing a high-quality SiC single crystal substrate surface.

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