A cmp composition for obtaining a high-quality si c single crystal substrate surface and a preparation method thereof

Abstract

The application relates to a CMP composition for obtaining a high-quality SiC single crystal substrate surface, which is prepared from the following raw materials in percentage by weight: 20-50 wt% of polishing abrasive, 3-5 wt% of oxidizing agent, 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 defoaming agent, and the balance of water; the CMP composition is neutral. The CMP composition uses silicon oxide as the abrasive, introduces the hydrogen bond regulator, the polishing accelerator and the oxidizing agent, improves the polishing rate of the silicon carbide wafer CMP, realizes that the surface roughness Ra of the silicon surface after cleaning can reach below 0.07 nm, the surface after cleaning is free of large particles (>0.2 um), meanwhile, the silicon oxide raw material does not need to be treated, has excellent long-term storage stability, and the system does not have the phenomena of particle agglomeration and sedimentation with the prolongation of the storage time, and excellent polishing surface quality can be obtained in the subsequent polishing process.

Description

Technical Field

[0001] This invention belongs to the field of silicon carbide substrate CMP polishing technology, specifically relating to a CMP composition for obtaining a high-quality SiC single crystal substrate surface and its preparation method. Background Technology

[0002] Chemical mechanical polishing (CMP) is a common process for achieving global planarization in integrated circuit manufacturing and other fields. This process primarily aims to obtain a smooth surface that is both flat and free of scratches and impurities. It achieves surface material removal and planarization through the synergistic effect of chemical etching and mechanical wear.

[0003] Silicon carbide (SiC), as the most representative third-generation wide-bandgap semiconductor material, possesses characteristics such as wide bandgap, high critical breakdown electric field, high thermal conductivity, high carrier saturation migration velocity, low relative permittivity, high temperature resistance, and radiation resistance. It can meet the demands of high-frequency, high-power, high-temperature, and radiation-resistant integrated electronic devices, and has broad application prospects in aerospace, new energy vehicles, 5G base stations, and other scientific and technological fields, making it irreplaceable by traditional semiconductors. Therefore, the surface processing technology of SiC substrate materials has a significant impact on the fabrication quality of subsequent epitaxial layers and power devices. Furthermore, due to the high integration of electronic devices and the trend of feature size miniaturization, 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, poor surface roughness after fine polishing, with problems such as particles, pits, and cracks, will affect subsequent epitaxial growth or back-end development processes, and even seriously affect the performance and reliability of electronic devices. Therefore, in order to improve the yield of silicon carbide device back-end processing, the industry has become increasingly strict in the evaluation standards for surface quality after silicon carbide fine polishing. Ordinary silica sol formulation systems have a lot of particle residue. After fine polishing, the surface roughness Ra of SiC substrate should be less than 0.2nm, and the lower the better. At the same time, there are strict requirements on the number and length of large particle residues and scratches on the surface.

[0004] However, due to the high hardness and good chemical stability of SiC single crystal materials, and the fact that the compressive strength of SiC single crystals is higher than their flexural strength, the material exhibits significant hardness and brittleness, making the fine polishing of SiC single crystal substrates extremely difficult. Currently, conventional silicon carbide fine polishing solution formulations optimize the system environment by introducing acids and alkalis, which is not conducive to long-term storage and results in significant particle residue and agglomeration, causing micro-scratches and orange peel-like defects on the silicon carbide wafer surface during polishing.

[0005] Many scholars have conducted research on the polishing of silicon carbide crystals. Chinese patent CN117987015A discloses a CMP polishing slurry for fine polishing of single-crystal silicon carbide substrates and its preparation method. The key point of this patent is to achieve a high removal rate on SiC single-crystal substrates by simultaneously introducing chelating agents, oxidants, and dispersants through composite abrasives. However, this patent has drawbacks. Although the polishing composition has a high removal rate, the surface roughness of the Si surface after polishing is still relatively high (>0.2nm), which cannot meet the requirements of subsequent epitaxial processes in actual industrial production. Furthermore, the mixed abrasives used in this patent contain high-hardness abrasives, which can cause micro-scratches on the silicon surface during polishing and remain in the surface damage layer, making them difficult to remove. Moreover, this patent does not provide data on large particle residues on the silicon surface after the fine polishing process. Chinese patent CN117866536A discloses a method for preparing a CMP polishing slurry for silicon carbide substrates. This patent solves the problems of scratches easily caused during SiC polishing and the weak suspension and polishing stability of the slurry by using rare earth oxide cerium oxide abrasives, a proprietary formula, and environmentally friendly raw materials. However, this patent uses potassium permanganate oxidant for polishing under acidic conditions, which adversely affects the stability of the polishing slurry system, easily leading to soft agglomeration and gelation. It is not suitable for fine polishing of silicon carbide single-crystal substrates. Furthermore, the cerium oxide abrasive used in this patent is difficult to clean in subsequent cleaning processes, resulting in large particle residues. The patent also does not provide final Ra data or particle residue data. Chinese patent CN201010591103.1 discloses a method for preparing and using a polishing slurry for silicon carbide. This patent uses silicon oxide as an abrasive for fine polishing of silicon carbide surfaces. Because silicon oxide has a lower hardness than silicon carbide, the silicon oxide polishing slurry can effectively improve surface scratches caused during rough polishing and reduce surface roughness. The surface roughness Ra after polishing reaches 0.07 nm. However, because the polishing slurry preparation process provided in this patent requires the addition of an external alkali as a pH adjuster, it affects the stability of the silica sol itself, easily causing problems such as poor solution stability.

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

[0007] The purpose of this invention is to overcome the defects of the prior art and provide a CMP composition for obtaining high-quality SiC single crystal substrate surfaces. It uses silicon oxide as the abrasive and introduces hydrogen bond modifiers, polishing promoters and oxidants to improve the CMP polishing rate of silicon carbide wafers. The resulting silicon surface roughness Ra can reach below 0.07 nm after cleaning, and the surface is free of large particles (>0.2 μm). At the same time, no treatment is required for the abrasive used for polishing. It has excellent long-term storage stability, and the system does not exhibit particle agglomeration or sedimentation as the storage time increases. It can obtain excellent polished surface quality in subsequent polishing processes.

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

[0009] To achieve the above objectives, the present invention adopts the following technical solution:

[0010] A CMP composition for obtaining a high-quality SiC single-crystal substrate surface, comprising the following raw materials in weight percentages:

[0011] Polishing abrasive 20-50 wt%.

[0012] Oxidizing agent 3-5 wt%,

[0013] Surfactant 0.1-0.5 wt%.

[0014] Hydrogen bond modifier 0.2-0.5 wt%.

[0015] Polishing accelerator 0.2-1 wt%,

[0016] Defoamer 0.01-0.05wt%,

[0017] The remainder is water;

[0018] The CMP composition is neutral (pH between 7 and 8).

[0019] The abrasive slurry used in this invention is alkaline. By adding a weakly acidic oxidant according to the formulation ratio of this application, the final polishing liquid can be made neutral.

[0020] Specifically, the abrasive can be silicon oxide (silicon dioxide) abrasive grains. The specific gravity (density) of the abrasive is preferably 1.05 or higher, more preferably 1.1 or higher, and even more preferably 1.2 or higher. 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.

[0021] Preferably, the abrasive slurry has an alkaline pH. The pH range of the abrasive slurry is between 7 and 12, more preferably between 8 and 10, and most preferably between 9 and 10.

[0022] Preferably, the shape (appearance) of the abrasive grains can be spherical or non-spherical. The abrasive grains used are mostly peanut-shaped or cocoon-shaped. The abrasive grains contain at least 25 wt% (by weight), more preferably at least 32 wt%, and even more preferably at least 37 wt% of silica abrasive.

[0023] Preferably, the particle size of the abrasive grains is not particularly limited, and the particle size distribution of the abrasive grains is divided into two categories: unimodal and multimodal. A unimodal distribution is characterized by a single peak on the particle size distribution curve, with only one mode particle size. A multimodal distribution, on the other hand, has two or more peaks on the particle size distribution curve, meaning there are two or more mode particle sizes. Preferably, the abrasive grains have only one peak. From the perspective of polishing efficiency and surface morphology control, a particle size of 30 nm or more is preferred, and 50 nm or more is more preferred. Furthermore, from the viewpoint of the localized pressure exerted by the abrasive grains on the surface of the object being polished, the particle size of the abrasive grains is preferably 150 nm or less, more preferably 120 nm or less, and even more preferably 110 nm or less.

[0024] Specifically, the oxidant can be an oxidant of one or more materials suitable for polishing a substrate using a polishing assembly. Preferably, the oxidant is selected from one or more of hydrogen peroxide, ketones, nitrates, ammonium nitrates, iodates, periodates, persulfates, and ozone. More preferably, the oxidant can be one or more mixtures of hydrogen peroxide, periodates, and persulfates. Preferably, the oxidant contains at least 3 wt% (weight percentage), more preferably at least 3.2 wt%, and even more preferably at least 3.5 wt%.

[0025] Specifically, surfactants can effectively reduce large particle residues after surface polishing and improve surface morphology. Surfactants can be one of three types: anionic, cationic, and nonionic surfactants. Preferably, anionic or nonionic surfactants can be used. More preferably, considering both the foaming properties and solvent charge balance during the polishing process, nonionic surfactants are preferred; for example, polyvinyl alcohols (polyethylene glycol, polypropylene glycol, polybutanediol) and polyoxyalkylene copolymers (e.g., diblock copolymers, triblock copolymers, random copolymers, cross-linked copolymers), etc., are nonionic surfactants. Preferably, the surfactant includes a polyvinyl alcohol structure.

[0026] Preferably, the surfactant has a molecular weight of at least 5000, more preferably 7000, more preferably 10000, and even more preferably 15000. On the other hand, considering the reduction of surface particle residue, the molecular weight should be less than 30000, more preferably less than 25000, and most preferably less than 20000. The molecular weight of the surfactant is the weight-average molecular weight obtained by molecular gel chromatography. Preferably, the surfactant contains at least 0.1 wt%, more preferably at least 0.15 wt%, and even more preferably at least 0.2 wt%.

[0027] Specifically, the hydrogen bond modifier improves the binding rate between the silicon carbide surface and the surfactant during polishing by controlling the hydrogen bond rate between the silanol bonds on the surface of the silica sol in the polishing slurry. This effectively reduces the number of large particles on the Si surface after polishing and cleaning, thus improving surface roughness. The hydrogen bond modifier used here refers to a hydrogen bond regulating component present in the composition in any form, such as an additive capable of reducing the binding between the silica sol and the surfactant. Preferably, the hydrogen bond modifier can be an inorganic acid, base, or salt. The hydrogen bond inhibitor is preferably aminobenzamide, guanidine hydrochloride, aminoguanidine, phenylboronic acid, urea, and alkylboronic acid and their 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 alkylborate, potassium alkylborate, etc. More preferably, the hydrogen bond modifier is one or more of urea, guanidine hydrochloride, and aminoguanidine. Preferably, the hydrogen bond modifier contains at least 0.2 wt%, more preferably at least 0.3 wt%, and even more preferably at least 0.35 wt%.

[0028] 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.; and 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 0.2 wt%, more preferably at least 0.3 wt%, and more preferably at least 0.5 wt%.

[0029] Specifically, the defoamer can be a polysiloxane defoamer, containing at least 0.01 wt%, more preferably at least 0.02 wt%. Further, the polysiloxane defoamer includes, but is not limited to, BYK028 (BYK Chemical), DF689 (Guanzhi Chemical), AF9000 NE (Momentive), LY770 (Liqi Chemical), etc.

[0030] A method for preparing a CMP composition for obtaining a high-quality SiC single-crystal substrate surface, comprising the following steps:

[0031] Step 1: Weigh out the surfactant, polishing accelerator, hydrogen bond modifier and defoamer, add them to some water (the amount of water added here accounts for 1 / 3 to 2 / 3 of the total water volume), mix well, and obtain polishing accelerator solution CS1;

[0032] Step 2: Weigh the oxidant, add the remaining water, stir well to obtain the oxidant solution CS2;

[0033] Step 3: Prepare the polishing abrasive into an abrasive slurry CS3 with a solid content >25wt%;

[0034] Step 4: Add the polishing accelerator CS1 solution prepared in Step 1 to the abrasive slurry CS3 prepared in Step 3, mix well, and prepare a mixed solution CS4.

[0035] Step 5: Add the oxidant solution CS2 prepared in Step 2 to the mixed solution CS4 prepared in Step 4, mix well, and then filter through a 50-100 micrometer (preferably 50 micrometer) precision filter to finally obtain the CMP composition for obtaining a high-quality SiC single crystal substrate surface.

[0036] This invention provides the application of the above-described CMP composition in the preparation of high-quality SiC single-crystal substrate surfaces.

[0037] To address the shortcomings of existing technologies, this invention develops a CMP composition for obtaining high-quality SiC single-crystal substrate surfaces. It uses silicon oxide as the abrasive and introduces a hydrogen bond modifier. By adjusting the ratio of bridging hydrogen bonds in the silica sol surface groups and surfactant molecules, the binding rate between the silicon carbide surface and the surfactant active groups during polishing is improved. This effectively reduces the number of large particles remaining on the Si surface after polishing and cleaning, achieving a surface roughness Ra (10µm × 10µm) of less than 0.07nm after polishing. After cleaning, the surface is free of large particles (>0.2µm). Furthermore, no treatment of the silica sol raw material is required, exhibiting excellent long-term storage stability. The system does not show particle agglomeration or sedimentation over extended storage time, resulting in excellent polished surface quality in subsequent polishing processes.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] 1. This invention uses silica sol as the main abrasive, eliminating the need for grafting or modification on the silica sol surface. It preserves the silica sol's own structure, effectively extending its dispersion stability during room temperature storage. Furthermore, the prepared oxidant and polishing accelerator solutions do not contain inorganic alkali, ensuring the charge balance of the silica sol in the mixed solution, inhibiting particle agglomeration, preventing self-agglomeration of abrasive particles in the polishing fluid, and thus enhancing the suspension stability of the polishing fluid.

[0040] 2. The formulation of this invention introduces a hydrogen bond modifier. By adjusting the ratio of bridging hydrogen bonds in the surface groups of silica sol and the molecular structure of surfactants, the binding rate between the silicon carbide surface and the active groups of surfactants during the polishing process is improved, thereby effectively reducing the number of large particles on the Si surface after polishing and cleaning, and improving the surface roughness.

[0041] 3. The formula of this invention introduces a polishing accelerator, which improves the polishing efficiency during the precision polishing of ultra-hard silicon carbide materials. At the same time, it is not easy for silica sol crystallization to occur during the high-efficiency polishing process, does not corrode the machine, has strong process versatility, and has good performance in both single polishing and double polishing cycle processes.

[0042] 4. After polishing, the hydrogen bond modifier of this invention can improve the active sites of silanol bonds on the surface of silica sol particles, forming more hydrogen bond linkage sites. This results in a stronger adsorption effect of the surfactant on the silica sol surface, 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, making it easy to clean and remove the particle residue after polishing. This solves the problem of many large particles remaining after polishing and cleaning, achieving ideal surface smoothness and low surface roughness. Attached Figure Description

[0043] Figure 1 The surface roughness of the polishing slurry prepared in Example 2 before polishing is measured by an atomic force microscope (Ra=0.242).

[0044] Figure 2 The surface roughness test under an atomic force microscope after polishing with the polishing slurry prepared in Example 2 (Ra=0.063).

[0045] Figure 3 Surface roughness test under an atomic force microscope before polishing with the polishing slurry used in Comparative Example 1 (Ra=0.215).

[0046] Figure 4 Surface roughness test under an atomic force microscope after polishing with the polishing slurry used in Comparative Example 1 (Ra=0.105).

[0047] Figure 5 The surface morphology image obtained by observing under a white light interferometer after polishing with the polishing slurry used in Comparative Example 1;

[0048] Figure 6 The surface morphology image obtained by observing under a white light interferometer after polishing with the polishing slurry used in Comparative Example 2. Detailed Implementation

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the content of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0050] In the following examples, all raw materials used are commercially available products that can be directly purchased in the art. The polishing abrasive silica sol has a specific gravity of 1.05 or higher and can be a commercially available product. The surfactant has a molecular weight of at least 5000 and less than 30000. The defoamer is a polysiloxane defoamer, wherein BYK028 (BYK Chemical) was used in Examples 1 to 3 and Comparative Examples 8 and 9, DF689 (Guanzhi Chemical) was used in Examples 4 to 6 and Comparative Examples 10 and 11, AF9000 NE (Momentive) was used in Examples 7 and Comparative Example 12, and LY770 (Liqi Chemical) was used in Examples 8 and Comparative Example 13.

[0051] Example 1

[0052] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0053] The composition comprises 37% silica sol polishing abrasive with a particle size of 100 nm, 3.5% potassium periodate oxidant, 0.2% polyethylene glycol surfactant, 0.35% urea hydrogen bond modifier, 0.5% sodium nitrate polishing accelerator, 0.02% polysiloxane defoamer, and the balance being water. The pH of the CMP composition is 7.6.

[0054] The preparation method of the above-mentioned CMP composition for improving the surface quality of SiC single crystal substrates specifically includes the following steps:

[0055] Step 1: Weigh out the surfactant, polishing accelerator, hydrogen bond modifier and defoamer, add them to 1 / 3 to 2 / 3 of water, mix well to obtain polishing accelerator solution CS1;

[0056] Step 2: Weigh the oxidant, add the remaining water, stir well to obtain the oxidant solution CS2;

[0057] Step 3: Prepare the polishing abrasive into an abrasive slurry CS3 with a solid content >25wt%;

[0058] Step 4: Add the polishing accelerator CS1 solution prepared in Step 1 to the abrasive slurry CS3 prepared in Step 3, mix well, and prepare a mixed solution CS4.

[0059] Step 5: Add the oxidant solution CS2 prepared in 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 the CMP composition for improving the surface quality of SiC single crystal substrates.

[0060] Example 2

[0061] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0062] The composition consists of 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 defoamer, and the balance being water. The pH of the CMP composition is 7.9.

[0063] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0064] Figure 1 The surface roughness test of the polishing slurry prepared in Example 2 before polishing is given under an atomic force microscope. As can be seen from the figure, there are many particles remaining on the surface of the SiC single crystal substrate before polishing, and the surface roughness is large (Ra>0.2nm), with Ra being 0.242.

[0065] Figure 2 The surface roughness test under an atomic force microscope after polishing with the polishing slurry prepared in Example 2 is given. After polishing the SiC single crystal substrate with the polishing slurry prepared in Example 2, no scratches, particles and corrosion marks were observed on the surface under AFM, and Ra < 0.07 nm (10 × 10 μm), and Ra was 0.063, indicating that the polishing composition prepared in Example 2 improved the surface quality of SiC after polishing.

[0066] Example 3

[0067] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0068] The composition consists of 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 defoamer, and the balance being water. The pH of the CMP composition is 7.2.

[0069] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0070] Example 4

[0071] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0072] The composition consists of 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 defoamer, and the balance being water. The pH of the CMP composition is 7.5.

[0073] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0074] Example 5

[0075] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0076] The composition consists of 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 defoamer, and the balance being water. The pH of the CMP composition is 7.4.

[0077] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0078] Example 6

[0079] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0080] The composition consists of 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 defoamer, and the balance being water. The pH of the CMP composition is 7.8.

[0081] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0082] Example 7

[0083] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0084] The composition consists of 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 defoamer, and the balance being water. The pH of the CMP composition is 7.5.

[0085] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0086] Comparative Example 8

[0087] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0088] The composition consists of 37% silica sol with a particle size of 100 nm, 3.5% potassium periodate, 0.2% polyethylene glycol, 0.02% polysiloxane defoamer, and the balance being water. The pH of the CMP composition is 7.6.

[0089] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0090] Comparative Example 9

[0091] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0092] The composition consists of 37% silica sol with a particle size of 100 nm, 3.5% potassium periodate, 0.2% polyethylene glycol, 0.35% urea, 0.02% polysiloxane defoamer, and the balance being water. The pH of the CMP composition is 7.6.

[0093] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0094] Comparative Example 10

[0095] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0096] The composition comprises, by weight, 37% silica sol with a particle size of 100 nm, 3.5% potassium periodate, 0.2% polyethylene glycol, 0.5% sodium nitrate, 0.02% polysiloxane defoamer, and the balance being water. The pH of the CMP composition is 7.6.

[0097] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0098] Comparative Example 11

[0099] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0100] The composition comprises, by weight, 20% silica sol with a particle size of 80 nm, 3.5% potassium periodate, 0.5% polyethylene glycol, 0.05% polysiloxane defoamer, and the remainder being water. The pH of the CMP composition is 7.5.

[0101] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0102] Comparative Example 12

[0103] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0104] The composition comprises, by weight, 20% silica sol with a particle size of 80 nm, 3.5% potassium periodate, 0.5% polyethylene glycol, 0.4% urea, 0.05% polysiloxane defoamer, and the balance being water. The pH of the CMP composition is 7.5.

[0105] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0106] Comparative Example 13

[0107] A CMP composition for improving the surface quality of SiC single crystal substrates, which is made from the following raw materials in weight percentages:

[0108] The composition comprises, by weight, 20% silica sol with a particle size of 80 nm, 3.5% potassium periodate, 0.5% polyethylene glycol, 0.6% sodium nitrate, 0.05% polysiloxane defoamer, and the balance being water. The pH of the CMP composition is 7.5.

[0109] The preparation method of the CMP composition for improving the surface quality of SiC single crystal substrates described above is the same as the steps in Example 1 above.

[0110] Comparative Example 1

[0111] We selected the mainstream silicon carbide CMP polishing slurry from Company A, and mixed it according to the seller's recommended ratio to obtain Comparative Example 1.

[0112] Comparative Example 2

[0113] We selected the mainstream silicon carbide CMP polishing slurry from Company B, and mixed it according to the seller's recommended ratio to obtain Comparative Example 2.

[0114] Figure 3The surface roughness test under an atomic force microscope before polishing with the polishing slurry used in Comparative Example 1 is given. It can be seen from the figure that there are many particles remaining on the surface of the SiC single crystal substrate before polishing, and the surface roughness is large (Ra>0.2nm), with Ra being 0.215.

[0115] Figure 4 The surface roughness test under an atomic force microscope after polishing with the polishing slurry used in Comparative Example 1 is given. It can be seen from the figure that the surface Ra decreased after polishing with the commercially available SiC polishing slurry, but Ra is still >0.1nm and Ra is 0.105. Moreover, the surface particles were not completely removed, which cannot meet the requirements of high-power and high-precision devices in actual production.

[0116] Figure 5 The surface morphology of the wafer after polishing with the polishing slurry used in Comparative Example 1 is shown in the white light interferometer. It can be seen from the figure that a small number of particles still exist on the wafer surface after polishing with the polishing slurry used in Comparative Example 1.

[0117] Figure 6 The surface morphology images observed under a white light interferometer after polishing with the polishing slurry used in Comparative Example 2 are shown. It can be seen from the images that a small number of particles still exist on the wafer surface after polishing with the polishing slurry used in Comparative Example 2.

[0118] Polishing test

[0119] The prepared silicon carbide CMP polishing slurry was compared and tested in all examples under the following conditions and polishing parameters:

[0120] Using a Chuangji single-sided polishing machine, the polishing pad is a black damping cloth pad, and the polishing disc is a 6-inch silicon carbide coarse polishing disc. The pressure is 200~250g / cm. 2 The relevant data testing methods include visual inspection under strong light, weighing with a precision balance, wafer surface particle size inspection system, microscope, and atomic force microscope.

[0121] The polishing effects of the polishing solutions obtained in Examples 1 to 7, Comparative Examples 8 to 13, and Comparative Examples 1 and 2 on silicon carbide wafers are shown in Table 1 below.

[0122] Table 1 Polishing performance of CMP polishing slurries obtained from different examples

[0123]

[0124] As can be seen from the polishing results in Table 1 above, the addition of hydrogen bond modifier to the formulation system can weaken the adsorption of silica sol particles on the substrate surface. During the competitive adsorption process, it is shown that the adsorption rate of the activator on the wafer surface increases, which is beneficial to the cleaning of particles on the material surface after polishing. It has a significant effect on improving the particle residue on the polished surface, with surface Ra < 0.07 nm and no large particles on the surface after cleaning.

[0125] Polishing accelerators can catalyze and accelerate the chemical corrosion that occurs during the polishing process. In the CMP process, polishing accelerators can increase the ionic strength in the chemical solution and accelerate the dissolution of the oxide layer on the wafer surface. From the above results, it can be seen that the polishing efficiency is significantly improved after the addition of polishing accelerators.

[0126] From the polishing effect, the addition of a hydrogen bond modifier in the formulation of the example effectively increased the number of large particles remaining on the silicon carbide surface after polishing, and simultaneously improved the surface roughness. The addition of a polishing accelerator significantly increased the polishing process rate.

Claims

1. A CMP composition for obtaining a high-quality SiC single-crystal substrate surface, characterized in that, It is made from the following raw materials in weight percentages: 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 0.01-0.05 wt%, balance being water; The CMP composition is neutral, with a pH between 7 and 8; The surfactant is one of anionic, cationic, and nonionic surfactants, wherein 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 20000; The hydrogen bond modifier is one or more of the following: 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 alkylborate, and potassium alkylborate.

2. The CMP composition for obtaining a high-quality SiC single-crystal substrate surface as described in claim 1, characterized in that, The abrasive is silicon oxide abrasive grains, and the specific gravity of the abrasive is 1.05 or higher.

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

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

5. The CMP composition for obtaining a high-quality SiC single-crystal substrate surface as described in claim 1, characterized in that, The defoamer is a polysiloxane-based defoamer.

6. A method for preparing the CMP composition for obtaining a high-quality SiC single-crystal substrate surface as described in any one of claims 1 to 5, characterized in that, Includes the following steps: Step 1: Weigh out the surfactant, polishing accelerator, hydrogen bond modifier and defoamer, add them to some water, mix well, and obtain polishing accelerator solution CS1; Step 2: Weigh the oxidant, add the remaining water, stir well to obtain the oxidant solution CS2; Step 3: Prepare the polishing abrasive into an abrasive slurry CS3 with a solid content >25wt%; Step 4: Add the polishing accelerator CS1 solution prepared in Step 1 to the abrasive slurry CS3 prepared in Step 3, mix well, and prepare a mixed solution CS4. Step 5: Add the oxidant solution CS2 prepared in Step 2 to the mixed solution CS4 prepared in Step 4, mix well, and then filter through a 50-100 micrometer precision filter to obtain the final product.

7. The use of the CMP composition according to any one of claims 1 to 5 in the preparation of a high-quality SiC single crystal substrate surface.

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