High-purity SiC biscuit and forming method thereof

Abstract

The invention belongs to the technical field of silicon carbide ceramic material processing, and particularly relates to a high-purity SiC biscuit and a forming method thereof. The method comprises the following steps that S1, primary ball milling, airing and sieving are conducted on SiC crude sand, and SiC sand is obtained; s2, slurry is prepared, secondary ball milling, vacuum defoaming, initiation, grouting, demolding and drying are conducted, and the high-purity SiC biscuit is obtained. According to the forming method of the high-purity SiC biscuit, by controlling the surface appearance of the crude sand and the cleanliness of an environmental tool and combining with a traditional gel casting means, forming of the high-purity and high-solid-phase-content SiC biscuit is achieved, operation is easy, the period is short, a leading foundation is provided for subsequent sintering and vapor deposition, and the method is suitable for industrial production. And the preparation method has important significance on preparation of high-purity SiC ceramic precision parts for semiconductor equipment. The forming method disclosed by the invention is environment-friendly and is easy to popularize and apply in the field of silicon carbide ceramic material processing.

Description

Technical Field

[0001] The present invention belongs to the technical field of silicon carbide ceramic material processing, and specifically relates to the preparation of high-purity SiC ceramics, gel injection molding and precision components for semiconductor equipment, and more particularly to a high-purity SiC green blank and a molding method thereof. Background Art

[0002] As key components in semiconductor equipment, SiC precision ceramic components come into direct or indirect contact with wafers. Their research, development, and manufacturing directly impact the development of my country's semiconductor equipment manufacturing industry and the entire semiconductor industry chain. To prevent ionic contamination of wafers, SiC components are often required to have an impurity content below 10 ppm, meaning a primary component purity of at least 99.999% (5N).

[0003] Since metal elements or impurities such as B and P are inevitably introduced into pressureless sintering additives, high-purity SiC components currently used in semiconductor equipment often adopt reactive sintering to first prepare a relatively high-purity (≥99.95%) SiC substrate, and then chemical vapor deposition of high-purity SiC is performed on its surface to prevent impurities from escaping, thereby increasing the surface purity to above 5N.

[0004] In order to achieve the preparation of high-purity SiC substrates, elements such as Fe, Al, Ca, and Mg in metal or gypsum molds used in conventional pressure molding and slip casting are all sources of contamination, and these impurity elements will enter the SiC lattice to form solid solutions, which cannot be removed under high vacuum using the principle of saturated vapor pressure. Studies have found that the use of gel casting, a method of molding pure polymer materials, can effectively avoid the introduction of metal ions. However, all traditional gel casting molding methods, such as Chinese patents CN117800736A, CN116674080A, CN116924806A, and CN111548183A, have not been studied for high-purity SiC raw sand. At present, the domestic preparation of 5N high-purity SiC raw sand mainly adopts chemical synthesis or vapor deposition. The particles prepared by these two methods have extremely strong adsorption properties, and their microscopic morphology is irregular concave bodies such as spindles and paddles, with poor sphericity.

[0005] Previous experiments have shown that if high-purity SiC sand is directly used to replace ordinary SiC powder, on the one hand, due to the increase in the specific surface area and surface energy of the particles, a large amount of dispersant and alkaline balancing agent needs to be added, which in turn affects the pH, Zeta potential and rheological properties of the slurry, and may even cause the collapse of the entire gel system and sedimentation and solidification; on the other hand, it is difficult to achieve dense stacking of irregular particles, which ultimately results in a low solid content of the green body (<58%), which in turn limits the preparation of high-purity silicon carbide.

[0006] Therefore, the present invention aims to readjust the gel system process for high-purity SiC raw sand, and adopt pretreatment and reasonable grading to prepare high-purity and high-solid content SiC blanks to improve their performance. Summary of the Invention

[0007] The present invention aims to address the problem of easy introduction of metal elements or impurities such as B and P during the existing high-purity SiC substrate preparation process and the defects of the existing high-purity SiC substrate preparation process, and to provide a method for molding a high-purity SiC green billet. By adjusting the high-purity SiC raw sand system and improving the pretreatment and post-treatment processes, the performance of the SiC green billet is improved. The molding method is easy to operate and has a simple process.

[0008] In order to achieve the above object, the present invention adopts the following technical solutions: A method for forming a high-purity SiC blank comprises the following steps: S1: ball milling, drying and sieving the SiC raw sand to obtain SiC sand with good surface morphology; S2: Prepare slurry, perform secondary ball milling, vacuum degassing, initiation, slurry casting, demoulding, and drying to obtain a high-purity SiC green billet.

[0009] Furthermore, in step S1, the cleanliness level needs to be controlled during the process of obtaining SiC sand.

[0010] Specifically, the cleanliness in step S1 includes environmental cleanliness and tool cleanliness; the environmental cleanliness is an environment of a Class 10,000 clean room or above; the tool cleanliness includes that the stirring rods, ball mills, grinding balls, molds, tooling, bottles and tubes used in the process, and the parts that are in direct contact with the slurry and raw materials should all be made of materials that do not produce metal ion impurities, such as acrylic, polyvinyl chloride, polyurethane or polytetrafluoroethylene-coated stainless steel.

[0011] Specifically, the SiC raw sand in the present invention is a composite SiC raw sand including five gradations, wherein the five gradations refer to SiC raw sands having particle sizes D50 values ​​of 120 μm, 45 μm, 10 μm, 2.5 μm, and 0.5 μm, respectively.

[0012] Furthermore, the single ball milling of the SiC raw sand in step S1 refers to ball milling the SiC raw sand with D50 ≥ 20 μm in the five gradations, the ball milling jar and grinding balls used for ball milling are made of polyurethane; the ball milling liquid medium is acetone or ethanol; during ball milling, the ball-to-material ratio is between 1:2 and 1:3, the ball milling time is 4 to 20 hours, the SiC sand particles after ball milling are convex and the sphericity is above 0.86, and the SiC sand particles are dried for 0.5 to 4 hours after ball milling.

[0013] Furthermore, the volume solid content of the slurry prepared in step S2 is 62-69%.

[0014] Furthermore, in the slurry prepared in step S2, the mass percentages of the components are: 2.83% to 3.15% monomer, 0.2% to 0.4% cross-linking agent, 9.46% to 10.63% water, 0.011% to 0.014% polymerization inhibitor, 0.41% to 1.21% additive, and the balance is SiC sand.

[0015] Furthermore, in the slurry prepared in step S2, the SiC sand has five graded configurations, and the particle size D50 values ​​of the five graded SiC sands are 120 μm, 45 μm, 10 μm, 2.5 μm, and 0.5 μm, respectively, and the mass percentages are 40%-45%, 25%-30%, 15%-18%, 10%-12%, and 2%-3%, respectively.

[0016] Further preferably, in the SiC sand, the mass percentages of the five graded SiC sands are: D50 value 120 μm: D50 value 45 μm: D50 value 10 μm: D50 value 2.5 μm: D50 value 0.5 μm = 42.5%: 27.5%: 16.5%: 11%: 2.5%.

[0017] Specifically, the monomer is acrylamide and the cross-linking agent is MBAM, which stands for N,N-methylenebisacrylamide, also known as methylenebisacrylamide; The polymerization inhibitors are catechol and phenothiazine, and the molar ratio of the two is (4~5):1; The additive is a multi-component composite additive, which is selected from at least five of carbon black, urea, melamine, dimethylformamide, tetramethylammonium hydroxide, diethyl phthalate, polyethylene glycol, glycerol, isopropyl alcohol, n-butanol and cyclohexanol.

[0018] Further preferably, in the slurry prepared in step S2, the mass percentages of the additive components are: 30%-35% tetramethylammonium hydroxide, 15%-20% cyclohexanol, 6%-10% polyethylene glycol, 5%-9% isopropanol, 15%-20% n-butanol, and 15%-20% melamine.

[0019] Furthermore, in step S2, the secondary ball milling time is 1 h to 5 h.

[0020] Furthermore, in step S2, the vacuum value during vacuum degassing is less than 20 kPa, and other process parameters are all conventionally set, which are not the inventive point of the present invention and are therefore not described in detail.

[0021] Furthermore, the initiation in step S2 is to uniformly add a catalyst in an amount of 3% to 8% by weight of the crosslinking agent to the prepared slurry, and then uniformly add an initiator in an amount of 3% to 5% by weight of the crosslinking agent; The catalyst is any one of tetramethylethylenediamine, triethanolamine and dimethylaminopropionitrile; and the initiator is ammonium persulfate powder or its aqueous solution.

[0022] More preferably, when the added initiator is an aqueous ammonium persulfate solution, the amount of the solvent (water) in the aqueous ammonium persulfate solution is included in the amount of water used in preparing the slurry.

[0023] Furthermore, the drying in step S2 is as follows: soaking the demoulded green body step by step in aqueous solutions of low-molecular organic matter with a certain concentration, and then air-drying or baking the soaked green body.

[0024] More preferably, the low molecular weight organic compound may be any one of methanol, ethanol, acetone, isopropanol, and n-butanol.

[0025] Specifically, during soaking, a low-molecular organic aqueous solution with a certain volume concentration is used for soaking, and the low-molecular organic aqueous solution is set to a volume concentration of 3 to 10 levels, and the volume concentration of each level is 10% to 100%, and the volume concentration of each level increases successively. For example, when it is set to level 3, a low-molecular organic aqueous solution with a volume fraction of 33%, 66%, and 100% is used for soaking; when it is set to level 4, a low-molecular organic aqueous solution with a volume fraction of 25%, 50%, 75%, and 100% is used for soaking; when it is set to level 5, a low-molecular organic aqueous solution with a volume fraction of 20%, 40%, 60%, 80%, and 100% is used for soaking, and so on.

[0026] Specifically, the soaking time of the low-molecular organic matter aqueous solution with each level of volume concentration is 4 hours to 28 hours.

[0027] Furthermore, the air-drying is to stand at room temperature (20°C~25°C) for 24h~36h to dry, and the oven-drying is to keep warm in an environment of 100°C-120°C for 0.5h~2h.

[0028] Furthermore, based on a general inventive concept, the present invention also provides a high-purity SiC blank prepared by the above method.

[0029] Furthermore, based on a general inventive concept, the present invention also provides the use of products prepared from the high-purity SiC blank through subsequent processes in high-purity SiC ceramic precision components for semiconductor equipment.

[0030] Specifically, the high-purity SiC ceramic precision components for semiconductor equipment include vacuum suction cups, robotic arms, crystal boats, water-cooled plates, process furnace tubes, etc. for equipment such as photolithography, vapor deposition, heat treatment, and chemical mechanical polishing.

[0031] Compared with the prior art, the present invention has the following beneficial effects: 1. The high-purity SiC green billet molding method provided by the present invention realizes the molding of high-purity and high-solid content SiC green billets by controlling the surface morphology of the raw sand and the cleanliness of the environment and tools, combined with traditional gel casting methods. The method is easy to operate and has a short cycle, providing a leading foundation for subsequent sintering and vapor deposition, and is of great significance for the preparation of high-purity SiC ceramic precision components for semiconductor equipment.

[0032] 2. The molding method of the present invention is environmentally friendly and can be easily promoted and applied in the field of silicon carbide ceramic material processing. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 The SEM photos of the high-purity SiC raw sand with D50 values ​​of 45 μm and 2.5 μm in Example 1; Figure 2 This is a macroscopic photograph of the Φ200 blank prepared in Example 1; Figure 3 This is a SEM photograph of the fracture surface of the high-purity green billet sample prepared in Example 1; Figure 4 The GDMS test results of the high-purity green billet sample prepared in Example 1 after sintering; Figure 5 A top view of the finished vacuum chuck prepared in Example 3; Figure 6 A side view of the finished vacuum chuck prepared in Example 3; Figure 7 This is a bottom view of the finished vacuum chuck prepared in Example 3. DETAILED DESCRIPTION

[0034] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and do not limit the present invention.

[0035] Unless otherwise specified, the instruments and equipment used in the following examples are all commercially available conventional instruments and equipment; the other reagents and materials used are all commercially available conventional reagents and materials, unless otherwise specified. The experimental methods involved in the following examples are all conventional methods, unless otherwise specified.

[0036] Example 1 Example 1 provides a method for forming a high-purity SiC blank Ø200 sample, the specific steps of which are as follows: S1: ball milling, drying and sieving the SiC raw sand to obtain SiC sand with good surface morphology; Specifically, in step S1, the cleanliness of the SiC sand needs to be controlled during the process of obtaining the SiC sand; The cleanliness level mentioned above includes environmental cleanliness and tool cleanliness. The environmental cleanliness level should be above Class 10,000 clean room level. Tool cleanliness level includes the stirring rods, ball mills, grinding balls, molds, tooling, bottles and tubes used in the process. Parts that come into direct contact with the slurry and raw materials should be made of materials that do not produce metal ion impurities, such as acrylic, polyvinyl chloride, polyurethane or polytetrafluoroethylene coated stainless steel. The specific settings for controlling cleanliness in this embodiment are as follows: PVC tubes with an inner diameter of Ø200 are used as bottle tubes in a Class 1000 clean room; the mold material is acrylic plate; the custom stirring rod is a 304 stainless steel rod sprayed with polytetrafluoroethylene; the stirring blade on the stirring rod is made of acrylic; the ball mill jar and grinding balls are made of polyurethane; and the weighing tools are all made of plastic instead of glass; The specific operation of step S1 is to ball-mill high-purity SiC raw sand with a D50 value of 120 μm and 45 μm for 6 hours respectively. During the ball milling, the ball-to-material ratio (mass ratio) is 1:2, and the ball milling liquid medium is acetone. After ball milling, the SiC sand particles are convex and the sphericity is greater than 0.86. Then, the SiC sand particles are dried in a fume hood for 2 hours and then sieved to obtain SiC sand with good surface morphology. S2: Prepare slurry, perform secondary ball milling, vacuum degassing, initiation, slurry casting, demoulding, and drying to obtain high-purity SiC green billet; The specific operation of step S2 is to prepare a slurry with a volume solid content of 68%, wherein the mass percentages of the components in the slurry are: 36.835% SiC sand with a D50 value of 120 μm, 23.834% SiC sand with a D50 value of 45 μm, 14.301% SiC sand with a D50 value of 10 μm, 9.533% SiC sand with a D50 value of 2.5 μm, 2.166% SiC sand with a D50 value of 0.5 μm, 3.15% acrylamide (monomer), 0.3% MBAM (cross-linking agent, full name N,N-methylenebisacrylamide, also known as methylenebisacrylamide), 9.46% pure water, 0.011% polymerization inhibitor, and 0.41% additives; The polymerization inhibitor includes phenothiazine and catechol, and the molar ratio of the two is 1:5; the additive is a multi-component composite additive, and the mass percentage of each component in the additive is: 35% tetramethylammonium hydroxide, 20% cyclohexanol, 10% polyethylene glycol, 5% isopropanol, 15% n-butanol, and 15% melamine; The prepared slurry was subjected to secondary ball milling for 2 hours. When the viscosity was measured to be 4.7 Pa·s and the pH was 13.91, the casting requirements were met. Subsequently, vacuum degassing (i.e., vacuum degassing, the vacuum value during vacuum degassing was less than 20 kPa, and other process parameters were conventionally set and are not the inventive point of the present invention and are therefore not described in detail), and then slurry casting (injection molding) was performed to obtain a green body. After the green body was solidified, it was demolded, the surface was rinsed with pure water, and then dried. The initiation step is as follows: 3% of the cross-linking agent weight of tetramethylethylenediamine liquid is evenly added to the prepared slurry as a catalyst, and 3% of the cross-linking agent weight of ammonium persulfate powder is evenly added as an initiator; The drying process comprises placing the green body in a 33% by volume ethanol solution and allowing it to stand for 4 hours, then transferring it to a 66% by volume ethanol solution and allowing it to stand for 4 hours, then transferring it to pure ethanol and allowing it to stand for 4 hours before taking it out, and then allowing it to stand in the air for 30 hours, thereby obtaining a high-purity and high-solid content Φ200-SiC green body porous sample.

[0037] The porous sample was tested by ICP and the purity was 99.992% and the apparent density was 2.35 g / cm 2 , the average bending strength is ~39MPa.

[0038] Performance Testing 1. If Figure 1 The following are SEM images of high-purity SiC raw sand from Example 1. The D50 values ​​in the left and right images are 45 μm and 2.5 μm, respectively. This demonstrates their strong adsorption, low sphericity, poor surface morphology, and large specific surface area. Furthermore, after multiple attempts, it was found that while ball milling of particles with a D50 below 20 μm can improve their surface morphology, it can lead to reagglomeration, making sieving difficult. Therefore, this additional ball milling process is not limited in this invention.

[0039] 2. If Figure 2 The image shown is of a high-purity Ø200-SiC blank prepared in Example 1. Compared to the off-white or off-black color of standard-purity blanks, its macroscopic surface appears slightly yellow-green, due to the high-purity green α-SiC. Micrometer measurements show that the average linear shrinkage of this blank relative to the mold's inner diameter is only 1.08%.

[0040] 3. If Figure 3 This is the fracture morphology of the green sample prepared in Example 1. It shows that after ball milling, the 120μm and 45μm particles exhibit convex surfaces and good sphericity (>0.86). Furthermore, the large particles exhibit transgranular cleavage, while the small particles act as a barrier to crack propagation, resulting in a high flexural strength (~40 MPa) for this multi-graded, high-purity SiC green sample.

[0041] 4. If Figure 4This is the GDMS test result of the green blank sample prepared in Example 1 after debinding and sintering, and the purity is 99.981%, which meets the substrate purity requirement (>99.95%) for precision SiC components used in semiconductor equipment, and lays the foundation for subsequent fine processing and CVD coating to prepare products with a purity of 5N or above.

[0042] Example 2 Example 2 provides a method for forming a high-purity SiC water-cooling plate blank for a photolithography machine. The prepared blank is used to prepare a high-purity water-cooling plate for a photolithography machine, requiring dimensions of 332 mm (Ø) and 21 mm (H), a surface purity greater than 5N, and no particle loss. The forming method of Example 2 differs from that of Example 1 in that: In step S1, the specific settings for controlling cleanliness include using an acrylic ring mold and a cover mold with an inner diameter of 340 mm in a Class 10,000 clean room, customizing a stirring rod made of a stainless steel rod sprayed with polytetrafluoroethylene, and a stirring blade made of acrylic. The ball mill and grinding balls are made of polyurethane, and the weighing tools are all made of plastic instead of glass. The specific operation of step S1 is to ball mill high-purity SiC raw sand with a D50 value of 120 μm and 45 μm for 6 hours respectively. During the ball milling, the ball-to-material ratio (mass ratio) is 1:3, and the ball milling liquid medium is ethanol. For safety reasons, in order to neutralize the self-grinding heat, the outer wall of the ball mill is placed in an ice water bath for 5 minutes every hour during the ball milling process; after ball milling, the SiC sand particles are convex and have a sphericity of greater than 0.86, and then dried in a fume hood for 4 hours and sieved to obtain SiC sand with good surface morphology; The specific operation of step S2 is to prepare a slurry with a volume solid content of 65%, wherein the mass percentages of the components in the slurry are: 36.193% SiC sand with a D50 value of 120 μm, 24.415% SiC sand with a D50 value of 45 μm, 13.991% SiC sand with a D50 value of 10 μm, 9.292% SiC sand with a D50 value of 2.5 μm, 2.034% SiC sand with a D50 value of 0.5 μm, 2.922% acrylamide (monomer), 0.3% MBAM (cross-linking agent, full name N,N-methylenebisacrylamide, also known as methylenebisacrylamide), 9.885% pure water, 0.012% polymerization inhibitor, and 0.956% additives; The additive is a multi-component composite additive, and the mass percentage of each component in the additive is: 33% tetramethylammonium hydroxide, 18% cyclohexanol, 8% polyethylene glycol, 7% isopropanol, 17% n-butanol, and 17% melamine; The prepared slurry was ball-milled for a second time for 5 hours. When the viscosity was measured to be 0.9 Pa·s and the pH was 13.69, the casting requirements were met. Subsequently, vacuum degassing (i.e., vacuum degassing, the vacuum value during vacuum degassing was less than 20 kPa, and other process parameters were conventionally set and are not the inventive point of the present invention and are therefore not described in detail), and then slurry was cast (injection molding) to obtain a green body. After the green body was solidified, it was demolded, the surface was rinsed with pure water, and then dried. The initiation is as follows: tetramethylethylenediamine liquid with a weight percentage of 3% of the crosslinking agent is evenly added to the prepared slurry as a catalyst, and then an ammonium persulfate aqueous solution with a weight percentage of 3% of the crosslinking agent is evenly added (the amount of the solvent (pure water) in the ammonium persulfate aqueous solution is included in the amount of pure water used in preparing the slurry) as an initiator; The drying step comprises placing the green body in a 20% ethanol solution by volume and allowing it to stand for 8 hours, then transferring it to a 40% ethanol solution by volume and allowing it to stand for 8 hours, then transferring it to a 60% ethanol solution by volume and allowing it to stand for 8 hours, then transferring it to an 80% ethanol solution by volume and allowing it to stand for 8 hours, and then transferring it to pure ethanol and allowing it to stand for 8 hours before taking it out; After being taken out, the green body is placed in a 105°C environment and dried for 1 hour to obtain a high-purity and high-solid content SiC green body with a green body diameter of 336mm*H25mm, which meets the requirements of subsequent processing allowance and precision of the product.

[0043] Subsequently, after debinding, shaping, sintering, fine milling, deposition and fine grinding, the finished water-cooling plate with a purity of >5N and a parallelism of 0.002 on the upper and lower surfaces is obtained.

[0044] The processes of debinding, shaping, sintering, fine milling, deposition, and fine grinding described in this embodiment are post-processing processes for the SiC blank when preparing a vacuum chuck. These processes can be performed using conventional process methods in the prior art and are not the focus of the present invention, so they will not be described in detail.

[0045] Example 3 Example 3 provides a method for forming a high-purity SiC vacuum chuck blank for wafer testing. The prepared blank is used to prepare a high-purity vacuum chuck for wafer testing, with a maximum external size of 303mm*303mm*12mm. Figure 5 、 6 7, the purity of the adsorbed wafer portion is required to be greater than 5N, and no particles are lost; the molding method of Example 3 is different from that of Example 1 in that: In step S1, the specific settings for controlling cleanliness are as follows: a square acrylic mold with a side length of 320 mm and a height of 20 mm is processed in a Class 10,000 clean room; a customized stirring rod is a stainless steel rod sprayed with polytetrafluoroethylene; the stirring blade on the stirring rod is made of acrylic; the ball mill jar and grinding balls are made of polyurethane; and the weighing tools are all made of plastic instead of glass; The specific operation of step S1 is to ball mill high-purity SiC raw sand with a D50 value of 120 μm and 45 μm for 6 hours respectively. During the ball milling, the ball-to-material ratio (mass ratio) is 1:3, and the ball milling liquid medium is ethanol. For safety reasons, in order to neutralize the self-grinding heat, the outer wall of the ball mill is placed in an ice water bath for 5 minutes every hour during the ball milling process; after ball milling, the SiC sand particles are convex and have a sphericity of greater than 0.86, and then dried in a fume hood for 4 hours and sieved to obtain SiC sand with good surface morphology; The specific operation of step S2 is to prepare a slurry with a volume solid content of 65%, wherein the mass percentages of the components in the slurry are: 36.193% SiC sand with a D50 value of 120 μm, 24.415% SiC sand with a D50 value of 45 μm, 13.991% SiC sand with a D50 value of 10 μm, 9.292% SiC sand with a D50 value of 2.5 μm, 2.034% SiC sand with a D50 value of 0.5 μm, 2.922% acrylamide (monomer), 0.3% MBAM (cross-linking agent, full name N,N-methylenebisacrylamide, also known as methylenebisacrylamide), 9.885% pure water, 0.012% polymerization inhibitor, and 0.956% additives; The additive is a multi-component composite additive, and the mass percentage of each component in the additive is: 33% tetramethylammonium hydroxide, 18% cyclohexanol, 8% polyethylene glycol, 7% isopropanol, 17% n-butanol, and 17% melamine; The prepared slurry was ball-milled for a second time for 5 hours. When the viscosity was measured to be 0.9 Pa·s and the pH was 13.69, the casting requirements were met. Subsequently, vacuum degassing (i.e., vacuum degassing, the vacuum value during vacuum degassing was less than 20 kPa, and other process parameters were conventionally set and are not the inventive point of the present invention and are therefore not described in detail), and then slurry was cast (injection molding) to obtain a green body. After the green body was solidified, it was demolded, the surface was rinsed with pure water, and then dried. The initiation is as follows: tetramethylethylenediamine liquid with a weight percentage of 3% of the crosslinking agent is evenly added to the prepared slurry as a catalyst, and then an ammonium persulfate aqueous solution with a weight percentage of 3% of the crosslinking agent is evenly added (the amount of the solvent (pure water) in the ammonium persulfate aqueous solution is included in the amount of pure water used in preparing the slurry) as an initiator; The drying comprises the following steps: placing the green body in a 10% ethanol solution by volume and letting it stand for 24 hours, then transferring it to a 20% ethanol solution by volume and letting it stand for 24 hours, then transferring it to a 30% ethanol solution by volume and letting it stand for 24 hours, then transferring it to a 40% ethanol solution by volume and letting it stand for 24 hours, then transferring it to a 50% ethanol solution by volume and letting it stand for 24 hours, then transferring it to a 60% ethanol solution by volume and letting it stand for 24 hours, then transferring it to a 70% ethanol solution by volume and letting it stand for 24 hours, then transferring it to an 80% ethanol solution by volume and letting it stand for 24 hours, then transferring it to a 90% ethanol solution by volume and letting it stand for 24 hours, then transferring it to pure ethanol and letting it stand for 24 hours before taking it out; After taking out, the blank was placed in a drying oven at 120°C and dried for 2 hours to obtain a high-purity and high-solid content SiC blank with a diameter of 316.8mm*316.8mm*14.6mm, which meets the requirements of subsequent processing allowance and precision of the product.

[0046] Subsequently, the chuck is finished by debinding at 650°C, rough machining with a single-side allowance of 1mm to produce the product appearance, reaction sintering at 1500°C, semi-fine grinding of the reference surface, milling of the appearance and slots, upper air intake CVD single-sided 50μm coating, fine grinding, fine milling, and sleeve insertion.

[0047] The processes of debinding, rough machining, sintering, semi-finishing, milling, CVD single-side coating, fine grinding, fine milling, and sleeve inserting described in this embodiment are post-processing processes of the SiC blank when preparing a vacuum chuck. This process can be carried out using conventional process methods in the prior art and is not the inventive point of the present invention, so it will not be described in detail.

[0048] The above embodiments are illustrative of the implementation methods of the present invention. The implementation methods of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be considered as equivalent replacement methods and are included in the scope of protection of the present invention.

Claims

1. A method for forming a high-purity SiC blank, It is characterized in that The steps include: S1: ball milling, drying and sieving the SiC raw sand to obtain SiC sand; S2: Prepare slurry, perform secondary ball milling, vacuum degassing, initiation, slurry injection, demoulding, and drying to obtain a high-purity SiC green billet.

2. The method for forming a high-purity SiC blank according to claim 1, It is characterized in that In step S1, the cleanliness level of SiC sand needs to be controlled during the process of obtaining the SiC sand.

3. The method for forming a high-purity SiC blank according to claim 1, It is characterized in that The SiC raw sand is a composite SiC raw sand including five gradations, wherein the five gradations refer to SiC raw sands having particle sizes D50 of 120 μm, 45 μm, 10 μm, 2.5 μm and 0.5 μm, respectively; The one-time ball milling of SiC raw sand in step S1 refers to ball milling SiC raw sand with D50≥20 μm in 5 gradations; the ball milling liquid medium is acetone or ethanol; during ball milling, the ball-to-material ratio is between 1:2 and 1:3, the ball milling time is 4 to 20 hours, and the ball milling is dried for 0.5 to 4 hours.

4. The method for forming a high-purity SiC blank according to claim 1, It is characterized in that In the slurry prepared in step S2, the mass percentages of the components are: 2.83% to 3.15% monomer, 0.2% to 0.4% cross-linking agent, 9.46% to 10.63% water, 0.011% to 0.014% polymerization inhibitor, 0.41% to 1.21% additive, and the balance is SiC sand; The monomer is acrylamide, the crosslinking agent is MBAM, and the inhibitors are catechol and phenothiazine, and the molar ratio of the two is (4-5):1; The additive is a multi-component additive, which is selected from at least five of carbon black, urea, melamine, dimethylformamide, tetramethylammonium hydroxide, diethyl phthalate, polyethylene glycol, glycerol, isopropanol, n-butanol and cyclohexanol.

5. The method for forming a high-purity SiC blank according to claim 4, It is characterized in that In the slurry prepared in step S2, SiC sand has five graded configurations, and the particle size D50 values ​​of the five graded SiC sands are 120 μm, 45 μm, 10 μm, 2.5 μm, and 0.5 μm, respectively, and the mass percentages are 40%-45%, 25%-30%, 15%-18%, 10%-12%, and 2%-3%, respectively.

6. The method for forming a high-purity SiC blank according to claim 4, It is characterized in that In the slurry prepared in step S2, the mass percentages of the additive components are: 30%-35% tetramethylammonium hydroxide, 15%-20% cyclohexanol, 6%-10% polyethylene glycol, 5%-9% isopropanol, 15%-20% n-butanol, and 15%-20% melamine.

7. The method for forming a high-purity SiC blank according to claim 4, It is characterized in that In step S2, the secondary ball milling time is 1h~5h; The initiation in step S2 is to uniformly add a catalyst of 3% to 8% by weight of the crosslinking agent to the prepared slurry, and then uniformly add an initiator of 3% to 5% by weight of the crosslinking agent; The catalyst is any one of tetramethylethylenediamine, triethanolamine and dimethylaminopropionitrile; the initiator is ammonium persulfate powder or its aqueous solution.

8. The method for forming a high-purity SiC blank according to claim 1, It is characterized in that The drying in step S2 is as follows: the demoulded green body is soaked step by step in a low-molecular organic aqueous solution with a certain concentration, and then the soaked green body is air-dried or baked; The low molecular weight organic matter is any one of methanol, ethanol, acetone, isopropanol and n-butanol; During soaking, a low-molecular organic aqueous solution with a certain volume concentration is used for soaking, wherein the low-molecular organic aqueous solution is set to a volume concentration of 3-10 levels, the volume concentration of each level is 10% to 100%, and the volume concentration of each level increases sequentially; The soaking time of each level of volume concentration of low molecular organic aqueous solution is 4h~28h.

9. A high-purity SiC blank product prepared by the method according to any one of claims 1 to 8.

10. Use of the high-purity SiC green blank product according to claim 9 in the preparation of high-purity SiC ceramic precision parts for semiconductor equipment.

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