A method for preparing high-purity silicon carbide parts based on low-pressure injection molding

Abstract

This invention provides a method for preparing high-purity silicon carbide parts based on low-pressure injection molding, belonging to the field of silicon carbide material preparation technology. The invention involves mixing wax, dispersant, reinforcing agent, and silicon carbide powder with a purity ≥99.995wt% in a mixer. The resulting slurry is placed in a low-pressure injection molding machine and injected into a mold under heating and pressurization conditions for molding. After demolding, the resulting preform undergoes dewaxing and debinding treatment. The dewaxed preform is then placed in a purified graphite kiln and sintered in a high-temperature resistance furnace to obtain the high-purity silicon carbide parts. This invention eliminates all possible introduction of metallic impurities during the material preparation, molding, dewaxing, and sintering processes, enabling the preparation of high-purity silicon carbide parts with a purity ≥99.99wt%.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide material preparation technology, and in particular to a method for preparing high-purity silicon carbide parts based on low-pressure injection molding. Background Technology

[0002] Silicon carbide possesses stable chemical properties, high thermal conductivity, low coefficient of thermal expansion, and excellent wear resistance, making it widely used in abrasives, refractory materials, and functional ceramic materials. In the semiconductor manufacturing field, vertical furnaces and diffusion furnaces are crucial equipment for achieving high-temperature heat treatment of semiconductor materials. Silicon carbide ceramic components are key parts within the hot zone of these furnaces, exhibiting complex structures, large dimensions, and extremely high requirements for precision and material quality (purity ≥99.99wt%).

[0003] The equipment used in the preparation of silicon carbide materials in related technologies is usually made of carbon steel. The silicon carbide materials prepared on this basis have high impurity content and do not meet the purity requirements. Summary of the Invention

[0004] The purpose of this invention is to provide a method for preparing high-purity silicon carbide parts based on low-pressure injection molding. The method of this invention can prepare high-purity silicon carbide parts with a purity of ≥99.99wt%, which is applicable to the semiconductor field.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution:

[0006] This invention provides a method for preparing high-purity silicon carbide parts based on low-pressure injection molding, comprising the following steps:

[0007] The wax, dispersant, reinforcing agent and silicon carbide powder with a purity of ≥99.995wt% are placed in a mixer and stirred to obtain a mixed slurry;

[0008] The mixed slurry is placed in a low-pressure injection molding machine and injected into a low-pressure injection molding mold under heating and pressurization conditions for molding. The molded blank is then demolded to obtain the molded blank.

[0009] The molded blank is subjected to dewaxing and debinding treatment to obtain a dewaxed blank;

[0010] The dewaxed and degummed blank is placed in a purified graphite kiln, and the purified graphite kiln containing the dewaxed and degummed blank is placed in a purified high-temperature resistance furnace for sintering to obtain high-purity silicon carbide parts with a purity ≥99.99wt%.

[0011] The materials of the parts in contact with the mixed slurry in the mixer, the parts in contact with the mixed slurry in the low-pressure injection molding machine, and the low-pressure injection molding mold are all reaction-sintered silicon carbide; the purified high-temperature resistance furnace and the purified graphite kiln furniture are obtained by purifying the high-temperature resistance furnace and the graphite kiln furniture, respectively, and the purification process includes sequential nitrogen cleaning and chlorine cleaning.

[0012] Preferably, the components in the mixer that come into contact with the mixed slurry include a stirring paddle, a stirring paddle connector, and a stirring tank;

[0013] The components in the low-pressure injection molding machine that come into contact with the mixed slurry include a slurry tank and a riser pipe.

[0014] Before injecting the mixed slurry into the low-pressure injection molding die, the process further includes polishing the contact surface between the low-pressure injection molding die and the mixed slurry.

[0015] Preferably, the purification process is carried out at a temperature of 1000~1300℃, and the purification process is repeated 30~50 times. Each purification process independently includes: introducing nitrogen gas with a purity ≥99.9999% to a pressure of 9~13kPa for nitrogen purging for 10~20min, followed by introducing chlorine gas with a purity ≥99.999% to a pressure of 74~107kPa for chlorine purging for 20~30min; wherein, before the first introduction of nitrogen gas, the process also includes: evacuating to a vacuum degree ≤10Pa.

[0016] Preferably, the wax material comprises paraffin wax and / or beeswax, and the mass of the wax material is 5-8% of the mass of the silicon carbide powder;

[0017] The dispersant comprises oleic acid and / or glycerol, and the mass of the dispersant is 2-4% of the mass of the silicon carbide powder.

[0018] The reinforcing agent includes acrylate emulsion and / or JM-609 reinforcing agent, and the mass of the reinforcing agent is 0.5~1% of the mass of silicon carbide powder.

[0019] Preferably, the silicon carbide powder is obtained by sequentially ball milling and drying a first type of silicon carbide powder and a second type of silicon carbide powder;

[0020] The purity of the first type of silicon carbide powder is ≥99.995wt%, and the particle size D50 is 2~3μm; the purity of the second type of silicon carbide powder is ≥99.995wt%, and the particle size D50 is 100~120μm; the mass ratio of the first type of silicon carbide powder to the second type of silicon carbide powder is 1~1.2:1;

[0021] The ball mill used in the ball mill is a ball mill lined with polyurethane, and the grinding balls used in the ball mill are polyurethane balls; the ball milling conditions include: a ball-to-material ratio of 1~1.5:1, a rotation speed of 200~300 rpm, and a time of 5~8 hours;

[0022] The drying process includes: placing the mixed powder obtained after ball milling into a recrystallized silicon carbide crucible, and drying the recrystallized silicon carbide crucible containing the mixed powder.

[0023] Preferably, the mixing process includes: placing the wax, dispersant, and reinforcing agent in a mixer for a first round of mixing to obtain a wax slurry; and adding the silicon carbide powder to the mixer containing the wax slurry for a second round of mixing.

[0024] Preferably, the barrel temperature of the low-pressure injection molding machine is 60~80℃, and the outlet temperature is 50~70℃; the injection pressure for injecting the mixed slurry into the low-pressure injection molding mold is 0.6~0.8MPa, and the holding time is 10~30s.

[0025] Preferably, the dewaxing process includes: embedding the molded blank in carbon black with a purity ≥99.9999 wt% and placing it in a recrystallized silicon carbide sagger; placing the recrystallized silicon carbide sagger containing the molded blank and carbon black in a dewaxing furnace; and performing a first dewaxing process and a second dewaxing process sequentially; the temperature of the first dewaxing process is 65~90℃, and the holding time is 1~2h; the temperature of the second dewaxing process is 100~150℃, and the holding time is 12~20h.

[0026] Preferably, the sintering temperature is 2200~2400℃ and the holding time is 2~4h.

[0027] Preferably, the surface roughness Ra of the unmachined surface of the high-purity silicon carbide component is ≤6.4μm.

[0028] Beneficial effects: This invention provides a method for preparing high-purity silicon carbide components for the semiconductor field based on low-pressure injection molding. By systematically solving the problem of impurity introduction during the preparation of silicon carbide components, this invention eliminates all possible steps that may introduce metal impurities during the processes of material preparation, molding, dewaxing, and sintering. This method can produce high-purity silicon carbide components with a purity of ≥99.99wt%, meeting the requirements of the semiconductor field for high-purity silicon carbide components. Specifically, this invention, based on low-pressure injection molding, uses high-purity silicon carbide powder (purity ≥99.995wt%) as raw material. Through precise control of the production process, starting from all links in contact with the slurry mixture, it utilizes the high thermal conductivity (120~150W / (m·K)) of reaction-sintered silicon carbide to replace commonly used carbon steel components in various stages such as the agitator, agitator connector, agitator tank, slurry tank, riser pipe, and low-pressure injection molding die. In other words, by non-metallicizing the components in contact with the slurry mixture, the introduction of metallic impurities is eliminated, ultimately producing high-purity silicon carbide parts with a purity ≥99.99wt%. Furthermore, this invention has good feasibility, is suitable for large-scale production, and facilitates the widespread use of high-purity silicon carbide parts in the semiconductor field. Attached Figure Description

[0029] Figure 1 This is a process flow diagram of the preparation of high-purity silicon carbide parts based on low-pressure injection molding in an embodiment of the present invention.

[0030] Figure 2 This is a schematic diagram of the modified mixer in an embodiment of the present invention;

[0031] Figure 3 This is a schematic diagram of the modification of the low-pressure injection molding machine in an embodiment of the present invention;

[0032] Figure 4 This is a schematic diagram of a low-pressure injection molding die in an embodiment of the present invention;

[0033] Figure 5 The image shows the test results of the unmachined surface roughness of the sample in Test Example 2;

[0034] Figure 6 The image shows the test results of the machined surface roughness of the sample in Test Example 2;

[0035] Figure 7 This is a distribution diagram of the test sites of the sample in Test Example 3;

[0036] Figure 8 This is a diagram showing the size measurement of the sample in Test Example 4. Detailed Implementation

[0037] This invention provides a method for preparing high-purity silicon carbide parts based on low-pressure injection molding, comprising the following steps:

[0038] The wax, dispersant, reinforcing agent and silicon carbide powder with a purity >99.995wt% are placed in a mixer and stirred to obtain a mixed slurry;

[0039] The mixed slurry is placed in a low-pressure injection molding machine and injected into a low-pressure injection molding mold under heating and pressurization conditions for molding. The molded blank is then demolded to obtain the molded blank.

[0040] The molded blank is subjected to dewaxing and debinding treatment to obtain a dewaxed blank;

[0041] The dewaxed and degummed blank is placed in a purified graphite kiln, and the purified graphite kiln containing the dewaxed and degummed blank is placed in a purified high-temperature resistance furnace for sintering to obtain high-purity silicon carbide parts with a purity ≥99.99wt%.

[0042] The materials of the parts in contact with the mixed slurry in the mixer, the parts in contact with the mixed slurry in the low-pressure injection molding machine, and the low-pressure injection molding mold are all reaction-sintered silicon carbide; the purified high-temperature resistance furnace and the purified graphite kiln furniture are obtained by purifying the high-temperature resistance furnace and the graphite kiln furniture, respectively, and the purification process includes sequential nitrogen cleaning and chlorine cleaning.

[0043] In this invention, the thermal conductivity of reaction-sintered silicon carbide is 120~150 W / (m·K), which is higher than that of carbon steel (80 W / (m·K), enabling the metal-free replacement of parts in contact with the mixed slurry in related equipment. Specifically, reaction-sintered silicon carbide is used to manufacture various parts that come into contact with the mixed slurry. Simultaneously, the high-temperature resistance furnace and graphite kiln furniture are purified, and the process is controlled during product preparation. This means that all steps that could introduce metal impurities are eliminated during the batching, molding, dewaxing, and sintering processes, ultimately yielding high-purity silicon carbide parts with a purity ≥99.99 wt%. Furthermore, the high-purity silicon carbide parts prepared using this method also exhibit good product uniformity and high dimensional accuracy. The method of this invention will be described in detail below.

[0044] In this invention, unless otherwise specified, all raw materials used are commercially available products known to those skilled in the art or prepared by methods known to those skilled in the art; unless otherwise specified, all equipment used is equipment known to those skilled in the art.

[0045] This invention involves targeted modifications or treatments to some of the equipment used in the preparation of high-purity silicon carbide parts, which is beneficial for the final preparation of silicon carbide parts with a purity of ≥99.99wt%. The equipment modification or treatment methods are described in detail below.

[0046] This invention involves mixing various components (i.e., wax, dispersant, reinforcing agent, and silicon carbide powder) in a mixer to obtain a mixed slurry. The material of the parts in contact with the mixed slurry in the mixer is reaction-sintered silicon carbide. In one embodiment of this invention, the mixer is specifically a high-speed mixer with a rotation speed of up to 1000 rpm. The parts in contact with the mixed slurry in the mixer include a stirring paddle, a stirring paddle connector, and a mixing tank. The dimensions of the stirring paddle and the mixing tank can refer to the dimensions of existing equipment; specifically, the stirring paddle can be Φ30mm × 260mm, and the mixing tank can be Φ300mm × Φ284mm × 300mm. This invention does not specifically limit the preparation method of the stirring paddle, stirring paddle connector, and mixing tank; they can be prepared according to the reaction-sintered silicon carbide molding process. This invention does not specifically limit the specific steps and conditions. In this embodiment, the diameter tolerance of the stirring paddle is required to be ±0.2mm, and the outer diameter tolerance of the mixing tank is required to be ±0.5mm. When installing the stirring paddle and mixing tank, the installation accuracy requirements are met through machining as needed.

[0047] This invention utilizes a low-pressure injection molding machine and a low-pressure injection molding die to prepare a preform from a mixed slurry using a low-pressure injection molding process. The materials of the components in contact with the mixed slurry in the low-pressure injection molding machine and the low-pressure injection molding die are both reaction-bonded silicon carbide. In one embodiment of this invention, the components in contact with the mixed slurry in the low-pressure injection molding machine include a slurry tank and a riser pipe. The dimensions of the slurry tank and riser pipe can refer to the dimensions of existing equipment; specifically, the slurry tank can be Φ300mm×300mm, and the riser pipe can be Φ8mm×220cm. The dimensions of the low-pressure injection molding die can be selected according to the target high-purity silicon carbide component; this invention does not have any special limitations on this. This invention does not have any special limitations on the preparation method of the slurry tank, riser pipe, and low-pressure injection molding die; they can be prepared according to the reaction-bonded silicon carbide molding process. This invention does not have any special limitations on the specific steps and conditions. In this embodiment of the invention, the diameter tolerance of the slurry tank and the riser pipe is required to be ±0.2mm. When installing the slurry tank and the riser pipe, the installation accuracy requirements are met by machining as needed.

[0048] As one embodiment of the present invention, before injecting the mixed slurry into the low-pressure injection molding mold, the method further includes polishing the contact surface between the low-pressure injection molding mold and the mixed slurry; in this embodiment of the present invention, a surface grinder and an internal cylindrical grinder are specifically used for polishing to ensure that the contact surface roughness is ≤1.6μm, which helps to ensure that the mixed slurry does not stick to the wall and finally obtains a product with high dimensional accuracy and a smooth surface.

[0049] This invention involves purifying a high-temperature resistance furnace and graphite kiln furniture, then sintering the dewaxed and degummed green body obtained after debinding in the shaped green body within the purified high-temperature resistance furnace and graphite kiln furniture (i.e., the purified high-temperature resistance furnace and purified graphite kiln furniture). The purification process includes sequential nitrogen and chlorine purging. In one embodiment, the purification temperature can be 1000~1300℃, specifically 1000℃, 1050℃, 1100℃, 1150℃, 1200℃, 1250℃, or 1300℃; the purification cycle can be 30~50 times, specifically 30, 35, 40, 45, or 50 times; each purification cycle independently includes: introducing nitrogen gas with a purity ≥99.9999% to a pressure of 9~13 kPa for nitrogen purging. After 10-20 minutes, chlorine gas with a purity ≥99.999% is introduced to a pressure of 74-107 kPa for chlorine purging for 20-30 minutes. Each purification process may include: introducing nitrogen gas with a purity ≥99.9999% to a pressure of 10 kPa for nitrogen purging for 15 minutes, followed by introducing chlorine gas with a purity ≥99.999% to a pressure of 100 kPa for chlorine purging for 25 minutes. Before the first introduction of nitrogen gas, a vacuum is drawn to a vacuum level ≤10 Pa. In this embodiment of the invention, the graphite kiln furniture is placed in a high-temperature resistance furnace, evacuated to a vacuum level ≤10 Pa, and heated to 1000~1300℃. Nitrogen gas with a purity ≥99.9999% is introduced to a pressure of 9~13 kPa and maintained for 10~20 min. Subsequently, chlorine gas is injected to a pressure of 74~107 kPa and maintained for 20~30 min. This cycle is repeated 30~50 times to complete the purification treatment of the high-temperature resistance furnace and the graphite kiln furniture. This invention uses chlorine gas to clean the high-temperature resistance furnace and graphite kiln furniture, enabling the removal of metallic impurities by forming chlorides.

[0050] The following is a detailed description of the method for preparing high-purity silicon carbide parts based on low-pressure injection molding according to the present invention.

[0051] This invention involves mixing wax, dispersant, reinforcing agent, and silicon carbide powder with a purity ≥99.995wt% in a mixer to obtain a mixed slurry. In one embodiment, the wax may include paraffin wax and / or beeswax, specifically refined paraffin wax. The refined paraffin wax used in this embodiment is grade 68, with a melting point range of 48~72℃ and a kinematic viscosity ≤10mm at 100℃. 2 / s; the mass of the wax can be 5-8% of the mass of the silicon carbide powder, specifically 5.5%, 6%, 6.5%, 7%, 7.5% or 8%; the dispersant can include oleic acid and / or glycerin, and the mass of the dispersant can be 2-4% of the mass of the silicon carbide powder, specifically 2%, 2.5%, 3%, 3.5% or 4%; the reinforcing agent can include acrylate emulsion and / or JM-609 reinforcing agent (the JM-609 reinforcing agent is purchased from Hubei Jiaming New Materials Co., Ltd.), and the acrylate emulsion used in the examples is model IRW-E037; the mass of the reinforcing agent can be 0.5-1% of the mass of the silicon carbide powder, specifically 0.5%, 0.6%, 0.7%, 0.8%, 0.9% or 1%.

[0052] In one embodiment of the present invention, the silicon carbide powder can be obtained by sequentially ball milling and drying a first type of silicon carbide powder and a second type of silicon carbide powder; the purity of the first type of silicon carbide powder is ≥99.995wt%, and the particle size D50 is 2~3μm, specifically 2.5μm; the purity of the second type of silicon carbide powder is ≥99.995wt%, and the particle size D50 is 100~120μm, specifically 115μm; the mass ratio of the first type of silicon carbide powder to the second type of silicon carbide powder can be 1~1.2:1, specifically 1:1. The present invention uses a compound of the first type of silicon carbide powder and the second type of silicon carbide powder, which is beneficial to improving the bulk density. In one embodiment of the present invention, the ball mill used for ball milling is a ball mill lined with polyurethane, and the grinding balls used for ball milling are polyurethane balls; the ball milling conditions include: a ball-to-material ratio of 1~1.5:1, a rotation speed of 200~300 rpm, and a time of 5~8 hours. In another embodiment of the present invention, the drying includes: placing the mixed powder obtained after ball milling into a recrystallized silicon carbide crucible, and drying the recrystallized silicon carbide crucible containing the mixed powder; the drying temperature can be 60~70℃, specifically 65℃; the time can be 4~6 hours, specifically 5 hours; the drying can be carried out in an oven.

[0053] In one embodiment of the present invention, the mixing process includes: placing the wax, dispersant, and reinforcing agent in a mixer for a first round of mixing to obtain a wax slurry; and adding the silicon carbide powder to the mixer containing the wax slurry for a second round of mixing. In another embodiment of the present invention, the wax, dispersant, and reinforcing agent are preferably added in batches, with each component added in 1-2 batches; the temperature of the first round of mixing can be 100-150℃, specifically 120℃, to ensure that the components melt and mix; the stirring speed of the first round of mixing can be 150-300 rpm, specifically 200 rpm, and the time can be 1-2 hours, specifically 1.5 hours. In one embodiment of the present invention, the silicon carbide powder is preferably added in batches, specifically in 5 to 10 batches; the temperature of the second round of stirring and mixing can be 100 to 150°C, specifically 120°C; the rotation speed can be 600 to 1000 rpm, specifically 850 rpm; and the time can be 12 to 24 hours, specifically 16 hours, to ensure sufficient dispersion.

[0054] After obtaining the mixed slurry, the present invention places the mixed slurry in a low-pressure injection molding machine and injects it into a low-pressure injection molding mold under heating and pressurization conditions for molding. The molded preform is then demolded. In one embodiment of the present invention, the barrel temperature of the low-pressure injection molding machine can be 60~80℃, specifically 60℃, 65℃, 70℃, 75℃, or 80℃; the outlet temperature can be 50~70℃, specifically 50℃, 55℃, 60℃, 65℃, or 70℃; the injection pressure of injecting the mixed slurry into the low-pressure injection molding mold can be 0.6~0.8MPa, specifically 0.6MPa, 0.65MPa, 0.7MPa, 0.75MPa, or 0.8MPa; the holding time can be 10~30s, specifically 10s, 15s, 20s, 25s, or 30s; preferably, the mold is disassembled after the holding time is completed to obtain the molded preform.

[0055] After obtaining the shaped preform, the present invention performs a dewaxing and debinding process on the shaped preform to obtain a dewaxed and debinded preform. In one embodiment of the present invention, the dewaxing and debinding process includes: embedding the shaped preform in carbon black with a purity ≥99.9999 wt% and placing it in a recrystallized silicon carbide crucible; placing the recrystallized silicon carbide crucible containing the shaped preform and carbon black in a dewaxing and debinding furnace, and sequentially performing a first dewaxing and debinding process and a second dewaxing and debinding process. Specifically, in this embodiment of the present invention, the shaped preform is placed in a recrystallized silicon carbide crucible containing carbon black, so that the shaped preform is completely embedded in the carbon black, and the carbon black protrudes 20-50 mm above the shaped preform, specifically 30 mm. The carbon black used in this embodiment of the present invention is GDF series carbon black. The present invention uses high-purity carbon black to embed the shaped preform, which has strong adsorption properties and can effectively adsorb wax and lock it in the carbon black, which is beneficial for meeting the wax content requirements during the firing process. The present invention does not have any particular limitation on the dewaxing furnace, and any dewaxing furnace well known to those skilled in the art can be used.

[0056] In one embodiment of the present invention, the temperature of the first dewaxing treatment can be 65~75℃, specifically 70℃; the heating rate from room temperature to the temperature of the first dewaxing treatment can be 8~12℃ / h, specifically 10℃ / h; the holding time of the first dewaxing treatment can be 0.5~1.5h, specifically 1h. In another embodiment of the present invention, the temperature of the second dewaxing treatment can be 100~150℃, specifically 120℃; the heating rate from the temperature of the first dewaxing treatment to the temperature of the second dewaxing treatment can be 8~12℃ / h, specifically 10℃ / h; the holding time of the second dewaxing treatment can be 12~20h, specifically 16h. In another embodiment of the present invention, the dewaxing treatment preferably includes: stopping heating and then naturally cooling to room temperature.

[0057] After obtaining the dewaxed and degummed blank, the present invention places the dewaxed and degummed blank in a purified graphite kiln, and then places the purified graphite kiln containing the dewaxed and degummed blank in a purified high-temperature resistance furnace for sintering to obtain high-purity silicon carbide parts with a purity ≥99.99wt%. As one embodiment of the present invention, preferably, the dewaxed and degummed blank is subjected to dewaxing powder removal, burr removal, and blank trimming in sequence before being placed in the purified graphite kiln for sintering. As one embodiment of the present invention, the sintering temperature can be 2200~2400℃, specifically 2200℃, 2250℃, 2300℃, 2350℃, or 2400℃; the sintering holding time can be 2~4h, specifically 2.5h; the sintering is preferably carried out under a vacuum of 100~500Pa (i.e., slightly positive pressure), specifically by argon gas providing pressure. In one embodiment of the present invention, the temperature rise from room temperature to the sintering temperature is preferably achieved using a gradient heating method. Specifically, the temperature can be raised from room temperature to the sintering temperature through 8 to 12 heating gradients. The number of heating gradients can be 8, 9, 10, 11, or 12. The temperature difference between each heating gradient can be 150 to 300°C, specifically 150°C, 175°C, 200°C, 250°C, or 300°C. The heating time for each heating gradient can be 3 to 10 hours, specifically 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, or 10 hours. It is preferable to hold the temperature for 1 to 3 hours between two adjacent heating gradients, specifically 1 hour, 1.5 hours, 2 hours, 2.5 hours, or 3 hours. That is, after each heating gradient is completed, it is preferable to hold the temperature for 1 to 3 hours before proceeding to the next heating gradient. In an embodiment of the present invention, taking a sintering temperature of 2350℃ as an example, the temperature can be uniformly increased from room temperature to 200℃ over 3 hours and held for 1 hour; then uniformly increased from 200℃ to 500℃ over 5 hours and held for 1 hour; then uniformly increased from 500℃ to 650℃ over 6 hours and held for 3 hours; then uniformly increased from 650℃ to 850℃ over 6 hours and held for 3 hours; then uniformly increased from 850℃ to 1150℃ over 6 hours and held for 1 hour; then uniformly increased from 1150℃ to 1150℃ over 7 hours. The temperature was uniformly increased from 0℃ to 1350℃ and held for 1 hour; then, after 7 hours, the temperature was uniformly increased from 1350℃ to 1550℃ and held for 1 hour; then, after 8 hours, the temperature was uniformly increased from 1550℃ to 1850℃ and held for 1 hour; then, after 10 hours, the temperature was uniformly increased from 1850℃ to 2000℃ and held for 1 hour; then, after 10 hours, the temperature was uniformly increased from 2000℃ to 2150℃ and held for 2.5 hours; then, after 10 hours, the temperature was uniformly increased from 2150℃ to 2350℃ and held for sintering.As one embodiment of the present invention, the sintering process preferably includes: stopping heating, then naturally cooling to room temperature, and then sequentially performing grinding, ultrasonic cleaning, and drying to obtain the high-purity silicon carbide parts; the cleaning reagent used for ultrasonic cleaning is prepared from HCl solution, HF solution, H2O2 solution, and water, and by mass fraction, the cleaning reagent can specifically be prepared from 3-5 parts of HCl solution, 2-3 parts of HF solution, 1-3 parts of hydrogen peroxide, and 90-94 parts of water; the concentration of the HCl solution can be 37 wt%, the concentration of the HF solution can be 40 wt%, the concentration of the H2O2 solution can be 30 wt%, and the water can be ultrapure water.

[0058] As one embodiment of the present invention, the high-purity silicon carbide components may include high-purity silicon carbide heat insulation sheets, high-purity silicon carbide oxygen pipes, or high-purity silicon carbide tile boats.

[0059] In one embodiment of the present invention, the surface roughness Ra of the unmachined surface of the high-purity silicon carbide component can be ≤6.4μm. The present invention solves the key problems restricting the purity of high-purity silicon carbide components by controlling the equipment and processes during the manufacturing process. Based on low-pressure injection molding, high-purity silicon carbide components with a purity ≥99.99wt% are prepared, exhibiting high dimensional accuracy, smooth surface, and an unmachined surface roughness Ra ≤6.4μm, fully meeting the substrate requirements of vapor deposition processes in semiconductor device fabrication.

[0060] Figure 1 This is a process flow diagram for preparing high-purity silicon carbide parts based on low-pressure injection molding in an embodiment of the present invention. The technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0061] Example 1

[0062] A method for preparing high-purity silicon carbide components (specifically, high-purity silicon carbide heat insulation sheets) based on low-pressure injection molding includes the following steps:

[0063] Step 1: The components in contact with the mixed slurry in the mixer (specifically a high-speed mixer with a rotation speed of up to 1000 rpm) are fabricated using a reaction-bonded silicon carbide molding method. These components mainly include the mixing blade, the mixing blade connector, and the mixing tank (e.g.,...). Figure 2As shown, the dimensions of the stirring paddle are Φ30mm×260mm, with a diameter tolerance of ±0.2mm; the dimensions of the stirring tank are Φ300mm×Φ284mm×300mm, with an outer diameter tolerance of ±0.5mm; the stirring paddle and stirring tank are installed to meet the installation accuracy requirements through machining as needed.

[0064] Step Two: The components in contact with the mixed slurry in the low-pressure injection molding machine are prepared using a reaction-bonded silicon carbide molding method. These mainly include the slurry tank and the riser pipe (e.g.,...). Figure 3 As shown, the slurry tank has dimensions of Φ300mm×300mm and a diameter tolerance of ±0.2mm; the riser pipe has dimensions of Φ8mm×220mm and a diameter tolerance of ±0.2mm; the slurry tank and riser pipe are installed by machining to meet the installation accuracy requirements as needed.

[0065] Step 3: Prepare low-pressure injection molding dies using a reaction-bonded silicon carbide molding method (e.g., Figure 4 As shown, from top to bottom, it includes a gate mold, a positioning block, a heat insulation sheet through hole occupant mold, a heat insulation sheet upper mold, and a heat insulation sheet lower mold. The contact surface between the low-pressure injection molding mold and the mixed slurry is polished, specifically by using a surface grinder and an internal cylindrical grinder to ensure that the contact surface roughness meets the requirement of ≤1.6μm.

[0066] Step 4: Purify the high-temperature resistance furnace and all the graphite kiln furniture used to obtain a purified high-temperature resistance furnace and purified graphite kiln furniture. The specific steps of the purification process are as follows: Under empty furnace conditions, load the graphite kiln furniture into the high-temperature resistance furnace, evacuate to a vacuum degree ≤10Pa, start heating to a temperature of 1200℃, first introduce nitrogen gas (purity ≥99.999%) to a pressure of 10kPa to clean the furnace cavity and remove oxygen. The nitrogen gas (purity ≥99.999%) introduction time is maintained for 15min, then chlorine gas is introduced to a pressure of 100kPa and maintained for 25min. After that, nitrogen gas is introduced again to clean the furnace cavity. One introduction of nitrogen gas and one introduction of chlorine gas is counted as one cycle. This cycle is repeated 30 times to complete the purification process of the furnace cavity and graphite kiln furniture of the high-temperature resistance furnace.

[0067] Step 5: Weigh two raw materials according to the following mass ratio: the first raw material is silicon carbide powder with a purity >99.995wt% and a particle size D50 of 2.5μm, accounting for 50% of the mass; the second raw material is silicon carbide powder with a purity >99.995wt% and a particle size D50 of 115μm, accounting for 50% of the mass. After weighing the two raw materials, place them in a ball mill lined with polyurethane, add polyurethane balls, and ball mill. The mass ratio of the total mass of the two raw materials to the mass of the polyurethane balls in the ball mill is 1:1.5. The ball milling speed is 200rpm, and the ball milling time is 8h. Place the mixed powder obtained after ball milling in a recrystallized silicon carbide crucible, and place the recrystallized silicon carbide crucible containing the mixed powder in a drying oven at 65℃ for 5h to obtain dried silicon carbide powder.

[0068] Step Six: Add the wax material (specifically, refined paraffin wax, grade 68, melting point range 48~72℃, kinematic viscosity ≤10mm at 100℃) to the mixer from Step One. 2 The mixture consists of a wax, a dispersant (specifically oleic acid), and a reinforcing agent (specifically an acrylate emulsion, model IRW-E037). The wax is added in 6% of the total mass of the dried silicon carbide powder in step five, the dispersant in 2% of the total mass of the dried silicon carbide powder in step five, and the reinforcing agent in 1% of the total mass of the dried silicon carbide powder in step five. Each component is added in two batches. After the wax, dispersant, and reinforcing agent are added, the mixture is heated to 120°C to melt and stirred at 200 rpm for 1.5 hours to obtain a wax slurry.

[0069] Step 7: Add the dried silicon carbide powder from Step 5 to the wax slurry from Step 6 in 5 batches, and stir and mix for 16 hours at a temperature of 120°C and a rotation speed of 850 rpm to obtain a mixed slurry.

[0070] Step 8: Add the mixed slurry from Step 7 to the low-pressure injection molding machine from Step 2. Under heating and pressurization conditions, inject the mixed slurry into the low-pressure injection molding mold for molding. The barrel temperature and outlet temperature of the low-pressure injection molding machine are set to 70°C. The injection pressure of the mixed slurry into the low-pressure injection molding mold is set to 0.8MPa, and the holding time is set to 20s. After the holding time is completed, disassemble the low-pressure injection molding mold to obtain the molded preform.

[0071] Step Nine: Place the shaped blank described in Step Eight into a recrystallized silicon carbide sagger containing highly absorbent high-purity carbon black (purity 99.9999wt%, model GDF series), ensuring the shaped blank is completely embedded in the high-purity carbon black, with the high-purity carbon black extending 30mm above the shaped blank. Then place the recrystallized silicon carbide sagger containing the shaped blank and high-purity carbon black into a dewaxing furnace. Increase the temperature from room temperature (25℃) to 70℃ at a rate of 10℃ / h and hold for 1 hour. Then increase the temperature from 70℃ to 120℃ at a rate of 10℃ / h and hold for 16 hours. After that, stop heating and allow it to cool naturally to room temperature to obtain a dewaxed blank.

[0072] Step 10: The dewaxed blanks described in Step 9 are then subjected to dewaxing powder removal, burr removal, and blank trimming to obtain trimmed blanks.

[0073] Step 11: Place the trimmed blank from Step 10 into the purified graphite kiln furniture from Step 4. Place the purified graphite kiln furniture containing the trimmed blank into a high-temperature resistance furnace. In an argon atmosphere (pressure 200 Pa), the temperature is uniformly increased from room temperature to 200°C over 3 hours and held for 1 hour. Then, the temperature is uniformly increased from 200°C to 500°C over 5 hours and held for 1 hour. Next, the temperature is uniformly increased from 500°C to 650°C over 6 hours and held for 3 hours. Then, the temperature is uniformly increased from 650°C to 850°C over 6 hours and held for 3 hours. Finally, the temperature is uniformly increased from 850°C to 1150°C over 6 hours and held. 1 hour; then for 7 hours, the temperature is uniformly increased from 1150℃ to 1350℃ and held for 1 hour; then for 7 hours, the temperature is uniformly increased from 1350℃ to 1550℃ and held for 1 hour; then for 8 hours, the temperature is uniformly increased from 1550℃ to 1850℃ and held for 1 hour; then for 10 hours, the temperature is uniformly increased from 1850℃ to 2000℃ and held for 1 hour; then for 10 hours, the temperature is uniformly increased from 2000℃ to 2150℃ and held for 2.5 hours; then for 10 hours, the temperature is uniformly increased from 2150℃ to 2350℃ and held for sintering for 2.5 hours. After the holding period, the temperature is naturally cooled to room temperature to obtain the sintered body.

[0074] Step 12: The sintered body described in Step 11 is then subjected to grinding and cleaning, ultrasonic cleaning (the cleaning reagent is prepared by mixing 37wt% HCl solution, 40wt% HF solution, 30wt% H2O2 solution and ultrapure water in a mass ratio of 3:2:1:94) and drying to obtain high-purity silicon carbide parts.

[0075] Example 2

[0076] Following the method described in Example 1, high-purity silicon carbide components (specifically, high-purity silicon carbide oxygen tubing) were prepared using a low-pressure injection molding method, with the following differences:

[0077] The low-pressure injection molding die prepared in step three is compatible with the high-purity silicon carbide oxygen tube;

[0078] In step six, the amount of wax added is 5.5% of the total mass of the dried silicon carbide powder in step five, the amount of dispersant added is 2.5% of the total mass of the dried silicon carbide powder in step five, and the amount of reinforcing agent added is 0.5% of the total mass of the dried silicon carbide powder in step five.

[0079] In step eight, the barrel temperature of the low-pressure injection molding machine is set to 80℃.

[0080] Example 3

[0081] Following the method described in Example 1, high-purity silicon carbide parts (specifically, high-purity silicon carbide tile boats) were prepared using a low-pressure injection molding method, with the following differences:

[0082] The low-pressure injection molding mold prepared in step three is compatible with the high-purity silicon carbide tile boat;

[0083] In step six, the amount of wax added is 5.5% of the total mass of the dried silicon carbide powder in step five, the amount of dispersant added is 2.5% of the total mass of the dried silicon carbide powder in step five, and the amount of reinforcing agent added is 1% of the total mass of the dried silicon carbide powder in step five.

[0084] In step eight, the barrel temperature of the low-pressure injection molding machine is set to 80℃, and the holding time is 30s.

[0085] Comparative Example 1

[0086] The method is the same as in Example 1, except that the material of the low-pressure injection molding die used in step three is carbon steel; other related operations are the same as in Example 1.

[0087] Test Example 1

[0088] Silicon carbide has a Mohs hardness of approximately 9.8, second only to diamond (10), making it the best material for abrasives and grinding tools. In contrast, carbon steel has a Mohs hardness of only 4-5. During the entire low-pressure injection molding process, the slurry enters from the bottom of the mold and fills the entire cavity along the gaps. Under certain temperature and pressure conditions, the slurry can easily scrape metal from the carbon steel mold into it. This metal remains in the product after it is formed, affecting the product's purity.

[0089] The purity of the silicon carbide products prepared in Example 1 and Comparative Example 1 was tested using glow discharge mass spectrometry (GDMS), and the results are shown in Table 1. It can be seen that the purity of the silicon carbide product prepared in Comparative Example 1 is 99.85%, while the purity of the silicon carbide product prepared in Example 1 is 99.99%.

[0090] Table 1. Purity test results of silicon carbide products prepared in Example 1 and Comparative Example 1

[0091]

[0092] Test Example 2

[0093] The roughness of the silicon carbide product prepared according to the method in Example 1 was tested using a TR200 surface roughness tester. Figure 5 This is a graph showing the surface roughness test results of the unmachined sample in Test Example 2. Figure 6 The table below shows the results of the surface roughness test of the machined surface of the sample in Test Example 2. The specific results are listed in Table 2. It can be seen that the unmachined surface roughness Ra of the silicon carbide product prepared using the method of this invention is ≤6.4μm, which fully meets the requirements of the vapor deposition process for the substrate in the fabrication of semiconductor devices.

[0094] Table 2. Roughness test results of silicon carbide products prepared according to the method of Example 1

[0095]

[0096] Test Example 3

[0097] The uniformity of the silicon carbide products prepared according to the method of Example 1 and the silicon carbide products prepared according to the method of Comparative Example 1 was tested. Specifically, the uniformity was characterized by measuring the volume density of each part of the sample using the segmentation method.

[0098] Figure 7 This is a distribution diagram of the test sites of the samples in Test Example 3. The left side shows the silicon carbide product prepared according to the method of Comparative Example 1, and the right side shows the silicon carbide product prepared according to the method of Example 1. The low-pressure injection molding mold used to prepare each silicon carbide product is compared with... Figure 7 The shapes shown are compatible. Table 3 shows the uniformity test results of different silicon carbide products. It can be seen that the test results of each part of the silicon carbide product prepared by the method of Example 1 of the present invention have a small deviation from the average value, which is only 0.010%, which is close to the measured value and the fluctuation range is small, indicating that the uniformity of the product is relatively good.

[0099] Table 3 Uniformity test results of different silicon carbide products

[0100]

[0101] Test Example 4

[0102] The dimensional accuracy of the silicon carbide products prepared according to the method of Example 1 was tested, specifically by comparing the dimensional deviations of the products obtained after injection molding with those required by the drawings.

[0103] Figure 8 This is a dimensional measurement diagram of the sample in Test Example 4, showing the low-pressure injection molding die used in the preparation of the silicon carbide product and... Figure 8The shapes shown are compatible. Table 4 shows the comparison results between the silicon carbide products prepared according to the method of Example 1 and the dimensions required by the drawings. It can be seen that the deviation of the measured values ​​of the products is very small, indicating that the data dispersion is extremely low and the fluctuation range is very small; moreover, all measuring points of the products are within the tolerance range given in the drawings. This fully demonstrates that the product itself has good conformity and high dimensional accuracy.

[0104] Table 4. Comparison of the dimensions of the silicon carbide products prepared according to the method in Example 1 with the dimensions required by the drawings.

[0105]

[0106] As can be seen from the above, the present invention has at least the following beneficial effects compared to the prior art:

[0107] 1. The method of this invention for preparing high-purity silicon carbide parts uses silicon carbide powder with a purity ≥99.995wt% as raw material, fundamentally eliminating metallic impurities in the material. Simultaneously, by replacing carbon steel materials in the equipment with reaction-sintered silicon carbide during the preparation process, the problem of introducing metallic impurities during molding is solved. Furthermore, the purification methods using a high-temperature resistance furnace and graphite kiln furniture eliminate the possibility of introducing metallic impurities during sintering. Compared to other molding methods, the high-purity silicon carbide parts prepared using the method of this invention have a purer material and better overall process stability.

[0108] 2. The method of this invention for preparing high-purity silicon carbide parts has the advantage of controllable dimensions due to low-pressure injection molding, making it easier to achieve complex shapes, reducing machining processes, and further eliminating the introduction of metal impurities. This results in a significant improvement in production efficiency and product qualification rate, and has excellent market expansion prospects and significant economic benefits.

[0109] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing high-purity silicon carbide parts based on low-pressure injection molding, characterized in that, Includes the following steps: The wax, dispersant, reinforcing agent and silicon carbide powder with a purity of ≥99.995wt% are placed in a mixer and stirred to obtain a mixed slurry; The mixed slurry is placed in a low-pressure injection molding machine and injected into a low-pressure injection molding mold under heating and pressurization conditions for molding. The molded blank is then demolded to obtain the molded blank. The molded blank is subjected to dewaxing and debinding treatment to obtain a dewaxed blank; The dewaxed and degummed blank is placed in a purified graphite kiln, and the purified graphite kiln containing the dewaxed and degummed blank is placed in a high-temperature resistance furnace for sintering to obtain high-purity silicon carbide parts with a purity ≥99.99wt%; the sintering is carried out under a vacuum of 100~500Pa, with argon gas providing pressure. The materials of the parts in contact with the mixed slurry in the mixer, the parts in contact with the mixed slurry in the low-pressure injection molding machine, and the low-pressure injection molding die are all reaction-sintered silicon carbide. The purified high-temperature resistance furnace and the purified graphite kiln furniture are obtained by purification treatment of the high-temperature resistance furnace and the graphite kiln furniture, respectively. The purification treatment includes sequential nitrogen cleaning and chlorine cleaning. The temperature of the purification treatment is 1000~1300℃, and the number of purification treatment cycles is 30~50 times. Each purification treatment independently includes: introducing nitrogen gas with a purity ≥99.9999% to a pressure of 9~13kPa for nitrogen cleaning for 10~20min, followed by introducing chlorine gas with a purity ≥99.999% to a pressure of 74~107kPa for chlorine cleaning for 20~30min. The first nitrogen gas introduction also includes: evacuating to a vacuum degree ≤10Pa.

2. The method according to claim 1, characterized in that, The components in the mixer that come into contact with the mixed slurry include a mixing blade, a mixing blade connector, and a mixing tank. The components in the low-pressure injection molding machine that come into contact with the mixed slurry include a slurry tank and a riser pipe. Before injecting the mixed slurry into the low-pressure injection molding die, the process further includes polishing the contact surface between the low-pressure injection molding die and the mixed slurry.

3. The method according to claim 1, characterized in that, The wax material includes paraffin wax and / or beeswax, and the mass of the wax material is 5-8% of the mass of the silicon carbide powder; The dispersant comprises oleic acid and / or glycerol, and the mass of the dispersant is 2-4% of the mass of the silicon carbide powder. The reinforcing agent includes acrylate emulsion and / or JM-609 reinforcing agent, and the mass of the reinforcing agent is 0.5~1% of the mass of silicon carbide powder.

4. The method according to claim 1, characterized in that, The silicon carbide powder is obtained by sequentially ball milling and drying a first type of silicon carbide powder and a second type of silicon carbide powder; The purity of the first type of silicon carbide powder is ≥99.995wt%, and the particle size D50 is 2~3μm; the purity of the second type of silicon carbide powder is ≥99.995wt%, and the particle size D50 is 100~120μm; the mass ratio of the first type of silicon carbide powder to the second type of silicon carbide powder is 1~1.2:1; The ball mill used in the ball mill is a ball mill lined with polyurethane, and the grinding balls used in the ball mill are polyurethane balls; the ball milling conditions include: a ball-to-material ratio of 1~1.5:1, a rotation speed of 200~300 rpm, and a time of 5~8 hours; The drying process includes: placing the mixed powder obtained after ball milling into a recrystallized silicon carbide crucible, and drying the recrystallized silicon carbide crucible containing the mixed powder.

5. The method according to claim 1, characterized in that, The mixing process includes: placing the wax, dispersant, and reinforcing agent in a mixer for a first round of mixing to obtain a wax slurry; and adding the silicon carbide powder to the mixer containing the wax slurry for a second round of mixing.

6. The method according to claim 1, characterized in that, The barrel temperature of the low-pressure injection molding machine is 60~80℃, and the outlet temperature is 50~70℃; the injection pressure of injecting the mixed slurry into the low-pressure injection molding mold is 0.6~0.8MPa, and the holding time is 10~30s.

7. The method according to claim 1, characterized in that, The dewaxing process includes: embedding the molded preform in carbon black with a purity ≥99.9999 wt% and placing it in a recrystallized silicon carbide sagger; placing the recrystallized silicon carbide sagger containing the molded preform and carbon black in a dewaxing furnace; and performing a first dewaxing process and a second dewaxing process sequentially; the temperature of the first dewaxing process is 65~90℃, and the holding time is 1~2h; the temperature of the second dewaxing process is 100~150℃, and the holding time is 12~20h.

8. The method according to claim 1, characterized in that, The sintering temperature is 2200~2400℃, and the holding time is 2~4h.

9. The method according to any one of claims 1 to 8, characterized in that, The surface roughness Ra of the unmachined surface of the high-purity silicon carbide component is ≤6.4μm.

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