Production method of porous graphite material for SiC semiconductor crystal growth

Abstract

The invention discloses a production method of a porous graphite material for SiC semiconductor crystal growth, and relates to the technical field of graphite material production. The method comprises the following steps: preparing raw material powder: grinding and screening a graphite raw material to obtain powder with different particle sizes, preparing an additive, selecting a proper additive, accurately weighing and proportioning, preparing a binder, and preparing the binder capable of effectively binding the graphite powder. The particle size D50 of artificial graphite powder is precisely controlled to be 20-30 [mu] m by using an impact jet mill, the particle size D50 of high-temperature asphalt is controlled to be 5-8 [mu] m, real-time regulation and control are performed through an intelligent particle size monitoring system, and technologies such as ultrasonic-assisted mixing and kneading, vacuum vibration screening and far infrared radiation drying are matched, so that high quality and uniformity of raw materials are ensured, and the production efficiency is improved. And in the additive preparation process, airflow classification grinding, magnetic field auxiliary stirring and an online component analysis system are adopted, it is ensured that the additive is evenly dispersed, the proportion is accurate, and the product performance is effectively enhanced and modified.

Description

Technical Field

[0001] The present invention relates to the technical field of graphite material production, and particularly to a production method of porous graphite material for SiC semiconductor crystal growth. Background Art

[0002] The third-generation semiconductors, also known as wide bandgap semiconductors, refer to semiconductor materials represented by gallium nitride (GaN) and silicon carbide (SiC), which can operate at higher temperatures, stronger voltages, and faster switching frequencies. They are applicable to fields such as smart power grids, new energy vehicles, 5G communications, microwave radio frequency, and deep space equipment. The third-generation semiconductors include materials such as silicon carbide, gallium nitride, aluminum nitride, diamond, and zinc oxide. They have the characteristics of a wide bandgap width, better electron mobility, and can adapt to environments with high temperature, high pressure, and high radiation.

[0003] The PVT method is the most widely used SiC crystal growth method at present. The SiC semiconductor crystal growth furnace is the main equipment for producing SiC semiconductors. A large amount of graphite material is required in the SiC crystal growth furnace. One of the key graphite components is the porous graphite material, which is mainly used to maintain the uniform and stable rate during the crystal growth process, thereby improving the crystal quality.

[0004] In terms of production technology, most of the production processes of porous graphite still use molding or isostatic pressing methods to form secondary powder. This method is difficult to obtain products with uniform pore size and higher porosity, reducing the production quality of porous graphite and unable to meet the current market demand. Therefore, we provide a production method of porous graphite material for SiC semiconductor crystal growth to solve the above problems. Summary of the Invention

[0005] The purpose of the present invention is to provide a production method of porous graphite material for SiC semiconductor crystal growth. By combining 3D printing technology with precise raw material and additive treatment, it solves the problems in the prior art that the pore size adjustment means is single, it is difficult to obtain porous graphite materials with uniform pore size and high porosity, and the product performance is unstable and unable to meet the stringent requirements of SiC semiconductor crystal growth.

[0006] To solve the above technical problems, the present invention is realized through the following technical solutions: The present invention relates to a production method of a porous graphite material for SiC semiconductor crystal growth, comprising the following steps: Step A: Preparation of raw material powder: a1: Raw material selection: Artificial graphite powder is selected as the basic raw material. Due to its good purity and graphitization degree, it can provide a stable performance basis for the final product. The artificial graphite powder is crushed by an impact air-flow mill. The high-speed air flow makes the materials collide and rub against each other in the mill, so as to achieve the purpose of refinement. Its particle size D50 is controlled between 20 - 30 μm. This particle size range helps to uniformly mix with other powders and form a suitable microstructure during the 3D printing process; a2: Crushing of high-temperature pitch: High-temperature pitch with a softening point of 200 °C is selected and also crushed by an air-flow mill. Its crushing particle size D50 is controlled between 5 - 8 μm. The high-temperature pitch can be used as a binder in the subsequent kneading process. The lower crushing particle size enables it to better combine with the graphite powder, enhancing the adhesion between the materials. At the same time, during the subsequent carbonization and graphitization processes, the decomposition and transformation of the high-temperature pitch also contribute to the formation of a porous structure; a3: Material mixing and kneading: The above two powders are mixed in a ratio of 7:3. The precise control of the ratio is crucial for the product performance. The mixed materials are put into a high-temperature mixer and kneaded at a temperature of 300 - 320 °C. The high-temperature mixer can provide strong stirring and shearing forces to make the materials fully and uniformly mixed. During the kneading process, the high-temperature pitch gradually softens and wraps around the surface of the graphite powder, forming a paste with certain plasticity. The volatile content of the kneaded paste is controlled between 13 - 14%. The volatile content directly affects the viscosity of the paste and the subsequent processing performance. Too high or too low volatile content may lead to product quality problems; a4: Crushing, screening and drying: The kneaded paste is crushed and screened. The screening range is 100 mesh - 300 mesh. By screening, too large or too small particles can be removed to ensure the uniformity of the powder particle size and improve the stability of the product quality. After screening, the paste powder is dried to remove moisture and other volatile substances to prevent defects such as pores caused by water evaporation during the subsequent printing process. The dried powder is reserved; Step B: Preparation of additives: b1: Pretreatment of additives: The high-purity ferric chloride particles are dried to remove the moisture therein to prevent the moisture from affecting the dispersibility and stability of the additives during the grinding and mixing processes. After drying, they are ground to a particle size between 400 mesh - 600 mesh by a grinder to meet the requirements for mixing with PS microspheres. The PS microspheres are selected with a particle size of 500 mesh. The two are put into a mixer in proportion and pre-mixed first. During the pre-mixing process, the mixing speed should not be too fast to avoid electrostatic adsorption or particle agglomeration caused by high-speed stirring. At the same time, the temperature is controlled not to exceed 80 °C to prevent the PS microspheres from deforming or decomposing at high temperatures;b2: Secondary mixing: The pre-mixed powder is secondarily mixed with the sieved paste powder at a ratio of 5-10%, and the addition ratio of the additive is precisely controlled to ensure its expected strengthening, modification, etc. effects in the product. The mixed powder after secondary mixing is used as the printing raw material powder, and the mixing uniformity directly affects the performance consistency of the 3D printed product; Step C: Binder preparation: Phenolic resin, epoxy resin, furan resin, and polyvinylpyrrolidone (PVP) are mixed in proportion. One or several of phenolic resin, epoxy resin, and furan resin are taken. Phenolic resin has good heat resistance and adhesiveness, epoxy resin has high strength and good chemical corrosion resistance, and furan resin performs excellently in terms of acid and alkali resistance. Then, 2%-8% polyvinylpyrrolidone (PVP) is added. (PVP) can improve the rheological properties of the binder and enhance its jetting stability and uniformity during printing. A certain proportion of curing agent needs to be added to the mixed resin. The curing agent is selected and its addition amount is precisely controlled so that the binder can be cured below 160°C after forming to meet the requirements of subsequent production processes; Step D: 3D printing: Binder jetting technology is used for printing. This technology sprays the binder onto the laid powder layer through a nozzle and stacks layer by layer to form a three-dimensional entity. The powder laying thickness is set to 0.1 mm. A thinner powder laying thickness can improve printing accuracy and make the microstructure of the product more delicate. The binder dosage is 5-10%. The control of the dosage has an important impact on the strength and porosity of the product. Too little dosage may lead to insufficient powder bonding and insufficient product strength; too much dosage may reduce the porosity of the product and affect its air permeability and other properties; Step E: Curing and forming: The printed green body is transferred to a curing furnace and cured using a specific heating curve. The heating curve includes room temperature - 50°C, 50 - 80°C, 80 - 120°C, 120 - 140°C, 140 - 160°C, and 160°C heat preservation; Step F: Product carbonization: The cured green body is transferred to a carbonization furnace and carbonized according to a specific heating curve. The heating curve includes room temperature - 300°C, 300 - 380°C, 380 - 430°C, 430 - 480°C, 480 - 550°C, 550 - 650°C, 650 - 750°C, 750 - 850°C, 850 - 950°C, and 950°C heat preservation; Step G: Product graphitization: The carbonized product is transferred to a graphitization furnace and graphitized according to a specific heating curve. The heating curve includes room temperature - 300°C, 300 - 1000°C, 1000°C heat preservation, 1000 - 1200°C, 1200°C heat preservation, 1200 - 1800°C, 1800°C heat preservation, 1800 - 2400°C, 2400°C heat preservation, 2400 - 2950°C, and 2950°C heat preservation;Step H: Product testing: During product testing, professional testing equipment and standard testing methods are adopted to ensure the accuracy and reliability of test data. By comparing with the technical indicators of advanced foreign products, the performance level of the products produced by this process can be intuitively evaluated, providing a basis for further optimization and improvement of the products.

[0007] The present invention is further configured such that an intelligent particle size monitoring system is introduced in a1 to provide real-time feedback on the particle size change of graphite powder during the pulverization process, and the parameters of the air classifier mill are automatically adjusted through an AI algorithm to ensure precise control of the particle size.

[0008] The present invention is further configured such that during the air pulverization of high-temperature pitch in a2, low-temperature liquid nitrogen is used for auxiliary cooling to avoid premature softening and agglomeration of pitch caused by the heat generated during the pulverization process, ensuring uniform particle size of the pulverized pitch.

[0009] The present invention is further configured such that an ultrasonic-assisted kneading technique is adopted in a3, and ultrasonic waves are applied during the kneading process to enhance the interaction between materials, enabling the high-temperature pitch to coat the graphite powder more evenly.

[0010] The present invention is further configured such that a vacuum vibration screening technique is used in a4 for screening in a vacuum environment to reduce dust pollution. At the same time, vibration is utilized to promote material screening, and a far-infrared radiation drying technique is adopted in the drying process, featuring fast drying speed and uniform heating.

[0011] The present invention is further configured such that an air classification grinding technique is adopted in b1. When grinding high-purity ferric chloride particles, the ground particles are classified by particle size using air flow, ensuring that the particle size is more concentrated within the target range. During the premixing process, magnetic field-assisted stirring is used to enhance the dispersion effect between particles and prevent agglomeration.

[0012] The present invention is further configured such that an on-line composition analysis system is used in b2 to monitor the mixing ratio of additives and paste powder in real time during the secondary mixing process. Once the ratio deviates, the addition amount is automatically adjusted.

[0013] The present invention is further configured such that the curing agent is encapsulated in microcapsules and uniformly dispersed during the binder mixing. During the curing process, the microcapsules rupture and release the curing agent at a specific temperature or pressure, achieving more precise curing control.

[0014] The present invention is further configured such that a multi-channel adaptive nozzle is adopted in step D to automatically adjust the injection amount and injection angle of the binder according to different parts and structures of the printing model.

[0015] The present invention is further configured such that in step G, the magnetic field-induced graphitization technology is utilized. During the graphitization process, a magnetic field with a specific intensity and direction is applied to guide the arrangement of carbon atoms, improve the graphitization degree and crystallinity, thereby enhancing the electrical conductivity and mechanical properties of the product.

[0016] The present invention has the following beneficial effects: 1. The present invention uses an impact air classifier to accurately control the particle size D50 of artificial graphite powder within 20 - 30 μm and the particle size D50 of high-temperature pitch within 5 - 8 μm, and real-time regulation is carried out through an intelligent particle size monitoring system. Combined with technologies such as ultrasonic-assisted kneading, vacuum vibration screening, and far-infrared radiation drying, it ensures the high quality and uniformity of the raw materials, laying a good foundation for subsequent 3D printing. During the preparation process of the additive, air classification grinding, magnetic field-assisted stirring, and an on-line composition analysis system are adopted to ensure the uniform dispersion and accurate proportion of the additive, effectively enhancing and modifying the product performance.

[0017] 2. In the 3D printing process of the present invention, the binder jetting technology of a multi-channel adaptive nozzle is used, combined with a curing forming process assisted by microwave curing. It not only realizes high-precision printing of complex structures but also improves the curing quality of the green body. During the carbonization and graphitization stages of the product, the application of the magnetic field-induced graphitization technology greatly improves the carbon structure quality and graphitization degree, optimizing the physical properties of the product. Description of the Drawings

[0018] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for describing the embodiments will be briefly introduced below.

[0019] Figure 1 It is a flowchart of a production method of a porous graphite material for SiC semiconductor crystal growth. Detailed Embodiments

[0020] The technical solutions in the embodiments of the present invention will be described below with reference to the drawings in the embodiments of the present invention. The described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

[0021] Embodiment 1 Please refer to Figure 1, the present invention is a production method of a porous graphite material for SiC semiconductor crystal growth, comprising the following steps: Step A: Preparation of raw material powder: a1: Selection of raw materials: Artificial graphite powder is selected as the basic raw material. Due to its good purity and graphitization degree, it can provide a stable performance basis for the final product. An impact air classifier is used to crush the artificial graphite powder. The high-speed air flow makes the materials collide and rub against each other in the classifier, so as to achieve the purpose of refinement. Its particle size D50 is controlled between 20 - 30 μm. This particle size range helps to uniformly mix with other powder materials and form a suitable microstructure during the 3D printing process. An intelligent particle size monitoring system is introduced to real-time feedback the particle size change of the graphite powder during the crushing process. The parameters of the air classifier are automatically adjusted through AI algorithms to ensure accurate control of the particle size; a2: Crushing of high-temperature pitch: High-temperature pitch with a softening point of 200 °C is selected and also crushed by an air classifier. Its crushing particle size D50 is controlled between 5 - 8 μm. The high-temperature pitch can be used as a binder in the subsequent kneading process. The lower crushing particle size enables it to better combine with the graphite powder, enhancing the adhesion between the materials. At the same time, during the subsequent carbonization and graphitization processes, the decomposition and transformation of the high-temperature pitch also contribute to the formation of a porous structure. When crushing the high-temperature pitch by air, low-temperature liquid nitrogen is used for auxiliary cooling to avoid premature softening and agglomeration of the pitch due to the heat generated during the crushing process, ensuring uniform crushing particle size of the pitch; a3: Mixing and kneading of materials: The above two kinds of powder materials are mixed in a ratio of 7:3. The accurate control of the ratio is crucial for the product performance. The mixed materials are put into a high-temperature mixer and kneaded at a temperature of 300 - 320 °C. The high-temperature mixer can provide strong stirring and shearing forces to make the materials fully and uniformly mixed. During the kneading process, the high-temperature pitch gradually softens and wraps around the surface of the graphite powder, forming a paste with a certain plasticity. The volatile content of the kneaded paste is controlled between 13 - 14%. The volatile content directly affects the viscosity of the paste and the subsequent processing performance. Too high or too low may lead to product quality problems. The ultrasonic-assisted kneading technology is adopted to apply ultrasonic waves during the kneading process to enhance the interaction between the materials and make the high-temperature pitch more uniformly wrap around the graphite powder; a4: Crushing, screening and drying: The kneaded paste is crushed and screened. The screening range is 100 mesh - 300 mesh. By screening, too large or too small particles can be removed to ensure the uniformity of the powder particle size and improve the stability of the product quality. After screening, the paste powder is dried to remove moisture and other volatile substances to prevent defects such as pores caused by water evaporation during the subsequent printing process. The dried powder is reserved. The vacuum vibration screening technology is used for screening in a vacuum environment to reduce dust pollution and at the same time use vibration to promote material screening. The far-infrared radiation drying technology is adopted in the drying link, with fast drying speed and uniform heating;Step B: Additive Preparation: b1: Additive Pretreatment: Dry high-purity ferric chloride particles to remove the moisture therein to prevent the moisture from affecting the dispersibility and stability of the additive during grinding and mixing. After drying, grind them with a grinder to a particle size between 400 mesh and 600 mesh to meet the requirements for mixing with PS microspheres. The PS microspheres are selected with a particle size of 500 mesh. Put the two into a mixer in proportion for preliminary mixing. During the preliminary mixing process, the mixing speed should not be too fast to avoid electrostatic adsorption or particle agglomeration caused by high-speed stirring. At the same time, control the temperature not to exceed 80°C to prevent the PS microspheres from deforming or decomposing at high temperatures. Adopt air classification grinding technology. When grinding high-purity ferric chloride particles, use air flow to classify the ground particles according to particle size to ensure that the particle size is more concentrated within the target range. During the preliminary mixing process, use magnetic field-assisted stirring to enhance the dispersion effect between particles and prevent agglomeration; b2: Secondary Mixing: Secondary mix the above-prepared premixed powder with the sieved paste powder at a ratio of 5-10% to accurately control the addition ratio of the additive to ensure its expected strengthening, modification and other effects in the product. The mixed powder after secondary mixing is used as the printing raw material powder. The mixing uniformity directly affects the performance consistency of 3D printing products. Use an on-line composition analysis system to monitor the mixing ratio of the additive and the paste powder in real time during secondary mixing. Once the ratio deviates, automatically adjust the addition amount; Step C: Binder Preparation: Mix phenolic resin, epoxy resin, furan resin and polyvinylpyrrolidone (PVP) in proportion. Select one or several of phenolic resin, epoxy resin and furan resin. Phenolic resin has good heat resistance and adhesiveness. Epoxy resin has high strength and good chemical corrosion resistance. Furan resin performs excellently in terms of acid and alkali resistance. Then add 2%-8% polyvinylpyrrolidone (PVP). (PVP) can improve the rheological properties of the binder and enhance its jetting stability and uniformity during printing. A certain proportion of curing agent needs to be added to the mixed resin. Select the curing agent and accurately control its addition amount so that the binder can be cured below 160°C after forming to meet the requirements of subsequent production processes. Wrap the curing agent in microcapsules and disperse them evenly during the binder mixing. During the curing process, the microcapsules rupture and release the curing agent at a specific temperature or pressure to achieve more precise curing control; Step D: 3D Printing: Adopt binder jetting technology for printing. This technology sprays the binder onto the laid powder layer through a nozzle and stacks layer by layer to form a three-dimensional entity. The powder laying thickness is set to 0.1 mm. A thinner powder laying thickness can improve the printing accuracy and make the microstructure of the product more delicate. The binder dosage is 5-10%. The control of the dosage has an important impact on the strength and porosity of the product. Too little dosage may cause the powder to be not firmly bonded and the product to have insufficient strength; too much dosage may reduce the porosity of the product and affect its air permeability and other properties. In Step D, a multi-channel adaptive nozzle is adopted to automatically adjust the binder jetting amount and jetting angle according to different parts and structures of the printing model;Step E: Curing and forming: Transfer the printed green body to a curing furnace and perform curing treatment on the green body using a specific heating curve. The heating curve includes room temperature - 50°C, 50 - 80°C, 80 - 120°C, 120 - 140°C, 140 - 160°C, and insulation at 160°C; Step F: Product carbonization: Transfer the cured green body to a carbonization furnace and perform carbonization according to a specific heating curve. The heating curve includes room temperature - 300°C, 300 - 380°C, 380 - 430°C, 430 - 480°C, 480 - 550°C, 550 - 650°C, 650 - 750°C, 750 - 850°C, 850 - 950°C, and insulation at 950°C; Step G: Product graphitization: Transfer the carbonized product to a graphitization furnace and perform graphitization according to a specific heating curve. The heating curve includes room temperature - 300°C, 300 - 1000°C, insulation at 1000°C, 1000 - 1200°C, insulation at 1200°C, 1200 - 1800°C, insulation at 1800°C, 1800 - 2400°C, insulation at 2400°C, 2400 - 2950°C, and insulation at 2950°C. In Step G, the magnetic field-induced graphitization technology is used to apply a magnetic field with a specific intensity and direction during the graphitization process to guide the arrangement of carbon atoms, improve the degree of graphitization and crystallinity, and thus enhance the conductivity and mechanical properties of the product; Step H: Product testing: During the product testing process, professional testing equipment and standard testing methods are used to ensure the accuracy and reliability of the test data. By comparing with the technical indicators of advanced foreign products, the performance level of the products produced by this process can be intuitively evaluated, providing a basis for further optimization and improvement of the products.;

[0022] Example 2 I. Preparation of raw material powder Raw material selection: Select artificial graphite powder as the basic raw material. Due to its good purity and degree of graphitization, it can provide a stable performance basis for the final product. Use an impact air classifier to crush the artificial graphite powder. Utilize high-speed air flow to make the materials collide and rub against each other in the classifier to achieve the purpose of refinement, and control its particle size D50 between 20 - 30 μm. This particle size range helps to uniformly mix with other powders and form a suitable microstructure during the 3D printing process.

[0023] Crushing of high-temperature pitch: Select high-temperature pitch with a softening point of 200°C and also use an air classifier to crush it, and control its crushing particle size D50 between 5 - 8 μm. High-temperature pitch can be used as a binder in the subsequent kneading process. A lower crushing particle size can make it better combine with graphite powder, enhance the bonding force between materials, and at the same time, during the subsequent carbonization and graphitization processes, the decomposition and transformation of high-temperature pitch also contribute to the formation of a porous structure.

[0024] Material mixing and kneading: Mix the above two kinds of powder materials in a ratio of 7:3. The precise control of the ratio is crucial for the product performance. The mixed materials are put into a high-temperature kneading machine and kneaded at a temperature of 300 - 320°C. The high-temperature kneading machine can provide strong stirring and shearing forces to make the materials fully and evenly mixed. During the kneading process, the high-temperature pitch gradually softens and wraps around the surface of the graphite powder, forming a paste with a certain plasticity. Control the volatile content of the kneaded paste between 13 - 14%. The volatile content directly affects the viscosity of the paste and the subsequent processing performance. Too high or too low volatile content may lead to product quality problems.

[0025] Crushing, screening and drying: Crush and screen the kneaded paste. The screening range is 100 mesh - 300 mesh. By screening, too large or too small particles can be removed to ensure the uniformity of the powder particle size and improve the stability of the product quality. After screening, the paste powder is dried to remove moisture and other volatile substances to prevent defects such as pores caused by water evaporation during the subsequent printing process. The dried powder is reserved for use.

[0026] II. Additive preparation Additive pretreatment: Dry the high-purity ferric chloride particles to remove the moisture in them to prevent the moisture from affecting the dispersibility and stability of the additive during the grinding and mixing processes. After drying, grind them with a grinder to a particle size between 400 mesh - 600 mesh to meet the requirements for mixing with PS microspheres. The PS microspheres are selected with a particle size of 500 mesh. Put the two into a mixer in proportion for preliminary mixing. During the preliminary mixing process, the mixing speed should not be too fast to avoid static adsorption or particle agglomeration caused by high-speed stirring. At the same time, control the temperature not to exceed 80°C to prevent the PS microspheres from deforming or decomposing at high temperatures.

[0027] Secondary mixing: Mix the above-preliminary-mixed powder materials with the screened paste powder in a ratio of 5 - 10%. Precisely control the addition ratio of the additive to ensure its expected strengthening, modification and other effects in the product. The secondary-mixed powder is used as the printing raw material powder. The mixing uniformity directly affects the performance consistency of the 3D printed product.

[0028] III. Binder preparation Mix phenolic resin, epoxy resin, furan resin and polyvinylpyrrolidone (PVP) in proportion. One or several of phenolic resin, epoxy resin and furan resin can be selected for combination according to the specific performance requirements of the product. Phenolic resin has good heat resistance and adhesiveness, epoxy resin has high strength and good chemical corrosion resistance, and furan resin performs excellently in terms of acid and alkali resistance. Then add 2%-8% polyvinylpyrrolidone (PVP). PVP can improve the rheological properties of the binder and enhance its jetting stability and uniformity during the printing process. A certain proportion of curing agent needs to be added to the mixed resin. Select a suitable curing agent and precisely control its addition amount to enable the binder to cure below 160°C after forming, so as to meet the requirements of subsequent production processes.

[0029] IV. 3D Printing Use the binder jetting technology for printing. This technology sprays the binder onto the laid powder layer through a nozzle and stacks layer by layer to form a three-dimensional entity. The powder laying thickness is set to 0.1 mm. A thinner powder laying thickness can improve the printing accuracy and make the microstructure of the product more delicate. The binder dosage is 5-10%. The control of the dosage has an important impact on the strength and porosity of the product. Too little dosage may lead to insufficient powder bonding and insufficient product strength; too much dosage may reduce the porosity of the product and affect its air permeability and other properties.

[0030] V. Curing and Forming Transfer the printed green body to a curing furnace and perform curing treatment on the green body using a specific heating curve.

[0031] Room temperature - 50°C: The heating time is 60 min. Slowly heating can avoid stress concentration caused by rapid temperature changes in the green body, resulting in defects such as cracking.

[0032] 50 - 80°C: The heating time is 120 min and the heating rate is 0.25°C / min. Further promote the curing reaction of the binder, and at the same time maintain a relatively stable heating rate to ensure the uniformity of the curing process.

[0033] 80 - 120°C: The heating time is 360 min and the heating rate is 0.11°C / min. In this temperature range, the curing reaction of the binder gradually accelerates. Slowly heating helps to fully cure and improve the strength of the product.

[0034] 120 - 140°C: The heating time is 400 min and the heating rate is 0.05°C / min. Continue to promote the curing reaction to make the binder cure more completely and enhance the structural stability of the green body.

[0035] 140-160℃: Heating time 420min, heating rate 0.048℃ / min, close to the upper limit of the curing temperature of the adhesive, further ensuring the curing effect.

[0036] 160℃ insulation: insulation time is 360min, so that the green body can fully react at the curing temperature and reach the best curing state. The furnace temperature control accuracy is ±0.2℃. High-precision temperature control is the key to ensure the consistency of the curing effect. Slight temperature fluctuations may affect product quality.

[0037] 6. Product Carbonization The solidified green body is transferred to the carbonization furnace for carbonization according to a specific curve.

[0038] Room temperature - 300 °C: Heating time 20h, heating rate 15 °C / h, start heating at a lower temperature to gradually remove the organic components in the green body, while avoiding damage to the green body structure due to too fast heating.

[0039] 300-380℃: Heating time 65h, heating rate 1.23℃ / h. In this temperature range, the organic matter in the green body further decomposes and volatilizes, and the initial carbon structure begins to form.

[0040] 380-430℃: Heating time 80h, heating rate 0.63℃ / h, continuously promoting the formation and improvement of carbon structure, slow heating helps to form a uniform carbon skeleton.

[0041] 430-480℃: Heating time 80h, heating rate 0.63℃ / h, further strengthening the carbon structure and improving the thermal stability of the product.

[0042] 480-550℃: Heating time 78h, heating rate 0.64℃ / h. At this stage, the carbon structure gradually densifies and some impurities are removed.

[0043] 550-650℃: Heating time 68h, heating rate 1.47℃ / h, continue to promote the carbonization process to further increase the carbon content of the product.

[0044] 650-750℃: Heating time 50h, heating rate 2℃ / h, accelerate the carbonization reaction and make the carbonization degree of the product closer to the graphitization requirements.

[0045] 750-850℃: Heating time 40h, heating rate 2.5℃ / h, to further improve the purity and crystallinity of carbon.

[0046] 850-950℃: Heating time 20h, heating rate 2℃ / h, making final preparation for graphitization.

[0047] Insulation at 950°C: The insulation time is 8 hours to allow the carbonization reaction to proceed fully and ensure the carbonization quality of the product. The furnace temperature control accuracy is ±5°C. A higher temperature control accuracy is crucial for the stability of the carbonization process and the consistency of product quality.

[0048] VII. Graphitization of the Product The carbonized product is transferred to a graphitization furnace and graphitized according to a specific heating curve.

[0049] Room temperature - 300°C: The heating time is 60 minutes. Heat up slowly in the low-temperature stage to avoid damage to the product structure due to temperature shock.

[0050] 300 - 1000°C: The heating time is 60 minutes. Gradually increase the temperature to promote the rearrangement and crystallization of carbon atoms.

[0051] Insulation at 1000°C: The insulation time is 5 minutes to allow the product to react fully at this temperature and initially form a graphite structure.

[0052] 1000 - 1200°C: The heating time is 35 minutes. Continue to increase the temperature to further improve the graphite structure.

[0053] Insulation at 1200°C: The insulation time is 5 minutes to consolidate the graphitization effect.

[0054] 1200 - 1800°C: The heating time is 25 minutes. Rapidly heat up to a higher temperature to accelerate the graphitization process.

[0055] Insulation at 1800°C: The insulation time is 5 minutes to make the graphite structure more stable.

[0056] 1800 - 2400°C: The heating time is 120 minutes. Further promote the orderly arrangement of carbon atoms at high temperature to improve the crystallinity of graphite.

[0057] Insulation at 2400°C: The insulation time is 5 minutes to ensure the full completion of graphitization.

[0058] 2400 - 2950°C: The heating time is 60 minutes. Reach the highest temperature of graphitization to make the graphitization degree of the product reach the best.

[0059] Insulation at 2950°C: The insulation time is 90 minutes. Fully maintain the high-temperature state to make the various properties of the product reach stability. The furnace temperature control accuracy is ±20°C. At such a high temperature, a relatively large temperature control accuracy range can still ensure the smooth progress of the graphitization process, taking into account the actual operating capacity and cost factors of the equipment.

[0060] VIII. Product Testing The developed product testing indicators are as follows: The technical indicators of similar products of a foreign company are as follows: The 3D printed porous graphite material produced by this process has reached the technical indicators of foreign advanced products. During the product testing process, professional testing equipment and standard testing methods are used to ensure the accuracy and reliability of the test data.

[0061] Example 3 Scheme 1: Take 25% of high-purity ferric chloride of 400-600 mesh, 75% of PS microspheres (500 mesh), premix them, then take 6% of the mixed powder, and mix it with 94% of the mixed powder of 100-300 mesh. The binder uses a mixed binder of 4% furan resin + 2% PVP, and the binder dosage is 6%. After the green body is printed, cured, roasted, and graphitized, the bulk density of the test piece is 1.18 g / cm3, the porosity is 40%, the average pore diameter is 29 μm, and the compressive strength is 10 MPa. The test performance is poor.

[0062] Scheme 2: Take 28% of high-purity ferric chloride of 400-600 mesh, 72% of PS microspheres (500 mesh), premix them, then take 8% of the mixed powder, and mix it with 92% of the mixed powder of 100-300 mesh. The binder uses a mixed binder of epoxy resin, 2% furan resin + 3% + 3% PVP, and the binder dosage is 8%. After the green body is printed, cured, roasted, and graphitized, the bulk density of the test piece is 1.12 g / cm3, the porosity is 45%, the average pore diameter is 32 μm, and the compressive strength is 19 MPa, meeting the usage requirements.

[0063] Scheme 3: Take 35% of high-purity ferric chloride of 400-600 mesh, 65% of PS microspheres (500 mesh), premix them, then take 8% of the mixed powder, and mix it with 92% of the mixed powder of 100-300 mesh. The binder uses a mixed binder of epoxy resin, 2% furan resin + 3% + 3% PVP, and the binder dosage is 8%. After the green body is printed, cured, roasted, and graphitized, the bulk density of the test piece is 1.07 g / cm3, the porosity is 50%, the average pore diameter is 26 μm, and the compressive strength is 11 MPa, not meeting the usage requirements.

[0064] The preferred embodiments of the present invention disclosed above are only used to help illustrate the present invention. The preferred embodiments do not describe all the details in detail, nor do they limit the invention to the specific embodiments described. These embodiments are selected and specifically described in this specification to better explain the principle and practical application of the present invention, so that those skilled in the art can well understand and utilize the present invention.

Claims

1. A method for producing a porous graphite material for SiC semiconductor crystal growth, characterized in that: The following steps are involved: Step A: Raw powder preparation: a1: Raw material selection: artificial graphite powder is selected as the basic raw material, and the artificial graphite powder is crushed by an impact airflow mill. The high-speed airflow is used to make the materials collide and rub against each other in the mill, and the particle size D50 is controlled between 20-30μm; a2: High-temperature asphalt crushing: Select high-temperature asphalt with a softening point of 200°C, and crush it using a jet mill. The crushing particle size D50 is controlled between 5-8μm. The high-temperature asphalt is used as a binder in the subsequent kneading process; a3: Material mixing and kneading: Mix the above two powders in a ratio of 7:3, put the mixed materials into a high-temperature mixer, and knead them at a temperature of 300-320℃. During the kneading process, the high-temperature asphalt gradually softens and wraps around the surface of the graphite powder to form a paste with a certain plasticity. The volatile matter of the paste after kneading is controlled between 13-14%; a4: Crushing, screening and drying: The kneaded paste is crushed and screened, and the screening range is 100 mesh-300 mesh. After screening, the paste powder is dried to remove the volatile substances in the water to prevent the defect of pores caused by water evaporation in the subsequent printing process. The dried powder is used for standby; Step B: Additive preparation: b1: Additive pretreatment: Dry the high-purity ferric chloride particles to remove the moisture in them, and then grind them to between 400 mesh and 600 mesh with a grinder to make the particle size meet the requirements for mixing with PS microspheres. PS microspheres are selected to be 500 mesh. Put the two into the mixer in proportion for premixing, and control the temperature not to exceed 80°C; b2: Secondary mixing: The premixed powder is mixed with the sieved paste powder at a ratio of 5-10%, and the addition ratio of the additive is precisely controlled to ensure that it plays the expected role of enhancement and modification in the product; Step C: Preparation of binder: Phenolic resin, epoxy resin, furan resin and polyvinyl pyrrolidone (PVP) are mixed in proportion. A certain proportion of curing agent needs to be added to the mixed resins. The curing agent is selected and its addition amount is precisely controlled so that the binder can be cured below 160°C after molding to meet the subsequent production process requirements; Step D: 3D printing: Printing is performed using binder jetting technology, which uses a nozzle to spray the binder onto the paved powder layer, and stacks it layer by layer to form a three-dimensional entity. The powder thickness is set to 0.1mm, and the binder dosage is 5-10%; Step E: Curing and molding: The printed green body is transferred to a curing furnace and cured using a specific heating curve; Step F: Product carbonization: The solidified green body is transferred to a carbonization furnace for carbonization according to a specific heating curve; Step G: Product graphitization: The carbonized product is transferred to a graphitization furnace and graphitized according to a specific heating curve; Step H: Product testing: Conduct product testing. During the product testing process, use professional testing equipment and standard testing methods to ensure the accuracy and reliability of the test data. Compare the test results with foreign advanced product indicators to determine whether the product meets the standards.

2. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: The intelligent particle size monitoring system is introduced in a1 to provide real-time feedback on the particle size changes of graphite powder during the pulverization process, and automatically adjust the parameters of the air flow pulverizer through the AI ​​algorithm to ensure accurate control of the particle size.

3. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: In the above a2, when air flow pulverizes high-temperature asphalt, low-temperature liquid nitrogen is used to assist cooling to avoid premature softening and agglomeration of the asphalt due to the heat generated during the pulverization process, thereby ensuring that the asphalt pulverization particle size is uniform.

4. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: The ultrasonic assisted kneading technology is adopted in a3, and ultrasonic waves are applied during the kneading process to enhance the interaction between materials so that the high-temperature asphalt can more evenly wrap the graphite powder.

5. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: The vacuum vibration screening technology is used in the a4 to perform screening in a vacuum environment to reduce dust pollution. Vibration is used to promote material screening. The far-infrared radiation drying technology is used in the drying process, which has a fast drying speed and uniform heating.

6. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: In b1, airflow classification grinding technology is adopted. When grinding high-purity ferric chloride particles, airflow is used to classify the ground particles according to particle size to ensure that the particle size is more concentrated within the target range. Magnetic field is used to assist stirring during the premixing process to enhance the dispersion effect between particles and prevent agglomeration.

7. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: In b2, an online component analysis system is used to monitor the mixing ratio of the additive and the paste powder in real time during the secondary mixing process, and once the ratio deviates, the addition amount is automatically adjusted.

8. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: In step C, the curing agent is encapsulated in microcapsules and evenly dispersed when the binder is mixed. During the curing process, the microcapsules rupture at a specific temperature or pressure to release the curing agent, thereby achieving more precise curing control.

9. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: In the step D, a multi-channel adaptive nozzle is used to automatically adjust the binder injection amount and injection angle according to different parts and structures of the printed model.

10. The method for producing a porous graphite material for SiC semiconductor crystal growth according to claim 1, characterized in that: In step G, magnetic field-induced graphitization technology is used to apply a magnetic field of specific strength and direction during the graphitization process to guide the arrangement of carbon atoms, improve the degree of graphitization and crystallinity, and thus improve the conductivity and mechanical properties of the product.

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