Eight-inch silicon carbide crystal production device and assembly method

Abstract

The invention provides an eight-inch silicon carbide crystal production device and an assembly method, and belongs to the technical field of crystal growth, the eight-inch silicon carbide crystal production device comprises a crucible and a filter cartridge located in the crucible, and the filter cartridge is sequentially provided with an upper filter part, a middle filter part and a lower filter part from top to bottom; the upper filtering part, the middle filtering part and the lower filtering part respectively form an upper placing cavity, a middle placing cavity and a lower placing cavity which are communicated in sequence with the inner wall of the crucible, and the upper placing cavity, the middle placing cavity and the lower placing cavity are used for placing silicon carbide source powder with different granularities. According to the eight-inch silicon carbide crystal production device provided by the invention, the filter cartridge is provided with the upper filter part, the middle filter part and the lower filter part from top to bottom, and an upper placing cavity, a middle placing cavity and a lower placing cavity are respectively formed between the upper filter part, the middle filter part and the lower filter part and the inner wall of the crucible; effective control over the speed and components of the sublimation gas of the silicon carbide source powder passing through the filter cartridge is achieved.

Description

Technical Field

[0001] This application belongs to the field of crystal growth technology, and more specifically, relates to an eight-inch silicon carbide crystal production apparatus and an assembly method for the eight-inch silicon carbide crystal production apparatus. Background Technology

[0002] With the rapid development of third-generation semiconductor technology, eight-inch silicon carbide crystals have become a research focus in the silicon carbide semiconductor field due to their significant advantages in improving device manufacturing efficiency and reducing costs. During its growth process, the flow rate and chemical ratio of the sublimation gas from the silicon carbide source powder are key factors affecting crystal quality. A suitable sublimation gas flow rate ensures a stable material supply to the growth interface, while a precise chemical ratio helps to form a complete, low-defect crystal structure.

[0003] However, current technologies have many problems. Traditional gas control methods struggle to precisely regulate the flow rate of sublimation gas from silicon carbide source powder, making them unsuitable for the complex mass transfer and reaction processes within the crucible. Furthermore, the limited means of controlling the chemical stoichiometry of the sublimation gas often results in excessively high impurity content or elemental imbalances in the crystal, leading to numerous defects and severely impacting the crystal's electrical and optical properties. Summary of the Invention

[0004] The purpose of this application is to provide an eight-inch silicon carbide crystal production apparatus, which aims to solve the problem that existing eight-inch silicon carbide crystal production apparatuses cannot effectively control the ratio of sublimation gas for silicon carbide crystals, resulting in excessively high impurity content or imbalanced element ratios in the generated crystals.

[0005] To achieve the above objectives, the technical solution adopted in this application is as follows: an eight-inch silicon carbide crystal production apparatus is provided, comprising: a crucible and a filter cylinder located inside the crucible. The filter cylinder is provided with an upper filter section, a middle filter section and a lower filter section from top to bottom. The upper filter section, the middle filter section and the lower filter section form an upper placement cavity, a middle placement cavity and a lower placement cavity that are sequentially connected to the inner wall of the crucible, respectively. The upper placement cavity, the middle placement cavity and the lower placement cavity are used to place silicon carbide source powder of different particle sizes.

[0006] In one possible implementation, the filter cartridge is made of porous graphite.

[0007] In one possible implementation, the upper filter section has a porosity of 30%-36% and a pore diameter of 25μm-32μm; the middle filter section has a porosity of 40%-42% and a pore diameter of 30μm-35μm; and the lower filter section has a porosity of 45%-50% and a pore diameter of 30μm-40μm.

[0008] In one possible implementation, the upper filter section, the middle filter section, and the lower filter section are separate structures.

[0009] In one possible implementation, the upper filter section is a frustum-shaped structure with a larger upper section and a smaller lower section, and the outer diameter of the upper end of the upper filter section is the same as the inner diameter of the crucible. The middle filter section and the lower filter section are both cylindrical.

[0010] In one possible implementation, a base plate is mounted on the bottom of the crucible, the base plate being used to seal the bottom opening of the crucible.

[0011] In one possible implementation, a flow guide tube is installed at the top of the inner cavity of the crucible, the bottom surface of the flow guide tube abuts against the top surface of the filter tube, the top surface of the flow guide tube abuts against the top surface of the inner cavity of the crucible, the inner cavity of the flow guide tube is connected to the inner cavity of the filter tube, and the inner diameter of the flow guide tube gradually decreases from bottom to top.

[0012] In one possible implementation, the guide tube is made of porous graphite.

[0013] In one possible implementation, the outer surface of the filter cartridge is coated.

[0014] Compared with the prior art, the solution shown in this application's embodiment provides an eight-inch silicon carbide crystal production apparatus. The filter cylinder is configured with an upper filter section, a middle filter section, and a lower filter section from top to bottom. These three filter sections form an upper placement cavity, a middle placement cavity, and a lower placement cavity with the inner walls of their respective crucibles. Different particle sizes of silicon carbide source powder can be placed in these three placement cavities according to actual needs. The porosity and pore size of the upper, middle, and lower filter sections are adapted to the corresponding particle sizes of the silicon carbide source powder, thereby achieving effective control over the rate and composition of the sublimation gas from the silicon carbide source powder passing through the filter cylinder. During the heating process of the crucible, the heat inside is transferred upwards. Since the placement cavities are interconnected and there are no physical obstructions, heat can be smoothly transferred into the three placement cavities, ensuring the sublimation rate of the silicon carbide source powder within each cavity. Since the eight-inch silicon carbide crystal production apparatus of this application does not require the introduction of auxiliary gas into the crucible, it will not introduce new impurities or disrupt the chemical balance of the original gas, thus ensuring the quality of the final crystal.

[0015] Another objective of this application is to provide an assembly method for an eight-inch silicon carbide crystal production apparatus, comprising the following steps: S101: Turn the crucible 180° so that the bottom opening of the crucible faces upward; S102: Place the inverted guide tube into the crucible; S103: Place the inverted upper filter section, middle filter section and lower filter section into the crucible in sequence; S104: Place silicon carbide source powder with a particle size of 1mm-3mm into and fill the upper placement cavity, then place silicon carbide source powder with a particle size of 0.5mm-1mm into and fill the middle placement cavity, and then place silicon carbide source powder with a particle size of 0.2mm-0.5mm into and fill the lower placement cavity. S105: Secure the base plate to the crucible and heat-seal the bottom opening of the crucible. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0017] Figure 1 This is a cross-sectional view of an eight-inch silicon carbide crystal production apparatus provided in an embodiment of this application.

[0018] In the diagram: 1. Crucible; 101. Filter cylinder; 102. Upper filter section; 103. Middle filter section; 104. Lower filter section; 105. Upper placement cavity; 106. Middle placement cavity; 107. Lower placement cavity; 108. Adapter ring; 109. Base plate; 110. Flow guide tube; 111. Silicon carbide seed crystal. Detailed Implementation

[0019] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0020] Please see Figure 1 This application describes an eight-inch silicon carbide crystal production apparatus. The apparatus includes a crucible 1 and a filter cylinder 101 located inside the crucible 1. The filter cylinder 101 has an upper filter section 102, a middle filter section 103, and a lower filter section 104 arranged sequentially from top to bottom. The upper filter section 102, the middle filter section 103, and the lower filter section 104 form an upper placement cavity 105, a middle placement cavity 106, and a lower placement cavity 107 that are sequentially connected to the inner wall of the crucible 1. The upper placement cavity 105, the middle placement cavity 106, and the lower placement cavity 107 are used to place silicon carbide source powder of different particle sizes.

[0021] The existing technology adjusts the growth quality of silicon carbide crystals through the following three aspects: 1. Gas control method based on crucible 1 structural design: The flow of sublimation gas from silicon carbide source powder is indirectly controlled by optimizing the shape, size, and internal structure of crucible 1. For example, a special layout of vent holes at the bottom of crucible 1 or an internal flow guiding structure is designed to guide the sublimation gas to a uniform distribution. However, this method mainly focuses on controlling the macroscopic flow direction of the gas, and has limited ability to precisely adjust the sublimation gas flow rate and accurately control the chemical ratio. Moreover, once the structure of crucible 1 is determined, it is difficult to make flexible adjustments during the growth process, and it cannot meet the diverse gas control requirements of different growth stages.

[0022] The gas control method based on the structural design of crucible 1, while focusing on the macroscopic flow direction of the gas, cannot precisely adjust the sublimation gas flow rate through specific regions of the silicon carbide source powder within crucible 1. The fixed structure of crucible 1 makes it difficult to adjust the gas control effect in real time based on factors such as silicon carbide source powder consumption and temperature changes during growth. This results in significant differences in the sublimation gas flow rate at different locations within crucible 1, affecting the uniformity of crystal growth. Furthermore, this method has almost no direct effect on controlling the chemical stoichiometry of the sublimation gas, and cannot solve the crystal defect problem caused by inaccurate chemical stoichiometry.

[0023] 2. External Gas Purging Control Method: This method involves introducing auxiliary gas from outside the crucible 1 to purge the sublimation gas from the silicon carbide source powder, thereby influencing the distribution and concentration of the sublimation gas. By adjusting the flow rate and type of the external purging gas, the transport and mixing of the sublimation gas within the crucible 1 can be altered to some extent. However, this method does not directly control the flow rate and chemical composition of the sublimation gas itself, and the introduction of external gas may introduce new impurities, disrupting the chemical balance of the original gas and increasing the complexity and uncertainty of the crystal growth process.

[0024] While the external gas purging method can alter the distribution of sublimation gas to some extent, its introduction changes the existing gas environment within crucible 1. The newly introduced gas may carry impurities, contaminating the growth environment and affecting crystal quality. Furthermore, the mixing process between the external gas and the sublimation gas is difficult to control precisely, making the chemical composition of the sublimation gas more complex and unstable. In addition, this method only indirectly controls the sublimation gas flow rate, failing to achieve precise flow rate adjustment and thus failing to meet the stringent gas flow rate requirements for high-quality eight-inch silicon carbide crystal growth.

[0025] 3. Temperature-based indirect regulation method: By precisely controlling the heating temperature curve of crucible 1, the sublimation rate of silicon carbide source powder is indirectly controlled, thereby affecting the flow rate of sublimation gas. However, the effect of temperature on the sublimation process of silicon carbide source powder is complex, not only related to the sublimation rate but also affecting the chemical composition of the sublimation gas. Relying solely on temperature control makes it difficult to achieve independent and precise control of the sublimation gas flow rate and chemical ratio, and achieving uniform temperature control within a large-size crucible 1 is also a significant challenge.

[0026] An indirect temperature-controlled regulation method is employed, but due to the multifaceted influence of temperature on the sublimation process of silicon carbide source powder, simply adjusting the temperature cannot independently and precisely control the flow rate and chemical composition of the sublimation gas. Within crucible 1, achieving a completely uniform temperature distribution is difficult, leading to inconsistent sublimation rates of the silicon carbide source powder at different locations, which in turn causes deviations in the flow rate and chemical composition of the sublimation gas. Furthermore, temperature changes may trigger other side reactions, further interfering with the chemical composition of the sublimation gas, making it difficult to stably control the crystal growth process and ultimately affecting the quality of the eight-inch silicon carbide crystal.

[0027] This embodiment provides an eight-inch silicon carbide crystal production apparatus. Compared with the prior art, the filter cylinder 101 is configured with an upper filter section 102, a middle filter section 103, and a lower filter section 104 from top to bottom. The upper filter section 102, middle filter section 103, and lower filter section 104 form an upper placement cavity 105, a middle placement cavity 106, and a lower placement cavity 107 between themselves and the inner walls of the crucible 1, respectively. These three placement cavities can hold silicon carbide source powder of different particle sizes according to actual needs. The porosity and pore size of the upper filter section 102, middle filter section 103, and lower filter section 104 are adapted to the corresponding particle size of the silicon carbide source powder, thereby achieving effective control over the rate and composition of the sublimation gas from the silicon carbide source powder passing through the filter cylinder 101. During the heating process of the crucible 1, the heat inside is transferred upwards. Since the placement chamber, middle placement chamber 106, and lower placement chamber 107 are interconnected without any physical obstruction, heat can be smoothly transferred to the three placement chambers, ensuring the sublimation rate of the silicon carbide source powder within them. Because the eight-inch silicon carbide crystal production apparatus of this application does not require the introduction of auxiliary gas into the crucible 1, it does not introduce new impurities or disrupt the chemical balance of the existing gas, thus ensuring the quality of the final crystal.

[0028] The porous structure of graphite not only controls gas flow rate but also filters and selects the chemical composition of sublimation gases. Appropriate pore sizes can block some impurity particles and gas molecules that do not meet chemical stoichiometric requirements, resulting in a more precise chemical composition of the sublimation gas passing through porous graphite. Furthermore, during the growth process, the chemical composition of the sublimation gas can be further optimized by adjusting the growth conditions and relevant parameters of the porous graphite device and silicon carbide source powder. Precise chemical stoichiometry helps form a complete, low-defect crystal structure, improving the electrical and optical properties of eight-inch silicon carbide crystals (single crystals) and meeting the stringent crystal quality requirements of high-end applications.

[0029] Eight-inch silicon carbide crystal: refers to a silicon carbide crystal with a diameter of eight inches (200 mm). It has excellent physical and chemical properties, such as high breakdown electric field, high electron mobility and high thermal conductivity, and has broad application prospects in high-end fields such as power electronics and radio frequency devices.

[0030] Silicon carbide source powder: a raw material used for silicon carbide crystal growth. It sublimates into gas under high temperature conditions, providing the silicon and carbon elements required for crystal growth.

[0031] Sublimation gas: A substance in which silicon carbide source powder is directly transformed from a solid to a gaseous state at high temperature. Its flow rate and chemical ratio directly affect the growth process and crystal quality of silicon carbide crystals.

[0032] In some embodiments, please refer to Figure 1 The filter cartridge 101 is made of porous graphite. In this embodiment, porous graphite is a graphite material containing a large number of pores. Its pore structure determines the gas passage rate and selectivity, and can be used to control gas flow rate and chemical ratio. The porosity of the porous graphite has been optimized through extensive experiments and simulations, and is controlled within the range of 30%-50% to ensure that it has suitable permeation resistance and selectivity for the sublimation gas from silicon carbide source powder. The pore size of the porous graphite is distributed between 25μm and 40μm, and the pore size uniformity is ensured through a special preparation process, allowing the gas to pass through uniformly and avoiding excessively fast or slow local flow rates. Different combinations of porosity and pore size can achieve differentiated control of sublimation gas flow rate and chemical ratio for different growth requirements. For example, smaller pore size and lower porosity can more effectively filter out larger particle impurities while slowing down the gas passage speed, which is beneficial for precise control of gas flow rate; while larger pore size and higher porosity are suitable for growth stages that require a larger gas flow rate.

[0033] In some embodiments, please refer to Figure 1The upper filter section 102 has a porosity of 30%-36% and a pore diameter of 25μm-32μm; the middle filter section 103 has a porosity of 40%-42% and a pore diameter of 30μm-35μm; and the lower filter section 104 has a porosity of 45%-50% and a pore diameter of 30μm-40μm.

[0034] In some embodiments, please refer to Figure 1 The upper filter section 102, the middle filter section 103, and the lower filter section 104 are separate structures. In this embodiment, since the upper filter section 102, the middle filter section 103, and the lower filter section 104 are separate structures, they can be replaced individually, thereby facilitating the adjustment of the porosity and pore size on the filter cylinder 101.

[0035] In some embodiments, please refer to Figure 1 The upper filter section 102 is a frustum-shaped cone, wider at the top and narrower at the bottom. The outer diameter of the upper end of the upper filter section 102 is the same as the inner diameter of the crucible 1. The middle filter section 103 and the lower filter section 104 are both cylindrical. In this embodiment, the upper filter section 102 is a hollow frustum, and the middle filter section 103 and the lower filter section 104 are both hollow cylinders. The crucible 1 is cylindrical, and its inner cavity diameter remains consistent from top to bottom. The outer diameter of the upper end of the upper filter section 102 is the same as the inner cavity size of the crucible 1. The outer diameters of the middle filter section 103 and the lower filter section 104 are consistent with the outer diameter of the bottom of the upper filter section 102. Adapter rings 108 are installed between the upper filter section 102 and the middle filter section 103, and between the middle filter section 103 and the lower filter section 104. The adapter ring 108 has right-circular slots at both its upper and lower ends. The upper filter part 102, the middle filter part 103, and the lower filter part 104 are all inserted into the slots to achieve a fixed connection between the three parts. The lower end of the upper filter part 102 has a vertical section to facilitate the installation of the adapter ring 108.

[0036] The filter cartridge 101 is designed as a combination of a hollow frustum and a hollow cylinder. The outer diameter of the cylinder is 40%-60% of the inner diameter of the crucible 1 to ensure sufficient space for placing the silicon carbide source powder. The thickness of all parts of the filter cartridge 101 is consistent; that is, the upper filter section 102, the middle filter section 103, and the lower filter section 104 all have the same thickness. The thickness of the filter cartridge 101 is determined based on the required gas control effect and mechanical strength requirements, generally between 5mm and 10mm. A thicker filter cartridge 101 provides stronger gas filtration and flow rate control capabilities, but also increases gas resistance; a thinner filter cartridge 101 has lower gas resistance, but the control effect may be relatively weaker. In practical applications, the appropriate thickness of the filter cartridge 101 is selected based on the specific growth process and gas control requirements.

[0037] In some embodiments, please refer to Figure 1 A base plate 109 is installed at the bottom of the crucible 1, and the base plate 109 is used to seal the bottom opening of the crucible 1. In this embodiment, the base plate 109 is fixed to the bottom of the crucible 1 by fasteners, thereby sealing the bottom opening of the crucible 1. A circular limiting groove is formed on the top surface of the base plate 109. The outer diameter of the limiting groove is the same as the outer diameter of the bottom of the crucible 1, and the inner diameter of the limiting groove is the same as the inner diameter of the lower filter part 104. The bottoms of both the crucible 1 and the lower filter part 104 are installed in the limiting groove, which plays a positioning role for the crucible 1 and the lower filter part 104, ensuring the stability of the installation structure.

[0038] In some embodiments, please refer to Figure 1 A guide tube 110 is installed at the top of the inner cavity of crucible 1. The bottom surface of the guide tube 110 abuts against the top surface of the filter tube 101, and the top surface of the guide tube 110 abuts against the top surface of the inner cavity of crucible 1. The inner cavity of the guide tube 110 is connected to the inner cavity of the filter tube 101. The inner diameter of the guide tube 110 gradually decreases from bottom to top. In this embodiment, the guide tube 110 is cylindrical, and its outer diameter is the same as the inner diameter of the crucible 1. The top of the guide tube 110 abuts against the top surface of the inner cavity of crucible 1, and the bottom of the guide tube 110 abuts against the bottom surface of the inner cavity of crucible 1. The inner hole of the guide tube 110 is a conical hole with a small opening at the top and a large opening at the bottom. The inner diameter of the lower end of the guide tube 110 is the same as the inner diameter of the top of the upper filter part 102.

[0039] The guide tube 110 is used to control the growth shape of silicon carbide crystals, so that the crystals grow along the prescribed shape of the inner surface of the guide tube 110. The angle between the inclined inner surface of the guide tube 110 and the vertical direction is in the range of 8°-15°, which ensures that the silicon carbide crystals grow slowly and uniformly release internal growth stress.

[0040] In some embodiments, please refer to Figure 1 The guide tube 110 is made of porous graphite. In this embodiment, another purpose of the guide tube 110 is to supplement the carbon source for silicon carbide crystal growth. The guide tube 110 is made of porous graphite. Since the saturated vapor pressure of the silicon atmosphere in the sublimated silicon carbide powder source is higher, at the growth temperature, the sublimated gas will react with the guide tube 110 to generate an atmosphere closer to a carbon-silicon ratio of 1, providing the necessary energy for crystal growth. In addition, the supersaturation of the sublimated atmosphere of the silicon carbide powder source is easily too high, leading to an increased probability of edge nucleation and the formation of polycrystalline impurities. The porous graphite of the guide tube 110 can absorb excess sublimated atmosphere to reduce supersaturation and protect the stable growth of crystal edges.

[0041] In some embodiments, please refer to Figure 1The outer surface of the filter cartridge 101 is coated. In this embodiment, a CVD process is used to deposit a pyrolytic graphite layer or a tantalum carbide coating. Both have good thermal conductivity, which can further make heat transfer more uniform and improve the temperature uniformity of the raw material area; both have the characteristics of high purity and dense structure, which can prevent the release of impurities in porous graphite, reduce the generation of crystal defects, improve the strength and wear resistance of porous graphite, and protect the integrity of porous graphite in the high temperature and high chemical corrosion environment of single crystal growth environment, thereby ensuring the stability of the thermal field.

[0042] The porous graphite filter cartridge 101, coated with a protective layer, effectively filters the sublimation gas from the silicon carbide source powder, preventing some impurity particles from entering the growth region. Compared to traditional methods such as external gas purging, this invention reduces the risk of contamination from introduced external gases, maintaining the purity of the gas environment within the crucible 1. A pure gas environment is beneficial for improving the quality of the eight-inch silicon carbide crystal, reducing the impurity content in the crystal, minimizing defect generation, and thus enhancing the crystal's performance and reliability.

[0043] The parameters of the porous graphite device (filter cartridge 101), such as porosity, pore size, thickness, and placement height, can be customized and adjusted according to different growth processes and requirements. During growth, relevant parameters and control strategies can also be changed to adapt to variations in the sublimation gas flow rate and chemical composition of the silicon carbide source powder at different growth stages. This adaptability improves the controllability of the eight-inch silicon carbide single crystal growth process, expands the application range of this technology in different production scenarios, and helps promote the large-scale, high-quality production of eight-inch silicon carbide single crystals.

[0044] This application also provides an assembly method for an eight-inch silicon carbide crystal production apparatus, the steps of which are as follows: S101: Rotate crucible 1 180° so that the bottom opening of crucible 1 faces upward; S102: Place the inverted guide tube 110 into the crucible 1; S103: Place the inverted upper filter section 102, middle filter section 103 and lower filter section 104 into the crucible 1 in sequence; S104: Place silicon carbide source powder with a particle size of 1mm-3mm into and fill the upper placement cavity 105, then place silicon carbide source powder with a particle size of 0.5mm-1mm into and fill the middle placement cavity 106, and then place silicon carbide source powder with a particle size of 0.2mm-0.5mm into and fill the lower placement cavity 107. S105: Fix the base plate 109 onto the crucible 1 and heat-seal the bottom opening of the crucible 1.

[0045] In step S103, before installing the middle filter 103, the adapter ring 108 needs to be installed on the upper filter 102; before installing the lower filter 104, the adapter ring 108 needs to be installed on the middle filter 103.

[0046] The components inside crucible 1 abut against each other from top to bottom, and are finally pressed and fixed by the base plate 109. After assembly, the entire device is rotated 180° to be placed upright, and then the normal production of silicon carbide crystals can continue.

[0047] The top of the inner cavity of crucible 1 is the crystal growth region, and the biochemically treated gas eventually forms silicon carbide seed crystal 111 in the crystal growth region.

[0048] Smaller silicon carbide source powder has a larger specific surface area. When combined with porous graphite with corresponding high porosity and large pore size, it can ensure a sufficient supply of sublimation material in the growth region far from the crystal to pass through the long transport path, thus guaranteeing the continuous growth of high-quality crystals. In the growth region near the crystal, the use of large-particle-size silicon carbide source powder combined with fine-grained porous graphite controls the large amount of sublimation transport of silicon carbide source powder in the early stage of growth, suppresses the generation of defects such as basal plane dislocations caused by rapid disordered atomic stacking, and improves the growth quality of silicon carbide crystals.

[0049] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An eight-inch silicon carbide crystal production apparatus, characterized in that, include: The crucible and the filter cylinder located inside the crucible are provided with an upper filter section, a middle filter section and a lower filter section arranged sequentially from top to bottom. The upper filter section, the middle filter section and the lower filter section form an upper placement cavity, a middle placement cavity and a lower placement cavity that are sequentially connected to the inner wall of the crucible, respectively. The upper placement cavity, the middle placement cavity and the lower placement cavity are used to place silicon carbide source powder of different particle sizes.

2. The eight-inch silicon carbide crystal production apparatus as described in claim 1, characterized in that, The filter cartridge is made of porous graphite.

3. The eight-inch silicon carbide crystal production apparatus as described in claim 1, characterized in that, The upper filter section has a porosity of 30%-36% and a pore diameter of 25μm-32μm; the middle filter section has a porosity of 40%-42% and a pore diameter of 30μm-35μm; and the lower filter section has a porosity of 45%-50% and a pore diameter of 30μm-40μm.

4. The eight-inch silicon carbide crystal production apparatus as described in claim 3, characterized in that, The upper filter section, the middle filter section, and the lower filter section are separate structures.

5. The eight-inch silicon carbide crystal production apparatus as described in claim 4, characterized in that, The upper filter section is a frustum-shaped structure with a larger upper part and a smaller lower part. The outer diameter of the upper end of the upper filter section is the same as the inner diameter of the crucible. The middle filter section and the lower filter section are both cylindrical.

6. The eight-inch silicon carbide crystal production apparatus as described in claim 5, characterized in that, A base plate is installed at the bottom of the crucible, and the base plate is used to seal the bottom opening of the crucible.

7. The eight-inch silicon carbide crystal production apparatus as described in claim 6, characterized in that, A flow guide tube is installed at the top of the inner cavity of the crucible. The bottom surface of the flow guide tube abuts against the top surface of the filter tube, and the top surface of the flow guide tube abuts against the top surface of the inner cavity of the crucible. The inner cavity of the flow guide tube is connected to the inner cavity of the filter tube, and the inner diameter of the flow guide tube gradually decreases from bottom to top.

8. The eight-inch silicon carbide crystal production apparatus as described in claim 7, characterized in that, The guide tube is made of porous graphite.

9. The eight-inch silicon carbide crystal production apparatus as described in claim 1, characterized in that, The outer surface of the filter cartridge is coated.

10. An assembly method for an eight-inch silicon carbide crystal production apparatus, applied to the eight-inch silicon carbide crystal production apparatus as described in claim 7, comprising the following steps: S101: Turn the crucible 180° so that the bottom opening of the crucible faces upward; S102: Place the inverted guide tube into the crucible; S103: Place the inverted upper filter section, middle filter section and lower filter section into the crucible in sequence; S104: Place silicon carbide source powder with a particle size of 1mm-3mm into and fill the upper placement cavity, then place silicon carbide source powder with a particle size of 0.5mm-1mm into and fill the middle placement cavity, and then place silicon carbide source powder with a particle size of 0.2mm-0.5mm into and fill the lower placement cavity. S105: Secure the base plate to the crucible and heat-seal the bottom opening of the crucible.

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