Silicon carbide crystal growing apparatus

Abstract

The application discloses a silicon carbide crystal growing device, which comprises a crucible in the shape of a barrel for growing silicon carbide, and a heat preservation cylinder sleeved on the outer wall of the crucible. The heat preservation cylinder comprises a plurality of first carbon-based felt cylinders arranged at intervals along the wall thickness direction of the heat preservation cylinder, and second carbon-based felt cylinders between adjacent first carbon-based felt cylinders. The density of the first carbon-based felt cylinder is greater than that of the second carbon-based felt cylinder, and the wall thickness of the first carbon-based felt cylinder gradually increases along the direction towards the central axis of the heat preservation cylinder. Thus, the silicon carbide crystal growing device can reduce the loss of the heat preservation cylinder during the silicon carbide crystal growing process, maintain the stability of the synthesis temperature during the crystal growing process, and further improve the quality of the silicon carbide crystal.

Description

Technical Field

[0001] This application relates to the field of silicon carbide crystal growth technology, and more specifically, to a silicon carbide crystal growth apparatus. Background Technology

[0002] Silicon carbide (SiC), with its excellent physicochemical properties such as wide bandgap, high thermal conductivity, and high critical breakdown electric field strength, exhibits significant technological advantages in high-temperature, high-frequency, and high-power electronic devices, and is widely used in fields such as rail transportation, smart grids, 5G communications, and aerospace. In particular, transistors fabricated on semi-insulating silicon carbide substrates show significantly higher power density than gallium arsenide (GaAs) microwave components in the 10GHz band, making them of significant application value in high-end electronic devices.

[0003] It should be noted that the above statements are only used to provide background information related to this application and do not necessarily constitute prior art. Utility Model Content

[0004] In a first aspect of this application, a silicon carbide crystal growth apparatus is provided, comprising: a crucible, the crucible being barrel-shaped and used for growing silicon carbide; and a heat-insulating cylinder, the heat-insulating cylinder being sleeved on the outer wall of the crucible; the heat-insulating cylinder comprising a plurality of first carbon-based felt cylinders spaced apart along the wall thickness direction of the heat-insulating cylinder, and second carbon-based felt cylinders located between adjacent first carbon-based felt cylinders; the density of the first carbon-based felt cylinders is greater than the density of the second carbon-based felt cylinders; and the wall thickness of the first carbon-based felt cylinders gradually increases along the direction toward the central axis of the heat-insulating cylinder.

[0005] This application has at least the following technical effects: the high-density first carbon-based felt tube provides structural support for the low-density second carbon-based felt tube to improve the structural stability of the insulation tube; secondly, the high-density first carbon-based felt tube forms a physical barrier with its dense structure of low porosity, preferentially resisting hydrogen corrosion; the low-density second carbon-based felt tube uses its high-porosity structure to construct an air insulation layer to maintain the insulation performance of the crystal growth device; thus, the first carbon-based felt tube and the second carbon-based felt tube work together to form a composite functional system of "corrosion resistance-insulation". Meanwhile, the wall thickness of the first carbon-based felt tube gradually increases along the central axis of the insulation tube. This matches the higher hydrogen partial pressure and gaseous substance concentration characteristics of the inner side of the insulation tube (near the crucible) due to high temperature. The inner first carbon-based felt tube has more corrosion allowance to compensate for the faster corrosion rate under high temperature conditions, thereby reducing the difference in corrosion loss among the layers of the first carbon-based felt tube and making the expected corrosion life of each layer of the first carbon-based felt tube more consistent. This reduces the sharp drop in the insulation performance of the insulation tube caused by premature corrosion penetration of the inner first carbon-based felt tube, which exposes the second carbon-based felt tube. Therefore, the silicon carbide crystal growth apparatus of this application can reduce the loss of the insulation tube and maintain the stability of the synthesis temperature during the crystal growth process, thereby improving the quality of silicon carbide crystals.

[0006] In some embodiments, the wall thickness of the second carbon-based felt tube gradually decreases along the direction towards the central axis of the insulation tube. This gradient design, with thinner walls for easy replacement in high-temperature zones and thicker walls for longer lifespan in low-temperature zones, effectively reduces production costs by matching the corrosion and wear requirements of different areas.

[0007] In some embodiments, the first carbon-based felt tubes near the inner side of the crucible are fitted against the outer wall of the crucible, with two or more first carbon-based felt tubes and one or more second carbon-based felt tubes. Thus, the first carbon-based felt tubes can preferentially resist hydrogen corrosion; and the presence of two or more first carbon-based felt tubes creates a multi-level anti-corrosion protection system, further improving the corrosion resistance of the insulation tube. Simultaneously, the presence of one or more second carbon-based felt tubes, located between two adjacent first carbon-based felt tubes, utilizes the high-strength support structure of the first carbon-based felt tubes to wrap and support the second carbon-based felt tubes, effectively improving the structural stability of the second carbon-based felt tubes at high temperatures, thereby enhancing the structural stability of the insulation tube.

[0008] In some embodiments, the number of first carbon-based felt tubes is 5, and the wall thickness of the first carbon-based felt tubes along the direction toward the central axis of the insulation cylinder is successively: 5mm-9mm, 6mm-10mm, 8mm-12mm, 10mm-14mm, 13mm-17mm; and / or, the number of second carbon-based felt tubes is 4, and the wall thickness of the second carbon-based felt tubes along the direction toward the central axis of the insulation cylinder is successively: 18mm-22mm, 14mm-16mm, 13mm-15mm, 8mm-12mm.

[0009] In some embodiments, the minimum distance between adjacent first carbon-based felt tubes is H, and the wall thickness of the second carbon-based felt tube is h, where 0 ≤ Hh ≤ 0.5 mm. Therefore, by controlling the dimension of Hh, it is convenient to assemble the second carbon-based felt tube and the gap between the second and first carbon-based felt tubes can be reduced, thereby improving the structural stability and thermal insulation performance of the insulation cylinder.

[0010] In some embodiments, the first carbon-based felt tube is a rigid carbon-based felt tube, and the second carbon-based felt tube is a soft carbon-based felt tube. The rigid carbon-based felt tube has a dense carbon network, which provides better resistance to hydrogen corrosion than the soft carbon-based felt tube; the soft carbon-based felt tube retains a loose fibrous structure, with air layers between the fibers forming low thermal conductivity channels. Therefore, the rigid carbon-based felt tube preferentially absorbs corrosion, while the soft carbon-based felt tube maintains the temperature of the crystal growth apparatus, further maintaining the stability of the synthesis temperature during crystal growth, thereby improving the quality of silicon carbide crystals.

[0011] In some embodiments, the second carbon-based felt tube includes a first connecting end arranged circumferentially and a second connecting end abutting against the first connecting end, the first connecting end and the second connecting end being sewn together by graphite rope. Therefore, the graphite rope sewing method is not limited by a fixed mold, and the size of the second carbon-based felt tube can be flexibly designed according to the size of the first carbon-based felt tube; at the same time, the flexible sewing process allows the second carbon-based felt tube to be adaptively fine-tuned during installation, thereby improving the assembly adaptability and reliability of the insulation tube.

[0012] In some embodiments, the first connecting end includes a first plane, the radial plane containing the intersection of the first plane and the inner wall of the second carbon-based felt cylinder and the radial plane containing the intersection of the first plane and the outer wall of the second carbon-based felt cylinder coincide; and / or, the first connecting end includes a first inclined surface, the radial plane containing the intersection of the first inclined surface and the inner wall of the second carbon-based felt cylinder and the radial plane containing the intersection of the first inclined surface and the outer wall of the second carbon-based felt cylinder have an included angle; and / or, the first connecting end includes a first boss, the second connecting end includes a second boss adapted to the first boss, and the first boss and the second boss are fitted together.

[0013] In some embodiments, the first carbon-based felt tube and the second carbon-based felt tube have equal lengths along the central axis of the insulation tube. This allows for the maintenance of the structural stability of the insulation tube and the stability of the synthesis temperature during silicon carbide crystal growth.

[0014] In some embodiments, the silicon carbide crystal growth apparatus further includes: a graphite cap located at the open end of the crucible; the outer diameter of the graphite cap is the same as the inner diameter of the insulation cylinder; a top carbon felt located on the side of the graphite cap away from the crucible; the outer diameter of the top carbon felt is the same as the inner diameter of the insulation cylinder; and the end of the top carbon felt away from the graphite cap is flush with the first carbon-based felt cylinder. This improves the sealing capability of the crystal growth apparatus, reducing the leakage of high-temperature gases from the top. Attached Figure Description

[0015] The above and / or additional aspects and advantages of this application will become apparent and readily understood from the description of the embodiments taken in conjunction with the following drawings, in which:

[0016] Figure 1 This is a schematic diagram of the silicon carbide crystal growth apparatus in one embodiment of this application.

[0017] Figure 2 This is a schematic diagram of the structure of the heat-insulating cylinder in one embodiment of this application.

[0018] Figure 3 This is an exploded view of the insulation cylinder according to one embodiment of this application.

[0019] Figure 4 This is a schematic diagram of the structure of the second carbon-based felt tube in one embodiment of this application.

[0020] Figure 5 This is a schematic diagram of the structure of the second carbon-based felt tube in one embodiment of this application.

[0021] Figure 6 This is a schematic diagram of the structure of the second carbon-based felt tube in one embodiment of this application.

[0022] Figure 7 This is a line graph showing the change of synthesis temperature over time in Example 1.

[0023] Figure 8 This is a line graph showing the change of synthesis temperature over time in Comparative Example 1.

[0024] Explanation of reference numerals in the attached figures:

[0025] 1. First carbon-based felt tube; 2. Second carbon-based felt tube; 21. First connecting end; 22. Second connecting end; 3. Crucible; 4. Graphite cover; 5. Top carbon felt; 6. Graphite rope. Detailed Implementation

[0026] The embodiments of this application are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this application, and should not be construed as limiting this application.

[0027] Commonly used silicon carbide crystal growth devices mainly include heating components and insulation components. The heating components include graphite-based components such as graphite crucible 3 and graphite cover 4, while the insulation components include carbon-based soft felt. The carbon-based soft felt is wrapped around the outer wall of the graphite crucible 3 in a winding manner to form a thermal insulation structure.

[0028] The growth temperature of silicon carbide crystals typically exceeds 2200℃. Under these conditions, carbon-based soft felt rapidly caking and pulverizing due to the high temperature, causing a sharp decline in the thermal insulation performance of the insulation components. Especially during the preparation of semi-insulating silicon carbide substrates and high-purity silicon carbide powder, the hydrogen gas introduced in the process is highly corrosive to the carbon-based soft felt, accelerating its thermal insulation performance degradation. Simultaneously, from a heat transfer mechanism perspective, the anisotropy of heat conduction in the thermal field and the heat dissipation effect of the porous structure of the carbon-based soft felt further contribute to this degradation. The seams and interlayer gaps of carbon-based soft felt form a relatively low-temperature zone. Hydrogen and gaseous substances volatilized from the thermal field (such as silicon carbide vapor and graphite decomposition products) permeate into the micropores and interlayer gaps of the carbon-based soft felt with the process gas flow, reacting with the carbon-based soft felt and accelerating the caking and pulverization in this area. This further exacerbates the degradation of the thermal insulation performance of the carbon-based soft felt, leading to fluctuations in the growth temperature of semi-insulating silicon carbide crystals and the synthesis temperature of high-purity silicon carbide powder, thus affecting the consistency of silicon carbide crystals. Therefore, maintaining the stability of the synthesis temperature during crystal growth becomes particularly critical.

[0029] In a first aspect of this application, a silicon carbide crystal growth apparatus is provided, specifically, referring to... Figure 1 The device includes: a crucible 3, which is barrel-shaped and used for growing silicon carbide; an insulation cylinder, which is fitted onto the outer wall of the crucible 3; the insulation cylinder includes a plurality of first carbon-based felt cylinders 1 arranged at intervals along the wall thickness direction of the insulation cylinder, and second carbon-based felt cylinders 2 located between adjacent first carbon-based felt cylinders 1; the density of the first carbon-based felt cylinders 1 is greater than the density of the second carbon-based felt cylinders 2; the wall thickness of the first carbon-based felt cylinders 1 gradually increases along the direction toward the central axis of the insulation cylinder.

[0030] In this application, the high-density first carbon-based felt tube 1 provides structural support for the low-density second carbon-based felt tube 2 to improve the structural stability of the insulation tube; secondly, the high-density first carbon-based felt tube 1 forms a physical barrier with its dense structure of low porosity, preferentially resisting hydrogen corrosion; the low-density second carbon-based felt tube 2 uses its high-porosity structure to construct an air insulation layer to maintain the insulation performance of the crystal growth device; thus, the first carbon-based felt tube 1 and the second carbon-based felt tube 2 work together to form a composite functional system of "corrosion resistance-insulation". Meanwhile, the wall thickness of the first carbon-based felt tube 1 gradually increases along the direction towards the central axis of the insulation tube, which can match the higher hydrogen partial pressure and gaseous substance concentration characteristics of the inner side of the insulation tube (near the crucible 3) due to high temperature. The inner first carbon-based felt tube 1 has more corrosion margin to compensate for the faster corrosion rate under high temperature environment, so as to reduce the difference in corrosion loss of each layer of the first carbon-based felt tube 1, and make the expected corrosion life of each layer of the first carbon-based felt tube 1 more consistent, so as to reduce the sudden drop in the heat insulation performance of the insulation tube caused by the premature corrosion penetration of the inner first carbon-based felt tube 1 and the exposure of the second carbon-based felt tube 2.

[0031] Therefore, the silicon carbide crystal growth apparatus of this application can reduce the wear of the insulation cylinder and maintain the stability of the synthesis temperature during the silicon carbide crystal growth process, thereby improving the quality of silicon carbide crystals.

[0032] The structure of the silicon carbide crystal growth device will be further explained below.

[0033] In some embodiments, the first carbon-based felt tube 1 is a carbon-based hard felt tube, and the second carbon-based felt tube 2 is a carbon-based soft felt tube.

[0034] Carbon-based rigid felt tubes possess a dense carbon network, exhibiting superior resistance to hydrogen corrosion compared to carbon-based soft felt tubes. In contrast, carbon-based soft felt tubes retain a loose fibrous structure, with air layers between the fibers forming low thermal conductivity channels. Consequently, the carbon-based rigid felt tube preferentially absorbs corrosion, while the carbon-based soft felt tube maintains the temperature of the crystal growth apparatus, further ensuring the stability of the synthesis temperature during crystal growth and thus improving the quality of silicon carbide crystals.

[0035] In some embodiments, a first carbon-based felt tube 1 near the central axis of the crucible 3 is fitted to the outer wall of the crucible 3, and the number of first carbon-based felt tubes 1 is greater than or equal to 2, and the number of second carbon-based felt tubes 2 is greater than or equal to 1.

[0036] Therefore, the first carbon-based felt tube 1 can preferentially resist the corrosion of hydrogen; and the number of the first carbon-based felt tube 1 is ≥2, so that the insulation tube forms a multi-level anti-corrosion protection system, further improving the corrosion resistance of the insulation tube; at the same time, the number of the second carbon-based felt tube 2 is ≥1, and the second carbon-based felt tube 2 is located between two adjacent first carbon-based felt tubes 1. Relying on the high-strength support structure of the first carbon-based felt tube 1, it wraps around and supports the second carbon-based felt tube 2, effectively improving the structural stability of the second carbon-based felt tube 2 at high temperature, thereby improving the structural stability of the insulation tube.

[0037] As an example, the number of first carbon-based felt tubes 1 includes, but is not limited to, 2, 3, 4, 5, 6, 7 or 8; the number of second carbon-based felt tubes 2 includes, but is not limited to, 1, 3, 4, 5, 6 or 7.

[0038] It is understandable that the number of first carbon-based felt tubes 1 should be greater than the number of second carbon-based felt tubes 2.

[0039] In some embodiments, the wall thickness of the second carbon-based felt cylinder 2 gradually decreases along the direction toward the central axis of the insulation cylinder.

[0040] The temperature is higher inside the insulation cylinder (near the crucible 3), causing the caking and pulverization rate of the inner second carbon-based felt cylinder 2 to be higher than that of the outer side. The wall thickness of the second carbon-based felt cylinder 2 gradually decreases along the direction towards the central axis of the insulation cylinder, making the inner second carbon-based felt cylinder 2 a thin-walled structure. When the inner second carbon-based felt cylinder 2 reaches the corrosion threshold, only the thinner inner layer needs to be replaced; while the outer, thick-walled second carbon-based felt cylinder 2, being farther from the heat source, has a lower corrosion rate, allowing for a longer replacement cycle.

[0041] Therefore, by utilizing a gradient design that features thin walls for easy replacement in high-temperature zones and thick walls for long lifespan in low-temperature zones to match the corrosion and wear requirements of different areas, production costs can be effectively reduced.

[0042] In some embodiments, the number of first carbon-based felt tubes 1 is 5, and the wall thickness of the first carbon-based felt tubes 1 along the direction of the central axis toward the heat insulation tube is successively: 5mm-9mm, 6mm-10mm, 8mm-12mm, 10mm-14mm, and 13mm-17mm.

[0043] As an example, such as Figure 1 and Figure 2 As shown, along the direction toward the central axis of the insulation cylinder, the first carbon-based felt cylinder 1 includes a first carbon-based felt cylinder 1a, a first carbon-based felt cylinder 1b, a first carbon-based felt cylinder 1c, a first carbon-based felt cylinder 1d, and a first carbon-based felt cylinder 1e.

[0044] The wall thickness of the first carbon-based felt cylinder 1a can be 5mm, 5.5mm, 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, or a range of any two of the above values.

[0045] The wall thickness of the first carbon-based felt cylinder 1b can be 6mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, 9.5mm, 10mm, or a range of any two of the above values.

[0046] The wall thickness of the first carbon-based felt tube 1c can be 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm, 11.5mm, 12mm, etc., or a range consisting of any two of the above values.

[0047] The wall thickness of the first carbon-based felt tube 1d can be 10mm, 10.5mm, 11mm, 11.5mm, 12mm, 12.5mm, 13mm, 13.5mm, 14mm, or a range of any two of the above values.

[0048] The wall thickness of the first carbon-based felt cylinder 1e can be 13mm, 13.5mm, 14mm, 14.5mm, 15mm, 15.5mm, 16mm, 16.5mm, 17mm, etc., or a range consisting of any two of the above values.

[0049] In some embodiments, there are four second carbon-based felt tubes 2, and the wall thicknesses of the second carbon-based felt tubes 2 along the direction of the central axis toward the heat insulation tube are 18mm-22mm, 14mm-16mm, 13mm-15mm, and 8mm-12mm, respectively.

[0050] As an example, such as Figure 1 and Figure 2 As shown, along the direction of the central axis of the insulation cylinder, the second carbon-based felt cylinder 2 includes a second carbon-based felt cylinder 2a, a second carbon-based felt cylinder 2b, a second carbon-based felt cylinder 2c, and a second carbon-based felt cylinder 2d.

[0051] The wall thickness of the second carbon-based felt tube 2a can be 18mm, 18.5mm, 19mm, 19.5mm, 20mm, 20.5mm, 21mm, 21.5mm, 22mm, or a range of any two of the above values.

[0052] The wall thickness of the second carbon-based felt tube 2b can be 14mm, 14.5mm, 15mm, 15.5mm, 16mm, or any range of two of the above values.

[0053] The wall thickness of the second carbon-based felt cylinder 2c can be 13mm, 13.5mm, 14mm, 14.5mm, 15mm, or any range of two of the above values.

[0054] The wall thickness of the second carbon-based felt tube 2d can be 8mm, 8.5mm, 9mm, 9.5mm, 10mm, 10.5mm, 11mm, 11.5mm, 12mm, etc., or a range consisting of any two of the above values.

[0055] In this application, the wall thickness of the first carbon-based felt cylinder 1 refers to the radial distance from the inner surface to the outer surface of the first carbon-based felt cylinder 1; the wall thickness of the second carbon-based felt cylinder 2 refers to the radial distance from the inner surface to the outer surface of the second carbon-based felt cylinder 2.

[0056] In some embodiments, the minimum distance between adjacent first carbon-based felt cylinders 1 is H, and the wall thickness of the second carbon-based felt cylinder 2 is h, wherein 0 ≤ Hh ≤ 0.5 mm.

[0057] Therefore, by controlling the size of Hh, it is not only convenient to assemble the second carbon-based felt cylinder 2, but also to reduce the gap between the second carbon-based felt cylinder 2 and the first carbon-based felt cylinder 1, so as to improve the structural stability and thermal insulation performance of the insulation cylinder.

[0058] As an example, Hh can be 0, 0.1mm, 0.2mm, 0.3mm, 0.4mm, 0.5mm, etc., or a range consisting of any two of the above values.

[0059] In some embodiments, the first carbon-based felt tube 1 is formed by compression molding. Therefore, the first carbon-based felt tube 1 does not require physical stitching; that is, there are no seams on the first carbon-based felt tube 1, which further improves its resistance to hydrogen corrosion.

[0060] In some implementations, such as Figure 3 and Figure 4 As shown, the second carbon-based felt cylinder 2 includes a first connecting end 21 arranged circumferentially and a second connecting end 22 abutting against the first connecting end 21. The first connecting end 21 and the second connecting end 22 are sewn together by graphite rope 6. Therefore, the sewing method of the graphite rope 6 is not limited by a fixed mold, and the size of the second carbon-based felt cylinder 2 can be flexibly designed according to the size of the first carbon-based felt cylinder 1. At the same time, the flexible sewing process allows the second carbon-based felt cylinder 2 to be adaptively fine-tuned during installation, thereby improving the assembly adaptability and reliability of the insulation cylinder.

[0061] In some implementations, such as Figure 4 As shown, the first connecting end 21 includes a first plane, and the radial plane containing the intersection of the first plane and the inner wall of the second carbon-based felt cylinder 2 coincides with the radial plane containing the intersection of the first plane and the outer wall of the second carbon-based felt cylinder 2.

[0062] In some implementations, such as Figure 5 As shown, the first connecting end 21 includes a first inclined surface, and there is an angle between the radial plane containing the intersection of the first inclined surface and the inner wall of the second carbon-based felt cylinder 2 and the radial plane containing the intersection of the first inclined surface and the outer wall of the second carbon-based felt cylinder 2. Therefore, when the graphite rope 6 applies a tightening force to the second carbon-based felt cylinder 2 during the sewing process, it can reduce the stress concentration acting perpendicularly on the second carbon-based felt cylinder 2, thereby reducing the deformation generated during the sewing of the second carbon-based felt cylinder 2 and thus improving the structural stability of the insulation cylinder.

[0063] In some implementations, such as Figure 6 As shown, the first connecting end 21 includes a first boss, and the second connecting end 22 includes a second boss that matches the first boss. The first boss and the second boss are fitted together. Therefore, when the graphite rope 6 applies a fastening force to the second carbon-based felt cylinder 2 during the sewing process, it can reduce the stress concentration acting perpendicularly on the second carbon-based felt cylinder 2, thereby reducing the deformation generated during the sewing of the second carbon-based felt cylinder 2 and thus improving the structural stability of the insulation cylinder.

[0064] In some embodiments, the first carbon-based felt cylinder 1 and the second carbon-based felt cylinder 2 have equal lengths along the central axis of the insulation cylinder. This allows for the maintenance of the structural stability of the insulation cylinder and the stability of the synthesis temperature during the silicon carbide crystal growth process.

[0065] In some implementations, such as Figure 1 As shown, the silicon carbide crystal growth apparatus also includes a graphite cap 4, located at the open end of the crucible 3; the outer diameter of the graphite cap 4 is the same as the inner diameter of the insulation cylinder. This allows the crucible 3 to be sealed, reducing the leakage of high-temperature gases.

[0066] In some implementations, such as Figure 1 As shown, the silicon carbide crystal growth apparatus also includes a top carbon felt located on the side of the graphite cover 4 away from the crucible 3; the outer diameter of the top carbon felt is the same as the inner diameter of the insulation cylinder; the end of the top carbon felt away from the graphite cover 4 is flush with the first carbon-based felt cylinder 1. This improves the sealing capability of the crystal growth apparatus, reducing the leakage of high-temperature gas from the top.

[0067] Example

[0068] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0069] Example 1

[0070] Take a graphite crucible 3, and with the graphite crucible 3 as the center, sequentially connect a first carbon-based felt cylinder 1 (carbon-based hard felt cylinder) and a second carbon-based felt cylinder 2 (carbon-based soft felt cylinder). Specifically, as follows... Figure 1 and Figure 2 As shown, with the graphite crucible 3 as the center, from the inside out, the first carbon-based felt tube 1e, the second carbon-based felt tube 2d, the first carbon-based felt tube 1d, the second carbon-based felt tube 2c, the first carbon-based felt tube 1c, the second carbon-based felt tube 2b, the first carbon-based felt tube 1b, the second carbon-based felt tube 2a, and the first carbon-based felt tube 1a are sequentially nested.

[0071] The wall thicknesses of the first carbon-based felt cylinder 1a, the first carbon-based felt cylinder 1b, the first carbon-based felt cylinder 1c, the first carbon-based felt cylinder 1d, and the first carbon-based felt cylinder 1e are 7mm, 8mm, 10mm, 12mm, and 15mm, respectively; the wall thicknesses of the second carbon-based felt cylinder 2a, the second carbon-based felt cylinder 2b, the second carbon-based felt cylinder 2c, and the second carbon-based felt cylinder 2d are 20mm, 15mm, 15mm, and 10mm, respectively.

[0072] The assembled silicon carbide crystal growth apparatus was placed in a crystal growth furnace for the synthesis of high-purity silicon carbide powder. In the initial stage of high-purity silicon carbide powder synthesis, the initial synthesis temperature was raised to approximately 2300℃ under constant power conditions, while 20 sccm of hydrogen gas was introduced. The synthesis time was 30 hours. The synthesis temperature was recorded every 2 hours, and the line graph showing the change in synthesis temperature over time is shown below. Figure 7 As shown.

[0073] Depend on Figure 7 It can be seen that during the 30-hour synthesis time, the synthesis temperature of silicon carbide decreased from 2312.2℃ to 2289.2℃, with a total decrease temperature of 23℃.

[0074] Specifically, the temperature decay in the early stage of synthesis is faster than that in the middle stage. This is mainly because in the early stage, after hydrogen is introduced, it begins to corrode the first carbon-based felt cylinder 1 at high temperature, resulting in a faster temperature decay. In the middle stage, the corrosion reaction between hydrogen and the first carbon-based felt cylinder 1 reaches equilibrium, and the corrosion particles formed in the early stage form a protective layer to slow down the corrosion reaction, thereby slowing down the temperature decay. However, in the later stage of synthesis, due to the saturation of the reaction gas pressure in the crucible, some silicon carbide gas overflows from the crucible 3, causing secondary corrosion of the first carbon-based felt cylinder 1, which accelerates the temperature decay.

[0075] Comparative Example 1

[0076] The difference between Comparative Example 1 and Example 1 is that Comparative Example 1 includes 9 layers of a second carbon-based felt tube 2 (carbon-based soft felt tube) with a thickness of 10 mm.

[0077] The line graph showing the change of synthesis temperature over time in Comparative Example 1 is shown below. Figure 8As shown.

[0078] Depend on Figure 8 It can be seen that during the 30-hour synthesis time, the synthesis temperature of silicon carbide decreased from 2307.5℃ to 2253.5℃, with a total decrease temperature of 54℃.

[0079] Specifically, in Comparative Example 1, the temperature decay during the entire synthesis process was accelerated. The temperature decay rate in the early stage of synthesis was approximately 0.4℃ / h, in the middle stage it was approximately 1.5℃ / h, and in the later stage it reached 3.9℃ / h. As the carbon-based soft felt tube was continuously eroded by hydrogen and silicon carbide gases, the gaps at the joints of the carbon-based soft felt tube became larger and larger, resulting in a lower temperature at that location. Under the influence of the temperature gradient, more hydrogen and silicon carbide gases accumulated in this area, accelerating the erosion of the carbon-based soft felt tube and causing the temperature decay of the synthesis to accelerate simultaneously.

[0080] After crystal growth, the second carbon-based felt tube 2 of Example 1 and Comparative Example 1 were taken out for observation. Among them, the innermost second carbon-based felt tube 2 of Example 1 showed slight corrosion and improved shrinkage; if it is to be used again, only the innermost second carbon-based felt tube 2 needs to be replaced.

[0081] The second carbon-based felt tube 2 in Comparative Example 1 showed more severe caking and corrosion than that in Example 1, and most of the second carbon-based felt tube 2 would need to be replaced if reused, which is not conducive to cost reduction and efficiency improvement.

[0082] The lifespan of the crystal growth devices in Example 1 and Comparative Example 1 was tested. The lifespan of the crystal growth device in Example 1 was 1.5-2 times longer than that in Comparative Example 1.

[0083] In the description of this application, "first feature" and "second feature" may include one or more of the features.

[0084] In the description of this application, "multiple" means two or more.

[0085] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of this application. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0086] Although embodiments of this application have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of this application, the scope of which is defined by the claims and their equivalents.

Claims

1. A silicon carbide crystal growth apparatus, characterized in that, include: A crucible, which is barrel-shaped, is used for growing silicon carbide; A heat-insulating cylinder, which is fitted onto the outer wall of the crucible; The insulation cylinder includes a plurality of first carbon-based felt cylinders spaced apart along the wall thickness direction of the insulation cylinder, and a second carbon-based felt cylinder located between adjacent first carbon-based felt cylinders; the density of the first carbon-based felt cylinder is greater than the density of the second carbon-based felt cylinder. The wall thickness of the first carbon-based felt tube gradually increases along the direction toward the central axis of the insulation tube.

2. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The wall thickness of the second carbon-based felt tube gradually decreases along the direction towards the central axis of the insulation tube.

3. The silicon carbide crystal growth apparatus according to claim 2, characterized in that, The first carbon-based felt tube, which is close to the inner side of the crucible, is fitted to the outer wall of the crucible. The number of the first carbon-based felt tube is greater than or equal to 2, and the number of the second carbon-based felt tube is greater than or equal to 1.

4. The silicon carbide crystal growth apparatus according to claim 3, characterized in that, The number of the first carbon-based felt tubes is five, and along the central axis toward the insulation cylinder, the wall thicknesses of the first carbon-based felt tubes are successively: 5mm-9mm, 6mm-10mm, 8mm-12mm, 10mm-14mm, and 13mm-17mm; and / or, The number of the second carbon-based felt tubes is 4, and the wall thicknesses of the second carbon-based felt tubes along the central axis direction toward the heat insulation tube are 18mm-22mm, 14mm-16mm, 13mm-15mm, and 8mm-12mm respectively.

5. The silicon carbide crystal growth apparatus according to claim 1, characterized in that, The minimum distance between adjacent first carbon-based felt tubes is H, and the wall thickness of the second carbon-based felt tube is h, where 0 ≤ Hh ≤ 0.5 mm.

6. The silicon carbide crystal growth apparatus according to any one of claims 1-5, characterized in that, The first carbon-based felt tube is a carbon-based hard felt tube, and the second carbon-based felt tube is a carbon-based soft felt tube.

7. The silicon carbide crystal growth apparatus according to any one of claims 1-5, characterized in that, The second carbon-based felt tube includes a first connecting end arranged circumferentially and a second connecting end that abuts against the first connecting end, the first connecting end and the second connecting end being sewn together by graphite rope.

8. The silicon carbide crystal growth apparatus according to claim 7, characterized in that, The first connecting end includes a first plane, wherein the radial plane containing the intersection of the first plane and the inner wall of the second carbon-based felt cylinder coincides with the radial plane containing the intersection of the first plane and the outer wall of the second carbon-based felt cylinder; and / or, The first connecting end includes a first inclined surface, and there is an included angle between the radial plane containing the intersection of the first inclined surface and the inner wall of the second carbon-based felt cylinder and the radial plane containing the intersection of the first inclined surface and the outer wall of the second carbon-based felt cylinder; and / or, The first connecting end includes a first protrusion, and the second connecting end includes a second protrusion adapted to the first protrusion, wherein the first protrusion and the second protrusion are fitted together.

9. The silicon carbide crystal growth apparatus according to any one of claims 1-5, characterized in that, The first carbon-based felt tube and the second carbon-based felt tube have the same length along the central axis of the insulation tube.

10. The silicon carbide crystal growth apparatus according to any one of claims 1-5, characterized in that, Also includes: A graphite cap is located at the open end of the crucible; the outer diameter of the graphite cap is the same as the inner diameter of the insulation cylinder; The top carbon felt is located on the side of the graphite cover away from the crucible; the outer diameter of the top carbon felt is the same as the inner diameter of the insulation cylinder; the end of the top carbon felt away from the graphite cover is flush with the first carbon-based felt cylinder.

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