Device and method for increasing longitudinal growth thickness of silicon carbide single crystal
By using a split crucible and a multi-heater structure, the problem of limited thickness in the vertical growth of silicon carbide single crystals was solved, enabling efficient and low-cost SiC ingot growth, thus improving production efficiency and product quality.
Patent Information
- Application Number
- CN202511402281.8
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-28
- Publication Date
- 2025-11-14
AI Technical Summary
Existing technologies are insufficient to effectively increase the vertical growth thickness of silicon carbide single crystals, which limits the development of the SiC industry. Furthermore, traditional methods increase equipment costs and control difficulties.
The system employs a split crucible and multi-heater structure, which allows for flexible adjustment of the crucible cylinder and heater positions to control axial and radial temperature gradients, increase feed rate and growth rate, and use TaC coating to reduce graphite corrosion.
This technology enables the increase of longitudinal growth thickness of silicon carbide single crystals under low stress conditions, reduces crack rate, improves production efficiency and crystal uniformity, and extends equipment lifespan.
Smart Images
Figure CN120945490A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of SiC semiconductor crystal growth technology, and in particular to an apparatus and method for increasing the longitudinal growth thickness of silicon carbide single crystals. Background Technology
[0002] Silicon carbide (SiC) single crystals, as a third-generation semiconductor material, possess numerous advantages over first- and second-generation semiconductor materials, including a wider bandgap, higher thermal conductivity, faster carrier migration speed, stronger critical breakdown field, stronger radiation resistance, lower coefficient of thermal expansion, and higher hardness. Based on these superior properties, SiC is widely used in photovoltaics, aerospace, new energy vehicles, and information communication fields.
[0003] Currently, the main methods for SiC crystal preparation include the physical vapor transport method (PVT), high-temperature chemical vapor deposition (CVD), and liquid-phase deposition (LPE). Among these, the commercially available SiC crystal growth method both domestically and internationally primarily employs the physical vapor transport method. This method utilizes a high-temperature, low-pressure environment to induce a solid-gas-solid recrystallization process in a graphite crucible. Specifically, the silicon carbide powder decomposes into gaseous substances such as silicon atoms, SiC2 molecules, and Si2C molecules at high temperatures. Driven by a temperature gradient, these gaseous substances are transported from the high-temperature region (powder) to the low-temperature region (seed crystal), and their atoms arrange themselves systematically on the carbon surface of the seed crystal according to its crystal form, causing the crystal to gradually thicken and grow into a solid.
[0004] SiC ingots.
[0005] Currently, the main factors restricting the rapid development of the SiC industry are high cost and low production capacity. The most effective way to reduce costs and increase production capacity is to increase the thickness of the SiC ingot during longitudinal growth. Based on the crystal growth principle of PVT and the growth characteristics of SiC, it is known that increasing the thickness of the SiC ingot during longitudinal growth requires addressing the following issues: increasing the amount of raw material fed into the SiC crystal growth system; maintaining the same or similar axial temperature gradient between the raw material and the seed crystal; and reducing the increase in stress within the crystal caused by the increased radial temperature gradient.
[0006] Currently, the main domestic solution to the problem of limited vertical thickness of SiC ingots is to increase the number of induction coils or graphite heaters on the side of the crucible to increase the effective heating area within the crucible, thereby increasing the amount of material fed into the crucible. However, this method not only increases the height of the crystal growth equipment and raises manufacturing costs, but also the increase in the amount of material fed into the crucible remains limited, and temperature gradient control within the crucible becomes more difficult with the increase in the number of induction coils / heaters. Furthermore, the increase in SiC ingot thickness achieved using these methods is still limited, with the vertical thickness only increasing from <30mm to 30-50mm. Summary of the Invention
[0007] The purpose of this invention is to overcome the shortcomings of the prior art and provide an apparatus and method for increasing the longitudinal growth thickness of silicon carbide single crystals, so as to at least achieve the goal of increasing the longitudinal growth thickness of silicon carbide single crystals under low stress and high crystal growth rate conditions.
[0008] The objective of this invention is achieved through the following technical solution:
[0009] An apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals includes a split crucible and a first heater disposed directly above the split crucible.
[0010] The split-type crucible includes a crucible body, a crucible top cover, and a crucible bottom cover; the crucible body includes multiple vertically overlapping crucible cylinders, a first porous graphite sheet and a second heater disposed in the lower part of the crucible cylinder and distributed vertically, and a second porous graphite sheet movably disposed in the upper part of the crucible cylinder.
[0011] The bottom wall of the crucible top cover is detachably provided with a graphite shoulder tube, which includes a cylindrical tube and a conical tube disposed at its bottom end.
[0012] Preferably, the inner wall of the graphite shoulder tube is provided with a TaC coating.
[0013] Preferably, the distance between the first heater and the crucible top cover is 25-35 mm.
[0014] Preferably, adjacent crucible cylinders are threaded together, and the graphite shoulder cylinder is threaded together with the crucible top cover.
[0015] Preferably, both the first heater and the second heater are provided with vents, and the first heater and the second heater are disc structures, ring structures, or mosquito coil structures, etc.
[0016] Furthermore, to achieve the above objectives, the present invention also provides a method for increasing the longitudinal growth thickness of silicon carbide single crystals, which is implemented based on the aforementioned apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals, comprising the following steps:
[0017] S1. Attach a SiC seed crystal to the side of the crucible top cover near the crucible body, and then connect the graphite shoulder tube to the crucible top cover.
[0018] SiC powder, SiC carbide powder, and a second porous graphite sheet are placed sequentially from bottom to top on a first porous graphite sheet in one of the crucibles; SiC powder and a second porous graphite sheet are placed sequentially from bottom to top on a first porous graphite sheet in the remaining crucibles.
[0019] S2. First, connect multiple different crucible cylinders vertically and cover them with crucible top covers. Then, place the assembled crucible inside the crystal growth system. Next, install the first heater directly above the crucible and inside the crystal growth system. Finally, place the crucible and the crystal growth system together into the crystal growth furnace.
[0020] The crystal growth system includes a graphite support barrel and a graphite insulation barrel arranged sequentially from the inside to the outside; the uppermost crucible barrel is a crucible barrel containing SiC carbide powder; and a graphite insulation barrel top cover is provided at the top of the graphite insulation barrel.
[0021] S3. Under negative pressure and inert gas conditions, first turn on the first heater and the uppermost second heater. After crystal growth for a certain period of time, turn off the second heater and turn on the adjacent second heater below. After crystal growth for a certain period of time, turn off the second heater and turn on the adjacent second heater below. Continue in this manner until crystal growth in the lowermost crucible is complete.
[0022] The temperature of the multiple second heaters increases gradually from top to bottom.
[0023] S4. After crystal growth is complete, slowly lower the temperature inside the crystal growth furnace to room temperature, and at the same time introduce nitrogen gas into the crystal growth furnace to atmospheric pressure; then remove the first heater, then take out the crucible, and after opening the crucible top cover, SiC ingots with a longitudinal thickness greater than 100mm can be obtained on the surface of the crucible top cover.
[0024] Preferably, a 200μm thick graphite paper is disposed between the SiC seed crystal and the crucible top cover.
[0025] Preferably, the thickness of the SiC carbide powder is 10 mm.
[0026] Preferably, the heating temperature of the first heater is 2100-2150℃, the heating temperature of the uppermost second heater is 2300-2350℃, and the temperature difference between adjacent second heaters is 100-150℃.
[0027] Preferably, the particle size of the SiC powder is 8 to 20 mesh.
[0028] Compared with the prior art, the present invention has the following advantages:
[0029] 1. Increased flexibility: Compared with traditional fixed crucibles, the detachable crucible can be adjusted according to the size requirements of the ingot, making it more flexible to use and effectively improving production efficiency.
[0030] 2. Reduce crack rate: By using multiple heaters (first and second types) to reduce the temperature difference in the radial direction inside the crucible, cracking caused by excessive internal stress due to temperature fluctuations is reduced, thereby improving the production qualification rate.
[0031] 3. Improve product uniformity: Compared with traditional heaters, the first and second heaters are set above and below the material respectively, which reduces the temperature difference between the core and the outside of the material and prevents SiC ingots from cracking due to excessive differences between the inside and outside.
[0032] 4. Increased production efficiency: Compared with traditional sidewall heaters, the first and second heaters can effectively increase the heating area and improve the crystal growth rate of SiC ingots, which can reach up to 0.5 to 1 mm / h according to tests.
[0033] 5. Extended lifespan: Adding SiC carbide powder to the uppermost crucible of the crystal growth apparatus allows it to react with the carbon powder as silicon gas diffuses upwards, effectively preventing corrosion of the graphite crucible. Simultaneously, it ensures a 1:1 silicon-to-carbon ratio, leading to better silicon carbide crystal formation. Based on this principle, as silicon gas diffuses upwards from the lower crucible, it reacts with the carbon powder in the adjacent upper crucible.
[0034] 6. In this invention, the temperature of the first heater is consistently maintained at 2100–2150°C, while the temperature of the second heater is maintained above 2300°C. Furthermore, as the number of crucible tubes increases, the temperature of the second heater also increases sequentially according to its location; for each additional crucible tube, the temperature of the bottom heater increases by 100–150°C. This ensures both the axial temperature gradient between the raw material and the seed crystal and that the radial temperature gradient remains unchanged during the ingot growth process. Moreover, the amount of material fed can be maximized based on the height limit of the crystal growth equipment, achieving maximum utilization of the furnace space and silicon carbide raw material. Attached Figure Description
[0035] Figure 1 This is a cross-sectional view of the crucible from the front view during Zhang Jing's operation;
[0036] Figure 2 This is a top view of the structure of the first heater or the second heater.
[0037] Figure 3 A schematic diagram of the crucible cylinder viewed from the side.
[0038] In the figure: 1-Crucible top cover, 2-Crucible cylinder, 3-First porous graphite sheet, 4-First heater, 5-Second heater, 6-Second porous graphite sheet, 7-Graphite shoulder support cylinder, 8-Graphite support cylinder, 9-Graphite insulation cylinder, 10-SiC seed crystal, 11-SiC powder, 12-SiC carbide powder. Detailed Implementation
[0039] Example 1
[0040] A device for increasing the longitudinal growth thickness of silicon carbide single crystals, such as... Figure 1 As shown, it includes a split-type crucible and a first heater 4 disposed directly above the split-type crucible; the split-type crucible includes a crucible body, a crucible top cover 1, and a crucible bottom cover; as shown... Figure 1 As shown, the crucible body includes multiple vertically overlapping crucible cylinders 2, a first porous graphite sheet 3 and a second heater 5 disposed in the lower part of the crucible cylinder 2 and distributed vertically, and a second porous graphite sheet 6 movably disposed in the upper part of the crucible cylinder 2; the bottom wall of the crucible top cover 1 is detachably provided with a graphite shoulder cylinder 7, which includes a cylindrical cylinder and a conical cylinder disposed at its bottom end. Furthermore, the inner wall of the graphite shoulder cylinder 7 is provided with a TaC coating, which can ensure that the silicon carbide ingot grows with the same diameter while its longitudinal thickness increases. In this invention, the first porous graphite sheet 3 and the second porous graphite sheet 6 can play a role in heat preservation. The axial temperature gradient between the SiC powder 11 and the SiC crystal growth surface can be slightly adjusted according to the thickness of the first and second porous graphite sheets. At the same time, the first porous graphite sheet 3 can also support the SiC powder 11.
[0041] Furthermore, the distance between the first heater 4 and the crucible top cover 1 is 25-35mm. Furthermore, adjacent crucible cylinders 2 are threaded together, and the graphite shoulder cylinder 7 is threaded together with the crucible top cover 1. Furthermore, both the first heater 4 and the second heater 5 are provided with vents (to allow silicon gas to pass through), and the first heater 4 and the second heater 5 can be a disc structure (e.g., Figure 2 As shown, embodiments 1-3 all use this structure), a ring structure, or a mosquito coil structure, etc. In actual implementation, the first porous graphite sheet 3 and the second heater 5 in each crucible cylinder 2 can be fixedly installed in the crucible cylinder 2, or they can be movably installed in the crucible cylinder 2. If they are movably installed in the crucible cylinder 2, two rings of steps need to be set on the inner wall of the crucible cylinder 2 to facilitate the placement of the first porous graphite sheet 3 and the second heater 5. However, regardless of the method used, it is best to install both in the crucible cylinder 2 in advance. In the following specific embodiments, the crucible cylinder 2 is pre-installed with the first porous graphite sheet 3 (thickness is 10mm, and the pore size needs to be set to ensure that the SiC powder 11 does not fall) and the second heater 5. In addition, as Figure 3As shown, each of the crucible cylinders 2 has holes on its sidewalls to facilitate the passage of the electrode feet of the second heater 5.
[0042] The specific implementation method is as follows:
[0043] S1. Placing the SiC seed crystal 10: A 500μm thick SiC seed crystal 10 is bonded to the surface of the crucible top cover 1, with the C polarity face of the seed crystal facing the SiC powder 11. In actual implementation, a SiC seed crystal 10 support plate is provided on the crucible top cover 1, such as... Figure 1 As shown. In addition, in actual implementation, a 200μm thick graphite paper (not shown in the figure) is required as a transition layer between the SiC seed crystal 10 and the crucible top cover 1.
[0044] S2. Placement of graphite shoulder support cylinder 7: The cylindrical height of graphite shoulder support cylinder 7 is 120mm, the conical angle is 30°, and the height is 20mm. The inner wall of graphite shoulder support cylinder 7 is coated with TaC (not shown in the figure). Graphite shoulder support cylinder 7 is connected to crucible top cover 1 by threads.
[0045] S3. Feeding: In the uppermost crucible cylinder 2, SiC powder 11 (weighing 1.5kg, with a thickness of 40-50mm inside the crucible and a particle size of 8-20 mesh), SiC carbide powder 12 (with a flat thickness of 10mm), and the second porous graphite sheet 6 (with a thickness of 4mm) are placed sequentially from bottom to top. In the remaining crucible cylinder 2, SiC powder 11 (weighing 1.5kg, with a thickness of 40-50mm inside the crucible and a particle size of 8-20 mesh) and the second porous graphite sheet 6 are placed sequentially from bottom to top.
[0046] S4. Install the crucible: (e.g.) Figure 1 As shown, multiple crucible cylinders 2 are connected by threads and vertically overlapped. After assembly, the entire crucible is placed as shown in the image. Figure 1 The crystal growth system shown contains a graphite support container 8 and a graphite insulation container 9 arranged sequentially from the inside to the outside. Then, the first heater 4 is placed 30 mm directly above the crucible, and then the crucible and the crystal growth system are placed together in the crystal growth furnace.
[0047] S5, SiC ingot growth: First, the crystal growth furnace is evacuated to 10... -3Pa, then a mixture of argon and nitrogen gas is introduced into the crystal growth furnace to 500 Pa, the heating power is turned on, the temperature of the first heater 4 is controlled at 2130℃, the temperature of the uppermost second heater 5 (i.e., the first-stage second heater 5) is controlled at 2300℃, after crystal growth for 100 hours, the second heater 5 is turned off, and the adjacent second heater 5 below (i.e., the second-stage second heater 5) is turned on, the temperature of the second heater 5 is controlled at 2400℃, that is, for each stage of the second heater 5 turned on, the temperature of the second heater 5 increases by 100℃, and so on, so that the SiC powder 11 in different stages of the crucible 2 is decomposed and sublimated.
[0048] S6. Taking SiC ingots: After the crystal growth process is completed, slowly lower the temperature inside the crystal growth furnace to room temperature, and at the same time introduce nitrogen gas into the crystal growth furnace to atmospheric pressure. First remove the first heater 4, then take out the crucible. After opening the crucible top cover 1, a SiC ingot with a longitudinal thickness greater than 100mm can be obtained on the crucible top cover 1.
[0049] Example 2
[0050] A method for increasing the longitudinal growth thickness of silicon carbide single crystals, based on the apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals described in Example 1, includes the following steps:
[0051] S1. Attach a 500μm thick SiC seed crystal 10 (e.g., ...) to the side of the crucible top cover 1 closest to the crucible body. Figure 1 As shown, in actual implementation, a SiC seed crystal 10 support plate can also be set at the place where the SiC seed crystal 10 is pasted on the crucible top cover 1. The C polarity surface of the SiC seed crystal 10 faces the direction of the SiC powder 11. A graphite paper with a thickness of 200μm is set between the SiC seed crystal 10 and the crucible top cover 1. Then, the graphite shoulder tube 7 is threaded onto the crucible top cover 1. The cylindrical tube of the graphite shoulder tube 7 has a height of 120mm, and the conical tube at the bottom has an angle of 30° and a height of 20mm. The inner wall of the graphite shoulder tube 7 is coated with a TaC coating (not shown in the figure).
[0052] In one of the crucible tubes 2 (i.e., the uppermost crucible tube 2, referred to here as the primary crucible tube 2), SiC powder 11 (weighing 1.5 kg, with a particle size of 8-20 mesh), SiC carbide powder 12 (with a thickness of 10 mm) and a second porous graphite sheet 6 are placed sequentially from bottom to top on the first porous graphite sheet 3; in the remaining crucible tubes 2, SiC powder 11 (weighing 1.5 kg, with a particle size of 8-20 mesh) and a second porous graphite sheet 6 are placed sequentially from bottom to top.
[0053] It is worth noting that the crucible cylinder 2 is pre-installed with a first porous graphite sheet 3 (10mm thick, the pore size needs to be set to ensure that the SiC powder 11 does not fall) and a second heater 5.
[0054] S2. First, vertically overlap multiple crucible cylinders 2 using threaded connections, and then cover them with the crucible top cover 1. Next, place the assembled crucible inside the crystal growth system, and then install the first heater 4 directly above the crucible within the crystal growth system. Finally, place the crucible and crystal growth system together into the crystal growth furnace. Figure 1 As shown, the crystal growth system includes a graphite support barrel 8 and a graphite insulation barrel 9 (which is essentially a graphite felt for insulation, and can be made of various materials such as long fiber hard felt, long fiber soft felt and short fiber soft felt) arranged sequentially from the inside to the outside.
[0055] S3. First, evacuate the crystal growth furnace to 10°C. -3 Pa, then a mixture of argon and nitrogen gas is introduced into the crystal growth furnace to 500 Pa, the heating power is turned on, the temperature of the first heater 4 is controlled at 2130℃, the temperature of the uppermost second heater 5 (i.e., the first-stage second heater 5) is controlled at 2300℃, after crystal growth for 100 hours, the second heater 5 is turned off, and the adjacent second heater 5 below (i.e., the second-stage second heater 5) is turned on, the temperature of the second heater 5 is controlled at 2400℃, that is, for each stage of the second heater 5 turned on, the temperature of the second heater 5 increases by 100℃, and so on, so that the SiC powder 11 in different stages of the crucible 2 is decomposed and sublimated.
[0056] S4. After crystal growth is completed, slowly lower the temperature inside the crystal growth furnace to room temperature, and at the same time introduce nitrogen gas into the crystal growth furnace to atmospheric pressure; then remove the first heater 4, then take out the crucible, and after opening the crucible top cover 1, a SiC ingot with a longitudinal thickness of 112mm can be obtained on the surface of the crucible top cover 1. The SiC ingot has no obvious cracking.
[0057] Example 3
[0058] A method for increasing the longitudinal growth thickness of silicon carbide single crystals, based on the apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals described in Example 1, includes the following steps:
[0059] S1. Attach a 500μm thick SiC seed crystal 10 (e.g., ...) to the side of the crucible top cover 1 closest to the crucible body. Figure 1 As shown, in actual implementation, a SiC seed crystal 10 support plate can also be set at the place where the SiC seed crystal 10 is pasted on the crucible top cover 1. The C polarity surface of the SiC seed crystal 10 faces the direction of the SiC powder 11. A graphite paper with a thickness of 200μm is set between the SiC seed crystal 10 and the crucible top cover 1. Then, the graphite shoulder tube 7 is threaded onto the crucible top cover 1. The cylindrical tube of the graphite shoulder tube 7 has a height of 120mm, and the conical tube at the bottom has an angle of 30° and a height of 20mm. The inner wall of the graphite shoulder tube 7 is coated with a TaC coating (not shown in the figure).
[0060] In one of the crucible tubes 2 (i.e., the uppermost crucible tube 2, referred to here as the primary crucible tube 2), SiC powder 11 (weighing 1.5 kg, with a particle size of 8-20 mesh), SiC carbide powder 12 (with a thickness of 10 mm) and a second porous graphite sheet 6 are placed sequentially from bottom to top on the first porous graphite sheet 3; in the remaining crucible tubes 2, SiC powder 11 (weighing 1.5 kg, with a particle size of 8-20 mesh) and a second porous graphite sheet 6 are placed sequentially from bottom to top.
[0061] It is worth noting that the crucible cylinder 2 is pre-installed with a first porous graphite sheet 3 (10mm thick, the pore size needs to be set to ensure that the SiC powder 11 does not fall) and a second heater 5.
[0062] S2. First, vertically overlap multiple crucible cylinders 2 using threaded connections, and then cover them with the crucible top cover 1. Next, place the assembled crucible inside the crystal growth system, and then install the first heater 4 directly above the crucible within the crystal growth system. Finally, place the crucible and crystal growth system together into the crystal growth furnace. Figure 1 As shown, the crystal growth system includes a graphite support tank 8 and a graphite insulation tank 9 arranged sequentially from the inside to the outside.
[0063] S3. First, evacuate the crystal growth furnace to 10°C. -3 Pa, then a mixture of argon and nitrogen gas is introduced into the crystal growth furnace to 500 Pa, the heating power is turned on, the temperature of the first heater 4 is controlled at 2150℃, the temperature of the uppermost second heater 5 (i.e., the first-stage second heater 5) is controlled at 2350℃, after crystal growth for 100 hours, the second heater 5 is turned off, and the adjacent second heater 5 below (i.e., the second-stage second heater 5) is turned on, the temperature of the second heater 5 is controlled at 2460℃, that is, for each stage of the second heater 5 turned on, the temperature of the second heater 5 increases by 110℃, and so on, so that the SiC powder 11 in different stages of the crucible 2 is decomposed and sublimated.
[0064] S4. After crystal growth is completed, slowly lower the temperature inside the crystal growth furnace to room temperature, and at the same time introduce nitrogen gas into the crystal growth furnace to atmospheric pressure; then remove the first heater 4, then take out the crucible, and after opening the crucible top cover 1, a SiC ingot with a longitudinal thickness of 120mm can be obtained on the surface of the crucible top cover 1. The SiC ingot has no obvious cracking.
[0065] It is worth noting that in the above embodiments 1-3, the first heater 4, the second heater 5, and the crucible are all made of graphite.
Claims
1. An apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals, characterized in that, It includes a split crucible and a first heater (4) disposed directly above the split crucible; The split crucible includes a crucible body, a crucible top cover (1) and a crucible bottom cover; the crucible body includes a plurality of vertically overlapping crucible cylinders (2), a first porous graphite sheet (3) and a second heater (5) disposed in the lower part of the crucible cylinder (2) and distributed vertically, and a second porous graphite sheet (6) movably disposed in the upper part of the crucible cylinder (2). The bottom wall of the crucible top cover (1) is detachably provided with a graphite shoulder tube (7), which includes a cylindrical tube and a conical tube disposed at its bottom end.
2. The apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 1, characterized in that, The inner wall of the graphite shoulder tube (7) is coated with TaC.
3. The apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 1, characterized in that, The distance between the first heater (4) and the crucible top cover (1) is 25-35 mm.
4. The apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 1, characterized in that, The adjacent crucible cylinders (2) are threaded together, and the graphite shoulder cylinder (7) is threaded together with the crucible top cover (1).
5. The apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 1, characterized in that, Both the first heater (4) and the second heater (5) are provided with vents.
6. A method for increasing the longitudinal growth thickness of silicon carbide single crystals, implemented based on the apparatus for increasing the longitudinal growth thickness of silicon carbide single crystals according to any one of claims 1-5, characterized in that, Includes the following steps: S1. A SiC seed crystal (10) is attached to the side of the crucible top cover (1) near the crucible body, and then a graphite shoulder tube (7) is attached to the crucible top cover (1). SiC powder (11), SiC carbide powder (12) and a second porous graphite sheet (6) are placed sequentially from bottom to top on a first porous graphite sheet (3) in one of the crucible tubes (2); SiC powder (11) and a second porous graphite sheet (6) are placed sequentially from bottom to top on a first porous graphite sheet (3) in the remaining crucible tubes (2); S2. First, connect multiple different crucible cylinders (2) vertically and cover them with crucible top cover (1). Then, place the assembled crucible in the crystal growth system and install the first heater (4) directly above the crucible and inside the crystal growth system. Finally, put the crucible and the crystal growth system into the crystal growth furnace together. The crystal growth system includes a graphite support barrel (8) and a graphite insulation barrel (9) arranged sequentially from the inside to the outside; the uppermost crucible barrel (2) is a crucible barrel (2) containing SiC carbide powder (12); S3. Under negative pressure and inert gas conditions, first turn on the first heater (4) and the uppermost second heater (5). After crystal growth for a certain period of time, turn off the second heater (5) and turn on the adjacent second heater (5) below. After crystal growth for a certain period of time, turn off the second heater (5) and turn on the adjacent second heater (5) below. Continue in this manner until the crystal growth of the lowermost crucible ends. The heating temperature of the multiple second heaters (5) gradually increases from top to bottom. S4. After the crystal growth is completed, slowly lower the temperature inside the crystal growth furnace to room temperature, and at the same time introduce nitrogen into the crystal growth furnace to atmospheric pressure; then remove the first heater (4), then take out the crucible, and after opening the crucible top cover (1), a SiC ingot with a longitudinal thickness greater than 100mm can be obtained on the surface of the crucible top cover (1).
7. The method for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 6, characterized in that, A 200μm thick graphite paper is placed between the SiC seed crystal (10) and the crucible top cover (1).
8. The method for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 6, characterized in that, The thickness of the SiC carbide powder (12) is 10 mm.
9. A method for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 6, characterized in that, The first heater (4) has a heating temperature of 2100-2150℃, the uppermost second heater (5) has a heating temperature of 2300-2350℃, and the temperature difference between adjacent second heaters (5) is 100-150℃.
10. A method for increasing the longitudinal growth thickness of silicon carbide single crystals according to claim 6, characterized in that, The particle size of the SiC powder (11) is 8-20 mesh.