PVT-based ultra-thick silicon carbide crystal growth equipment and process

Abstract

The invention discloses PVT-based ultra-thick silicon carbide crystal growth equipment and process in the technical field of silicon carbide production. The PVT-based ultra-thick silicon carbide crystal growth equipment comprises a powder processing unit, a growth and crystallization unit, a lifting and rotating system and a seed crystal fixing unit. According to the invention, the lifting and rotating system capable of controlling lifting and rotating in the crystal growth process, the independent powder sublimation area and powder sublimation heating system, and the independently controlled crystal growth area and growth temperature area regulation and control system are arranged to cooperate with each other; a single heater lifting and rotating thermal field adjusting mode of a traditional structure is changed into a multi-heater lifting and rotating adjusting mode, and meanwhile, a powder sublimation area and a growth area are separately heated, adjusted and controlled, so that the change of the thermal field in the growth process is controllable, the axial and radial temperature gradients of the thermal field can be more finely controlled, and the growth efficiency is improved. Meanwhile, the filling amount of the powder is increased, the dimension in the growth direction is lengthened, and a solid guarantee is provided for growth of super-thick silicon carbide crystal ingots.

Description

Technical Field

[0001] This invention relates to the field of silicon carbide production technology, and in particular to an ultra-thick silicon carbide crystal growth equipment and process based on PVT. Background Technology

[0002] Physical vapor transport (PVT) is a method for growing SiC crystals through three steps: high-temperature sublimation, vapor transport, and seed crystal condensation. The reaction principle is as follows: at a high temperature above 2000℃, SiC powder sublimates to produce vapor components such as Si, Si2C, and SiC2. Driven by the temperature gradient between the seed crystal and the powder, the vapor components are transported to the surface of the seed crystal for crystal growth.

[0003] Existing PVT growth equipment generally suffers from the following drawbacks when growing ultra-thick silicon carbide crystals (thickness greater than 100 mm): 1. Thermal imbalance: Crystal thickening leads to increased axial / radial temperature gradient coupling, causing stress cracking; 2. Growth rate decay: The growth rate of traditional processes is only 0.3-0.5 mm / h, and ultra-thick crystals require tens of days to grow, resulting in an exponential increase in energy consumption and defect risk; 3. Low powder utilization: The powder utilization rate of conventional PVT methods is <50%, which cannot support long-term ultra-thick growth; 4. Poor flexibility: The silicon carbide seed crystals used for growth are mostly fixed by "sticking" in the PVT crucible, and must be removed by mechanical scraping afterward, resulting in poor overall flexibility in use. Summary of the Invention

[0004] In view of the problems existing in the existing ultra-thick silicon carbide crystal growth equipment based on PVT, the present invention proposes an ultra-thick silicon carbide crystal growth equipment based on PVT to solve these problems.

[0005] To solve the above-mentioned technical problems, the present invention provides the following technical solution: an ultra-thick silicon carbide crystal growth device based on PVT, comprising a powder processing unit, a growth and crystallization unit, a lifting and rotating system, and a seed crystal fixing unit. The growth and crystallization unit is disposed above the powder processing unit and is internally connected to the powder processing unit. A graphite filter is disposed at the connection position between the two. The lifting and rotating system is located at the top of the growth and crystallization unit and is connected to the growth and crystallization unit by a graphite rod. The seed crystal fixing unit is disposed inside the growth and crystallization unit and is provided with a seed crystal disk. The powder processing unit includes a lower outer shell located below, a powder crucible disposed inside the lower outer shell, and a powder sublimation heating system distributed on the inner wall of the lower outer shell, wherein the powder sublimation heating system is located between the lower outer shell and the powder crucible. The growth crystallization unit includes an upper outer shell located above the lower outer shell, a growth crucible located inside the upper outer shell with its lower end connected to the top end of the powder crucible, a graphite filter disposed inside the lower end of the growth crucible, a growth temperature control system disposed inside the upper outer shell with its growth temperature control system located between the upper outer shell and the growth crucible, and a top plate fixedly disposed at the top end of the growth crucible with a seed crystal fixing unit disposed on the top plate, and the end of a graphite rod fixedly connected to the top plate.

[0006] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT described in this invention, wherein: a powder sublimation zone is formed inside the powder crucible, the seed crystal fixing unit and the seed crystal disk are both located in the powder sublimation zone, a crystal growth zone is formed inside the growth crucible, and a top cover is provided at the top of the upper shell.

[0007] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT described in this invention, the top plate is provided with multiple sets of clearance grooves evenly spaced apart, the clearance grooves including an upper groove formed on the bottom surface of the top plate and a lower groove formed on the top surface of the top plate.

[0008] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT described in this invention, the lifting and rotating system includes a rotating component and a lifting component, both of which are connected to a graphite rod. The rotating component drives the graphite rod to move vertically, while the lifting component drives the graphite rod to rotate circumferentially.

[0009] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT according to the present invention, the seed crystal fixing unit includes a collar sleeved on a graphite rod, a threaded rod threaded to the side of the collar, and the lower end of the threaded rod rotatably connected to a top plate, multiple sets of transmission components equally distributed on the collar, and the transmission components extending through the clearance groove into the growth crucible, a limiting component provided at the lower end of each set of transmission components, and a limiting shaft laterally inserted into the inner side of the limiting component, and the limiting shaft is fixedly connected to the bottom surface of the top plate.

[0010] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT according to the present invention, the transmission component includes a main shaft rotatably connected to a collar, the main shaft extending into the upper groove, a secondary shaft inserted into the lower end of the main shaft, the secondary shaft extending into the lower groove, and a rotating shaft disposed on the main shaft and located at the connection between the upper and lower grooves.

[0011] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT according to the present invention, the limiting component includes a connecting block rotatably connected to the end of the sub-shaft, two sets of side support rods rotatably connected to the lower end of the connecting block, the two sets of side support rods being symmetrically arranged, and a chain connecting the ends of the two sets of side support rods.

[0012] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT described in this invention, the chain is composed of multiple sets of contact blocks that are rotatably connected end to end, and the two ends of the chain are respectively rotatably connected to the ends of two sets of side support rods.

[0013] As a preferred embodiment of the ultra-thick silicon carbide crystal growth equipment based on PVT described in this invention, the connecting block is provided with a transverse insertion hole, and the limiting shaft is transversely inserted into the insertion hole. The outer ends of the two sets of side support rods are provided with arc-shaped retaining springs, and the two ends of the retaining springs are respectively connected to the two sets of side support rods.

[0014] A growth process for growing ultra-thick silicon carbide ingots using the PVT method includes the following steps: S1. Fix the seed crystal disk to the top of the inside of the growth crucible through the seed crystal fixing unit. Install a graphite filter at the bottom of the inside of the growth crucible. Connect the growth crucible to the lifting and rotating system through the graphite rod. Fill the powder crucible with silicon carbide raw powder. Finally, connect the bottom of the growth crucible with the top of the powder crucible. S2. Given the heating power of the powder sublimation heating system, heat the powder crucible, thereby causing the powder sublimation zone inside the powder crucible to reach 2300-2500℃, thus sublimating the silicon carbide raw powder inside the powder crucible. S3. The heating power of the growth temperature zone control system is synchronously given so that it heats the growth crucible and causes the crystal growth zone inside the growth crucible to reach a temperature suitable for silicon carbide crystal growth, thereby facilitating the crystal growth of the sublimated silicon carbide raw powder. S4. When the silicon carbide raw powder sublimated in the powder crucible enters the growth crucible, it will be filtered by the graphite filter sheet located between the two. The graphite filter sheet will block impurities from entering the growth crucible and ensure the crystal crystallization quality. The silicon carbide raw powder entering the growth crucible will eventually react with the seed crystal disk at the top of the growth crucible and then begin crystal growth. S5. During the growth process, the lifting and rotating system will drive the growth crucible to rotate at 0-5 r / min and lift at 0.01-1 mm / min. The rotating growth crucible is heated more evenly, which can reduce the impact of the unevenness of the furnace thermal field on the growth results. The lifting makes the temperature gradient of the crystal growth zone remain at a high level as the growth progresses, and the crystallization driving force at the crystallization interface is maintained at a high level, ensuring the crystallization speed and crystallization quality.

[0015] The beneficial effects of this invention are as follows: By setting up a lifting and rotating system that can control the lifting and rotating during crystal growth, a separate powder sublimation zone and powder sublimation heating system, and a separately controlled crystal growth zone and growth temperature zone regulation system to work together, the traditional single heater lifting and rotating heat field regulation method is changed to multi-heater lifting and rotating regulation. At the same time, the powder sublimation zone and growth zone are heated and regulated separately, which can increase the overall powder filling amount of the powder crucible. The separate powder sublimation zone and powder sublimation heating system allow the temperature of the powder sublimation zone to be adjusted independently, so that the powder sublimation zone can be continuously sublimated without affecting the temperature field changes in the crystal growth zone, thereby improving the amount and utilization of powder sublimation and providing a good material basis for the growth of ultra-thick silicon carbide ingots. The separate control of the crystal growth zone and the growth temperature zone control system allows the growth crucible to adjust the temperature gradient of the crystal growth zone at any time without being affected, so that the growth rate of the crystal growth zone can be maintained at a considerable rate for a long time. The Czochralski system connects the growth crucible to the Czochralski device via a graphite rod, rotating and pulling the growth crucible during the growth process. The rotation method can uniformly distribute the thermal field of the growth crucible and reduce the impact of thermal field inhomogeneity on the growth results. The pulling method can prevent the generation of some dislocations during the crystallization process, thereby ensuring the overall growth effect of silicon carbide. Meanwhile, a graphite filter is placed between the growth crucible and the powder crucible. The graphite filter can effectively block some impurity particles from entering the crystal growth area, further ensuring the growth quality of the crystal. By setting up a seed crystal fixing unit to clamp and limit the seed crystal disk, compared with the traditional adhesive operation, the mechanized clamping method can more easily pick up and put down the seed crystal disk, making the installation and fixing of the seed crystal disk and the removal of the grown ultra-thick silicon carbide crystal easier and more convenient, thus significantly improving the overall work efficiency. Meanwhile, the seed crystal fixing unit surrounds the outer wall of the seed crystal disk with three sets of chain-linked limiting components. The three sets of limiting components can clamp the seed crystal disk from three directions, and the surrounding range formed by the three sets of limiting components can be adjusted according to the actual size of the seed crystal disk. This allows the seed crystal fixing unit to not be limited to fixing seed crystal disks of the same size, thus achieving the purpose of fixing seed crystal disks of different sizes. Furthermore, the chain-like component on the limiting part can be driven by external force to wrap around and adhere to the arc-shaped outer wall of the seed crystal disk. The way the chain adheres to the arc surface of the seed crystal disk makes the clamping force on the arc-shaped outer wall of the seed crystal disk more uniform, thereby enhancing the safety of the clamping action. At the same time, the way the chain adheres to the arc surface of the seed crystal disk also increases the contact area between the chain and the seed crystal disk, thereby increasing the limiting friction force of the seed crystal fixing unit on the seed crystal disk, further strengthening the clamping and limiting force on the seed crystal disk, and ensuring the limiting effect. Attached Figure Description

[0016] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Wherein: Figure 1 This is a schematic diagram of the overall structure of the ultra-thick silicon carbide crystal growth equipment based on PVT according to the present invention.

[0017] Figure 2 This is a schematic diagram showing the installation position of the seed crystal fixing unit in the ultra-thick silicon carbide crystal growth equipment based on PVT according to the present invention.

[0018] Figure 3 This is a schematic diagram of the seed crystal fixing unit of the ultra-thick silicon carbide crystal growth equipment based on PVT according to the present invention.

[0019] Figure 4 This invention relates to an ultra-thick silicon carbide crystal growth device based on PVT. Figure 3 Enlarged schematic diagram of the structure at point A in the middle.

[0020] Figure 5 This is a schematic diagram of the limiting component of the ultra-thick silicon carbide crystal growth equipment based on PVT according to the present invention.

[0021] Figure 6 This is a schematic diagram of the structure of the seed crystal fixing unit of the ultra-thick silicon carbide crystal growth equipment based on PVT of the present invention when clamping and limiting the seed crystal disk.

[0022] Figure 7 This is a schematic diagram of the structure of the limiting component of the ultra-thick silicon carbide crystal growth equipment based on PVT of the present invention when it surrounds the seed crystal disk.

[0023] Attached reference numerals: 1. Powder processing unit; 11. Lower outer shell; 12. Powder crucible; 13. Powder sublimation heating system; 14. Powder sublimation zone; 2. Growth and crystallization unit; 21. Upper outer shell; 22. Growth crucible; 23. Growth temperature control system; 24. Crystal growth zone; 25. Top cover; 26. Top plate; 27. Clearance groove; 271. Upper groove; 272. Lower groove; 3. Lifting and rotating system; 1. Rotating component; 32. Lifting component; 4. Graphite rod; 5. Seed crystal fixing unit; 51. Collar; 52. Threaded rod; 53. Transmission component; 531. Main shaft; 532. Secondary shaft; 533. Rotating shaft; 54. Limiting component; 541. Connecting block; 542. Side support rod; 543. Chain; 544. Snap ring; 545. Insertion hole; 55. Limiting shaft; 6. Seed crystal disk; 7. Graphite filter. Detailed Implementation

[0024] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the specific embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0025] Many specific details are set forth in the following description in order to provide a full understanding of the invention. However, the invention may also be practiced in other ways different from those described herein, and those skilled in the art can make similar extensions without departing from the spirit of the invention. Therefore, the invention is not limited to the specific embodiments disclosed below.

[0026] Example 1: Refer to Figures 1 to 7 This is the first embodiment of the present invention, which includes an ultra-thick silicon carbide crystal growth device based on PVT, including a powder processing unit 1, a growth and crystallization unit 2, a lifting and rotating system 3, and a seed crystal fixing unit 5. The growth and crystallization unit 2 is located above the powder processing unit 1, and the powder processing unit 1 and the growth and crystallization unit 2 are internally connected. At the connection position between the two, a graphite filter 7 is provided. The lifting and rotating system 3 is located at the top of the growth and crystallization unit 2, and a graphite rod 4 is connected between the growth and crystallization unit 2 and the lifting and rotating system 3. The seed crystal fixing unit 5 is located inside the growth and crystallization unit 2, and a seed crystal disk 6 is provided on the seed crystal fixing unit 5. The powder processing unit 1 and the growth and crystallization unit 2 are relatively independent. The lifting and rotating system 3 can drive the graphite rod 4 to rotate and move vertically. Reference Figure 1The powder processing unit 1 includes a lower outer shell 11 located below, a powder crucible 12 disposed inside the lower outer shell 11, and a powder sublimation heating system 13 distributed on the inner wall of the lower outer shell 11. The powder sublimation heating system 13 is located between the lower outer shell 11 and the powder crucible 12. The powder crucible 12 is a container for holding silicon carbide raw powder and is also the place for its sublimation reaction. The powder sublimation heating system 13 is used to heat the powder crucible 12 so that the silicon carbide raw powder inside it can sublimate. Reference Figure 1 The growth and crystallization unit 2 includes an upper outer shell 21 located above the lower outer shell 11, a growth crucible 22 located inside the upper outer shell 21, and the lower end of the growth crucible 22 communicating with the top end of the powder crucible 12. A graphite filter 7 is disposed inside the lower end of the growth crucible 22. A growth temperature control system 23 is disposed inside the upper outer shell 21 and located between the upper outer shell 21 and the growth crucible 22. A top plate 26 is fixedly disposed at the top end of the growth crucible 22, and a seed crystal fixing unit 5 is disposed on the top plate 26. The end of the graphite rod 4 is fixedly connected to the top plate 26. The upper outer shell 21 and the lower outer shell 11 can be freely disassembled. The powder sublimation heating system 13 and the growth temperature control system 23 are controlled independently, so their heating temperatures can be adjusted as needed. The growth crucible 22 is the crystal growth site. Through its fixed connection with the graphite rod 4, the growth crucible 22 can rotate and move vertically along with it.

[0027] Furthermore, refer to Figure 1 The powder crucible 12 has a powder sublimation zone 14 inside, and the seed crystal fixing unit 5 and the seed crystal disk 6 are both located in the powder sublimation zone 14. The growth crucible 22 has a crystal growth zone 24 inside, and the top of the upper shell 21 is provided with a top cover 25. The powder sublimation zone 14 and the crystal growth zone 24 are the places where silicon carbide raw powder sublimates and crystallizes, respectively. The temperature of the two thermal fields is adjusted according to their corresponding heaters. The independent control of the crystal growth zone 24 and the growth temperature control system 23 allows the growth crucible 22 to adjust the temperature gradient of the crystal growth zone 24 at any time without being affected, so that the crystal growth rate can be maintained at a considerable speed for a long time. The top cover 25 is connected to the upper shell 21 by a flange, which can be disassembled according to the usage requirements, facilitating the subsequent replacement of the growth crucible 22 and the installation of the seed crystal disk 6.

[0028] Furthermore, refer to Figure 1 The upper shell 21 is equipped with multiple growth temperature control systems 23. The design of multiple growth temperature control systems 23 makes the change of the thermal field during the growth process controllable, and can more precisely control the axial and radial temperature gradient of the thermal field, so as to achieve uniform nucleation in the early stage of crystal growth, reduce defects, improve crystal growth quality, and significantly improve the utilization rate of silicon carbide powder.

[0029] Furthermore, the separately configured powder crucible 12 and powder sublimation heating system 13 allow for individual temperature adjustment of the powder sublimation heating system 13. This ensures that the powder sublimation zone 14 continuously sublimates without affecting the temperature field changes in the crystal growth zone 24, thereby increasing the amount and utilization rate of powder sublimation and providing a material basis for growing ultra-thick silicon carbide ingots.

[0030] Furthermore, both the powder sublimation heating system 13 and the growth temperature control system 23 are composed of high-density graphite heaters. The growth crucible 22 and the powder crucible 12 are detachably connected by a connector. The powder crucible 12 can be tilted at 45-90° to increase the sublimation gas phase contact area.

[0031] Furthermore, refer to Figure 2 The top plate 26 is provided with multiple sets of clearance grooves 27. The clearance grooves 27 include an upper groove 271 opened on the bottom surface of the top plate 26 and a lower groove 272 opened on the top surface of the top plate 26. The top plate 26 is fixedly connected to the growth crucible 22. The upper groove 271 opens upward and the lower groove 272 opens downward.

[0032] Among them, reference Figure 1 The lifting and rotating system 3 includes a rotating component 31 and a lifting component 32, both of which are connected to the graphite rod 4. The rotating component 31 drives the graphite rod 4 to move vertically, while the lifting component 32 drives the graphite rod 4 to rotate circumferentially. The lifting and rotating system 3 is connected to the growth crucible 22 through the graphite rod 4. The rotating component 31 and the lifting component 32 are relatively mature existing technologies, such as using a telescopic cylinder for lifting and a motor for rotation. The system rotates and lifts the growth crucible 22 and the powder crucible 12 connected to the growth crucible 22 during the growth process. The rotation method can uniformly heat the internal thermal field of both crucibles and reduce the impact of uneven thermal field differences on the growth results. The lifting method can prevent the generation of some dislocation phenomena during the crystal crystallization process, thereby ensuring the overall growth effect of silicon carbide.

[0033] Furthermore, the powder processing unit 1 and the growth and crystallization unit 2 are set up independently. Therefore, the powder sublimation zone 14, the powder sublimation heating system 13, the crystal growth zone 24, and the growth temperature control system 23 within them are also independent. Thus, in actual use, the temperature adjustment of the powder sublimation zone 14 will not affect the crystal growth zone 24, thereby effectively reducing the interference between the two, further enhancing the crystal growth efficiency, and improving the crystal growth quality.

[0034] Among them, reference Figure 2The seed crystal fixing unit 5 includes a collar 51 sleeved on the graphite rod 4, a threaded rod 52 threaded to the side of the collar 51, and the lower end of the threaded rod 52 rotatably connected to the top plate 26. Multiple sets of transmission components 53 are equally distributed on the collar 51, and the transmission components 53 extend through the relief groove 27 into the growth crucible 22. Each set of transmission components 53 has a limiting component 54 at its lower end, and a limiting shaft 55 is laterally inserted into the inner side of the limiting component 54. The limiting shaft 55 is fixedly connected to the bottom surface of the top plate 26. The threaded rod 52 can drive the transmission components 53 to move through the threaded connection with the collar 51, thereby driving the multiple sets of transmission components 53 to drive their corresponding limiting components 54 to slide in a relative direction along the limiting shaft 55, thereby achieving the purpose of circumferentially clamping and limiting the seed crystal disk 6.

[0035] Among them, reference Figure 6 The transmission component 53 includes a main shaft 531 rotatably connected to the collar 51, with the main shaft 531 extending into the upper groove 271; a secondary shaft 532 inserted into the lower end of the main shaft 531, with the secondary shaft 532 extending into the lower groove 272; and a rotating shaft 533 disposed on the main shaft 531 and located at the connection between the upper groove 271 and the lower groove 272. The secondary shaft 532 can be moved within the main shaft 531. The moved secondary shaft 532 can change the overall length of the transmission component 53, thereby adapting to the changes when the collar 51 drives the main shaft 531 to move. At the same time, the spherical rotating shaft 533 is the axis of rotation of the entire transmission component 53, and the rotating shaft 533 also seals the connection between the upper groove 271 and the lower groove 272, thereby playing a certain degree of sealing role.

[0036] Among them, reference Figure 5 The limiting component 54 includes a connecting block 541 rotatably connected to the end of the secondary shaft 532, two sets of side support rods 542 rotatably connected to the lower end of the connecting block 541 and the two sets of side support rods 542 are symmetrically arranged, and a chain 543 connected between the ends of the two sets of side support rods 542. The two sets of side support rods 542 support the chain 543 outward and can provide sufficient support force to both ends of the chain 543. The connecting block 541 can be driven by the secondary shaft 532 through its connection with the secondary shaft 532.

[0037] Furthermore, refer to Figure 5The chain 543 is composed of multiple sets of contact blocks that are connected end to end in a sequential rotation. At the same time, the two ends of the chain 543 are respectively rotatably connected to the ends of two sets of side support rods 542. The chain-like part on the limiting component 54 can be driven by external force to wrap around and adhere to the arc-shaped outer wall of the seed crystal disk 6. The way the chain adheres to the arc surface of the seed crystal disk makes the clamping force on the arc-shaped outer wall of the seed crystal disk 6 more uniform, thereby enhancing the safety of the clamping action. At the same time, the way the chain 543 adheres to the arc surface of the seed crystal disk 6 also increases the contact area between the chain 543 and the seed crystal disk 6, thereby increasing the limiting friction force of the seed crystal fixing unit 5 on the seed crystal disk, further strengthening the clamping and limiting force on the seed crystal disk, and ensuring the limiting effect.

[0038] Furthermore, refer to Figure 4 The connecting block 541 has a transverse insertion hole 545, and the limiting shaft 55 is transversely inserted into the insertion hole 545. The outer ends of the two sets of side support rods 542 are provided with arc-shaped retaining springs 544, and the two ends of the retaining springs 544 are respectively connected to the two sets of side support rods 542. The retaining springs 544 can elastically support the two sets of side support rods 542 to open outward, thereby stretching the chain 543 to be straight through the two sets of side support rods 542, thus ensuring that there is sufficient pressure when the chain 543 contacts the outer wall of the seed crystal disk 6. The cooperation between the insertion hole 545 and the limiting shaft 55 allows the connecting block 541 to slide horizontally along the limiting shaft 55.

[0039] Reference Figure 6 and Figure 7During the clamping and limiting process of the seed crystal fixing unit 5 on the seed crystal disk 6, the threaded rod 52 drives the collar 51 to move upward along the graphite rod 4. The upward movement of the collar 51 will synchronously drive the main shaft 531 to move synchronously. At this time, the main shaft 531 driven by the collar 51 will rotate around the pivot 533. The rotating main shaft 531 will press the secondary shaft 532 at its end. The secondary shaft 532 will form a limit between the connecting block 541 and the limiting shaft 55. At this time, in order to adapt to the change when the main shaft 531 deflects upward, the secondary shaft 532 will retract into the main shaft 531. At the same time, the retracting secondary shaft 532 will synchronously drive the connecting block 541 to slide along the limiting shaft 55. At this time, the limiting component 54 as a whole Driven by the connecting block 541, the crystal will slide and translate. Multiple sets of limiting components 54 will simultaneously perform the same movements as described above through the corresponding transmission components 53, placing the seed crystal disk 6 between the multiple sets of limiting components 54. Finally, driven by the continuous upward movement of the collar 51, the multiple sets of limiting components 54 will firmly clamp the seed crystal disk 6 to the top of the inside of the growth crucible 22 from multiple directions, thereby realizing the mechanical clamping operation of the seed crystal disk 6. Compared with the adhesive operation in the traditional technology, the mechanized clamping method can more conveniently perform the picking and placing operations of the seed crystal disk 6, making the installation and fixing of the seed crystal disk 6 and the removal of the ultra-thick silicon carbide crystal after growth easier and more convenient, thus significantly improving the overall work efficiency. Meanwhile, the encircling range formed by the three sets of limiting components 54 can be adjusted according to the actual size of the seed crystal disk. That is, by controlling the height of the collar 51, the amplitude of the rotation of the transmission component 53 driven by it can be controlled, thereby controlling the distance that the limiting component 54 driven by the transmission component 53 moves on the limiting shaft 55, so as to control the overall clamping range. This allows the seed crystal fixing unit 5 to not be limited to limiting and fixing seed crystal disks 6 of the same size, but to realize the function of limiting and fixing seed crystal disks 6 of different sizes.

[0040] Example 2: Refer to Figure 1 A growth process for growing ultra-thick silicon carbide ingots using the PVT method includes the following steps: S1. The seed crystal disk 6 is fixed to the top of the inside of the growth crucible 22 through the seed crystal fixing unit 5. A graphite filter 7 is installed at the bottom of the inside of the growth crucible 22. The growth crucible 22 is connected to the lifting and rotating system 3 through the graphite rod 4. Silicon carbide raw powder is filled into the powder crucible 12. Finally, the bottom of the growth crucible 22 is connected to the top of the powder crucible 12. The seed crystal disk 6 can be quickly disassembled by fixing the seed crystal disk 6 through the seed crystal fixing unit 5. S2. Given the heating power of the powder sublimation heating system 13, it heats the powder crucible 12, thereby causing the powder sublimation zone 14 inside the powder crucible 12 to reach 2300-2500℃, thus sublimating the silicon carbide raw powder inside the powder crucible 12. The individual control of the powder sublimation heating system 13 allows the temperature of the powder sublimation zone 14 to be adjusted at any time, so that the powder sublimation zone 14 can sublimate continuously without affecting the temperature field change of the crystal growth zone 24, thereby improving the amount and utilization rate of powder sublimation and providing a good material basis for growing ultra-thick silicon carbide ingots. S3. The heating power of the growth temperature zone control system 23 is synchronously given to heat the growth crucible 22, so that the crystal growth zone 24 inside the growth crucible 22 reaches a temperature suitable for silicon carbide crystal growth, thereby facilitating the crystal growth of the sublimated silicon carbide powder. The independent control of the growth temperature zone control system 23 can adjust the temperature gradient of the crystal growth zone 24 at any time without being affected, so that the crystal growth rate can be kept at a considerable level for a long time. S4. When the silicon carbide raw powder sublimated in the powder crucible 12 enters the growth crucible 22, it will be filtered by the graphite filter 7 located between the two. The graphite filter 7 will block impurities from entering the growth crucible 22, ensuring the crystal crystallization quality. The silicon carbide raw powder entering the growth crucible 22 will eventually react with the seed crystal disk 6 at the top of the growth crucible 22, and then begin crystal growth. S5. During the growth process, the lifting and rotating system 3 will drive the growth crucible 22 to rotate at 0-5 r / min and lift at 0.01-1 mm / min. The rotating growth crucible 22 is heated more evenly, which can reduce the impact of the unevenness of the furnace thermal field on the growth results. The lifting makes the temperature gradient of the crystal growth zone 24 remain at a high level as the growth progresses, and the crystallization driving force at the crystallization interface is maintained at a high level, ensuring the crystallization speed and crystallization quality. At the same time, the lifting can also prevent the generation of some dislocations during the crystallization process.

[0041] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. A PVT-based ultra-thick silicon carbide crystal growth device, comprising a powder processing unit (1), a growth and crystallization unit (2), a pulling and rotating system (3), and a seed crystal fixing unit (5), characterized in that: The growth crystallization unit (2) is located above the powder processing unit (1), and the powder processing unit (1) and the growth crystallization unit (2) are internally connected. At the same time, a graphite filter (7) is provided at the connection position between the two. The lifting and rotating system (3) is located at the top of the growth crystallization unit (2), and a graphite rod (4) is connected between the growth crystallization unit (2) and the lifting and rotating system (3). The seed crystal fixing unit (5) is located inside the growth crystallization unit (2), and a seed crystal disk (6) is provided on the seed crystal fixing unit (5). The powder processing unit (1) includes a lower outer shell (11) located below, a powder crucible (12) disposed inside the lower outer shell (11), and a powder sublimation heating system (13) distributed on the inner wall of the lower outer shell (11), and the powder sublimation heating system (13) is located between the lower outer shell (11) and the powder crucible (12). The growth crystallization unit (2) includes an upper shell (21) located above the lower shell (11), a growth crucible (22) located inside the upper shell (21), and the lower end of the growth crucible (22) is connected to the top end of the powder crucible (12). Meanwhile, a graphite filter (7) is disposed inside the lower end of the growth crucible (22), a growth temperature control system (23) is disposed inside the upper shell (21), and the growth temperature control system (23) is located between the upper shell (21) and the growth crucible (22), and a top plate (26) is fixedly disposed at the top end of the growth crucible (22). A seed crystal fixing unit (5) is disposed on the top plate (26), and the end of the graphite rod (4) is fixedly connected to the top plate (26).

2. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 1, characterized in that: The powder crucible (12) has a powder sublimation zone (14) inside, and the seed crystal fixing unit (5) and the seed crystal disk (6) are both located in the powder sublimation zone (14). The growth crucible (22) has a crystal growth zone (24) inside, and the top of the upper shell (21) is provided with a top cover (25).

3. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 2, characterized in that: The top plate (26) is provided with multiple sets of clearance grooves (27) evenly spaced apart. The clearance grooves (27) include an upper groove (271) opened on the bottom surface of the top plate (26) and a lower groove (272) opened on the top surface of the top plate (26).

4. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 1, characterized in that: The lifting and rotating system (3) includes a rotating component (31) and a lifting component (32), both of which are connected to the graphite rod (4). The rotating component (31) drives the graphite rod (4) to move vertically, while the lifting component (32) drives the graphite rod (4) to rotate circumferentially.

5. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 1 or 3, characterized in that: The seed crystal fixing unit (5) includes a collar (51) sleeved on the graphite rod (4), a threaded rod (52) threaded to the side of the collar (51), and the lower end of the threaded rod (52) rotatably connected to the top plate (26), multiple sets of transmission components (53) equally arranged on the collar (51), and the transmission components (53) extending through the relief groove (27) into the growth crucible (22), a limiting component (54) provided at the lower end of each set of transmission components (53), and a limiting shaft (55) laterally inserted into the inner side of the limiting component (54), and the limiting shaft (55) is fixedly connected to the bottom surface of the top plate (26).

6. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 5, characterized in that: The transmission component (53) includes a main shaft (531) rotatably connected to a collar (51), the main shaft (531) extending into an upper groove (271), a secondary shaft (532) inserted into the lower end of the main shaft (531), the secondary shaft (532) extending into a lower groove (272), and a rotating shaft (533) disposed on the main shaft (531) and located at the connection between the upper groove (271) and the lower groove (272).

7. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 6, characterized in that: The limiting component (54) includes a connecting block (541) rotatably connected to the end of the secondary shaft (532), two sets of side support rods (542) rotatably connected to the lower end of the connecting block (541), the two sets of side support rods (542) being symmetrically arranged, and a chain (543) connecting the ends of the two sets of side support rods (542).

8. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 7, characterized in that: The chain (543) is composed of multiple sets of contact blocks that are rotatably connected end to end, and the two ends of the chain (543) are respectively rotatably connected to the ends of two sets of side support rods (542).

9. The ultra-thick silicon carbide crystal growth equipment based on PVT according to claim 8, characterized in that: The connecting block (541) has a transverse insertion hole (545), and the limiting shaft (55) is transversely inserted into the insertion hole (545). The outer ends of the two sets of side support rods (542) are provided with arc-shaped retaining rings (544), and the two ends of the retaining rings (544) are respectively connected to the two sets of side support rods (542).

10. A growth process for an ultra-thick silicon carbide crystal growth apparatus based on PVT according to any one of claims 1 to 9, characterized in that, It also includes the following steps: S1. Fix the seed crystal disk (6) to the top of the inside of the growth crucible (22) through the seed crystal fixing unit (5), install the graphite filter (7) at the bottom of the inside of the growth crucible (22), connect the growth crucible (22) to the lifting and rotating system (3) through the graphite rod (4), fill the powder crucible (12) with silicon carbide raw powder, and finally connect the bottom of the growth crucible (22) with the top of the powder crucible (12). S2. Given the heating power of the powder sublimation heating system (13), heat the powder crucible (12) to promote the powder sublimation zone (14) inside the powder crucible (12) to reach 2300-2500℃, thereby sublimating the silicon carbide raw powder inside the powder crucible (12); S3. The heating power of the growth temperature zone control system (23) is given synchronously so that it heats the growth crucible (22) and causes the crystal growth zone (24) inside the growth crucible (22) to reach a temperature suitable for silicon carbide crystal growth, thereby facilitating the crystal growth of the sublimated silicon carbide raw powder. S4. When the silicon carbide raw powder sublimated in the powder crucible (12) enters the growth crucible (22), it will be filtered by the graphite filter (7) located between the two. The graphite filter (7) will block impurities from entering the growth crucible (22) to ensure the crystal crystallization quality. The silicon carbide raw powder entering the growth crucible (22) will eventually react with the seed crystal disk (6) at the top of the inside of the growth crucible (22) and then begin crystal growth. S5. During the growth process, the lifting and rotating system (3) will drive the growth crucible (22) to rotate at 0-5 r / min and lift at 0.01-1 mm / min. The rotating growth crucible (22) is heated more evenly, which can reduce the impact of the unevenness of the furnace thermal field on the growth results. The lifting makes the temperature gradient of the crystal growth area (24) remain at a high level as the growth progresses, and the crystallization driving force at the crystallization interface is maintained at a high level, ensuring the crystallization speed and crystallization quality.

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