Crucible structure for growing silicon carbide single crystals through PVT method and installation method
By designing a new crucible structure, optimizing the temperature gradient and mass transfer process, the problem of low growth quality of silicon carbide single crystals in the existing technology is solved, and the growth of high-quality and large-size silicon carbide single crystals is achieved.
Patent Information
- Application Number
- CN202411984860.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-31
- Publication Date
- 2025-03-28
AI Technical Summary
In the prior art, the crucible structure of the PVT method for growing silicon carbide single crystals is unreasonable, resulting in small crystal size, unstable crystal shape, many defective impurities, and the inability to grow high-quality large-size silicon carbide single crystals.
A new crucible structure was designed, including a heat-generating body crucible, a top insulation layer, a seed crystal pressure ring, a seed crystal support, a flow guide ring and a raw material crucible. Through the mass transfer channel formed by the double flow guide structure, the axial and radial temperature gradients are optimized and the crystal growth quality of silicon carbide single crystal is improved.
By optimizing the temperature gradient and mass transfer process, high-quality, large-size silicon carbide single crystals are successfully grown, reducing the generation of impurities and defects, and improving the stability and quality of the crystal.
Smart Images
Figure CN119710905A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of semiconductor single crystal preparation, and relates to a crucible structure and an installation method for growing silicon carbide single crystals using a PVT method. Background Art
[0002] As a representative of the third-generation semiconductors, silicon carbide (SiC) has excellent physical and chemical properties such as large bandgap, high thermal conductivity, high electron saturation mobility, and strong critical breakdown field. It has become a widely used material in 5G communications, aerospace, radar communications, electronic devices, high-frequency devices and other fields.
[0003] At present, the main methods for preparing SiC single crystals are: High Temperature Chemical Vapor Deposition (HTCVD), Top Seeded Solution Growth (TSSG) and Physical Vapor Deposition (PVT). Among them, the high temperature chemical vapor deposition method has the disadvantages of high cost and difficult to control defects; the top seed solution growth method has the disadvantage of easy doping of metal elements during the crystal growth process; in comparison, the physical vapor transport method is simple to operate, mature technology and low consumables cost.
[0004] Combined with the above, the most successful preparation method is the physical vapor transport method. The basic principle of growing silicon carbide single crystals is to place silicon carbide powder in the cavity of the growth crucible, and to bond or suspend a seed crystal at the top of the crucible cover. The presence of the seed crystal can well inhibit the spontaneous nucleation phenomenon during the growth of silicon carbide single crystals, and can effectively improve the quality of the grown silicon carbide single crystals. At the same time, the outer periphery of the crucible is wrapped with insulation felt as an insulation layer to insulate the crucible. On the one hand, the specific structure of the insulation layer can effectively improve the temperature gradient inside the crucible, and the temperature gradient inside the crucible directly affects the growth quality of silicon carbide crystals. On the other hand, the presence of the insulation layer greatly reduces the loss of heat and reduces production costs. At the same time, the structure of the crucible can have an important influence on the distribution of the temperature field inside the crucible, and the distribution of the temperature field inside the crucible will directly determine the mass transfer process during the growth of silicon carbide, thereby affecting the quality of the grown silicon carbide single crystals. Reasonable insulation layer structure and crucible structure form a temperature gradient inside the crucible that is beneficial to the growth of silicon carbide single crystals and is beneficial to the mass transfer process of the silicon carbide raw material sublimation atmosphere, thereby increasing the growth rate of silicon carbide single crystals and reducing the generation of impurities and defects in the silicon carbide single crystals.
[0005] At present, the common heating methods for growing silicon carbide single crystals by the PVT method are resistive heating and electromagnetic induction heating. Compared with resistive heating, electromagnetic induction heating has obvious advantages. Electromagnetic induction heating has the advantages of fast heating speed, high efficiency and low cost. A multi-turn spiral induction heating coil is wound around the outer periphery of the insulation layer. An alternating current of a certain frequency is passed through the coil, which is the heat source of the entire growth system. Through electromagnetic induction heating, a strong eddy current is generated inside the heating element crucible, thereby generating heat to sublimate the powder, transfer mass to the surface of the seed crystal through the area between the powder and the seed crystal, and then deposit on the surface around the seed crystal, thereby growing high-quality silicon carbide single crystals.
[0006] The prior art has the following problems: The silicon carbide single crystals grown by the existing crucible structure have problems such as small crystal size, unstable crystal shape, and many defects and impurities, and cannot meet the market demand well. The main reason is that the structure of the crucible is unreasonable, which results in that when the crucible structure is subjected to electromagnetic induction heating, a temperature field that is conducive to the growth of silicon carbide single crystals cannot be generated inside the crucible. Specifically, the axial temperature gradient required for upward mass transfer of silicon carbide raw materials after sublimation and the radial temperature gradient to ensure the quality of silicon carbide single crystals cannot be generated, resulting in the inability to grow high-quality large-sized silicon carbide single crystals. Summary of the invention
[0007] In order to solve the above problems, the present invention provides a crucible structure for growing silicon carbide single crystals by the PVT method, which can improve the axial temperature gradient in the raw material area and the radial temperature gradient around the seed crystal. At the same time, the mass transfer channel formed by the double flow guide structure is conducive to the growth of high-quality and large-sized silicon carbide single crystals.
[0008] Another object of the present invention is to provide a method for installing a crucible structure for growing silicon carbide single crystals using a PVT method.
[0009] The technical solution adopted by the present invention is a crucible structure for growing silicon carbide single crystals by a PVT method, comprising a heating element crucible, wherein the center of the top insulation layer of the heating element crucible has a cylindrical protrusion protruding upward, and a temperature measuring hole is provided at the center of the cylindrical protrusion; The edge of the seed crystal located inside the heating element crucible is clamped and suspended between the seed crystal pressure ring and the seed crystal holder, the seed crystal pressure ring is located above the seed crystal, the seed crystal holder is located below the seed crystal, and the seed crystal and the seed crystal holder are coaxial; a seed crystal heat insulation layer is filled between the seed crystal pressure ring and the inner wall of the heating element crucible, and between the seed crystal holder and the inner wall of the heating element crucible; A guide ring is provided below the seed crystal holder, the inner side of the guide ring is a curved surface, and the inner side of the top of the seed crystal holder is an inclined surface, so that the calibers of the guide ring, the seed crystal holder and the seed crystal pressure ring distributed from bottom to top gradually decrease, which is used to guide the mass transfer atmosphere; A raw material crucible is arranged below the guide ring, and silicon carbide raw material is filled in the raw material crucible.
[0010] Furthermore, the heating element crucible comprises a heating tube top cover, a heating tube and a heating tube base, the heating tube top cover and the heating tube are detachably sealed and connected, and the heating tube and the heating tube base are detachably sealed and connected.
[0011] Furthermore, the ratio of the diameter of the cylindrical protrusion to the diameter of the top insulation layer is in the range of 0.35 to 0.4:1.
[0012] Furthermore, the raw material crucible is embedded in the internal cavity of the heating element crucible below the guide ring, and the top of the silicon carbide raw material is 8 mm to 12 mm away from the top of the raw material crucible; a raw material insulation layer is provided between the middle of the raw material crucible and the inner wall of the heating element crucible, and the raw material insulation layer is located at the middle height position of the silicon carbide raw material; a crucible side wall cavity is provided between other positions of the raw material crucible and the inner wall of the heating element crucible.
[0013] Furthermore, the inclined surface on the inner side of the top of the seed crystal holder has an inclination angle of 40° to 50°.
[0014] Furthermore, the radius of the curved surface on the inner side of the guide ring is 40 mm to 60 mm.
[0015] Furthermore, a notch is provided at the lower inner portion of the seed crystal pressure ring, and the shape and height of the notch match the edge of the seed crystal.
[0016] Furthermore, the area enclosed by the seed crystal pressure ring, the seed crystal and the top of the heating element crucible forms a seed crystal pressure ring cavity, and the thickness of the seed crystal pressure ring cavity is 18 mm to 22 mm.
[0017] Furthermore, the top of the silicon carbide raw material is at a fixed distance from the top of the raw material crucible.
[0018] A method for installing a crucible structure for growing silicon carbide single crystals by a PVT method comprises the following steps: S1, placing a raw material crucible on a heating tube base, and loading silicon carbide raw material into the raw material crucible; S2, setting a raw material heat insulation layer between the middle of the outer wall of the raw material crucible and the inner wall of the heating element crucible; S3, detachably and hermetically connecting the heating tube to the heating tube base; S4, installing the guide ring above the raw material crucible; S5, installing the seed crystal heat insulation layer above the guide ring; S6, installing the seed crystal holder above the guide ring; S7, installing the seed crystal above the seed crystal holder, with the seed crystal and the seed crystal holder being coaxial; S8, installing the seed crystal pressure ring above the seed crystal holder and engaging it with the seed crystal, so that the edge of the seed crystal is clamped and suspended between the seed crystal pressure ring and the seed crystal holder; S9, removably and hermetically connect the heating tube top cover to the heating tube; S10, a top insulation layer, a side wall insulation layer and a bottom insulation layer are respectively provided on the outer sides of the top, side wall and bottom of the heating element crucible.
[0019] The beneficial effects of the present invention are: 1. The center of the top insulation layer of the present invention has an upwardly protruding cylindrical protrusion, and a temperature measuring hole is provided at the center of the cylindrical protrusion. The top surface temperature of the seed crystal during the crystal growth process is monitored through the temperature measuring hole, and the temperature of the center of the top surface of the seed crystal is reduced at the same time; the cylindrical protrusion improves the insulation effect near the temperature measuring hole and reduces the insulation effect around it, thereby reducing the radial temperature gradient of the heating element crucible, and further reducing the radial temperature gradient of the crystal growth.
[0020] 2. The edge of the seed crystal of the present invention is clamped and suspended between the seed crystal pressure ring and the seed crystal holder, avoiding the silicon carbide single crystal defects caused by the seed crystal bonding process. At the same time, the seed crystal insulation layer can prevent the periphery of the crystal from absorbing heat from the high-temperature heating element crucible, which can effectively reduce the temperature of the periphery of the crystal, thereby effectively reducing the radial temperature gradient in the crystal.
[0021] 3. The curved surface on the inside of the guide ring and the inclined surface on the inside of the top of the seed crystal holder make the diameters of the guide ring, seed crystal holder and seed crystal pressure ring distributed from bottom to top gradually decrease. The guide ring and the seed crystal holder work together to realize the double guide of the mass transfer process of the raw material sublimation atmosphere, so that the mass transfer atmosphere reaches the surface of the seed crystal more evenly and efficiently, and at the same time avoids the reaction between the mass transfer atmosphere and the crucible wall, thereby improving the growth quality of silicon carbide single crystals. In addition, the seed crystal holder can also play a role in expanding the diameter while supporting the seed crystal. The diameter expansion effect of the seed crystal holder can make up for the disadvantage that the clamping suspension connection cannot fully utilize the edge of the seed crystal.
[0022] 4. The seed crystal pressure ring cavity of the present invention can strengthen the thermal radiation heat transfer effect of the cavity wall, thereby reducing the radial temperature gradient of the crystal; the setting of the raw material crucible and the raw material insulation layer reduces the axial temperature gradient inside the raw material, and at the same time reduces the temperature at the center of the raw material, avoids the recrystallization phenomenon of the raw material, improves the sublimation decomposition process of the raw material, and is conducive to the growth of high-quality silicon carbide single crystals. The existence of the cavity on the side wall of the raw material crucible strengthens the thermal radiation heat transfer effect of the cavity wall, thereby reducing the temperature gradient inside the raw material.
[0023] 5. The heating tube top cover and the heating tube of the present invention are detachably sealed and connected, and the heating tube and the heating tube base are detachably sealed and connected, which facilitates the loading and unloading of the internal structure of the crucible. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.
[0025] Figure 1 Schematic cross-sectional view of an embodiment of the present invention.
[0026] Figure 2 is an exploded view of an embodiment of the present invention.
[0027] Figure 3 This is the isotherm distribution diagram of the simulation of Example 1 of the present invention in Ansys Wokbench.
[0028] Figure 4 This is the isotherm distribution diagram of comparative example 1 of the present invention simulated in Ansys Wokbench.
[0029] Figure 5 This is the isotherm distribution diagram of comparative example 2 of the present invention simulated in Ansys Wokbench.
[0030] Figure 6 This is the isotherm distribution diagram of comparative example 3 of the present invention simulated in Ansys Wokbench.
[0031] In the figure, 1. temperature measuring hole; 2. top insulation layer; 3. side wall insulation layer; 4. heating tube top cover; 5. thread A; 6. seed crystal pressure ring cavity; 7. seed crystal pressure ring; 8. seed crystal; 9. heating tube; 10. seed crystal insulation layer; 11. guide ring; 12. seed crystal support; 13. raw material crucible; 14. mass transfer zone; 15. silicon carbide raw material; 16. crucible side wall cavity; 17. thread B; 18. raw material insulation layer; 19. heating tube base; 20. bottom insulation layer; 21. positioning ring. DETAILED DESCRIPTION
[0032] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0033] Embodiment 1, A crucible structure for growing silicon carbide single crystal by PVT method, such as Figure 1-2As shown, it includes an insulation layer, a heating element crucible, a seed crystal pressure ring 7, a seed crystal 8, a seed crystal holder 12, a guide ring 11 and a raw material crucible 13. The insulation layer includes a top insulation layer 2, a side wall insulation layer 3 and a bottom insulation layer 20. The heating element crucible includes a heating tube top cover 4, a heating tube 9 and a heating tube base 19, which are sealed and connected by threads A5 and B17, or snap-fit sealing connections, respectively, which allows the heating element crucible to be reused, reduces production costs, and facilitates the loading and unloading of the internal structure.
[0034] The top insulation layer 2 presents a structural feature of being high in the middle and low around the periphery. The center of the top insulation layer 2 has a cylindrical protrusion that protrudes upward. The ratio of the diameter of the cylindrical protrusion to the diameter of the top insulation layer 2 is in the range of 0.35~0.4:1. If the diameter of the protrusion is too small, a large amount of temperature in the crucible will flow out from the periphery of the top of the crucible, resulting in a situation where the surface temperature of the seed crystal is high in the middle and low on both sides, which is not conducive to the growth of high-quality silicon carbide single crystals; if the diameter of the protrusion is too large, the temperature in the crucible cannot effectively flow out from the top of the crucible, resulting in a situation where the overall temperature above the seed crystal is high, which is not conducive to the growth of high-quality silicon carbide single crystals.
[0035] A temperature measuring hole 1 is provided in the middle area of the top insulation layer 2, which improves the insulation effect near the temperature measuring hole 1 and reduces the insulation effect around it, thereby reducing the radial temperature gradient of the crucible cover, and further reducing the radial temperature gradient of crystal growth to a certain extent. Specifically, the top insulation layer 2 is formed by winding a circle of insulation felt around the outer periphery of the heating element crucible.
[0036] The function of the temperature measuring hole 1 is, on the one hand, to monitor the top surface temperature of the seed crystal during the crystal growth process; on the other hand, to reduce the temperature of the center of the top surface of the seed crystal 8. However, the existence of the temperature measuring hole alone will make the center temperature of the top surface of the seed crystal too low, resulting in an excessively large radial temperature gradient on the top surface of the seed crystal. The top insulation layer 2 has a structural feature of being high in the middle and low around the periphery, which plays a role in heat preservation of the middle part of the seed crystal, allowing heat to flow out from the periphery of the top of the crucible, reducing the radial temperature gradient on the surface of the seed crystal, which is conducive to the growth of high-quality silicon carbide single crystals.
[0037] A notch is provided at the lower inner part of the seed crystal pressure ring 7, and the height of the notch is consistent with the thickness of the seed crystal 8, specifically 2 mm; the seed crystal 8 is connected to the seed crystal pressure ring 7 through the notch. The area surrounded by the seed crystal pressure ring 7, the seed crystal 8 and the heating tube top cover 4 forms a seed crystal pressure ring cavity 6. The existence of the cavity, on the one hand, makes the seed crystal 8 and the heating tube top cover 4 have a certain distance (18 mm~22 mm) between them, which can effectively reduce the temperature around the crystal. On the other hand, the heat transfer mode between the top surface of the seed crystal 8 and the heating tube top cover 4 is changed from heat transfer to heat radiation. The seed crystal 8 connection mode of the traditional crucible is a bonding connection, that is, the seed crystal 8 is bonded to the bottom of the heating tube top cover 4 with an adhesive, and the heat transfer mode between the seed crystal 8 and the heating tube top cover 4 is heat transfer. In comparison, the heat radiation heat transfer of the embodiment of the present invention is more uniform, which can effectively reduce the radial temperature gradient inside the crystal. Under high temperature and low pressure, the seed crystal pressure ring cavity 6 can enhance the heat radiation heat transfer effect of the cavity wall, thereby reducing the radial temperature gradient of the crystal.
[0038] The thickness of the seed crystal pressure ring cavity 6 is 18 mm to 22 mm. If it is less than 18 mm, the effect of reducing the temperature around the seed crystal 8 is not obvious, affecting the growth quality of high-quality silicon carbide single crystals. If it is greater than 22 mm, the temperature around the seed crystal 8 is too low, which is not conducive to the growth of high-quality silicon carbide single crystals.
[0039] The seed crystal holder 12 is located below the seed crystal pressure ring 7, and works together with the seed crystal pressure ring 7 to form a clamping suspension connection of the seed crystal 8. The suspension connection does not require a seed crystal bonding process, thereby avoiding the influence of the seed crystal bonding process on the quality of the grown silicon carbide single crystal. In some prior arts, the crystal is directly bonded to the lowest temperature on the top of the crucible cover, and there is a large gap between the crystal and the surrounding crucible wall. The carbon- and silicon-containing gases evaporated from the bottom raw material area will flow from the bottom and side of the crystal to the crystal under the action of the temperature gradient, and form turbulence, which is not only not conducive to the stable growth of the crystal, but also the high-temperature turbulence will reduce the stability of the temperature field near the growing crystal, thereby affecting the stability of crystal growth and the quality of the crystal.
[0040] The top inner side of the seed crystal holder 12 is an inclined surface structure, and the top of the seed crystal holder 12 contacts the bottom of the seed crystal 8, supporting the seed crystal 8. In the initial stage, the mass transfer atmosphere reaches the inner cavity of the seed crystal holder 12 through the mass transfer zone 14, and the inclined surface plays a guiding role, guiding the mass transfer atmosphere to the surface of the seed crystal 8, which is conducive to the growth of high-quality silicon carbide single crystals; during the crystal growth process, the crystal will grow along the specific structure inside the seed crystal holder 12, and the inner inclined surface of the top of the seed crystal holder 12 will gradually expand the diameter of the silicon carbide single crystal, that is, it plays a role in expanding the diameter of the crystal growth.
[0041] The inclined surface of the top inner side of the seed crystal holder 12 has an inclination angle of 40° to 50°. If the angle of the inclined surface is less than 40°, the inclined surface structure of the seed crystal holder 12 cannot play a good role in expanding the diameter; if the angle of the inclined surface is greater than 50°, the bottom of the silicon carbide single crystal obtained by crystal growth will present a large inclination angle, resulting in large stress at the bottom of the crystal, which is prone to large crystal growth defects and affects the quality of the silicon carbide single crystal.
[0042] The seed crystal pressure ring 7 and the seed crystal holder 12 can form a regular annular cavity with the inner wall of the heating element crucible, and the seed crystal insulation layer 10 is filled in the annular cavity. The seed crystal insulation layer 10 can prevent the periphery of the crystal from absorbing heat from the high-temperature heating tube 9, and can effectively reduce the temperature of the periphery of the crystal, thereby effectively reducing the radial temperature gradient in the crystal and improving the quality of crystal growth.
[0043] The guide ring 11 is arranged below the seed crystal holder 12. The inner side of the guide ring 11 is a curved surface with a radius of 40 mm to 60 mm. If the radius is less than 40 mm, the curvature of the inner curved surface of the guide ring 11 is too large, and the mass transfer atmosphere is prone to lateral flow in the mass transfer zone or even reflux, which will lead to reduced mass transfer efficiency and reduced crystal growth speed. If the radius is greater than 50 mm, the curvature of the inner curved surface of the guide ring 11 is too small, and the mass transfer atmosphere flow rate is too fast, which is prone to cross in the middle of the mass transfer zone 14 to form turbulence, which will affect the crystal quality of the silicon carbide single crystal.
[0044] The inner cavities of the guide ring 11 and the seed crystal holder 12 constitute the mass transfer zone 14 of the crucible structure. The inner curved surface of the guide ring 11 and the inner inclined surface of the top of the seed crystal holder 12 make the diameters of the guide ring 11, the seed crystal holder 12 and the seed crystal pressure ring 7 distributed from bottom to top gradually decrease. The guide ring 11 and the seed crystal holder 12 work together (i.e., the mass transfer zone 14) to realize the double flow guidance of the mass transfer process of the sublimation atmosphere of the silicon carbide raw material 15. The double flow guidance can make the mass transfer atmosphere reach the surface of the seed crystal 8 more uniformly and efficiently, while avoiding the reaction between the mass transfer atmosphere and the crucible wall, thereby improving the growth quality of the silicon carbide single crystal. Specifically, the carbon- and silicon-containing gases evaporated from the bottom raw material area flow to the area directly below the seed crystal 8, flowing smoothly, which can not only avoid the formation of turbulence, but also form a heat transfer channel from bottom to top, forming a stable temperature field distribution at the front of the crystal growth, thereby ensuring the stable growth of high-quality silicon carbide crystals. The silicon carbide raw material 15 is heated and sublimated in the raw material crucible 13. The sublimation atmosphere is driven by the axial temperature gradient inside the crucible to transfer mass upwards. It first passes through the guide ring 11, and continues to transfer upwards under the guidance of the inner curved surface of the guide ring 11. Then the mass transfer atmosphere reaches the seed crystal holder 12. Under the guidance of the inner inclined surface of the top of the seed crystal holder 12, the mass transfer atmosphere reaches the surface of the seed crystal 8 through the specific channel of the mass transfer zone 14 and is deposited, so as to grow high-quality silicon carbide single crystals. At the same time, the double guidance effect prevents the mass transfer atmosphere from reacting with the side wall of the crucible, which is conducive to the growth of high-quality silicon carbide single crystals.
[0045] The structure of the seed crystal holder 12 is designed with an inclined surface. During the crystal growth process, the crystal will grow along the inner inclined surface of the seed crystal holder 12, so that the diameter of the silicon carbide single crystal will gradually expand, that is, it will play a role in expanding the diameter of the silicon carbide single crystal. In short, the seed crystal holder 12 can support the seed crystal 8 while also playing the role of guiding and expanding the diameter. The diameter expansion effect of the seed crystal holder 12 makes up for the shortcoming that the clamping and hanging connection cannot fully utilize the edge of the seed crystal.
[0046] The raw material crucible 13 is embedded in the internal cavity of the heating element crucible. The existence of the raw material crucible 13 avoids direct contact between the heating element crucible and the silicon carbide raw material 15. On the one hand, the heating element crucible can be reused, reducing production costs. On the other hand, it makes the temperature inside the silicon carbide raw material 15 more uniform, reduces the axial temperature gradient inside the silicon carbide raw material 15, and is beneficial to the decomposition and sublimation process of the silicon carbide raw material 15.
[0047] A raw material heat insulation layer 18 is provided between the middle of the raw material crucible 13 and the inner wall of the heating element crucible. Specifically, it is formed by winding a circle of thermal insulation felt. The raw material heat insulation layer 18 is fixed by a group of positioning rings 21. The raw material heat insulation layer 18 is located at the middle height position of the silicon carbide raw material 15, which plays a role of heat insulation. On the one hand, the raw material heat insulation layer 18 reduces the temperature of the middle position of the silicon carbide raw material 15, avoids the recrystallization of the silicon carbide powder during the sublimation process, and can ensure that the channel for the upward mass transfer of the silicon carbide powder remains unobstructed; on the other hand, it reduces the axial temperature gradient inside the silicon carbide raw material 15, making the decomposition and sublimation of the silicon carbide powder more stable, thereby improving the growth quality of the silicon carbide single crystal. The positioning ring 21 promotes the heat transfer from the heating tube 9 to the silicon carbide raw material 15 in a heat transfer manner. The crucible side wall cavity 16 is located on the upper and lower sides of the positioning ring 21. The cavity strengthens the heat radiation heat transfer effect of the cavity wall, thereby reducing the temperature gradient inside the silicon carbide raw material 15 and improving the growth quality of the silicon carbide single crystal; in addition, the silicon carbide raw material 15 is loaded inside the raw material crucible 13, and the top of the silicon carbide raw material 15 is 8 mm to 12 mm away from the top of the raw material crucible 13. On the one hand, the height of the mass transfer zone 14 is conducive to the sublimation and decomposition of the silicon carbide raw material 15 and the upward mass transfer, which is conducive to the growth of high-quality silicon carbide; on the other hand, an appropriate amount of silicon carbide raw material 15 can be loaded, which is conducive to the installation of the crucible structure and the growth of high-quality silicon carbide. If the distance is less than 8 mm, the mass transfer channel is too short, which is not conducive to the mass transfer process; on the other hand, the loading amount of the silicon carbide raw material 15 is too much, which is not conducive to the installation of the crucible structure. If the distance is greater than 12 mm, on the one hand, the mass transfer channel will be too long, which is not conducive to the mass transfer process; on the other hand, the loading amount of the silicon carbide raw material 15 will be too small, which may lead to insufficient raw material 15 and insufficient thickness of the silicon carbide single crystal obtained by crystal growth.
[0048] The setting of the raw material heat insulation layer 18 and the crucible side wall cavity 16 makes the temperature distribution inside the silicon carbide raw material 15 more conducive to the decomposition of the silicon carbide raw material 15, so as to facilitate the mass transfer and growth of high-quality silicon carbide single crystals. Specifically: the existence of the raw material heat insulation layer 18 reduces the temperature at the center of the silicon carbide raw material 15, avoids the recrystallization phenomenon inside the raw material, improves the sublimation decomposition process of the silicon carbide raw material 15, and is conducive to the growth of high-quality silicon carbide single crystals; the existence of the crucible side wall cavity 16 strengthens the heat radiation heat transfer effect at the upper and lower ends of the raw material crucible 13, thereby reducing the axial temperature gradient inside the silicon carbide raw material 15, improving the sublimation decomposition process of the silicon carbide raw material 15, and is conducive to the growth of high-quality silicon carbide single crystals.
[0049] Embodiment 2, A method for installing a crucible structure for growing high-quality silicon carbide single crystals using a PVT method, comprising the following steps: S1, placing the raw material crucible 13 on the heating tube base 19, and filling the silicon carbide raw material 15 into the raw material crucible 13; S2, wrapping the raw material heat insulation layer 18 between the middle of the outer wall of the raw material crucible 13 and the inner wall of the heating element crucible; S3, the heating tube 9 is detachably threadedly connected to the heating tube base 19 via the thread B17; S4, installing the guide ring 11 above the raw material crucible 13; S5, installing the seed crystal heat insulation layer 10 above the guide ring 11; S6, installing the seed crystal holder 12 above the guide ring 11; S7, installing the seed crystal 8 above the seed crystal holder 12, with the seed crystal 8 and the seed crystal holder 12 being coaxial; S8, installing the seed crystal pressure ring 7 above the seed crystal holder 12 and engaging with the seed crystal 8, so that the edge of the seed crystal 8 is clamped and suspended between the seed crystal pressure ring 7 and the seed crystal holder 12, forming a clamping and hanging connection of the seed crystal 8; S9, the heating tube top cover 4 is detachably threadedly connected to the heating tube 9 via the thread A5; S10, respectively wrapping the top insulation layer 2, the side wall insulation layer 3 and the bottom insulation layer 20 around the outside of the heating element crucible.
[0050] The installed crucible structure for growing high-quality silicon carbide single crystals by the PVT method is placed in the middle of a multi-turn electromagnetic induction coil, and the entire crucible structure is heated by electromagnetic induction heating, so that high-quality silicon carbide single crystals can be grown; resistive heating can be used as an alternative heating method.
[0051] Technical effect verification: The embodiment of the present invention improves the radial temperature gradient around the seed crystal 8, the axial temperature gradient inside the silicon carbide raw material 15, the sublimation decomposition inside the silicon carbide raw material 15, and the mass transfer process of the sublimation atmosphere. The temperature field distribution inside the crucible was simulated and verified by the simulation software Ansys Workbench.
[0052] Example 1 A crucible structure for growing high-quality silicon carbide single crystals by PVT method isothermal distribution diagram simulated in Ansys Wokbench, as shown in Figure 3 As shown in Figure 2, the crystal morphology of SiC single crystal grown by PVT method is basically consistent with the isotherm shape near the seed crystal. Figure 3 It can be seen that the isotherms near the seed crystal 8 present a slightly convex feature, which is conducive to the growth of high-quality silicon carbide single crystals. The surface morphology of the obtained silicon carbide single crystal is consistent with the isotherms and presents a slightly convex feature. The silicon carbide single crystal with such a surface morphology has the advantages of stable crystal form and few impurity defects. Figure 3It can be seen that the isotherms in the powder area (the area where the silicon carbide raw material 15 is located) are sparsely distributed, which indicates that the axial temperature gradient is low, which is conducive to the sublimation and decomposition of the silicon carbide raw material 15, and further conducive to the mass transfer of the silicon carbide raw material 15 and the growth of high-quality silicon carbide single crystals.
[0053] In comparative example 1, the top insulation layer 2 is a flat plate structure of equal height, and the seed crystal insulation layer 10 is replaced by a cavity; the rest of the structure is the same as that of example 1.
[0054] Comparative Example 2, The top insulation layer 2 is a flat plate structure of equal height, and the rest of the structure is the same as that of Example 1.
[0055] Comparative Example 3, The seed crystal heat insulation layer 10 is replaced by a cavity, and the rest of the structure is the same as that of the first embodiment.
[0056] The isotherm distribution of the structures of comparative examples 1-3 is simulated in Ansys Workbench, as shown in Figure 4-6 As shown, from Figure 4 It can be seen from the figure that the radial temperature gradient near the seed crystal 8 is too large and is not suitable for the growth of high-quality silicon carbide single crystals. Figure 5 It can be seen that the radial temperature gradient near the seed crystal 8 is Figure 4 However, the surface isotherms of the seed crystal 8 are "concave" because the top insulation layer 2 of the equal-height flat plate structure prevents the heat inside the crucible from flowing out from the top, which is not conducive to the growth of high-quality silicon carbide single crystals. Figure 6 It can be seen that the temperature near the seed crystal 8 is Figure 4 The radial temperature gradient on the surface of the seed crystal 8 is also significantly reduced. However, the isotherms on the surface of the seed crystal 8 are horizontal, which is also not conducive to the growth of high-quality silicon carbide single crystals.
[0057] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention are included in the protection scope of the present invention.
Claims
1. A crucible structure for growing silicon carbide single crystal by PVT method, comprising a heating element crucible, characterized in that: The center of the top heat-insulating layer (2) of the heating element crucible has a cylindrical protrusion protruding upward, and a temperature measuring hole (1) is provided at the center of the cylindrical protrusion; The edge of the seed crystal (8) located inside the heating element crucible is clamped and suspended between the seed crystal pressure ring (7) and the seed crystal holder (12), the seed crystal pressure ring (7) is located above the seed crystal (8), the seed crystal holder (12) is located below the seed crystal (8), and the seed crystal (8) and the seed crystal holder (12) are coaxial; a seed crystal heat insulation layer (10) is filled between the seed crystal pressure ring (7) and the inner wall of the heating element crucible, and between the seed crystal holder (12) and the inner wall of the heating element crucible; A guide ring (11) is provided below the seed crystal holder (12), the inner side of the guide ring (11) is a curved surface, and the inner side of the top of the seed crystal holder (12) is an inclined surface, so that the diameters of the guide ring (11), the seed crystal holder (12) and the seed crystal pressure ring (7) distributed from bottom to top gradually decrease, so as to guide the mass transfer atmosphere; A raw material crucible (13) is provided below the guide ring (11), and silicon carbide raw material (15) is loaded into the raw material crucible (13).
2. A crucible structure for growing silicon carbide single crystals by PVT method according to claim 1, characterized in that: The heating element crucible comprises a heating tube top cover (4), a heating tube (9) and a heating tube base (19); the heating tube top cover (4) and the heating tube (9) are detachably sealed and connected; and the heating tube (9) and the heating tube base (19) are detachably sealed and connected.
3. The crucible structure for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The ratio of the diameter of the cylindrical protrusion to the diameter of the top thermal insulation layer (2) is in the range of 0.35-0.4:
1.
4. The crucible structure for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The raw material crucible (13) is embedded in the inner cavity of the heating element crucible below the guide ring (11); the top of the silicon carbide raw material (15) is 8 mm to 12 mm away from the top of the raw material crucible (13); a raw material heat insulation layer (18) is provided between the middle of the raw material crucible (13) and the inner wall of the heating element crucible; the raw material heat insulation layer (18) is located at the middle height position of the silicon carbide raw material (15); and a crucible side wall cavity (16) is provided between other positions of the raw material crucible (13) and the inner wall of the heating element crucible.
5. The crucible structure for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The inclined surface on the inner side of the top of the seed crystal holder (12) has an inclination angle of 40° to 50°.
6. The crucible structure for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The radius of the curved surface on the inner side of the guide ring (11) is 40 mm to 60 mm.
7. The crucible structure for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: A notch is provided at the lower inner portion of the seed crystal pressure ring (7), and the shape and height of the notch match the edge of the seed crystal (8).
8. The crucible structure for growing silicon carbide single crystal by PVT method according to claim 1, characterized in that: The area enclosed by the seed crystal pressure ring (7), the seed crystal (8) and the top of the heating element crucible forms a seed crystal pressure ring cavity (6), and the thickness of the seed crystal pressure ring cavity (6) is 18 mm to 22 mm.
9. The crucible structure for growing silicon carbide single crystal by PVT method according to claim 4, characterized in that: The top of the silicon carbide raw material (15) is at a fixed distance from the top of the raw material crucible (13).
10. The method for installing a crucible structure for growing silicon carbide single crystals by a PVT method as claimed in claim 2, characterized in that: The following steps are involved: S1, placing a raw material crucible (13) on a heating tube base (19), and loading silicon carbide raw material (15) into the raw material crucible (13); S2, arranging a raw material heat insulation layer (18) between the middle of the outer wall of the raw material crucible (13) and the inner wall of the heating element crucible; S3, connecting the heating tube (9) and the heating tube base (19) in a detachable and sealed manner; S4, installing the guide ring (11) above the raw material crucible (13); S5, installing the seed crystal heat insulation layer (10) above the guide ring (11); S6, installing the seed crystal holder (12) above the guide ring (11); S7, installing the seed crystal (8) above the seed crystal holder (12), with the seed crystal (8) being coaxial with the seed crystal holder (12); S8, installing the seed crystal pressure ring (7) above the seed crystal holder (12) and engaging it with the seed crystal (8), so that the edge of the seed crystal (8) is clamped and suspended between the seed crystal pressure ring (7) and the seed crystal holder (12); S9, connecting the heating tube top cover (4) and the heating tube (9) in a detachable and sealed manner; S10, a top insulation layer (2), a side wall insulation layer (3) and a bottom insulation layer (20) are respectively provided on the top, side wall and bottom outer sides of the heating element crucible.