Silicon carbide single crystal growth apparatus and method for improving powder utilization

Abstract

The application provides a silicon carbide single crystal growth device and method for improving powder utilization, which comprises a heating barrel, a crucible and a heat conduction component, the heating barrel comprises a barrel body and a matched upper cover, the barrel body contains the crucible, the bottom of the crucible is provided with a through hole, the bottom of the barrel body is provided with a heat conduction rod, and the heat conduction rod extends into the crucible; the crucible comprises a crucible cover and a crucible body, the lower end of the crucible cover is provided with a silicon carbide seed crystal, the crucible body contains silicon carbide powder, the heat conduction component is arranged in a charging area, the heat conduction component comprises a heat conduction tower and a heat conduction ring, the heat conduction tower is internally provided with a hollow structure, the heat conduction tower is sleeved outside the heat conduction rod, a plurality of layers of heat conduction rings are arranged on the heat conduction tower, the heat conduction rings extend outward and act on different areas of the charging area. The application introduces the heating barrel and the heat conduction structure in the silicon carbide single crystal growth process, improves the powder utilization, improves the growth structure sealing performance and realizes the efficient utilization of the powder in the growth process.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor technology, specifically relating to a silicon carbide single crystal growth apparatus and method for improving powder utilization. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Silicon carbide, as a third-generation semiconductor material, has great application potential in fields such as rail transportation, electric vehicles, high-voltage power transmission and transformation, photovoltaics, and chips due to its many characteristics, including large bandgap, strong critical breakdown field, high thermal conductivity, and high saturation drift velocity.

[0004] The primary growth method for silicon carbide single crystals is physical vapor transport (PVT). In this process, silicon carbide powder is placed at the bottom of the crucible, and a silicon carbide seed crystal is placed at the top. The powder at the bottom of the crucible, with its higher temperature, sublimates and, driven by the temperature gradient, is transported to the lower-temperature silicon carbide seed crystal at the top for deposition and growth. Induction heating is a commonly used heating mode in PVT for silicon carbide single crystal growth due to its low power consumption. However, in induction heating, the crucible wall acts as the heat source, and due to the skin effect, the temperature of the crucible wall is significantly higher than that of the center, resulting in a significant radial temperature gradient within the crucible. The growth of large-diameter silicon carbide single crystals requires large-diameter crucibles as both the reaction vessel and the heating element; increasing the crucible diameter further exacerbates this radial temperature gradient within the crucible.

[0005] During silicon carbide single crystal growth, the temperature at the bottom of the powder is high, while the temperature at the seed crystal is low. When the axial temperature gradient in the powder increases, the gaseous components are prone to crystallizing at the top of the powder, hindering the transport of growth gaseous components to the seed crystal and resulting in a significant reduction in powder utilization. Furthermore, after sublimation and decomposition, some residual carbon remains at the bottom of the crucible, affecting heat transfer from the crucible bottom to the powder surface. If the radial temperature gradient is too large, the powder on the sidewalls may move towards the center after sublimation, potentially causing recrystallization at the center of the powder, thus affecting powder utilization efficiency and reducing the growth rate.

[0006] Meanwhile, during the PVT growth process, due to the porosity of the graphite crucible and the inability to completely seal its structure, the silicon carbide powder decomposes and sublimates upon heating. The sublimated components not only deposit at the seed crystal position to achieve crystal growth, but also leak from the crucible structure through voids and gaps, thereby corroding the insulation structure and even the growth furnace structure. This will affect the service life of the insulation, crucible, and even the furnace chamber, increasing the cost of use.

[0007] Existing technology CN118461121A discloses setting multiple induction components inside the crucible body to inductively heat silicon carbide powder, reducing the temperature gradient within the powder and improving the temperature uniformity of the powder inside the crucible. However, due to the skin effect and the conversion efficiency of induction heating, the multiple induction components inside the crucible cannot be effectively heated, and the powder utilization rate cannot be effectively improved. Existing technology CN216688415U discloses using accessories inserted into the center of the powder source inside the crucible to increase the surface area for sublimation of the powder source and increase the sublimation rate of the central powder source. However, since the silicon carbide powder sublimated at the bottom will recrystallize on the lower-temperature accessories, the powder utilization rate cannot be effectively improved. Existing technology CN221918323U discloses placing a double layer of porous graphite inside the crucible to adjust the temperature field and improve the powder utilization rate. However, the axial and radial temperature gradients of the powder are both too large, which will hinder the efficient utilization of the powder. Summary of the Invention

[0008] To address the issues of low powder utilization and leakage of silicon carbide vapor components affecting the lifespan of the growth assembly under the aforementioned crucible structure, this invention proposes a silicon carbide single crystal growth apparatus and method to improve powder utilization. This invention introduces a heating chamber and heat-conducting structure during the silicon carbide single crystal growth process, thereby improving powder utilization, enhancing the sealing of the growth structure, achieving efficient powder utilization during growth, extending the lifespan of the growth apparatus, and reducing costs.

[0009] According to some embodiments, the present invention adopts the following technical solution:

[0010] In a first aspect, the present invention provides a silicon carbide single crystal growth apparatus that improves powder utilization, thereby increasing the airtightness of the growth system and extending the service life of the growth crucible, heat preservation unit, and single crystal furnace.

[0011] A silicon carbide single crystal growth apparatus for improving powder utilization includes a heating barrel, a crucible, and a heat-conducting component. The heating barrel includes a matching top cover and a barrel body. The crucible is housed inside the barrel body. A through hole is provided at the bottom of the crucible, and a heat-conducting rod is provided at the bottom of the barrel body. The heat-conducting rod extends upward into the interior of the crucible through the through hole.

[0012] The crucible includes a matching crucible lid and crucible body. A silicon carbide seed crystal is provided at the lower end of the crucible lid. The lower part of the crucible body is a loading area, which carries silicon carbide powder. The space between the silicon carbide seed crystal and the surface of the silicon carbide powder is a growth cavity.

[0013] A heat-conducting component is provided in the loading area. The heat-conducting component includes a heat-conducting tower and heat-conducting rings. The heat-conducting tower has a hollow structure inside and is sleeved on the outside of the heat-conducting rod. Several layers of heat-conducting rings are provided on the heat-conducting tower and extend outward to act on different areas of the loading area.

[0014] As an alternative implementation, the heating barrel and heat-conducting rod are made of graphite, and the heat-conducting tower and heat-conducting ring are made of at least one of graphite, metal carbide, or metal.

[0015] As a further defined embodiment, the graphite material includes at least one of isostatic graphite and extruded graphite, the metal carbide material includes at least one of tantalum carbide and niobium carbide, and the metal material includes at least one of tantalum and niobium.

[0016] As an alternative implementation, the wall thickness of the heating barrel is the same as that of the crucible, the inner diameter of the heating barrel is adapted to the outer diameter of the crucible, and the height of the heating barrel is 120% to 200% of the height of the crucible.

[0017] As an alternative implementation, the diameter and height of the crucible can be adjusted according to the required size of the grown crystal.

[0018] As an alternative implementation, the height of the loading zone is 30% to 60% of the crucible height, and the growth chamber is 40% to 70% of the crucible height.

[0019] As an alternative implementation, the height of the heat-conducting rod is less than the height of the loading area, the diameter of the heat-conducting rod is 5% to 15% of the diameter of the crucible, and the diameter of the hollow structure inside the heat-conducting tower is 10% to 20% of the diameter of the crucible; the total height of the heat-conducting tower is the same as the height of the loading area and is higher than the height of the heat-conducting rod.

[0020] As an alternative implementation, the heat transfer tower includes several layers, and each layer has a variable diameter structure on the side in contact with the silicon carbide material, with the diameter increasing from top to bottom.

[0021] Preferably, the variable diameter structure is frustum-shaped.

[0022] As a further defined embodiment, the top diameter of the heat-conducting tower is 10% to 20% of the crucible diameter, and the bottom diameter of the heat-conducting tower is 15% to 30% of the crucible diameter, which is consistent with the size of the central hole at the bottom of the crucible.

[0023] As an alternative implementation, the heat-conducting ring includes an inner ring, an outer ring, and spokes. The diameter of the inner ring is set according to the number of layers in the heat-conducting tower or the diameter at the location where it is installed in the heat-conducting tower. The diameter of the outer ring is 80% to 90% of the diameter of the loading area.

[0024] The inner and outer rings are connected by multiple spokes arranged in a circular pattern.

[0025] The inner ring, outer ring, and spokes are all made of thermally conductive materials, and the diameters of the inner and outer rings, as well as the number of spokes, can be flexibly set according to thermal conductivity requirements.

[0026] As an alternative implementation, the silicon carbide single crystal growth apparatus further includes a heating system disposed outside the heating barrel, with insulation material filling the space between the heating barrel and the heating system.

[0027] Secondly, the present invention provides a method for growing silicon carbide single crystals, using the silicon carbide single crystal growth apparatus described above.

[0028] A method for growing silicon carbide single crystals includes the following steps:

[0029] The heat-conducting tower and the bottom hole of the crucible are sealed by a threaded connection. Then the crucible is placed into the heating barrel, so that the heat-conducting rod is embedded in the cylindrical hole inside the heat-conducting tower.

[0030] Spread silicon carbide powder evenly on the bottom of the graphite crucible, with the powder height level with the height of the heat conduction tower. Depending on the shape of the heat conduction tower and the inner diameter of the inner ring of the heat conduction ring, place the heat conduction ring on the surface of the powder or embed it in the powder. Fit the inner ring of the heat conduction ring into the heat conduction tower. Fix the silicon carbide seed crystal on the top cover of the crucible.

[0031] Place the heating tank along with the graphite crucible into the growth device, seal the growth device, and evacuate its interior.

[0032] The inside of the growth device after vacuum treatment is heated, and carrier gas is introduced into the growth device. After the temperature reaches the expected temperature, it is kept constant to sublimate the silicon carbide powder. The sublimated powder is transported to the surface of the silicon carbide seed crystal to achieve crystal growth.

[0033] After the crystal growth is complete, the inside of the growth device is cooled down, and a carrier gas is introduced into the growth device to allow the crystal to cool naturally, thus obtaining a silicon carbide single crystal.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention innovatively introduces a heating barrel and a heat-conducting structure into the silicon carbide single crystal growth process. The heating barrel is heated by induction heating. The graphite heating barrel conducts or radiates the heat generated by induction to the crucible wall and the heat-conducting rods extending into the crucible, thereby heating the heating tower and heating ring. This allows for the regulation of the temperature field in the material loading area of ​​the crucible, effectively improving the utilization rate of powder.

[0036] The inner diameter and number of spokes of the heat-conducting ring of this invention can be adjusted as needed to achieve efficient utilization of silicon carbide powder. After the powder sublimates at the bottom of the crucible, a loose graphitized residue forms at the bottom of the crucible. The sublimated silicon carbide component grows into crystals at the top along the temperature gradient and carrier gas, while the other part recrystallizes into polycrystalline silicon carbide on the heat-conducting ring, increasing the weight of the heat-conducting ring. When the graphitized residue can no longer support the heat-conducting ring and the polycrystalline silicon carbide crystals on it, the heat-conducting ring slowly moves along the heat-conducting tower towards the bottom of the crucible, achieving automatic transfer of the powder from the low-temperature zone to the high-temperature zone. Furthermore, the heat-conducting tower of this invention can be a frustum structure, allowing the heat-conducting ring to gradually approach the high-temperature position during its descent, gradually improving heat transfer efficiency. This fully heats the remaining powder and the recrystallized polycrystalline silicon carbide, solving the problem of powder crystallization affecting crystal growth in traditional crucibles.

[0037] The heating barrel in this invention is designed as a closed system, which ensures the airtightness of the growth crucible chamber. This effectively prevents the leakage of silicon carbide components during the growth process from affecting the insulation structure or even the single crystal growth furnace, extending the service life of the graphite components, and significantly reducing the complexity of the crystal growth process and the growth cost of silicon carbide single crystals.

[0038] Compared to structures that only use a heating barrel to heat the crucible, this invention introduces a heat-conducting component to achieve direct heating of the powder's interior, avoiding the problem of crystallization at the center of the powder, effectively improving heat transfer efficiency, reducing power loss, and significantly lowering production costs.

[0039] The various structures of this invention are compatible with current growth processes, and the dimensions of different components can be adjusted and adapted according to existing silicon carbide growth equipment, making it easy to promote and use.

[0040] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0041] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0042] Figure 1 This is a schematic diagram of a silicon carbide single crystal growth apparatus in one embodiment. (a) shows the initial growth state, and (b) shows the state during the growth process.

[0043] Figure 2 This is a three-dimensional disassembled view of a silicon carbide crystal growth apparatus in one embodiment;

[0044] Figure 3 This is a temperature field distribution diagram of a graphite crucible for silicon carbide single crystal growth obtained from numerical simulation in one embodiment.

[0045] Figure 4 This is a temperature field diagram inside a graphite crucible for silicon carbide single crystal growth obtained through numerical simulation in one embodiment.

[0046] Figure 5 This is a temperature field diagram of the graphite crucible powder for silicon carbide single crystal growth obtained from numerical simulation in another embodiment.

[0047] Among them, 1 is the heating barrel cover, 2 is the heating barrel body, 3 is the crucible cover, 4 is the silicon carbide seed crystal, 5 is the crucible body, 6 is the heat-conducting tower, 7 is the heat-conducting ring, 8 is the heat-conducting rod, 9 is the growth chamber, and 10 is the silicon carbide powder.

[0048] 61 - Upper circular surface of the heat conduction tower; 62 - Middle circular surface of the heat conduction tower; 63 - Lower circular surface of the heat conduction tower.

[0049] 71-Inner ring of the heat-conducting ring, 72-Spokes of the heat-conducting ring, 73-Outer ring of the heat-conducting ring. Detailed Implementation

[0050] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0051] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0052] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0053] Where there is no conflict, the embodiments and features described in this application may be combined with each other.

[0054] To make the technical solution of this invention clearer to those skilled in the art, the following definitions are provided:

[0055] Radial temperature gradient within the powder: In this invention, this refers to the temperature difference between the center and the edge of the silicon carbide powder surface per unit length. In a typical crucible structure, a larger radial temperature gradient within the material makes it easier for the sublimated powder at the edges to agglomerate towards the center, leading to recrystallization. This affects the transport of components to the growth chamber and is detrimental to crystal growth.

[0056] Axial temperature gradient within the powder: In this invention, this refers to the temperature difference between the surface of the silicon carbide powder and the corresponding bottom position per unit length. In a typical crucible structure, a larger axial temperature gradient within the powder makes it easier for the components released by sublimation to crystallize on the powder surface, affecting the transport of components to the growth chamber and hindering crystal growth.

[0057] Location of low-temperature zone: In this invention, it refers to the location of the region in the powder with a lower internal temperature during the growth process.

[0058] Location of high-temperature zone: In this invention, it refers to the location of the area with a high internal temperature in the powder during the growth process.

[0059] Crystal growth rate: In this invention, it refers to the change in weight of a silicon carbide single crystal per unit time. The faster the crystal growth rate, the higher the crystal growth efficiency.

[0060] Powder utilization rate: In this invention, it refers to the proportion of silicon carbide powder mass converted into silicon carbide single crystal mass during the silicon carbide single crystal growth process. From the perspective of SiC single crystal preparation cost, a higher powder utilization rate indicates a higher crystal growth efficiency.

[0061] Example 1

[0062] Silicon carbide crystal growth apparatus, such as Figure 1 As shown in (a) and (b), the device includes a heating barrel, a crucible, and a heat-conducting assembly. The heating barrel comprises a heating barrel cover 1 and a heating barrel body 2. In this embodiment, it is suitable for a graphite crucible with a silicon carbide seed crystal on top and containing silicon carbide powder inside. A cylindrical heat-conducting rod 8 extending upward into the crucible is mounted at the center of the bottom of the barrel body. The crucible comprises a crucible cover 3 and a crucible body 5. The silicon carbide seed crystal 4 is fixed at the crucible cover position above the crucible. The area from the silicon carbide seed crystal 4 to the surface of the silicon carbide powder 10 forms a growth cavity 9. Below the growth cavity 9 is a loading area. The center of the bottom of the crucible body 5 has a hole that allows the heat-conducting rod 8 at the bottom of the heating barrel to extend into the loading area. The heat-conducting assembly comprises a heat-conducting tower 6 and a heat-conducting ring 7. Both the heat-conducting tower 6 and the heat-conducting ring 7 are located in the crucible loading area. The heat-conducting tower 6 can be assembled and sealed with the center hole at the bottom of the crucible via a bottom thread. The interior of the heat-conducting tower 6 is a hollow structure, as shown in the figure. Figure 2 and Figure 3 As shown, the heat-conducting rod 8 at the bottom of the heating barrel can be embedded in the heat-conducting tower 6. The heat-conducting ring 7 is divided into an inner heat-conducting ring 71 and an outer heat-conducting ring 73. The inner heat-conducting ring 71 and the outer heat-conducting ring 73 are connected by multiple heat-conducting ring spokes 72. The inner heat-conducting ring 71 can be fitted onto the heat-conducting tower 6.

[0063] In this embodiment, the heating barrel and heat-conducting rod 8 are made of graphite, and the heat-conducting tower 6 and heat-conducting ring 7 are at least one of graphite, metal carbide, or metal. The graphite material includes at least one of isostatic graphite and extruded graphite; the metal carbide material includes at least one of tantalum carbide and niobium carbide; and the metal material includes at least one of tantalum and niobium.

[0064] In some preferred embodiments, the wall thickness of the heating barrel is the same as the wall thickness of the crucible, the inner diameter of the heating barrel is the same as the outer diameter of the crucible, and the height of the heating barrel is 120% to 200% of the height of the crucible.

[0065] In other embodiments, the diameter and height of the crucible can be adjusted according to the actual size requirements of the grown crystal.

[0066] In some preferred embodiments, the height of the loading zone is 30% to 60% of the crucible height, and the growth chamber is 40% to 70% of the crucible height.

[0067] In some preferred embodiments, the height of the heat-conducting rod 8 is slightly lower than the height of the loading area, and the diameter of the heat-conducting rod is 5% to 15% of the diameter of the crucible, which is slightly smaller than the diameter of the hollow cylinder inside the heat-conducting tower.

[0068] In some preferred embodiments, the total height of the heat-conducting tower 6 is the same as the height of the loading area and slightly higher than the height of the heat-conducting rod. The diameter of the internal cylindrical hollow structure of the heat-conducting tower 6 is 10% to 20% of the diameter of the crucible and slightly larger than the diameter of the heat-conducting rod 8.

[0069] In some preferred embodiments, the side of the heat-conducting tower 6 that contacts the silicon carbide powder 10 in the crucible is frustum-shaped, and the number of frustum layers in the heat-conducting tower can be adjusted according to actual requirements. The top diameter of the heat-conducting tower 6 is 10% to 20% of the crucible diameter, and the bottom diameter of the heat-conducting tower 6 is 15% to 30% of the crucible diameter, consistent with the size of the central hole at the bottom of the crucible. The inner diameter of the heat-conducting ring 7 is adjusted according to the number of frustum layers in the heat-conducting tower 6, and the outer diameter of the heat-conducting ring 7 is 80% to 90% of the diameter of the loading area.

[0070] In other preferred embodiments, the silicon carbide single crystal growth apparatus includes the graphite crucible, a heating barrel, and a heating system disposed around the heating barrel, with insulation material filling the space between the heating barrel and the heating system.

[0071] Example 2

[0072] This embodiment provides a silicon carbide single crystal growth apparatus, the operation of which specifically includes the following steps:

[0073] (1) A heat-conducting tower 6 with a double-layer frustum structure is selected. The height of the heat-conducting tower 6 is 56% of the height of the crucible 5, and the height of both frustums is 28% of the height of the crucible 5. The diameters of the frustum surfaces 61 and 62 are 15% and 25% of the crucible diameter, respectively, and the diameters of the lower surfaces of the two frustums are 20% and 30% of the crucible diameter, respectively. The heat-conducting tower 6 is connected to the bottom hole of the crucible 5, and then the crucible 5 is placed in the heating barrel 2. The height of the heating barrel 2 is 130% of the height of the crucible 5. The heat-conducting rod 8 is embedded in the cylindrical cavity inside the heat-conducting tower 6. The internal diameter of the heat-conducting tower 6 is 12% of the diameter of the crucible 5, and the diameter of the heat-conducting rod 8 is 10% of the diameter of the crucible 5.

[0074] (2) Spread silicon carbide powder evenly in the bottom loading area 10 of crucible 5 until the powder height is level with the height of the circular surface 62 of the heat conduction tower 6. Then, insert a heat conduction ring with an inner diameter 71 that matches the size of the lower circular surface 63 of the heat conduction tower into the circular surface 62 of the heat conduction tower and place it on the powder surface. Continue to add silicon carbide powder until the powder height is finally level with the circular surface 61 of the heat conduction tower. Place a heat conduction ring with an inner diameter 71 that matches the size of the circular surface 62 of the heat conduction tower on the powder surface. The inner ring 71 of the heat conduction ring is inserted into the circular surface 61 of the heat conduction tower. The outer diameter 73 of both heat conduction rings is 90% of the diameter of the loading area 10. The final height of the loading area 10 is 60% of the height of crucible 5, and the total loading is 5000g.

[0075] (3) Fix the silicon carbide seed crystal 4 to the position of the crucible cover 3, and then place the crucible cover 3 on the crucible 5 to form a sealed structure. Then place the heating barrel cover 1 on the heating barrel 2 to form a sealed structure.

[0076] (4) Place the heating barrel 2 together with the graphite crucible 5 into the growth device, seal the growth device, and perform vacuum treatment on its interior.

[0077] (5) The inside of the growth apparatus after vacuum treatment is heated, and carrier gas is introduced into the growth apparatus. The heating barrel is heated to 2150℃ for crystal growth and held at this temperature for 200h. The power of the heating power supply during the growth process is 18570W. After the growth is completed, the system is cooled to obtain silicon carbide single crystals.

[0078] The graphite crucible 5 was removed from the growth furnace, yielding silicon carbide single crystals. It was found that the silicon carbide powder consisted entirely of loose, graphitized residue, with no crystals inside or on the surface. No silicon carbide powder crystals were observed on the heat-conducting tower 6 or the two heat-conducting rings 7, and both heat-conducting rings 7 showed significant displacement towards the bottom of the crucible 5 relative to their initial positions. This indicates that the powder moved from a low-temperature region to a high-temperature region during the growth process.

[0079] The mass of the silicon carbide single crystal was weighed using a balance and found to be 4563g. The mass of the leaked component was 102g, and the remaining silicon carbide powder was 335g. Calculations showed that the crystal growth rate was 22.8g / H, and the powder conversion rate was 91.26%. This indicates that the silicon carbide powder utilization rate is high in this method, and the increase in single crystal mass per unit time is significant. Numerical simulation of this embodiment yielded the temperature field diagram within the powder in graphite crucible 5, as shown below. Figure 4 As shown, the isotherms inside the graphite crucible 5 are sparsely distributed, indicating a small radial temperature gradient in the powder. This results in uniform heating of the powder overall, suppressing crystallization of the powder at the edges and improving powder utilization. Simultaneously, the temperature field diagram shows that the top of the loading area 10 near the growth chamber 9 is a low-temperature zone, while the loading area 10 near the bottom of the crucible 5 and the heat-conducting tower 6 is a high-temperature zone. During growth, the powder moves from the low-temperature zone to the high-temperature zone along with the movement of the heat-conducting ring 7 towards the bottom of the crucible 5, reducing the axial temperature gradient of the powder. This allows for near-equilibrium crystal growth in the loading area with a small axial gradient while maintaining a high single crystal growth rate.

[0080] Weighing the insulation structure with a balance revealed an increase in weight of 8g. Weighing the heating tank 2 structure with the same balance revealed an increase in weight of 89g, indicating that the heating tank 2 structure has good sealing properties and can effectively prevent component leakage.

[0081] Example 3

[0082] The difference from Example 1 is:

[0083] This embodiment provides a method for growing silicon carbide crystals, which specifically includes the following steps:

[0084] (1) Select a heat-conducting tower 6 with only a single-layer frustum structure, i.e., the heat-conducting tower 6 only includes an upper circular surface 61 and a lower circular surface 62. The height of the heat-conducting tower 6 is 56% of the crucible height, the diameter of the upper circular surface 61 is 15% of the crucible diameter, the diameter of the lower circular surface 62 is 30% of the crucible diameter, and the height of the heat-conducting tower 6 is 56% of the crucible height. The heat-conducting tower 6 is connected to the bottom hole of the crucible 5, and then the crucible 5 is placed in the heating barrel 2. The height of the heating barrel 2 is 130% of the height of the crucible 5. The heat-conducting rod 8 is embedded in the cylindrical cavity inside the heat-conducting tower 6. The diameter of the cavity inside the heat-conducting tower 6 is 12% of the crucible diameter, and the diameter of the heat-conducting rod 8 is 10% of the crucible diameter.

[0085] (2) Spread silicon carbide powder evenly in the bottom loading area 10 of crucible 5. The final height of the powder is slightly higher than the upper circular surface 61 of the heat conduction tower. Place a heat conduction ring with an inner diameter 71 that is the same as the lower circular surface 63 of the heat conduction tower on the powder surface. The inner ring 71 of the heat conduction ring fits into the upper circular surface 61 of the heat conduction tower. The outer diameter 73 of the heat conduction ring is 90% of the diameter of the loading area. The final height of the loading area 10 is 60% of the height of crucible 5. The total weight of the powder is 5320g.

[0086] (3) Fix the silicon carbide seed crystal 4 to the position of the crucible cover 3, and then place the crucible cover 3 on the crucible 5 to form a sealed structure. Then place the heating barrel cover 1 on the heating barrel 2 to form a sealed structure.

[0087] (4) Place the heating barrel together with the graphite crucible 5 into the growth device, seal the growth device, and perform vacuum treatment on its interior.

[0088] (5) The inside of the growth apparatus after vacuum treatment is heated, and carrier gas is introduced into the growth apparatus. The heating barrel 2 is heated to 2150℃ for crystal growth and held at that temperature for 200h. The power of the heating power supply during the growth process is 18300W. After the growth is completed, the system is cooled down to obtain silicon carbide single crystal.

[0089] The graphite crucible 5 was removed from the growth furnace, yielding a silicon carbide single crystal. The silicon carbide powder was found to be a loose, scattered residue of graphitized material, containing very few silicon carbide crystalline particles. No silicon carbide powder crystals were found on the heat-conducting tower 6 and the heat-conducting ring 7. The heat-conducting ring 7 had partially shifted downwards from its initial position. This indicates that the powder moved from a low-temperature region to a high-temperature region during growth, but the single layer of the heat-conducting ring 7 was insufficient to heat the temperature field inside the crucible 5. The mass of the silicon carbide single crystal was weighed to be 4183g, the mass of the leaked component was 98g, and the mass of the remaining silicon carbide powder was 1039g. Calculations showed a crystal growth rate of 20.9g / H and a powder conversion rate of 78.6%. This indicates that the utilization rate of silicon carbide powder in this method is still relatively high.

[0090] Weighing the insulation structure with a balance revealed an increase in weight of 9g. Weighing the heating tank 2 structure with the same balance revealed an increase in weight of 81g, indicating that the heating tank 2 structure has good sealing properties and can effectively prevent component leakage.

[0091] Example 4

[0092] Unlike Example 1:

[0093] This embodiment provides a method for growing silicon carbide crystals, which specifically includes the following steps:

[0094] (1) Select a heat-conducting tower 6 with a three-layer frustum structure. The heat-conducting tower 6 is connected to the bottom hole of the crucible 5. The height of the heat-conducting tower 6 is 56% of the height of the crucible. The upper surface diameters of the three frustums are 12%, 17%, and 25% of the diameter of the crucible 5, respectively. The lower surface diameters of the three frustums are 15%, 20%, and 30% of the diameter of the crucible, respectively. The heights of the three frustums are 18%, 18%, and 20% of the height of the crucible, respectively. Then, place the crucible 5 into the heating barrel 2. The height of the heating barrel 2 is 140% of the height of the crucible 5. The heat-conducting rod 8 is embedded in the cylindrical cavity inside the heat-conducting tower 6. The inner diameter of the heat-conducting tower 6 is 11% of the diameter of the crucible 5, and the diameter of the heat-conducting rod 8 is 10% of the diameter of the crucible.

[0095] (2) Spread silicon carbide powder evenly in the bottom loading area 10 of crucible 5. The final powder height is slightly higher than the upper circular surface 61 of the heat conduction tower. Then, embed two heat conduction rings with inner diameters decreasing in size into the silicon carbide powder. The position of the heat conduction ring 7 is consistent with the height of the circular surface of the heat conduction tower corresponding to its inner diameter. The heat conduction ring 7 with the smallest inner diameter is fitted into the heat conduction tower. The outer diameter of the three heat conduction rings is 90% of the diameter of the loading area 10. The final height of the loading area 10 is 60% of the height of crucible 5. The total loading is 4570g. Due to the large number of components, the loading amount is relatively small.

[0096] (3) Fix the silicon carbide seed crystal 4 to the position of the crucible cover 3, and then place the crucible cover 3 on the crucible 5 to form a sealed structure. Then place the heating barrel cover 1 on the heating barrel 2 to form a sealed structure.

[0097] (4) Place the heating barrel 2 together with the graphite crucible 5 into the growth device, seal the growth device, and perform vacuum treatment on its interior.

[0098] (5) The inside of the growth apparatus after vacuum treatment is heated, and carrier gas is introduced into the growth apparatus. The heating barrel 2 is heated to 2150℃ for crystal growth and held at that temperature for 200h. The power of the heating power supply during the growth process is 19010W. After the growth is completed, the system is cooled down to obtain silicon carbide single crystal.

[0099] (6) The graphite crucible 5 was removed from the growth furnace, yielding a silicon carbide single crystal. It was found that the silicon carbide powder was a loose, scattered graphitized residue. No silicon carbide powder crystals were found on the heat-conducting tower and heat-conducting rings. The three heat-conducting rings 7 had shifted downwards relative to their initial positions, indicating that the powder had moved from a low-temperature region to a high-temperature region during growth. The mass of the silicon carbide single crystal was weighed using a balance and found to be 3946g. The mass of the leaked component was 107g, and the mass of the remaining silicon carbide powder was 417g. Calculations showed that the crystal growth rate was 19.73g / H, and the powder conversion rate was 86.3%. This indicates that the utilization rate of the silicon carbide powder in this method is high, but the increase in crystal mass per unit time is smaller. This is because the amount of material loaded is smaller, resulting in more residual graphitized residue in the later stages of growth, which is detrimental to heat transfer in crucible 5. The remaining powder is difficult to sublimate, thus reducing the crystal growth rate.

[0100] Weighing the insulation structure with a balance revealed an increase in weight of 7g. Weighing the heating tank structure with the same balance revealed an increase in weight of 69g, indicating that the heating tank structure has good sealing properties and can effectively prevent component leakage.

[0101] Comparative Example 1

[0102] In this comparative example, silicon carbide powder, used as raw material, was placed directly at the bottom of a graphite crucible 5. No heating chamber 2 was added outside the crucible 5, and no heat-conducting components were placed inside. Silicon carbide single crystal growth was performed, with all other growth conditions identical to those in Example 1. After growth, the graphite crucible 5 was removed from the growth furnace, yielding a silicon carbide single crystal. Severe crystallization was observed inside and on the surface of the silicon carbide powder, indicating a large axial and radial temperature gradient within the powder and low powder utilization. The mass of the silicon carbide single crystal was 2842g, the mass of leaked silicon component was 113g, and the remaining silicon carbide powder was 2045g. The crystal growth rate was 14.21g / H, and the powder utilization rate was only 56.8%. This indicates that the internal temperature field distribution of the powder in this example is uneven, resulting in low silicon carbide powder utilization.

[0103] Numerical simulation was performed on this comparative example to obtain the temperature field diagram inside the graphite crucible powder, as shown below. Figure 5 As shown, due to the reduction in the height of the heating tank, the corresponding crucible position will shift downwards, and the corresponding high-temperature zone will shift upwards. This is in... Figure 5 This is reflected in the temperature field distribution diagram. (And...) Figure 4 The temperature field distribution diagrams are different. The isotherm distribution in the charging area shows that there are more at the edge of the crucible and fewer in the center of the powder. This indicates that the temperature field of the powder has a large radial and axial gradient. This also explains why the powder center is severely crystallized during the actual growth process, which greatly hinders the transport of components, is not conducive to the sublimation of the powder, and causes powder waste.

[0104] Weighing the insulation structure using a balance revealed that it had gained 101g, indicating that most of the components that seeped out of the crucible condensed on the insulation structure, while the remainder condensed inside the single crystal furnace.

[0105] Comparative Example 2

[0106] In this comparative example, the heat-conducting tower shape 7 was replaced with a hollow cylindrical graphite barrel, and the heating barrel 2 assembly was no longer added outside the crucible 5. Silicon carbide single crystal growth was performed, with all other growth conditions identical to Example 1. After growth, the graphite crucible 5 was removed from the growth furnace, yielding silicon carbide single crystals. Crystallization was observed inside and on the surface of the silicon carbide powder, and a large amount of recrystallized polycrystalline silicon carbide was present on the side of the hollow cylindrical graphite barrel in contact with the powder. This indicates that the axial and radial temperature gradients inside the powder are both large, leading to extensive crystallization of components on the hollow cylindrical graphite barrel, severely hindering upward component transport and resulting in low powder utilization.

[0107] The mass of the silicon carbide single crystal was measured using a balance and found to be 2725g. The mass of the leaked silicon component was 107g, and the mass of the remaining silicon carbide powder was 2168g. Calculations show that the crystal growth rate is 13.63g / H, and the powder utilization rate is only 54.5%.

[0108] Numerical simulation of this comparative example shows that the isotherms are densely distributed inside the powder in graphite crucible 5, indicating that the radial and axial temperature gradients in the loading area are large and the temperature field distribution is uneven. At the same time, the temperature of the hollow cylindrical graphite barrel is low, which is consistent with the actual situation.

[0109] Weighing the insulation structure using a balance revealed that it had gained 83g, indicating that most of the components that seeped out of the crucible condensed on the insulation structure, while the remainder condensed inside the single crystal furnace.

[0110] Comparative Example 3

[0111] In this comparative example, the heat-conducting tower 6, heat-conducting ring 7, and heat-conducting rod 8 are removed. A heating barrel assembly is added outside the crucible 5 for silicon carbide single crystal growth. All other growth conditions are identical to those in Example 1. During growth, the power supply for heating is 19510W, 5% higher than in Example 1. After growth, the graphite crucible 5 is removed from the growth furnace, yielding a silicon carbide single crystal. Extensive crystallization is observed inside and on the surface of the silicon carbide powder. This indicates a large axial and radial temperature gradient within the powder, resulting in low powder utilization. Weighing the silicon carbide single crystal using a balance yields 2417g, with 98g of leaked silicon component, leaving 2485g of remaining silicon carbide powder. The calculated crystal growth rate is 12.08g / H, resulting in a powder utilization rate of only 48.3%. This indicates an uneven temperature distribution within the powder in this example, leading to low silicon carbide powder utilization.

[0112] Numerical simulation of this comparative example revealed a dense distribution of isotherms within the graphite crucible powder, indicating a large temperature gradient and uneven temperature field distribution within the loading zone. This resulted in severe crystallization at the powder center, hindering the upward transport of components and negatively impacting powder utilization.

[0113] Weighing the insulation structure with a balance revealed that it increased in weight by 10g. Weighing the heating tank structure with the same balance revealed that it increased in weight by 79g, indicating that the heating tank structure effectively prevents component leakage.

[0114] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made by those skilled in the art without creative effort within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A silicon carbide single crystal growth apparatus for improving powder utilization, characterized in that, The device includes a heating barrel, a crucible, and a heat-conducting assembly. The heating barrel includes a matching top cover and a barrel body. The crucible is housed inside the barrel body. A through hole is provided at the bottom of the crucible, and a heat-conducting rod is provided at the bottom of the barrel body. The heat-conducting rod extends upward into the interior of the crucible through the through hole. The crucible includes a matching crucible lid and crucible body. A silicon carbide seed crystal is provided at the lower end of the crucible lid. The lower part of the crucible body is a loading area, which carries silicon carbide powder. The space between the silicon carbide seed crystal and the surface of the silicon carbide powder is a growth cavity. A heat-conducting assembly is provided in the loading area. The heat-conducting assembly includes a heat-conducting tower and heat-conducting rings. The heat-conducting tower has a hollow structure inside and is sleeved on the outside of the heat-conducting rod. The heat-conducting rod is embedded in the cylindrical hole inside the heat-conducting tower. The heat-conducting tower and the hole at the bottom of the crucible are sealed by a threaded connection. Several layers of heat-conducting rings are provided on the heat-conducting tower, and the heat-conducting rings extend outward to act on different areas of the loading area. The heat transfer tower comprises several layers, and each layer has a variable diameter structure on the side in contact with the silicon carbide material, with the diameter increasing from top to bottom; the variable diameter structure is frustum-shaped. The heat-conducting ring includes an inner ring, an outer ring, and spokes. After the silicon carbide powder sublimates, when the graphitized residue can no longer support the heat-conducting ring, the heat-conducting ring slowly moves along the heat-conducting tower towards the bottom of the crucible. The inner and outer rings are connected by multiple spokes arranged in a circular pattern; the inner and outer rings and spokes are all made of thermally conductive materials, and the diameters of the inner and outer rings and the number of spokes are set according to the thermal conductivity requirements.

2. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The heating barrel and heat-conducting rod are made of graphite, and the heat-conducting tower and heat-conducting ring are made of at least one of graphite, metal carbide, or metal. The graphite material includes at least one of isostatic graphite and extruded graphite, the metal carbide material includes at least one of tantalum carbide and niobium carbide, and the metal material includes at least one of tantalum and niobium.

3. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The wall thickness of the heating barrel is the same as that of the crucible, the inner diameter of the heating barrel is adapted to the outer diameter of the crucible, and the height of the heating barrel is 120% to 200% of the height of the crucible.

4. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The diameter and height of the crucible are adjusted according to the required dimensions of the grown crystal.

5. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The height of the loading zone is 30% to 60% of the height of the crucible, and the height of the growth chamber is 40% to 70% of the height of the crucible.

6. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The height of the heat-conducting rod is less than the height of the loading area, the diameter of the heat-conducting rod is 5% to 15% of the diameter of the crucible, and the diameter of the hollow structure inside the heat-conducting tower is 10% to 20% of the diameter of the crucible; the total height of the heat-conducting tower is the same as the height of the loading area and is higher than the height of the heat-conducting rod.

7. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The top diameter of the heat-conducting tower is 10% to 20% of the crucible diameter, and the bottom diameter of the heat-conducting tower is 15% to 30% of the crucible diameter, which is the same size as the central hole at the bottom of the crucible.

8. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The diameter of the inner ring is set according to the number of layers of the heat conduction tower or the diameter at the location where it is installed in the heat conduction tower, and the diameter of the outer ring is 80% to 90% of the diameter of the loading area.

9. The silicon carbide single crystal growth apparatus for improving powder utilization as described in claim 1, characterized in that, The silicon carbide single crystal growth apparatus also includes a heating system disposed outside the heating barrel, and the space between the heating barrel and the heating system is filled with heat-insulating material.

10. A method for growing silicon carbide single crystals, employing a silicon carbide single crystal growth apparatus for improving powder utilization as described in any one of claims 1-9, characterized in that, Includes the following steps: The heat-conducting tower and the bottom hole of the crucible are sealed by a threaded connection. Then the crucible is placed into the heating barrel, so that the heat-conducting rod is embedded in the cylindrical hole inside the heat-conducting tower. Spread silicon carbide powder evenly on the bottom of the graphite crucible, with the powder height level with the height of the heat conduction tower. Depending on the shape of the heat conduction tower and the inner diameter of the inner ring of the heat conduction ring, place the heat conduction ring on the surface of the powder or embed it in the powder. Fit the inner ring of the heat conduction ring into the heat conduction tower. Fix the silicon carbide seed crystal on the top cover of the crucible. Place the heating tank along with the graphite crucible into the growth device, seal the growth device, and evacuate its interior. The inside of the growth device after vacuum treatment is heated, and carrier gas is introduced into the growth device. After the temperature reaches the expected temperature, it is kept constant to sublimate the silicon carbide powder. The sublimated powder is transported to the surface of the silicon carbide seed crystal to achieve crystal growth. After the crystal growth is complete, the inside of the growth device is cooled down, and a carrier gas is introduced into the growth device to allow the crystal to cool naturally, thus obtaining a silicon carbide single crystal.

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