Silicon carbide single crystal production tool

Abstract

The application provides a silicon carbide single crystal production tool, which comprises a first crucible assembly, a second crucible assembly and a heat-conducting insulation assembly. The first crucible assembly is connected with a heating device. The silicon carbide powder is placed in the second crucible assembly. The second crucible assembly is placed in the first crucible assembly. The heat-conducting insulation assembly is located on the circumferential outer side of the first crucible assembly and in the first crucible assembly. The technical scheme of the application effectively solves the problem of inconsistent product thickness caused by uneven heating in the production process of large-size silicon carbide single crystals in the prior art.

Description

Technical Field

[0001] This application relates to the technical field of silicon carbide crystallization, and more particularly to a tool for producing silicon carbide single crystals. Background Technology

[0002] Silicon carbide possesses excellent properties such as high hardness, high thermal conductivity, low coefficient of thermal expansion, large bandgap, high saturated electron drift velocity, high chemical stability, and strong radiation resistance. It is currently one of the most popular third-generation semiconductor materials. Semiconductor devices made of silicon carbide can operate in extreme environments of high temperature, high pressure, and strong radiation, and have broad application prospects in power electronics and microwave communications.

[0003] The mainstream silicon carbide growth method currently is the PVT method, which uses high-purity SiC powder as raw material. The silicon carbide powder is loaded into a high-purity graphite crucible, and under certain pressure, it is heated to a certain temperature, at which the silicon carbide crystal is grown.

[0004] When growing large-sized crystals, the crucible size also needs to be increased accordingly. After the increase, the distance between the center and the periphery of the crucible and the heating coil is inconsistent, which causes the temperature difference between the center and the periphery of the crucible to be inconsistent. When the crystal size is very small, the temperature difference between the two points is not obvious when the crucible is very small. However, when growing crystals larger than 6 inches, the temperature difference between the two points will gradually increase due to the increase in the crucible size. This is reflected in the grown crystal as the thickness of the crystal edge and the center is inconsistent, resulting in poor product quality, such as CN113308732A. Utility Model Content

[0005] One of the technical problems this application aims to solve is that, during the production of large-size silicon carbide single crystals, there is an issue of inconsistent product thickness due to uneven heating.

[0006] To address the aforementioned technical problems, this application provides a tool for producing silicon carbide single crystals.

[0007] A silicon carbide single crystal production tool provided in this application includes: a first crucible assembly connected to a heating device; a second crucible assembly in which silicon carbide powder is placed, and the second crucible assembly is placed inside the first crucible assembly; and a thermally conductive and heat-insulating assembly located circumferentially outside the first crucible assembly and inside the first crucible assembly.

[0008] In some embodiments, the sidewalls of the first crucible assembly and the sidewalls of the second crucible assembly are both cylindrical.

[0009] In some embodiments, the diameter difference between the first crucible assembly and the second crucible assembly is 8 to 15 mm.

[0010] In some embodiments, the thermally conductive and heat-insulating assembly includes a thermally conductive and heat-insulating layer, which wraps around the outside of the second crucible assembly and is fitted to the inner wall of the first crucible assembly.

[0011] In some embodiments, the thermally conductive insulation layer is made of graphite felt.

[0012] In some embodiments, the thermally conductive insulation component further includes an isolation structure, which is attached to the thermally conductive insulation layer, and the vertical height of the isolation structure is greater than the vertical height of the thermally conductive insulation layer.

[0013] In some embodiments, the isolation structure is made of tantalum material.

[0014] In some embodiments, the length of the isolation structure in the vertical direction is 0.1 to 0.25 times the length of the thermally conductive insulation layer in the vertical direction.

[0015] In some embodiments, the sum of the lengths of the thermally conductive insulation layer and the isolation structure in the vertical direction is greater than or equal to the length of the second crucible assembly in the vertical direction.

[0016] In some embodiments, the first crucible assembly has a limiting protrusion and the second crucible assembly has a limiting groove, the limiting groove being disposed corresponding to the limiting protrusion.

[0017] The silicon carbide single crystal production tool provided in this application, through the above technical solution, places silicon carbide powder in a second crucible assembly. A heating device heats the first crucible assembly, and the heat is conducted through thermal radiation to the thermally conductive and insulating components, and then to the second crucible assembly. This results in more uniform heating of the second crucible assembly, avoiding localized overheating that could lead to uneven silicon carbide single crystal thickness and affect product quality. The technical solution of this application effectively solves the problem of inconsistent product thickness caused by uneven heating in the production of large-size silicon carbide single crystals in the prior art. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A cross-sectional view of the silicon carbide single crystal production tool disclosed in Embodiment 1 of this application is shown.

[0020] Figure 2A cross-sectional view of the silicon carbide single crystal production tool disclosed in Embodiment 2 of this application is shown.

[0021] Explanation of reference numerals in the attached figures:

[0022] 10. First crucible assembly; 11. Limiting protrusion; 20. Second crucible assembly; 21. Limiting groove; 30. Thermally conductive and insulating assembly; 31. Thermally conductive and insulating layer; 32. Isolation structure. Detailed Implementation

[0023] The embodiments of this application will be further described in detail below with reference to the accompanying drawings and examples. The detailed description of the following embodiments and the accompanying drawings are used to illustrate the principles of this application by way of example, but should not be used to limit the scope of this application. This application can be implemented in many different forms and is not limited to the specific embodiments of the application herein, but includes all technical solutions falling within the scope of the claims.

[0024] These embodiments are provided to make the application thorough and complete, and to fully express the scope of the application to those skilled in the art. It should be noted that, unless otherwise specifically stated, the relative arrangement of components and steps, material composition, numerical expressions, and values ​​illustrated in these embodiments should be interpreted as merely exemplary and not as limiting.

[0025] It should be noted that, in the description of this application, unless otherwise stated, "a plurality of" means two or more; the terms "upper," "lower," "left," "right," "inner," and "outer," etc., indicating orientation or positional relationship, are only for the convenience of describing this application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this application. When the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0026] Furthermore, the terms "first," "second," and similar terms used in this application do not indicate any order, quantity, or importance, but are merely used to distinguish different parts. "Vertical" is not strictly vertical, but within the permissible margin of error. "Parallel" is not strictly parallel, but within the permissible margin of error. Terms such as "including" or "contains" mean that the element preceding the word encompasses the element listed after it, and do not exclude the possibility of encompassing other elements as well.

[0027] It should also be noted that, in the description of this application, unless otherwise expressly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can understand the specific meaning of the above terms in this application depending on the specific circumstances. When a specific device is described as being located between a first device and a second device, an intermediary device may or may not be present between the specific device and the first or second device.

[0028] All terms used in this application have the same meaning as understood by one of ordinary skill in the art to which this application pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as idealized or highly formalized, unless expressly defined herein.

[0029] Techniques, methods, and equipment known to those skilled in the art may not be discussed in detail, but where appropriate, they should be considered part of the specification.

[0030] like Figure 1 As shown, the silicon carbide single crystal production tool disclosed in Embodiment 1 of this application includes: a first crucible assembly 10, a second crucible assembly 20, and a thermally conductive and heat-insulating assembly 30. The first crucible assembly 10 is connected to a heating device, silicon carbide powder is placed inside the second crucible assembly 20, and the second crucible assembly 20 is placed inside the first crucible assembly 10. The thermally conductive and heat-insulating assembly 30 is located on the circumferential outer side of the first crucible assembly 10 and inside the first crucible assembly 10.

[0031] Applying the technical solution of Embodiment 1, silicon carbide powder is placed inside the second crucible assembly 20. A heating device heats the first crucible assembly 10, and the heat is conducted through thermal radiation to the thermally conductive and insulating assembly 30, and then to the second crucible assembly 20. This results in more uniform heating of the second crucible assembly 20, preventing localized overheating and ensuring uniform silicon carbide single crystal thickness, which would affect product quality. The technical solution of Embodiment 1 effectively solves the problem of inconsistent product thickness caused by uneven heating in the production of large-size silicon carbide single crystals in the prior art.

[0032] It should be noted that in the technical solution of Embodiment 1, a graphite cover containing the seed crystal needs to be placed on the first crucible assembly 10 before heating.

[0033] like Figure 1As shown, in the technical solution of Embodiment 1, the sidewalls of the first crucible assembly 10 and the second crucible assembly 20 are both cylindrical. The cylindrical structure further ensures that the distance between the outer walls of the second crucible assembly 20 and the first crucible assembly 10 is equal, resulting in consistent thermal radiation effects and a temperature difference only in the internal radial direction. This structure further reduces the magnitude of the temperature difference within the second crucible assembly 20.

[0034] like Figure 1 As shown, in the technical solution of Embodiment 1, the diameter difference between the first crucible assembly 10 and the second crucible assembly 20 is 8 to 15 mm. During use, to ensure that the second crucible assembly 20 is heated evenly and has a small internal temperature difference, it is necessary to ensure that the axis of the second crucible assembly 20 coincides with the axis of the first crucible assembly 10. When the diameter difference between the first crucible assembly 10 and the second crucible assembly 20 is less than 8 mm, that is, the distance between the outer wall of the second crucible assembly 20 and the outer wall of the first crucible assembly 10 is less than 4 mm, during heating, the outer wall of the second crucible assembly 20 is prone to rapid heating while the internal temperature remains low, resulting in uneven internal temperature and uneven product thickness. When the diameter difference between the first crucible assembly 10 and the second crucible assembly 20 is greater than 15 mm, that is, the distance between the outer wall of the second crucible assembly 20 and the outer wall of the first crucible assembly 10 is greater than 7.5 mm, the second crucible assembly 20 heats up slowly, resulting in low production efficiency, and a thicker thermally conductive and insulating component 30 is required, leading to higher costs.

[0035] like Figure 1 As shown, in the technical solution of Embodiment 1, the thermally conductive and insulating component 30 includes a thermally conductive and insulating layer 31. The thermally conductive and insulating layer 31 wraps around the outside of the second crucible component 20 and is fitted to the inner wall of the first crucible component 10. The thermally conductive and insulating layer 31, by wrapping around the outside of the second crucible component 20, conducts heat from the first crucible component 10 to the second crucible component 20 and insulates the second crucible component 20, preventing heat loss.

[0036] like Figure 1As shown, in the technical solution of Embodiment 1, the thermally conductive and insulating layer 31 is made of graphite soft felt. Graphite material has good thermal conductivity, minimizing heat loss and saving energy. Graphite soft felt is easily deformable, facilitating workers to completely wrap it around the outside of the second crucible assembly 20. Furthermore, because graphite soft felt is relatively loose and compressible, a suitable thickness ensures it adheres to both the outer wall of the second crucible assembly 20 and the inner wall of the first crucible assembly 10, further guaranteeing good thermal conductivity. Graphite material has stable chemical properties and a high melting point, making it less prone to deformation, chemical reactions, or melting at high temperatures, resulting in a long service life and further reducing costs. The thickness of the thermally conductive and insulating layer 31 made of graphite soft felt is preferably 10 mm. Graphite soft felt is also wrapped around the outside of the first crucible assembly 10 to further ensure uniform heating inside the second crucible assembly 20 and to insulate the entire silicon carbide single crystal production tool.

[0037] like Figure 1 As shown, in the technical solution of Embodiment 1, the thermally conductive and insulating component 30 further includes an isolation structure 32. The isolation structure 32 is attached to the thermally conductive and insulating layer 31, and the vertical height of the isolation structure 32 is higher than that of the thermally conductive and insulating layer 31. The isolation structure 32 is disposed between the first crucible assembly 10 and the second crucible assembly 20, and is located above the thermally conductive and insulating layer 31. This prevents carbon volatilized from the thermally conductive and insulating layer 31 made of graphite soft felt from entering the interior of the second crucible assembly 20 under high-temperature conditions, affecting the generation of silicon carbide crystals, resulting in lower product purity and affecting product quality.

[0038] like Figure 1 As shown, in the technical solution of Embodiment 1, the isolation structure 32 is made of tantalum material. The tantalum material reacts with carbon at high temperatures, and the resulting reactants adhere to the tantalum surface, preventing volatile carbon from entering the second crucible assembly 20 and affecting the silicon carbide crystallization reaction inside the second crucible assembly 20.

[0039] like Figure 1As shown, in the technical solution of Embodiment 1, the vertical length of the isolation structure 32 is 0.1 to 0.25 times the vertical length of the thermally conductive and insulating layer 31. When the vertical length of the isolation structure 32 made of tantalum material is less than 0.1 times the vertical length of the thermally conductive and insulating layer 31 made of graphite felt material, during use, the volatile graphite may fail to react with the isolation structure 32 in time and mix into the second crucible assembly 20, resulting in poor quality of the silicon carbide single crystal product. When the vertical length of the isolation structure 32 made of tantalum material is greater than 0.25 times the vertical length of the thermally conductive and insulating layer 31 made of graphite felt material, the isolation structure 32 has a large mass, and the graphite felt below is easily compressed and deformed due to the gravity of the isolation structure 32, affecting the thermal conductivity and insulation effect.

[0040] like Figure 1 As shown, in the technical solution of Embodiment 1, the sum of the vertical lengths of the thermally conductive insulation layer 31 and the isolation structure 32 is greater than or equal to the vertical length of the second crucible assembly 20. The vertical length of the thermally conductive insulation layer 31 is less than the numerical length of the second crucible assembly 20, ensuring that the thermally conductive insulation layer 31 is located within the enclosed space formed by the first crucible assembly 10, the second crucible assembly 20, and the isolation structure 32, thus preventing the volatiles of the graphite felt in a high-temperature environment from entering the second crucible assembly 20. Simultaneously, it ensures that the isolation structure 32 is at least partially located between the first crucible assembly 10 and the second crucible assembly 20, with the first crucible assembly 10 and the second crucible assembly 20 limiting the isolation structure 32.

[0041] like Figure 2 As shown, the difference between the technical solution of Embodiment 2 and Embodiment 1 is that the first crucible assembly 10 has a limiting protrusion 11, and the second crucible assembly 20 has a limiting groove 21, with the limiting groove 21 corresponding to the limiting protrusion 11. The relative positional relationship between the first crucible assembly 10 and the second crucible assembly 20 is determined by the cooperation of the limiting protrusion 11 and the limiting groove 21, ensuring that the axis of the second crucible assembly 20 coincides with that of the first crucible assembly 10 after placement. This avoids errors during manual operation that could cause the second crucible assembly 20 to shift position. It should be noted that the limiting protrusion 11 can be any cylindrical shape. When the limiting protrusion 11 is cylindrical, it needs to be positioned to coincide with the axis of the first crucible assembly 10, and the second crucible assembly 20 should be correspondingly positioned there.

[0042] The difference between the technical solution of Embodiment 3 and Embodiment 1 is that the silicon carbide single crystal production tool further includes a vertical drive component. This vertical drive component is installed inside the first crucible assembly 10 and located at the bottom of the first crucible assembly 10. The output end of the vertical drive component is connected to the bottom of the second crucible assembly 20. The vertical drive component can be an electric actuator, cylinder, or other similar structure. The vertical drive component drives the second crucible assembly 20 to move vertically, allowing the second crucible assembly 20 to automatically enter or exit the first crucible assembly 10. This facilitates the removal of the internal product by operators and avoids problems such as burns from high temperatures during operation.

[0043] In summary, two graphite crucibles were designed. The inner crucible (second crucible assembly 20) is a small graphite crucible, mainly used to hold high-purity silicon carbide powder. Its height is about half that of the outer crucible (first crucible assembly 10), and its diameter is 10mm smaller than that of the outer crucible. The outer wall of the inner crucible (second crucible assembly 20) is wrapped with a 5mm thick layer of graphite soft felt (thermal conductive and insulating layer 31). The wrapped inner crucible (second crucible assembly 20) is placed inside the outer crucible (first crucible assembly 10), ensuring that the two are concentric to the naked eye. After the outer crucible (first crucible assembly 10) is covered with a graphite cap containing the seed crystal, it is then wrapped with a graphite soft felt of a certain thickness. The wrapped outer crucible (first crucible assembly 10) is placed in the center of the furnace cavity. To reduce carbon volatilization of the graphite components at high temperatures, 1-2 layers of tantalum rings (isolation structure 32) are placed on the graphite soft felt (thermal conductive and insulating layer 31) between the inner and outer crucibles. Tantalum rings are used to reduce carbon volatilization from graphite felt at high temperatures. The original single crucible is replaced with a double crucible method, with the inner crucible (second crucible assembly 20) filled with high-purity silicon carbide powder, and the outer crucible (first crucible assembly 10) generating an induced current as the main heating source. The space between the inner and outer crucibles is filled with graphite felt (thermally conductive and insulating layer 31). This method avoids direct contact between the silicon carbide powder and the heating source. Instead, the heat is transferred to the silicon carbide powder through the heat radiation after heating by the outer crucible (first crucible assembly 10), which reduces the axial temperature gradient of the powder and is beneficial for growing large-size crystals. In order to reduce the carbon content volatilized from the graphite, tantalum sheets (isolation structure 32) of appropriate thickness and number of layers are added between the inner crucible (second crucible assembly 20) and the outer crucible (first crucible assembly 10), which reduces the carbon content in the gas at high temperatures, thereby reducing the formation of carbon inclusions in the crystal. Through a novel dual-crucible thermal field design, the raw material does not directly contact the heating element crucible. Heat is conducted to the raw material via thermal radiation from the heating element, thereby reducing the temperature difference between the center and edge of the raw material. This effectively controls the axial temperature gradient during crystal growth, which is beneficial for the growth of large-size crystals. The added high-purity tantalum ring reacts with carbon gas volatilized from graphite at high temperatures to form tantalum carbide on the surface of the tantalum ring (isolation structure 32), thereby reducing the carbon gas content during crystal growth and thus reducing the possibility of carbon inclusions forming in silicon carbide crystals.

[0044] The embodiments of this application have now been described in detail. To avoid obscuring the concept of this application, some details known in the art have not been described. Those skilled in the art can fully understand how to implement the technical solutions of this application based on the above description.

[0045] While specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustrative purposes only and are not intended to limit the scope of this application. Those skilled in the art should understand that modifications can be made to the above embodiments or equivalent substitutions can be made to some technical features without departing from the scope and spirit of this application. In particular, as long as there is no structural conflict, the various technical features mentioned in the embodiments can be combined in any manner.

Claims

1. A tool for producing silicon carbide single crystals, characterized in that, include: The first crucible assembly (10) is connected to the heating device; The second crucible assembly (20) contains silicon carbide powder placed inside the second crucible assembly (20), which is placed inside the first crucible assembly (10). A thermally conductive and heat-insulating component (30) is located on the circumferential outer side of the first crucible assembly (10) and inside the first crucible assembly (10).

2. The silicon carbide single crystal production tool according to claim 1, characterized in that, The sidewalls of the first crucible assembly (10) and the second crucible assembly (20) are both cylindrical.

3. The silicon carbide single crystal production tool according to claim 1, characterized in that, The diameter difference between the first crucible assembly (10) and the second crucible assembly (20) is 8 to 15 mm.

4. The silicon carbide single crystal production tool according to claim 1, characterized in that, The thermally conductive and heat-insulating component (30) includes a thermally conductive and heat-insulating layer (31), which is wrapped around the outside of the second crucible component (20) and is fitted to the inner wall of the first crucible component (10).

5. The silicon carbide single crystal production tool according to claim 4, characterized in that, The thermally conductive and insulating layer (31) is made of graphite soft felt.

6. The silicon carbide single crystal production tool according to claim 4, characterized in that, The thermally conductive and heat-insulating component (30) further includes an isolation structure (32), which is attached to the thermally conductive and heat-insulating layer (31). The vertical height of the isolation structure (32) is higher than that of the thermally conductive and heat-insulating layer (31).

7. The silicon carbide single crystal production tool according to claim 6, characterized in that, The isolation structure (32) is made of tantalum material.

8. The silicon carbide single crystal production tool according to claim 6, characterized in that, The length of the isolation structure (32) in the vertical direction is 0.1 to 0.25 times the length of the thermally conductive insulation layer (31) in the vertical direction.

9. The silicon carbide single crystal production tool according to claim 6, characterized in that, The sum of the vertical lengths of the thermally conductive insulation layer (31) and the isolation structure (32) is greater than or equal to the vertical length of the second crucible assembly (20).

10. The silicon carbide single crystal production tool according to claim 1, characterized in that, The first crucible assembly (10) has a limiting protrusion (11), and the second crucible assembly (20) has a limiting groove (21), the limiting groove (21) being correspondingly provided with the limiting protrusion (11).

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