Crucible Structure for Preparing Low-Basal-Plane-Dislocation Silicon Carbide Single Crystal

Abstract

The present invention provides a crucible structure for preparing silicon carbide single crystal with low basal plane dislocations, belonging to the technical field of semiconductor preparation. It includes a crucible body, a seed wafer, a short graphite ring, and a restraint member. The crucible body has a receiving cavity, and the bottom of the receiving cavity can store silicon carbide raw materials. The seed wafer is horizontally arranged at the top of the receiving cavity. The short graphite ring has an annular ring portion located below the seed wafer and in contact with the seed wafer, and the annular ring portion can enclose with the seed wafer to form an initial growth cavity with an open bottom. The restraint member is arranged in the receiving cavity and has a restraint graphite cylinder cavity surrounding the annular ring portion, and an annular gap is formed between the restraint graphite cylinder cavity and the annular ring portion. The crucible structure for preparing silicon carbide single crystal with low basal plane dislocations provided by the present invention can effectively solve the problem of the restraint member restricting the single crystal during the cooling process, reduce the internal stress of the single crystal, and at the same time inhibit basal plane dislocations, realizing the growth of single crystal with low basal plane dislocations.

Description

Technical Field

[0001] The present invention belongs to the technical field of semiconductor preparation, and particularly relates to a crucible structure for preparing a silicon carbide single crystal with low basal plane dislocations. Background Art

[0002] As a third-generation semiconductor material, silicon carbide has obvious advantages such as high critical breakdown electric field strength, high saturated electron migration velocity, lower impedance, and wider bandgap compared with the traditional semiconductor material silicon. It is an excellent semiconductor material for manufacturing power semiconductor devices with high voltage resistance, high temperature resistance, and radiation resistance. It has been widely used in fields such as smart power grids, electric vehicles, rail transit, new energy grid connection, switching power supplies, industrial motors, and household appliances, showing good development prospects.

[0003] In the prior art, the commonly used method for growing silicon carbide crystals is the physical vapor transport method. This growth method usually uses a crucible structure, and a graphite ring is arranged between the seed crystal and the silicon carbide raw material in the crucible structure to restrict and guide the growth of the single crystal to control the diameter of the single crystal. By heating the crucible structure, the gas components formed by the sublimation and decomposition of the silicon carbide raw material are transported to the seed crystal and deposited on the seed crystal to achieve single crystal growth. However, during the single crystal growth process, it will contact the inner wall of the graphite ring, and the graphite ring is usually made of isostatic graphite, whose expansion coefficient is greater than that of silicon carbide. Therefore, during the cooling process, the graphite ring will tightly bind the single crystal, inducing internal stress in the single crystal and causing serious basal plane dislocations in the single crystal. Summary of the Invention

[0004] An embodiment of the present invention provides a crucible structure for preparing a silicon carbide single crystal with low basal plane dislocations, aiming to solve the problem of poor practicability caused by serious basal plane dislocations in the crucible structure used in the existing silicon carbide single crystal preparation.

[0005] To achieve the above object, the technical solution adopted by the present invention is: to provide a crucible structure for preparing a silicon carbide single crystal with low basal plane dislocations, including:

[0006] A crucible body having a receiving cavity, and the bottom of the receiving cavity is used for storing silicon carbide raw materials;

[0007] A seed wafer horizontally arranged at the top of the receiving cavity;

[0008] A short graphite ring having an annular ring portion located below the seed wafer and in contact with the seed wafer, and the annular ring portion is used to enclose the seed wafer to form an initial growth cavity with an open bottom;

[0009] A constraint member arranged in the receiving cavity, having a constraint graphite cylinder cavity surrounding the annular ring portion, and an annular gap is formed between the constraint graphite cylinder cavity and the annular ring portion.

[0010] In a possible implementation, the initial growth cavity is coaxially arranged with the constrained graphite cylinder cavity.

[0011] In a possible implementation, the constraint member includes:

[0012] A graphite support ring, horizontally arranged in the accommodation cavity;

[0013] An outer graphite ring, arranged on the graphite ring, and the bottom end is communicated with the central hole of the graphite support ring. The inner cavity of the outer graphite ring is the constrained graphite cylinder cavity.

[0014] In a possible implementation, the accommodation cavity is a cylindrical cavity with its axis arranged vertically;

[0015] Wherein, an annular platform for the graphite support ring to rest on is provided on the inner wall of the accommodation cavity.

[0016] In a possible implementation, the outer graphite ring is coaxially arranged with the graphite support ring.

[0017] In a possible implementation, the crucible body includes:

[0018] A pot body, having an open cavity with an open top;

[0019] A pot lid, which is used to cover the top of the pot body and enclose the accommodation cavity with the open cavity.

[0020] In a possible implementation, the seed wafer is fixedly arranged on the pot lid.

[0021] In a possible implementation, the pot lid is provided with a groove corresponding to the open cavity, and an annular side wall is formed around the periphery of the groove; the seed wafer is fixedly arranged on the bottom surface of the groove;

[0022] Wherein, an annular slot for the annular side wall to be adaptively inserted into is provided on the outer edge of the top end of the pot body.

[0023] In a possible implementation, the short graphite ring includes:

[0024] A lapping circular plate, lapping on the annular table surface formed at the top end of the pot body and having a central hole;

[0025] A graphite ring, fixedly arranged in the central hole, with the top end abutting against the seed wafer and the bottom end extending below the lapping circular plate.

[0026] In a possible implementation, the lapping circular plate and the top end of the constraint member are arranged at an interval in the vertical direction.

[0027] In this implementation method, after the crucible body is heated, the sublimated silicon carbide raw material can be transported to the seed wafer by relying on the temperature gradient and deposited on the seed wafer. At this time, the annular ring part provided by the short graphite ring and the seed wafer enclose an initial growth cavity, which can guide the initial single crystal growth and ensure that the diameter of the single crystal meets the target diameter. The single crystal continues to grow and enters the constrained graphite tube cavity. At this time, due to the annular gap between the constrained graphite tube cavity and the annular ring part, for the single crystal growing into the annular gap, since there is no blocking object at the top, the single crystal in the vertical area corresponding to the annular gap will sublime and cause negative growth. After the growth is completed, an annular cavity will be formed between the single crystal and the constrained graphite tube cavity. Furthermore, during the cooling process, the problem of the constraint member binding the single crystal can be effectively solved, the internal stress of the single crystal can be reduced, and the basal plane dislocations can be suppressed, realizing the growth of single crystals with low basal plane dislocations. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a schematic cross-sectional structure view of the crucible structure for preparing silicon carbide single crystals with low basal plane dislocations provided by an embodiment of the present invention; Figure 1 ;

[0029] Figure 2 is a schematic cross-sectional structure view of the crucible structure for preparing silicon carbide single crystals with low basal plane dislocations provided by another embodiment of the present invention; Figure 2 ;

[0030] Figure 3 is Figure 2 an enlarged schematic structure view of part A of the crucible structure for preparing silicon carbide single crystals with low basal plane dislocations provided by an embodiment.

[0031] Description of the reference numerals:

[0032] 10. Crucible body; 11. Pot body; 111. Annular groove; 12. Pot lid; 121. Groove; 122. Annular side wall; 13. Slide post; 14. Circular limiting plate; 15. Accommodation cavity; 16. Annular gap; 17. Annular platform;

[0033] 20. Seed wafer;

[0034] 30. Short graphite ring; 31. Lapping round plate; 32. Graphite ring; 321. Annular inclined surface part;

[0035] 40. Constraint member; 41. Graphite support ring; 42. Outer graphite ring; 43. Constrained graphite tube cavity;

[0036] 50. Silicon carbide raw material. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0037] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present invention more clear and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0038] Please refer to Figure 1 and Figure 2 , and now the crucible structure for preparing low basal plane dislocation silicon carbide single crystal provided by the present invention will be described.

[0039] It involves a relatively large graphite ring deformation rate. Therefore, during the cooling process, the single crystal will be tightly constrained, inducing internal stress in the single crystal and causing relatively serious basal plane dislocations in the single crystal. Most or lighter basal plane dislocations in the substrate will be transformed into harmless through-type edge dislocations during the epitaxial process, but there will still be some basal plane dislocations that will extend into the epitaxial layer. SSF nucleates and expands at the BPD, resulting in an increase in the on-resistance and an increase in the reverse leakage current of bipolar devices and MOSFETs, generating the "bipolar degradation" phenomenon.

[0040] In response to this, the crucible structure for preparing low basal plane dislocation silicon carbide single crystal provided in this embodiment includes a crucible body 10, a seed wafer 20, a short graphite ring 30, and a constraint member 40. The crucible body 10 has a receiving cavity 15, and the bottom of the receiving cavity 15 can store silicon carbide raw material 50. The seed wafer 20 is horizontally arranged at the top of the receiving cavity 15. The short graphite ring 30 has an annular ring portion located below the seed wafer 20 and in contact with the seed wafer 20, and the annular ring portion can enclose with the seed wafer 20 to form an initial growth cavity with an open bottom. The constraint member 40 is arranged in the receiving cavity 15 and has a constraint graphite tube cavity 43 surrounding the annular ring portion, and an annular gap 16 is formed between the constraint graphite tube cavity 43 and the annular ring portion.

[0041] Regarding the process of the physical vapor transport method (PVT method), that is, the above-mentioned crucible structure for preparing low basal plane dislocation silicon carbide single crystal is placed in graphite fiber insulation, and it is heated to the growth temperature by induction heating or resistance heating, and a temperature gradient with the silicon carbide raw material 50 temperature higher than the seed wafer 20 temperature is established. The gaseous components formed by the sublimation and decomposition of the silicon carbide raw material 50 are transported to the seed wafer 20 under the action of the above temperature gradient and deposited on the seed wafer 20 to realize single crystal growth.

[0042] Compared with the prior art, for the crucible structure used in the preparation of a low basal plane dislocation silicon carbide single crystal provided in this embodiment, after the crucible body 10 is placed and heated, after the silicon carbide raw material 50 sublimes, it can be transported to the seed wafer 20 by temperature gradient and deposited on the seed wafer 20. At this time, the annular ring part provided by the short graphite ring 30 and the seed wafer 20 enclose an initial growth cavity, which can guide the initial single crystal growth and ensure that the diameter of the single crystal meets the target diameter. The single crystal continues to grow and enters the constrained graphite cylinder cavity 43. At this time, because there is an annular gap 16 between the constrained graphite cylinder cavity 43 and the annular ring part, for the single crystal growing into the annular gap 16, since there is no blocking object at the top, the single crystal in the vertical area corresponding to the annular gap 16 will sublime and cause negative growth. After the growth is completed, an annular cavity will be formed between the single crystal and the constrained graphite cylinder cavity 43. Furthermore, during the cooling process, the problem of the constraint member 40 restricting the single crystal can be effectively solved, the internal stress of the single crystal can be reduced, and at the same time, the basal plane dislocation can be inhibited, realizing the growth of a low basal plane dislocation single crystal.

[0043] For further understanding, in this embodiment, two temperature fields will appear in the accommodation cavity 15. One temperature field is in the vertical direction, that is, the temperature of the silicon carbide raw material 50 is higher than the temperature gradient of the seed wafer 20, so as to ensure that the silicon carbide raw material 50 can be deposited on the seed wafer 20 after sublimation. The other temperature field is in the radial direction of the constrained graphite cylinder cavity 43. In the annular gap 16, the closer to the constrained graphite cylinder cavity 43, the higher the temperature. Therefore, it is more difficult for the single crystal closer to the constrained graphite cylinder cavity 43 to expand to this position. The crystal grows freely without attaching to the radial direction of the constrained graphite cylinder cavity 43, reducing the internal thermal stress of the crystal. At the same time, during the cooling process, the proliferation of basal plane dislocations caused by the different thermal expansion coefficients of the constraint member 40 and the single crystal during the cooling process is eliminated.

[0044] It should be noted that in the vertical direction, the length of the annular ring part needs to be less than the length of the constrained graphite cylinder cavity 43. The length of the annular ring part only realizes guiding the initial growth of the single crystal. The smaller the length of the annular ring part or the initial growth cavity in the vertical direction, the more the basal plane dislocation density can be further reduced.

[0045] In some embodiments, the above-mentioned initial growth cavity can adopt structures such as Figure 1 and Figure 2 as shown. Refer to Figure 1 and Figure 2 , the initial growth cavity is coaxially arranged with the constrained graphite cylinder cavity 43.

[0046] The initial growth cavity is a circular cavity with an open bottom, and the top of the constraining graphite cylinder cavity 43 corresponds to the open bottom of the initial growth cavity. Therefore, the two are coaxially arranged, that is, their central axes are collinear. At this time, a uniform arrangement of the annular gap 16 can be ensured. Furthermore, under the axial temperature gradient, the single crystal in the vertical region corresponding to the annular gap 16 is likely to sublime and cause negative growth, which can, to a certain extent, prevent the single crystal from expanding to the inner wall surface of the constraining graphite cylinder cavity 43.

[0047] In some embodiments, the above-mentioned constraining member 40 can adopt structures such as Figure 1 and Figure 2 as shown. Refer to Figure 1 and Figure 2 , the constraining member 40 includes a graphite support ring 41 and an outer graphite ring 42. The graphite support ring 41 is horizontally arranged in the accommodating cavity 15. The outer graphite ring 42 is arranged on the graphite ring, and the bottom end is communicated with the central hole of the graphite support ring 41. The inner cavity of the outer graphite ring 42 is the constraining graphite cylinder cavity 43.

[0048] The graphite support ring 41 is horizontally arranged in the accommodating cavity 15, which will divide the accommodating cavity 15 into two sub-spaces. The central hole of the graphite ring support will make the two sub-spaces in a communicating state. The silicon carbide raw material 50 is stored in the area below the graphite support ring 41, and a seed wafer 20 is provided in the area above the graphite ring. At the same time, the outer graphite ring 42 is vertically arranged, and the outer graphite ring 42 is communicated with the central hole of the graphite support ring 41 to ensure that the sublimated silicon carbide raw material 50 can pass through the central hole of the graphite support ring 41 and enter the outer graphite ring 42, thereby ensuring the growth of the single crystal.

[0049] Regarding the outer graphite ring 42, it can be directly placed on the graphite ring. Of course, the outer graphite ring 42 can also be fixedly connected to the graphite support ring 41. This technology is well-known in the prior art and will not be elaborated here.

[0050] It should be noted that the outer graphite ring 42 needs to have a certain height to provide sufficient constraining space for single crystal growth. Of course, the height of the top end of the outer graphite ring 42 can be higher than the height of the bottom end of the annular ring part, or the height of the top end of the outer graphite ring 42 can be flush with the height of the bottom end of the annular ring part.

[0051] In some embodiments, the above-mentioned accommodating cavity 15 can adopt structures such as Figure 1 and Figure 2 as shown. Refer to Figure 1 and Figure 2 , the accommodating cavity 15 is a cylindrical cavity with its axis along the vertical direction. A circular platform 17 for the graphite support ring 41 to be placed on is provided on the inner wall of the corresponding accommodating cavity 15.

[0052] The accommodating cavity 15 is a cylindrical cavity, which can ensure adaptation to the structure of the graphite support ring 41. The annular platform 17 can ensure the horizontal placement of the graphite support ring 41 and ensure the support of the graphite support ring 41.

[0053] Specifically, for the manufacture of the annular platform 17, the top section of the accommodating cavity 15 can be reamed to form the annular platform 17. Refer to Figure 1 and Figure 2 ; of course, an integrally connected annular protrusion can also be provided on the inner wall surface of the accommodating cavity 15 to form the annular platform 17.

[0054] In some embodiments, the above-mentioned outer graphite ring 42 and graphite support ring 41 can adopt the structures as shown in Figure 1 and Figure 2 . Refer to Figure 1 and Figure 2 . The outer graphite ring 42 and the graphite support ring 41 are coaxially arranged. This structure can further ensure the uniform arrangement of the annular gap 16. Furthermore, it can ensure that under the axial temperature gradient, the single crystal in the vertical region corresponding to the annular gap 16 is prone to sublimation and negative growth, and to a certain extent, it can avoid the single crystal from spreading to the inner wall surface of the constrained graphite cylinder cavity 43. In addition, this structure can also facilitate the coaxial arrangement of the initial growth cavity and the constrained graphite cylinder cavity 43 during the initial assembly process.

[0055] In this embodiment, the outer graphite ring 42 can be directly placed on the graphite ring. During crystal growth, there may be irregular protrusions in the radial direction of the graphite support ring 41. This connection method of the outer graphite ring 42 can facilitate the movement of the outer graphite ring 42 on the graphite support ring 41 after contact between a certain position of the outer graphite ring 42 and the protrusion during the cooling process, so as to avoid generating corresponding stress on the crystal and facilitate the crystal preparation effect.

[0056] In some embodiments, the above-mentioned crucible body 10 can adopt the structures as shown in Figure 1 and Figure 2 . Refer to Figure 1 and Figure 2 . The crucible body 10 includes a pot body 11 and a pot lid 12. The pot body 11 has an open cavity with an open top. After the pot lid 12 is buckled on the top of the pot body 11, it encloses the accommodating cavity 15 with the open cavity.

[0057] The crucible body 10 is formed by combining the pot body 11 and the pot lid 12, which is convenient for placing other components and raw materials, and at the same time can also facilitate the extraction of the formed crystal.

[0058] In this embodiment, the crucible body 10 can have a cylindrical outer shape structure.

[0059] In some embodiments, the above-mentioned seed wafer 20 can adopt the structures as shown in Figure 1 andFigure 2 The structure shown. Refer to Figure 1 and Figure 2 , the seed wafer 20 is fixedly arranged on the pot cover 12.

[0060] Regarding the fixed connection manner between the seed wafer 20 and the pot cover 12, it can be bonding, which is well-known to those skilled in the art and will not be elaborated here.

[0061] In some embodiments, the above-mentioned pot cover 12 and the pot body 11 can adopt the structure as shown in Figure 2 Refer to Figure 2 , the pot cover 12 is provided with a groove 121 corresponding to the open cavity, and an annular side wall 122 is formed around the periphery of the groove 121. The seed wafer 20 is fixedly arranged on the bottom surface of the groove 121.

[0062] Specifically, the outer edge of the top end of the pot body 11 is provided with an annular slot 111 for the annular side wall 122 to be adaptively inserted.

[0063] After the pot cover 12 is buckled on the pot body 11, the annular side wall 122 will extend into the annular slot 111, and then the pot cover 12 and the pot body 11 form a rabbet docking structure, which can enhance the sealing effect between the two.

[0064] In some embodiments, the above-mentioned short graphite ring 30 can adopt the structure as shown in Figure 2 Refer to Figure 2 , the short graphite ring 30 includes a lapping round plate 31 and a graphite ring 32. The lapping round plate 31 is lapped on the annular tabletop formed at the top end of the pot body 11 and has a central hole. The graphite ring 32 is fixedly arranged in the central hole, with the top end abutting against the seed wafer 20 and the bottom end extending below the lapping round plate 31.

[0065] The lapping round plate 31 can be directly lapped on the annular tabletop formed at the top end of the pot body 11, which is convenient for fixing the graphite ring 32. At the same time, after the pot cover 12 is buckled on the top end of the pot body 11, it can directly act on the graphite ring 32, so that the graphite ring 32 stably contacts the lower surface of the seed wafer 20 to form an initial growth cavity.

[0066] In some embodiments, an implementation manner of the above-mentioned short graphite ring 30 and the pot cover 12 can adopt the structure as shown in Figure 3 Refer to Figure 3, the seed wafer 20 is a circular wafer. An annular groove for embedding the seed wafer 20 is provided at the top end of the inner hole of the graphite ring 32. This annular groove can be understood as reaming the inner hole at the top end of the graphite ring 32. An annular inclined surface portion 321 is provided at the bottom end of the inner hole of the graphite ring 32. Correspondingly, a sliding column 13 is provided on the pot lid 12. The sliding column 13 is arranged along the vertical direction and is slidably connected to the sliding hole on the pot lid 12. The length of the sliding column 13 is greater than the length of the graphite ring 32 in the vertical direction. Circular limiting plates 14 are provided at both ends of the sliding column 13. The circular limiting plate 14 located in the groove 121 is for fixedly connecting the seed wafer 20. At the same time, a circular embedding groove for accommodating the corresponding circular limiting plate 14 is provided on the bottom surface of the groove 121.

[0067] This structure can further ensure that the graphite ring 32 stably contacts the lower surface of the seed wafer 20. At the same time, after the crucible body 10 is heated and a temperature gradient is established, the silicon carbide raw material 50 preferentially grows under guidance in the initial growth cavity. When the guided growth continues for a period of time, the graphite ring 32 gradually expands until the inner hole diameter is larger than the outer diameter of the seed wafer 20. At this time, the combination of the seed wafer 20 and the sliding column 13 will descend below the graphite ring 32 due to its own gravity. Therefore, during the subsequent cooling process, the graphite ring 32 will not be able to restrain the crystals on the seed wafer 20, further realizing the growth of single crystals with low basal plane dislocations. The annular inclined surface portion 321 can prevent the seed wafer 20 from being clamped in the inner hole of the graphite ring 32 during the cooling process, facilitating the separation of the seed wafer 20 and the formed single crystal from the graphite ring 32.

[0068] In some embodiments, the above-mentioned overlapping circular plate 31 and the restraint 40 can adopt structures such as Figure 1 and Figure 2 as shown. See Figure 1 and Figure 2 . The top ends of the overlapping circular plate 31 and the restraint 40 are spaced apart in the vertical direction.

[0069] The overlapping circular plate 31 and the restraint 40 are spaced apart in the vertical direction, which can ensure that the top of the annular gap 16 formed between the graphite ring 32 and the constrained graphite cylinder cavity 43 is open, avoiding crystal deposition here.

[0070] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention shall be included in the protection scope of the present invention.

Claims

1. Crucible structure for preparing low-base-plane dislocation silicon carbide single crystal, characterized in that, Comprising: A crucible body having a receiving cavity at the bottom of which silicon carbide raw materials are stored; the crucible body includes a pot body and a pot lid; the pot body has an open cavity with an open top; the pot lid is used to be buckled on the top of the pot body and enclose the receiving cavity with the open cavity; the pot lid is provided with a groove corresponding to the open cavity; an annular side wall is formed around the periphery of the groove; an annular slot for the annular side wall to be adaptively inserted is provided at the outer edge of the top of the pot body; A seed wafer, horizontally arranged at the top of the receiving cavity; A short graphite ring having an annular ring portion located below the seed wafer and in contact with the seed wafer, the annular ring portion being used to enclose an initial growth cavity with an open bottom with the seed wafer; the short graphite ring includes a lapping round plate and a graphite ring; the lapping round plate is lapped on the annular tabletop formed at the top of the pot body and has a central hole; the graphite ring is fixedly arranged in the central hole, with the top abutted against the seed wafer and the bottom extending below the lapping round plate; an annular groove for the seed wafer to be embedded is provided at the top of the inner hole of the graphite ring; A constraint member, arranged in the receiving cavity and having a constraint graphite tube cavity surrounding the annular ring portion, with an annular gap formed between the constraint graphite tube cavity and the annular ring portion; A sliding column, arranged along the vertical direction and slidably connected with the sliding hole on the pot lid, the length of the sliding column being greater than the length of the graphite ring in the vertical direction, and circular limiting plates being provided at both ends of the sliding column; the circular limiting plate located in the groove is used for the seed wafer to be fixedly connected; a circular embedding groove for accommodating the circular limiting plate is provided on the bottom surface of the groove; Wherein, during guided growth, after the graphite ring gradually expands until the inner hole diameter is greater than the outer diameter of the seed wafer, the combination of the seed wafer and the sliding column descends below the graphite ring under the action of its own gravity.

2. The crucible structure for preparing a low basal plane dislocation silicon carbide single crystal according to claim 1, characterized in that, The initial growth cavity and the constraint graphite tube cavity are coaxially arranged.

3. The crucible structure for preparing a low basal plane dislocation silicon carbide single crystal according to claim 1, wherein, The constraint member includes: A graphite support ring, horizontally arranged in the receiving cavity; An outer graphite ring, arranged on the graphite ring and having its bottom end communicated with the central hole of the graphite support ring, the inner cavity of the outer graphite ring being the constraint graphite tube cavity.

4. The crucible structure for preparing a low basal plane dislocation silicon carbide single crystal according to claim 3, wherein The receiving cavity is a cylindrical cavity with its axis along the vertical direction; Wherein, an annular platform for the graphite support ring to be erected is provided on the inner wall of the receiving cavity.

5. The crucible structure for preparing a low basal plane dislocation silicon carbide single crystal according to claim 3, wherein, The outer graphite ring and the graphite support ring are coaxially arranged.

6. The crucible structure for preparing a low basal plane dislocation silicon carbide single crystal according to claim 1, characterized in that, The lapping round plate and the top end of the constraint member are spaced apart in the vertical direction.

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