Graphite ring structure
By designing the inclined inner side wall in the graphite ring structure, the problem of excess edge growth caused by inertia in semiconductor epitaxial growth is solved, and the integrity of the wafer and the quality of epitaxial preparation are improved.
Patent Information
- Application Number
- CN202421141106.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-05-23
- Publication Date
- 2024-12-27
- Estimated Expiration
- 2034-05-23
AI Technical Summary
During the epitaxial growth of semiconductors, when the wafer rotates on the air float disk, it is pushed to the edge of the graphite ring structure due to inertia, which easily grows excess 3C-SiC, resulting in cards or lobes appearing in the grown wafer, which in turn leads to the growth of the wafer. The edge collapses and the entire wafer epitaxial film will be scrapped when taking the chip.
A graphite ring structure is designed, including a first annular portion and a second annular portion, the second annular portion is located on one side of the first annular portion, and the outer side walls of both are flush, and the inner side walls of the second annular portion are in the positioning area. The angle between the sub-inner side wall and the plane where the first annular portion is located is an acute angle to form an inclined structure, thereby reducing the formation of the edge redundant structure in the epitaxial process.
Through the inclined graphite ring structure, the formation of excess structure at the edges in the epitaxial process is reduced, the generation of lobes and cards is reduced, and the yield of epitaxial preparation is improved.
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Figure CN222251122U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the technical field of semiconductor epitaxial growth, in particular to a graphite ring structure. Background Art
[0002] During the semiconductor epitaxial growth process, when the wafer rotates on the air floating plate, the inertia will cause the wafer to press against the edge of the graphite ring structure. At this time, epitaxial growth is carried out, and excess 3C-SiC is easily grown on the edge of the graphite ring, which will cause the wafer to get stuck or cracked after growth. When the wafer gets stuck or cracked, the edge will collapse when the wafer is taken out, causing the entire wafer epitaxial wafer to be scrapped.
[0003] Therefore, how to study a graphite ring structure that reduces the number of slivers or cards has become a technical problem that those skilled in the art need to solve urgently. Utility Model Content
[0004] In view of the above problems, the utility model provides a fault alarm circuit, the specific scheme is as follows:
[0005] A graphite ring structure, comprising:
[0006] a first annular portion and a second annular portion;
[0007] The second annular portion is located at one side of the first annular portion, and the first annular portion is flush with an outer side wall of the second annular portion, and the second annular portion at least exposes a portion of the first annular portion;
[0008] The inner side wall of the second annular portion of the positioning area of the graphite ring structure includes: at least one sub-inner side wall, and the included angle between the sub-inner side wall and the plane where the first annular portion is located is an acute angle.
[0009] Optionally, in the above graphite ring structure, the inner side wall of the second annular portion of the positioning area of the graphite ring structure includes two sub-inner side walls;
[0010] The inner side wall of the second annular portion includes a first sub-inner side wall close to the first annular portion, and a second sub-inner side wall away from the first annular portion;
[0011] The angle between the first sub-inner sidewall and the plane where the first annular portion is located is a first angle; the angle between the second sub-inner sidewall and the plane where the first annular portion is located is a second angle; and the first angle is smaller than the second angle.
[0012] Optionally, in the above graphite ring structure, the inner side wall of the second annular portion of the positioning area of the graphite ring structure includes two sub-inner side walls;
[0013] The inner side wall of the second annular portion includes a first sub-inner side wall close to the first annular portion, and a second sub-inner side wall away from the first annular portion;
[0014] The angle between the first sub-inner sidewall and the plane where the first annular portion is located is a first angle; the angle between the second sub-inner sidewall and the plane where the first annular portion is located is a second angle; and the first angle is greater than the second angle.
[0015] Optionally, in the above graphite ring structure, an orthographic projection area of the first sub-inner sidewall on the plane where the first annular portion is located is different from an orthographic projection area of the second sub-inner sidewall on the plane where the first annular portion is located.
[0016] Optionally, in the above graphite ring structure, a thickness of the first annular portion in a first direction ranges from 0.3 mm to 0.4 mm, and the first direction is perpendicular to a plane where the first annular portion is located.
[0017] Optionally, in the above graphite ring structure, a thickness of the graphite ring structure in a first direction ranges from 2 mm to 3 mm, and the first direction is perpendicular to a plane where the first annular portion is located.
[0018] Optionally, in the above graphite ring structure, the maximum inner diameter of the graphite ring structure is in the range of 145mm-150mm.
[0019] Optionally, in the above graphite ring structure, the outer diameter of the graphite ring structure ranges from 160 mm to 170 mm.
[0020] Optionally, in the above graphite ring structure, in the area of the graphite ring structure other than the positioning area, the inner side wall of the second annular portion includes a first inner side wall close to the first annular portion, and a second inner side wall away from the first annular portion;
[0021] The first inner side wall is perpendicular to the plane where the first annular portion is located; and the angle between the second inner side wall and the plane where the first annular portion is located is an acute angle.
[0022] Optionally, in the above graphite ring structure, in an area of the graphite ring structure other than the positioning area, an inner side wall of the second annular portion is perpendicular to a plane where the first annular portion is located.
[0023] Compared with the prior art, the beneficial effects achieved by the utility model are:
[0024] The utility model provides a graphite ring structure, which comprises a first ring part and a second ring part; the second ring part is located on one side of the first ring part, and the first ring part is flush with the outer side wall of the second ring part, and the second ring part exposes at least part of the first ring part; the inner side wall of the second ring part in the positioning area of the graphite ring structure comprises: at least one sub-inner side wall, and the angle between the sub-inner side wall and the plane where the first ring part is located is an acute angle. Since the angle between the sub-inner side wall of the second ring part in the positioning area and the plane where the first ring part is located is an acute angle, that is, the inner side wall of the second ring part in the positioning area is an inclined structure, so when performing an epitaxial process, it is not easy to form redundant structures at the edge of the positioning area, further reducing the generation of cracks and cards, and improving the yield of epitaxial preparation. BRIEF DESCRIPTION OF THE DRAWINGS
[0025] The above and other features, advantages and aspects of the embodiments of the present disclosure will become more apparent with reference to the following detailed description in conjunction with the accompanying drawings. Throughout the accompanying drawings, the same or similar reference numerals represent the same or similar elements. It should be understood that the drawings are schematic and the originals and elements are not necessarily drawn to scale.
[0026] Figure 1 A schematic diagram of the cross-sectional structure of a positioning area of a graphite ring structure provided in an embodiment of the present application;
[0027] Figure 2 A schematic diagram of a top view of a graphite ring structure provided in an embodiment of the present application;
[0028] Figure 3 A schematic diagram of the cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application;
[0029] Figure 4 A schematic diagram of the cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application;
[0030] Figure 5 A schematic diagram of the cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application;
[0031] Figure 6 A schematic diagram of the cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application;
[0032] Figure 7 A schematic diagram of a top view of another graphite ring structure provided in an embodiment of the present application;
[0033] Figure 8 A schematic diagram of the cross-sectional structure of a graphite ring structure excluding the positioning area provided in an embodiment of the present application;
[0034] Fig. 9 A schematic diagram of the cross-sectional structure of another graphite ring structure excluding the positioning area provided in an embodiment of the present application. DETAILED DESCRIPTION
[0035] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0036] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0037] refer to Figure 1 , Figure 1 A schematic diagram of the cross-sectional structure of a positioning area of a graphite ring structure provided in an embodiment of the present application; Figure 2 , Figure 2 A schematic diagram of a top view of a graphite ring structure provided in an embodiment of the present application; the graphite ring structure comprises:
[0038] A first annular portion 01 and a second annular portion 02 .
[0039] The second annular portion 02 is located at one side of the first annular portion 01 , and the first annular portion 01 is flush with the outer sidewall of the second annular portion 02 , and the second annular portion 02 at least partially exposes the first annular portion 01 .
[0040] The inner side wall of the second annular portion 02 of the positioning area 03 of the graphite ring structure includes: at least one sub-inner side wall 021, and the included angle between the sub-inner side wall 021 and the plane where the first annular portion 01 is located is an acute angle.
[0041] Specifically, along Figure 1The dotted line shown divides the graphite ring structure into a first annular portion 01 and a second annular portion 02. It should be noted that the first annular portion 01 and the second annular portion 02 are a whole, and the division is only for better explanation. The second annular portion 02 is located on one side of the first annular portion 01, and along the radius of the graphite ring structure, from the edge of the graphite ring structure to the direction of the geometric center of the graphite ring structure, the first annular structure 01 is flush with the outer side wall of the second annular structure 02, and the first annular portion 01 exposed by the second annular structure 02 is the area close to the geometric center. It should be noted that a main positioning edge is provided in the positioning area 03 of the graphite ring structure, which is located on the inner side of the graphite ring structure, that is, a part of the inner side of the graphite ring structure is filled along a minor arc of a chord smaller than the diameter, thereby forming a shape as shown in the figure. Figure 2 It should be noted that the material of the graphite ring structure is a graphite material with a SiC coating.
[0042] In this embodiment, reference Figure 3 , Figure 3 A schematic diagram of a cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application; the graphite ring structure is divided into area A, area B and area C, the second annular structure 02 at least does not cover area A, and the inner side wall of the second annular portion 02 of the positioning area 03 of the graphite ring structure is chamfered to form at least one sub-inner side wall 021, Figure 3 In the figure, a sub-inner wall 021 is taken as an example. Of course, multiple sub-inner walls 021 can also be provided. No further examples are given here. The angle α between any sub-inner wall 021 and the plane where the first annular portion 01 is located is an acute angle. In other words, the orthographic projection area of the surface of the second annular portion 02 away from the first annular portion 01 on the plane where the first annular portion 01 is located is smaller than the orthographic projection area of the surface of the second annular portion 02 close to the first annular portion 01 on the plane where the first annular portion 01 is located. Figure 3 As shown, along the radius of the graphite ring structure, in the direction X from the edge of the graphite ring structure to the geometric center of the graphite ring structure, the area of the C region is smaller than the area of the D region, and one end of the inner side wall of the second ring structure 02 borders on the side of the A region of the first ring structure 01 away from the geometric center of the graphite ring structure, and the other end of the inner side wall of the second ring structure 02 borders on the side of the C region of the second ring structure 02 close to the geometric center of the graphite ring structure. Since the angle α between the sub-inner side wall 021 of the second ring portion 02 in the positioning area 03 and the plane where the first ring portion 01 is located is an acute angle, that is, the inner side wall of the second ring portion 02 in the positioning area 03 is an inclined structure, so when the epitaxial process is performed, it is not easy to form a 3C-SiC structure at the edge of the positioning area 03, which further reduces the generation of cracks and cards and improves the yield of epitaxial preparation.
[0043] Optional, reference Figure 4 , Figure 4 A schematic diagram of the cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application; in another embodiment of the present application, the inner side wall of the second annular portion 02 of the positioning area 03 of the graphite ring structure includes two sub-inner side walls.
[0044] The inner sidewall of the second annular portion 02 includes a first sub-inner sidewall 021 a close to the first annular portion 01 , and a second sub-inner sidewall 021 b away from the first annular portion 01 .
[0045] The angle between the first sub-inner sidewall 021a and the plane where the first annular portion 01 is located is a first angle α1; the angle between the second sub-inner sidewall 021b and the plane where the first annular portion 01 is located is a second angle α2; the first angle α1 is smaller than the second angle α2.
[0046] Specifically, Figure 4 The example in which the inner side wall of the second annular portion 02 of the positioning area 03 of the graphite ring structure includes two sub-inner side walls is used for explanation. Among them, the angle between the first sub-inner side wall 021a close to the first annular portion 01 and the plane where the first annular portion 01 is located is the first angle α1, and the first angle α1 is an acute angle, that is, the angle range is between 0 degrees and 90 degrees, excluding the endpoint value; the angle between the second sub-inner side wall 021b away from the first annular portion 01 and the plane where the first annular portion 01 is located is the second angle α2, and the second angle α2 is an acute angle, that is, the angle range is between 0 degrees and 90 degrees, excluding the endpoint value; in this embodiment, the angle of the first angle α1 is smaller than the angle of the second angle α2, so that the following can be formed: Figure 4 The inwardly concave inclined structure shown in the figure makes it difficult for a 3C-SiC structure to be formed at the edge of the positioning area 03 during the epitaxial process, thereby further reducing the generation of cracks and cards and improving the yield of epitaxial preparation.
[0047] Optional, reference Figure 5 , Figure 5 A schematic diagram of the cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application; in another embodiment of the present application, the inner side wall of the second annular portion 02 of the positioning area 03 of the graphite ring structure includes two sub-inner side walls.
[0048] The inner sidewall of the second annular portion 02 includes a first sub-inner sidewall 021 a close to the first annular portion 01 , and a second sub-inner sidewall 021 b away from the first annular portion 01 .
[0049] The angle between the first sub-inner sidewall 021a and the plane where the first annular portion 01 is located is a first angle α3; the angle between the second sub-inner sidewall 021b and the plane where the first annular portion 01 is located is a second angle α4; the first angle α3 is greater than the second angle α4.
[0050] Specifically, Figure 5 The example in which the inner side wall of the second annular portion 02 of the positioning area 03 of the graphite ring structure includes two sub-inner side walls is used for explanation. Among them, the angle between the first sub-inner side wall 021a close to the first annular portion 01 and the plane where the first annular portion 01 is located is a first angle α3, and the first angle α3 is an acute angle, that is, the angle range is between 0 degrees and 90 degrees, excluding the endpoint value; the angle between the second sub-inner side wall 021b away from the first annular portion 01 and the plane where the first annular portion 01 is located is a second angle α4, and the second angle α4 is an acute angle, that is, the angle range is between 0 degrees and 90 degrees, excluding the endpoint value; in this embodiment, the angle of the first angle α3 is smaller than the angle of the second angle α4, so that the following can be formed: Figure 5 The inwardly convex inclined structure shown in the figure makes it difficult for a 3C-SiC structure to be formed at the edge of the positioning area 03 during the epitaxial process, thereby further reducing the generation of cracks and cards and improving the yield of epitaxial preparation.
[0051] Optionally, in another embodiment of the present application, the orthographic projection area of the first sub-inner wall 021a on the plane where the first annular portion 01 is located is different from the orthographic projection area of the second sub-inner wall 021b on the plane where the first annular portion 01 is located.
[0052] Specifically, Figure 4 As shown, the first angle α1 between the first sub-inner wall 021a and the plane where the first annular portion 01 is located is smaller than the second angle α2 between the second sub-inner wall 021b and the plane where the first annular portion 01 is located. At this time, the orthographic projection area B1 of the first sub-inner wall 021a on the plane where the first annular portion 01 is located is larger than the orthographic projection area B2 of the second sub-inner wall 021b on the plane where the first annular portion 01 is located.
[0053] like Figure 5As shown, the first angle α3 between the first sub-inner wall 021a and the plane where the first annular portion 01 is located is greater than the second angle α4 between the second sub-inner wall 021b and the plane where the first annular portion 01 is located. At this time, the orthographic projection area B3 of the first sub-inner wall 021a on the plane where the first annular portion 01 is located is smaller than the orthographic projection area B4 of the second sub-inner wall 021b on the plane where the first annular portion 01 is located. It should be noted that there is no specific limitation on the orthographic projection area of the first sub-inner wall 021a on the plane where the first annular portion 01 is located and the orthographic projection area of the second sub-inner wall 021b on the plane where the first annular portion 01 is located, and in some cases, they can also be the same.
[0054] Optional, reference Figure 6 , Figure 6 A schematic diagram of the cross-sectional structure of a positioning area of another graphite ring structure provided in an embodiment of the present application; in another embodiment of the present application, the thickness range H1 of the first annular portion 01 in the first direction Y is 0.3mm-0.4mm, and the first direction Y is perpendicular to the plane where the first annular portion 01 is located.
[0055] Specifically, in the first direction Y, the thickness range H1 of the first annular portion 01 may be 0.3 mm-0.4 mm, including end values, such as 0.3 mm, 0.35 mm, etc., which will not be exhaustively listed here, and no specific limitation is made, and it can be set according to specific needs. The first direction Y is perpendicular to the plane where the first annular portion 01 is located.
[0056] Optional, such as Figure 6 As shown, in another embodiment of the present application, the thickness range H2 of the graphite ring structure in the first direction Y is 2 mm-3 mm, and the first direction Y is perpendicular to the plane where the first annular portion 01 is located.
[0057] Specifically, in the first direction Y, the total thickness range H2 of the graphite ring structure, i.e., the first ring portion 01 and the second ring portion 02, can be 2mm-3mm, including endpoint values, for example, 2.5mm, 3mm, etc., which will not be enumerated here and will not be specifically limited. It can be set according to specific needs.
[0058] Optional, reference Figure 7 , Figure 7 A schematic diagram of a top view of another graphite ring structure provided in an embodiment of the present application; in another embodiment of the present application, the maximum inner diameter of the graphite ring structure is in the range of 145mm-150mm.
[0059] Optionally, in another embodiment of the present application, the outer diameter of the graphite ring structure ranges from 160 mm to 170 mm.
[0060] Specifically, in this embodiment, the maximum inner diameter of the graphite ring structure can range from 145mm to 150mm, including endpoint values, such as 144mm, 148mm, etc., without specific limitation, and can be set according to specific needs. The outer diameter of the graphite ring structure can range from 160mm to 170mm, including endpoint values, such as 160mm, 165mm, etc., without specific limitation, and can be set according to specific needs. It should be noted that setting the inner diameter and outer diameter can make the graphite ring structure adapt to the wafer.
[0061] Optional, reference Figure 8 , Figure 8 A schematic diagram of the cross-sectional structure of a graphite ring structure excluding a positioning area is provided in an embodiment of the present application; in another embodiment of the present application, in the area of the graphite ring structure excluding the positioning area, the inner side wall of the second annular portion 02 includes a first inner side wall 022a close to the first annular portion 01, and a second inner side wall 022b away from the first annular portion 01.
[0062] The first inner side wall 022a is perpendicular to the plane where the first annular portion 01 is located; the angle β between the second inner side wall 022b and the plane where the first annular portion 01 is located is an acute angle.
[0063] Specifically, in this embodiment, the configuration of other regions of the graphite ring structure except the positioning region is described. Figure 8 As shown, the inner wall of the second annular portion 02 includes a first inner wall 022a perpendicular to the plane where the first annular portion 01 is located, and a second inner wall 022b having an angle β with the plane where the first annular portion 01 is located. The angle β between the second inner wall 022b and the plane where the first annular portion 01 is located is an acute angle, that is, 0 degrees-90 degrees, excluding endpoint values, for example, it can be 30 degrees, 40 degrees, 50 degrees, etc., and is not specifically limited.
[0064] Optional, reference Fig. 9 , Fig. 9 A schematic diagram of the cross-sectional structure of another graphite ring structure excluding the positioning area provided in an embodiment of the present application; in another embodiment of the present application, in the area of the graphite ring structure excluding the positioning area, the inner side wall 023 of the second annular portion 02 is perpendicular to the plane where the first annular portion 01 is located.
[0065] Specifically, in this embodiment, the configuration of other regions of the graphite ring structure except the positioning region is described. Fig. 9As shown, the inner side wall 023 of the second annular portion 02 may be directly perpendicular to the plane where the first annular portion 01 is located. It should be noted that there is no specific limitation on the arrangement of other areas of the graphite ring structure except the positioning area, and the arrangement may be performed as required.
[0066] Based on the above description, a graphite ring structure provided by the present application has an acute angle between the sub-inner wall of the second annular portion 02 in the positioning area and the plane where the first annular portion 01 is located, that is, the inner wall of the second annular portion 02 in the positioning area is an inclined structure. Therefore, when the epitaxial process is carried out, it is not easy to form redundant structures at the edge of the positioning area, which further reduces the generation of cracks and cards and improves the yield of epitaxial preparation.
[0067] The above is a detailed introduction to a graphite ring structure provided by the utility model. Specific examples are used in this article to illustrate the principle and implementation method of the utility model. The description of the above embodiments is only used to help understand the method and core idea of the utility model. At the same time, for general technicians in this field, according to the idea of the utility model, there will be changes in the specific implementation method and application scope. In summary, the content of this specification should not be understood as a limitation on the utility model.
[0068] It should be noted that each embodiment in this specification focuses on the differences from other embodiments, and the same or similar parts between the embodiments can be referenced to each other.
[0069] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or device that includes a series of elements is inherent to the elements, or also includes elements inherent to these processes, methods, articles or devices. In the absence of further restrictions, the elements defined by the sentence "including a..." do not exclude the presence of other identical elements in the process, method, article or device that includes the elements.
[0070] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.
Claims
1. A graphite ring structure, characterized in that: The graphite ring structure comprises: a first annular portion and a second annular portion; The second annular portion is located at one side of the first annular portion, and the first annular portion is flush with an outer side wall of the second annular portion, and the second annular portion at least exposes a portion of the first annular portion; The inner side wall of the second annular portion of the positioning area of the graphite ring structure includes: at least one sub-inner side wall, and the included angle between the sub-inner side wall and the plane where the first annular portion is located is an acute angle.
2. The graphite ring structure according to claim 1, characterized in that: The inner side wall of the second annular portion of the positioning area of the graphite ring structure includes two sub-inner side walls; The inner side wall of the second annular portion includes a first sub-inner side wall close to the first annular portion, and a second sub-inner side wall away from the first annular portion; The angle between the first sub-inner sidewall and the plane where the first annular portion is located is a first angle; the angle between the second sub-inner sidewall and the plane where the first annular portion is located is a second angle; and the first angle is smaller than the second angle.
3. The graphite ring structure according to claim 1, characterized in that: The inner side wall of the second annular portion of the positioning area of the graphite ring structure includes two sub-inner side walls; The inner side wall of the second annular portion includes a first sub-inner side wall close to the first annular portion, and a second sub-inner side wall away from the first annular portion; The angle between the first sub-inner sidewall and the plane where the first annular portion is located is a first angle; the angle between the second sub-inner sidewall and the plane where the first annular portion is located is a second angle; and the first angle is greater than the second angle.
4. The graphite ring structure according to claim 2 or 3, characterized in that: An orthographic projection area of the first sub-inner sidewall on the plane where the first annular portion is located is different from an orthographic projection area of the second sub-inner sidewall on the plane where the first annular portion is located.
5. The graphite ring structure according to claim 1, characterized in that: The thickness of the first annular portion in a first direction ranges from 0.3 mm to 0.4 mm, and the first direction is perpendicular to the plane where the first annular portion is located.
6. The graphite ring structure according to claim 1, characterized in that: The thickness of the graphite ring structure in a first direction ranges from 2 mm to 3 mm, and the first direction is perpendicular to the plane where the first annular portion is located.
7. The graphite ring structure according to claim 1, characterized in that: The maximum inner diameter of the graphite ring structure is in the range of 145 mm to 150 mm.
8. The graphite ring structure according to claim 1, characterized in that: The outer diameter of the graphite ring structure ranges from 160 mm to 170 mm.
9. The graphite ring structure according to claim 1, characterized in that: In the area of the graphite ring structure other than the positioning area, the inner side wall of the second annular portion includes a first inner side wall close to the first annular portion and a second inner side wall away from the first annular portion; The first inner side wall is perpendicular to the plane where the first annular portion is located; and the angle between the second inner side wall and the plane where the first annular portion is located is an acute angle.
10. The graphite ring structure according to claim 1, characterized in that: In the area of the graphite ring structure other than the positioning area, the inner side wall of the second annular portion is perpendicular to the plane where the first annular portion is located.