Adhesive discharging and sintering method for electrostatic chuck

Abstract

The invention discloses a glue discharging and sintering method for an electrostatic chuck, and belongs to the technical field of electrostatic chucks, and the glue discharging and sintering method comprises the following steps: material preparation: preparing an electrostatic chuck ceramic biscuit, a gasket biscuit and a cover plate biscuit, and preparing a setter plate, the materials for preparing the gasket biscuit and the cover plate biscuit being the same as the materials for preparing the electrostatic chuck ceramic biscuit; the gasket biscuit is placed on a load bearing plate, the electrostatic chuck ceramic biscuit is placed on the gasket biscuit, the cover plate biscuit is placed on the electrostatic chuck ceramic biscuit, and then the gasket biscuit, the electrostatic chuck ceramic biscuit and the cover plate biscuit are placed into a glue discharging furnace together for glue discharging; and sintering: sintering the electrostatic chuck ceramic biscuit, the gasket biscuit, the cover plate biscuit and the setter plate in a sintering furnace. According to the application, the gasket biscuit and the electrostatic chuck biscuit are placed on the device for glue discharging and sintering, and during glue discharging, organic matters of the electrostatic chuck biscuit can be discharged from all directions, so that the phenomenon that the overall density of the sintered ceramic plate is not uniform is avoided.

Description

Technical Field

[0001] The present invention relates to the technical field of electrostatic chucks, and in particular to a debinding and sintering method for electrostatic chucks. Background Art

[0002] Currently, during the debinding and sintering process of electrostatic chuck ceramic plates, the ceramic plate blank is generally placed directly on the setter, and then the setter and the ceramic plate are placed in the debinding furnace for debinding. After debinding, they are placed in the sintering furnace for sintering. This debinding and sintering process has the following two problems:

[0003] 1. Because the lower surface of the ceramic plate is in direct contact with the setter without a gap, and the rest of the surface is exposed, the organic matter cannot be discharged uniformly in all directions during the debinding and sintering process of the ceramic plate. The amount of debinding on the upper surface is much greater than that on the lower surface, which affects the debinding and sintering effect. As a result, the ceramic plate is prone to uneven overall density and cracking after debinding and sintering, reducing the qualified rate of finished products.

[0004] 2. Because the material of the setter plate and the ceramic plate cannot be completely consistent, during the sintering process, the ceramic plate shrinks and there is a relative force between the setter plate and the ceramic plate, which can easily cause the ceramic plate to crack under stress and reduce the qualified rate of the finished product. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a debinding and sintering method for an electrostatic chuck, so as to solve the problems raised in the background technology.

[0006] In order to solve the above technical problems, the technical solution of the present invention is:

[0007] A debinding and sintering method for an electrostatic chuck, comprising:

[0008] Material preparation: preparing an electrostatic chuck ceramic blank, a gasket blank, and a cover plate blank, and preparing a setter, wherein the materials for preparing the gasket blank and the cover plate blank are the same as those for preparing the electrostatic chuck ceramic blank, and the preparation processes of the gasket blank and the cover plate blank are the same, the gasket blank comprises a plurality of first upper grooves and a plurality of first lower grooves, the openings of the first grooves face upward, the openings of the first lower grooves face downward, and the first upper grooves and the first lower grooves are spaced apart, the cover plate blank comprises a plurality of second upper grooves and a plurality of second lower grooves, the openings of the second upper grooves face upward, the openings of the second lower grooves face downward, and the second upper grooves and the second lower grooves are spaced apart;

[0009] Debinding: Place the gasket green blank on the setter plate, place the electrostatic chuck ceramic green blank on the gasket green blank, place the cover sheet green blank on the electrostatic chuck ceramic green blank, and then put the four together into the debinding furnace for debinding;

[0010] Sintering: After the debinding is completed, the electrostatic chuck ceramic blank, the gasket blank, the cover plate blank and the support plate are placed in a sintering furnace for sintering. The gasket blank made of the same material is sintered together to avoid direct contact between the electrostatic chuck ceramic blank and the support plate, which may cause cracking.

[0011] Preferably, the preparation method of the gasket blank and the cover plate blank includes:

[0012] Lamination: prepare several blank ceramic green sheets, and laminate them to the required thickness of the gasket green sheet and the cover green sheet using a laminating machine. The lamination pressure is 20-50 MPa, and the lamination time is 5-10 minutes to prepare several laminated green sheets.

[0013] Isostatic pressing: vacuum pack the laminated green sheets after lamination. Place the first PET film, the first laminated green sheet, the screen filter cloth, the second laminated green sheet, and the second PET film in order from bottom to top, and then put them into a vacuum packaging bag for vacuum packaging. After packaging, put them into a static isostatic press for lamination. The lamination pressure is 80-200MPa and the time is 30-60min.

[0014] Shape processing: the first laminated green sheet and the second laminated green sheet after isostatic pressing are subjected to shape processing by CNC to form the gasket green sheet and the cover plate green sheet.

[0015] Preferably, the thickness of the gasket blank is equal to that of the cover plate blank, and the thickness of the gasket blank is 1-3 mm.

[0016] Preferably, after the electrostatic chuck ceramic blank is placed on the gasket blank, its projection on the gasket blank is located above the gasket blank.

[0017] Preferably, the distance between any two adjacent first upper grooves and the first lower groove is equal, and the distance between any two adjacent second upper grooves and the second lower groove is equal.

[0018] Preferably, the shape of the first upper groove is the same as that of the first lower groove, and the shape of the second upper groove is the same as that of the second lower groove.

[0019] Preferably, the shape of the first upper groove is the same as that of the second upper groove, and the first upper groove is an arc-shaped groove.

[0020] The above technical solution has the following beneficial effects:

[0021] The present application sets a gasket blank, on which the electrostatic chuck blank is placed for debinding and sintering. During debinding, the organic matter of the electrostatic chuck blank can be discharged from all directions, thereby avoiding the phenomenon of uneven overall density of the ceramic plate after sintering. When sintering is performed after debinding, the electrostatic chuck blank is in close contact with the gasket blank. Since the two are made of the same material and basically maintain the same shrinkage, the relative force generated by the gasket blank and the supporting plate directly acts on the gasket blank, which can reduce the chance of cracking of the electrostatic chuck blank after sintering into a ceramic plate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the prior art electrostatic chuck ceramic green blank debinding and sintering method;

[0023] Figure 2 This is a structural schematic diagram of a debinding and sintering method for an electrostatic chuck according to the present invention;

[0024] Figure 3 for Figure 2 Schematic diagram of the enlarged structure of A;

[0025] Figure 4 Another structural schematic diagram of the gasket blank of the present invention;

[0026] Figure 5 for Figure 4 Schematic diagram of the enlarged structure of B;

[0027] Figure 6 This is another schematic diagram of the three-dimensional structure of the gasket blank of the present invention;

[0028] Figure 7 This is another schematic top view of the structure of the gasket blank of the present invention. DETAILED DESCRIPTION

[0029] The following is a further description of specific embodiments of the present invention in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is intended to facilitate understanding of the present invention and does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below may be combined with each other as long as they do not conflict with each other.

[0030] In the prior art, during the debinding and sintering process of the electrostatic chuck ceramic plate, the electrostatic chuck ceramic blank 2 is generally placed directly on the support plate 1. Figure 1 Then, the setter plate 1 and the ceramic plate are placed in the debinding furnace for debinding. After debinding, they are placed in the sintering furnace for sintering. There are two problems in this debinding and sintering process:

[0031] 1. Because the lower surface of the ceramic plate is in direct contact with the setter plate 1 without a gap, and the rest of the surface is exposed, the organic matter cannot be discharged uniformly in all directions during the debinding and sintering process of the ceramic plate, which affects the debinding and sintering effect. In turn, it leads to uneven overall density and cracking of the ceramic plate after debinding and sintering, reducing the qualified rate of the finished product;

[0032] 2. Because the material of the setter plate 1 cannot be completely consistent with that of the ceramic plate, during the sintering process, the ceramic plate shrinks and there is a relative force between the setter plate 1, which can easily cause the ceramic plate to crack under stress and reduce the qualified rate of the finished product.

[0033] The present application discloses a debinding and sintering method for an electrostatic chuck to solve the problems existing in the above-mentioned prior art. The present application sets a gasket blank 3, on which the electrostatic chuck blank is placed for debinding and sintering. During debinding, organic matter in the electrostatic chuck blank can be discharged from all directions, thereby avoiding the phenomenon of uneven overall density of the ceramic plate after sintering. When sintering after debinding is completed, the electrostatic chuck blank is in close contact with the gasket blank 3. Since the two are made of the same material and basically maintain the same shrinkage, the relative force generated by the gasket blank 3 and the supporting plate 1 directly acts on the gasket blank 3, which can reduce the probability of cracking of the electrostatic chuck blank after sintering into a ceramic plate.

[0034] refer to Figures 2 and 3 A method for debinding and sintering electrostatic chuck ceramics can improve the uniformity of debinding of electrostatic chuck ceramics and reduce the possibility of cracks during sintering of electrostatic chuck ceramics. The method specifically includes the following steps:

[0035] Material preparation: Prepare an electrostatic chuck ceramic blank 2, a gasket blank 3, and a cover plate blank 4, and prepare a setter 1. The materials for preparing the gasket blank 3 and the cover plate blank 4 are the same as those for preparing the electrostatic chuck ceramic blank 2, and the preparation processes of the gasket blank 3 and the cover plate blank 4 are the same. The gasket blank 3 includes a plurality of first upper grooves 5 and a plurality of first lower grooves 6, the openings of the first grooves face upward, the openings of the first lower grooves 6 face downward, and the first upper grooves 5 and the first lower grooves 6 are spaced apart. The cover plate blank 4 includes a plurality of second upper grooves 7 and a plurality of second lower grooves 8, the openings of the second upper grooves 7 face upward, the openings of the second lower grooves 8 face downward, and the second upper grooves 7 and the second lower grooves 8 are spaced apart.

[0036] Specifically, the firing plate 1 is used to place the electrostatic chuck ceramic blank 2, the gasket blank 3, and the cover plate blank 4, and plays a supporting role during the debinding and sintering process. The materials of the gasket blank 3 and the cover plate blank 4 are the same as the materials used to prepare the electrostatic chuck ceramic blank 2. For example, the electrostatic chuck ceramic can be alumina ceramic or aluminum nitride ceramic, or other ceramics. It can be selected according to needs, and the preparation materials of the gasket and the electrostatic chuck ceramic are set to be the same. During sintering, since the materials of the two are the same, basically the same shrinkage is maintained. The relative force generated by the gasket blank 3 and the firing plate 1 directly acts on the gasket blank 3, which can reduce the probability of cracking of the electrostatic chuck blank after sintering into ceramics, and improve the yield rate of the electrostatic chuck ceramic.

[0037] Specifically, during debinding, the electrostatic chuck ceramic blank 2 is placed between the gasket blank 3 and the cover plate blank 4. Since the gasket blank 3 includes a plurality of first upper grooves 5 and a plurality of first lower grooves 6, and the cover plate blank 4 includes a plurality of second upper grooves 7 and a plurality of second lower grooves 8, the electrostatic chuck ceramic blank 2 can be debinded in all directions, specifically on the top, bottom and side walls, thereby improving the debinding uniformity of the electrostatic chuck ceramic blank 2 and avoiding the phenomenon of uneven overall density of the ceramic plate after sintering. Specifically, the gasket blank 3 and the cover plate blank 4 can be of equal size and have the same shape, so that the debinding conditions of the top and bottom of the electrostatic chuck ceramic blank 2 are closer during debinding. In other implementations of this embodiment, other electrostatic chuck ceramic blanks 2 can be placed on the cover plate blank 4, and another cover plate blank 4 can be placed on the other electrostatic chuck ceramic blank 2, that is, two or more electrostatic chuck ceramic blanks 2 can be debinded and sintered together;

[0038] The first groove 5 and the second groove 6 are provided with a plurality of grooves 5 for supporting the groove 2, and the grooves 5 for supporting the groove 2 are provided with a plurality of grooves 6 for supporting the groove 2. Specifically, the gasket blank 3 includes a plurality of first upper grooves 5 and a plurality of first lower grooves 6, the opening of the first groove faces upward, and the opening of the first lower groove 6 faces downward. The first upper groove 5 and the first lower groove 6 are arranged at intervals. The shape of the first upper groove 5 can be the same as the shape of the first lower groove 6, but the directions of the two are different. The first upper groove 5 is arranged upward, and the first lower groove 6 is arranged downward. The side where the first upper groove 5 is provided is the side where the electrostatic chuck ceramic blank 2 is placed. By providing the first upper groove 5, the bottom of the electrostatic chuck ceramic blank 2 can also be debinded during sintering and debinding. For the first lower groove 6 with the opening facing downward, it is avoided that the shrinkage difference between the second upper groove 7 and the second lower groove 8 is too large due to the contact surface between the second upper groove 5 and the first lower groove 6. The second upper groove 7 and the second lower groove 8 can be provided in the same form, shape and size as the first upper groove 5 and the first lower groove 6, and the form of the arrangement is also arranged alternately, which makes the manufacturing process easier.

[0039] Specifically, the electrostatic chuck ceramic blank 2 can be disc-shaped, the gasket blank 3 and the cover plate blank 4 can be the same size, and both can be square structures. At this time, a plurality of first upper grooves 5 are arranged in parallel, and a plurality of first lower grooves 6 are also arranged in parallel, and the two are evenly spaced and arranged on the gasket blank 3. Similarly, a plurality of second upper grooves 7 and a plurality of second lower grooves 8 on the cover plate blank 4 are also arranged in the same manner. In other implementations of this embodiment, the gasket blank 3 and the cover plate blank 4 can also be disc-shaped, refer to Figures 6 and 7 At this time, a plurality of first upper grooves 5 and a plurality of first lower grooves 6 are evenly arranged along the circumferential direction. A hole 9 can be set in the center of the gasket blank 3 and the cover plate blank 4. One end of the first upper groove 5 and one end of the first lower groove 6 are connected to the central hole 9. The width of the end of the first upper groove 5 connected to the central hole 9 is smaller than that of the other end, that is, a larger portion of the first upper groove 5 is dug out, so as to facilitate faster glue removal. The first upper groove 5 and the first lower groove 6 are also arranged at intervals. Similarly, the plurality of second upper grooves 7 and the plurality of second lower grooves 8 on the cover plate blank 4 are also arranged in the same way.

[0040] Debinding: Place the gasket blank 3 on the setter 1, place the electrostatic chuck ceramic blank 2 on the gasket blank 3, place the cover blank on the electrostatic chuck ceramic blank 2, and then put the four together into the debinding furnace for debinding;

[0041] Specifically, after the electrostatic chuck ceramic blank 2, the gasket blank 3, and the cover plate blank 4 are prepared, they are placed on the setter plate 1 and then put into the debinding furnace for debinding. During debinding, since the gasket blank 3 includes a plurality of first upper grooves 5 and a plurality of first lower grooves 6, and the cover plate blank 4 includes a plurality of second upper grooves 7 and a plurality of second lower grooves 8, the upper and lower sides of the electrostatic chuck ceramic blank 2 can be debinded, and the conditions on the upper and lower sides are similar, and the debinding conditions are also similar, thereby improving the uniformity of debinding.

[0042] Sintering: After the debinding process, the electrostatic chuck ceramic blank 2, the gasket blank 3, the cover plate blank 4 and the setter plate 1 are placed in a sintering furnace for sintering. The gasket blank 3 made of the same material is sintered together to prevent the electrostatic chuck ceramic blank 2 from directly contacting the setter plate 1 and causing cracking.

[0043] Specifically, the electrostatic chuck ceramic blank 2, gasket blank 3, cover plate blank 4 and supporting plate 1 after debinding are placed in a sintering furnace together for sintering. Since the debinding in the previous step is relatively uniform, the phenomenon of uneven overall density of the ceramic plate after sintering is avoided. During sintering, the electrostatic chuck blank is in close contact with the gasket blank 3. Since the two are made of the same material and basically maintain the same shrinkage, the relative force generated by the gasket blank 3 and the supporting plate 1 directly acts on the gasket blank 3, which can reduce the probability of cracking of the electrostatic chuck blank after sintering into a ceramic plate, improve the quality of the electrostatic chuck ceramic, and improve the yield rate of electrostatic chuck ceramic sintering.

[0044] In some embodiments, the preparation method of the gasket blank 3 and the cover plate blank 4 includes:

[0045] Lamination: prepare several blank ceramic green sheets, and laminate them to the required thickness of the gasket green sheet 3 and the cover green sheet 4 using a laminating machine. The lamination pressure is 20-50 MPa and the lamination time is 5-10 minutes to prepare several laminated green sheets.

[0046] Specifically, according to the required thickness of the gasket blank 3 and the cover plate blank 4, a laminating machine is used to press the green plate at a pressure of 20-50 MPa for 5-10 minutes to obtain a laminated ceramic green plate. The material of the ceramic green plate is consistent with the material used to prepare the electrostatic chuck ceramic. In other embodiments of this embodiment, the lamination pressure can be 20 MPa, 50 MPa, or 35 MPa, and the pressing time can be 5 minutes, 10 minutes, or 8 minutes. After lamination and pressing, the green plate is ready for use.

[0047] Isostatic pressing: vacuum pack the laminated green sheets after lamination. Place the first PET film, the first laminated green sheet, the screen filter cloth, the second laminated green sheet, and the second PET film in order from bottom to top, and then put them into a vacuum packaging bag for vacuum packaging. After packaging, put them into a static isostatic press for lamination. The lamination pressure is 80-200MPa and the time is 30-60min.

[0048] Specifically, the gasket blank 3 and the cover blank 4 pressed in the previous step are vacuum-packed and then placed in an isostatic press for lamination. The lamination pressure is 80 MPa, 200 MPa, or 140 MPa, and the lamination time is 30 min, 60 min, or 45 min.

[0049] Shape processing: the first and second laminated green sheets after isostatic pressing are subjected to shape processing by CNC to form a gasket green sheet 3 and a cover plate green sheet 4;

[0050] Specifically, the first laminated blank and the second laminated blank are processed by a CNC machine tool, that is, the first upper groove 5, the first lower groove 6, and the second upper groove 7, the second lower groove 8 are processed. After the processing is completed, the gasket blank 3 and the cover plate blank 4 are formed. The gasket blank 3 and the cover plate blank 4 are prepared by the above method, ensuring that the same process is used for the two.

[0051] In some embodiments, the thickness of the gasket blank 3 and the cover plate blank 4 are equal, and the thickness of the gasket blank 3 is 1-3 mm.

[0052] Specifically, the thickness of the gasket blank 3 and the cover plate blank 4 is equal to facilitate manufacturing. The thickness of the manufactured gasket blank 3 and the cover plate blank 4 can be 1mm-3mm, that is, the thickness after processing can be 1mm-3mm. Figures 4 and 5 Through processing, the thickness of the gasket blank 3 and the cover plate blank 4 can be basically consistent at all places, within 1-3mm, so that the entire structure is wavy. The thickness of the unprocessed first laminated blank and the second laminated blank is larger than this thickness, such as 8-12mm. The gasket blank 3 and the cover plate blank 4 with a thickness of 1-3mm can play a supporting role, better carry out debinding, and ensure the stability of its structure.

[0053] In some embodiments, after the electrostatic chuck ceramic green sheet 2 is placed on the gasket green sheet 3 , its projection on the gasket green sheet 3 is located above the gasket green sheet 3 .

[0054] Specifically, the projection of the gasket blank 3 in the upper and lower directions is still located inside the gasket blank 3, that is, the size of the gasket blank 3 and the cover plate blank 4 are both larger than the electrostatic chuck ceramic, to ensure support for the electrostatic chuck ceramic, and the size and shape of the cover plate blank 4 can be the same as the size and shape of the gasket blank 3.

[0055] In some embodiments, the distance between any two adjacent first upper grooves 5 and the first lower groove 6 is equal, and the distance between any two adjacent second upper grooves 7 and the second lower groove 8 is equal.

[0056] Specifically, the distance between any two adjacent first upper grooves 5 and the first lower grooves 6 is equal, that is, the first upper grooves 5 and the first lower grooves 6 are evenly distributed on the gasket blank 3, and the distance between any two adjacent second upper grooves 7 and the second lower grooves 8 is equal, that is, the second upper grooves 7 and the second lower grooves 8 are evenly arranged on the cover plate blank 4.

[0057] In some embodiments, the shape of the first upper groove 5 is the same as that of the first lower groove 6 , and the shape of the second upper groove 7 is the same as that of the second lower groove 8 .

[0058] Specifically, the shape of the first upper groove 5 is the same as that of the first lower groove 6 , and the shape of the second upper groove 7 is the same as that of the second lower groove 8 , which facilitates processing, simplifies the processing flow, and improves processing efficiency.

[0059] In some embodiments, the shape of the first upper groove 5 is the same as that of the second upper groove 7 , and the first upper groove 5 is an arc-shaped groove.

[0060] Specifically, the first upper groove 5 , the second upper groove 7 , the first lower groove 6 , and the second lower groove 8 are all configured as arcuate grooves of the same shape and size, and the configuration transition of the arcuate grooves is more stable.

[0061] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. It is apparent to those skilled in the art that various changes, modifications, substitutions, and variations to these embodiments may be made without departing from the principles and spirit of the present invention, and these changes and modifications still fall within the scope of protection of the present invention.

Claims

1. A debinding and sintering method for an electrostatic chuck, characterized in that: include: Material preparation: preparing an electrostatic chuck ceramic blank, a gasket blank, and a cover plate blank, and preparing a setter, wherein the materials for preparing the gasket blank and the cover plate blank are the same as those for preparing the electrostatic chuck ceramic blank, and the preparation processes of the gasket blank and the cover plate blank are the same, the gasket blank comprises a plurality of first upper grooves and a plurality of first lower grooves, the openings of the first grooves face upward, the openings of the first lower grooves face downward, and the first upper grooves and the first lower grooves are spaced apart, the cover plate blank comprises a plurality of second upper grooves and a plurality of second lower grooves, the openings of the second upper grooves face upward, the openings of the second lower grooves face downward, and the second upper grooves and the second lower grooves are spaced apart; Debinding: Place the gasket green blank on the setter plate, place the electrostatic chuck ceramic green blank on the gasket green blank, place the cover sheet green blank on the electrostatic chuck ceramic green blank, and then put the four together into the debinding furnace for debinding; Sintering: After the debinding is completed, the electrostatic chuck ceramic blank, the gasket blank, the cover plate blank and the support plate are placed in a sintering furnace for sintering. The gasket blank made of the same material is sintered together to avoid direct contact between the electrostatic chuck ceramic blank and the support plate, which may cause cracking.

2. A debinding and sintering method for an electrostatic chuck according to claim 1, characterized in that: The preparation method of the gasket blank and the cover plate blank comprises: Lamination: prepare several blank ceramic green sheets, and laminate them to the required thickness of the gasket green sheet and the cover green sheet using a laminating machine. The lamination pressure is 20-50 MPa, and the lamination time is 5-10 minutes to prepare several laminated green sheets. Isostatic pressing: vacuum pack the laminated green sheets after lamination. Place the first PET film, the first laminated green sheet, the screen filter cloth, the second laminated green sheet, and the second PET film in order from bottom to top, and then put them into a vacuum packaging bag for vacuum packaging. After packaging, put them into a static isostatic press for lamination. The lamination pressure is 80-200MPa and the time is 30-60min. Shape processing: the first laminated green sheet and the second laminated green sheet after isostatic pressing are subjected to shape processing by CNC to form the gasket green sheet and the cover plate green sheet.

3. The debinding and sintering method for an electrostatic chuck according to claim 1, characterized in that: The thickness of the gasket blank is equal to that of the cover plate blank, and the thickness of the gasket blank is 1-3 mm.

4. A debinding and sintering method for an electrostatic chuck according to claim 1, characterized in that: After the electrostatic chuck ceramic green blank is placed on the gasket green blank, its projection on the gasket green blank is located above the gasket green blank.

5. The debinding and sintering method for an electrostatic chuck according to claim 1, characterized in that: The distance between any two adjacent first upper grooves and the first lower groove is equal, and the distance between any two adjacent second upper grooves and the second lower groove is equal.

6. The debinding and sintering method for an electrostatic chuck according to claim 1, characterized in that: The shape of the first upper groove is the same as that of the first lower groove, and the shape of the second upper groove is the same as that of the second lower groove.

7. A debinding and sintering method for an electrostatic chuck according to claim 6, characterized in that: The shape of the first upper groove is the same as that of the second upper groove, and the first upper groove is an arc-shaped groove.

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