Sucking disc

Abstract

The utility model relates to a suction cup which comprises a cup body, a suction cup cover and a suction cup cover. A plurality of adsorption areas are sequentially arranged on the adsorption surface from the middle to the periphery in a sleeving manner, and a plurality of adsorption holes are formed in each adsorption area; the multiple adsorption holes formed in the adsorption area on the outermost periphery are densely distributed in the surrounding direction of the adsorption area on the inner periphery, an annular flow channel is formed in the position, corresponding to the adsorption area on the outermost periphery, in the disc body, and all the adsorption holes in the adsorption area on the outermost periphery communicate with the annular flow channel. And a first air hole, communicated with the outside, of the annular flow channel is formed in the peripheral surface of the disc body. The adsorption holes in the outermost adsorption area are densely distributed in the surrounding direction of the adsorption area surrounding the inner periphery, namely, the adsorption holes are distributed in all positions of the warping part in the circumferential direction, the densely distributed adsorption holes can increase the adsorption area of vacuum adsorption, the adsorption effect on the warping part is guaranteed, and therefore the adsorption effect on the warping wafer is guaranteed.

Description

Technical Field

[0001] This utility model relates to the field of testing equipment technology, and in particular to a suction cup. Background Technology

[0002] When inspecting wafers, a vacuum chuck is often used to pick up the wafer, fixing it on the chuck before inspection.

[0003] Some wafers exhibit edge warping. For warped wafers, a transition disk structure is often used to assist the chuck in adhering to them. Generally, the following steps can be taken: a robotic arm transports the warped wafer to below the transition disk, the transition disk adsorbs and flattens the warped wafer, and the stage moves the chuck below the transition disk to pick up and adsorb the warped wafer.

[0004] However, in the above method, the transition disk only plays an auxiliary role in the wafer adsorption process. After the transition disk places the wafer on the chuck and completes the wafer loading process, when the chuck is used for related actions such as pinning, the warped wafer will return to its warped state due to the lack of external force from the transition disk. The vacuum adsorption effect of the conventional chuck alone cannot completely adsorb the warped wafer, thus affecting the test results. Utility Model Content

[0005] Therefore, it is necessary to provide a suction cup that can completely adsorb warped wafers to address the problem of warped wafers not being able to be completely adsorbed.

[0006] A suction cup, comprising:

[0007] The disc body has an adsorption surface; the adsorption surface is arranged with multiple adsorption areas from the center to the periphery, and each adsorption area is provided with multiple adsorption holes.

[0008] The adsorption pores in the outermost adsorption region are densely distributed along the circumferential direction of the adsorption region surrounding the inner periphery. An annular flow channel is formed in the part of the disk body corresponding to the outermost adsorption region. All the adsorption pores in the outermost adsorption region are connected to the annular flow channel, and the first air hole connecting the annular flow channel to the outside is provided on the outer peripheral surface of the disk body.

[0009] In the aforementioned suction cup, when adsorbing a warped wafer, the middle part of the warped wafer contacts the inner adsorption area, while the edge part (the warped portion) contacts the outermost adsorption area. The adsorption holes in the inner and outermost adsorption areas work together to flatten the warped wafer onto the adsorption surface. Since the adsorption holes in the outermost adsorption area are densely distributed along the circumferential direction surrounding the inner adsorption area—meaning adsorption holes are distributed circumferentially around the warped portion—the dense distribution of adsorption holes increases the adsorption area for vacuum adsorption, ensuring effective adsorption of the warped portion and thus guaranteeing effective adsorption of the warped wafer. Simultaneously, all the adsorption holes in the outermost adsorption area are connected to the same annular flow channel. When the first gas vent is connected to the vacuum pump, the gas from each adsorption hole corresponding to the outermost adsorption area flows to the vacuum pump through the annular flow channel, facilitating the synchronous formation of a vacuum state in each adsorption hole corresponding to the outermost adsorption area, further ensuring the adsorption effect.

[0010] In one embodiment, the outermost adsorption region is densely covered with multiple rings of adsorption pores along the circumferential direction;

[0011] And / or,

[0012] The disc body includes a main body and a bottom plate that are separated. The adsorption surface is formed on the main body, and the bottom plate is located on the side of the main body away from the adsorption surface. An annular flow channel is formed between the main body and the bottom plate, and the first air hole is formed on the outer peripheral surface of the main body.

[0013] In one embodiment, the main body has an annular groove on the side facing the base plate; the base plate covers the main body and defines the annular flow channel with the groove wall of the annular groove.

[0014] In one embodiment, the disc body further has an annular mounting groove surrounding the outside of the adsorption surface, the mounting groove being used to install a sealing ring, the sealing ring being protruding from the adsorption surface.

[0015] In one embodiment, the assembly groove has an opening, and the sealing ring is installed in the assembly groove through the opening;

[0016] The width of the assembly groove gradually decreases from the end near the bottom wall to the end near the opening, and the shape of the sealing ring is adapted to the shape of the assembly groove.

[0017] In one embodiment, a plurality of adsorption pores in the adsorption region located in the inner periphery are arranged radially to form a plurality of adsorption segments.

[0018] In one embodiment, in two adjacent adsorption regions located in the inner perimeter, the number of adsorption segments formed by the radial arrangement of the plurality of adsorption pores in the outer adsorption region is greater than the number of adsorption segments formed by the radial arrangement of the plurality of adsorption pores in the inner adsorption region.

[0019] In one embodiment, the adsorption surface is provided with three adsorption regions. The adsorption pores of the innermost adsorption region are arranged in a radial direction to form an adsorption line segment, and the adsorption pores of the middle adsorption region are arranged in a radial direction to form 12 adsorption lines distributed at intervals.

[0020] In one embodiment, the disk body is provided with a plurality of pen direct current channels, the number of the pen direct current channels being equal to and corresponding one-to-one with the number of the adsorption line segments, and each of the adsorption holes being connected to its corresponding pen direct current channel. The pen direct current channel is provided with a second air hole for communicating with the outside world on the outer peripheral surface of the disk body.

[0021] In one embodiment, the adsorption region near the outermost adsorption region has a first adsorption pore and a second adsorption pore, wherein the cross-sectional area of ​​the first adsorption pore is smaller than the cross-sectional area of ​​the second adsorption pore.

[0022] The adsorption surface is provided with an annular groove, and the first adsorption hole is provided in the annular groove. The first adsorption hole and the second adsorption hole are arranged alternately from the middle to the outer edge. Attached Figure Description

[0023] Figure 1 This is a structural diagram of a suction cup provided in one embodiment of this application;

[0024] Figure 2 for Figure 1 Enlarged view of point A on the suction cup shown;

[0025] Figure 3 for Figure 1 An exploded view of the suction cup shown;

[0026] Figure 4 for Figure 1 The image shows a cross-sectional view of the suction cup.

[0027] Explanation of reference numerals in the attached figures:

[0028] 100. Suction cup; 10. Disc body; 11. Adsorption surface; 12. Adsorption area; 13. Adsorption hole; 13a. First adsorption hole; 13b. Second adsorption hole; 141. First vent; 15. Main body; 151. Annular groove; 16. Base plate; 17. Assembly groove; 171. Opening; 18. Pen direct flow channel; 181. Second vent; 19. Annular groove. Detailed Implementation

[0029] To make the above-mentioned objects, features, and advantages of this utility model more apparent and understandable, the specific embodiments of this utility model will be described in detail below with reference to the accompanying drawings. Many specific details are set forth in the following description to provide a full understanding of this utility model. However, this utility model can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this utility model. Therefore, this utility model is not limited to the specific embodiments disclosed below.

[0030] In the description of this utility model, it should be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc., indicating the orientation or positional relationship are based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing this utility model and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this utility model.

[0031] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this utility model, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0032] In this utility model, unless otherwise explicitly specified and limited, the terms "installation," "connection," "joining," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this utility model according to the specific circumstances.

[0033] In this utility model, unless otherwise explicitly specified and limited, "above" or "below" the second feature can mean that the first feature is in direct contact with the second feature, or that the first feature is in indirect contact with the second feature through an intermediate medium. Furthermore, "above," "on top of," and "over" the second feature can mean that the first feature is directly above or diagonally above the second feature, or simply that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature can mean that the first feature is directly below or diagonally below the second feature, or simply that the first feature is at a lower horizontal level than the second feature.

[0034] It should be noted that when an element is referred to as being "fixed to" or "set on" another element, it can be directly on the other element or there may be an intervening element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intervening element. The terms "vertical," "horizontal," "upper," "lower," "left," "right," and similar expressions used herein are for illustrative purposes only and do not represent the only possible implementation.

[0035] See Figure 1 This application provides a suction cup 100, including a disk body 10 with an adsorption surface 11. Specifically, the adsorption surface 11 is formed on one end surface of the disk body 10 in the thickness direction. In some embodiments, the cross-sectional shape of the disk body 10 is circular, in which case the suction cup 100 is a disc. In other embodiments, the cross-sectional shape of the disk body 10 is not limited; for example, the cross-sectional shape of the disk body 10 can also be square, in which case the suction cup 100 is a square disc. It should be noted that the cross-sectional shape of the disk body 10 can be selected according to different working conditions. Generally, the cross-sectional shape of the disk body 10 is circular to facilitate the adsorption of wafers through the adsorption surface 11.

[0036] See Figure 1 and Figure 2 The adsorption surface 11 has multiple adsorption regions 12 arranged sequentially from the center to the periphery, and each adsorption region 12 has multiple adsorption holes 13. That is, the adsorption surface 11 has multiple adsorption regions 12 arranged from the center to the edge, and the multiple adsorption regions 12 are interlocked (the outermost adsorption region 12 is interlocked with the outer side of the innermost adsorption region 12). Each adsorption region 12 has multiple adsorption holes 13, and the wafer is adsorbed onto the adsorption surface 11 through the adsorption holes 13. Since the multiple adsorption regions 12 are interlocked, there is an innermost adsorption region 12 and an outermost adsorption region 12.

[0037] In some specific embodiments, when the adsorption surface 11 has two adsorption regions 12, the outer adsorption region 12 forms the outermost adsorption region 12, and the inner adsorption region 12 forms the innermost adsorption region 12. In other specific embodiments, when the adsorption surface 11 has more than two adsorption regions 12, the outermost adsorption region 12 forms the outermost adsorption region 12, and the innermost adsorption region 12 forms the innermost adsorption region 12. The outermost adsorption region 12 and the innermost adsorption region 12 can be either the innermost adsorption region 12 of the outermost adsorption region 12 or the outermost adsorption region 12 of the innermost adsorption region 12. The innermost adsorption region 12 can be circular, square, or other irregular shapes, and the outermost adsorption region 12 can be annular or other irregular shapes.

[0038] Furthermore, the adsorption pores 13 located in the outermost adsorption region 12 are densely distributed along the circumferential direction surrounding the inner adsorption region 12. That is, the density of the adsorption pores 13 in the outermost adsorption region 12 is relatively high, meaning the adsorption pores 13 are arranged in a relatively dense manner in the outermost adsorption region 12. This ensures that adsorption pores 13 are distributed throughout the outermost adsorption region 12 along the circumferential direction, increasing the number of adsorption pores 13 in the outermost adsorption region 12 and improving the adsorption effect. An annular flow channel is formed within the disk body 10 corresponding to the outermost adsorption region 12. All adsorption pores 13 in the outermost adsorption region 12 are connected to the annular flow channel, and a first air hole 141 connecting the annular flow channel to the outside is located on the outer circumferential surface of the disk body 10 (see...). Figure 1 Specifically, the first vent 141 can be connected to the vacuum pump. Optionally, the annular flow channel is circular, and multiple first vents 141 are provided on the outer circumferential surface of the disk 10 to increase the vacuum flow rate and ensure the adsorption effect. Of course, in some other embodiments, the annular flow channel may also have one first vent 141, and the specific shape of the annular flow channel is not limited.

[0039] In the above configuration, when the suction cup 100 adsorbs the warped wafer, the middle part of the warped wafer contacts the inner adsorption area 12, and the edge part (warped part) of the warped wafer contacts the outermost adsorption area 12. The adsorption holes 13 of the inner and outermost adsorption areas 12 work together to flatten and adsorb the warped wafer onto the adsorption surface 11. Since the adsorption holes 13 of the outermost adsorption area 12 are densely distributed along the circumferential direction surrounding the inner adsorption area 12, that is, adsorption holes 13 are distributed around the warped part, the densely distributed adsorption holes 13 can increase the adsorption area of ​​vacuum adsorption, ensuring the adsorption effect on the warped part, thereby ensuring the adsorption effect on the warped wafer. Meanwhile, the adsorption holes 13 of the outermost adsorption region 12 are all connected to the same annular flow channel. When the first gas hole 141 is connected to the vacuum pump, the gas of each adsorption hole 13 corresponding to the outermost adsorption region 12 flows to the vacuum pump through the annular flow channel, which facilitates the synchronous formation of a vacuum state in each adsorption hole 13 corresponding to the outermost adsorption region 12, further ensuring the adsorption effect.

[0040] In some embodiments, the outermost adsorption region 12 is densely covered with multiple rings of adsorption holes 13 along the circumferential direction. In this way, the adsorption effect of the multiple rings of adsorption holes 13 is further guaranteed for the warped wafer.

[0041] In some specific embodiments, the outermost adsorption region 12 is densely covered with two concentric rings of adsorption holes 13 along the circumferential direction. It is understood that in other specific embodiments, the outermost adsorption region 12 may also be densely covered with more than two concentric rings of adsorption holes 13 along the circumferential direction, which is not limited here. Alternatively, multiple adsorption holes 13 may be densely distributed in an irregular manner along the circumferential direction in the outermost adsorption region 12.

[0042] In some embodiments, see Figure 3 The disk body 10 includes a separate main body 15 and a base plate 16. An adsorption surface 11 is formed on the main body 15, and the base plate 16 is located on the side of the main body 15 opposite to the adsorption surface 11. An annular flow channel is formed between the main body 15 and the base plate 16, and a first vent 141 is formed on the outer peripheral surface of the main body 15. The disk body 10 is designed with separate main body 15 and base plate 16 to facilitate the formation of the annular flow channel. The base plate 16 and the main body 15 can be welded or connected by screws, etc., and are not limited here. Of course, in some other embodiments, the disk body 10 can also be a one-piece molded structure.

[0043] Specifically, the main body 15 has an annular groove 151 on the side facing the back plate 16; the bottom plate 16 covers the main body 15 and defines an annular flow channel with the groove wall of the annular groove 151. In some embodiments, the annular groove 151 may also be formed on the bottom plate 16, and the groove walls of the annular groove 151 on the main body 15 and the bottom plate 16 define an annular flow channel. In still some embodiments, annular grooves 151 are formed on both the main body 15 and the bottom plate 16, and the groove walls of the annular groove 151 on the main body 15 and the groove walls of the annular groove 151 on the bottom plate 16 define an annular flow channel.

[0044] In some embodiments, see further reference. Figure 1 and Figure 2 The disk body 10 also has an annular mounting groove 17 surrounding the outside of the adsorption surface 11. The mounting groove 17 is used to install a sealing ring, which protrudes from the adsorption surface 11. It should be noted that the sealing ring protruding from the adsorption surface 11 means that the sealing ring protrudes from the adsorption surface 11 when the suction cup 100 is not adsorbing a wafer.

[0045] The above configuration ensures that when the suction cup 100 is activated to vacuum-adsorb the wafer, the wafer compresses the sealing ring under the vacuum suction force. The compressed sealing ring fills the gap between the warped portion of the wafer and the suction cup 100, reducing the connection between the adsorption area 12 and the outside world, thus ensuring the adsorption effect of the suction cup 100 on the warped hard wafer. When the vacuum is turned off, the compressed sealing ring can return to its initial state due to its own elasticity, ready for the adsorption of the next wafer.

[0046] In some embodiments, the assembly groove 17 has an opening 171 through which the sealing ring is installed. The width of the assembly groove 17 gradually narrows from one end near the bottom wall to the other end near the opening 171, and the shape of the sealing ring is adapted to the shape of the assembly groove 17. Because the sealing ring is elastic, it can be installed in the assembly groove 17 through the narrow opening 171. Due to the narrow opening 171, the sealing ring is not easily dislodged from the assembly groove 17 after it is installed.

[0047] It is understood that in other embodiments, the width of the assembly slot 17 may be equal at all points, which is not limited here.

[0048] In some embodiments, see further reference. Figure 1 Multiple adsorption holes 13 located in the inner perimeter adsorption region 12 are arranged radially to form several adsorption segments. Thus, the inner perimeter adsorption region 12 has multiple adsorption holes 13 in the extension direction of the adsorption segments, ensuring the adsorption effect on the wafer.

[0049] Specifically, in two adjacent adsorption regions 12 located in the inner perimeter, the number of adsorption lines formed by the radially arranged adsorption holes 13 in the outer adsorption region 12 is greater than the number of adsorption lines formed by the radially arranged adsorption holes 13 in the inner adsorption region 12. This results in a stronger adsorption effect in the outer adsorption region 12 compared to the inner adsorption region 12, thus ensuring effective adsorption of warped wafers.

[0050] In one specific implementation, see further details. Figure 1 The adsorption surface 11 has three adsorption regions 12. The innermost adsorption region 12 has multiple adsorption holes 13 arranged radially to form an adsorption line segment, while the middle adsorption region 12 has multiple adsorption holes 13 arranged radially to form 12 alternately distributed adsorption line segments. That is, the innermost adsorption region 12 has one adsorption hole 13, and the middle adsorption region 12 has 12 adsorption holes 13, making the adsorption effect of the middle adsorption region 12 stronger than that of the innermost adsorption region 12.

[0051] Optionally, the innermost adsorption region 12 is suitable for adsorbing 8-inch wafers, meaning the outer ring of the innermost adsorption region 12 is 8 inches; the middle adsorption region 12 is suitable for adsorbing 12-inch wafers, meaning the outer ring of the middle adsorption region 12 is 12 inches; and the outermost adsorption region 12 surrounds the adsorption region 12 suitable for adsorbing 12-inch wafers. Of course, in some other embodiments, the size of the adsorption region 12 is not limited.

[0052] Further reading Figure 4 The disk body 10 has multiple pen-shaped direct current channels 18, the number of which is equal to and corresponds one-to-one with the number of adsorption segments formed. Each adsorption hole 13 is connected to its corresponding pen-shaped direct current channel 18. Second air holes 181, used to connect the pen-shaped direct current channels 18 to the outside, are located on the outer circumferential surface of the disk body 10. Specifically, the second air holes 181 can be connected to a vacuum pump. Thus, the number of pen-shaped direct current channels 18 formed corresponds to the number of adsorption segments formed. Since the pen-shaped direct current channels 18 can be directly formed on the main body 15 without needing to be formed through two separate parts, it is convenient for processing.

[0053] In some embodiments, see further reference. Figure 2The adsorption region 12 closest to the outermost adsorption region 12 has a first adsorption hole 13a and a second adsorption hole 13b, the cross-sectional area of ​​the first adsorption hole 13a being smaller than that of the second adsorption hole 13b. For example, when the adsorption surface 11 has three adsorption regions 12, the middle adsorption region 12 has a first adsorption hole 13a and a second adsorption hole 13b. The adsorption surface 11 has an annular groove 19, and the first adsorption hole 13a is located within the annular groove 19. The first adsorption hole 13a and the second adsorption hole 13b are arranged alternately from the center outwards. The alternating arrangement of the first adsorption hole 13a and the second adsorption hole 13b with different cross-sectional areas can increase the adsorption effect of the adsorption region 12 closest to the outermost edge on the wafer, thereby further improving the adsorption effect of the chuck 10 on the warped wafer.

[0054] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0055] The embodiments described above are merely illustrative of several implementations of this utility model, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the utility model patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this utility model, and these all fall within the protection scope of this utility model. Therefore, the protection scope of this utility model patent should be determined by the appended claims.

Claims

1. A suction cup, characterized in that, include: The disc body (10) has an adsorption surface (11); the adsorption surface (11) has multiple adsorption areas (12) arranged sequentially from the center to the periphery, and each adsorption area (12) is provided with multiple adsorption holes (13). A plurality of adsorption holes (13) located in the outermost adsorption region (12) are densely distributed along the circumferential direction of the adsorption region (12) surrounding the inner periphery. An annular flow channel is formed in the part of the disk body (10) corresponding to the outermost adsorption region (12). All the adsorption holes (13) in the outermost adsorption region (12) are connected to the annular flow channel. The first air hole (141) connecting the annular flow channel to the outside is located on the outer peripheral surface of the disk body (10).

2. The suction cup according to claim 1, characterized in that, The outermost adsorption region (12) is densely covered with multiple rings of adsorption pores (13) along the circumferential direction; And / or, The disc body (10) includes a main body (15) and a bottom plate (16) that are separately arranged. The adsorption surface (11) is formed on the main body (15). The bottom plate (16) is located on the side of the main body (15) away from the adsorption surface (11). An annular flow channel is formed between the main body (15) and the bottom plate (16). The first air hole (141) is formed on the outer peripheral surface of the main body (15).

3. The suction cup according to claim 2, characterized in that, The main body (15) has an annular groove (151) on the side facing the bottom plate (16); the bottom plate (16) covers the main body (15) and defines the annular flow channel with the groove wall of the annular groove (151).

4. The suction cup according to claim 1, characterized in that, The disc body (10) also has an annular assembly groove (17) surrounding the outside of the adsorption surface (11), the assembly groove (17) being used to install a sealing ring, the sealing ring being protruding from the adsorption surface (11).

5. The suction cup according to claim 4, characterized in that, The assembly groove (17) has an opening (171), and the sealing ring is installed in the assembly groove (17) through the opening (171); The width of the assembly groove (17) gradually decreases from one end near the bottom wall to the other end near the opening (171), and the shape of the sealing ring is adapted to the shape of the assembly groove (17).

6. The suction cup according to claim 1, characterized in that, The adsorption pores (13) located in the inner periphery of the adsorption region (12) are arranged radially to form several adsorption segments.

7. The suction cup according to claim 6, characterized in that, In two adjacent adsorption regions (12) located in the inner perimeter, the number of adsorption segments formed by the radial arrangement of the adsorption holes (13) in the outer adsorption region (12) is greater than the number of adsorption segments formed by the radial arrangement of the adsorption holes (13) in the inner adsorption region (12).

8. The suction cup according to claim 7, characterized in that, The adsorption surface (11) is provided with three adsorption regions (12). The adsorption pores (13) of the innermost adsorption region (12) are arranged in the radial direction to form an adsorption line segment. The adsorption pores (13) of the middle adsorption region (12) are arranged in the radial direction to form 12 adsorption lines distributed at intervals.

9. The suction cup according to claim 6, characterized in that, The disc body (10) is provided with a plurality of pen direct current channels (18), the number of the pen direct current channels (18) is equal to the number of the adsorption line segments and corresponds one-to-one. Each adsorption hole (13) is connected to its corresponding pen direct current channel (18). The second air hole (181) of the pen direct current channel (18) for communicating with the outside is provided on the outer peripheral surface of the disc body (10).

10. The suction cup according to claim 1, characterized in that, The adsorption region (12) near the outermost edge has a first adsorption pore (13a) and a second adsorption pore (13b), the cross-sectional area of ​​the first adsorption pore (13a) being smaller than the cross-sectional area of ​​the second adsorption pore (13b). The adsorption surface (11) is provided with an annular groove (19), and the first adsorption hole (13a) is provided in the annular groove (19). The first adsorption hole (13a) and the second adsorption hole (13b) are arranged alternately from the middle to the outer periphery.

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