Retainer

Abstract

To provide a retainer that is less likely to cause a hot spot and is capable of making a temperature distribution uniform.SOLUTION: A retainer 1 includes: a plate-shaped member 10 having a first surface 10A; a base member 20 disposed on a side opposite to the first surface 10A with respect to the plate-shaped member 10; and an adhesive member 30 disposed between the plate-shaped member 10 and the base member 20. The plate-shaped member 10 includes a first hole part 55 whose central axis extends in a first direction intersecting the first surface 10A. The adhesive member 30 includes a second hole part 35 which is continuous with the first hole part 55 and whose central axis extends in the first direction. The base member 20 includes a third hole part 25 which is continuous with the second hole part 35 and whose central axis extends in the first direction. At least one of a central axis L1 of the first hole part 55, a central axis L2 of the second hole part 35, a central axis L3 of the third hole part 25, and the other central axis are disposed at different positions when viewed in the first direction.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present disclosure relates to a retention device. [Background technology]

[0002] Conventionally, the technology described in Patent Document 1 is known as a holding device. Specifically, the holding device (wafer mounting table) described in JP 2023-58845 A (Patent Document 1 below) includes a ceramic base, a cooling base, and a metal bonding layer. This wafer mounting table has multiple holes that penetrate the wafer mounting table (ceramic base, cooling base, and metal bonding layer) in the vertical direction. These holes include multiple gas holes that open to the wafer mounting surface and lift pin holes for inserting lift pins that move the wafer up and down relative to the wafer mounting surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2023-58845 Summary of the Invention [Problem to be solved by the invention]

[0004] With regard to the configuration disclosed in Patent Document 1, the holes (spaces) that penetrate the wafer mounting table are less likely to transfer heat (have poor heat dissipation) than areas other than the holes, so the temperature of the wafer directly above the holes is higher than other areas, which can create hot spots and result in uneven temperature distribution.

[0005] The present disclosure is a technology that has been completed based on the above circumstances, and aims to provide a holding device that is less likely to cause hot spots and can achieve a uniform temperature distribution. [Means for solving the problem]

[0006] The holding device of the present disclosure comprises a plate-shaped member having a first surface, a base member arranged on the opposite side of the plate-shaped member from the first surface, and an adhesive member arranged between the plate-shaped member and the base member, wherein the plate-shaped member has a first hole portion having a central axis extending in a first direction intersecting the first surface, the adhesive member has a second hole portion connected to the first hole portion and having a central axis extending in the first direction, the base member has a third hole portion connected to the second hole portion and having a central axis extending in the first direction, and at least one central axis of the first hole portion, the second hole portion, and the third hole portion and the other central axes are arranged at different positions when viewed in the first direction. [Effects of the Invention]

[0007] According to the present disclosure, a holding device can be provided that is less likely to cause hot spots and can achieve a uniform temperature distribution. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is an explanatory diagram that schematically shows the general configuration of a holding device according to a first embodiment. [Figure 2] FIG. 2 is a cross-sectional view that schematically illustrates the internal structure of the holding device according to the first embodiment. [Figure 3] FIG. 3 is a schematic cross-sectional view showing an enlarged view of the first hole portion, the second hole portion, and the periphery of the third hole portion. [Figure 4] FIG. 4 is a schematic plan view showing an enlarged view of the first hole portion, the second hole portion, and the periphery of the third hole portion. [Figure 5] FIG. 5 is a schematic cross-sectional view showing an enlarged view of the first hole portion, the second hole portion, and the third hole portion and their surroundings of the holding device according to the second embodiment. [Figure 6] FIG. 6 is a schematic cross-sectional view showing an enlarged view of the first hole portion, the second hole portion, and the periphery of the third hole portion of the holding device according to the third embodiment. [Figure 7] FIG. 7 is a schematic cross-sectional view showing an enlarged view of the periphery of the first hole portion, the second hole portion, and the third hole portion of a holding device according to another embodiment. [Figure 8]FIG. 8 is a schematic cross-sectional view showing an enlarged view of the periphery of the first hole portion, the second hole portion, and the third hole portion of a holding device according to another embodiment. [Figure 9] FIG. 9 is a schematic cross-sectional view showing an enlarged view of the periphery of the first hole portion, the second hole portion, and the third hole portion of a holding device according to another embodiment. [Figure 10] FIG. 10 is a schematic cross-sectional view showing an enlarged view of the periphery of the first hole portion, the second hole portion, and the third hole portion of a holding device according to another embodiment. [Figure 11] FIG. 11 is a schematic cross-sectional view showing an enlarged view of the periphery of a first hole portion, a second hole portion, and a third hole portion of a holding device according to another embodiment. [Figure 12] FIG. 12 is a schematic cross-sectional view showing an enlarged view of the periphery of the first hole portion, the second hole portion, and the third hole portion of a holding device according to another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] First, embodiments of the present disclosure will be listed and described. (1) The holding device of the present disclosure comprises a plate-shaped member having a first surface, a base member arranged on the opposite side of the plate-shaped member from the first surface, and an adhesive member arranged between the plate-shaped member and the base member, wherein the plate-shaped member has a first hole portion having a central axis extending in a first direction intersecting the first surface, the adhesive member has a second hole portion connected to the first hole portion and having a central axis extending in the first direction, the base member has a third hole portion connected to the second hole portion and having a central axis extending in the first direction, and at least one central axis of the first hole portion, the second hole portion, and the third hole portion is arranged at a different position from the other central axes when viewed in the first direction.

[0010] In this holding device, at least one of the central axes of each hole is positioned at a different position from the other central axes as viewed in the first direction. By disposing a portion of a component constituting one of the first, second, and third holes, whose central axis is positioned at a different position from that of the other hole, heat can be conducted between the holes via a portion of the component constituting the other hole. This improves the thermal conductivity within the space formed by the interconnection of the holes compared to when the central axes of the first, second, and third holes are positioned at the same position as viewed in the first direction. Therefore, compared to when the central axes of the holes are positioned at the same position as viewed in the first direction, for example, hot spots are less likely to occur, resulting in a holding device with a more uniform temperature distribution.

[0011] (2) In the holding device described in (1), it is preferable that the first hole portion comprises a first surface side hole portion located on the first surface side and a first back surface side hole portion connected to the first surface side hole portion and located on the opposite side of the first surface, and the central axis of the hole of the first back surface side hole portion is positioned at a different position when viewed in the first direction from the central axis of the hole of the first surface side hole portion.

[0012] With this holding device, heat is more easily conducted between the first front-surface-side hole and the first back-surface-side hole via the members that constitute the first front-surface-side hole and the first back-surface-side hole, which are arranged in the space inside the first hole. This improves thermal conductivity inside the first hole compared to when the central axes of the first front-surface-side hole and the first back-surface-side hole are aligned in the first direction. In this way, the holding device can prevent hot spots from occurring directly above the holes formed by the first, second, and third holes, thereby achieving a more uniform temperature distribution overall.

[0013] (3) In the holding device described in (1) or (2), it is preferable that the second hole portion comprises a second surface side hole portion located on the first surface side and a second back surface side hole portion connected to the second surface side hole portion and located on the opposite side of the first surface, and the central axis of the hole of the second back surface side hole portion is positioned at a different position when viewed in the first direction from the central axis of the hole of the second surface side hole portion.

[0014] With this holding device, heat is more easily conducted between the second front-surface-side hole and the second back-surface-side hole via the member that constitutes the second front-surface-side hole and the second back-surface-side hole, which is disposed in the space inside the second hole. This improves thermal conductivity inside the second hole compared to when the central axis of the second front-surface-side hole and the central axis of the second back-surface-side hole are disposed at the same position when viewed in the first direction. By improving heat dissipation in the adhesive member, the holding device can prevent hot spots from occurring directly above the holes formed by the first, second, and third holes, thereby achieving a more uniform temperature distribution overall.

[0015] (4) In the holding device described in any one of (1) to (3), it is preferable that the diameter of the second hole portion is larger than the diameter of the first hole portion and the diameter of the third hole portion.

[0016] According to such a holding device, the second hole portion is arranged in the first direction of the first hole portion and the third hole portion, thereby preventing small pieces of adhesive material from entering the first hole portion and the third hole portion.

[0017] <Details of the first embodiment of the present disclosure> The schematic configuration of a first embodiment of the present disclosure will be described with reference to FIGS. 1 and 2. The present disclosure is not limited to these examples, but is defined by the claims, and all modifications within the meaning and scope equivalent to the claims are intended to be included. In the following description, for multiple identical components, only some components may be designated by reference numerals, and the reference numerals for other components may be omitted. In this specification, the configuration of the holding device 1 will be described with the positive Z-axis direction as the upward direction, the negative Z-axis direction as the downward direction, and the XY plane direction as the horizontal direction. However, in actual use of the holding device 1, different arrangements may be used. Furthermore, in this specification, the terms "orthogonal," "horizontal," and "parallel" are intended to include arrangements that are substantially recognized as orthogonal, horizontal, and parallel.

[0018] The holding device 1 of the first embodiment is an electrostatic chuck that can attract and hold a workpiece (hereinafter referred to as a "wafer W"). The workpiece may be a semiconductor wafer, a glass substrate, or the like. The electrostatic chuck is attached, for example, inside a processing chamber of a semiconductor manufacturing device (not shown), and is used to perform various processes, such as film formation and etching, on the wafer W using plasma.

[0019] 1, the holding device 1 of the first embodiment includes a plate-shaped member 10 and a base member 20. The plate-shaped member 10 and the base member 20 are bonded together by an adhesive member 30 disposed between the plate-shaped member 10 and the base member 20. The adhesive member 30 is made of an adhesive such as a silicone-based resin, an acrylic-based resin, or an epoxy-based resin. The holding device 1 is capable of attracting and holding the wafer W by electrostatic attraction.

[0020] The base member 20 is mainly composed of a metal such as aluminum or an aluminum alloy. The base member 20 is a disk-shaped member with a larger diameter than the plate-shaped member 10, and can be formed into a shape with a diameter of about 340 mm and a thickness of about 20 mm, for example.

[0021] The base member 20 has a third surface 20A disposed on the plate-shaped member 10 side and a fourth surface 20B located on the opposite side to the third surface 20A. The third surface 20A and the fourth surface 20B are each a surface portion extending in the horizontal direction. The third surface 20A is disposed on the upper side of the base member 20, and the fourth surface 20B is disposed on the lower side of the base member 20. The third surface 20A of the base member 20 is adhered to the second surface 10B of the plate-shaped member 10 (described later) by an adhesive member 30.

[0022] A coolant flow path 21 is provided inside the base member 20. The coolant flow path 21 is connected to a coolant circulation device (not shown). The coolant circulation device is configured to circulate a coolant through the coolant flow path 21. A fluorine-based inert liquid, water, or the like is used as the coolant. When the coolant flows through the coolant flow path 21, the base member 20 is cooled. The plate-shaped member 10 is cooled by heat conduction between the base member 20 and the plate-shaped member 10 via the adhesive member 30. This cools the wafer W held by protrusions (not shown) formed on a first surface 10A of the plate-shaped member 10 (described later).

[0023] As shown in FIG. 2, an upper hole 22A is formed in the third surface 20A of the base member 20. A lower hole 22B is formed in the fourth surface 20B. A gas injection hole 22 is formed inside the base member 20, allowing a fluid to move between the upper hole 22A and the lower hole 22B. The gas injection hole 22 is formed to penetrate the base member 20 in the vertical direction. The gas injection hole 22 is connected to a gas outlet hole 52 of the plate-shaped member 10, which will be described later, via a gas circulation hole 32 formed in the adhesive member 30. A thermally conductive gas, such as helium gas, is injected from the gas injection hole 22 toward the gas outlet hole 52.

[0024] An upper hole portion 23A is formed in the third surface 20A of the base member 20. A lower hole portion 23B is formed in the fourth surface 20B. The upper hole portion 23A and the lower hole portion 23B are connected to each other inside the base member 20, thereby providing a plurality of lift pin insertion holes 23 through which lift pins (not shown) can be inserted. The lift pin insertion holes 23 are formed to penetrate the base member 20 in the vertical direction. The lift pin insertion holes 23 are connected to lift pin protrusion holes 53 of the plate-like member 10, which will be described later, via lift pin insertion holes 33 formed in the adhesive member 30.

[0025] The plate-shaped member 10 is an insulating member whose main component is ceramic. In this embodiment, the plate-shaped member 10 is made of alumina (Al2O3). In other embodiments, the plate-shaped member 10 may be made of other ceramics such as aluminum nitride (AlN). The plate-shaped member 10 is disk-shaped and can be formed into a shape having, for example, a diameter of about 300 mm and a thickness of about 3 mm.

[0026] The plate-shaped member 10 has a first surface 10A for holding the wafer W and a second surface 10B (shown in FIG. 2 ) located opposite the first surface 10A. The first surface 10A and the second surface 10B are each horizontally extending surfaces. The first surface 10A is located on the upper side of the plate-shaped member 10, and the second surface 10B is located on the lower side of the plate-shaped member 10. A chuck electrode 51 is located inside the plate-shaped member 10. The chuck electrode 51 is, for example, flat and substantially parallel to the first surface 10A and is connected to a power source via terminals (not shown). Power is supplied to the chuck electrode 51 as needed, generating an electrostatic attraction force that attracts and holds the wafer W on the first surface 10A. The chuck electrode 51 can be formed of a conductive material containing, for example, tungsten or molybdenum.

[0027] An upper hole 52A is formed in the first surface 10A of the plate-shaped member 10. A lower hole 52B is formed in the second surface 10B. A gas outflow hole 52 is formed inside the plate-shaped member 10, allowing fluid to move between the upper hole 52A and the lower hole 52B. The gas outflow hole 52 is formed to penetrate the plate-shaped member 10 in the vertical direction.

[0028] Additionally, upper hole portions 53A are formed in the first surface 10A of the plate-shaped member 10. Lower hole portions 53B are formed in the second surface 10B. The upper hole portions 53A and the lower hole portions 53B are connected to each other inside the plate-shaped member 10, thereby providing a plurality of lift pin protrusion holes 53 through which the above-mentioned lift pins can be inserted. The lift pin protrusion holes 53 are formed to penetrate the plate-shaped member 10 in the vertical direction.

[0029] The adhesive member 30 is disposed between the second surface 10B of the plate-like member 10 and the third surface 20A of the base member 20. The thickness of the adhesive member 30 is, for example, about 0.1 mm to 1 mm. The adhesive member 30 is made of an organic resin material such as silicone resin, fluororesin, acrylic resin, or epoxy resin.

[0030] An upper hole 32A is formed in the adhesive member 30 at a position on the first surface 10A side of the plate-shaped member 10, facing the lower hole 52B of the gas outlet hole 52 formed in the plate-shaped member 10. A lower hole 32B is formed in the adhesive member 30 at a position opposite the first surface 10A of the plate-shaped member 10, i.e., on the third surface 20A side of the base member 20, facing the upper hole 22A of the gas injection hole 22 formed in the base member 20. Gas circulation holes 32 are formed inside the adhesive member 30, allowing fluid to move between the upper hole 32A and the lower hole 32B. This allows the thermally conductive gas injected into the gas injection hole 22 to flow through the gas circulation holes 32 to the gas outlet hole 52. The thermally conductive gas flowing upward from the gas outlet hole 52 fills the gap between the underside of the wafer W and the first surface 10A, thereby improving thermal conductivity between the underside of the wafer W and the first surface 10A.

[0031] An upper hole portion 33A is formed in the adhesive member 30 at a position on the first surface 10A side of the plate-shaped member 10, facing the lower hole portion 53B of the lift pin protrusion hole 53 formed in the plate-shaped member 10. A lower hole portion 33B is formed in the adhesive member 30 at a position opposite to the first surface 10A of the plate-shaped member 10, i.e., on the third surface 20A side of the base member 20, facing the upper hole portion 23A of the lift pin insertion hole 23 formed in the base member 20. A lift pin insertion hole 33 is formed inside the adhesive member 30, allowing the lift pin to be inserted between the upper hole portion 33A and the lower hole portion 33B. This allows the lift pin inserted into the lift pin insertion hole 23 from the fourth surface 20B side to pass through the lift pin insertion hole 33, causing the tip of the lift pin to protrude upward from the lift pin protrusion hole 53. The tips of the lift pins protruding upward from the lift pin protruding holes 53 can push up the wafer W held by suction on the first surface 10A, thereby separating the wafer W from the first surface 10A.

[0032] Hereinafter, the hole portion that penetrates the holding device 1 in the vertical direction and is formed by communication between the gas injection hole 22, the gas circulation hole 32, and the gas outflow hole 52 will be referred to as a gas hole 60. The hole portion that penetrates the holding device 1 in the vertical direction and is formed by communication between the lift pin insertion hole 23, the lift pin insertion hole 33, and the lift pin protrusion hole 53 will be referred to as a lift pin hole 70. Furthermore, these gas holes 60 and lift pin holes 70 that penetrate the holding device 1 in the vertical direction will be collectively referred to as through holes 80.

[0033] Furthermore, the gas outlet holes 52 and lift pin ejection holes 53 that penetrate the plate-like member 10 in the vertical direction are collectively referred to as first hole portions 55 (see FIG. 4 , the same applies below). The gas circulation holes 32 and lift pin insertion holes 33 that are connected to the first hole portions 55 and penetrate the adhesive member 30 in the vertical direction are collectively referred to as second hole portions 35. The gas injection holes 22 and lift pin insertion holes 23 that are connected to the second hole portions 35 and penetrate the base member 20 in the vertical direction are collectively referred to as third hole portions 25. The upper hole portion 52A of the gas outlet holes 52 and the upper hole portion 53A of the lift pin ejection holes 53 are collectively referred to as first upper hole portions 55A (see FIG. 3 , the same applies below). The lower hole portion 52B of the gas outlet holes 52 and the lower hole portion 53B of the lift pin ejection holes 53 are collectively referred to as first lower hole portions 55B. The upper hole 32A of the gas flow hole 32 and the upper hole 33A of the lift pin insertion hole 33 are collectively referred to as second upper hole 35A. The lower hole 32B of the gas flow hole 32 and the lower hole 33B of the lift pin insertion hole 33 are collectively referred to as second lower hole 35B. The upper hole 22A of the gas injection hole 22 and the upper hole 23A of the lift pin insertion hole 23 are collectively referred to as third upper hole 25A. The lower hole 22B of the gas injection hole 22 and the lower hole 23B of the lift pin insertion hole 23 are collectively referred to as third lower hole 25B.

[0034] 3 and 4, the detailed configurations of the first hole portion 55, the second hole portion 35, and the third hole portion 25 in the holding device 1 will be described. Fig. 3 shows a cross section of the holding device 1 cut along the XZ plane that passes through the first hole portion 55, the second hole portion 35, and the third hole portion 25. Fig. 4(A) shows the first hole portion 55, the second hole portion 35, the third hole portion 25, and their vicinity of the holding device 1 as viewed from above.

[0035] As shown in FIG. 3, the first upper hole 55A and the first lower hole 55B are circular holes having approximately the same diameter and are provided in each of the first and second surfaces 10A, 10B. The first upper hole 55A and the first lower hole 55B are arranged at approximately the same position on each of the first and second surfaces 10A, 10B, when viewed from above or below. The first hole 55 formed by connecting the first upper hole 55A and the first lower hole 55B is a cylindrical hole extending in a first direction intersecting with the first surface 10A. That is, the central axis L1 of the first hole 55 extends in the first direction. In the first embodiment, the first direction is the vertical direction, which is perpendicular to the first surface 10A.

[0036] The second upper hole 35A and the second lower hole 35B are round holes having approximately the same diameter and are provided in the upper and lower parts of the adhesive member 30. The second upper hole 35A and the second lower hole 35B are arranged in approximately the same positions in the upper and lower parts of the adhesive member 30 when viewed from above or below. The second hole 35 formed by connecting the second upper hole 35A and the second lower hole 35B is a cylindrical hole extending in the first direction, similar to the first hole 55. In other words, the central axis L2 of the second hole 35 extends in the first direction.

[0037] The third upper hole 25A and the third lower hole 25B are circular holes having approximately the same diameter and are provided in the third surface 20A and the fourth surface 20B, respectively. The third upper hole 25A and the third lower hole 25B are arranged at approximately the same position on the third surface 20A and the fourth surface 20B when viewed from above or below. The third hole 25 formed by connecting the third upper hole 25A and the third lower hole 25B is a cylindrical hole extending in the first direction, similar to the first hole 55 and the second hole 35. That is, the central axis L3 of the third hole 25 extends in the first direction.

[0038] In the first embodiment, the central axis L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third hole portion 25 are disposed at different positions when viewed from above or below. That is, the central axis L1, the central axis L2, and the central axis L3 extend parallel to one another in the through hole 80 and are disposed without overlapping.

[0039] FIG. 4A shows the arrangement of the first hole portion 55, the second hole portion 35, and the third hole portion 25 in the holding device 1 as viewed from above. FIG. 4B shows the arrangement of the first hole portion 55, the second hole portion 35, and the third hole portion 25 in a conventional holding device 11 as viewed from above. In the conventional holding device 11, the central axis L1, the central axis L2, and the central axis L3 are generally positioned at the same position when viewed from above or below, forming the first hole portion 55, the second hole portion 35, and the third hole portion 25. In this case, the space formed inside the through hole 80 formed by the first hole portion 55, the second hole portion 35, and the third hole portion 25 is filled with air or a thermally conductive gas. Because the gas layer inside the through hole 80 has lower thermal conductivity than the surrounding area of the through hole 80, a hot spot, or a portion with a higher temperature than other areas, may occur directly above the first hole portion 55.

[0040] To solve this problem, as shown in FIG. 4A , the holding device 1 has the first hole 55, the second hole 35, and the third hole 25 formed such that the central axes L1, L2, and L3 are positioned at different positions when viewed from above or below. As a result, when the through hole 80 is viewed from above, a portion of the third surface 20A of the base member 20, which is the periphery of the third hole 25, overlaps with a portion of the space inside the first hole 55. The overlapping of a portion of the third surface 20A with a portion of the space inside the first hole 55 facilitates heat conduction between the first hole 55, the second hole 35, and the third hole 25 through the overlapping portion. This improves the thermal conductivity inside the through hole 80 compared to when only a gas layer is provided inside the through hole 80, thereby preventing hot spots from occurring directly above the first hole 55.

[0041] In the first embodiment, the hole diameter R1 of the first hole portion 55 in the horizontal direction parallel to the first surface 10A is smaller than the hole diameter R3 of the third hole portion 25 in the horizontal direction. The hole diameter R1 may be the same as the hole diameter R3. The hole diameter R1 may be larger than the hole diameter R3. On the other hand, as in the first embodiment, the hole diameter R2 of the second hole portion 35 in the horizontal direction is preferably larger than the hole diameters R1 and R3. In the through hole 80, the second hole portion 35 is disposed between the first hole portion 55 and the third hole portion 25. If a portion of the adhesive member 30 is disposed in a position overlapping at least one of the first hole portion 55 and the third hole portion 25 when viewed from above or below, there is a possibility that a portion of the adhesive member 30 will break off and enter the first hole portion 55 or the third hole portion 25 when the thermally conductive gas or the lift pin moves inside the through hole 80. Furthermore, it is considered that the adhesive member 30 is more susceptible to the influence of plasma if a part of the adhesive member 30 protrudes into the through-hole 80. By forming the hole diameter R2 of the second hole portion 35 to be larger than the hole diameters R1 and R3, the occurrence of such a situation is suppressed.

[0042] In the first embodiment, the central axes L1, L2, and L3 are disposed at different positions relative to one another when viewed in the first direction, i.e., when viewed from above or below. In this regard, it is sufficient that at least one of the central axes L1, L2, and L3 is disposed at a different position relative to the other central axes when viewed in the first direction. For example, the central axes L2 and L3 may be disposed at the same position when viewed in the first direction, and the central axis L1 may be disposed at a different position relative to the central axes L2 and L3 when viewed in the first direction. The central axes L1 and L3 may be disposed at the same position when viewed in the first direction, and the central axis L2 may be disposed at a different position relative to the central axes L1 and L3 when viewed in the first direction. The central axes L1 and L2 may be disposed at the same position when viewed in the first direction, and the central axis L3 may be disposed at a different position relative to the central axes L1 and L2 when viewed in the first direction. As a result, when the first hole portion 55, the second hole portion 35, and the third hole portion 25 are viewed in the first direction, a portion of the material constituting one of the first hole portion 55, the second hole portion 35, and the third hole portion 25 is arranged inside the other hole portion, thereby improving the thermal conductivity inside the through hole 80.

[0043] The first upper hole 55A, the first lower hole 55B, the second upper hole 35A, the second lower hole 35B, the third upper hole 25A, and the third lower hole 25B may be formed in a shape other than a circle, such as an ellipse or a polygon. The diameter of the first upper hole 55A and the diameter of the first lower hole 55B may be the same or different. The diameter of the second upper hole 35A and the diameter of the second lower hole 35B may be the same or different. The diameter of the third upper hole 25A and the diameter of the third lower hole 25B may be the same or different.

[0044] Furthermore, the first upper hole 55A and the first lower hole 55B may be arranged at different positions when viewed from above, and the first hole 55 may be formed so that the central axis L1 extends obliquely rather than perpendicularly to the first surface 10A. The second upper hole 35A and the second lower hole 35B may be arranged at different positions when viewed from above, and the second hole 35 may be formed so that the central axis L2 extends obliquely rather than perpendicularly to the first surface 10A. The third upper hole 25A and the third lower hole 25B may be arranged at different positions when viewed from above, and the third hole 25 may be formed so that the central axis L3 extends obliquely rather than perpendicularly to the first surface 10A. In other words, the first direction is not limited to the up-down direction perpendicular to the first surface 10A, but may also be a direction obliquely intersecting the first surface 10A.

[0045] Furthermore, the holding device 1 may be configured such that, for either or both of the gas hole 60 and the lift pin hole 70 among the through holes 80, at least one of the central axes L1, L2, and L3 is positioned at a different position from the other central axes when viewed in the first direction.

[0046] As described above, the holding device 1 comprises a plate-shaped member 10 having a first surface 10A, a base member 20 arranged on the opposite side of the plate-shaped member 10 from the first surface 10A, and an adhesive member 30 arranged between the plate-shaped member 10 and the base member 20, wherein the plate-shaped member 10 has a first hole portion 55 whose central axis extends in a first direction intersecting the first surface 10A, the adhesive member 30 has a second hole portion 35 connected to the first hole portion 55 and whose central axis extends in the first direction, and the base member 20 has a third hole portion 25 connected to the second hole portion 35 and whose central axis extends in the first direction, and at least one central axis of the central axis L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third hole portion 25 is arranged at a different position from the other central axes when viewed in the first direction.

[0047] In this holding device 1, at least one of the central axes of each hole portion is positioned at a different position from the other central axes as viewed in the first direction. By disposing a portion of a component constituting one of the first hole portion 55, the second hole portion 35, and the third hole portion 25, whose central axis is positioned at a different position from that of the other hole portion, heat can be conducted between the holes via a portion of the component constituting the other hole portion. This allows the holding device 1 to improve thermal conductivity within the through hole 80 compared to a case in which the central axis L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third hole portion 25 are positioned at the same position as viewed in the first direction. Therefore, for example, compared to a case in which the central axes of the holes are positioned at the same position as viewed in the first direction, hot spots are less likely to occur directly above the through hole 80, resulting in a holding device 1 with a more uniform temperature distribution.

[0048] The hole diameter R2 of the second hole portion 35 is larger than the hole diameter R1 of the first hole portion 55 and the hole diameter R3 of the third hole portion 25.

[0049] According to such a holding device 1, the second hole portion 35 is arranged in the first direction of the first hole portion 55 and the third hole portion 25, thereby preventing small pieces of the adhesive member 30 from entering the first hole portion 55 and the third hole portion 25.

[0050] <Details of the second embodiment of the present disclosure> Next, a second embodiment of the present disclosure will be described with reference to Fig. 5. In the second embodiment, the same components as those in the first embodiment are designated by the same reference numerals, and redundant descriptions of the structure, operation, and effects will be omitted.

[0051] As shown in FIG. 5 , the holding device 100 of the second embodiment includes a plate-shaped member 10, a base member 20, and an adhesive member 30. A first front-side hole 56 is formed on the first surface 10A of the plate-shaped member 10. The first front-side hole 56 extends cylindrically in a first direction from a first upper hole 55A, which is a circular hole formed in the first surface 10A. A central axis L11 of the first front-side hole 56 extends in the first direction. A first rear-side hole 57 is formed on the second surface 10B of the plate-shaped member 10. The first rear-side hole 57 extends cylindrically in the first direction from a first lower hole 55B, which is a circular hole formed in the second surface 10B. A central axis L12 of the first rear-side hole 57 extends in the first direction. In the second embodiment, the first direction is the vertical direction, which is perpendicular to the first surface 10A, as in the first embodiment. The hole diameter R11 of the first front surface side hole portion 56 and the hole diameter R12 of the first back surface side hole portion 57 are substantially the same. Note that the hole diameter R11 of the first front surface side hole portion 56 and the hole diameter R12 of the first back surface side hole portion 57 may be different sizes.

[0052] In the second embodiment, the central axis L11 of the first front surface side hole 56 and the central axis L12 of the first back surface side hole 57 are disposed at different positions when viewed in the first direction. Furthermore, the first upper hole 55A and the first lower hole 55B are disposed at positions that overlap when viewed in the first direction on the first surface 10A and the second surface 10B of the plate-shaped member 10, respectively. Therefore, a first hole 59 is formed in which the lower end, which is an end on one side in the first direction of the first front surface side hole 56, and the upper end, which is an end on the other side in the first direction of the first back surface side hole 57, are connected inside the plate-shaped member 10. In the second embodiment, the first hole 59 is a hole formed to penetrate the plate-shaped member 10 in the first direction.

[0053] Similar to the holding device 1 of the first embodiment, the holding device 100 includes a second hole 35 in the adhesive member 30, which is connected to the first hole 59 and has a central axis extending in the first direction. Similarly to the holding device 1 of the first embodiment, the holding device 100 also includes a third hole 25 in the base member 20, which is connected to the second hole 35 and has a central axis extending in the first direction. The first hole 59, the second hole 35, and the third hole 25 form a through hole 81 that penetrates the holding device 100 in the first direction. The through hole 81 may be configured as a gas hole 60 or as a lift pin hole 70.

[0054] By configuring the first hole portion 59 as described above, the peripheral edges of the first front-surface-side hole 56 and the first back-surface-side hole 57, which are part of the plate-like member 10, are arranged in part of the space extending in the first direction inside the first hole portion 59. Heat is more easily conducted between the first front-surface-side hole 56 and the first back-surface-side hole 57 via the peripheral edges of the first front-surface-side hole 56 and the first back-surface-side hole 57 arranged in the space inside the first hole portion 59. This allows the holding device 100 to improve thermal conductivity inside the first hole portion 59 compared to a case in which the central axis L11 of the first front-surface-side hole 56 and the central axis L12 of the first back-surface-side hole 57 are arranged at the same position when viewed in the first direction. This prevents hot spots from occurring directly above the through holes 81.

[0055] In the second embodiment, the central axes L11, L12, L2, and L3 are arranged at different positions from one another as viewed in the first direction. In this regard, it is sufficient that at least one of the central axes L11, L12, L2, and L3 is arranged at a different position from the other central axes as viewed in the first direction. This allows a portion of the member constituting one of the first hole portion 59, the second hole portion 35, and the third hole portion 25 to be arranged relative to the other hole portion as viewed in the first direction, thereby improving thermal conductivity inside the through hole 81.

[0056] In the second embodiment, the first upper hole 55A, the first lower hole 55B, the second upper hole 35A, the second lower hole 35B, the third upper hole 25A, and the third lower hole 25B are arranged so as to overlap one another when viewed in the first direction. This ensures a space inside the through hole 81 that penetrates the holding device 100 in the first direction. Therefore, when the through hole 81 is a lift pin hole 70, the lift pin is smoothly inserted through the through hole 81 from the third lower hole 25B toward the first upper hole 55A. When the through hole 81 is a gas hole 60, the thermally conductive gas can smoothly flow through the through hole 81 in the first direction from the third lower hole 25B toward the first upper hole 55A.

[0057] As described above, the first hole portion 59 of the holding device 100 comprises a first surface side hole portion 56 located on the first surface 10A side, and a first back surface side hole portion 57 connected to the first surface side hole portion 56 and located on the second surface 10B opposite the first surface 10A, and the central axis L11 of the first surface side hole portion 56 is positioned at a different position when viewed in the first direction from the central axis L12 of the first back surface side hole portion 57.

[0058] With this holding device 100, heat is more easily conducted between the first front-surface-side hole 56 and the first back-surface-side hole 57 via the peripheral edges of the first front-surface-side hole 56 and the first back-surface-side hole 57, which are arranged in the space inside the first hole 59. This allows the holding device 100 to improve thermal conductivity inside the first hole 59 compared to a case where the central axis L11 of the first front-surface-side hole 56 and the central axis L12 of the first back-surface-side hole 57 are arranged at the same position when viewed in the first direction. In this way, the holding device 100 can prevent hot spots from occurring directly above the through holes 81, and can make the temperature uniform overall.

[0059] <Details of the third embodiment of the present disclosure> Next, a third embodiment of the present disclosure will be described with reference to Fig. 6. In the third embodiment, the same components as those in the first and second embodiments are designated by the same reference numerals, and redundant descriptions of the structure, operation, and effects will be omitted.

[0060] As shown in FIG. 6 , a holding device 200 of the third embodiment includes a plate-shaped member 10, a base member 20, and an adhesive member 30. A second front-side hole 36 extending cylindrically in the first direction from the second upper hole 35A is formed on an upper side of the adhesive member 30, which is the first surface 10A side of the plate-shaped member 10. The second front-side hole 36 has a central axis L21 extending in the first direction. A second rear-side hole 37 extending cylindrically in the first direction from the second lower hole 35B is formed on a lower side of the adhesive member 30, which is the side opposite to the first surface 10A side. The central axis L22 of the second rear-side hole 37 extends in the first direction. In the third embodiment, the first direction is the vertical direction, which is a direction perpendicular to the first surface 10A, as in the first and second embodiments. The hole diameter R21 of the second front surface side hole 36 and the hole diameter R22 of the second back surface side hole 37 are substantially the same. Note that the hole diameter R21 of the second front surface side hole 36 and the hole diameter R22 of the second back surface side hole 37 may be different sizes.

[0061] In the third embodiment, the central axis L21 of the second front-surface-side hole 36 and the central axis L22 of the second back-surface-side hole 37 are positioned at different positions when viewed in the first direction. The second upper hole 35A and the second lower hole 35B are positioned so as to overlap when viewed in the first direction. Therefore, the lower end, which is the end on one side of the second front-surface-side hole 36 in the first direction, and the upper end, which is the end on the other side of the second back-surface-side hole 37 in the first direction, are connected inside the adhesive member 30, forming second holes 38 that penetrate the adhesive member 30 in the first direction.

[0062] Similar to the holding device 1 of the first embodiment, the holding device 200 includes a first hole portion 55 in the plate-like member 10, which is connected to the second hole portion 38 and has a central axis extending in the first direction. Similarly to the holding device 1 of the first embodiment, the holding device 200 also includes a third hole portion 25 in the base member 20, which is connected to the second hole portion 38 and has a central axis extending in the first direction. The first hole portion 55, the second hole portion 38, and the third hole portion 25 form a through hole 82 that penetrates the holding device 200 in the first direction.

[0063] By configuring the second hole portion 38 as described above, the peripheral edges of the second front-side hole portion 36 and the second back-side hole portion 37, which are part of the adhesive member 30, are arranged in part of the space inside the second hole portion 38. Heat is more easily conducted between the second front-side hole portion 36 and the second back-side hole portion 37 via the peripheral edges of the second front-side hole portion 36 and the second back-side hole portion 37. This allows the holding device 200 to improve heat conductivity inside the second hole portion 38 compared to a case in which the central axis L21 of the second front-side hole portion 36 and the central axis L22 of the second back-side hole portion 37 are arranged at the same position when viewed in the first direction. This prevents hot spots from occurring directly above the through holes 82.

[0064] In the third embodiment, the central axes L1, L21, L22, and L3 are arranged at different positions from one another as viewed in the first direction. In this regard, it is sufficient that at least one of the central axes L1, L21, L22, and L3 is arranged at a different position from the other central axes as viewed in the first direction. This allows a portion of the member constituting one of the first hole portion 55, the second hole portion 38, and the third hole portion 25 to be arranged relative to the other hole portion as viewed in the first direction, thereby improving thermal conductivity inside the through hole 82.

[0065] As described above, the second hole portion 38 of the holding device 200 comprises a second surface side hole portion 36 located on the first surface 10A side, and a second back surface side hole portion 37 connected to the second surface side hole portion 36 and located on the opposite side of the first surface 10A, and the central axis L22 of the second back surface side hole portion 37 is positioned at a different position when viewed in the first direction from the central axis L21 of the second surface side hole portion 36.

[0066] With this holding device 200, heat is more easily conducted between the second front-surface-side hole 36 and the second back-surface-side hole 37 via the peripheral edges of the second front-surface-side hole 36 and the second back-surface-side hole 37, which are arranged in the space inside the second hole 38. This allows the holding device 200 to improve thermal conductivity inside the second hole 38 compared to a case where the central axis L21 of the second front-surface-side hole 36 and the central axis L22 of the second back-surface-side hole 37 are arranged at the same position when viewed in the first direction. By improving heat dissipation in the adhesive member 30, the holding device 200 can prevent hot spots from occurring directly above the through holes 82, thereby achieving a more uniform temperature distribution overall.

[0067] <Other embodiments> The present disclosure is not limited to the embodiments described above and in the drawings, and for example, the following embodiments are also included within the technical scope of the present disclosure. Furthermore, various modifications other than those described below can be made without departing from the spirit of the present disclosure.

[0068] (1) When the through hole 80 of the first embodiment is a gas hole 60, a porous body 90 may be disposed somewhere inside the through hole 80. The porous body 90 is a porous, gas-permeable, and insulating member. The porous body 90 may be formed of the same ceramic material as the plate-shaped member 10. The porous body 90 may be formed of a ceramic material different from the ceramic material of the plate-shaped member 10. When plasma processing is performed on a wafer W, a bias voltage is generated on the wafer W by applying high-frequency power to the base member 20 while the holding device 1 holding the wafer W on its first surface 10A is disposed inside the processing chamber. In recent years, in order to speed up plasma processing, the high-frequency power applied to the base member 20 has been increased in voltage. This increases the potential difference between the wafer W and the base member 20, which can cause abnormal discharge in the vertically extending space inside the through hole 80. Disposing the porous body 90 inside the through hole 80 can reduce such abnormal discharge.

[0069] The porous body 90 may be disposed inside a first hole portion 55 formed inside the plate-shaped member 10 of the through hole 80. FIG. 7 shows an example of a holding device 300 in which the porous body 90 is disposed inside the first hole portion 55. As shown in FIG. 7, the lower surface 90B of the porous body 90 may be disposed so as to be flush with the second surface 10B of the plate-shaped member 10. In this case, the porous body 90 forms the lower portion of the first hole portion 55, and the lower surface 90B of the porous body 90 functions as the first lower hole portion 55B of the first hole portion 55. Even in such a case, the thermal conductivity inside the through hole 80 is improved by disposing at least one of the central axis L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third hole portion 25 at a different position from the other central axes when viewed in the first direction.

[0070] (2) FIG. 8 shows an example of a holding device 400 in which a porous body 90 is disposed inside the first hole portion 55. As shown in FIG. 8, the upper surface 90A of the porous body 90 may be disposed so as to be in the same position as the first surface 10A of the plate-like member 10. In this case, the porous body 90 forms the upper portion of the first hole portion 55, and the upper surface 90A of the porous body 90 functions as the first upper hole portion 55A of the first hole portion 55. Even in such a case, at least one of the central axes L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third hole portion 25 is disposed at a different position from the other central axes when viewed in the first direction, thereby improving thermal conductivity inside the through hole 80.

[0071] (3) Even when the through hole 81 of the second embodiment is a gas hole 60, a porous body 90 may be disposed somewhere inside the through hole 81. When the through hole 81 is a gas hole 60, the first upper hole portion 55A and the first lower hole portion 55B do not necessarily have to be disposed in positions where they overlap when viewed in the first direction. Fig. 9 shows an example of a holding device 500 in which the first front surface side hole portion 56 extending downward from the first upper hole portion 55A and the first back surface side hole portion 57 extending upward from the first lower hole portion 55B are not disposed in the same position in the first direction.

[0072] In the holding device 500, similarly to the holding device 100 of the second embodiment, the central axis L11 of the first front surface side hole 56 and the central axis L12 of the first back surface side hole 57 are arranged at different positions when viewed in the first direction. Meanwhile, in the holding device 500, a horizontal hole 58 is formed inside the plate-shaped member 10. The horizontal hole 58 communicates with the lower end of the first front surface side hole 56 and the upper end of the first back surface side hole 57 and extends parallel to the first surface 10A. That is, in the holding device 500, the first front surface side hole 56 and the first back surface side hole 57 communicate with each other via the horizontal hole 58, thereby forming a first hole 59 that penetrates the plate-shaped member 10 in the first direction.

[0073] The holding device 500 arranges the upper surface 90A of the porous body 90 so as to be in the same position as the first surface 10A of the plate-like member 10, and arranges the lower surface 90B of the porous body 90 so as to be in the same position as the lower end of the first surface-side hole portion 56. In other words, the holding device 500 arranges the porous body 90 throughout the interior of the first surface-side hole portion 56, causing the entire porous body 90 to function as the first surface-side hole portion 56. The lower surface 90B of the porous body 90 contacts one end of the horizontal hole portion 58 from above. The other end of the horizontal hole portion 58 communicates with the upper end of the first back surface-side hole portion 57.

[0074] Among the first holes 59, the first back surface side holes 57, the second holes 35, and the third holes 25 are arranged in positions that overlap one another when viewed in the first direction. Furthermore, the central axis L12 of the first back surface side hole 57, the central axis L2 of the second holes 35, and the central axis L3 of the third holes 25 are arranged in different positions when viewed in the first direction. This improves the thermal conductivity in the spaces extending in the first direction that are formed inside the first back surface side holes 57, the second holes 35, and the third holes 25, compared to when the central axis L12, the central axis L2, and the central axis L3 are arranged in the same position when viewed in the first direction.

[0075] The holding device 500 may have a porous body 90 disposed in a portion of the first front surface side hole 56. Although not shown, the holding device 500 may have a porous body 90 disposed in a portion or all of the interior of the first rear surface side hole 57 of the first hole 59. The holding device 500 may have a porous body 90 disposed in a portion or all of the interior of the horizontal hole 58.

[0076] (4) The porous body 90 may be disposed inside a third hole portion 25 of the through hole 80 formed in the base member 20. FIG. 10 shows an example of a holding device 600 in which the porous body 90 is disposed inside the third hole portion 25. As shown in FIG. 10, the upper surface 90A of the porous body 90 may be disposed so as to be flush with the third surface 20A of the base member 20. In this case, the porous body 90 forms the upper portion of the third hole portion 25, and the upper surface 90A of the porous body 90 functions as the third upper hole portion 25A of the third hole portion 25. Even in such a case, the thermal conductivity inside the through hole 80 is improved by disposing at least one of the central axis L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third hole portion 25 at a different position from the other central axes when viewed in the first direction.

[0077] (5) FIG. 11 shows an example of a holding device 700 in which a porous body 90 is disposed inside the third hole portion 25. As shown in FIG. 11, the lower surface 90B of the porous body 90 may be disposed so as to be in the same position as the fourth surface 20B of the base member 20. In this case, the porous body 90 forms the lower portion of the third hole portion 25, and the lower surface 90B of the porous body 90 functions as the third lower hole portion 25B of the third hole portion 25. Even in such a case, at least one of the central axis L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third hole portion 25 is disposed at a different position from the other central axes when viewed in the first direction, thereby improving thermal conductivity inside the through hole 80.

[0078] (6) Figure 12 shows an example of a holding device 800 in which the third upper hole 25A and the third lower hole 25B of the third hole 25 are positioned so as not to overlap when viewed in the first direction. A third front surface side hole 26 extending from the third upper hole 25A in the first direction is formed on the third surface 20A side of the base member 20. The central axis L3 of the third front surface side hole 26 extends in the first direction. A third rear surface side hole 27 extending from the third lower hole 25B in the first direction is formed on the fourth surface 20B side of the base member 20. The central axis L4 of the third rear surface side hole 27 extends in the first direction. The central axis L3 and the central axis L4 are positioned at different positions when viewed in the first direction. Furthermore, a horizontal hole 28 that communicates with the lower end of the third front surface side hole 26 and the upper end of the third back surface side hole 27 and extends parallel to the third surface 20A is formed inside the base member 20. That is, in the holding device 800, the third front surface side hole 26 and the third back surface side hole 27 communicate with each other via the horizontal hole 28, thereby forming a third hole 29.

[0079] The holding device 800 arranges the upper surface 90A of the porous body 90 so as to be in the same position as the third surface 20A of the base member 20, and arranges the lower surface 90B of the porous body 90 so as to be in the same position as the lower end of the third surface-side hole 26. In other words, the holding device 800 arranges the porous body 90 throughout the entire interior of the third surface-side hole 26, causing the entire porous body 90 to function as the third surface-side hole 26. One end of the horizontal hole 28 is in contact with the side surface of the porous body 90. The other end of the horizontal hole 28 is in communication with the upper end of the third back surface-side hole 27.

[0080] The first hole portions 55, the second hole portions 35, and the third surface side hole portions 26 of the third hole portions 29 are arranged in positions that overlap one another when viewed in the first direction. Furthermore, the central axis L1 of the first hole portion 55, the central axis L2 of the second hole portion 35, and the central axis L3 of the third surface side hole portion 26 are arranged in different positions when viewed in the first direction. This improves the thermal conductivity in the spaces extending in the first direction that are formed inside the first hole portions 55, the second hole portions 35, and the third surface side hole portions 26, compared to when the central axis L1, the central axis L2, and the central axis L3 are arranged in the same position when viewed in the first direction.

[0081] The holding device 800 may have a porous body 90 disposed in a portion of the third front surface side hole 26. Although not shown, the holding device 800 may have a porous body 90 disposed in a portion or all of the interior of the third rear surface side hole 27 of the third hole 29. The holding device 800 may have a porous body 90 disposed in a portion or all of the interior of the horizontal hole 28.

[0082] (7) In the examples of the holding devices 300, 400, and 500, the porous bodies 90 are disposed in the first hole portions 55 and 59. However, in these examples, the porous bodies 90 may also be disposed in the third hole portions 25 and 29.

[0083] (8) In the examples of the holding devices 600, 700, and 800, the porous body 90 is disposed in the third hole portions 25 and 29. However, in these examples, the porous body 90 may also be disposed in the first hole portions 55 and 59. Furthermore, the porous body 90 may be disposed inside the adhesive member 30.

[0084] (9) The present disclosure can also be applied to holes formed to penetrate the holding device 1 in the vertical direction, in addition to the gas holes 60 and lift pin holes 70. [Explanation of symbols]

[0085] 1,100,200,300,400,500,600,700,800: Holding device 10: Plate-shaped member 10A: First surface 20: Base member 30: Adhesive member 36: Second front surface side hole 37: Second rear surface side hole 56: 1st front side hole 57: 1st back side hole L1,L2,L3,L11,L12,L12,L21,L22: Central axis R1,R2,R3,R11,R12,R21,R22: Hole diameter W: wafer

Claims

1. a plate-like member having a first surface; a base member disposed on the opposite side of the plate-like member from the first surface; an adhesive member disposed between the plate-like member and the base member, the plate-like member includes a first hole portion having a central axis extending in a first direction intersecting with the first surface, the adhesive member includes a second hole portion that is connected to the first hole portion and has a central axis extending in the first direction, the base member includes a third hole portion that is connected to the second hole portion and has a central axis that extends in the first direction, A holding device in which at least one of the central axes of the first hole portion, the second hole portion, and the third hole portion is positioned at a different position from the other central axes when viewed in the first direction.

2. The first hole portion is a first surface side hole portion located on the first surface side; a first back surface side hole portion connected to the first front surface side hole portion and located on the opposite side from the first surface, The holding device according to claim 1 , wherein a central axis of the hole of the first rear surface side hole portion is disposed at a different position from a central axis of the hole of the first front surface side hole portion when viewed in the first direction.

3. The second hole portion is a second surface side hole portion located on the first surface side; a second back surface side hole connected to the second front surface side hole and located on the opposite side to the first surface, The holding device according to claim 1 or 2, wherein a central axis of the hole of the second rear surface side hole portion is disposed at a different position from a central axis of the hole of the second front surface side hole portion when viewed in the first direction.

4. The holding device according to claim 1 or 2, wherein a diameter of the second hole portion is larger than a diameter of the first hole portion and a diameter of the third hole portion.

Images