Wafer carrying table

Abstract

A wafer mounting table 10 is provided with a ceramic plate 20, a plug arrangement hole 24, a plug 50, and a plug joint 60. The upper surface of the ceramic plate (20) is provided with a wafer carrying surface (21), and an electrode (22) is arranged in the ceramic plate (20). The plug arrangement hole (24) is formed so as to extend from the lower surface to the upper surface of the ceramic plate (20). The plug (50) is disposed in the plug arrangement hole (24), and gas can pass through the inside of the plug arrangement hole (24). The plug joining part 60 is provided so as to join the outer edge of the upper surface of the plug 50 and the upper opening edge of the plug placement hole 24, and so as to cover the outer edge of the upper surface of the plug 50 from above.

Description

Technical Field The present invention relates to a wafer loading platform. Background Art In the past, a wafer carrier was used in a semiconductor manufacturing device. For example, the wafer carrier of Patent Document 1 includes: a ceramic plate having a wafer carrier surface and a built-in heater; an air path provided on the ceramic plate; and an air-permeable component arranged on the air path. Examples of the air-permeable component include: a component formed of a porous body, a component provided with one or more through holes, etc. As methods for fixing the air-permeable component to the air path, there are described: a method of pressing the air-permeable component into the air path, and a method of bonding the air-permeable component to the air path using an adhesive. In addition, it is described that it is preferable to form a protrusion on the inner wall of the air path to lock the air-permeable component so that the air-permeable component does not move due to vacuum suction. Prior art literature Patent Literature Patent Document 1: Japanese Patent No. 6767829 Summary of the Invention However, it is not easy to form a protrusion on the inner wall of the ventilation path in order to prevent the air-permeable member from moving. The present invention has been made to solve the above-mentioned problems, and a main object thereof is to achieve removal of a plug from a plug arrangement hole with a simple structure.

[0001] The wafer loading platform of the present invention comprises: a ceramic plate having a wafer placement surface on its upper surface and having electrodes built therein; a plug configuration hole extending from the lower surface of the ceramic plate to the upper surface; a plug, the plug being disposed in the plug disposition hole, and gas being able to pass through the interior of the plug; and A plug engaging portion is provided so as to engage an upper surface outer edge of the plug with an upper opening edge of the plug placement hole and to cover the upper surface outer edge of the plug from above. In this wafer loading platform, a plug, through which gas can pass, is positioned in the plug placement hole. The upper outer edge of the plug is joined to the upper opening edge of the plug placement hole by a plug joint. The plug joint is configured to cover the upper outer edge of the plug from above. The plug joint is configured to engage with the upper outer edge of the plug, thereby preventing the plug from moving upward from the plug placement hole. This simple structure, in which the upper outer edge of the plug is covered from above by the plug joint, prevents the plug from moving upward from the plug placement hole. It should be noted that, while this specification sometimes uses terms such as up and down, left and right, and front and back to describe the present invention, these terms are merely relative positional relationships. Therefore, if the orientation of the wafer stage is changed, up and down may become left and right, or left and right may become up and down. However, such situations are also within the technical scope of the present invention.

[0002] In the wafer loading platform of the present invention (the wafer loading platform described in [1] above), the plug joint portion can be provided along the entire periphery of the outer edge of the upper surface of the plug. Accordingly, the plug joint portion is provided along the entire periphery of the plug, thereby improving the joint strength of the plug joint portion.

[0003] In the wafer stage of the present invention (the wafer stage described in [1] above), the plug engagement portion may be locally present at two or more locations along the circumference of the outer edge of the upper surface of the plug. Thus, the plug engagement portion is provided at two or more locations along the circumference of the outer edge of the upper surface of the plug, rather than being provided along the entire circumference. This makes it easier to remove the plug engagement portion from the rear. For example, when the plug needs to be replaced, the plug replacement operation becomes easier.

[0004] In the wafer placement table of the present invention (the wafer placement table described in any one of [1] to [3] above), a plug inclined surface may be provided on the outer edge of the upper surface of the plug, and a placement hole inclined surface may be provided on the upper opening edge of the plug placement hole. The plug joint portion may be a thermally sprayed portion configured to fill the groove formed by the plug inclined surface and the placement hole inclined surface. Thus, the plug joint portion can be formed relatively simply by thermal spraying. It should be noted that the inclined surface may be a flat surface or a curved surface (concave or convex).

[0005] In the chip carrier of the present invention (the chip carrier described in any one of [1] to [3] above), the plug joint can be a laser welded portion obtained by laser welding the outer edge of the upper surface of the plug and the upper opening edge of the plug configuration hole. Accordingly, the plug joint can be formed relatively simply by laser welding. Here, when the laser welded portion, i.e., the plug joint, is arranged to be locally present in two or more places along the circumferential direction, the risk of cracks caused by laser welding can be reduced because the number of welding parts is reduced. In addition, when it is necessary to replace the plug, since there are fewer laser welded parts to be removed, the operation of removing the old plug becomes easier. In addition, after removing the old plug, when a new plug is arranged in the plug configuration hole and laser welding is performed, laser welding can be performed on parts other than the parts that have been laser welded in the past.

[0006] In the wafer stage of the present invention (the wafer stage described in [5] above), the laser weld portion can be configured such that, when viewed in a longitudinal cross-section, it has an inverted triangular shape, with the bottom of the laser weld portion located on the plug side. Consequently, the laser irradiation position during the laser weld portion formation process is located on the plug side. Therefore, even with laser irradiation, cracks are less likely to form in the ceramic plate. If cracks form in the ceramic plate, the plug arrangement hole and the electrode may become connected due to the cracks, but this phenomenon can be prevented.

[0007] The wafer placement table of the present invention (the wafer placement table described in any one of [1] to [6] above) may further include a conductive plate bonded to the lower surface of the ceramic plate and provided with a gas supply passage communicating with the plug arrangement hole. The conductive plate may serve as a cooling plate for cooling the ceramic plate or as a high-frequency electrode for generating plasma above the wafer placement surface. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a longitudinal sectional view of the wafer stage 10 . Figure 2 is a plan view of the ceramic plate 20 . Figure 3 yes Figure 1 A partial enlarged view of . Figure 4 1 is a diagram showing the manufacturing process of the wafer stage 10 . Figure 5 It is an enlarged longitudinal cross-sectional view of the wafer stage 110 including the plug joint 160 . Figure 6 160 is a plan view of the periphery of the plug engagement portion 160 . Figure 7 It is a manufacturing process diagram of the wafer stage 110. Figure 8 It is a longitudinal cross-sectional view of the wafer placement table 210 . Figure 9 It is an enlarged longitudinal cross-sectional view of a wafer stage including a plug joint 260 . Figure 10 It is an enlarged longitudinal cross-sectional view of a wafer stage including a plug joint 360 . Figure 11 4 is a plan view of the periphery of the plug engagement portion 460 . Figure 12 46 is a plan view of the periphery of the plug engagement portion 466 . Figure 13 It is an enlarged longitudinal cross-sectional view of a wafer stage including a plug joint 560 . DETAILED DESCRIPTION [First embodiment] The first embodiment will be described with reference to the drawings. Figure 1 is a longitudinal sectional view of the wafer stage 10, Figure 2 is a plan view of the ceramic plate 20, Figure 3 yes Figure 1 A partial enlarged view of . The wafer stage 10 includes a ceramic plate 20 , plug placement holes 24 , a substrate (conductive plate) 30 , a metal bonding layer 40 , plugs 50 , and plug bonding portions 60 . The ceramic plate 20 is a circular plate made of ceramics such as alumina sintered body or aluminum nitride sintered body (for example, 300mm in diameter and 5mm in thickness). The upper surface of the ceramic plate 20 serves as a wafer placement surface 21. The ceramic plate 20 has electrodes 22 built into it. Figure 2 As shown, a sealing tape 21a is formed along the outer edge of the chip loading surface 21 of the ceramic plate 20, and a plurality of small circular protrusions 21b are formed on the entire surface. The sealing tape 21a and the small circular protrusions 21b are of the same height, for example, a few μm to several tens of μm. The electrode 22 is a planar mesh electrode that serves as an electrostatic electrode and can be subjected to an external DC voltage. When a DC voltage is applied to the electrode 22, the chip W is adsorbed and fixed to the chip loading surface 21 (specifically, the upper surface of the sealing tape 21a and the upper surface of the small circular protrusions 21b) by electrostatic adsorption force; when the application of the DC voltage is removed, the adsorption and fixation of the chip W to the chip loading surface 21 is released. It should be noted that the portion of the chip loading surface 21 where the sealing tape 21a and the small circular protrusions 21b are not provided is referred to as the reference surface 21c. The plug arrangement hole 24 is a hole extending from the lower surface to the upper surface of the ceramic plate 20, and is a through hole that penetrates the ceramic plate 20 in the vertical direction. The plug arrangement hole 24 is opposite to the gas hole 34 of the substrate 30. The plug arrangement hole 24 penetrates the electrode 22 in the vertical direction, but the electrode 22 is not exposed on the inner circumference of the plug arrangement hole 24. The plug arrangement hole 24 is a conical hole having a truncated cone space with an upper opening area larger than a lower opening area. Figure 3 As shown, the upper opening edge of the plug configuration hole 24 is chamfered at 45 degrees around the entire periphery to form a configuration hole inclined surface 24c. The configuration hole inclined surface 24c is a flat surface rather than a curved surface. Figure 2 As shown, the plug arrangement holes 24 are provided at a plurality of locations of the ceramic plate 20 (eg, a plurality of locations provided at equal intervals along the circumferential direction). The substrate 30 is a conductive circular plate with good thermal conductivity (a circular plate with a diameter equal to or larger than that of the ceramic plate 20). A refrigerant flow path 32 for circulating a refrigerant (for example, an electrically insulating liquid such as a fluorine-based inert liquid) and a gas hole 34 for supplying gas to the plug 50 are formed inside the substrate 30. The gas hole 34 is arranged to pass through the substrate 30 in the up and down directions and has a large diameter portion 34a at the top. The large diameter portion 34a includes the lower opening of the plug configuration hole 24 when viewed from above. The refrigerant flow path 32 is formed in a single stroke from the inlet to the outlet on the entire surface of the substrate 30 when viewed from above. Examples of materials for the substrate 30 include metals, composite materials, and the like. Examples of metals include Mo, and the like. Examples of composite materials include composite materials of metals and ceramics, and the like. Examples of composite materials of metals and ceramics include metal matrix composites (MMC) and ceramic matrix composites (CMC). Specific examples of the composite material include materials containing Si, SiC, and Ti, and materials obtained by impregnating a SiC porous body with Al and / or Si. The material containing Si, SiC, and Ti is referred to as SiSiCTi, the material obtained by impregnating a SiC porous body with Al is referred to as AlSiC, and the material obtained by impregnating a SiC porous body with Si is referred to as SiSiC. As the material of the substrate 30, a material having a thermal expansion coefficient close to that of the material of the ceramic plate 20 is preferably used. The substrate 30 also serves as an RF electrode. Specifically, an upper electrode (not shown) is arranged above the wafer placement surface 21, and when high-frequency power is applied between the parallel plate electrodes formed by the upper electrode and the substrate 30, plasma is generated. The metal bonding layer 40 bonds the lower surface of the ceramic plate 20 and the upper surface of the substrate 30. The metal bonding layer 40 is formed using, for example, TCB (Thermal compression bonding). TCB refers to a well-known method in which a metal bonding material is sandwiched between two components to be bonded and the two components are press-bonded in a state heated to a temperature below the solidus temperature of the metal bonding material. The metal bonding layer 40 can be a layer formed by solder or metal brazing. The metal bonding layer 40 has a through hole 42. The through hole 42 is arranged at a position opposite to the large diameter portion 34a of the gas hole 34. The through hole 42 is coaxially arranged with the large diameter portion 34a, and the diameter of the through hole 42 is consistent with the diameter of the large diameter portion 34a. In this specification, "consistent" includes not only completely consistent situations, but also substantially consistent situations (for example, situations falling within the tolerance range, etc.) (the same applies hereinafter). The plug 50 is arranged in the plug arrangement hole 24. The plug 50 is an electrically insulating component that allows gas to flow in the vertical direction. Here, the plug 50 is a ceramic porous body, for example, a porous body made of the same material as the ceramic plate 20 can be used. The porosity of the plug 50 is preferably 30% or more, and the average pore diameter is preferably 20 μm or more. Figure 3 As shown, the outer edge of the upper surface of the plug 50 is chamfered at 45 degrees around the entire circumference to form a plug inclined surface 50c. The plug inclined surface 50c is a plane rather than a curved surface. The plug 50 is a component in the shape of a truncated cone with an area of ​​the upper surface larger than that of the lower surface. Therefore, the plug 50 will not move downward from the plug configuration hole 24. The upper surface 50a of the plug 50 is exposed at the upper opening of the plug configuration hole 24 and forms the same plane as the reference surface 21c. In this specification, "same" includes not only completely identical situations but also substantially identical situations (such as situations falling within the tolerance range, etc.) (the same below). The plug 50 and the plug configuration hole 24 are designed so that when the plug 50 is inserted into the plug configuration hole 24 in advance and the outer peripheral surface of the plug 50 and the inner peripheral surface of the plug configuration hole 24 are aligned, the height of the upper surface 50a of the plug 50 is aligned with the height of the reference surface 21c of the ceramic plate 20. Therefore, the upper surface 50a of the plug 50 can be easily flush with the reference surface 21c of the ceramic plate 20. The lower surface 50b of the plug 50 may be the same height as, higher than, or lower than the lower surface of the ceramic plate 20. The plug joint 60 is configured to join the upper outer edge of the plug 50 with the upper opening edge of the plug receiving hole 24, and to cover both the upper outer edge of the plug 50 and the upper opening edge of the plug receiving hole 24 from above. The plug joint 60 is formed by filling a groove formed by the plug inclined surface 50c, which is formed along the entire circumference of the upper outer edge of the plug 50, and the receiving hole inclined surface 24c, which is formed along the entire circumference of the upper opening edge of the plug receiving hole 24, with ceramic material by thermal spraying. Inclined surfaces 24c and 50c are flat, not curved. The groove is annular in plan view and V-shaped in cross section. Both the plug inclined surface 50c and the receiving hole inclined surface 24c are covered from above by the plug joint 60. The upper surface of the plug joint 60 is flush with the upper surface 50a of the plug 50 and the reference surface 21c of the wafer placement surface 21. However, the height of the upper surface of the plug engagement portion 60 may protrude from the reference surface 21 c within a range not exceeding the height of the upper surface of the small circular protrusion 21 b , or may be slightly recessed from the reference surface 21 c . Next, an example of using the wafer stage 10 constructed in this manner will be described. First, with the wafer stage 10 installed in a chamber (not shown), a wafer W is placed on the wafer loading surface 21. The chamber is then depressurized using a vacuum pump to a predetermined vacuum level. A DC voltage is applied to the electrodes 22 of the ceramic plate 20, generating an electrostatic attraction force that secures the wafer W to the wafer loading surface 21 (specifically, the upper surface of the sealing tape 21a and the upper surface of the small circular protrusions 21b). Next, the chamber is set to a reaction gas atmosphere at a predetermined pressure (e.g., tens to hundreds of Pa). In this state, a high-frequency voltage is applied between the upper electrode (not shown) located at the top of the chamber and the substrate 30 of the wafer stage 10, generating plasma. The surface of the wafer W is treated using the generated plasma. A coolant circulates through the coolant flow path 32 of the substrate 30. A backside gas is introduced from a gas cylinder (not shown) into the gas port 34. A heat-conductive gas (e.g., helium) is used as the backside gas. Backside gas is supplied through gas holes 34, through-holes 42, and plugs 50 and sealed in the space between the back surface of wafer W and reference surface 21c of wafer placement surface 21. The presence of this backside gas allows efficient heat conduction between wafer W and ceramic plate 20. Next, based on Figure 4 , a manufacturing example of the wafer placement table 10 is described. Figure 4 1 is a manufacturing process diagram of the wafer stage 10. First, prepare the ceramic plate 20, the substrate 30 and the metal bonding material 90 ( Figure 4 (A)). Ceramic plate 20 has an electrode 22 built into it and a plug placement hole 24. The upper opening edge of plug placement hole 24 is chamfered 45° to form a placement hole inclined surface 24c. Substrate 30 has a coolant flow path 32 and a gas hole 34. Gas hole 34 has a large diameter portion 34a at its upper portion. Metal bonding material 90 has a through hole 92 at a position opposite large diameter portion 34a of gas hole 34. Next, the metal bonding material 90 is sandwiched between the lower surface of the ceramic plate 20 and the upper surface of the substrate 30, thereby forming a laminate. At this time, the plug configuration hole 24 of the ceramic plate 20, the through hole 92 of the metal bonding material 90, and the gas hole 34 of the substrate 30 are stacked in a coaxial manner. Then, the laminate is pressurized and bonded at a temperature below the solidus temperature of the metal bonding material 90 (for example, a temperature above the solidus temperature minus 20°C and below the solidus temperature), and then returned to room temperature (TCB). As a result, the metal bonding material 90 and the through hole 92 become the metal bonding layer 40 and the through hole 42, respectively, and a bonded body 94 ( Figure 4(B)). Note that an Al-Mg-based bonding material or an Al-Si-Mg-based bonding material can be used as the metal bonding material 90. The metal bonding material 90 preferably has a thickness of approximately 100 μm. Next, prepare a truncated cone-shaped plug 50 ( Figure 4 (B)). The outer edge of the upper surface of the plug 50 is chamfered at 45 degrees to form a plug inclined surface 50c. Next, the plug 50 is inserted into the plug arrangement hole 24 ( Figure 4 (C)) Thus, the plug inclined surface 50c of the plug 50 and the arrangement hole inclined surface 24c of the plug arrangement hole 24 form a groove 70 that is annular in plan view and V-shaped in cross section. Next, the groove 70 is filled with ceramic material by spraying. Thus, the groove 70 is filled with the plug joint 60. The plug inclined surface 50c and the arrangement hole inclined surface 24c are covered from above by the plug joint 60. The raised portion of the plug joint 60 is flattened by grinding. Finally, the sealing tape 21a and the small circular protrusions 21b are provided on the upper surface of the ceramic plate 20, thereby obtaining the wafer placement table 10 ( Figure 4 (D) Note that the plug joint 60 may be formed by thermal spraying after providing the sealing tape 21 a and the small circular protrusions 21 b on the upper surface of the ceramic plate 20 . In the wafer stage 10 described in detail above, a plug 50, through which gas can pass, is disposed in the plug receiving hole 24. The outer edge of the upper surface of the plug 50 and the upper opening edge of the plug receiving hole 24 are joined by a plug joint 60. The plug joint 60 is provided so as to cover the outer edge of the upper surface of the plug 50 from above, thereby preventing the plug 50 from moving upward from the plug receiving hole 24. In this manner, the plug 50 can be prevented from moving upward from the plug receiving hole 24 with a simple structure in which the outer edge of the upper surface of the plug 50 is covered from above by the plug joint 60. Furthermore, since the plug joint portion 60 is provided on the entire circumference of the plug 50 , the joint strength of the plug joint portion 60 is improved. Furthermore, the plug joint portion 60 is a thermally sprayed portion provided to fill the groove 70 formed by the plug inclined surface 50c and the arrangement hole inclined surface 24c. Therefore, the plug joint portion 60 can be formed relatively easily by thermal spraying. [Second embodiment] The wafer stage 110 according to the second embodiment will be described with reference to the drawings. Figure 5 1 is an enlarged longitudinal cross-sectional view of the wafer stage 110 having the plug joint 160. Figure 6 is a plan view of the periphery of the plug 160, Figure 7 This is a diagram (part) of the manufacturing process of the wafer carrier 110. Figures 5 to 7Components of the wafer stage 110 that are identical to those of the wafer stage 10 are denoted by the same reference numerals, and description thereof will be omitted. The wafer stage 110 includes a ceramic plate 20 , plug placement holes 24 , a substrate (conductive plate) 30 , a metal bonding layer 40 , plugs 50 , and plug bonding portions 160 . Plug joint 160 is a laser-welded portion formed by laser welding the upper outer edge of the plug 50 to the upper opening edge of the plug receiving hole 24. Plug joint 160 has an inverted triangular shape when viewed in longitudinal section, with its base located at the boundary between the plug 50 and the plug receiving hole 24. Plug joint 160 is configured to join the upper outer edge of the plug 50 to the upper opening edge of the plug receiving hole 24 and to cover the upper outer edge of the plug 50 and the upper opening edge of the plug receiving hole 24 from above. Plug joint 160 extends along the entire circumference of the upper outer edge of the plug 50. The usage example of the wafer stage 110 is the same as that of the wafer stage 10 , and thus the description thereof is omitted. The differences between the manufacturing example of the wafer stage 110 and the manufacturing example of the wafer stage 10 will be described. When manufacturing the wafer stage 10, the upper opening edge of the plug placement hole 24 is chamfered at 45 degrees to form the placement hole inclined surface 24c, and the upper surface outer edge of the plug 50 is chamfered at 45 degrees to form the plug inclined surface 50c. However, when manufacturing the wafer stage 110, such chamfering is not performed. Therefore, when the plug 50 is inserted into the plug placement hole 24, the upper opening edge of the plug placement hole 24 and the upper surface outer edge of the plug 50 are in contact with each other ( Figure 7 (A)). In this state, the boundary between the upper opening edge of the plug configuration hole 24 and the outer edge of the upper surface of the plug 50 is irradiated with a laser (e.g., nanosecond laser, picosecond laser, femtosecond laser, etc.) to locally increase the temperature. As a result, the upper opening edge of the plug configuration hole 24 and the outer edge of the upper surface of the plug 50 are welded to form a laser welded portion. From the characteristics of laser welding, the width (diameter) of the cross section of the laser welded portion decreases from top to bottom. The portion of the laser welded portion that is raised from the surface is flattened by grinding. Thus, the plug joint 160 ( Figure 7 (B)). In the wafer stage 110 described above, the plug engaging portion 160 is provided so as to cover the outer edge of the upper surface of the plug 50 from above. The plug engaging portion 160 is provided so as to engage with the outer edge of the upper portion of the plug 50, thereby preventing the plug 50 from moving upward from the plug receiving hole 24. In this manner, the plug 50 can be prevented from moving upward from the plug receiving hole 24 with a simple structure in which the outer edge of the upper surface of the plug 50 is covered from above by the plug engaging portion 160. Furthermore, since the plug engaging portion 160 is provided along the entire periphery of the outer edge of the upper surface of the plug 50 , the engaging strength of the plug engaging portion 160 is improved. Furthermore, the plug joint 160 is a laser-welded portion formed by laser welding the boundary between the upper outer edge of the plug 50 and the upper opening edge of the plug receiving hole 24. Therefore, the plug joint 160 can be formed relatively simply by laser welding. When the plug joint 160 is formed by laser welding, there is no need to chamfer the upper outer edge of the plug 50 and the upper opening edge of the plug receiving hole 24, as in the first embodiment. It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented in various forms as long as it falls within the technical scope of the present invention. In the first and second embodiments described above, a plug 50 formed of a porous body is exemplified as a plug that allows gas to flow in the vertical direction, but the present invention is not particularly limited thereto. For example, a dense plug having a flow path (e.g., a straight flow path or a spiral flow path) inside that allows gas to flow in the vertical direction may be used as the plug. In the first and second embodiments described above, the truncated cone-shaped plug 50 is exemplified, but the present invention is not particularly limited thereto. For example, a cylindrical plug may be used. In the first and second embodiments described above, a stepped hole having a large diameter portion 34 a above the gas hole 34 is used, but the present invention is not particularly limited thereto. For example, a straight hole may be used as the gas hole 34 . In the first and second embodiments described above, an electrostatic electrode is exemplified as the electrode 22 built into the ceramic plate 20, but the present invention is not particularly limited thereto. For example, a heater electrode (resistive heating element) or an RF electrode may be built into the ceramic plate 20 instead of or in addition to the electrode 22. In the first and second embodiments described above, the ceramic plate 20 and the substrate 30 are bonded together by the metal bonding layer 40 . However, a resin adhesive layer may be used instead of the metal bonding layer 40 . In the first embodiment described above, the substrate 30 is provided with the gas holes 34 constituting the gas supply path, but the present invention is not particularly limited thereto. Figure 8 As shown, the substrate 30 may be provided with a ring portion 64a that is concentric with the substrate 30 in a plan view, an introduction portion 64b that introduces gas from the back surface of the substrate 30 into the ring portion 64a, and a distribution portion 64c that distributes gas from the ring portion 64a to each plug 50. Figure 8Components identical to those in the first embodiment are denoted by the same reference numerals. The number of inlet portions 64b is less than the number of distribution portions 64c, and may be, for example, one. This arrangement allows the number of external gas pipes connected to the lower surface of the substrate 30 to be less than the number of plugs 50. This configuration can also be used in the second embodiment. In the first embodiment described above, the outer edge of the upper surface of the plug 50 and the upper opening edge of the plug arrangement hole 24 are chamfered at 45 degrees. However, the chamfer is not limited to 45 degrees. For example, a circular chamfer may be implemented. In this case, each inclined surface 24c, 50c is a curved surface (convex surface). In addition, in the state before the plug joint 60 is formed ( Figure 4 In the embodiment (C), the outer edge of the upper surface of the plug 50 and the upper opening edge of the plug receiving hole 24 form a groove 70 with a V-shaped cross section, but this is not particularly limiting. For example, the outer edge of the upper surface of the plug 50 and the upper opening edge of the plug receiving hole 24 can be processed so that the outer edge of the upper surface of the plug 50 and the upper opening edge of the plug receiving hole 24 form a groove with a U-shaped cross section. In this case, the cross section of the plug joint 60 is generally quadrilateral. In the first embodiment described above, the entire circumference of the upper opening edge of the plug placement hole 24 is chamfered to form the placement hole inclined surface 24c. However, the placement hole inclined surface 24c may not be formed. An example of this is shown in FIG. Figure 9 . Figure 9 In the drawings, the same components as those in the first embodiment are denoted by the same reference numerals. Figure 9 The plug-joining portion 260 is a thermally sprayed portion formed by joining the plug-in inclined surface 50c provided on the outer edge of the upper surface of the plug 50 with the upper opening edge of the plug receiving hole 24, which does not have the receiving hole inclined surface 24. Furthermore, the plug-joining portion 260 is formed by thermal spraying so as to cover the upper outer edge of the plug-in inclined surface 50c from above. Even so, this simple structure can prevent the plug 50 from moving upward from the plug receiving hole 24. In the first embodiment described above, the entire circumference of the outer edge of the upper surface of the plug 50 is chamfered to form the plug inclined surface 50c. However, the plug inclined surface 50c may not be formed. An example of this is shown in FIG. Figure 10 . Figure 10 In the drawings, the same components as those in the first embodiment are denoted by the same reference numerals. Figure 10 The plug joint portion 360 is a thermally sprayed portion formed by joining the outer edge of the upper surface of the plug 50 (which does not have the plug inclined surface 50c) with the inclined surface 24c provided at the upper opening edge of the plug receiving hole 24. Furthermore, the plug joint portion 360 is formed by thermal spraying so that the outer edge of the upper surface of the plug 50 and the inclined surface 24c of the plug receiving hole 24 overlap from above. Even so, this simple structure prevents the plug 50 from moving upward from the plug receiving hole 24. In the first embodiment described above, the plug joint 60 is formed by spraying, but the present invention is not limited to spraying. For example, the plug joint 60 may be formed by aerosol deposition. Alternatively, Figure 4 The groove 70 with a V-shaped cross section (C) is filled with ceramic powder and then locally heated by laser or the like to sinter the ceramic powder, thereby forming the plug joint 60 . In the second embodiment described above, the plug engagement portion 160 is provided on the entire periphery of the upper surface outer edge of the plug 50, but the present invention is not particularly limited thereto. Figure 11 As shown, the plug engaging portion 460 may be provided so as to be locally present at two or more locations (here, eight locations) along the circumferential direction of the outer edge of the upper surface of the plug 50 . Figure 11 In the figure, the same symbols are given to the same structures as those in the second embodiment. Accordingly, although the joint strength is reduced compared with the second embodiment, a strength that is not problematic at a practical level is obtained. In addition, compared with the second embodiment, there are fewer parts to be laser irradiated, so it is not easy to generate cracks in the plug 50 or the ceramic plate 20. In addition, when it is necessary to replace the plug 50, since the length of the plug joint 460 is shorter than that of the second embodiment, it is easy to remove the plug joint 460. After removing the old plug 50, when another new plug 50 is arranged in the plug arrangement hole 24 and laser welding is performed, as shown in FIG. Figure 12 As shown, laser welding is performed on a portion 464 different from the previously laser-welded portion 462 (hatched), forming a new plug joint 466. This is because the previously laser-welded portion 462 cannot be laser-welded again. Note that if the plug is to be replaced two or more times, only the portions that can be laser-welded can be retained corresponding to the number of times. The plug engagement portion 60 of the first embodiment may also be configured as follows: Figure 11 Similarly, the plug joint 460 is locally present in two or more locations. Thus, although the joint strength is reduced compared to the first embodiment, a strength that is not problematic at a practical level is achieved. Furthermore, since fewer areas are subjected to spraying than in the first embodiment, cracks are less likely to form in the plug 50 or the ceramic plate 20. Furthermore, if the plug 50 needs to be replaced, the sprayed portion is easily removed due to its shorter length. However, in the case of spraying, even areas that have been sprayed previously can be sprayed again. Therefore, even if the plug joint 60 is provided along the entire circumference of the upper surface outer edge of the plug 50 as in the first embodiment, the upper surface outer edge of the replaced plug 50 and the upper opening edge of the plug configuration hole 24 can be sprayed again along the entire circumference. In the second embodiment described above, the bottom 160a of the laser welding portion, i.e., the plug joint portion 160 having an inverted triangular cross section, is located at the boundary between the plug 50 and the plug arrangement hole 24, but the present invention is not particularly limited thereto. Figure 13 The plug engaging portion 560 is shown such that the bottom 560 a of the plug engaging portion 560 is located on the plug 50 side. Figure 13 In the embodiment, the same reference numerals are given to the same components as those in the second embodiment. In this case, the laser irradiation position in the process of forming the plug joint 560 is on the plug side. Therefore, even if laser irradiation is performed, it is difficult to generate cracks in the ceramic plate 20. If cracks are generated in the ceramic plate 20, the plug arrangement hole 24 and the electrode 22 may be connected due to the cracks, which may easily cause problems. However, if the laser irradiation is used, the plug arrangement hole 24 and the electrode 22 may be connected due to the cracks. Figure 13 , this undesirable situation can be prevented from occurring. In the first and second embodiments described above, the outer peripheral surface of the plug 50 can be brought into close contact with the inner peripheral surface of the plug receiving hole 24. This can suppress discharge between the outer peripheral surface of the plug 50 and the inner peripheral surface of the plug receiving hole 24 when plasma is generated. Industrial applicability The present invention can be used for a wafer placement table used in a semiconductor manufacturing apparatus, such as a ceramic heater, an electrostatic chuck heater, an electrostatic chuck, and the like. Explanation of symbols 10 Wafer carrier, 20 Ceramic plate, 21 Wafer carrier surface, 21a Sealing tape, 21b Small circular protrusion, 21c Reference surface, 22 Electrode, 24 Plug configuration hole, 24c Configuration hole inclined surface, 30 Substrate, 32 Refrigerant flow path, 34 Gas hole, 34a Large diameter portion, 40 Metal bonding layer, 42 Through hole, 50 Plug, 50a Upper surface, 50b Lower surface, 50c Plug inclined surface, 64a Ring portion, 64b Inlet portion, 64c Distribution portion, 90 Metal bonding material, 92 Through hole, 94 Bonding body, 110, 210 Wafer carrier, 60, 160, 260, 360, 460, 466, 560 Plug bonding portion, 160a, 560a Bottom, W wafer.

Claims

1. A wafer loading platform, wherein: have: a ceramic plate having a wafer placement surface on its upper surface and having electrodes built therein; a plug configuration hole extending from the lower surface of the ceramic plate to the upper surface; a plug, the plug being disposed in the plug-disposing hole, and gas being able to pass through the interior of the plug; as well as A plug engaging portion is provided so as to engage an upper surface outer edge of the plug with an upper opening edge of the plug placement hole and to cover the upper surface outer edge of the plug from above.

2. The wafer stage according to claim 1, wherein: The plug engaging portion is provided on the entire circumference of the outer edge of the upper surface of the plug.

3. The wafer stage according to claim 1, wherein: The plug engaging portions are present at two or more locations along the circumferential direction of the outer edge of the upper surface of the plug.

4. The wafer stage according to any one of claims 1 to 3, wherein: A plug inclined surface is provided on the outer edge of the upper surface of the plug. An inclined surface for the plug configuration hole is provided at the upper opening edge of the plug configuration hole. The plug joint portion is a thermally sprayed portion provided to fill a groove formed by the plug inclined surface and the arrangement hole inclined surface.

5. The wafer stage according to any one of claims 1 to 3, wherein: The plug joint portion is a laser welded portion formed by laser welding an outer edge of an upper surface of the plug and an upper opening edge of the plug placement hole.

6. The wafer stage according to claim 5, wherein: The laser weld portion is configured such that a longitudinal cross-section thereof is in the shape of an inverted triangle, with a bottom of the laser weld portion being located on the plug side.

7. The wafer stage according to any one of claims 1 to 3, wherein: The wafer stage includes a conductive plate that is bonded to the lower surface of the ceramic plate and is provided with a gas supply path that communicates with the plug placement hole.

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