Wafer placement base

Abstract

This wafer placement base 10 comprises a ceramic plate 20, plug arrangement holes 24, plugs 50, and plug joining parts 60. The ceramic plate 20 has a wafer placement surface 21 on the upper surface thereof and embeds an electrode 22. The plug arrangement holes 24 are formed so as to reach the upper surface from the lower surface of the ceramic plate 20. The plugs 50 are members disposed in the plug arrangement holes 24 and each having an inner section through which a gas can pass. The plug joining parts 60 join the upper surface outer edges of the plugs 50 and the upper opening edges of the plug arrangement holes 24, and are provided so as to cover the upper surface outer edges of the plugs 50 from above.

Description

Wafer mounting table

[0001] The present invention relates to a wafer stage.

[0002] Conventionally, wafer mounting tables have been used in semiconductor manufacturing equipment. For example, Patent Document 1 discloses a wafer mounting table that includes a ceramic plate having a wafer mounting surface and a built-in heater, a ventilation path provided in the ceramic plate, and a breathable member disposed in the ventilation path. Examples of the breathable member include a porous member and a member having one or more through holes. Methods of fixing the breathable member to the ventilation path include press-fitting the breathable member into the ventilation path and bonding the breathable member to the ventilation path using an adhesive. It also discloses that it is preferable to form protrusions or the like on the inner wall of the ventilation path to lock the breathable member in place so that the breathable member does not move due to vacuum suction.

[0003] Patent No. 6767829

[0004] However, it is not easy to form protrusions or the like on the inner wall of the ventilation path in order to prevent the breathable member from moving.

[0005] The present invention has been made to solve the above-mentioned problems, and a main object of the present invention is to realize a plug that can be removed from a plug placement hole with a simple structure.

[0006] [1] A wafer mounting table according to the present invention comprises: a ceramic plate having a wafer mounting surface on its upper surface and incorporating an electrode; a plug placement hole extending from the lower surface to the upper surface of the ceramic plate; a plug placed in the plug placement hole and allowing gas to pass through; and a plug joint portion that joins the outer edge of the upper surface of the plug to the edge of the upper opening of the plug placement hole and is provided so as to cover the outer edge of the upper surface of the plug from above.

[0007] In this wafer mounting table, a plug, through which gas can pass, is placed in the plug placement hole. The outer edge of the top surface of the plug and the edge of the upper opening of the plug placement hole are joined by a plug joint. The plug joint is provided so as to cover the outer edge of the top surface of the plug from above. The plug joint is provided so as to hook onto the upper outer edge of the plug, thereby preventing the plug from slipping out upward from the plug placement hole. In this way, the plug can be prevented from slipping out upward from the plug placement hole with a simple structure in which the outer edge of the top surface of the plug is covered from above with the plug joint.

[0008] Although the present invention is sometimes described using terms such as up / down, left / right, front / back, etc., these terms merely refer to relative positional relationships. Therefore, when the orientation of the wafer table is changed, up / down may become left / right, or left / right may become up / down, and such cases are also within the technical scope of the present invention.

[0009] [2] In the wafer mounting table of the present invention (the wafer mounting table described in [1] above), the plug bonding portion may be provided along the entire periphery of the upper surface of the plug. In this case, the plug bonding portion is provided along the entire periphery of the plug, thereby increasing the bonding strength of the plug bonding portion.

[0010] [3] In the wafer mounting table of the present invention (the wafer mounting table described in [1] above), the plug bonding portion may be partially present at two or more locations along the circumferential direction of the outer edge of the upper surface of the plug. In this case, the plug bonding portion is provided so as to be partially present at two or more locations along the circumferential direction of the outer edge of the upper surface of the plug rather than along the entire circumference of the outer edge of the upper surface of the plug, making it easier to remove the plug bonding portion later. For example, if the plug needs to be replaced, this facilitates the plug replacement work.

[0011] [4] In the wafer mounting table of the present invention (the wafer mounting table according to any one of [1] to [3] above), the plug may have an inclined plug surface on the outer edge of its upper surface, and the plug mounting hole may have an inclined hole surface on the upper opening edge, and the plug joint portion may be a sprayed portion formed so as to fill a groove formed by the inclined plug surface and the inclined hole surface. This allows the plug joint portion to be formed relatively easily by spraying. The inclined surface may be flat or curved (concave or convex).

[0012] [5] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [3] above), the plug joint may be a laser welded portion formed by laser welding the outer edge of the top surface of the plug to the edge of the upper opening of the plug placement hole. This allows the plug joint to be formed relatively easily by laser welding. Here, if the plug joint, which is a laser welded portion, is provided so as to exist partially in two or more locations along the circumferential direction, the number of welded locations is reduced, thereby reducing the risk of cracks occurring due to laser welding. Furthermore, if the plug needs to be replaced, the task of removing the old plug is simplified because there are fewer laser welds to remove. Furthermore, when a new plug is placed in the plug placement hole after removing the old plug and laser welding is performed, it is sufficient to laser weld only the locations other than the previously laser welded locations.

[0013] [6] In the wafer mounting table of the present invention (the wafer mounting table described in [5] above), the laser weld may have an inverted triangular shape when viewed in vertical cross section, with the bottom of the laser weld located on the plug side. In this way, the laser irradiation position in the process of forming the laser weld is on the plug side. Therefore, even if laser irradiation is performed, cracks are unlikely to occur in the ceramic plate. If a crack occurs in the ceramic plate, the plug placement hole and the electrode may become connected by the crack, but this can be prevented.

[0014] [7] The wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [6] above) may further include a conductive plate bonded to the underside of the ceramic plate and provided with a gas supply passage communicating with the plug placement hole. The conductive plate may be used as a cooling plate for cooling the ceramic plate, or as a high-frequency electrode for generating plasma above the wafer mounting surface.

[0015] 1A and 1B are a longitudinal sectional view of the wafer mounting table 10, a plan view of the ceramic plate 20, an enlarged partial view of FIG. 1, a manufacturing process diagram of the wafer mounting table 10, an enlarged longitudinal sectional view of the wafer mounting table 110 including a plug bonding portion 160, a plan view of the periphery of the plug bonding portion 160, and a manufacturing process diagram of the wafer mounting table 110, a longitudinal sectional view of the wafer mounting table 210, an enlarged longitudinal sectional view of the wafer mounting table including a plug bonding portion 260, an enlarged longitudinal sectional view of the wafer mounting table including a plug bonding portion 360, a plan view of the periphery of the plug bonding portion 460, a plan view of the periphery of the plug bonding portion 466, and an enlarged longitudinal sectional view of the wafer mounting table including a plug bonding portion 560.

[0016] [First Embodiment] A first embodiment will be described with reference to the drawings, in which Fig. 1 is a vertical cross-sectional view of a wafer mounting table 10, Fig. 2 is a plan view of a ceramic plate 20, and Fig. 3 is an enlarged view of a portion of Fig. 1.

[0017] The wafer mounting table 10 includes a ceramic plate 20 , a plug placement hole 24 , a base plate (conductive plate) 30 , a metal bonding layer 40 , a plug 50 , and a plug bonding portion 60 .

[0018] The ceramic plate 20 is a circular ceramic plate (e.g., 300 mm in diameter and 5 mm in thickness) made of sintered alumina, sintered aluminum nitride, or the like. The upper surface of the ceramic plate 20 serves as a wafer mounting surface 21. The ceramic plate 20 incorporates an electrode 22. As shown in FIG. 2 , a seal band 21a is formed along the outer edge of the wafer mounting surface 21 of the ceramic plate 20, and multiple small circular protrusions 21b are formed over the entire surface. The seal band 21a and the small circular protrusions 21b have the same height, e.g., several micrometers to several tens of micrometers. The electrode 22 is a flat mesh electrode used as an electrostatic electrode, to which a DC voltage can be applied. When a DC voltage is applied to the electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the upper surfaces of the seal band 21a and the small circular protrusions 21b) by electrostatic attraction. When the DC voltage is removed, the wafer W is released from the wafer mounting surface 21. The portion of the wafer mounting surface 21 on which the seal band 21a and the small circular protrusions 21b are not provided is referred to as a reference surface 21c.

[0019] The plug arrangement hole 24 is a hole extending from the lower surface to the upper surface of the ceramic plate 20. In this example, it is a through-hole that penetrates the ceramic plate 20 in the vertical direction. The plug arrangement hole 24 faces the gas hole 34 of the base plate 30. The plug arrangement hole 24 penetrates the electrode 22 in the vertical direction, but the electrode 22 is not exposed at the inner circumferential surface of the plug arrangement hole 24. The plug arrangement hole 24 is a tapered hole having a truncated cone space in which the area of ​​the upper opening is larger than the area of ​​the lower opening. As shown in FIG. 3 , the edge of the upper opening of the plug arrangement hole 24 is chamfered along the entire periphery to form an arrangement hole inclined surface 24c. The arrangement hole inclined surface 24c is flat, not curved. As shown in FIG. 2 , the plug arrangement holes 24 are provided at multiple locations on the ceramic plate 20 (e.g., multiple locations equally spaced along the circumferential direction).

[0020] The base plate 30 is a conductive disk (having the same diameter as or larger than the ceramic plate 20) with good thermal conductivity. The base plate 30 includes a coolant flow path 32 through which a coolant (e.g., an electrically insulating liquid such as a fluorine-based inert liquid) circulates, and a gas hole 34 through which gas is supplied to the plug 50. The gas hole 34 is disposed to vertically penetrate the base plate 30 and has a large-diameter portion 34a at its upper end. The large-diameter portion 34a encompasses the lower opening of the plug placement hole 24 in a plan view. The coolant flow path 32 is formed in a single stroke from the inlet to the outlet across the entire surface of the base plate 30 in a plan view. Examples of materials for the base plate 30 include metals and composite materials. Examples of metals include molybdenum (Mo). Examples of composite materials include a composite material of metal and ceramic. Examples of composite materials of metal and ceramic include metal matrix composites (MMCs) and ceramic matrix composites (CMCs). Specific examples of such composite materials include materials containing Si, SiC, and Ti, and materials in which porous SiC is impregnated with Al and / or Si. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which porous SiC is impregnated with Al is called AlSiC, and a material in which porous SiC is impregnated with Si is called SiSiC. It is preferable to select a material for the base plate 30 that has a thermal expansion coefficient close to that of the material for the ceramic plate 20. The base plate 30 also serves as an RF electrode. Specifically, an upper electrode (not shown) is disposed above the wafer mounting surface 21, and plasma is generated when high-frequency power is applied between the parallel plate electrodes consisting of the upper electrode and the base plate 30.

[0021] The metal bonding layer 40 bonds the lower surface of the ceramic plate 20 to the upper surface of the base plate 30. The metal bonding layer 40 is formed, for example, by thermal compression bonding (TCB). TCB is a known method in which a metal bonding material is sandwiched between two components to be bonded and the two components are pressure-bonded while heated to a temperature below the solidus temperature of the metal bonding material. The metal bonding layer 40 may be a layer formed of solder or a brazing metal. The metal bonding layer 40 has a through hole 42. The through hole 42 is located opposite the large-diameter portion 34a of the gas hole 34. The through hole 42 is coaxial with the large-diameter portion 34a, and the diameter of the through hole 42 matches the diameter of the large-diameter portion 34a. In this specification, "match" includes not only perfect match but also substantial match (e.g., within a tolerance range) (the same applies hereinafter).

[0022] The plug 50 is disposed in the plug placement hole 24. The plug 50 is an electrically insulating member that allows gas to flow vertically. Here, the plug 50 is a porous ceramic body, and may be made of, for example, the same material as the ceramic plate 20. The porosity of the plug 50 is preferably 30% or more, and the average pore diameter is preferably 20 μm or more. As shown in FIG. 3 , the outer edge of the upper surface of the plug 50 is chamfered along the entire circumference to form a plug inclined surface 50c. The plug inclined surface 50c is flat, not curved. The plug 50 is a truncated cone-shaped member with an upper surface area larger than the lower surface area. Therefore, the plug 50 does not slip out downward from the plug placement hole 24. The upper surface 50a of the plug 50 is exposed at the upper opening of the plug placement hole 24 and is flush with the reference surface 21c. In this specification, the term "same" includes not only completely identical but also substantially identical (e.g., within a tolerance range) (the same applies hereinafter). The plug 50 and the plug positioning hole 24 are designed in advance so that when the plug 50 is inserted into the plug positioning hole 24 and the outer peripheral surface of the plug 50 is aligned with the inner peripheral surface of the plug positioning hole 24, 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 and the reference surface 21c of the ceramic plate 20 can be easily made flush with each other. The height of the lower surface 50b of the plug 50 may be the same as, higher than, or lower than the height of the lower surface of the ceramic plate 20.

[0023] The plug joint 60 joins the outer edge of the top surface of the plug 50 to the edge of the upper opening of the plug placement hole 24 and is provided so as to cover the outer edge of the top surface of the plug 50 and the edge of the upper opening of the plug placement hole 24 from above. Here, the plug joint 60 is formed by filling a groove formed by a plug inclined surface 50c provided around the entire periphery of the outer edge of the top surface of the plug 50 and an arrangement hole inclined surface 24c provided around the entire periphery of the upper opening edge of the plug placement hole 24 with a ceramic material by a thermal spraying method. The inclined surfaces 24c, 50c are flat rather than curved. This groove is ring-shaped in plan view and has a V-shaped cross section. Both the plug inclined surface 50c and the arrangement hole inclined surface 24c are covered from above by the plug joint 60. The top surface of the plug joint 60 is flush with the top surface 50a of the plug 50 and the reference surface 21c of the wafer mounting surface 21. However, the height of the upper surface of the plug joint portion 60 may protrude from the reference surface 21c within a range that does not exceed the height of the upper surface of the small circular protrusion 21b, or may be slightly recessed below the reference surface 21c.

[0024] Next, an example of how the wafer mounting table 10 configured as described above is described. First, the wafer mounting table 10 is installed in a chamber (not shown), and a wafer W is placed on the wafer mounting surface 21. The chamber is then depressurized using a vacuum pump to a predetermined vacuum level, and a DC voltage is applied to the electrode 22 of the ceramic plate 20 to generate an electrostatic attraction force, thereby attracting and fixing the wafer W to the wafer mounting surface 21 (specifically, the upper surface of the seal band 21a or the upper surface of the small circular protrusions 21b). Next, a reactive gas atmosphere at a predetermined pressure (e.g., several tens to several hundreds of Pa) is created in the chamber. In this state, a high-frequency voltage is applied between an upper electrode (not shown) installed in the ceiling of the chamber and the base plate 30 of the wafer mounting table 10 to generate plasma. The surface of the wafer W is treated with the generated plasma. A coolant circulates through the coolant flow path 32 in the base plate 30. A backside gas is introduced through the gas hole 34 from a gas cylinder (not shown). A thermally conductive gas (e.g., helium) is used as the backside gas. The backside gas is supplied and sealed in the space between the back surface of the wafer W and the reference surface 21c of the wafer mounting surface 21 through the gas holes 34, the through-holes 42, and the plug 50. The presence of this backside gas allows efficient heat conduction between the wafer W and the ceramic plate 20.

[0025] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to FIG. 4. FIG. 4 is a manufacturing process diagram for the wafer mounting table 10. First, a ceramic plate 20, a base plate 30, and a metal bonding material 90 are prepared (FIG. 4A). The ceramic plate 20 incorporates an electrode 22 and has a plug mounting hole 24. The upper opening edge of the plug mounting hole 24 is chamfered to form a mounting hole inclined surface 24c. The base plate 30 has a coolant flow path 32 and a gas hole 34. The gas hole 34 has a large diameter portion 34a at its upper portion. The metal bonding material 90 has a through hole 92 at a position facing the large diameter portion 34a of the gas hole 34.

[0026] Next, a metal bonding material 90 is sandwiched between the underside of the ceramic plate 20 and the top side of the base plate 30 to form a laminate. The ceramic plate 20 is stacked so that the plug placement hole 24, the through-hole 92 in the metal bonding material 90, and the gas hole 34 in the base plate 30 are coaxial. The laminate is then pressed and bonded at a temperature below the solidus temperature of the metal bonding material 90 (e.g., a temperature 20°C below the solidus temperature but below the solidus temperature), and then returned to room temperature (TCB). This results in the metal bonding material 90 and the through-hole 92 becoming the metal bonding layer 40 and the through-hole 42, respectively, resulting in a bonded assembly 94 in which the ceramic plate 20 and the base plate 30 are bonded by the metal bonding layer 40 ( FIG. 4B ). The metal bonding material 90 can be an Al-Mg-based bonding material or an Al-Si-Mg-based bonding material. It is preferable to use a metal bonding material 90 with a thickness of approximately 100 μm.

[0027] Next, a truncated cone-shaped plug 50 is prepared ( FIG. 4B ). The outer edge of the top surface of the plug 50 is C-chamfered to form a plug inclined surface 50c. Next, the plug 50 is inserted into the plug placement hole 24 ( FIG. 4C ). As a result, the plug inclined surface 50c of the plug 50 and the placement hole inclined surface 24c of the plug placement hole 24 form a groove 70 that is ring-shaped in plan view and has a V-shaped cross section.

[0028] Next, the groove 70 is filled with a ceramic material by thermal spraying. As a result, the groove 70 is filled with the plug joint 60. The plug inclined surface 50c and the placement 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 wafer mounting table 10 is obtained by providing a seal band 21a and small circular protrusions 21b on the upper surface of the ceramic plate 20 (FIG. 4D). Note that the plug joint 60 may be formed by thermal spraying after the seal band 21a and small circular protrusions 21b are provided on the upper surface of the ceramic plate 20.

[0029] In the wafer mounting table 10 described above in detail, the plug 50, through which gas can pass, is placed in the plug placement hole 24. The outer edge of the top surface of the plug 50 is joined to the edge of the upper opening of the plug placement hole 24 by a plug joint 60. The plug joint 60 is provided so as to cover the outer edge of the top surface of the plug 50 from above, and therefore prevents the plug 50 from slipping out upward from the plug placement hole 24. In this way, with the simple structure in which the outer edge of the top surface of the plug 50 is covered from above by the plug joint 60, it is possible to prevent the plug 50 from slipping out upward from the plug placement hole 24.

[0030] Furthermore, since the plug joint 60 is provided over the entire circumference of the plug 50, the joint strength of the plug joint 60 is increased.

[0031] Furthermore, the plug joint portion 60 is a sprayed portion provided so as to fill the groove 70 formed by the plug inclined surface 50 c and the arrangement hole inclined surface 24 c. Therefore, the plug joint portion 60 can be formed relatively easily by spraying.

[0032] Second Embodiment A wafer mounting table 110 according to a second embodiment will be described with reference to the drawings. Fig. 5 is an enlarged vertical cross-sectional view of the wafer mounting table 110 equipped with a plug bonding portion 160, Fig. 6 is a plan view of the periphery of the plug 160, and Fig. 7 is a diagram (part) showing the manufacturing process of the wafer mounting table 110. Note that in Figs. 5 to 7, the same components of the wafer mounting table 110 as those of the wafer mounting table 10 are designated by the same reference numerals, and their description will be omitted.

[0033] The wafer mounting table 110 includes a ceramic plate 20 , a plug placement hole 24 , a base plate (conductive plate) 30 , a metal bonding layer 40 , a plug 50 , and a plug bonding portion 160 .

[0034] The plug joint portion 160 is a laser welded portion formed by laser welding the outer edge of the top surface of the plug 50 to the upper opening edge of the plug positioning hole 24. The plug joint portion 160 has an inverted triangular shape when viewed in vertical cross section, and the bottom of the plug joint portion 160 is located at the boundary between the plug 50 and the plug positioning hole 24. The plug joint portion 160 joins the outer edge of the top surface of the plug 50 to the upper opening edge of the plug positioning hole 24, and is provided so as to cover the outer edge of the top surface of the plug 50 and the upper opening edge of the plug positioning hole 24 from above. The plug joint portion 160 is provided around the entire outer edge of the top surface of the plug 50.

[0035] The use of the wafer stage 110 is similar to that of the wafer stage 10, and therefore a description thereof will be omitted.

[0036] The following describes the differences between the manufacturing example of the wafer mounting table 110 and the manufacturing example of the wafer mounting table 10. When manufacturing the wafer mounting table 10, the upper opening edge of the plug placement hole 24 was C-chamfered to form the placement hole inclined surface 24c, and the upper surface outer edge of the plug 50 was C-chamfered to form the plug inclined surface 50c. However, when manufacturing the wafer mounting table 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 come into contact with each other ( FIG. 7A ). In this state, a laser (e.g., a nanosecond laser, a picosecond laser, a femtosecond laser, or the like) is irradiated to the boundary between the upper opening edge of the plug placement hole 24 and the upper surface outer edge of the plug 50 to locally raise the temperature. This welds the upper opening edge of the plug placement hole 24 and the upper surface outer edge of the plug 50, forming a laser weld. Due to the characteristics of laser welding, the width (diameter) of the cross section of the laser weld decreases from top to bottom. The raised portion of the laser weld is flattened by grinding. This forms the plug joint 160 (FIG. 7B).

[0037] In the wafer mounting table 110 described above, the plug bonding portion 160 is provided so as to cover the outer edge of the upper surface of the plug 50 from above. The plug bonding portion 160 is provided so as to hook onto the upper outer edge of the plug 50, thereby preventing the plug 50 from slipping out upward from the plug placement hole 24. In this way, with the simple structure in which the outer edge of the upper surface of the plug 50 is covered from above with the plug bonding portion 160, it is possible to prevent the plug 50 from slipping out upward from the plug placement hole 24.

[0038] Furthermore, since the plug joint 160 is provided around the entire periphery of the upper surface of the plug 50, the joint strength of the plug joint 160 is increased.

[0039] Furthermore, the plug joint portion 160 is a laser welded portion formed by laser welding the boundary between the outer edge of the top surface of the plug 50 and the edge of the upper opening of the plug placement hole 24. Therefore, the plug joint portion 160 can be formed relatively easily by laser welding. When the plug joint portion 160 is formed by laser welding, there is no need to chamfer the outer edge of the top surface of the plug 50 or the edge of the upper opening of the plug placement hole 24 as in the first embodiment.

[0040] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0041] In the first and second embodiments described above, the plug 50 made of a porous material is exemplified as a plug that allows gas to flow in the vertical direction, but the present invention is not limited to this. For example, a dense plug having a flow path (e.g., a straight flow path or a spiral flow path) therein that allows gas to flow in the vertical direction may be used as such a plug.

[0042] In the first and second embodiments described above, the plug 50 has a truncated cone shape, but the plug is not limited to this. For example, a cylindrical plug may be used.

[0043] In the first and second embodiments described above, a stepped hole having a large diameter portion 34a above the gas hole 34 is used, but the present invention is not limited to this. For example, a straight hole may be used as the gas hole 34.

[0044] In the first and second embodiments described above, an electrostatic electrode is exemplified as the electrode 22 built into the ceramic plate 20, but this is not particularly limited. For example, instead of or in addition to the electrode 22, a heater electrode (resistive heating element) or an RF electrode may be built into the ceramic plate 20.

[0045] In the first and second embodiments described above, the ceramic plate 20 and the base plate 30 are joined together by the metal joining layer 40, but a resin adhesive layer may be used instead of the metal joining layer 40.

[0046] In the first embodiment described above, the base plate 30 is provided with gas holes 34 forming gas supply paths. However, this is not particularly limited. For example, as shown in FIG. 8 , the base plate 30 may be provided with a ring portion 64a that is concentric with the base plate 30 in a plan view, an inlet portion 64b that introduces gas from the back surface of the base plate 30 into the ring portion 64a, and a distributor portion 64c that distributes gas from the ring portion 64a to each plug 50. In FIG. 8 , the same components as those in the first embodiment described above are denoted by the same reference numerals. The number of inlet portions 64b may be less than the number of distributor portions 64c, for example, one. This allows the number of external gas pipes connected to the underside of the base plate 30 to be less than the number of plugs 50. Such a configuration may also be adopted in the second embodiment.

[0047] In the first embodiment described above, the outer edge of the top surface of the plug 50 and the upper opening edge of the plug positioning hole 24 are C-chamfered, but this is not limited to C-chamfering. For example, R-chamfering may be applied. In this case, each inclined surface 24c, 50c becomes a curved surface (convex surface). Furthermore, in the state before the plug joint portion 60 is formed ( FIG. 4C ), the outer edge of the top surface of the plug 50 and the upper opening edge of the plug positioning hole 24 form a groove 70 with a V-shaped cross section, but this is not particularly limited. For example, the outer edge of the top surface of the plug 50 and the upper opening edge of the plug positioning hole 24 may be machined so that they form a groove with a U-shaped cross section. In this case, the cross section of the plug joint portion 60 will be approximately rectangular.

[0048] In the first embodiment described above, the upper opening edge of the plug positioning hole 24 is chamfered along the entire periphery to form the positioning hole inclined surface 24c. However, the positioning hole inclined surface 24c may not be formed. An example of such a configuration is shown in FIG. 9 . In FIG. 9 , the same components as in the first embodiment are designated by the same reference numerals. The plug joint portion 260 in FIG. 9 is a sprayed portion that joins the plug inclined surface 50c provided on the outer edge of the upper surface of the plug 50 to the upper opening edge of the plug positioning hole 24, which does not have the positioning hole inclined surface 24. The plug joint portion 260 is also formed by spraying so as to cover the upper outer edge of the plug inclined surface 50c from above. This configuration also makes it possible to prevent the plug 50 from slipping out of the plug positioning hole 24 upward with a simple structure.

[0049] In the first embodiment described above, the plug inclined surface 50c is formed by chamfering the entire outer edge of the top surface of the plug 50. However, the plug inclined surface 50c may not be formed. An example of such a configuration is shown in FIG. 10 . In FIG. 10 , the same components as those in the first embodiment are denoted by the same reference numerals. The plug joint portion 360 in FIG. 10 is a sprayed portion that joins the outer edge of the top surface of the plug 50, which does not have the plug inclined surface 50c, to the arrangement hole inclined surface 24c provided on the upper opening edge of the plug arrangement hole 24. The plug joint portion 360 is also formed by spraying so as to cover the outer edge of the top surface of the plug 50 and the arrangement hole inclined surface 24c of the plug arrangement hole 24 from above. This configuration also makes it possible to prevent the plug 50 from slipping out upward from the plug arrangement hole 24 with a simple structure.

[0050] In the first embodiment described above, the plug joint 60 is formed by thermal spraying, but the method is not limited to thermal spraying. For example, the plug joint 60 may be formed by aerosol deposition. Alternatively, the plug joint 60 may be formed by filling ceramic powder into the V-shaped groove 70 shown in FIG. 4C and then locally heating it with a laser or the like to sinter the ceramic powder.

[0051] In the second embodiment described above, the plug joint 160 is provided around the entire periphery of the upper surface of the plug 50, but this is not particularly limited. For example, as shown in FIG. 11 , the plug joint 460 may be provided partially at two or more locations (eight locations in this example) along the circumferential direction of the upper surface of the plug 50. In FIG. 11 , the same components as in the second embodiment are denoted by the same reference numerals. In this manner, although the joint strength is lower than in the second embodiment, it is still strong enough for practical use. Furthermore, since fewer locations are irradiated with the laser than in the second embodiment, cracks are less likely to occur in the plug 50 or the ceramic plate 20. Furthermore, if the plug 50 needs to be replaced, the plug joint 460 is easier to remove because its length is shorter than in the second embodiment. When the old plug 50 is removed and a new plug 50 is placed in the plug placement hole 24 and laser-welded, as shown in FIG. 12 , a new plug joint 466 is formed by laser-welding a location 464 different from the previously laser-welded location 462 (shaded). This is because the previously laser-welded portion 462 cannot be laser-welded again. If it is desired to change the spark plug two or more times, it is sufficient to leave portions that can be laser-welded according to the number of times.

[0052] The plug joint 60 of the first embodiment described above may also be provided partially at two or more locations, similar to the plug joint 460 of FIG. 11 . In this case, although the joint strength is lower than that of the first embodiment, sufficient strength can be obtained at a practical level. Furthermore, since fewer locations are sprayed than in the first embodiment, cracks are less likely to occur in the plug 50 or the ceramic plate 20, and when the plug 50 needs to be replaced, the sprayed portion is easy to remove because the length of the sprayed portion is short. However, in the case of spraying, it is possible to spray again even on locations that were previously sprayed. Therefore, even when the plug joint 60 is provided along the entire circumference of the outer edge of the top surface of the plug 50 as in the first embodiment, it is possible to spray again along the entire circumference of the outer edge of the top surface of the replaced plug 50 and the upper opening edge of the plug placement hole 24.

[0053] In the second embodiment described above, the bottom 160a of the plug joint 160, which is a laser welded portion and has an inverted triangular cross section, is located at the boundary between the plug 50 and the plug placement hole 24. However, this is not particularly limited. For example, as in the plug joint 560 shown in FIG. 13 , the bottom 560a of the plug joint 560 may be located on the plug 50 side. In FIG. 13 , the same components as in the second embodiment are denoted by the same reference numerals. 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, cracks are unlikely to occur in the ceramic plate 20. If a crack occurs in the ceramic plate 20, the crack may cause communication between the plug placement hole 24 and the electrode 22, which can easily cause problems. However, adopting the configuration of FIG. 13 can prevent such problems from occurring.

[0054] In the first and second embodiments described above, the outer peripheral surface of the plug 50 may be brought into close contact with the inner peripheral surface of the plug placement hole 24. This has the effect of suppressing discharge between the outer peripheral surface of the plug 50 and the inner peripheral surface of the plug placement hole 24 when plasma is generated.

[0055] The present invention can be used for wafer mounting tables used in semiconductor manufacturing equipment, such as ceramic heaters, electrostatic chuck heaters, and electrostatic chucks.

[0056] 10 wafer mounting table, 20 ceramic plate, 21 wafer mounting surface, 21a seal band, 21b small circular protrusion, 21c reference surface, 22 electrode, 24 plug placement hole, 24c placement hole inclined surface, 30 base plate, 32 coolant 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 introduction portion, 64c distribution portion, 90 metal bonding material, 92 through hole, 94 bonded body, 110, 210 wafer mounting table, 60, 160, 260, 360, 460, 466, 560 plug bonding portion, 160a, 560a bottom, W wafer.

Claims

1. a ceramic plate having a wafer mounting surface on an upper surface thereof and incorporating an electrode; a plug placement hole extending from the lower surface to the upper surface of the ceramic plate; a plug disposed in the plug placement hole and allowing gas to pass therethrough; a plug joint portion that joins an outer edge of an upper surface of the plug and an edge of an upper opening of the plug placement hole and is provided so as to cover the outer edge of the upper surface of the plug from above; Equipped with The plug arrangement hole is a tapered hole having a truncated cone space in which the area of ​​an upper opening is larger than the area of ​​a lower opening, The plug is a truncated cone-shaped member having an upper surface area larger than a lower surface area. Wafer placement stage.

2. The plug joint portion is provided around the entire periphery of the upper surface of the plug. The wafer stage according to claim 1 .

3. the plug joint portion is present at two or more locations along the circumferential direction of the outer edge of the upper surface of the plug; The wafer stage according to claim 1 .

4. The plug has an inclined plug surface on an outer edge of an upper surface thereof, The plug arrangement hole has an inclined surface on an upper opening edge thereof, The plug joint portion is a sprayed portion provided so as to fill a groove formed by the plug inclined surface and the arrangement hole inclined surface. The wafer mounting table according to any one of claims 1 to 3.

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

6. The laser weld has a shape of an inverted triangle when viewed in vertical cross section, and the bottom of the laser weld is located on the plug side. The wafer stage according to claim 5 .

7. The wafer mounting table according to any one of claims 1 to 3, a conductive plate joined to the lower surface of the ceramic plate and provided with a gas supply passage communicating with the plug placement hole; A wafer mounting table comprising: