Wafer mounting stage

Abstract

To fasten a wafer mount table including a fragile cooling base material onto an installation board without a trouble.SOLUTION: A wafer mount table 10 includes an alumina base material 20, a cooling base material 30, and an extendable female screw member 38. The alumina base material 20 includes a wafer mount surface 22a on an upper surface thereof, and incorporates an electrode 26. The cooling base material 30 is bonded to a lower surface of the alumina base material 20 and has a coolant passage 32 formed internally. The female screw member 38 is housed in a housing hole 36 that opens at a lower surface of the cooling base material 30 in a state in which the axial rotation is restricted and in a state of being engaged with an engagement part of the housing hole 36. The female screw member 38 can be screwed with a male screw of a bolt 98 inserted from a lower surface side of the cooling base material 30.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a wafer mounting table.

Background Art

[0002] Conventionally, a wafer mounting table in which a ceramic substrate incorporating electrodes and a cooling substrate having a refrigerant flow path formed therein are joined via an adhesive is known. Patent Document 1 describes an example in which such a wafer mounting table is placed on an installation plate and fixed with screws. Specifically, female screw holes are provided on the lower surface of the cooling substrate, and male screws of bolts inserted from below into screw insertion holes penetrating the installation plate in the vertical direction are screwed into the female screw holes.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when a female screw hole is provided on the lower surface of the cooling substrate and the male screw of the bolt inserted through the installation plate is screwed, there is no problem if the material of the cooling substrate is a ductile material (e.g., aluminum), but there is a problem if it is a brittle material (e.g., metal matrix composite material). Specifically, since the female screw hole of the cooling substrate is locally pulled downward by a large force by the bolt, there is a risk of cracking if the material has no ductility.

[0005] The present invention has been made to solve such problems, and the main object is to enable a wafer mounting table having a brittle cooling substrate to be fastened to an installation plate without any trouble.

Means for Solving the Problems

[0006] [1] The wafer mounting table of the present invention It has a wafer placement surface on the top, an alumina substrate with built-in electrodes, and a brittle cooling substrate joined to the lower surface of the alumina substrate, and a ductile coupling member having a male screw portion or a female screw portion, which is housed in a storage hole opening on the lower surface of the cooling substrate in a state where its axial rotation is restricted and engaged with an engaging portion of the storage hole. It is equipped with the above.

[0007] In this wafer placement table, the coupling member having a male screw portion or a female screw portion is housed in a storage hole opening on the lower surface of the cooling substrate in a state where its axial rotation is restricted and engaged with an engaging portion of the storage hole. Since the axial rotation of the coupling member is restricted, it can be screwed into a coupled member having a female screw portion or a male screw portion disposed on the lower surface side of the cooling substrate. Further, even if the coupling member is pulled toward the installation plate by a coupled member provided on the installation plate in a state of being engaged with the engaging portion of the storage hole, it has ductility and is difficult to break. Therefore, the wafer placement table provided with a brittle cooling substrate can be fastened to the installation plate without any trouble.

[0008] In this specification, the present invention may be described using up and down, left and right, front and back, etc. However, up and down, left and right, front and back are merely relative positional relationships. Therefore, when the orientation of the wafer placement table is changed, up and down may become left and right or left and right may become up and down, but such cases are also included in the technical scope of the present invention.

[0009] [2] In the above-described wafer placement table (the wafer placement table described in [1] above), the coupling member may be a member that can be screwed with a male screw of a bolt inserted from the lower surface side of the cooling substrate and has the female screw portion.

[0010] [3] In the above-described wafer stage (the wafer stage described in [1] or [2] above), the cooling base material may be formed of a composite material of metal and ceramic or an alumina material. Since the composite material of metal and ceramic and the alumina material are brittle materials, the significance of applying the present invention is high. For example, when using a composite material of metal and ceramic, it is preferable to use a composite material having a thermal expansion coefficient equivalent to that of alumina.

[0011] [4] In the above-described wafer stage (the wafer stage described in any one of [1] to [3] above), the engaging portion may be a stepped portion or an inclined portion provided on the inner peripheral surface of the storage hole, and the coupling member may have an engaged portion that engages with the engaging portion so that the coupling member does not fall out of the storage hole. In this way, the engaging portion and the engaged portion can be manufactured relatively easily. For example, when the engaging portion is a stepped portion, the coupling member may be provided with an engaged portion that catches on the stepped portion. Also, when the engaging portion is an inclined portion, the coupling member may be provided with an inclined surface that matches the inclined portion as the engaged portion.

[0012] [5] In the above-described wafer stage (the wafer stage described in any one of [1] to [4] above), the coupling member may be configured such that when it attempts to rotate about an axis, it hits the wall of the storage hole and the axis rotation is restricted. In this way, the axis rotation of the coupling member can be restricted with a relatively simple configuration.

[0013] [6] In the above-described wafer stage (the wafer stage described in any one of [1] to [5] above), the cooling base material has a refrigerant flow path inside, and the storage hole may be provided in a region of the cooling base material that is lower than the bottom surface of the refrigerant flow path. In this way, since the storage hole does not interfere with the refrigerant flow path, the degree of freedom in the design of the refrigerant flow path is not impaired.

[0014] [7] In the above-described wafer mounting table (the wafer mounting table according to any one of [1] to [6] above), the coupling member may be stored in a free state without being joined to the cooling base material in the storage hole. In this way, since it is only necessary to put the coupling member into the storage hole, it is not troublesome.

[0015] [8] In the above-described wafer mounting table (the wafer mounting table according to any one of [1] to [7] above), the coupling member may be engaged with the engaging portion via a stress buffer member having a lower Young's modulus than the coupling member. In this way, even if the coupling member is pulled toward the installation plate by the member to be coupled provided on the installation plate, since the stress buffer member is interposed between the coupling member and the engaging portion, the stress is easily dispersed.

[0016] [9] In the above-described wafer mounting table (the wafer mounting table according to any one of [1] to [8] above), the gap between the coupling member and the storage hole may be filled with a filler. In this way, compared with the case where the gap between the coupling member and the storage hole forms a space, the heat conduction becomes better. Therefore, the heat uniformity of the wafer is improved.

[0017]

[10] In the above-described wafer mounting table (the wafer mounting table according to any one of [1] to [9] above), the storage hole may include a first storage portion for storing the coupling member and a second storage portion provided so as to reach the lower surface of the cooling base material from the first storage portion, and the engaging portion may be a stepped surface provided at the joint between the first storage portion and the second storage portion.

[0018]

[11] In the above-described wafer mounting table (the wafer mounting table according to

[10] above), the first storage portion may open to the upper surface of the cooling base material, and the AluminaThe opening surface may be covered by a bonding layer that bonds the base material and the cooling base material. In this way, the first storage portion can be manufactured relatively easily compared to the case where the first storage portion is built inside the cooling base material. In such a structure, since it is necessary to provide a refrigerant flow path (or a refrigerant flow path groove) avoiding the storage hole, the heat uniformity in the vicinity directly above the storage hole in the wafer tends to decrease. To suppress such a decrease in heat uniformity, it is preferable to fill the gap between the coupling member and the storage hole with a filler. In this way, since the heat conduction around the storage hole becomes good, a decrease in heat uniformity can be suppressed.

[0019]

[12] In the wafer mounting table described above (the wafer mounting table according to

[10] or

[11] ), the width of the annular region where the stepped surface and the coupling member are in direct or indirect contact is preferably 3 mm or more. If the width of such an annular region is 3 mm or more, even if the coupling member is pulled toward the installation plate by the member to be coupled provided on the installation plate, since the annular region where the stepped surface and the coupling member are in direct or indirect contact is wide, the stress is likely to be dispersed.

Brief Description of the Drawings

[0020]

Figure 1

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Mode for Carrying Out the Invention

[0021] [First Embodiment] Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a vertical cross-sectional view of the wafer stage 10 installed in the chamber 94 (a cross-sectional view when cut along a plane including the central axis of the wafer stage 10), FIG. 2 is a plan view of the wafer stage 10, FIG. 3 is an enlarged cross-sectional view showing the periphery of the storage hole 36 and the female screw member 38, and FIG. 4 is a cross-sectional view seen from above of the cross-section when the cooling base material 30 is horizontally cut along the ceiling surface of the storage hole 36.

[0022] The wafer stage 10 is used for performing CVD, etching, etc. on the wafer W using plasma, and is fixed to the installation plate 96 provided inside the chamber 94 for semiconductor processes. The wafer stage 10 includes an alumina base material 20, a cooling base material 30, and a metal bonding layer 40.

[0023] The alumina base material 20 includes an outer peripheral portion 24 having an annular focus ring mounting surface 24a on the outer periphery of a central portion 22 having a circular wafer mounting surface 22a. Hereinafter, the focus ring may be abbreviated as "FR". The wafer W is placed on the wafer mounting surface 22a, and the focus ring 78 is placed on the FR mounting surface 24a. The FR mounting surface 24a is one step lower than the wafer mounting surface 22a.

[0024] In the central portion 22 of the alumina substrate 20, an electrostatic chucking electrode 26 for wafer adsorption is incorporated on the side closer to the wafer mounting surface 22a. The electrostatic chucking electrode 26 for wafer adsorption is formed of a material containing, for example, W, Mo, WC, MoC, or the like. The electrostatic chucking electrode 26 for wafer adsorption is a disk-shaped or mesh-shaped single-pole type electrostatic chucking electrode. The layer above the electrostatic chucking electrode 26 in the alumina substrate 20 functions as a dielectric layer. The electrostatic chucking electrode 26 for wafer adsorption is connected to a DC power supply 52 for wafer adsorption via a power supply terminal 54. The power supply terminal 54 passes through an insulating tube 55 disposed in a through hole penetrating the cooling substrate 30 and the metal bonding layer 40 in the vertical direction, and is provided so as to reach the electrostatic chucking electrode 26 for wafer adsorption from the lower surface of the alumina substrate 20. A low-pass filter (LPF) 53 is provided between the DC power supply 52 for wafer adsorption and the electrostatic chucking electrode 26 for wafer adsorption.

[0025] The cooling base material 30 is a disc member. As the material of the cooling base material 30, a composite material of metal and ceramic or the like is preferable. Examples of such composite materials include metal matrix composites (also referred to as metal matrix composites (MMC)) and ceramic matrix composites (also referred to as ceramic matrix composites (CMC)). Such composite materials are a kind of brittle material. The cooling base material 30 is provided with a refrigerant flow path 32 through which a refrigerant can circulate inside. This refrigerant flow path 32 is connected to a refrigerant supply path and a refrigerant discharge path (not shown), and the refrigerant discharged from the refrigerant discharge path is temperature-adjusted and then returned to the refrigerant supply path again. The refrigerant flowing through the refrigerant flow path 32 is preferably a liquid and preferably has electrical insulation. Examples of the electrically insulating liquid include fluorine-based inert liquids. Examples of the composite material of metal and ceramic include materials containing Si, SiC, and Ti, materials obtained by impregnating a SiC porous body with Al and / or Si, and composite materials of Al2O3 and TiC. A material containing Si, SiC, and Ti is called SiSiCTi, a material obtained by impregnating a SiC porous body with Al is called AlSiC, and a material obtained by impregnating a SiC porous body with Si is called SiSiC. As the composite material used for the cooling base material 30, AlSiC, SiSiCTi, etc. having a coefficient of thermal expansion close to that of alumina are preferable. The cooling base material 30 is connected to the RF power supply 62 via a power supply terminal 64. A high-pass filter (HPF) 63 is disposed between the cooling base material 30 and the RF power supply 62. The cooling base material 30 has a flange portion 34 used to clamp the wafer mounting table 10 to the installation plate 96 on the lower surface side.

[0026] The cooling base material 30 is provided with a plurality of storage holes 36, and a female screw member 38 (coupling member) is stored in the storage holes 36. The plurality of storage holes 36 are provided in a region of the cooling base material 30 that is lower than the bottom surface 32a of the refrigerant flow path 32. The plurality of storage holes 36 are provided at equal intervals along a concentric circle of the cooling base material 30 (for example, a circle with a diameter of 1 / 2 or 1 / 3 of the diameter of the wafer W) (for example, 6 or 8). That is, as shown in FIG. 2, the plurality of storage holes 36 are provided in a region close to the center of the wafer mounting table 10. The storage hole 36 opens to the lower surface of the cooling base material 30 as shown in FIG. 3. The storage hole 36 includes a first storage portion 36a, a second storage portion 36b, and a step portion 36c. The first storage portion 36a is a rectangular parallelepiped-shaped space provided in the upper part of the storage hole 36. The second storage portion 36b is a cylindrical space provided in the lower part of the storage hole 36. The step portion 36c is a connecting portion between the first storage portion 36a and the second storage portion 36b. A female screw member 38 is stored in the storage hole 36. The female screw member 38 has a rectangular parallelepiped-shaped head 38a and a cylindrical portion 38b provided on the lower surface of the head 38a, and a screw is cut on the inner peripheral surface of the cylindrical portion 38b. The head 38a of the female screw member 38 is stored in the first storage portion 36a of the storage hole 36. Since the lower surface of the head 38a of the female screw member 38 is engaged with the step portion 36c of the storage hole 36, the female screw member 38 does not fall from the storage hole 36. The cylindrical portion 38b of the female screw member 38 is stored in the second storage portion 36b of the storage hole 36. When the female screw member 38 tries to rotate about its axis, as shown in FIG. 4, the head 38a hits the side wall of the first storage portion 36a and the rotation about the axis is restricted. The female screw member 38 is formed of a ductile material (for example, Ti, Mo, W, etc.).

[0027] The metal bonding layer 40 bonds the lower surface of the alumina base material 20 and the upper surface of the cooling base material 30. The metal bonding layer 40 may be, for example, a layer formed of solder or a metal brazing material. The metal bonding layer 40 is formed, for example, by TCB (Thermal compression bonding). TCB refers to a known method in which a metal bonding material is sandwiched between two members to be joined, and the two members are pressure-bonded in a state where they are heated to a temperature below the solidus temperature of the metal bonding material.

[0028] The side surface of the outer peripheral portion 24 of the alumina substrate 20, the outer periphery of the metal bonding layer 40, and the side surface of the cooling substrate 30 are covered with an insulating film 42. Examples of the insulating film 42 include a sprayed film such as alumina or yttria.

[0029] Such a wafer mounting table 10 is attached via a seal ring 76 on an installation plate 96 provided inside the chamber 94. The seal ring 76 is made of metal or resin and has an outer diameter slightly smaller than the outer diameter of the cooling substrate 30. The outer peripheral region of the wafer mounting table 10 is attached to the installation plate 96 using a clamp member 70. The clamp member 70 is an annular member having a substantially inverted L-shaped cross section and has an inner peripheral stepped surface 70a. With the inner peripheral stepped surface 70a of the clamp member 70 placed on the flange portion 34 of the cooling substrate 30 of the wafer mounting table 10, bolts 72 are inserted from the upper surface of the clamp member 70 and screwed into screw holes provided on the upper surface of the installation plate 96. The bolts 72 are attached at a plurality of locations (for example, 8 locations or 12 locations) provided at equal intervals along the circumferential direction of the clamp member 70. The clamp member 70 and the bolts 72 may be made of an insulating material or a conductive material (such as metal). Also, the central region of the wafer mounting table 10 is attached to the installation plate 96 using a bolt 98 (member to be joined). As shown in FIG. 3, a male screw 98a is provided on the leg portion of the bolt 98. The bolt 98 is inserted from the lower surface of the installation plate 96 into a through hole 97 provided at a position facing the storage hole 36 in the installation plate 96, and the male screw 98a is screwed into a female screw member 38 in the storage hole 36. The through hole 97 has a small diameter at the upper part and a large diameter at the lower part, and has a stepped portion 97a between the upper part and the lower part. The head of the bolt 98 is caught by the stepped portion 97a of the through hole 97. Since the female screw member 38 is stored in the first storage portion 36a of the storage hole 36 in a state where its axial rotation is restricted, the bolt 98 can be screwed into the female screw member 38. When the bolt 98 is screwed into the female screw member 38, the female screw member 38 is in a state of being pulled toward the installation plate 96 with its head 38a engaged with the stepped portion 36c of the storage hole 36.

[0030] When the wafer stage 10 is in use, since the wafer placement surface 22a side of the alumina base material 20 is in a vacuum and the lower surface side of the cooling base material 30 is in the atmosphere, the wafer stage 10 tends to bulge upward. Also, when processing the wafer W with high-power plasma, since the wafer placement surface 22a side of the alumina base material 20 is at a high temperature and the lower surface side is cooled to a low temperature, the wafer placement surface 22a side is more likely to expand, and the wafer stage 10 tends to bulge upward. However, in the present embodiment, since the central region of the wafer stage 10 is fixed by the bolt 98, it is possible to prevent the wafer stage 10 from bulging upward. Further, even if a seal ring (not shown) is disposed between the central region of the lower surface of the cooling base material 30 and the upper surface of the installation plate 96, since the central region of the wafer stage 10 is fixed by the bolt 98, the seal ring is maintained in a firmly crushed state.

[0031] For example, as shown in FIG. 5, assume that the refrigerant supply path 321 is composed of a first supply path 32p passing through the installation plate 96, the inside of a refrigerant supply seal ring 32q disposed between the installation plate 96 and the cooling base material 30, and a second supply path 32r leading from the lower surface of the cooling base material 30 to the refrigerant flow path 32. Assume that the refrigerant discharge path 322 is composed of a first discharge path 32s leading from the refrigerant flow path 32 to the lower surface of the cooling base material 30, the inside of a refrigerant discharge seal ring 32t disposed between the cooling base material 30 and the installation plate 96, and a second discharge path 32u passing through the installation plate 96 and leading to the lower surface of the installation plate 96. In this case, since the central region of the wafer stage 10 is fixed by screwing the female screw member 38 in the storage hole 36 and the bolt 98, these seal rings 32q, 32t are maintained in a firmly crushed state. Therefore, the seal rings 32q, 32t can sufficiently ensure the sealing performance.

[0032] Next, a manufacturing example of the wafer stage 10 will be described with reference to FIG. 6. FIG. 6 is a manufacturing process diagram of the wafer stage 10. First, a disk-shaped alumina sintered body 120 that serves as the base material of the alumina substrate 20 is produced by hot press sintering a molded body of alumina powder (FIG. 6A). The alumina sintered body 120 incorporates the wafer adsorption electrode 26. Next, a hole 27 is drilled from the lower surface of the alumina sintered body 120 to the wafer adsorption electrode 26 (FIG. 6B), and a power supply terminal 54 is inserted into the hole 27 to join the power supply terminal 54 and the wafer adsorption electrode 26 (FIG. 6C).

[0033] In parallel with this, three MMC disk members 131, 133, and 135 are produced (FIG. 6D). Then, a groove 132 that will ultimately become the refrigerant flow path 32 is formed on the lower surface of the upper MMC disk member 131, a stepped hole 136 that will ultimately become the storage hole 36 is formed in the lower MMC disk member 135, and further, through holes that penetrate in the vertical direction are formed in the three MMC disk members 131, 133, and 135 (FIG. 6E). These through holes will ultimately become the holes through which the power supply terminal 54 is inserted. When the alumina sintered body 120 is made of alumina, the MMC disk members 131, 133, and 135 are preferably made of SiSiCTi or AlSiC. This is because the thermal expansion coefficient of alumina and the thermal expansion coefficients of SiSiCTi and AlSiC are generally the same.

[0034] The SiSiCTi disk member can be produced, for example, as follows. First, silicon carbide, metallic Si, and metallic Ti are mixed to produce a powder mixture. Next, the obtained powder mixture is formed into a disk-shaped molded body by uniaxial pressure molding, and the molded body is hot press sintered in an inert atmosphere to obtain a SiSiCTi disk member.

[0035] Next, the female screw member 38 is housed in the stepped hole 136 of the lower MMC disc member 135. Then, a metal bonding material is disposed between the lower surface of the upper MMC disc member 131 and the upper surface of the middle MMC disc member 133, a metal bonding material is disposed between the lower surface of the middle MMC disc member 133 and the upper surface of the lower MMC disc member 135, and a metal bonding material is further disposed on the upper surface of the upper MMC disc member 131. Each metal bonding material is provided with a through hole at a position through which the power supply terminal 54 is inserted. Next, the power supply terminal 54 of the alumina sintered body 120 is inserted into the through holes of the MMC disc members 131, 133, and 135, and the alumina sintered body 120 is placed on the metal bonding material disposed on the upper surface of the upper MMC disc member 131. Thereby, a laminate in which the MMC disc member 135, the metal bonding material, the MMC disc member 133, the metal bonding material, the MMC disc member 131, the metal bonding material, and the alumina sintered body 120 are laminated in order from the bottom is obtained. By heating and pressing this laminate (TCB), the joined body 110 is obtained (FIG. 6F). The joined body 110 is one in which the alumina sintered body 120 is joined to the upper surface of the MMC block 130 that becomes the cooling base material 30 via the metal bonding layer 40. The MMC block 130 is one in which the upper MMC disc member 131 and the middle MMC disc member 133 are joined via a metal bonding layer, and the middle MMC disc member 133 and the lower MMC disc member 135 are joined via a metal bonding layer. The MMC block 130 has a refrigerant flow path 32 and a storage hole 36 inside. Further, the female screw member 38 is stored in the storage hole 36.

[0036] TCB is performed, for example, as follows. That is, the laminate is pressed and joined at a temperature equal to or lower than the solidus temperature of the metal bonding material (for example, a temperature equal to or higher than the temperature obtained by subtracting 20°C from the solidus temperature and equal to or lower than the solidus temperature), and then returned to room temperature. Thereby, the metal bonding material becomes a metal bonding layer. As the metal bonding material at this time, an Al-Mg based bonding material or an Al-Si-Mg based bonding material can be used. For example, when performing TCB using an Al-Si-Mg based bonding material, the laminate is pressed in a heated state under a vacuum atmosphere. It is preferable to use a metal bonding material having a thickness of around 100 μm.

[0037] Subsequently, by cutting the outer periphery of the alumina sintered body 120 to form a step, an alumina substrate 20 having a central portion 22 and an outer peripheral portion 24 is obtained. Also, by cutting the outer periphery of the MMC block 130 to form a step, a cooling substrate 30 having a flange portion 34 is obtained. Further, an insulating tube 55 is disposed in the insertion holes of the power supply terminals 54 provided in the MMC block 130 and the metal bonding layer 40. Furthermore, an insulating film 42 is formed by spraying alumina powder on the side surface of the outer peripheral portion 24 of the alumina substrate 20, around the metal bonding layer 40, and the side surface of the cooling substrate 30 (FIG. 6G). Thereby, the wafer mounting stage 10 is obtained.

[0038] Note that although the cooling substrate 30 in FIG. 1 is described as an integral part, it may have a structure in which three members are joined by a metal bonding layer as shown in FIG. 6G, or a structure in which two or four or more members are joined by a metal bonding layer.

[0039] Next, a usage example of the wafer mounting stage 10 will be described with reference to FIG. 1. As described above, the outer peripheral region of the wafer mounting stage 10 is fixed by the clamp member 70, and the central region of the wafer mounting stage 10 is fixed by the bolt 98 on the installation plate 96 of the chamber 94. A shower head 95 for discharging process gas from a large number of gas injection holes into the chamber 94 is disposed on the ceiling surface of the chamber 94. The installation plate 96 is formed of an insulating material such as alumina, for example.

[0040] On the FR placement surface 24a of the wafer placement table 10, a focus ring 78 is placed, and on the wafer placement surface 22a, a disk-shaped wafer W is placed. The focus ring 78 has a step along the inner circumference of the upper end so as not to interfere with the wafer W. In this state, a DC voltage of the wafer adsorption DC power supply 52 is applied to the wafer adsorption electrode 26 to adsorb the wafer W to the wafer placement surface 22a. Then, the inside of the chamber 94 is set to a predetermined vacuum atmosphere (or reduced pressure atmosphere), and while supplying a process gas from the shower head 95, an RF voltage from the RF power supply 62 is applied to the cooling base material 30. Then, plasma is generated between the wafer W and the shower head 95. Then, CVD film formation or etching is performed on the wafer W using the plasma. Although the focus ring 78 is also consumed as the wafer W is plasma-processed, since the focus ring 78 is thicker than the wafer W, the replacement of the focus ring 78 is performed after processing a plurality of wafers W.

[0041] When processing the wafer W with high-power plasma, it is necessary to efficiently cool the wafer W. In the wafer placement table 10, as a bonding layer between the alumina base material 20 and the cooling base material 30, a metal bonding layer 40 having a high thermal conductivity is used instead of a resin layer having a low thermal conductivity. Therefore, the ability to draw heat from the wafer W (heat extraction ability) is high. Further, since the thermal expansion difference between the alumina base material 20 and the cooling base material 30 is small, even if the stress relaxation property of the metal bonding layer 40 is low, problems are less likely to occur.

[0042] In the wafer mounting table 10 described above, the female screw member 38 is housed in the storage hole 36 that opens to the lower surface of the cooling base material 30 in a state where its axial rotation is restricted and so as not to fall out of the storage hole 36, and is engaged with the stepped portion 36c (engaging portion) of the storage hole 36. Since the axial rotation of the female screw member 38 is restricted, the male screw 98a of the bolt 98 inserted from the lower surface side of the cooling base material 30 can be screwed into the female screw member 38. Further, even if the female screw member 38 is pulled toward the installation plate 96 by the bolt 98 inserted through the installation plate 96 while being engaged with the stepped portion 36c of the storage hole 36, it has ductility and is less likely to crack. Therefore, the wafer mounting table 10 having the brittle cooling base material 30 can be fastened to the installation plate 96 without any trouble.

[0043] Further, the cooling base material 30 is formed of MMC. Since MMC is a brittle material, the significance of applying the present invention is high.

[0044] Furthermore, the storage hole 36 includes a stepped portion 36c as an engaging portion, and the female screw member 38 includes a head portion 38a as an engaged portion. Therefore, the engaging portion and the engaged portion can be manufactured relatively easily.

[0045] Furthermore, when the female screw member 38 attempts to rotate axially, it hits the side wall of the first storage portion 36a of the storage hole 36 and its axial rotation is restricted. Therefore, the axial rotation of the female screw member 38 can be restricted with a relatively simple configuration.

[0046] And the storage hole 36 is provided in a region of the cooling base material 30 that is lower than the bottom surface 32a of the refrigerant flow path 32. Therefore, the storage hole 36 does not interfere with the refrigerant flow path 32. Accordingly, the degree of freedom in the design of the refrigerant flow path 32 is not impaired.

[0047] Also, the female screw member 38 is not joined to the cooling base material 30 in the storage hole 36 and is stored in a free state. When manufacturing the wafer mounting table 10, it is only necessary to put the female screw member 38 into the storage hole 36, so it is not troublesome.

[0048] Note that the present invention is not limited to the above-described embodiments, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

[0049] In the above-described first embodiment, the storage hole 36 is provided in a region of the cooling base material 30 that is lower than the bottom surface 32a of the refrigerant flow path 32, but it is not limited thereto. For example, as shown in FIG. 7, the ceiling surface 36d of the storage hole 36 may be provided so as to be higher than the bottom surface 32a of the refrigerant flow path 32. In FIG. 7, the same reference numerals are given to the same components as those in the above-described first embodiment. In FIG. 7, the first storage portion 36a of the storage hole 36 has the same size as that in the above-described first embodiment, but the vertical length of the second storage portion 36b is longer than that in the above-described first embodiment. Further, the head 38a of the female screw member 38 has the same size as that in the above-described first embodiment, but the vertical length of the cylindrical portion 38b is longer than that in the above-described first embodiment. Even in this case, substantially the same effects as those in the above-described first embodiment can be obtained. However, the degree of freedom in the design of the refrigerant flow path 32 is limited as compared with the above-described first embodiment.

[0050] In the above-described first embodiment, the step portion 36c is provided on the inner peripheral surface of the storage hole 36, but it is not limited thereto. For example, as shown in FIG. 8, the opposing side surfaces of the head 38a of the female screw member 38 may be inclined surfaces 38c, and an inclined portion 36e that coincides with the inclined surface 38c may be provided on the inner peripheral surface of the storage hole 36. In this case, since the inclined surface 38c of the female screw member 38 engages with the inclined portion 36e of the storage hole 36, the female screw member 38 does not fall out of the storage hole 36. Further, when the bolt 98 is screwed into the female screw member 38, the female screw member 38 is pulled toward the installation plate 96 in a state where the inclined surface 38c is engaged with the inclined portion 36e of the storage hole 36.

[0051] In the above-described first embodiment, the shape of the head 38a of the female screw member 38 is rectangular in plan view, but it is not particularly limited thereto. For example, the shape of the head 38a may be a polygon such as a triangle or a pentagon in plan view, a plus (+) shape, or an oval shape. The shape of the first storage portion 36a of the storage hole 36 may be such that the head 38a hits the side wall when the female screw member 38 tries to rotate axially. This also applies to the female screw member 538 of the second embodiment described later.

[0052] In the above-described first embodiment, the female screw member 38 is adopted as the coupling member and the bolt 98 is adopted as the coupled member. However, as shown in FIG. 9, a male screw member 80 may be adopted as the coupling member and a nut 82 may be adopted as the coupled member. In FIG. 9, the same components as those in the above-described first embodiment are denoted by the same reference numerals. The male screw member 80 is formed of a ductile material. The male screw member 80 has a head 80a having the same shape as the head 38a, a leg portion 80b provided at the center of the back surface of the head 80a, and a male screw portion 80c provided at the tip of the leg portion 80b. The head 80a is stored in the first storage Part portion 36a of the storage hole 36. The leg portion 80b is inserted through the second storage Part portion 36b and the through hole 97 of the installation plate 96. The male screw portion 80c is screwed into the nut 82. The nut 82 is adapted to be caught by the stepped portion 97a of the through hole 97. Since the lower surface of the head 80a of the male screw member 80 is engaged with the stepped portion 36c of the storage hole 36, the male screw member 80 does not fall from the storage hole 36. When the male screw member 80 tries to rotate axially, the head 80a hits the side wall of the first storage portion 36a and the axial rotation is restricted. Therefore, the nut 82 can be screwed onto the male screw portion 80c of the male screw member 80. When the nut 82 is screwed onto the male screw portion 80c of the male screw member 80, the male screw member 80 is pulled toward the installation plate 96 in a state where the head 80a is engaged with the stepped portion 36c of the storage hole 36. Even when the configuration of FIG. 9 is adopted, the same effects as those in the above-described first embodiment can be obtained. Also in the second embodiment described later, a male screw member may be adopted instead of the female screw member 538 as the coupling member, and a nut may be adopted instead of the bolt 98 as the coupled member.

[0053] In the above-described first embodiment, a hole may be provided that penetrates the wafer stage 10 from the lower surface of the cooling base 30 to the wafer placement surface 22a. Examples of such holes include a gas supply hole for supplying a heat-conducting gas (e.g., He gas) to the back surface of the wafer W, and a lift pin hole for inserting lift pins for moving the wafer W up and down with respect to the wafer placement surface 22a. The heat-conducting gas is supplied to the space formed by a number of small protrusions (supporting the wafer W), not shown, provided on the wafer placement surface 22a and the wafer W. The lift pin holes are provided at three locations when the wafer W is supported by, for example, three lift pins. A resin or metal seal ring (e.g., an O-ring) is disposed at a position facing these holes between the lower surface of the cooling base 30 and the upper surface of the installation plate 96. Since the central region of the wafer stage 10 is fixed by bolts 98, these seal rings are maintained in a well-crushed state. Therefore, these seal rings can sufficiently ensure the sealing property. This also applies to the second embodiment described later.

[0054] In the above-described first embodiment, the cooling base 30 is made of MMC, but it may be made of a brittle material other than MMC (e.g., an alumina material). This also applies to the cooling base 530 of the second embodiment described later.

[0055] In the above-described first embodiment, the wafer adsorption electrode 26 is incorporated in the central portion 22 of the alumina base 20. Instead of or in addition to this, an RF electrode for plasma generation may be incorporated, or a heater electrode (resistance heating element) may be incorporated. Further, an electrode for adsorbing a focus ring (FR) may be incorporated in the outer peripheral portion 24 of the alumina base 20, or an RF electrode or a heater electrode may be incorporated. This also applies to the second embodiment described later.

[0056] In the above-described first embodiment, the alumina sintered body 120 in FIG. 6A was produced by hot press sintering a molded body of alumina powder. At that time, the molded body may be produced by laminating a plurality of tape molded bodies, or may be produced by a mold casting method, or may be produced by compacting alumina powder. This also applies to the second embodiment described later.

[0057] In the above-described first embodiment, the alumina base material 20 and the cooling base material 30 were joined by the metal joining layer 40, but a resin joining layer may be used instead of the metal joining layer 40. This also applies to the second embodiment described later.

[0058] In the above-described first embodiment, a filler may be filled in the gap between the female screw member 38 and the first storage portion 36a of the storage hole 36. By doing so, heat conduction becomes better compared to the case where this gap is a space. Therefore, the heat uniformity of the wafer W is improved. Examples of the filler include adhesive resins, non-adhesive resins, and those obtained by adding thermally conductive powders (such as metal powders) to these resins. It is preferable to provide a through hole (a through hole extending from the internal space of the cylindrical portion 38b to the top surface of the head portion 38a) in the female screw member 38 that penetrates the female screw member 38 in the vertical direction. In this way, at the stage of FIG. 6F, the fluid filler can be easily injected into the gap between the female screw member 38 and the first storage portion 36a of the storage hole 36 through the through hole.

[0059] [Second Embodiment] FIG. 10 is a longitudinal sectional view of the wafer stage 510 installed in the chamber 94 (a sectional view when cut along a plane including the central axis of the wafer stage 510), and FIG. 11 is an enlarged sectional view showing the periphery of the storage hole 536 and the female screw member 538.

[0060] The wafer stage 510 is also used to perform CVD, etching, etc. on the wafer W using plasma, and is fixed to an installation plate 96 provided inside a chamber 94 for semiconductor processes. Since the chamber 94 has been described in the first embodiment, the same components are denoted by the same reference numerals and their description is omitted. The wafer stage 510 includes an alumina substrate 20, a cooling substrate 530, and a metal bonding layer 540.

[0061] Since the alumina substrate 20 has been described in the first embodiment, the same components are denoted by the same reference numerals and their description is omitted.

[0062] The cooling substrate 530 is a disk member and is formed of the same material as the cooling substrate 30. Here, the cooling substrate 530 is a disk member made of MMC. The cooling substrate 530 has a refrigerant flow path groove 582. The refrigerant flow path groove 582 is formed in one stroke from one end to the other end and is provided in the cooling substrate 530 so as to open to the lower surface of the cooling substrate 530. The opening of the refrigerant flow path groove 582 is blocked by the upper surface of the installation plate 96 of the chamber 94, thereby forming a refrigerant flow path 532. Therefore, the refrigerant flow path groove 582 constitutes the side wall and the ceiling surface of the refrigerant flow path 532. Similar to the refrigerant flow path 32 of the first embodiment described above, the refrigerant flow path 532 is connected to a refrigerant supply path and a refrigerant discharge path (not shown), and the refrigerant discharged from the refrigerant discharge path is temperature-adjusted and then returned to the refrigerant supply path again. The thickness of the cooling substrate 530 above the refrigerant flow path groove 582 is preferably 5 mm or less, and more preferably 3 mm or less. Also, the upper corner portion (the corner portion where the side wall and the ceiling surface intersect) of the refrigerant flow path groove 582 preferably has an R surface, and the radius of curvature of the R surface is preferably, for example, 0.5 to 2 mm. The cooling substrate 530 is connected to an RF power supply 62 via a power supply terminal 64. An HPF 63 is disposed between the cooling substrate 530 and the RF power supply 62. The cooling substrate 530 has a flange portion 534 used for clamping to the installation plate 96.

[0063] The cooling base material 530 is provided with a plurality of storage holes 536, and a female screw member 538 (coupling member) is stored in the storage holes 536. Similar to the storage holes 36 of the first embodiment, a plurality of the storage holes 536 are provided at equal intervals along the concentric circles of the cooling base material 530. As shown in FIG. 11, the storage hole 536 includes a first storage portion 536a, a second storage portion 536b, and a step portion 536c. The first storage portion 536a is a space provided at the upper part of the storage hole 536 and opens to the upper surface of the cooling base material 530. The opening surface (upper surface) of the first storage portion 536a is covered by a metal bonding layer 540. The second storage portion 536b is a passage provided thinner than the first storage portion 536a so as to reach the lower surface of the cooling base material 530 from the first storage portion 536a. The step portion 536c is a step surface provided at the joint between the first storage portion 536a and the second storage portion 536b. The female screw member 538 is stored in the first storage portion 536a. The female screw member 538 is a nut having a screw hole (female screw) in the center and having a rectangular parallelepiped shape (rectangular shape in plan view). The first storage portion 536a is also a space having a rectangular parallelepiped shape (substantially rectangular shape in plan view) and stores the female screw member 538 playfully. The gap between the female screw member 538 and the first storage portion 536a is filled with a filler 539. Specifically, the gap surrounded by the upper surface and side surfaces of the female screw member 538, the inner peripheral surface of the first storage portion 536a, and the metal bonding layer 540 is filled with the filler 539. Examples of the filler 539 include adhesive resins, non-adhesive resins, and those obtained by adding thermally conductive powders (such as metal powders) to these resins. The thermal conductivity of the filler 539 is preferably 1×10 -4 W / mm·K or more, more preferably 1×10 -3 W / mm·K or more, and 1×10 -2More preferably, it is above W / mm·K. The thermal conductivity of the filler 539 can be adjusted, for example, by the amount of the thermally conductive powder added to the resin. Considering injecting a fluid uncured filler into this gap, the width d of the gap between the female screw member 538 and the first storage portion 536a is preferably 0.2 mm or more. The stepped portion 536c is disposed below the ceiling surface of the refrigerant flow path groove 582. The female screw member 538 is engaged with the stepped portion 536c of the storage hole 536. When the female screw member 538 tries to rotate about its axis, it hits the side wall of the first storage portion 536a and the rotation about the axis is restricted. In this embodiment, since the filler 539 exists, the rotation of the female screw member 538 about its axis is also restricted by the filler 539. The female screw member 538 is formed of a ductile material (for example, Ti, Mo, W, etc.).

[0064] The metal bonding layer 540 bonds the lower surface of the alumina substrate 20 and the upper surface of the cooling substrate 530. Since the metal bonding layer 540 is the same as the metal bonding layer 40 of the first embodiment, the description thereof is omitted.

[0065] The side surface of the outer peripheral portion 24 of the alumina substrate 20, the outer periphery of the metal bonding layer 540, and the side surface of the cooling substrate 530 are covered with an insulating film 542. Examples of the insulating film 542 include a sprayed film such as alumina or yttria.

[0066] Such a wafer mounting stage 510 is attached onto an installation plate 96 provided inside the chamber 94 via a large-diameter seal ring 576 and small-diameter seal rings 577 to 579. The seal rings 576 to 579 are made of metal or resin. The seal ring 576 is disposed slightly inside the outer edge of the cooling substrate 530 to prevent the refrigerant from leaking outside the seal ring 576. The seal ring 577 is disposed so as to surround the periphery of the leg portion of the bolt 98 to prevent the refrigerant from entering inside the seal ring 577. The seal ring 578 is disposed at the opening edge of the insulating tube 55 to prevent the refrigerant from entering inside the seal ring 578. The seal ring 579 is disposed so as to surround the periphery of the power supply terminal 64 to prevent the refrigerant from entering inside the seal ring 579.

[0067] The flange portion 534 provided on the outer periphery of the cooling base material 530 is attached to the installation plate 96 using the clamp member 70 and the bolt 72. Since the clamp member 70, the bolt 72, and the clamping method have been described in the first embodiment, the description thereof is omitted. Further, the central region of the cooling base material 530 is attached to the installation plate 96 using a bolt 98 (member to be joined). As shown in FIG. 11, a male screw 98a is provided on the leg portion of the bolt 98. The bolt 98 is inserted from the lower surface of the installation plate 96 into a through hole 97 provided at a position of the installation plate 96 facing the storage hole 536, and the male screw 98a is screwed into a female screw member 538 in the first storage portion 536a. The through hole 97 has a small diameter at the upper portion and a large diameter at the lower portion, and has a step portion 97a between the upper portion and the lower portion. The head of the bolt 98 is caught by the step portion 97a of the through hole 97. Since the female screw member 538 is stored in the first storage portion 536a in a state where its axial rotation is restricted, the bolt 98 can be screwed into the female screw member 538. When the bolt 98 is screwed into the female screw member 538, the female screw member 538 is pulled toward the installation plate 96 in a state of being engaged with the step portion 536c of the storage hole 536.

[0068] In the present embodiment, since the central region of the wafer mounting table 510 is fixed by the bolt 98, it is possible to prevent the wafer mounting table 510 from bulging upward, and it is possible to maintain the state in which the seal rings 576 to 578 are firmly crushed.

[0069] Note that the supply and discharge of the refrigerant to and from the refrigerant flow path 582 are performed by adopting the same structure as that of FIG. 5 described in the first embodiment.

[0070] Next, a manufacturing example of the wafer mounting table 510 will be described with reference to FIG. 12. FIG. 12 is a manufacturing process diagram of the wafer mounting table 510. First, in the same manner as in the first embodiment, an alumina sintered body 120 provided with a power supply terminal 54 is produced (FIGS. 12A to C).

[0071] In parallel with this, an MMC disk member 630 is fabricated (FIG. 12D), a refrigerant flow path groove 582 is formed on the lower surface of the MMC disk member 630, and a storage hole 536 (a first storage portion 536a, a second storage portion 536b, and a step portion 536c) that penetrates the MMC disk member 630 in the vertical direction and a through hole for inserting the power supply terminal 54 are formed (FIG. 12E). In this case, the MMC disk member 630 is preferably made of SiSiC-Ti or AlSiC. This is because the thermal expansion coefficient of alumina is approximately the same as that of SiSiC-Ti and AlSiC.

[0072] Next, after the female screw member 538 is stored in the first storage portion 536a, a metal bonding material is disposed on the upper surface of the MMC disk member 630. The metal bonding material is provided with a through hole for inserting the power supply terminal 54. Next, while inserting the power supply terminal 54 of the alumina sintered body 120 into the through hole of the metal bonding material and the through hole of the MMC disk member 630, the alumina sintered body 120 is placed on the metal bonding material. Thereby, a laminate in which the MMC disk member 630, the metal bonding material, and the alumina sintered body 120 are laminated in order from the bottom is obtained. By heating and pressing this laminate (TCB), a joined body 610 is obtained (FIG. 12F). The joined body 610 is one in which the alumina sintered body 120 and the MMC disk member 630 are joined by a metal bonding layer 540. The female screw member 538 is stored in the first storage portion 536a of the joined body 610. Note that since the metal bonding material and the TCB have been described in the first embodiment, the description thereof is omitted here.

[0073] Subsequently, a fluid uncured filler is injected into the gap between the female screw member 538 and the first storage portion 536a through the screw holes of the second storage portion 536b and the female screw member 538. Considering the ease of injecting the uncured filler, this gap is preferably 0.2 mm or more. By curing the injected uncured filler, the filler 539 is obtained. Subsequently, by cutting the outer periphery of the alumina sintered body 120 to form a step, an alumina base material 20 having a central portion 22 and an outer peripheral portion 24 is obtained. Further, by cutting the outer periphery of the MMC disc member 630 to form a step, a cooling base material 530 having a flange portion 534 is obtained. Further, an insulating tube 55 is disposed in the insertion hole of the power supply terminal 54. Further, an insulating film 542 is formed by spraying alumina powder on the side surface of the outer peripheral portion 24 of the alumina base material 20, around the metal bonding layer 540, and the side surface of the cooling base material 530 (FIG. 12G). Thereby, the wafer mounting table 510 is obtained.

[0074] Regarding the usage example of the wafer mounting table 510, since it is the same as the usage example of the wafer mounting table 10 of the first embodiment described above, the description thereof is omitted.

[0075] In the wafer mounting table 510 described above, the female screw member 538 is stored in the step portion 536c (engaging portion) of the storage hole 536 in a state where the axial rotation is restricted and does not fall from the storage hole 536 in the storage hole 536 that opens to the lower surface of the cooling base material 530. Since the axial rotation of the female screw member 538 is restricted, the male screw 98a of the bolt 98 inserted from the lower surface side of the cooling base material 530 can be screwed into the female screw member 538. Further, even if the female screw member 538 is pulled toward the installation plate 96 by the bolt 98 inserted through the installation plate 96 in a state of being engaged with the step portion 536c of the storage hole 536, it has ductility and is difficult to crack. Therefore, the wafer mounting table 510 having the brittle cooling base material 530 can be fastened to the installation plate 96 without any trouble.

[0076] Further, the cooling base material 530 is formed of MMC. Since MMC is a brittle material, the significance of applying the present invention is high.

[0077] Furthermore, the storage hole 536 includes a stepped portion 536c as an engaging portion, and the bottom surface of the female screw member 538 functions as an engaged portion. Therefore, the engaging portion and the engaged portion can be manufactured relatively easily.

[0078] Furthermore, when the female screw member 538 attempts to rotate about its axis, it contacts the side wall of the first storage portion 536a of the storage hole 536 and its axial rotation is restricted. Therefore, the axial rotation of the female screw member 538 can be restricted with a relatively simple configuration. Also, the axial rotation of the female screw member 538 is restricted by the filling material 539.

[0079] And further, the first storage portion 536a opens to the upper surface of the cooling base material 530, and the opening surface is covered by the metal bonding layer 540. Therefore, compared with the case where the first storage portion 36a is built inside the cooling base material 30 as in the first embodiment, the first storage portion 536a can be manufactured relatively easily. In such a structure, since it is necessary to provide the refrigerant flow path 532 (refrigerant flow path groove 582) avoiding the storage hole 536, the heat uniformity is likely to decrease in the vicinity directly above the storage hole 536 of the wafer W. In order to suppress such a decrease in heat uniformity, the gap between the female screw member 538 and the first storage portion 536a of the storage hole 536 is filled with the filling material 539. Thereby, since the heat conduction around the storage hole 536 becomes good, a decrease in heat uniformity can be suppressed.

[0080] It should be noted that the present invention is not limited to the above-described embodiments at all, and it goes without saying that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

[0081] In the second embodiment described above, as shown in FIG. 13, the female screw member 538 may be engaged with the step portion 536c of the storage hole 536 via a stress buffer member 537 having a lower Young's modulus than the female screw member 538. For example, the female screw member 538 may be made of a Ti alloy, and the stress buffer member 537 may be made of pure Al. In this way, even if the female screw member 538 is pulled toward the installation plate 96 by the bolt 98 provided on the installation plate 96, since the stress buffer member 537 is interposed between the female screw member 538 and the step portion 536c, the stress is likely to be dispersed. In order to reduce the stress in the first storage portion 536a, first, the width w of the annular region where the step portion 536c and the female screw member 538 are indirectly in contact is preferably 3 mm or more, and more preferably 5 mm or more. Second, the inner diameter x of the screw hole of the female screw member 538 is preferably 10 mm or less, and more preferably 7 mm or less. Third, when the corner between the bottom surface and the side surface of the first storage portion 536a is an R surface (rounded surface), the radius of curvature r is preferably 0.3 mm or more, and more preferably 0.5 mm or more. The first to third represent the order of the stress reduction effect, and the first condition has the highest stress reduction effect. Also, the corner between the bottom surface and the side surface of the female screw member 538 is preferably an R surface or a C surface. The thickness t from the step portion 536c to the lower surface of the cooling base material 530 is preferably 3 mm or more and 10 mm or less. These numerical ranges are the same even in the case where there is no stress buffer member 537 or in the first embodiment.

[0082] In the second embodiment described above, the refrigerant flow path groove 582 is provided on the lower surface of the cooling base material 530, the installation plate 96 (lower base material) is disposed below the cooling base material 530, and a seal ring for liquid-tightly closing the refrigerant flow path groove 582 is disposed between the lower surface of the cooling base material 530 and the installation plate 96. However, it is not particularly limited thereto. For example, the refrigerant flow path groove may be provided on the upper surface of the installation plate instead of the lower surface of the cooling base material, and a seal ring for liquid-tightly closing the refrigerant flow path groove may be disposed between the lower surface of the cooling base material and the installation plate. The cooling base material is a brittle MMC, alumina, or the like, and a first storage portion is provided in the cooling base material.

[0083] In the above-described second embodiment, as the female screw member 538, as shown in FIG. 14A, a nut having a triangular prism shape (triangular in plan view) and having a screw hole in the center may be used. In that case, the storage hole 536 may be formed as shown in FIG. 14B. FIG. 14B is a partial enlarged view when the periphery of the storage hole 536 is viewed from below the cooling base material 530. In FIG. 14B, the second storage portion 536b is a hole having a triangular shape in plan view through which the female screw member 538 can pass, and the first storage portion 536a is a space (a composite figure of a triangle and a circle in plan view) in which the female screw member 538 can rotate axially by a predetermined angle. The state immediately after the female screw member 538 is inserted into the second storage portion 536b and stored in the first storage portion 536a is shown by a two-dot chain line, and the state in which the female screw member 538 stored in the first storage portion 536a is axially rotated in the direction of the arrow by a predetermined angle is shown by a one-dot chain line. At this time, the step portion 536c is a portion inside the outer edge of the first storage portion 536a and outside the opening edge of the second storage portion 536b, and this portion engages with the female screw member 538. According to such a structure, the female screw member 538 can be stored in the first storage portion 536a after the alumina base material 20 and the cooling base material 530 are joined. For example, first, the alumina base material 20 and the cooling base material 530 are joined with the metal bonding layer 540 without storing the female screw member 538 in the first storage portion 536a. Next, a fluid uncured filler is injected into the first storage portion 536a with the lower surface of the cooling base material 30 facing upward. Next, the female screw member 538 is stored from the second storage portion 536b into the first storage portion 536a, and then the female screw member 538 is axially rotated by a predetermined angle. As a result, the uncured filler is evenly filled between the female screw member 538 and the first storage portion 536a. Thereafter, the uncured filler is cured to form the filler 539. Note that such a structure can be applied not only to nuts having a triangular prism shape but also to nuts having a polygonal prism shape (such as a quadrangular prism shape or a hexagonal prism shape).

[0084] Instead of the female screw member 538 of the second embodiment described above, the female screw member 38 (Figs. 3, 7, or 8) of the first embodiment may be employed. In that case, it is preferable to provide the female screw member 38 with a through-hole (a through-hole extending from the internal space of the cylindrical portion 38b to the top surface of the head portion 38a) that penetrates the female screw member 38 in the vertical direction. This is because it is easy to fill the gap between the head portion 38a and the first storage portion of the storage hole with a fluid uncured filler by utilizing this through-hole.

[0085] In the second embodiment described above, as shown in Fig. 15, instead of providing the cooling base material 530 with the refrigerant flow path groove 582 (refrigerant flow path 532), a refrigerant flow path groove 91 may be provided on the upper surface of the installation plate 96, and the refrigerant flow path 92 may be formed by closing the upper opening of the refrigerant flow path groove 91 with the cooling base material 530. In Fig. 15, the same reference numerals are given to the same components as those in the second embodiment described above. Note that also in the first embodiment, instead of providing the cooling base material 30 with the refrigerant flow path 32, a refrigerant flow path groove may be provided on the upper surface of the installation plate 96 as shown in Fig. 15, and the refrigerant flow path may be formed by closing the upper opening of the refrigerant flow path groove with the cooling base material 30.

Explanation of Reference Numerals

[0086] 10 Wafer stage, 20 Alumina substrate, 22 Central part, 22a Wafer placement surface, 24 Outer peripheral part, 24a Focus ring placement surface, 26 Wafer adsorption electrode, 27 Hole, 30 Cooling substrate, 32 Refrigerant flow path, 32a Bottom surface, 32p First supply path, 32q Refrigerant supply seal ring, 32r Second supply path, 32s First discharge path, 32t Refrigerant discharge seal ring, 32u Second discharge path, 34 Flange part, 36 Storage hole, 36a First storage part, 36b Second storage part, 36c Step part, 36d Ceiling surface, 36e Inclined part, 38 Female screw member, 38a Head part, 38b Cylindrical part, 38c Inclined surface, 40 Metal bonding layer, 42 Insulating film, 52 DC power supply for wafer adsorption, 53 Low-pass filter, 54 Power supply terminal, 55 Insulating tube, 62 RF power supply, 63 High-pass filter, 64 Power supply terminal, 70 Clamp member, 70a Inner peripheral step surface, 72 Bolt, 76 Seal ring, 78 Focus ring, 80 Male screw member, 80a Head part, 80b Foot part, 80c Male screw part, 82 Nut, 91 Refrigerant flow path groove, 92 Refrigerant flow path, 94 Chamber, 95 Shower head, 96 Installation plate, 97 Through hole, 97a Step part, 98 Bolt, 98a Male screw, 110 Bonded body, 120 Alumina sintered body, 130 MMC block, 131, 133, 135 MMC disk member, 132 Groove, 136 Step hole, 321 Refrigerant supply path, 322 Refrigerant discharge path, 510 Wafer stage, 530 Cooling substrate, 532 Refrigerant flow path, 534 Flange part, 536 Storage hole, 536 Storage part, 536a First storage part, 536b Second storage part, 536c Step part, 537 Stress buffer member, 538 Female screw member, 539 Filling material, 540 Metal bonding layer, 542 Insulating film, 576 - 579 Seal ring, 582 Refrigerant flow path groove, 610 Bonded body, 630 MMC disk member, W Wafer.

Claims

1. An alumina substrate having a wafer placement surface on the upper surface and incorporating electrodes, a brittle cooling substrate joined to the lower surface of the alumina substrate, a ductile coupling member having a male screw portion or a female screw portion, which is housed in a storage hole opening on the lower surface of the cooling substrate in a state where axial rotation is restricted and engaged with an engaging portion of the storage hole, comprising: the engaging portion is a stepped portion or an inclined portion provided on the inner peripheral surface of the storage hole, the coupling member has an engaged portion that engages with the engaging portion so that the coupling member does not fall out of the storage hole, the coupling member has the female screw portion and is a member that can be screwed with the male screw of a bolt inserted from the lower surface side of the cooling substrate, or the coupling member has the male screw portion and is a member that can be screwed with the female screw disposed on the lower surface side of the cooling substrate, a wafer placement table.

2. An alumina substrate having a wafer placement surface on the upper surface and incorporating electrodes, a brittle cooling substrate joined to the lower surface of the alumina substrate, a ductile coupling member having a male screw portion or a female screw portion, which is housed in a storage hole opening on the lower surface of the cooling substrate in a state where axial rotation is restricted and engaged with an engaging portion of the storage hole, comprising: the cooling substrate has a refrigerant flow path inside, the storage hole is provided in a region of the cooling substrate that is lower than the bottom surface of the refrigerant flow path, the coupling member has the female screw portion and is a member that can be screwed with the male screw of a bolt inserted from the lower surface side of the cooling substrate, or the coupling member has the male screw portion and is a member that can be screwed with the female screw disposed on the lower surface side of the cooling substrate, a wafer placement table.

3. An alumina substrate having a wafer placement surface on the upper surface and incorporating electrodes, a brittle cooling substrate joined to the lower surface of the alumina substrate, a ductile coupling member having a male screw portion or a female screw portion, which is housed in a storage hole opening on the lower surface of the cooling substrate in a state where axial rotation is restricted and engaged with an engaging portion of the storage hole, comprising: a gap between the coupling member and the storage hole is filled with a filler, the coupling member has the female screw portion and is a member that can be screwed with the male screw of a bolt inserted from the lower surface side of the cooling substrate, or the coupling member has the male screw portion and is a member that can be screwed with the female screw disposed on the lower surface side of the cooling substrate, a wafer placement table.

4. An alumina substrate having a wafer placement surface on the upper surface and incorporating electrodes, A brittle cooling substrate joined to the lower surface of the alumina substrate, A ductile coupling member having a male screw portion or a female screw portion, which is housed in a storage hole opening on the lower surface of the cooling substrate while being restricted from axial rotation and engaged with an engaging portion of the storage hole, Comprising, The storage hole includes a first storage portion for storing the coupling member, and a second storage portion provided so as to reach the lower surface of the cooling substrate from the first storage portion, The engaging portion is a stepped surface provided at the joint between the first storage portion and the second storage portion, The coupling member has the female screw portion and is a member capable of screwing with a male screw of a bolt inserted from the lower surface side of the cooling substrate, or the coupling member has the male screw portion and is a member capable of screwing with a female screw disposed on the lower surface side of the cooling substrate, A wafer mounting table.

5. The cooling substrate is formed of a composite material of metal and ceramic or an alumina material, The wafer mounting table according to any one of claims 1 to 4.

6. When the coupling member attempts to rotate axially, it hits the wall of the storage hole and is restricted from axial rotation, The wafer mounting table according to any one of claims 1 to 4.

7. The coupling member is not joined to the cooling substrate in the storage hole and is stored in a free state, The wafer mounting table according to any one of claims 1 to 4.

8. The coupling member is engaged with the engaging portion via a stress buffer member having a lower Young's modulus than the coupling member, The wafer mounting table according to any one of claims 1 to 4.

9. The first storage portion opens on the upper surface of the cooling substrate, and the opening surface is covered by a bonding layer that bonds the alumina substrate and the cooling substrate, The wafer mounting table according to claim 4.

10. The width of the annular region where the stepped surface and the coupling member are in direct or indirect contact is 3 mm or more, The wafer mounting table according to claim 4 or 9.

Images