Wafer mounting table

Abstract

To increase plasma density in a region right above a ceramic base material.SOLUTION: A wafer mounting table 10 comprises: a ceramic base material 20 which has a wafer mounting surface 22a on its upper surface and is internally provided with an electrode 26; a conductive base material 30, provided on a lower surface side of the ceramic base material 20, which is also used as a plasma generating electrode and has the diameter equal to that of the ceramic base material 20; a support base material 40, provided on a lower surface side of the conductive base material 30, which has a diameter greater than that of the conductive base material 30 and is electrically insulated from the conductive base material 30; and a fitting flange 42 which is a portion, of the support base material 40, protruding further outward in the radial direction than the conductive base material 30.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] Conventionally, as a wafer mounting table, there is known one including a ceramic substrate having a wafer mounting surface and incorporating electrodes, and a conductive cooling substrate provided on the lower surface side of the ceramic substrate. For example, Patent Document 1 discloses a wafer mounting table of this type provided with a cooling substrate having a diameter larger than that of the ceramic substrate. In the description of the usage example of the wafer mounting table, it is described that a high-frequency voltage may be applied to the cooling substrate when generating plasma.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, since the diameter of the cooling substrate is larger than that of the ceramic substrate, plasma is generated not only in the region overlapping the wafer in plan view but also in the region protruding from the wafer. The plasma generated in the region protruding from the wafer is wasted because it is not used for wafer processing. Therefore, there has been a problem that the plasma density in the region directly above the ceramic substrate (the plasma generation region in design) decreases.

[0005] The present invention has been made to solve such problems, and the main object is to increase the plasma density in the region directly above the ceramic substrate.

Means for Solving the Problems

[0006] [1] The wafer mounting table of the present invention is It has a wafer placement surface on the top and a ceramic substrate incorporating electrodes, a conductive substrate which is provided on the lower surface side of the ceramic substrate, has a refrigerant flow path or a refrigerant flow path groove, and also serves as a plasma generation electrode, and has the same diameter as the ceramic substrate, a support substrate which is provided on the lower surface side of the conductive substrate, has a larger diameter than the conductive substrate, and is electrically insulated from the conductive substrate, and a mounting flange which is a portion of the support substrate that protrudes radially outward beyond the conductive substrate, and is provided with the above.

[0007] In the wafer placement table of the present invention, a portion of the support substrate that protrudes radially outward beyond the conductive substrate is used as a mounting flange, but the support substrate is electrically insulated from the conductive substrate. Therefore, the mounting flange does not function as a plasma generation electrode, and the generation of plasma in the region directly above the mounting flange is suppressed. As a result, the plasma density in the region directly above the ceramic substrate can be increased.

[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, and front and back are only 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. Even in such cases, it is 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 support substrate may be formed of an insulating material. In this way, the support substrate can be electrically insulated from the conductive substrate relatively easily.

[0010] [3] In the above-described wafer mounting table (the wafer mounting table described in [2] above), the first bonding layer that bonds the ceramic base material and the conductive base material and the second bonding layer that bonds the conductive base material and the support base material may both be metal bonding layers. By doing so, since the bonding of the ceramic base material and the conductive base material and the bonding of the conductive base material and the support base material can be performed in the same process, the manufacturing cost can be suppressed.

[0011] [4] In the above-described wafer mounting table (the wafer mounting table described in [2] or [3] above), the conductive base material may have the refrigerant flow path groove, and the refrigerant flow path groove may have an opening on the surface of the conductive base material that faces the support base material. By doing so, compared with the case where the conductive base material is provided with a refrigerant flow path, the material on the lower surface side of the refrigerant flow path becomes unnecessary, so that the manufacturing cost can be suppressed accordingly.

[0012] [5] In the above-described wafer mounting table (the wafer mounting table described in [1] above), the support base material is formed of metal, and an insulating layer may be provided between the support base material and the conductive base material. By doing so, even if the support base material is made of metal, the support base material and the conductive base material can be electrically insulated.

[0013] [6] In the above-described wafer mounting table (the wafer mounting table described in [5] above), screw holes may be provided on the lower surface of the support base material. Since the support base material is made of metal, that is, a ductile material, screw holes can be provided on the lower surface of the support base material. On the other hand, when the support base material is made of a brittle material (for example, a composite material of ceramic or metal and ceramic), it is difficult to provide screw holes in the support base material.

Brief Description of the Drawings

[0014]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Mode for Carrying Out the Invention

[0015] [First Embodiment] The first embodiment 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), and FIG. 2 is a plan view of the wafer stage 10.

[0016] 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 a ceramic substrate 20, a conductive substrate 30, and a support substrate 40.

[0017] The ceramic substrate 20 is a disk having a circular wafer placement surface 22a on its upper surface. The wafer W is placed on the wafer placement surface 22a. The ceramic substrate 20 is formed of a ceramic material typified by alumina, aluminum nitride, etc.

[0018] The ceramic substrate 20 incorporates an electrostatic chucking electrode 26 for wafer adsorption on the side closer to the wafer placement surface 22a. The electrostatic chucking electrode 26 for wafer adsorption is formed of a material containing, for example, W, Mo, WC, MoC, etc. 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 ceramic substrate 20 functions as a dielectric layer. A DC power supply 52 for wafer adsorption is connected to the electrostatic chucking electrode 26 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 that vertically penetrates the conductive substrate 30, the support substrate 40, the first bonding layer 46, and the second bonding layer 48, and is provided so as to reach the electrostatic chucking electrode 26 for wafer adsorption from the lower surface of the ceramic 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.

[0019] The conductive substrate 30 is a disk having the same diameter as the ceramic substrate 20 and is provided on the lower surface side of the ceramic substrate 20. The conductive substrate 30 is used as a cooling substrate for cooling the ceramic substrate 20 and has good thermal conductivity. A refrigerant flow path 32 through which refrigerant circulates is formed inside the conductive substrate 30. The refrigerant flow path 32 is formed in one stroke from one end (inlet) to the other end (outlet) over the entire conductive substrate 30 in a plan view. A supply port and a recovery port of an external refrigerant device (not shown) are connected to one end and the other end of the refrigerant flow path 32, respectively. The refrigerant supplied from the supply port of the external refrigerant device to one end of the refrigerant flow path 32 returns from the other end of the refrigerant flow path 32 to the recovery port of the external refrigerant device after passing through the refrigerant flow path 32, and after being temperature-adjusted, is supplied again from the supply port to one end of the refrigerant flow path 32. 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.

[0020] Examples of the material of the conductive base 30 include metal materials and composite materials of metal and ceramic. Examples of the metal materials include Al, Ti, Mo, or their alloys. Examples of the 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 (also referred to as SiSiCTi), materials obtained by impregnating a SiC porous body with Al and / or Si, and composite materials of Al2O3 and TiC. As the material of the conductive base 30, it is preferable to select a material having a coefficient of thermal expansion close to that of the ceramic base 20. The conductive base 30 also serves as a plasma generation electrode and is connected to the RF power supply 62 via a power supply terminal 64. The power supply terminal 64 is provided to pass through an insulating tube 65 disposed in a through hole penetrating the support base 40 and the second bonding layer 48 and reach the lower surface of the conductive base 30. The power supply terminal 64 is provided in the chamber 94 and is biased upward from below by a spring (not shown). Therefore, the upper end of the power supply terminal 64 is in elastic contact with the lower surface of the conductive base 30. In the first embodiment, the insulating tube 65 may be omitted. A high-pass filter (HPF) 63 is disposed between the conductive base 30 and the RF power supply 62.

[0021] The support base 40 is a disk having a diameter larger than that of the conductive base 30 and is provided on the lower surface side of the conductive base 30. The support base 40 has a central portion 41 having the same diameter as the conductive base 30 and a mounting flange 42 which is a portion protruding radially outward from the conductive base 30. The support base 40 is formed of an insulating material. Therefore, the support base 40 is electrically insulated from the conductive base 30. Examples of the insulating material include ceramic materials typified by alumina and aluminum nitride. As the material of the support base 40, it is preferable to select a material having a coefficient of thermal expansion close to that of the conductive base 30, that is, a material having a coefficient of thermal expansion close to that of the ceramic base 20.

[0022] The ceramic substrate 20 and the conductive substrate 30 are joined via a first bonding layer 46. Also, the conductive substrate 30 and the support substrate 40 are joined via a second bonding layer 48. Both the first bonding layer 46 and the second bonding layer 48 are metal bonding layers. The metal bonding layer may be, for example, a layer formed of solder or a metal brazing material. The metal bonding layer 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 while being heated to a temperature below the solidus temperature of the metal bonding material.

[0023] The side surface of the ceramic substrate 20, the outer periphery of the first bonding layer 46, the side surface of the conductive substrate 30, the outer periphery of the second bonding layer 48, and the upper surface and side surface of the mounting flange 42 of the support substrate 40 are covered with an insulating film 50. Examples of the insulating film 50 include a sprayed film such as alumina or yttria. In the first embodiment, part or all of the insulating film 50 provided on the side surface of the ceramic substrate 20 and the upper surface and side surface of the mounting flange 42 may be omitted.

[0024] Such a wafer mounting table 10 is attached to an installation plate 96 provided inside the chamber 94 using a clamp member 70. A seal ring 78 is disposed between the wafer mounting table 10 and the installation plate 96. The seal ring 78 is made of metal or resin and is disposed slightly inside the outer edge of the support base material 40. The clamp member 70 is an annular member having a substantially inverted L-shaped cross section and has an inner peripheral stepped surface 70a. The wafer mounting table 10 and the installation plate 96 are integrated by the clamp member 70. With the inner peripheral stepped surface 70a of the clamp member 70 placed on the mounting flange 42 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). The bolts 72 are preferably formed of a ductile material (for example, Ti, Mo, W, etc.).

[0025] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to FIG. 3. FIG. 3 is a manufacturing process diagram of the wafer mounting table 10. Here, a case where the conductive base material 30 is made of MMC and the support base material 40 is made of ceramic will be exemplified. First, a ceramic base material 20 incorporating a wafer adsorption electrode 26 is prepared (FIG. 3A). For example, a molded body of ceramic powder incorporating the wafer adsorption electrode 26 is produced, and the molded body is hot press fired to obtain the ceramic base material 20. Next, a hole 27 is drilled from the lower surface of the ceramic base material 20 to the wafer adsorption electrode 26 (FIG. 3B), 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. 3C).

[0026] In parallel with this, two MMC disk members 131 and 136 are fabricated (Fig. 3D), 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, and through holes 134 and 138 that penetrate vertically through both MMC disk members 131 and 136 are formed (Fig. 3E). When the ceramic substrate 20 is made of alumina, the MMC disk members 131 and 136 are preferably made of SiSiC-Ti or AlSiC. This is because the thermal expansion coefficients of alumina and SiSiC-Ti or AlSiC are generally the same.

[0027] The SiSiC-Ti disk member can be fabricated, 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 compact by uniaxial pressing, and the compact is hot press sintered in an inert atmosphere to obtain the SiSiC-Ti disk member.

[0028] Furthermore, in parallel with these, a support substrate 40 made of a ceramic material is prepared (Fig. 3F). For example, a compact of ceramic powder is fabricated, and the support substrate 40 is obtained by hot press firing the compact. When the ceramic substrate 20 is made of alumina, the support substrate 40 is preferably made of alumina. The alumina of the support substrate 40 may have a lower purity than the alumina of the ceramic substrate 20 from the perspective of cost reduction. Next, through holes 43 and 45 that penetrate vertically through the support substrate 40 are formed (Fig. 3G).

[0029] Next, a metal bonding material is disposed between the lower surface of the lower MMC disk member 136 and the upper surface of the support substrate 40. The metal bonding material is provided with through holes communicating with the through hole 43 and through holes communicating with the through hole 45. Further, a metal bonding material is disposed between the lower surface of the upper MMC disk member 131 and the upper surface of the lower MMC disk member 136, and a metal bonding material is disposed on the upper surface of the upper MMC disk member 131. Each metal bonding material is provided with through holes communicating with the through holes 134 and 138. The power supply terminal 54 of the ceramic substrate 20 is inserted into the through holes 134 and 138 of the MMC disk members 131 and 136 and the through hole 43 of the support substrate 40, and the ceramic substrate 20 is placed on the metal bonding material disposed on the upper surface of the upper MMC disk member 131. Thereby, a laminate is obtained in which the support substrate 40, the metal bonding material, the lower MMC disk member 136, the metal bonding material, the upper MMC disk member 131, the metal bonding material, and the ceramic substrate 20 are laminated in this order from the bottom. By heating and pressing this laminate (TCB), a joined body 110 is obtained (FIG. 3H). In the joined body 110, the conductive substrate 30 is joined to the upper surface of the support substrate 40 via the second joining layer 48 which is a metal joining layer, and the ceramic substrate 20 is joined to the upper surface of this conductive substrate 30 via the first joining layer 46 which is a metal joining layer. The conductive substrate 30 is one in which the upper MMC disk member 131 and the lower MMC disk member 136 are joined via the metal joining layer 135. The conductive substrate 30 has a refrigerant flow path 32 inside.

[0030] 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.

[0031] Subsequently, an insulating tube 55 through which a power supply terminal 54 is inserted is disposed in the through holes 134, 138, 43 and the holes of the metal bonding material. Also, an insulating tube 65 through which a power supply terminal 64 is inserted is disposed in the through hole 45 and the holes of the metal bonding material. Further, an insulating film 50 is formed by spraying ceramic powder on the side surface of the ceramic base material 20, around the first bonding layer 46, the side surface of the conductive base material 30, around the second bonding layer 48, and the upper surface and side surface of the mounting flange 42 of the support base material 40 (FIG. 3I). Thereby, the wafer mounting stage 10 is obtained.

[0032] Note that although the conductive base material 30 in FIG. 1 is described as an integral part, it may have a structure in which two members are joined by a metal bonding layer as shown in FIG. 3I, or may have a structure in which three or more members are joined by a metal bonding layer.

[0033] Next, a usage example of the wafer mounting stage 10 will be described with reference to FIG. 1. As described above, the wafer mounting stage 10 is fixed to the installation plate 96 of the chamber 94 by the clamp member 70. On the ceiling surface of the chamber 94, a shower head 98 for discharging process gas from a number of gas injection holes into the chamber 94 is disposed.

[0034] A disk-shaped wafer W is placed on the wafer mounting surface 22a of the wafer mounting stage 10. 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 mounting surface 22a. Then, the inside of the chamber 94 is set to a predetermined vacuum atmosphere (or reduced pressure atmosphere), and while supplying process gas from the shower head 98, an RF voltage from the RF power supply 62 is applied to the conductive base material 30. Then, plasma is generated between the wafer W and the shower head 98. Then, CVD film formation or etching is performed on the wafer W using the plasma.

[0035] When processing the wafer W with high-power plasma, it is necessary to efficiently cool the wafer W. In the wafer mounting table 10, as the first bonding layer 46 between the ceramic base material 20 and the conductive base material 30, a metal bonding layer with high thermal conductivity is used instead of a resin layer with low thermal conductivity. Therefore, the ability to draw heat from the wafer W (heat extraction ability) is high. In addition, since the thermal expansion difference between the ceramic base material 20 and the conductive base material 30 is small, even if the stress relaxation property of the first bonding layer 46 is low, problems are less likely to occur.

[0036] In the wafer mounting table 10 described above, the portion of the support base material 40 that protrudes radially outward from the conductive base material 30 is used as the mounting flange 42. Since the support base material 40 is formed of an insulating material, it is electrically insulated from the conductive base material 30. Therefore, the mounting flange 42 does not function as a plasma generation electrode, and the generation of plasma in the region directly above the mounting flange 42 is suppressed. As a result, the plasma density in the region directly above the ceramic base material 20 can be increased.

[0037] In addition, since the support base material 40 is formed of an insulating material, the support base material 40 can be electrically insulated from the conductive base material 30 relatively easily.

[0038] Furthermore, since both the first bonding layer 46 and the second bonding layer 48 are metal bonding layers, the bonding between the ceramic base material 20 and the conductive base material 30 and the bonding between the conductive base material 30 and the support base material 40 can be performed in the same process. Thereby, the manufacturing cost can be suppressed.

[0039] [Second Embodiment] The second embodiment of the present invention will be described below with reference to the drawings. FIG. 4 is a longitudinal sectional view of the wafer mounting table 210 installed in the chamber 94 (a sectional view when cut along a plane including the central axis of the wafer mounting table 210). The wafer mounting table 210 is used for performing CVD, etching, etc. on the wafer W using plasma, and is fixed to an installation plate 96 provided inside the chamber 94 for semiconductor processes. The wafer mounting table 210 includes a ceramic substrate 20, a conductive substrate 30, and a support substrate 240. In the second embodiment, the same components as those in the first embodiment are denoted by the same reference numerals and the description thereof is omitted.

[0040] The support substrate 240 is a disk having a diameter larger than that of the conductive substrate 30, and is provided on the lower surface of the conductive substrate 30. The support substrate 240 has a central portion 241 having the same diameter as the conductive substrate 30 and a mounting flange 242 which is a portion protruding radially outward from the conductive substrate 30. The support substrate 240 is formed of a metal material. Examples of the metal material include Al, Ti, Mo, or alloys thereof. A plurality of screw holes 244 are provided on the lower surface of the support substrate 240. The plurality of screw holes 244 are provided in the central portion 241 of the support substrate 240 at substantially equal intervals along a concentric circle of the support substrate 240 (for example, a circle with a diameter of 1 / 2 or 1 / 3 of the diameter of the wafer W), and a plurality of them (for example, 6 or 8) are provided. The plurality of screw holes 244 have female threads cut on the inner peripheral surface and open on the lower surface of the support substrate 240. A plurality of through holes 246 are provided in the mounting flange 242 of the support substrate 240. The plurality of through holes 246 are provided at substantially equal intervals along a concentric circle of the support substrate 240, and a plurality of them (for example, 8 or 12) are provided. The plurality of through holes 246 penetrate the mounting flange 242 in the vertical direction and open on the upper surface and the lower surface of the mounting flange 242.

[0041] A second bonding layer 248, which is an insulating layer, is provided between the conductive substrate 30 and the support substrate 240. Due to this second bonding layer 248, the support substrate 240 is electrically insulated from the conductive substrate 30. This second bonding layer 248 is a layer formed of an adhesive sheet made of a resin having insulating properties, such as a silicone resin, an acrylic resin, a polyimide resin, or an epoxy resin, and is a circular layer having the same diameter as the lower surface of the conductive substrate 30. The second bonding layer 248 may have a single-layer structure or a multi-layer structure. The second bonding layer 248 may be a sheet having acrylic resin layers on both sides of a polypropylene core material, a sheet having silicone resin layers on both sides of a polyimide core material, a sheet of epoxy resin alone, or the like.

[0042] Such a wafer mounting table 210 is attached to an installation plate 96 provided inside the chamber 94 using bolts 274 and 276. A seal ring 278 is disposed between the wafer mounting table 210 and the installation plate 96. The seal ring 278 is made of metal or resin and is disposed slightly inside the outer edge of the central portion 241 of the support substrate 240. The bolt 274 has a male thread cut on the outer peripheral surface of its leg portion, is inserted from the lower surface of the installation plate 96 into a through hole provided at a position facing the screw hole 244 in the installation plate 96, and is screwed into the screw hole 244 of the support substrate 240. The bolt 276 has a male thread cut on the outer peripheral surface of its leg portion, is inserted from the upper surface of the mounting flange 242 into a through hole 246 provided in the mounting flange 242, and is screwed into a screw hole provided at a position facing the through hole 246 in the installation plate 96. This screw hole has a female thread cut on its inner peripheral surface and opens on the upper surface of the installation plate 96. The bolts 274 and 276 may be made of an insulating material or a conductive material (such as metal). The bolts 274 and 276 are preferably formed of a ductile material (for example, Ti, Mo, W, etc.).

[0043] Next, a manufacturing example of the wafer stage 210 will be described with reference to FIG. 5. FIG. 5 is a manufacturing process diagram showing the manufacturing process of the wafer stage 210. Here, a case where the conductive base material 30 is made of MMC and the support base material 240 is made of metal will be exemplified. When manufacturing this wafer stage 210, first, the same processes as those in FIGS. 3A to E are performed (FIGS. 5A to E). In parallel with this, a support base material 240 made of a metal material is prepared (FIG. 5F), and through holes 243 and 245 penetrating the support base material 240 in the vertical direction, screw holes 244 provided on the lower surface of the support base material 240, and through holes 246 penetrating the outer peripheral portion of the support base material 240 in the vertical direction are formed (FIG. 5G).

[0044] Next, a metal bonding material is disposed between the lower surface of the upper MMC disk member 131 and the upper surface of the lower MMC disk member 136, and a metal bonding material is disposed on the upper surface of the upper MMC disk member 131. Each metal bonding material is provided with a through hole communicating with the through holes 134 and 138. The power supply terminals 54 of the ceramic base material 20 are inserted into the through holes 134 and 138 of the MMC disk members 131 and 136, and the ceramic base material 20 is placed on the metal bonding material disposed on the upper surface of the upper MMC disk member 131. Thereby, a laminate in which the lower MMC disk member 136, the metal bonding material, the upper MMC disk member 131, the metal bonding material, and the ceramic base material 20 are laminated in this order from the bottom is obtained. By heating and pressurizing this laminate (TCB), a bonded body 305 is obtained (FIG. 5H). The bonded body 305 is one in which the ceramic base material 20 is bonded to the upper surface of the conductive base material 30 via the first bonding layer 46 which is a metal bonding layer.

[0045] Subsequently, an adhesive sheet that becomes the second bonding layer 248 is placed on the upper surface of the support substrate 240. The adhesive sheet is provided with through-holes that communicate with the through-holes 134, 138, 243 and through-holes that communicate with the through-hole 245. The power supply terminal 54 of the bonded body 305 is inserted into the through-hole 243 of the support substrate 240, and the bonded body 305 is placed on the adhesive sheet disposed on the upper surface of the support substrate 240. Thereby, a laminate in which the support substrate 240, the adhesive sheet, and the bonded body 305 are laminated in this order from the bottom is obtained. While heating this laminate, pressure is applied by vacuum pressing to cure the adhesive sheet, and the bonded body 305 and the support substrate 240 are bonded with the second bonding layer 248 which is an insulating layer, thereby obtaining the bonded body 310 (FIG. 5I).

[0046] Subsequently, an insulating tube 55 through which the power supply terminal 54 is inserted is disposed in the through-holes 134, 138, 243 and the holes of the metal bonding material and the adhesive sheet. Also, an insulating tube 65 through which the power supply terminal 64 is inserted is disposed in the through-hole 245 and the holes of the adhesive sheet. Further, an insulating film 50 is formed by spraying ceramic powder on the side surface of the ceramic substrate 20, around the first bonding layer 46, the side surface of the conductive substrate 30, around the second bonding layer 248, and the upper surface and side surface of the mounting flange 242 of the support substrate 240 (FIG. 5J). Thereby, the wafer mounting stage 210 is obtained. In the second embodiment, a part or all of the insulating film 50 provided around the side surface of the ceramic substrate 20 and around the second bonding layer 248 may be omitted. The timing of forming the insulating film 50 may be before forming the bonded body 310. For example, the insulating film 50 may be formed on each of the bonded body 305 and the support substrate 240 and then the two may be bonded.

[0047] This wafer mounting stage 210 can be used in the same manner as the usage example of the wafer mounting stage 10.

[0048] In the wafer mounting stage 210 described above, the portion of the support substrate 240 that protrudes radially outward from the conductive substrate 30 is used as the mounting flange 242. However, since the support substrate 240 is joined to the conductive substrate 30 via the second bonding layer 248 which is an insulating layer, it is electrically insulated from the conductive substrate 30. Therefore, the mounting flange 242 does not function as a plasma generating electrode, and the generation of plasma in the region directly above the mounting flange 242 is suppressed. As a result, the plasma density in the region directly above the ceramic substrate 20 can be increased.

[0049] Also, since the second bonding layer 248 which is an insulating layer is provided between the support substrate 240 and the conductive substrate 30, even if the support substrate 240 is made of metal, the support substrate 240 and the conductive substrate 30 can be electrically insulated. Further, since the support substrate 240 is made of metal, that is, a ductile material, screw holes 244 can be provided on the lower surface of the support substrate 240. Since screw holes 244 can be provided on the lower surface of the support substrate 240, the wafer mounting stage 210 can also be attached to the installation plate 96 at the central portion 241 of the support substrate 240.

[0050] 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.

[0051] For example, in the above-described first and second embodiments, the conductive substrate 30 is configured to have a refrigerant flow path 32 inside, but it is not particularly limited thereto. For example, as shown in FIG. 6, the conductive substrate 30 may have a refrigerant flow path groove 34 on its lower surface, and the lower opening of the refrigerant flow path groove 34 may be closed by a second bonding layer 48 disposed on the lower surface side of the conductive substrate 30 to form the refrigerant flow path 32. In this way, compared with the case where the conductive substrate 30 is provided with the refrigerant flow path 32 inside, the material (MMC disk member 136) on the lower surface side of the refrigerant flow path 32 becomes unnecessary, so that the manufacturing cost can be reduced accordingly. In FIG. 6, the same reference numerals are given to the same components as those in the above-described embodiments. Further, for example, the conductive substrate 30 may have a refrigerant flow path groove on its upper surface, or may have neither a refrigerant flow path nor a refrigerant flow path groove.

[0052] In the above-described first and second embodiments, holes may be provided to penetrate the wafer mounting tables 10 and 210 from the lower surface of the conductive substrate 30 to the wafer mounting surface 22a. Such holes include a gas supply hole for supplying a heat conductive gas (for example, He gas) to the back surface of the wafer W, and a lift pin hole for inserting a lift pin for moving the wafer W up and down with respect to the wafer mounting surface 22a. The heat conductive gas is supplied to the space formed by a large number of small protrusions (supporting the wafer W) provided on the wafer mounting surface 22a and the wafer W. The lift pin holes are provided at three positions when the wafer W is supported by, for example, three lift pins. A resin or metal seal ring (for example, an O-ring) may be disposed at a position facing such holes between the lower surface of the support substrate 40, 240 and the upper surface of the installation plate 96.

[0053] In the above-described first and second embodiments, the wafer adsorption electrode 26 is incorporated in the ceramic substrate 20, but instead of or in addition to this, a heater electrode (resistance heating element) may be incorporated. In this case, a heater power source is connected to the heater electrode. The ceramic substrate 20 may incorporate one layer of electrodes or may incorporate two or more layers with a space therebetween.

[0054] In the above-described first and second embodiments, the ceramic base material 20 and the conductive base material 30 are joined by the first joining layer 46 which is a metal joining layer. However, the first joining layer 46 may be a resin joining layer.

[0055] In the above-described first embodiment, the second joining layer 48 is a metal joining layer. However, the second joining layer 48 may be a resin joining layer.

[0056] In the above-described first embodiment, it is assumed that the upper end of the power supply terminal 64 is in contact with the lower surface of the conductive base material 30. However, when the second joining layer 48 is a metal joining layer, it may be assumed that the upper end of the power supply terminal 64 is in contact with the lower surface of the second joining layer 48. In that case, in the second joining layer 48 and the metal joining material that is its source, a through hole (a through hole communicating with the through hole 45) for inserting the power supply terminal 64 may be omitted.

[0057] In the above-described second embodiment, the support base material 240 is assumed to have screw holes 244 and through holes 246 formed therein. However, one or both of these may be omitted. Further, instead of providing the through holes 246, the mounting flange 242 may be attached to the mounting plate 96 using the clamp member 70 in the same manner as in the first embodiment. Also, the screw holes 244 may be formed on the lower surface of the mounting flange 242 instead of the lower surface of the central portion 241.

[0058] In the above-described first and second embodiments, the ceramic base material 20 is produced by hot press firing a molded body of ceramic powder. However, the molded body at that time may be produced by laminating a plurality of tape molded bodies, or may be produced by the mold casting method, or may be produced by pressing the ceramic powder. The same applies to the support base material 40 of the first embodiment.

Description of Reference Numerals

[0059] 10 Wafer mounting stage, 20 Ceramic substrate, 22a Wafer mounting surface, 26 Wafer adsorption electrode, 27 Hole, 30 Conductive substrate, 32 Refrigerant flow path, 40 Support substrate, 41 Central part, 42 Mounting flange, 43 Through hole, 45 Through hole, 46 First bonding layer, 48 Second bonding layer, 50 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, 65 Insulating tube, 70 Clamping member, 70a Inner peripheral stepped surface, 72 Bolt, 94 Chamber, 96 Installation plate, 98 Shower head, 110 Bonded body, 131, 136 MMC disk member, 132 Groove, 134, 138 Through hole, 135 Metal bonding layer, 210 Wafer mounting stage, 240 Support substrate, 241 Central part, 242 Mounting flange, 243 Through hole, 244 Screw hole, 245 Through hole, 246 Through hole, 248 Second bonding layer, 274 Bolt, 276 Bolt, 278 Seal ring, 305 Bonded body, 310 Bonded body.

Claims

1. A ceramic substrate having a wafer placement surface on the upper surface and incorporating electrodes, A conductive substrate provided on the lower surface side of the ceramic substrate, having a refrigerant flow path or a refrigerant flow path groove, and also serving as a plasma generation electrode, and having the same diameter as the ceramic substrate, A support substrate provided on the lower surface side of the conductive substrate, having a diameter larger than that of the conductive substrate and being electrically insulated from the conductive substrate, A mounting flange which is a portion of the support substrate protruding radially outward beyond the conductive substrate, A wafer placement table comprising the above.

2. The support substrate is formed of an insulating material. The wafer placement table according to Claim 1.

3. The first bonding layer that bonds the ceramic substrate and the conductive substrate and the second bonding layer that bonds the conductive substrate and the support substrate are both metal bonding layers. The wafer placement table according to Claim 2.

4. The conductive substrate has the refrigerant flow path groove. The refrigerant flow path groove has an opening on the surface of the conductive substrate facing the support substrate. The wafer placement table according to Claim 2 or 3.

5. The support substrate is formed of metal, and an insulating layer is provided between the support substrate and the conductive substrate. The wafer placement table according to Claim 1.

6. A screw hole is provided on the lower surface of the support substrate. The wafer placement table according to Claim 5.

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