Wafer placement table

Abstract

To prevent damage caused by thermal stress, in a wafer mounting table provided with a coolant passage.SOLUTION: A wafer mounting table 10 provided with a coolant passage for circulating a coolant comprises: an upper base material 12 which is provided with a ceramic base material 20 having a built-in electrode 26, and which has a wafer mounting surface 22a on an upper face of the ceramic base material 20; a lower base material 80 which is provided, on its upper face, with a passage groove 88 constituting a lateral wall and a bottom of the coolant passage; and a sealing member 16 which is disposed between the upper base material 12 and the lower base material 80 such that it seals between the coolant passage 18 and the outside.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] Conventionally, a wafer mounting table is known in which a ceramic base material such as alumina in which an electrostatic electrode is embedded and a cooling base material made of a metal such as aluminum are bonded via a resin layer (see, for example, Patent Document 1). With such a wafer mounting table, the resin layer can mitigate the effect of the thermal expansion difference between the ceramic base material and the cooling base material. A wafer mounting table is also known in which a ceramic base material and a cooling base material having a coolant flow path therein are bonded using a metal bonding layer instead of a resin layer (see, for example, Patent Documents 2 and 3). Since the metal bonding layer has a higher thermal conductivity than the resin layer, it can realize the heat extraction ability required when processing a wafer with high-power plasma. On the other hand, since the metal bonding layer has a larger Young's modulus and a lower stress relaxation property than the resin layer, it is almost impossible to mitigate the effect of the thermal expansion difference between the ceramic base material and the cooling base material. Therefore, in Patent Documents 2 and 3, a metal matrix composite material (MMC) having a small difference in thermal expansion coefficient from the ceramic base material is used as the material of the cooling base material. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-287344 [Patent Document 2] Patent No. 5666748 [Patent Document 3] Patent No. 5666749 Summary of the Invention [Problem to be solved by the invention]

[0004] However, when a cooling substrate having an internal coolant flow path is used, the large heat input from the high-power plasma causes thermal expansion of the portion above the coolant flow path, and there is a risk that the wafer mounting table may be damaged starting from the boundary between the ceiling surface and the side wall surface of the coolant flow path due to the difference in thermal expansion, etc.

[0005] The present invention has been made to solve the above problems, and a main object of the present invention is to prevent damage caused by thermal stress in a wafer mounting table having a coolant flow path. [Means for solving the problem]

[0006] [1] The wafer mounting table of the present invention comprises: A wafer mounting table having a coolant flow path for circulating a coolant, an upper substrate including a ceramic substrate having an electrode built therein and a wafer mounting surface on an upper surface of the ceramic substrate; a lower base material having a flow channel on an upper surface thereof, the flow channel forming a side wall and a bottom of the refrigerant flow channel; a seal member disposed between the upper base material and the lower base material so as to seal between the refrigerant flow path and the outside; It is equipped with the following:

[0007] In this wafer stage, the upper base material constituting the ceiling surface of the coolant flow path and the lower base material constituting the sidewall surface of the coolant flow path are not integrated, and a seal member is disposed between the two, so that even if a difference in thermal expansion occurs between the ceiling surface and the sidewall surface of the coolant flow path, the seal member absorbs the effect of the difference in thermal expansion. Therefore, in the wafer stage equipped with the coolant flow path, the wafer stage can be prevented from being damaged by thermal stress.

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

[0009] [2] In the above-mentioned wafer supporting table (the wafer supporting table described in [1] above), the upper base material may include the ceramic base material, a ceiling base material bonded to an underside of the ceramic base material to form a ceiling of the refrigerant flow path, and a metal bonding layer bonding the ceramic base material and the ceiling base material.

[0010] [3] In the above-mentioned wafer mounting table (the wafer mounting table described in [2]), the absolute value of the difference in linear thermal expansion coefficient between the ceiling base material and the ceramic base material at 40 to 400°C is 1.5 × 10 -6 / K or less. In this way, the difference in thermal expansion between the ceramic base material and the ceiling base material is small, so that warping or damage of the upper base material due to thermal stress can be suppressed. In this specification, the linear thermal expansion coefficient obtained by measuring the length at 40°C and 400°C is referred to as the linear thermal expansion coefficient from 40 to 400°C.

[0011] [4] In the above-mentioned wafer mounting table (the wafer mounting table described in [2] or [3] above), the ceiling base material may be made of a composite material of metal and ceramic. The composite material of metal and ceramic has a small absolute value of the difference in linear thermal expansion coefficient from the ceramic base material, so thermal stress is unlikely to occur in the upper base material. In addition, since the composite material has higher toughness than the ceramic material, it is unlikely to break even if thermal stress occurs.

[0012] [5] In the above-mentioned wafer mounting table (the wafer mounting table described in [2] or [3] above), the ceiling base material may be made of a ceramic material having the same main component as the ceramic base material. Since the absolute value of the difference in linear thermal expansion coefficient between ceramic materials having the same main component is small, thermal stress is unlikely to occur in the upper base material. In this specification, the main component refers to a component that occupies 50 mass% or more of the total components contained therein, preferably 70 mass% or more, and more preferably 90 mass% or more.

[0013] [6] In the above-mentioned wafer stage (the wafer stage described in [1] above), the upper base material may be a single layer of the ceramic base material.

[0014] [7] In the above-mentioned wafer stage (the wafer stage according to any one of [1] to [6] above), the lower base material may be made of an easily processable material. If the material is an easily processable material, flow channel formation is easy, and therefore processing costs can be reduced.

[0015] [8] The wafer stage described above (the wafer stage described in any one of [1] to [7] above) may include, as the sealing member, multiple outer sealing members provided so as to surround the outermost edge of the flow channel. In this way, the outer sealing member on the flow channel side is protected from process gas and plasma by the outermost outer sealing member, thereby improving corrosion resistance.

[0016] [9] In the above-mentioned wafer stage (the wafer stage described in any one of [1] to [8] above), a heat dissipation sheet may be disposed between the lower surface of the upper base material and the upper surface of the lower base material. In this way, the heat dissipation sheet facilitates rapid conduction of heat from the upper base material to the lower base material. As a result, the efficiency of cooling the wafer is improved.

[0017]

[10] In the above-mentioned wafer mounting table (the wafer mounting table described in [9]), the thermal resistance of the heat dissipation sheet is 0.5 K cm 2 1 / W or less, which allows heat from the upper substrate to be transferred to the lower substrate more quickly, thereby providing a more efficient cooling of the wafer.

[0018]

[11] In the above-mentioned wafer support (the wafer support described in [9] or

[10] above), the Young's modulus of the heat dissipation sheet may be 100 MPa or less. In this way, the heat dissipation sheet is firmly attached to the upper and lower substrates, so that heat from the upper substrate is more quickly conducted to the lower substrate, and the efficiency of cooling the wafer is improved.

[0019]

[12] In the above-mentioned wafer mounting table (the wafer mounting table described in any one of [9] to

[11] above), the heat dissipation sheet may include a main body portion disposed on a portion of the upper surface of the lower base material where the flow path groove is not provided, and a bridging portion spanning over the flow path groove. The main body portion quickly conducts heat from the upper base material to the lower base material. The bridging portion maintains the sheet shape of the heat dissipation sheet and improves the handleability of the heat dissipation sheet. Therefore, a wafer mounting table including a main body portion and a bridging portion can improve the efficiency of cooling the wafer and the workability during assembly of the wafer mounting table.

[0020]

[13] In the above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to

[12] above), the upper base material and the lower base material may be mechanically joined so that the sealing member is crushed from above and below. With mechanical joining, the sealing member can be sufficiently crushed from above and below, so that the sealing function of the sealing member can be fully exerted. Furthermore, due to the mechanical joining, the heat dissipation sheet is firmly attached to the upper base material and the lower base material, so that heat from the upper base material is more quickly conducted to the lower base material, and the efficiency of cooling the wafer is further improved.

[0021]

[14] The above-mentioned wafer mounting table (the wafer mounting table described in any one of [1] to

[13] ) may include a through hole that passes through the lower base material in the vertical direction, a screw hole provided in a lower surface of the upper base material at a position facing the through hole, and a screw member that is inserted into the through hole from the lower surface of the lower base material and screwed into the screw hole. In this wafer mounting table, the upper base material and the lower base material are mechanically joined by the screw member. [Brief description of the drawings]

[0022] [Figure 1] FIG. 2 is a vertical cross-sectional view of the wafer mounting table 10 installed in the chamber 94. [Diagram 2] FIG. [Diagram 3] FIG. [Figure 4] 3A to 3C are diagrams showing the manufacturing process of the wafer mounting table 10 (the manufacturing process of the upper base material 12). [Diagram 5] 5A to 5C are diagrams showing the manufacturing process of the wafer mounting table 10 (the manufacturing process of the lower base material 80). [Figure 6] 3A to 3C are diagrams showing the manufacturing process of the wafer mounting table 10 (assembly process of the wafer mounting table 10). [Figure 7] FIG. 2 is a vertical cross-sectional view of the wafer mounting table 210. [Figure 8] FIG. 3 is a vertical cross-sectional view of the wafer mounting table 310. [Figure 9] FIG. 13 is an explanatory diagram showing an example in which the wafer mounting table 10 is fastened to a mounting plate 96 with bolts 76. [Figure 10] FIG. 4 is a vertical cross-sectional view of a wafer mounting table 410 installed in a chamber 94. [Figure 11] 4 is a cross-sectional view of the wafer mounting table 410 cut on a horizontal plane including the heat dissipation sheet 417 as viewed from above. FIG. [Figure 12] 12 is a cross-sectional view showing an example in which a heat dissipation sheet 417 in the cross-sectional view of FIG. 11 is modified. [Figure 13] FIG. 4 is a vertical cross-sectional view of a wafer mounting table 510 installed in a chamber 94. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] A preferred embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a vertical cross-sectional view of a wafer mounting table 10 installed in a chamber 94 (a cross-sectional view when cut along a plane including the central axis of the wafer mounting table 10), Fig. 2 is a plan view of the wafer mounting table 10, and Fig. 3 is a plan view of a lower base material 80. In this specification, the symbol "to" indicating a range of numerical values ​​is used to mean that the numerical values ​​before and after it are included as the lower limit and upper limit.

[0024] The wafer mounting table 10 is used for performing CVD, etching, etc. on the wafer W using plasma, and is fixed to a mounting plate 96 provided inside a chamber 94 for semiconductor processing. The wafer mounting table 10 includes an upper base material 12, a lower base material 80, and a seal member 16. The wafer mounting table 10 includes a coolant flow path 18 inside the wafer W, through which a coolant can circulate. The coolant flow path 18 is an area between the lower surface of the upper base material 12 and the upper surface of the lower base material 80, inside the outer seal member 16a and outside the inner seal member 16b. There is a gap between the lower surface of the upper base material 12 and the upper surface of the lower base material 80, and the coolant flow path 18 allows the coolant to flow through this gap.

[0025] The upper base material 12 includes a ceramic base material 20, a ceiling base material 30 disposed below the ceramic base material 20 and constituting the ceiling of the refrigerant flow path 18, and a metal bonding layer 40 bonding the ceramic base material 20 and the ceiling base material 30. The thickness of the upper base material 12 is preferably 8 mm or more or 10 mm or more in consideration of strength, and is preferably 25 mm or less in consideration of cooling efficiency.

[0026] The ceramic base 20 has a central portion 22 having a circular wafer mounting surface 22a, and an outer peripheral portion 24 having an annular focus ring mounting surface 24a on the outer periphery of the central portion 22. Hereinafter, the focus ring may be abbreviated as "FR." A wafer W is mounted on the wafer mounting surface 22a, and a focus ring 78 is mounted on the FR mounting surface 24a. The ceramic base 20 is made of a ceramic material such as alumina or aluminum nitride. The FR mounting surface 24a is one step lower than the wafer mounting surface 22a.

[0027] The center portion 22 of the ceramic base material 20 incorporates a wafer adsorption electrode 26 on the side close to the wafer placement surface 22a. The wafer adsorption electrode 26 is formed of a material containing, for example, W, Mo, WC, MoC, etc. The wafer adsorption electrode 26 is a disk-shaped or mesh-shaped monopolar electrostatic electrode. The layer of the ceramic base material 20 above the wafer adsorption electrode 26 functions as a dielectric layer. A wafer adsorption DC power source 52 is connected to the wafer adsorption electrode 26 via a power supply terminal 54. The power supply terminal 54 is provided so as to pass through an insulating tube 55 disposed in a through hole that vertically penetrates the lower base material 80, the ceiling base material 30, and the metal bonding layer 40, and reach the wafer adsorption electrode 26 from the lower surface of the ceramic base material 20. A low pass filter (LPF) 53 is provided between the wafer adsorption DC power source 52 and the wafer adsorption electrode 26.

[0028] The ceiling base material 30 is a disk member made of a composite material of metal and ceramic (hereinafter also referred to as a metal-ceramic composite material). Examples of the metal-ceramic composite material include a metal matrix composite material (metal matrix composite (MMC)) and a ceramic matrix composite material (ceramic matrix composite (CMC)). The outer diameter of the ceiling base material 30 is larger than that of the ceramic base material 20, and the ceiling base material 30 has an inner peripheral portion 32 in which the ceramic base material 20 is disposed, and an outer peripheral portion 34 that protrudes from the outer periphery of the ceramic base material 20. The upper base material 12 is clamped to the installation plate 96 together with the lower base material 80 on the outer peripheral side (outer peripheral portion 34) of the ceiling base material 30. The absolute value of the difference in linear thermal expansion coefficient between the metal-ceramic composite material used for the ceiling base material 30 and the ceramic material used for the ceramic base material 20 at 40 to 400°C is 1.5×10 -6 / K or less, and 1.0×10 -6 / K or less is more preferable, and 0.5×10 -6 / K or less. Specific examples of such metal-ceramic composite materials include materials containing Si, SiC, and Ti, and materials in which a porous SiC body is impregnated with Al and / or Si. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which a porous SiC body is impregnated with Al is called AlSiC, and a material in which a porous SiC body is impregnated with Si is called SiSiC. When the ceramic substrate 20 is an alumina substrate, AlSiC, SiSiCTi, and the like are preferable as metal-ceramic composite materials used for the ceiling substrate 30. The linear thermal expansion coefficient at 40 to 400°C for alumina is 7.2×10 -6 / K, and AlSiC (SiC75%) is 7.8×10 -6 / K, and SiSiCTi is 7.3 × 10 -6 / K. When the ceramic substrate 20 is an aluminum nitride substrate, the metal-ceramic composite material used for the ceiling substrate 30 is preferably AlSiC or SiSiC. The linear thermal expansion coefficient of aluminum nitride at 40 to 400°C is 4.6×10 -6 / K, and AlSiC (SiC85%) is 5.6×10 -6 / K. The thermal conductivity of the material used for the ceiling base material 30 is preferably 50 W / (m·K) or more, more preferably 70 W / (m·K) or more, and even more preferably 80 W / (m·K) or more. The ceiling base material 30 also functions as a radio frequency (RF) electrode for generating plasma, and is connected to an RF power source 62 via a power supply terminal 64. The power supply terminal 64 is provided so as to pass through an insulating tube 65 arranged in a through hole that penetrates the lower base material 80 in the vertical direction and reach the lower surface of the ceiling base material 30. The power supply terminal 64 is provided in the chamber 94 and is biased from the bottom to the top 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 ceiling base material 30. A high pass filter (HPF) 63 is provided between the ceiling base material 30 and the RF power source 62. The thickness of the ceiling base material 30 is preferably 3 mm or more or 6 mm or more in consideration of strength, and is preferably 20 mm or less in consideration of cooling efficiency.

[0029] The metal bonding layer 40 bonds the lower surface of the ceramic base material 20 and the upper surface of the ceiling base material 30. The metal bonding layer 40 may be, for example, a layer formed of solder or a brazing metal 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 bonded, and the two members are pressure-bonded while being heated to a temperature equal to or lower than the solidus temperature of the metal bonding material.

[0030] The side surface of the outer periphery 24 of the ceramic base material 20, the outer periphery of the metal bonding layer 40, and the upper surface and side surface of the ceiling base material 30 are covered with an insulating film 42. The insulating film 42 may be, for example, a thermally sprayed film of alumina, yttria, or the like.

[0031] The lower substrate 80 is a disk member made of an easily processable material. The outer diameter of the lower substrate 80 is the same as the outer diameter of the ceiling substrate 30. As shown in FIG. 3, a flow groove 88 and a seal groove 89 are provided on the upper surface of the lower substrate 80. The flow groove 88 constitutes the side wall and bottom of the refrigerant flow path 18, and is provided in a spiral shape from an inlet 88a to an outlet 88b so as to spread over the entire area where the ceramic substrate 20 is arranged. The inlet 88a and the outlet 88b of the flow groove 88 penetrate the lower substrate 80 in the vertical direction and open to the bottom surface of the flow groove 88. The inlet 88a and the outlet 88b of the flow groove 88 are connected to a refrigerant cooling device (not shown), and the refrigerant discharged from the outlet 88b is returned to the inlet 88a again after being temperature-adjusted by the refrigerant cooling device and is supplied into the flow groove 88 (refrigerant flow path 18). The refrigerant flowing through the refrigerant flow path 18 is preferably a liquid, and is preferably electrically insulating. An example of an electrically insulating liquid is a fluorine-based inert liquid. The seal groove 89 is a groove in which the seal member 16 is disposed. The outer groove 89a of the seal groove 89 is provided in a double layer so as to surround the outermost edge of the flow channel groove 88, and the inner groove 89b is provided so as to surround each of the insulating pipes 55 and 65. The easily machinable material used for the lower base material 80 is preferably one that is easier to process than the ceiling base material 30 made of a metal-ceramic composite material. As an index of processability, for example, the machinability index shown in JIS B 0170 (2020) can be used. As the easily machinable material, a material with a machinability index of 40 or more is preferable, a material with a machinability index of 100 or more is more preferable, and a material with a machinability index of 140 or more is even more preferable. As the easily machinable material, for example, aluminum, aluminum alloy, stainless steel (SUS material), resin (heat-resistant resin), etc. can be mentioned. From the viewpoint of increasing the efficiency of cooling the wafer W, the material used for the lower base material 80 is preferably one with high thermal conductivity. The thermal conductivity of the material used for the lower base material 80 is, for example, preferably 80 W / (m·K) or more, more preferably 100 W / (m·K) or more, and even more preferably 150 W / (m·K) or more.

[0032] The seal member 16 is disposed between the upper base material 12 and the lower base material 80, and seals between the refrigerant flow path 18 and the outside. The seal member 16 is an elastically deformable annular member, and is pressed vertically to seal between the refrigerant flow path 18 and the outside, thereby preventing the refrigerant in the refrigerant flow path 18 from leaking to the outside. Of the seal members 16, the outer seal member 16a is provided in a double layer so as to surround the outermost edge of the flow path groove 88, and the inner seal member 16b is provided so as to surround each of the insulating tubes 55 and 65. The outer seal member 16a prevents the refrigerant in the refrigerant flow path 18 from leaking from the outer periphery of the wafer mounting table 10, and the inner seal member 16b prevents the refrigerant in the refrigerant flow path 18 from leaking to the periphery of the insulating tubes 55 and 65. The seal member 16 may be an O-ring or a packing. The seal member 16 may be made of an insulating material or a conductive material. The seal member 16 may be made of resin, rubber, or metal. The outer seal member 16a is disposed in the outer groove 89a, and the inner seal member 16b is disposed in the inner groove 89b, and they are positioned accordingly.

[0033] The wafer mounting table 10 is attached to a mounting plate 96 provided inside a chamber 94 using a clamp member 70, with the lower base material 80, seal member 16, and upper base material 12 stacked in this order from below. As a result, the upper base material 12 and the lower base material 80 of the wafer mounting table 10 are mechanically joined by the clamp, and the seal member 16 is pressed vertically to seal between the coolant flow path 18 and the outside. The clamp member 70 is an annular member with a cross section that is approximately inverted L-shaped, and has an inner peripheral step surface 70a. The wafer mounting table 10 and the mounting plate 96 are integrated by the clamp member 70. Specifically, in a state where the inner peripheral step surface 70a of the clamp member 70 is placed on the outer peripheral portion 34 of the upper base material 12 (ceiling base material 30) of the wafer placement table 10, the bolts 72 are inserted from the upper surface of the clamp member 70 and screwed into the screw holes provided on the upper surface of the installation plate 96, thereby integrating the wafer placement table 10 and the installation plate 96. The bolts 72 are attached to a plurality of locations (e.g., 8 locations or 12 locations) that are 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 may be made of a conductive material (metal, etc.). It is preferable that the clamp member 70 is disposed with a play between the inner peripheral surface of the clamp member 70 and the outer peripheral surface of at least one of the upper base material 12 and the lower base material 80 so that the upper base material 12 and the lower base material 80 can move relative to each other in the horizontal direction.

[0034] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to Figures 4 to 6. Figures 4 to 6 are manufacturing process diagrams of the wafer mounting table 10, with Figure 4 showing the manufacturing process of the upper base material 12, Figure 5 showing the manufacturing process of the lower base material 80, and Figure 6 showing the assembly process of the wafer mounting table 10.

[0035] The upper base material 12 is produced, for example, as follows. First, a disk-shaped ceramic sintered body 120, which is the base material for the ceramic base material 20, is produced by hot-pressing and sintering a ceramic powder compact (FIG. 4A). The ceramic sintered body 120 has a built-in wafer adsorption electrode 26. Next, a hole 27 is made from the bottom surface of the ceramic sintered body 120 to the wafer adsorption electrode 26 (FIG. 4B), 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. 4C).

[0036] In parallel with this, a disk member 130 made of a metal-ceramic composite material is produced (FIG. 4D), and a through hole 131 is formed vertically through the disk member 130 (FIG. 4E). When the ceramic sintered body 120 is made of alumina, the disk member 130 is preferably made of SiSiCTi or AlSiC. This is because the thermal expansion coefficient of alumina is roughly the same as that of SiSiCTi or AlSiC.

[0037] The SiSiCTi disk member can be manufactured, for example, as follows. First, silicon carbide, metal Si, and metal Ti are mixed to produce a powder mixture. Next, the obtained powder mixture is uniaxially pressed to produce a disk-shaped compact, which is then hot-press sintered in an inert atmosphere to obtain the SiSiCTi disk member.

[0038] Next, a metal bonding material is placed on the upper surface of the disk member 130 made of a metal-ceramic composite material. A through hole communicating with the through hole 131 is provided in the metal bonding material. The power supply terminal 54 of the ceramic sintered body 120 is inserted into the through hole 131 of the disk member 130, and the ceramic sintered body 120 is placed on the metal bonding material placed on the upper surface of the disk member 130. This results in a laminate in which the disk member 130, the metal bonding material, and the ceramic sintered body 120 are laminated in this order from below. This laminate is heated and pressurized (TCB) to obtain the bonded body 112 (FIG. 4F). The bonded body 112 is formed by bonding the ceramic sintered body 120 to the upper surface of the disk member 130, which is the base material for the ceiling base material 30, via the metal bonding layer 40.

[0039] For example, TCB is performed as follows. That is, the laminate is pressed and bonded 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 solidus temperature minus 20°C and equal to or lower than the solidus temperature), and then returned to room temperature. This causes the metal bonding material to become a metal bonding layer (or a conductive bonding layer). As the metal bonding material, an Al-Mg-based bonding material or an Al-Si-Mg-based bonding material can be used. For example, when TCB is performed 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 with a thickness of about 100 μm.

[0040] Next, the outer periphery of the ceramic sintered body 120 is cut to form a step, thereby forming the ceramic substrate 20 having a central portion 22 and an outer periphery 24. The outer periphery of the disk member 130 is cut as necessary to form the ceiling substrate 30. At this time, the outer periphery 34 of the ceiling substrate 30 is made to protrude from the outer periphery of the ceramic substrate 20. Furthermore, the side surface of the outer periphery 24 of the ceramic substrate 20, the periphery of the metal bonding layer 40, and the upper surface and side surface of the ceiling substrate 30 are sprayed with ceramic powder to form an insulating film 42 (FIG. 4G). In this way, the upper substrate 12 is obtained.

[0041] The lower base material 80 is produced, for example, as follows. First, a disk-shaped easily processable disk member 180 made of an easily processable material is prepared as the base of the lower base material 80 (FIG. 5A). The easily processable disk member 180 is preferably made of aluminum, aluminum alloy, stainless steel, or resin. Next, a flow path groove 88 and a seal groove 89 (two outer grooves 89a and two inner grooves 89b) are formed on the upper surface of the easily processable disk member 180, and an inlet 88a and an outlet 88b are formed that penetrate in the vertical direction from the lower surface of the easily processable disk member 180 to the bottom surface of the flow path groove 88. In addition, through holes 181 and 182 that penetrate in the vertical direction are formed in the easily processable disk member 180 (FIG. 5B). In this way, the lower base material 80 is obtained.

[0042] The wafer mounting table 10 is assembled, for example, as follows, using the upper base material 12 and the lower base material 80 prepared as described above, and the seal member 16. First, the outer seal member 16a is placed in the outer groove 89a of the lower base material 80, and the inner seal member 16b is placed in the inner groove 89b. Next, the power supply terminal 54 of the upper base material 12 is inserted into the through hole 181, and the upper base material 12 is placed on the seal member 16 placed on the upper surface of the lower base material 80 (FIG. 6A). Then, the insulating tube 55 through which the power supply terminal 54 is inserted is placed in the through holes 131 and 181, and the insulating tube 65 through which the power supply terminal 64 is inserted is placed in the through hole 182 (FIG. 6B). This results in the wafer mounting table 10 in which the lower base material 80, the seal member 16, and the upper base material 12 are stacked in this order from below. The obtained wafer mounting table 10 is used by clamping the upper base material 12 and the lower base material 80 so that the seal member 16 is crushed from above and below.

[0043] Next, an example of use of the wafer stage 10 will be described with reference to Fig. 1. As described above, the wafer stage 10 is fixed to the mounting plate 96 of the chamber 94 by the clamp members 70. A shower head 98 is disposed on the ceiling surface of the chamber 94, which ejects process gas into the chamber 94 from a number of gas injection holes.

[0044] A focus ring 78 is placed on the FR mounting surface 24a of the wafer mounting table 10, and a disk-shaped wafer W is placed on the wafer mounting surface 22a. 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 from the wafer suction DC power supply 52 is applied to the wafer suction electrode 26 to suction the wafer W onto the wafer mounting surface 22a. Then, the interior of the chamber 94 is set to a predetermined vacuum atmosphere (or reduced pressure atmosphere), and an RF voltage from the RF power supply 62 is applied to the ceiling base material 30 while supplying a process gas from the shower head 98. Then, plasma is generated between the wafer W and the shower head 98. Then, the plasma is used to perform CVD film formation or etching on the wafer W. The focus ring 78 is also worn out as the wafer W is plasma-processed, but since the focus ring 78 is thicker than the wafer W, the focus ring 78 is replaced after processing a plurality of wafers W.

[0045] In the wafer mounting table 10 described above, the cooling base material having a refrigerant flow path inside is not used, but the refrigerant flow path 18 is formed by the lower surface of the upper base material 12, the upper surface of the lower base material 80 having a flow path groove 88 on the upper surface, and the seal member 16 arranged between them. In this wafer mounting table 10, the upper base material 12 constituting the ceiling surface of the refrigerant flow path 18 and the lower base material 80 constituting the side wall surface of the refrigerant flow path 18 are not integral with each other, and the seal member 16 is arranged between them. Therefore, even if a thermal expansion difference occurs between the ceiling surface and the side wall surface of the refrigerant flow path 18, the seal member 16 absorbs the effect. Therefore, in the wafer mounting table having the refrigerant flow path, the wafer mounting table can be prevented from being damaged by thermal stress. In addition, since the seal member 16 mitigates the effect of the thermal expansion difference that may occur between the ceiling surface and the side wall surface of the refrigerant flow path 18, it is not necessary to match the thermal expansion coefficients of the ceiling base material 30 constituting the ceiling surface and the lower base material 80 constituting the side wall surface, and the freedom of selection of the materials of the ceiling base material 30 and the lower base material 80 is high.

[0046] In addition, the ceiling base material 30 made of a metal-ceramic composite material, which has higher toughness than ceramic materials, is arranged on the lower surface side of the upper base material 12 where thermal stress is likely to occur, so that it is less likely to break even if thermal stress occurs. In addition, since the ceramic base material 20 and the ceiling base material 30 are joined with a metal joining layer 40, the heat extraction capacity is higher than that of those joined with a resin layer. In addition, since the ceiling base material 30 is made of a metal-ceramic composite material and the absolute value of the difference in linear thermal expansion coefficient with the ceramic base material 20 is small, thermal stress is less likely to occur in the upper base material 12, and warping or breakage of the upper base material 12 due to thermal stress is less likely to occur. Furthermore, since the metal-ceramic composite material has conductivity, the ceiling base material 30 can also be used as an RF electrode, and there is no need to prepare a separate RF electrode. Here, the absolute value of the difference in linear thermal expansion coefficient with the ceramic base material 20 at 40 to 400 °C is 1.5 × 10 -6 / K or less. In this way, the difference in thermal expansion between the ceramic substrate 20 and the ceiling substrate 30 is small, so that thermal stress is unlikely to occur in the upper substrate 12. When the ceramic substrate 20 is an alumina substrate, the metal-ceramic composite material of the ceiling substrate 30 is preferably, for example, AlSiC or SiSiCTi. Since the absolute value of the difference in linear thermal expansion coefficient between the AlSiC or SiSiCTi constituting the ceiling substrate 30 and the alumina constituting the ceramic substrate 20 is small, thermal stress is unlikely to occur in the upper substrate 12. Note that instead of using the ceiling substrate 30 as the RF electrode, the metal bonding layer 40 may be used as the RF electrode, or the lower substrate 80 may be used as the RF electrode.

[0047] Furthermore, since the lower base material 80 is made of an easily processable material, it is easy to form the flow channel groove 88 and the seal groove 89, and processing costs can be reduced. Also, since the seal groove 89 is provided on the upper surface of the lower base material 80, it is easy to position the seal member 16.

[0048] Furthermore, since the outer seal members 16a are provided in multiple layers, the outer seal member 16a on the flow channel 88 side is protected from process gas and plasma by the outermost outer seal member 16a, thereby improving corrosion resistance. In this case, if the outermost outer seal member 16a is made of a material more corrosion resistant than the outer seal member 16a on the flow channel 88 side, corrosion resistance can be further improved. For example, if the outermost outer seal member 16a is made of metal and the outer seal member on the flow channel 88 side is made of metal, Materials 16a may be made of resin.

[0049] The upper base material 12 and the lower base material 80 are clamped by a clamp member 70. In mechanical joining such as clamping, the seal member 16 can be sufficiently crushed from above and below, so that the sealing function of the seal member 16 can be fully exhibited. Note that examples of mechanical joining include clamping, bolt fastening, riveting, and the like.

[0050] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms within the technical scope of the present invention.

[0051] For example, in the wafer mounting table 10 of the above-mentioned embodiment, a hole may be provided penetrating the wafer mounting table 10 from the lower surface of the lower base material 80 to the wafer mounting surface 22a. Examples of such holes include a gas supply hole for supplying a thermally conductive gas (e.g., He gas) to the rear surface of the wafer W, and a lift pin hole for inserting a lift pin for moving the wafer W up and down relative to the wafer mounting surface 22a. The thermally conductive gas is supplied to a space formed by the wafer W and a number of small protrusions (not shown) provided on the wafer mounting surface 22a. When the wafer W is supported by three lift pins, for example, three lift pin holes are provided. When such a through hole is provided, a seal member 16 (inner seal member 16b) is arranged around the gas supply hole and the lift pin hole as well as around the insulating tubes 55, 65 in the space between the lower surface of the upper base material 12 and the upper surface of the lower base material 80.

[0052] In the wafer mounting table 10 of the embodiment described above, the ceiling base material 30 made of a metal-ceramic composite material is used, but a metal ceiling base material may be used instead. In this case, the metal ceiling base material is preferably one that has high toughness and is conductive, similar to the ceiling base material 30 made of a metal-ceramic composite material. In addition, the absolute value of the difference in linear thermal expansion coefficient between the metal ceiling base material and the ceramic base material 20 at 40 to 400°C is 1.5×10 -6 / K or less. For example, when the ceramic substrate 20 is an aluminum nitride substrate, the metal ceiling substrate may be a molybdenum substrate. The linear thermal expansion coefficient of aluminum nitride at 40 to 400°C is 4.6×10 -6 / K, and molybdenum is 5.6×10 -6 / K.

[0053] In the wafer mounting table 10 of the above embodiment, the ceiling base material 30 made of a metal-ceramic composite material is used, but as in the wafer mounting table 210 of FIG. 7, a ceiling base material 230 made of a ceramic material having the same main component as the ceramic base material 20 may be used. FIG. 7 is a vertical cross-sectional view of the wafer mounting table 210 equipped with the ceiling base material 230. In FIG. 7, the same components as those in the above embodiment are given the same reference numerals. In the wafer mounting table 210, the upper base material 212 includes the ceramic base material 20, the ceiling base material 230 arranged below the ceramic base material 20 and constituting the ceiling of the refrigerant flow path 18, and a metal bonding layer 40 bonding the ceramic base material 20 and the ceiling base material 230. The ceiling base material 230 is made of a ceramic material having the same main component as the ceramic base material 20. The main component refers to a component that occupies 50 mass% or more of the total components contained therein, preferably 70 mass% or more, and more preferably 90 mass% or more. When the absolute value of the difference in linear thermal expansion coefficient between ceramic materials having the same main component is 100%, the absolute value of the difference in linear thermal expansion coefficient between the ceramic base material 20 and the ceiling base material 230 is 100%, and the absolute value of the difference in linear thermal expansion coefficient between the ceramic base material 20 and the ceiling base material 230 is 100%. smallTherefore, in the upper base material 212 provided with such a ceiling base material 230, the difference in thermal expansion between the ceiling base material 230 and the ceramic base material 20 is small, and the upper base material 212 is less likely to warp or break due to thermal stress. The ceiling base material 230 may be made of a material with a lower purity than the ceramic base material 20. For example, the ceramic base material 20 may be made of alumina with a high purity (e.g., alumina 99% or more) from the viewpoint of improving the electrical characteristics as a dielectric layer, and the ceiling base material 230 may be made of alumina with a low purity (e.g., alumina less than 99%) from the viewpoint of improving mechanical characteristics (toughness and strength) and reducing costs. The material with a low purity may contain more glass such as SiO2 than the material with a high purity. The ceiling base material 230 made of a ceramic material is not conductive, and therefore cannot be used as an RF electrode. Therefore, in the wafer mounting table 210, an RF power source may be connected to the metal bonding layer 40 via the power supply terminal 64 to provide the function as an RF electrode. The power supply terminal 64 is provided so as to pass through the insulating tube 65 and reach the metal bonding layer 40 from the lower surface of the ceiling base material 230. In the above-described wafer mounting table 210, the ceiling base material 230 has a lower toughness than the ceiling base material 30 made of a metal-ceramic composite material, and the ceiling base material 230 cannot function as an RF electrode, but otherwise the same effects as the wafer mounting table 10 can be obtained. In addition, the wafer mounting table 210 has an advantage that the thermal expansion coefficients of the ceramic base material 20 and the ceiling base material 230 can be easily matched, and the procurement cost can be kept low compared to the case of using a metal-ceramic composite material. In the wafer mounting table 210, the ceiling base material 230 is made of a ceramic material having the same main component as the ceramic base material 20, but it may be made of a ceramic material having a different main component from the ceramic base material 20. In this case, the absolute value of the linear thermal expansion coefficient difference between the ceramic base material 20 and the ceramic base material 20 at 40 to 400°C is 1.5×10 -6 / K or less. Also, instead of using the metal bonding layer 40 as the RF electrode, the lower base material 80 may be used as the RF electrode. Also, although the ceramic base material 20 and the ceiling base material 230 are bonded to each other by the metal bonding layer 40, the ceramic base material 20 and the ceiling base material 230 may be integrally sintered during production to omit the metal bonding layer 40.

[0054] In the wafer mounting table 10 of the embodiment described above, the upper base material 12 includes the ceramic base material 20, the ceiling base material 30, and the metal bonding layer 40. However, as in the wafer mounting table 310 of FIG. 8, the upper base material 312 may be a single layer of the ceramic base material 320. FIG. 8 is a vertical cross-sectional view of the wafer mounting table 310 including the upper base material 312 including the single layer of the ceramic base material 320. In FIG. 8, the same components as those in the embodiment described above are denoted by the same reference numerals. In the wafer mounting table 310, the upper base material 312 is a single layer of the ceramic base material 320. The material of the ceramic base material 320 is the same as that of the ceramic base material 20. The ceramic base material 320 includes an outermost portion 325 on the outer periphery of the outer periphery 24 having the focus ring mounting surface 24a. The upper surface of the outermost portion 325 is lower than the focus ring mounting surface 24a. The outer diameter of the outermost portion 325 is the same as the outer diameter of the lower base material 80. The upper substrate 312 is clamped to the mounting plate 96 together with the lower substrate 80 at the outermost periphery 325. The central portion 22 of the ceramic substrate 320 incorporates an RF electrode 328 between the wafer chucking electrode 26 and the lower surface of the ceramic substrate 320. The RF electrode 328 is made of a material containing, for example, W, Mo, WC, MoC, etc. An RF power source is connected to the RF electrode 328 via a power supply terminal 64. The power supply terminal 64 passes through an insulating tube 65 arranged in a through hole that passes through the lower substrate 80 in the vertical direction, and is connected to the ceramic substrate 320. 320 The ceramic substrate 320 is provided so as to extend from the lower surface of the ceramic substrate 320 to the RF electrode 328. The above-described wafer mounting table 310 does not provide the effect of protecting the ceramic substrate 20 by the ceiling substrate 30, but otherwise provides the same effects as the wafer mounting table 10. Also, in the wafer mounting table 310, the ceramic substrate 320 is provided so as to be attached to another member (ceiling substrate 30). 30 The advantage of this method is that it is not necessary to bond the ceramic base 320 to a substrate (such as a ceramic base), and therefore the TCB can be omitted. In the wafer mounting table 310, the ceramic base 320 has a built-in RF electrode 328, but the RF electrode 328 may be provided on the lower surface. Alternatively, the lower base 80 may be used as the RF electrode.

[0055] In the wafer mounting table 10 of the embodiment described above, the ceramic substrate 20 has a smaller outer diameter than the ceiling substrate 30 and the lower substrate 80, but the outer diameter may be the same as the ceiling substrate 30 and the lower substrate 80. In this case, the ceramic substrate 20 may have an outermost periphery that is one step lower than the focus ring mounting surface 24a, on the outer periphery of the outer periphery 24, as in the ceramic substrate 320 of the wafer mounting table 310 in FIG. 8. In this case, the wafer mounting table 10 and the mounting plate 96 are integrated in a state in which the inner peripheral step surface 70a of the clamp member 70 is placed on the outermost periphery of the ceramic substrate 320. As a result, the upper substrate 12 and the lower substrate 80 of the wafer mounting table 10 are clamped, the seal member 16 is pressed vertically, and the coolant flow path 18 is sealed from the outside. At this time, the outer periphery 34 of the ceiling base material 30 of the upper base material 12 is reinforced by the outermost periphery of the ceramic base material 20, increasing the rigidity of the clamped portion, so that the sealing member 16 is firmly pressed in the vertical direction by the clamp, thereby enabling a more reliable seal.

[0056] In the above-described embodiment, the wafer mounting table 10 is attached to the installation plate 96 using the clamp member 70. However, as shown in FIG. 9, the wafer mounting table 10 may be attached to the installation plate 96 using the bolt 76. This mechanically bonds the upper base material 12 and the lower base material 80 of the wafer mounting table 10. The bolt 76 is preferably disposed with a play between the outer peripheral surface of the bolt 76 and the inner peripheral surface of the mounting hole of at least one of the upper base material 12 and the lower base material 80 so that the upper base material 12 and the lower base material 80 can move relatively in the horizontal direction. The upper base material 12 and the lower base material 80 may be mechanically bonded (clamped or bolted, etc.) and attached to the installation plate 96 separately. Also, instead of bolting from above, the bolts may be bolted from below. In that case, the upper base material 12 and the lower base material 80 may be mechanically bonded on the inner peripheral side instead of the outer peripheral side.

[0057] In the above embodiment, the wafer adsorption electrode 26 is built into the center portion 22 of the ceramic substrate 20. Instead of or in addition to this, an RF electrode for generating plasma may be built into the ceramic substrate 20. In this case, a high frequency power source is connected to the RF electrode, not to the ceiling substrate 30. Also, a focus ring (FR) adsorption electrode may be built into the outer periphery 24 of the ceramic substrate 20. In this case, a DC power source is connected to the FR adsorption electrode. Also, the ceramic substrate 20 may have a heater electrode (resistance heating element) built into it. In this case, a heater power source is connected to the heater electrode. In this way, the ceramic substrate 20 may have one layer of electrodes built into it, or two or more layers built into it. The same applies to the ceramic substrate 320.

[0058] In the embodiment described above, the seal groove 89 in which the seal member 16 is disposed is provided on the upper surface of the lower base material 80, but the seal groove 89 may be omitted, or a seal groove may be provided on the lower surface of the upper base material 12.

[0059] In the above embodiment, the outer seal member 16a is doubled, but may be singled, or may be tripled or more. The inner seal member 16b is singled, but may be doubled or more. Also, instead of or in addition to the outer seal member 16a or the inner seal member 16b, a parallel seal member provided along the flow channel 88 so as to surround the flow channel 88 may be arranged. When the parallel seal member is used, the flow of the refrigerant through the gap between the lower surface of the upper base material 12 and the upper surface of the lower base material 80 is suppressed. Even if the parallel seal member is not present, the flow of the refrigerant through the gap between the lower surface of the upper base material 12 and the upper surface of the lower base material 80 is not so much, so there is almost no effect on the thermal uniformity due to the flow of the refrigerant through the gap. Also, it is easier to manufacture without the parallel seal member.

[0060] In the above-described embodiment, the flow passage groove 88 is provided in a spiral shape from the inlet 88a to the outlet 88b, but there is no particular limitation on the shape of the flow passage groove 88. In addition, a plurality of flow passage grooves 88 may be provided.

[0061] In the above-described embodiment, the insulating tube 65 may be omitted.

[0062] In the above-described embodiment, the ceramic sintered body 120 in FIG. 4A was produced by hot-press sintering a ceramic powder compact. However, the compact may be produced by stacking a plurality of tape compacts, by a mold casting method, or by compressing ceramic powder.

[0063] In the above embodiment, the lower substrate 80 is made of an easily processable material, but the lower substrate 80 may be made of a composite material of metal and ceramic, or may be made of a low thermal expansion metal such as molybdenum. In this way, the difference in thermal expansion coefficient between the lower substrate 80 and the upper substrate 12 is small, so that warping and damage of the upper substrate 12 and the lower substrate 80 due to thermal stress can be further suppressed.

[0064] In the wafer mounting table 10 of the above embodiment, a gap exists between the lower surface of the upper base material 12 and the upper surface of the lower base material 80. However, as in the wafer mounting table 410 shown in FIGS. 10 and 11, a heat dissipation sheet 417 may be disposed between the lower surface of the upper base material 412 and the upper surface of the lower base material 480. FIG. 10 is a vertical cross-sectional view of the wafer mounting table 410 provided with the heat dissipation sheet 417. FIG. 11 is a cross-sectional view of the wafer mounting table 410 cut along a horizontal plane including the heat dissipation sheet 417, as viewed from above. In FIGS. 10 and 11, the same components as those in the above embodiment are denoted by the same reference numerals. In this wafer mounting table 410, the upper base material 412 and the lower base material 480 are fastened to each other by a screw member 477 (e.g., a bolt). The wafer mounting table 410 is fastened to a mounting plate 96 provided inside a chamber 94 by a screw member 472 (e.g., a bolt). The screw member 472 is inserted from the underside of the installation plate 96 and screwed into a screw hole 488 opening in the underside of the lower base material 480. The power supply terminal 64 is connected to the lower base material 480, not to the ceiling base material 430. Note that a configuration similar to that of the wafer mounting table 410 can be appropriately adopted not only for the wafer mounting table 10, but also for the wafer mounting table 210 and the wafer mounting table 310.

[0065] The upper base material 412 is configured similarly to the upper base material 12, except that it is provided with a ceiling base material 430 having a plurality of screw holes 437 opened on its underside. The ceiling base material 430 is configured similarly to the ceiling base material 30, except that it has a plurality of screw holes 437 opened on its underside. Here, the screw holes 437 are provided at one location in the center of the ceiling base material 430, six locations on the outer periphery of the ceiling base material 430 at equal intervals along the circumferential direction of the ceiling base material 430, and four locations on the outer periphery of the ceiling base material 430 at equal intervals along the circumferential direction of the ceiling base material 430. Ceiling Base Material Six screw holes 437 are provided at equal intervals along the circumferential direction of the ceiling base material 430, but are not limited thereto. In this embodiment, the screw holes 437 are formed by providing a cylindrical hole on the lower surface of the ceiling base material 430 and directly cutting a screw groove (not shown) in the cylindrical hole, but are not limited thereto. For example, the screw holes 437 may be formed by inserting a spiral screw insert into the cylindrical hole, or may be formed by inserting a female threaded terminal (such as a cap nut) into the cylindrical hole and soldering it. The depth of the screw holes 437 is not particularly limited, but may be 2 times or less the nominal diameter of the screw member 477, or may be 1.5 times or less. In this way, the thickness of the upper base material 412 and the ceiling base material 430 can be reduced. The depth of the screw holes 437 is preferably 1 time or more the nominal diameter of the screw member 477 from the viewpoint of generating sufficient axial force of the screw member 477. The center-to-center distance between two adjacent screw holes 437 is not particularly limited, but is preferably 100 mm or less, for example. In this way, the ceiling base material 430 and the lower base material 480 can be tightly fastened together by the screw members 477, which in turn improves the thermal conductivity of the heat dissipation sheet 417. The center-to-center distance between two adjacent screw holes 437 may be, for example, 50 mm or more. The screw holes 437 are provided on the lower surface of the ceiling base material 430 at a density of 150 holes / m. 2 It is preferable that the number of particles is 200 / m or more. 2 It is more preferable that the screw members are arranged in the above ratio. 477This allows the ceiling base material 430 and the lower base material 480 to be more tightly fastened together, thereby improving the thermal conductivity of the heat dissipation sheet 417. The screw hole 437 only needs to open to the lower surface of the ceiling base material 430, and may be a blind hole as shown in FIG. 10, or a through hole penetrating from the lower surface to the upper surface of the ceiling base material 430. In the wafer placement table 310 of FIG. 8, the upper base material 312 does not have a member equivalent to the ceiling base material 430, but a screw hole similar to the screw hole 437 may be provided in the lower surface of the upper base material 312 made of the ceramic base material 320. In this case, it is preferable that the screw hole is a blind hole that does not reach the wafer suction electrode 26.

[0066] The lower base material 480 has a plurality of through holes 487, and is configured similarly to the lower base material 80, except that it has a screw hole 488 on the lower surface. The through holes 487 are provided at positions facing the screw holes 437, and penetrate the lower base material 480 in the up-down direction. The through holes 487 are stepped holes with a large diameter on the lower side and a small diameter on the upper side. The through holes 487 have a large diameter portion 487a that receives the head 477a of the screw member 477, and a small diameter portion 487b through which the foot portion 477b of the screw member 477 can pass but the head 477a cannot pass.

[0067] The heat dissipation sheet 417 is disposed between the lower surface of the upper base material 412 and a portion of the upper surface of the lower base material 480 where neither the flow path groove 88 nor the seal member 16 is provided. The heat dissipation sheet 417 is sandwiched between the upper base material 412 and the lower base material 480 and compressed in the vertical direction. This allows the heat dissipation sheet 417 to be firmly attached to the lower surface of the upper base material 412 and the upper surface of the lower base material 480, so that heat from the upper base material 412 is rapidly conducted to the lower base material 480. The thermal resistance of the heat dissipation sheet 417 is 0.5 K·cm 2 / W or less is preferable, and 0.35K cm 2 / W or less is preferable, and 0.1K cm 2 / W or less is more preferable. In this way, the efficiency of cooling the wafer W can be further improved. The thermal conductivity of the heat dissipation sheet 417 is preferably 2 W / (m·K) or more, more preferably 3 W / (m·K) or more, and even more preferably 10 W / (m·K) or more. In this way, the efficiency of cooling the wafer W can be further improved. The thermal resistance and thermal conductivity of the heat dissipation sheet 417 are the thermal resistance and thermal conductivity in the vertical direction in a state in which the heat dissipation sheet 417 is assembled (i.e., a state in which the heat dissipation sheet 417 is compressed in the vertical direction with a predetermined pressure), and can be measured in accordance with ASTM-D5470. The Young's modulus of the heat dissipation sheet 417 is preferably 100 MPa or less, more preferably 20 MPa or less, and even more preferably 5 MPa or less. The smaller the Young's modulus of the heat dissipation sheet 417, the more evenly the fastening force of the screw member 477 is transmitted over the entire surface of the heat dissipation sheet 417, and the heat dissipation sheet 417 is tightly attached to the upper base material 412 and the lower base material 480 over the entire surface. Therefore, the wafer W can be cooled more uniformly. The Poisson's ratio of the heat dissipation sheet 417 is preferably 0.4 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. The smaller the Poisson's ratio of the heat dissipation sheet 417, the more evenly the fastening force of the screw member 477 is transmitted over the entire surface of the heat dissipation sheet 417, and the less likely it is to escape in the lateral direction, and the heat dissipation sheet 417 is tightly attached to the upper base material 412 and the lower base material 480 over the entire surface. Therefore, the wafer W can be cooled more uniformly. The Shore hardness (Shore OO) of the heat dissipation sheet 417 may be 50 or more and 80 or less. The thickness of heat dissipation sheet 417 is preferably, for example, 0.05 mm or more and 1 mm or less, and more preferably 0.1 mm or more and 0.3 mm or less.

[0068] Specifically, the heat dissipation sheet 417 is preferably a sheet containing carbon and resin. Examples of carbon include graphite, carbon fiber, and carbon nanotubes, and examples of resin include silicone resin. When the carbon is graphite, it is preferable to arrange the graphene constituting the graphite so that the plane direction is along the vertical direction, and when the carbon is carbon fiber or carbon nanotubes, it is preferable to arrange the graphene so that the axial direction is along the vertical direction. For example, a thermal interface material (TIM) can be used as the material of the heat dissipation sheet 417. Specific examples of the heat dissipation sheet 417 include the EX20000C9 series and the EX20000C4S series (both manufactured by Dexerials Corporation), GraphitePAD, and GraphiteTIM (registered trademark) (both manufactured by Panasonic Corporation).

[0069] The screw member 477 has a large-diameter head 477a and a small-diameter foot 477b. The screw member 477 is inserted into the through hole 487 from the lower surface of the lower base material 480 and screwed into the screw hole 437 of the ceiling base material 430. The head 477a of the screw member 477 is stored in the large-diameter part 487a so as not to protrude below the lower surface of the lower base material 480. By screwing the screw member 477 into the screw hole 437, the upper base material 412 and the lower base material 480 are fastened with the heat dissipation sheet 417 and the seal member 16 sandwiched between them. As a result, the heat dissipation sheet 417 and the seal member 16 are compressed in the vertical direction. The material of the screw member 477 is preferably a material with good electrical conductivity and thermal conductivity, for example, stainless steel. The nominal diameter of the screw member 477 may be, for example, 3 mm or more and 10 mm or less, 4 mm or more and 8 mm or less, or 6 mm or more and 8 mm or less.

[0070] In this wafer mounting table 410, the heat dissipation sheet 417 makes it easier for the heat of the upper base material 412 to be quickly conducted to the lower base material 480. Therefore, the effect of cooling the wafer W is enhanced. In addition, the upper base material 412 and the lower base material 480 are fastened with screw members 477. As a result, the heat dissipation sheet 417 is firmly attached to the upper base material 412 and the lower base material 480, so that the heat of the upper base material 412 is quickly conducted to the lower base material 480. As a result, the effect of cooling the wafer is enhanced. In addition, if the heat dissipation sheet 417 is not present, a refrigerant will enter instead of the heat dissipation sheet 417, but the refrigerant that enters the gap between the upper base material 412 and the lower base material 480 is difficult to flow and often remains there. Therefore, it becomes difficult to use the gap to release the heat of the upper base material 412 to the lower base material 480. Therefore, it is preferable to place the heat dissipation sheet 417 with low thermal resistance (good thermal conductivity) in the gap, as in the wafer mounting table 410.

[0071] The thermal resistance of the heat dissipation sheet 417 is 0.50K·cm 2 / W or less. In this way, heat from the upper base material 412 is more quickly conducted to the lower base material 480, and the efficiency of cooling the wafer W is further increased. To achieve such thermal resistance, the pressure for compressing the heat dissipation sheet 417 in the vertical direction is preferably, for example, 0.05 MPa or more or 0.2 MPa or more. In this way, the heat dissipation sheet 417 is firmly attached to the upper base material 412 and the lower base material 480, and the thermal resistance of the heat dissipation sheet 417 can be reduced. From the viewpoint of suppressing damage to the heat dissipation sheet 417, the pressure for compressing the heat dissipation sheet 417 in the vertical direction is preferably, for example, 0.6 MPa or less or 0.55 MPa or less. Incidentally, the pressure for compressing the heat dissipation sheet 417 in the vertical direction tends to be smaller the farther it is from the screw member 477, and there is a range of pressure in the in-plane direction. When the pressure variation [-] is evaluated by dividing the pressure range [MPa] by the surface pressure [MPa] applied to the heat dissipation sheet 417 when the axial force of the screw member 477 is assumed to be evenly applied to the heat dissipation sheet 417, the pressure variation is preferably 2.0 or less, more preferably 1.7 or less, and even more preferably 1.0 or less. The pressure variation can be reduced as the Young's modulus of the heat dissipation sheet 417 is smaller and as the center-to-center distance of the screw holes 437 is smaller. On the other hand, if the center-to-center distance of the screw holes 437 is reduced in order to reduce the pressure variation, a large number of screw holes 437 are required, which may make it difficult to arrange the screw holes 437. According to a simulation, when the Young's modulus of the heat dissipation sheet 417 is 80 MPa or less, the pressure variation is 2.0 or less if the center-to-center distance of the screw holes 437 is 70 mm or less, and the pressure variation is 1.0 or less if the center-to-center distance of the screw holes is 55 mm or less. Furthermore, when the Young's modulus of heat dissipation sheet 417 is 10 MPa or less, even if the center-to-center distance of screw holes 437 is 100 mm, the pressure variation is approximately 1. Thus, from the viewpoint of reducing the pressure variation without making the center-to-center distance of screw holes 437 too small, the Young's modulus of heat dissipation sheet 417 is preferably 80 MPa or less, and more preferably 10 MPa or less. It is desirable to set the number and arrangement of screw holes 437 taking into account the pressure required to compress heat dissipation sheet 417 and seal member 16, the pressure required to withstand the pressure of the refrigerant flowing through refrigerant flow path 18, and the pressure variation.

[0072] Heat dissipation sheet 417 is conductive. As a result, lower base material 480 has the same potential as ceiling base material 430 and metal bonding layer 40, and therefore, by connecting power supply terminal 64 to lower base material 480, ceiling base material 430 and metal bonding layer 40 can be used as RF electrodes, making it easier to generate plasma above wafer W. Note that conductive screw member 477 may be used to set lower base material 480 and ceiling base material 430 to the same potential via screw member 477.

[0073] In addition, in the wafer mounting table 410, a heat dissipation sheet 418 shown in FIG. 12 may be used instead of the heat dissipation sheet 417. The heat dissipation sheet 418 includes a main body portion 418a having the same shape as the heat dissipation sheet 417, and a bridge portion 418b that is bridged over the flow channel 88. The main body portion 418a can quickly conduct heat from the upper base material 412 to the lower base material 480. The bridge portion 418b can maintain the sheet shape of the heat dissipation sheet 418 and improve the handleability of the heat dissipation sheet 418. In order to increase the efficiency of cooling the wafer W, it is preferable that the area ratio of the heat dissipation sheet present on the flow channel 88 is low. Therefore, the area of ​​the bridge portion 418b is, for example, preferably 1 / 5 or less of the area of ​​the flow channel 88, more preferably 1 / 10 or less.

[0074] In the above-described wafer mounting table 410, the seal member 16 and the heat dissipation sheet 417 are used in combination, but the heat dissipation sheet 417 may also function as a seal member.

[0075] 10, the wafer mounting table 410 in which the upper base material 412 and the lower base material 480 are fastened with the screw members 477 is mounted on the mounting plate 96 of the chamber 94, but the present invention is not particularly limited to this. For example, as in the wafer mounting table 510 shown in FIG 13, the lower base material 480 may also serve as the mounting plate 96 of the chamber 94. Note that in FIG 13, the same components as those in the above-mentioned embodiments are denoted by the same reference numerals. [Explanation of symbols]

[0076] 10 wafer mounting table, 12 upper substrate, 16 seal member, 16a outer seal member, 16b inner seal member, 18 coolant flow path, 20 ceramic substrate, 22 center, 22a wafer mounting surface, 24 outer periphery, 24a focus ring mounting surface, 26 wafer suction electrode, 27 hole, 30 ceiling substrate, 32 inner periphery, 34 outer periphery, 40 metal bonding layer, 42 insulating film, 52 wafer suction DC power source, 53 low pass filter, 54 power supply terminal, 55 insulating tube, 62 RF power source, 63 high pass filter, 64 power supply terminal, 65 insulating tube, 70 clamp member, 70a inner peripheral step surface, 72 bolt, 76 bolt, 78 focus ring, 80 lower substrate, 88 flow path groove, 88a inlet, 88b outlet, 89 seal groove, 89a Outer groove, 89b Inner groove, 94 Chamber, 96 Installation plate, 98 Shower head, 112 Bonded body, 120 Ceramic sintered body, 130 Disk member, 131 Through hole, 180 Easily processable disk member, 181, 182 Through hole, 210 Wafer placement table, 212 Upper base material, 230 Ceiling base material, 310 Wafer placement table, 312 Upper base material, 320 Ceramic base material, 325 Outermost periphery, 328 RF electrode, 410 Wafer placement table, 412 Upper base material, 417 Heat dissipation sheet, 418 Heat dissipation sheet, 418a Main body, 418b Bridge, 430 Ceiling base material, 437 Screw hole, 472 Screw member, 477 Screw member, 477a Head, 477b Foot, 487 Through hole, 487a Large diameter part, 487b small diameter part, 488 screw hole, 510 wafer placement platform.

Claims

1. A wafer mounting table having a coolant flow path for circulating a coolant, an upper substrate including a ceramic substrate having an electrode built therein and a wafer mounting surface on an upper surface of the ceramic substrate; a lower base material having a flow channel on an upper surface thereof, the flow channel forming a side wall and a bottom of the refrigerant flow channel; a seal member disposed between the upper base material and the lower base material so as to seal between the refrigerant flow path and the outside; Equipped with a heat dissipation sheet is disposed between the lower surface of the upper substrate and the upper surface of the lower substrate; The heat dissipation sheet is a separate member from the sealing member. Wafer placement stage.

2. The upper base material includes the ceramic base material, a ceiling base material bonded to a lower surface of the ceramic base material to form a ceiling of the refrigerant flow path, and a metal bonding layer bonding the ceramic base material and the ceiling base material. The wafer stage according to claim 1 .

3. The absolute value of the difference in linear thermal expansion coefficient between the ceiling base material and the ceramic base material at 40 to 400° C. is 1.5×10 -6 / K or less, The wafer stage according to claim 2 .

4. The ceiling substrate is made of a composite material of metal and ceramic. The wafer stage according to claim 2 or 3.

5. The ceiling base material is made of a ceramic material having the same main component as the ceramic base material. The wafer stage according to claim 2 or 3.

6. The upper substrate is a single layer of the ceramic substrate. The wafer stage according to claim 1 .

7. The lower substrate is made of an easily processable material; The wafer mounting table according to any one of claims 1 to 3 and 6.

8. The sealing member includes an outer sealing member provided in multiple layers so as to surround the outermost edge of the flow channel. The wafer mounting table according to any one of claims 1 to 3 and 6.

9. The thermal resistance of the heat dissipation sheet is 0.5 K cm 2 / W or less, The wafer mounting table according to any one of claims 1 to 3 and 6.

10. The Young's modulus of the heat dissipation sheet is 100 MPa or less. The wafer mounting table according to any one of claims 1 to 3 and 6.

11. A wafer mounting table having a coolant flow path for circulating a coolant, an upper substrate including a ceramic substrate having an electrode built therein and a wafer mounting surface on an upper surface of the ceramic substrate; a lower base material having a flow channel on an upper surface thereof, the flow channel forming a side wall and a bottom of the refrigerant flow channel; a seal member disposed between the upper base material and the lower base material so as to seal between the refrigerant flow path and the outside; Equipped with a heat dissipation sheet is disposed between the lower surface of the upper substrate and the upper surface of the lower substrate; The heat dissipation sheet includes a main body portion disposed on a portion of the upper surface of the lower base material where the flow path groove is not provided, and a bridging portion bridged over the flow path groove. Wafer placement stage.

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