Wafer carrying table

Abstract

A wafer placement table 10 is provided with: a ceramic plate 20 having a wafer placement surface 22a and having built-in electrodes; a cooling plate (30) made of a metal-ceramic composite material, the cooling plate (30) having a refrigerant flow path (32); and a bonding layer (40) that bonds the two plates (20, 30). The length from the wafer placement surface (22a) to at least one of the upper bottom and the lower bottom of the refrigerant flow path (32) is not constant in the entire refrigerant flow path (32), but there is a portion in which the length changes. The cooling plate (30) has a structure in which a plurality of plate sections including a first thin plate section (81) and a second thin plate section (82) that are joined to each other are metal-joined, and the first thin plate section (81) has a first flow path section that is a through-channel provided in the same shape as the refrigerant flow path (32) in plan view. The second thin plate section 82 has a second flow path section that is a bottomed groove provided in at least a portion of a position facing the first flow path section.

Description

Technical Field The present invention relates to a wafer loading platform. Background Art In the past, the following wafer carrier is known, which includes: a ceramic plate having a wafer carrier surface and a built-in electrode; a cooling plate having a coolant flow path; and a bonding layer that bonds the ceramic plate and the cooling plate. For example, Patent Document 1 records the following content, that is, as the cooling plate of the above-mentioned wafer carrier, a plate made of a metal-based composite material having a linear thermal expansion coefficient of the same degree as that of the ceramic plate is used. When making the cooling plate, first, an upper substrate, a middle substrate and a lower substrate are prepared, all of which are disc-shaped plates. Next, a punching portion is formed in the middle substrate by punching from one surface to the other surface of the middle substrate in the same shape as the coolant flow path. Both surfaces of the upper substrate and the lower substrate are flat surfaces. Then, a metal bonding material is sandwiched between the upper substrate and the middle substrate, and a metal bonding material is sandwiched between the middle substrate and the lower substrate, and these substrates are thermally pressed together. Accordingly, a cooling plate in which the punching portion becomes a coolant flow path is obtained. Prior art literature Patent Literature Patent Document 1: Japanese Patent No. 5666748 Summary of the invention However, in Patent Document 1, the distance from the upper bottom of the coolant flow path to the wafer placement surface and the distance from the lower bottom of the coolant flow path to the wafer placement surface are constant throughout the coolant flow path, so sometimes it is not possible to fully obtain thermal uniformity of the wafer. Therefore, it is desired to develop a wafer placement table that fully obtains thermal uniformity of the wafer. In addition, it is also desired to suppress the manufacturing cost of the wafer placement table to a low level. The present invention has been made to solve the above-mentioned problems, and its main object is to improve the thermal uniformity of a wafer and to suppress the manufacturing cost to a low level.

[0001] The wafer loading platform of the present invention comprises: A ceramic plate having a wafer placement surface on an upper surface thereof on which a wafer can be placed and having electrodes built therein; A cooling plate made of a metal-ceramic composite material, the cooling plate having a refrigerant flow path; and a bonding layer bonding the ceramic plate and the cooling plate, The wafer stage is characterized in that: The length from the wafer placement surface to at least one of the upper bottom and the lower bottom of the coolant flow path is not constant throughout the coolant flow path, but there is a portion where the length changes. The cooling plate is a structure obtained by metal bonding of multiple plate portions including a first plate portion and a second plate portion that are bonded to each other, the first plate portion having a first flow path portion, which is a through groove arranged to have the same shape as the refrigerant flow path when viewed from above, and the second plate portion having a second flow path portion, which is a bottomed groove arranged at at least a portion of a position opposite to the first flow path portion. In the wafer carrier, the length from the wafer carrier surface to at least one of the upper bottom and the lower bottom of the coolant flow path is not constant in the whole of the coolant flow path, but there is a part where the length changes. For example, corresponding to the part of the wafer carrier surface that is easy to become high temperature and the part that is easy to become low temperature, the length from the wafer carrier surface to at least one of the upper bottom and the lower bottom of the coolant flow path changes, thereby improving the thermal uniformity of the wafer. On the other hand, the cooling plate is a structure obtained by metal bonding of multiple plate parts including a first plate part and a second plate part that are bonded to each other. The first plate part has a first flow path part, which is a through groove that is arranged to be the same shape as the coolant flow path when viewed from above. The second plate part has a second flow path part, which is a bottomed groove that is arranged at least a part of the position opposite to the first flow path part. The first flow path part can be formed at low cost by, for example, hollowing processing. The second flow path part can be formed by, for example, cutting processing and grinding processing, but since the depth is relatively shallow, it can be formed in a short time and can be formed at low cost.

[0002] In the wafer placement platform (the wafer placement platform described in [1]), the width of the coolant flow path may not be constant throughout the coolant flow path, but may have a portion where the width changes. Accordingly, the width of the coolant flow path changes in accordance with a portion of the wafer placement surface that is prone to high temperature and a portion that is prone to low temperature, thereby improving the thermal uniformity of the wafer.

[0003] In the wafer placement table (the wafer placement table described in [1] or [2]), the coolant flow path may have a portion having fins on at least one of the upper and lower bottoms of the coolant flow path. Accordingly, by providing fins in the coolant flow path of the portion of the wafer placement surface that is prone to high temperature, efficient cooling can be achieved.

[0004] In the wafer placement table (the wafer placement table described in any one of [1] to [3]), the cooling plate may include a third plate portion, the third plate portion being joined to a surface of the first plate portion on the opposite side to the second plate portion, and the third plate portion may include a third flow path portion, the third flow path portion being a bottomed groove disposed at at least a portion of a position opposite to the first flow path portion. In this way, the position of one of the upper bottom and the lower bottom of the coolant flow path or the positions of both can be changed.

[0005] In the wafer placement table (the wafer placement table described in any one of [1] to [3]), the cooling plate may include a third plate portion, the third plate portion being joined to a surface of the first plate portion on the opposite side to the second plate portion, and the surface of the third plate portion facing the first flow path portion may be flat. In this way, the position of one of the upper bottom and the lower bottom of the coolant flow path can be changed. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a longitudinal cross-sectional view of the wafer stage 10 installed in the chamber 94 . Figure 2 This is a cross-sectional view when a cross section of the cooling plate 30 cut along a horizontal plane passing through the first thin plate portion 81 is viewed from above. Figure 3 It is a longitudinal cross-sectional view of the cooling plate 30 . Figure 4 It is a manufacturing process diagram of the wafer stage 10. Figure 5 It is a process diagram of the first to third thin plate parts 81 to 83 . Figure 6 It is a longitudinal cross-sectional view of the cooling plate 130 . Figure 7 It is a longitudinal cross-sectional view of the cooling plate 230 . Figure 8 It is a longitudinal cross-sectional view of the cooling plate 330 . Fig. 9 4 is a longitudinal cross-sectional view of the cooling plate 430 . DETAILED DESCRIPTION Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 1 is a longitudinal cross-sectional view of the wafer stage 10 provided in the chamber 94 (a cross-sectional view when cut along a plane including the central axis of the wafer stage 10). Figure 2 This is a cross-sectional view of the cooling plate 30 cut along a horizontal plane passing through the first thin plate portion 81 when viewed from above. Figure 2 The terminal hole 51, power supply terminal 54 and insulation tube 55 are omitted. The wafer stage 10 is a member used to perform CVD, etching, etc. on the wafer W using plasma, and is fixed to a mounting plate 96 provided inside a chamber 94 for semiconductor processes. The wafer stage 10 includes a ceramic plate 20 , a cooling plate 30 , and a metal bonding layer 40 . The ceramic plate 20 has an outer peripheral portion 24 having an annular focus ring placement surface 24a on the outer periphery of a central portion 22 having a circular wafer placement surface 22a. Hereinafter, the focus ring is sometimes referred to as "FR". A wafer W is placed on the wafer placement surface 22a, and a focus ring 78 is placed on the FR placement surface 24a. The ceramic plate 20 is formed of a ceramic material represented by aluminum oxide, aluminum nitride, etc. The FR placement surface 24a is one level lower than the wafer placement surface 22a. The central portion 22 of the ceramic plate 20 has a built-in chip adsorption electrode 26 on the side close to the chip placement surface 22a. The chip adsorption electrode 26 is formed of a material containing, for example, W, Mo, WC, MoC, etc. The chip adsorption electrode 26 is a disk-shaped or mesh-shaped monopolar electrostatic adsorption electrode. The layer of the ceramic plate 20 that is higher than the chip adsorption electrode 26 functions as a dielectric layer. The chip adsorption DC power supply 52 is connected to the chip adsorption electrode 26 via a power supply terminal 54. The power supply terminal 54 is inserted into a terminal hole 51 provided between the lower surface of the chip adsorption electrode 26 and the lower surface of the cooling plate 30 of the chip placement table 10. The power supply terminal 54 is provided so as to pass through an insulating tube 55 arranged in a through hole of the terminal hole 51 that penetrates the cooling plate 30 and the metal bonding layer 40 in the up-down direction, and reach the chip adsorption electrode 26 from the lower surface of the ceramic plate 20. A low-pass filter (LPF) 53 is provided between the wafer adsorption DC power supply 52 and the wafer adsorption electrode 26 . The cooling plate 30 is a disc-shaped plate having a coolant flow path 32 through which a coolant can flow, and is obtained by metal bonding the first to third thin plate portions 81 to 83 to each other. The coolant flowing in the coolant flow path 32 is preferably a liquid, and preferably electrically insulating. As electrically insulating liquids, for example, fluorine-based inactive liquids and the like can be cited. The first to third thin plate portions 81 to 83 are all formed of a composite material of metal and ceramic (hereinafter also referred to as a metal-ceramic composite material). The cooling plate 30 is configured as follows: the second thin plate portion 82 is bonded to the lower surface of the first thin plate portion 81 by means of a first metal bonding layer 84, and the third thin plate portion 83 is bonded to the upper surface of the first thin plate portion 81 by means of a second metal bonding layer 85. As metal-ceramic composite materials, metal matrix composites (Metal matrix composite (MMC)), ceramic matrix composites (Ceramic matrix composite (CMC)), etc. can be cited. Specific examples of the metal-ceramic composite material include: materials containing Si, SiC and Ti, materials obtained by impregnating SiC porous bodies with Al and / or Si, etc. The material containing Si, SiC and Ti is called SiSiCTi, the material obtained by impregnating SiC porous bodies with Al is called AlSiC, and the material obtained by impregnating Si into SiC porous bodies is called SiSiC. In the case where the ceramic plate 20 is an alumina plate, the metal-ceramic composite material used for the cooling plate 30 is preferably MMC (AlSiC, SiSiCTi, etc.) having a thermal expansion coefficient close to that of alumina. The cooling plate 30 is connected to the RF power supply 62 via the power supply terminal 64. A high-pass filter (HPF) 63 is arranged between the cooling plate 30 and the RF power supply 62. The cooling plate 30 has a flange portion 34 on the lower surface side for clamping the wafer carrier 10 to the setting plate 96. like Figure 2 As shown, when observing the cross section of the refrigerant flow path 32 cut in a horizontal plane from above, the refrigerant flow path 32 is formed in a single stroke from the inlet 32a to the outlet 32b in the entire area of ​​the cooling plate 30 except the flange portion 34. The inlet 32a is connected to the refrigerant supply path 36, and the outlet 32b is connected to the refrigerant discharge path 38. The refrigerant passes through the refrigerant flow path 32 from the refrigerant supply path 36 via the inlet 32a and is discharged from the refrigerant discharge path 38 via the outlet 32b. The refrigerant discharged from the refrigerant discharge path 38 is temperature-adjusted by an external refrigerant circulator (not shown) and then returns to the refrigerant supply path 36. In the present embodiment, the refrigerant flow path 32 is formed in a spiral shape. As shown Figure 1As shown in FIG. 1 , the distance d1 from the wafer placement surface 22a to the upper bottom of the coolant flow path 32 and the distance d2 from the wafer placement surface 22a to the lower bottom of the coolant flow path 32 are both short and long in the entire coolant flow path 32 and are not constant. The distances d1 and d2 are set corresponding to the portion where the wafer W is likely to become high temperature and the portion where the wafer W is likely to become low temperature when the wafer placement table 10 is used. Figure 1 As shown, the width w of the refrigerant flow path 32 is not constant, and has both narrow and wide parts throughout the refrigerant flow path 32. The width w is set corresponding to the part where the chip W is prone to high temperature and the part where the chip W is prone to low temperature when the chip carrier 10 is in use. For example, in the refrigerant flow path 32 directly below the part where the chip W is prone to high temperature, in order to promote heat exchange between the refrigerant and the chip W, the distance d1 can be shortened or the pressure loss can be increased. In order to increase the pressure loss, for example, the distance d2 can be shortened or the width w can be narrowed to reduce the cross-sectional area of ​​the flow path. It should be noted that Figure 2 In the figure, for convenience, the width w of the refrigerant flow path 32 is constant throughout the entire refrigerant flow path 32 . The first thin plate portion 81 has a first flow path portion 86. The first flow path portion 86 is a through groove (a groove that penetrates the first thin plate portion 81 in the up-down direction) of the same shape as the refrigerant flow path 32 when viewed from above. The second thin plate portion 82 has a second flow path portion 87. The second flow path portion 87 is a bottomed groove (stop groove) that is arranged at least in part at a position opposite to the first flow path portion 86. The third thin plate portion 83 has a third flow path portion 88. The third flow path portion 88 is a bottomed groove that is arranged at least in part at a position opposite to the first flow path portion 86. Through grooves 84a and 85b that are the same shape as the first flow path portion 86 when viewed from above are arranged at positions of each metal bonding layer 84 and 85 that are opposite to the first flow path portion 86. Therefore, the refrigerant flow path 32 is composed of the second flow path portion 87, the through groove 84a, the first flow path portion 86, the through groove 85a and the third flow path portion 88. Each of the metal bonding layers 84 and 85 can be formed in the same manner as the metal bonding layer 40 described later. The metal bonding layer 40 bonds the lower surface of the ceramic plate 20 and the upper surface of the cooling plate 30. The metal bonding layer 40 may be a layer formed of, for example, solder or metal brazing material. For example, the metal bonding layer 40 is formed by TCB (Thermal compression bonding). TCB refers to a well-known method of sandwiching a metal bonding material between two components to be bonded, heating the two components to a temperature below the solidus temperature of the metal bonding material, and pressurizing and bonding the two components. The side surface of the outer peripheral portion 24 of the ceramic plate 20, the outer periphery of the metal bonding layer 40, and the side surface of the cooling plate 30 are covered with an insulating film 42. Examples of the insulating film 42 include a thermal sprayed film of aluminum oxide, yttrium trioxide, and the like. The wafer stage 10 is mounted on a setting plate 96 provided inside a chamber 94 by using a clamping member 70. The clamping member 70 is an annular member having a substantially inverted L-shaped cross section and having an inner peripheral step surface 70a. The wafer stage 10 and the setting plate 96 are integrated by the clamping member 70. In a state where the inner peripheral step surface 70a of the clamping member 70 is placed on the flange portion 34 of the cooling plate 30 of the wafer stage 10, the bolt 72 is inserted from the upper surface of the clamping member 70 and screwed into the screw hole provided on the upper surface of the setting plate 96. The bolt 72 is installed at a plurality of locations (e.g., 8 locations, 12 locations) provided at equal intervals along the circumferential direction of the clamping member 70. The clamping member 70 and the bolt 72 may be made of an insulating material or a conductive material (metal, etc.). Next, use Figure 4 and Figure 5 , a manufacturing example of the wafer placement table 10 is described. Figure 4 is a manufacturing process diagram of the wafer stage 10. Figure 5 It is a process diagram of the first to third thin plate parts 81 to 83 . First, a ceramic powder compact is hot-pressed and fired to produce a ceramic plate 20 ( Figure 4 (A)). The ceramic plate 20 has a built-in chip adsorption electrode 26. Next, a terminal hole upper portion 151a ( Figure 4 (B)). Then, the power supply terminal 54 is inserted into the upper portion 151a of the terminal hole, and the power supply terminal 54 and the chip adsorption electrode 26 are joined ( Figure 4 (C)). At the same time, a circular plate member without holes or grooves, namely, first to third thin plate portions 81 to 83 ( Figure 5 (A)) When the ceramic plate 20 is made of alumina, the first to third thin plate portions 81 to 83 are preferably made of SiSiCTi or AlSiC. This is because SiSiCTi and AlSiC can make the thermal expansion coefficient substantially the same as that of alumina. For example, a SiSiCTi disc component can be made as follows. First, silicon carbide, metal Si and metal Ti are mixed to make a powder mixture. Next, the obtained powder mixture is molded by uniaxial pressure molding to make a disc-shaped molded body, and the molded body is hot-pressed and sintered in an inert atmosphere to obtain a SiSiCTi disc component. Next, the first flow path 86 and the first terminal hole forming part 81a are formed on the first thin plate part 81. In addition, the second flow path 87, the refrigerant supply path 36, the refrigerant discharge path 38 and the second terminal hole forming part 82a are formed on the second thin plate part 82. In addition, the third flow path 88 and the third terminal hole forming part 83a ( Figure 5 (B)). The first flow path portion 86 is a through groove that passes through the first thin plate portion 81 in the up-down direction, and therefore, can be formed by hollowing out. The hollowing out process can be performed, for example, by a wire saw or wire discharge, or by cutting or grinding. When using a wire saw or wire discharge, first, a through hole is set somewhere in the area where the through groove is to be formed, and after the wire passes through the through hole, the processing can be started. The first to third terminal hole forming portions 81a to 83a can also be formed by hollowing out. On the other hand, the second flow path portion 87 and the third flow path portion 88 are bottomed grooves, and therefore, can be formed by cutting or grinding. The boundary between the side and the bottom surface of the bottomed groove is preferably curved. The refrigerant supply path 36 and the refrigerant discharge path 38 are holes in the up-down direction that are connected to the second flow path portion 87 from the lower surface of the second thin plate portion 82, and can be formed by cutting or grinding. return Figure 4 A metal bonding material 90 is disposed between the lower surface of the ceramic plate 20 on which the power supply terminal 54 is mounted and the third thin plate portion 83, a second metal bonding material 185 is disposed between the lower surface of the third thin plate portion 83 and the upper surface of the first thin plate portion 81, and a first metal bonding material 184 is disposed between the lower surface of the first thin plate portion 81 and the second thin plate portion 82, and these are stacked ( Figure 4 (D)). Through holes are pre-set at positions of the first metal bonding material 184 and the second metal bonding material 185 that are opposite to the first flow path portion 86 and the first terminal hole forming portion 81a of the first thin plate portion 81. The power supply terminal 54 is passed through the first to third terminal hole forming portions 81a to 83a. The laminated body thus obtained is heated and pressurized (TCB), thereby obtaining a bonded body 110 ( Figure 4 (E)). The joint body 110 is obtained by joining the ceramic plate 20 to the upper surface of the cooling plate 30 by means of the metal joining layer 40. The cooling plate 30 is configured such that the second thin plate portion 82 and the first thin plate portion 81 are joined by means of the first metal joining layer 84, and the first thin plate portion 81 and the third thin plate portion 83 are joined by means of the second metal joining layer 85. The terminal hole 51 is a hole obtained by connecting the terminal hole upper portion 151a and the first to third terminal hole forming portions 81a to 83a. For example, TCB is performed as follows. That is, the stack is pressurized and bonded at a temperature below the solidus temperature of the metal bonding material (for example, a temperature above the solidus temperature minus 20°C and below the solidus temperature), and then returned to room temperature. Accordingly, the metal bonding material becomes a metal bonding layer. As the metal bonding material at this time, Al-Mg bonding materials and Al-Si-Mg bonding materials can be used. For example, when TCB is performed using an Al-Si-Mg bonding material, the stack is pressurized in a heated state under a vacuum atmosphere. The metal bonding material preferably uses a bonding material with a thickness of about 100 μm. Next, the periphery of the ceramic plate 20 is cut to form a step, thereby forming a structure having a central portion 22 and a peripheral portion 24. In addition, the periphery of the cooling plate 30 is cut to form a step, thereby forming a structure having a flange portion 34. In addition, in the terminal hole 51, an insulating tube 55 for inserting the power supply terminal 54 is arranged from the lower surface of the ceramic plate 20 to the lower surface of the cooling plate 30. In addition, the side surface of the peripheral portion 24 of the ceramic plate 20, the surrounding of the metal bonding layer 40, and the side surface of the cooling plate 30 are sprayed with ceramic powder to form an insulating film 42 ( Figure 4 (F)). Thus, the wafer placement table 10 is obtained. Next, use Figure 1 , an example of using the wafer stage 10 is described. As described above, the wafer stage 10 is fixed to the setting plate 96 of the chamber 94 by the clamping member 70. A shower head 98 is arranged on the top surface of the chamber 94 to release the process gas into the chamber 94 from a large number of gas injection holes. A focus ring 78 is placed on the FR placement surface 24a of the wafer placement table 10, and a disc-shaped wafer W is placed on the wafer placement surface 22a. The focus ring 78 has a step along the inner circumference of the upper end portion so as not to interfere with the wafer W. In this state, a DC voltage of a DC power supply 52 for wafer adsorption is applied to the wafer adsorption electrode 26, so that the wafer W is adsorbed on the wafer placement surface 22a. Then, the interior of the chamber 94 is set to a predetermined vacuum atmosphere (or a reduced pressure atmosphere), and while a process gas is supplied from the shower head 98, an RF voltage from an RF power supply 62 is applied to the cooling plate 30. Thus, 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 this plasma. A refrigerant whose temperature is adjusted circulates in the refrigerant flow path 32. It should be noted that the focus ring 78 is also consumed 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 a plurality of wafers W are processed. When the wafer W is processed by high-power plasma, the wafer W needs to be efficiently cooled. In the wafer carrier 10, as the bonding layer between the ceramic plate 20 and the cooling plate 30, a metal bonding layer 40 with high thermal conductivity is used instead of a resin layer with low thermal conductivity. Therefore, the ability to remove heat from the wafer W (heat dissipation ability) is high. In addition, since the thermal expansion difference between the ceramic plate 20 and the cooling plate 30 is small, even if the stress relaxation of the metal bonding layer 40 is low, it is not easy to cause obstacles. In addition, the size of the flow path cross-sectional area of ​​the coolant flow path 32 is set corresponding to the part where the wafer W is prone to high temperature and the part where it is prone to low temperature when the wafer carrier 10 is used. When adjusting the size of the flow path cross-sectional area of ​​the coolant flow path 32, the distance d1 from the wafer loading surface 22a to the upper bottom of the coolant flow path 32 and the distance d2 from the wafer loading surface 22a to the lower bottom of the coolant flow path 32 can be changed, and the width w of the coolant flow path 32 can also be changed. In addition, the distance d1 can be shortened at a portion where the temperature of the wafer W is likely to rise. The flow rate of the coolant flowing through the coolant flow path 32 is preferably 15 to 50 L / min, and more preferably 20 to 40 L / min. In the above-described embodiment, the first thin plate portion 81 corresponds to the first plate portion of the present invention, the second thin plate portion 82 corresponds to the second plate portion of the present invention, and the third thin plate portion 83 corresponds to the third plate portion of the present invention. According to the wafer placement table 10 of the present embodiment described above, the length of at least one of the upper bottom and the lower bottom of the cooling medium flow path 32 from the wafer placement surface 22a is changed in accordance with the portion of the wafer W placed on the wafer placement surface 22a that is prone to high temperature and the portion of the wafer W that is prone to low temperature. Therefore, the thermal uniformity of the wafer W can be improved. In addition, the cooling plate 30 is a structure obtained by metal bonding of multiple thin plate parts including a first thin plate part 81 and a second thin plate part 82 that are bonded to each other. The first thin plate part 81 has a first flow path part 86, which is a through groove arranged to have the same shape as the refrigerant flow path 32 when viewed from above. The second thin plate part 82 has a second flow path part 87, which is a bottomed groove arranged at at least a part of a position opposite to the first flow path part 86. The first flow path part 86 arranged in the first thin plate part 81 can be formed at low cost by, for example, hollowing processing. The second flow path part 87 arranged in the second thin plate part 82 can be formed by, for example, cutting processing or grinding processing, but since the depth is relatively shallow, it can be formed in a short time and can be formed at low cost. In addition, the width w of the coolant flow path 32 is not constant throughout the coolant flow path 32, but there is a portion where the width w changes. By changing the width w of the coolant flow path 32 in accordance with the portion of the wafer placement surface 22a that is prone to high temperature and the portion that is prone to low temperature, the thermal uniformity of the wafer W can be improved. In addition, the cooling plate 30 includes a third thin plate portion 83, which is joined to the surface of the first thin plate portion 81 on the opposite side to the second thin plate portion 82, and has a third flow path portion 88, which is a bottomed groove provided at least in part at a position opposite to the first flow path portion 86. Therefore, the position of one of the upper bottom and the lower bottom of the coolant flow path 32 can be changed, or the positions of both can be changed. The boundary between the side surface and the upper bottom, and the boundary between the side surface and the lower bottom of the coolant flow path 32 are preferably curved. This makes it difficult for cracks to occur starting from these boundaries. It should be noted that the present invention is not limited to the above-mentioned embodiments, and can be implemented in various forms as long as they fall within the technical scope of the present invention. In the above implementation, it is possible to use Figure 6 A cooling plate 130 is shown instead of the cooling plate 30 . Figure 6 In the embodiment, the same symbols are marked for the same components as those in the above-mentioned embodiment. The cooling plate 130 has one or more fins 33 at the upper bottom of the coolant flow path 32. By providing the fins 33 in the coolant flow path 32 of the chip loading surface 22a that is prone to high temperature, the chip W can be efficiently cooled. The fins 33 can be arranged so that the more the part of the chip loading surface 22a that is prone to high temperature, the more (or longer) the fins 33 are. The fins 33 are arranged on the bottom surface of the third flow path portion 88, which is a relatively shallow bottomed groove, and therefore can be easily processed. The fins 33 can be arranged on the lower bottom of the coolant flow path 32 (the bottom surface of the second flow path portion 87 as a bottomed groove), or can be arranged on the upper bottom and the lower bottom at the same time, instead of being arranged on the upper bottom of the coolant flow path 32. In the above implementation, it is possible to use Figure 7 A cooling plate 230 is shown instead of the cooling plate 30 . Figure 7 , the same reference numerals are used for the same components as those in the above-mentioned embodiment. The cooling plate 230 is a two-layer structure in which a first thin plate portion 81 and a second thin plate portion 82 are bonded by a metal bonding layer 84. The upper surface of the first thin plate portion 81 of the cooling plate 230 and the lower surface of the ceramic plate 20 are bonded by means of a metal bonding layer 40. In this case, the upper opening of the coolant flow path 32 is closed by the metal bonding layer 40 (ceramic plate 20). In the above implementation, it is possible to use Figure 8 A cooling plate 330 is shown instead of the cooling plate 30 . Figure 8In the embodiment, the same symbols are marked for the same components as those in the above-mentioned embodiment. The cooling plate 330 is a three-layer structure obtained by joining the first thin plate portion 81 and the second thin plate portion 82 with a metal bonding layer 84 and joining the first thin plate portion 81 and the third thin plate portion 83 with a metal bonding layer 85. The first thin plate portion 81 has a first flow path portion 86 (through groove), and the second thin plate portion 82 has a second flow path portion 87 (bottom groove). The upper surface of the third thin plate portion 83 of the cooling plate 330 and the lower surface of the ceramic plate 20 are joined by means of the metal bonding layer 40. The third thin plate portion 83 does not have a third flow path portion 88 (bottom groove). That is, the surface of the third thin plate portion 83 opposite to the first thin plate portion 81 is flat. In this case, the positions of the upper bottoms of the refrigerant flow path 32 are all at the same height. In the above implementation, it is possible to use Fig. 9 A cooling plate 430 is shown instead of the cooling plate 30 . Fig. 9 In the embodiment, the same symbols are marked for the same components as those in the above-mentioned embodiment. The cooling plate 430 is a three-layer structure obtained by joining the first thin plate portion 81 and the second thin plate portion 82 with a metal bonding layer 84 and joining the first thin plate portion 81 and the third thin plate portion 83 with a metal bonding layer 85. The first thin plate portion 81 has a first flow path portion 86 (through groove), and the third thin plate portion 83 has a third flow path portion 88 (bottom groove). The upper surface of the third thin plate portion 83 of the cooling plate 430 and the lower surface of the ceramic plate 20 are joined by means of the metal bonding layer 40. The second thin plate portion 82 does not have a second flow path portion 87 (bottom groove). That is, the surface of the second thin plate portion 82 opposite to the first thin plate portion 81 is flat. In this case, the positions of the lower bottoms of the refrigerant flow path 32 are all at the same height. In the cooling plate 430 only, the first thin plate portion 81 corresponds to the first plate portion of the present invention, the third thin plate portion 83 corresponds to the second plate portion of the present invention, and the second thin plate portion 82 corresponds to the third plate portion of the present invention. In the above-described embodiment, the cooling plate 30 is configured as a three-layer structure including the first to third thin plate portions 81 to 83 , but may be configured as a structure having four or more layers. In the above embodiment, a sealing band can be formed along the outer edge of the wafer loading surface 22a, and a plurality of small protrusions can be formed on the entire surface of the wafer loading surface 22a, and the wafer W can be supported by the top surface of the sealing band and the top surfaces of the plurality of small protrusions. In the above-mentioned embodiment, the wafer stage 10 may have a plurality of holes penetrating the wafer stage 10 in the vertical direction. As the above-mentioned holes, there are: a plurality of gas holes opening on the wafer loading surface 22a, and lift pin holes for inserting lift pins for moving the wafer W up and down relative to the wafer loading surface 22a. When the wafer loading surface 22a is viewed from above, the plurality of gas holes are arranged at appropriate positions. A heat conductive gas such as He gas is supplied to the gas holes. Usually, the gas holes are arranged so as to be open at the portion of the wafer loading surface 22a where the sealing tape and small protrusions are not provided. When the heat conductive gas is supplied to the gas holes, the space on the back side of the wafer W placed on the wafer loading surface 22a is filled with the heat conductive gas. When the wafer loading surface 22a is viewed from above, a plurality of lift pin holes are arranged at equal intervals along the concentric circles of the wafer loading surface 22a. In the above-mentioned embodiment, the ceramic plate 20 and the cooling plate 30 are bonded via the metal bonding layer 40 , but the present invention is not particularly limited thereto. For example, a resin bonding layer may be used instead of the metal bonding layer 40 . In the above-mentioned embodiment, the wafer adsorption electrode 26 is built into the central portion 22 of the ceramic plate 20, but, instead of or in addition thereto, an RF electrode for plasma generation or a heater electrode (resistance heating element) may be built into it. In addition, a focusing ring (FR) adsorption electrode may be built into the outer peripheral portion 24 of the ceramic plate 20, or an RF electrode or a heater electrode may be built into it. In the above-mentioned embodiment, the ceramic plate 20 is produced by hot pressing and sintering a ceramic powder molded body. In this case, the molded body can be produced by stacking multiple pieces of cast molded bodies, or by casting, or by compacting ceramic powder. In the above-mentioned embodiment, as the first to third thin plate portions 81 to 83, thin plate portions formed of metal-ceramic composite materials are exemplified, however, thin plate portions formed of easily processed materials may also be used. As an indicator of processability, for example, the machinability index given in JIS B 0170 (2020) may be used. As a material for easy processing, a material with a machinability index of 40 or more is preferred, a material with a machinability index of 100 or more is more preferred, and a material with a machinability index of 140 or more is further preferred. As a material for easy processing, for example, aluminum, aluminum alloy, stainless steel (SUS material), etc. may be cited. In the above-mentioned embodiment, the coolant flow path 32 is formed in a spiral shape, but the shape is not particularly limited to this as long as it is a straight line shape. For example, the coolant flow path 32 may be formed in a zigzag shape. In the above-mentioned embodiment, the ceramic plate 20 may have the wafer placement surface 22 a but may not have the FR placement surface. Industrial Applicability The present invention can be used in an apparatus for processing, for example, a wafer. Explanation of symbols 10 wafer mounting table, 20 ceramic plate, 22 central portion, 22a wafer mounting surface, 24 outer peripheral portion, 24a focusing ring mounting surface, 26 wafer adsorption electrode, 30 cooling plate, 32 coolant flow path, 32a inlet, 32b outlet, 33 fin, 34 flange portion, 36 coolant supply path, 38 coolant discharge path, 40 metal bonding layer, 42 insulating film, 51 terminal hole, 52 DC power supply for wafer adsorption, 54 power supply terminal, 55 insulating tube, 62 RF power supply, 64 power supply terminal, 70 clamping member, 70a inner peripheral step surface, 72 bolt, 78 focusing ring, 81 first thin Plate portion, 81a first terminal hole constituting portion, 82 second thin plate portion, 82a second terminal hole constituting portion, 83 third thin plate portion, 83a third terminal hole constituting portion, 84 first metal bonding layer, 84a through groove, 85 second metal bonding layer, 85a through groove, 86 first flow path portion, 87 second flow path portion, 88 third flow path portion, 90 metal bonding material, 94 chamber, 96 setting plate, 98 nozzle, 110 bonding body, 130, 230, 330, 430 cooling plate, 151a upper portion of the terminal hole, 184 first metal bonding material, 185 second metal bonding material.

Claims

1. A wafer loading platform, comprising: A ceramic plate having a wafer placement surface on an upper surface thereof on which a wafer can be placed and having electrodes built therein; A cooling plate made of a metal-ceramic composite material, the cooling plate having a refrigerant flow path; and a bonding layer bonding the ceramic plate and the cooling plate, The wafer stage is characterized in that: The length from the wafer placement surface to at least one of the upper bottom and the lower bottom of the coolant flow path is not constant throughout the coolant flow path, but there is a portion where the length changes. The cooling plate is a structure obtained by metal bonding of multiple plate portions including a first plate portion and a second plate portion that are bonded to each other, the first plate portion having a first flow path portion, which is a through groove arranged to have the same shape as the refrigerant flow path when viewed from above, and the second plate portion having a second flow path portion, which is a bottomed groove arranged at at least a portion of a position opposite to the first flow path portion.

2. The wafer stage according to claim 1, wherein: The width of the refrigerant flow path is not constant throughout the entire refrigerant flow path, but there is a portion where the width changes.

3. The wafer stage according to claim 1 or 2, characterized in that: The coolant flow path has a portion having a fin on at least one of an upper bottom and a lower bottom of the coolant flow path.

4. The wafer stage according to claim 1 or 2, characterized in that: The cooling plate includes a third plate portion joined to a surface of the first plate portion opposite to the second plate portion, and the third plate portion has a third flow path portion which is a bottomed groove at least partially disposed at a position opposite to the first flow path portion.

5. The wafer stage according to claim 1 or 2, characterized in that: The cooling plate includes a third plate portion joined to a surface of the first plate portion on the opposite side to the second plate portion, and a surface of the third plate portion facing the first flow path portion is flat.

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