Wafer placement table

Abstract

The wafer mounting stage 10 includes: a ceramic plate 20 with at least a wafer mounting portion 22 on its top surface; a cooling plate 30 bonded to the bottom surface of the ceramic plate 20 and having a refrigerant flow path 32; gas common paths 51b, 52b, and 53b disposed above the refrigerant flow path 32; gas inlet paths 51a, 52a, and 53a respectively extending from the bottom surface of the cooling plate 30 to the gas common paths 51b, 52b, and 53b; and a plurality of gas distribution paths 51e, 52e, and 53e respectively disposed for the gas common paths 51b, 52b, and 53b. The gas distribution path 53e disposed on the outermost periphery of the ceramic plate 20 is positioned so as not to overlap with the refrigerant flow path 32 when viewed from above.

Description

Wafer loading table The present invention relates to a wafer mounting table. In the past, a wafer mounting table was known, which includes: a ceramic plate having a wafer mounting portion on its top surface; a cooling plate connected to the bottom surface of the ceramic plate; and a refrigerant flow path provided on the cooling plate. For example, in the wafer mounting table of Patent Document 1, the gas introduced from the bottom surface of the cooling plate is supplied to the top surface of the ceramic plate through a gas distribution path that passes through a gas common path that is C-shaped when viewed from above and is provided above the refrigerant flow path, and then passes through a plurality of gas diversion portions that extend radially outward from this gas common path. [Prior Art Document] [Patent Document] [Patent Document 1] Japanese Patent Publication No. 2021-141116 [Problems to be solved by the invention] However, when using a wafer stage, significant stress may be generated in the gas distribution path at the outermost periphery of the wafer stage. Since Patent Document 1 does not take this into account, cracks may form in the wafer stage. Such cracks are particularly prone to occur when high-power plasma is used to process wafers. The present invention is designed to solve this problem, with the main purpose of preventing cracks from forming on the wafer mounting table. [Means for Solving the Problem] [1] The wafer mounting table of the present invention comprises: a ceramic plate having at least a wafer mounting portion on its top surface; and a cooling plate connected to the bottom surface of the ceramic plate and having a refrigerant flow path. The wafer mounting table further comprises: a gas common path arranged above the refrigerant flow path inside the wafer mounting table; a gas introduction path reaching the gas common path from the bottom surface of the cooling plate; and a plurality of gas distribution paths arranged for one gas common path and reaching the top surface of the ceramic plate from the gas common path. The outermost gas distribution path arranged at the outermost periphery of the ceramic plate among the gas distribution paths is arranged at a position that does not overlap with the refrigerant flow path when viewed from above. In this wafer stage, the outermost gas distribution path, which is arranged at the outermost periphery of the ceramic plate in the gas distribution path, is set at a position that does not overlap with the refrigerant flow path when viewed from above. When the wafer stage is used, large stress is easily generated at the outermost periphery of the wafer stage. When the outermost gas distribution path overlaps with the refrigerant flow path when viewed from above, cracks are easily generated near the outermost gas distribution path because the thickness of the refrigerant flow path immediately above is small and easily deformed. However, here, since the outermost gas distribution path is set at a position that does not overlap with the refrigerant flow path when viewed from above, the stress near the outermost gas distribution path is reduced, which can prevent the occurrence of cracks. In addition, in this specification, the terms "up, down, left, right, front, and back" are sometimes used to describe the present invention. However, these terms are merely relative positions. Therefore, when the orientation of the wafer stage is changed, up, down, and left, right, and left, right, and front, and back may become left, right, and up. Such situations are also within the technical scope of the present invention. [2] In the wafer mounting table (such as the wafer mounting table of [1]), the gas distribution path may be connected to the gas common path via a gas diversion portion. In this way, for example, as long as the gas diversion portion crosses the coolant flow path from the gas common path to a position that does not overlap with the coolant flow path when viewed from above, it is easier to set the gas distribution path at a position that does not overlap with the coolant flow path. [3] In the above-mentioned wafer mounting table (such as the wafer mounting table of [1] or [2] above), the gas common paths may be provided in a plurality of concentric circles, and the outermost gas distribution path may be connected to the gas common path located at the outermost periphery among the plurality of gas common paths. In this way, the number of gas distribution paths opening on the top surface of the ceramic plate can be increased. In addition, since the gas distribution path connected to the gas common path located at the outermost periphery is prone to generate large stress, the application of the present invention is of great significance. [4] In the above-mentioned wafer mounting table (such as the wafer mounting table of any one of [1] to [3] above), the width of at least the portion of the gas distribution path connected to the gas common path may be wider than the gas common path. In this case, since the wide portion of the gas distribution path connected to the gas common path is more likely to generate greater stress, the application of the present invention is highly significant. [5] In the above-mentioned wafer mounting table (such as the wafer mounting table of any one of the above-mentioned [1] to [4]), the cooling plate can also be formed of a composite material of metal and ceramic. Since such a composite material is relatively fragile and prone to cracking, the application of the present invention is of great significance. [6] In the above-mentioned wafer mounting table (such as the wafer mounting table of any one of the above-mentioned [1] to [5]), a circular wafer mounting portion and an annular focus ring mounting portion surrounding the wafer mounting portion can also be set on the top surface of the ceramic plate, and the outermost gas distribution path can also be a path from the common gas path to the focus ring mounting portion. [7] In the above-mentioned wafer loading platform (such as the wafer loading platform of any one of the above-mentioned [1] to [5]), a circular wafer loading portion can also be set on the top surface of the ceramic plate, and the outermost gas distribution path can also be a path from the common gas path to the wafer loading portion. [Modes for carrying out the invention] Next, preferred embodiments of the present invention will be described using the drawings. FIG1 is a longitudinal cross-sectional view of the wafer stage 10 (a cross-sectional view taken along a plane including the central axis of the wafer stage 10), FIG2 is a cross-sectional view taken along line AA in FIG1 , FIG3 is a plan view of the wafer stage 10, FIG4 is a partially enlarged view of FIG3 , and FIG5 is a perspective view of the vicinity of the gas relay groove 53d of the cooling plate 30. In FIG2 , components other than the coolant flow path 32 are omitted from illustration. The wafer stage 10 is used to perform CVD and etching using plasma on the wafer W. The wafer stage 10 includes a ceramic plate 20 , a cooling plate 30 , and a metal bonding layer 40 . The ceramic plate 20 is formed of a ceramic material represented by aluminum oxide, aluminum nitride, etc., and has a circular wafer loading portion 22 on the top surface. Wafer W is loaded on the wafer loading portion 22. A sealing ring 22a is formed along the outer edge of the wafer loading portion 22, and a plurality of circular protrusions 22b are formed on the entire surface of the wafer loading portion. The sealing ring 22a and the circular protrusions 22b have the same height, and their height is, for example, several μm to several 10 μm. The electrode 23 is a planar mesh electrode used as an electrostatic electrode, and a DC voltage can be applied. When a DC voltage is applied to this electrode 23, the wafer W is adsorbed and fixed to the wafer loading portion 22 (specifically, the top surface of the sealing ring 22a and the top surface of the circular protrusion 22b) due to the electrostatic adsorption force. When the application of the DC voltage is released, the wafer W is released from the adsorption and fixation on the wafer loading portion 22. Furthermore, the portion of the wafer mounting portion 22 where the sealing band 22a and the small circular protrusion 22b are not provided is referred to as the reference surface 22c. FIG3 shows the small circular protrusion 22b provided in the area of ​​the wafer mounting portion 22 surrounded by a dotted chain line. In reality, the small circular protrusion 22b is provided on the entire surface of the area of ​​the wafer mounting portion 22 surrounded by the sealing band 22a. In addition to the wafer mounting portion 22, an annular focus ring mounting portion 24 is provided on the top surface of the ceramic plate 20 around the wafer mounting portion 22. Hereinafter, the focus ring may be abbreviated as "FR". The FR mounting portion 24 is lower than the wafer mounting portion 22. A circular annular focus ring 60 is mounted on the FR mounting portion 24. Above the inner side surface of the focus ring 60, a circumferential groove 60a is provided so as not to contact the wafer W. The FR mounting portion 24 has: an annular groove 24a; and FR support surfaces 24b provided on the inner and outer circumferential sides of the groove 24a. The depth of the groove 24a is, for example, several μm to several 10 μm. The FR support surface 24b is formed as an annular surface and directly contacts the focus ring 60 to support the focus ring 60. The cooling plate 30 is a circular plate member made of a brittle conductive material. The cooling plate 30 includes a refrigerant flow path 32 in which a refrigerant can circulate. As shown in FIG2 , the refrigerant flow path 32 is arranged to extend from one end (inlet) to the other end (outlet) in a straight line throughout the entire cooling plate 30 when viewed from above. In this embodiment, the refrigerant flow path 32 is formed into a spiral shape when viewed from above. Such a cooling plate 30 can be made with reference to, for example, Japanese Patent Gazette No. 5666748. The refrigerant is supplied to one end (inlet) of the refrigerant flow path 32 from a refrigerant circulation device not shown in the figure, passes through the refrigerant flow path 32, and is discharged from the other end (outlet) of the refrigerant flow path 32 and returns to the refrigerant circulation device. The refrigerant circulation device can adjust the refrigerant to a desired temperature. The refrigerant is preferably a liquid, and preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inert liquids. Examples of brittle conductive materials include composite materials of metals and ceramics. Examples of composite materials of metals and ceramics include metal matrix composites (MMC) and ceramic matrix composites (CMC). Specific examples of such composite materials include materials containing Si, SiC and Ti, materials in which Al and / or Si are impregnated into SiC porous bodies, Al 2O 3 and TiC composite materials as an example. The material containing Si, SiC and Ti is called SiSiCTi, the material in which Al is impregnated into a porous SiC body is called AlSiC, and the material in which Si is impregnated into a porous SiC body is called SiSiC. The conductive material used for the cooling plate 30 is preferably a material having a thermal expansion coefficient close to that of the ceramic plate 20. When the ceramic plate 20 is made of alumina, the cooling plate 30 is preferably made of SiSiCTi or AlSiC. The reason is that the thermal expansion coefficients of SiSiCTi and AlSiC are approximately the same as that of alumina. A SiSiCTi circular plate component can be produced as follows: First, silicon carbide, metal Si and metal Ti are mixed to produce a powder mixture. Then, the obtained powder mixture is formed by uniaxial pressing to produce a circular plate-shaped formed body, and the formed body is hot-pressed and sintered in an inert gas environment, thereby obtaining a SiSiCTi circular plate component. The metal bonding layer 40 bonds the bottom surface of the ceramic plate 20 to the top surface of the cooling plate 30. The metal bonding layer 40 can be formed, for example, from soft solder or brazing solder. The metal bonding layer 40 is formed, for example, using TCB (Thermal Compression Bonding). TCB is a well-known method in which a metal bonding material is sandwiched between two components to be joined and, while heated to a temperature below the solidus temperature of the metal bonding material, the two components are press-bonded. The wafer stage 10 has gas supply paths 51, 52, and 53. Gas supply paths 51 and 52 are paths for supplying gas to the space surrounded by the wafer W, the seal ring 22a, the small circular protrusion 22b, and the reference surface 22c. Gas supply path 53 is a path for supplying gas to the space surrounded by the focus ring 60 and the groove 24a. The gas supply path 51 comprises a gas inlet path 51a, a common gas path 51b, a gas branching portion 51c, a gas relay groove 51d, and a gas distribution path 51e. The gas supply path 52 comprises a gas inlet path 52a, a common gas path 52b, a gas branching portion 52c, a gas relay groove 52d, and a gas distribution path 52e. The gas supply path 53 comprises a gas inlet path 53a, a common gas path 53b, a gas branching portion 53c, a gas relay groove 53d, and a gas distribution path 53e. Common gas paths 51b, 52b, and 53b are circular concentric paths with different radii when viewed from above. They are formed above the coolant flow path 32 within the wafer stage 10. In this embodiment, this is the interface between the cooling plate 30 and the metal bonding layer 40, specifically, the top surface of the cooling plate 30. Common gas path 51b is located at the innermost periphery, and common gas path 53b is located at the outermost periphery. Gas inlet paths 51a, 52a, and 53a are arranged to extend from the bottom surface of the cooling plate 30 to the common gas paths 51b, 52b, and 53b, respectively, without intersecting the coolant flow path 32. The outermost gas common path 53b has a plurality of gas diversion portions 53c extending radially outward. A gas distribution path 53e that passes through the ceramic plate 20 in the vertical direction is connected to each gas diversion portion 53c. The connection between the gas diversion portion 53c and the gas distribution path 53e is formed as a gas relay groove 53d consisting of a circular groove. The diameter (width) of the gas relay groove 53d is greater than the width of the gas distribution path 53e and the width of the gas common path 53b (including the gas diversion portion 53c), for example, 1.5 to 2.5 times the width of the gas distribution path 53e. The innermost gas common path 51b is also connected to the gas distribution path 51e via the gas diversion portion 51c and the gas relay groove 51d, similarly to the gas common path 53b. The gas common path 52b is also connected to the gas distribution path 52e via the gas diversion portion 52c and the gas relay groove 52d, similarly to the gas common path 53b. As shown in Figures 3 and 4, among the multiple gas distribution paths 51e, 52e, and 53e, the gas distribution path 53e (outermost gas distribution path) arranged at the outermost periphery of the ceramic plate 20 is set at a position that does not overlap with the refrigerant flow path 32 when viewed from above. The gas relay groove 53d is also set at a position that does not overlap with the refrigerant flow path 32 when viewed from above. At the position that does not overlap with the refrigerant flow path 32 when viewed from above, the thickness of the cooling plate 30 is large. Therefore, even if a gas relay groove 53d with a large diameter is set at this position, the stress generated in the gas relay groove 53d can be suppressed to a small level. In contrast, at the position that overlaps with the refrigerant flow path 32 when viewed from above, the thickness of the cooling plate 30 is small. Therefore, when the gas relay groove 53d is set at this position, a large stress will be generated in the gas relay groove 53d. The stress generated in the gas relay grooves 51d and 52d is smaller than that generated in the outermost gas relay groove 53d. Therefore, the gas relay grooves 51d and 52d and the gas distribution paths 51e and 52e can be positioned so as to overlap with the refrigerant flow path 32 when viewed from above, but preferably, they should not overlap with the refrigerant flow path 32. Furthermore, since the gas common paths 51b, 52b, and 53b are narrow, they can be positioned so as to overlap with the refrigerant flow path 32 when viewed from above, but preferably, they should not overlap with the refrigerant flow path 32. Next, an example of using the wafer stage 10 will be described. The wafer stage 10 is fixed inside a semiconductor process chamber (not shown). The focus ring 60 is placed on the FR placement portion 24, and the wafer W is placed on the wafer placement portion 22. In this state, a DC voltage is applied to the electrode 23 to adsorb the wafer W onto the wafer placement portion 22. At the same time, gas (in this case, a heat-conducting gas such as He) is supplied to the gas supply paths 51, 52, and 53. This ensures good heat conduction between the wafer W and the top surface of the ceramic plate 20, and between the focus ring 60 and the top surface of the ceramic plate 20. Furthermore, the interior of the chamber is set to a predetermined vacuum gas environment (or a reduced pressure gas environment), and while supplying process gas from a showerhead installed at the top of the chamber, an RF voltage is applied to the cooling plate 30. This generates plasma between the wafer W and the showerhead. This plasma is then used to perform CVD film formation or etching on the wafer W. In addition, as the wafer W is subjected to plasma processing, the focus ring 60 is also consumed. Since the focus ring 60 is thicker than the wafer W, the focus ring 60 is replaced after processing a plurality of wafers W. When the wafer W is processed with high-power plasma, the plasma must be efficiently cooled. In the wafer mounting table 10, the bonding layer between the ceramic plate 20 and the cooling plate 30 does not use a resin layer with low thermal conductivity, but uses a metal bonding layer 40 with high thermal conductivity. Therefore, the ability to remove heat from the wafer W (heat dissipation capacity) 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, problems are not likely to occur. Furthermore, since the top surface of the ceramic plate 20 is at a high temperature and the bottom surface is cooled to a low temperature, the top surface of the ceramic plate 20 is easier to extend, and the wafer mounting table 10 is easy to bulge upward. Therefore, at the outermost periphery of the wafer mounting table 10, the deformation increases and stress is easily generated. In this embodiment, since the outermost gas distribution path 53e is provided at a position that does not overlap with the refrigerant flow path 32 in a plan view (a position where the thickness of the cooling plate 30 is large), the stress near the gas distribution path 53e is reduced. In the wafer stage 10 described above, the gas distribution path 53e disposed at the outermost periphery of the ceramic plate 20 is set at a position that does not overlap with the refrigerant flow path 32 when viewed from above. When the wafer stage 10 is used, large stress is easily generated at the outermost periphery of the wafer stage 10. When the outermost gas distribution path 53e overlaps with the refrigerant flow path 32 when viewed from above, cracks are easily generated near the gas distribution path 53e because the thickness of the cooling plate 30 immediately above the refrigerant flow path 32 is small and easily deformed. However, in this embodiment, since the gas distribution path 53e is set at a position that does not overlap with the refrigerant flow path 32 when viewed from above (a position where the thickness of the cooling plate 30 is large), the stress near the gas distribution path 53e becomes smaller, and the generation of cracks can be prevented. Furthermore, the diameter (width) of the gas relay groove 53d in the outermost gas distribution path 53e, which connects to the gas branching portion 53c of the gas common path 53b, is larger than the width of both the gas common path 53b and the width of the gas branching portion 53c. Therefore, while significant stress tends to be generated in the gas relay groove 53d, the present invention can suppress this stress to a minimum. Furthermore, the outermost gas distribution path 53e is connected to the gas common path 53b via the radially extending gas diverter 53c. Therefore, even if the refrigerant flow path 32 is provided near the gas common path 53b, the gas diverter 53c crosses the refrigerant flow path 32 and reaches a position that does not overlap with the refrigerant flow path 32 when viewed from above. This makes it easier to dispose the gas distribution path 53e and the gas relay tank 53d at a position that does not overlap with the refrigerant flow path 32. Furthermore, since the common gas paths 51b, 52b, and 53b are arranged concentrically and connected to a plurality of gas distribution paths 51e, 52e, and 53e, respectively, gas can be supplied from multiple locations on the top surface of the ceramic plate 20. Furthermore, since the gas distribution path 53e connected to the outermost common gas path 53b is prone to generating large stress, the application of the present invention is highly significant. Furthermore, the cooling plate 30 is formed of a composite material of metal and ceramics. Since such a composite material is relatively fragile and prone to cracking, the application of the present invention is of great significance. Furthermore, the top surface of the ceramic plate 20 is provided with a circular wafer mounting portion 22 and an annular FR mounting portion 24 surrounding the wafer mounting portion 22. The outermost gas distribution path 53e is the path from the common gas path 53b to the FR mounting portion 24. In a ceramic plate 20 having such an FR mounting portion 24, the path for supplying gas to the FR mounting portion 24 is located at the outermost periphery. Furthermore, the present invention is not limited to the above-described embodiments, and needless to say, it can be implemented in various forms as long as it falls within the technical scope of the present invention. In the above embodiment, the gas common path 53b is connected to the gas distribution path 53e (gas relay groove 53d) via the gas diverter 53c extending from the gas common path 53b to the radially outer direction, but is not particularly limited to this. For example, as shown in Figure 6, the gas common path 53b can also be connected to the gas distribution path 53e (gas relay groove 53d) via the gas diverter 53c extending from the annular gas common path 53b to the radially inner direction. At this time, the gas distribution path 53e (gas relay groove 53d) is also arranged at a position that does not overlap with the refrigerant flow path 32 when viewed from above. Alternatively, as shown in Figure 7, at least a portion of the annular gas common path 53b can be arranged at a position that does not overlap with the refrigerant flow path 32 when viewed from above, and the gas relay groove 53d and the gas distribution path 53e are directly connected thereto. In Figures 6 and 7, the same symbols are attached to the components that are the same as those in the above embodiment. In the above embodiment, the top surface of the ceramic plate 20 is illustrated as having a wafer loading portion 22 and a FR loading portion 24, but the present invention is not particularly limited to this. For example, like the wafer loading table 110 shown in FIG8 , the top surface of the ceramic plate 20 may also have a wafer loading portion 22, but not have a FR loading portion. The wafer loading table 110 has two gas supply paths 51 and 52. The gas supply path 51 is similar to the above embodiment and is composed of a gas inlet path 51a, a gas common path 51b, a gas diversion portion 51c, a gas relay groove 51d, and a gas distribution path 51e. The gas supply path 52 is also similar to the above embodiment and is composed of a gas inlet path 52a, a gas common path 52b, a gas diversion portion 52c, a gas relay groove 52d, and a gas distribution path 52e. However, here, since the gas distribution path 52e is the outermost gas distribution path, the gas distribution path 52e and the gas relay groove 52d are located so as not to overlap with the coolant flow path 32 when viewed from above. This prevents cracks from forming in the wafer mounting table 110. In FIG8 , components identical to those in the above-described embodiment are assigned the same reference numerals. In the above embodiment, the common gas paths 51b, 52b, 53b; the gas flow dividers 51c, 52c, 53c; and the gas relay grooves 51d, 52d, 53d are disposed at the interface between the cooling plate 30 and the metal bonding layer 40 (specifically, on the top surface of the cooling plate 30), but this is not particularly limiting. For example, the common gas paths 51b, 52b, 53b; the gas flow dividers 51c, 52c, 53c; and the gas relay grooves 51d, 52d, 53d may also be disposed at the metal bonding layer 40, or at the interface between the ceramic plate 20 and the metal bonding layer 40 (specifically, on the bottom surface of the ceramic plate 20). In the above embodiment, the common gas paths 51b, 52b, and 53b are annular in plan view, but the present invention is not limited thereto. For example, the common gas paths 51b, 52b, and 53b may be arc-shaped (e.g., C-shaped), straight-line-shaped, or zigzag-shaped (e.g., along the sides of a polygon) in plan view. In the above embodiment, one gas introduction path 51a, 52a, 53a is connected to each of the common gas paths 51b, 52b, and 53b, but this is not particularly limiting. For example, multiple gas introduction paths 51a, 52a, and 53a may be connected to each of the common gas paths 51b, 52b, and 53b. However, it is preferred that the number of gas introduction paths 51a, 52a, and 53a is less than the number of gas distribution paths connected to a single common gas path. In the above embodiment, the coolant flow path 32 is formed in a spiral shape when viewed from above, but the present invention is not particularly limited to this. For example, the coolant flow path 32 may be formed in a zigzag shape when viewed from above. In the above embodiment, the cooling plate 30 is made of a composite material of metal and ceramics, but it may also be made of other materials (such as aluminum or aluminum alloy). In the above embodiment, the electrodes 23 built into the ceramic plate 20 are exemplified as electrostatic electrodes, but are not particularly limited thereto. For example, in addition to or instead of the electrodes 23, heating electrodes (resistive heating elements) or RF electrodes may be built into the ceramic plate 20. In the above embodiment, the ceramic plate 20 and the cooling plate 30 are bonded together by the metal bonding layer 40 . However, a resin bonding layer may be used instead of the metal bonding layer 40 . This application claims priority based on international application PCT / JP2022 / 038367 filed on October 14, 2022, the entire contents of which are incorporated herein by reference. [Industrial Applicability] The present invention can be used in, for example, an apparatus for performing plasma processing on a wafer. 10: Wafer mounting table 20: Ceramic plate 22: Wafer mounting portion 22a: Sealing ring 22b: Small circular protrusion 22c: Reference surface 23: Electrode 24: FR mounting portion (focus ring mounting portion) 24a: Groove 24b: Focus ring support surface (FR support surface) 30: Cooling plate 32: Refrigerant flow path 40: Metal bonding layer 51: Gas supply path 51a: Gas inlet path 51b: Gas common path 51c: Gas diversion part 51d: Gas relay groove 51e: Gas distribution path 52: Gas supply path 52a: Gas inlet path 52b: Gas common path 52c: Gas diversion part 52d: Gas relay groove 52e: Gas distribution path 53: Gas supply path 53a: Gas inlet path 53b: Gas common path 53c: Gas diversion part 53d: Gas relay groove 53e: Gas distribution path 60: Focusing ring 60a: Circumferential groove 110: Wafer mounting table W: Wafer AA: Cross-section line FIG1 is a longitudinal cross-sectional view of the wafer mounting table 10. FIG2 is a cross-sectional view taken along line AA in FIG1. ​​FIG3 is a plan view of the wafer mounting table 10. FIG4 is a partially enlarged view of FIG3. FIG5 is a perspective view of the vicinity of the gas relay groove 53d of the cooling plate 30. FIG6 is an explanatory diagram of a modified example of the gas supply path 53. FIG7 is an explanatory diagram of a modified example of the gas supply path 53. FIG8 is a longitudinal cross-sectional view of the wafer mounting table 110. 10: Wafer loading platform 20: Ceramic plate 22: Wafer loading unit 22a: Sealing ring 22b: small round protrusion 22c: Reference plane 23: Electrode 24: FR mounting portion (focus ring mounting portion) 24a: groove 24b: Focus ring support surface (FR support surface) 30: Cooling plate 32:Refrigerant flow path 40:Metal bonding layer 51: Gas supply path 51a: Gas introduction path 51b: Gas common path 51c: Gas diversion part 51d: Gas relay tank 51e: Gas distribution path 52: Gas supply path 52a: Gas introduction path 52b: Gas common path 52c: Gas diversion part 52d: Gas relay tank 52e: Gas distribution path 53: Gas supply path 53a: Gas introduction path 53b: Gas common path 53c: Gas diversion part 53d: Gas relay tank 53e: Gas distribution path 60: Focus ring 60a: Circumferential groove W: Wafer AA: Section line

Claims

1. A wafer mounting stage, comprising: a ceramic plate having at least a wafer mounting portion on its top surface; a cooling plate joined to the bottom surface of the ceramic plate and having a refrigerant flow path; the wafer mounting stage further comprising: a gas common path disposed above the refrigerant flow path inside the wafer mounting stage; a gas inlet path extending from the bottom surface of the cooling plate to the gas common path; and a gas distribution path, having a plurality of such gas common paths extending from the gas common path to the top surface of the ceramic plate; wherein the outermost gas distribution path disposed on the outermost periphery of the ceramic plate is positioned in a position that does not overlap with the refrigerant flow path when viewed from above; the plurality of gas common paths are arranged in concentric circles; the outermost gas distribution path is connected to the outermost gas common path among the plurality of gas common paths; and the width of at least the portion of the gas distribution path connected to the gas common path is wider than the gas common path. The gas distribution path is connected to the common gas path via a gas splitter.

2. The wafer mounting stage as described in claim 1, wherein, The cooling plate is made of a composite material of metal and ceramic.

3. The wafer stage as described in Request 1 or Request 2, wherein, A circular wafer mounting portion and an annular focusing ring mounting portion surrounding the wafer mounting portion are provided on the top surface of the ceramic plate. The outermost gas distribution path is the path from the gas common path to the focusing ring mounting portion.

4. The wafer stage as described in Request 1 or Request 2, wherein, A circular wafer mounting portion is provided on the top surface of the ceramic plate, and the outermost gas distribution path is the path from the gas common path to the wafer mounting portion.

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