Wafer carrying table

Abstract

A wafer placement table 10 includes a ceramic plate 20 having a wafer placement surface 22 on an upper surface, and a cooling plate provided on a lower surface of the ceramic plate 20. A refrigerant flow path (32) built in a cooling plate has a first portion (32x) and a second portion (32y) which is divided into two or more branches from the first portion (32x) and which branches are parallel to each other, and the cross-sectional area of the first portion (32x) is smaller than the total of the cross-sectional areas of the branches of the second portion (32y).

Description

Technical Field This invention relates to a wafer mounting stage. Background Technology Conventionally, wafer stage configurations are known, comprising: a ceramic plate having a wafer placement surface on its upper surface, a cooling plate disposed on the lower surface of the ceramic plate, and a refrigerant flow path built into the cooling plate. For example, Patent Document 1 discloses that in a wafer stage where the cooling plate is formed of a material with high thermal conductivity such as Al, the distance between the upper surface of the refrigerant flow path and the wafer placement surface is constant from the inlet to the outlet of the refrigerant flow path, and the cross-sectional shape of the refrigerant flow path varies depending on its position. Patent Document 1 further describes that the cross-sectional area of ​​the flow path corresponding to the portion with a relatively high temperature relative to the wafer placement surface is smaller than the cross-sectional area of ​​the flow path corresponding to the portion with a relatively low temperature relative to the wafer placement surface. Additionally, it describes that the width of the upper surface of the refrigerant flow path between the inlet and outlet is constant, and the length in the height direction of the refrigerant flow path at the position corresponding to the portion with a relatively high temperature relative to the wafer placement surface is shorter in the height direction than the length in the height direction of the refrigerant flow path at the position corresponding to the portion with a relatively low temperature relative to the wafer placement surface. Existing technical documents Patent documents Patent Document 1: Japanese Patent Application Publication No. 2021-28961 Summary of the Invention However, regarding the configuration of Patent Document 1, the uneven heat dissipation of the coolant flow path is suppressed by working on the cross-sectional shape of the cooling plate. However, in cases where the width through which the coolant flow path can pass is relatively narrow, it is not possible to sufficiently ensure the flow path cross-sectional area corresponding to the relatively low temperature area of ​​the wafer mounting surface, and sometimes it is not possible to sufficiently suppress uneven heat dissipation. The present invention was implemented to solve the above-mentioned problems, and its main objective is to suppress temperature unevenness on the wafer placement surface for a wafer placement stage.

[0001] The wafer stage of the present invention comprises: A ceramic plate having a wafer mounting surface on its upper surface; A cooling plate disposed on the lower surface of the ceramic plate; and The refrigerant flow path is built into the cooling plate. Its features are, The refrigerant flow path has: a first part, and a second part that branches from the first part into two or more parallel branches. The cross-sectional area of ​​the first part is less than the sum of the cross-sectional areas of all branches of the second part. In this wafer mounting stage, the coolant flow path has a first section and a second section that branches into two or more parallel streams from the first section. Therefore, even in cases where the width of the coolant flow path is narrow, each branch of the second section can fall within its width, and a relatively large flow path cross-sectional area can be ensured for the second section as a whole. Furthermore, the cross-sectional area of ​​the first section is smaller than the sum of the cross-sectional areas of the branches of the second section. Therefore, compared to the second section, the first section of the coolant flow path has a faster flow rate, resulting in improved cooling efficiency. Thus, by adjusting the configuration of the first and second sections in the wafer mounting stage to correspond to areas with high cooling requirements, temperature unevenness on the wafer mounting surface can be suppressed.

[0002] Based on the wafer stage of the present invention (the wafer stage described above [1]), the first portion can be configured corresponding to the outer peripheral region of the wafer placement surface, and the second portion can be configured corresponding to the central region of the wafer placement surface. Generally, the outer peripheral region of the wafer placement surface receives more heat input from the plasma in the wafer stage than the central region. Taking this into consideration, by configuring the first and second portions as described above, the cooling efficiency of the outer peripheral region of the wafer placement surface can be higher than that of the central region, thereby effectively suppressing temperature unevenness of the wafer placement surface.

[0003] Based on the wafer stage of the present invention (the wafer stage described above [2]), the ceramic plate may have an annular focusing ring mounting surface around the wafer mounting surface that is one level lower than the height of the wafer mounting surface, and an annular focusing ring with an outer diameter larger than the outer diameter of the ceramic plate and the outer diameter of the cooling plate may be mounted on the focusing ring mounting surface. In this case, the focusing ring protrudes to the outside of the wafer stage (overhanging), so the outer peripheral area of ​​the wafer mounting surface is more likely to become hot. Therefore, the application of the present invention is of great significance.

[0004] Based on the wafer stage of the present invention (the wafer stage described in any one of [1] to [3] above), the cross-sectional area of ​​each branch of the second part can be greater than 1 / 2 of the cross-sectional area of ​​the first part. The larger the cross-sectional area of ​​each branch of the second part, the slower the flow rate of each branch. Therefore, relatively speaking, the flow rate of the first part becomes faster, which can further suppress uneven heat dissipation.

[0005] Based on the wafer stage of the present invention (the wafer stage described in any one of [1] to [4] above), the refrigerant flow path may have a reversing section that reverses the orientation of the flow path, and the flow path is divided into two branches midway through the reversing section, thereby suppressing the deviation in the amount of refrigerant distributed to each branch of the second part. Accordingly, the deviation in the heat dissipation capacity of each branch is suppressed, and uneven heat dissipation can be further suppressed.

[0006] Based on the wafer stage of the present invention (the wafer stage described in any one of [1] to [4] above), the refrigerant flow path can be divided into branches that inherit the bending trend before the branch and branches that temporarily deviate outward relative to the bending trend, thereby suppressing the deviation of the amount of refrigerant allocated to each branch of the second part. Even so, the deviation of the heat dissipation capacity of each branch is suppressed, and uneven heat dissipation can be further suppressed.

[0007] Based on the wafer stage of the present invention (the wafer stage described in any one of [1] to [6] above), when viewed from above, in the region where the second part is arranged, the area of ​​the portion where the coolant flow path is not formed, i.e., the non-flow path area, can be 50% or more. The larger the non-flow path area, the greater the degree of freedom in the configuration of the structure other than the coolant flow path.

[0008] Based on the wafer placement stage of the present invention (the wafer placement stage described in any of [1] to [7] above), the wafer placement surface may have a region with high cooling demand and a region with low cooling demand. The first portion is configured corresponding to the region with high cooling demand of the wafer placement surface, and the second portion is configured in the region with low cooling demand of the wafer placement surface. For example, the region with high cooling demand may be the outer peripheral region of the wafer placement surface, and the region with low cooling demand may be the central region of the wafer placement surface.

[0009] Based on the wafer mounting stage of the present invention (the wafer mounting stage described in any of [1] to [8] above), the heat exchange efficiency of the region corresponding to the first portion of the wafer mounting surface can be higher than the heat exchange efficiency of the region corresponding to the second portion. In this case, the region corresponding to the first portion of the wafer mounting surface can be the outer peripheral region of the wafer mounting surface, and the region corresponding to the second portion of the wafer mounting surface can be the central region of the wafer mounting surface. Attached Figure Description Figure 1 This is a cross-sectional view of the wafer stage 10. Figure 2 This is a plan view of the chip placement stage 10. Figure 3 yes Figure 1 A-A cross-sectional view. Figure 4 yes Figure 1 A magnified view of a portion of the image. Figure 5 It is an explanatory diagram illustrating the results of refrigerant flow within the refrigerant flow path. Figure 6 This is a cross-sectional view of the wafer stage 110. Figure 7 This is a plan view of the chip placement stage 110. Figure 8 yes Figure 6 B-B cross-sectional view. Figure 9 yes Figure 6 A magnified view of a portion of the image. Detailed Implementation [First Implementation Method] The first embodiment of the present invention will be described with reference to the accompanying drawings. Figure 1 This is a cross-sectional view of the wafer stage 10 (a cross-sectional view when the wafer stage 10 is cut along a plane including its central axis). Figure 2 This is a plan view of the chip stage 10. Figure 3 yes Figure 1 A-A cross-sectional view, Figure 4 yes Figure 1 A magnified view of a portion of the image. Figure 5 This is an explanatory diagram illustrating the results of refrigerant flow within the refrigerant flow path. It should be noted that... Figure 5 (A) in the diagram is a vector diagram representing the velocity distribution within the refrigerant flow path (the original diagram is a color subplot showing the velocity distribution starting from the fastest flow rate, in the order of red → orange → yellow → green → cyan → blue → purple). Figure 5 (B) and Figure 5 (C) in the diagram is an illustration of the preferred branch configuration. The wafer stage 10 is a component used for performing CVD, etching, and other processes on the wafer W using plasma. The wafer stage 10 includes a ceramic plate 20, a cooling plate 30, and a bonding layer 40. The ceramic plate 20 is formed of ceramic materials such as alumina and aluminum nitride. The ceramic plate 20 has: a wafer mounting surface 22, an electrostatic electrode 23, and a focusing ring mounting surface 24. Hereinafter, the focusing ring is sometimes simply referred to as "FR". The wafer mounting surface 22 is circular and is disposed on the upper surface of the ceramic plate 20. The wafer W is mounted on the wafer mounting surface 22. Multiple (six in this embodiment) gas holes 50 are formed on the wafer mounting surface 22, penetrating the wafer mounting stage 10 in the vertical direction, supplying a heat-conducting gas such as He gas from a gas supply source (not shown). Although not shown, an annular sealing strip is formed along the outer edge of the wafer mounting surface 22, and multiple small circular protrusions are formed on the entire surface of the area surrounded by this sealing strip. The sealing strip and the small circular protrusions are of the same height, for example, several μm to tens of μm. The wafer mounting surface 22 contains areas that easily become hot (areas with high cooling requirements) and areas that do not easily become hot (areas with low cooling requirements). In this embodiment, when processing the wafer W using plasma, the heat input of the plasma increases on the outer periphery; therefore, as... Figure 2As shown, the outer peripheral region 22a (the region with light dots) of the wafer mounting surface 22 becomes the region with high cooling requirements, while the central region 22b (the region with dense dots) of the wafer mounting surface 22 becomes the region with low cooling requirements. The electrostatic electrode 23 is a planar mesh electrode or a plate electrode, connected to a DC power supply (not shown) via a power supply terminal 26. When a DC voltage is applied to the electrostatic electrode 23, the wafer W is attracted and fixed to the wafer mounting surface 22 (specifically, the upper surface of the sealing strip and the upper surface of the small circular protrusion) by electrostatic attraction; when the DC voltage is released, the wafer W is released from its attraction and fixation on the wafer mounting surface 22. The power supply terminal 26 is inserted through a terminal hole 56 provided between the lower surface of the electrostatic electrode 23 and the lower surface of the cooling plate 30 in the wafer mounting stage 10. A FR (Front-Relief) mounting surface 24 is arranged in a ring around the wafer mounting surface 22. The height of the FR mounting surface 24 is one level lower than the height of the wafer mounting surface 22. An annular focusing ring 60 is mounted on the FR mounting surface 24. The focusing ring 60 is formed of, for example, Si. A circumferential groove 62 is provided above the inner surface of the focusing ring 60 in a manner that does not contact the wafer W. The outer diameter of the focusing ring 60 is larger than the outer diameter of the ceramic plate 20 and the outer diameter of the cooling plate 30. Therefore, the focusing ring 60 is mounted on the FR mounting surface 24 in a state that protrudes beyond the outer side of the wafer stage 10 (in a cantilevered state). The cooling plate 30 is a disc-shaped plate with an internal refrigerant flow path 32 for refrigerant circulation. For example... Figure 3 As shown, the refrigerant flow path 32, viewed from top view, is disposed on the entire surface of the ceramic plate 20 from one end (inlet 32in) to the other end (outlet 32out). In this embodiment, the refrigerant flow path 32 is formed in a vortex shape when viewed from top view. Such a cooling plate 30 can be manufactured, for example, by diffusion bonding of multiple layered components. Refrigerant is supplied from a refrigerant circulation device (not shown) to the inlet 32in of the refrigerant flow path 32, passes through the refrigerant flow path 32, and is discharged from the outlet 32out of the refrigerant flow path 32, returning to the refrigerant circulation device. The refrigerant circulation device can regulate the refrigerant to a desired temperature. The refrigerant is preferably a liquid, and preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inactive liquids. Examples of materials used for the cooling plate 30 include: metallic materials and composites of metals and ceramics. Examples of metallic materials include: Al, Ti, Mo, or alloys thereof. Examples of composites of metals and ceramics include: metal matrix composites (MMC) and ceramic matrix composites (CMC). Specific examples of such composites include: materials containing Si, SiC, and Ti (also called SiSiCTi), materials obtained by impregnating Al and / or Si into a porous SiC body, and composites of Al2O3 and TiC. From the viewpoint of suppressing warping of the wafer stage 10, a material with a coefficient of thermal expansion close to that of the ceramic plate 20 is preferred for the cooling plate 30. If the ceramic plate 20 is made of alumina, the material of the cooling plate 30 is preferably pure Ti or an α-βTi alloy. This is because the coefficients of thermal expansion of pure Ti and α-βTi alloys are close to those of alumina. From the viewpoint of improving heat dissipation performance, a material with high thermal conductivity is preferred for the cooling plate 30, for example, Al. The thermal conductivity of Al is 150–200 W / mK. The cooling plate 30 can be formed of a material with a lower thermal conductivity than Al. Examples of such materials include Ti-containing materials. The thermal conductivity of the cooling plate 30 can be below 50 W / mK, or it can be between 5 and 20 W / mK. For example, pure Ti has a thermal conductivity of 17 W / mK, and α-βTi alloy has a thermal conductivity of 7.5 W / mK. Furthermore, the material used for the cooling plate 30 can be a conductive material. The bonding layer 40 bonds the lower surface of the ceramic plate 20 and the upper surface of the cooling plate 30. The bonding layer 40 can be, for example, a metal layer formed by solder or brazing filler metal, or a resin layer formed by a resin adhesive. The refrigerant flow path 32 is described in detail. For example... Figure 2 As shown, the refrigerant flow path 32 contains a first portion 32x corresponding to the outer peripheral region 22a (region with high cooling demand) of the wafer mounting surface 22, and a second portion 32y corresponding to the central region 22b (region with low cooling demand). The first portion 32x corresponding to the outer peripheral region 22a is the part from the inlet 32in to the midpoint 32mid of the refrigerant flow path 32. The second portion 32y corresponding to the central region 22b is the part from the midpoint 32mid to the outlet 32out of the refrigerant flow path 32. The second portion 32y splits into two branches, 32y1 and 32y2, at the branch point 32div located at the midpoint 32mid, and they merge at the confluence point 32join, reaching the outlet 32out. It should be noted that... Figure 2 , 3 In the middle, a branch point 32div is configured at position 32mid. However, a branch point 32div can also be configured at a position away from the middle position 32mid. The refrigerant flow path 32 has a reversing section 32turn that reverses the direction of the flow path. At a branch point 32div located midway through the reversing section 32turn, it splits into two branches: branch 32y1 and branch 32y2. The reversing section 32turn reverses the counter-clockwise direction from the inlet 32in to the reversing section 32turn, making it clockwise from the reversing section 32turn to the outlet 32out. The refrigerant flow path 32 is configured such that at the branch point 32div located midway through the reversing section 32turn, it splits into two branches: branch 32y1 and branch 32y2. This prevents the amount of refrigerant distributed to each branch 32y1 and 32y2 from being biased towards one branch (hereinafter referred to as...). Figure 5 To explain this point. Regarding the cross-sectional area S of the refrigerant flow path 32, as follows: Figure 4 As shown, the flow path cross-sectional area Sx of the first part 32x corresponding to the outer peripheral region 22a is smaller than the sum of the flow path cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2 of the second part 32y corresponding to the central region 22b, that is, Sx < Sy1 + Sy2. The smaller the flow path cross-sectional area S, the faster the flow velocity of the refrigerant flowing through the refrigerant flow path 32, and the higher the cooling efficiency. It should be noted that the flow path cross-sectional area S is the area of ​​the cross section (flow path cross section) when the refrigerant flow path 32 is cut off by a plane perpendicular to the length direction of the refrigerant flow path 32 (each branch 32y1 and 32y2 in the second part 32y). The flow path cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2 of the second part 32y can be set appropriately. In this embodiment, they are the same as the flow path cross-sectional area Sx of the first part 32x, that is, Sy1 = Sy2 = Sx. The cross-sectional area S of the refrigerant flow path 32 is the value obtained by multiplying the lateral length W by the longitudinal length H. The lateral length W and the longitudinal length H can be appropriately set according to the cross-sectional area S. In this embodiment, the lateral lengths Wy1 and Wy2 of each branch 32y1 and 32y2 of the second part 32y are the same as the lateral length Wx of the first part 32x, that is, Wy1 = Wy2 = Wx. In addition, the longitudinal lengths Hy1 and Hy2 of each branch 32y1 and 32y2 of the second part 32y are the same as the longitudinal length Hx of the first part 32x, that is, Hy1 = Hy2 = Hx. 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 focusing ring 60 is placed on the FR placement surface 24, and the wafer W is placed on the wafer placement surface 22. In this state, a DC voltage is applied to the electrostatic electrode 23, causing the wafer W to adhere to the wafer placement surface 22. At the same time, a heat-conducting gas (such as He gas) is supplied to a gas hole 50 (a passage from the lower surface of the cooling plate 30 to the wafer placement surface 22) provided inside the wafer stage 10. Accordingly, the space surrounded by the sealing strip of the lower surface of the wafer W and the wafer placement surface 22 is filled with gas, thus improving the heat conduction between the wafer W and the wafer placement surface 22. Then, the interior of the chamber is set to a predetermined vacuum atmosphere (or reduced pressure atmosphere), and process gas is supplied from a spray head provided at the top of the chamber, while an RF voltage is applied to the cooling plate 30. Plasma is then generated between the wafer W and the spray head. Subsequently, CVD film deposition or etching is performed on the wafer W using this plasma. In the case where plasma is used to process wafer W as described above, the heat input from the plasma is greater in the outer peripheral region of wafer W than in the central region. Therefore, the outer peripheral region is more prone to overheating compared to the central region of wafer W. Thus, to ensure uniform temperature of wafer W, the outer peripheral region 22a needs to be cooled more efficiently than the central region 22b of the wafer mounting surface 22. Considering this, in this embodiment, the cross-sectional area S of the coolant flow path 32 is adjusted as described above. As a result, the cooling efficiency of the first portion 32x of the coolant flow path 32 corresponding to the outer peripheral region 22a is higher than the cooling efficiency of the second portion 32y corresponding to the central region 22b. In the wafer stage 10 described above, the refrigerant flow path 32 has a first portion 32x corresponding to areas with high cooling demand and a second portion 32y corresponding to areas with low cooling demand. Furthermore, the second portion 32y branches into two parallel branches 32y1 and 32y2 at a branch point 32div from the first portion 32x. Therefore, even when the refrigerant flow path 32 has a narrow width, such as when the distance between the gas port 50 and the terminal port 56 is close, each branch 32y1 and 32y2 of the second portion falls within its width, and a relatively large flow path cross-sectional area is ensured for the second portion 32y as a whole. Additionally, the flow path cross-sectional area Sx of the first portion 32x corresponding to areas with high cooling demand in the refrigerant flow path 32 is less than the sum of the flow path cross-sectional areas Sy1 + Sy2 of each branch 32y1 and 32y2 of the second portion 32y corresponding to areas with low cooling demand. Therefore, the first portion 32x corresponding to the region with high cooling demand has a faster flow rate than the second portion 32y corresponding to the region with low cooling demand in the refrigerant flow path 32, thus improving cooling efficiency. In this way, the first portion 32x corresponding to the region with high cooling demand has one stream, while the second portion 32y corresponding to the region with low cooling demand has two or more streams, thereby controlling the flow rate. Furthermore, the flow rate can be controlled by changing the cross-sectional area of ​​the flow path in the first portion 32x and the second portion 32y. Therefore, in the wafer stage 10, by adjusting the configuration of the first portion 32x and the second portion 32y to correspond to the region with high cooling demand, temperature unevenness on the wafer mounting surface 22 can be suppressed, and the heat uniformity of the wafer W can be improved. It should be noted that the cross-sectional area S of the refrigerant flow path 32 can satisfy 1.5Sx < Sy1 + Sy2 < 2.5Sx, or it can satisfy 1.8Sx < Sy1 + Sy2 < 2.2Sx. Furthermore, regarding the heat input of the plasma in the wafer placement stage 10, the outer peripheral region 22a of the wafer placement surface 22 is typically larger than the central region 22b. Taking this into account, by positioning the first portion 32x at a position corresponding to the outer peripheral region 22a of the wafer placement surface 22 and positioning the second portion 32y at a position corresponding to the central region 22b of the wafer placement surface 22, the cooling efficiency of the outer peripheral region 22a of the wafer placement surface 22 can be made higher than that of the central region 22b, thereby effectively suppressing temperature unevenness of the wafer placement surface 22. Furthermore, the ceramic plate 20 has an annular focusing ring mounting surface 24 around the wafer mounting surface 22, which is one level lower than the height of the wafer mounting surface 22. An annular focusing ring 60 with an outer diameter larger than the outer diameter of the ceramic plate 20 and the outer diameter of the cooling plate 30 is mounted on the focusing ring mounting surface 24. In this case, the focusing ring 60 protrudes beyond the outer side of the wafer mounting stage 10 (overhanging), so the outer peripheral region 22a of the wafer mounting surface 22 is more prone to high temperatures. Therefore, the application of this invention is of great significance. Furthermore, the flow path cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2 in the second part 32y are both greater than half of the flow path cross-sectional area Sx of the first part 32x. The larger the flow path cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2 in the second part 32y, the slower the flow velocity in each branch 32y1 and 32y2, which can further suppress uneven heat dissipation. The flow path cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2 can be more than 2 / 3 or more than 3 / 4 of the flow path cross-sectional area Sx of the first part 32x. The flow path cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2 can be less than twice or less than 1.5 times the flow path cross-sectional area Sx of the first part 32x. Furthermore, the refrigerant flow path 32 has a reversing section 32turn that reverses the direction of the flow path. At the midpoint of the reversing section 32turn, it branches into two branches 32y1 and 32y2, thereby suppressing the deviation in the amount of refrigerant distributed to each branch 32y1 and 32y2 of the second part 32y. Accordingly, the deviation in the heat dissipation capacity of each branch 32y1 and 32y2 is suppressed, further suppressing uneven heat dissipation. Regarding this, use Figure 5 The results of the study on refrigerant flow within the refrigerant flow path are explained. When the refrigerant flow path has a vortex-like or other tortuous shape, it exhibits the following trend: due to centrifugal force, like... Figure 5 As in part (1) of (A), the flow velocity increases towards the outer periphery of the flow path (outer side of the curve). Therefore, if the flow path branches only at a branch point near the center, the amount of refrigerant allocated may be biased towards the outer periphery branch. On the other hand, if a bend with a curvature smaller than the previous bend shape (e.g., a curvature radius R of 50 mm or more) (e.g., a curvature radius R of 20 mm or less) is provided in the middle of the bend, the previous centrifugal force is temporarily canceled in the middle of the bend, like... Figure 5 As in part (2) of (A), the flow velocity is greatest near the center of the flow path, and the difference in velocity between the outer periphery (outer side of the curve) and the inner periphery (inner side of the curve) decreases. Therefore, for example, if like Figure 5 As in (B), if the refrigerant is split into two streams at a branch point located in the middle of the reversing section, the bias of the refrigerant amount distributed to each branch towards one branch can be suppressed. It should be noted that when the branch point is set in the middle part of the reversing section, the branch point is preferably located near the center where the flow velocity is greater than that on both sides of the flow path. Furthermore, when viewed from above the wafer stage 10, in the region where the second part 32y is configured (e.g., the central region 22b with low cooling requirements), the area where the coolant flow path 32 is not formed, i.e., the non-flow path area, can be more than 50%. The larger the non-flow path area, the greater the freedom in configuring the components other than the coolant flow path (gas holes 50, terminal holes 56, lifting pin holes, etc., described later). Regarding this, a comparison was made between the case where the second part 32y in the coolant flow path 32 is not branched and the flow path cross-sectional area Sy is twice that of the first part 32x, and the case where the second part 32y is divided into branches 32y1 and 32y2 and the flow path cross-sectional areas Sy1 and Sy2 of each branch are the same as those of the first part 32x (the total cross-sectional area is twice that of the first part 32x). The results showed that the non-flow path area when the temperature unevenness of the wafer is within a specified range (e.g., within 10°C) is 41.3% in the former and 54.6% in the latter, indicating that the non-flow path area can be increased by more than 50%. For the comparison, the materials used for the cooling plate are a first material with a thermal conductivity of 20 W / mK (e.g., Ti), a second material with a thermal conductivity of 100 W / mK, and a third material with a thermal conductivity of 200 W / mK (e.g., Al). Regarding the first part 32x, the flow path cross-sectional area Sx = 84 mm². 2 Length Wx = 7mm, length Hx = 12mm. Without the second 32y branch, its flow path cross-sectional area Sy = 168mm². 2 The lengths are Wy = 14 mm and Hy = 12 mm. When the second part 32y branches, the cross-sectional area of ​​the flow path for branch 32y1 of the second part 32y is Sy1 = 84 mm². 2 The lengths are Wy1 = 7 mm and Hy1 = 12 mm. Regarding the branch 32y2 of the second part 32y, the flow path cross-sectional area Sy2 = 84 mm². 2 Length Wy2 = 7mm, length Hy2 = 12mm. It should be noted that the non-flow area can be, for example, less than 70%. In addition, the region where the second part 32y is configured (here, the central region 22b) can be the smallest circumcircle that includes all branches 32y1 and 32y2. Furthermore, regarding the flow path length L of the refrigerant flow path 32, the ratio of the lengths Ly1 and Ly2 (not shown) of each branch 32y1 and 32y2 to Ly1 / Ly2 is preferably 4 / 5 or more and 5 / 4 or less. This reduces the pressure loss difference between branches 32y1 and 32y2. It should be noted that if the ratio Ly1 / Ly2 is large, the pressure loss difference between branches 32y1 and 32y2 can be reduced by adjusting the cross-sectional shape of each branch 32y1 and 32y2. The lengths Ly1 and Ly2 of each branch 32y1 and 32y2 can be more than half the length Lx of the first part 32x, or more than the length Lx of the first part 32x. Additionally, the lengths Ly1 and Ly2 of each branch 32y1 and 32y2 can be less than 10 times or less than 5 times the length Lx of the first part 32x. Furthermore, the length Lx of the first part 32x, and the lengths Ly1 and Ly2 of each branch 32y1 and 32y2 can each be 20 mm or more. Additionally, regarding the cross-sectional area S of the refrigerant flow path 32, the ratio of the cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2, Sy1 / Sy2, is preferably 4 / 5 or more and 5 / 4 or less. This reduces the pressure loss difference between branches 32y1 and 32y2. [Second Implementation] The second embodiment of the present invention will be described with reference to the accompanying drawings. Figure 6 This is a cross-sectional view of the wafer stage 110 (a cross-sectional view of the wafer stage 110 when cut along a plane including the central axis of the wafer stage 110). Figure 7 This is a plan view of the chip stage 110. Figure 8 yes Figure 6 B-B cross-section diagram, Figure 9 yes Figure 6 A magnified view of a portion of the image. Figures 6-9 In this document, the same symbols are used for the same constituent elements as in the above embodiments, and their descriptions are omitted. like Figure 8 As shown, the refrigerant flow path 132, viewed from top, extends from one end (inlet 132in) to the other end (outlet 132out) across the entire surface of the ceramic plate 20. The refrigerant flow path 132 is formed in a vortex shape. The refrigerant, refrigerant circulation device, etc., can be the same as in the embodiment described above. like Figure 7As shown, the refrigerant flow path 132 contains a first portion 132x corresponding to the outer peripheral region 22a (region with high cooling demand) of the wafer placement surface 22, and a second portion 132y corresponding to the central region 22b (region with low cooling demand). The first portion 132x of the refrigerant flow path 132, corresponding to the outer peripheral region 22a, extends from the inlet 132in of the refrigerant flow path 132 to the midpoint 132mid. The second portion 132y of the refrigerant flow path 132, corresponding to the central region 22b, extends from the midpoint 132mid of the refrigerant flow path 132 to the outlet 132out. The second portion 132y splits into two branches, 132y1 and 132y2, at the branch point 132div, and merges at the confluence point 132join, reaching the outlet 132out. The refrigerant flow path 132 is formed such that at the branch point 132div, it is divided into a branch 132y1 that inherits the bending trend before the branch and a branch 132y2 that temporarily deviates outward relative to the bending trend. Accordingly, the amount of refrigerant allocated to each branch 132y1 and 132y2 is suppressed from being biased towards one branch. Regarding the cross-sectional area S of the refrigerant flow path 132, the cross-sectional area Sx of the first part 132x corresponding to the outer peripheral region 22a is smaller than the sum of the cross-sectional areas Sy1 and Sy2 of the branches 132y1 and 132y2 of the second part 132y corresponding to the central region 22b, i.e., Sx < Sy1 + Sy2. Therefore, the flow rate of the first part 132x, corresponding to the region with high cooling demand, is faster and the cooling efficiency is improved compared to the second part 132y, corresponding to the region with low cooling demand. It should be noted that the cross-sectional area S, lateral length W, and longitudinal length H of the refrigerant flow path 132 are based on the cross-sectional area S, lateral length W, and longitudinal length H of the refrigerant flow path 32. The usage examples of the wafer placement stage 110 are based on the manufacturing and usage examples of the wafer placement stage 10, therefore, their descriptions are omitted here. In the wafer stage 110 described above, similarly to the wafer stage 10 described above, the first portion 132x corresponding to the area with high cooling demand has one flow path, and the second portion 132y corresponding to the area with low cooling demand has two flow paths, thereby controlling the flow rate. In addition, the flow path cross-sectional area is changed in the first portion 132x and the second portion 132y to control the flow rate. As a result, the temperature unevenness of the wafer placement surface 22 can be suppressed in the wafer stage 110, thereby improving the heat uniformity of the wafer W. Furthermore, the refrigerant flow path 132 is formed at the branch point 132div into a branch 132y1 that inherits the bending trend before the branch and a branch 132y2 that temporarily deviates outward relative to the bending trend, thereby suppressing the refrigerant amount allocated to each branch 132y1 and 132y2 from being biased towards one branch. Accordingly, the deviation in the heat dissipation capacity of each branch 132y1 and 132y2 is suppressed, and uneven heat dissipation can be further suppressed. It should be noted that the branch 132y2 can be branched at an angle of 30° or more and 90° or less relative to the branch 132y1. Regarding this point, such as using Figure 5 As explained, there is a trend that the flow velocity increases towards the outer periphery of the flow path (outer side of the curve). Therefore, if the flow path branches only near the center, the amount of refrigerant allocated may be biased towards the outer branch. Thus, in Figure 5 In the case of setting branch points in part (1) of (A), for example, like Figure 5 As in (C), branching points are set near the outer periphery of the flow path before the branch, thus dividing it into branches that inherit the bending trend before the branch and branches that temporarily deviate outward relative to the bending trend. Accordingly, the flow path that becomes the main flow path through the branch on the inner periphery (inner side of the curve) is suppressed, thereby suppressing the amount of refrigerant distributed to the branch on the outer periphery (outer side of the curve), and thus suppressing the bias of the amount of refrigerant distributed to each branch towards one branch. Furthermore, when viewed from above, in the area where the second part 132y is located (e.g., the central area 22b with low cooling demand), the area where the refrigerant flow path 132 is not formed, i.e., the non-flow path area, can be 50% or more. The larger the non-flow path area, the greater the flexibility in configuring components other than the refrigerant flow path (gas holes 50, terminal holes 56, lifting pin holes, etc., described later). The non-flow path area can, for example, be 70% or less. In addition, regarding the length L and cross-sectional area S of the refrigerant flow path 132, the length L and cross-sectional area S of the refrigerant flow path 32 can be used as a reference to reduce the pressure loss difference between branch 132y1 and branch 132y2. It should be noted that the present invention is not limited to any of the above embodiments. Of course, as long as it falls within the technical scope of the present invention, it can be implemented in various ways. For example, in the first and second embodiments described above, the refrigerant flow paths 32 and 132 are divided into two branches; however, they can be divided into three or more branches. Furthermore, the configuration of the branch points 32div and 132div of the refrigerant flow paths 32 and 132 is not limited to the configuration described above, and can be appropriately set to ensure that the amount of refrigerant distributed to each branch 32y1 and 32y2 or each branch 132y1 and 132y2 reaches the desired amount. In the first and second embodiments described above, the refrigerant flow paths 32 and 132 converge at the junction points 32join and 132join. However, they may not converge, but instead reach the outlets set at each branch 32y1 and 32y2 or each branch 132y1 and 132y2 respectively. In the first and second embodiments described above, the region with high cooling requirements is designated as the outer peripheral region 22a of the wafer mounting surface 22, and the region with low cooling requirements is designated as the central region 22b of the wafer mounting surface 22, but this is not particularly limited to this. In the first and second embodiments described above, the heat exchange efficiency of the outer peripheral region 22a corresponding to the first portions 32x and 132x in the wafer mounting surface 22 can be higher than the heat exchange efficiency of the central region 22b corresponding to the second portions 32y and 132y. Taking the wafer mounting stage 10 as an example, the heat exchange efficiency can be calculated as follows. First, a first cooler capable of controlling the temperature of the cooler while circulating it is connected to the inlet 32in and outlet 32out of the cooler flow path 32, so that the cooler at the same temperature as room temperature (e.g., 25°C) circulates in the cooler flow path 32. At the same time, a cooler at a specified temperature (e.g., 80-100°C) is prepared in advance using a second cooler. Then, the cooler at the same temperature as room temperature is switched to the cooler at the specified temperature using a valve, so that the cooler at the specified temperature circulates in the cooler flow path 32. After switching the cooler and waiting for a specified time (e.g., 10 seconds), the temperature distribution of the wafer mounting surface 22 is measured. Based on the temperature distribution, the temperature rise rate (temperature rise per unit time (°C / second)) is calculated and used as an indicator of heat exchange efficiency. For example, in the wafer stage 10, when the coolant is switched from 25°C to 80°C, the temperature rise rate of the outer peripheral region 22a of the wafer placement surface 22 is greater than 5.5°C / second, while the temperature rise rate of the central region 22b is less than 5°C / second. Therefore, it can be seen that the heat exchange efficiency of the outer peripheral region 22a is higher than that of the central region 22b. It should be noted that the temperature rise rate at the boundary between the outer peripheral region 22a and the central region 22b is an intermediate value. In the first and second embodiments described above, an electrostatic electrode 23 is built into the ceramic plate 20 at a position opposite to the wafer placement surface 22. However, in addition, an FR adsorption electrode for electrostatic adsorption focusing ring 60 can be provided inside the ceramic plate 20 at a position opposite to the FR placement surface 24. In the first and second embodiments described above, the ceramic plate 20 is exemplified as having a wafer placement surface 22 and an FR placement surface 24, but is not particularly limited thereto. For example, the ceramic plate 20 may be a ceramic plate having a wafer placement surface 22 but not having an FR placement surface 24. In the first and second embodiments described above, the outer diameter of the focusing ring 60 is illustrated as being larger than the outer diameter of the wafer stage 10 (the outer diameter of the ceramic plate 20 and the outer diameter of the cooling plate 30), but this is not a limitation. For example, the outer diameter of the focusing ring 60 may be the same as the outer diameter of the wafer stage 10. In the first and second embodiments described above, the refrigerant flow paths 32 and 132 are formed in a vortex shape when viewed from above, but this is not a particular limitation. For example, the refrigerant flow paths 32 and 132 can be formed in a serrated shape when viewed from above. In the first and second embodiments described above, a wafer stage 10 with an electrostatic electrode 23 built into the ceramic plate 20 is illustrated, but it is not particularly limited to this. For example, instead of the electrostatic electrode 23 or other than the electrostatic electrode 23, a heater electrode (resistive heating element) or a plasma generating electrode (RF electrode) may be built into the ceramic plate 20. In the first and second embodiments described above, the wafer mounting stages 10 and 110 may have a plurality of vertically penetrating lifting pin holes. The lifting pin holes are holes through which lifting pins for moving the wafer W vertically relative to the wafer mounting surface 22 are inserted. For example, when viewed from above, a plurality of lifting pin holes are provided at equal intervals along concentric circles of the wafer mounting surface 22. Industrial availability The present invention can be used, for example, in apparatus for plasma processing of wafers. Symbol Explanation 10, 110 Wafer stage, 20 Ceramic plate, 22 Wafer placement surface, 22a Outer peripheral region, 22b Central region, 23 Electrostatic electrode, 24 Focusing ring placement surface, 26 Power supply terminal, 30 Cooling plate, 32, 132 Refrigerant flow path, 32in, 132in inlet, 32mid, 132mid midway position, 32out, 132out outlet, 32x, 132x first part, 32y, 132y second part, 32div, 132div branch point, 32join, 132join confluence point, 32turn foldback section, 40 Bonding layer, 50 Gas hole, 56 Terminal hole, 60 Focusing ring, 62 Circumferential groove, W Wafer.

Claims

1. A wafer boat comprising: a ceramic plate having a wafer loading surface on an upper surface; a cooling plate provided on a lower surface of the ceramic plate; and a coolant flow path built in the cooling plate, the wafer boat being characterized in that the coolant flow path has a first portion and a second portion that is divided into two or more branches from the first portion and the branches are parallel to each other, and a cross-sectional area of the first portion is smaller than a total of cross-sectional areas of the branches of the second portion.

2. The wafer boat according to claim 1, characterized in that the first portion is disposed corresponding to an outer peripheral region of the wafer loading surface, and the second portion is disposed corresponding to a central region of the wafer loading surface.

3. The wafer boat according to claim 2, characterized in that the ceramic plate has an annular focus ring loading surface that is one level lower in height than the wafer loading surface around the wafer loading surface, and an annular focus ring having an outer diameter larger than an outer diameter of the ceramic plate and an outer diameter of the cooling plate is loaded on the focus ring loading surface.

4. The wafer boat according to any one of claims 1 to 3, characterized in that the cross-sectional area of each of the branches of the second portion is larger than 1 / 2 of the cross-sectional area of the first portion.

5. The wafer boat according to any one of claims 1 to 3, characterized in that the coolant flow path has a turnaround portion that reverses a direction of flow, and is divided into two at a middle of the turnaround portion, thereby suppressing a variation in an amount of coolant distributed to each of the branches of the second portion.

6. The wafer boat according to any one of claims 1 to 3, characterized in that the coolant flow path has a branch that follows a tendency of a curvature before a branch, and a branch that temporarily deviates to an outer side with respect to the tendency of the curvature, thereby suppressing a variation in an amount of coolant distributed to each of the branches of the second portion.

7. The wafer boat according to any one of claims 1 to 3, characterized in that, in a region where the second portion is disposed, an area of a portion where the coolant flow path is not formed, i.e., a non-flow path area, is 50% or more when viewed from above. ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​ ​

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