Wafer mounting table

Abstract

A wafer placement table 10 comprises: a ceramic plate 20 having a wafer placement surface 22 on the upper surface thereof; and a cooling plate provided on the lower surface of the ceramic plate 20. A refrigerant flow path 32 built into the cooling plate has a first portion 32x, and a second portion 32y branching from the first portion 32x into two or more paths that run in parallel to each other. The cross-sectional area of the first portion 32x is smaller than the sum of the cross-sectional areas of the paths of the second portion 32y.

Description

[Technical Field]

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

[0002] Conventionally, a wafer mounting table has been known that includes a ceramic plate having a wafer mounting surface on its upper surface, a cooling plate provided on the lower surface of the ceramic plate, and a refrigerant flow path built into the cooling plate. For example, Patent Document 1 discloses a wafer mounting table in which the cooling plate is formed of a material with high thermal conductivity, such as aluminum, in which the distance between the upper surface of the refrigerant flow path and the wafer mounting 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 the position of the refrigerant flow path. Patent Document 1 describes that the cross-sectional area of the flow path corresponding to the relatively high-temperature portion of the wafer mounting surface is smaller than the cross-sectional area of the flow path corresponding to the relatively low-temperature portion of the wafer mounting surface. It also describes that the width of the upper surface of the refrigerant flow path from the inlet to the outlet is constant, and the height of the refrigerant flow path is shorter at the position corresponding to the relatively high-temperature portion of the wafer mounting surface than at the position corresponding to the relatively low-temperature portion of the wafer mounting surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-28961 Summary of the Invention [Problem to be solved by the invention]

[0004] However, although the configuration of Patent Document 1 suppresses uneven heat dissipation in the refrigerant flow path by devising the cross-sectional shape of the cooling plate, for example, when the width through which the refrigerant flow path can pass is narrow, it is sometimes not possible to ensure a sufficient cross-sectional area of the flow path corresponding to the area where the temperature of the wafer mounting surface is relatively low, and thus it is not possible to sufficiently suppress uneven heat dissipation.

[0005] The present invention has been made to solve the above problems, and a main object of the present invention is to suppress temperature variations on the wafer mounting surface of a wafer mounting table. [Means for solving the problem]

[0006] [1] The wafer mounting table of the present invention comprises: a ceramic plate having a wafer mounting surface on its upper surface; a cooling plate provided on the lower surface of the ceramic plate; a refrigerant flow path built into the cooling plate; A wafer mounting table comprising: the refrigerant flow path has a first portion and a second portion that branches into two or more branches from the first portion and runs parallel to each other, The cross-sectional area of the first portion is smaller than the sum of the cross-sectional areas of the branches of the second portion. It is something.

[0007] In this wafer mounting table, the coolant flow path has a first portion and a second portion that branches off from the first portion into two or more branches that run parallel to each other. Therefore, even when the width through which the coolant flow path can be passed is narrow, each branch in the second portion can fit within that width, while ensuring a relatively large flow path cross-sectional area for the entire second portion. The cross-sectional area of the first portion is smaller than the sum of the cross-sectional areas of the branches in the second portion. Therefore, the flow velocity in the first portion of the coolant flow path is faster than that in the second portion, resulting in higher cooling efficiency. Therefore, by adjusting the arrangement of the first and second portions of the wafer mounting table, such as by arranging the first portion to correspond to an area with high cooling demands, temperature unevenness on the wafer mounting surface can be suppressed.

[0008] [2] In the wafer mounting table of the present invention (the wafer mounting table described in [1] above), the first portion may be disposed in correspondence with the outer periphery of the wafer mounting surface, and the second portion may be disposed in correspondence with the central region of the wafer mounting surface. Generally, the heat input of plasma into the wafer mounting table is greater in the outer periphery of the wafer mounting surface than in the central region. In consideration of this, by disposing the first and second portions as described above, the cooling efficiency of the outer periphery of the wafer mounting surface can be made higher than that of the central region, and thus temperature unevenness on the wafer mounting surface can be effectively suppressed.

[0009] [3] In the wafer mounting table of the present invention (the wafer mounting table described in [2] above), the ceramic plate may have an annular focus ring mounting surface around the wafer mounting surface that is one step lower than the wafer mounting surface, and an annular focus ring having 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 focus ring mounting surface. In this case, since the focus ring overhangs the wafer mounting table, the peripheral region of the wafer mounting surface is likely to become hotter. Therefore, the application of the present invention is highly significant.

[0010] [4] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [3] above), the cross-sectional area of each branch in the second portion may be greater than half the cross-sectional area of the first portion. The larger the cross-sectional area of each branch in the second portion, the slower the flow velocity in each branch, and therefore the relatively faster the flow velocity in the first portion, thereby further suppressing uneven heat removal.

[0011] [5] In 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 turning portion that reverses the flow path direction and branches into two at the turning portion, thereby suppressing unevenness in the amount of refrigerant distributed to each branch in the second section. This suppresses unevenness in the heat removal capacity of each branch, and further suppresses uneven heat removal.

[0012] [6] In the wafer stage of the present invention (the wafer stage described in any one of [1] to [4] above), the refrigerant flow path may be branched into a branch that continues the curved shape before branching and a branch that temporarily deviates from the curved shape, thereby suppressing unevenness in the amount of refrigerant distributed to each branch in the second section. This also suppresses unevenness in the heat removal capacity of each branch, thereby further suppressing uneven heat removal.

[0013] [7] In the wafer stage of the present invention (the wafer stage described in any one of [1] to [6] above), a non-flow path area, which is an area of a portion where the refrigerant flow path is not formed, may be 50% or more in a region where the second portion is arranged when viewed from above. The larger the non-flow path area, the greater the degree of freedom in arranging components other than the refrigerant flow path.

[0014] [8] In the wafer mounting table of the present invention (the wafer mounting table according to any one of [1] to [7] above), the wafer mounting surface has an area where cooling is required more highly and an area where cooling is required less highly, and the first portion is disposed in correspondence with the area where cooling is required more highly on the wafer mounting surface, and the second portion is disposed in correspondence with the area where cooling is required less highly on the wafer mounting surface. In response For example, the area requiring high cooling may be the outer periphery of the wafer mounting surface, and the area requiring low cooling may be the central area of the wafer mounting surface.

[0015] [9] In the wafer mounting table of the present invention (the wafer mounting table described in any one of [1] to [8] above), the heat exchange efficiency of a region of the wafer mounting surface corresponding to the first portion may be higher than the heat exchange efficiency of a region of the wafer mounting surface corresponding to the second portion. In this case, the region of the wafer mounting surface corresponding to the first portion may be a peripheral region of the wafer mounting surface, and the region of the wafer mounting surface corresponding to the second portion may be a central region of the wafer mounting surface. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. [Figure 2]FIG. [Figure 3] Cross section AA of Figure 1. [Figure 4] Enlarged view of a portion of Figure 1. [Figure 5] FIG. 10 is an explanatory diagram of the results of examining the flow of a refrigerant in a refrigerant flow path. [Figure 6] FIG. [Figure 7] FIG. [Figure 8] Cross section B-B of Figure 6. [Figure 9] A partial enlarged view of Figure 6. DETAILED DESCRIPTION OF THE INVENTION

[0017] [First embodiment] A first embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a cross-sectional view of a wafer mounting table 10 (a cross-sectional view of the wafer mounting table 10 cut along a plane including the central axis of the wafer mounting table 10), Fig. 2 is a plan view of the wafer mounting table 10, Fig. 3 is a cross-sectional view taken along the line AA in Fig. 1, Fig. 4 is an enlarged view of a portion of Fig. 1, and Fig. 5 is an explanatory diagram showing the results of an investigation into the flow of refrigerant in a refrigerant flow channel. Fig. 5A is a vector diagram showing the flow velocity distribution in the refrigerant flow channel (the original diagram is a color diagram in which the flow velocity is represented in descending order by red, orange, yellow, green, blue, indigo, and purple), and Figs. 5B and 5C are explanatory diagrams showing preferred branching configurations.

[0018] The wafer mounting table 10 is used to perform CVD, etching, or the like using plasma on the wafer W. The wafer mounting table 10 includes a ceramic plate 20, a cooling plate 30, and a bonding layer 40.

[0019] Ceramic plate 20 is made of a ceramic material such as alumina or aluminum nitride. Ceramic plate 20 has a wafer mounting surface 22, an electrostatic electrode 23, and a focus ring mounting surface 24. Hereinafter, focus ring may be abbreviated as "FR."

[0020] The wafer mounting surface 22 is a circular surface provided on the upper surface of the ceramic plate 20. A wafer W is mounted on the wafer mounting surface 22. The wafer mounting surface 22 has a plurality of gas holes 50 (six in this embodiment) that penetrate the wafer mounting table 10 in the vertical direction, through which a thermally conductive gas such as He gas is supplied from a gas supply source (not shown). Although not shown, the wafer mounting surface 22 has an annular seal band formed along its outer edge, and a plurality of small circular protrusions formed on the entire surface of the area surrounded by the seal band. The seal band and the small circular protrusions have the same height, for example, several μm to several tens of μm. The wafer mounting surface 22 has areas that are prone to high temperatures (areas requiring high cooling) and areas that are less likely to become high temperatures (areas requiring low cooling). In this embodiment, when processing the wafer W with plasma, the heat input of the plasma is greater on the outer periphery side, so as shown in Figure 2, the outer periphery region 22a (lightly shaded region) of the wafer mounting surface 22 is an area requiring high cooling, and the central region 22b (darkly shaded region) of the wafer mounting surface 22 is an area requiring low cooling.

[0021] The electrostatic electrode 23 is a planar mesh electrode or plate electrode, and is 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 seal band and the upper surfaces of the small circular protrusions) by electrostatic attraction, and when the application of the DC voltage is stopped, the wafer W is released from the attraction and fixation to the wafer mounting surface 22. The power supply terminal 26 is inserted into a terminal hole 56 provided in the wafer mounting table 10 between the lower surface of the electrostatic electrode 23 and the lower surface of the cooling plate 30.

[0022] The FR mounting surface 24 is provided in an annular shape around the wafer mounting surface 22. The height of the FR mounting surface 24 is one step lower than the height of the wafer mounting surface 22. An annular focus ring 60 is mounted on the FR mounting surface 24. The focus ring 60 is made of, for example, Si. A circumferential groove 62 is formed above the inner surface of the focus ring 60 to prevent it from coming into contact with the wafer W. The outer diameter of the focus ring 60 is larger than the outer diameter of the ceramic plate 20 and the outer diameter of the cooling plate 30. Therefore, the focus ring 60 is mounted on the FR mounting surface 24 in a state where it protrudes outside the wafer mounting table 10 (in an overhanging state).

[0023] The cooling plate 30 is a disc-shaped plate having a refrigerant flow path 32 therein through which a refrigerant can circulate. As shown in FIG. 3, the refrigerant flow path 32 is provided across the entire surface of the ceramic plate 20 from one end (inlet 32in) to the other end (outlet 32out) in a plan view. In this embodiment, the refrigerant flow path 32 is formed in a spiral shape in a plan view. Such a cooling plate 30 can be fabricated, for example, by diffusion bonding multiple layered members. The refrigerant is supplied to the inlet 32in of the refrigerant flow path 32 from a refrigerant circulation device (not shown), passes through the refrigerant flow path 32, and is discharged from the outlet 32out 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 is preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inert liquids.

[0024] Materials used for the cooling plate 30 include metal materials and composite materials of metal and ceramic. Metal materials include Al, Ti, Mo, and alloys thereof. Composite materials of metal and ceramic include metal matrix composites (MMC) and ceramic matrix composites (CMC). Specific examples of such composite materials include a material containing Si, SiC, and Ti (also known as SiSiCTi), a material in which porous SiC is impregnated with Al and / or Si, and a composite material of Al2O3 and TiC. To prevent warping of the wafer mounting table 10, a material with a thermal expansion coefficient similar to that of the ceramic plate 20 is preferred for the cooling plate 30. When the ceramic plate 20 is made of alumina, the cooling plate 30 is preferably made of pure Ti or an α-β Ti alloy. This is because the thermal expansion coefficients of pure Ti and α-β Ti alloys are similar to that of alumina. To enhance heat dissipation performance, a material with high thermal conductivity, such as Al, is preferred for the cooling plate 30. The thermal conductivity of Al is 150 to 200 W / mK. The cooling plate 30 may be made 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 may be 50 W / mK or less, or may be 5 to 20 W / mK. For example, the thermal conductivity of pure Ti is 17 W / mK, and the thermal conductivity of an α-β Ti alloy is 7.5 W / mK. The material used for the cooling plate 30 may also be a conductive material.

[0025] The bonding layer 40 bonds the lower surface of the ceramic plate 20 to the upper surface of the cooling plate 30. The bonding layer 40 may be, for example, a metal layer formed from solder or a metal brazing material, or a resin layer formed from a resin adhesive.

[0026] The refrigerant flow path 32 will be described in detail. As shown in Fig. 2, the refrigerant flow path 32 has a first portion 32x corresponding to the outer circumferential region 22a (region requiring high cooling) of the wafer mounting surface 22 and a second portion 32y corresponding to the central region 22b (region requiring low cooling). The first portion 32x corresponding to the outer circumferential region 22a of the refrigerant flow path 32 is a portion from an inlet 32in to an intermediate position 32mid of the refrigerant flow path 32. The second portion 32y corresponding to the central region 22b of the refrigerant flow path 32 is a portion from an intermediate position 32mid to an outlet 32out of the refrigerant flow path 32. The second portion 32y branches into two branches, 32y1 and 32y2, at a branch point 32div located at the intermediate position 32mid, join at a joining point 32join, and reach the outlet 32out. Although the branch point 32div is located at the midpoint 32mid in FIGS. 2 and 3, the branch point 32div may be located at a position away from the midpoint 32mid.

[0027] The refrigerant flow path 32 has a turn-back portion 32turn that reverses the direction of the flow path, and branches into two branches, 32y1 and 32y2, at a branch point 32div located midway through the turn-back portion 32turn. The turn-back portion 32turn reverses the counterclockwise direction from the inlet 32in to the turn-back portion 32turn to a clockwise direction from the turn-back portion 32turn to the outlet 32out. The refrigerant flow path 32 is formed to branch into two branches, 32y1 and 32y2, at the branch point 32div located midway through the turn-back portion 32turn, thereby preventing the amount of refrigerant distributed to each branch 32y1, 32y2 from being biased toward one of the branches (this point will be described later using FIG. 5).

[0028] Regarding the flow path cross-sectional area S of the refrigerant flow path 32, as shown in FIG. 4, the flow path cross-sectional area Sx of the first portion 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 portion 32y corresponding to the central region 22b, that is, Sx < Sy1 + Sy2. The smaller the flow path cross-sectional area S, the higher the flow velocity of the refrigerant flowing through the refrigerant flow path 32 and the higher the cooling efficiency. 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 by a plane perpendicular to the longitudinal direction of the refrigerant flow path 32 (in the second portion 32y, each branch 32y1 and 32y2). The flow path cross-sectional areas Sy1 and Sy2 of each branch 32y1 and 32y2 of the second portion 32y may be set as appropriate. In this embodiment, they are the same as the flow path cross-sectional area Sx of the first portion 32x, that is, Sy1 = Sy2 = Sx. The flow path cross-sectional area S of the refrigerant flow path 32 is a value obtained by multiplying the horizontal length W by the vertical length H. The horizontal length W and the vertical length H may be set as appropriate according to the flow path cross-sectional area S. In this embodiment, the horizontal lengths Wy1 and Wy2 of each branch 32y1 and 32y2 of the second portion 32y are the same as the horizontal length Wx of the first portion 32x, that is, Wy1 = Wy2 = Wx. Also, the vertical lengths Hy1 and Hy2 of each branch 32y1 and 32y2 of the second portion 32y are the same as the vertical length Hx of the first portion 32x, that is, Hy1 = Hy2 = Hx.

[0029] Next, an example of how the wafer mounting table 10 is used will be described. The wafer mounting table 10 is fixed inside a semiconductor process chamber (not shown). A focus ring 60 is placed on the FR mounting surface 24, and a wafer W is placed on the wafer mounting surface 22. In this state, a DC voltage is applied to the electrostatic electrode 23 to attract the wafer W to the wafer mounting surface 22. At the same time, a thermally conductive gas (e.g., He gas) is supplied to a gas hole 50 (a passage leading from the underside of the cooling plate 30 to the wafer mounting surface 22) provided inside the wafer mounting table 10. This fills the space surrounded by the underside of the wafer W and the seal band of the wafer mounting surface 22 with gas, improving thermal conduction between the wafer W and the wafer mounting surface 22. The interior of the chamber is then set to a predetermined vacuum atmosphere (or reduced-pressure atmosphere), and an RF voltage is applied to the cooling plate 30 while a process gas is supplied from a showerhead provided on the ceiling of the chamber. This generates plasma between the wafer W and the showerhead. The plasma is then used to perform CVD film formation or etching on the wafer W.

[0030] When processing the wafer W with plasma in this manner, the heat input from the plasma is greater in the outer peripheral region of the wafer W than in the central region, and therefore the outer peripheral region of the wafer W is more likely to reach a higher temperature than the central region. Therefore, to make the temperature of the wafer W uniform, it is necessary to cool the outer peripheral region 22a of the wafer mounting surface 22 more efficiently than the central region 22b. Taking this into consideration, in this embodiment, the refrigerant flow path 32 flow path The cross-sectional area S is adjusted as described above. As a result, the first portion 32x of the coolant flow path 32 corresponding to the outer circumferential region 22a has a higher cooling efficiency than the second portion 32y corresponding to the central region 22b.

[0031] In the wafer mounting stage 10 described above, the refrigerant flow path 32 has a first portion 32x corresponding to a region with a high cooling requirement and a second portion 32y corresponding to a region with a low cooling requirement. Further, the second portion 32y branches into two branches 32y1 and 32y2 at a branch point 32div from the first portion 32x, and the branches run parallel to each other. Therefore, for example, even when the width through which the refrigerant flow path 32 can pass is narrow, such as when the distance between the gas hole 50 and the terminal hole 56 is short, each branch 32y1, 32y2 of the second portion 32y can be made to fit within that width, while ensuring a relatively large flow path cross-sectional area for the entire second portion 32y. Also, the flow path cross-sectional area Sx of the first portion 32x of the refrigerant flow path 32 corresponding to the region with a high cooling requirement is smaller than the sum Sy1 + Sy2 of the flow path cross-sectional areas of each of the branches 32y1, 32y2 of the second portion 32y corresponding to the region with a low cooling requirement. Therefore, the first portion 32x of the refrigerant flow path 32 corresponding to the region with a high cooling requirement has a higher flow velocity and higher cooling efficiency than the second portion 32y corresponding to the region with a low cooling requirement. Thus, the flow velocity can be controlled by making the first portion 32x corresponding to the region with a high cooling requirement a single flow path and the second portion 32y corresponding to the region with a low cooling requirement two or more flow paths, and further by changing the flow path cross-sectional area between the first portion 32x and the second portion 32y. Therefore, in the wafer mounting stage 10, by adjusting the arrangement of the first portion 32x and the second portion 32y, such as arranging the first portion 32x to correspond to the region with a high cooling requirement, the temperature unevenness of the wafer mounting surface 22 can be suppressed, and thus the heat uniformity of the wafer W is improved. Note that the flow path cross-sectional area S of the refrigerant flow path 32 may satisfy 1.5Sx < Sy1 + Sy2 < 2.5Sx, or may satisfy 1.8Sx < Sy1 + Sy2 < 2.2Sx.

[0032] Furthermore, the plasma heat input to the wafer mounting table 10 is generally greater in the outer circumferential region 22a of the wafer mounting surface 22 than in the central region 22b. Taking this into consideration, the first portion 32x is disposed at a position corresponding to the outer circumferential region 22a of the wafer mounting surface 22, and the second portion 32y is disposed at a position corresponding to the central region 22b of the wafer mounting surface 22. This makes it possible to increase the cooling efficiency of the outer circumferential region 22a of the wafer mounting surface 22 compared to the central region 22b, thereby effectively suppressing temperature variations in the wafer mounting surface 22.

[0033] Furthermore, ceramic plate 20 has an annular focus ring mounting surface 24 around wafer mounting surface 22, which is one step lower than wafer mounting surface 22. An annular focus ring 60 having an outer diameter larger than the outer diameters of ceramic plate 20 and cooling plate 30 is mounted on focus ring mounting surface 24. In this case, because focus ring 60 overhangs (extends outside) wafer mounting table 10, the temperature in outer peripheral region 22a of wafer mounting surface 22 is likely to become higher. For this reason, the application of the present invention is highly significant.

[0034] Furthermore, the flow path cross-sectional areas Sy1 and Sy2 of the branches 32y1 and 32y2 of the second portion 32y are both greater than half the flow path cross-sectional area Sx of the first portion 32x. The larger the flow path cross-sectional areas Sy1 and Sy2 of the branches 32y1 and 32y2 of the second portion 32y, the slower the flow velocity of the branches 32y1 and 32y2, thereby further suppressing uneven heat removal. The flow path cross-sectional areas Sy1 and Sy2 of the branches 32y1 and 32y2 may be greater than or equal to two-thirds or three-quarters of the flow path cross-sectional area Sx of the first portion 32x. The flow path cross-sectional areas Sy1 and Sy2 of the branches 32y1 and 32y2 may be less than two times or less than 1.5 times the flow path cross-sectional area Sx of the first portion 32x.

[0035] The refrigerant flow path 32 has a turn-back portion 32turn that reverses the flow path direction, and branches into two branches 32y1 and 32y2 at a branch point 32div midway through the turn-back portion 32turn, thereby suppressing bias in the amount of refrigerant distributed to the branches 32y1 and 32y2 of the second portion 32y. This suppresses bias in the heat removal capacity of the branches 32y1 and 32y2, and further suppresses uneven heat removal.

[0036] Regarding this point, the results of an investigation into the refrigerant flow within the refrigerant flow path are explained using Figure 5. When the refrigerant flow path has a curved shape, such as a spiral, centrifugal force tends to increase the flow velocity toward the outer periphery (outside the curve), as shown in Figure 5A (part (1)). Therefore, simply branching the flow path at a branch point near the center of the flow path may result in a bias of the refrigerant volume distributed to the outer branch. On the other hand, if a turning section with a smaller curvature (e.g., a curvature radius R of 20 mm or less) than the previous curve (e.g., a curvature radius R of 50 mm or more) is added midway through the curve, the centrifugal force is temporarily canceled in the turning section. As a result, the flow velocity becomes the highest near the center of the flow path, as shown in Figure 5A (part (2)). This reduces the difference in flow velocity between the outer periphery (outside the curve) and the inner periphery (inside the curve). Therefore, for example, if the refrigerant is branched into two at a branch point midway through the turning section, as shown in Figure 5B, the refrigerant volume distributed to each branch is prevented from being biased toward one of the branches. When the branch point is provided in the middle of the turning portion, it is preferable to place the branch point near the center of the part where the flow velocity is higher near the center than on either side of the flow path.

[0037] Furthermore, when the wafer mounting table 10 is viewed from above, in the region where the second portion 32y is arranged (for example, the central region 22b where cooling is less required), the non-flow path area, which is the area of the portion where the refrigerant flow path 32 is not formed, may be 50% or more. The larger the non-flow path area, the greater the degree of freedom in arranging components other than the refrigerant flow path (gas holes 50, terminal holes 56, lift pin holes described below, etc.). In this regard, there are two cases where the second portion 32y of the refrigerant flow path 32 is not branched and the flow path cross-sectional area Sy is set to twice that of the first portion 32x, and where the second portion 32y is branched into branches 32y1 and 32y2 and the flow path cross-sectional areas Sy1 and Sy2 of the branches are set to twice that of the first portion 32x. S When compared with the case where y2 is the same as the first portion 32x (the total cross-sectional area is twice that of the first portion 32x), the non-flow-path area when the wafer temperature unevenness is within a predetermined range (for example, within 10°C) was 41.3% in the former case and 54.6% in the latter case, and the non-flow-path area was able to be increased to 50% or more. In the comparison, the cooling plate materials used were a first material (for example, Ti) with a thermal conductivity of 20 W / mK, a second material (for example, Al) with a thermal conductivity of 100 W / mK, and a third material (for example, Al) with a thermal conductivity of 200 W / mK. For the first portion 32x, the flow-path cross-sectional area Sx = 84 mm 2 When the second portion 32y is not branched, the cross-sectional area of the flow path is Sy=168 mm. 2 When the second portion 32y is branched, the cross-sectional area of the branch 32y1 of the second portion 32y is set to Sy1=84 mm. 2 The length Wy1 was 7 mm, and the length Hy1 was 12 mm. The branch 32y2 of the second portion 32y had a flow path cross-sectional area Sy2 of 84 mm. 2 , length Wy2 = 7 mm, and length Hy2 = 12 mm. The non-flow path area may be, for example, 70% or less. The region where the second portion 32y is arranged (here, the central region 22b) may be the smallest circumscribed circle that includes all of the branches 32y1 and 32y2.

[0038] Furthermore, with respect to the flow path length L of the refrigerant flow path 32, it is preferable that the ratio Ly1 / Ly2 of the lengths Ly1 and Ly2 (not shown) of the branches 32y1 and 32y2 be 4 / 5 or more and 5 / 4 or less. This reduces the difference in pressure loss between the branches 32y1 and 32y2. Note that, when the ratio Ly1 / Ly2 is large, the difference in pressure loss between the branches 32y1 and 32y2 may be reduced by adjusting the cross-sectional shape of the branches 32y1 and 32y2. The lengths Ly1 and Ly2 of the branches 32y1 and 32y2 may be half or more of the length Lx of the first portion 32x, or may be greater than or equal to the length Lx of the first portion 32x. Furthermore, the lengths Ly1 and Ly2 of the branches 32y1 and 32y2 may be 10 times or less, or 5 times or less, the length Lx of the first portion 32x. The length Lx of the first portion 32x and the lengths Ly1 and Ly2 of the branches 32y1 and 32y2 may each be 20 mm or more. Regarding the cross-sectional area S of the refrigerant flow path 32, the ratio Sy1 / Sy2 of the cross-sectional areas Sy1 and Sy2 of the branches 32y1 and 32y2 is preferably 4 / 5 or more and 5 / 4 or less. This reduces the difference in pressure loss between the branches 32y1 and 32y2.

[0039] [Second embodiment] A second embodiment of the present invention will be described with reference to the drawings. Fig. 6 is a cross-sectional view of the wafer mounting table 110 (a cross-sectional view of the wafer mounting table 110 cut along a plane including the central axis of the wafer mounting table 110), Fig. 7 is a plan view of the wafer mounting table 110, Fig. 8 is a cross-sectional view B-B of Fig. 6, and Fig. 9 is a partially enlarged view of Fig. 6. In Figs. 6 to 9, the same components as those in the above-described embodiment are designated by the same reference numerals, and their description will be omitted.

[0040] 8, the refrigerant flow path 132 is provided so as to cover the entire surface of the ceramic plate 20 from one end (inlet 132in) to the other end (outlet 132out) in a plan view. The refrigerant flow path 132 is formed in a spiral shape. The refrigerant, the refrigerant circulation device, etc. may be the same as those in the above-described embodiment.

[0041] As shown in FIG. 7, in the refrigerant flow path 132, there are a first portion 132x corresponding to the outer peripheral region 22a (region with high cooling requirement) of the wafer mounting surface 22 and a second portion 132y corresponding to the central region 22b (region with low cooling requirement). The first portion 132x of the refrigerant flow path 132 corresponding to the outer peripheral region 22a is the portion from the inlet 132in to the intermediate position 132mid of the refrigerant flow path 132. The second portion 132y of the refrigerant flow path 132 corresponding to the central region 22b is the portion from the intermediate position 132mid to the outlet 132out of the refrigerant flow path 132. The second portion 132y branches into two branches, branch 132y1 and branch 132y2, at the branch point 132div, and merges at the merge point 132join and leads to the outlet 132out.

[0042] The refrigerant flow path 132 is formed at the branch point 132div to branch into a branch 132y1 that continues the tendency of bending before branching and a branch 132y2 that deviates outward from this bending tendency, thereby suppressing the deviation of the amount of refrigerant distributed to each of the branches 132y1 and 132y2 to one branch.

[0043] Regarding the flow path cross-sectional area S of the refrigerant flow path 132, the flow path cross-sectional area Sx of the first portion 132x corresponding to the outer peripheral region 22a is smaller than the sum of the flow path cross-sectional areas Sy1 and Sy2 of each of the branches 132y1 and 132y2 of the second portion 132y corresponding to the central region 22b, that is, Sx < Sy1 + Sy2. Therefore, the first portion 132x of the refrigerant flow path 132 corresponding to the region with high cooling requirement has a higher flow velocity and higher cooling efficiency than the second portion 132y corresponding to the region with low cooling requirement. Regarding the flow path cross-sectional area S, the horizontal length W, and the vertical length H of the refrigerant flow path 132, they conform to the flow path cross-sectional area S, the horizontal length W, and the vertical length H of the refrigerant flow path 32.

[0044] Examples of the use of the wafer mounting table 110 conform to the manufacturing and use examples of the wafer mounting table 10, so the description thereof is omitted here.

[0045] In the wafer mounting table 110 described above, similarly to the wafer mounting table 10 described above, the first portion 132x corresponding to the area with high cooling demand is branched into one branch, and the second portion 132y corresponding to the area with low cooling demand is branched into two or more branches to control the flow rate. Furthermore, by controlling the flow rate by changing the flow path cross-sectional area between the first portion 132x and the second portion 132y, it is possible to suppress temperature unevenness on the wafer mounting surface 22 in the wafer mounting table 110, thereby improving the thermal uniformity of the wafer W.

[0046] Furthermore, the refrigerant flow path 132 is formed to branch into a branch 132y1 that continues the curved shape before the branch at a branch point 132div, and a branch 132y2 that deviates from the curved shape. This prevents the amount of refrigerant distributed to each branch 132y1, 132y2 from being biased toward one branch. This prevents bias in the heat removal capabilities of each branch 132y1, 132y2, and further reduces uneven heat removal. The branch 132y2 may branch at an angle of 30° to 90° relative to the branch 132y1.

[0047] Regarding this point, as explained using FIG. 5, the flow velocity tends to be higher toward the outer periphery of the flow path (outside the curve). Therefore, simply branching the flow path by providing a branch point near the center of the flow path may result in a bias in the amount of refrigerant distributed to the branch on the outer periphery. Therefore, when providing a branch point at a portion such as (1) in FIG. 5A, for example, as shown in FIG. 5C, the branch point may be provided closer to the outer periphery of the flow path before branching, thereby branching into a branch that continues the curved flow before branching and a branch that temporarily deviates from this curved flow to the outside. As a result, the branch on the inner periphery (inside the curve) becomes the main flow path, thereby reducing the amount of refrigerant distributed to the branch on the outer periphery (outside the curve), and preventing the amount of refrigerant distributed to each branch from being biased toward one branch.

[0048] Furthermore, in a plan view, in the region where the second portion 132y is arranged (for example, the central region 22b where cooling requirements are low), the non-flow path area, which is the area of the portion where the refrigerant flow path 132 is not formed, may be 50% or more. The larger the non-flow path area, the greater the degree of freedom in arranging components other than the refrigerant flow path (gas holes 50, terminal holes 56, lift pin holes described below, etc.). The non-flow path area may be, for example, 70% or less.

[0049] Furthermore, the length L and cross-sectional area S of the refrigerant flow path 132 may be made to correspond to the length L and cross-sectional area S of the refrigerant flow path 32, thereby reducing the difference in pressure loss between the branch 132y1 and the branch 132y2.

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

[0051] For example, in the first and second embodiments described above, the refrigerant flow paths 32, 132 are branched into two paths, but may be branched into three or more paths. The arrangement of the branch points 32div, 132div of the refrigerant flow paths 32, 132 is not limited to that described above, and may be set appropriately so that the amount of refrigerant distributed to each branch 32y1, 32y2 and each branch 132y1, 132y2 is a desired amount.

[0052] In the first and second embodiments described above, the refrigerant flow paths 32, 132 are assumed to merge at the junctions 32join, 132join, but they may not merge and instead lead to outlets provided individually in each branch 32y1, 32y2 or each branch 132y1, 132y2.

[0053] In the first and second embodiments described above, the area requiring high cooling is the peripheral area 22a of the wafer mounting surface 22, and the area requiring low cooling is the central area 22b of the wafer mounting surface 22, but this is not particularly limited.

[0054] In the first and second embodiments described above, the heat exchange efficiency of the peripheral region 22a of the wafer mounting surface 22 corresponding to the first portions 32x and 132x may be higher than the heat exchange efficiency of the central region 22b corresponding to the second portions 32y and 132y. Taking the wafer mounting table 10 as an example, the heat exchange efficiency can be determined as follows. First, a first chiller capable of circulating a refrigerant while controlling the temperature of the refrigerant is connected to the inlet 32in and the outlet 32out of the refrigerant flow path 32, and a refrigerant at the same temperature as room temperature (e.g., 25°C) is circulated through the refrigerant flow path 32. At the same time, a refrigerant at a predetermined temperature (e.g., 80 to 100°C) is prepared in a second chiller. Then, a valve is used to switch from the refrigerant at the same temperature as room temperature to a refrigerant at the predetermined temperature, and the refrigerant at the predetermined temperature is circulated through the refrigerant flow path 32. After a predetermined time (e.g., 10 seconds) has elapsed since the refrigerant was switched, the temperature distribution of the wafer mounting surface 22 is measured. The temperature rise rate (temperature rise amount per unit time (°C / sec)) is calculated from the temperature distribution, and the temperature rise rate is used as an index of heat exchange efficiency. For example, when the refrigerant at 25°C is switched to a refrigerant at 80°C in the wafer mounting table 10, the temperature rise rate of the outer peripheral region 22a of the wafer mounting surface 22 is 5.5°C / sec or more, and the temperature rise rate of the central region 22b is 5°C / sec or less. 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. The temperature rise rate at the boundary between the outer peripheral region 22a and the central region 22b is an intermediate value.

[0055] In the first and second embodiments described above, the electrostatic electrode 23 is built into the ceramic plate 20 at a position facing the wafer mounting surface 22. In addition, an FR adsorption electrode for electrostatically adsorbing the focus ring 60 may be provided inside the ceramic plate 20 at a position facing the FR mounting surface 24.

[0056] In the first and second embodiments described above, the ceramic plate 20 has been exemplified as having the wafer mounting surface 22 and the FR mounting surface 24, but is not particularly limited to this. For example, the ceramic plate 20 may have the wafer mounting surface 22 but not the FR mounting surface 24.

[0057] In the first and second embodiments described above, the focus ring 60 has an outer diameter larger than the outer diameter of the wafer mounting table 10 (the outer diameter of the ceramic plate 20 and the outer diameter of the cooling plate 30), but is not limited thereto. For example, the outer diameter of the focus ring 60 may be the same as the outer diameter of the wafer mounting table 10.

[0058] In the first and second embodiments described above, the refrigerant flow paths 32, 132 are formed in a spiral shape in plan view, but are not limited to this. For example, the refrigerant flow paths 32, 132 may be formed in a zigzag shape in plan view.

[0059] In the first and second embodiments described above, the wafer stage 10 has the electrostatic electrode 23 built into the ceramic plate 20. ,110 However, the present invention is not limited to this. For example, instead of or in addition to the electrostatic electrode 23, the ceramic plate 20 may have a built-in heater electrode (resistance heating element) or a built-in electrode for generating plasma (RF electrode).

[0060] In the first and second embodiments described above, the wafer mounting table 10, 110 may have a plurality of lift pin holes that penetrate vertically through the wafer mounting table 10, 110. The lift pin holes are holes for inserting lift pins that move the wafer W up and down relative to the wafer mounting surface 22. For example, when the wafer mounting surface 22 is viewed from above, a plurality of lift pin holes are provided at equal intervals along concentric circles of the wafer mounting surface 22. [Industrial Applicability]

[0061] The present invention can be used, for example, in an apparatus for plasma processing a wafer. [Explanation of symbols]

[0062] 10,110 wafer mounting table, 20 ceramic plate, 22 wafer mounting surface, 22a peripheral region, 22b central region, 23 electrostatic electrode, 24 focus ring mounting surface, 26 power supply terminal, 30 cooling plate, 32,132 coolant flow path, 32in, 132in inlet, 32mid, 132mid midway position, 32out, 132out outlet, 32x, 132x first portion, 32y, 132y second portion, 32div, 132div branch point, 32join, 132join junction point, 32turn turning portion, 40 bonding layer, 50 gas hole, 56 terminal hole, 60 focus ring, 62 circumferential groove, W wafer.

Claims

1. a ceramic plate having a wafer mounting surface on its upper surface; a cooling plate provided on the lower surface of the ceramic plate; a refrigerant flow path built into the cooling plate; A wafer mounting table comprising: the refrigerant flow path has a first portion and a second portion that branches into two or more branches from the first portion and runs parallel to each other, a cross-sectional area of the first portion is smaller than the sum of the cross-sectional areas of the branches of the second portion; The refrigerant flow path has a curved turning portion that reverses the direction of the flow path, and branches into two at the midpoint of the curve of the turning portion to suppress unevenness in the amount of refrigerant distributed to each branch of the second portion. Wafer stage.

2. a ceramic plate having a wafer mounting surface on its upper surface; a cooling plate provided on the lower surface of the ceramic plate; a refrigerant flow path built into the cooling plate; A wafer mounting table comprising: the refrigerant flow path has a first portion and a second portion that branches into two or more branches from the first portion and runs parallel to each other, a cross-sectional area of the first portion is smaller than the sum of the cross-sectional areas of the branches of the second portion; The refrigerant flow path is curved before branching, and branches into a branch that continues the tendency of the curve before branching and a branch that temporarily deviates from the tendency of the curve to an outside of the curve, thereby suppressing unevenness in the amount of refrigerant distributed to each branch in the second portion. Wafer stage.

3. the first portion is disposed in correspondence with an outer peripheral region of the wafer mounting surface, and the second portion is disposed in correspondence with a central region of the wafer mounting surface; The wafer stage according to claim 1 or 2.

4. the ceramic plate has an annular focus ring mounting surface around the wafer mounting surface, the focus ring mounting surface being one step lower than the wafer mounting surface, and an annular focus ring having an outer diameter larger than the outer diameter of the ceramic plate and the outer diameter of the cooling plate is mounted on the focus ring mounting surface. The wafer stage according to claim 3 .

5. a cross-sectional area of each branch of the second portion is greater than half the cross-sectional area of the first portion; The wafer stage according to claim 1 or 2.

6. In a plan view, in the region where the second portion is arranged, a non-flow path area, which is an area of a portion where the refrigerant flow path is not formed, is 50% or more. The wafer stage according to claim 1 or 2.

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