Wafer mounting table

Abstract

A wafer mounting table 10 comprises: a ceramic plate 20 that has a wafer mounting surface 21 on the upper surface thereof and in which an electrostatic electrode 22 is installed; a cooling plate 30 that is provided on the lower surface of the ceramic plate 20; and a refrigerant flow passage 32 that is provided inside the cooling plate 30. The cooling plate 30 has a plurality of upper and lower cooling plate layers 31U and 31L arranged in the vertical direction. The upper cooling plate layer 31U and the cooling plate layer 31L having a vertical relationship therebetween are bonded by a partition plate 34. Sections of the refrigerant flow passage 32 excluding an inlet 32a and an outlet 32b are divided into two levels in the vertical direction by the partition plate 34.

Description

Wafer mounting table

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

[0002] Semiconductor manufacturing equipment employs wafer mounting tables such as ceramic heaters for heating wafers and electrostatic chucks for attracting and holding wafers. Patent Document 1 (JP-A-2005-102626) discloses a wafer mounting table of this type that includes a ceramic plate having an upper wafer mounting surface and built-in electrodes, and a cooling plate provided on the lower surface of the ceramic plate. A coolant flow path is provided inside the cooling plate. Patent Document 1 (JP-A-2005-102626) shows, as an example, a configuration in which fins are provided on the inner surface of the coolant flow path to enhance cooling capacity.

[0003] JP 2023-58845 A (FIG. 7)

[0004] However, providing fins on the inner surface of the coolant flow path is not an easy task.

[0005] The present invention has been made to solve such problems, and a main object of the present invention is to increase the cooling capacity with a simple structure.

[0006] [1] The wafer mounting table of the present invention is a wafer mounting table comprising: a ceramic plate having a wafer mounting surface on its upper surface and incorporating an electrode; a cooling plate provided on the lower surface of the ceramic plate; and a refrigerant flow path provided inside the cooling plate, wherein the cooling plate has multiple cooling plate layers arranged in a vertical direction, and the two cooling plate layers in a vertical relationship are joined by a partition plate, and a section of the refrigerant flow path excluding an inlet and an outlet is divided into multiple stages in a vertical direction by the partition plate.

[0007] In this wafer mounting table, the coolant flow path, excluding the inlet and outlet, is divided into multiple sections in the vertical direction by partition plates. This increases the area where the coolant comes into contact with the inner surface of the coolant flow path compared to a system without partition plates. This allows for increased cooling capacity with a simple structure.

[0008] In this specification, "upper" and "lower" do not represent absolute positional relationships, but rather relative positional relationships. Therefore, depending on the orientation of the semiconductor manufacturing equipment component, "upper" and "lower" may become "lower" and "upper," "left" and "right," or "front" and "rear."

[0009] [2] In the wafer stage of the present invention (the wafer stage described in [1] above), the thermal conductivity of the partition plate may be higher than the thermal conductivity of the cooling plate layer. This increases the cooling capacity of the refrigerant.

[0010] [3] In the wafer stage of the present invention (the wafer stage described in [1] or [2] above), the cooling plate layer may be formed of a difficult-to-process material. The wafer stage of the present invention employs a simple structure in which the coolant flow path is divided into multiple stages by partition plates, eliminating the need for detailed processing such as forming fins on the inner surface of the coolant flow path. Therefore, even if the cooling plate layer is formed of a difficult-to-process material, it can be manufactured relatively easily.

[0011] [4] In the wafer mounting table of the present invention (the wafer mounting table described in [3] above), the difficult-to-process material may be a composite material of metal and ceramic, a ceramic material, a W-containing material, or an Mo-containing material.

[0012] [5] In the wafer stage of the present invention (the wafer stage according to any one of [1] to [4] above), the partition plate may be formed of a metal material. This makes it easier to make the thermal conductivity of the partition plate higher than that of the cooling plate layer.

[0013] [6] In the wafer stage of the present invention (the wafer stage according to any one of [1] to [5] above), the partition plate may have fins on the upper and / or lower surfaces thereof that protrude into the coolant flow path. In this case, the coolant comes into contact with the fins, thereby further increasing the cooling capacity of the coolant.

[0014] 1. A plan view of the wafer mounting table 10. A cross-sectional view taken along the line AA in FIG. 1. A manufacturing process diagram of the cooling plate 30. A vertical cross-sectional view of the wafer mounting table 110. A vertical cross-sectional view of the wafer mounting table 210.

[0015] Fig. 1 is a plan view of the wafer stage 10 of this embodiment, and Fig. 2 is a cross-sectional view taken along line AA in Fig. 1. For convenience, the seal band 21a and the small circular protrusions 21b are omitted from Fig. 2.

[0016] The wafer mounting table 10 is an example of a semiconductor manufacturing apparatus component used to process a wafer W. The wafer mounting table 10 includes a ceramic plate 20, a cooling plate 30, and a bonding layer 40.

[0017] The ceramic plate 20 is a stepped circular plate member having a wafer mounting surface 21 on its upper surface. For example, the diameter of the upper portion of the ceramic plate 20 is 300 mm, the diameter of the lower portion is 340 mm, and the diameter of the wafer W is approximately 300 mm. The ceramic plate 20 is formed of a ceramic-containing material. The ceramic-containing material is a material whose main component is ceramic and may contain, in addition to ceramic, components derived from sintering aids (e.g., rare earth elements) and unavoidable components. The term "main component" refers to a material whose proportion of the total is 50 mass% or more. Examples of ceramic include alumina and aluminum nitride. As shown in FIG. 1 , a seal band 21a is formed along the outer edge of the wafer mounting surface 21, and multiple circular small protrusions 21b are formed on the entire inner surface of the seal band 21a. The seal band 21a and the circular small protrusions 21b have the same height, e.g., several microns to several tens of microns.

[0018] An electrostatic electrode (attraction electrode) 22 is embedded in the upper part of the ceramic plate 20. The electrostatic electrode 22 is formed of a material containing a metal such as W, Mo, WC, or MoC. The metal used for the electrostatic electrode 22 preferably has a thermal expansion coefficient close to that of the ceramic plate 20. To make the thermal expansion coefficient of the electrostatic electrode 22 closer to that of the ceramic plate 20, the electrostatic electrode 22 may contain ceramic contained in the ceramic plate 20. The electrostatic electrode 22 is a disk-shaped or mesh-shaped monopolar electrostatic electrode. The layer of the ceramic plate 20 above the electrostatic electrode 22 functions as a dielectric layer. Although not shown, a DC power supply for electrostatic attraction is connected to the electrostatic electrode 22 via a power supply member.

[0019] The cooling plate 30 is a circular plate member having a refrigerant flow path 32 therein through which a refrigerant can circulate. The diameter of the cooling plate 30 is the same as or slightly larger than the diameter of the lower part of the ceramic plate 20. The refrigerant flow path 32 is provided so as to cover the entire surface of the ceramic plate 20 in a plan view. In this embodiment, the refrigerant flow path 32 is formed in a spiral shape from an inlet 32a provided on the outer periphery of the cooling plate 30 to an outlet 32b provided on the center side of the cooling plate 30. The refrigerant flowing through the refrigerant flow path 32 is preferably a liquid, and is preferably electrically insulating. Examples of electrically insulating liquids include a fluorine-based inert liquid.

[0020] The cooling plate 30 includes an upper cooling plate layer 31U and a lower cooling plate layer 31L arranged vertically. The upper cooling plate layer 31U and the lower cooling plate layer 31L are joined by a partition plate 34. The partition plate 34 is preferably made of a metal bonding material, more preferably an Al bonding material. The thickness of the partition plate 34 is preferably 0.1 mm or more and 1 mm or less. When the partition plate 34 is made of a metal bonding material, the partition plate 34 bonds the upper cooling plate layer 31U and the lower cooling plate layer 31L by, for example, thermal compression bonding (TCB). TCB is a known method in which a metal bonding material is sandwiched between two components to be joined and the two components are pressure-bonded while heated to a temperature below the solidus temperature of the metal bonding material. The section of the refrigerant flow path 32 excluding the inlet 32 ​​a and the outlet 32 ​​b is vertically divided into two stages, i.e., an upper refrigerant flow path 32U and a lower refrigerant flow path 32L, by a partition plate 34. After being divided into the upper refrigerant flow path 32U and the lower refrigerant flow path 32L at the inlet 32 ​​a, the refrigerant flow paths 32 continue downstream while remaining divided and finally merge at the outlet 32 ​​b. A flow path groove that forms the upper refrigerant flow path 32U is provided in the lower surface of the upper cooling plate layer 31U, and a flow path groove that forms the lower refrigerant flow path 32L is provided in the upper surface of the lower cooling plate layer 31L.

[0021] The upper and lower cooling plate layers 31U, 31L are made of, for example, a conductive material. Examples of conductive materials include metals and composite materials. Examples of metals include W-containing materials (e.g., Cu-W alloys) and Mo-containing materials (e.g., metallic Mo). Examples of composite materials include metal matrix composites (MMCs) and ceramic matrix composites (CMCs). Specific examples of such composite materials include materials containing Si, SiC, and Ti, and materials in which porous SiC is impregnated with Al and / or Si. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which porous SiC is impregnated with Al is called AlSiC, and a material in which porous SiC is impregnated with Si is called SiSiC. The upper and lower cooling plate layers 31U, 31L may also be made of a difficult-to-machine material (e.g., a material less machineable than metallic Al). The above-mentioned W-containing materials, Mo-containing materials, MMCs, and CMCs are included in the category of difficult-to-process materials.

[0022] The thermal expansion coefficients of the ceramic plate 20 and the cooling plate upper layer 31U are preferably the same or similar, and the thermal expansion coefficients of the cooling plate upper layer 31U and the cooling plate lower layer 31L are preferably the same or similar. When the ceramic plate 20 is made of alumina, the cooling plate upper and lower layers 31U and 31L are preferably made of SiSiCTi, AlSiC, or Cu-W. This is because the thermal expansion coefficients of SiSiCTi, AlSiC, and CuW can be made the same or similar to that of alumina by adjusting their compositions. When the ceramic plate 20 is made of aluminum nitride, the cooling plate upper and lower layers 31U and 31L are preferably made of Mo, W, or AlSiC. This is because the thermal expansion coefficients of Mo and W are similar to that of aluminum nitride. Furthermore, the thermal expansion coefficient of AlSiC can be made the same or similar to that of aluminum nitride by adjusting its composition.

[0023] 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 a metal bonding layer or a resin bonding layer, but a metal bonding layer is preferable in consideration of cooling efficiency. The metal bonding layer may be formed by the above-mentioned TCB using a metal bonding material (e.g., an Al bonding material), or may be formed by using solder or a metal brazing material.

[0024] Next, an example of how the wafer mounting table 10 is used will be described. First, the wafer mounting table 10 is installed in a vacuum chamber (not shown), and a wafer W is placed on the wafer mounting surface 21 of the wafer mounting table 10. Then, a voltage is applied to the electrostatic electrode 22 from a DC power supply (not shown). This causes the wafer W to be attracted and fixed to the wafer mounting surface 21 (specifically, the upper surfaces of the seal band 21 a and the small circular protrusions 21 b). The vacuum chamber is then set to a vacuum or reduced-pressure atmosphere, and the wafer W is processed in the vacuum chamber. For example, when processing the wafer W with plasma, an upper electrode equipped with a showerhead is placed on the ceiling of the vacuum chamber, and a reactive gas is supplied from the showerhead into the space between the wafer W and the upper electrode while a high-frequency voltage is applied between the upper electrode and the cooling plate 30 to generate plasma. In this case, the cooling plate 30 also serves as a plasma generating electrode. After processing of the wafer W is completed, the voltage application to the electrostatic electrode 22 is released. This causes the wafer W to be released from its attraction and fixed to the wafer mounting surface 21. A coolant whose temperature has been adjusted is circulated through the coolant flow passage 32 of the cooling plate 30 at appropriate times.

[0025] Next, a description will be given of a manufacturing example of the wafer mounting table 10. Since manufacturing examples of the ceramic plate 20 are known, a manufacturing example of the cooling plate 30 will be described here. FIG. 3 is a manufacturing process diagram of the cooling plate 30.

[0026] First, the disk-shaped upper and lower cooling plate layers 31U and 31L are fabricated ( FIG. 3A ). Next, the upper and lower cooling plate layers 31U and 31L are processed ( FIG. 3B ). Specifically, a flow channel 32UC having the same shape as the upper refrigerant flow channel 32U in a plan view is formed on the underside of the upper cooling plate layer 31U, and a flow channel 32LC having the same shape as the lower refrigerant flow channel 32L in a plan view is formed on the upper surface of the lower cooling plate layer 31L. Furthermore, holes are provided at both ends of the flow channel 32LC, each penetrating to the underside of the lower cooling plate layer 31L, to form an inlet 32a and an outlet 32b of the refrigerant flow channel 32.

[0027] Next, a partition plate 34 made of a metal bonding material (e.g., an Al bonding material) is placed between the upper cooling plate layer 31U and the lower cooling plate layer 31L ( FIG. 3C ). Holes 34a and 34b are pre-formed in the partition plate 34 at positions facing the inlet 32a and outlet 32b, respectively. The partition plate 34 is then positioned so that the hole 34a faces the inlet 32a and the hole 34b faces the outlet 32b. These layers are then stacked and heated while compressing from above and below (TCB). This process bonds the upper cooling plate layer 31U and the lower cooling plate layer 31L together with the partition plate 34 made of a metal bonding material, forming the cooling plate 30 ( FIG. 3D ). The flow channel 32UC becomes the upper refrigerant flow channel 32U, and the flow channel 32LC becomes the lower refrigerant flow channel 32L, completing the refrigerant flow channel 32. During TCB, the partition plate 34 maintains its shape because it is processed below its solidus temperature.

[0028] When the cooling plate upper layer 31U and the cooling plate lower layer 31L are bonded by TCB using a metal bonding material, the ceramic plate 20 and the cooling plate upper layer 31U may be bonded by TCB using a metal bonding material at the same time.

[0029] In the wafer mounting table 10 of this embodiment described above, the section of the coolant flow path 32 excluding the inlet 32 ​​a and the outlet 32 ​​b is divided into multiple sections in the vertical direction by the partition plate 34. This increases the area where the coolant comes into contact with the inner surface of the coolant flow path 32 compared to a case without the partition plate 34. Therefore, the cooling capacity of the coolant can be increased with a simple structure.

[0030] Furthermore, it is preferable that the thermal conductivity of the partition plate 34 be higher than that of the upper and lower cooling plate layers 31U and 31L, thereby increasing the cooling capacity of the refrigerant.

[0031] Furthermore, the upper and lower cooling plate layers 31U, 31L may be made of a material that is difficult to process. The wafer mounting table 10 employs a simple structure in which the coolant flow path 32 is divided into multiple stages by the partition plates 34, and therefore does not require detailed processing such as forming fins on the inner surface of the coolant flow path 32. Therefore, even if the upper and lower cooling plate layers 31U, 31L are made of a material that is difficult to process, they can be manufactured relatively easily.

[0032] Furthermore, the partition plate 34 may be formed of a metal material. This makes it easier to make the thermal conductivity of the partition plate 34 higher than that of the upper and lower cooling plate layers 31U, 31L. For example, if Al, which has a thermal conductivity of 200 W / mK or more, is used for the partition plate 34, the upper and lower cooling plate layers 31U, 31L may be made of a metal ceramic composite material (MMC or CMC), which has a thermal conductivity of less than 100 W / mK.

[0033] 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.

[0034] In the wafer mounting table 10 of the above-described embodiment, the cooling plate 30 includes an upper cooling plate layer 31U and a lower cooling plate layer 31L arranged vertically, and the upper cooling plate layer 31U and the lower cooling plate layer 31L are joined together by a partition plate 34. However, this is not particularly limited. For example, the configuration of the wafer mounting table 110 shown in FIG. 4 may be adopted. In FIG. 4, the same components as those in the above-described embodiment are denoted by the same reference numerals. The cooling plate 130 of FIG. 4 includes an upper cooling plate layer 31U, a middle cooling plate layer 31M, and a lower cooling plate layer 31L arranged vertically. The upper cooling plate layer 31U and the middle cooling plate layer 31M are joined together by a partition plate 34, and the middle cooling plate layer 31M and the lower cooling plate layer 31L are joined together by a partition plate 35 (metallic joining material). The section of the refrigerant flow path 32 excluding the inlet 32 ​​a and the outlet 32 ​​b is vertically divided into three stages (upper refrigerant flow path 32U, middle refrigerant flow path 32M, and lower refrigerant flow path 32L) by two partition plates 34, 35. This configuration also provides the same effects as the above-described embodiment. In FIG. 4 , the area over which the refrigerant comes into contact with the inner surface of the refrigerant flow path 32 is further increased compared to the above-described embodiment, thereby further increasing the cooling capacity. The number of partition plates may be increased to three or more.

[0035] In the wafer mounting table 10 of the above-described embodiment, the upper and lower surfaces of the partition plate 34 are flat, but this is not particularly limited. For example, the configuration of the wafer mounting table 210 shown in FIG. 5 may be adopted. In FIG. 5, the same components as those in the above-described embodiment are denoted by the same reference numerals. In FIG. 5, the lower surface of the partition plate 234 is provided with fins 234a that protrude into the refrigerant flow path 32 (the lower refrigerant flow path 32L). The fins 234a are provided along the entire length of the lower refrigerant flow path 32L. The lower ends of the fins 234a reach the lower surface of the lower refrigerant flow path 32L. Therefore, the fins 234 form a vertical wall that divides the lower refrigerant flow path 32L into two flow paths. The wafer mounting table 234 allows the refrigerant to come into contact with the fins 234a, thereby enhancing the cooling capacity of the refrigerant. In FIG. 5 , the lower ends of the fins 234a reach the lower surface of the lower-stage refrigerant flow path 32L, but the lower ends of the fins 234a may be positioned higher than the lower surface of the lower-stage refrigerant flow path 32L. Although the fins 234a are provided along the entire length of the lower-stage refrigerant flow path 32L, they may be provided along a portion of the lower-stage refrigerant flow path 32L rather than along the entire length. Furthermore, although the fins 234a are provided on the lower surface of the partition plate 234, they may alternatively or additionally be provided on the upper surface of the partition plate 234. The upper ends of the fins provided on the upper surface of the partition plate 234 may reach the upper surface of the upper-stage refrigerant flow path 32U or may be positioned lower than the upper surface of the upper-stage refrigerant flow path 32U. The fins may be provided along the entire length of the upper-stage refrigerant flow path 32U or along a portion of the upper-stage refrigerant flow path 32U.

[0036] In the above-described embodiment, at least one of a heater electrode and a plasma generation electrode may be embedded in the ceramic plate 20 instead of or in addition to the electrostatic electrode 22 .

[0037] In the above-described embodiment, the upper and lower cooling plate layers 31U and 31L are formed of a conductive material. However, they may be formed of an insulating material such as a ceramic material. Ceramic materials (e.g., alumina and aluminum nitride) are difficult to process. In this case, the cooling plate 30 cannot be used as a plasma generating electrode. Therefore, a plasma generating electrode may be embedded in the ceramic plate 20, or the partition plate 34, which is a metal bonding material, may be used as the plasma generating electrode.

[0038] In the above-described embodiment, the inlets 32a of the coolant flow channels 32 are provided on the outer periphery of the cooling plate 30, and the outlets 32b of the coolant flow channels 32 are provided on the center side of the cooling plate 30, but this is not particularly limited. For example, the inlets of the coolant flow channels 32 may be provided on the center side of the cooling plate 30, and the outlets of the coolant flow channels 32 may be provided on the outer periphery of the cooling plate 30. Furthermore, although the coolant flow channels 32 are formed in a spiral shape in a plan view, they may be formed in any shape (e.g., a zigzag shape) as long as they can cover the entire surface of the wafer mounting surface 21 in a plan view.

[0039] In the above-described embodiment, the upper and lower cooling plate layers 31U and 31L may be made of an easily workable conductive material such as aluminum, an aluminum alloy, or stainless steel (SUS material).

[0040] In the above-described embodiment, holes may be provided through the wafer mounting table 10 so as to extend from the lower surface of the cooling plate 30 to the wafer mounting surface 21. Examples of such holes include gas supply holes for supplying a thermally conductive gas (e.g., He gas) to the backside of the wafer W, and lift pin holes for inserting lift pins that move the wafer W up and down relative to the wafer mounting surface 21. The thermally conductive gas is supplied to a space formed by the wafer W, a seal band 21 a provided on the wafer mounting surface 21, and numerous small circular protrusions 21 b.

[0041] The present invention can be used in a wafer mounting table.

[0042] 10 wafer mounting table, 20 ceramic plate, 21 wafer mounting surface, 21a seal band, 21b circular small protrusion, 22 electrostatic electrode, 30 cooling plate, 31L cooling plate lower layer, 31M cooling plate middle layer, 31U cooling plate upper layer, 32 refrigerant flow path, 32a inlet, 32b outlet, 32L lower refrigerant flow path, 32M middle refrigerant flow path, 32U upper refrigerant flow path, 32LC, 32UC flow path groove, 34, 35 partition plate, 34a, 34b hole, 40 bonding layer, 110 wafer mounting table, 130 cooling plate, 234 partition plate, 234a fin.

Claims

1. A wafer mounting table comprising: a ceramic plate having a wafer mounting surface on its upper surface and incorporating an electrode; a cooling plate provided on the underside of said ceramic plate; and a refrigerant flow path provided inside said cooling plate, wherein said cooling plate has multiple cooling plate layers arranged in a vertical direction, and the two cooling plate layers in a vertical relationship are joined by a partition plate, and the section of said refrigerant flow path excluding an inlet and an outlet is divided into multiple stages in a vertical direction by said partition plate.

2. The wafer stage according to claim 1, wherein the partition plate has a higher thermal conductivity than the cooling plate layer.

3. The wafer stage according to claim 1 or 2, wherein the cooling plate layer is made of a material that is difficult to process.

4. The wafer stage according to claim 3, wherein the difficult-to-process material is a composite material of metal and ceramic, a ceramic material, a W-containing material, or an Mo-containing material.

5. The wafer stage according to claim 1 or 2, wherein the partition plate is made of a metal material.

6. The wafer stage according to claim 1 or 2, wherein the partition plate has an upper surface and / or a lower surface provided with fins that protrude into the coolant flow path.

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