Wafer mounting table

Abstract

To further improve thermal uniformity of a wafer.SOLUTION: A wafer mounting table 10 is provided with a cooling plate 30 having a coolant flow path 32 on a lower surface side of a ceramic plate 20 incorporating an electrode 22. A gas intermediate passage 50, which is a horizontal space, is provided in parallel with a wafer mounting surface 21 at a position closer to the wafer mounting surface 21 than the coolant flow path 32 inside the wafer mounting table 10, and has an overlapping portion that overlaps the coolant flow path along the coolant flow path 32 in a plan view.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Conventionally, a wafer mounting table is known that includes a ceramic plate with a built-in electrode having a wafer mounting surface on the upper surface thereof, and a metal cooling plate bonded to the lower surface of the ceramic plate. Patent Document 1 describes a wafer mounting table in which a metal cooling plate is provided inside the ceramic plate parallel to the wafer mounting surface. be established The cooling plate is provided with a gas intermediate passage, a plurality of gas supply passages extending from the gas intermediate passage to the wafer mounting surface, and a gas introduction passage that passes vertically through the cooling plate and communicates with the gas intermediate passage. The number of gas introduction passages provided in the gas intermediate passage is less than the number of gas supply passages. This reduces the number of gas introduction passages that pass vertically between the refrigerant channels compared to the number of gas supply passages, thereby improving wafer temperature uniformity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2003-188247 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in Patent Document 1, there is a problem in that the portion of the wafer directly above the coolant flow path is more likely to become colder because the cooling effect of the coolant is greater there than in other portions.

[0005] The present invention has been made to solve such problems, and its main object is to further improve the temperature uniformity of the wafer. [Means for solving the problem]

[0006] [1] The wafer mounting table of the present invention comprises: A wafer mounting table including a ceramic plate having a wafer mounting surface on its upper surface and a built-in electrode, and a cooling plate having a coolant flow path provided on the lower surface side of the ceramic plate, a horizontal space provided parallel to the wafer mounting surface at a position inside the wafer mounting table closer to the wafer mounting surface than the coolant flow path, the horizontal space having an overlapping portion that overlaps with the coolant flow path along the coolant flow path in a plan view; It is equipped with the following.

[0007] This wafer mounting table is provided with a horizontal space. The horizontal space is located inside the wafer mounting table, closer to the wafer mounting surface than the refrigerant flow path, and is parallel to the wafer mounting surface. The horizontal space has an overlapping portion that overlaps with the refrigerant flow path along the refrigerant flow path in a plan view. Because the horizontal space is hollow, the portion where the horizontal space is formed is less susceptible to heat conduction than the portion where the horizontal space is not formed. The portion of the wafer directly above the refrigerant flow path is likely to become cold due to the refrigerant, but this decrease in temperature is suppressed by the overlapping portion of the horizontal space, which is less susceptible to heat conduction. As a result, the temperature uniformity of the wafer is improved.

[0008] The "horizontal space" may be provided anywhere inside the wafer mounting table as long as it is closer to the wafer mounting surface than the coolant flow path, for example, inside the ceramic plate, inside the cooling plate, or between the ceramic plate and the cooling plate. "Parallel" does not necessarily mean perfectly parallel, but also means that even if the parallelism is not perfect, it is considered to be parallel as long as it is within an allowable error range (for example, tolerance).

[0009] [2] In the wafer stage described in [1] above, the coolant flow path may be arranged so as to extend from one end to the other end in a single stroke based on a multiple circle formed by arranging multiple imaginary circles of different diameters so as not to overlap each other in a plan view, and the horizontal space may be arranged in a circular shape so as to overlap with any of the multiple imaginary circles in a plan view. This makes it easier to increase the overlapping portion of the horizontal space.

[0010] [3] In the above-described wafer mounting table (the wafer mounting table described in [2] above), the horizontal space may not overlap with the outermost imaginary circle among the plurality of imaginary circles. When processing a wafer with plasma, the outermost region of the wafer tends to reach a relatively high temperature. Therefore, it is preferable to actively dissipate heat from the outermost region of the wafer by not providing a horizontal space directly above the outermost region of the coolant flow path.

[0011] [4] In the wafer mounting table described above (the wafer mounting table described in any one of [1] to [3] above), the horizontal space may be an intermediate gas passage through which gas passes. This wafer mounting table may include a plurality of gas supply passages extending from the intermediate gas passage to the wafer mounting surface, and a smaller number of gas introduction passages than the number of gas supply passages communicating with the intermediate gas passages, which penetrate vertically between the refrigerant channels of the cooling plate and communicate with the intermediate gas passages. When gas is introduced through a gas introduction passage opening at the lower surface of the cooling plate, the gas passes through the intermediate gas passage, is distributed to the plurality of gas supply passages, and is supplied to the lower surface of the wafer. In this wafer mounting table, the number of gas introduction passages penetrating the cooling plate is smaller than the number of gas supply passages. Therefore, the temperature uniformity of the wafer is improved compared to when the number of gas introduction passages penetrating the cooling plate is the same as the number of gas supply passages.

[0012] [5] In the wafer stage described above (the wafer stage described in [4] above), the cooling plate may be a conductive plate or may have at least a conductive plate on its upper surface, and the conductive plate may be bonded to the lower surface of the ceramic plate via a conductive bonding layer, and the gas intermediate passage may be provided at the interface between the conductive bonding layer and the conductive plate. In this way, the conductive bonding layer forming the upper surface of the gas intermediate passage and the conductive plate forming the lower surface of the gas intermediate passage are in contact with each other and have the same potential. Therefore, no potential gradient is generated above and below the gas intermediate passage, and discharge within the gas intermediate passage can be prevented.

[0013] [6] In the wafer stage described above (the wafer stage described in [5] above), the gas supply passage may have an electrically insulating porous plug, and the lower end of the porous plug may be in contact with at least one of the conductive bonding layer and the conductive plate. In this way, the lower end of the porous plug has the same potential as the conductive bonding layer and the conductive plate. Therefore, no potential gradient occurs between the lower end of the porous plug and the conductive bonding layer or between the lower end of the porous plug and the conductive plate. Therefore, discharge around the lower end of the porous plug can be suppressed. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. [Figure 2] Cross section AA of Figure 1. [Figure 3] 10 is a cross-sectional view of the wafer stage 10 cut by a horizontal plane passing through the intermediate gas passage 50, as viewed from above. FIG. [Figure 4] 3 is a cross-sectional view of the wafer stage 10 cut by a horizontal plane passing through the coolant flow path 32, as viewed from above. FIG. [Figure 5] FIG. 2 is an explanatory diagram in which a coolant flow path 32 and the like are drawn on a plan view of the wafer mounting table 10. [Figure 6] 3A to 3C are diagrams showing the manufacturing process of the wafer mounting table 10. [Figure 7] FIG. 10 is a vertical cross-sectional view of an example in which an intermediate gas passage 50 is provided inside a ceramic plate 20. [Figure 8] 10 is an explanatory diagram of an example in which the intermediate gas passage 50 does not overlap the outermost periphery of the refrigerant flow passage 32. FIG. [Figure 9] FIG. 10 is a partially enlarged cross-sectional view showing another example of the bonding layer penetrating portion 52a. [Figure 10] FIG. 10 is a partially enlarged cross-sectional view showing another example of the bonding layer penetrating portion 52a. [Figure 11] FIG. 2 is a vertical cross-sectional view of the wafer mounting table 110. [Figure 12] FIG. 2 is a vertical cross-sectional view of the wafer mounting table 210. DETAILED DESCRIPTION OF THE INVENTION

[0015] Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the wafer mounting table 10, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, FIG. 3 is a cross-sectional view of the wafer mounting table 10 cut on a horizontal plane passing through the intermediate gas passage 50, as viewed from above, FIG. 4 is a cross-sectional view of the wafer mounting table 10 cut on a horizontal plane passing through the refrigerant flow path 32, as viewed from above, and FIG. 5 is an explanatory diagram of the plan view of the wafer mounting table 10 with the refrigerant flow path 32 and other components written in. Note that in this specification, "upper" and "lower" do not represent absolute positional relationships, but rather represent relative positional relationships. Therefore, depending on the orientation of the wafer mounting table 10, "upper" and "lower" may become "lower" and "upper," "left" and "right," or "front" and "rear."

[0016] As shown in FIG. 2, the wafer mounting table 10 includes a ceramic plate 20, a cooling plate 30, a conductive bonding layer 40, a gas intermediate passage 50, a gas supply passage 52, and a gas introduction passage .

[0017] The ceramic plate 20 is a circular plate (e.g., 300 mm in diameter and 5 mm in thickness) made of ceramic such as sintered alumina or sintered aluminum nitride. The upper surface of the ceramic plate 20 serves as a wafer mounting surface 21 on which a wafer W is mounted. The ceramic plate 20 incorporates an electrode 22. As shown in FIG. 1, an annular seal band 21a is formed along the outer edge of the wafer mounting surface 21 of the ceramic plate 20, and a plurality of small circular protrusions 21b are formed on the entire inner surface of the seal band 21a. The seal band 21a and the small circular protrusions 21b have the same height, e.g., several μm to several tens of μm. The electrode 22 is a planar mesh electrode used as an electrostatic electrode and is connected to an external DC power supply via a power supply member (not shown). A low-pass filter may be disposed along the power supply member. The power supply member is electrically insulated from the conductive bonding layer 40 and the cooling plate 30. When a DC voltage is applied to this electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the upper surfaces of the seal band and the small circular protrusions) by electrostatic attraction, and when the application of the DC voltage is stopped, the wafer W is released from being attracted and fixed to the wafer mounting surface 21. The portion of the wafer mounting surface 21 on which the seal band 21a and the small circular protrusions 21b are not provided is referred to as the reference surface 21c.

[0018] The cooling plate 30 is an electrically conductive disk (having the same diameter as or larger than the ceramic plate 20) with good thermal conductivity. A refrigerant flow path 32 through which a refrigerant circulates is formed inside 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 fluorine-based inert liquids. The refrigerant flow path 32 is formed in a single stroke from one end (inlet) to the other end (outlet) across the entire cooling plate 30 in a planar view. As shown in FIG. 4, the refrigerant flow path 32 is arranged in a single stroke from one end to the other end based on a multiple circle formed by arranging multiple imaginary circles (chain-dotted circles C1 to C4, here C1 to C4 are concentric circles) of different diameters so that they do not overlap each other in a planar view. Specifically, when the refrigerant flow path 32 is routed from one end to the other in a single stroke, the route is routed so as to trace the imaginary circles while connecting two imaginary circles that are the inside and outside of the multiple circles. One end and the other end of the refrigerant flow path 32 are connected to a supply port and a recovery port, respectively, of an external refrigerant device (not shown). The refrigerant supplied from the supply port of the external refrigerant device to one end of the refrigerant flow path 32 passes through the refrigerant flow path 32, returns from the other end of the refrigerant flow path 32 to the recovery port of the external refrigerant device, and is temperature-adjusted before being supplied again from the supply port to one end of the refrigerant flow path 32. The cooling plate 30 is connected to a radio frequency (RF) power source and is also used as an RF electrode.

[0019] Examples of materials for the cooling plate 30 include metal materials and composite materials of metal and ceramic. Metal materials include Al, Ti, Mo, and alloys thereof. Metal and ceramic composite materials 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. It is preferable to select a material for the cooling plate 30 that has a thermal expansion coefficient close to that of the material of the ceramic plate 20.

[0020] The conductive bonding layer 40 is, for example, a metal bonding layer, and bonds the lower surface of the ceramic plate 20 and the upper surface of the cooling plate 30. The conductive bonding layer 40 is formed, for example, by TCB (thermal compression bonding). TCB is a known method in which a metal bonding material is sandwiched between two members to be joined, and the two members are pressure-bonded while heated to a temperature below the solidus temperature of the metal bonding material.

[0021] The gas intermediate passage 50 is a horizontal space and is provided inside the wafer mounting table 10 at a position (here, at the interface between the conductive bonding layer 40 and the cooling plate 30) closer to the wafer mounting surface 21 than the coolant flow path 32, parallel to the wafer mounting surface 21. Note that "parallel" refers to not only perfect parallelism but also non-perfect parallelism within an allowable error range (e.g., tolerance). The gas intermediate passage 50 has a groove 31 provided on the upper surface of the cooling plate 30, and the upper surface of the groove 31 is covered with the conductive bonding layer 40, thereby forming the gas intermediate passage 50. As shown in FIG. 5, the gas intermediate passage 50 is provided in an annular shape so as to overlap with any of the multiple imaginary circles C1 to C4 in a plan view. Specifically, of the three gas intermediate passages 50, the first gas intermediate passage 50 from the outer periphery of the wafer mounting table 10 overlaps with the imaginary circle C1 with the largest diameter, the second gas intermediate passage 50 overlaps with the imaginary circle C2 with the second largest diameter, and the third gas intermediate passage overlaps with the imaginary circle C3 with the third largest diameter. Each gas intermediate passage 50 has an overlapping portion 50p (shaded portion in FIG. 5) that overlaps with the refrigerant flow path 32 along the refrigerant flow path 32 in a plan view. Note that overlapping with the refrigerant flow path 32 along the refrigerant flow path 32 does not necessarily mean that the center line of the refrigerant flow path 32 in the length direction and the center line of the gas intermediate passage 50 in the length direction are parallel to each other. In addition, The intermediate gas passage 50 Complete overlap over the entire coolant flow path 32 is not required.

[0022] As shown in FIG. 2, the gas supply passage 52 is a passage that extends from the gas intermediate passage 50 through the conductive bonding layer 40 and the ceramic plate 20 in the vertical direction to the reference surface 21c (FIG. 1) of the wafer mounting surface 21. The gas supply passage 52 has a bonding layer through-hole 52a that penetrates the conductive bonding layer 40 and a ceramic plate through-hole 52b that penetrates the ceramic plate 20. In this embodiment, the diameter of the bonding layer through-hole 52a is the same as or larger than the diameter of the ceramic plate through-hole 52b. A plurality of gas supply passages 52 (here, 12) are provided for each gas intermediate passage 50. The gas supply passage 52 has an electrically insulating porous plug 55 that allows gas to flow through. Here, the porous plug 55 is filled and fixed in the ceramic plate through-hole 52b of the gas supply passage 52. Specifically, the outer peripheral surface of the porous plug 55 may be bonded to the inner peripheral surface of the ceramic plate penetrating portion 52b, or a male thread provided on the outer peripheral surface of the porous plug 55 may be threaded into a female thread provided on the inner peripheral surface of the ceramic plate penetrating portion 52b. The upper surface of the porous plug 55 is flush with the reference plane 21c of the wafer mounting surface 21, and the lower surface of the porous plug 55 is flush with the lower surface of the ceramic plate 20. The porous plug 55 may be a porous bulk obtained by sintering ceramic powder. Examples of ceramics that may be used include alumina and aluminum nitride. The porosity of the porous plug 55 is preferably 30% or more, and the average pore diameter is preferably 20 μm or more.

[0023] The gas introduction passage 54 penetrates the cooling plate 30 in the vertical direction and is provided to communicate with the gas intermediate passage 50 via the gas auxiliary passage 53 (FIG. 3). The gas auxiliary passage 53 is a passage that connects the gas introduction passage 54 and the gas intermediate passage 50, and is provided at the interface between the conductive bonding layer 40 and the cooling plate 30 parallel to the wafer mounting surface 21. A plurality of gas supply passages 52 are provided for one gas intermediate passage 50, but the number of gas introduction passages 54 provided is smaller than the number of gas supply passages 52 (here, one). The gas introduction passage 54 penetrates between the refrigerant channels 32 of the cooling plate 30 in the vertical direction.

[0024] Next, an example of how the wafer mounting table 10 configured as described above is described. First, the wafer mounting table 10 is installed in a chamber (not shown), and the wafer W is placed on the wafer mounting surface 21. The chamber is then depressurized using a vacuum pump to a predetermined vacuum level, and a DC voltage is applied to the electrode 22 of the ceramic plate 20 to generate an electrostatic attraction force, thereby attracting and fixing the wafer W to the wafer mounting surface 21 (specifically, the upper surface of the seal band 21a or the upper surface of the small circular protrusions 21b). Next, a reactive gas atmosphere at a predetermined pressure (e.g., several tens to several hundreds of Pa) is created in the chamber. In this state, an RF voltage is applied between an upper electrode (not shown) installed on the ceiling of the chamber and the cooling plate 30 of the wafer mounting table 10 to generate plasma. The surface of the wafer W is treated with the generated plasma. A coolant circulates through the coolant flow path 32 of the cooling plate 30. A backside gas is introduced into the gas introduction path 54 from a gas cylinder (not shown). A thermally conductive gas (e.g., He gas) is used as the backside gas. The backside gas introduced into the gas introduction passage 54 passes through the intermediate gas passage 50 and is distributed to the plurality of gas supply passages 52, and is then supplied to and sealed in the space between the back surface of the wafer W and the reference surface 21c of the wafer mounting surface 21. The presence of this backside gas ensures efficient heat conduction between the wafer W and the ceramic plate 20.

[0025] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to FIG. 6. FIG. 6 is a manufacturing process diagram of the wafer mounting table 10. Here, an example is shown in which the cooling plate 30 is manufactured using MMC. First, a ceramic plate 20 incorporating an electrode 22 is prepared (FIG. 6A). For example, a ceramic powder compact incorporating the electrode 22 is produced, and the compact is hot-pressed and fired to obtain the ceramic plate 20. A ceramic plate penetration 52b, which will eventually become part of the gas supply passage 52, is formed in the ceramic plate 20 (FIG. 6B). The ceramic plate penetration 52b is formed to penetrate the ceramic plate 20 in the vertical direction, avoiding the electrode 22.

[0026] Concurrently, two MMC disk members 81 and 82 are prepared (FIG. 6C). Then, grooves and holes are formed in these MMC disk members 81 and 82 by machining (FIG. 6D). Specifically, a recessed groove 32a, which will ultimately become the refrigerant flow path 32, is formed in the lower surface of the upper MMC disk member 81, and a recessed groove 31, which will ultimately become the intermediate gas passage 50, is formed in the upper surface of the MMC disk member 81. A through-hole 54a, which will ultimately become part of the gas introduction passage 54, is formed from the recessed groove 31 to the lower surface of the MMC disk member 81. Furthermore, a through-hole 54b, which will ultimately become part of the gas introduction passage 54, is formed in the lower MMC disk member 82. When the ceramic plate 20 is made of alumina, the MMC disk members 81 and 82 are preferably made of SiSiCTi or AlSiC. This is because the thermal expansion coefficient of alumina can be made approximately the same as that of SiSiCTi or AlSiC.

[0027] The SiSiCTi disk member can be fabricated, for example, as follows: First, silicon carbide, metallic Si, and metallic Ti are mixed to produce a powder mixture. Next, the resulting powder mixture is uniaxially pressed to produce a disk-shaped compact, which is then hot-press sintered in an inert atmosphere to obtain the SiSiCTi disk member.

[0028] Next, the ceramic plate 20, the MMC disk members 81, and the MMC disk members 82 are TCB-bonded together, and the overall shape is adjusted. Then, a porous plug 55 is attached to obtain the wafer stage 10 (FIGS. 6E and 6F). Specifically, a metal bonding material 83 is sandwiched between the upper surface of the lower MMC disk member 82 and the lower surface of the upper MMC disk member 81, and a metal bonding material 90 is sandwiched between the upper surface of the upper MMC disk member 81 and the lower surface of the ceramic plate 20, thereby obtaining a laminate. A through-hole that will eventually become part of the gas introduction passage 54 is pre-formed in the metal bonding material 83, and a through-hole that will eventually become part of the gas supply passage 52 (bonding layer penetration portion 52a) is pre-formed in the metal bonding material 90. The laminate is then pressure-bonded at a temperature below the solidus temperature of the metal bonding materials 83 and 90 (e.g., a temperature between the solidus temperature minus 20°C and the solidus temperature), and then returned to room temperature. As a result, the two MMC disk members 81, 82 are bonded together by the metal bonding material 83 to form the cooling plate 30. The ceramic plate 20 and the cooling plate 30 are also bonded together by the metal bonding material 90. The metal bonding material 90 forms the conductive bonding layer 40. The metal bonding materials 83, 90 can be Al-Mg based bonding materials or Al-Si-Mg based bonding materials. For example, when TCB is performed using an Al-Si-Mg based bonding material, the stack is heated and pressurized in a vacuum atmosphere. The metal bonding materials 83, 90 preferably have a thickness of approximately 100 μm.

[0029] The wafer mounting table 10 described above is provided with a gas intermediate passage 50, which is a horizontal space. The gas intermediate passage 50 is disposed inside the wafer mounting table 10 at a position closer to the wafer mounting surface 21 than the refrigerant flow passage 32 and parallel to the wafer mounting surface. The gas intermediate passage 50 has an overlapping portion 50p (FIG. 5) that overlaps with the refrigerant flow passage 32 along the refrigerant flow passage 32 in a plan view. Because the gas intermediate passage 50 is hollow, the portion where the gas intermediate passage 50 is formed is less susceptible to heat conduction than the portion where the gas intermediate passage 50 is not formed. The portion of the wafer W directly above the refrigerant flow passage 32 is likely to be cooled by the refrigerant, but this temperature drop is suppressed by the overlapping portion 50p of the gas intermediate passage 50, which is less susceptible to heat conduction. As a result, the temperature uniformity of the wafer W is improved.

[0030] The refrigerant flow path 32 is formed by drawing a plurality of imaginary circles C1 to C4 with different diameters in a plan view so as not to overlap each other, and the gas intermediate passage 50 is formed in a circular shape so as to overlap with any of the imaginary circles C1 to C4 in a plan view. This makes it easy to enlarge the overlapping portion 50p of the gas intermediate passage 50.

[0031] Furthermore, when gas is introduced through the gas inlet passages 54 opening at the lower surface of the cooling plate 30, the gas passes through the intermediate gas passages 50 and is distributed to the plurality of gas supply passages 52 before being supplied to the lower surface of the wafer W. In this wafer mounting table 10, the number of gas inlet passages 54 penetrating the cooling plate 30 is smaller than the number of gas supply passages 52. Therefore, the temperature uniformity of the wafer W is improved compared to when the number of gas inlet passages 54 penetrating the cooling plate 30 is the same as the number of gas supply passages 52.

[0032] Furthermore, the cooling plate 30 is a conductive plate and is bonded to the lower surface of the ceramic plate 20 via a conductive bonding layer 40, and the gas intermediate passage 50 is provided at the interface between the conductive bonding layer 40 and the cooling plate 30. Therefore, the conductive bonding layer 40 forming the upper surface of the gas intermediate passage 50 and the cooling plate 30 forming the lower surface of the gas intermediate passage 50 are in contact with each other and have the same potential. Therefore, no potential gradient occurs above and below the gas intermediate passage 50, and discharge within the gas intermediate passage 50 can be prevented.

[0033] Furthermore, gas supply passage 52 has electrically insulating porous plug 55, which can suppress discharge within gas supply passage 52. For example, without porous plug 55, electrons generated as gas molecules are ionized would accelerate and collide with other gas molecules, causing arc discharge. However, with porous plug 55, the electrons strike porous plug 55 before colliding with other gas molecules, suppressing arc discharge.

[0034] Furthermore, the width of the gas intermediate passage 50 is preferably 1 mm or more, and the depth of the gas intermediate passage 50 is preferably 0.1 mm or more. If the width of the gas intermediate passage 50 is 1 mm or more, the diameter of the grinding stone used to form the grooves 31 is not too small, thereby shortening the processing time and reducing processing costs. If the depth of the gas intermediate passage 50 is 0.1 mm or more, gas flows easily through the gas intermediate passage 50. Furthermore, the thickness of the portion of the cooling plate 30 above the refrigerant flow path 32 is preferably 3 mm or less. This makes it difficult for a large temperature difference to occur in the vertical direction in the portion of the cooling plate 30 above the refrigerant flow path 32, and therefore, stress is unlikely to occur in that portion, preventing damage to that portion due to stress. In this case, the depth of the gas intermediate passage 50 is preferably 0.1 mm or more and 2 mm or less.

[0035] 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.

[0036] In the above-described embodiment, the gas supply passage 52 and the gas introduction passage 54 are provided in communication with the gas intermediate passage 50 as a horizontal space, but the present invention is not limited to this. For example, in the above-described embodiment, the gas introduction passage 54 in communication with the gas intermediate passage 50 may be provided, but the gas supply passage 52 may not be provided. In this case, gas may be introduced from the gas introduction passage 54 into the gas intermediate passage 50, and then the gas may be sealed inside the gas intermediate passage 50, and the gas pressure may be controlled to adjust the uniform heating of the wafer. Alternatively, in the above-described embodiment, the gas intermediate passage 50 may be provided, but the gas supply passage 52 and the gas introduction passage 54 may not be provided. In this case, the gas intermediate passage 50 becomes a closed space.

[0037] In the above-described embodiment, the intermediate gas passage 50 is provided at the interface between the conductive bonding layer 40 and the cooling plate 30. However, the intermediate gas passage 50 may also be provided inside the ceramic plate 20 (below the electrostatic electrode 22). An example of this is shown in FIG. 7. In FIG. 7, the same components as in the above-described embodiment are denoted by the same reference numerals. Alternatively, the intermediate gas passage 50 may be provided in the cooling plate 30 above the refrigerant flow path 32.

[0038] In the above-described embodiment, the gas intermediate passage 50 may be formed so as not to overlap with the outermost imaginary circle C1 among the multiple imaginary circles C1 to C4, as shown in FIG. 8. In FIG. 8, the same components as those in the above-described embodiment are denoted by the same reference numerals. When processing the wafer W with plasma, the outermost region of the wafer W tends to reach a relatively high temperature. Therefore, it is preferable to actively dissipate heat from the outermost region of the wafer W by not providing the gas intermediate passage 50 directly above the outermost region of the coolant flow path 32.

[0039] In the above-described embodiment, when viewed in a plan view, it is preferable that the total length of the area where the center lines of each gas intermediate passage 50 overlap with the refrigerant flow path 32 is 75% or more of the total length of the center lines of each gas intermediate passage 50.

[0040] In the above-described embodiment, the lower end of the porous plug 55 may be in contact with the conductive bonding layer 40. For example, as shown in FIG. 9 , the hole diameter of the bonding layer penetrating portion 52a of the gas supply passage 52 may be smaller than the hole diameter of the ceramic plate penetrating portion 52b, so that the lower end of the porous plug 55 is in contact with the conductive bonding layer 40. The hole diameter of the bonding layer penetrating portion 52a is preferably 5 mm or less. Alternatively, as shown in FIG. 10 , the bonding layer penetrating portion 52a of the gas supply passage 52 may be formed of a plurality of small holes 40a, each having a hole diameter smaller than the hole diameter of the ceramic plate penetrating portion 52b, so that the lower end of the porous plug 55 is in contact with the conductive bonding layer 40. The hole diameter of the small holes 40a is preferably 5 mm or less. In FIGS. 9 and 10 , the same components as those in the above-described embodiment are denoted by the same reference numerals. In both FIGS. 9 and 10 , no potential gradient is generated between the lower end of the porous plug 55 and the conductive bonding layer 40 or between the lower end of the porous plug 55 and the cooling plate 30. This makes it possible to suppress discharge from occurring around the lower end of porous plug 55. Furthermore, when inserting porous plug 55 into gas supply passage 52, the lower end of porous plug 55 can be brought into contact with conductive bonding layer 40 simply by inserting porous plug 55 until it hits the periphery of bonding layer penetrating portion 52a of conductive bonding layer 40.

[0041] In the above-described embodiment, the porous plug 55 is filled in the ceramic plate penetration portion 52b of the gas supply passage 52, but this is not particularly limited. For example, the porous plug 55 may fill the entire gas supply passage 52 (the bonding layer penetration portion 52a and the ceramic plate penetration portion 52b), or the lower end of the porous plug 55 may reach the lower surface of the intermediate gas passage 50. Even in this case, as in FIGS. 7 and 8, no potential gradient occurs between the lower end of the porous plug 55 and the conductive bonding layer 40 or between the lower end of the porous plug 55 and the cooling plate 30. Therefore, discharge around the lower end of the porous plug 55 can be suppressed.

[0042] In the above-described embodiment, a conductive plate is used as the cooling plate 30, but this is not intended to be limiting. For example, as in the wafer mounting table 110 shown in FIG. 11 , the cooling plate 130 may have a conductive plate 131 as an upper layer and a circular plate 136 as a lower layer. In FIG. 11 , the same components as those in the above-described embodiment are denoted by the same reference numerals. The conductive plate 131 has a refrigerant flow channel groove 134 on its lower surface. The refrigerant flow channel 32 is formed by closing the lower opening of the refrigerant flow channel groove 134 with the circular plate 136 disposed on the lower surface of the conductive plate 131. The conductive plate 131 and the circular plate 136 are integrated by a clamping mechanism (not shown) provided on the outer periphery in a liquid-tight seal to prevent the refrigerant from leaking from the refrigerant flow channel 32 to the outer periphery. The gas introduction passage 54 is composed of a portion passing through the conductive plate 131 and a portion passing through the circular plate 136, and the joint between these portions (between the conductive plate 131 and the circular plate 136) is airtightly sealed. The conductive plate 131 and the circular plate 136 may both be made of the same material (e.g., MMC), but the conductive plate 131 may be made of an expensive material (e.g., MMC) and the circular plate 136 may be made of a cheaper material (e.g., metal such as aluminum or an aluminum alloy, or ceramic such as alumina).

[0043] Alternatively, as in the wafer mounting table 210 shown in FIG. 12 , the cooling plate 230 may have a conductive plate 231 as an upper layer and a circular plate 236 as a lower layer. In FIG. 12 , the same components as those in the above-described embodiment are denoted by the same reference numerals. The conductive plate 231 does not have a refrigerant flow path or a refrigerant flow groove. The circular plate 236 has a refrigerant flow groove 234 on its upper surface. The refrigerant flow path 32 is formed by closing the upper opening of the refrigerant flow groove 234 with the conductive plate 231. The conductive plate 231 and the circular plate 236 are integrated by a clamping mechanism (not shown) provided on the outer periphery in a liquid-tight seal to prevent the refrigerant from leaking from the refrigerant flow path 32 to the outer periphery. The gas introduction passage 54 is composed of a portion passing through the conductive plate 231 and a portion passing through the circular plate 236, and the joint between these portions (between the conductive plate 231 and the circular plate 236) is airtightly sealed. The conductive plate 231 and the circular plate 236 may both be made of the same material (e.g., MMC), but the conductive plate 231 may be made of an expensive material (e.g., MMC) and the circular plate 236 may be made of a cheaper material (e.g., metal such as aluminum or aluminum alloy, or ceramic such as alumina).

[0044] In the above-described embodiment, the porous plug 55 is disposed in the gas supply passage 52 , but the porous plug 55 does not necessarily have to be disposed in the gas supply passage 52 .

[0045] In the above-described embodiment, the gas intermediate passage 50 is formed by providing a groove 31 (first recess) on the upper surface of the cooling plate 30 and placing the lower surface (flat surface) of the conductive bonding layer 40 on the groove 31. However, this is not particularly limited. For example, the gas intermediate passage 50 may be formed by providing a groove (second recess) on the lower surface of the conductive bonding layer 40 and placing the upper surface (flat surface) of the cooling plate 30 below the groove. In this case, the conductive bonding layer 40 may have a two-layer structure, with a groove (a groove penetrating in the vertical direction) that will ultimately become the gas intermediate passage 50 provided in the lower layer and the above-described bonding layer penetration portion 52a provided in the upper layer. This configuration also allows the wafer mounting table 10 to be manufactured relatively easily.

[0046] In the above-described embodiment, the upper surface of the porous plug 55 is at the same height as the reference surface 21c of the wafer mounting surface 21, but this is not particularly limited. For example, the difference between the height of the reference surface 21c of the wafer mounting surface 21 and the height of the upper surface of the porous plug 55 may be set to be 0.5 mm or less (preferably 0.2 mm or less, more preferably 0.1 mm or less). In other words, the upper surface of the porous plug 55 may be positioned lower than the reference surface 21c of the wafer mounting surface 21 by 0.5 mm or less (preferably 0.2 mm or less, more preferably 0.1 mm or less). Even in this case, the height of the space between the lower surface of the wafer W and the upper surface of the porous plug 55 can be kept relatively low. Therefore, it is possible to prevent arc discharge from occurring in this space.

[0047] In the above-described embodiment, the ceramic plate 20 has an electrostatic electrode built in as the electrode 22. However, instead of or in addition to this, a heater electrode (resistance heating element) may be built in. In this case, a heater power supply is connected to the heater electrode. The ceramic plate 20 may have one layer of electrodes built in, or two or more layers of electrodes spaced apart.

[0048] In the above-described embodiment, lift pin holes may be provided through the wafer mounting table 10. The lift pin holes are holes for inserting lift pins that move the wafer W up and down relative to the wafer mounting surface 21. When the wafer W is supported by, for example, three lift pins, three lift pin holes are provided. When through holes such as lift pin holes are present, the temperature tends to be higher around such through holes, so the intermediate gas passage 50 and the refrigerant flow path 32 may not overlap.

[0049] In the above-described embodiment, the coolant flow path 32 may overlap with the gas intermediate passage 50 near the inlet where the coolant temperature is low, and may not overlap with the gas intermediate passage 50 near the outlet where the coolant temperature is high.

[0050] In the above-described embodiment, the ceramic plate 20 is produced by hot-pressing and firing a ceramic powder compact. However, the compact may be produced by stacking multiple tape compacts, by mold casting, or by compressing ceramic powder.

[0051] In the above-described embodiment, the ceramic plate 20 and the cooling plate 30 are joined by the conductive joining layer 40, but this is not limited to the conductive joining layer 40. For example, a resin joining layer may be used instead of the conductive joining layer 40. When a resin joining layer is used, a conductive filler (e.g., a metal filler) may be added to the resin to increase thermal conductivity.

[0052] In the above-described embodiment, the refrigerant flow path 32 is formed in a single stroke, but this is not particularly limited. For example, the refrigerant flow path 32 may have a branch along the way. Alternatively, the refrigerant flow path 32 may have multiple parallel flow paths extending from one end to the other. Furthermore, the imaginary circle used to form the refrigerant flow path 32 may be deformed in places to avoid singular points (such as terminals). [Explanation of symbols]

[0053] 10 wafer mounting table, 20 ceramic plate, 21 wafer mounting surface, 21a seal band, 21b small circular protrusion, 21c reference surface, 22 electrode, 30 cooling plate, 31 groove, 32 coolant flow path, 32a groove, 34, 35 coolant flow path groove, 36 circular plate, 40 conductive bonding layer, 40a small hole, 50 gas intermediate passage, 50p overlapping portion, 52 gas supply passage, 52a bonding layer penetration portion, 52b ceramic plate penetration portion, 53 gas auxiliary passage, 54 gas introduction passage, 54a through hole, 54b through hole, 55 porous plug, 81, 82 MMC disc member, 83, 90 metal bonding material.

Claims

1. A wafer mounting table including a ceramic plate having a wafer mounting surface on its upper surface and a built-in electrode, and a cooling plate having a coolant flow path provided on the lower surface side of the ceramic plate, a horizontal space provided parallel to the wafer mounting surface at a position inside the wafer mounting table closer to the wafer mounting surface than the coolant flow path, the horizontal space having an overlapping portion that overlaps with the coolant flow path along the coolant flow path in a plan view; Equipped with The horizontal space is a gas intermediate passage through which gas passes, the cooling plate is a conductive plate or has at least a conductive plate on its upper layer; the conductive plate is bonded to the lower surface of the ceramic plate via a conductive bonding layer; the intermediate gas passage is provided at the interface between the conductive bonding layer and the conductive plate; Wafer stage.

2. the refrigerant flow path is provided so as to be routed from one end to the other end in a single stroke based on a multiple circle formed by arranging a plurality of imaginary circles having different diameters in a plan view so as not to overlap one another, The horizontal space is provided in an annular shape so as to overlap with any one of the plurality of virtual circles in a plan view. The wafer stage according to claim 1 .

3. the horizontal space does not overlap with the outermost virtual circle among the plurality of virtual circles; The wafer stage according to claim 2 .

4. A wafer mounting table according to any one of claims 1 to 3, a plurality of gas supply passages extending from the intermediate gas passage to the wafer mounting surface; The cooling plate has a cooling passage that extends vertically between the refrigerant flow paths and is connected to the intermediate gas passage. the number of gas introduction passages being less than the number of the gas supply passages communicating with the gas intermediate passage; A wafer mounting table comprising:

5. the gas supply passage has an electrically insulating porous plug, and a lower end of the porous plug is in contact with at least one of the conductive bonding layer and the conductive plate; The wafer stage according to claim 4 .

Images