Wafer placement table

Abstract

An upper base material 20 of this wafer placement table 10 comprises a ceramic base material 21 that has an electrode 22 built therein, and has a wafer placement surface 21a on the upper surface of the ceramic base material 21. A lower base material 30 is disposed on the lower surface side of the upper base material 20 and comprises a coolant flow path 35. Through-holes 36 penetrate the lower base material 30 in the up-down direction. Protrusions 38 are provided in a dotted shape over the entire upper surface of the lower base material 30 and abut the lower surface of the upper base material 20. A heat dissipation sheet 40 has protrusion insertion holes 44 into which the protrusions 38 are inserted, and is disposed in a compressed state between the upper base material 20 and the lower base material 30. Screw holes 24 are provided in positions facing the through-holes 36 on the lower surface of the upper base material 20, and screw members 50 are inserted into the through-holes 36 from the lower surface of the lower base material 30 and are screwed into the screw holes 24. A heat conductive paste 60 is interposed between the side surfaces of the protrusions 38 and the inner circumferential surfaces of the protrusion insertion holes 44 of the heat dissipation sheet 40.

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 substrate having a wafer mounting surface and an electrode built therein, and a metal plate disposed on the surface of the ceramic substrate opposite to the wafer mounting surface. Patent Document 1 discloses such a wafer mounting table in which a plurality of through holes are provided in the metal plate, and screw holes are provided on the lower surface of the ceramic substrate at positions facing the through holes, and screws are inserted into the through holes from the lower surface of the metal plate and screwed into the screw holes to fasten the ceramic substrate and the metal plate. A non-adhesive heat conductive sheet (a type of heat dissipation sheet) is disposed between the ceramic substrate and the metal plate. The heat conductive sheet serves to transfer heat from the ceramic substrate to the metal plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2018 / 038044 Brochure Summary of the Invention [Problem to be solved by the invention]

[0004] In Patent Document 1, when manufacturing the wafer mounting table, it is necessary to position the thermally conductive sheet while avoiding terminal holes, etc., but since there is no means for positioning the thermally conductive sheet, the thermally conductive sheet may shift from its original position. Also, since the amount of deformation of the thermally conductive sheet (and therefore its thermal conductivity) depends on the degree of fastening of each screw member, any variation in the degree of fastening of each screw member may deteriorate the thermal uniformity of the wafer.

[0005] The present invention has been made to solve these problems, and its main object is to facilitate the positioning of a heat dissipation sheet when manufacturing a wafer mounting table, and to improve the thermal uniformity of the wafer. [Means for solving the problem]

[0006] [1] The wafer mounting table of the present invention comprises: an upper substrate including a ceramic substrate having an electrode built therein and a wafer mounting surface on an upper surface of the ceramic substrate; a lower base material disposed on a lower surface side of the upper base material and including a refrigerant flow path through which a refrigerant flows or a refrigerant flow path groove constituting a side wall and a bottom of the refrigerant flow path; A through hole penetrating the lower base material in the vertical direction; A plurality of protrusions are provided in a dot pattern on the entire upper surface of the lower substrate and abut against the lower surface of the upper substrate, or are provided in a dot pattern on the entire lower surface of the upper substrate and abut against the upper surface of the lower substrate; a heat dissipation sheet having a protrusion insertion hole into which the protrusion is inserted and disposed in a compressed state between the upper base material and the lower base material; a screw hole provided in a lower surface of the upper base material at a position facing the through hole; a screw member inserted into the through hole from the underside of the lower base material and screwed into the screw hole; a thermally conductive paste interposed between at least one of a side surface of the protrusion and an inner peripheral surface of the protrusion insertion hole of the heat dissipation sheet and a top surface of the protrusion and a lower surface of the upper base material; It is equipped with the following:

[0007] In this wafer mounting table, the heat dissipation sheet has a plurality of protrusion insertion holes into which a plurality of protrusions are inserted. When manufacturing the wafer mounting table, the protrusions provided in a dot pattern on the entire upper surface of the lower substrate or the entire lower surface of the upper substrate are inserted into the protrusion insertion holes of the heat dissipation sheet, so that the heat dissipation sheet is easily positioned. Furthermore, the screw member is screwed in until the distance between the upper substrate and the lower substrate coincides with the height of the protrusions. As a result, the heat dissipation sheet disposed between the upper substrate and the lower substrate is compressed until the entire thickness is the same as or approximately the same as the height of the protrusions. Therefore, the thermal conductivity of the heat dissipation sheet does not vary greatly depending on the location. Furthermore, a thermally conductive paste is interposed at least one between the side surface of the protrusion and the inner peripheral surface of the protrusion insertion hole of the heat dissipation sheet and between the top surface of the protrusion and the lower surface of the upper substrate. Therefore, the upper substrate, the heat dissipation sheet, and the lower substrate can be closely attached with as few gaps as possible. Therefore, the thermal uniformity of the wafer is improved.

[0008] In this specification, the present invention may be described using terms such as up / down, left / right, front / back, etc., but these terms are merely relative positional relationships. Therefore, when the orientation of the wafer mounting table is changed, up / down may become left / right and left / right may become up / down, but such cases are also included in the technical scope of the present invention.

[0009] [2] In the above-mentioned wafer mounting table (the wafer mounting table described in [1] above), the upper base may include the ceramic base and a support base made of a metal or a metal ceramic composite material bonded to the lower surface of the ceramic base via a metal bonding layer, and the screw hole may be provided in the lower surface of the support base. In this way, the support base is made of a metal or a metal ceramic composite material and has superior thermal conductivity compared to the ceramic base. Therefore, heat from the ceramic base can be efficiently conducted to the lower base.

[0010] [3] In the above-mentioned wafer mounting table (the wafer mounting table described in [1] or [2] above), the through holes may be provided so as to penetrate the protrusions. In this way, since it is not necessary to provide communication holes in the heat dissipation sheet that communicate with the through holes, the function of the heat dissipation sheet can be fully exhibited.

[0011] [4] In the above-mentioned wafer mounting table (the wafer mounting table described in any one of [1] to [3] above), the thermal resistance of the heat dissipation sheet is 0.35 K cm 2 / W or less. In this way, the heat of the upper substrate is rapidly conducted to the lower substrate.

[0012] [5] In the above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to [4] above), the Young's modulus of the heat dissipation sheet may be 100 MPa or less. This allows the fastening force of the screw members to be transmitted evenly across the entire surface of the heat dissipation sheet, so that the entire surface of the heat dissipation sheet is firmly attached to the upper base material and the lower base material.

[0013] [6] In the above-mentioned wafer stage (the wafer stage according to any one of [1] to [5] above), the thermally conductive paste may have a thermal conductivity of 0.5 W / mK or more. This further promotes thermal conduction from the upper base material to the lower base material.

[0014] [7] In the above-described wafer stage (the wafer stage described in any one of [1] to [6] above), the through hole may be provided so as not to intersect with the coolant flow path or the coolant flow path groove. This prevents the coolant from leaking from the through hole through which the screw member is inserted.

[0015] [8] In the above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to [6] above), the through hole may be provided so as to intersect with the refrigerant flow path or the refrigerant flow path groove, and the lower base material may have a refrigerant leakage prevention member that prevents the refrigerant from leaking out to the lower surface of the lower base material from the through hole into which the screw member is inserted. In this way, it is not necessary to provide a refrigerant flow path that bypasses the screw member, and therefore the degree of freedom in designing the refrigerant flow path or the refrigerant flow path groove is improved. In addition, the refrigerant leakage prevention member may be provided so as to prevent the refrigerant from leaking out to the lower surface of the lower base material from the through hole into which the screw member is inserted. prevention The member prevents the refrigerant from leaking out from the through hole into which the screw member is inserted.

[0016] [9] In the above-mentioned wafer stage (the wafer stage according to any one of [1] to [8] above), the lower base material may be made of an easily processable material. This allows the refrigerant flow path or the refrigerant flow path groove to be easily formed in the lower base material, thereby reducing processing costs. [Brief description of the drawings]

[0017] [Figure 1] FIG. 2 is a vertical cross-sectional view of the wafer mounting table 10 installed in the chamber 94. [Diagram 2] FIG. [Diagram 3] 4 is a cross-sectional view of the wafer mounting table 10 cut horizontally by the heat dissipation sheet 40 as viewed from above. FIG. [Figure 4] 3A to 3C are diagrams showing the manufacturing process of the wafer mounting table 10 (the manufacturing process of the upper base material 20). [Diagram 5] 3A to 3C are diagrams showing the manufacturing process of the wafer mounting table 10 (the manufacturing process of the lower base material 30). [Figure 6] 3A to 3C are diagrams showing the manufacturing process of the wafer mounting table 10 (assembly process of the wafer mounting table 10). [Figure 7] FIG. 13 is a partially enlarged cross-sectional view of another example in which a through hole 36 is provided so as to penetrate a protrusion 38. [Figure 8] FIG. 2 is a vertical cross-sectional view of the wafer mounting table 110. [Figure 9] FIG. 2 is a vertical cross-sectional view of the wafer mounting table 210. [Figure 10] FIG. 3 is a vertical cross-sectional view of the wafer mounting table 310. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] A preferred embodiment of the present invention will be described below with reference to the drawings. Fig. 1 is a vertical cross-sectional view of a wafer mounting table 10 installed in a chamber 94 (a cross-sectional view taken 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, and Fig. 3 is a cross-sectional view of the wafer mounting table 10 cut horizontally by a heat dissipation sheet 40 as viewed from above.

[0019] The wafer mounting table 10 is used for performing CVD, etching, and the like on a wafer W using plasma, and is fixed to a mounting plate 96 provided inside a semiconductor process chamber 94. The wafer mounting table 10 includes an upper base material 20, a lower base material 30, a heat dissipation sheet 40, and screw members 50.

[0020] The upper base material 20 includes a ceramic base material 21, a support base material 23 disposed below the ceramic base material 21, and a metal bonding layer 25 that bonds the ceramic base material 21 and the support base material 23. The thickness of the upper base material 20 is preferably 8 mm or more or 10 mm or more in consideration of strength, and is preferably 25 mm or less in consideration of cooling efficiency.

[0021] The ceramic base material 21 has a circular wafer mounting surface 21a. A wafer W is mounted on the wafer mounting surface 21a. The ceramic base material 21 is made of a ceramic material such as alumina or aluminum nitride. The ceramic base material 21 has a wafer adsorption electrode 22 built in on the side closer to the wafer mounting surface 21a. The wafer adsorption electrode 22 is made of a material containing, for example, W, Mo, WC, MoC, etc. The wafer adsorption electrode 22 is a disk-shaped or mesh-shaped monopolar electrostatic electrode. The layer of the ceramic base material 21 above the wafer adsorption electrode 22 functions as a dielectric layer. A wafer adsorption DC power source 52 is connected to the wafer adsorption electrode 22 via a power supply terminal 54. The power supply terminal 54 is provided so as to pass through an insulating tube 55 arranged in a hole that vertically penetrates the lower base material 30, the support base material 23, and the metal bonding layer 25, and reach the wafer adsorption electrode 22 from the lower surface of the ceramic base material 21. A low pass filter (LPF) 57 is provided between the wafer attracting DC power supply 52 and the wafer attracting electrode 22 .

[0022] The support base 23 is a disk one size larger than the ceramic base 21, and is made of a conductive material. Examples of the conductive material include composite materials and metals. Examples of the composite material include composite materials of metal and ceramic. Examples of the composite material of metal and ceramic include metal matrix composite materials (metal matrix composites (MMC)) and ceramic matrix composite materials (ceramic matrix composites (CMC)). Specific examples of such composite materials include materials containing Si, SiC, and Ti, and materials in which a porous SiC body is impregnated with Al and / or Si. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which a porous SiC body is impregnated with Al is called AlSiC, and a material in which a porous SiC body is impregnated with Si is called SiSiC. Examples of the metal include Mo. The material used for the support base 23 is a ceramic material used for the ceramic base 21, and the absolute value of the linear thermal expansion coefficient difference at 40 to 400°C is 1.5×10 -6 / K or less, and 1.0×10 -6 / K or less is more preferable, and 0.5×10 -6 / K or less is more preferable. Taking strength into consideration, the thickness of the support base 23 is preferably 3 mm or more or 6 mm or more, and taking cooling efficiency into consideration, the thickness is preferably 20 mm or less.

[0023] A plurality of screw holes 24 are provided on the lower surface of the support base material 23. The screw holes 24 are provided at positions facing the through holes 36 described later. The screw holes 24 are formed by providing a cylindrical hole on the lower surface of the support base material 23 and directly cutting a screw groove in the cylindrical hole, but are not particularly limited to this. For example, the screw holes 24 may be formed by inserting a spiral thread insert into the cylindrical hole, or may be formed by inserting a female threaded terminal (e.g., a cap nut) of Patent Document 1 into the cylindrical hole and soldering it. The center-to-center distance between two adjacent screw holes 24 is not particularly limited, but is preferably 100 mm or less, for example.

[0024] The metal bonding layer 25 bonds the lower surface of the ceramic base material 21 and the upper surface of the support base material 23. The metal bonding layer 25 may be, for example, a layer formed of solder or a metal brazing material. The metal bonding layer 25 is formed, for example, by TCB (thermal compression bonding). TCB refers to a known method in which a metal bonding material is sandwiched between two members to be bonded, and the two members are pressure-bonded while being heated to a temperature equal to or lower than the solidus temperature of the metal bonding material.

[0025] The lower base material 30 is a disk member made of an easily processable material. In this embodiment, the outer diameter of the lower base material 30 is the same as the outer diameter of the support base material 23. The lower base material 30 incorporates a refrigerant flow path 35. The refrigerant flow path 35 is formed in a spiral shape from the inlet 35a to the outlet 35b of the refrigerant flow path 35 in a single stroke so that the refrigerant flows over the entire area in which the ceramic base material 21 is disposed. The inlet 35a is provided on the outer periphery of the wafer mounting table 10, and the outlet 35b is provided on the center side of the wafer mounting table 10. The inlet 35a and the outlet 35b are connected to a refrigerant cooling device (not shown), and the refrigerant discharged from the outlet 35b is adjusted to a predetermined low temperature by the refrigerant cooling device, and then returned to the inlet 35a and supplied into the refrigerant flow path 35. The refrigerant flowing through the refrigerant flow path 35 is preferably a liquid, and is preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inert liquids. The easily processable material used for the lower base material 30 is preferably one that is easier to process than the support base material 23. As an index of workability, for example, the machinability index shown in JIS B 0170 (2020) can be used. As the easily machinable material, a material with a machinability index of 40 or more is preferable, a material with a machinability index of 100 or more is more preferable, and a material with a machinability index of 140 or more is even more preferable. As the easily machinable material, for example, aluminum, aluminum alloy, stainless steel (SUS material), etc. can be mentioned.

[0026] The lower substrate 30 is connected to an RF power supply 62 via a power supply terminal 64. Therefore, the lower substrate 30 also functions as a radio frequency (RF) electrode for generating plasma. A high pass filter (HPF) 63 is disposed between the lower substrate 30 and the RF power supply 62.

[0027] The lower base material 30 has a plurality of through holes 36. The through holes 36 are holes for inserting the screw members 50, and penetrate the lower base material 30 in the vertical direction so as not to intersect with the refrigerant flow path 35. The through holes 36 have a large diameter portion 36a for accommodating the head 50a of the screw member 50, and a small diameter portion 36b through which the foot portion 50b of the screw member 50 can pass but the head 50a cannot pass. As shown in FIG. 3, a plurality of protrusions 38 are provided in a dot pattern over the entire upper surface of the lower base material 30. At least one of the plurality of protrusions 38 is provided directly above the inlet 35a of the refrigerant flow path 35. The protrusions 38 may be, for example, flat cylindrical protrusions. The top surface of the protrusions 38 abuts against the lower surface of the upper base material 20 (i.e., the lower surface of the support base material 23). The height of the protrusions 38 is, for example, preferably 0.05 mm or more and 1 mm or less, more preferably 0.1 mm or more and 0.5 mm or less. The protrusions 38 are preferably arranged on the upper surface of the lower base material 30 so as not to be aligned in a straight line in the radial direction.

[0028] The heat dissipation sheet 40 is disposed between the lower surface of the upper base material 20 and the upper surface of the lower base material 30. The heat dissipation sheet 40 has protrusion insertion holes 44 at positions facing each of the multiple protrusions 38. The protrusion insertion holes 44 are holes that penetrate the heat dissipation sheet 40 in the vertical direction. The protrusions 38 are inserted into the protrusion insertion holes 44. The thickness of the heat dissipation sheet 40 before being assembled to the wafer mounting table 10 is greater than the height of the protrusions 38, but the thickness of the heat dissipation sheet 40 after being assembled to the wafer mounting table 10 is equal to or almost equal to the height of the protrusions 38. Therefore, the heat dissipation sheet 40 is sandwiched between the upper base material 20 and the lower base material 30 and compressed in the vertical direction. By doing so, the heat dissipation sheet 40 is firmly attached to the lower surface of the upper base material 20 and the upper surface of the lower base material 30, so that the heat of the upper base material 20 is quickly conducted to the lower base material 30. The heat dissipation sheet 40 is preferably conductive. The thermal resistance of the heat dissipation sheet 40 is 0.35 K·cm 2 / W or less is preferable, and 0.1K cm 2 / W or less is more preferable. The Young's modulus of the heat dissipation sheet 40 is preferably 100 MPa or less, more preferably 20 MPa or less, and even more preferably 5 MPa or less. The thermal resistance can be measured, for example, in accordance with ASTM D5470. The heat dissipation sheet 40 has no or almost no adhesiveness.

[0029] Specifically, the heat dissipation sheet 40 is preferably a sheet containing carbon and resin. Examples of carbon include graphite, carbon fiber, and carbon nanotubes, and examples of resin include silicone resin. In the case of graphite, it is preferable to arrange the graphene constituting the graphite so that the plane direction is along the vertical direction, and in the case of carbon fiber and carbon nanotubes, it is preferable to arrange them so that the axial direction is along the vertical direction. For example, a thermal interface material (TIM) can be used as the material of the heat dissipation sheet 40. Specific examples of the heat dissipation sheet 40 include EX20000C4S (manufactured by Dexerials), GraphitePAD, and GraphiteTIM (registered trademark) (all manufactured by Panasonic). The Poisson's ratio of the heat dissipation sheet 40 is preferably 0.4 or less, more preferably 0.3 or less, and even more preferably 0.2 or less. The smaller the Poisson's ratio of the heat dissipation sheet 40, the more evenly the fastening force of the screw members 50 is transmitted over the entire surface of the heat dissipation sheet 40 and the less likely it is to escape laterally, so that the heat dissipation sheet 40 adheres firmly over its entire surface to the support base material 23 and the lower base material 30. This allows the wafer W to be cooled more uniformly. The Shore hardness (Shore OO) of the heat dissipation sheet 40 may be 50 or more and 80 or less.

[0030] The thermally conductive paste 60 is interposed between the side surface of the protrusion 38 and the inner peripheral surface of the protrusion insertion hole 44 of the heat dissipation sheet 40. The thermally conductive paste 60 is also interposed between the top surface of the protrusion 38 and the lower surface of the upper base material 20 (the lower surface of the support base material 23). The thermally conductive paste 60 may be electrically insulating or conductive. The thermally conductive paste 60 is preferably a paste having a thermal conductivity of 0.5 W / mK or more, and more preferably a paste having a thermal conductivity of 1 W / mK or more. m K or higher paste is preferable, and 2W / m More preferably, the paste has a thermal conductivity of 2.8 W / mK or higher. Examples of such pastes include Tran-Q clay from NOK (thermal conductivity 2.8 W / mK), BERGQUIST TLF 6000HG from Henkel (thermal conductivity 6.0 W / mK), and X-23-7921-5 from Shin-Etsu Chemical Co., Ltd. (thermal conductivity 6.0 W / mK).

[0031] As shown in the enlarged view of FIG. 1, the screw member 50 has a large-diameter head 50a and a small-diameter foot 50b. The screw member 50 is inserted from the bottom surface of the lower base material 30 into the through hole 36 provided so as not to intersect with the refrigerant flow path 35, and is screwed into the screw hole 24 of the support base material 23. The screw member 50 is screwed into the screw hole 24 until the top surface of the protrusion 38 of the lower base material 30 contacts the bottom surface of the upper base material 20. As a result, the head 50a of the screw member 50 presses the step surface 36c (the boundary between the large-diameter portion 36a and the small-diameter portion 36b) of the through hole 36 upward. In addition, the support base material 23 of the upper base material 20 and the lower base material 30 are fastened with the heat dissipation sheet 40 sandwiched therebetween, and the heat dissipation sheet 40 is compressed in the vertical direction. The head 50a of the screw member 50 is stored in the large-diameter portion 36a so as not to protrude downward from the bottom surface of the lower base material 30. In this embodiment, as shown in Fig. 3, a large number of screw members 50 are provided along multiple (here, three) circles (indicated by dashed dotted lines in Fig. 3) that are concentric with the heat dissipation sheet 40. The screw members 50 are preferably made of a material having good electrical and thermal conductivity, such as stainless steel.

[0032] The side surface (outer peripheral surface) of the metal bonding layer 25, the upper and side surfaces of the support substrate 23, and the side surface of the lower substrate 30 may be covered with an insulating film as required. Examples of the insulating film include a thermally sprayed film of alumina or yttria. Also, a metal or resin O-ring may be disposed so as to surround the outer periphery of the heat dissipation sheet 40. The O-ring is compressed in the vertical direction between the upper substrate 20 and the lower substrate 30 to provide a seal. In this way, the heat dissipation sheet 40 is protected by the O-ring.

[0033] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to Fig. 4 to Fig. 6. Fig. 4 to Fig. 6 are manufacturing process diagrams of the wafer mounting table 10, with Fig. 4 showing the manufacturing process of the upper base material 20, Fig. 5 showing the manufacturing process of the lower base material 30, and Fig. 6 showing the assembly process of the wafer mounting table 10.

[0034] The upper base material 20 is produced, for example, as follows. First, the ceramic base material 21 is produced by hot-pressing and sintering a ceramic powder compact (FIG. 4A). The ceramic base material 21 has a built-in wafer adsorption electrode 22. Next, a hole 21b is opened from the lower surface of the ceramic base material 21 to the wafer adsorption electrode 22 (FIG. 4B), and a power supply terminal 54 is inserted into the hole 21b to join the power supply terminal 54 and the wafer adsorption electrode 22 (FIG. 4C).

[0035] In parallel with this, a disk-shaped support base 23 is prepared (FIG. 4D), and a hole 23b penetrating vertically is formed in the support base 23, and a screw hole 24 is formed at a predetermined position on the lower surface of the support base 23 (FIG. 4E). The hole 23b in the support base 23 is formed at a position that allows communication with the hole 21b in the ceramic base 21. When the ceramic base 21 is made of alumina, the support base 23 is preferably made of SiSiCTi or AlSiC. This is because SiSiCTi and AlSiC can have a thermal expansion coefficient that is approximately the same as that of alumina.

[0036] The SiSiCTi support substrate 23 can be produced, for example, as follows. First, silicon carbide, metal Si, and metal 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 support substrate 23.

[0037] Next, a circular metal bonding material is placed on the upper surface of the support base 23. A hole communicating with the hole 23b of the support base 23 is provided in the metal bonding material. Then, the ceramic base 21 is placed on the metal bonding material while inserting the power supply terminal 54 of the ceramic base 21 into the hole of the metal bonding material and the hole 23b of the support base 23. This results in a laminate in which the support base 23, the metal bonding material, and the ceramic base 21 are laminated in this order from below. The laminate is heated and pressurized (TCB) to obtain the upper base 20 (FIG. 4F). The upper base 20 is formed by bonding the ceramic base 21 to the upper surface of the support base 23 via the metal bonding layer 25.

[0038] For example, TCB is performed as follows. That is, the laminate is pressed and bonded at a temperature equal to or lower than the solidus temperature of the metal bonding material (for example, a temperature equal to or higher than the solidus temperature minus 20°C and equal to or lower than the solidus temperature), and then returned to room temperature. This causes the metal bonding material to become a metal bonding layer (or a conductive bonding layer). As the metal bonding material, an Al-Mg-based bonding material or an Al-Si-Mg-based bonding material can be used. For example, when TCB is performed using an Al-Si-Mg-based bonding material, the laminate is pressed in a heated state under a vacuum atmosphere. It is preferable to use a metal bonding material with a thickness of about 100 μm.

[0039] In parallel with the preparation of the upper base material 20, the lower base material 30 is prepared, for example, as follows, using an easily processable material. First, two disk-shaped disk members 31, 32 made of an easily processable material are prepared as the base of the lower base material 30 (FIG. 5A). The disk members 31, 32 are preferably made of aluminum, aluminum alloy, or stainless steel. Next, a groove 35c that will eventually become the refrigerant flow path 35 is formed on the lower surface of the upper disk member 31 (FIG. 5B). After that, the lower surface of the upper disk member 31 and the upper surface of the lower disk member 32 are joined with a joining material (e.g., brazing material) not shown in the figure, thereby preparing the lower base material 30 incorporating the refrigerant flow path 35 (FIG. 5C). Then, an inlet 35a and an outlet 35b are formed that vertically penetrate from the lower surface of the lower base material 30 to the bottom surface of the refrigerant flow path 35, and a terminal hole 30b is formed that vertically penetrates the lower base material 30. Furthermore, a through hole 36 having a large diameter portion 36a and a small diameter portion 36b is formed at a predetermined position in the lower base material 30, and a plurality of protrusions 38 are formed over the entire upper surface of the lower base material 30 (FIG. 5D).

[0040] Next, as shown in FIG. 6A, a heat conductive paste 60 is applied to the top surface of the protrusions 38, and then, as shown in FIG. 6B, a heat dissipation sheet 40 is placed on the upper surface of the lower base material 30. The heat dissipation sheet 40 is a circular sheet having the same diameter as the lower base material 30. The heat dissipation sheet 40 has protrusion insertion holes 44 that penetrate the heat dissipation sheet 40 in the vertical direction at positions facing the multiple protrusions 38, and has holes 46, 47 that penetrate the heat dissipation sheet 40 in the vertical direction at positions facing the small diameter portion 36b of the through hole 36 and at positions facing the terminal hole 30b. By inserting the protrusions 38 into the protrusion insertion holes 44, the heat dissipation sheet 40 is positioned so that the hole 46 faces the small diameter portion 36b and the hole 47 faces the terminal hole 30b. In this state, the thickness of the heat dissipation sheet 40 is greater than the height of the protrusions 38. In addition, a gap is provided between the inner peripheral surface of the protrusion insertion hole 44 and the outer peripheral surface of the protrusions 38.

[0041] Next, the upper base material 20 is placed on the heat dissipation sheet 40 arranged on the upper surface of the lower base material 30 while inserting the power supply terminal 54 of the upper base material 20 into the terminal hole 30b. Next, the screw member 50 is inserted into each through hole 36 from the lower surface of the lower base material 30 and screwed into the screw hole 24 of the support base material 23. The screw member 50 is screwed in until the protrusion 38 contacts the lower surface of the support base material 23. As a result, the heat dissipation sheet 40 is compressed almost evenly between the support base material 23 and the lower base material 30, and exhibits high heat conduction performance. At the same time, the heat conductive paste 60 applied to the top surface of the protrusion 38 enters the gap between the inner circumferential surface of the protrusion insertion hole 44 and the outer circumferential surface of the protrusion 38. Therefore, the heat conduction from the upper base material 20 to the lower base material 30 is promoted compared to the case where a gap remains in this gap. Also, a part of the heat conductive paste 60 remains between the top surface of the protrusion 38 and the lower surface of the support base material 23. Although minute irregularities exist on the top surfaces of the protrusions 38, the irregularities are filled with the thermally conductive paste 60. Therefore, heat conduction from the upper base material 20 to the lower base material 30 is promoted compared to when the minute irregularities remain on the top surfaces of the protrusions 38. Thereafter, an insulating tube 55 through which the power supply terminal 54 is inserted is placed in the terminal hole 30b (FIG. 6C). In this manner, the wafer mounting table 10 can be obtained.

[0042] Next, an example of use of the wafer mounting table 10 will be described with reference to FIG. 1. First, the wafer mounting table 10 is mounted on a mounting plate 96 of a chamber 94. Specifically, first, the seal members 80, 82a, and 82b are disposed between the upper surface of the mounting plate 96 and the lower surface of the lower base material 30. The seal member 80 is a metal or resin ring whose outer diameter is slightly smaller than the diameter of the lower base material 30 and can be compressed in the vertical direction. The seal members 82a and 82b are metal or resin rings disposed along the opening edges of the inlet 35a and the outlet 35b of the refrigerant flow path 35 and can be compressed in the vertical direction. Next, the screw member 70 is screwed into the screw hole 39 provided on the lower surface of the lower base material 30 through the screw insertion hole 97 from the lower surface of the mounting plate 96. In this way, the seal members 82a and 82b are compressed in the vertical direction to exert a sealing property and prevent the refrigerant from leaking outward from the seal members 82a and 82b.

[0043] A disk-shaped wafer W is placed on the wafer placement surface 21a of the wafer placement table 10 placed on the placement plate 96. In this state, a DC voltage from the wafer adsorption DC power source 52 is applied to the wafer adsorption electrode 22 to adsorb the wafer W onto the wafer placement surface 21a. A temperature-adjusted coolant is supplied to the inlet 35a of the coolant flow path 35 and discharged from the outlet 35b. The interior of the chamber 94 is set to a predetermined vacuum atmosphere (or reduced pressure atmosphere), and an RF voltage from the RF power source 62 is applied to the lower base material 30 while a process gas is supplied from the shower head 98. Then, a plasma is generated between the wafer W and the shower head 98. The plasma is used to perform CVD film formation or etching on the wafer W.

[0044] In the wafer mounting table 10 described above, the heat dissipation sheet 40 has a plurality of protrusion insertion holes 44 into which a plurality of protrusions 38 are inserted. When manufacturing the wafer mounting table 10, the protrusions 38 provided in a dot pattern on the entire upper surface of the lower base material 30 are inserted into the protrusion insertion holes 44 of the heat dissipation sheet 40, so that the heat dissipation sheet 40 is easily positioned. Furthermore, the screw member 50 is screwed in until the distance between the upper base material 20 and the lower base material 30 coincides with the height of the protrusions 38. As a result, the heat dissipation sheet 40 disposed between the upper base material 20 and the lower base material 30 is compressed until the entire sheet has the same thickness as or approximately the same thickness as the height of the protrusions 38. Therefore, the thermal conductivity of the heat dissipation sheet 40 does not vary greatly depending on the location. Furthermore, the thermally conductive paste 60 is interposed between the side surface of the protrusions 38 and the inner peripheral surface of the protrusion insertion hole 44 of the heat dissipation sheet 40, and between the top surface of the protrusions 38 and the lower surface of the upper base material 20. Therefore, the upper base material 20, the heat dissipation sheet 40, and the lower base material 30 can be closely attached to each other with as few gaps as possible. Therefore, the temperature uniformity of the wafer W is improved.

[0045] The thermally conductive paste 60 used is preferably a paste having a thermal conductivity of 0.5 W / mK or more. This further promotes thermal conduction from the upper base material 20 to the lower base material 30.

[0046] The upper base material 20 includes a ceramic base material 21 and a support base material 23 made of a metal or a metal ceramic composite material bonded to the lower surface of the ceramic base material 21 via a metal bonding layer 25, and the screw holes 24 are provided in the lower surface of the support base material 23. The support base material 23 is made of a metal or a metal ceramic composite material, and therefore has superior thermal conductivity compared to the ceramic base material 21. Therefore, the heat of the ceramic base material 21 can be efficiently conducted to the lower base material 30.

[0047] Furthermore, at least one of the multiple protrusions 38 is provided directly above the inlet 35a of the refrigerant flow path 35. The portion of the upper base material 20 directly above the inlet 35a of the refrigerant flow path 35 is more likely to be cooled by the refrigerant than other portions, but since the protrusion 38 is provided directly above the inlet 35a of the refrigerant flow path 35, excessive cooling by the refrigerant can be suppressed.

[0048] Furthermore, the through holes 36 of the lower base material 30 are provided so as not to intersect with the refrigerant flow paths 35. Therefore, there is no risk of the refrigerant leaking out from the through holes 36 into which the screw members 50 are inserted.

[0049] Furthermore, the lower base material 30 is made of an easily processable material. This allows the refrigerant flow paths 35 and protrusions 38 to be easily formed in the lower base material 30, thereby reducing processing costs. Furthermore, material costs can be kept lower than when the lower base material 30 is made of a composite material of metal and ceramic (e.g., MMC or CMC).

[0050] The thermal resistance of the heat dissipation sheet 40 is 0.35K cm 2 1 / W or less. In this way, heat from the upper substrate is quickly conducted to the lower substrate. The Young's modulus of the heat dissipation sheet 40 is preferably 100 MPa or less. In this way, the fastening force of the screw members 50 is easily transmitted evenly over the entire surface of the heat dissipation sheet 40, so that the entire surface of the heat dissipation sheet 40 is firmly attached to the upper substrate 20 and the lower substrate 30.

[0051] The absolute value of the difference in linear thermal expansion coefficient between the supporting substrate 23 and the ceramic substrate 21 at 40 to 400° C. is 1.5×10-6 / K or less. In this way, the difference in thermal expansion between the ceramic base 21 and the supporting base 23 is small, so that warping or damage to the upper base 20 due to thermal stress can be suppressed, and damage to the metal bonding layer 25 that bonds the ceramic base 21 and the supporting base 23 can also be suppressed. Furthermore, the metal bonding layer 25 improves the thermal conduction between the ceramic base 21 and the supporting base 23 compared to resin.

[0052] The support substrate 23 is preferably made of a composite material of metal and ceramic. The composite material of metal and ceramic can reduce the absolute value of the difference in linear thermal expansion coefficient with the ceramic substrate 21, and is tougher than ceramic materials, so it is less likely to break even when thermal stress occurs. In addition, such a composite material is conductive, so it can also be used as an RF electrode.

[0053] It is preferable that the heat dissipation sheet 40 is conductive. In this case, the lower base material 30 has the same potential as the supporting base material 23 and the metal bonding layer 25, so that the supporting base material 23 and the metal bonding layer 25 can be used as RF electrodes, and plasma can be easily generated above the wafer W. Note that a conductive screw member 50 may be used to set the lower base material 30 and the supporting base material 23 to the same potential via the screw member 50.

[0054] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms within the technical scope of the present invention.

[0055] In the above-mentioned embodiment, the through-hole 36 penetrating the lower base material 30 in the vertical direction is provided so as not to penetrate the protrusion 38 of the lower base material 30, but is not particularly limited thereto. For example, as shown in FIG. 7, the through-hole 36 may be provided so as to penetrate the protrusion 38. In this case, too, the thermally conductive paste 60 is interposed between the side surface of the protrusion 38 and the inner peripheral surface of the protrusion insertion hole 44 of the heat dissipation sheet 40, or between the top surface of the protrusion 38 and the lower surface of the upper base material 20 (the lower surface of the support base material 23). In this way, since it is not necessary to provide the heat dissipation sheet 40 with a communication hole (hole 46 in FIGS. 6A and 6B) communicating with the through-hole 36, the function of the heat dissipation sheet 40 is fully exhibited. In FIG. 7, the same components as those in the above-mentioned embodiment are given the same reference numerals.

[0056] In the above-mentioned embodiment, the lower base material 30 has the refrigerant flow passage 35 built therein, but the present invention is not limited thereto. For example, as in the wafer mounting table 110 shown in FIG. 8, the lower base material 130 may have a refrigerant flow passage groove 132 opening on the upper surface of the lower base material 130. In this case, the refrigerant flow passage 135 is formed by covering the opening of the refrigerant flow passage groove 132 with a heat dissipation sheet 40. The refrigerant flow passage groove 132 forms the side wall and bottom of the refrigerant flow passage 135, and the heat dissipation sheet 40 forms the ceiling of the refrigerant flow passage 135. In this way, the lower base material 130 can be formed by processing a single disk member. In FIG. 8, the same components as those in the above-mentioned embodiment are denoted by the same reference numerals.

[0057] In the above-described embodiment, the upper base material 20 includes the ceramic base material 21 and the support base material 23 bonded to the lower surface of the ceramic base material 21 via the metal bonding layer 25, and the screw hole 24 is provided in the lower surface of the support base material 23, but is not particularly limited to this. For example, as in the wafer mounting table 210 shown in FIG. 9, the upper base material 220 may be formed only of the ceramic base material 221. In this case, the screw hole 224 into which the screw member 50 is screwed is provided in the lower surface of the ceramic base material 221. Note that in FIG. 9, the same components as those in the above-described embodiment are denoted by the same reference numerals.

[0058] In the above-described embodiment, the through-hole 36 of the lower base material 30 is provided so as not to intersect with the refrigerant flow path 35, but this is not particularly limited. For example, as in the wafer mounting table 310 shown in FIG. 10, the through-hole 336 may be provided so as to intersect with the refrigerant flow path 35. As in the above-described embodiment, the through-hole 336 has a large diameter portion 336a and a small diameter portion 336b. An O-ring 51 made of resin or metal is disposed on a step surface 336c (the boundary between the large diameter portion 336a and the small diameter portion 336b) of the through-hole 336. The O-ring 51 is provided to prevent refrigerant leakage. prevention The through hole 336 is a member, and is compressed in the vertical direction by the step surface 336c of the through hole 336 and the head 50a of the screw member 50. In this way, it is not necessary to provide the refrigerant flow path 35 by detouring the screw member 50, and the degree of freedom in designing the refrigerant flow path 35 is improved. In addition, the O-ring 51 prevents the refrigerant from leaking out to the lower surface of the lower base material 30 from the through hole 336 into which the screw member 50 is inserted. In FIG. 10, the same components as those in the above-mentioned embodiment are denoted by the same reference numerals. In FIG. 8 described above, the through hole 36 may also be provided so as to intersect with the refrigerant flow path groove 132.

[0059] In the above-described embodiment, the protrusions 38 are provided in a dot pattern on the entire upper surface of the lower base material 30, but the present invention is not limited to this. For example, instead of providing the protrusions 38 on the upper surface of the lower base material 30, the protrusions 38 may be provided in a dot pattern on the entire lower surface of the upper base material 20 (the lower surface of the support base material 23), and the top surfaces of the protrusions may be in contact with the upper surface of the lower base material 30. In this case, too, the heat dissipation sheet 40 disposed between the upper base material 20 and the lower base material 30 is compressed until the entire sheet has the same thickness as or approximately the same thickness as the height of the protrusions. Therefore, the thermal conductivity of the heat dissipation sheet 40 does not vary significantly depending on the location, and the thermal uniformity of the wafer W is improved.

[0060] In the above embodiment, the heat dissipation sheet 40 is illustrated as being conductive, but the heat dissipation sheet 40 may be insulating.

[0061] In the above-described embodiment, the ceramic base material 21 has the wafer adsorbing electrode 22 built in. However, instead of or in addition to this, an RF electrode for generating plasma may be built in. In this case, a high-frequency power source is connected to the RF electrode instead of the lower base material 30. The ceramic base material 21 may also have a built-in heater electrode (resistance heating element). In this case, a heater power source is connected to the heater electrode. The ceramic base material 21 may have one built-in layer of electrodes, or two or more built-in layers of electrodes.

[0062] In the above-described embodiment, the coolant flow passage 35 is provided in a spiral shape from the inlet 35a to the outlet 35b, but the shape of the coolant flow passage 35 is not particularly limited.

[0063] In the above-described embodiment, the ceramic substrate 21 was produced by hot-press sintering a ceramic powder compact, but the compact may also be produced by stacking multiple tape compacts, by a mold casting method, or by compressing ceramic powder.

[0064] In the above-described embodiment, the lower base material 30 is made of an easily processable material, but is not limited thereto. For example, the lower base material 30 may be made of a composite material of metal and ceramic. However, in consideration of material costs, it is preferable to use an easily processable material such as aluminum or an aluminum alloy.

[0065] In the wafer mounting table 10 of the above-described embodiment, holes may be provided penetrating the wafer mounting table 10 from the lower surface of the lower base material 30 to the wafer mounting surface 21a. Examples of such holes include gas supply holes for supplying a thermally conductive gas (e.g., He gas) to the rear surface of the wafer W, and lift pin holes for inserting lift pins for raising and lowering the wafer W relative to the wafer mounting surface 21a. It is preferable to place a resin or metal O-ring at the location where the gas supply hole or lift pin hole penetrates the heat dissipation sheet 40. [Industrial Applicability]

[0066] The wafer stage of the present invention is used in, for example, a semiconductor manufacturing device. [Explanation of symbols]

[0067] 10 wafer mounting table, 20 upper substrate, 21 ceramic substrate, 21a wafer mounting surface, 21b hole, 22 wafer suction electrode, 23 support substrate, 23b hole, 24 screw hole, 25 metal bonding layer, 30 lower substrate, 30b terminal hole, 31, 32 disk member, 35 coolant flow path, 35a inlet, 35b outlet, 35c groove, 36 through hole, 36a large diameter portion, 36b small diameter portion, 36c step surface, 38 protrusion, 39 screw hole, 40 heat dissipation sheet, 44 protrusion insertion hole, 46, 47 hole, 50 screw member, 50a head, 50b foot, 51 O-ring, 52 wafer suction DC power source, 54 power supply terminal, 55 insulating tube, 60 thermal conductive paste, 62 RF power source, 64 power supply terminal, 70 Screw member, 80, 82a, 82b sealing member, 94 chamber, 96 mounting plate, 97 screw insertion hole, 98 shower head, 110 wafer mounting table, 130 lower base material, 132 coolant flow channel groove, 135 coolant flow channel, 210 wafer mounting table, 220 upper base material, 221 ceramic base material, 224 screw hole, 310 wafer mounting table, 336 through hole, 336a large diameter portion, 336b small diameter portion, 336c step surface.

Claims

1. an upper substrate including a ceramic substrate having an electrode built therein and a wafer mounting surface on an upper surface of the ceramic substrate; a lower base material disposed on a lower surface side of the upper base material and including a refrigerant flow path through which a refrigerant flows or a refrigerant flow path groove constituting a side wall and a bottom of the refrigerant flow path; A through hole penetrating the lower base material in the vertical direction; A plurality of protrusions are provided in a dot pattern on the entire upper surface of the lower substrate and abut against the lower surface of the upper substrate, or are provided in a dot pattern on the entire lower surface of the upper substrate and abut against the upper surface of the lower substrate; a heat dissipation sheet having a protrusion insertion hole into which the protrusion is inserted and disposed in a compressed state between the upper base material and the lower base material; a screw hole provided in a lower surface of the upper base material at a position facing the through hole; a screw member inserted into the through hole from the underside of the lower base material and screwed into the screw hole; a thermally conductive paste interposed between at least one of a side surface of the protrusion and an inner peripheral surface of the protrusion insertion hole of the heat dissipation sheet and a top surface of the protrusion and a lower surface of the upper base material; A wafer mounting table comprising:

2. The upper substrate comprises the ceramic substrate and a supporting substrate made of a metal or a metal-ceramic composite material bonded to a lower surface of the ceramic substrate via a metal bonding layer; The screw hole is provided on the lower surface of the support base material. The wafer stage according to claim 1 .

3. The through hole is provided so as to penetrate the protrusion. The wafer stage according to claim 1 .

4. The thermal resistance of the heat dissipation sheet is 0.35 K cm 2 / W or less, The wafer stage according to claim 1 .

5. The Young's modulus of the heat dissipation sheet is 100 MPa or less. The wafer stage according to claim 1 .

6. The thermal conductive paste has a thermal conductivity of 0.5 W / mK or more. The wafer stage according to claim 1 .

7. The through hole is provided so as not to intersect with the refrigerant flow path or the refrigerant flow path groove. The wafer stage according to claim 1 .

8. The through hole is provided so as to intersect with the refrigerant flow path or the refrigerant flow path groove, The lower base material has a refrigerant leakage prevention member that prevents the refrigerant from leaking out to a lower surface of the lower base material through the through hole into which the screw member is inserted. The wafer stage according to claim 1 .

9. The lower substrate is made of an easily processable material; The wafer stage according to claim 1 .

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