Wafer Placement Table

Abstract

A wafer placement plate (10) comprises a ceramic plate (20), a cooling plate (30), a bonding layer (40), a concave groove (21d), a plug placement hole (24), and a porous plug (50). The ceramic plate (20) has a wafer placement section (21) in which a plurality of small protrusions (21b) supporting the wafer (W) are installed on a reference surface (21c), and contains an electrode (22). The cooling plate (30) has a refrigerant flow path (32). The bonding layer (40) bonds the ceramic plate (20) and the cooling plate (30). The concave groove (21d) is formed on the reference surface (21c), and its bottom surface is lower than the reference surface (21c). The plug placement hole (24) penetrates the ceramic plate (20) in the thickness direction and is open on the bottom surface of the concave groove (21d). A porous plug (50) is placed in a plug placement hole (24), its top surface is at the same height as the bottom surface of a concave groove (21d), its outer surface is joined to the inner surface of the plug placement hole (24), and it allows for the flow of gas.

Description

Technology Field

[0001] The present invention relates to a wafer placement table. Background Technology

[0002] Conventionally, a wafer placement plate is known to have a ceramic plate containing an electrode, a cooling plate having a refrigerant flow path, and a bonding layer that bonds the ceramic plate and the cooling plate. For example, Patent Document 1 discloses that a through hole is formed penetrating the ceramic plate, and a porous plug is bonded to the through hole by sintering. Gas is supplied to the porous plug from a gas supply path installed in the cooling plate. In manufacturing such a wafer placement plate, a paste-type ceramic mixture serving as a precursor for the porous plug is filled into the through hole of the ceramic plate, and the ceramic mixture is fired to form the porous plug. If the top of the porous plug protrudes from the upper surface of the ceramic plate after firing, the protruding part of the porous plug is ground to make the top of the porous plug and the upper surface of the ceramic plate flat (a flat surface). Prior art literature

[0003] Patent Document 1: Japanese Patent Publication No. 2019-29384 The problem to be solved

[0004] However, when the protruding part of the porous plug is ground using a surface plate to eliminate the step between the top of the porous plug and the upper surface of the ceramic plate, there was a risk that particles would fall off from the porous plug and damage the upper surface of the ceramic plate. In addition, in Patent Document 1, a space for sealing gas was not installed on the lower side of the wafer, but if such a space were installed, a number of small protrusions would be formed on the upper surface of the ceramic plate by blast processing, etc. At that time, if there is no step between the top of the porous plug and the upper surface of the ceramic plate, there was a problem that fine dust would enter the porous plug. In addition, there was also a problem that the position of the wafer facing the porous plug was prone to becoming low temperature.

[0005] The present invention has been made to solve these problems, and its main purpose is to prevent problems from occurring in ceramic plates or porous plugs during manufacturing, as well as to prevent damage to the crack resistance of wafers during use. means of solving the problem

[0006] [1] The wafer placement unit of the present invention is,

[0007] A ceramic plate having a wafer placement section with a plurality of small protrusions supporting the wafer installed on a reference plane, and an electrode embedded therein,

[0008] A cooling plate having a refrigerant passage, and

[0009] A bonding layer that bonds the ceramic plate and the cooling plate, and

[0010] A concave groove formed on the above reference surface, the bottom surface of which is lower than the above reference surface, and

[0011] A plug placement hole that penetrates the ceramic plate in the thickness direction and is opened on the bottom surface of the concave groove, and

[0012] A porous plug that is placed in the plug placement hole, has a normal surface at the same height as the bottom surface of the concave groove, has an outer surface joined to the inner surface of the plug placement hole, and allows gas flow, and

[0013] Gas supply path supplying gas to the above porous plug

[0014] It is equipped with.

[0015] In this wafer placement stand, during the manufacturing process, a porous plug, whose top surface is at the same height as the bottom surface of a concave groove, may be polished on the surface of a ceramic plate (located higher than the reference surface of the ceramic plate) to which it is bonded in the plug placement hole. In this case, since the top surface of the porous plug is located lower than the reference surface, the top surface of the porous plug is not polished. Additionally, during a subsequent manufacturing process, a number of small protrusions may be formed on the surface of the ceramic plate. In this case, by masking the location where each small protrusion is formed and masking the top surface of the porous plug within the concave groove, and then milling away the unmasked area, it is possible to prevent fine dust from entering the porous plug. Meanwhile, when using the wafer placement stand, gas is supplied to the porous plug from the gas supply path. In this case, the location on the wafer facing the porous plug is prone to becoming colder than other locations because the gas pressure is high. However, here, the top surface of the porous plug is located lower than the reference surface. Therefore, compared to the case where the normal surface of the porous plug is at the same height as the reference surface, heat conduction from the region of the wafer facing the porous plug to the ceramic plate is suppressed. Consequently, it is possible to prevent that region from becoming excessively low in temperature.

[0016] In addition, in this specification, the term "identical" includes cases of substantially identical (e.g., within a tolerance range) in addition to cases of completely identical.

[0017] [2] In the wafer placement table described above (the wafer placement table described in [1]), the outer surface of the porous plug may be joined to the inner surface of the plug placement hole by sintering.

[0018] [3] In the wafer placement plate described above (the wafer placement plate described in [2] above), the durability temperature of the bonding layer may be lower than the sintering temperature of the ceramic plate. When manufacturing such a wafer placement plate, a porous plug is bonded to the plug placement hole of the ceramic plate by sintering, and then the ceramic plate and the cooling plate are bonded. This is because if the ceramic plate and the cooling plate are bonded while the plug placement hole is hollow, and then the porous plug is bonded to the plug placement hole by sintering, the sintering temperature will exceed the durability temperature of the bonding layer.

[0019] [4] In the wafer placement table described above (the wafer placement table described in any one of [1] to [3]), the distance from the bottom surface of the concave groove to the reference surface may be 0.005 mm or more and 0.5 mm or less. If this distance is 0.5 mm or less, it is possible to prevent discharge from occurring within the concave groove even if the wafer is treated with plasma when using the wafer placement table. In addition, if it is 0.005 mm or more, the effect of preventing problems from occurring in the ceramic plate or porous plug during manufacturing is obtained.

[0020] [5] In the wafer placement table described above (a wafer placement table described in any one of [1] to [4]), the top surface of the porous plug may be covered with a protective cover having a plurality of pores, and the top surface of the protective cover may be positioned lower than the top surface of the small protrusion. By doing so, the lifespan of the porous plug can be extended, and the protective cover can be prevented from lifting the wafer.

[0021] [6] In the wafer placement table described above (a wafer placement table described in any one of [1] to [5]), the gas supply path may be a path that supplies gas to the porous plug through a bonding layer penetration hole formed at a position facing the porous plug among the bonding layers from the lower surface of the cooling plate, and the bonding layer penetration hole may be of a size that the porous plug cannot pass through. In this way, the bonding layer supports the porous plug from below, so that the porous plug can be prevented from coming out of the plug placement hole during manufacturing or use of the wafer placement table. Brief explanation of the drawing

[0022] FIG. 1 is a cross-sectional view of a wafer placement table (10). FIG. 2 is a plan view of a ceramic plate (20). Fig. 3 is a partial enlarged view of Fig. 1. FIG. 4 is a manufacturing process diagram of a ceramic plate (20). FIG. 5 is a manufacturing process diagram of a wafer placement table (10). Fig. 6 is a partial enlarged view of another example. Fig. 7 is a partial enlarged view of another example. Specific details for implementing the invention

[0023] Suitable embodiments of the present invention are described below with reference to the drawings. FIG. 1 is a longitudinal cross-sectional view of a wafer placement table (10) (a cross-sectional view when cut along a plane including the central axis of the wafer placement table (10)), FIG. 2 is a plan view of a ceramic plate (20), and FIG. 3 is a partial enlarged view of FIG. 1.

[0024] A wafer placement plate (10) is used to perform CVD or etching, etc., on a wafer (W) using plasma, and is equipped with a ceramic plate (20), a cooling plate (30), a metal bonding layer (40), and a porous plug (50).

[0025] The ceramic plate (20) is a ceramic disc (e.g., diameter 300 mm, thickness 5 mm) made of alumina sintered body or aluminum nitride sintered body. A wafer placement section (21) is installed on the upper surface of the ceramic plate (20). The ceramic plate (20) contains an electrode (22). In the wafer placement section (21), a seal band (21a) is formed along the outer edge, and a plurality of circular small protrusions (21b) are formed in the area surrounded by the seal band (21a). The seal band (21a) and the circular small protrusions (21b) are of the same height, and the height is, for example, several μm to several tens of μm. The electrode (22) is a flat mesh electrode used as an electrostatic electrode and is capable of applying a DC voltage. When a DC voltage is applied to this electrode (22), the wafer (W) is fixed by electrostatic adsorption to the wafer placement portion (21) (specifically, the upper surface of the seal band (21a) and the upper surface of the circular small protrusion (21b)), and when the application of the DC voltage is released, the adhesive fixation of the wafer (W) to the wafer placement portion (21) is released. Meanwhile, the part of the wafer placement portion (21) where the seal band (21a) or the circular small protrusion (21b) is not installed is called the reference surface (21c). The reference surface (21c) is a horizontal surface.

[0026] In the reference surface (21c), a circular concave groove (21d) is formed in a flat surface. The bottom surface of the concave groove (21d) is lower than the reference surface (21c). The concave groove (21d) is formed at multiple locations on the ceramic plate (20) (e.g., multiple locations installed at equal intervals along the circumferential direction as shown in FIG. 2). The height from the bottom surface of the concave groove (21d) to the reference surface (21c) is preferably 0.005 mm or more and 0.5 mm or less, more preferably 0.005 mm or more and 0.2 mm or less, and in a device that applies high voltage, it is particularly preferably 0.005 mm or more and 0.1 mm or less.

[0027] The plug placement hole (24) is a cylindrical hole that penetrates the ceramic plate (20) in the vertical direction (thickness direction) and is opened on the bottom surface of the concave groove (21d). The plug placement hole (24) is also formed at multiple locations on the ceramic plate (20) (e.g., multiple locations installed at equal intervals along the circumferential direction as shown in FIG. 2), just like the concave groove (21d). A porous plug (50), which will be described later, is placed in the plug placement hole (24).

[0028] The cooling plate (30) is a disc with good thermal conductivity (a disc with the same diameter as or larger than that of the ceramic plate (20). Inside the cooling plate (30), a refrigerant passage (32) through which refrigerant circulates and a gas hole (34) for supplying gas to a porous plug (50) are formed. The refrigerant passage (32) is formed so as to be continuous from the inlet to the outlet without interruption across the entire front surface of the cooling plate (30) in a flat state. The gas hole (34) is a cylindrical hole and is formed at a position opposite to the plug placement hole (24). The material of the cooling plate (30) may be, for example, a metal material or a composite material of metal and ceramic. Examples of metal materials include Al, Ti, Mo, or alloys thereof. Examples of composite materials of metal and ceramic include metal matrix composites (metal matrix composites (MMC)) and ceramic matrix composites (ceramic matrix composites (CMC)). Specific examples of such composite materials include materials containing Si, SiC, and Ti, or materials in which Al and / or Si are impregnated into a porous SiC body. A material containing Si, SiC, and Ti is called SiSiCTi, a material in which Al is impregnated into a porous SiC body is called AlSiC, and a material in which Si is impregnated into a porous SiC body is called SiSiC. When the ceramic plate (20) is an alumina plate, it is preferable to use an MMC (such as AlSiC or SiSiCTi) with a coefficient of thermal expansion close to that of alumina as the material used for the cooling plate (30).

[0029] The metal bonding layer (40) bonds the lower surface of the ceramic plate (20) and the upper surface of the cooling plate (30). The metal bonding layer (40) is formed, for example, by thermal compression bonding (TCB). TCB refers to a known method in which a metal bonding material is inserted between two members to be bonded, and the two members are pressure-bonded while heated to a temperature below the solidus temperature of the metal bonding material. The metal bonding layer (40) has a bonding layer penetration hole (42) that penetrates the metal bonding layer (40) in the vertical direction at a position opposite to the gas hole (34). In FIG. 3, the diameter of the bonding layer penetration hole (42) is made larger than the diameter of the porous plug (50), but the diameter of the bonding layer penetration hole (42) may be made smaller than the diameter of the porous plug (50) so that the porous plug (50) cannot pass through it.

[0030] The porous plug (50) is a cylindrical plug that allows gas flow and is placed in the plug placement hole (24). The height of the top surface of the porous plug (50) is the same as the height of the bottom surface of the concave groove (21d). The outer surface of the porous plug (50) is joined to the inner surface of the plug placement hole (24) by sintering. The height of the bottom surface of the porous plug (50) is the same as the height of the bottom surface of the ceramic plate (20). In this embodiment, the porous plug (50) is a porous bulk body obtained by sintering ceramic powder. For the ceramic, for example, alumina or aluminum nitride can be used. The porosity of the porous plug (50) is preferably 30% or more, and the average pore diameter is preferably 20 μm or more. The porous plug (50) can be manufactured, for example, in accordance with the method described in Patent Document 1.

[0031] In this embodiment, the gas hole (34) of the cooling plate (30) is connected to an external gas supply device (not shown). The gas supplied to the gas hole (34) from the gas supply device is sealed in a space installed on the lower side of the wafer (W) of the wafer placement section (21) through the gas supply path (gas hole (34), bonding layer penetration hole (42), and porous plug (50)) of the wafer placement section (10). The space installed on the lower side of the wafer (W) is a space surrounded by the wafer (W), the seal band (21a), the circular small protrusion (21b), the reference surface (21c), the bottom surface of the concave groove (21d), and the top surface of the porous plug (50).

[0032] Next, an example of use of the wafer placement unit (10) configured in this way will be described. First, with the wafer placement unit (10) installed in a chamber not shown, a wafer (W) is placed in the wafer placement section (21). Then, the inside of the chamber is depressurized by a vacuum pump to adjust to a predetermined vacuum level, and a DC voltage is applied to the electrode (22) of the ceramic plate (20) to generate an electrostatic adsorption force, thereby adsorbing and fixing the wafer (W) to the wafer placement section (21) (specifically, the upper surface of the seal band (21a) or the upper surface of the circular protrusion (21b)). Next, the inside of the chamber is made into a reaction gas atmosphere at a predetermined pressure (e.g., tens to hundreds of Pa), and in this state, a high-frequency voltage is applied between the upper electrode not shown installed in the ceiling part of the chamber and the cooling plate (30) of the wafer placement unit (10) to generate plasma. The surface of the wafer (W) is treated by the generated plasma. A refrigerant is circulated in the refrigerant flow path (32) of the cooling plate (30). Gas is introduced into the gas hole (34) from a gas supply device not shown. As the gas, a heat-conducting gas (e.g., helium) is used. The gas passes through the gas hole (34), the bonding layer penetration hole (42), and the porous plug (50), and is supplied to and sealed in a space installed on the lower side of the wafer (W). Due to the presence of this backside gas, heat conduction between the wafer (W) and the ceramic plate (20) is carried out efficiently.

[0033] Next, an example of manufacturing a wafer placement table (10) will be described based on FIGS. 4 and FIGS. 5. FIGS. 4 is a manufacturing process diagram of a ceramic plate (20), and FIGS. 5 is a manufacturing process diagram of a wafer placement table (10).

[0034] First, a disc-shaped ceramic molded body containing an electrode (22) is produced, and the ceramic molded body is fired to obtain a ceramic plate (20) as a ceramic sintered body (Fig. 4a). The ceramic molded body can be produced by, for example, by placing raw material powder, such as ceramic powder mixed with a sintering aid, into a mold and pressurizing it.

[0035] Next, a plug placement hole (24) is formed in the ceramic plate (20) (Fig. 4b), and a paste-type ceramic mixture (56) that serves as a precursor for the porous plug (50) is filled into the plug placement hole (24) (Fig. 4c). The ceramic mixture (56) is a mixture of ceramic particles, a sintering aid, combustion loss particles, etc. As for the combustion loss particles, it is preferable to use, for example, organic particles that have an average particle size larger than the average particle size of the ceramic particles and are combusted and lost at the temperature at which the ceramic particles are sintered.

[0036] Next, the ceramic plate (20), which has the ceramic mixture (56) filled into the plug placement hole (24), is heated to a temperature at which the ceramic particles of the ceramic mixture (56) can be sintered. As a result, the combustion-lost particles in the ceramic mixture (56) are lost, and the ceramic particles sinter with each other, and the ceramic particles and the particles on the inner surface of the plug placement hole (24) are sintered. By this, a porous plug (50) is formed within the plug placement hole (24) (Fig. 4d). The porous plug (50) is a sintered ceramic body having pores. Additionally, the outer surface of the porous plug (50) and the inner surface of the plug placement hole (24) are joined by sintering.

[0037] Next, a cylindrical grinding stone (90) (Fig. 4d) with a larger diameter than the porous plug (50) is used to grind the porous plug (50) and its surroundings to form a circular concave groove (28) on the flat surface (Fig. 4e). Next, the upper surface of the ceramic plate (20) is polished using a polishing plate (92) (Fig. 4e) (Fig. 4f). Polishing is performed until the depth of the concave groove (28) reaches a predetermined depth (the depth of the concave groove (21d)). By doing so, the concave groove (28) becomes the concave groove (21d). At this time, since the polishing plate (92) does not come into contact with the top surface of the porous plug (50), particles fall out from the top surface of the porous plug (50) and do not damage the upper surface of the ceramic plate (20).

[0038] Next, the upper surface of a pre-fabricated cooling plate (30) (a cooling plate (30) having a refrigerant flow path (32) and a plurality of gas holes (34)) and the lower surface of a ceramic plate (20) are joined by a TCB to obtain a bonded body (84) (Fig. 5a). The TCB is performed, for example, as follows. First, a metal bonding material is inserted between the lower surface of the ceramic plate (20) and the upper surface of the cooling plate (30) to form a laminate. At this time, the plug placement hole (24) of the ceramic plate (20), the round hole pre-formed in the metal bonding material, and the gas hole (34) of the cooling plate (30) are laminated so that they are coaxial. Then, the laminated body is bonded by applying pressure at a temperature below the solidus temperature of the metal bonding material (e.g., between a temperature 20°C less than the solidus temperature and the solidus temperature), and then returned to room temperature. By this, the metal bonding material becomes a metal bonding layer (40), and the round hole of the metal bonding material becomes a bonding layer penetration hole (42), thereby obtaining a bonded body (84) in which the ceramic plate (20) and the cooling plate (30) are bonded to the metal bonding layer (40). At this time, an Al-Mg-based bonding material or an Al-Si-Mg-based bonding material may be used as the metal bonding material. For example, when performing TCB using an Al-Si-Mg-based bonding material, the laminated body is pressed while heated under a vacuum atmosphere. It is preferable to use a metal bonding material with a thickness of approximately 100 μm.

[0039] Next, the area forming the seal band (21a) and the area forming the circular small protrusion (21b) on the flat upper surface of the ceramic plate (20) are covered with a mask (M), and the bottom surface of the concave groove (21d) (including the top surface of the porous plug (50)) is also covered with a mask (M) (Fig. 5b). In this state, blast processing is performed on the exposed area of ​​the ceramic plate (20) that is not covered by the mask (M) to lower the height of the exposed area. At this time, since the top surface of the porous plug (50) is covered with the mask (M), fine dust is not generated from the porous plug (50) by the blast. Afterward, the mask is removed. By doing so, a ceramic plate (20) is obtained in which the seal band (21a), the circular small protrusion (21b), and the reference surface (21c) are formed on the upper surface (Fig. 5c). A wafer placement plate (10) is obtained in this manner.

[0040] In the wafer placement table (10) described in detail above, during the manufacturing process, a porous plug (50), whose top surface is at the same height as the bottom surface of the concave groove (28), is polished on the surface of the ceramic plate (20) coupled to the plug placement hole (24) (at least at a position higher than the reference surface of the ceramic plate). In that case, since the top surface of the porous plug (50) is at a position lower than the surface of the ceramic plate (20), the top surface of the porous plug (50) is not polished (Figs. 4e and 4f). In addition, in the subsequent manufacturing process, a plurality of circular small protrusions (21b) are formed on the surface of the ceramic plate (20). In that case, the location where each circular small protrusion (21b) is formed is masked, and the top surface of the porous plug (50) within the concave groove (21d) is masked, and then the unmasked area is cut away, thereby preventing fine dust from entering the porous plug (50) (Figs. 5b and 5c).

[0041] Meanwhile, when using the wafer placement unit (10), gas is supplied to the porous plug (50) from the gas supply path (gas hole (34), etc.). In this case, the location of the wafer (W) facing the porous plug (50) is prone to becoming colder than other locations because the gas pressure is high. However, here, the top surface of the porous plug (50) is lower than the reference surface (21c). Therefore, compared to the case where the top surface of the porous plug (50) is at the same height as the reference surface (21c), heat conduction from the area of ​​the wafer (W) facing the porous plug (50) to the ceramic plate (20) is suppressed (because the gas has a lower thermal conductivity than the ceramic plate (20)). Thus, it is possible to prevent that area from becoming excessively cold.

[0042] Additionally, the durability temperature of the metal bonding layer (40) is lower than the sintering temperature of the ceramic plate (20). Therefore, when manufacturing a wafer placement table (10), a porous plug (50) is bonded to the plug placement hole (24) of the ceramic plate (20) by sintering, and then the ceramic plate (20) and the cooling plate (30) are bonded. This is because if the ceramic plate (20) and the cooling plate (30) are bonded while the plug placement hole (24) is hollow, and then the porous plug (50) is bonded to the plug placement hole (24) by sintering, the sintering temperature will exceed the durability temperature of the metal bonding layer (40). Therefore, in the final process of manufacturing the wafer placement table (10), the porous plug (50) cannot be attached to the ceramic plate (20). For example, in the wafer placement table (10), a porous plug (50) is not placed in the plug placement hole (24), and finally, the porous plug (50) cannot be joined to the plug placement hole (24) by sintering.

[0043] In addition, it is preferable that the distance from the bottom surface of the concave groove (21d) to the reference surface (21c) be 0.005 mm or more and 0.5 mm or less. If this distance is excessively long, there is a risk that an arc discharge may occur when the wafer (W) is treated with plasma, as electrons generated as gas (e.g., helium gas) ionizes within the concave groove (21d) accelerate and collide with other helium. However, if this distance is 0.5 mm or less, such a discharge can be prevented. Furthermore, if it is 0.005 mm or more, the effect of preventing problems with the ceramic plate or porous plug during manufacturing is obtained.

[0044] Meanwhile, the present invention is not limited at all to the aforementioned embodiments and can be implemented in various forms as long as they fall within the technical scope of the present invention.

[0045] In the above-described embodiment, as shown in FIG. 6, the top surface of the porous plug (50) may be covered with an electrically insulating protective cover (60) having a plurality of pores (62). The top surface of this protective cover (60) is located at a lower position than the top surface of the circular protrusion (21b) (e.g., at the same height as the reference surface (21c)). By doing so, the lifespan of the porous plug (50) can be extended, and the protective cover (60) can be prevented from lifting the wafer (W). Meanwhile, in FIG. 6, the same reference numerals are used for components identical to those in the above-described embodiment.

[0046] In the above-described embodiment, as illustrated in FIG. 7, gas may be supplied to the porous plug (50) through a plurality of bonding layer penetration holes (44) formed in the metal bonding layer (40) at a position facing the porous plug (50) from the gas hole (34) of the cooling plate (30). In this case as well, the metal bonding layer (40) supports the porous plug (50) from below. By doing so, the porous plug (50) can be more reliably prevented from falling out of the plug placement hole (24) during manufacturing or use of the wafer placement table (10). Meanwhile, in FIG. 7, the same reference numerals are used for components identical to those in the above-described embodiment.

[0047] In the above-described embodiment, a porous plug (50) is formed within the plug placement hole (24) by filling the plug placement hole (24) of the ceramic plate (20) with a paste-type ceramic mixture (56) and then heating the ceramic particles of the ceramic mixture (56) to a temperature at which they can be sintered, but this is not particularly limited to this. For example, a porous plug (50) may be manufactured separately, and after inserting the porous plug (50) into the plug placement hole (24) of the ceramic plate (20), the particles on the outer surface of the porous plug (50) and the particles on the inner surface of the plug placement hole (24) may be processed at a temperature at which they sinter. At this time, a paste-type ceramic mixture may be interposed between the outer surface of the porous plug (50) and the inner surface of the plug placement hole (24) before sintering. Alternatively, a porous plug (50) may be formed by depositing a ceramic spray film or a laser sintered film in the empty plug placement hole (24) of the ceramic plate (20).

[0048] In the above-described embodiment, the gas holes (34) of the cooling plate (30) are formed corresponding to each of the plurality of porous plugs (50), but are not particularly limited to this. For example, instead of forming the gas holes (34), a circular or arc-shaped gas common path may be formed in a planar manner at the interface between the cooling plate (30) and the metal bonding layer (40), a gas introduction path connected to the gas common path may be installed from the lower surface of the cooling plate (30), and a gas distribution path may be installed to distribute gas from the gas common path to each porous plug (50).

[0049] In the above-described embodiment, an electrostatic electrode is exemplified as the electrode (22) embedded in the ceramic plate (20), but it is not particularly limited thereto. For example, instead of or in addition to the electrode (22), a heater electrode (resistive heating element) may be embedded in the ceramic plate (20), or an RF electrode may be embedded.

[0050] In the above-described embodiment, the ceramic plate (20) and the cooling plate (30) are bonded with a metal bonding layer (40), but a resin adhesive layer may be used instead of the metal bonding layer (40). The durability temperature of the resin adhesive layer is lower than the sintering temperature of the ceramic plate (20).

[0051] In the above-described embodiment, a circular projection (21b) was exemplified as a projection, but it is not particularly limited to this. For example, the projection may be polygonal when viewed in planar form. Industrial applicability

[0052] The present invention can be used, for example, in a device for processing wafers. Explanation of the symbols

[0053] 10: Wafer placement base, 20: Ceramic plate, 21: Wafer placement section, 21a: Seal band, 21b: Circular small protrusion, 21c: Reference plane, 21d: Concave groove, 22: Electrode, 24: Plug placement hole, 28: Concave groove, 30: Cooling plate, 32: Refrigerant flow path, 34: Gas hole, 40: Metal bonding layer, 42: Bonding layer through hole, 44: Bonding layer through hole, 50: Porous plug, 56: Ceramic mixture, 60: Protective cover, 62: Pore, 84: Assembly, 90: Grinding stone, 92: Surface plate, W: Wafer.

Claims

Claim 1 A wafer placement section having a plurality of small protrusions supporting a wafer installed on a reference surface, a ceramic plate containing an electrode, a cooling plate having a refrigerant flow path, a bonding layer bonding the ceramic plate and the cooling plate, a concave groove formed on the reference surface with a bottom surface lower than the reference surface, a plug placement hole penetrating the ceramic plate in the thickness direction and open at the bottom surface of the concave groove, a porous plug disposed in the plug placement hole with a top surface at the same height as the bottom surface of the concave groove and an outer surface bonded to the inner surface of the plug placement hole allowing gas flow, and a gas supply path supplying gas to the porous plug, wherein the top surface of the porous plug is covered by a protective cover having a plurality of pores, and the top surface of the protective cover is located at a position lower than the top surface of the small protrusions. Claim 2 In claim 1, the outer surface of the porous plug is a wafer placement plate that is joined to the inner surface of the plug placement hole by sintering. Claim 3 In paragraph 2, the durability temperature of the bonding layer is lower than the sintering temperature of the ceramic plate. Claim 4 A wafer placement plate according to any one of claims 1 to 3, wherein the distance from the bottom surface of the concave groove to the reference surface is 0.005 mm or more and 0.5 mm or less. Claim 5 delete Claim 6 A wafer placement section having a plurality of small protrusions supporting a wafer installed on a reference surface, a ceramic plate containing an electrode, a cooling plate having a refrigerant flow path, a bonding layer bonding the ceramic plate and the cooling plate, a concave groove formed on the reference surface with a bottom surface lower than the reference surface, a plug placement hole penetrating the ceramic plate in the thickness direction and open at the bottom surface of the concave groove, a porous plug disposed in the plug placement hole with a top surface at the same height as the bottom surface of the concave groove and an outer surface bonded to the inner surface of the plug placement hole allowing gas flow, and a gas supply path supplying gas to the porous plug, wherein the gas supply path is a path extending from the bottom surface of the cooling plate to the bottom surface of the porous plug through a bonding layer penetration hole formed at a position facing the porous plug in the bonding layer, and the bonding layer penetration hole is of a size through which the porous plug cannot pass.

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