Wafer placement table

Abstract

The wafer mounting table 10 includes a ceramic plate 20 having a wafer mounting surface 21 on its upper surface, a vertically penetrating pore 26, and a built-in electrode 22, a conductive plate 30 joined to the lower surface of the ceramic plate 20 and provided with a gas supply passage 31, a plug chamber 32 formed as a recess extending from the upper surface of the conductive plate 30 toward the lower surface of the conductive plate 30 and communicating with the pore 26 and the gas supply passage 31, an insulating gas permeable plug 40 disposed in the plug chamber 32 and allowing gas to pass therethrough, and a dense insulating film 50. The dense insulating film 50 allows ventilation of a gas outlet portion 44 on the upper surface of the insulating gas permeable plug 40, which serves as a gas flow path to the pore 26, and is disposed across the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 40, thereby covering the boundary between the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 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 plate having a wafer mounting surface on the upper surface thereof and a base plate that is joined to the lower surface of the ceramic plate and has a gas introduction passage. In Patent Document 1, such a wafer mounting table is provided with an insulating first porous portion disposed in a through hole of the ceramic plate, and an insulating second porous portion that is fitted in a recess provided on the ceramic plate side of the base plate so as to face the first porous portion. Gas supplied to the gas introduction passage passes through the second porous portion and the first porous portion and flows into the space between the wafer mounting surface and the wafer, and is used to cool the object. The second porous portion has a ceramic porous body and a ceramic insulating film formed by thermal spraying on the side surface of the ceramic porous body. The ceramic insulating film is in contact with the inner peripheral surface of the recess of the base plate. It is described that the presence of such a second porous portion enables high insulation to be achieved. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2020-72262 A Summary of the Invention [Problem to be solved by the invention]

[0004] However, even when an insulating second porous portion is present as in Patent Document 1, discharges may occur along the path between the side surface of the ceramic porous body in the second porous portion and the ceramic insulating film.

[0005] The present invention has been made to solve these problems, and has as its main object to suppress discharge around the side surface of an insulating gas passing plug. [Means for solving the problem]

[0006] In order to achieve the above-mentioned main object, the present invention adopts the following means.

[0007] [1] The wafer mounting table of the present invention comprises: a ceramic plate having a wafer mounting surface on an upper surface thereof, a vertically extending hole formed therethrough, and a built-in electrode; a conductive plate bonded to a lower surface of the ceramic plate and having a gas supply passage; a plug chamber formed as a recess extending from an upper surface of the conductive plate toward a lower surface of the conductive plate and communicating with the fine hole and the gas supply passage; an insulating gas-permeable plug disposed in the plug chamber and allowing gas to pass therethrough; a dense insulating film that allows ventilation of a gas outlet portion of an upper surface of the insulating gas passing plug, the gas outlet portion being a flow path of gas to the pore, and that is disposed across the upper surface of the conductive plate and the upper surface of the insulating gas passing plug to cover a boundary portion between the upper surface of the conductive plate and the upper surface of the insulating gas passing plug; It is equipped with the following:

[0008] In this wafer mounting table, the dense insulating film is disposed across the upper surface of the conductive plate and the upper surface of the insulating gas permeable plug, thereby covering the boundary between the upper surface of the conductive plate and the upper surface of the insulating gas permeable plug. The presence of such a dense insulating film makes it possible to suppress discharge from occurring in a path in the vertical direction from the boundary between the upper surface of the conductive plate and the upper surface of the insulating gas permeable plug along the side surface of the insulating gas permeable plug. In addition, the dense insulating film allows ventilation of the gas outlet portion of the insulating gas permeable plug, so that gas can flow from the gas supply passage to the pores via the insulating gas permeable plug.

[0009] [2] In the above-mentioned wafer mounting table (the wafer mounting table described in [1] above), a convex portion is formed on the upper surface of the insulating gas passing plug, the upper surface of which becomes the gas outlet portion, and the upper surface of the dense insulating film and the upper surface of the convex portion may be located on the same plane.

[0010] [3] In the above-mentioned wafer stage (the wafer stage according to the above-mentioned [1] or [2]), the dense insulating film may be a thermal spray film or an aerosol deposition film. In this way, the dense insulating film can be produced relatively easily.

[0011] [4] The above-mentioned wafer mounting table (the wafer mounting table described in any one of [1] to [3] above) may include an elastic member disposed between the lower surface of the insulating gas passing plug and the bottom surface of the plug chamber. In this way, the presence of the elastic member can prevent the insulating gas passing plug from being pushed upward when the wafer mounting table is heated during use and the conductive plate is warped into an upwardly convex shape. This can prevent cracks from occurring in the dense insulating film. In this case, the elastic member may provide a gap between the lower surface of the insulating gas passing plug and the bottom surface of the plug chamber.

[0012] [5] In the above-mentioned wafer stage (the wafer stage described in the above [4]), the elastic member may be made of a heat-resistant resin. In this way, the elastic member can be produced relatively easily.

[0013] [6] In the above-mentioned wafer stage (the wafer stage described in any one of [1] to [5] above), the insulating gas passing plug may be a porous body. [Brief description of the drawings]

[0014] [Figure 1] FIG. [Diagram 2] Enlarged view of part A in Figure 1. [Diagram 3] Cross-sectional view of FIG. 2 taken along line B-B. [Figure 4]5A to 5C are diagrams showing the manufacturing process of the wafer mounting table 10. [Diagram 5] 3 is an enlarged view of a wafer mounting table 910 of a comparative embodiment, corresponding to FIG. 2. FIG. [Figure 6] 3 is an enlarged view of the wafer mounting table 110 corresponding to FIG. 2; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] A preferred embodiment of the present invention will be described with reference to the drawings. Fig. 1 is a vertical cross-sectional view of the wafer mounting table 10, Fig. 2 is an enlarged view of part A in Fig. 1, and Fig. 3 is a cross-sectional view along the line BB in Fig. 2 (a cross-sectional view of the front view (overall view) of the wafer mounting table 10 cut along the line BB in Fig. 2). 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" can become "lower" and "upper", "left" and "right", or "front" and "rear".

[0016] 1, the wafer mounting table 10 includes a ceramic plate 20, a conductive plate 30, and an insulating gas passing plug 40. In addition, the wafer mounting table 10 includes a dense insulating film 50 and a bonding sheet 60, as shown in FIG.

[0017] The ceramic plate 20 is a ceramic disk (e.g., 300 mm in diameter and 5 mm in thickness) made of sintered alumina or sintered aluminum nitride. The upper surface of the ceramic plate 20 is a wafer mounting surface 21 on which the wafer W is mounted. The ceramic plate 20 has a built-in electrode 22. The electrode 22 is a flat mesh electrode used as an electrostatic electrode, and is connected to an external DC power source via a power supply member (not shown). A low-pass filter may be disposed midway through the power supply member. The power supply member is electrically insulated from the conductive plate 30. When a DC voltage is applied to the electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 by electrostatic attraction force, and when the application of the DC voltage is stopped, the wafer W is released from the attraction and fixation to the wafer mounting surface 21. The ceramic plate 20 is provided with pores 26. The pores 26 penetrate the ceramic plate 20 in the vertical direction, and serve as gas passages from the lower surface of the ceramic plate 20 to the wafer mounting surface 21. The ceramic plate 20 has a plurality of pores 26 therein.

[0018] The conductive plate 30 is a disk (having the same diameter as or larger than the ceramic plate 20) with good thermal conductivity. The conductive plate 30 has a gas supply passage 31 and a plug chamber 32. The plug chamber 32 is opened on the upper surface (the surface on the ceramic plate 20 side) of the conductive plate 30, and is configured as a recess provided from the upper surface toward the lower surface. The internal space of the plug chamber 32 is, for example, cylindrical. The gas supply passage 31 is a gas passage from the plug chamber 32 to the lower surface of the conductive plate 30. In this embodiment, the gas supply passage 31 is configured as a through hole that penetrates in the vertical direction from the bottom surface of the plug chamber 32 of the conductive plate 30 to the lower surface of the conductive plate 30. A refrigerant flow passage (not shown) is formed inside the conductive plate 30. The refrigerant flowing through the refrigerant flow passage is preferably a liquid, and is preferably electrically insulating. An example of the electrically insulating liquid is a fluorine-based inert liquid. The coolant flow path is formed in a single stroke from one end (inlet) to the other end (outlet) across the entire conductive plate 30 in a plan view. A supply port and a recovery port of an external coolant device (not shown) are connected to one end and the other end of the coolant flow path, respectively. The conductive plate 30 is connected to a radio frequency (RF) power source and is also used as an RF electrode.

[0019] Examples of the material of the conductive plate 30 include metal materials and composite materials of metal and ceramic. Examples of the metal materials include Al, Ti, Mo, and alloys thereof. Examples of the composite materials of metal and ceramic include metal matrix composite materials (MMC) and ceramic matrix composite materials (CMC). Specific examples of such composite materials include a material containing Si, SiC, and Ti (also called SiSiCTi), a material in which a porous SiC body is impregnated with Al and / or Si, and a composite material of Al2O3 and TiC. It is preferable to select a material for the conductive plate 30 that has a thermal expansion coefficient close to that of the material of the ceramic plate 20.

[0020] The insulating gas-permeable plug 40 is an insulating member through which gas can pass, and is disposed in the plug chamber 32. In this embodiment, the insulating gas-permeable plug 40 is a porous body. The insulating gas-permeable plug 40 communicates with the gas supply passage 31 and the pores 26, and this allows the gas in the gas supply passage 31 to reach the wafer mounting surface 21. The insulating gas-permeable plugs 40 are provided in the conductive plate 30 in the same number as the pores 26, the gas supply passages 31, and the plug chamber 32, and they correspond one-to-one to each other. The insulating gas-permeable plug 40 has a cylindrical main body 41 and a cylindrical protrusion 42 that is provided in the center of the upper surface of the main body 41 and has a smaller diameter than the main body 41. The upper surface of the protrusion 42 is located directly below the pores 26, and serves as an outlet for gas from the insulating gas-permeable plug 40 to the pores 26. More specifically, a portion of the upper surface of the protrusion 42 that is not in contact with the bonding sheet 60 (a circular region indicated by a dotted line in FIG. 3) serves as a gas outlet portion 44. The insulating gas-permeable plug 40 may have a side surface (outer peripheral surface) of the main body 41 bonded to the inner peripheral surface of the plug chamber 32, or a male thread portion provided on the side surface of the insulating gas-permeable plug 40 may be screwed into a female thread portion provided on the inner peripheral surface of the plug chamber 32. The upper surface of the insulating gas-permeable plug 40 excluding the protrusion 42 is located on the same plane as the upper surface of the conductive plate 30.

[0021] The insulating gas passing plug 40 may be a porous bulk body obtained by sintering ceramic powder. As the ceramic, for example, alumina or aluminum nitride may be used. The porosity of the insulating gas passing plug 40 is preferably 30% or more, and the average pore diameter is preferably 15 μm or more. The porosity of the insulating gas passing plug 40 may be 70% or less.

[0022] An elastic member 48 is disposed between the lower surface of the insulating gas passing plug 40 and the bottom surface of the plug chamber 32 of the conductive plate 30. In this embodiment, the elastic member 48 has a ring-like shape centered on the position of the opening of the gas supply passage 31 when viewed from above. The elastic member 48 is in contact with only a part of the lower surface of the insulating gas passing plug 40 and a part of the bottom surface of the plug chamber 32, so that a gap S exists between the lower surface of the insulating gas passing plug 40 and the bottom surface of the plug chamber 32 of the conductive plate 30. The vertical height of the gap S may be, for example, 0.1 mm or more and 1 mm or less. The elastic member 48 is disposed at a position on the bottom surface of the plug chamber 32 other than the opening of the gas supply passage 31 so as not to impede the passage of gas from the gas supply passage 31 to the insulating gas passing plug 40. For example, a heat-resistant resin can be used as the elastic member 48. Examples of the heat-resistant resin include fluorine-based resins such as Teflon (Teflon is a registered trademark), acrylic resins, and polyimide resins. These materials are preferable because they have the heat resistance of 200° C. or more required for the wafer stage 10 and do not easily generate gas even when used in a vacuum.

[0023] The dense insulating film 50 is a dense insulating film that covers the upper surfaces of the conductive plate 30 and the insulating gas permeable plug 40. More specifically, the dense insulating film 50 is disposed across the upper surface of the conductive plate 30 and the upper surface of the main body 41 of the insulating gas permeable plug 40. As a result, the dense insulating film 50 covers the boundary portion (see the dashed line in FIG. 3) between the upper surface of the conductive plate 30 and the upper surface of the main body 41 of the insulating gas permeable plug 40. In addition, the dense insulating film 50 does not cover the upper surface of the protrusion 42, and therefore does not cover the gas outlet portion 44, which is a part of the protrusion 42. As a result, the dense insulating film 50 allows ventilation of the gas outlet portion 44. The thickness of the dense insulating film 50 is equal to the height of the protrusion 42, and therefore the upper surface of the dense insulating film 50 and the upper surface of the protrusion 42 are located on the same plane. In this specification, being located on the same plane includes being located on approximately the same plane, and also includes, for example, a case where there is a height difference that is unavoidable during manufacturing, and a case where there are fine irregularities on the upper surface of the dense insulating film 50 and / or the upper surface of the protrusion 42. In this embodiment, the dense insulating film 50 covers the entire upper surface of the conductive plate 30 (the bonding surface with the ceramic plate 20) and the upper surface of the main body 41 of the insulating gas passing plug 40. The dense insulating film 50 is in contact with the side surface of the protrusion 42, and covers the entire side surface of the protrusion 42.

[0024] The dense insulating film 50 is, for example, a sprayed film or an aerosol deposition film (AD film). When the dense insulating film 50 is a sprayed film, the sprayed film may be made of the same material as the insulating gas passing plug 40. For example, when the insulating gas passing plug 40 is made of alumina, the sprayed film may also be made of alumina. Alternatively, the sprayed film may be made of the same material as the ceramic material contained in the conductive plate 30. The AD film is a film formed by the AD method (including the plasma AD method). In the AD method, ceramic particles can be formed into a film by the impact solidification phenomenon, so that there is no need to sinter the ceramic particles at a high temperature. When the dense insulating film 50 is an AD film, the same material as the sprayed film described above can be used.

[0025] In this specification, "dense" means dense enough that gas cannot pass through. The dense insulating film 50 may have a porosity of less than 3%, and preferably has a porosity of less than 1%. The porosity is defined as the area ratio of pores observed in an image obtained by observing a representative cross section at a magnification of 50 times using a scanning electron microscope (SEM).

[0026] The bonding sheet 60 is an insulating adhesive layer disposed between the lower surface of the ceramic plate 20 and the upper surface of the dense insulating film 50, and is, for example, a resin sheet. The conductive plate 30 is bonded to the lower surface of the ceramic plate 20 via the bonding sheet 60 and the dense insulating film 50. The bonding sheet 60 has a through hole with a diameter equal to or slightly larger than the opening diameter of the fine hole 26 at a position directly below the fine hole 26. The gas outlet portion 44 and the fine hole 26 communicate with each other through the space inside the through hole, and this space is called the fine hole side space 27. The part of the upper surface of the protrusion 42 of the insulating gas passing plug 40 that is exposed to the fine hole side space 27 is the gas outlet portion 44. The part of the upper surface of the protrusion 42 other than the gas outlet portion 44 is bonded to the lower surface of the bonding sheet 60.

[0027] Next, an example of use of the wafer mounting table 10 thus configured will be described. First, the wafer W is mounted on the wafer mounting surface 21 with the wafer mounting table 10 installed in a chamber (not shown). Then, the chamber is depressurized by a vacuum pump to adjust the chamber 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, so that the wafer W is adsorbed and fixed to the wafer mounting surface 21. Next, the chamber is made into a reactive gas atmosphere with a predetermined pressure (for example, several tens to several hundreds of Pa), and in this state, an RF voltage is applied between an upper electrode (not shown) provided on the ceiling of the chamber and the conductive plate 30 of the wafer mounting table 10 to generate plasma. The surface of the wafer W is treated by the generated plasma. A coolant is circulated through the coolant flow passage of the conductive plate 30. A backside gas is introduced into the gas supply passage 31 from a gas cylinder (not shown). A thermally conductive gas (for example, He gas, etc.) is used as the backside gas. The backside gas introduced into the gas supply passage 31 passes through the gap S of the plug chamber 32, the insulating gas passing plug 40, the hole-side space 27, and the hole 26 in this order, and is supplied to the back surface of the wafer W. The presence of this backside gas allows efficient thermal conduction between the wafer W and the ceramic plate 20.

[0028] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to FIG. 4. FIG. 4 is a manufacturing process diagram of the wafer mounting table 10. First, the ceramic plate 20 and the conductive plate 30 before being bonded to each other, and the insulating gas passing plug 40 before being placed in the plug chamber 32 are prepared (FIG. 4A). The ceramic plate 20 is obtained by, for example, preparing a ceramic powder compact incorporating the electrode 22 and hot press firing the compact. In addition, the ceramic plate 20 has pores 26 formed therein, and the conductive plate 30 has gas supply passages 31, plug chambers 32, and coolant passages formed therein. The plug chambers 32 may be formed when the conductive plate 30 is molded, or the plug chambers 32 may be formed by processing the conductive plate 30 after it is manufactured. When manufacturing the conductive plate 30, a plurality of MMC disk members may first be manufactured, and grooves and holes may be formed in these MMC disk members by machining. The plurality of MMC disk members may then be joined together using a metal bonding material, so that the grooves and holes ultimately become the gas supply passage 31, the plug chamber 32, and the refrigerant flow path.

[0029] Next, an elastic member 48 is attached to the lower surface of the insulating gas-permeable plug 40 (FIG. 4B), and then the insulating gas-permeable plug 40 is attached to the conductive plate 30 (FIG. 4C). The insulating gas-permeable plug 40 may be attached, for example, by applying an adhesive to at least one of the inner peripheral surface of the plug chamber 32 and the outer peripheral surface of the insulating gas-permeable plug 40, and then inserting the insulating gas-permeable plug 40 from above the plug chamber 32 to adhesively fix the outer peripheral surface of the insulating gas-permeable plug 40 to the inner peripheral surface of the plug chamber 32. Next, a dense insulating film 70 is formed on the upper surfaces of the conductive plate 30 and the insulating gas-permeable plug 40 by thermal spraying or AD method using the material of the dense insulating film 50 (FIG. 4D). The dense insulating film 70 is formed to be thicker than the dense insulating film 50 and is formed so as to cover the entire upper surfaces of the conductive plate 30 and the insulating gas-permeable plug 40, including the upper surfaces of the protrusions 42. Thereafter, the upper surface of the dense insulating film 70 is ground to reduce the thickness of the dense insulating film 70, and the upper surfaces of the protrusions 42 are exposed (FIG. 4E). As a result, the dense insulating film 70 becomes the dense insulating film 50. Then, the ceramic plate 20 and Insulating gas passing plug 40The conductive plate 30 having the dense insulating film 50 and the insulating film 52 attached thereto is bonded to each other via a bonding sheet 60 to obtain the wafer mounting table 10 (FIG. 4F).

[0030] In the wafer mounting table 10 of the present embodiment described above in detail, the dense insulating film 50 is disposed across the upper surface of the conductive plate 30 and the upper surface of the main body 41 of the insulating gas permeable plug 40, thereby covering the boundary between the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 40. The presence of such a dense insulating film 50 can suppress discharge from the boundary between the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 40 along a vertical path along the side surface of the insulating gas permeable plug 40. In addition, the dense insulating film 50 allows ventilation of the gas outlet portion 44 of the insulating gas permeable plug 40, so that gas can flow from the gas supply passage 31 to the pores 26 via the insulating gas permeable plug 40 even when the dense insulating film 50 is present.

[0031] Here, for comparison with the above-mentioned embodiment, a wafer mounting table 910 in a form (referred to as a comparative form) not including a dense insulating film 50 will be described with reference to FIG. 5. FIG. 5 is an enlarged view of the wafer mounting table 910 in the comparative form, corresponding to FIG. 2. The same components as those in the wafer mounting table 10 will be described using the same reference numerals. In the wafer mounting table 910, a cylindrical insulating gas passing plug 940 not including a protrusion 42 is disposed in the plug chamber 32 instead of the insulating gas passing plug 40. Moreover, instead of including the dense insulating film 50, the wafer mounting table 910 includes a dense insulating film 951 provided on the outer peripheral surface of the insulating gas passing plug 940 and a dense insulating film 952 covering the upper surface of the conductive plate 30. In this wafer mounting table 910, the side surface (outer peripheral surface) of the insulating gas passing plug 940 is in contact with the dense insulating film 951 and the dense insulating film 952, so that the contact surface between the insulating gas passing plug 940 and the dense insulating film 951 and the dense insulating film 952 is along the vertical direction. Since the potential difference caused by the voltage applied to the wafer mounting table 910 during use is also along the vertical direction, discharge is likely to occur in the portion between the insulating gas passing plug 940 and the dense insulating film 951 and the dense insulating film 952, that is, around the side surface of the insulating gas passing plug 940. As a result, discharge may occur along a discharge path R1 (see dotted line) from the side surface of the insulating gas passing plug 940 to the wafer W via the upper surface of the insulating gas passing plug 940 and the inner peripheral surface of the pore 26. In addition, when manufacturing the wafer mounting table 910, the dense insulating film 951 on the side surface of the insulating gas permeable plug 940 and the dense insulating film 952 on the upper surface of the conductive plate 30 are formed separately, so that discharge is likely to occur at the interface between the dense insulating film 951 and the dense insulating film 952. As a result, discharge may occur along a discharge path R2 (see dotted line) from the interface between the dense insulating film 951 and the dense insulating film 952 to the wafer W via the side surface, upper surface, and inner peripheral surface of the pore 26 of the insulating gas permeable plug 940. In contrast, in the wafer mounting table 10 of the present embodiment, the dense insulating film 50 is disposed on the upper surface, not the side surface, of the insulating gas permeable plug 40, and the contact surface between the dense insulating film 50 and the insulating gas permeable plug 40 is along the left-right direction, so that the area between the dense insulating film 50 and the insulating gas permeable plug 40 is unlikely to become a discharge path.Furthermore, since the dense insulating film 50 is formed across the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 40, there is no interface between the part of the dense insulating film 50 covering the upper surface of the conductive plate 30 and the part covering the upper surface of the insulating gas permeable plug 40. Therefore, the boundary part between the conductive plate 30 and the insulating gas permeable plug 40 is unlikely to become a discharge path. From the above, in the wafer mounting table 10, the presence of the dense insulating film 50 can suppress discharge from occurring in a vertical path along the side surface of the insulating gas permeable plug 40 from the boundary part between the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 40.

[0032] In addition, in the wafer mounting table 910, the upper surface of the insulating gas permeable plug 140 is in direct contact with the bonding sheet 60. When the insulating gas permeable plug 140 is a porous body, the upper surface of the insulating gas permeable plug 140 has irregularities due to open pores, which may reduce the adhesion between the insulating gas permeable plug 140 and the bonding sheet 60. In contrast, in the wafer mounting table 10, the dense insulating film 50 is present between the insulating gas permeable plug 40 and the bonding sheet 60, which makes it easy to increase the adhesion between the insulating gas permeable plug 40, the dense insulating film 50, and the bonding sheet 60. For example, when the insulating gas permeable plug 40 is a porous body and the dense insulating film 50 is formed on the upper surface of the insulating gas permeable plug 40 by thermal spraying or the AD method, constituent particles of the dense insulating film 50 enter the irregularities on the upper surface of the insulating gas permeable plug 40, so that the adhesion between the insulating gas permeable plug 40 and the dense insulating film 50 is increased. Furthermore, since the dense insulating film 50 is dense, the adhesion between the dense insulating film 50 and the bonding sheet 60 is stronger than the adhesion between the porous insulating gas passing plug 940 and the bonding sheet 60 .

[0033] Moreover, a convex portion 42, the upper surface of which becomes the gas outlet portion 44, is formed on the upper surface of the body portion 41 of the insulating gas permeable plug 40, and the upper surface of the dense insulating film 50 and the upper surface of the convex portion 42 are located on the same plane. As a result, as explained in Fig. 4D and Fig. 4E, by forming the dense insulating film 70 so as to cover the entire upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 40, and then grinding the dense insulating film 70 until the upper surface of the convex portion 42 is exposed, it is possible to relatively easily form the dense insulating film 50 that allows ventilation of the gas outlet portion 44. Furthermore, since the upper surface of the dense insulating film 50 and the upper surface of the convex portion 42 are located on the same plane, gaps other than the gas flow path are unlikely to occur when the conductive plate 30 and the ceramic plate 20 are joined after the dense insulating film 50 is formed, so that discharge can be further suppressed.

[0034] Furthermore, since the dense insulating film 50 is a thermal spray film or an aerosol deposition film, the dense insulating film 50 can be produced relatively easily.

[0035] Furthermore, the wafer mounting table 10 includes an elastic member 48 disposed between the lower surface of the insulating gas passing plug 40 and the bottom surface of the plug chamber 32. The presence of this elastic member 48 can prevent the insulating gas passing plug 40 from being pushed up when the wafer mounting table 10 is heated during use and the conductive plate 30 is warped into an upwardly convex shape. When the insulating gas passing plug 40 is pushed up, cracks may occur in the dense insulating film 50 in a portion covering the boundary between the conductive plate 30 and the insulating gas passing plug 40. However, the elastic member 48 acts as a buffer material to prevent the insulating gas passing plug 40 from being pushed up, and therefore the occurrence of cracks in the dense insulating film 50 can be prevented.

[0036] In addition, since the elastic member 48 is made of a heat-resistant resin, the elastic member can be produced relatively easily.

[0037] 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.

[0038] For example, in the above-described embodiment, the insulating gas passing plug 40 has the convex portion 42, but is not limited thereto. FIG. 6 is an enlarged view of a wafer placing table 110, which is another example of the wafer placing table 10, corresponding to FIG. 2. In FIG. 6, the same components as those in the wafer placing table 10 are given the same reference numerals and will not be described. The wafer placing table 110 has a cylindrical insulating gas passing plug 140 without the convex portion 42, instead of the insulating gas passing plug 40. The dense insulating film 150 has an opening formed directly above the gas outlet portion 44 so as to allow ventilation of the gas outlet portion 44, which is a part of the upper surface of the insulating gas passing plug 140, and does not cover the gas outlet portion 44. The dense insulating film 150 covers the entire upper surface of the insulating gas passing plug 140 other than the above. The dense insulating film 150 is disposed across the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 140, thereby covering the boundary between the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 140. In this wafer mounting table 110, as in the above-mentioned embodiment, the presence of the dense insulating film 150 can suppress discharge from the boundary between the upper surface of the conductive plate 30 and the upper surface of the insulating gas permeable plug 140 along the vertical path along the side of the insulating gas permeable plug 140. However, since the insulating gas permeable plug 140 does not have the protrusion 42, when forming the dense insulating film 150, it is necessary to form an opening so that the dense insulating film 150 does not cover the gas outlet portion 44. For example, when forming the dense insulating film 150, it is necessary to mask a part of the upper surface of the insulating gas permeable plug 140, or to form the dense insulating film 150 and then open a hole in the dense insulating film 150 so that the gas outlet portion 44 is exposed. Therefore, the dense insulating film 50 is preferable because it can be manufactured relatively easily compared to the dense insulating film 150. Moreover, the wafer mounting table 110 does not have the protrusion 42, but has an opening provided in the dense insulating film 150 so as not to cover the gas outlet portion 44. Therefore, compared to the pore-side space 27 in FIG. Figure 6In the case of the wafer mounting table 10 shown in FIG. 2, the hole-side space 127 is larger by the thickness of the dense insulating film 150. Therefore, from the viewpoint of suppressing discharge in the space, it is preferable to use an insulating gas passing plug 40 having a protrusion 42 as shown in FIG. 2. In the wafer mounting table 10 shown in FIG. 2, the protrusion 42 is present and the dense insulating film 50 covers the entire side surface of the protrusion 42, so that the hole-side space 27 is only the through-hole portion of the bonding sheet 60, and the hole-side space 27 can be made smaller.

[0039] In the above-described embodiment, the elastic member 48 exists to provide a gap S between the lower surface of the insulating gas passing plug 40 and the bottom surface of the plug chamber 32 of the conductive plate 30, but this is not limited thereto. For example, the elastic member 48 may be in contact with the entire lower surface of the insulating gas passing plug 40 except for the portion directly above the gas supply passage 31, and no gap other than the gas flow path may exist between the lower surface of the insulating gas passing plug 40 and the bottom surface of the plug chamber 32. Even in this case, the presence of the elastic member 48 can suppress the insulating gas passing plug 40 from being pushed up. The shape of the elastic member 48 is not limited to a ring shape, and may be a rod shape or the like. The elastic member 48 may be in a shape that is easily deformed, such as a shape having a hollow portion or a wave shape. The wafer mounting table 10 may not include the elastic member 48. In this case, the lower surface of the insulating gas passing plug 40 may be in contact with the bottom surface of the plug chamber 32. A plurality of elastic members 48 may be disposed on the lower surface of one insulating gas passing plug 40.

[0040] In the above-described embodiment, a gap may exist between the outer circumferential surface of the insulating gas passing plug 40 and the inner circumferential surface of the plug chamber 32. Due to the presence of the dense insulating film 50, even if a gap exists between the outer circumferential surface of the insulating gas passing plug 40 and the inner circumferential surface of the plug chamber 32, discharge is unlikely to occur.

[0041] In the above-described embodiment, the insulating gas passing plug 40 is a porous body, but it is not limited to a porous body and may be any body that allows gas to pass through the inside. For example, the insulating gas passing plug 40 may be made of finely crushed insulating ceramics solidified with an inorganic adhesive so as to have air permeability, or may be glass fiber or a heat-resistant Teflon resin sponge (Teflon is a registered trademark). Alternatively, the insulating gas passing plug 40 may be a dense plug having an internal gas flow path. The internal gas flow path may be a straight through hole along the vertical direction, or may be a passage that passes through the upper and lower surfaces of the dense plug while bending. Examples of the passage that passes through the upper and lower surfaces of the dense plug while bending include a spiral passage and a zigzag passage. The diameter of the flow path cross section of the internal gas flow path is preferably 0.1 mm or more and 1 mm or less. One dense plug may have multiple internal gas flow paths. The porosity of the dense part of the dense plug is preferably less than 0.1%. As the dense plug, ceramics such as alumina or aluminum nitride can be used, as in the insulating gas-passing plug 40 as the porous body described above. The dense plug may be manufactured, for example, by firing a compact formed using a 3D printer, or by firing a compact formed by mold casting. Details of the dense plug having an internal gas flow path that runs through while bending, and the mold casting are disclosed in, for example, Japanese Patent No. 7149914.

[0042] In the above-described embodiment, the gas supply passage 31 is a through hole that penetrates the conductive plate 30 in the vertical direction, but is not limited to this. The gas supply passage 31 is not limited to extending in the vertical direction and may be bent along the way. The gas supply passage 31 may have one or more first gas passages that open to the lower surface of the conductive plate 30 and are fewer in number than the plug chambers 32, and a plurality of second gas passages that branch off from the first gas passages and extend in one-to-one correspondence with the plug chambers 32.

[0043] In the above-described embodiment, the ceramic plate 20 and the conductive plate 30 are bonded together by the insulating bonding sheet 60. However, instead of the bonding sheet 60, a conductive bonding layer such as a metal bonding layer may be used.

[0044] In the above-described embodiment, the ceramic plate 20 has an electrostatic electrode built in as the electrode 22, but instead of or in addition to this, a heater electrode (resistance heating element) may be built in. In this case, a heater power source 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 from each other.

[0045] In the above-described embodiment, lift pin holes may be provided penetrating 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, the lift pin holes are provided in three locations. [Industrial Applicability]

[0046] The present invention can be used, for example, in an apparatus for processing wafers. [Explanation of symbols]

[0047] 10,110 wafer mounting table, 20 ceramic plate, 21 wafer mounting surface, 22 electrode, 26 hole, 27,127 hole side space, 30 conductive plate, 31 gas supply passage, 32 plug chamber, 40,140 insulating gas passing plug, 41 main body, 42 convex portion, 44 gas outlet portion, 48 elastic member, 50,150 dense insulating film, 60 bonding sheet, 70 dense insulating film, 910 wafer mounting table, 940 insulating gas passing plug, 951,952 dense insulating film, R1,R2 discharge path, S gap, W wafer.

Claims

1. a ceramic plate having a wafer mounting surface on an upper surface thereof, a vertically extending hole formed therethrough, and a built-in electrode; a conductive plate bonded to a lower surface of the ceramic plate and having a gas supply passage; a plug chamber formed as a recess extending from an upper surface of the conductive plate toward a lower surface of the conductive plate and communicating with the fine hole and the gas supply passage; an insulating gas-permeable plug disposed in the plug chamber and allowing gas to pass therethrough; a dense insulating film that allows ventilation of a gas outlet portion of an upper surface of the insulating gas passing plug, the gas outlet portion being a flow path of gas to the pore, and that is disposed across the upper surface of the conductive plate and the upper surface of the insulating gas passing plug to cover a boundary portion between the upper surface of the conductive plate and the upper surface of the insulating gas passing plug; Equipped with a protrusion is formed on the upper surface of the insulating gas passing plug, the upper surface of the protrusion being the gas outlet portion; an upper surface of the dense insulating film and an upper surface of the protrusion are located on the same plane; Wafer placement stage.

2. The dense insulating film is a thermal spray film or an aerosol deposition film. The wafer stage according to claim 1 .

3. 3. The wafer mounting table according to claim 1, an elastic member disposed between a lower surface of the insulating gas passing plug and a bottom surface of the plug chamber; A wafer mounting table comprising:

4. The elastic member is made of a heat-resistant resin. The wafer stage according to claim 3 .

5. The insulating gas-passing plug is a porous body. The wafer stage according to claim 1 .

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