Wafer placement table

Abstract

This wafer stage 10 is provided with: a ceramic plate 20 which has a wafer stage surface 21 in the upper surface and internally comprises an electrode 22; a conductive plate 30 which is bonded to the lower surface of the ceramic plate 20; a ceramic plate through part 50 which penetrates through the ceramic plate 20; a porous plug 55 which is provided in the ceramic plate through part 50, and the inside of which a gas can pass through; a gas introduction path 60 which is provided at least inside the conductive plate 30, and is in communication with the ceramic plate through part 50; and a conductive gas passing part 70, which is provided within the gas introduction path 60, inside which a gas can pass through, and which is in contact with the lower surface of the porous plug 55 and is electrically connected to the conductive plate 30.

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 having a gas introduction passage bonded to the lower surface of the ceramic plate. 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 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. It is described that the presence of the first porous portion and the second porous portion can ensure the flow rate of gas from the gas introduction passage to the wafer mounting surface while suppressing the occurrence of discharge (arc discharge) caused by plasma when processing the wafer. [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 if an insulating second porous portion is present as in Patent Document 1, discharge may occur around the end of the first porous portion on the base plate side.

[0005] The present invention has been made to solve these problems, and has as its main object to suppress discharge around the end of the insulating gas passing plug on the conductive plate side. [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 and incorporating an electrode; a conductive plate bonded to a lower surface of the ceramic plate; a ceramic plate penetration portion penetrating the ceramic plate; an insulating gas-passing plug that is provided in the ceramic plate penetration portion and through which gas can pass; a gas introduction passage provided at least inside the conductive plate and communicating with the ceramic plate penetration portion; a conductive gas passage provided in the gas introduction passage, in contact with a lower surface of the insulating gas passing plug, electrically connected to the conductive plate, and allowing gas to pass therethrough; It is equipped with the following:

[0008] In this wafer mounting table, the conductive gas passage is provided in the gas introduction passage, is in contact with the lower surface of the insulating gas passing plug, and is electrically connected to the conductive plate. This makes it difficult for a potential difference to occur around the end of the insulating gas passing plug on the conductive plate side, compared to, for example, a case in which an insulating porous member is present on the lower surface side of the insulating gas passing plug. Therefore, discharge around the end of the insulating gas passing plug on the conductive plate side can be suppressed.

[0009] [2] In the above-mentioned wafer mounting table (the wafer mounting table described in [1] above), the conductive gas passage may be separate from the conductive plate. In this case, the wafer mounting table is easier to manufacture than, for example, a case in which the conductive gas passage is an integral member with the conductive plate rather than a separate member. In this case, the conductive gas passage may be in contact with the conductive plate.

[0010] [3] In the above-mentioned wafer mounting table (the wafer mounting table described in [2] above), the conductive gas passage portion may have an elastic member, and the elastic member may be pressed and compressed against the lower surface of the insulating gas passing plug. In this way, the elastic member is pressed and compressed against the lower surface of the insulating gas passing plug, which makes it easier to maintain contact between the conductive gas passage portion and the insulating gas passing plug.

[0011] [4] In the above-mentioned wafer mounting table (the wafer mounting table described in the above [2] or [3]), the conductive gas passage may have at least one of a conductive mesh and a mass of conductive fibers. The conductive mesh and the mass of conductive fibers are suitable for the conductive gas passage because gas can easily flow therethrough.

[0012] [5] In the above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to [4] above), the conductive gas passage portion may have a conductive bulk body having holes through which gas can pass in the vertical direction, and the diameter of the holes may be 0.1 mm or more and 1 mm or less. In this way, since the diameter of the holes through which gas can pass in the vertical direction is 0.1 mm or more, the gas flow rate is unlikely to be insufficient. In addition, since the diameter of the holes is 1 mm or less, a potential difference is unlikely to occur within the holes, and discharge within the holes can be suppressed.

[0013] [6] In the above-mentioned wafer stage (the wafer stage described in any one of [1] to [5] above), the conductive gas passage may have a conductive porous body.

[0014] [7] In the above-mentioned wafer mounting table (the wafer mounting table described in any one of [2] to [6] above), the conductive gas passage portion may have a structure in which one or more conductive meshes and one or more conductive sheets having holes through which gas can pass in the vertical direction are laminated, and the diameter of the holes may be 0.1 mm or more and 1 mm or less.

[0015] [8] In the above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to [7] above), the conductive gas passing portion may be disposed so as to overlap with the entire lower surface of the insulating gas passing plug when viewed virtually from above. In this manner, the conductive gas passing portion is present below the entire lower surface of the insulating gas passing plug, so that discharge around the end of the insulating gas passing plug on the conductive plate side can be more reliably suppressed.

[0016] [9] In the above-mentioned wafer stage (the wafer stage described in any one of [1] to [8] above), the insulating gas passing plug may be a porous body.

[0017]

[10] In the above-described wafer mounting table (the wafer mounting table described in any one of [1] to [9] above), the conductive gas passage portion may have a coating layer that covers the lower surface of the insulating gas passing plug. In this case, the insulating gas passing plug may be a dense plug having an internal gas flow path, and the coating layer may be a dense layer having holes that connect the internal gas flow path of the dense plug to the gas introduction passage. Alternatively, the coating layer may be a porous layer that covers the lower surface of the dense plug.

[0018]

[11] In the above-mentioned wafer mounting table (the wafer mounting table according to any one of [1] to

[10] above), the conductive gas passage may have a covering layer that covers the lower surface of the insulating gas passage plug, and an elastic body that presses the covering layer upward with an elastic force. This makes it easier to maintain contact between the conductive gas passage and the insulating gas passage plug. [Brief description of the drawings]

[0019] [Figure 1] FIG. [Diagram 2] Cross section AA of Figure 1. [Diagram 3] 4 is a partially enlarged cross-sectional view showing the periphery of a second gas passage 62 and a conductive gas passage 70. FIG. [Figure 4]13 is a cross-sectional view of the wafer stage 10 cut along a horizontal plane passing through a second gas passage 62, as viewed from above. FIG. [Diagram 5] 3 is a cross-sectional view of the wafer mounting table 10 cut by a horizontal plane passing through a coolant flow path 32 as viewed from above. FIG. [Figure 6] FIG. 2 is an explanatory diagram in which a coolant flow path 32 and the like are drawn on a plan view of the wafer mounting table 10. [Figure 7] 5A to 5C are diagrams showing the manufacturing process of the wafer mounting table 10. [Figure 8] 6 is a partially enlarged cross-sectional view showing another example of the conductive gas passage 70. FIG. [Figure 9] 6 is a partially enlarged cross-sectional view showing another example of the conductive gas passage 70 and the gas introduction passage 60. FIG. [Figure 10] 6 is a partially enlarged cross-sectional view showing another example of the conductive gas passage 70 and the gas introduction passage 60. FIG. [Figure 11] FIG. 2 is an enlarged partial cross-sectional view showing a dense plug 155 and a conductive gas passage 170. [Figure 12] FIG. 4 is a partially enlarged cross-sectional view showing the periphery of a conductive gas passage portion 270. [Figure 13] FIG. 4 is a partially enlarged cross-sectional view showing the periphery of a conductive gas passage portion 370. [Figure 14] FIG. 4 is a partially enlarged cross-sectional view showing the periphery of a conductive gas passage portion 470. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0020] Next, a preferred embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a plan view of the wafer mounting table 10, FIG. 2 is an AA cross-sectional view of FIG. 1, FIG. 3 is a partially enlarged cross-sectional view showing the periphery of the second gas passage 62 and the conductive gas passage 70, FIG. 4 is a cross-sectional view of the wafer mounting table 10 cut along a horizontal plane passing through the second gas passage 62 as viewed from above, FIG. 5 is a cross-sectional view of the wafer mounting table 10 cut along a horizontal plane passing through the refrigerant passage 32 as viewed from above, and FIG. 6 is an explanatory diagram in which the refrigerant passage 32 and the like are drawn on the plan view of the wafer mounting table 10. The partially enlarged view in FIG. 1 is an explanatory diagram in which the conductive gas passage 70 is drawn on the plan view of the wafer mounting table 10. FIG. 3 is a partially enlarged view of the cut surface of the wafer mounting table 10 cut along a vertical plane along the second gas passage 62 and a vertical plane passing through the conductive gas passage 70. In this specification, "upper" and "lower" do not represent absolute positional relationships, but represent relative positional relationships. Therefore, depending on the orientation of the wafer mounting table 10, "up" and "down" can become "down" and "up," "left" and "right," or "front" and "back."

[0021] As shown in FIG. 2, the wafer mounting table 10 includes a ceramic plate 20, a conductive plate 30, a conductive bonding layer 40, a ceramic plate penetration portion 50, a gas introduction passage 60, and a conductive gas passage portion 70.

[0022] The ceramic plate 20 is a circular plate (e.g., 300 mm in diameter and 5 mm in thickness) made of ceramic such as sintered alumina or sintered aluminum nitride. The upper surface of the ceramic plate 20 is a wafer mounting surface 21 on which a wafer W is mounted. The ceramic plate 20 has an electrode 22 built in. As shown in FIG. 1, a ring-shaped seal band 21a is formed along the outer edge of the wafer mounting surface 21 of the ceramic plate 20, and a plurality of small circular protrusions 21b are formed on the entire inner surface of the seal band 21a. The seal band 21a and the small circular protrusions 21b have the same height, 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 connected to an external DC power source via a power supply member (not shown). A low-pass filter may be disposed midway along the power supply member. The power supply member is electrically insulated from the conductive bonding layer 40 and the conductive plate 30. When a DC voltage is applied to this electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the upper surface of the seal band and the upper surfaces of the small circular protrusions) by electrostatic attraction, 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 portion of the wafer mounting surface 21 on which the seal band 21a and the small circular protrusions 21b are not provided is referred to as the reference surface 21c.

[0023] The conductive plate 30 is a disk (having the same diameter as or larger than the ceramic plate 20) with good thermal conductivity. Inside the conductive plate 30, a refrigerant flow path 32 is formed through which a refrigerant circulates. The refrigerant flowing through the refrigerant flow path 32 is preferably a liquid, and is preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inert liquids. The refrigerant flow path 32 is formed in a single stroke from one end (inlet) to the other end (outlet) over the entire conductive plate 30 in a plan view. As shown in FIG. 5, the refrigerant flow path 32 is provided so as to be drawn from one end to the other end in a single stroke based on multiple circles (circles C1 to C4 of dashed lines, here, the circles C1 to C4 are concentric circles) having different diameters in a plan view and arranged so as not to overlap each other. Specifically, when the refrigerant flow passage 32 is laid out from one end to the other in a single stroke, the refrigerant flow passage 32 is laid out so as to trace the imaginary circles while connecting two imaginary circles that are in an inner and outer relationship among the multiple circles. A supply port and a recovery port of an external refrigerant device (not shown) are connected to one end and the other end of the refrigerant flow passage 32, respectively. The refrigerant supplied to one end of the refrigerant flow passage 32 from the supply port of the external refrigerant device passes through the refrigerant flow passage 32, returns to the recovery port of the external refrigerant device from the other end of the refrigerant flow passage 32, and is supplied again to one end of the refrigerant flow passage 32 from the supply port after being temperature-adjusted. The conductive plate 30 is connected to a radio frequency (RF) power source and is also used as an RF electrode.

[0024] Examples of the material of the conductive plate 30 include metal materials and composite materials of metal and ceramic. Metal materials include Al, Ti, Mo, and alloys thereof. Composite materials of metal and ceramic include metal matrix composites (MMC) and ceramic matrix composites (CMC). Specific examples of such composite materials include a material containing Si, SiC, and Ti (also called SiSiCTi), a material in which a porous SiC body is impregnated with Al and / or Si, and Al. 2 O 3 A composite material of TiC and the like can be used as the material for the conductive plate 30. It is preferable to select a material for the conductive plate 30 that has a thermal expansion coefficient close to that of the material for the ceramic plate 20.

[0025] The conductive bonding layer 40 is, for example, a metal bonding layer, and bonds the lower surface of the ceramic plate 20 and the upper surface of the conductive plate 30. The conductive bonding layer 40 is formed, for example, by thermal compression bonding (TCB). TCB is 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.

[0026] As shown in FIG. 2, the ceramic plate through-hole 50 is a hole that penetrates the ceramic plate 20 in the vertical direction. The ceramic plate through-hole 50 is a gas passage that extends from the lower surface of the ceramic plate 20 to the reference surface 21c (FIG. 1) of the wafer mounting surface 21. As shown in FIG. 1, a plurality of ceramic plate through-holes 50 (36 in this example) are provided. The ceramic plate through-hole 50 has an electrically insulating porous plug 55 that allows gas to flow. Here, the porous plug 55 is fixed in a state where it is filled in the ceramic plate through-hole 50. Specifically, the outer peripheral surface of the porous plug 55 and the inner peripheral surface of the ceramic plate through-hole 50 may be bonded, or a male screw portion provided on the outer peripheral surface of the porous plug 55 may be screwed into a female screw portion provided on the inner peripheral surface of the ceramic plate through-hole 50. The upper surface of the porous plug 55 is at the same height as the reference surface 21c of the wafer mounting surface 21, and the lower surface of the porous plug 55 is at the same height as the lower surface of the ceramic plate 20. The porous plug 55 may be a porous bulk body obtained by sintering ceramic powder. The ceramic may be, for example, alumina or aluminum nitride. The porosity of the porous plug 55 is preferably 30% or more, and the average pore diameter is preferably 20 μm or more. The porosity of the porous plug 55 may be 70% or less.

[0027] The gas introduction passage 60 is a gas passage provided at least inside the conductive plate 30 and communicating with the ceramic plate penetration portion 50. The gas introduction passage 60 includes a first gas passage 61, a second gas passage 62, an auxiliary gas passage 63 (FIG. 4), and a bonding layer penetration portion 64. The gas introduction passage 60 includes gas passages (the first gas passage 61, the second gas passage 62, and the auxiliary gas passage 63) provided inside the conductive plate 30, and a gas passage (the bonding layer penetration portion 64) provided inside the conductive bonding layer 40.

[0028] The first gas passages 61 vertically penetrate the conductive plate 30. The first gas passages 61 vertically penetrate between the refrigerant channels 32 of the conductive plate 30. A plurality of first gas passages 61 (three in this example) are provided.

[0029] The second gas passage 62 is provided at the interface between the conductive bonding layer 40 and the conductive plate 30 in parallel with the wafer mounting surface 21. In addition, "parallel" refers to completely parallel, and also refers to parallel if not completely parallel but within a range of allowable error (e.g., tolerance). The second gas passage 62 has a groove 31 (first recess) provided on the upper surface of the conductive plate 30, and is formed by covering the upper surface of the groove 31 with the conductive bonding layer 40. As shown in FIG. 6, the second gas passage 62 is provided in an annular shape so as to overlap with any of a plurality of imaginary circles C1 to C4 in a plan view. Specifically, of the three second gas passages 62, the first second gas passage 62 from the outer periphery of the wafer mounting table 10 overlaps with the imaginary circle C1 with the largest diameter, the second second gas passage 62 overlaps with the imaginary circle C2 with the second largest diameter, and the third second gas passage 62 overlaps with the imaginary circle C3 with the largest diameter. Second gas passage 62 6) that overlaps with the refrigerant passage 32 along the refrigerant passage 32 in plan view.

[0030] The auxiliary gas passage 63 is a passage connecting the first gas passage 61 and the second gas passage 62, and is provided in parallel to the wafer mounting surface 21 at the interface between the conductive bonding layer 40 and the conductive plate 30. A plurality of (12 in this example) ceramic plate penetration parts 50 are provided for one second gas passage 62, but the number of the first gas passages 61 and the auxiliary gas passages 63 provided is smaller than the number of the ceramic plate penetration parts 50 (one for one second gas passage 62 in this example).

[0031] As shown in FIG. 2, the bonding layer through-hole 64 is a hole that penetrates the conductive bonding layer 40 in the vertical direction. The bonding layer through-hole 64 is a gas passage that reaches from the upper surface of the conductive plate 30 to the lower surface of the ceramic plate 20. A plurality of bonding layer through-holes 64 (36 in this example) are provided, and are arranged in one-to-one correspondence with the ceramic plate through-holes 50. In this embodiment, the diameter of the bonding layer through-hole 64 is the same as or larger than the diameter of the ceramic plate through-hole 50. The diameter of the bonding layer through-hole 64 is the same as or larger than the diameter of the conductive gas passage 70.

[0032] The conductive gas passage 70 is provided in the gas introduction passage 60 and is provided so as to contact the lower surface of the porous plug 55. In this embodiment, the conductive gas passage 70 is provided as a separate body from the conductive plate 30, and the lower surface is in contact with the conductive plate 30. More specifically, the conductive gas passage 70 is provided across the inside of the bonding layer penetration portion 64 and the inside of the second gas passage 62 in the gas introduction passage 60, and is in contact with the conductive plate 30 at a portion of the lower surface (bottom surface) of the second gas passage 62 (recessed groove 31) located directly below the bonding layer penetration portion 64. The conductive gas passage 70 is electrically connected to the conductive plate 30 by contacting with the conductive plate 30. A plurality of conductive gas passages 70 (36 in this embodiment) are provided, and are arranged in one-to-one correspondence with the porous plugs 55. In this embodiment, the conductive gas passage 70 is a substantially cylindrical member that is circular when viewed from above.

[0033] The conductive gas passage 70 is a member through which gas can pass. Therefore, the gas in the gas introduction passage 60 can pass through the conductive gas passage 70 and flow to the ceramic plate penetration part 50. Examples of the member through which gas can pass include a conductive mesh or a mass of conductive fibers. Examples of the material of the conductive gas passage 70 include metal materials and carbon. Examples of the metal materials include Al, Ti, Mo, or alloys thereof, and steel. Examples of the mass of conductive fibers include steel wool and carbon felt. When the conductive gas passage 70 is a conductive mesh, the mesh size may be 0.062 mm (250 mesh) to 0.154 mm (100 mesh).

[0034] The conductive gas passage portion 70 is preferably an elastic member. For example, the conductive mesh and the conductive fiber mass described above are also examples of elastic members. When the conductive gas passage portion 70 has a directional property in terms of expansion and contraction, it is preferable that the conductive gas passage portion 70 is expandable at least in the vertical direction. The conductive gas passage portion 70 is preferably compressed by being pressed against the lower surface of the porous plug 55. In this embodiment, the conductive gas passage portion 70 is an elastic member, and the conductive gas passage portion 70 is compressed vertically between the porous plug 55 and the conductive plate 30 by being pressed against the lower surface of the porous plug 55.

[0035] The conductive gas passage 70 is preferably disposed so as to overlap the entire lower surface of the porous plug 55 when viewed virtually from above. In this embodiment, as shown in the partially enlarged view of Fig. 1, the diameter of the conductive gas passage 70 is larger than the diameter of the porous plug 55, and the entire lower surface of the porous plug 55 is included in the conductive gas passage 70 when viewed virtually from above.

[0036] The conductive gas passage 70 preferably has a conductance larger than that of the porous plug 55, and more preferably has a conductance at least twice that of the porous plug 55. The conductance can be calculated, for example, by dividing the amount of gas (flow rate) flowing inside per unit time by the difference in gas pressure between the inlet side and the outlet side of the gas. When comparing the conductance of the conductive gas passage 70 and the porous plug 55, gas of the same pressure is supplied to the inlet side of each of the conductive gas passage 70 and the porous plug 55, and the conductance of each is calculated. The conductance of the conductive gas passage 70 can be adjusted, for example, by adjusting the mesh size when the conductive gas passage 70 is a conductive mesh, or by adjusting the thickness of the fibers and / or the void ratio inside the agglomerate when the conductive gas passage 70 is a conductive fiber aggregate.

[0037] 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 (specifically, the upper surface of the seal band 21a or the upper surface of the small circular protrusion 21b). Next, the chamber is set to 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 passage 32 of the conductive plate 30. A backside gas is introduced from a gas cylinder (not shown) into the first gas passage 61 of the gas introduction passage 60. A thermally conductive gas (e.g., He gas, etc.) is used as the backside gas. The backside gas introduced into the first gas passage 61 passes through the gas auxiliary passage 63, the second gas passage 62, and the conductive gas passage 70 in this order, and is distributed to the multiple ceramic plate penetrations 50, and is supplied to and sealed in the space between the back surface of the wafer W and the reference surface 21c of the wafer mounting surface 21. The presence of this backside gas allows efficient thermal conduction between the wafer W and the ceramic plate 20. In addition, the provision of the porous plug 55 in the ceramic plate penetration 50 makes it possible to suppress discharge within the ceramic plate penetration 50. For example, in the absence of the porous plug 55, electrons generated as a result of ionization of gas molecules by application of an RF voltage are accelerated and collide with other gas molecules, causing glow discharge and then arc discharge. However, with the porous plug 55, the electrons collide with the porous plug 55 before colliding with other gas molecules, suppressing discharge.

[0038] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to FIG. 7. FIG. 7 is a manufacturing process diagram of the wafer mounting table 10. Here, a case where the conductive plate 30 is manufactured from MMC is illustrated. First, the ceramic plate 20 incorporating the electrode 22 is prepared (FIG. 7A). For example, a ceramic powder compact incorporating the electrode 22 is manufactured, and the compact is hot-pressed and fired to obtain the ceramic plate 20. A ceramic plate penetration part 50 is formed in the ceramic plate 20 (FIG. 7B). The ceramic plate penetration part 50 is formed so as to penetrate the ceramic plate 20 in the vertical direction while avoiding the electrode 22.

[0039] In parallel with this, two MMC disk members 81 and 82 are prepared (FIG. 7C). Then, by machining, grooves and holes are appropriately formed in these MMC disk members 81 and 82 (FIG. 7D). Specifically, a groove 32a that will eventually become the refrigerant flow path 32 is formed in the lower surface of the upper MMC disk member 81, and a groove 31 that will eventually become the second gas passage 62 is formed in the upper surface of the MMC disk member 81. In addition, a through hole 61a that will eventually become a part of the first gas passage 61 is formed so as to reach the lower surface of the MMC disk member 81. Furthermore, a through hole 61b that will eventually become a part of the first gas passage 61 is formed in the lower MMC disk member 82. When the ceramic plate 20 is made of alumina, it is preferable that the MMC disk members 81 and 82 are made of SiSiCTi or AlSiC. This is because the thermal expansion coefficient of alumina can be made approximately the same as that of SiSiCTi or AlSiC.

[0040] The SiSiCTi disk member can be manufactured, for example, as follows. First, silicon carbide, metal Si, and metal Ti are mixed to produce a powder mixture. Next, the obtained powder mixture is uniaxially pressed to produce a disk-shaped compact, which is then hot-press sintered in an inert atmosphere to obtain the SiSiCTi disk member.

[0041] Next, the ceramic plate 20, the MMC disk member 81, and the MMC disk member 82 are TCB-bonded, and then the overall shape is adjusted and a porous plug 55 is attached to obtain the wafer mounting table 10 (FIGS. 7E and 7F). Specifically, a metal bonding material 83 is sandwiched between the upper surface of the lower MMC disk member 82 and the lower surface of the upper MMC disk member 81, and a metal bonding material 90 is sandwiched between the upper surface of the upper MMC disk member 81 and the lower surface of the ceramic plate 20 to obtain a laminate. A through hole that will eventually become a part of the first gas passage 61 is formed in advance in the metal bonding material 83, and a through hole that will eventually become the bonding layer penetration portion 64 is formed in advance in the metal bonding material 90. After the metal bonding material 90 is placed on the upper surface of the MMC disk member 81, the conductive gas passage portion 70 is inserted in advance into the through hole that will eventually become the bonding layer penetration portion 64 and into the recessed groove 31 directly below it. Next, the laminate is pressed and bonded at a temperature equal to or lower than the solidus temperature of the metal bonding materials 83, 90 (for example, equal to or higher than a temperature 20°C lower than the solidus temperature and equal to or lower than the solidus temperature), and then returned to room temperature. As a result, the two MMC disk members 81, 82 are bonded by the metal bonding material 83 to form the conductive plate 30. The ceramic plate 20 and the conductive plate 30 are bonded by the metal bonding material 90. The metal bonding material 90 becomes the conductive bonding layer 40. As the metal bonding materials 83, 90, Al-Mg based bonding materials or Al-Si-Mg based bonding materials 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 metal bonding materials 83, 90 having a thickness of about 100 μm.

[0042] The porous plug 55 may be attached, for example, by preparing a porous plug 55 formed in advance by firing, applying an adhesive to the ceramic plate through-hole 50, and then inserting the porous plug 55 from above the ceramic plate through-hole 50 to adhesively fix the outer peripheral surface of the porous plug 55 to the inner peripheral surface of the ceramic plate through-hole 50. Alternatively, a male screw portion may be formed on the outer peripheral surface of the porous plug 55, a female screw portion may be formed on the inner peripheral surface of the ceramic plate through-hole 50, and the porous plug 55 may be screwed into the ceramic plate through-hole 50 to screw the male screw portion of the porous plug 55 into the female screw portion of the ceramic plate through-hole 50, thereby attaching the porous plug 55. When inserting the porous plug 55 into the ceramic plate through-hole 50, the insertion is performed at least until the lower surface of the porous plug 55 comes into contact with the conductive gas passage 70.

[0043] When the porous plug 55 is inserted into the ceramic plate penetration portion 50, the porous plug 55 may be inserted not only until the porous plug 55 contacts the conductive gas passage portion 70, but also until the porous plug 55 presses the conductive gas passage portion 70 downward to compress the conductive gas passage portion 70. In this way, the conductive gas passage portion 70 can be more reliably brought into contact with the lower surface of the porous plug 55. In addition, since the conductive gas passage portion 70 is in a compressed state in the wafer mounting table 10 after manufacture, the contact between the conductive gas passage portion 70 and the porous plug 55 is more easily maintained. In this case, for example, the conductive gas passage portion 70 may be disposed so that the upper end of the conductive gas passage portion 70 is inserted into the ceramic plate penetration portion 50 before the porous plug 55 is mounted (before the conductive gas passage portion 70 is compressed). In this way, the conductive gas passage portion 70 can be easily pressed by the porous plug 55 when the porous plug 55 is inserted.

[0044] In the wafer mounting table 10 described above, the conductive gas passage 70 is provided in the gas introduction passage 60 (here, in the second gas passage 62 and the bonding layer penetrating portion 64), contacts the lower surface of the porous plug 55, and is electrically connected to the conductive plate 30. Therefore, since the conductive gas passage 70, which has the same potential as the conductive plate 30, contacts the porous plug 55, discharge can be suppressed around the end of the porous plug 55 on the conductive plate 30 side, i.e., around the lower end of the porous plug 55. Note that, for example, even if an insulating porous member exists on the lower surface of the porous plug 55 instead of the conductive gas passage 70, discharge can be suppressed around the lower end of the porous plug 55. However, the presence of the conductive gas passage 70 makes it difficult for a potential difference to occur around the end of the porous plug 55 on the conductive plate 30 side, and discharge can be suppressed more effectively. As a result, in the wafer mounting table 10 of this embodiment, the power of a radio frequency (RF) power source connected to the conductive plate 30 can be increased, for example, compared to the case where an insulating porous member exists instead of the conductive gas passage 70. Also, there is a demand to increase the gas pressure of the backside gas in order to further increase the efficiency of thermal conduction between the wafer W and the ceramic plate 20, but generally, increasing the gas pressure makes discharge more likely to occur. In the wafer mounting table 10 of this embodiment, discharge can be further suppressed by the conductive gas passage 70, so the gas pressure can be increased compared to the case where an insulating porous member is used instead of the conductive gas passage 70. Furthermore, when the gas pressure is the same, discharge can be suppressed even if the internal space (gap) of the conductive gas passage 70 is larger than the pores of the insulating porous member, so that gas filling is completed quickly and the gas pressure can be easily controlled to a constant value.

[0045] In addition, the conductive gas passage 70 is a member separate from the conductive plate 30 and is in contact with the gas introduction passage 60. Therefore, the wafer mounting table 10 is easier to manufacture than when, for example, the conductive gas passage 70 is an integral member with the conductive plate 30 rather than a separate member.

[0046] Furthermore, the conductive gas passage 70 is an elastic member, and is compressed by being pressed against the lower surface of the porous plug 55. Therefore, contact between the conductive gas passage 70 and the porous plug 55 is easily maintained.

[0047] Furthermore, the conductive gas passage portion 70 is formed of a conductive mesh or a mass of conductive fibers, so that gas can easily flow through the inside of the conductive gas passage portion 70.

[0048] The conductive gas passage 70 is disposed so as to overlap the entire lower surface of the porous plug 55 when viewed virtually from above. Therefore, the conductive gas passage 70 is present below the entire lower surface of the porous plug 55, so that discharge around the end of the porous plug 55 on the conductive plate 30 side can be more reliably suppressed.

[0049] 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.

[0050] In the above-described embodiment, the conductive gas passage 70 may be a conductive bulk body having holes that open toward the lower surface of the porous plug 55 and allow gas to pass in the vertical direction. For example, as shown in FIG. 8, the conductive gas passage 70 may be a conductive bulk body having holes 70a that open toward the lower surface of the porous plug 55 and allow gas to pass in the vertical direction, and grooves 70b that are provided on the lower surface of the conductive gas passage 70 and open horizontally to the second gas passage 62. The lower surface of the conductive gas passage 70 in FIG. 8 is in contact with the conductive plate 30. The conductive gas passage 70 allows gas to pass through the holes 70a and grooves 70b inside. In this case, the diameter of the holes 70a is preferably 0.1 mm or more and 1 mm or less. The holes 70 AIf the diameter is 0.1 mm or more, the gas flow rate is unlikely to be insufficient. If the diameter of the hole 70a is 1 mm or less, a potential difference is unlikely to occur in the hole 70a, and discharge in the hole 70a can be suppressed. The width and depth of the groove 70b are also preferably 0.1 mm or more from the viewpoint of the gas flow rate. Although the width and depth of the groove 70b are unlikely to affect the discharge, the width and depth of the groove 70b may be 1 mm or less. At least one of the holes 70a and the groove 70b may be provided in multiple numbers. In addition to the metal materials and carbon listed as the materials of the conductive gas passage section 70 described above, the conductive bulk body may also be made of a composite material of metal and ceramic listed as the materials of the conductive plate 30. The conductive gas passage section 70 and the conductive plate 30 may be formed of the same material. When the conductive gas passage section 70 is a conductive bulk body, the conductance of the conductive gas passage section 70 can be adjusted, for example, by adjusting the size and / or number of at least one of the holes 70a and the groove 70b.

[0051] In the above-described embodiment, the conductive gas passage 70 may be an integral member rather than a separate member from the conductive plate 30. For example, the conductive gas passage 70 of the conductive bulk body shown in FIG. 8 may be a part of the conductive plate 30. In this case, the conductive gas passage 70 is formed as a protrusion provided on the upper surface of the conductive plate 30.

[0052] In the above-described embodiment, the conductive gas passage 70 may be a conductive porous body. For example, the conductive porous material may be SiC or SiSiC. The conductive porous body may have an average pore diameter of 0.05 mm or more and 1 mm or less. If the average pore diameter is 0.05 mm or more, the gas flow rate is unlikely to be insufficient. If the average pore diameter is 1 mm or less, a potential difference is unlikely to occur in the conductive porous body, and discharge in the conductive porous body can be suppressed. The porosity of the conductive porous body may be 30% or more, or 70% or less.

[0053] In the above-mentioned embodiment, the second gas passage 62 has a groove 31 (first recess) provided on the upper surface of the conductive plate 30, and is formed by arranging the lower surface (flat surface) of the conductive bonding layer 40 on the groove 31, but is not particularly limited thereto. For example, the second gas passage 62 may be formed by having a groove (second recess) provided on the lower surface of the conductive bonding layer 40, and arranging the upper surface (flat surface) of the conductive plate 30 below the groove. In addition, the conductive bonding layer 40 may have a two-layer structure, with a groove (groove penetrating in the vertical direction) that will eventually become the second gas passage 62 provided in the lower layer, and the above-mentioned bonding layer penetration portion 64 provided in the upper layer. In this case, too, a conductive gas passage 70 is provided inside the gas introduction passage 60 (bonding layer penetration portion 64), and the conductive gas passage 70 is provided so as to contact the lower surface of the porous plug 55 and to be electrically conductive with the conductive plate 30, thereby suppressing discharge around the end of the porous plug 55 on the conductive plate 30 side.

[0054] In the above-mentioned embodiment, the second gas passage 62 may be built into the conductive plate 30 instead of being provided at the interface between the conductive bonding layer 40 and the conductive plate 30. For example, as shown in FIG. 9, the second gas passage 62 may be built into the conductive plate 30, and the third gas passage 65, which is a vertical hole that communicates the second gas passage 62 with the bonding layer penetration portion 64, may be provided in the conductive plate 30. Even in this case, as in the above-mentioned embodiment, the conductive gas passage portion 70 is present, so that discharge around the end portion of the porous plug 55 on the conductive plate 30 side can be suppressed. When manufacturing the wafer mounting table 10 in which the second gas passage 62 is built into the conductive plate 30, a first MMC disk member having a through hole that serves as the third gas passage 65 and a second MMC disk member having a recessed groove 32a that serves as the coolant flow path 32 and a through hole 61a that serves as a part of the first gas passage 61 may be used instead of the MMC disk member 81 shown in FIG. At least one of the lower surface of the first MMC disk member and the upper surface of the second MMC disk member may have a recessed groove that serves as the second gas passage 62.

[0055] In the above-described embodiment, the second gas passages 62 and the auxiliary gas passages 63 may be omitted, and the first gas passages 61 and the ceramic plate penetrations 50 may be in one-to-one communication with each other.

[0056] In the above-described embodiment, as shown in FIG. 3, the gas flowing in the horizontal direction through the second gas passage 62 flows into the conductive gas passage 70, but the direction of the gas flow is not limited to this. For example, as shown in FIG. 10, the gas introduction passage 60 may have a fourth gas passage 66 provided directly below the conductive gas passage 70 and having a smaller diameter than the conductive gas passage 70, and the gas flowing upward from the fourth gas passage 66 may flow into the conductive gas passage 70. The conductive gas passage 70 in FIG. 10 is disposed inside the bonding layer penetration portion 64 of the gas introduction passage 60 and is in contact with the lower surface of the porous plug 55 and the upper surface of the conductive plate 30. The fourth gas passage 66 may be a hole communicating with the second gas passage 62, similar to the third gas passage 65 in FIG. 9. Alternatively, the second gas passage 62 and the auxiliary gas passage 63 may be omitted in the gas introduction passage 60, and the fourth gas passage 66 may be a hole communicating with the first gas passage 61 or a part of the first gas passage 61.

[0057] In the above-described embodiment, the diameter of the conductive gas passage portion 70 may be the same as the diameter of the porous plug 55. Even in this case, the conductive gas passage portion 70 can be arranged so as to overlap the entire lower surface of the porous plug 55, as long as the conductive gas passage portion 70 and the porous plug 55 are arranged so that their contours coincide when viewed virtually from above. The diameter of the conductive gas passage portion 70 may be smaller than the diameter of the porous plug 55. In this case, the diameter of the bonding layer penetrating portion 64 may be smaller than the diameter of the porous plug 55 so that part of the lower surface of the porous plug 55 comes into contact with the upper surface of the conductive bonding layer 40.

[0058] In the above-described embodiment, the conductive gas passage 70 is a substantially cylindrical member having a circular shape when viewed from above, but is not limited thereto. For example, the conductive gas passage 70 may be a substantially rectangular parallelepiped (including cubic) member.

[0059] In the above-described embodiment, the conductive gas passage portion 70 is in contact with the conductive plate 30 to be electrically connected to the conductive plate 30, but this is not particularly limited. For example, the conductive gas passage portion 70 may be in contact with the conductive bonding layer 40 while being separated from the conductive plate 30, and the conductive gas passage portion 70 may be electrically connected to the conductive plate 30 via the conductive bonding layer 40.

[0060] In the above-mentioned embodiment, the upper surface of the porous plug 55 is set to the same height as the reference surface 21c of the wafer mounting surface 21, but is not particularly limited thereto. For example, the difference obtained by subtracting the height of the upper surface of the porous plug 55 from the height of the reference surface 21c of the wafer mounting surface 21 may be set to a range of 0.5 mm or less (preferably 0.2 mm or less, more preferably 0.1 mm or less). In other words, the upper surface of the porous plug 55 may be disposed at a position lower than the reference surface 21c of the wafer mounting surface 21 by a range of 0.5 mm or less (preferably 0.2 mm or less, more preferably 0.1 mm or less). Even in this way, the height of the space between the lower surface of the wafer W and the upper surface of the porous plug 55 is kept relatively low. Therefore, it is possible to prevent glow discharge and therefore arc discharge from occurring in this space.

[0061] In the above-described embodiment, the lower surface of the porous plug 55 is at the same height as the lower surface of the ceramic plate 20, but this is not particularly limited. For example, the lower end of the porous plug 55 may protrude below the lower surface of the ceramic plate 20, or the lower end of the porous plug 55 may be located above the lower surface of the ceramic plate 20 and the conductive gas passage 70 may be in contact with the lower surface of the porous plug 55 inside the ceramic plate penetration portion 50.

[0062] In the above-described embodiment, the porous plug 55 prepared in advance is inserted into the ceramic plate through-hole 50 when the wafer mounting table 10 is manufactured, but the present invention is not limited to this. For example, before the ceramic plate 20 is joined to the MMC disk member 81 and the MMC disk member 82, a paste-like ceramic mixture serving as a precursor of the porous plug 55 may be injected into the ceramic plate through-hole 50 of the ceramic plate 20 and fired to form the porous plug 55. In this case, the lower surface of the porous plug 55 may be brought into contact with the conductive gas passage 70 when the ceramic plate 20, the MMC disk member 81, and the MMC disk member 82 are laminated together.

[0063] In the above-described embodiment, the ceramic plate penetration portion 50 is provided with the porous plug 55, but the insulating gas-permeable plug through which gas can pass may be provided in the ceramic plate penetration portion 50, and may be any insulating gas-permeable plug, such as the porous plug 55, as long as it is capable of passing through the inside of the insulating gas-permeable plug. For example, as shown in FIG. 11, an electrically insulating dense plug 155 having an internal gas flow path 155a may be used as the insulating gas-permeable plug. The internal gas flow path 155a is a flow path that allows gas to flow between the upper and lower sides of the dense plug 155. The internal gas flow path 155a is a path that passes through the dense plug 155 while bending between the upper and lower sides, and is more specifically configured as a spiral path. Another example of a path that passes through the dense plug 155 while bending is a zigzag path. The internal gas flow path 155a may be a straight through hole along the vertical direction. The diameter of the cross section of the internal gas flow path 155a is preferably 0.1 mm or more and 1 mm or less. One dense plug 155 may have multiple internal gas flow paths 155a. The porosity of the dense part of the dense plug 155 is preferably less than 0.1%. As the dense plug 155, ceramics such as alumina or aluminum nitride can be used, as in the porous plug 55. The dense plug 155 may be manufactured by firing a molded body formed using a 3D printer, or by firing a molded body formed by mold casting. Details of the dense plug 155 having an internal gas flow path that penetrates while bending, and mold casting are disclosed in, for example, Japanese Patent No. 7149914. Even when such a dense plug 155 is provided in the ceramic plate penetration part 50 instead of the porous plug 55, discharge in the ceramic plate penetration part 50 can be suppressed in the same manner as in the above-mentioned embodiment.

[0064] In the above-described embodiment, the conductive gas passage 70 may be a coating layer that covers the lower surface of the insulating gas passage plug. For example, the conductive gas passage 170 shown in FIG. 11 is formed as a coating layer that covers the lower surface of the dense plug 155. The conductive gas passage 170 is formed as a dense layer and has holes 170a that allow gas to pass in the vertical direction. The holes 170a communicate the opening of the internal gas flow path 155a on the lower surface of the dense plug 155 with the gas introduction passage 60. The conductive gas passage 170 can be manufactured, for example, by forming a coating layer on the lower surface of the dense plug 155 by sputtering or electroless plating before mounting the dense plug 155 on the ceramic plate 20, and opening the holes 170a. The material of the conductive gas passage 170 can be, for example, a metal material, and metals with excellent corrosiveness such as Au, Ag, and Al are preferable. In this way, even when the conductive gas passage 170 is a coating layer that covers the lower surface of the dense plug 155, the conductive gas passage 170 is in contact with the lower surface of the dense plug 155 and is electrically connected to the conductive plate 30, so that discharge around the lower end of the dense plug 155 can be suppressed. The diameter of the hole 170a is preferably 0.1 mm or more and 1 mm or less. In FIG. 11, the conductive gas passage 170 is not in direct contact with the conductive plate 30, but is in contact with the conductive bonding layer 40 and is electrically connected to the conductive plate 30 via the conductive bonding layer 40.

[0065] The conductive gas passage 170 is not limited to a dense layer and may be a porous layer. In this case, it is not necessary to form the holes 170a as long as the gas can pass through the pores inside the conductive gas passage 170. For example, the conductive gas passage 170 can be formed as a metal porous layer on the lower surface of the dense plug 155 by using porous plating.

[0066] 11 , the lower surface of the dense plug 155 is covered with the conductive gas passage portion 170, but the conductive gas passage portion 170 may be formed so as to cover the lower surface of the porous plug 55. In this case, the conductive gas passage portion 170 is preferably a porous layer. When the conductive gas passage portion 170 is formed on the lower surface of the porous plug 55 by sputtering or the like, some of the constituent particles of the conductive gas passage portion 170 may penetrate into the pores of the porous plug 55.

[0067] In the above-mentioned embodiment and other examples, the conductive gas passage portion 70 has been described as a single member, but the conductive gas passage portion 70 may be composed of a plurality of members. For example, the conductive gas passage portion 70 may have one or more of the above-mentioned elastic member, conductive mesh, conductive fiber mass, conductive bulk body, conductive porous body, and a coating layer that covers the lower surface of the insulating gas passage plug, and may have two or more of different types of members in combination, or may have two or more of the same type of members. Even when the conductive gas passage portion 70 has a plurality of members in this way, it is sufficient that the plurality of members are electrically connected to each other, the conductive gas passage portion 70 as a whole is electrically connected to the conductive plate, and gas can pass through the inside. Furthermore, when the conductive gas passage portion 70 has a plurality of members, it is sufficient that any one of the plurality of members is in contact with the lower surface of the insulating gas passage plug. When the conductive gas passage section 70 is composed of multiple components including an elastic component, it is sufficient that the elastic component is compressed by pressing the conductive gas passage section 70 against the underside of the insulating gas passage plug, and it is not necessary for the elastic component to be pressed in direct contact with the underside of the insulating gas passage plug.

[0068] For example, the conductive gas passage portion may have a structure in which one or more conductive meshes and one or more conductive sheets having holes through which gas can pass in the vertical direction are laminated. The conductive gas passage portion 270 shown in FIG. 12 has a plurality of conductive gas passage members, specifically, a plurality (two in this case) of meshes 271 and a plurality (two in this case) of conductive sheets 272. The plurality of meshes 271 and the plurality of conductive sheets 272 are laminated alternately in the vertical direction. The meshes 271 can be made of the same material as the conductive mesh given as an example of the conductive gas passage portion 70 described above. The conductive sheet 272 is also an example of a conductive bulk body, and can be made of the same material as the conductive gas passage portion 70, which is a conductive bulk body shown in FIG. 8. The conductive sheet 272 only needs to have one or more holes 272a through which gas can pass in the vertical direction, and in FIG. 12, the conductive sheet 272 has a plurality of holes 272a (only three are shown). The diameter of the holes 272a is preferably 0.1 mm or more and 1 mm or less, similar to the hole 70a. The thickness of the conductive sheet 272 may be, for example, 0.01 mm or more and 2 mm or less. In the conductive gas passage 270, the upper surface of the mesh 271 located at the top is in contact with the lower surface of the porous plug 55, and the lower surface of the conductive sheet 272 located at the bottom is in contact with the conductive plate 30. All of the meshes 271 are pressed and compressed against the lower surface of the porous plug 55. The conductive gas passage 270 may include the above-mentioned conductive porous body instead of the conductive sheet 272. That is, the conductive gas passage 270 may have a structure in which one or more meshes 271 and one or more conductive porous bodies are stacked in the vertical direction. Since the conductive gas passage 270 has a structure in which a member having elasticity such as the mesh 271 and a member having no elasticity such as the conductive sheet 272 or the conductive porous body are stacked, the thickness of the entire conductive gas passage 270 can be easily adjusted to a desired value by the thickness of the member having no elasticity. The conductive gas passage 270 may not include the conductive sheet 272 and may be a laminate in which a plurality of meshes 271 are stacked in the vertical direction.

[0069] For example, the conductive gas passage may have a plurality of conductive gas passage members including a coating layer that covers the lower surface of the insulating gas passage plug. The conductive gas passage 370 shown in FIG. 13 has a coating layer 371 and a mesh 372 as a plurality of conductive gas passage members. The coating layer 371 covers the lower surface of the dense plug 155, similarly to the conductive gas passage 170 of FIG. 11. The coating layer 371 has holes 371a similar to the holes 170a. The mesh 372 has an upper surface in contact with the lower surface of the coating layer 371. The mesh 372 can be made of the same material as the conductive mesh given as an example of the conductive gas passage 70 described above. In the conductive gas passage 370, the coating layer 371 is in contact with the lower surface of the dense plug 155, and the lower surface of the mesh 372 is in contact with the conductive plate 30. Instead of the mesh 372, the conductive gas passage portion 370 may have any one of an elastic member, a mass of conductive fibers, a conductive bulk body, and a conductive porous body.

[0070] In the above-described embodiment, the ceramic plate 20 and the conductive plate 30 are joined by the conductive bonding layer 40, but a non-conductive bonding layer such as a resin bonding layer may be used instead of the conductive bonding layer 40. In this case, a metal such as Al or Ti can be used for the conductive plate.

[0071] 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.

[0072] 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.

[0073] In the above-described embodiment, the ceramic plate 20 is produced by hot-pressing and sintering a ceramic powder compact. However, the compact may be produced by stacking multiple tape compacts, by a mold casting method, or by compressing ceramic powder.

[0074] In the above-mentioned embodiment, the conductive gas passage section 70 may be an elastic body. Examples of the elastic body include a conductive spring. The spring may be made of the metal materials (Al, Ti, Mo or alloys thereof, steel) mentioned in the above-mentioned embodiment. It is preferable that the elastic body is disposed in a state in which the insulating gas passage plug is pressed upward by elastic force. In this way, contact between the conductive gas passage section and the insulating gas passage plug is easily maintained. In addition, when the above-mentioned conductive gas passage section 70 has a plurality of conductive gas passage members, one or more of the plurality of conductive gas passage members may be an elastic body. For example, the conductive gas passage section 70 may have an elastic body and one or more of the various members described above. When the conductive gas passage section 70 has a plurality of conductive gas passage members including an elastic body, it is not necessary for the elastic body itself to directly contact and press the insulating gas passage plug, and it is sufficient that the conductive gas passage section 70 presses the insulating gas passage plug upward by the elastic force of the elastic body.

[0075] For example, the conductive gas passage may have a coating layer that covers the lower surface of the insulating gas permeable plug, and an elastic body that presses the coating layer upward with an elastic force. A conductive gas passage 470 shown in FIG. 14 has a coating layer 471 and an elastic body 472 as a plurality of conductive gas permeable members. The coating layer 471, like the conductive gas passage 170 in FIG. 11 and the coating layer 371 in FIG. 13, is in contact with the lower surface of the dense plug 155 by coating the latter. The coating layer 471 has holes 471a similar to the holes 371a. The coating layer 471 is a layer formed in advance on the lower surface of the dense plug 155 by sputtering, and is made of Ti. The coating layer 471 may be made of the above-mentioned TiN. Conductive gas passage170 may be used. The elastic body 472 is a conductive spring, and the upper surface of the elastic body 472 is in contact with the lower surface of the coating layer 471. The lower surface of the elastic body 472 is in contact with the conductive plate 30. The elastic body 472 allows gas to pass through the inside. Specifically, gas can pass through the direction along the central axis of the elastic body 472 (up and down direction) and between the wires of the springs that constitute the elastic body 472. The elastic body 472 is disposed inside the wafer mounting table 10 in a state compressed more than its natural length, and presses the coating layer 471 and the dense plug 155 upward with its elastic force. Similarly, the elastic body 472 presses the conductive plate 30 downward with its elastic force. The coating layer 471 and the elastic body 472 are in contact with each other and are electrically connected, and the elastic body 472 and the conductive plate 30 are in contact with each other and are electrically connected. In the conductive gas passage 470 configured in this manner, the elastic body 472 presses the lower surface of the coating layer 471 upward with its elastic force, so that the conductive gas passage 470 and the dense plug 155 are easily maintained in contact with each other. This allows the conductive gas passage 470, which has the same potential as the conductive plate 30, to more reliably contact the dense plug 155, so that discharge can be more effectively suppressed around the end of the dense plug 155 on the conductive plate 30 side, i.e., around the lower end of the dense plug 155.

[0076] In the above-mentioned embodiment, the porous plug 55 is screwed to the ceramic plate 20. In the above-mentioned modified example, the porous plug 55 is formed by injecting a paste-like ceramic mixture, which is a precursor of the porous plug 55, into the ceramic plate 20 and then firing the mixture. In these embodiments, the porous plug 55 and the ceramic plate 20 are in direct contact with each other. As described above, the insulating gas-permeable plug may be provided in the ceramic plate through-hole so as to be in direct contact with the ceramic plate. In this way, it is not necessary to use an adhesive such as a resin for bonding the insulating gas-permeable plug and the ceramic plate. The insulating gas-permeable plug may be a member having a shape (for example, a truncated cone) in which the area of ​​the lower surface is larger than that of the upper surface. In this case, the ceramic plate is formed so that the ceramic plate through-hole has a shape (a shape in which the cross-sectional area of ​​the lower surface is larger than that of the upper surface) that matches the insulating gas-permeable plug, and the ceramic plate and the conductive plate are joined together after the insulating gas-permeable plug is inserted into the ceramic plate through-hole from the lower surface of the ceramic plate in advance. In this embodiment, the insulating gas-permeable plug can be provided in the ceramic plate through-hole so as to be in direct contact with the ceramic plate, and no adhesive is required.

[0077] This application claims priority from international application PCT / JP2023 / 2417, filed on January 26, 2023, the entire contents of which are incorporated herein by reference. [Industrial Applicability]

[0078] The present invention can be used, for example, in an apparatus for processing wafers. [Explanation of symbols]

[0079] 10 wafer mounting table, 20 ceramic plate, 21 wafer mounting surface, 21a seal band, 21b small circular protrusion, 21c reference surface, 22 electrode, 30 conductive plate, 31 groove, 32 coolant flow path, 32a groove 、40 conductive bonding layer, 50 ceramic plate penetration, 55 porous plug, 60 gas introduction passage, 61 first gas passage, 61a through hole, 61b through hole, 62 second gas passage, 62p overlapping portion, 63 auxiliary gas passage, 64 bonding layer penetration, 65 third gas passage, 66 fourth gas passage, 70 conductive gas passage, 70a hole, 70b groove, 81, 82 MMC disk member, 83, 90 metal bonding material, 155 dense plug, 155a internal gas flow path, 170 conductive gas passage, 170a hole, 270 conductive gas passage, 271 mesh, 272 conductive sheet, 272a hole, 371 coating layer, 371a hole, 372 mesh, 470 conductive gas passage, 471 coating layer, 471a Holes, 472 Elastic bodies.

Claims

1. a ceramic plate having a wafer mounting surface on an upper surface thereof and incorporating an electrode; a conductive plate bonded to a lower surface of the ceramic plate; a ceramic plate penetration portion penetrating the ceramic plate; an insulating gas-passing plug that is provided in the ceramic plate penetration portion and through which gas can pass; a gas introduction passage provided at least inside the conductive plate and communicating with the ceramic plate penetration portion; a conductive gas passage provided in the gas introduction passage, in contact with a lower surface of the insulating gas passing plug, electrically connected to the conductive plate, and allowing gas to pass therethrough; A wafer mounting table comprising:

2. The conductive gas passage is separate from the conductive plate. The wafer stage according to claim 1 .

3. the conductive gas passage portion has an elastic member, and the elastic member is pressed and compressed against a lower surface of the insulating gas passage plug. The wafer stage according to claim 2 .

4. The conductive gas passage portion has at least one of a conductive mesh and a conductive fiber mass. The wafer stage according to claim 2 or 3.

5. the conductive gas passage portion has a conductive bulk body having holes through which gas can pass in a vertical direction, The diameter of the hole is 0.1 mm or more and 1 mm or less. The wafer stage according to claim 1 .

6. The conductive gas passage portion has a conductive porous body. The wafer stage according to claim 1 .

7. the conductive gas passage portion has a structure in which one or more conductive meshes and one or more conductive sheets having holes through which gas can pass in the vertical direction are laminated, The diameter of the hole is 0.1 mm or more and 1 mm or less. The wafer stage according to claim 2 or 3.

8. the conductive gas passage portion is disposed so as to overlap with the entire lower surface of the insulating gas passage plug when viewed virtually from above. The wafer mounting table according to any one of claims 1 to 3.

9. The insulating gas-passing plug is a porous body. The wafer mounting table according to any one of claims 1 to 3.

10. the conductive gas passage portion has a coating layer that covers the lower surface of the insulating gas passage plug. The wafer stage according to claim 1 .

11. the conductive gas passage portion has a coating layer that coats the lower surface of the insulating gas passage plug, and an elastic body that presses the coating layer upward with an elastic force. The wafer stage according to claim 1 .

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