Wafer carrying table

Abstract

A wafer mounting table (10) is provided with: a ceramic plate (20) having a wafer mounting surface (21) on the upper surface and having built-in electrodes (22); a conductive plate (30) joined to the lower surface of the ceramic plate (20); a ceramic plate penetrating part (50) penetrating through the ceramic plate (20); a dense plug (55) which is provided in the ceramic plate through-hole (50) and through which gas can pass; a gas introduction passage (60) that is provided at least inside the conductive plate (30) and that communicates with the ceramic plate penetration section (50); and a conductive gas passage (70) which is provided inside the gas introduction passage (60), is in contact with the lower surface of the dense plug (55), is electrically connected to the conductive plate (30), and allows the passage of gas between the dense plug (55) and the gas introduction passage (60). The conductive gas passage section (70) has a plate spring (72) that presses the dense plug (55) upward by means of an elastic force.

Description

Technical Field The present invention relates to a wafer loading platform. Background Art Conventionally, there is a known wafer carrier comprising: a ceramic plate having a wafer placement surface on its upper surface; and a base plate joined to the lower surface of the ceramic plate and having a gas inlet passage. Patent Document 1 discloses that the wafer carrier comprises: an insulating first porous portion disposed within a through-hole of the ceramic plate; and an insulating second porous portion embedded in a recess provided on the ceramic plate side of the base plate in a manner opposing the first porous portion. Gas supplied to the gas inlet passage passes through the second porous portion and the first porous portion and flows into the space between the wafer placement surface and the wafer, thereby cooling the object. It is described that the presence of the first and second porous portions ensures a sufficient gas flow rate from the gas inlet passage to the wafer placement surface, and suppresses discharge (arc discharge) caused by plasma when processing the wafer. Prior art literature Patent Literature Patent Document 1: Japanese Patent Application Laid-Open No. 2020-72262 Summary of the Invention However, even if an insulating second porous portion is present as in Patent Document 1, discharge may occur around the end portion on the bottom plate side of the first porous portion. The present invention has been made to solve the above-mentioned problems, and its main object is to suppress the occurrence of discharge around the end portion on the conductive plate side of the insulating gas passage plug. The present invention adopts the following means to achieve the above-mentioned main object.

[0001] The wafer loading platform of the present invention comprises: a ceramic plate having a wafer placement surface on its upper surface and having electrodes built therein; a conductive plate bonded to the lower surface of the ceramic plate; a ceramic plate through-hole, the ceramic plate through-hole penetrating the ceramic plate; an insulating gas passage plug, the insulating gas passage plug being provided in the ceramic plate through-hole portion, and gas being able to pass therethrough; a gas introduction passage, the gas introduction passage being provided at least inside the conductive plate and communicating with the ceramic plate through-hole; and a conductive gas passage portion provided in the gas introduction passage, contacting the lower surface of the insulating gas passage plug and electrically connected to the conductive plate, and allowing gas to pass between the insulating gas passage plug and the gas introduction passage; The conductive gas passage portion includes a leaf spring that presses the insulating gas passage plug upward by elastic force. In this wafer stage, a conductive gas passage is provided within the gas introduction passage, in contact with the bottom surface of the insulating gas passage plug and electrically connected to the conductive plate. This reduces the potential difference generated around the end of the insulating gas passage plug on the conductive plate side, compared to, for example, a case where an insulating porous member is located on the bottom surface of the insulating gas passage plug. Consequently, discharges around the end of the insulating gas passage plug on the conductive plate side can be suppressed. Furthermore, the leaf spring's elastic force presses the insulating gas passage plug upward, facilitating electrical continuity from the portion of the conductive gas passage that contacts the insulating gas passage plug to the conductive plate.

[0002] In the wafer stage (the wafer stage described in [1] above), the leaf spring can be arranged so as to be pressed from above by the insulating gas passage plug and to extend in a lateral direction perpendicular to the vertical direction. Thus, by extending the leaf spring in the lateral direction, the area directly below the insulating gas passage plug where the leaf spring is absent can be reduced. This can further suppress discharge around the end portion of the insulating gas passage plug on the conductive plate side.

[0003] In the above-mentioned wafer placing table (the wafer placing table described in the above-mentioned [2]), the leaf spring may have a plurality of folded portions folded back in the up-down direction.

[0004] In the wafer carrier (the wafer carrier described in [3] above), the plurality of folding portions may include: a first folding portion folded from top to bottom, and a second folding portion folded from bottom to top, wherein the first folding portion includes a first plate-shaped portion extending in the horizontal direction and whose upper surface constitutes the upper surface of the leaf spring, and the second folding portion includes a second plate-shaped portion extending in the horizontal direction and whose lower surface constitutes the lower surface of the leaf spring. Accordingly, by having the first plate-shaped portion, the contact area between the leaf spring and the upper component can be increased, and by having the second plate-shaped portion, the contact area between the leaf spring and the lower component can be increased. As a result, the leaf spring and the upper and lower components can be more reliably contacted, and further, the conduction from the contact portion of the conductive gas passage portion with the insulating gas passage plug to the conductive plate can be more reliably maintained.

[0005] In the wafer placement table described above (the wafer placement table described in any one of [1] to [4] above), the conductive gas passage portion may include a coating layer that covers the lower surface of the insulating gas passage plug. In this case, the coating layer may be a dense layer having pores that allow gas passage. Alternatively, the coating layer may be a porous layer that allows gas passage. Alternatively, the coating layer may cover a portion of the lower surface of the insulating gas passage plug, allowing gas to pass through the uncovered portion of the lower surface.

[0006] In the above-mentioned wafer placement table (the wafer placement table described in any one of the above-mentioned [1] to [5]), the insulating gas passage plug may be a dense body or a porous body having an internal gas flow path.

[0007] In the wafer placement table (the wafer placement table described in any one of [1] to [6] above), the insulating gas passage plug may be a dense body having an internal gas flow path, and the opening at the lower end of the internal gas flow path may be located outside the range of movement caused by displacement of the upper surface of the leaf spring within the gas introduction passage when viewed from above. Thus, even if the leaf spring is displaced within the gas introduction passage, the upper surface of the leaf spring does not overlap with the opening at the lower end of the internal gas flow path when viewed from above, and thus the leaf spring is less likely to obstruct the flow of gas between the gas introduction passage and the internal gas flow path.

[0008] In the wafer placement table (the wafer placement table described in any one of [1] to [7]), the leaf spring may have a hole that allows gas to pass through. This allows gas to pass more easily through the conductive gas passage portion.

[0009] The wafer stage (the wafer stage described in [5]) may include a conductive layer covering the portion of the lower surface of the ceramic plate exposed to the gas introduction passage, with the leaf spring in contact with the conductive layer. Thus, the portion of the lower surface of the ceramic plate exposed to the gas introduction passage is covered with the conductive layer, and the conductive layer is in contact with the leaf spring, thereby electrically conducting with the conductive plate via the leaf spring. This makes it difficult to generate a potential difference around the portion of the lower surface of the ceramic plate facing the gas introduction passage. Consequently, it is possible to suppress discharge around the portion of the lower surface of the ceramic plate facing the gas introduction passage.

[0010] The wafer stage (the wafer stage described in [5]) may include: a conductive layer covering the portion of the lower surface of the ceramic plate exposed within the gas introduction passage; and a conductive conducting member in contact with the conductive plate and the conductive layer, respectively. Thus, the lower surface of the ceramic plate is covered with the conductive layer, and the conductive layer is electrically connected to the conductive plate via the conducting member. Therefore, a potential difference is less likely to occur around the portion of the lower surface of the ceramic plate facing the gas introduction passage. Therefore, discharge can be suppressed around the portion of the lower surface of the ceramic plate facing the gas introduction passage.

[0011] In the wafer stage (the wafer stage described in

[10] ), the conductive member may be an elastic member that presses the conductive layer upward using a spring force. Thus, since the conductive member presses the conductive layer upward using a spring force, it is easy to maintain conductivity from the conductive layer to the conductive plate.

[0012] In the above-mentioned wafer placing table (the wafer placing table described in any one of the above-mentioned [1] to

[11] ), the conductive gas passing portion may have a gas passing component that allows electrical conduction between the conductive plate and the leaf spring.

[0013] In the above-mentioned wafer placing table (the wafer placing table described in the above-mentioned

[12] ), the gas passing component can be an elastic body. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 It is a plan view of the wafer stage 10 . Figure 2 yes Figure 1 A-A cross-section diagram. Figure 3 It is a partially enlarged cross-sectional view showing the periphery of the second gas passage 62 and the conductive gas passage portion 70 . Figure 4 It is a perspective view of the leaf spring 72 of the conductive gas passage 70 . Figure 5 This is a cross-sectional view when a cut surface obtained by cutting the wafer stage 10 along a horizontal plane passing through the second gas passage 62 is viewed from above. Figure 6 This is a cross-sectional view when a cut surface obtained by cutting the wafer stage 10 along a horizontal plane passing through the coolant flow path 32 is viewed from above. Figure 7 This is an explanatory diagram showing a plan view of the wafer placement table 10 in which the coolant flow path 32 and the like are drawn. Figure 8 1 is a diagram showing the manufacturing process of the wafer stage 10 . Figure 9This is an explanatory diagram showing the appearance of the leaf spring 72 being pressed by the dense plug 55 when the wafer stage 10 is manufactured. Figure 10 It is a partially enlarged cross-sectional view showing the porous plug 155 and the covering layer 171 . Figure 11 It is a partially enlarged cross-sectional view showing the conductive gas passage portion 270 . Figure 12 It is a partially enlarged cross-sectional view showing the leaf spring 372 . Figure 13 It is a partially enlarged cross-sectional view showing the leaf spring 472 . Figure 14 This is a partially enlarged cross-sectional view showing another embodiment of the leaf spring 472 . Figure 15 It is a partially enlarged cross-sectional view showing the leaf spring 572 . Figure 16 It is an explanatory diagram showing the positions of the upper surface 572a of the leaf spring 572 and the gas internal flow path 55a in a plan view. Figure 17 It is an explanatory diagram showing the horizontal movement range of the leaf spring 572. Figure 18 It is a partially enlarged cross-sectional view showing an example of a leaf spring 472 including a hole 672c. Figure 19 yes Figure 18 A three-dimensional view of the leaf spring 472 in FIG. Figure 20 It is a partially enlarged cross-sectional view showing the conductive layer 25 and the leaf spring 772 . Figure 21 It is a partially enlarged cross-sectional view showing the conductive component 875 . Figure 22 It is a partially enlarged cross-sectional view showing the gas passage component 975. Figure 23 This is an explanatory diagram showing how the ceramic plate 20 and the conductive plate 30 are bonded together using the insulating bonding layer 940 . DETAILED DESCRIPTION Next, preferred embodiments of the present invention will be described with reference to the accompanying drawings. Figure 1 is a plan view of the wafer stage 10, Figure 2 yes Figure 1 A-A cross-section diagram, Figure 3 FIG. 1 is a partially enlarged cross-sectional view showing the periphery of the second gas passage 62 and the conductive gas passage portion 70. Figure 5 This is a cross-sectional view obtained by cutting the wafer stage 10 along a horizontal plane passing through the second gas passage 62 as viewed from above. Figure 6This is a cross-sectional view obtained by cutting the wafer stage 10 along a horizontal plane passing through the coolant flow path 32 from above. Figure 7 This is an explanatory diagram showing a plan view of the wafer placement table 10 in which the coolant flow path 32 and the like are drawn. Figure 3 This is a partially enlarged view of a cross-section of the wafer stage 10, taken along a plane perpendicular to the second gas passage 62 and passing through the conductive gas passage 70. In this specification, the terms "up" and "down" do not denote absolute positions, but rather relative positions. Therefore, depending on the orientation of the wafer stage 10, "up" and "down" may refer to "down," "up," "left," "right," or "front," "back." like Figure 2 As shown, the wafer stage 10 includes a ceramic plate 20 , a conductive plate 30 , a conductive bonding layer 40 , a ceramic plate through-hole 50 , a gas introduction passage 60 , and a conductive gas passage 70 . The ceramic plate 20 is a circular plate made of ceramics such as alumina sintered body or aluminum nitride sintered body (for example, 300 mm in diameter and 5 mm in thickness). The upper surface of the ceramic plate 20 is a wafer loading surface 21 for loading the wafer W. The ceramic plate 20 has an electrode 22 built in. Figure 1 As shown, an annular sealing tape 21a is formed along the outer edge of the chip loading surface 21 of the ceramic plate 20, and a plurality of small circular protrusions 21b are formed on the entire inner surface of the sealing tape 21a. The sealing tape 21a and the small circular protrusions 21b are of the same height, for example, a few μm to several tens of μm. The electrode 22 is a planar mesh electrode used as an electrostatic electrode and is connected to an external DC power supply via a power supply component (not shown). A low-pass filter can be arranged in the middle of the power supply component. The power supply component is electrically insulated from the conductive bonding layer 40 and the conductive plate 30. When a DC voltage is applied to the electrode 22, the chip W is adsorbed and fixed to the chip loading surface 21 (specifically, the upper surface of the sealing tape and the upper surface of the small circular protrusions) by electrostatic adsorption force. When the application of the DC voltage is released, the adsorption and fixation of the chip W on the chip loading surface 21 is released. It should be noted that a portion of the wafer placement surface 21 where the sealing tape 21 a and the small circular protrusions 21 b are not provided is referred to as a reference surface 21 c . The conductive plate 30 is a circular plate with good thermal conductivity (a circular plate with a diameter that is the same as or larger than the diameter of the ceramic plate 20). A refrigerant flow path 32 for refrigerant circulation is formed inside the conductive plate 30. The refrigerant flowing in the refrigerant flow path 32 is preferably a liquid, and is preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inactive liquids. The refrigerant flow path 32 is formed in a single stroke from one end (inlet) to the other end (outlet) of the conductive plate 30 as a whole when viewed from above. The refrigerant flow path 32 is configured as follows: Figure 6As shown, based on a multiple circle obtained by arranging multiple virtual circles (single-dash circles C1 to C4, where circles C1 to C4 are concentric circles) of different diameters when viewed from above in a non-overlapping manner, it is drawn from one end to the other end in a single stroke. Specifically, when drawing the refrigerant flow path 32 from one end to the other end in a single stroke, the drawing is performed in a manner that connects two virtual circles in an inner and outer relationship in the multiple circles to draw the virtual 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 path 32, respectively. The refrigerant supplied to one end of the refrigerant flow path 32 from the supply port of the external refrigerant device passes through the refrigerant flow path 32, returns to the recovery port of the external refrigerant device from the other end of the refrigerant flow path 32, and after temperature adjustment, is supplied to one end of the refrigerant flow path 32 from the supply port again. The conductive plate 30 is connected to a high-frequency (RF) power supply and is also used as an RF electrode. Regarding the material of the conductive plate 30, for example, metal materials, composite materials of metal and ceramics, etc. can be cited. Examples of metal materials include: Al, Ti, Mo or alloys thereof. Examples of composite materials of metal and ceramics include: metal matrix composite materials (MMC), ceramic matrix composite materials (CMC), etc. Specific examples of such composite materials include: materials containing Si, SiC and Ti (also called SiSiCTi), materials obtained by impregnating a SiC porous body with Al and / or Si, composite materials of Al2O3 and TiC, etc. As the material of the conductive plate 30, it is preferable to select a material having a thermal expansion coefficient close to that of the material of the ceramic plate 20. Conductive bonding layer 40 is, for example, a metal bonding layer, and bonds the lower surface of ceramic plate 20 to the upper surface of conductive plate 30. Conductive bonding layer 40 is formed, for example, using TCB (Thermal Compression Bonding). TCB is a well-known method in which a metal bonding material is sandwiched between two components to be bonded and the two components are pressurized and bonded while being heated to a temperature below the solidus temperature of the metal bonding material. like Figure 2 As shown, 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 hole that extends from the lower surface of the ceramic plate 20 to the reference surface 21c ( Figure 1 ) gas passage. Figure 1 As shown, there are multiple (here 36) ceramic plate through-holes 50. Figure 2 As shown, the ceramic plate through-hole 50 is a space with a shape (e.g., an inverted truncated cone) whose cross-sectional area decreases from the upper opening toward the lower opening. The ceramic plate through-hole 50 has an electrically insulating dense plug 55 (an example of an insulating gas passage plug) that allows gas to flow in the vertical direction. The dense plug 55 is a component having a shape (for example, a truncated cone shape) in which the cross-sectional area decreases from the upper surface to the lower surface, similar to the shape of the ceramic plate through-hole 50. The dense plug 55 has an internal gas flow path 55a. The internal gas flow path 55a is a flow path that allows gas to flow between the upper surface side and the lower surface side of the dense plug 55. The internal gas flow path 55a is a passage that passes through the upper surface side and the lower surface side of the dense plug 55 in a curved state, and more specifically, is configured as a serrated passage. As another example of a passage that passes through in a curved state, a spiral passage can be cited. The internal gas flow path 55a can be a straight through hole along the up and down direction. The diameter of the flow path cross section of the internal gas flow path 55a is preferably greater than 0.1 mm and less than 1 mm. One dense plug 55 can have multiple internal gas flow paths 55a. The porosity of the dense portion of the dense plug 55 is preferably less than 0.1%. The dense plug 55 is fixed by being press-fitted into the ceramic plate through-hole 50. For example, ceramics such as alumina and aluminum nitride can be used as the dense plug 55. The dense plug 55 can be manufactured by, for example, firing a molded body formed using a 3D printer or firing a molded body formed by die casting. Details of a dense plug having a curved internal gas flow path extending therethrough and die casting are disclosed in, for example, Japanese Patent No. 7149914. The upper surface of the dense plug 55 is at the same height as the reference surface 21c of the wafer placement surface 21. The lower surface of the dense plug 55 is covered with a coating layer 71 which is a part of the conductive gas passage 70. Figure 2 、 3 As shown, the lower surface of the dense plug 55 is located above the lower opening surface of the ceramic plate through-hole 50 (which is at the same height as the lower surface of the ceramic plate 20). The lower surface of the dense plug 55 may also be at the same height as the lower opening surface of the ceramic plate through-hole 50. The lower surface of the dense plug 55 may also be located below the lower opening surface of the ceramic plate through-hole 50. In other words, the lower end of the dense plug 55 may protrude below the lower surface of the ceramic plate 20. The gas introduction passage 60 is a gas passage provided at least inside the conductive plate 30 and communicating with the ceramic plate through-hole 50. The gas introduction passage 60 includes: a first gas passage 61, a second gas passage 62, and a gas auxiliary passage 63 ( Figure 5 ), and a bonding layer penetration portion 64. The gas introduction passage 60 includes: a gas passage (a first gas passage 61, a second gas passage 62, and a gas auxiliary passage 63) provided inside the conductive plate 30, and a gas passage (bonding layer penetration portion 64) provided inside the conductive bonding layer 40. The first gas passage 61 vertically penetrates the conductive plate 30. The first gas passage 61 vertically penetrates the refrigerant flow paths 32 of the conductive plate 30. A plurality of first gas passages 61 (here, three) are provided. 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 placement surface 21. It should be noted that the so-called "parallel" is considered to be parallel even if it is not completely parallel, as long as it is within the range of an allowable error (such as a tolerance). The second gas passage 62 is formed by having a groove 31 (first recess) provided on the upper surface of the conductive plate 30 and covering the upper surface of the groove 31 with the conductive bonding layer 40. The second gas passage 62 is as shown in FIG. Figure 7 The second gas passages 62 are arranged in an annular shape in a manner that repeats any one of the multiple virtual circles C1 to C4 when viewed from above. Specifically, the first second gas passage 62 of the three gas passages 62, counting from the outer periphery of the wafer carrier 10, repeats the virtual circle C1 of the largest diameter, the second second gas passage 62 repeats the virtual circle C2 of the second largest diameter, and the third second gas passage 62 repeats the virtual circle C3 of the third largest diameter. Each second gas passage 62 has an overlapping portion 62p ( Figure 7 Grid section in the . The gas-assist passage 63 connects the first gas passage 61 and the second gas passage 62 and is provided parallel to the wafer placement surface 21 at the interface between the conductive bonding layer 40 and the conductive plate 30. A plurality of ceramic plate through-holes 50 are provided for each second gas passage 62 (here, twelve). However, the number of first gas passages 61 and gas-assist passages 63 provided is less than the number of ceramic plate through-holes 50 (here, one for each second gas passage 62). like Figure 2 As shown, the bonding layer through-holes 64 are holes that penetrate the conductive bonding layer 40 in the vertical direction. The bonding layer through-holes 64 serve as gas passages 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 (here, 36) are provided, arranged in a one-to-one correspondence with the ceramic plate through-holes 50. In this embodiment, the diameter of the bonding layer through-holes 64 is the same as or larger than the diameter of the opening at the bottom of the ceramic plate through-hole 50. The conductive gas passage 70 is provided within the gas introduction passage 60, in contact with the lower surface of the dense plug 55, electrically conductive with the conductive plate 30, and configured to allow gas to pass between the dense plug 55 and the gas introduction passage 60. The conductive gas passage 70 includes a coating layer 71 and a leaf spring 72. The coating layer 71 covers the lower surface of the dense plug 55, thereby contacting the lower surface of the dense plug 55. The coating layer 71 is formed as a dense layer and has holes 71a extending in the vertical direction for gas to pass through. The holes 71a connect the opening of the internal gas flow path 55a on the lower surface of the dense plug 55 with the gas introduction passage 60. The coating layer 71 can be manufactured by, for example, forming a coating layer on the lower surface of the dense plug 55 by sputtering, electroless plating, or the like before press-fitting the dense plug 55 into the ceramic plate 20, and providing the holes 71a. Examples of the material of the coating layer 71 include metal materials, preferably metals having excellent corrosion resistance such as Au, Ag, Al, Ti, SUS316L, or Hastelloy (Ni—Fe—Mo alloy, Hastelloy is a registered trademark). The leaf spring 72 is a conductive elastic body that uses elastic force to press the dense plug 55 upward. Metal materials such as Al, Ti, Mo, or alloys thereof, steel, SUS316L, and Hastelloy (registered trademark) can be used as materials for the leaf spring 72. The leaf spring 72 is manufactured by bending a metal plate, for example. In this embodiment, the leaf spring 72 has a zigzag shape. The zigzag shape of the leaf spring 72 folds back in the vertical direction. That is, the leaf spring 72 has multiple folded portions 73 that fold back in the vertical direction. The folded portions 73 of the leaf spring 72 are formed in a V-shape. The multiple folded portions 73 of the leaf spring 72 include: one or more (here, multiple, specifically four) first folded portions 73a folded back from top to bottom; and one or more (here, multiple, specifically three) second folded portions 73b folded back from bottom to top. Therefore, in this embodiment, the leaf spring 72 has seven folded portions. The upper surface 72a of the leaf spring 72 (the upper surface of the first folded portion 73a of the leaf spring 72, see also Figure 4 ) is in contact with the lower surface of the coating layer 71. The leaf spring 72 is provided across the interior of the ceramic plate through-hole 50, the interior of the bonding layer through-hole 64 in the gas introduction passage 60, and the interior of the second gas passage 62. The lower surface 72b of the leaf spring 72 (the lower surface of the second folded portion 73b of the leaf spring 72, also refer to Figure 4) The portion of the lower surface (bottom surface) of the second gas passage 62 (groove 31) located directly below the bonding layer penetration portion 64 contacts the conductive plate 30. The leaf spring 72 contacts the conductive plate 30, thereby electrically conducting with the conductive plate 30. In this embodiment, the zigzag folding direction of the leaf spring 72 is along the up-down direction, so the main expansion and contraction direction of the leaf spring 72 is not Figure 2 The up and down direction in the figure is the direction in which the dense plug 55 is pressed, but Figure 2 In the left-right direction. That is, the leaf spring 72 is arranged in the horizontal direction. However, the leaf spring 72 has a serrated shape. The leaf spring 72 is pressed from above by the dense plug 55 and becomes stretched in the horizontal direction perpendicular to the vertical direction (causing the plate of the leaf spring 72 to be more inclined relative to the vertical direction). Therefore, as a force to return the stretched plate (a force to return the inclined plate of the leaf spring 72 to a direction along the vertical direction), the leaf spring 72 also exerts an elastic force in the vertical direction. Due to this elastic force, the leaf spring 72 presses the dense plug 55 upward. Similarly, the leaf spring 72 uses its elastic force to press the conductive plate 30 downward. Regarding the leaf spring 72, at least one of the shape and the arrangement position is adjusted so that the hole 71a of the coating layer 71 (and the opening at the lower end of the gas internal flow path 55a) is not completely blocked to prevent the gas flow. Figure 2 As shown, the widths of the four upper surfaces 72a of the leaf spring 72, which form the contact surfaces with the coating layer 71, are each smaller than the opening diameter of the hole 71a. Regardless of the placement position, the leaf spring 72 is adjusted so as not to completely block the hole 71a (and the opening at the lower end of the internal gas flow path 55a). Thus, because the coating layer 71 has the hole 71a, the leaf spring 72 does not block the flow of gas through the hole 71a. Therefore, gas in the gas introduction passage 60 can pass through the interior and / or surroundings of the conductive gas passage 70 and flow into the ceramic plate through-portion 50. In other words, the conductive gas passage 70 allows gas to pass between the dense plug 55 and the gas introduction passage 60. The leaf spring 72 is arranged so that the surface direction of the leaf spring 72 is along the gas flow direction ( Figure 5 The tangent direction of the arc of the second gas passage 62 is shown as ( Figure 2 、 3 Thus, the leaf spring 72 is less likely to obstruct the gas flow in the second gas passage 62. However, the leaf spring 72 may be arranged so that the surface direction of the leaf spring 72 is perpendicular to the gas flow direction in the second gas passage 62 in which the leaf spring 72 is arranged. In this embodiment, a plurality of conductive gas passages 70 (here, 36) are provided, and are arranged in a one-to-one correspondence with the dense plugs 55. That is, the coating layer 71 and the leaf spring 72 are arranged in a one-to-one correspondence with the dense plugs 55, respectively. Next, an example of using the wafer stage 10 constructed as described above will be described. First, with the wafer stage 10 installed in a chamber (not shown), a wafer W is placed on the wafer placement surface 21. The chamber is then depressurized using a vacuum pump to a predetermined vacuum level. A DC voltage is applied to the electrodes 22 of the ceramic plate 20 to generate an electrostatic attraction force, which secures the wafer W to the wafer placement surface 21 (specifically, the upper surface of the sealing tape 21a and the upper surface of the small circular protrusions 21b). Next, a reaction gas atmosphere is created in the chamber at a predetermined pressure (e.g., tens to hundreds of Pa). In this state, an RF voltage is applied between an upper electrode (not shown) located at the top of the chamber and the conductive plate 30 of the wafer stage 10 to generate plasma. The generated plasma treats the surface of the wafer W. A coolant circulates through the coolant flow path 32 of the conductive plate 30. Backside gas is introduced from a gas cylinder (not shown) into the first gas passage 61 of the gas introduction passage 60. As the back side gas, a heat conductive gas (such as He gas) is used. The back side 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 sequence and is distributed to the plurality of ceramic plate through-holes 50, and is supplied and sealed in the space between the back side surface of the chip W and the reference surface 21c of the chip loading surface 21. Due to the presence of this back side gas, heat conduction between the chip W and the ceramic plate 20 can be carried out efficiently. In addition, by providing a dense plug 55 in the ceramic plate through-hole 50, it is possible to suppress the occurrence of discharge in the ceramic plate through-hole 50. In addition, by making the internal gas flow path 55a a curved flow path, it is possible to suppress the occurrence of discharge in the internal gas flow path 55a compared to the case where it is a straight flow path. Next, based on Figure 8 and Figure 9 , a manufacturing example of the wafer placement table 10 is described. Figure 8 1 is a diagram showing the manufacturing process of the wafer stage 10 . Figure 9 This is an explanatory diagram showing the appearance of the leaf spring 72 pressed by the dense plug 55 when manufacturing the wafer stage 10. Here, the case where the conductive plate 30 is made of MMC is exemplified. First, a ceramic plate 20 ( Figure 8 (A) in the figure). For example, a ceramic powder compact having an electrode 22 is produced, and the compact is hot-pressed to obtain a ceramic plate 20. A ceramic plate through portion 50 ( Figure 8 (B) The ceramic plate through-hole 50 is formed so as to penetrate the ceramic plate 20 in the vertical direction while avoiding the electrode 22 . At the same time, prepare two MMC disc components 81 and 82 ( Figure 8Then, grooves and holes are appropriately formed in these MMC disc parts 81 and 82 by machining. Figure 8 (D) in the figure). Specifically, a groove 32a that eventually becomes the refrigerant flow path 32 is formed on the lower surface of the upper MMC disc part 81, and a groove 31 that eventually becomes the second gas passage 62 is formed on the upper surface of the MMC disc part 81. In addition, a through hole 61a that eventually becomes a part of the first gas passage 61 is formed from the groove 31 to the lower surface of the MMC disc part 81. In addition, a through hole 61b that eventually becomes a part of the first gas passage 61 is formed on the lower MMC disc part 82. In the case where the ceramic plate 20 is made of alumina, the MMC disc parts 81 and 82 are preferably made of SiSiCTi or AlSiC. This is because the thermal expansion coefficient of alumina can be roughly the same as the thermal expansion coefficient of SiSiCTi and AlSiC. For example, a SiSiCTi disc component can be produced as follows. First, silicon carbide, metallic Si, and metallic Ti are mixed to form a powder mixture. Next, the resulting powder mixture is uniaxially pressed to form a disc-shaped compact. This compact is then hot-pressed and sintered in an inert atmosphere to produce the SiSiCTi disc component. Next, the ceramic plate 20, the MMC disk member 81, and the MMC disk member 82 are subjected to TCB bonding, and the overall shape is adjusted and the dense plug 55 is assembled, thereby obtaining the wafer placement table 10 ( Figure 8(E), (F) in it). Specifically, the metal bonding material 83 is sandwiched between the upper surface of the lower MMC disc part 82 and the lower surface of the upper MMC disc part 81, and the metal bonding material 90 is sandwiched between the upper surface of the upper MMC disc part 81 and the lower surface of the ceramic plate 20, thereby obtaining a stacked body. A through hole that will eventually become a part of the first gas passage 61 is pre-formed in the metal bonding material 83, and a through hole that will eventually become the bonding layer through-hole 64 is pre-formed in the metal bonding material 90. After the metal bonding material 90 is arranged on the upper surface of the MMC disc part 81, the leaf spring 72 is pre-inserted into the through hole that will become the bonding layer through-hole 64 and into the groove 31 directly below it. Next, the stacked body is pressurized and bonded at a temperature below the solidus temperature of the metal bonding materials 83 and 90 (for example, a temperature above the solidus temperature minus 20°C and below the solidus temperature), and then returned to room temperature. Thus, the two MMC disc components 81 and 82 are joined by the metal bonding material 83 to form the conductive plate 30. In addition, the ceramic plate 20 and the conductive plate 30 are joined by the metal bonding material 90. The metal bonding material 90 forms the conductive bonding layer 40. As the metal bonding materials 83 and 90, Al-Mg bonding materials or Al-Si-Mg bonding materials can be used. For example, when TCB is performed using an Al-Si-Mg bonding material, the stack is pressurized in a heated state under a vacuum atmosphere. The metal bonding materials 83 and 90 preferably have a thickness of about 100 μm. For example, the dense plug 55 is assembled as follows. First, a dense plug 55 formed by firing is prepared, and a coating layer 71 is formed on the lower surface of the dense plug 55. Then, the dense plug 55 is inserted from above the ceramic plate through-hole 50 so that the coating layer 71 on the lower surface of the dense plug 55 contacts the leaf spring 72 ( Figure 9 (A) and (B) in the figure), and then, the dense plug 55 is pressed downward. As a result, the dense plug 55 is pressed into the ceramic plate through-hole 50, and the dense plug 55 presses the leaf spring 72 (the dense plug 55 presses the leaf spring 72 via the coating layer 71), and the leaf spring 72 is elastically deformed ( Figure 9 (C) in the wafer placement table 10 is thus manufactured such that the leaf spring 72 is arranged in a state of being extended in the horizontal direction perpendicular to the vertical direction. That is, the leaf spring 72 has a natural length before being pressed by the dense plug 55, that is, a width W1 in the horizontal direction ( Figure 9 (A)) in the figure stretches to become a width W2 larger than the width W1 ( Figure 9 (C)). In addition, the leaf spring 72 is extended in the horizontal direction from the height T1 in the vertical direction before being pressed by the dense plug 55 ( Figure 9(A) in the figure changes to a height T2 smaller than the height T1 ( Figure 9 (C) in the figure). As described above, the leaf spring 72 generates not only a lateral elastic force but also a vertical elastic force, causing the upper surface 72a of the leaf spring 72 to press the dense plug 55 upward. By pressing the dense plug 55 into the ceramic plate through-hole 50 in this manner, such that the dense plug 55 not only contacts the leaf spring 72 via the coating 71 but also presses the leaf spring 72 downward, the dense plug 55 is more reliably in contact with the leaf spring 72 via the coating 71. This allows for more reliable electrical conduction between the coating 71, the leaf spring 72, and the conductive plate 30. In the wafer stage 10 described in detail above, the conductive gas passage 70 is provided within the gas introduction passage 60 (here, within the second gas passage 62 and within the bonding layer penetration portion 64), contacts the bottom surface of the dense plug 55, and is electrically conductive with the conductive plate 30. Therefore, since the conductive gas passage 70, which is at the same potential as the conductive plate 30, contacts the dense plug 55, it is possible to suppress discharge around the end of the dense plug 55 on the conductive plate 30 side, i.e., around the bottom end of the dense plug 55. Note that even if, for example, an insulating porous member is provided on the bottom surface of the dense plug 55 instead of the conductive gas passage 70, discharge around the bottom end of the dense plug 55 can still be suppressed. However, the presence of the conductive gas passage 70 makes it less likely that a potential difference will occur around the end of the dense plug 55 on the conductive plate 30 side, further suppressing discharge. Thus, in the wafer stage 10 of this embodiment, the power of the high-frequency (RF) power source connected to the conductive plate 30 can be increased, for example, compared to a case where an insulating porous member is included in place of the conductive gas passage 70. Furthermore, while it is desirable to increase the backside gas pressure to further improve the efficiency of heat transfer between the wafer W and the ceramic plate 20, increasing the gas pressure generally increases the likelihood of discharge. In the wafer stage 10 of this embodiment, the conductive gas passage 70 further suppresses discharge, allowing the gas pressure to be increased compared to a case where an insulating porous member is included in place of the conductive gas passage 70. Furthermore, the conductive gas passage 70 includes a leaf spring 72 that uses its elastic force to press the dense plug 55 upward. This allows the dense plug 55 to more reliably contact the leaf spring 72 via the coating 71, making it easier to maintain electrical continuity from the portion of the conductive gas passage 70 that contacts the dense plug 55 (here, the upper surface of the coating 71) to the conductive plate 30. Furthermore, since the conductive gas passage 70, including the leaf spring 72, suppresses discharge, it is easier to simultaneously reduce the height of the space around the lower end of the dense plug 55 (here, the height from the lower surface of the coating 71 to the bottom surface of the groove 31) and suppress discharge. For example, the height of the space around the lower end of the dense plug 55 can be 0.5 mm or less, 0.3 mm or less, or even 0.17 mm or less. Furthermore, the leaf spring 72 is arranged in a state of being stretched in the lateral direction perpendicular to the vertical direction by being pressed from above by the dense plug 55. Thus, by the leaf spring 72 stretching in the lateral direction, the area directly below the dense plug 55 where the leaf spring 72 is absent can be reduced. This can further suppress the occurrence of discharge around the end portion of the dense plug 55 on the conductive plate 30 side. For example, in the case of Figure 9When the leaf spring 72 is not stretched in the horizontal direction as in (B) in FIG, the effect of suppressing discharge in the space to the left and right of the leaf spring 72 in the space directly below the dense plug 55 may be reduced. Figure 9 As shown in (C), the leaf spring 72 is expanded in the lateral direction, thereby improving the discharge suppression effect. In addition, there is a case where the elastic force of the leaf spring 72 decreases with the long-term use of the wafer carrier 10, and it is desired to replace the leaf spring 72 in the wafer carrier 10. In this case, in the above embodiment, by removing the dense plug 55 from the ceramic plate 20 of the wafer carrier 10, Figure 9 As shown in (A) in FIG. 1 , the leaf spring 72 returns to the state before being stretched in the lateral direction (the lateral width becomes W1 which is smaller than W2 ), so that the leaf spring 72 can be easily removed and replaced. It should be noted that the present invention is not limited to the above-described embodiment, and can be implemented in various forms as long as it falls within the technical scope of the present invention. For example, in the above embodiment, a dense plug 55 having a gas internal flow path 55a is provided in the ceramic plate through-hole 50. However, the present invention is not limited to a dense plug 55. An insulating gas-passing plug through which gas can pass from the inside may be provided in the ceramic plate through-hole 50. For example, a porous plug may be used as the insulating gas-passing plug. Similarly, the coating layer 71 may allow gas to pass through. For example, the coating layer 71 may be a conductive porous layer instead of having the pores 71a. For example, Figure 10 The porous plug 155 and the coating layer 171 shown are constructed as a porous body. The porous plug 155 can be made of, for example, a porous block obtained by sintering ceramic powder. Examples of ceramics include alumina and aluminum nitride. The porosity of the porous plug 155 is preferably 30% or greater, and the average pore diameter is preferably 20 μm or greater. The porosity of the porous plug 155 can be 70% or less. Furthermore, by using porous plating, a coating layer 171, which is a porous metal layer, can be formed on the lower surface of the porous plug 155. The dense plug 55 and the coating layer 171 can be combined, or the porous plug 155 and the coating layer 71 can be combined. In the above embodiment, the coating layer 71 has pores 71 a to allow gas to pass through. However, the coating layer 71 may cover a portion of the lower surface of the dense plug 55, while the uncovered portion of the lower surface allows gas to pass through. In the above embodiment, the conductive gas passage portion 70 may not have the coating layer 71. For example, Figure 11 The conductive gas passage portion 270 shown includes the leaf spring 72 but does not include the coating layer 71 . Figure 11In the embodiment, the upper surface 72a of the leaf spring 72 is in direct contact with the dense plug 55, and the dense plug 55 is pressed upward by the elastic force. Even so, as in the above embodiment, it is possible to suppress the occurrence of discharge around the end of the dense plug 55 on the conductive plate 30 side, that is, around the lower end of the dense plug 55. In the above embodiment, the leaf spring 72 is arranged in a state of being stretched in the lateral direction perpendicular to the vertical direction by being pressed from above by the dense plug 55, but the present invention is not limited thereto, and the leaf spring 72 may not be stretched in the lateral direction. Figure 12 The zigzag-shaped folding direction of the leaf spring 372 shown is along the horizontal direction, and the leaf spring 372 has multiple (here, two) folding portions 373 that fold back in the horizontal direction. The leaf spring 372 includes, as multiple folding portions 373, one or more (here, one) first folding portions 373a that fold back from left to right, and one or more (here, one) second folding portions 373b that fold back from right to left. Therefore, the direction of expansion and contraction of the leaf spring 372 is the direction of pressing the dense plug 55 in the vertical direction. In other words, the leaf spring 372 is arranged longitudinally. Even with this leaf spring 372, the dense plug 55 can be pressed upward by elastic force, so it is easy to maintain conductivity from the contact portion of the conductive gas passage 70 with the dense plug 55 (here, the upper surface of the coating layer 71) to the conductive plate 30. In the above embodiment, the folded portion 73 of the leaf spring 72 is formed into a V shape, but the present invention is not limited thereto. For example, the wafer placement table 10 may include Figure 13 The leaf spring 472 shown in the figure replaces the leaf spring 72. The leaf spring 472 has a plurality of folded portions 473 that fold back in the vertical direction. The leaf spring 472 includes, as the plurality of folded portions 473, at least one (here, a plurality, specifically four) first folded portions 473a that fold back from the top to the bottom, and at least one (here, a plurality, specifically three) second folded portions 473b that fold back from the bottom to the top. Therefore, the leaf spring 472 folds back seven times. The first folded portion 473a has a first plate-shaped portion 475 that extends in the horizontal direction, the upper surface of which constitutes the upper surface 472a of the leaf spring 472. The second folded portion 473b has a second plate-shaped portion 476 that extends in the horizontal direction, the lower surface of which constitutes the lower surface 472b of the leaf spring 472. Therefore, the plurality of folded portions 473 of the leaf spring 472 each have a trapezoidal upper base portion and two oblique sides on the left and right, rather than a V-shape. Figure 13 The leaf spring 472 shown is arranged in a state of being stretched in the lateral direction perpendicular to the vertical direction by being pressed from above by the dense plug 55 in the same manner as the leaf spring 72. Figure 2Compared with the upper surface 72a of the leaf spring 72 in FIG. 4 , it is easy to make the width of the upper surface 472a in the horizontal direction wider. Therefore, the contact area between the upper surface 472a and the component above the leaf spring 472 (here, the coating layer 71) can be increased. Similarly, by having the second plate-shaped portion 476 of the leaf spring 472, for example, Figure 2 Compared with the lower surface 72b of the leaf spring 72 in the figure, it is easy to widen the horizontal width of the lower surface 472b. Therefore, the contact area between the lower surface 472b and the component below the leaf spring 472 (here, the conductive plate 30) can be increased. According to this, the leaf spring 472 and the components above and below it can be more reliably contacted, and further, the conduction from the contact portion of the conductive gas passage 70 with the dense plug 55 to the conductive plate 30 can be more reliably maintained. In addition, due to the large contact area between the leaf spring 472 and the components above and below it, the contact resistance can be reduced, and the effect of suppressing discharge around the lower end of the dense plug 55 is improved. It should be noted that the leaf spring 72 of the above embodiment can also be referred to as a shape in which the first plate-shaped portion 475 and the second plate-shaped portion 476 are omitted from the leaf spring 472. Figure 13 In the leaf spring 472 shown, Figure 14 As shown, the corners of leaf spring 472 can be curved. This prevents the electric field from concentrating at the corners of leaf spring 472, further suppressing discharge around the lower end of dense plug 55. Leaf springs 72 and 372 can also have curved corners. Figure 2 The leaf spring 72 and Figure 13 The leaf spring 472 shown has a folding frequency of 7 times, but is not limited thereto. The leaf spring may have a folding frequency of at least 1 time, or may have a folding frequency of multiple times. Figure 15 The leaf spring 572 shown is obtained by changing the number of folds in the leaf spring 472 to three. The leaf spring 572 has multiple folded portions 573 that fold back in the vertical direction. The leaf spring 572 includes two first folded portions 573a that fold back from top to bottom, and one second folded portion 573b that folds back from bottom to top. The first folded portion 573a includes a first plate-shaped portion 575 that extends horizontally and whose upper surface constitutes the upper surface 572a of the leaf spring 572. The second folded portion 573b includes a second plate-shaped portion 576 that extends horizontally and whose lower surface constitutes the lower surface 572b of the leaf spring 572. Figure 15 The illustrated leaf spring 572, like leaf spring 72, is arranged in a state of being stretched in a lateral direction perpendicular to the vertical direction by being pressed from above by the dense plug 55. By reducing the number of folds, as in leaf spring 572, the volume of the leaf spring can be easily reduced. By reducing the volume, leaf spring 572 is less likely to interfere with the flow of gas in the gas introduction passage 60. In the above embodiment, at least one of the shape and placement of the leaf spring 72 is adjusted so that it does not completely block the hole 71a in the coating 71 (and the opening at the lower end of the internal gas flow path 55a), thereby preventing gas flow. In this case, the leaf spring 72 may partially block the hole 71a in the coating 71, that is, the upper surface 72a of the leaf spring 72 may overlap with a portion of the hole 71a when viewed from above. However, it is preferred that the upper surface 72a of the leaf spring 72 and a portion of the hole 71a do not overlap at all when viewed from above. Furthermore, the leaf spring 72 may sometimes be horizontally misaligned within the gas inlet passage 60. Therefore, it is more preferred that the opening at the lower end of the internal gas flow path 55a be located outside the range of movement caused by the misalignment of the upper surface 72a of the leaf spring 72 within the gas inlet passage 60 when viewed from above. This applies similarly to leaf springs 372, 472, and 572. This will be described in detail using leaf spring 572 as an example. Figure 16 It is an explanatory diagram showing the positions of the upper surface 572a of the leaf spring 572 and the gas internal flow path 55a in a plan view. Figure 17 It is an explanatory diagram showing the horizontal movement range of the leaf spring 572. Figure 16 In the figure, the outline of the upper surface 572a of the leaf spring 572 (i.e., the outline of the first plate-shaped portion 575) is indicated by a dotted line, the outline of the lower end surface of the dense plug 55 and the outline of the lower end opening of the internal gas flow path 55a are indicated by a single-dot chain line, and the outline of the gas introduction passage 60 (more specifically, the groove 31 of the second gas passage 62) is indicated by a double-dot chain line. The outline of the lower end opening of the internal gas flow path 55a and the outline of the opening of the hole 71a of the coating layer 71 are located at the same position when viewed from above. Figure 17 In FIG. 5 , the leaf spring 572 is shown in a solid line when positioned at the far left side in the groove 31 , and in a dotted line when positioned at the far right side in the groove 31 . Figure 16 In the state shown, the upper surface 572a of the leaf spring 572 does not overlap with the opening of the lower end of the gas internal flow path 55a. However, if the leaf spring 572 is misaligned in the groove 31 of the gas introduction path 60, the position of the upper surface 572a will also change. Figure 17 As shown, the opening at the lower end of the internal gas flow path 55a (and the hole 71a) does not overlap with the ranges of movement M1 and M2 caused by the displacement of the upper surface 572a within the groove 31, and is located outside the ranges of movement M1 and M2. Therefore, regardless of the degree of left-right displacement of the leaf spring 572, the upper surface 572a will never overlap with the opening at the lower end of the internal gas flow path 55a (and the hole 71a) when viewed from above. Figure 17Only the ranges of movement M1 and M2 of the upper surface 572a caused by the horizontal misalignment of the leaf spring 572 are shown. However, it is more preferable that the opening at the lower end of the gas flow path 55a (and the hole 71a) be located outside the range of movement of the upper surface 572a caused by the misalignment, regardless of any horizontal misalignment (including horizontal rotation). For example, the difference between the horizontal width of the leaf spring 572 and the horizontal width of the groove 31 can be reduced, or the opening diameter at the lower end of the ceramic plate through-hole 50 can be reduced to limit the range of movement of the upper end of the leaf spring 572, thereby limiting the range of movement of the upper surface 572a caused by the misalignment. Therefore, even if the leaf spring 572 is misaligned in the gas inlet passage 60, the upper surface 572a of the leaf spring 572 will not overlap with the opening at the lower end of the gas internal flow path 55a when viewed from above. Therefore, the leaf spring 572 is not likely to hinder the gas flow between the gas inlet passage 60 and the gas internal flow path 55a. The leaf springs 72, 372, 472, 572 can be constructed to have holes that allow gas to pass through. Figure 18 、 Figure 19 In the example shown, holes 672 c for allowing gas to pass are provided in the plate-shaped portion of the leaf spring 472 that is inclined relative to the vertical direction. This prevents the leaf spring 472 from obstructing the flow of gas, allowing gas to pass more easily through the conductive gas passage 70 . The leaf springs 72, 372, 472, and 572 may be provided with insertion holes for inserting a member such as tweezers to hold the leaf spring when the leaf spring is replaced. There may be two or more such holes. Figure 18 、 Figure 19 A hole that allows gas to pass through, such as the hole 672c shown, can also serve as the insertion hole. In the above embodiment, the leaf spring 72 is formed by bending a metal plate into a zigzag shape, but the present invention is not limited thereto. For example, the leaf spring 72 may be a U-shaped leaf spring. In the above embodiment, the second gas passage 62 is formed by having a groove 31 (first recess) provided on the upper surface of the conductive plate 30 and the lower surface (flat surface) of the conductive bonding layer 40 disposed above the groove 31, but this is not particularly limited to this. 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 the upper surface (flat surface) of the conductive plate 30 disposed below the groove. Alternatively, the conductive bonding layer 40 may be configured as a two-layer structure, with the groove (groove extending vertically through the groove) that ultimately becomes the second gas passage 62 provided in the lower layer and the bonding layer penetration portion 64 provided in the upper layer. In this case, similarly, by providing a conductive gas passage 70 inside the gas inlet passage 60 (bonding layer penetration portion 64), and providing the conductive gas passage 70 in a manner that contacts the lower surface of the dense plug 55 and is electrically conductive with the conductive plate 30, discharge can be suppressed from occurring around the end portion on the conductive plate 30 side in the dense plug 55. In the above embodiment, the second gas passage 62 and the auxiliary gas passage 63 may be omitted, and the plurality of first gas passages 61 and the plurality of ceramic plate through-holes 50 may be connected one to one. In the above embodiment, the upper surface of the dense plug 55 is at the same height as the reference surface 21c of the wafer loading surface 21, but this is not particularly limiting. For example, the difference between the height of the reference surface 21c of the wafer loading surface 21 and the height of the upper surface of the dense plug 55 can be within 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 dense plug 55 can be positioned within a range of 0.5 mm or less (preferably 0.2 mm or less, more preferably 0.1 mm or less) below the reference surface 21c of the wafer loading surface 21. Even so, the height of the space between the lower surface of the wafer W and the upper surface of the dense plug 55 is kept relatively low. Therefore, the occurrence of glow discharge or even arc discharge in this space can be prevented. In the above embodiment, the ceramic plate 20 and the conductive plate 30 are bonded together using the conductive bonding layer 40. However, a non-conductive bonding layer such as a resin bonding layer may be used in place of the conductive bonding layer 40. In this case, the conductive plate may be made of a metal such as Al or Ti. If the conductive bonding layer 40 is a resin bonding layer, the ceramic plate 20 and the conductive plate 30 can be bonded together using the resin bonding layer while being pressurized in an autoclave. In the above embodiment, an electrostatic electrode is built into the ceramic plate 20 as the electrode 22. However, a heater electrode (resistive heating element) may be built into the ceramic plate 20 instead of or in addition to the electrode 22. In this case, a heater power supply is connected to the heater electrode. The ceramic plate 20 may have a single layer of electrodes built into it, or two or more layers may be built into it with intervals. In the above embodiment, lift pin holes may be provided that extend through the wafer stage 10. These holes are holes through which lift pins are inserted to move the wafer W vertically relative to the wafer placement surface 21. If the wafer W is supported by, for example, three lift pins, three lift pin holes are provided. In the above embodiment, the ceramic plate 20 is produced by hot pressing and sintering a ceramic powder molded body. However, the molded body in this case can also be produced by stacking multiple cast molded bodies, or by die casting, or by compacting ceramic powder. In the above embodiment, the dense plug 55 is fixed by being pressed into the ceramic plate through-hole 50, but the present invention is not limited thereto. For example, the outer circumference of the dense plug 55 and the inner circumference of the ceramic plate through-hole 50 may be bonded together, or an external thread provided on the outer circumference of the dense plug 55 may be screwed into an internal thread provided on the inner circumference of the ceramic plate through-hole 50. Figure 2 In the enlarged cross-sectional view, the diameter of the bonding layer through portion 64 is shown to be the same as the diameter of the opening at the bottom of the ceramic plate through portion 50. However, as described above, the diameter of the bonding layer through portion 64 may be larger than the diameter of the opening at the bottom of the ceramic plate through portion 50. In this case, Figure 20 The scheme shown. Figure 20 In the embodiment, the wafer carrier 10 has an insulating bonding layer 740 having no conductivity (having insulating properties) such as a resin bonding layer instead of the conductive bonding layer 40. As the resin used for the insulating bonding layer 740, there can be cited: silicone resin, acrylic resin, polyimide resin, epoxy resin, etc. In addition, a leaf spring 772 is provided instead of the leaf spring 72. A hole, namely a bonding layer through-hole 764, which penetrates the insulating bonding layer 740 in the up and down directions is formed in the insulating bonding layer 740. The bonding layer through-hole 764 is a part of the gas inlet passage 60, and is a passage for gas from the second gas passage 62 to the hole 71a of the coating layer 71. As Figure 20 As shown, the diameter of the bonding layer through-hole 764 is larger than the diameter of the opening at the bottom of the ceramic plate through-hole 50. Therefore, a portion of the lower surface of the ceramic plate 20 (the periphery of the opening of the ceramic plate through-hole 50) is located directly above the bonding layer through-hole 764, resulting in a configuration in which the bonding layer through-hole 764 is exposed in the gas introduction passage 60. However, Figure 20 In the embodiment, the conductive layer 25 is provided so as to cover the portion of the lower surface of the ceramic plate 20 exposed at the bonding layer penetration portion 764. Therefore, the lower surface of the ceramic plate 20 is not exposed at the bonding layer penetration portion 764 due to the presence of the bonding layer penetration portion 764. The conductive layer 25 has a larger diameter than the bonding layer penetration portion 764 when viewed from above. Figure 20As shown, a portion of the conductive layer 25 is sandwiched between the lower surface of the ceramic plate 20 and the upper surface of the insulating bonding layer 740. The conductive layer 25 only needs to be a conductor, but the same material as the material of the coating layer 71 (for example, a metal material) can be used. The conductive layer 25 can be a layer formed in advance on the lower surface of the ceramic plate 20 by sputtering or chemical plating, etc., in the same way as the coating layer 71. In the leaf spring 772, as a plurality of folding portions 773, there are: two first folding portions 773a folded from top to bottom, and three second folding portions 773b folded from bottom to top. Like the leaf spring 72, the leaf spring 772 is arranged in a state of being stretched in the lateral direction perpendicular to the up and down direction by being pressed from above by the dense plug 55. The leaf spring 772 is similar to the leaf spring 72. The upper surface 772a of the first folded portion 773a contacts the lower surface of the coating layer 71, and the lower surface 772b of the second folded portion 773b contacts the conductive plate 30, thereby electrically conducting the coating layer 71 and the conductive plate 30. In addition, the leaf spring 772 also contacts the conductor layer 25. Specifically, the upper surfaces 774a of the two plate-shaped parts located at the left and right ends of the leaf spring 772 are respectively in contact with the lower surface of the conductor layer 25. In this way, Figure 20 In the embodiment, the portion of the lower surface of the ceramic plate 20 exposed at the bonding layer penetration portion 764 of the gas introduction passage 60 is covered with the conductive layer 25, and the conductive layer 25 is in contact with the leaf spring 772, thereby being electrically connected to the conductive plate 30 via the leaf spring 772. Therefore, it is difficult for the portion of the lower surface of the ceramic plate 20 facing the gas introduction passage 60 ( Figure 20 A potential difference is generated around the portion of the lower surface of the ceramic plate 20 directly above the bonding layer penetration portion 764. Therefore, discharge can be suppressed around the portion of the lower surface of the ceramic plate 20 facing the gas introduction passage 60. Figure 20 In, with Figure 2 In contrast, the lower end of the dense plug 55 protrudes to a position lower than the lower surface of the ceramic plate 20. Figure 20 In the leaf spring 772, the lengths of the two plate-like members located at the left and right ends are longer than those of the four plate-like members located at other locations, so that even in such a situation, they can reliably contact the conductive layer 25. However, even when all the multiple (here, six) plate-like members are of the same length, only the height of the plate-like members in the portion of the leaf spring 772 pressed by the dense plug 55 is reduced (the inclination angle relative to the vertical direction of the plate-like members is increased). As a result, the upper surfaces 774a of the plate-like members not pressed by the dense plug 55 (here, the two plate-like members located at the left and right ends) can contact the conductive layer 25. Figure 20In the embodiment, the leaf spring 772 contacts both the coating layer 71 and the conductor layer 25 to electrically connect them to the conductive plate 30. However, instead of the leaf spring 772, a conductive member that electrically connects the conductor layer 25 and the conductive plate 30 may be provided separately from the leaf spring 772 on the wafer stage 10. For example, Figure 21 In the example shown, the wafer stage 10 includes a leaf spring 872 instead of Figure 20 The leaf spring 772 in the leaf spring 872 also has a conductive component 875. The leaf spring 872 includes a plurality of folding portions 873, including a first folding portion 873a folded from top to bottom and two second folding portions 873b folded from bottom to top. Like the leaf spring 772, the leaf spring 872 is arranged in a state of being stretched in a lateral direction perpendicular to the up-down direction by being pressed from above by the dense plug 55. Like the leaf spring 772, the leaf spring 872 has an upper surface 872a of the first folding portion 873a in contact with the lower surface of the coating 71, and a lower surface 872b of the second folding portion 873b in contact with the conductive plate 30. In addition, unlike the leaf spring 772, the leaf spring 872 has two plate-like components located at the left and right ends, each of which has an upper surface 874a that is also in contact with the lower surface of the coating 71. Thus, the leaf spring 872 electrically connects the coating layer 71 and the conductive plate 30. On the other hand, the leaf spring 872 does not contact the conductor layer 25. The conductive member 875 is a conductive elastic body. Figure 21 It is constructed as a coil spring. As the material of the conductive component 875, the same material as that of the above-mentioned leaf spring 72 (for example, a metal material) can be used. The conductive component 875 is arranged in the gas inlet passage 60 in such a way that the axial direction of the coil is the up-down direction, and the upper end is in contact with the lower surface of the conductor layer 25 and the lower end is in contact with the conductive plate 30. Thus, the conductive component 875 electrically connects the conductor layer 25 and the conductive plate 30. The leaf spring 872 is arranged on the inner side of the coil of the conductive component 875. That is, the leaf spring 872 is surrounded by the conductive component 875 when viewed from above. The up-down direction of the conductive component 875 is the expansion and contraction direction, and it is arranged in the gas inlet passage 60 in a state contracted compared to its natural length. Therefore, the conductive component 875 presses the conductor layer 25 upward by elastic force. Similarly, the conductive component 875 presses the conductive plate 30 downward by elastic force. In this way, even if the conductive member 875 provided separately from the leaf spring 872 electrically connects the conductor layer 25 and the conductive plate 30, Figure 20 Similarly to the embodiment of the present invention, it is also possible to suppress discharge around the portion of the lower surface of the ceramic plate 20 that faces the gas introduction passage 60. In addition, since the conductive member 875 presses the conductive layer 25 upward by elastic force, it is easy to maintain conductivity from the conductive layer 25 to the conductive plate 30. The conductive component 875 can be an elastomer and is not limited to a coil spring. For example, the conductive component 875 can be a leaf spring that is another component different from the leaf spring 872. However, compared with a leaf spring, when it is set as a coil spring, gas can pass more easily in the axial direction of the coil or between the wires. In addition, by arranging the leaf spring 872 on the inner side of the coil of the conductive component 875, the leaf spring 872 and the conductive component 875 can be compactly arranged in the gas inlet passage 60. Therefore, when the conductive component 875 is used as another component different from the leaf spring 872, the conductive component 875 is preferably a coil spring. It should be noted that the conductive component 875 does not need to be an elastomer as long as it is a conductive component. However, since it is easy to maintain the conductivity between the conductor layer 25 and the conductive plate 30 as described above, the conductive component 875 is preferably an elastomer. It should be explained that Figure 20 and Figure 21 In the embodiment, if the lower end face of the dense plug 55 is located at the same or close height as the lower surface of the ceramic plate 20, the conductive layer 25 and the coating layer 71 are in contact and conduction. Therefore, in this case, even if the leaf spring 772 or the conductive component 875 is not in contact with the conductive layer 25, the conductive layer 25 and the conductive plate 30 can be electrically connected. In addition, when manufacturing the chip carrier 10, before joining the ceramic plate 20 and the conductive plate 30, the dense plug 55 can be inserted into the ceramic plate 20 in such a way that the lower end face of the dense plug 55 is located at the same or close height as the lower surface of the ceramic plate 20, thereby forming the coating layer 71 and the conductive layer 25 as a whole. However, sometimes the coating layer 71 and the conductive layer 25 cannot be in contact due to deviation of the insertion position of the dense plug 55. Therefore, it is preferable to Figure 20 In this way, the leaf spring 772 is in contact with the conductor layer 25 . Figure 20 and Figure 21 In the embodiment, the conductive layer 25 covers the entire portion of the lower surface of the ceramic plate 20 exposed at the bonding layer penetration portion 764, but is not limited thereto and may cover only a portion. Figure 20 and Figure 21 That will cover everything. In the above embodiment, the conductive gas passage portion 70 includes the coating layer 71 and the leaf spring 72, and the leaf spring 72 is in direct contact with the conductive plate 30 to provide electrical continuity. However, the present invention is not limited thereto. For example, the conductive gas passage portion 70 may include a gas passage member that provides electrical continuity between the conductive plate 30 and the leaf spring 72. Figure 22 It is a partially enlarged cross-sectional view showing the gas passage component 975. Figure 22 The conductive gas passage portion 70 in the embodiment includes a coating layer 71, a leaf spring 972, and a gas passage member 975. Figure 22 In, by Figure 20The insulating bonding layer 940, which is formed of the same material as the insulating bonding layer 740 in the ceramic plate 20, bonds the ceramic plate 20 and the conductive plate 30. A bonding layer penetration portion 964 is formed in the insulating bonding layer 940, which penetrates the insulating bonding layer 940 in the vertical direction. The bonding layer penetration portion 964 constitutes a part of the gas introduction path 60. The leaf spring 972 has a plurality of folding portions 973, including two first folding portions 973a folded from top to bottom and one second folding portion 973b folded from bottom to top. Like the leaf spring 72, the leaf spring 972 is arranged in a state of being stretched in the lateral direction perpendicular to the vertical direction by being pressed from above by the dense plug 55. Regarding the leaf spring 972, the upper surface 972a is in contact with the lower surface of the coating layer 71, and the lower surface 972b is in contact with the upper surface of the gas passage component 975. The gas passing member 975 is a conductive member that allows gas to pass between the dense plug 55 and the second gas passage 62. The gas passing member 975 is a member that is, for example, a generally cylindrical member that is circular when viewed from above. The upper surface of the gas passing member 975 contacts the lower surface 972b of the leaf spring 972, and the lower surface contacts the upper surface of the conductive plate 30. As a result, the gas passing member 975 provides electrical conduction between the leaf spring 972 and the conductive plate 30. A hole 975a is formed in the gas passing member 975 that passes through the gas passing member 975 in the vertical direction. Gas in the second gas passage 62 can pass through the hole 975a and the bonding layer through-portion 964 to reach the hole 71a of the coating layer 71. Examples of the material of the gas passing member 975 include metal. The material of the gas passing member 975 is preferably a low-resistance non-magnetic body. The material of the gas passing member 975 is preferably a material having a thermal expansion coefficient close to that of the ceramic plate 20 and the conductive plate 30. Specific examples of materials for the gas passage member 975 include Ti. The gas passage member 975 may be a member independent of the conductive plate 30 or a film formed on the upper surface of the conductive plate 30. Even when the conductive gas passage portion 70 includes the gas passage member 975, similar to the above-described embodiment, discharge can be suppressed around the end portion of the dense plug 55 on the conductive plate 30 side, i.e., around the lower end portion of the dense plug 55. Additionally, by the presence of gas passing through component 975, as Figure 22 As shown, the gas passing component 975 occupies a part of the bonding layer through-hole 964, so that the height T3 of the space portion in the bonding layer through-hole 964 can be made smaller than the thickness T4 of the insulating bonding layer 940 (i.e., the height of the bonding layer through-hole 964 as a whole). In this way, the discharge in the bonding layer through-hole 964 can be suppressed. The thickness T3 is preferably, for example, less than 0.2 mm, and more preferably less than 0.1 mm. Since the existence of the gas passing component 975 can reduce the height T3 and suppress the discharge, Figure 20 different, Figure 22 In the embodiment, the conductive layer 25 is not provided on the exposed portion of the lower surface of the ceramic plate 20. Even if the conductive layer 25 is not provided, the discharge in the bonding layer penetration portion 964 can be suppressed. Figure 20 Similarly, a conductive layer 25 is provided on the lower surface of the ceramic plate 20. In addition, since the presence of the gas passage member 975 can reduce the height T3 and suppress discharge, it is easy to simultaneously suppress discharge and increase the thickness T4 of the insulating bonding layer 940 to improve the thermal resistance of the insulating bonding layer 940. By increasing the thermal resistance of the insulating bonding layer 940, it is possible to suppress heat conduction from the ceramic plate 20 to the conductive plate 30 and suppress the cooling of the chip W. By suppressing the cooling of the chip W, it is also possible to, for example, allow the chip W to reach a higher temperature. It should be noted that, generally, the thermal resistance of a conductor is lower than that of an insulator. Therefore, from the viewpoint of improving thermal resistance, it is preferable to bond the ceramic plate 20 and the conductive plate 30 using the insulating bonding layer 940 rather than using the conductive bonding layer 40. When the gas passing member 975 occupies a part of the bonding layer penetrating portion 964 to suppress discharge in the bonding layer penetrating portion 964, it is preferable that the side surface ( Figure 22 The gap (space) between the gas passing member 975 and the insulating bonding layer 940 is small. More preferably, the side of the gas passing member 975 contacts the insulating bonding layer 940, and further preferably, Figure 22 The entire side of the gas passing member 975 is in contact with the insulating bonding layer 940 without any gaps. Figure 22 In the embodiment, a portion of the insulating bonding layer 940 forms an overhang 940a that covers a portion of the upper surface of the gas passage member 975. Therefore, the diameter of the space above the gas passage member 975 in the bonding layer through-hole 964 is smaller than the diameter of the gas passage member 975. The presence of the overhang 940a allows separation of the gap from the space above the gas passage member 975 in the bonding layer through-hole 964, even if a gap exists on a portion of the side surface of the gas passage member 975. This allows discharge to be suppressed. For example, the insulating bonding layer 940 can be collapsed during bonding of the ceramic plate 20 and the conductive plate 30, thereby eliminating a gap between the side surface of the gas passage member 975 and the insulating bonding layer 940, or forming the overhang 940a. Figure 23 9 is an explanatory diagram showing how the ceramic plate 20 and the conductive plate 30 are bonded together using the insulating bonding layer 940. Figure 23As shown in (A) in FIG. 1 , a sheet-like insulating bonding material 990 is disposed on the upper surface of the conductive plate 30 (or the MMC disc component 81), and a gas passing component 975 and a leaf spring 972 are disposed in a through hole pre-formed in the insulating bonding material 990. The through hole of the insulating bonding material 990 is pre-formed to have a diameter larger than the final diameter of the bonding layer through portion 964 of the insulating bonding layer 940. In this state, the insulating bonding layer 940 can be formed as shown in FIG. Figure 23 As shown in (A), there is a gap between the side of the gas passing component 975 and the insulating bonding material 990. After the gas passing component 975 and the leaf spring 972 are arranged in this way, the insulating bonding material 990 is sandwiched between the ceramic plate 20 and the conductive plate 30, and the insulating bonding material 990 is heated and pressurized, thereby bonding the ceramic plate 20 and the conductive plate 30 through the insulating bonding material 990. In this way, the insulating bonding material 990 becomes the insulating bonding layer 940 ( Figure 23 (B)). After that, the dense plug 55 is assembled, thereby becoming Figure 22 state. When the ceramic plate 20 and the conductive plate 30 are joined, the insulating bonding material 990 is crushed by the pressure from above and below, so that the through-hole of the insulating bonding material 990 provided with the gas passing component 975 is narrowed to form a bonding layer through-hole 964. As a result, it is possible to make it so that the side of the gas passing component 975 is in contact with the insulating bonding layer 940, and the gap between the side of the gas passing component 975 and the insulating bonding layer 940 can be eliminated. In addition, when the through-hole of the insulating bonding material 990 is narrowed, a part of the insulating bonding material 990 protrudes above the gas passing component 975, thereby forming a protruding portion 940a. By adjusting the diameter of the through-hole of the insulating bonding material 990 and the diameter of the gas passing component 975, it is possible to adjust the degree of contact between the side of the gas passing component 975 and the insulating bonding layer 940, the protrusion amount of the protruding portion 940a, the presence or absence of the protruding portion 940a, etc. From the perspective of ensuring the gas flow in the bonding layer through-hole 964, it is preferable that the extension 940a does not exist directly below the hole 71a (does not block a portion of the hole 71a). Figure 22 As shown, it is more preferable that the protruding portion 940 a does not exist directly below the lower surface of the dense plug 55 (and the coating layer 71 ). like Figure 22As shown, the diameter of the gas passing member 975 is preferably larger than the lower surface (and coating layer 71) of the dense plug 55. More specifically, the gas passing member 975 and the dense plug 55 are preferably positioned so that, when viewed from above, the lower surface (and coating layer 71) of the dense plug 55 is included in a range that is inside the contour of the upper surface of the gas passing member 975. Thus, when viewed from above, the gas passing member 975 is present in a range that is outside the lower surface (and coating layer 71) of the dense plug 55, making it easier to achieve a state in which the side surface of the gas passing member 975 contacts the insulating bonding layer 940 and the protruding portion 940a is not located directly below the lower surface (and coating layer 71) of the dense plug 55. Figure 22 In the embodiment, gas passes through the holes 975a of the gas passing member 975. However, it is sufficient for gas to be able to pass through the gas passing member 975. For example, the gas passing member 975 may be a porous body. In this case, the porosity of the gas passing member 975 may be 50% or more and 80% or less. Alternatively, the gas passing member 975 may be an elastomer. For example, by making the gas passing member 975 a porous metal body (porous metal), the gas passing member 975 can be an elastomer member through which gas can pass. Figure 22 In the above description, it is explained that the conductive gas passage portion 70 may include a gas passage member 975 that allows the plate spring 972 and the conductive plate 30 to be electrically connected. Similarly, the conductive gas passage portion 70 may include a gas passage member that allows the plate spring 972 and the coating layer 71 to be electrically connected, for example, Figure 22 The positional relationship between the leaf spring 972 and the gas passing member 975 is reversed upside down. Alternatively, gas passing members similar to the gas passing member 975 may be arranged above and below the leaf spring 72, respectively. Industrial applicability The present invention can be utilized in, for example, an apparatus for processing wafers. This application claims priority based on International Application No. PCT / JP2024 / 011681 filed on March 25, 2024, and Japanese Patent Application No. 2024-181488 filed on October 17, 2024, the contents of which are incorporated herein by reference in their entirety.

Claims

1. A wafer loading platform comprising: a ceramic plate having a wafer placement surface on its upper surface and having electrodes built therein; a conductive plate bonded to the lower surface of the ceramic plate; a ceramic plate through-hole, the ceramic plate through-hole penetrating the ceramic plate; an insulating gas passage plug, the insulating gas passage plug being provided in the ceramic plate through-hole portion, and gas being able to pass therethrough; a gas introduction passage, the gas introduction passage being provided at least inside the conductive plate and communicating with the ceramic plate through-hole; and a conductive gas passage portion provided in the gas introduction passage, contacting the lower surface of the insulating gas passage plug and electrically connected to the conductive plate, and allowing gas to pass between the insulating gas passage plug and the gas introduction passage; The conductive gas passage portion includes a leaf spring that presses the insulating gas passage plug upward by elastic force.

2. The wafer stage according to claim 1, wherein: The leaf spring is arranged in a state of being pressed from above by the insulating gas through the plug and being stretched in a lateral direction perpendicular to the up-down direction.

3. The wafer stage according to claim 2, wherein: The leaf spring has a plurality of folded portions folded back in the up-down direction.

4. The wafer stage according to claim 3, wherein: The plurality of folding portions include a first folding portion folded from top to bottom and a second folding portion folded from bottom to top. The first folded portion includes a first plate-shaped portion extending in the horizontal direction and having an upper surface constituting an upper surface of the leaf spring. The second folded portion includes a second plate-shaped portion extending in the horizontal direction and having a lower surface constituting a lower surface of the leaf spring.

5. The wafer stage according to any one of claims 1 to 4, wherein: The conductive gas passage portion includes a coating layer that covers the lower surface of the insulating gas passage plug.

6. The wafer stage according to any one of claims 1 to 4, wherein: The insulating gas passage plug is a dense body or a porous body having an internal gas flow path.

7. The wafer stage according to any one of claims 1 to 4, wherein: The insulating gas passage plug is a dense body having an internal gas flow path. The opening at the lower end of the internal gas flow path is located outside a range of movement caused by displacement of the upper surface of the leaf spring within the gas introduction passage in a plan view.

8. The wafer stage according to any one of claims 1 to 4, wherein: The leaf spring has a hole that allows gas to pass through.

9. The wafer stage according to claim 5, wherein: The wafer stage includes a conductive layer covering a portion of the lower surface of the ceramic plate exposed to the gas introduction passage. The leaf spring is in contact with the conductor layer.

10. The wafer stage according to claim 5, comprising: a conductive layer covering a portion of the lower surface of the ceramic plate exposed in the gas introduction passage; and A conductive conducting member is in contact with the conductive plate and the conductor layer, respectively.

11. The wafer stage according to claim 10, wherein: The conductive component is an elastic body that presses the conductive layer upward using elastic force.

12. The wafer stage according to any one of claims 1 to 4, wherein: The conductive gas passage portion includes a gas passage member that allows electrical conduction between the conductive plate and the leaf spring.

13. The wafer stage according to claim 12, wherein: The gas passing component is an elastomer.

Images