Wafer placement table

Abstract

A wafer placement table 10 comprises: a ceramic plate 20 which has a wafer placement surface 21 on an upper surface and which incorporates an electrode 22; an electrically conductive plate 30 which is disposed on a lower surface side of the ceramic plate 20; a bonding layer 40 which bonds the ceramic plate 20 to the electrically conductive plate 30; ceramic plate penetrating portions 50 which penetrate through the ceramic plate 20; dense plugs 55 which are provided in the ceramic plate penetrating portions 50 and through which gas can pass; and a gas introduction passage 60 which is provided at least inside the bonding layer 40 and the electrically conductive plate 30 and which communicates with the ceramic plate penetrating portions 50. The bonding layer 40 has a structure in which first and second insulator layers 41, 42 and a first conductor layer 45 are stacked, and the first conductor layer 45 is exposed to a bonding layer penetrating portion 64, which is a part that penetrates through the bonding layer 40.

Description

Wafer mounting table

[0001] The present invention relates to a wafer mounting table.

[0002] Conventionally, a wafer mounting table including a ceramic plate having a wafer mounting surface on the upper surface and a base plate joined to the lower surface of the ceramic plate via a bonding layer and having a gas introduction passage is known. In Patent Document 1, in such a wafer mounting table, an insulating first porous portion disposed in a through hole of the ceramic plate and an insulating second porous portion fitted into a recess provided on the ceramic plate side of the base plate so as to face the first porous portion are provided. The gas supplied to the gas introduction path 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 for cooling an object. As the bonding layer for bonding the ceramic plate and the base plate, for example, a cured silicone adhesive is used. It is described that the presence of the first porous portion and the second porous portion can suppress the occurrence of discharge (arc discharge) caused by plasma when processing the wafer while ensuring the gas flow rate from the gas introduction passage to the wafer mounting surface.

[0003] Japanese Patent Application Laid-Open No. 2020-7226

[0004] However, even when the insulating second porous portion exists as in Patent Document l, discharge may occur around the end portion on the base plate side of the first porous portion. Also, in order to suppress this discharge, it is conceivable to change the bonding layer to a conductor such as metal instead of an insulator such as resin. However, generally, a conductor has a lower thermal resistance (higher thermal conductivity rate) than an insulator. Therefore, when the bonding layer is a conductor, there is a problem that the wafer easily cools.

[0005] The present invention has been made to solve such problems, and the main object is to suppress the cooling of the wafer while suppressing discharge around the end portion on the conductive plate side of the insulating gas passage plug.

[0006] The present invention has adopted the following means to achieve the above-described main object.

[0007] [1] The wafer mounting stage of the present invention comprises: a ceramic plate having a wafer mounting surface on its upper surface and containing electrodes; a conductive plate disposed on the lower side of the ceramic plate; a bonding layer joining the ceramic plate and the conductive plate; a ceramic plate penetration portion penetrating the ceramic plate; an insulating gas passage plug provided in the ceramic plate penetration portion through which gas can pass; and a gas introduction passage provided at least inside the bonding layer and the conductive plate and communicating with the ceramic plate penetration portion, wherein the bonding layer has a structure in which an insulating layer and a conductive layer are laminated, and the conductive layer is exposed in the bonding layer penetration portion, which is the portion of the gas introduction passage that penetrates the bonding layer.

[0008] In this wafer mounting platform, the bonding layer that joins the ceramic plate and the conductive plate has a structure in which an insulating layer and a conductive layer are stacked. This makes it easier to increase the thermal resistance of the bonding layer compared to a case where the bonding layer is composed entirely of conductors, thereby suppressing wafer cooling. Furthermore, since the conductive layer is exposed at the bonding layer penetration portion, which is the part of the gas introduction passage that penetrates the bonding layer, discharge around the conductive plate side end of the insulating gas passage plug can be suppressed. As a result of the above, this wafer mounting platform can suppress wafer cooling while suppressing discharge around the conductive plate side end of the insulating gas passage plug.

[0009] [2] The wafer mounting stand described above (the wafer mounting stand described in [1] above) may include a conductive member that electrically connects the conductive plate and the conductive layer. This allows the conductive plate and the conductive layer to be electrically connected and a potential to be supplied to the conductive layer, so that the two can be brought to approximately the same potential. Therefore, the effect of suppressing discharge around the conductive plate side end of the insulating gas passage plug is enhanced.

[0010] [3] In the wafer mounting stand described above (the wafer mounting stand described in [2] above), the conductive member may be positioned at a location other than the bonding layer penetration portion.

[0011] [4] In the wafer mounting stand described above (the wafer mounting stand described in any of [1] to [3] above), the vertical distance L1 between the lower surface of the ceramic plate and the conductive layer may be 200 μm or less. When the distance L1 is 200 μm or less, the height of the space between the lower surface of the insulating gas passage plug and the conductive layer is reduced, thereby increasing the effect of suppressing discharge around the conductive plate side end of the insulating gas passage plug.

[0012] [5] In the wafer mounting stage described above (the wafer mounting stage described in [4] above), the distance L1 may be 100 μm or less. This further reduces the height of the space between the lower surface of the insulating gas passage plug and the conductive layer, thereby further enhancing the discharge suppression effect described above.

[0013] [6] The wafer stand described above (the wafer stand described in any of [1] to [5] above) may include a conductive gas passage portion provided in the gas introduction passage, in contact with the lower surface of the insulating gas passage plug, electrically conductive with the conductive plate and / or the conductive layer, and allowing gas to pass between the insulating gas passage plug and the gas introduction passage. This makes it less likely for a potential difference to occur around the conductive plate side end of the insulating gas passage plug compared to, for example, the case where an insulating porous member is present on the lower surface side of the insulating gas passage plug. Therefore, discharge around the conductive plate side end of the insulating gas passage plug can be further suppressed.

[0014] [7] In the wafer mounting stand described above (the wafer mounting stand described in [6]), the conductive gas passage portion may have a conductive elastic body that elastically presses the insulating gas passage plug upward. This makes it easier to maintain conductivity from the contact portion of the conductive gas passage portion with the insulating gas passage plug to the conductive plate and / or conductive layer.

[0015] [8] In the wafer mounting stand described above (the wafer mounting stand described in [7] above), the conductive elastic body may be a leaf spring.

[0016] [9] In the wafer mounting stand described above (the wafer mounting stand described in any of [6] to [8] above), the conductive gas passage portion may have 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 holes that allow gas to pass through. Alternatively, the coating layer may be a porous layer that allows gas to pass through. Or, the coating layer may cover a part of the lower surface of the insulating gas passage plug, allowing gas to pass through the uncovered portion of the lower surface.

[0017] Plan view of the wafer mounting table 10. Cross-sectional view along line A-A in Figure 1. Explanatory diagram showing the positions of the upper surface 72a of the leaf spring 72, the internal gas flow path 55a, and the bonding layer penetration portion 64 in a plan view. Perspective view of the leaf spring 72 of the conductive gas passage portion 70. Cross-sectional view of the wafer mounting table 10 as seen from above, when the wafer mounting table 10 is cut along a horizontal plane passing through the second gas passage 62. Cross-sectional view of the wafer mounting table 10 as seen from above, when the wafer mounting table 10 is cut along a horizontal plane passing through the refrigerant flow path 32. Explanatory diagram showing the plan view of the wafer mounting table 10 with the refrigerant flow path 32 and the like drawn on it. Manufacturing process diagram of the wafer mounting table 10. Explanatory diagram showing the state of the leaf spring 72 being pressed by the dense plug 55 during the manufacturing of the wafer mounting table 10. Partially enlarged cross-sectional view showing the conductive member 49. Partially enlarged cross-sectional view showing the bonding layer 140. Partially enlarged cross-sectional view showing the porous plug 155 and the coating layer 171. Partially enlarged cross-sectional view showing the conductive gas passage portion 270. A partially enlarged cross-sectional view showing the leaf spring 472. A perspective view of the leaf spring 472. A partially enlarged cross-sectional view showing the conductive elastic body 572. A partially enlarged cross-sectional view showing the first conductive layer 645 of a modified example.

[0018] Next, preferred embodiments of the present invention will be described with reference to the drawings. Figure 1 is a plan view of the wafer mounting table 10, Figure 2 is a cross-sectional view taken along line A-A in Figure 1, Figure 3 is an explanatory diagram showing the positions of the upper surface 72a of the leaf spring 72, the internal gas flow path 55a, and the bonding layer penetration portion 64 in a plan view, Figure 5 is a cross-sectional view taken from above of the cut surface obtained by cutting the wafer mounting table 10 with a horizontal plane passing through the second gas passage 62, Figure 6 is a cross-sectional view taken from above of the cut surface obtained by cutting the wafer mounting table 10 with a horizontal plane passing through the refrigerant flow path 32, and Figure 7 is an explanatory diagram showing the plan view of the wafer mounting table 10 with the refrigerant flow path 32 and the like drawn on it. In this specification, "up" and "down" do not represent an absolute positional relationship, but rather a relative positional relationship. Therefore, depending on the orientation of the wafer mounting table 10, "up" and "down" may become "down" and "up," or "left" and "right," or "front" and "back."

[0019] As shown in Figure 2, the wafer mounting stage 10 includes a ceramic plate 20, a conductive plate 30, a bonding layer 40, a ceramic plate penetration portion 50, a gas introduction passage 60, and a conductive gas passage portion 70.

[0020] The ceramic plate 20 is a ceramic disc (for example, 300 mm in diameter and 5 mm thick) made of an alumina sintered body or an aluminum nitride sintered body. The upper surface of the ceramic plate 20 is a wafer mounting surface 21 on which the wafer W is placed. The ceramic plate 20 incorporates electrodes 22. As shown in Figure 1, an annular sealing 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 sealing band 21a. The sealing band 21a and the small circular protrusions 21b are of the same height, for example, several μm to several tens of μm. The electrodes 22 are planar mesh electrodes used as electrostatic electrodes and are connected to an external DC power supply via a power supply member (not shown). A low-pass filter may be placed in the middle of the power supply member. The power supply member is electrically insulated from the insulating layer 40a of the bonding layer 40 and the conductive plate 30. When a DC voltage is applied to the electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the upper surface of the seal band and the upper surface of the small circular protrusions) by electrostatic attraction force, and when the application of the DC voltage is removed, the attraction and fixation of the wafer W to the wafer mounting surface 21 is released. The portion of the wafer mounting surface 21 that does not have the seal band 21a or the small circular protrusions 21b is referred to as the reference surface 21c.

[0021] The conductive plate 30 is a disc with good thermal conductivity (a disc with the same diameter as or larger than the ceramic plate 20). Inside the conductive plate 30, a refrigerant channel 32 is formed through which the refrigerant circulates. The refrigerant flowing through the refrigerant channel 32 is preferably a liquid and preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inert liquids. In plan view, the refrigerant channel 32 is formed in a continuous, single-stroke manner across the entire conductive plate 30 from one end (inlet) to the other end (outlet). As shown in Figure 6, the refrigerant channel 32 is provided to be routed in a continuous, single-stroke manner from one end to the other, based on multiple circles formed by arranging several virtual circles of different diameters (circles C1 to C4, shown as dashed lines, where circles C1 to C4 are concentric circles) in a non-overlapping manner in plan view. Specifically, the refrigerant flow path 32 is routed in a single continuous line from one end to the other, by connecting two virtual circles that are in an inner and outer relationship among multiple circles, and tracing these 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 from the supply port of the external refrigerant device to one end of the refrigerant flow path 32 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, is temperature-adjusted, and then supplied again from the supply port to one end of the refrigerant flow path 32. The conductive plate 30 is connected to a high-frequency (RF) power supply and is also used as an RF electrode.

[0022] The material of the conductive plate 30 can be, for example, a metal material or a composite material of metal and ceramic. Examples of metal materials include Al, Ti, Mo, or alloys thereof. Examples of composite materials of metal and ceramic include metal matrix composite materials (MMC) and ceramic matrix composite materials (CMC). Specific examples of such composite materials include materials containing Si, SiC, and Ti (also called SiSiCTi), materials in which Al and / or Si are impregnated into a porous SiC body, and composite materials of Al2O3 and TiC. It is preferable to select a material for the conductive plate 30 that has a coefficient of thermal expansion similar to that of the ceramic plate 20.

[0023] The bonding layer 40 joins the lower surface of the ceramic plate 20 to the upper surface of the conductive plate 30. It has a structure in which an insulating layer 40a and a conductive layer 40b are laminated. In this embodiment, the insulating layer 40a has two layers, a first insulating layer 41 and a second insulating layer 42, and the conductive layer 40b has one layer, a first conductive layer 45. The first insulating layer 41, the first conductive layer 45, and the second insulating layer 42 are laminated in this order from top to bottom, and the insulating layers 40a and conductive layers 40b are laminated alternately. The material of the insulating layer 40a (here, the first insulating layer 41 and the second insulating layer 42) is an insulating resin such as silicone resin, acrylic resin, polyimide resin, or epoxy resin. The material of the conductive layer 40b (here, the first conductive layer 45) is a metal, for example. The material of the conductive layer 40b is preferably low resistance and non-magnetic. Examples of nonmagnetic metals used for the conductive layer 40b include Al and Cu, with Al being particularly preferred. A second insulating layer 42 exists between the first conductive layer 45 and the conductive plate 30, and the first conductive layer 45 and the conductive plate 30 are not directly electrically connected.

[0024] The vertical distance L1 (see Figure 2) between the lower surface of the ceramic plate 20 and the conductive layer 40b (here, the first conductive layer 45) is preferably 200 μm or less, and more preferably 100 μm or less. Similarly, the vertical distance L2 between the upper surface of the conductive plate 30 and the conductive layer 40b (here, the first conductive layer 45) is preferably 200 μm or less, and more preferably 100 μm or less. In this embodiment, distance L1 is equal to the thickness of the first insulating layer 41, and distance L2 is equal to the thickness of the second insulating layer 42.

[0025] As shown in Figure 2, the ceramic plate penetration portion 50 is a hole that penetrates the ceramic plate 20 in the vertical direction. The ceramic plate penetration portion 50 is a gas passage from the lower surface of the ceramic plate 20 to the reference surface 21c of the wafer mounting surface 21 (Figure 1). As shown in Figure 1, there are multiple (36 in this case) ceramic plate penetration portions 50. As shown in Figure 2, the ceramic plate penetration portion 50 is a space with a shape (for example, an inverted frustoconical shape) in which the cross-sectional area decreases from the upper opening to the lower opening. The ceramic plate penetration portion 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.

[0026] The dense plug 55 is a component with a shape (for example, a frustoconical shape) in which the cross-sectional area decreases from the top surface to the bottom surface, similar to the shape of the ceramic plate penetration portion 50. The dense plug 55 has an internal gas flow path 55a. In Figure 3, the contour of the top surface of the dense plug 55 is shown by a solid line, and the contour of the bottom surface of the dense plug 55 and the contour of the opening at the lower end of the internal gas flow path 55a are shown by dashed lines. The internal gas flow path 55a is a flow path that allows gas to flow between the top and bottom surfaces of the dense plug 55. The internal gas flow path 55a is a passage that penetrates the top and bottom surfaces of the dense plug 55 while bending, and more specifically, it is configured as a zigzag passage. Another example of a passage that penetrates while bending is a spiral passage. The internal gas flow path 55a may also be a straight through-hole along the vertical direction. The diameter of the cross-sectional area of ​​the internal gas flow path 55a is preferably 0.1 mm or more and 1 mm or less. A single dense plug 55 may have multiple internal gas passages 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 press-fitting it into the ceramic plate penetration portion 50. As the dense plug 55, ceramics such as alumina or aluminum nitride can be used. The dense plug 55 may be manufactured, for example, by firing a molded body formed using a 3D printer, or by firing a molded body formed by mold casting. Details of dense plugs having internal gas passages that penetrate while bending and mold casting are disclosed, for example, in Japanese Patent No. 7149914.

[0027] The upper surface of the dense plug 55 is at the same height as the reference surface 21c of the wafer mounting surface 21. The lower surface of the dense plug 55 is covered by a coating layer 71 which is part of the conductive gas passage portion 70. As shown in Figure 2, the lower surface of the dense plug 55 is located above the lower opening surface of the ceramic plate penetration portion 50 (at the same height as the lower surface of the ceramic plate 20). The lower surface of the dense plug 55 may be at the same height as the lower opening surface of the ceramic plate penetration portion 50. The lower surface of the dense plug 55 may be located below the lower opening surface of the ceramic plate penetration portion 50. That is, the lower end of the dense plug 55 may protrude below the lower surface of the ceramic plate 20.

[0028] The gas introduction passage 60 is a gas passage provided at least inside the bonding layer 40 and the conductive plate 30, and communicates with the ceramic plate penetration 50. The gas introduction passage 60 comprises a first gas passage 61, a second gas passage 62, an auxiliary gas passage 63 (Figure 5), and a bonding layer penetration 64. The gas introduction passage 60 comprises a gas passage provided inside the conductive plate 30 (first gas passage 61, second gas passage 62, and auxiliary gas passage 63) and a gas passage provided inside the bonding layer 40 (bonding layer penetration 64).

[0029] The first gas passage 61 penetrates the conductive plate 30 in the vertical direction. The first gas passage 61 penetrates the space between the refrigerant flow paths 32 of the conductive plate 30 in the vertical direction. Multiple (three in this case) first gas passages 61 are provided.

[0030] The second gas passage 62 is provided at the interface between the bonding layer 40 and the conductive plate 30, parallel to the wafer mounting surface 21. "Parallel" means not only perfectly parallel, but also parallel if not perfectly parallel but within an acceptable 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 bonding layer 40. As shown in Figure 7, the second gas passage 62 is provided in an annular shape so as to overlap with one of the multiple virtual circles C1 to C4 in a plan view. Specifically, of the three second gas passages 62, the first gas passage 62 from the outer edge of the wafer mounting base 10 overlaps with the virtual circle C1 with the largest diameter, the second gas passage 62 overlaps with the virtual circle C2 with the second largest diameter, and the third gas passage 62 overlaps with the virtual circle C3 with the third largest diameter. Each second gas passage 62 has an overlapping portion 62p (shaded portion in Figure 7) that overlaps with the refrigerant passage 32 in a plan view, along the refrigerant passage 32.

[0031] The gas auxiliary passage 63 is a passage connecting the first gas passage 61 and the second gas passage 62, and is provided parallel to the wafer mounting surface 21 at the interface between the bonding layer 40 and the conductive plate 30. Multiple ceramic plate penetrations 50 (12 in this case) are provided for one second gas passage 62, but the number of first gas passages 61 and gas auxiliary passages 63 is fewer than the number of ceramic plate penetrations 50 (one for each second gas passage 62 in this case).

[0032] As shown in Figure 2, the bonding layer penetration portion 64 is the portion of the gas introduction passage 60 that penetrates the bonding layer 40 in the vertical direction. The bonding layer penetration portion 64 is a gas passage from the upper surface of the conductive plate 30 to the lower surface of the ceramic plate 20. Multiple bonding layer penetration portions 64 are provided (36 in this case), and they are arranged in a one-to-one correspondence with the ceramic plate penetration portion 50. Each of the multiple bonding layer penetration portions 64 has a through hole 64a provided in the first insulator layer 41, a through hole 64b provided in the first conductive layer 45, and a through hole 64c provided in the second insulator layer 42. The bonding layer penetration portion 64 is formed by the vertical communication of these through holes 64a to 64c. Therefore, the portions of the first insulator layer 41, the second insulator layer 42, and the first conductive layer 45 that constitute the inner circumferential surfaces of these through holes 64a to 64c are exposed to the bonding layer penetration portion 64. The through-hole 64a is a circular hole when viewed from above (see Figure 3). The through-holes 64b and 64c are also circular holes when viewed from above. In this embodiment, as shown in Figure 2, the diameter of the through-hole 64a is larger than the diameter of the lower surface of the dense plug 55 and the diameter of the lower opening surface of the ceramic plate through-hole 50. Also, the diameter of the through-hole 64b is smaller than the diameter of the through-hole 64a. Therefore, a part of the upper surface of the first conductive layer 45 is exposed to the through-hole 64a of the first insulating layer 41, and thus this part is exposed to the bonding layer through-hole 64. The diameter of the through-hole 64b is smaller than the diameter of the through-hole 64c. Therefore, a part of the lower surface of the first conductive layer 45 is exposed to the through-hole 64c of the second insulating layer 42, and thus this part is exposed to the bonding layer through-hole 64. Also, the diameter of the through-hole 64c is larger than the width of the groove 31.

[0033] The conductive gas passage section 70 is provided within the gas introduction passage 60, in contact with the lower surface of the dense plug 55, electrically connected to the conductive plate 30 and / or the conductive layer 40b, and is provided to allow the passage of gas between the dense plug 55 and the gas introduction passage 60. The conductive gas passage section 70 has a coating layer 71 and a leaf spring 72 (an example of a conductive elastic body). The coating layer 71 covers the lower surface of the dense plug 55 and is in contact with the lower surface of the dense plug 55. The coating layer 71 is formed as a dense layer and has holes 71a through which gas can pass in the vertical direction. The holes 71a connect the opening of the internal gas flow path 55a on the lower surface of the dense plug 55 to the gas introduction passage 60. The coating layer 71 can be manufactured, for example, by forming a coating layer on the lower surface of the dense plug 55 by sputtering or electroless plating before press-fitting the dense plug 55 into the ceramic plate 20, and by creating a hole 71a. The material of the coating layer 71 can be a metal, for example, and metals with excellent corrosion resistance such as Au, Ag, Al, Ti, SUS316L, or Hastelloy (Ni-Fe-Mo alloy, Hastelloy is a registered trademark) are preferred.

[0034] The leaf spring 72 is an elastic body that presses the dense plug 55 upward with elastic force. The material of the leaf spring 72 can be a conductor, and more specifically, metal materials such as Al, Ti, Mo or their alloys, steel, SUS316L, Hastelloy®, etc. can be used. The leaf spring 72 is manufactured, for example, by bending a metal plate, and in this embodiment, the metal plate is bent in a zigzag shape. The zigzag folding direction of the leaf spring 72 is along the vertical direction. That is, the leaf spring 72 has a plurality of folded portions 73 that are folded along the vertical direction. The folded portions 73 of the leaf spring 72 are formed in a V shape. The leaf spring 72 has multiple folded portions 73, which include one or more (in this case, multiple, specifically three) first folded portions 73a folded from top to bottom, and one or more (in this case, multiple, specifically two) second folded portions 73b folded from bottom to top. Therefore, in this embodiment, the leaf spring 72 is folded multiple times (in this case, five times). However, the number of folds only needs to be one or more. 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. As a result, the leaf spring 72 and the coating layer 71 are electrically conductive. The leaf spring 72 is located inside the joint layer penetration portion 64 of the gas introduction passage 60. Furthermore, in this embodiment, since the lower surface of the dense plug 55 and the lower surface of the coating layer 71 are located above the lower opening surface of the ceramic plate penetration portion 50, the leaf spring 72 is also positioned inside the ceramic plate penetration portion 50. That is, the leaf spring 72 is positioned across the inside of the ceramic plate penetration portion 50 and the inside of the bonding layer penetration portion 64. The through hole 64a is formed to be larger than the leaf spring 72, and the through hole 64b is formed to be smaller than the leaf spring 72. As a result, the leaf spring 72 is positioned inside the through hole 64a, and the lower surface 72b of the leaf spring 72 (the lower surface of the second folded portion 73b of the leaf spring 72, see also Figure 4) is in contact with the portion of the upper surface of the first conductive layer 45 that is exposed to the through hole 64a of the first insulating layer 41, thereby supporting the leaf spring 72 in the first conductive layer 45. As a result, the leaf spring 72 is electrically connected to the first conductive layer 45.Therefore, the coating layer 71, the leaf spring 72, and the first conductive layer 45 are electrically conductive. Also, as mentioned above, the first conductive layer 45 and the conductive plate 30 are not directly conductive, so the leaf spring 72 and the conductive plate 30 are not directly conductive.

[0035] In this embodiment, since the zigzag folding direction of the leaf spring 72 is aligned with the vertical direction, the main direction of expansion and contraction of the leaf spring 72 is not the vertical direction in Figure 2, i.e., the direction in which it presses against the dense material plug 55, but rather the left-right direction in Figure 2. In other words, the leaf spring 72 is positioned horizontally. However, because the leaf spring 72 is zigzag-shaped, and is pressed from above by the dense material plug 55, it extends horizontally perpendicular to the vertical direction (the plate of the leaf spring 72 becomes more inclined from the vertical direction), an elastic force is exerted from the leaf spring 72 in the vertical direction as a force trying to return to its original position (a force trying to return the plate of the leaf spring 72 from its inclined state to a direction aligned with the vertical direction). Due to this elastic force, the leaf spring 72 presses the dense material plug 55 upward. Similarly, the leaf spring 72 presses the first conductive layer 45 and the conductive plate 30 downward with elastic force.

[0036] The leaf spring 72 is adjusted in shape and position to prevent it from completely blocking the holes 71a in the coating layer 71 (and the opening at the lower end of the internal gas flow path 55a) and obstructing the flow of gas. In this embodiment, as shown in Figures 2 and 3, the width of each of the three upper surfaces 72a of the leaf spring 72 that are in contact with the coating layer 71 is smaller than the opening diameter of the holes 71a, so that the leaf spring 72 does not completely block the holes 71a (and the opening at the lower end of the internal gas flow path 55a) regardless of its position. In this way, since the coating layer 71 has holes 71a and the leaf spring 72 does not obstruct the flow of gas through the holes 71a, the gas in the gas introduction passage 60 can flow through the inside and / or around the conductive gas passage 70 to the ceramic plate penetration 50. In this embodiment, as shown in Figures 2 and 3, one of the three upper surfaces 72a of the leaf spring 72 does not completely block the hole 71a of the coating layer 71, but it does block a portion of the hole 71a. That is, in a plan view, the upper surface 72a of the leaf spring 72 overlaps with a portion of the hole 71a. However, it is preferable that, in a plan view, the upper surface 72a of the leaf spring 72 does not overlap with the hole 71a at all.

[0037] In this embodiment, a plurality of conductive gas passage sections 70 (36 in this case) are provided, and they are arranged in a one-to-one correspondence with the dense plug 55. That is, the coating layer 71 and the leaf spring 72 are each arranged in a one-to-one correspondence with the dense plug 55.

[0038] Next, an example of using the wafer mounting stand 10 configured in this way will be described. First, with the wafer mounting stand 10 installed in a chamber (not shown), the wafer W is placed on the wafer mounting surface 21. Then, the pressure inside the chamber is reduced using a vacuum pump to adjust to a predetermined vacuum level, and a DC voltage is applied to the electrode 22 of the ceramic plate 20 to generate electrostatic adsorption force, thereby adsorbing and fixing the wafer W to the wafer mounting surface 21 (specifically, the upper surface of the seal band 21a and the upper surface of the circular protrusion 21b). Next, the inside of the chamber is made into a reaction gas atmosphere at a predetermined pressure (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 stand 10 to generate plasma. The surface of the wafer W is treated by the generated plasma. A refrigerant is circulated in the refrigerant flow path 32 of the 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. A thermal conductive gas (e.g., He gas) is used as the backside gas. The backside gas introduced into the first gas passage 61 passes through the auxiliary gas passage 63, the second gas passage 62, and the bonding layer penetration portion 64 in that order, and is distributed to a plurality of ceramic plate penetration portions 50, where it is supplied 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 for efficient heat conduction between the wafer W and the ceramic plate 20. In addition, the provision of a dense plug 55 in the ceramic plate penetration portion 50 suppresses discharge within the ceramic plate penetration portion 50. Furthermore, because the internal gas flow path 55a is a curved flow path, discharge in the internal gas flow path 55a can be suppressed compared to the case of a straight flow path.

[0039] Next, an example of the manufacturing of the wafer mounting table 10 will be described based on Figures 8 and 9. Figure 8 is a manufacturing process diagram of the wafer mounting table 10. Figure 9 is an explanatory diagram showing the state of the leaf spring 72 that is pressed by the dense plug 55 during the manufacturing of the wafer mounting table 10. Here, we will illustrate the case in which the conductive plate 30 is made of MMC. First, a ceramic plate 20 containing the electrodes 22 is prepared (Figure 8A). For example, a molded body of ceramic powder containing the electrodes 22 is made, and the ceramic plate 20 is obtained by hot-press firing the molded body. A ceramic plate penetration portion 50 is formed in the ceramic plate 20 (Figure 8B). The ceramic plate penetration portion 50 is formed to penetrate the ceramic plate 20 in the vertical direction, avoiding the electrodes 22.

[0040] In parallel with this, two MMC disc members 81 and 82 are prepared (Figure 8C). Then, grooves and holes are formed in these MMC disc members 81 and 82 as appropriate by machining (Figure 8D). Specifically, a recessed groove 32a, which will eventually become the refrigerant flow path 32, is formed on the lower surface of the upper MMC disc member 81, and a recessed groove 31, which will eventually become the second gas passage 62, is formed on the upper surface of the MMC disc member 81. In addition, a through hole 61a, which will eventually become part of the first gas passage 61, is formed from the recessed groove 31 to the lower surface of the MMC disc member 81. Furthermore, a through hole 61b, which will eventually become part of the first gas passage 61, is formed in the lower MMC disc member 82. If the ceramic plate 20 is made of alumina, it is preferable that the MMC disc members 81 and 82 be made of SiSiCTi or AlSiC. This is because the thermal expansion coefficients of alumina and SiSiCTi and AlSiC can be made to be approximately the same.

[0041] A disc member made of SiSiCTi can be manufactured, for example, as follows: First, a powder mixture is prepared by mixing silicon carbide, metallic Si, and metallic Ti. Next, a disc-shaped molded body is produced from the obtained powder mixture by uniaxial pressure molding, and the molded body is hot-press sintered in an inert atmosphere to obtain a disc member made of SiSiCTi.

[0042] Next, the ceramic plate 20 and the MMC disc members 81 and 82 are joined together, the overall shape is adjusted, and the dense plug 55 is attached to obtain the wafer mounting base 10 (Figures 8E and 8F). Specifically, first, a first laminate is obtained by sandwiching a metal bonding material 83 between the upper surface of the lower MMC disc member 82 and the lower surface of the upper MMC disc member 81. Through holes, which will ultimately become part of the first gas passage 61, are formed in advance in the metal bonding material 83. Subsequently, the two MMC disc members 81 and 82 are joined together with the metal bonding material 83, for example by thermal compression bonding (TCB), to obtain the conductive plate 30. TCB refers to a known method of joining two members by sandwiching a metal bonding material between them and pressurizing the two members while they are heated to a temperature below the solidus temperature of the metal bonding material (for example, a temperature between 20°C below the solidus temperature and the solidus temperature). As the metal bonding material 83, Al-Mg-based bonding material or Al-Si-Mg-based bonding material can be used. For example, when performing TCB using an Al-Si-Mg-based bonding material, the laminate is pressurized while heated in a vacuum atmosphere. It is preferable to use a metal bonding material 83 with a thickness of about 100 μm. Subsequently, a second laminate is obtained by sandwiching a sheet-like resin bonding material 91, a metal bonding material 95, and a resin bonding material 92 in this order between the lower surface of the ceramic plate 20 and the upper surface of the conductive plate 30. Through holes that will ultimately become part of the bonding layer penetration portion 64 are formed in advance in the resin bonding material 91, the metal bonding material 95, and the resin bonding material 92. The leaf spring 72 is pre-inserted into the through-hole of the resin bonding material 91 after the resin bonding material 91 is placed on the upper surface of the conductive plate 30. Then, by heating and pressurizing the second laminate, the ceramic plate 20 and the conductive plate 30 are joined by the resin bonding material 91, the metal bonding material 95, and the resin bonding material 92. As a result, the resin bonding material 91, the metal bonding material 95, and the resin bonding material 92 become a bonding layer 40 (first insulating layer 41, first conductive layer 45, and second insulating layer 42).

[0043] The dense plug 55 is installed, for example, as follows. First, a dense plug 55 formed in advance 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 penetration portion 50 (Figure 9A), bringing the coating layer 71 on the lower surface of the dense plug 55 into contact with the leaf spring 72, and the dense plug 55 is further pressed downwards (Figure 9B). As a result, the dense plug 55 is pressed into the ceramic plate penetration portion 50, and the dense plug 55 presses against the leaf spring 72 (the dense plug 55 presses against the leaf spring 72 via the coating layer 71), causing the leaf spring 72 to be elastically deformed (Figure 9B). As a result, in the manufactured wafer mounting table 10, the leaf spring 72 is positioned in a state where it extends horizontally perpendicular to the vertical direction. In other words, the leaf spring 72 extends from its natural horizontal width W1 (Figure 9A), which is its length before being pressed by the dense plug 55, to a width W2 that is greater than W1 (Figure 9B). Also, along with this horizontal extension, the leaf spring 72 changes from its vertical height T1 (Figure 9A), which was its height before being pressed by the dense plug 55, to a height T2 that is less than T1 (Figure 9B). As a result, the leaf spring 72 generates elastic force not only in the lateral direction but also in the vertical direction, causing the upper surface 72a of the leaf spring 72 to press the dense plug 55 upward. In this way, the dense plug 55 not only contacts the leaf spring 72 via the coating layer 71, but by press-fitting the dense plug 55 into the ceramic plate penetration portion 50 so that the dense plug 55 presses the leaf spring 72 downward, the dense plug 55 makes even more reliable contact with the leaf spring 72 via the coating layer 71, thereby ensuring more reliable electrical contact between the coating layer 71 and the leaf spring 72. Furthermore, the leaf spring 72 and the first conductive layer 45 can be made to conduct electricity more reliably.

[0044] In the wafer mounting stage 10 described in detail above, the bonding layer 40 that bonds the ceramic plate 20 and the conductive plate 30 has a structure in which an insulator layer 40a and a conductor layer 40b are laminated. Generally, since a conductor has a lower thermal resistance than an insulator, by having the insulator layer 40a in the bonding layer 40, it is easier to increase the thermal resistance of the bonding layer 40 compared to the case where the bonding layer 40 is entirely composed of a conductor. Therefore, in this wafer mounting stage 10, heat conduction from the ceramic plate 20 to the conductive plate 30 can be suppressed, and cooling of the wafer W can be suppressed. Further, since the conductor layer 40b (here, the first conductor layer 45) is exposed at the bonding layer penetration portion 64 that is the portion of the gas introduction passageway 60 that penetrates the bonding layer 40, it is possible to suppress discharge around the periphery of the end portion on the conductive plate 30 side of the dense plug 55, that is, around the lower end portion of the dense plug 55. From the above, in this wafer mounting stage 10, it is possible to suppress cooling of the wafer W while suppressing discharge around the periphery of the end portion on the conductive plate 30 side of the dense plug 55.

[0045] Here, regarding the temperature of the wafer W when using the wafer mounting stand 10, in recent years there has been a demand for higher temperatures, and in order to raise the temperature of the wafer W higher, it is necessary to increase the thermal resistance of the bonding layer 40. When the thermal resistance is increased by making the bonding layer 40 thicker, the vertical length of the bonding layer penetration portion 64 increases, and if the bonding layer 40 is made entirely of an insulator, a potential difference is more likely to occur on the inner surface of the bonding layer penetration portion 64 within the bonding layer 40, and discharge tends to occur within the bonding layer penetration portion 64. However, in the wafer mounting stand 10 of this embodiment, the bonding layer 40 is provided with a first conductive layer 45 that is exposed to the bonding layer penetration portion 64, so discharge can be suppressed by this first conductive layer 45. Moreover, since the bonding layer 40 is provided with a first insulating layer 41 and a second insulating layer 42, the thermal resistance of the bonding layer 40 can be increased even with the same thickness compared to the case where the entire bonding layer 40 is made of a conductor. In this embodiment, the first conductive layer 45 and the conductive plate 30 are not directly electrically connected. However, since the voltage that causes discharge when the wafer mounting stand 10 is used is an AC voltage such as a high-frequency (RF) voltage, potential can be supplied from the conductive plate 30 to the first conductive layer 45 through capacitive coupling between the conductive plate 30 and the first conductive layer 45. Therefore, the first conductive layer 45 can suppress discharge at the bonding layer penetration portion 64.

[0046] Furthermore, by setting the vertical distance L1 between the lower surface of the ceramic plate 20 and the first conductive layer 45 to 200 μm or less, the height of the space between the lower surface of the dense plug 55 and the upper surface of the first conductive layer 45 in the gas introduction passage 60 is reduced, thereby increasing the effect of suppressing discharge around the end of the dense plug 55 on the conductive plate 30 side, i.e., around the lower end of the dense plug 55. This effect is further enhanced by setting the distance L1 to 100 μm or less. Similarly, by setting the vertical distance L2 between the upper surface of the conductive plate 30 and the first conductive layer 45 to 200 μm or less, the height of the space between the lower surface of the first conductive layer 45 and the upper surface of the conductive plate 30 in the gas introduction passage 60 (here the same as the height of the through hole 64c) is reduced, thereby increasing the effect of suppressing discharge in this space. This effect is further enhanced by setting the distance L2 to 100 μm or less.

[0047] Furthermore, the wafer mounting table 10 is provided within the gas introduction passage 60 and includes a conductive gas passage section 70 that contacts the lower surface of the dense plug 55, is electrically conductive with the first conductive layer 45, and allows gas to pass between the dense plug 55 and the gas introduction passage 60. Therefore, since the conductive gas passage section 70, which is at the same potential as the first conductive layer 45, is in contact with the dense plug 55, discharge can be suppressed around the end of the dense plug 55 on the conductive plate 30 side, i.e., around the lower end of the dense plug 55. Note that even if an insulating porous member is present on the lower surface of the dense plug 55 instead of the conductive gas passage section 70, discharge can still be suppressed around the lower end of the dense plug 55. However, the presence of the conductive gas passage section 70 makes it less likely for a potential difference to occur around the end of the dense plug 55 on the conductive plate 30 side, thus further suppressing discharge. The conductive gas passage section 70 also has a leaf spring 72 that elastically presses the dense plug 55 upward. As a result, the dense plug 55 makes more reliable contact with the leaf spring 72 via the coating layer 71, making it easier to maintain conductivity from the contact portion of the conductive gas passage 70 with the dense plug 55 (in this case, the upper surface of the coating layer 71) to the first conductive layer 45.

[0048] Further, the leaf spring 72 is disposed in a state of extending in the lateral direction perpendicular to the vertical direction by being pressed from above by the dense plug 55. As a result, when the leaf spring expands in the lateral direction, it is easy to reduce the area where the leaf spring 72 does not exist directly below the dense plug 55. Thereby, it is possible to further suppress discharge around the end of the dense plug 55 on the side of the conductive plate 30. For example, in the wafer stage 10 after manufacturing, when the leaf spring 72 does not extend in the lateral direction as shown in FIG. 9A, there is a concern that the discharge suppression effect may be reduced in the space on the left or right side of the leaf spring among the spaces directly below the dense plugging 55. On the other hand, as shown in FIG. 9B, when the leaf spring 72 expands in the lateral direction, the discharge suppression effect is enhanced. Further, for example, when the elastic force of the leaf spring 72 decreases due to long-term use of the wafer stage 10, there may be a case where the leaf spring 72 needs to be replaced in the wafer stage In this case, in the above-described embodiment, by removing the dense plug 55 from the ceramic plate 20 of the wafer stage becomes the state before the leaf spring 72 extends in the lateral direction as shown in FIG. 9A (the lateral width becomes W1 smaller than W2), so that the leaf spring 72 can be easily taken out and the replacement of the leaf spring 72 becomes easy.

[0049] Note that the present invention is not limited to the above-described embodiments, and it is needless to say that the present invention can be implemented in various modes as long as it belongs to the technical scope of the present invention.

[0050] For example, in the embodiment described above, the conductive plate 30 and the first conductive layer 45 were not directly electrically connected, but this is not limited to this. The wafer mounting base 10 may include a conductive member 49 that electrically connects the conductive plate 30 and the first conductive layer 45, as shown in Figure 10, for example. In Figure 10, the conductive member 49 is placed in a mounting hole 49b provided on the upper surface of the conductive plate 30, and is positioned inside the mounting hole 49b and a through hole 49a provided in the second insulating layer 42, contacting the first conductive layer 45 and the conductive plate 30 and making them electrically connected. As a result, the conductive plate 30 and the conductive layer can be electrically connected and a potential can be supplied to the first conductive layer 45, so that the two can be brought to approximately the same potential. Therefore, the effect of suppressing discharge around the end of the dense plug 55 on the conductive plate 30 side is enhanced. In Figure 10, the conductive gas passage section 70 (coating layer 71 and leaf spring 72) and the first conductive layer 45 are directly electrically connected, so the conductive gas passage section 70 and the conductive plate 30 are also directly electrically connected. In Figure 10, the conductive member 49 is located at a position separate from the bonding layer penetration section 64. Specifically, the conductive member 49 is located in the through hole 49a and the mounting hole 49b, which are spaced apart from the bonding layer penetration section 64. Furthermore, the conductive member 49 is not exposed to the bonding layer penetration section 64. However, this is not the only option; for example, the conductive member 49 may be located inside the bonding layer penetration section 64 or in a position where it is exposed to the bonding layer penetration section 64.

[0051] In the embodiment described above, the conductive gas passage section 70 (coating layer 71 and leaf spring 72) was in direct electrical contact with the first conductive layer 45, but not with the conductive plate 30. However, as described above, the conductive gas passage section 70 only needs to be electrically connected to the conductive plate 30 and / or the conductive layer 40b. For example, the conductive gas passage section 70 may not be in direct electrical contact with the first conductive layer 45, but may be in direct electrical contact with the conductive plate 30. Specifically, the diameter of the through hole 64b may be made larger than in Figure 2, and the vertical height of the leaf spring 72 may be increased so that the leaf spring 72 does not contact the first conductive layer 45, while directly connecting the coating layer 71 and the conductive plate 30.

[0052] In the embodiment described above, the insulating layer 40a has two layers, a first insulating layer 41 and a second insulating layer 42, and the conductive layer 40b has one layer, a first conductive layer 45, but it is not limited to this. For example, in the bonding layer 140 shown in Figure 11, the insulating layer 40a has three layers, the first to third insulating layers 41 to 43, and the conductive layer 40b has two layers, the first to second conductive layers 45 to 46. The first insulating layer 41, the first conductive layer 45, the second insulating layer 42, the second conductive layer 46, and the third insulating layer 43 are stacked in this order from top to bottom. In addition to the through holes 64a to 64c described above, the bonding layer penetration portion 164 includes a through hole 64d provided in the second conductive layer 46 and a through hole 64e provided in the third insulating layer 43. In this case as well, since the first conductive layer 45 and the second conductive layer 46 are exposed to the bonding layer penetration portion 64, discharge can be suppressed by them. In Figure 11, as in the embodiment described above, the vertical distance L1 between the lower surface of the ceramic plate 20 and the insulating layer 40a (here, the vertical distance between the lower surface of the ceramic plate 20 and the first conductive layer 45) is preferably 200 μm or less, and more preferably 100 μm or less. The vertical distance L2 between the upper surface of the conductive plate 30 and the insulating layer 40a (here, the distance between the upper surface of the conductive plate 30 and the second conductive layer 46) is preferably 200 μm or less, and more preferably 100 μm or less. In addition, the vertical distance L3 between multiple conductive layers (here, the vertical distance between the first conductive layer 45 and the second conductive layer 46) is preferably 200 μm or less, and more preferably 100 μm or less.

[0053] In both Figure 2 and Figure 11, the uppermost and lowermost layers of the bonding layers 40 and 140 are both insulating layers. Thus, it is preferable that the portion of the bonding layer that is in contact with the ceramic plate 20 and the conductive plate 30 is an insulating layer rather than a conductive layer.

[0054] In the above-described embodiment, a dense plug 55 having an internal gas flow path 55a was provided in the ceramic plate penetration portion 50. However, it is not limited to a dense plug 55; any insulating gas passage plug that allows gas to pass through the inside may be provided in the ceramic plate penetration portion 50. For example, a porous plug may be used as the insulating gas passage plug. Similarly, the coating layer 71 may be any material that allows gas to pass through; for example, the coating layer 71 may be a conductive porous layer instead of having pores 71a. For example, the porous plug 155 and coating layer 171 shown in Figure 12 are constructed as porous bodies. The porous plug 155 can be made from a porous bulk body obtained by sintering, for example, ceramic powder. As the ceramic, alumina or aluminum nitride may be used. The porosity of the porous plug 155 is preferably 30% or more, and the average pore diameter is preferably 20 μm or more. The porosity of the porous plug 155 may be 70% or less. Furthermore, by using porous plating, the coating layer 171 as a metal porous layer can be formed on the lower surface of the porous plug 155. The dense plug 55 may be combined with the coating layer 171, or the porous plug 155 may be combined with the coating layer 71. In the above embodiment, the coating layer 71 has holes 71a to allow gas passage, but the coating layer 71 may cover a part of the lower surface of the dense plug 55, allowing gas passage in the uncovered portion of the lower surface.

[0055] In the above-described embodiment, the conductive gas passage portion 70 does not need to have a coating layer 71. For example, the conductive gas passage portion 270 shown in Figure 11 does not have a coating layer 71 but has a leaf spring 72. In Figure 11, the upper surface 72a of the leaf spring 72 is in direct contact with the dense material plug 55 and presses the dense material plug 55 upward with elastic force. Even in this case, discharge can be suppressed around the end of the dense material plug 55 on the conductive plate 30 side, that is, around the lower end of the dense material plug 55, similar to the above-described embodiment.

[0056] In the embodiment described above, the leaf spring 72 was positioned to extend horizontally perpendicular to the vertical direction by being pressed from above by the dense plug 55, but the leaf spring 72 is not limited to this configuration and does not have to extend horizontally. For example, the leaf spring 72 in Figure 2 may be rotated 90° and positioned vertically, so that the main direction of expansion and contraction of the leaf spring 72 is vertical. Even in this configuration, the leaf spring 72 can still press upward with elastic force against the dense plug 55.

[0057] In the embodiments described above, the folded portion 73 of the leaf spring 72 was formed in a V-shape, but is not limited to this. For example, the wafer mounting table 10 may be equipped with a leaf spring 472 as shown in Figures 14 and 15 instead of the leaf spring 72. In Figure 14, as in Figure 12, an example is shown in which the wafer mounting table 10 is equipped with a porous plug 155 and a coating layer 171 instead of a dense plug 55 and a coating layer 71. The leaf spring 472 has a plurality of folded portions 473 that are folded back along the vertical direction. The leaf spring 472 has one or more (in this case, multiple, specifically three) first folded portions 473a that are folded back from top to bottom, and one or more (in this case, multiple, specifically two) second folded portions 473b that are folded back from bottom to top. Therefore, the leaf spring 472 is folded five times. The first folded portion 473a extends horizontally and has a first plate-like portion 475 whose upper surface constitutes the upper surface 472a of the leaf spring 472. The second folded portion 473b extends horizontally and has a second plate-like portion 476 whose lower surface constitutes the lower surface 472b of the leaf spring 472. Therefore, each of the multiple folded portions 473 of the leaf spring 472 has a trapezoidal shape with an upper base portion and two adjacent slanted sides, rather than a V-shape. The leaf spring 472 shown in Figures 14 and 15, like the leaf spring 72, is arranged in a state where it extends horizontally perpendicular to the vertical direction by being pressed from above by the porous plug 155. Because this leaf spring 472 has the first plate-like portion 475, it is easier to make the horizontal width of the upper surface 472a wider compared to, for example, the upper surface 72a of the leaf spring 72 in Figure 2. Therefore, the contact area between the upper surface 472a and the upper member of the leaf spring 472 (in this case, the coating layer 171) can be increased. Similarly, because the leaf spring 472 has a second plate-shaped portion 476, it is easier to make the horizontal width of the lower surface 472b wider compared to, for example, the lower surface 72b of the leaf spring 72 in Figure 2. Therefore, the contact area between the lower surface 472b and the lower member of the leaf spring 472 (in this case, the first conductive layer 45) can be increased.These features allow for more reliable contact between the leaf spring 472 and its upper and lower components, thereby ensuring more reliable conductivity from the contact portion of the conductive gas passage 70 with the porous plug 155 to the conductive plate 30 and / or the first conductive layer 45. Furthermore, the larger contact area between the leaf spring 472 and its upper and lower components reduces contact resistance, enhancing the effect of suppressing discharge around the lower end of the porous plug 155. It should be noted that the leaf spring 72 in the above-described embodiment can be described as having the first plate-shaped portion 475 and the second plate-shaped portion 476 omitted from this leaf spring 472.

[0058] In the embodiment described above, the leaf spring 72 had a shape formed by bending a metal plate in a zigzag pattern, but it is not limited to this. For example, the leaf spring 72 may be a U-shaped leaf spring.

[0059] In the embodiments described above, a leaf spring 72 was given as an example of a conductive elastic body provided in the conductive gas passage section 70, but it is not limited to this. For example, as shown in Figure 16, the conductive gas passage section 70 may be provided with a conductive elastic body 572 instead of a leaf spring 72. The conductive elastic body 572 is, for example, a substantially cylindrical member with a circular top view, and is in contact with the coating layer 71 and the first conductive layer 45, and is electrically connected to them. Similar to the leaf spring 72, the conductive elastic body 572 presses the dense plug 55 upward with elastic force. The conductive elastic body 572 also presses the first conductive layer 45 and the conductive plate 30 downward with elastic force. It is preferable that the conductive elastic body 572 is a member through which gas can pass. Examples of the conductive elastic body 572 include a conductive mesh or a mass of conductive fibers. Examples of materials for the conductive elastic body 572 include metal materials and carbon. Examples of metallic materials include Al, Ti, Mo or their alloys, and steel. Examples of conductive fiber masses include steel wool or carbon felt. The conductive elastic body 572 may be a conductive porous body. For example, conductive porous materials include SiC and SiSiC.

[0060] In the embodiment described above, the bonding layer 40 was entirely a laminate of an insulating layer 40a and a conductive layer 40b, but the bonding layer 40 is not limited to this, and may have any structure in which an insulating layer 40a and a conductive layer 40b are laminated. For example, in the bonding layer 640 shown in Figure 17, the first conductive layer 645 of the conductive layer 40b is disposed only around the bonding layer penetration portion 64, and the fourth insulating layer 44 is disposed in the region between the first insulating layer 41 and the second insulating layer 42 where the first conductive layer 645 does not exist. In other words, the bonding layer 640 has a structure in which an insulating layer 40a and a conductive layer 40b are laminated in the region surrounding the bonding layer 40 (the first insulating layer 41, the first conductive layer 645, and the second insulating layer 42 are laminated), and in the other regions, the first insulating layer 41, the fourth insulating layer 44, and the third insulating layer 43 are laminated and there is no conductive layer. In this bonding layer 640 as well, since the first conductive layer 645 is exposed at the bonding layer penetration portion 64, discharge around the end of the dense plug 55 on the conductive plate 30 side can be suppressed by the first conductive layer 645, similar to the embodiment described above. Note that in Figure 17, since the first insulating layer 41, the fourth insulating layer 44, and the second insulating layer 42 are all insulators, they may be integrated and their boundaries with each other may not be clear.

[0061] In the embodiment described above, the diameter of the through hole 64b was larger than that of the through holes 64a and 64c, but this is not limited to this. For example, the diameter of the through hole 64b may be the same as or larger than the diameter of the through hole 64c. The through holes 64a to 64c may also have the same diameter.

[0062] In the embodiment described above, the second gas passage 62 and the auxiliary gas passage 63 may be omitted, and the multiple first gas passages 61 and the multiple ceramic plate penetrations 50 may be connected in a one-to-one relationship. In this case, the first gas passage 61 that penetrates the conductive plate 30 vertically may be provided directly below the bonding layer penetration 64 in the enlarged cross-sectional view of Figure 2.

[0063] In the embodiment described above, an electrostatic electrode is embedded in the ceramic plate 20 as the electrode 22, but a heater electrode (resistive heating element) may be embedded instead or in addition to this. In this case, a heater power supply is connected to the heater electrode. The ceramic plate 20 may have one layer of electrodes embedded, or it may have two or more layers with gaps in between.

[0064] In the embodiment described above, the ceramic plate 20 was manufactured by hot-press firing a molded body of ceramic powder. However, the molded body may be manufactured by stacking multiple tape molded bodies, by mold casting, or by compressing ceramic powder.

[0065] In the embodiment described above, the dense plug 55 was fixed by press-fitting it into the ceramic plate penetration portion 50, but it is not limited to this. For example, the outer surface of the dense plug 55 and the inner surface of the ceramic plate penetration portion 50 may be bonded together, or the male threaded portion provided on the outer surface of the dense plug 55 may be screwed into the female threaded portion provided on the inner surface of the ceramic plate penetration portion 50.

[0066] This application is based on the priority claim of Japanese Patent Application No. 2024-158405, filed on 12 September 2024, the entire contents of which are incorporated herein by reference.

[0067] This invention can be used, for example, in equipment for processing wafers.

[0068] 10 Wafer mounting platform, 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, 140, 640 Bonding layer, 40a Insulator layer, 40b Conductive layer, 41-44 First to fourth insulator layers, 45, 46 First and second conductive layers, 49 Conductive member, 49a Through hole, 49b Mounting hole, 50 Ceramic plate through section, 55 Dense plug, 55a Internal gas flow path, 60 Gas introduction passage, 61 First gas passage, 61a Through hole, 61b Through hole, 62 Second gas passage, 62p Overlap section, 63 Gas auxiliary passage, 64, 164 Joint layer penetration portion, 64a to 64e Through hole, 70, 270 Conductive gas passage portion, 71, 171 Coating layer, 71a Hole, 72 Leaf spring, 72a Upper surface, 72b Lower surface, 73 Folded portion, 73a First folded portion, 73b Second folded portion, 81, 82 MMC disc member, 83 Metal bonding material, 91, 92 Resin bonding material, 95 Metal bonding material, 155 Porous plug, 475 First plate-like portion, 476 Second plate-like portion, 572 Conductive elastic body, 645 First conductive layer.

Claims

1. A wafer mounting stand comprising: a ceramic plate having a wafer mounting surface on its upper surface and containing electrodes; a conductive plate disposed on the lower side of the ceramic plate; a bonding layer joining the ceramic plate and the conductive plate; a ceramic plate penetration portion penetrating the ceramic plate; an insulating gas passage plug provided in the ceramic plate penetration portion through which gas can pass; and a gas introduction passage provided at least inside the bonding layer and the conductive plate and communicating with the ceramic plate penetration portion, wherein the bonding layer has a structure in which an insulating layer and a conductive layer are laminated, and the conductive layer is exposed in the bonding layer penetration portion, which is the part of the gas introduction passage that penetrates the bonding layer.

2. A wafer mounting stand according to claim 1, comprising a conductive member for electrically connecting the conductive plate and the conductive layer.

3. A wafer mounting table according to claim 2, wherein the conductive member is located at a position separate from the bonding layer penetration portion.

4. A wafer mounting platform according to any one of claims 1 to 3, wherein the vertical distance L1 between the lower surface of the ceramic plate and the conductive layer is 200 μm or less.

5. A wafer mounting platform according to claim 4, wherein the distance L1 is 100 μm or less.

6. A wafer mounting table according to any one of claims 1 to 3, comprising: a conductive gas passage portion provided in the gas introduction passage, in contact with the lower surface of the insulating gas passage plug, electrically conductive with the conductive plate and / or the conductive layer, and allowing the passage of gas between the insulating gas passage plug and the gas introduction passage.

7. A wafer mounting table according to claim 6, wherein the conductive gas passage portion has a conductive elastic body that elastically presses the insulating gas passage plug upward.

8. A wafer mounting platform according to claim 7, wherein the conductive elastic body is a leaf spring.

9. A wafer mounting table according to claim 6, wherein the conductive gas passage portion has a coating layer that covers the lower surface of the insulating gas passage plug.

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