Wafer mounting table

Abstract

The wafer mounting table 10 includes a ceramic plate 20 having a plug 50 through which gas can pass in the vertical direction, a conductive plate 30 incorporating a gas inlet channel 34, and a resin layer 40 bonding the two together. A resin layer through-hole 42 is provided in the resin layer 40 at a position facing the plug 50 and is larger than the plug 50 in a plan view. The gas inlet channel 34 communicates with the plug 50 via the resin layer through-hole 42. A conductive film 60 is provided on the underside of the ceramic plate 20 at a position facing the resin layer through-hole 42 and is larger than the resin layer through-hole 42 in a plan view, allowing gas to flow from the gas inlet channel 34 to the plug 50. A contact member 70 is provided in the gas inlet channel 34, electrically connecting the conductive film 60 and the conductive plate 30 and allowing gas to flow from the gas inlet channel 34 to the plug 50.

Description

[Technical Field]

[0001] The present invention relates to a wafer stage. [Background technology]

[0002] Conventionally, a wafer mounting table has been known that includes a ceramic plate having a wafer mounting surface on its upper surface and a base plate bonded to the underside of the ceramic plate and having a gas inlet passage. Patent Document 1 discloses such a wafer mounting table, which includes an insulating first porous portion disposed within a through-hole in the ceramic plate and an insulating second porous portion fitted in a recess on the ceramic plate side of the base plate so as to face the first porous portion. Gas supplied to the gas inlet passage passes through the second and first porous portions and flows into the space between the wafer mounting surface and the wafer, where it is used to cool the object. The publication states that the presence of the first and second porous portions ensures a sufficient gas flow rate from the gas inlet passage to the wafer mounting surface while suppressing the occurrence of plasma-induced discharge (arc discharge) during wafer processing. The base plate is made of metal and is bonded to the underside of the ceramic plate via a resin layer. The resin layer has a communicating hole with a diameter larger than that of the through-hole in the ceramic plate at a position facing the through-hole in the ceramic plate. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Publication No. 2020-72262 Summary of the Invention [Problem to be solved by the invention]

[0004] However, even if an insulating second porous portion is present as in Patent Document 1, discharge may occur around the end of the first porous portion on the base plate side. Also, if the resin layer interferes with the first and second porous portions, there is a risk that their gas permeability may decrease.

[0005] The present invention has been made to solve these problems, and its main object is to suppress discharge in the space below the insulating gas-permeable plug while maintaining good gas permeability. [Means for solving the problem]

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

[0007] [1] The wafer mounting table of the present invention comprises: a ceramic plate having a wafer mounting surface on its upper surface and incorporating an electrode; a conductive plate provided on the lower surface of the ceramic plate; a resin layer that bonds the ceramic plate and the conductive plate; an insulating gas-passing plug that is provided in a ceramic plate penetration portion that penetrates the ceramic plate and allows gas to pass in the vertical direction; a resin layer penetration part that is provided in the resin layer at a position facing the insulating gas passing plug so as to penetrate the resin layer and that is larger than the insulating gas passing plug in a plan view; a gas introduction passage provided inside the conductive plate and communicating with the insulating gas passing plug through the resin layer penetration part; a conductive film that is provided on the lower surface of the ceramic plate at a position facing the resin layer penetration portion and that is larger than the resin layer penetration portion in a plan view, and that allows gas to flow from the gas introduction path to the insulating gas passing plug; a conductive connection portion that is provided in the gas introduction path, that is smaller than the resin layer penetration portion in a plan view, that electrically connects the conductive film and the conductive plate, and that allows gas to flow from the gas introduction path to the insulating gas passing plug; It is equipped with the following.

[0008] In this wafer mounting table, the resin layer penetration portion is larger than the insulating gas passage plug and the conductive connecting portion in plan view. Therefore, the resin layer can be prevented from interfering with the insulating gas passage plug and the conductive connecting portion, and good gas permeability can be maintained for these. Furthermore, the conductive film, which is made the same potential as the conductive plate by the conductive connecting portion, is larger than the resin layer penetration portion in plan view. Therefore, a potential difference is unlikely to occur in the entire space below the insulating gas passage plug, and discharge in that space can be suppressed.

[0009] Although the present invention is sometimes described using terms such as up / down, left / right, front / back, etc., these terms merely refer to relative positional relationships. Therefore, when the orientation of the wafer table is changed, up / down may become left / right, or left / right may become up / down, and such cases are also within the technical scope of the present invention.

[0010] [2] In the wafer mounting table described above (the wafer mounting table described in [1] above), the ceramic plate may have a plurality of ceramic plate through-holes, the insulating gas permeation plug may be provided in each of the plurality of ceramic plate through-holes, the gas introduction path may be provided at a position facing each of the plurality of insulating gas permeation plugs, the resin layer through-hole may be provided at a position facing each of the plurality of insulating gas permeation plugs, the conductive film may be provided at a position facing each of the plurality of resin layer through-holes, and the conductive connecting portion may be provided in each of the plurality of gas introduction paths, and any one of the plurality of conductive films may be electrically connected to at least one of the remaining conductive films. In this way, even if the plug lower-surface film provided on the lower surface of the insulating gas permeation plug and the annular film therearound are separated from each other, discharge in the space below the insulating gas permeation plug can still be suppressed. This is because the plug lower-surface film has the same potential as the conductive plate via the conductive connecting portion, and the annular film has the same potential as the conductive plate via the other electrically connected conductive film.

[0011] [3] In the wafer stage described above (the wafer stage described in [2] above), any one of the plurality of conductive films may be electrically connected to at least one of the remaining conductive films via a conductive link provided on the underside of the ceramic plate. In this way, the conductive link and the conductive film can be simultaneously formed on the underside of the ceramic plate in a single process.

[0012] [4] In the wafer stage described above (the wafer stage described in [2] above), at least one of the plurality of conductive films may be separated into a plug underside film provided on the underside of the insulating gas passing plug and an annular film provided on the outer periphery of the plug underside film, and the annular film may be electrically connected to the conductive plate via at least one of the remaining conductive films. In this way, even if the conductive film is separated into the plug underside film and the annular film, discharge in the space below the insulating gas passing plug can still be suppressed. This is because the plug underside film has the same potential as the conductive plate via the conductive connection portion, and the annular film has the same potential as the conductive plate via another conductive film electrically connected thereto.

[0013] [5] In the wafer stage described above (the wafer stage described in any one of [1] to [4] above), the conductive connecting portion may be a separate member from the conductive plate. This makes it easier to manufacture the wafer stage compared to, for example, a case in which the conductive connecting portion and the conductive plate are not separate members but are an integral (one-piece) member.

[0014] [6] In the wafer stage described above (the wafer stage described in [5] above), the conductive connecting portion may have an elastic member, and the elastic member may be disposed in a compressed state between the lower surface of the insulating gas passing plug and the conductive plate. This makes it easier to maintain the electrical connection between the insulating gas passing plug and the conductive plate.

[0015] [7] In the wafer stage described above (the wafer stage described in any one of [1] to [6] above), the insulating gas-passing plug may be a porous body or a dense body having a spiral or zigzag gas passage therein. This makes it difficult for discharge to occur even when gas passes through the insulating gas-passing plug. [Brief explanation of the drawings]

[0016] [Figure 1] FIG. [Figure 2] Cross section AA of Figure 1. [Figure 3] FIG. 3 is a partially enlarged cross-sectional view of FIG. 2. [Figure 4] FIG. [Figure 5] 3A to 3C are diagrams showing the manufacturing process of the wafer mounting table 10. [Figure 6] Process diagram for replacing plug 50 with plug 50X. [Figure 7] 10 is a bottom view of the ceramic plate 20 after replacement with the plug 50X. [Figure 8] FIG. 10 is a bottom view of another example of the ceramic plate 20. [Figure 9] FIG. 10 is a bottom view of another example of the ceramic plate 20. [Figure 10] FIG. 10 is a bottom view of another example of the ceramic plate 20. DETAILED DESCRIPTION OF THE INVENTION

[0017] Next, preferred embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a plan view of the wafer mounting table 10, Fig. 2 is a cross-sectional view taken along line AA in Fig. 1, Fig. 3 is a partially enlarged cross-sectional view of Fig. 2, and Fig. 4 is a bottom view of the ceramic plate 20 (including the conductive film 60 and conductive links 64, 66). For convenience, the seal band 21a, small circular protrusions 21b, and reference surface 21c of the wafer mounting surface 21 are omitted from Figs. 2 and 3.

[0018] As shown in FIG. 2, the wafer mounting table 10 includes a ceramic plate 20, a conductive plate 30, a resin layer 40, a plug 50, a resin layer through-hole 42, a gas introduction path 34, a conductive film 60, and a contact member 70.

[0019] The ceramic plate 20 is a circular plate (e.g., 300 mm in diameter and 5 mm in thickness) made of ceramic such as sintered alumina or sintered aluminum nitride. The upper surface of the ceramic plate 20 serves as a wafer mounting surface 21 on which a wafer W is mounted. The ceramic plate 20 incorporates an electrode 22. As shown in FIG. 1, an annular seal band 21a is formed along the outer edge of the wafer mounting surface 21 of the ceramic plate 20, and a plurality of small circular protrusions 21b are formed on the entire inner surface of the seal band 21a. The seal band 21a and the small circular protrusions 21b have the same height, which is, for example, several 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 member (not shown). A low-pass filter may be disposed along the power supply member. The power supply member is electrically insulated from the conductive plate 30. When a DC voltage is applied to this electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 (specifically, the upper surfaces of the seal bands 21a and the small circular protrusions 21b) by electrostatic attraction, and when the application of the DC voltage is stopped, the wafer W is released from being attracted and fixed to the wafer mounting surface 21. The portion of the wafer mounting surface 21 on which the seal bands 21a and the small circular protrusions 21b are not provided is referred to as the reference surface 21c.

[0020] The conductive plate 30 is a circular plate with good thermal conductivity (a circular plate with the same diameter as or larger than the ceramic plate 20). A refrigerant flow path 32 is formed inside the conductive plate 30, through which a refrigerant circulates. The refrigerant flowing through the refrigerant flow path 32 is preferably a liquid, preferably electrically insulating. Examples of electrically insulating liquids include fluorine-based inert liquids. In a plan view, the refrigerant flow path 32 is formed in a single stroke from one end (inlet) to the other end (outlet) across the entire conductive plate 30. One end and the other end of the refrigerant flow path 32 are connected to a supply port and a recovery port, respectively, of an external refrigerant device (not shown). 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 from the other end of the refrigerant flow path 32 to the recovery port of the external refrigerant device, and is temperature-adjusted before being supplied again from the supply port to one end of the refrigerant flow path 32. The conductive plate 30 is connected to a radio frequency (RF) power source and also serves as an RF electrode.

[0021] Examples of materials for the conductive plate 30 include metal materials and composite materials of metal and ceramic. Metal materials include Al, Ti, Mo, and alloys thereof. Metal and ceramic composite materials include metal matrix composites (MMC) and ceramic matrix composites (CMC). Specific examples of such composite materials include a material containing Si, SiC, and Ti (also known as SiSiCTi), a material in which porous SiC is impregnated with Al and / or Si, and a composite material of Al2O3 and TiC. It is preferable to select a material for the conductive plate 30 that has a thermal expansion coefficient close to that of the material of the ceramic plate 20.

[0022] The resin layer 40 is an electrically insulating layer that bonds the lower surface of the ceramic plate 20 to the upper surface of the conductive plate 30. The resin layer 40 may be formed, for example, of a silicone resin adhesive, an acrylic resin adhesive, or a bonding sheet. Examples of bonding sheets include a sheet having an acrylic resin layer on both sides of a polypropylene core, a sheet having a silicone resin layer on both sides of a polyimide core, and a sheet made of epoxy resin alone. The ceramic plate 20 and the conductive plate 30 are bonded together with the resin layer 40 rather than a metal layer in order to meet the demand for gentle cooling of the wafer W by the conductive plate 30.

[0023] The plug 50 is a component through which gas can pass in the vertical direction and is provided in a plug arrangement hole 24 that penetrates the ceramic plate 20 in the vertical direction. The plug arrangement hole 24 is an example of a ceramic plate penetration portion, and the plug 50 is an example of an insulating gas-permeable plug. The plug arrangement hole 24 penetrates the electrode 22 in the vertical direction, but the electrode 22 is not exposed at the inner circumferential surface of the plug arrangement hole 24. The plug arrangement hole 24 is a tapered hole having an inverted truncated cone space in which the area of ​​the upper opening is larger than the area of ​​the lower opening. The plug arrangement holes 24 are provided at multiple locations in the ceramic plate 20 in a planar view (for example, at the center of the ceramic plate 20 and multiple locations equally spaced around the center in the circumferential direction; a total of seven locations in FIG. 1). A plug 50 is provided in each of the multiple plug arrangement holes 24. The plug 50 is in the shape of an inverted truncated cone and is made of insulating dense ceramic or insulating porous ceramic (for example, the same material as the ceramic plate 20).

[0024] The plug 50 is provided with a spiral gas passage 52 extending from the bottom surface to the top surface of the plug 50. The vertical length L (FIG. 3) of the gas passage 52 is preferably set to 1 mm or less, more preferably 0.5 mm or less, and even more preferably 0.2 mm or less to suppress discharge within the gas passage 52. Discharge occurs when electrons generated by ionization of a gas (e.g., helium gas) within the gas passage 52 accelerate and collide with other helium gases. If the vertical length of the gas passage 52 is 1 mm or less, the ionized electrons are not sufficiently accelerated, thereby suppressing such discharge. Furthermore, considering the need to ensure a sufficient gas flow rate, the length L is preferably 0.1 mm or more. The plug 50 is fixed to the plug mounting hole 24. Specifically, the outer circumferential surface of the plug 50 and the inner circumferential surface of the plug mounting hole 24 may be bonded together, or a male thread provided on the outer circumferential surface of the plug 50 may be threadedly engaged with a female thread provided on the inner circumferential surface of the plug mounting hole 24. In another embodiment, the plug 50 may be tapered to fit into the plug positioning hole 24, and the plug 50 may be press-fitted into the plug positioning hole 24. From the viewpoint of improving the positioning accuracy in the height direction of the plug 50 when the plug 50 is press-fitted downward into the plug positioning hole 24, the taper angle may be set to, for example, 70° to 87°. The upper surface of the plug 50 is at the same height as the reference surface 21c of the wafer mounting surface 21, and the lower surface of the plug 50 is at the same height as the lower surface of the ceramic plate 20.

[0025] The resin layer through-hole 42 is an example of a resin layer through-portion, and is provided in the resin layer 40 at a position facing the plug 50 so as to penetrate the resin layer 40. The resin layer through-hole 42 is provided larger than the lower surface of the plug 50 in a plan view. Specifically, the diameter of the resin layer through-hole 42 is larger than the diameter of the lower surface of the plug 50. The resin layer through-hole 42 is provided in a position facing each of the multiple plugs 50.

[0026] The gas introduction path 34 is provided inside the conductive plate 30. The gas introduction path 34 is provided at a position facing each of the multiple plugs 50. The gas introduction path 34 communicates with the spiral gas passage 52 of the plug 50 via the resin layer through-hole 42. Here, the gas introduction path 34 is provided so as to penetrate the conductive plate 30 in the vertical direction. The gas introduction path 34 has a large-diameter portion 34a and a small-diameter portion 34b. The large-diameter portion 34a is a cylindrical space provided above the gas introduction path 34. The small-diameter portion 34b is a tubular space provided below the large-diameter portion 34a.

[0027] The conductive film 60 is provided in a circular shape on the underside of the ceramic plate 20 at a position facing each of the plurality of resin layer through-holes 42. The conductive film 60 is provided larger than the resin layer through-holes 42 in a plan view. Specifically, the diameter of the conductive film 60 is larger than the diameter of the resin layer through-holes 42. Therefore, the conductive film 60 covers the underside of the plug 50 and its periphery on the underside of the ceramic plate 20. The outer periphery of the conductive film 60 is sandwiched between the ceramic plate 20 and the resin layer 40. The conductive film 60 is provided with through-holes 62 that allow gas to flow from the gas inlet 34 to the gas passages 52 of the plug 50. The conductive film 60 is formed by, for example, sputtering or electroless plating. Any one of the plurality of conductive films 60 is electrically connected to at least one of the remaining conductive films 60. In this embodiment, as shown in FIG. 4 , of the six conductive films 60 arranged in the circumferential direction on the underside of the ceramic plate 20, two adjacent conductive films 60 are electrically connected to each other by an arc-shaped conductive link 64. Note that the conductive link 64 may be linear instead of arc-shaped. Also, the conductive film 60 provided at the center of the underside of the ceramic plate 20 is electrically connected to another conductive film 60 by a linear conductive link 66. Note that the central conductive film 60 may be electrically connected to two or more other conductive films 60. The conductive links 64, 66 are provided on the underside of the ceramic plate 20, along with the conductive films 60.

[0028] The contact member 70 is an example of a conductive connecting portion. A contact member 70 is provided in each of the multiple large-diameter portions 34a. The contact member 70 is conductive, electrically connects the conductive film 60 and the conductive plate 30, and allows gas to flow from the gas introduction path 34 to the gas passage 52 of the plug 50. The contact member 70 is smaller than the resin layer through-hole 42 in a plan view. Specifically, the diameter of the contact member 70 is smaller than the diameter of the resin layer through-hole 42. The contact member 70 is provided as a separate member from the conductive plate 30. The lower surface of the contact member 70 contacts the step surface 34c of the gas introduction path 34 of the conductive plate 30, and the upper surface of the contact member 70 contacts the conductive film 60. In this embodiment, the contact member 70 is a substantially cylindrical member with a circular upper surface.

[0029] The contact member 70 may be, for example, a conductive mesh or a mass of conductive fibers (steel wool, carbon felt, etc.). Examples of materials for the contact member 70 include metal materials and carbon. Examples of metal materials include Al, Ti, Mo, alloys thereof, and steel. When the contact member 70 is a conductive mesh, the mesh size may be 0.062 mm (250 mesh) to 0.154 mm (100 mesh). The contact member 70 is preferably a member that is stretchable in the vertical direction. For example, the above-mentioned conductive mesh and the mass of conductive fibers are also examples of members that are stretchable in the vertical direction. The contact member 70 is disposed in a compressed state between the lower surface of the plug 50 and the stepped surface 34c of the gas introduction path 34 of the conductive plate 30.

[0030] Next, an example of how the wafer mounting table 10 configured as described above is described. First, the wafer mounting table 10 is installed in a chamber (not shown), and the wafer W is placed on the wafer mounting surface 21. The chamber is then depressurized using a vacuum pump to a predetermined vacuum level, and a DC voltage is applied to the electrode 22 of the ceramic plate 20 to generate an electrostatic attraction force, thereby attracting and fixing the wafer W to the wafer mounting surface 21 (specifically, the upper surface of the seal band 21a or the upper surface of the small circular protrusions 21b). Next, a reactive gas atmosphere with a predetermined pressure (e.g., several tens to several hundreds of Pa) is created in the chamber. In this state, an RF voltage is applied between an upper electrode (not shown) installed on the ceiling of the chamber and the conductive plate 30 of the wafer mounting table 10 to generate plasma. The surface of the wafer W is processed by the generated plasma. A coolant is circulated through the coolant flow path 32 of the conductive plate 30. A backside gas is introduced into the gas inlet path 34 from a gas cylinder (not shown). A thermally conductive gas (e.g., He gas) is used as the backside gas. The backside gas introduced into the gas inlet path 34 passes through the contact member 70 and the gas passage 52 of the plug 50 and is supplied to and sealed in the space between the back surface of the wafer W and the reference surface 21c of the wafer mounting surface 21. The presence of this backside gas allows efficient thermal conduction between the wafer W and the ceramic plate 20.

[0031] During use of the wafer mounting table 10, the provision of the spiral gas passage 52 in the plug 50 can suppress discharge within the gas passage 52. For example, if a gas passage extending linearly in the vertical direction were provided instead of the spiral gas passage 52, discharge would occur when electrons generated as a result of ionization of gas molecules by application of RF voltage accelerate and collide with other gas molecules. However, in this embodiment, the gas passage 52 is spiral, and the vertical length L of the gas passage 52 is short. Therefore, electrons collide with other gas molecules before they are sufficiently accelerated (i.e., before they have sufficient energy). As a result, discharge within the gas passage 52 can be suppressed.

[0032] Furthermore, the conductive film 60 provided on the underside of the plug 50 is electrically connected to the conductive plate 30 by the contact member 70. In other words, the conductive film 60 has the same potential as the conductive plate 30. This prevents a potential difference from occurring across the entire large-diameter portion 34a, which is the space on the underside of the plug 50. This prevents discharge from occurring in the large-diameter portion 34a.

[0033] Next, a manufacturing example of the wafer mounting table 10 will be described with reference to FIG. 5. FIG. 5 is a manufacturing process diagram of the wafer mounting table 10. Here, an example in which the conductive plate 30 is manufactured using MMC is illustrated. First, a ceramic plate 20 incorporating an electrode 22 is prepared (FIG. 5A). For example, a ceramic powder compact incorporating the electrode 22 is prepared, and the compact is hot-pressed and fired to obtain the ceramic plate 20. A plug mounting hole 24 is formed in the ceramic plate 20 (FIG. 5B). The plug mounting hole 24 is formed to penetrate the ceramic plate 20 in the vertical direction, avoiding the electrode 22. Next, a pre-fabricated plug 50 is fixed in the plug mounting hole 24 of the ceramic plate 20 (FIG. 5C). The plug 50 with the spiral gas passage 52 can be manufactured using, for example, a 3D printer. Then, a conductive film 60 and conductive links 64 and 66 are formed on the underside of the ceramic plate 20 by sputtering or electroless plating (FIG. 5D). Note that the conductive links 64 and 66 are omitted from FIG. 5D.

[0034] Concurrently, two MMC disk members 81 and 85 are prepared (FIG. 5E). Then, grooves and holes are formed in these MMC disk members 81 and 85 by machining (FIG. 5F). Specifically, a recessed groove 82, which will eventually become the refrigerant flow path 32, is formed in the lower surface of the upper MMC disk member 81. A recessed portion 83, which will eventually become the large-diameter portion 34a of the gas introduction path 34, is formed in the upper surface of the MMC disk member 81, and a tubular space 84, which will eventually become part of the small-diameter portion 34b, is formed in the bottom surface of the recessed portion 83. A tubular space 86, which will eventually become part of the small-diameter portion 34b, is formed in the lower MMC disk member 85. If the ceramic plate 20 is made of alumina, the MMC disk members 81 and 85 are preferably made of SiSiCTi or AlSiC. This is because the thermal expansion coefficient of alumina can be made approximately the same as that of SiSiCTi or AlSiC.

[0035] The SiSiCTi disk member can be fabricated, for example, as follows: First, silicon carbide, metallic Si, and metallic Ti are mixed to produce a powder mixture. Next, the resulting powder mixture is uniaxially pressed to produce a disk-shaped compact, which is then hot-press sintered in an inert atmosphere to obtain the SiSiCTi disk member.

[0036] Next, the upper MMC disk member 81 and the lower MMC disk member 85 are bonded by thermal compression bonding (TCB) to obtain the conductive plate 30 (FIG. 5G). After TCB, the recess 83 becomes the large-diameter portion 34a, the tubular spaces 84 and 86 become the small-diameter portion 34b, and the recessed groove 82 becomes the coolant flow path 32. Next, the prefabricated contact member 70 is placed on the bottom surface (step surface 34c) of the large-diameter portion 34a of the conductive plate 30. A bonding sheet 90 is sandwiched between the lower surface of the ceramic plate 20 and the upper surface of the conductive plate 30 (FIG. 5D) to form a laminate. The laminate is then heated while being pressurized, bonding the ceramic plate 20 and the conductive plate 30 via the resin layer 40 (FIG. 5H). A through-hole 92 that will eventually become the resin layer through-hole 42 is pre-formed in the bonding sheet 90. The overall shape is then adjusted to obtain the wafer mounting table 10.

[0037] In the wafer mounting table 10 described above, the resin layer through-hole 42 is larger than the plug 50 and the contact member 70 in a plan view. This prevents the resin layer 40 from interfering with the plug 50 and the contact member 70, thereby maintaining good gas permeability. Furthermore, the conductive film 60, which is made the same potential as the conductive plate 30 by the contact member 70, is larger than the resin layer through-hole 42 in a plan view. This makes it difficult for a potential difference to occur across the entire space below the plug 50 (the large-diameter portion 34a of the gas inlet channel 34), thereby suppressing discharge in that space. This allows the wafer mounting table 10 to use a higher-power radio frequency (RF) power source connected to the conductive plate 30 compared to a case where an insulating porous member is used instead of the contact member 70. Furthermore, the efficiency of thermal conduction between the wafer W and the ceramic plate 20 can be further improved by increasing the gas pressure of the backside gas.

[0038] A plurality of plug placement holes 24 are provided in the ceramic plate 20. A plug 50 is provided in each of the plurality of plug placement holes 24. A gas introduction path 34 is provided at a position facing each of the plurality of plugs 50. A resin layer through-hole 42 is provided at a position facing each of the plurality of plugs 50. A conductive film 60 is provided at a position facing each of the plurality of resin layer through-holes 42. A contact member 70 is provided in each of the plurality of gas introduction paths 34. Any one of the plurality of conductive films 60 is electrically connected to at least one of the remaining conductive films 60. Therefore, even if the plug underside film provided on the underside of the plug 50 and the surrounding annular film are separated from each other, discharge in the space on the underside of the plug 50 (thick-diameter portion 34a) can still be suppressed. This point will be described in detail below.

[0039] For example, suppose that the plug 50 located at the center of the ceramic plate 20 of the wafer mounting table 10 needs to be replaced with a new plug 50X. FIG. 6 illustrates the process of replacing the plug 50 with the plug 50X, and FIG. 7 illustrates a bottom view of the ceramic plate 20 after the plug 50 has been replaced with the plug 50X. In this case, the currently installed plug 50 is first pulled upward (FIG. 6A). The plug lower surface film 60a of the conductive film 60 adheres to the pulled plug 50. After the plug 50 is pulled out, an annular film 60b remains around the plug placement hole 24 on the wafer mounting table 10. Next, a new plug 50X is prepared (FIG. 6B). The plug lower surface film 60Xa has been formed in advance on the bottom surface of the plug 50X by sputtering or the like. The plug 50X is then fixed in the empty plug placement hole 24. This completes the rework of the plug 50X on the wafer mounting table 10 (FIG. 6C). In the wafer mounting table 10 where the plug 50X has been reworked, a ring-shaped gap 60Xc may occur between the plug undersurface film 60Xa of the plug 50X and the surrounding annular film 60b, resulting in an electrical disconnection between the plug undersurface film 60Xa and the annular film 60b. In this case, the plug undersurface film 60Xa is at the same potential as the conductive plate 30 via the contact member 70. The annular film 60b is at the same potential as the conductive plate 30 via another conductive film 60 electrically connected by a conductive link 66 (FIG. 7). Therefore, even in such a case, a potential difference is unlikely to occur across the entire space (thick-diameter portion 34a) below the plug 50, thereby suppressing discharge in that space. While the case where the plug 50 located at the center of the ceramic plate 20 is replaced has been described here, the same applies when other plugs 50 are replaced. Note that FIGS. 6C and 7 illustrate an embodiment of claim 4.

[0040] Furthermore, the conductive links 64, 66 are provided on the lower surface of the ceramic plate 20. Therefore, the conductive links 64, 66 and the conductive film 60 can be simultaneously formed on the lower surface of the ceramic plate 20 in one step.

[0041] Furthermore, the contact member 70 is a separate member from the conductive plate 30. Therefore, the wafer mounting table 10 is easier to manufacture than when the contact member 70 and the conductive plate 30 are integrated (one piece).

[0042] The contact member 70 is a member that is stretchable in the vertical direction, and is disposed in a compressed state between the plug 50 and the conductive plate 30. Therefore, contact between the plug 50 and the conductive plate 30 can be easily maintained.

[0043] Furthermore, the plug 50 has a spiral gas passage 52 inside it. Therefore, compared to when the plug 50 has a linear gas passage extending in the vertical direction, discharge is less likely to occur when gas passes through the gas passage 52.

[0044] It goes without saying that the present invention is not limited to the above-described embodiment, and can be embodied in various forms as long as they fall within the technical scope of the present invention.

[0045] In the above-described embodiment, the conductive link 64 or 66 provided on the underside of the ceramic plate 20 is used to electrically connect any one of the plurality of conductive films 60 to at least one of the remaining conductive films 60. However, this is not particularly limited. For example, as shown in FIG. 8 , a linear conductive link 164 may be provided on the underside of the ceramic plate 20. Alternatively, as shown in FIG. 9 , a large conductive film 260 large enough to encompass the plurality of conductive films 60 (e.g., large enough to cover the entire underside of the ceramic plate 20) may be formed on the underside of the ceramic plate 20. The large conductive film 260 has a through-hole 262 located opposite the gas passage 52. In this case, the large conductive film 260 can be considered to be composed of the plurality of conductive films 60 and the remaining portion excluding the plurality of conductive films 60. The remaining portion serves as the conductive link. Note that in FIGS. 8 and 9 , the same components as those in the above-described embodiment are denoted by the same reference numerals. Alternatively, instead of the conductive links 64 and 66, wiring may be provided inside the ceramic plate 20 rather than on the underside.

[0046] In the above-described embodiment, any one of the plurality of conductive films 60 is electrically connected to at least one of the remaining conductive films 60. However, as shown in FIG. 10 , the plurality of conductive films 60 may be provided independently. That is, the plurality of conductive films 60 may not be electrically connected to the other conductive films 60. In this case, as shown in FIG. 6C , if the plug underside film 60Xa of the plug 50X and the surrounding annular film 60b are separated by a ring-shaped gap 60Xc in the wafer mounting table 10 after the plug 50X is replaced, the annular film 60b will not have the same potential as the conductive plate 30, and a discharge may occur between the annular film 60b and the conductive plate 30. However, other effects can be obtained similarly to those of the above-described embodiment.

[0047] In the above-described embodiment, the plug 50 having the spiral gas passage 52 is exemplified as the insulating gas-permeable plug, but the present invention is not particularly limited to this. For example, a porous plug may be used instead of the plug 50. In this case, a network of micropores inside the porous plug serves as a gas passage that allows gas to flow in the vertical direction.

[0048] In the above-described embodiment, the contact member 70, which is a separate member from the conductive plate 30, is used as the conductive connecting portion. However, a conductive connecting portion that is integral with the conductive plate 30 (one piece) may also be used.

[0049] In the above-described embodiment, the gas introduction path 34 is illustrated as penetrating the conductive plate 30 in the vertical direction, but the gas introduction path is not particularly limited to this. For example, instead of the narrow diameter portions 34b, a ring passage concentric with the conductive plate 30 in a plan view may be provided to connect the plurality of large diameter portions 34a, and an inlet passage may be provided to supply gas to the ring passage from the underside of the conductive plate 30. In this case, the gas introduction path is composed of the plurality of large diameter portions 34a, the ring passage connecting them, and the inlet passage communicating with the ring passage.

[0050] In the above-described embodiment, the upper surface of the plug 50 is at the same height as the reference surface 21c, but the upper surface of the plug 50 may also be at the same height as the top surface of the small circular protrusion 21b, or may be positioned between the reference surface 21c and the top surface of the small circular protrusion 21b.

[0051] In the above-described embodiment, the conductive film 60 is provided with the through-holes 62, but the conductive film 60 may be formed of a metal porous film or a metal mesh instead of providing the through-holes 62. Even in this case, the conductive film 60 allows gas to flow from the gas inlet path 34 to the gas passage 52 of the plug 50.

[0052] In the above-described embodiment, the ceramic plate 20 with the plugs 50 fixed in the plug placement holes 24 is bonded to the conductive plate 30 in manufacturing the wafer mounting table 10, but this is not particularly limited. For example, the ceramic plate 20 with empty plug placement holes 24 may be bonded to the conductive plate 30, and then the plugs 50 may be fixed in the plug placement holes 24. Alternatively, the ceramic plate 20 with empty plug placement holes 24 may be bonded to the conductive plate 30, and the plugs 50 may be bonded to the plug placement holes 24 at the same time.

[0053] In the above-described embodiment, a conductive mesh or a mass of conductive fibers having flexibility in the vertical direction is used as the contact member 70, but the contact member 70 is not limited to this. For example, the contact member 70 may be a conductive coil spring having flexibility in the vertical direction.

[0054] In the above-described embodiment, the contact member 70 is a member that is stretchable in the vertical direction, but is not limited to this. For example, the contact member 70 may be configured by combining a member that is stretchable in the vertical direction with a bulk member that is not stretchable. This also allows for maintaining a good electrical connection between the conductive film 60 and the conductive plate 30. Alternatively, the contact member 70 may be a bulk member that is not stretchable. However, in this case, it may be difficult to establish an electrical connection between the conductive film 60 and the conductive plate 30.

[0055] In the above-described embodiment, a dense plug 50 having a spiral gas passage 52 therein is used, but a porous plug may be used instead of the plug 50. In this case, the network of micropores inside the porous plug serves as a gas passage that allows gas to flow in the vertical direction. Also, instead of the spiral gas passage 52, a zigzag-shaped gas passage may be provided.

[0056] In the above-described embodiment, the ceramic plate 20 has an electrostatic electrode built in as the electrode 22. However, instead of or in addition to this, a heater electrode (resistance heating element) may be built in. In this case, a heater power supply is connected to the heater electrode. The ceramic plate 20 may have one layer of electrodes built in, or two or more layers of electrodes spaced apart.

[0057] In the above-described embodiment, lift pin holes may be provided that penetrate the wafer mounting table 10. The lift pin holes are holes for inserting lift pins that move the wafer W up and down relative to the wafer mounting surface 21. When the wafer W is supported by, for example, three lift pins, the lift pin holes are provided in three locations.

[0058] In the above-described embodiment, the ceramic plate 20 is produced by hot-pressing and firing a ceramic powder compact. However, the compact may be produced by stacking multiple tape compacts, by mold casting, or by compressing ceramic powder. [Industrial Applicability]

[0059] The present invention can be used in, for example, an apparatus for processing wafers. [Explanation of symbols]

[0060] 10 wafer mounting table, 20 ceramic plate, 21 wafer mounting surface, 21a seal band, 21b small circular protrusion, 21c reference surface, 22 electrode, 24 plug placement hole, 30 conductive plate, 32 coolant flow path, 34 gas introduction path, 34a large diameter portion, 34b small diameter portion, 34c step surface, 40 resin layer, 42 resin layer through hole, 50, 50X plug, 52 gas passage, 60 conductive film, 60a, 60Xa plug underside film, 60b annular film, 60Xc gap, 62 through hole, 64, 66, 164 conductive link, 70 contact member, 81, 85 MMC disk member, 82 groove, 83 recess, 84, 86 tubular space, 90 bonding sheet, 92 through hole, 260 large conductive film, 262 Through hole.

Claims

1. a ceramic plate having a wafer mounting surface on its upper surface and incorporating an electrode; a conductive plate provided on the lower surface of the ceramic plate; a resin layer that bonds the ceramic plate and the conductive plate; an insulating gas-passing plug that is provided in a ceramic plate penetration portion that penetrates the ceramic plate and allows gas to pass in the vertical direction; a resin layer penetration part that is provided in the resin layer at a position facing the insulating gas passing plug so as to penetrate the resin layer and that is larger than the insulating gas passing plug in a plan view; a gas introduction passage provided inside the conductive plate and communicating with the insulating gas passing plug through the resin layer penetration part; a conductive film that is provided on the lower surface of the ceramic plate at a position facing the resin layer penetration portion and that is larger than the resin layer penetration portion in a plan view, and that allows gas to flow from the gas introduction path to the insulating gas passing plug; a conductive connection portion that is provided in the gas introduction path, that is smaller than the resin layer penetration portion in a plan view, that electrically connects the conductive film and the conductive plate, and that allows gas to flow from the gas introduction path to the insulating gas passing plug; A wafer stage comprising:

2. The ceramic plate has a plurality of through-holes provided in the ceramic plate, the insulating gas-passing plug is provided in each of the plurality of ceramic plate penetration portions, the gas introduction passages are provided at positions facing the insulating gas passage plugs, the resin layer penetrating portions are provided at positions facing the insulating gas passing plugs, respectively; the conductive film is provided at a position facing each of the plurality of resin layer penetration portions, the conductive connecting portion is provided in each of the plurality of gas introduction paths, Any one of the plurality of conductive films is electrically connected to at least one of the remaining conductive films. The wafer stage according to claim 1 .

3. any one of the plurality of conductive films is electrically connected to at least one of the remaining conductive films via a conductive link provided on the lower surface of the ceramic plate; The wafer stage according to claim 2 .

4. At least one of the plurality of conductive films is separated into a plug lower surface film provided on the lower surface of the insulating gas permeable plug and an annular film provided on the outer periphery of the plug lower surface film, and the annular film is electrically connected to the conductive plate via at least one of the remaining conductive films. The wafer stage according to claim 2 .

5. the conductive connection portion is a separate member from the conductive plate; The wafer stage according to any one of claims 1 to 4.

6. the conductive connecting portion has an elastic member, and the elastic member is arranged in a compressed state by being pressed against the lower surface of the insulating gas passing plug. The wafer stage according to claim 5 .

7. the insulating gas-permeable plug is a porous body or a dense body having a spiral or zigzag gas passage therein; The wafer stage according to any one of claims 1 to 4.

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