Wafer mounting table

Abstract

A wafer mounting table 10 includes: a ceramic body 20 having a wafer mounting surface 21 and a focus ring mounting surface 26 located on an outer peripheral portion relative to the wafer mounting surface 21, and incorporating a first electrode 22; a conductive focus ring 60 mounted on the FR mounting surface 26; an outer peripheral plug arrangement hole 25 positioned below the focus ring 60 and penetrating the ceramic body 20; and an outer peripheral plug 55 provided in the outer peripheral plug arrangement hole 25 and through which gas can pass. The focus ring 60 has a gas reservoir recess 63 at a position facing the outer peripheral plug 55 in a lower surface 62b. An upper surface 55a of the outer peripheral plug 55 is disposed in the recess 63 and is located at a position higher than the lower surface 62b of the focus ring 60.

Description

Wafer mounting table

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

[0002] Conventionally, a wafer mounting table used in a semiconductor manufacturing apparatus is known. For example, the wafer mounting table of Patent Document 1 includes a substrate stage for mounting a wafer to be processed and a focus ring mounted on the substrate stage so as to surround the wafer. A heat transfer gas groove is provided on the upper surface of the portion of the substrate stage on which the focus ring is mounted. By supplying a heat transfer gas such as helium to this heat transfer gas groove through a gas introduction tube that penetrates the substrate stage vertically, heat conduction between the focus ring and the substrate stage can be promoted, or the temperature of the focus ring can be adjusted.

[0003] Japanese Patent No. 5357639

[0004] However, in the space (heat transfer gas groove) formed in the portion of the substrate stage on which the focus ring is mounted as in Patent Document 1, discharge may occur when plasma for processing the wafer is generated.

[0005] The present invention has been made to solve such problems, and the main object is to suppress discharge in the space for gas accumulation between the focus ring and the ceramic body.

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

[0007] [1] The wafer mounting table of the present invention has a wafer mounting surface and a focus ring mounting surface located on the outer peripheral portion rather than the wafer mounting surface, and includes a ceramic body incorporating an electrode, a conductive focus ring mounted on the focus ring mounting surface, a plug arrangement hole located below the focus ring and penetrating the ceramic body, and a plug provided in the plug arrangement hole through which gas can pass inside. The focus ring has a recess for gas accumulation at a position on the lower surface facing the plug, and the upper surface of the plug is disposed within the recess and is higher than the lower surface of the focus ring.

[0008] In this wafer mounting platform, a plug is provided in a plug placement hole located beneath a conductive focus ring and penetrating a ceramic body, through which gas can pass. The focus ring also has a gas reservoir recess on its underside, opposite the plug. The upper surface of the plug is positioned within this recess and higher than the underside of the focus ring. In this way, the recess for accumulating the gas supplied via the plug is located inside the conductive focus ring, so that the potential of the space within the recess during use of the wafer mounting platform is the same as or close to the potential of the focus ring, thereby reducing the potential difference within the space. Therefore, discharge in the space within the recess, i.e., the gas reservoir space between the focus ring and the ceramic body, can be suppressed.

[0009] [2] In the wafer mounting stand described above (the wafer mounting stand described in [1]), the bottom surface of the recess may be located lower than the wafer mounting surface. This ensures that the height from the top surface of the focus ring to the bottom surface of the recess is sufficiently large. Therefore, when the top surface of the focus ring is worn down by the use of the wafer mounting stand, the recess will not be exposed to the top surface.

[0010] [3] In the wafer mounting stand described above (the wafer mounting stand described in [1] or [2] above), the recess has an annular groove provided on the outer periphery of the wafer mounting surface, and a plurality of plug placement holes and plugs are provided below the focus ring, with the upper surface of each of the plurality of plugs positioned within the recess. In this case, compared to the case where a plurality of recesses are provided for each of the plurality of plugs and are scattered, the annular groove in the recess allows for better heat conduction between the focus ring and the ceramic body via the gas in the recess.

[0011] [4] In the wafer mounting stand described above (the wafer mounting stand described in [3]), the recess has one or more holes that are narrower in width and have a higher bottom surface than the annular groove, and the upper surfaces of each of the plurality of plugs may be placed within the holes. Here, for example, if the recess has only an annular groove, widening the width of the annular groove can improve the heat conduction between the focus ring and the ceramic body via the gas in the recess, but the space in the recess becomes larger and discharge tends to occur more easily within the recess. In contrast, by having an annular groove that is wide and has a lower bottom surface, and holes that are narrow and have a higher bottom surface, it is possible to place plugs in the recess while making the depth of the annular groove shallower and reducing the volume of space in the recess. Therefore, it is possible to improve the heat conduction between the focus ring and the ceramic body while suppressing discharge within the recess.

[0012] [5] In the wafer mounting stand described above (the wafer mounting stand described in [4]), the holes may be provided in multiple locations corresponding to each of the plurality of plugs, and the upper surface of each of the plurality of plugs may be located within the corresponding hole.

[0013] [6] In the wafer mounting stage described above (the wafer mounting stage described in any of [1] to [5] above), the plug may have a hole on its upper surface, and the focus ring may have a protruding portion that protrudes downward within the recess and is inserted into the hole. In this case, the lower end of the protruding portion of the focus ring is located lower than the upper surface of the plug and inside the plug, so that a potential difference is less likely to occur in the space around the upper surface of the plug, and discharge within the recess can be further suppressed.

[0014] [7] The wafer mounting stand described above (the wafer mounting stand described in any of [1] to [6] above) may further include an auxiliary member disposed between the side surface of the portion of the plug that is placed in the recess and the side surface of the recess. In this case, the presence of the auxiliary member can reduce the spatial volume between the side surface of the plug and the side surface of the recess in the recess. Therefore, discharge in the recess can be further suppressed.

[0015] [8] In the wafer mounting stand described above (the wafer mounting stand described in [7]), the auxiliary member may also be present between the upper surface of the plug and the bottom surface of the recess. This reduces not only the spatial volume between the side surface of the plug and the side surface of the recess within the recess, but also the spatial volume between the upper surface of the plug and the bottom surface of the recess. Therefore, discharge within the recess can be further suppressed.

[0016] [9] In the wafer mounting stand described above (the wafer mounting stand described in [7] or [8]), the auxiliary member may be made capable of passing gas through its interior. This makes it easier for the gas that has passed through the plug to spread throughout the space in the recess.

[0017]

[10] In the wafer mounting stage described above (the wafer mounting stage described in any of [7] to [9] above), the auxiliary member may be conductive and electrically connected to the focus ring. In this case, the auxiliary member will be at the same potential as the focus ring, which will reduce the potential difference in the space within the recess and further suppress discharge within the recess.

[0018]

[11] In the wafer mounting stage described above (the wafer mounting stage described in any of [7] to

[10] above), a plurality of plug placement holes and plugs are provided below the focus ring, and a plurality of recesses and auxiliary members are provided in a one-to-one correspondence with the plurality of plugs.

[0019] A vertical cross-sectional view of the wafer mounting table 10. A partial enlarged view of Figure 1. A top view of the ceramic body 20. A bottom view of the focus ring 60. A diagram of the manufacturing process of the wafer mounting table 10. A partial enlarged view of the vertical cross-section of the wafer mounting table 110. A bottom view of the focus ring 160. A partial enlarged view of the vertical cross-section of the wafer mounting table 210. A partial enlarged view of the vertical cross-section of the wafer mounting table 310. A partial enlarged view of the vertical cross-section of the wafer mounting table 410. A bottom view of the focus ring 60 and auxiliary member 470. A partial enlarged view of the vertical cross-section of the wafer mounting table 510. A partial enlarged view of the vertical cross-section of the wafer mounting table 610. A partial enlarged view of the vertical cross-section of the wafer mounting table 710. A bottom view of the focus ring 160 and auxiliary member 770. A partial enlarged view of the vertical cross-section of the wafer mounting table 810. A bottom view of the focus ring 160 and auxiliary member 870.

[0020] Embodiments of the present invention will be described with reference to the drawings. Figure 1 is a longitudinal cross-sectional view of a wafer mounting stage 10, which is one embodiment of the present invention. Figure 2 is a partially enlarged view of Figure 1. Figure 3 is a top view of the ceramic body 20. Figure 4 is a bottom view of the focus ring 60.

[0021] The wafer mounting stage 10 comprises a ceramic body 20, a base plate 30, a metal bonding layer 40, a central plug 50, an outer peripheral plug 55, and a focus ring 60.

[0022] The ceramic body 20 is a ceramic disc (for example, 300 mm in diameter) made of an alumina sintered body or an aluminum nitride sintered body. The ceramic body 20 is preferably dense. Dense means that the porosity is 5% or less (preferably 3% or less, more preferably 1% or less). The porosity of the ceramic body 20 is the open porosity measured according to JIS R1634:1998. The thickness of the ceramic body 20 is, for example, 1 mm or more and 5 mm or less. The ceramic body 20 has a wafer mounting surface 21 and a focus ring (FR) mounting surface 26 on its upper surface. The wafer mounting surface 21 is a surface with a circular outer edge on which the wafer W is placed. As shown in Figures 2 and 3, an annular seal band 21a and a plurality of small circular protrusions 21b formed in the center of the seal band 21a are formed on the upper surface of the ceramic body 20. The central region of the seal band 21a, where the small circular protrusions 21b are not provided, is referred to as the reference surface 21c. The seal band 21a and the small circular protrusions 21b are at the same height, and the height of the seal band 21a and the small circular protrusions 21b from the reference surface 21c is, for example, several μm to several tens of μm. The upper surface of the seal band 21a and the upper surface of the small circular protrusions 21b constitute the wafer mounting surface 21. The FR mounting surface 26 is an annular surface provided on the outer periphery and at a lower position than the wafer mounting surface 21. A step is provided between the FR mounting surface 26 and the wafer mounting surface 21 of the ceramic body 20, so that the height of the FR mounting surface 26 is one step lower than the height of the wafer mounting surface 21. The height of the FR mounting surface 26 is lower than the reference surface 21c. An annular focus ring 60 is placed on the FR mounting surface 26.

[0023] The ceramic body 20 incorporates a first electrode 22 and a second electrode 23. The first electrode 22 and the second electrode 23 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 metal bonding layer 40 and the base plate 30. The first electrode 22 is positioned in a region inside the outer edge of the wafer mounting surface 21 (i.e., the outer edge of the seal band 21a) when viewed from above. The second electrode 23 is positioned outside the first electrode 22 and overlaps with the FR mounting surface 26 when viewed from above. When a DC voltage is applied to the first electrode 22, the wafer W is attracted and fixed to the wafer mounting surface 21 by electrostatic attraction force, and when the application of the DC voltage is removed, the attraction and fixation of the wafer W to the wafer mounting surface 21 is released. When a DC voltage is applied to the second electrode 23, the focus ring 60 is attracted and fixed to the FR mounting surface 26 by electrostatic attraction force, and when the application of the DC voltage is removed, the attraction and fixation of the focus ring 60 to the FR mounting surface 26 is released.

[0024] The ceramic body 20 has a central plug placement hole 24 and an outer peripheral plug placement hole 25. Both the central plug placement hole 24 and the outer peripheral plug placement hole 25 are holes that penetrate the ceramic body 20 in the vertical direction. The central plug placement hole 24 is a through hole that extends from the lower surface of the ceramic body 20 to the reference surface 21c. The central plug placement hole 24 penetrates the first electrode 22 in the vertical direction, but the first electrode 22 is not exposed on the inner peripheral surface of the central plug placement hole 24. The outer peripheral plug placement hole 25 is a through hole that extends from the lower surface of the ceramic body 20 to the FR mounting surface 26. The outer peripheral plug placement hole 25 penetrates the second electrode 23 in the vertical direction, but the second electrode 23 is not exposed on the inner peripheral surface of the outer peripheral plug placement hole 25. Both the central plug placement hole 24 and the outer peripheral plug placement hole 25 face the gas holes 34 of the base plate 30. The central plug placement holes 24 and the outer peripheral plug placement holes 25 are both spaces with a shape (for example, an inverted frustocone shape) in which the cross-sectional area decreases from the upper opening to the lower opening. As shown in Figure 3, the central plug placement holes 24 are provided at multiple locations (for example, at multiple locations equally spaced along the circumferential direction) so as to open into the reference surface 21c of the ceramic body 20. As shown in Figure 3, the outer peripheral plug placement holes 25 are provided at multiple locations (for example, at multiple locations equally spaced along the circumferential direction) so as to open into the FR mounting surface 26 of the ceramic body 20.

[0025] The base plate 30 is a conductive disc with good thermal conductivity (a disc with the same diameter as or larger than the ceramic body 20). Inside the base plate 30, there is a refrigerant flow path 32 through which a refrigerant (for example, an electrically insulating liquid such as a fluorine-based inert liquid) circulates, and gas holes 34 that supply gas to the central plug 50 and the outer peripheral plug 55. The gas holes 34 are provided so as to penetrate the base plate 30 in the vertical direction and have a large diameter portion 34a at the top. Multiple gas holes 34 are provided in multiple locations on the base plate 30. The multiple gas holes 34 correspond one-to-one with the central plug placement holes 24 and the outer peripheral plug placement holes 25. In plan view, the large diameter portions 34a of the multiple gas holes 34 each enclose the lower opening of the corresponding placement hole among the central plug placement holes 24 and the outer peripheral plug placement holes 25. In plan view, the refrigerant flow path 32 is formed in a continuous line from the inlet to the outlet across the entire surface of the base plate 30. Examples of materials for the base plate 30 include metals and composite materials. Examples of metals include Mo. Examples of composite materials include metal-ceramic composite materials. Examples of metal-ceramic composite materials include metal matrix composites (MMCs) and ceramic matrix composites (CMCs). Specific examples of such composite materials include materials containing Si, SiC, and Ti, and materials in which Al and / or Si are impregnated into a porous SiC body. Materials containing Si, SiC, and Ti are called SiSiCTi, materials in which Al is impregnated into a porous SiC body are called AlSiC, and materials in which Si is impregnated into a porous SiC body are called SiSiC. It is preferable to select a material for the base plate 30 that has a similar coefficient of thermal expansion to the material of the ceramic body 20. The base plate 30 can also be used as an RF electrode. Specifically, an upper electrode (not shown) is placed above the wafer mounting surface 21, and when high-frequency power is applied between the upper electrode and the base plate 30, which are parallel plate electrodes, plasma is generated.

[0026] The metal bonding layer 40 joins the lower surface of the ceramic body 20 to the upper surface of the base plate 30. The metal bonding layer 40 is formed, for example, by TCB (Thermal Compression Bonding). TCB is a known method in which a metal bonding material is sandwiched between two members to be joined, and the two members are pressurized and joined while heated to a temperature below the solidus temperature of the metal bonding material. The metal bonding layer 40 may also be a layer formed of solder or metal brazing material. The metal bonding layer 40 has a through hole 42. The through hole 42 is provided at a position opposite the large diameter portion 34a of the gas hole 34. The through hole 42 is provided coaxially with the large diameter portion 34a, and the diameter of the through hole 42 is the same as the diameter of the large diameter portion 34a. In this specification, "agree" includes not only cases where they are perfectly aligned, but also cases where they are substantially aligned (for example, within tolerance) (the same applies hereinafter).

[0027] The central plug 50 and the outer periphery plug 55 are electrically insulating members through which gas can pass. The central plug 50 and the outer periphery plug 55 are porous bodies that allow gas to flow vertically. The central plug 50 and the outer periphery plug 55 are ceramic members such as alumina or aluminum nitride, and are formed from the same material as, for example, the ceramic body 20. The porosity of the central plug 50 and the outer periphery plug 55 is preferably 30% or more, and the average pore diameter is preferably 20 μm or more. The porosity of the central plug 50 and the outer periphery plug 55 may be 70% or less.

[0028] The central plug 50 is positioned in the central plug placement hole 24. The outer surface of the central plug 50 may be bonded to the inner surface of the central plug placement hole 24, or the male threaded portion provided on the outer surface of the central plug 50 may be screwed into the female threaded portion provided on the inner surface of the central plug placement hole 24. The central plug 50 has a shape (for example, an inverted frustoconical shape) in which the cross-sectional area decreases from the upper surface 50a to the lower surface 50b, similar to the central plug placement hole 24. Multiple central plugs 50 are provided, corresponding one-to-one to the multiple central plug placement holes 24. The upper surface 50a of the central plug 50 is exposed to the upper opening of the central plug placement hole 24 and is positioned on the same plane as the reference surface 21c. In this specification, "identical" includes not only cases where they are completely identical, but also cases where they are substantially identical (for example, cases where they fall within tolerance) (the same applies hereinafter). The central plug 50 and the central plug mounting hole 24 are designed such that when the central plug 50 is inserted into the central plug mounting hole 24 and the outer surface of the central plug 50 is aligned with the inner surface of the central plug mounting hole 24, the height of the upper surface 50a of the central plug 50 matches the height of the reference surface 21c of the ceramic body 20. Therefore, the upper surface 50a of the central plug 50 and the reference surface 21c of the ceramic body 20 can be easily made coplanar. The height of the lower surface 50b of the central plug 50 may be the same as the height of the lower surface of the ceramic body 20, or it may be higher or lower.

[0029] The outer peripheral plug 55 is positioned in the outer peripheral plug placement hole 25. The outer peripheral plug 55 may have its outer peripheral surface bonded to the inner peripheral surface of the outer peripheral plug placement hole 25, or the male threaded portion provided on the outer peripheral surface of the outer peripheral plug 55 may be screwed into the female threaded portion provided on the inner peripheral surface of the outer peripheral plug placement hole 25. The outer peripheral plug 55 has a shape (for example, an inverted frustoconical shape) in which the cross-sectional area decreases from the upper surface 55a to the lower surface 55b, similar to the outer peripheral plug placement hole 25. Multiple outer peripheral plugs 55 are provided, corresponding one-to-one to the multiple outer peripheral plug placement holes 25. The vertical length of the outer peripheral plug 55 is designed to be greater than the vertical length of the outer peripheral plug placement hole 25, and the upper end of the outer peripheral plug 55 protrudes above the FR mounting surface 26 and the upper opening of the outer peripheral plug placement hole 25. Therefore, the upper surface 55a of the outer peripheral plug 55 is positioned higher than the FR mounting surface 26. The height of the lower surface 55b of the outer peripheral plug 55 may be the same as, higher than, or lower than the height of the lower surface of the ceramic body 20.

[0030] The focus ring 60 is a conductive member placed on the FR mounting surface 26 of the ceramic body 20. Examples of materials for the focus ring 60 include metallic silicon. The material of the focus ring 60 is appropriately selected according to the type of film to be etched on the wafer W when the plasma treatment is plasma etching. An L-shaped annular stepped surface 62c is formed on the upper part of the focus ring 60 along its inner circumference. Therefore, the annular stepped surface 62c is lower than the upper surface 62a of the focus ring 60. The annular stepped surface 62c is coplanar with the wafer mounting surface 21. The annular stepped surface 62c is formed with an outer diameter slightly larger than the outer diameter of the wafer W and the wafer mounting surface 21 so as not to interfere with the wafer W. The outer diameter of the focus ring 60 is larger than the outer diameter of the ceramic body 20. Therefore, the focus ring 60 is placed on the FR mounting surface 26 in an overhanging state, extending beyond the outside of the wafer mounting base 10. The focus ring 60 is not adhered to the FR mounting surface 26, but is simply placed on the FR mounting surface 26.

[0031] The focus ring 60 has a gas reservoir recess 63 on its lower surface 62b, opposite the outer peripheral plug 55. As shown in Figure 4, the recess 63 is circular in plan view, and the space inside the recess 63 is cylindrical. The bottom surface 63a of the recess 63 is higher than the FR mounting surface 26 and the lower surface 62b, and lower than the wafer mounting surface 21. The bottom surface 63a is lower than the reference surface 21c. In plan view, the recess 63 is located outside the annular step surface 62c. That is, in plan view, the recess 63 is located in a position that does not overlap with the annular step surface 62c. The upper end of the outer peripheral plug 55 protrudes above the FR mounting surface 26 and is inserted into the recess 63. Therefore, the upper surface 55a of the outer peripheral plug 55 is located inside the recess 63 and is higher than the lower surface 62b of the focus ring. The bottom surface 63a of the recess 63 is located higher than the top surface 55a of the outer peripheral plug 55. The outer peripheral plug 55 does not come into contact with the bottom surface 63a or the side surface of the recess 63, but at least a portion of it may come into contact with the bottom surface 63a and / or the side surface. In this embodiment, multiple recesses 63 are provided, corresponding one-to-one with the multiple outer peripheral plugs 55, as shown in Figure 4. Therefore, the top surface 55a of each of the multiple outer peripheral plugs 55 is located within the corresponding recess 63 among the multiple recesses 63. The depth (height) of the recess 63 may be 1 mm or less, or 0.5 mm or less. The depth of the recess 63 may be 0.5 mm or more. The vertical distance between the bottom surface 63a of the recess 63 and the top surface 55a of the outer peripheral plug 55 may be 0.2 mm or less. In this embodiment, no recesses are formed around the top surface 55a of the outer peripheral plug 55 on the FR mounting surface 26. Therefore, the space for storing the gas supplied via the outer peripheral plug 55 does not exist at a position lower than the FR mounting surface 26.

[0032] 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 first electrode 22 of the ceramic body 20 to generate electrostatic attraction force, thereby adsorbing and fixing the wafer W to the wafer mounting surface 21. In addition, a DC voltage is applied to the second electrode 23 to generate electrostatic attraction force, thereby adsorbing and fixing the focus ring 60 to the FR mounting surface 26. Next, the inside of the chamber is made into a reaction gas atmosphere with a predetermined pressure (for example, several tens to several hundreds of Pa), and in this state, a high-frequency voltage is applied between an upper electrode (not shown) provided on the ceiling of the chamber and the base 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 base plate 30. Backside gas is introduced from a gas cylinder (not shown) into the gas hole 34. A thermal conductive gas (such as helium) is used as the backside gas. The backside gas is supplied and sealed into the space between the back surface of the wafer W and the reference surface 21c through the gas holes 34, the through holes 42, and the central plug 50. The presence of this backside gas allows for efficient heat conduction between the wafer W and the ceramic body 20. The backside gas is also supplied and sealed into the space within the recess 63 through the gas holes 34, the through holes 42, and the outer peripheral plug 55. The presence of this backside gas allows for efficient heat conduction between the focus ring 60 and the ceramic body 20.

[0033] Furthermore, since the recess 63 for storing backside gas is located inside the conductive focus ring 60, that is, above the lower surface 62b, the potential of the space within the recess 63 when the wafer mounting stage 10 is in use is the same as or close to the potential of the focus ring 60, thus reducing the potential difference within the space. Therefore, discharge in the space within the recess 63, i.e., the gas storage space between the focus ring 60 and the ceramic body 20, can be suppressed. For example, as a comparative example, consider a configuration in which the focus ring 60 does not have a recess 63, but instead a recess is provided in the FR mounting surface 26 of the ceramic body 20, and the upper surface of the outer peripheral plug 55 is the same as the bottom surface of this recess (a surface lower than the FR mounting surface 26), and backside gas is stored in this recess. In this comparative example, since the space within the recess is located below the lower surface 62b of the conductive focus ring 60, the potential difference within the space tends to be larger compared to the space within the recess 63 of this embodiment, and discharge is more likely to occur. In contrast, in the recess 63 of this embodiment, the potential difference within the space can be reduced compared to the recess of the comparative example, and discharge can be suppressed. Furthermore, since the FR mounting surface 26 is located lower than the wafer mounting surface 21, the vertical distance (distance between conductors) between the focus ring 60 and the base plate 30 is smaller than the vertical distance between the wafer W and the base plate 30. Therefore, compared to the space between the lower surface of the wafer W and the upper surface 50a of the central plug 50, the distance between conductors is smaller in the space within the recess 63 even at the same applied voltage, making it easier for the electric field strength to be higher. For this reason, it is important to suppress discharge in the recess 63.

[0034] Next, a manufacturing example of the wafer mounting table 10 will be described based on Figure 5. Figure 5 is a manufacturing process diagram of the wafer mounting table 10. First, a ceramic body 20, a base plate 30, and a metal bonding material 90 are prepared (Figure 5A). The ceramic body 20 incorporates a first electrode 22 and a second electrode 23 and has a central plug placement hole 24 and an outer peripheral plug placement hole 25. The base plate 30 has a refrigerant flow path 32 and a gas hole 34. The gas hole 34 has a large diameter portion 34a at the top. The metal bonding material 90 has a through hole 92 at a position opposite the large diameter portion 34a of the gas hole 34.

[0035] Next, a metal bonding material 90 is sandwiched between the lower surface of the ceramic body 20 and the upper surface of the base plate 30 to form a laminate. At this time, the laminate is stacked so that the central plug placement holes 24 and outer peripheral plug placement holes 25 of the ceramic body 20, the through holes 92 of the metal bonding material 90, and the gas holes 34 of the base plate 30 are coaxial. The laminate is then pressed and bonded at a temperature below the solidus temperature of the metal bonding material 90 (for example, between a temperature 20°C below the solidus temperature and the solidus temperature), and then returned to room temperature (TCB). As a result, the metal bonding material 90 and the through holes 92 become the metal bonding layer 40 and the through holes 42, respectively, and a bonded body 94 is obtained in which the ceramic body 20 and the base plate 30 are bonded by the metal bonding layer 40 (Figure 5B). As the metal bonding material 90, Al-Mg-based bonding material or Al-Si-Mg-based bonding material can be used. It is preferable to use a metal bonding material 90 with a thickness of about 100 μm.

[0036] Next, the central plug 50 is installed in the central plug placement hole 24 of the joint 94, and the outer-circumferential plug 55 is installed in the outer-circumferential plug placement hole 25 (Figure 5B). The central plug 50 may be installed, for example, by preparing a central plug 50 that has been formed in advance by firing, applying adhesive to the central plug placement hole 24, and then inserting the central plug 50 from above the central plug placement hole 24 to bond and fix the outer surface of the central plug 50 to the inner surface of the central plug placement hole 24. Alternatively, a male threaded portion may be formed on the outer surface of the central plug 50, and a female threaded portion may be formed on the inner surface of the central plug placement hole 24. The central plug 50 may then be screwed into the central plug placement hole 24, and the male threaded portion of the central plug 50 and the female threaded portion of the central plug placement hole 24 are screwed together to install the central plug 50. The outer-circumferential plug 55 can be installed in the same manner.

[0037] Alternatively, a focus ring 60 is prepared by first forming an annular stepped surface 62c and a recess 63 by machining (Figure 5B). Then, after attaching the central plug 50 and the outer peripheral plug 55 to the joint 94, the focus ring 60 is placed on the FR mounting surface 26. At this time, the focus ring 60 is placed so that the upper end of the outer peripheral plug 55 is inserted into the recess 63. This gives rise to the wafer mounting base 10 (Figure 5C).

[0038] Here, the correspondence between the components of this embodiment and the components of the present invention will be clarified. The ceramic body 20 of this embodiment corresponds to the ceramic body of the present invention, the first electrode 22 and the second electrode 23 correspond to electrodes, the focus ring 60 corresponds to a focus ring, the outer peripheral plug placement hole 25 corresponds to a plug placement hole, the outer peripheral plug 55 corresponds to a plug, the recess 63 corresponds to a recess, and the upper surface 55a corresponds to the upper surface of a plug.

[0039] In the wafer mounting stage 10 described in detail above, an outer peripheral plug 55 is provided in an outer peripheral plug placement hole 25 located below the conductive focus ring 60 and penetrating the ceramic body 20, through which gas can pass. The focus ring 60 also has a gas reservoir recess 63 on its lower surface 62b, opposite the outer peripheral plug 55. The upper surface 55a of the outer peripheral plug 55 is located within the recess 63 and is higher than the lower surface 62b of the focus ring 60. In this way, because the recess 63 for accumulating gas supplied via the outer peripheral plug 55 is located inside the conductive focus ring 60, the potential of the space within the recess 63 when the wafer mounting stage 10 is in use becomes the same as or close to the potential of the focus ring 60, thus reducing the potential difference within the space. Therefore, discharge in the space within the recess 63, i.e., the gas reservoir space between the focus ring 60 and the ceramic body 20, can be suppressed.

[0040] Furthermore, the bottom surface 63a of the recess 63 is located lower than the wafer mounting surface 21. This ensures that the height from the top surface 62a of the focus ring 60 to the bottom surface 63a of the recess 63 is sufficiently large. Therefore, when the top surface 62a of the focus ring 60 is worn down by the use of the wafer mounting base 10, it is possible to prevent the recess 63 from being exposed to the top surface 62a (i.e., the space within the recess 63 from communicating with the space above the top surface 62a).

[0041] It goes without saying that the present invention is not limited in any way to the embodiments described above, and can be implemented in various forms as long as they fall within the technical scope of the present invention.

[0042] For example, instead of the focus ring 60 of the embodiment described above, the form of the focus ring 160 shown in Figures 6 and 7 may be adopted. Figure 6 is a partially enlarged view of the longitudinal section of the wafer mounting table 110 equipped with the focus ring 160. Figure 7 is a plan view of the focus ring 160 seen from below. As shown in Figures 6 and 7, the recess 163 of the focus ring 160 has an annular groove 164 and a hole 165. The annular groove 164 is provided on the outer circumference of the wafer mounting surface 21. The annular groove 164 is provided so as to surround the wafer mounting surface 21 in a plan view. The hole 165 is narrower in width than the annular groove 164. The hole 165 is a hole formed in the bottom surface 164a of the annular groove 164, and the bottom surface 165a of the hole 165 is at a higher position than the bottom surface 164a of the annular groove 164. The recess 163 has one or more holes 165, and in Figures 6 and 7, there are multiple holes 165 corresponding to multiple outer peripheral plugs 55. Each of the multiple holes 165 is formed in a circular shape in plan view, as shown in Figure 7, and the space inside the hole 165 is cylindrical. The multiple holes 165 correspond one-to-one with the multiple outer peripheral plugs 55, and the upper surface 55a of each of the multiple outer peripheral plugs 55 is located within the corresponding hole 165. That is, each of the multiple outer peripheral plugs 55 is inserted into the annular groove 164 in the recess 163, and furthermore, the upper end of each of the multiple outer peripheral plugs 55 reaches into the hole 165. Therefore, the bottom surface 164a of the annular groove 164 is lower than the upper surface 55a of the outer peripheral plug 55.

[0043] In this focus ring 160, compared with the case where a plurality of concave portions 63 are provided independently for each of the plurality of outer peripheral plugs 55 and are scattered as in the above-described embodiment, the concave portion 163 has an annular groove 164, so that backside gas can be supplied as a whole between the focus ring 60 and the ceramic body 20. In addition, the contact area between the focus ring 60 and the backside gas can be increased. Therefore, the heat conduction between the focus ring 160 and the ceramic body 20 through the gas in the concave portion 163 can be improved.

[0044] Further, in this focus ring 160, the concave portion 163 has an annular groove 164 and a hole portion 165 that is narrower in width than the annular groove 164 and has a bottom surface 165a at a higher position. And the upper surface 55a of each of the plurality of outer peripheral plugs 55 is disposed in the hole portion 165. Here, for example, when the concave portion 163 has only the annular groove 164 with a depth up to the bottom surface 165a of the hole portion 165 (see the broken line in FIG. 6), if the width of the annular groove 164 is widened, the heat conduction between the focus ring 160 and the ceramic body 20 through the backside gas in the concave portion 163 can be made better, but the space in the concave portion 163 becomes larger and there is a tendency for discharge to occur easily in the concave portion 163. On the other hand, since the concave portion 163 has an annular groove 164 that is wide and has a bottom surface 164a at a low position and a hole portion 165 that is narrow and has a bottom surface 165a at a high position, the outer peripheral plug 55 can be disposed in the concave portion 163 while making the depth of the annular groove 164 shallow and reducing the space volume in the concave portion 163. Therefore, it is possible to suppress the discharge in the concave portion 163 while making the heat conduction between the focus ring 160 and the ceramic body 29 better.

[0045] In the focus ring 160 shown in Figures 6 and 7, the multiple holes 165 in the recess 163 correspond one-to-one with the multiple outer peripheral plugs 55, and the upper surface 55a of each of the multiple outer peripheral plugs 55 is positioned within the corresponding hole 165 among the multiple holes 165, but this is not limited to this. For example, the number of holes 165 in the recess 163 can be one or more. Specifically, the number of multiple holes 165 in the recess 163 may be less than the number of outer peripheral plugs 55, for example, two outer peripheral plugs 55 may be inserted into one hole 165. In this case, the hole 165 may be arc-shaped in plan view. Also, the recess 163 may have one hole 165, and this hole 165 may be an annular groove. That is, the recess 163 may have an annular groove 164 that is wide and has a low bottom surface 164a, and an annular groove (hole 165) that is narrow and has a high bottom surface 165a. Alternatively, the recess 163 may not have a hole 165 and may only have an annular groove 164. However, as described above, it is preferable for the recess 163 to have both an annular groove 164 and a hole 165, since the volume of space within the recess 163 can be reduced while arranging the outer peripheral plug 55 within the recess 163.

[0046] Instead of the focus ring 60 in the above-described embodiment, the configuration of the focus ring 260 shown in Figure 8 may be adopted. Figure 8 is a partially enlarged view of the longitudinal cross-section of the wafer mounting table 210 equipped with the focus ring 260. As shown in Figure 8, the focus ring 260 has a projection 266 that protrudes downward from the bottom surface 263a within the recess 263. The projection 266 is formed, for example, in a cylindrical shape. The wafer mounting table 210 is also equipped with an outer peripheral plug 255 instead of the outer peripheral plug 55. The upper surface 55a of the outer peripheral plug 255 is located within the recess 263 and is at a higher position than the lower surface 62b of the focus ring 260. The outer peripheral plug 255 has a hole 256 on its upper surface 55a. The hole 256 opens to the upper surface 55a. The projection 266 of the focus ring 60 is inserted into the hole 256 of the outer peripheral plug 255. In this wafer mounting table 210, the lower end of the protrusion 266, which is part of the conductive focus ring 260, is located lower than the upper surface 55a of the outer peripheral plug 255 and inside the outer peripheral plug 255. Therefore, when the wafer mounting table 210 is in use, the potential of the space around the protrusion 266, that is, the space around the upper surface 55a of the outer peripheral plug 255, is the same as or close to the potential of the focus ring 260. Consequently, a potential difference is less likely to occur in the space around the upper surface 55a of the outer peripheral plug 255, and discharge within the recess 263 can be further suppressed.

[0047] In the focus ring 260 shown in Figure 8, it is preferable that the lower end of the protrusion 266 is at the same position as or higher than the lower surface 62b of the focus ring 260. The protrusion 266 may or may not be in contact with the outer peripheral plug 255 within the hole 256 of the outer peripheral plug 255. If the protrusion 266 is in contact with the outer peripheral plug 255, the lower end of the protrusion 266 may be in contact with the outer peripheral plug 255, or the side surface of the protrusion 266 may be in contact with the outer peripheral plug 255. In addition, in the focus ring 160 shown in Figures 6 and 7, a protrusion may be provided that protrudes downward from the bottom surface 165a of the hole 165 and is inserted into the outer peripheral plug 55.

[0048] In the above-described embodiment, the outer peripheral plug 55 is a porous body. However, the present invention is not limited to this, and it is sufficient that gas can pass through the inside of the outer peripheral plug 55. For example, the outer peripheral plug 55 may be a dense body having a gas passage inside through which gas can pass. The wafer mounting table 310 shown in FIG. 9 includes an outer peripheral plug 355 instead of the outer peripheral plug 55. The outer peripheral plug 355 is an electrically insulating dense body and has a gas internal flow path 357. The gas internal flow path 357 is a flow path that allows the flow of gas between the upper surface 55a and the lower surface 55b of the outer peripheral plug 355. The gas internal flow path 357 opens to the upper surface 55a and the lower surface 55b, respectively. The gas internal flow path 357 is a passage that penetrates while bending from the upper surface side to the lower surface side of the outer peripheral plug 355, and more specifically, is configured as a spiral passage. Another example of the passage that penetrates while bending is a zigzag passage. The gas internal flow path 357 may be a straight through-hole along the vertical direction. The diameter of the cross-section of the gas internal flow path 357 is preferably 0.1 mm or more and 1 mm or less. One outer peripheral plug 355 may have a plurality of gas internal flow paths 357. The porosity of the dense portion of the outer peripheral plug 355 is preferably less than 0.1%. As the outer peripheral plug 355, similar to the outer peripheral plug 55, for example, ceramics such as alumina and aluminum nitride can be used. The outer peripheral plug 355 may have a hole 256 for inserting the protruding portion 266 shown in FIG. 8. In that case, the hole 256 and the opening of the gas internal flow path 357 may be provided at different locations on the upper surface 50a. Regarding the central plug 50, it may also be a dense body having a gas internal flow path similar to the outer peripheral plug 355.

[0049] In the above-described embodiment, the upper surfaces of the seal band 21a and the circular protrusion 21b constitute the wafer mounting surface 21. However, the ceramic body 20 may not have the seal band 21a or the circular protrusion 21b. In that case, the wafer mounting surface 21 may be a flat surface (reference surface 21c).

[0050] In the above-described embodiment, the ceramic body 20 incorporates the first electrode 22 and the second electrode 23. However, the first electrode 22 may be incorporated and the second electrode 23 may not be incorporated.

[0051] In the embodiments described above, the first electrode 22 and the second electrode 23 embedded in the ceramic body 20 are electrostatic electrodes, but the electrodes embedded in the ceramic body 20 are not particularly limited to these. For example, the ceramic body 20 may have a heater electrode (resistive heating element) embedded in it instead of or in addition to the first electrode 22, or it may have an RF electrode embedded in it.

[0052] In the embodiment described above, the ceramic body 20 and the base plate 30 were joined with a metal bonding layer 40, but a resin adhesive layer may be used instead of the metal bonding layer 40.

[0053] In the embodiment described above, the ceramic body 20 was a single, integrally formed component, but it may also be composed of multiple components. For example, the ceramic body 20 may be composed of a portion having a wafer mounting surface 21 and containing the first electrode 22, and a portion having a focus ring mounting surface 26 and containing the second electrode 23, which are separate components.

[0054] In the embodiment described above, the plurality of gas holes 34 formed in the base plate 30 correspond one-to-one with the central plug placement hole 24 and the outer peripheral plug placement hole 25, and the plurality of gas holes 34 are independent flow paths, but the embodiment is not limited to this. For example, the base plate 30 may have a gas introduction section for introducing gas from the lower surface of the base plate 30, and a distribution section that branches from the gas introduction section into a plurality of flow paths, which become gas flow paths to the central plug placement hole 24 and the outer peripheral plug placement hole 25, respectively.

[0055] In the above-described embodiment, the wafer mounting stage 10 is provided with a ceramic body 20, a base plate 30, a metal bonding layer 40, a central plug 50, an outer peripheral plug 55, and a focus ring 60. However, as long as the ceramic body 20, the outer peripheral plug 55, and the focus ring 60 are provided, the other components are not particularly limited. For example, the metal bonding layer 40 and the base plate 30 may not be provided.

[0056] In the embodiment described above, an auxiliary member may be placed between the focus ring 60 and the outer peripheral plug 55. Figure 10 is a partially enlarged view of the longitudinal section of a modified wafer mounting table 410. Figure 11 is a plan view of the focus ring 60 and auxiliary member 470 of the wafer mounting table 410 viewed from below. In Figure 11, the auxiliary member 470 is hatched to make its arrangement easier to understand. In addition to the components of the wafer mounting table 10 described above, the wafer mounting table 410 further includes an auxiliary member 470 placed between the focus ring 60 and the outer peripheral plug 55. The auxiliary member 470 is placed in the recess 63 of the focus ring 60. More specifically, as shown in Figure 10, the auxiliary member 470 is placed between the side surface of the portion of the outer peripheral plug 55 that is placed in the recess 63 and the side surface of the recess 63. The auxiliary member 470 has a ring-shaped (cylindrical) shape, and the outer peripheral plug 55 is placed inside the auxiliary member 470. As a result, the auxiliary member 470 surrounds the side surface of the portion of the outer peripheral plug 55 that is positioned within the recess 63. Furthermore, as shown in Figure 11, multiple recesses 63 and multiple auxiliary members 470 are provided in a one-to-one correspondence with multiple outer peripheral plugs 55. In this way, the presence of the auxiliary member 470 within the recess 63 allows the auxiliary member 470 to fill the gap between the focus ring 60 and the outer peripheral plug 55 within the recess 63. This reduces the spatial volume between the side surface of the outer peripheral plug 55 and the side surface of the recess 63 within the recess 63. Therefore, discharge within the recess 63 can be further suppressed.

[0057] The auxiliary member 470 is preferably made of a conductive material. The auxiliary member 470 may be made of the same material as the focus ring 60. It is preferable that the auxiliary member 470 is electrically conductive with the focus ring 60. For example, in Figure 10, the auxiliary member 470 is not in contact with the focus ring 60, but it is preferable that the auxiliary member 470 is in contact with the focus ring 60 and that the two are electrically conductive. If the auxiliary member 470 is conductive and electrically conductive with the focus ring 60, the auxiliary member 470 will be at the same potential as the focus ring 60, thereby reducing the potential difference in the space within the recess 63 and further suppressing discharge within the recess 63. The same applies to the auxiliary members 570 and 670, which will be described later.

[0058] Furthermore, when manufacturing multiple wafer mounting tables 410, variations in the manufacturing process of the focus ring 60 and the outer peripheral plug 55 may cause variations in the size of the space between the recess 63 and the outer peripheral plug 55, as well as the positional relationship between the inner surface of the recess 63 and the outer peripheral plug 55, for each wafer mounting table 410. Even in such cases, by placing an auxiliary member 470 of an appropriate size that takes into account the variations in manufacturing process into the recess 63 during the process of placing the focus ring 60 on the FR mounting surface 26 (Figure 5B), the volume of the space between the outer peripheral plug 55 and the recess 63 within the recess 63 can be reduced, thereby reducing the impact of variations in manufacturing. In addition, the size of the space between the recess 63 and the outer peripheral plug 55, as well as the positional relationship between the inner surface of the recess 63 and the outer peripheral plug 55, may change due to thermal expansion of the focus ring 60 during use of the wafer mounting table 410. For example, since the diameter of the focus ring 60 is often greater than its thickness, thermal expansion of the focus ring 60 tends to enlarge the space between the side of the outer peripheral plug 55 and the side of the recess 63, which may increase the likelihood of discharge occurring within that space. Even in such cases, the presence of an auxiliary member 470, which is a separate component from the focus ring 60, within the recess 63 reduces the volume of the space between the side of the outer peripheral plug 55 and the side of the recess 63, thereby suppressing discharge within that space. As can be seen from Figures 10 and 11, the auxiliary member 470 is a component with a smaller diameter than the focus ring 60 and undergoes less dimensional change due to thermal expansion. Therefore, the presence of the auxiliary member 470 effectively suppresses the effect of thermal expansion of the focus ring 60 on discharge. These effects are also true for the auxiliary members 570 and 670, which will be described later.

[0059] Instead of the auxiliary member 470 in Figure 10, the auxiliary member 570 shown in Figure 12 may be used. Figure 12 is a partially enlarged view of the longitudinal section of a modified wafer mounting table 510. In addition to the components of the wafer mounting table 10 described above, the wafer mounting table 510 further includes an auxiliary member 570 positioned between the focus ring 60 and the outer peripheral plug 55. The auxiliary member 570 is positioned between the side surface of the outer peripheral plug 55 and the side surface of the recess 63, similar to the auxiliary member 470, and is also present between the upper surface 55a of the outer peripheral plug 55 and the bottom surface 63a of the recess 63. The auxiliary member 570 has a shape that closes the opening at the upper end of the ring of the auxiliary member 470, that is, a bottomed cylindrical shape (cap-like shape). As a result, the auxiliary member 570 surrounds the upper surface 55a of the outer peripheral plug 55 and the periphery of the side surface of the portion of the outer peripheral plug 55 that is positioned within the recess 63. In other words, the auxiliary member 570 completely covers the upper end portion of the outer peripheral plug 55 that is positioned within the recess 63. Similar to the auxiliary member 470, the auxiliary member 570 not only reduces the spatial volume between the side surface of the outer peripheral plug 55 and the side surface of the recess 63 within the recess 63, but it can also reduce the spatial volume between the upper surface 55a of the outer peripheral plug 55 and the bottom surface 63a of the recess 63. Therefore, discharge within the recess 63 can be further suppressed.

[0060] The auxiliary member 570 may be capable of allowing gas to pass through its interior. Figure 13 is a partially enlarged view of the longitudinal section of a modified wafer mounting table 610. In addition to the components of the wafer mounting table 310 described above, the wafer mounting table 610 further includes an auxiliary member 670 positioned between the focus ring 60 and the outer peripheral plug 355. The auxiliary member 670 is the same as the auxiliary member 570 except that it has a gas passage hole 670a at its upper part, allowing gas to pass through its interior. The gas passage hole 670a is located opposite the opening of the internal gas flow path 357 in the recess 63, more specifically, directly above the upper surface 55a of the outer peripheral plug 355. By having a gas passage hole 670a in the auxiliary member 670 in this way, the gas that has passed through the internal gas flow path 357 of the outer peripheral plug 355 can easily spread throughout the space in the recess 63. As a result, when using the wafer mounting table 610, backside gas can be accumulated in the recess 63 in a short time. The position of the gas passage hole 670a is not limited to a position facing the opening of the internal gas flow path 357, but may also be a position facing the upper surface 55a of the outer peripheral plug 355. In addition, the auxiliary member 670 may have a gas passage hole in addition to or instead of the gas passage hole 670a, at a position facing the side surface of the outer peripheral plug 355 (a position between the side surface of the outer peripheral plug 355 and the side surface of the recess 63).

[0061] The auxiliary member 670 only needs to be able to pass gas through its interior. For example, the auxiliary member 670 may not have gas passage holes 670a and may be a porous material. For example, by making the auxiliary member 670 a porous metal, the auxiliary member 670 can be made a conductive material and a material through which gas can pass. The auxiliary members 470 and 570 may also be able to pass gas through their interiors, similar to the auxiliary member 670. For example, the auxiliary members 470 and 570 may have gas passage holes and / or be porous materials.

[0062] As shown in Figure 11, the auxiliary members 470 were provided in multiple quantities, corresponding one-to-one to the multiple outer peripheral plugs 55, but are not limited to this. Figure 14 is a partially enlarged view of the longitudinal section of a modified wafer mounting table 710. Figure 15 is a plan view of the focus ring 160 and auxiliary members 770 of the wafer mounting table 710, viewed from below. In Figure 15, the auxiliary members 770 are hatched to make their arrangement easier to understand. In addition to the components of the wafer mounting table 110 described above, the wafer mounting table 710 further includes auxiliary members 770 positioned between the focus ring 160 and the outer peripheral plugs 55. The auxiliary members 770 are ring-shaped members positioned within the recess 163 of the focus ring 160. The auxiliary members 770 are positioned within the annular groove 164 of the recess 163, approximately concentric with the annular groove 164. In the wafer mounting stage 770, one auxiliary member 770 is positioned between the side surface of the portion of the multiple outer peripheral plugs 55 that is located within the annular groove 164 and the side surface of the annular groove 164 in the recess 163. The auxiliary member 770 has multiple through holes 770a that correspond one-to-one with the multiple outer peripheral plugs 55. The outer peripheral plugs 55 are positioned inside these through holes 770a. As a result, the auxiliary member 770 surrounds the side surface of the portion of the outer peripheral plugs 55 that is located within the recess 63. The presence of this auxiliary member 770 allows it to fill the gap between the focus ring 160 and the outer peripheral plugs 55 within the recess 163. This reduces the volume of space between the side surface of the outer peripheral plugs 55 and the side surface of the recess 163 within the recess 163. Therefore, discharge within the recess 163 can be further suppressed. As shown in Figure 14, in the wafer mounting table 710, the diameter of the through hole 770a is smaller than the diameter of the hole 165 of the recess 163, but the diameter of the through hole 770a may be larger than the diameter of the hole 165 of the recess 163. Also, as shown in Figure 14, the auxiliary member 770 does not exist between the upper surface 55a of the outer peripheral plug 55 and the bottom surface 165a of the recess 163, but it may exist. For example, the through hole 770a may be a bottomed hole, and the auxiliary member 770 may cover the entire upper end of the outer peripheral plug 55 that is placed inside the recess 163, similar to the auxiliary member 570.Furthermore, the auxiliary member 770 may have gas passage holes and / or be a porous material, allowing gas to pass through its interior.

[0063] Instead of the auxiliary member 770 in Figures 14 and 15, the auxiliary member 870 shown in Figures 16 and 17 may be used. Figure 16 is a partially enlarged view of the longitudinal section of a modified wafer mounting table 810. Figure 17 is a plan view of the focus ring 160 and auxiliary member 870 of the wafer mounting table 810 viewed from below. In Figure 17, the auxiliary member 870 is hatched to make its arrangement easier to understand. In addition to the components of the wafer mounting table 110 described above, the wafer mounting table 810 further includes an auxiliary member 870 positioned between the focus ring 160 and the outer peripheral plug 55. The auxiliary member 870 has a first auxiliary member 871 and a second auxiliary member 872. The first auxiliary member 871 and the second auxiliary member 872 are positioned between the side surface of the outer peripheral plug 55 and the side surface of the annular groove 164 of the recess 163, respectively. The first auxiliary member 871 is a ring-shaped member having an inner diameter equal to or larger than one circumscribed circle that contacts the plurality of outer peripheral plugs 55. The second auxiliary member 872 is a ring-shaped member having an outer diameter equal to or smaller than one inscribed circle that contacts the plurality of outer peripheral plugs 55. The plurality of outer peripheral plugs 55 are all positioned inside the first auxiliary member 871 and outside the second auxiliary member 872. The presence of this auxiliary member 870 allows the auxiliary member 870 to fill the gap between the focus ring 160 and the outer peripheral plugs 55 in the recess 163. This reduces the spatial volume between the side surface of the outer peripheral plugs 55 and the side surface of the recess 163. Therefore, discharge within the recess 163 can be further suppressed. As can be seen from Figures 16 and 17, in the wafer mounting stage 810, the inner diameter of the first auxiliary member 871 is smaller than the diameter of one circumscribed circle that contacts the multiple holes 165 of the recess 163, but the inner diameter of the first auxiliary member 871 may be larger than the diameter of this circumscribed circle. Similarly, in the wafer mounting stage 810, the outer diameter of the second auxiliary member 872 is larger than the diameter of one inscribed circle that contacts the multiple holes 165 of the recess 163, but the outer diameter of the second auxiliary member 872 may be smaller than the diameter of this inscribed circle. Furthermore, the auxiliary member 870 may have gas passage holes and / or be a porous material, allowing gas to pass through its interior.

[0064] This application is based on the priority claim of Japanese Patent Application No. 2024-194356, filed on November 6, 2024, the entire contents of which are incorporated herein by reference.

[0065] This invention can be used in wafer mounting stages used in semiconductor manufacturing equipment, such as ceramic heaters, electrostatic chuck heaters, and electrostatic chucks.

[0066] 10 Wafer mounting stage, 20 Ceramic plate, 21 Wafer mounting surface, 21a Seal band, 21b Small circular protrusion, 21c Reference surface, 22 First electrode, 23 Second electrode, 24 Central plug placement hole, 25 Outer peripheral plug placement hole, 26 Focus ring (FR) mounting surface, 30 Base plate, 32 Refrigerant flow path, 34 Gas hole, 34a Large diameter section, 40 Metal bonding layer, 42 Through hole, 50 Central plug, 50a Top surface, 50b Bottom surface, 55 Outer peripheral plug, 55a Top surface, 55b Bottom surface, 60 Focus ring, 62a Top surface, 62b Bottom surface, 62c Annular stepped surface, 63 Recess, 63a Bottom surface, 160 Focus ring, 163 Recess, 164 Annular groove, 164a Bottom surface, 165 Hole, 165a Bottom surface, 255 Outer circumference plug, 256 Hole, 260 Focus ring, 263 Recess, 263a Bottom surface, 266 Protrusion, 355 Outer circumference plug, 357 Gas internal flow path, 470, 570, 670, 770, 870 Auxiliary member, 670a Gas passage hole, 770a Through hole, 871 First auxiliary member, 872 Second auxiliary member, 90 Metal bonding material, 92 Through hole, 94 Joint, 110, 210, 310, 410, 510, 610, 710, 810 Wafer mounting stage, W Wafer.

Claims

1. A wafer mounting platform comprising: a wafer mounting surface and a focus ring mounting surface located on the outer periphery of the wafer mounting surface, a ceramic body containing electrodes, a conductive focus ring mounted on the focus ring mounting surface, a plug placement hole located below the focus ring and penetrating the ceramic body, and a plug provided in the plug placement hole through which gas can pass, wherein the focus ring has a gas reservoir recess on its lower surface facing the plug, and the upper surface of the plug is located within the recess and is higher than the lower surface of the focus ring.

2. A wafer mounting platform according to claim 1, wherein the bottom surface of the recess is located at a lower position than the wafer mounting surface.

3. A wafer mounting table according to claim 1 or 2, wherein the recess has an annular groove provided on the outer periphery of the wafer mounting surface, and a plurality of plug placement holes and plugs are provided below the focus ring, with the upper surface of each of the plurality of plugs positioned within the recess.

4. A wafer mounting table according to claim 3, wherein the recess has one or more holes that are narrower in width and have a higher bottom surface than the annular groove, and the upper surface of each of the plurality of plugs is positioned within the holes.

5. A wafer mounting table according to claim 4, wherein the holes are provided in a plurality corresponding to each of the plurality of plugs, and the upper surface of each of the plurality of plugs is positioned within the corresponding hole.

6. A wafer mounting table according to claim 1 or 2, wherein the plug has a hole on its upper surface, and the focus ring has a projection that protrudes downward within the recess and is inserted into the hole.

7. A wafer mounting platform according to claim 1 or 2, further comprising: an auxiliary member disposed between the side surface of the portion of the plug disposed within the recess and the side surface of the recess.

8. A wafer mounting platform according to claim 7, wherein the auxiliary member is also present between the upper surface of the plug and the bottom surface of the recess.

9. A wafer mounting platform according to claim 7, wherein the auxiliary member is capable of passing gas through its interior.

10. A wafer mounting platform according to claim 7, wherein the auxiliary member is conductive and electrically connected to the focus ring.

11. A wafer mounting table according to claim 7, wherein a plurality of plug placement holes and plugs are provided below the focus ring, and a plurality of recesses and auxiliary members are provided in a one-to-one correspondence with the plurality of plugs.

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