Electrostatic chuck

Abstract

An electrostatic chuck is provided that can suppress deviations in the in-plane temperature distribution of a substrate. The electrostatic chuck includes: a dielectric substrate; a base plate; and a bonding layer for bonding the dielectric substrate and the base plate. The bonding layer includes: a first bonding layer; and a second bonding layer that annularly surrounds the first bonding layer from its outer periphery. The thermal conductivity of the second bonding layer is higher than that of the first bonding layer. When the pore formed closest to the outer periphery among a plurality of pores is designated as the outermost pore (140A), the outer periphery end (E1) of the first bonding layer is located closer to the inner periphery than the center (CT) of the outermost pore (140A), and the inner periphery end (E2) of the second bonding layer is located closer to the outer periphery than the center (CT) of the outermost pore (140A).

Description

Technical Field

[0001] This invention relates to an electrostatic chuck. Background Technology

[0002] For example, in semiconductor manufacturing apparatuses such as etching equipment, electrostatic chucks are provided as devices for adsorbing and holding substrates such as silicon wafers that are to be processed. An electrostatic chuck comprises: a dielectric substrate on which adsorption electrodes are provided; and a base plate supporting the dielectric substrate, having a structure in which these are joined together. When a voltage is applied to the adsorption electrodes, an electrostatic force is generated, adsorbing and holding the substrate placed on the dielectric substrate.

[0003] As described in Patent Document 1 below, for example, a bonding layer such as a cured silicone adhesive is used to bond the dielectric substrate and the base plate.

[0004] Patent documents Patent Document 1: Japanese Patent Application Publication No. 2020-23088 Summary of the Invention

[0005] During processing, it is necessary to suppress deviations in the in-plane temperature distribution of the substrate as much as possible. As a countermeasure to suppress deviations in the in-plane temperature distribution, the inventors have studied a technique in which the material of the bonding layer is different in different parts.

[0006] The present invention was made in view of the following problem, and its object is to provide an electrostatic chuck that can suppress deviations in the in-plane temperature distribution of a substrate.

[0007] To address the aforementioned problems, the electrostatic chuck of the present invention comprises: a dielectric substrate having a mounting surface for placing an object to be processed and having formed a plurality of pores; a base plate supporting the dielectric substrate; and a bonding layer for bonding the dielectric substrate and the base plate. The bonding layer includes: a first bonding layer; and a second bonding layer annularly surrounding the first bonding layer from its outer periphery. The thermal conductivity of the second bonding layer is higher than that of the first bonding layer. When the electrostatic chuck is viewed from a direction perpendicular to the mounting surface, if the pore formed closest to the outer periphery among the plurality of pores formed at a position closer to the inner periphery than the outer periphery of the mounting surface is taken as the outermost pore, the outer periphery of the first bonding layer is located closer to the inner periphery than the center of the outermost pore, and the inner periphery of the second bonding layer is located closer to the outer periphery than the center of the outermost pore.

[0008] In substrate processing, the temperature rises more easily on the outer peripheral side of the substrate compared to the inner peripheral side. However, depending on the structure of the electrostatic chuck, the temperature of the substrate may locally decrease in the area directly above the outermost vent.

[0009] In the electrostatic chuck with the above structure, the portion near the outermost peripheral pores of the dielectric substrate is not bonded to the base plate by either the first bonding layer or the second bonding layer. Since this portion is difficult to cool by the base plate, localized temperature drops directly above the outermost peripheral pores can be suppressed, and deviations in the in-plane temperature distribution of the substrate can be suppressed.

[0010] According to the present invention, an electrostatic chuck capable of suppressing deviations in the in-plane temperature distribution of a substrate can be provided. Attached Figure Description

[0011] Figure 1 This is a cross-sectional view showing the structure of the electrostatic chuck according to the first embodiment. Figure 2 It means Figure 1 A diagram showing the structure of the dielectric substrate of an electrostatic chuck. Figure 3 It means Figure 1 A diagram showing the structure of the bonding layer of an electrostatic chuck. Figure 4 It is a diagram used to illustrate the positional relationship between the bonding layer and the pores. Figure 5 It is a diagram used to illustrate the positional relationship between the bonding layer and the pores. Figure 6 This is a cross-sectional view showing the structure of the electrostatic chuck according to the second embodiment. Symbol Explanation 10-Electrostatic chuck; 100-Dielectric substrate; 110-Face; 140-Vacuum; 140A-Outermost peripheral vent; 200-Base plate; 300-Bonding layer; 310-First bonding layer; 320-Second bonding layer; CT-Center; E1, E2-Ends; W-Substrate. Detailed Implementation

[0012] Hereinafter, this embodiment will be described with reference to the accompanying drawings. For ease of understanding, the same symbols will be used to label the same components as much as possible in each drawing, and repeated descriptions will be omitted.

[0013] The first embodiment will be described. The electrostatic chuck 10 of this embodiment, for example, inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus, uses electrostatic force to attract and hold a substrate W that is to be processed. The substrate W corresponds to the "object to be processed," such as a silicon wafer. The electrostatic chuck 10 can also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0014] Figure 1The diagram shows the structure of an electrostatic chuck 10 in a state of adsorbing and holding a substrate W, as a schematic cross-sectional view. The electrostatic chuck 10 includes a dielectric substrate 100, a base plate 200, and a bonding layer 300.

[0015] The dielectric substrate 100 is a generally disk-shaped component made of sintered ceramic body. Although the dielectric substrate 100 may contain, for example, high-purity alumina (Al2O3), other materials may also be included. Considering the plasma resistance and other requirements of the dielectric substrate 100 in semiconductor manufacturing equipment, the purity and type of ceramic, additives, etc. in the dielectric substrate 100 can be appropriately set.

[0016] In dielectric substrate 100, Figure 1 The upper side surface 110 of the dielectric substrate 100 becomes the "mounting surface" of the substrate W. Additionally, in the dielectric substrate 100, Figure 1 The lower side surface 120 becomes the "joined surface" that is joined to the base plate 200 by the joining layer 300 described later. Hereinafter, the perspective when viewing the electrostatic chuck 10 from the side of surface 110 along a direction perpendicular to surface 110 will also be described as "top view".

[0017] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin, flat layer formed of a metal material such as tungsten, and is arranged parallel to the surface 110. In addition to tungsten, molybdenum, platinum, palladium, etc., can also be used as the material for the adsorption electrode 130. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply circuit (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. The adsorption electrode 130 can be provided as a so-called "monopolar" electrode as in this embodiment, or two can be provided as so-called "bipolar" electrodes.

[0018] like Figure 1 As shown, a space SP1 is formed between the dielectric substrate 100 and the substrate W. During etching or other processes in a semiconductor manufacturing apparatus, an inert gas for temperature control is supplied to the space SP1 from the outside through the vent 140 (described later). By having the inert gas present between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, thereby maintaining the temperature of the substrate W at an appropriate temperature. Furthermore, although helium is used in this embodiment as the inert gas supplied to the space SP1 for temperature control, a gas of a different type than helium can also be used.

[0019] Figure 2 This is a top-view drawing of the dielectric substrate 100. As shown in the figure, a sealing ring 111 and a dot 112 are provided on the mounting surface, i.e., surface 110, and the aforementioned space SP1 is formed around these.

[0020] The sealing ring 111 is an annular protrusion that serves as a wall dividing the space SP1 at the outermost periphery. The upper end of the sealing ring 111 becomes part of the surface 110 and abuts against the substrate W. Furthermore, multiple sealing rings 111 can be provided in a manner that divides the space SP1. By adopting such a structure, the pressure of helium gas in each space SP1 can be adjusted individually, and the surface temperature distribution of the substrate W during processing can be made more uniform.

[0021] Figure 1 and Figure 2 In the diagram, the portion marked with the symbol "116" is the bottom surface of space SP1. Hereinafter, this portion will also be referred to as "bottom surface 116". The sealing ring 111, together with point 112 described below, is formed as a result of excavating a portion of surface 110 up to the position of bottom surface 116.

[0022] Point 112 is a circular protrusion projecting from the bottom surface 116. (Example) Figure 2 As shown, a plurality of points 112 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The upper end surface of each point 112 becomes part of the surface 110 and abuts against the substrate W. By providing a plurality of such points 112, bending of the substrate W is suppressed.

[0023] A vent 140 is formed on the dielectric substrate 100. The vent 140 is a through hole formed in a direction perpendicular to the mounting surface, i.e., surface 110. The end of the vent 140 on the surface 110 side is connected to the space SP1. The vent 140 is part of a flow path for supplying helium gas to the space SP1.

[0024] Multiple vents 140 are provided and distributed to allow helium gas to be supplied to various parts of space SP1. The actual configuration of the vents 140 in the structure is as follows: Figure 2 As shown, but in Figure 1 Only four of the pores (140) were drawn in a stylized manner.

[0025] Among the multiple pores 140, the pore 140 formed closest to the outer periphery when viewed from above is hereinafter referred to as the "outermost peripheral pore 140A". It can also be said that the outermost peripheral pore 140A is the pore 140 located at the end closest to the outer periphery of the mounting surface, i.e., surface 110, from the inner periphery. Figure 2 As shown, in this embodiment, there are a plurality of outermost vents 140A, which are arranged in a circular pattern along the sealing ring 111.

[0026] The base plate 200 is a generally disk-shaped component that supports the dielectric substrate 100. The base plate 200 is formed, for example, of a metallic material such as aluminum. The base plate 200... Figure 1The upper side surface 210 becomes the "bonded surface" that is bonded to the dielectric substrate 100 by means of the bonding layer 300.

[0027] Inside the base plate 200, a cooling medium flow path 260 is formed for through which the cooling medium flows. During processes such as etching in the semiconductor manufacturing apparatus, a cooling medium is supplied from the outside to the cooling medium flow path 260, thereby cooling the base plate 200. During processing, heat generated on the substrate W is transferred to the cooling medium via helium gas in the space SP1, the dielectric substrate 100, and the base plate 200, and is discharged to the outside along with the cooling medium. In the base plate 200, the cooling medium for the cooling medium flow path 260 is supplied and discharged through an opening (not shown) formed on the surface 220 opposite to surface 210.

[0028] A perforation 240 is formed on the base plate 200. The perforation 240 is a through hole formed in a manner that extends vertically from the surface 210 to the opposite surface 220. When viewed from above, the perforations 240 are formed at positions that overlap with the perforations 140 of the dielectric substrate 100, and are connected to the perforations 140 by through holes provided on the bonding layer 300. The perforations 240 and the perforations 140 of the dielectric substrate 100 together constitute part of a flow path for supplying helium gas to the space SP1.

[0029] Furthermore, the vents 240 can be formed as a single unit extending in a straight line, as in this embodiment, but they can also be formed to bend along the path from surface 210 to surface 220. Alternatively, a structure can be adopted in which multiple vents 240 on the surface 210 side are combined into a few flow paths inside the base plate 200, and these flow paths are extended to the surface 220 side.

[0030] An insulating film may also be formed on the surface of the base plate 200. The insulating film may be formed to cover only a portion of the surface of the base plate 200, rather than the entire surface. For example, the insulating film may be formed to cover only the side portions other than surfaces 210 and 220, i.e., the exposed portions inside the semiconductor manufacturing apparatus exposed to plasma, etc. Conversely, the insulating film may be formed to cover at least the entire area including surface 210. For example, an alumina film formed by thermal spraying may be used as the insulating film. By covering the surface of the base plate 200 with an insulating film, the insulation withstand voltage of the base plate 200 can be improved.

[0031] The bonding layer 300 is a layer disposed between the dielectric substrate 100 and the base plate 200, bonding the two together. The bonding layer 300 is a layer formed by curing an adhesive material made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 can also be a layer formed by curing other types of adhesives. In any case, it is preferable to use a material with the highest possible thermal conductivity as the material for the bonding layer 300, so as to minimize the thermal resistance between the dielectric substrate 100 and the base plate 200.

[0032] Figure 3 The structure of the bonding layer 300 as viewed from above is shown in a stylized diagram. Furthermore, through holes are formed in portions of the bonding layer 300 that overlap with the pores 140 or with pin holes (not shown), etc. Figure 3 The illustration of the through hole is omitted. Additionally, Figure 3 The arrangement of the outermost vents 140A on the dielectric substrate 100 is also shown in the figure.

[0033] The bonding layer 300 in this embodiment includes a first bonding layer 310 and a second bonding layer 320. When viewed from above, the first bonding layer 310 is circular in shape. When viewed from above, the center of the first bonding layer 310 coincides with the center of the dielectric substrate 100. The second bonding layer 320 surrounds the first bonding layer 310 in a ring shape from its outer periphery. When viewed from above, the outer periphery ends of the first bonding layer 310, the inner periphery ends of the second bonding layer 320, and the outer periphery ends of the second bonding layer 320 are all circular, and these are arranged in a concentric circle.

[0034] The materials of the first bonding layer 310 and the second bonding layer 320 are different. Specifically, the materials of the two layers are selected such that the thermal conductivity of the second bonding layer 320 is higher than that of the first bonding layer 310. For example, such a difference in thermal conductivity is achieved by making the amount of filler added to the adhesive before the silicone adhesive that becomes the bonding layer 300 is cured different.

[0035] like Figure 3 In this embodiment, when viewed from above, all the outermost peripheral pores 140A provided on the dielectric substrate 100 are disposed between the first bonding layer 310 and the second bonding layer 320, and are arranged at equal intervals along the circumferential direction.

[0036] A space SP2 is formed between the first bonding layer 310 and the second bonding layer 320. As previously described, when viewed from above, the outer peripheral end of the first bonding layer 310 and the inner peripheral end of the second bonding layer 320 are arranged in a concentric circle. The space SP2 is an annular space formed between the two ends.

[0037] like Figure 1 and Figure 3 As shown, space SP2 is connected to the lower end of each of the outermost peripheral vents 140A. In this embodiment, multiple outermost peripheral vents 140A are all connected to one space SP2. Helium gas supplied to vent 240 is supplied to space SP1 via space SP2 and the outermost peripheral vents 140A. That is, space SP2, vent 240, and vent 140 together constitute part of the flow path for supplying helium gas to space SP1.

[0038] In the base plate 200, the number of vents 240 located directly below the outermost vent 140A can be less than the number of outermost vents 140A. In this structure, helium gas supplied to the vents 240 is distributed to each outermost vent 140A while flowing in space SP2, and is thus supplied to space SP1. That is, space SP2 can also be used as a distribution flow path for distributing helium gas to multiple vents 140.

[0039] However, when the substrate W is processed in a semiconductor manufacturing apparatus, it is preferable that the deviation in the in-plane temperature distribution of the substrate W be as small as possible. However, the temperature of the substrate W during processing tends to rise locally in the outer peripheral portion. Therefore, in this embodiment, as previously described, the thermal conductivity of the second bonding layer 320 disposed on the outer peripheral side is made higher than the thermal conductivity of the first bonding layer 310 disposed on the inner peripheral side. Since the outer peripheral portion of the dielectric substrate 100 (that is, the portion supporting the outer peripheral side of the substrate W) is more easily cooled by the base plate 200, the local temperature rise on the outer peripheral side of the substrate W can be suppressed.

[0040] In this embodiment, in order to further suppress the deviation of the in-plane temperature distribution of the substrate W, the relative positional relationship between the bonding layer 300 and the outermost peripheral pore 140A was also studied.

[0041] Figure 4 In the figure, the outermost stomata 140A and the surrounding structures are drawn in a patterned manner when viewed from above. Figure 4 In the diagram, the curve marked with the symbol "E1" represents the end of the outer periphery of the first bonding layer 310. Hereinafter, this end will also be referred to as "end E1". The curve marked with the symbol "E2" represents the end of the inner periphery of the second bonding layer 320. Hereinafter, this end will also be referred to as "end E2".

[0042] Figure 4 In the diagram, the point marked with the symbol CT indicates the center position of the outermost stomata 140A. Furthermore, the "center position of the outermost stomata 140A" is the central axis position of the outermost stomata 140A when viewed from above. Hereinafter, this center will also be referred to as the "center CT".

[0043] In this embodiment, the shapes of the first bonding layer 310 and the second bonding layer 320 are set such that, when viewed from above, the outer peripheral end E1 of the first bonding layer 310 is located closer to the inner peripheral side than the center CT of the outermost pore 140A, and the inner peripheral end E2 of the second bonding layer 320 is located closer to the outer peripheral side than the center CT of the outermost pore 140A.

[0044] The reason is as follows. As previously described, during the processing of substrate W, the temperature rises more easily on the outer peripheral side of substrate W compared to the inner peripheral side. However, depending on the different structures of the electrostatic chuck 10, the temperature of substrate W may locally decrease in the portion directly above the outermost peripheral vent 140A. For example, when other sealing rings are positioned closer to the inner peripheral side of the dielectric substrate 100 than sealing ring 111, and the outermost peripheral vent 140A is positioned close to these sealing rings, the temperature directly above the outermost peripheral vent 140A may locally decrease.

[0045] Therefore, in the electrostatic chuck 10 of this embodiment, as described above, the outer peripheral end E1 of the first bonding layer 310 is positioned closer to the inner peripheral side than the center CT of all the outermost peripheral pores 140A, and the inner peripheral end E2 of the second bonding layer 320 is positioned closer to the outer peripheral side than the center CT of all the outermost peripheral pores 140A.

[0046] In this structure, the portion of the dielectric substrate 100 near the outermost peripheral vent 140A is not bonded to the base plate 200 by either the first bonding layer 310 or the second bonding layer 320. Since this portion is difficult to cool by the base plate 200, localized temperature drops directly above the outermost peripheral vent 140A can be suppressed, and deviations in the in-plane temperature distribution of the substrate W can be suppressed.

[0047] Furthermore, the positional relationship between the first bonding layer 310 and the outermost peripheral vent 140A, as described above, and the positional relationship between the second bonding layer 320 and the outermost peripheral vent 140A, are determined by the cross-section that includes at least the central axis of the dielectric substrate 100 and the central axis of the outermost peripheral vent 140A (that is, as shown in the figure). Figure 1 This can be established on such a cross section. That is to say, "end E1" and "end E2" are the ends on the aforementioned cross section. The positions of end E1 and end E2 on the cross section that does not include the central axis of the outermost pore 140A are not specifically limited.

[0048] Hereinafter, the distance from the outer peripheral end E1 of the first bonding layer 310 to the center CT of the outermost peripheral vent 140A when viewed from above will also be referred to as "distance D1". Furthermore, the distance from the inner peripheral end E2 of the second bonding layer 320 to the center CT of the outermost peripheral vent 140A will also be referred to as "distance D2". When either distance D1 or D2 is too large, the temperature drop in the portion directly above the outermost peripheral vent 140A cannot be sufficiently suppressed. Experiments conducted by the inventors have confirmed that if distance D1 is controlled within a range of 2 mm or less and distance D2 is controlled within a range of 2 mm or less, deviations in the in-plane temperature distribution of the substrate W can be sufficiently suppressed.

[0049] In this embodiment, the outer peripheral end E1 of the first bonding layer 310 and the inner peripheral end E2 of the second bonding layer 320 are separated across the entire circumference, forming a space SP2 between them. By employing this structure, when the dielectric substrate 100 and the base plate 200 are bonded, it is possible to prevent the mixing of different types of adhesives, namely the first bonding layer 310 and the second bonding layer 320, and the resulting changes in their respective properties. Furthermore, if changes in the properties of the adhesive due to solid diffusion, etc., are not a problem, a bonding layer made of other materials can also exist between the first bonding layer 310 and the second bonding layer 320. In this case, it is preferable to use a material whose thermal conductivity is lower than that of both the first bonding layer 310 and the second bonding layer 320 as the material for this bonding layer.

[0050] Hereinafter, the distance from the outer peripheral end E1 of the first bonding layer 310 to the inner peripheral end E2 of the second bonding layer 320 when viewed from above will also be referred to as the "layer spacing". This definition of layer spacing applies not only to the portion of the first bonding layer 310 and the second bonding layer 320 separated by the outermost peripheral pore 140A, but also to the portion where they are not separated. Figure 3 The symbol “D3” indicates the interlayer spacing between the first bonding layer 310 and the second bonding layer 320 when they are adjacent, separated by the outermost pore 140A. The symbol “D4” indicates the interlayer spacing between the first bonding layer 310 and the second bonding layer 320 when they are adjacent, not separated by the outermost pore 140A.

[0051] In this embodiment, the interlayer spacing (D4) is controlled to be less than 2 mm in the portion of the first bonding layer 310 and the second bonding layer 320 that are adjacent without being separated by the outermost peripheral pore 140A. By adopting such a structure, it is possible to prevent the temperature of the substrate W from rising excessively locally in the portion directly above the first bonding layer 310 and the second bonding layer 320.

[0052] Furthermore, in this embodiment, including the portion of the first bonding layer 310 and the second bonding layer 320 that are adjacent to each other across the outermost peripheral pore 140A, the interlayer spacing mentioned above is not affected by the circumferential position (that is, it remains a certain size over the entire circumference). By adopting such a structure, deviations in the in-plane temperature distribution of the substrate W in the circumferential direction can be suppressed.

[0053] Figure 5 In China, through cooperation with Figure 4 Using the same method, the structure of the electrostatic chuck 10 according to a modified example of this embodiment was schematically drawn. In this modified example, the first bonding layer 310 and the second bonding layer 320 are arranged such that, when viewed from above, they avoid a circular area such as surrounding the outermost vent 140A. As a result, the interlayer spacing (D3) of the portions of the first bonding layer 310 and the second bonding layer 320 adjacent to each other across the outermost vent 140A is greater than the interlayer spacing (D4) of the portions of the first bonding layer 310 and the second bonding layer 320 adjacent to each other without being separated by the outermost vent 140A. In such a structure, it is also possible to adopt a structure in which D4 is controlled within the range of 2 mm, while D3 is greater than 2 mm.

[0054] Thus, the portion where the interlayer spacing is controlled to be less than 2 mm can also refer only to the portion where the first bonding layer 310 and the second bonding layer 320 are adjacent without being separated by the outermost peripheral pore 140A. Similarly, the portion where the interlayer spacing is kept constant can also refer only to the portion where the first bonding layer 310 and the second bonding layer 320 are adjacent without being separated by the outermost peripheral pore 140A. However, in either case, it is preferable to control the distances D1 and D2 to be less than 2 mm respectively.

[0055] Furthermore, if changes in the physical properties of the adhesive due to solid diffusion or other reasons are not a problem, the interlayer spacing (D3) between the first bonding layer 310 and the second bonding layer 320, which are adjacent without being separated by the outermost peripheral pore 140A, can be made 0 mm. In other words, the aforementioned range of "less than 2 mm" also includes 0 mm.

[0056] Reference Figure 6 The second embodiment will be described. Hereinafter, the parts that differ from the first embodiment will be mainly described, and the parts that are the same as those in the first embodiment will be omitted as appropriate.

[0057] In this embodiment, a flange portion 101 is provided on the dielectric substrate 100. The flange portion 101 is a portion that protrudes further outward from the mounting surface, i.e., surface 110. When viewed from above, the flange portion 101 surrounds the entire surface 110 from the outside. The surface of the flange portion 101 on the substrate W side ( Figure 6 The upper side of the surface), located closer to the base plate 200 side than surface 110 ( Figure 6The position is located on the lower side of the middle. When processing the substrate W, an annular member (not shown) such as a "focusing ring" is placed on the flange portion 101.

[0058] A perforation can also be formed on the flange portion 101 so that helium can also be supplied directly below the annular member. Such a perforation is located closer to the outer periphery than the outermost peripheral perforation 140A in the first embodiment. However, the "outermost peripheral perforation" is defined as the perforation 140 located closest to the outer periphery among a plurality of perforations 140 formed at a position closer to the inner periphery than the end of the mounting surface (surface 110) on which the workpiece (substrate W) is placed. Therefore, even when a perforation is formed on the flange portion 101, this perforation is not equivalent to the "outermost peripheral perforation".

[0059] like Figure 6 As shown, in this embodiment, the portion of the vent 140 on the side of surface 120 is enlarged compared to the portion on the side of surface 110. Hereinafter, this enlarged portion will also be referred to as the "enlarged diameter portion 141". A vent plug 150 is disposed inside the enlarged diameter portion 141. The vent plug 150 is, for example, a porous material formed of alumina, and is generally breathable. By disposing such a vent plug 150 inside the vent 140, the flow of gas in the vent 140 is ensured, while insulation breakdown along the path through the vent 140 can be suppressed. Furthermore, the breathable portion of the vent plug 150 may be only a part of it, rather than the entire plug. For example, only the central portion of the vent plug 150 may be breathable, while the outer peripheral portion may not be breathable.

[0060] like Figure 6 As shown, in this embodiment, the portion of the vent 240 on the side of surface 210 is enlarged compared to the portion on the side of surface 220. Hereinafter, this enlarged portion will also be referred to as the "enlarged diameter portion 241". A vent plug 250 is disposed inside the enlarged diameter portion 241. The vent plug 250 is, for example, a porous material formed of alumina, and is generally breathable. By disposing such a vent plug 250 inside the vent 240, the flow of gas in the vent 240 is ensured, while insulation breakdown along the path through the vent 240 can be suppressed. Furthermore, the breathable portion of the vent plug 250 may be only a part of it, rather than the entire vent plug. For example, only the central portion of the vent plug 250 may be breathable, while the outer peripheral portion may not be breathable.

[0061] Even in the structure described above, the same effects as those explained in the first embodiment are achieved.

[0062] Furthermore, even in a structure where a flange portion 101 is provided on the dielectric substrate 100 as in this embodiment, it is preferable that the second bonding layer 320 is provided at a position where a portion of it overlaps with the mounting surface (surface 110) when viewed from above.

[0063] The present embodiment has been described above with reference to specific examples. However, the present invention is not limited to these specific examples. Regarding these specific examples, any design modifications made by those skilled in the art that possess the features of the present invention are also included within the scope of the present invention. The elements, their configurations, conditions, shapes, etc., of the foregoing specific examples are not limited to the illustrated content, but can be appropriately modified. As long as there is no technical contradiction, the elements of the foregoing specific examples can be appropriately changed and combined.

Claims

1. An electrostatic chuck, characterized in that, It includes: a dielectric substrate having a mounting surface for placing the object to be processed and having multiple pores formed thereon; Base plate, supporting the dielectric substrate; A bonding layer is used to bond the dielectric substrate and the base plate. The bonding layer includes: a first bonding layer; and a second bonding layer, which surrounds the first bonding layer in a ring shape from the outer periphery. The thermal conductivity of the second bonding layer is higher than that of the first bonding layer. When viewed from a direction perpendicular to the mounting surface, When the pore formed at the position closest to the outer periphery among a plurality of pores formed at a position closer to the inner periphery than the outer periphery of the mounting surface is taken as the outermost pore, The outer peripheral end of the first bonding layer is located closer to the inner peripheral side than the center of the outermost peripheral pore. The inner peripheral end of the second bonding layer is located closer to the outer peripheral side than the center of the outermost peripheral pore.

2. An electrostatic chuck as recited in claim 1, characterized by The first bonding layer and the second bonding layer are separated over a full circumference.

3. An electrostatic chuck as recited in claim 2, characterized by A space is formed between the first bonding layer and the second bonding layer, and the space is connected to the plurality of pores.

4. The electrostatic chuck according to claim 1, characterized in that, When viewed from a direction perpendicular to the mounting surface, The distance from the end of the outer periphery of the first bonding layer to the center of the outermost pore is less than 2 mm. The distance from the end of the inner circumferential side of the second bonding layer to the center of the outermost pore is less than 2 mm.

5. The electrostatic chuck according to claim 1, characterized in that, When viewed from a direction perpendicular to the mounting surface, In the portion where the first bonding layer and the second bonding layer are adjacent without being separated by the pores, The distance from the end of the outer periphery of the first bonding layer to the end of the inner periphery of the second bonding layer is less than 2 mm.

6. The electrostatic chuck according to claim 5, characterized in that, When viewed from a direction perpendicular to the mounting surface, In the portion where the first bonding layer and the second bonding layer are adjacent without being separated by the pores, The distance from the end of the outer periphery of the first bonding layer to the end of the inner periphery of the second bonding layer remains constant regardless of the circumferential position.

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