Electrostatic chuck

Abstract

The present invention provides an electrostatic chuck which is configured so that an outer peripheral end portion of a dielectric substrate protrudes, but which is capable of suppressing variations in in-plane temperature distribution of the substrate during processing. An electrostatic chuck (10) is provided with: a dielectric substrate (100); an adsorption electrode (130) provided inside the dielectric substrate (100); and a base plate (200) that is bonded to the dielectric substrate (100). In a plan view, the dielectric substrate (100) has a protruding part (101) that protrudes further outward than the bonded surface of the base plate (200), and a part of the adsorption electrode (130) is provided on the protruding part (101).

Description

Technical Field

[0001] The present invention relates to an electrostatic chuck. Background Art

[0002] For example, in a semiconductor manufacturing apparatus such as an etching apparatus, an electrostatic chuck is provided as an apparatus for adsorbing and holding a substrate such as a silicon wafer that is an object to be processed. The electrostatic chuck includes: a dielectric substrate provided with an adsorption electrode; and a base plate that supports the dielectric substrate, and has a structure in which these are joined to each other. When a voltage is applied to the adsorption electrode, an electrostatic force is generated to adsorb and hold the substrate placed on the dielectric substrate. Although the adsorption electrode is sometimes formed on the surface on the base plate side in the dielectric substrate, as described in Patent Document 1 below, it is usually provided inside the dielectric substrate.

[0003] Patent Document Patent Document 1: Japanese Patent Application Laid-Open No. 2011-119654 Summary of the Invention

[0004] As a bonding layer for bonding between the dielectric substrate and the base plate, for example, a cured silicone adhesive is used. When performing a process such as etching, the end portion of the bonding layer is exposed to the plasma, ages, and scatters, which may have an adverse effect on the substrate being processed.

[0005] In order to prevent such a situation from occurring, the present inventors have developed an electrostatic chuck having such a structure in which the dielectric substrate is further enlarged compared to the bonded surface of the base plate, that is, an electrostatic chuck having a structure in which the outer peripheral side end portion of the dielectric substrate protrudes more outward than the bonded surface. By adopting such a structure, a member covering the periphery of the bonding layer can be disposed on the lower side of the dielectric substrate. Thereby, it is possible to suppress the bonding layer from affecting the substrate being processed.

[0006] However, when the outer peripheral side end portion of the dielectric substrate protrudes as described above, there is no base plate directly below the protruding portion, so it may not be possible to sufficiently cool the protruding portion. As a result, the deviation of the in-plane temperature distribution of the substrate being processed may become large.

[0007] The present invention has been made in view of such problems, and the technical problem to be solved is to provide an electrostatic chuck that can suppress the deviation of the in-plane temperature distribution of the substrate being processed although it has a structure in which the outer peripheral side end portion of the dielectric substrate protrudes.

[0008] In order to solve the above problems, the electrostatic chuck according to the present invention includes: a dielectric substrate having a placement surface for placing an object to be adsorbed; an adsorption electrode disposed inside the dielectric substrate; and a base plate joined to the dielectric substrate. When viewed from a direction perpendicular to the placement surface, the dielectric substrate has a protruding portion that protrudes more outward than the joined surface of the base plate, and a part of the adsorption electrode is disposed in the protruding portion.

[0009] By disposing a part of the adsorption electrode in the protruding portion, the adsorption force of the protruding portion of the substrate is increased, and the two are pressed against each other with a strong force. As a result, the thermal resistance between the protruding portion and the substrate decreases, so that the temperature rise of the substrate directly above the protruding portion can be suppressed. As a result, the deviation of the in-plane temperature distribution of the substrate during processing can be suppressed more than in the past.

[0010] According to the present invention, it is possible to provide an electrostatic chuck that can suppress the deviation of the in-plane temperature distribution of the substrate during processing, although it has a structure in which the outer peripheral side end portion of the dielectric substrate protrudes. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Figure 1 It is a cross-sectional view schematically showing the structure of the electrostatic chuck according to the first embodiment. Figure 2 is an enlarged and detailed view showing Figure 1 a part of the structure of Figure 3 It is a view schematically showing the structure of the cooling medium flow path formed in the base plate of the first embodiment. Figure 4 It is a cross-sectional view schematically showing the structure of the electrostatic chuck according to the second embodiment. Figure 5 It is a view schematically showing the structure of the cooling medium flow path formed in the base plate of the third embodiment. REFERENCE SIGNS 10 - Electrostatic chuck; 100 - Dielectric substrate; 101 - Protruding portion; 110 - Surface; 111 - Sealing ring; 130 - Adsorption electrode; 140 - RF electrode; E - End portion; 200 - Base plate; 210 - Surface; 250, 251 - Cooling medium flow path; P1 - First part; P2 - Second part. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0012] Hereinafter, the present embodiment will be described with reference to the drawings. For ease of understanding the description, in each drawing, the same reference signs are given to the same components as much as possible, and redundant description is omitted.

[0013] A description is given of the first embodiment. The electrostatic chuck 10 according to this embodiment adsorbs and holds a substrate W to be processed by electrostatic force inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus. The object to be adsorbed, i.e., the substrate W, is, for example, a silicon wafer. The electrostatic chuck 10 can also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0014] Figure 1 In [the figure], the structure of the electrostatic chuck 10 in a state of adsorbing and holding the substrate W is shown as a schematic cross-sectional view. The electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200.

[0015] The dielectric substrate 100 is a substantially disk-shaped member made of a ceramic sintered body. Although the dielectric substrate 100 contains, for example, high-purity alumina (Al2O3), it can also contain other materials. Considering the plasma resistance and the like required for the dielectric substrate 100 in a semiconductor manufacturing apparatus, the ceramic purity, type, additives, etc. in the dielectric substrate 100 can be appropriately set. The diameter of the dielectric substrate 100 is, for example, 290 to 300 mm. The thickness of the dielectric substrate 100 is, for example, 0.5 to 3.0 mm.

[0016] In the dielectric substrate 100, Figure 1 the upper surface 110 therein becomes the "placement surface" for placing the substrate W. Further, in the dielectric substrate 100, Figure 1 the lower surface 120 therein becomes the "surface to be joined" that is joined to the base plate 200 via the joining layer 300. Hereinafter, the viewpoint when observing the electrostatic chuck 10 from the side of the surface 110 in a direction perpendicular to the surface 110 will also be referred to as "top-down observation".

[0017] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is, for example, a thin plate-shaped layer formed of a metal material such as tungsten and is arranged parallel to the surface 110. As the material of the adsorption electrode 130, in addition to tungsten, molybdenum, platinum, palladium, etc. can also be used. If 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, and thereby the substrate W is adsorbed and held. As the structure of the above-mentioned power supply circuit, various known structures can be adopted. The adsorption electrode 130 can be provided as a so-called "single-pole" electrode, i.e., only one, as in this embodiment, or can be provided as a so-called "bipolar" electrode, i.e., two. The depth of the position where the adsorption electrode 130 is arranged, i.e., the distance from the bottom surface 116 (described later) to the adsorption electrode 130, is, for example, 0.1 to 0.5 mm.

[0018] Inside the dielectric substrate 100, in addition to the adsorption electrode 130, an RF electrode 140 is also embedded. In a semiconductor manufacturing apparatus, the RF electrode 140 is provided as one of a pair of opposing electrodes for generating plasma. The other of the opposing electrodes is provided at a position closer to the upper side than the electrostatic chuck 10 in the semiconductor manufacturing apparatus. If a high-frequency alternating voltage is applied between these opposing electrodes, plasma is generated on the upper side of the substrate W and is used for processes such as film formation or etching of the substrate W.

[0019] Similar to the adsorption electrode 130, the RF electrode 140 is also, for example, a thin flat plate-like layer formed of a metal material such as tungsten. As the material of the RF electrode 140, in addition to tungsten, molybdenum, platinum, palladium, etc. can also be used. The RF electrode 140 is embedded at a position closer to the surface 120 side than the adsorption electrode 130. Similar to the adsorption electrode 130, the RF electrode 140 is arranged parallel to the surface 110. When viewed from above, the RF electrode 140 is a substantially circular single electrode. When viewed from above, the center of the RF electrode 140 coincides with the center of the dielectric substrate 100. The distance from the adsorption electrode 130 to the RF electrode 140 is, for example, 0.2 to 2 mm. The distance from the RF electrode 140 to the surface 120 is, for example, 0.1 to 2.5 mm.

[0020] As Figure 1 shown, a space SP is formed between the dielectric substrate 100 and the substrate W. When performing processes such as etching in the semiconductor manufacturing apparatus, helium for temperature adjustment is supplied from the outside to the space SP through pores (not shown). By having helium present between the dielectric substrate 100 and the substrate W, the thermal resistance between the two is adjusted, and thus the temperature of the substrate W is maintained at an appropriate temperature. Also, the gas for temperature adjustment supplied to the space SP can be a gas of a different type from helium.

[0021] A sealing ring 111 and dots 112 are provided on the placement surface, i.e., the surface 110, and the above-mentioned space SP is formed around these.

[0022] The sealing ring 111 is a wall that divides the space SP at the outermost peripheral position. The sealing ring 111 is an annular protrusion formed on the surface 110 side. The top end ( Figure 1 the upper end in

[0023] this) of the sealing ring 111 becomes a part of the surface 110 and abuts against the substrate W. It can be said that the top end of the sealing ring 111 is the outermost peripheral side part of the placement surface, i.e., the surface 110.

[0024] Figure 1 In Figure 1 , the portion marked with the symbol "116" is the bottom surface of the space SP. Hereinafter, this portion will also be referred to as the "bottom surface 116". The sealing ring 111, together with the point 112 described below, is formed as a result of digging a part of the surface 110 to the position of the bottom surface 116.

[0025] The point 112 is a circular protrusion protruding from the bottom surface 116. A plurality of points 112 are provided and are disposed approximately evenly on the placement surface of the dielectric substrate 100. The top end of each point 112 becomes a part of the surface 110 and abuts against the substrate W. By providing a plurality of such points 112, the flexure of the substrate W is suppressed.

[0026] The base plate 200 is a substantially disk-shaped member that supports the dielectric substrate 100. The base plate 200 is formed of a metal material such as aluminum, for example. The base plate 200 is joined to the surface 120 of the dielectric substrate 100 by the joining layer 300. In the base plate 200, Figure 1 the upper surface 210 thereof becomes the "surface to be joined" joined to the dielectric substrate 100.

[0027] The joining layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200 and joins the two. The joining layer 300 is a layer formed by curing an adhesive made of an insulating material. In the present embodiment, a silicone adhesive is used as the above-mentioned adhesive. However, the joining layer 300 may also be a layer formed by curing other types of adhesives. In any case, it is preferable to use a material having a relatively high thermal conductivity as the material of the joining layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[0028] An insulating film may also be formed on the surface of the base plate 200. As the insulating film, for example, a film of alumina formed by spraying can be used. By covering the surface of the base plate 200 with the insulating film, the dielectric strength of the base plate 200 can be improved. The thickness of the insulating film is, for example, 1 mm or less.

[0029] The base plate 200 has a support portion 201 and a flange portion 202. The support portion 201 is the Figure 1 upper portion in the base plate 200 and is a substantially cylindrical portion that directly supports the dielectric substrate 100 from below. Although the diameter of the support portion 201, that is, the diameter of the surface 210, is, for example, 290 to 300 mm, the same as that of the dielectric substrate 100, it is slightly smaller than the diameter of the dielectric substrate 100. The thickness of the support portion 201, that is, the protruding amount of the support portion 201 toward the Figure 1 upper side (the protruding amount from the flange portion 202) is, for example, 3 to 15 mm.

[0030] The flange portion 202 is the Figure 1 lower side portion in the base plate 200. The shape of the flange portion 202 is substantially cylindrical, and its central axis coincides with the central axis of the support portion 201. The diameter of the flange portion 202 is larger than the diameter of the support portion 201. The protruding amount of the flange portion 202 starting from the outer side surface of the support portion 201 (that is, the protruding amount in the radial direction) is, for example, 20 to 30 mm. The thickness of the flange portion 202 is, for example, 25 to 40 mm. The overall thickness of the base plate 200 including the support portion 201 and the flange portion 202 is, for example, 30 to 40 mm.

[0031] When processing the substrate W in the semiconductor manufacturing apparatus, a focus ring (not shown) is provided on the upper surface 203 of the flange portion 202. The focus ring is a circular and plate-like member formed of an insulating material such as quartz, and is provided for the purpose of adjusting the distribution of plasma during processing. Substantially the whole of the dielectric substrate 100 and the support portion 201 is in a state of being surrounded by the focus ring from the outer peripheral side.

[0032] Inside the base plate 200, a coolant flow path 250 for allowing a coolant to pass through is formed. When performing processing such as etching in the semiconductor manufacturing apparatus, the coolant is supplied from the outside to the coolant flow path 250, thereby cooling the base plate 200. During processing, the heat generated on the substrate W is transferred to the coolant through the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the coolant. In the base plate 200, the supply and discharge of the coolant to the coolant flow path 250 are performed through openings 255 and 256 ( Figure 1 not shown in the figure, refer to Figure 3 ). The specific structure of the coolant flow path 250 will be described later.

[0033] As described above, in the electrostatic chuck 10 according to the present embodiment, the diameter of the support portion 201, which is the portion of the base plate 200 that directly supports the dielectric substrate 100, is smaller than the diameter of the dielectric substrate 100. As a result, the dielectric substrate 100 protrudes more outward than the joint surface, that is, the surface 210. Hereinafter, the protruding portion of the dielectric substrate 100 will also be referred to as the "protruding portion 101". The protruding amount of the protruding portion 101, that is, the protruding amount of the dielectric substrate 100 from the outer side surface of the support portion 201 (the protruding amount in the radial direction) is, for example, 1 mm to 3 mm.

[0034] When performing a process such as etching, the end portion of the bonding layer 300 is exposed to the plasma, aged, and scattered, which may have an adverse effect on the substrate W being processed. As in the present embodiment, when the protruding portion 101 is provided on the dielectric substrate 100, a member that covers the exposed portion of the bonding layer 300 from the surroundings can be disposed on the lower side of the dielectric substrate 100. Figure 2 In, the arrangement position of such a member is indicated by a two-dot chain line marked with the symbol "400". By arranging this member, the influence of the bonding layer 300 on the substrate W being processed can be suppressed.

[0035] However, in a process such as etching, it is well known that the temperature of the portion particularly on the outer peripheral side of the substrate W tends to increase. In addition, as in the present embodiment, when the protruding portion 101 is provided on the dielectric substrate 100, there is no base plate 200 directly below the protruding portion 101, so it may not be possible to sufficiently cool the protruding portion 101. As a result, the temperature of the portion particularly on the outer peripheral side of the substrate W may further increase and the deviation of the in-plane temperature distribution of the substrate W being processed may become larger.

[0036] Therefore, in the electrostatic chuck 10 of the present embodiment, in order to suppress the above-described local temperature rise and make the in-plane temperature distribution of the substrate W being processed as uniform as possible, various improvements described below are implemented.

[0037] Figure 2 In, the structure of the protruding portion 101 and its vicinity in the electrostatic chuck 10 of Figure 1 is enlarged and shown in detail. Figure 2 The dotted line DL1 shown indicates the position of the outer peripheral side end portion of the adsorption electrode 130. The dotted line DL2 indicates the position of the outer peripheral side end portion of the surface 210. In the present embodiment, the diameter of the surface 210 is equal to the diameter of the outer peripheral side end portion of the RF electrode 140. Therefore, the dotted line DL2 also indicates the position of the outer peripheral side end portion of the RF electrode 140.

[0038] Moreover, the "outer peripheral side end portion" of the adsorption electrode 130 refers to the portion where the smallest circle including the entire adsorption electrode 130 overlaps with the adsorption electrode 130 when viewed from above. The "outer peripheral side end portion" of the RF electrode 140 is defined in the same way. The diameter of the surface 210 and the diameter of the outer peripheral side end portion of the RF electrode 140 may be the same as each other as described above, or may be different from each other.

[0039] The diameter of the outer peripheral side end portion of the adsorption electrode 130 is larger than the diameter of the surface 210 of the base plate 200. Therefore, the outer peripheral side end portion (dotted line DL1) of the adsorption electrode 130 enters the inside of the protruding portion 101 in the dielectric substrate 100.

[0040] In a structure where a part of the adsorption electrode 130 is disposed on the protruding portion 101 like this, the adsorption force on the protruding portion 101 of the substrate W increases, and the two are pressed against each other with a stronger force. As a result, the thermal resistance between the protruding portion 101 and the substrate W decreases, and thus the temperature rise of the substrate W directly above the protruding portion 101 can be suppressed. Consequently, the deviation of the in-plane temperature distribution of the substrate W during processing can be suppressed more effectively than in the past.

[0041] The diameter of the outer peripheral side end portion of the adsorption electrode 130 is larger than the diameter of the inner peripheral side in the sealing ring 111 and smaller than the diameter of the outer peripheral side in the sealing ring 111. In addition, the diameter of the outer peripheral side in the sealing ring 111 is larger than the diameter of the surface 210 of the base plate 200. When viewed from above, a part of the sealing ring 111 overlaps both the protruding portion 101 and the adsorption electrode 130. Since the sealing ring 111, the protruding portion 101, and the adsorption electrode 130 overlap when viewed from above, the cooling of the substrate W in this part can be further improved. As a result, the deviation of the in-plane temperature distribution of the substrate W can be further suppressed.

[0042] Moreover, it can also be configured such that when viewed from above, not a part but the entire sealing ring 111 overlaps both the protruding portion 101 and the adsorption electrode 130. In this case, it is only necessary to make the diameter of the inner peripheral side in the sealing ring 111 larger than the diameter of the support portion 201. In addition, it is only necessary to make the diameter of the outer peripheral side in the sealing ring 111 smaller than the diameter of the dielectric substrate 100 and smaller than the diameter of the outer peripheral side end portion of the adsorption electrode 130.

[0043] In any case, it is preferable to ensure that the distance from the outer peripheral side end portion (dotted line DL1) of the adsorption electrode 130 to the outer side surface of the dielectric substrate 100 is about 0.1 mm to 3 mm. By ensuring such a distance, the insulation breakdown between the adsorption electrode 130 and the outside can be prevented.

[0044] It is preferable that the diameter of the outer peripheral side end portion (dotted line DL2) of the RF electrode 140 is equal to or smaller than the diameter of the outer peripheral side end portion (dotted line DL1) of the adsorption electrode 130. That is, when viewed from above, it is preferable to dispose the RF electrode 140 within a range where its outer peripheral side end portion does not overflow outward from the outer peripheral side end portion of the adsorption electrode 130. It is preferable to ensure that the distance from the outer peripheral side end portion (dotted line DL2) of the RF electrode 140 to the outer side surface of the dielectric substrate 100 is about 0.1 mm to 5 mm.

[0045] When processing the substrate W, Joule heat is generated in the RF electrode 140, which may cause the temperature of surrounding components to rise. That is, during the processing, the RF electrode 140 may become a heat source. Thus, in the present embodiment, as described above, the RF electrode 140 is disposed within a range where its outer peripheral side end portion does not overflow from the outer peripheral side end portion of the adsorption electrode 130. By accommodating the heat source, i.e., the RF electrode 140, within the above range, it is possible to further suppress the temperature rise in the portion on the outer peripheral side of the substrate W.

[0046] For ease of explanation, hereinafter, the outer peripheral side end portion of the placement surface, i.e., the surface 110, is also referred to as the "end portion E". When viewed from above, the end portion E has a circular ridgeline, but in a part thereof (e.g., the positioning edge portion), it may also have a non-circular ridgeline.

[0047] Hereinafter, the portion of the base plate 200 that overlaps with the end portion E when viewed from above is also referred to as the "first portion P1". The first portion P1 is, for example, a portion having a certain width so as to include the entire end portion E when viewed from above, but the manner of taking its width is not particularly limited.

[0048] Hereinafter, the portion of the base plate 200 that is closer to the outer peripheral side than the first portion P1 when viewed from above is also referred to as the "second portion P2". The second portion P2 is the portion of the base plate 200 that is adjacent to the first portion P1 from the outer peripheral side, and refers to the entire portion that is closer to the outer peripheral side than the first portion P1.

[0049] As Figure 1 shown, the cooling medium flow path 250 not only surrounds and is arranged in the first portion P1 and its inner side in the base plate 200, but also surrounds and is arranged in the outer second portion P2. That is, a cooling medium flow path 250 is also formed over the span of the second portion P2, which is closer to the outer side than the portion directly below the substrate W or the support portion 201 (i.e., the first portion P1, etc.). The cooling medium flowing through the cooling medium flow path 250 in the second portion P2 cools the focusing ring (not shown) and Figure 2 the member denoted by the symbol "400" in the figure, etc. By these, the outer peripheral side portion of the substrate W is also cooled.

[0050] In the present embodiment, the diameter of the flange portion 202 is relatively large, and accordingly, the second portion P2 also becomes larger. By enlarging the second portion P2 and forming a cooling medium flow path 250 over substantially the entire span thereof, and on this basis, circulating the cooling medium, it is possible to suppress the temperature rise in the outer peripheral side portion of the substrate W.

[0051] Figure 3In [the figure], the pattern depicts the structure of the cooling medium flow path 250 formed inside the base plate 200 when viewed from above. As previously described, openings 255 and 256 are provided on the surface 220 of the base plate 200. The cooling medium flow path 250 is formed along the path connecting the opening 255 and the opening 256. For example, the opening 255 is used as the inlet of the cooling medium, and the opening 256 is used as the outlet of the cooling medium. Figure 3 The circular dashed line shown represents the end E on the outer peripheral side of the placement surface, i.e., the surface 110.

[0052] In the present embodiment, an opening 255 is formed at a position near the outer peripheral end in the base plate 200, and an opening 256 is formed at the center of the base plate 200. The cooling medium flow path 250 is connected between the opening 255 and the opening 256 in a spiral shape and is arranged to surround a path through substantially the entire base plate 200.

[0053] Hereinafter, the part of the cooling medium flow path 250 that is arranged to surround in the first part P1 (that is, directly below the end E) is also referred to as "the cooling medium flow path 251". As Figure 3 shown, when viewed from above, the cooling medium flow path 251 is arranged to surround along the end E in an arc-shaped extension.

[0054] As Figure 1 shown, the width W1 of the cooling medium flow path 251 in the first part P1 is smaller than the width W2 of the cooling medium flow path 250 in the second part P2. Although the width of the cooling medium flow path 250 in the part closer to the inside than the first part P1 is the same as the width W2 of the cooling medium flow path 250 in the second part P2, it can also be of a different size. And the "width" of the cooling medium flow path 250 mentioned here refers to the size of the cooling medium flow path 250 in the direction perpendicular to the flow direction of the cooling medium when viewed from above.

[0055] In such a structure, the flow velocity of the cooling medium flowing through the cooling medium flow path 251 is higher than the flow velocity of the cooling medium flowing through other parts of the cooling medium flow path 250. Along with the increase in the flow velocity, the heat transfer efficiency in the cooling medium flow path 251 is improved, so the first part P1 is cooled more efficiently than the second part P2. That is to say, as a result of reducing the width of the cooling medium flow path 251 directly below the end E of the cooling medium flow path 250 of the present embodiment, the cooling performance of the first part P1 is higher than the cooling performance of the second part P2.

[0056] By setting a difference in the cooling performance between the first part P1 and the second part P2, while sufficiently suppressing the temperature rise of the outer peripheral side portion of the substrate W, it is also possible to prevent members such as the focus ring disposed at a position further outside than the outer peripheral side portion of the substrate W from being excessively cooled more than necessary. As a result, the in-plane temperature distribution of the substrate W during processing can be made more uniform than in the past.

[0057] The second embodiment will be described. Hereinafter, mainly the parts different from the first embodiment will be described, and the parts common to the first embodiment will be appropriately omitted.

[0058] Figure 4 In Figure 1 the same cross-sectional view as that of

[0059] the structure of the electrostatic chuck 10 according to the present embodiment is shown. Similar to the first embodiment, also in the present embodiment, a cooling medium flow path 250 is formed inside the base plate 200, and a part thereof (the cooling medium flow path 251) is arranged to surround the lower side of the end E, that is, the first part P1. In the whole including the cooling medium flow path 251, the width of the cooling medium flow path 250 in the present embodiment tends to be uniform. Figure 4 Hereinafter, the distance in the direction perpendicular to the placement surface, that is, the surface 110, and the distance between the cooling medium flow path 250 and the surface 110 will also be referred to as the "cooling medium distance". The cooling medium distance can be defined for each part of the cooling medium flow path 250, and it can be said that it is an index indicating the height position of the cooling medium flow path 250. As

[0060] In such a structure, the thermal resistance between the cooling medium flow path 251 in the first part P1 and the surface 110 is smaller than the thermal resistance between the cooling medium flow path 250 in the second part P2 and the surface 110. As a result, the first part P1 is cooled more efficiently than the second part P2. That is to say, the cooling medium flow path 250 of the present embodiment is as follows. As a result of reducing the distance of the cooling medium directly below the end E, the cooling performance of the first part P1 is higher than that of the second part P2. Even in such a structure, the same effects as those described in the first embodiment can be achieved.

[0061] The third embodiment will be described. Hereinafter, mainly the parts different from the first embodiment will be described, and the parts common to the first embodiment will be omitted as appropriate.

[0062] Figure 5 in which, by Figure 3 the same method shows the structure of the cooling medium flow path 250 formed in the base plate 200 of the present embodiment. Similar to the first embodiment, even in the present embodiment, a cooling medium flow path 250 is formed inside the base plate 200, and a part thereof (cooling medium flow path 251) is arranged so as to surround the first part P1 by passing directly below the end E. In the whole including the cooling medium flow path 251, the width of the cooling medium flow path 250 in the present embodiment tends to be uniform. In addition, in the whole including the cooling medium flow path 251, the cooling medium distance in the present embodiment also tends to be uniform.

[0063] As Figure 5 shown, in the present embodiment, an opening 255 serving as an inlet of the cooling medium for the cooling medium flow path 250 is formed at a position overlapping the end E in a top view. That is to say, the end on one side (inlet side) of the cooling medium flow path 250 is arranged at a position overlapping the end E in a top view.

[0064] When viewed from above, the cooling medium flow path 250 extends along the end E in an arc shape from the opening 255 and is arranged so as to surround the first part P1. That is, the part extending in an arc shape from the opening 255 as described above becomes the cooling medium flow path 251 in the present embodiment. As is clear from Figure 5 it, the cooling medium supplied to the opening 255 first passes through the cooling medium flow path 251 directly below the end E to cool the first part P1. After that, the cooling medium passes through the second part P2 closer to the outside than the end E to cool the second part P2. Then, the cooling medium passes through the part closer to the inside than the end E to cool that part. Finally, the cooling medium is discharged to the outside from the opening 256. While passing through the path as described above, the temperature of the cooling medium gradually rises.

[0065] Since the low-temperature cooling medium first passes through the first part P1, the first part P1 is cooled with higher efficiency. On the other hand, since the cooling medium whose temperature has risen after passing through the first part P1 passes through the second part P2, the second part P2 is cooled with relatively low efficiency. That is to say, the cooling medium flow path 250 of the present embodiment is as follows. As a result of arranging the inlet-side end connected to the opening 255 directly below the end E, the cooling performance of the first part P1 is higher than that of the second part P2. Even in such a structure, the same effects as those described in the first embodiment can be achieved.

[0066] Moreover, at the position overlapping the end E in a top view, either only one side end of the cooling medium flow path 250 can be arranged, or both ends can be arranged. That is to say, both the openings 255 and 256 can also be arranged directly below the end E. In such a structure, even when using either one of the arbitrary openings 255 and 256 as the inlet of the cooling medium, the first part P1 can be cooled with high efficiency.

[0067] As the structure of the cooling medium flow path 250 for making the cooling performance of the first part P1 higher than that of the second part P2, it is not limited to the examples described above, but various other forms can be adopted. For example, according to different places, the distance between adjacent cooling medium flow paths 250 in a top view, that is, the arrangement interval of the cooling medium flow paths 250, can also be changed. Specifically, the arrangement interval of the cooling medium flow paths 250 in the first part P1 can also be made smaller than the arrangement interval of the cooling medium flow paths 250 in the second part P2. Even in such a form, the same effects as those described in the above embodiments can be achieved.

[0068] The present embodiment has been described with reference to specific examples. However, the present invention is not limited to these specific examples. Regarding these specific examples, as long as they have the features of the present invention, the technologies appropriately designed and changed by those skilled in the art are also included in the scope of the present invention. The elements, their arrangements, conditions, shapes, etc. possessed by the foregoing specific examples are not limited to the illustrated contents, but can be appropriately changed. As long as there is no technical contradiction, the elements possessed by the foregoing specific examples can be appropriately changed in combination.

Claims

1. An electrostatic chuck, characterized in that, it includes: a dielectric substrate having a placement surface for placing an object to be adsorbed; an adsorption electrode disposed inside the dielectric substrate; and a base plate joined to the dielectric substrate, when viewed from a direction perpendicular to the placement surface, the dielectric substrate has a protruding portion that protrudes more outward than the joint surface of the base plate, and a part of the adsorption electrode is disposed in the protruding portion.

2. The electrostatic chuck according to claim 1, characterized in that, it further includes an RF electrode disposed inside the dielectric substrate, when viewed from a direction perpendicular to the placement surface, the RF electrode is disposed within a range where its outer peripheral side end does not overflow from the outer peripheral side end of the adsorption electrode.

3. The electrostatic chuck according to claim 1, characterized in that, a ring-shaped protrusion, i.e., a sealing ring, whose tip forms a part of the placement surface, is formed on the dielectric substrate, when viewed from a direction perpendicular to the placement surface, at least a part of the sealing ring overlaps the adsorption electrode.

4. The electrostatic chuck according to claim 1, characterized in that, when viewed from a direction perpendicular to the placement surface, the base plate has: a first part that overlaps with the outer peripheral side end of the placement surface; and a second part that is closer to the outer peripheral side than the first part, inside each of the first part and the second part, a cooling medium flow path through which a cooling medium passes is formed, the cooling medium flow path is formed such that the cooling performance of the first part is higher than that of the second part.

5. The electrostatic chuck according to claim 4, characterized in that, The width of the cooling medium flow path in the first part is smaller than the width of the cooling medium flow path in the second part.

6. The electrostatic chuck according to claim 4, characterized in that, when the distance in the direction perpendicular to the placement surface and the distance between the cooling medium flow path and the placement surface is defined as the cooling medium distance, the cooling medium distance in the first part is smaller than the cooling medium distance in the second part.

7. The electrostatic chuck according to claim 4, characterized in that, when viewed from a direction perpendicular to the placement surface, at least one end of the cooling medium flow path is disposed at a position overlapping with the outer peripheral side end of the placement surface.

Images