Electrostatic chuck

Abstract

The invention provides an electrostatic chuck, which is provided with a flange part on a dielectric substrate, but can ensure the strength of the flange part. An electrostatic chuck (10) is provided with: a dielectric substrate (100); and a base plate (200) that is bonded to the dielectric substrate (100). The dielectric substrate (100) is provided with a flange part (150) which is a part of the side surface of the dielectric substrate (100), said part being on the base plate (200) side and protruding outward over the entire circumference. The base plate (200) has a surface closest to the dielectric substrate (100) side, and a part of the base plate (200) is bonded to a surface (210) of the dielectric substrate (100). In a plan view, a portion of the surface (210) that is not bonded to the dielectric substrate (100) surrounds the flange portion (150) over the entire circumference.

Description

Technical Field

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

[0002] For example, in semiconductor manufacturing apparatuses such as etching apparatuses, an electrostatic chuck is provided as an apparatus for adsorbing and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes: a dielectric substrate provided with adsorption electrodes; and a base plate that supports the dielectric substrate, having a structure in which these are joined to each other. If a voltage is applied to the adsorption electrodes, an electrostatic force is generated to adsorb and hold the substrate placed on the dielectric substrate.

[0003] When viewed from above, the outer shape of the dielectric substrate is usually the same as the outer shape of the placement surface on which the substrate is placed. That is, the dielectric substrate is usually made into a thin cylindrical shape. However, in such a structure, the side surface of the bonding layer that joins the dielectric substrate and the base plate is exposed directly below the outer peripheral end of the placement surface. At a position on the placement surface close to the substrate, it is not preferable, for example, that the bonding layer such as a cured silicone adhesive is exposed.

[0004] Thus, as described in Patent Document 1 below, a structure in which a flange portion is provided on the dielectric substrate is sometimes adopted. The flange portion is a portion that causes a portion of the side surface of the dielectric substrate on the base plate side to project outward over the entire circumference. In the structure described in Patent Document 1 below, the flange portion extends to a position covering the entire upper surface of the base plate.

[0005] When a flange portion is provided on the dielectric substrate, the side surface of the bonding layer is exposed at a position closer to the outer periphery than the outer peripheral end of the placement surface. Thus, the exposed portion of the bonding layer can be made farther from the substrate than when no flange portion is provided on the dielectric substrate.

[0006] Patent Document Patent Document 1: International Publication No. 2022 / 255118 Summary of the Invention

[0007] In recent years, with the miniaturization and high performance of semiconductor devices, requirements such as cooling performance required for electrostatic chucks have increased dramatically. Along with this, the dielectric substrate has become thinner than before, and there is a dielectric substrate having a thickness less than 4 mm.

[0008] When a flange portion is provided on the dielectric substrate, the thickness of the flange portion becomes thinner, for example, it is required to be 1.5 mm or less. Since it is considered that the thinning of the dielectric substrate will also progress in the future, it may be difficult to sufficiently ensure its strength depending on the shape of the flange portion.

[0009] 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 ensure the strength of the flange portion even though it has a structure in which a flange portion is provided on a dielectric substrate.

[0010] 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; and a base plate joined to the dielectric substrate. A flange portion is provided on the dielectric substrate, and a portion on the base plate side in the side surface protrudes outward over the entire circumference. The base plate has a flat surface closest to the dielectric substrate side and a part of it is joined to the dielectric substrate. When viewed from a direction perpendicular to the placement surface, the portion of the flat surface that is not joined to the dielectric substrate surrounds the flange portion over the entire circumference.

[0011] In the electrostatic chuck having such a structure, the flange portion of the dielectric substrate does not extend to a position covering the entire flat surface in the base plate. That is, the protruding amount of the flange portion toward the outer peripheral side is limited so that the flat surface surrounds the periphery of the flange portion in an exposed state. By adopting such a structure, compared with the structure in which the flange portion protrudes to a position covering the entire flat surface, the strength of the flange portion can be ensured.

[0012] According to the present invention, it is possible to provide an electrostatic chuck that can ensure the strength of the flange portion even though it has a structure in which a flange portion is provided on a dielectric substrate. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a cross-sectional view schematically showing the structure of the electrostatic chuck according to the present embodiment. Figure 2 It is a cross-sectional view showing in detail the structure of the flange portion and its vicinity. Figure 3 It is a cross-sectional view showing in detail the structure of the flange portion and its vicinity. Figure 4 It is a view schematically showing the structure of the cooling medium flow path formed in the base plate. Figure 5 It is a cross-sectional view showing in detail the structure of the flange portion and its vicinity of the electrostatic chuck according to the modification. SYMBOL DESCRIPTION 10 - Electrostatic chuck; 100 - Dielectric substrate; 110 - Surface; 150 - Flange portion; 200 - Base plate; 210 - Surface; 250 - Cooling medium flow path; W - Substrate. DETAILED DESCRIPTION OF THE EMBODIMENT

[0014] Hereinafter, the present embodiment will be described with reference to the drawings. For ease of understanding the description, in each drawing, the same reference numerals are given to the same components as much as possible and redundant descriptions are omitted.

[0015] 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.

[0016] Figure 1 FIG. shows a patterned cross-sectional view of the structure of the electrostatic chuck 10 in a state where the substrate W is adsorbed and held. The electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200.

[0017] 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.

[0018] 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 view observation". The diameter of the surface 110 is, for example, 290 to 300 mm. The overall thickness of the dielectric substrate 100 is, for example, 1 to 5 mm.

[0019] 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 disposed 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 externally applied to the adsorption electrode 130 from a power supply circuit (not shown), an electrostatic force is generated between the surface 110 and the substrate W, whereby 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.

[0020] The depth of the position where the adsorption electrode 130 is disposed, that is, the distance from the bottom surface 116 described later to the adsorption electrode 130 is, for example, 0.1 to 0.5 mm. The distance from the outer peripheral side end of the adsorption electrode 130 to the outer side surface of the dielectric substrate 100 (the outer side surface of the portion other than the flange portion 202) is, for example, 0.1 to 3 mm.

[0021] Inside the dielectric substrate 100, in addition to the above-described adsorption electrode 130, an RF electrode may be buried. In a semiconductor manufacturing apparatus, the RF electrode 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 used for processes such as film formation or etching of the substrate W. Preferably, the RF electrode is buried at a position where the distance from the surface 120 is, for example, 0.1 to 4.5 mm. Preferably, the distance from the adsorption electrode 130 to the RF electrode is, for example, 0.2 to 2 mm. Preferably, the distance from the outer peripheral side end of the RF electrode to the outer side surface of the dielectric substrate 100 is ensured to be, for example, about 0.1 to 5 mm.

[0022] As Figure 1 shown, a space SP is formed between the dielectric substrate 100 and the substrate W. When performing a process such as etching in the semiconductor manufacturing apparatus, helium for temperature adjustment is supplied from the outside to the space SP through a gas hole (not shown). By making helium exist 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. Further, the gas for temperature adjustment supplied to the space SP may be a gas different from helium.

[0023] A sealing ring 111 and dots 112 are provided on the placement surface, that is, the surface 110, and the above-described space SP is formed around these.

[0024] The sealing ring 111 is a wall that divides the space SP at the outermost peripheral position. The upper end of the sealing ring 111 becomes a part of the surface 110 and abuts against the substrate W. Further, a plurality of sealing rings 111 may be provided so as to divide the space SP. With such a structure, the pressure of helium in each space SP can be adjusted independently, and the surface temperature distribution of the substrate W can be made uniform during the process.

[0025] Figure 1 In, 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 dots 112 described later, is formed as a result of digging a part of the surface 110 to the position of the bottom surface 116.

[0026] 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 upper ends of the respective points 112 become a part of the surface 110 and abut against the substrate W. By providing a plurality of such points 112, the substrate W is prevented from being deflected.

[0027] A flange portion 150 is provided on the dielectric substrate 100. The flange portion 150 is a portion having a shape in which a portion of the side surface of the dielectric substrate 100 on the base plate 200 side protrudes outward over the entire circumference. Thus, the overall shape of the dielectric substrate 100 does not have a simple (thin) cylindrical shape. By providing the flange portion 150, the bonding surface, i.e., the surface 120, is larger than the placement surface, i.e., the surface 110. When viewed from above, the center of the surface 110 coincides with the center of the surface 120. The outer shape of the surface 120 when viewed from above coincides with the outer shape of the flange portion 150 when viewed from above. The thickness of the flange portion 150 is, for example, 0.5 to 4 mm.

[0028] 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 bonded to the surface 120 of the dielectric substrate 100 by the bonding layer 300. In the base plate 200, Figure 1 a part of the upper surface 210 thereof becomes the "bonding surface" bonded to the dielectric substrate 100. The overall thickness of the base plate 200 is, for example, 30 to 40 mm.

[0029] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200 and bonds the two. The bonding 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-described adhesive. However, the bonding 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 bonding layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[0030] The surface 210 of the base plate 200 is the "flat surface" closest to the dielectric substrate 100 side in the base plate 200. In the present embodiment, the shape of the base plate 200 is a substantially cylindrical shape. Therefore, the entire surface on the dielectric substrate 100 side in the base plate 200 becomes a flat surface, i.e., the surface 210. In other words, the outer shape of the surface 210 (flat surface) when viewed from above coincides with the outer shape of the base plate 200 when viewed from above. The diameter of the surface 210 is, for example, 300 to 360 mm.

[0031] As described previously, a part of the surface 210 is joined to the dielectric substrate 100 by the joining layer 300. When viewed from above, the center of the surface 210 coincides with the center of the surface 110. The outer shape of the surface 210 when viewed from above is larger than the outer shape of the flange portion 150 when viewed from above. Therefore, when viewed from above, the portion of the surface 210 that is not joined to the dielectric substrate 100 surrounds the flange portion 150 from the outside over the entire circumference.

[0032] In the present embodiment, an insulating film 230 is formed on the surface of the base plate 200 ( Figure 1 not shown in the figure, refer to Figure 2 ). As the insulating film 230, for example, a film of aluminum oxide formed by sputtering can be used. By covering the surface of the base plate 200 with the insulating film 230, the dielectric breakdown voltage of the base plate 200 can be improved.

[0033] Preferably, the insulating film 230 is formed to cover at least the entire surface of the surface of the base plate 200 that faces the dielectric substrate 100. In the present embodiment, the entire surface of the surface 210, which is "the surface of the base plate 200 closest to the dielectric substrate 100 side", becomes the surface of the insulating film 230. The thickness of the insulating film 230 is, for example, 1 mm or less. Although the thickness of the insulating film 230 can be uniform as a whole, it can also be made to have different thicknesses depending on different positions. For example, the thickness of the portion of the insulating film 230 that contacts the joining layer 300 can be smaller than the thickness of the insulating film 230 located around it.

[0034] When the occurrence of dielectric breakdown can be prevented by other methods, the insulating film 230 may not be formed on the base plate 200. In this case, it can be said that the surface 210, which is "the surface of the base plate 200 closest to the dielectric substrate 100 side", is the surface of the metal portion of the base plate 200.

[0035] 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 a semiconductor manufacturing apparatus, the coolant is supplied from the outside to the coolant flow path 250, thereby cooling the base plate 200. During the 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, 256 ( Figure 1 not shown in the figure, refer to Figure 4 ) formed on the surface 220 opposite to the surface 210. The specific structure of the coolant flow path 250 will be described later.

[0036] When processing a substrate W in a semiconductor manufacturing apparatus, a focus ring (not shown in the figure) is provided in a portion of the surface 210 that is not bonded to the dielectric substrate 100. Figure 1 The dotted line labeled "FR" in Figure 2 indicates the portion where the focus ring is provided. Hereinafter, the focus ring provided at such a position is also referred to as "focus ring FR". The focus ring FR is a circular and plate-like member formed of an insulating material such as quartz, and is provided for the purpose of adjusting the plasma distribution during processing. Substantially the entire dielectric substrate 100 is in a state of being surrounded by the focus ring FR from the outer peripheral side. Figure 2 In the present embodiment, the diameter of the surface 210 is relatively large, and substantially the entire focus ring FR is supported from below by the surface 210. The cooling medium flow path 250 is formed not only in the range directly below the placement surface, that is, the surface 110, but also in the range directly below the focus ring FR. The portion near the outer peripheral end portion of the substrate W is cooled not only by the dielectric substrate 100 but also by the focus ring FR. Preferably, a heat transfer gel is provided between the surface 210 of the base plate 200 and the focus ring FR so as to efficiently cool the focus ring FR through the base plate 200.

[0037] For the sake of convenience of explanation, hereinafter, the outer peripheral end portion of the placement surface, that is, the surface 110, is also referred to as "end portion E1". When viewed from above, the end portion E1 forms a circular ridge line, but in a part (for example, the positioning edge portion), it can also form a non-circular ridge line.

[0038] In addition, hereinafter, the portion of the bonding layer 300 that is exposed to the outside at the outermost peripheral end portion is also referred to as "exposed portion E2".

[0039] When processing the substrate W such as etching, the end portion of the bonding layer 300 is exposed to the plasma, ages, and scatters, which may have an adverse effect on the substrate W being processed. For example, when the flange portion 150 is not provided on the dielectric substrate 100, the exposed portion E2 of the bonding layer 300 is exposed at a position directly below the end portion E1. Since the distance from the exposed portion E2 to the end portion E1 is relatively short, the influence on the substrate W as described above may become large.

[0040] Therefore, in the electrostatic chuck 10 according to the present embodiment, the flange portion 150 is provided on the dielectric substrate 100. The exposed portion E2 is arranged at a position closer to the outer peripheral side than directly below the end portion E1. As a result, the distance from the exposed portion E2 to the end portion E1 becomes longer, and thus the influence on the substrate W as described above can be suppressed.

[0041]

[0042] ​It is also possible to consider extending the flange portion 150 to a position that overlaps with the outer peripheral end of the surface 210 when viewed from above, so that the entire surface 210 is covered by the dielectric substrate 100. However, when such a structure is formed, it is difficult to sufficiently ensure the strength of the flange portion 150, and there is a possibility of breakage of the flange portion 150 due to thermal expansion.

[0043] As described above, the overall thickness of the dielectric substrate 100 is about 1 to 5 mm, and the thickness of the flange portion 150 is only about 0.5 to 4 mm. In recent years, the requirements for the cooling performance and the like of the electrostatic chuck 10 have increased. Therefore, it is considered that the thinning of the dielectric substrate 100 and the flange portion 150 will also be promoted in the future. Thus, when the flange portion 150 is extended greatly toward the outer peripheral side, the possibility of breakage of the flange portion 150 as described above is further increased. In addition, the processing of the flange portion 150 becomes difficult.

[0044] Therefore, in the electrostatic chuck 10 according to the present embodiment, the flange portion 150 is not extended to a position that covers the entire surface 210 (flat surface) of the base plate 200. That is, the protruding amount of the flange portion 150 toward the outer peripheral side is limited so that the surface 210 surrounds the periphery of the flange portion 150 in an exposed state. By forming such a structure, compared with the structure in which the flange portion 150 protrudes to a position that covers the entire surface 210, the strength of the flange portion 150 can be ensured.

[0045] Figure 3 is from Figure 2 FIG. that omits the illustration of the focusing ring FR and depicts the dimensions of "L1" and "L2" instead. Figure 3 The "L1" shown in the figure represents the length of the flange portion 150 in the radial direction, that is, the protruding amount of the flange portion 150 toward the outer peripheral side. The "L2" shown in the figure represents the length of the portion of the surface 210 (flat surface) that is not joined to the dielectric substrate 100 in the radial direction.

[0046] In the present embodiment, the flange portion 150 is provided such that the length (L1) of the flange portion 150 in the radial direction is smaller than the length (L2) of the portion of the surface 210 that is not joined to the dielectric substrate 100 in the radial direction. L1 is, for example, 1 to 10 mm. L2 is, for example, 20 to 30 mm.

[0047] The reason for this will be described. As Figure 2As shown, at a position directly above the flange portion 150, a part of the focusing ring FR is arranged in the present embodiment. As described above, it is preferable to provide a heat transfer gel between the surface 210 of the base plate 200 and the focusing ring FR. On the other hand, it is usually difficult to provide a heat transfer gel between the flange portion 150 and the focusing ring FR arranged directly above it. Since the thermal resistance between the two remains large due to the absence of the gel, sometimes the portion arranged directly above the flange portion 150 cannot be sufficiently cooled. As a result, the temperature of the focusing ring FR may locally rise.

[0048] Therefore, in the present embodiment, the length of the flange portion 150 in the radial direction is limited to the minimum necessary so that L1 < L2 as described above. Since the area directly above the flange portion 150, that is, the area that is difficult to be sufficiently cooled by the flange portion 150, becomes narrower, the temperature of the member arranged directly above the flange portion 150 can be adjusted more stably.

[0049] Moreover, directly above the flange portion 150, a part of the focusing ring FR can be arranged as in the present embodiment, or other members that are not the focusing ring FR can be arranged. In any case, the flange portion 150 is formed in such a way that the condition L1 < L2 is satisfied, so that the temperature of the flange portion 150 and the member arranged directly above it can be controlled more stably.

[0050] Figure 4 In [the figure], the structure of the cooling medium flow path 250 formed inside the base plate 200 when viewed from above is schematically depicted. As described above, 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 openings 255 and 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.

[0051] Figure 4 In [the figure], the circular dotted line marked with the symbol "DL1" indicates the position of the outer peripheral side end of the flange portion 150. The circular dotted line marked with the symbol "DL2" indicates the position of the inner peripheral side end of the flange portion 150. The area between the dotted line DL1 and the dotted line DL2 becomes the area that overlaps with the flange portion 150 when viewed from above. As Figure 4 shown, a part of the cooling medium flow path 250 (the part marked with the symbol "251") is formed to overlap with the flange portion 150 when viewed from above and extend in an arc shape along the flange portion 150.

[0052] By forming such a structure, the flange portion 150 can be efficiently cooled through the cooling medium flow path 250. By sufficiently cooling the flange portion 150 and the member directly above it, the temperature rise of these can be suppressed. In addition, the temperature rise of the outer peripheral side portion of the substrate W can also be suppressed.

[0053] As described above, in the present embodiment, the shape of the base plate 200 is substantially cylindrical, and the outer shape of the surface 210 (flat surface) in a plan view is the same as the outer shape of the base plate 200 in a plan view. However, the outer shapes of the two may also be different from each other.

[0054] For example, as Figure 5 In the modified example shown, the outer shape of the surface 210 in a plan view may also be smaller than the outer shape of the base plate 200 in a plan view. In this figure, the portion marked with the symbol "240" is the portion of the base plate 200 that is closer to the outer peripheral side than the surface 210, and is a recess formed so as to recede toward the opposite side of the dielectric substrate 100.

[0055] Even in this modified example, the surface 210 conforms to the "flat surface" of the base plate 200 that is closest to the dielectric substrate 100 side. Similar to the present embodiment, when viewed from above, the portion of the surface 210 (flat surface) that is not joined to the dielectric substrate 100 surrounds the flange portion 150 from the outside over the entire circumference. Even when such a structure is formed, the same effects as those described in the present embodiment can be achieved.

[0056] However, in Figure 5 In the modified example, the thickness of the focusing ring FR (not shown) needs to be increased directly above the portion marked with the symbol "240". Therefore, compared with the present embodiment, it may be difficult to adjust the temperature of the focusing ring FR. In view of this, as in the present embodiment, it is preferable that the outer shape of the surface 210 (flat surface) in a plan view is the same as the outer shape of the base plate 200 in a plan view.

[0057] As described above, 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 techniques 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. of each of the foregoing specific examples are not limited to the illustrated content, but can be appropriately changed. As long as there is no technical contradiction, the elements of each of 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; and a base plate joined to the dielectric substrate, a flange portion is provided on the dielectric substrate, and a portion on the side of the base plate in its side surfaces protrudes outward over the entire circumference; the base plate has a flat surface closest to the dielectric substrate side and a part of it is joined to the dielectric substrate, when viewed from a direction perpendicular to the placement surface, the portion of the flat surface not joined to the dielectric substrate surrounds the flange portion over the entire circumference.

2. The electrostatic chuck according to claim 1, characterized in that, when viewed from a direction perpendicular to the placement surface, the outer shape of the flat surface is the same as the outer shape of the base plate.

3. The electrostatic chuck according to claim 1, characterized in that, a cooling medium flow path for allowing a cooling medium to pass through is formed inside the base plate, when viewed from a direction perpendicular to the placement surface, a part of the cooling medium flow path is formed to overlap with the flange portion and extend along the flange portion.

4. The electrostatic chuck according to claim 1, characterized in that, the length of the flange portion in the radial direction, is less than the length of the portion of the flat surface not joined to the dielectric substrate in the radial direction.

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