Electrostatic chuck

Abstract

To provide an electrostatic chuck capable of suppressing occurrence of dielectric breakdown in the vicinity of a bonding layer.SOLUTION: An electrostatic chuck 10 includes: a dielectric substrate 100; a base plate 200 formed of a metal material; and a bonding layer 300 that bonds the dielectric substrate 100 and the base plate 200. At least a portion of the base plate 200 facing the bonding layer 300 is covered with a ceramic film 231, and a surface of the ceramic film 231 serves as a surface S to be bonded. The surface S to be bonded satisfies at least one of: a first condition of an arithmetic average height (Sa)=≤1.5 μm; and a second condition of a root mean square height (Sq)=≤2.0 μm, and satisfies at least one of: a third condition of a maximum valley depth (Sv)=≥20.0 μm; and a fourth condition of maximum height (Sz)=≥20.0 μm.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, in a semiconductor manufacturing device such as an etching device, an electrostatic chuck is provided as a device for attracting and holding a substrate such as a silicon wafer to be processed. As described in the following Patent Document 1, the electrostatic chuck includes a dielectric substrate provided with an attraction electrode and a base plate supporting the dielectric substrate, which are bonded together. The dielectric substrate and the base plate are bonded together via a bonding layer such as a silicone adhesive. When a voltage is applied to the attraction electrode, an electrostatic force is generated, and a substrate placed on the dielectric substrate is attracted and held. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-287344 Summary of the Invention [Problem to be solved by the invention]

[0004] When a process such as etching is performed in a semiconductor manufacturing device, the temperature of the substrate rises due to exposure to plasma, and the temperature of the dielectric substrate also rises. Meanwhile, a low-temperature coolant is supplied to the base plate, so the temperature of the base plate may drop to -60°C or even lower. Due to the temperature changes of each part associated with the substrate processing and the temperature difference between the dielectric substrate and the base plate, a large thermal stress is applied to the bonding layer and its neighboring parts.

[0005] If a part of the bonding layer peels off from the surface of the base plate due to thermal stress, the surface of the base plate becomes exposed, which may result in dielectric breakdown between the exposed part and the surrounding members.

[0006] Incidentally, the portion of the surface of the base plate that is exposed due to the peeling of the bonding layer as described above may be covered in advance with a ceramic film formed by thermal spraying, etc. However, there may be cases where such a ceramic film alone is not able to prevent dielectric breakdown when the bonding layer peels off.

[0007] The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrostatic chuck capable of suppressing the occurrence of dielectric breakdown in the vicinity of a bonding layer. [Means for solving the problem]

[0008] In order to solve the above problems, the electrostatic chuck according to the present invention includes a dielectric substrate, a base plate made of a metal material, and a bonding layer bonding the dielectric substrate and the base plate. At least a portion of the base plate facing the bonding layer is covered with a ceramic film, and a surface of the ceramic film serves as a bonding surface. The surfaces to be joined are First condition: arithmetic mean height (Sa) ≦ 1.5 μm Second condition: root mean square height (Sq) ≦ 2.0 μm At least one of the first and second conditions is satisfied, and Third condition: Maximum valley depth (Sv) ≥ 20.0 μm Fourth condition: Maximum height (Sz) ≧ 20.0 μm At least one of the above third and fourth conditions is satisfied.

[0009] Among the above conditions that the surface shape of the bonded surfaces must satisfy, the first and second conditions both stipulate that the bonded surfaces must be smooth. If the bonded surfaces are smooth enough to satisfy at least one of the first and second conditions, the thickness of the bonding layer will be generally uniform throughout, and the thermal resistance of the bonding layer will also be generally uniform. This allows the temperature distribution within the substrate during processing to be uniform.

[0010] On the other hand, the third and fourth conditions both require that a relatively deep recess be formed on the bonded surface. If the recess is formed on the bonded surface to such an extent that at least one of the third and fourth conditions is satisfied, the uncured adhesive will enter the recess when bonding the dielectric substrate and the base plate, and then harden. This will increase the so-called "anchor effect," and therefore the bonding strength between the bonding layer and the bonded surface (i.e., the ceramic film) will be greater.

[0011] In this manner, in the electrostatic chuck having the above-described configuration, the shape of the joining surface of the ceramic film can be designed to satisfy predetermined conditions, thereby making it possible to sufficiently increase the bonding strength between the joining layer and the joining surface due to the anchor effect while suppressing variation in the thickness of the joining layer.

[0012] If a large thermal stress is applied to the bonding layer or its vicinity during processing of the substrate, the bonding layer will peel off at the interface on the dielectric substrate side before peeling off at the interface on the ceramic film side, or will break inside the bonding layer. In either case, the bonded surface of the ceramic film will remain entirely covered with the bonding layer, and will not be exposed to the outside due to peeling of the bonding layer. This makes it possible to sufficiently suppress the occurrence of dielectric breakdown near the bonding layer, specifically, dielectric breakdown through the exposed portion of the ceramic film. Effect of the Invention

[0013] According to the present invention, it is possible to provide an electrostatic chuck capable of suppressing the occurrence of dielectric breakdown in the vicinity of a bonding layer. [Brief description of the drawings]

[0014] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of an electrostatic chuck according to an embodiment of the present invention. [Diagram 2] 2 is a diagram showing a schematic cross-sectional shape of a joining surface of a ceramic film. FIG. [Diagram 3] 13A and 13B are diagrams for explaining peeling of a bonding layer. [Figure 4] 1 is a table showing evaluation results for various ceramic membranes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0015] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0016] The electrostatic chuck 10 according to this embodiment is configured to electrostatically attract and hold a substrate W to be processed inside a semiconductor manufacturing apparatus (not shown), such as an etching apparatus. The substrate W is, for example, a silicon wafer. The electrostatic chuck 10 may be used in an apparatus other than a semiconductor manufacturing apparatus.

[0017] 1 shows, in a schematic cross-sectional view, the configuration of an electrostatic chuck 10 in a state in which the electrostatic chuck 10 attracts and holds a substrate W. The electrostatic chuck 10 includes a dielectric substrate 100, a base plate 200, and a bonding layer 300.

[0018] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment.

[0019] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a surface bonded to a base plate 200 via a bonding layer 300 described below.

[0020] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin flat layer made of a metal material such as tungsten, and is embedded in the dielectric substrate 100 in a state parallel to the surface 110. The material of the adsorption electrode 130 may be tungsten, molybdenum, platinum, palladium, or the like. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply path (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. As the configuration of the power supply path, various known configurations can be adopted. The adsorption electrode 130 may be provided as a so-called "monopolar" electrode, as in this embodiment, or may be provided as two so-called "bipolar" electrodes.

[0021] As shown in Fig. 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When a process such as etching is performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP through a gas hole (not shown). By providing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, and the temperature of the substrate W is thereby maintained at an appropriate temperature. The temperature adjustment gas supplied to the space SP may be a type of gas other than helium.

[0022] A seal ring 111, dots 112, etc. are provided on a surface 110 that is a mounting surface, and the above-mentioned space SP is formed around these.

[0023] The seal ring 111 is a wall that divides the space SP at the outermost position. The upper end surface of the seal ring 111 forms part of the surface 110 and abuts against the substrate W. Note that a plurality of seal rings 111 may be provided to divide the space SP. With this configuration, it is possible to individually adjust the pressure of the helium gas in each space SP and make the surface temperature distribution of the substrate W during processing more uniform.

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

[0025] The dots 112 are circular protrusions protruding from the bottom surface 116. A plurality of dots 112 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The upper end of each dot 112 forms part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, bending 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. The upper surface 210 of the base plate 200 in FIG. 1 is a portion that faces the bonding layer 300. However, in this embodiment, the surface 210 and the bonding layer 300 are not directly bonded to each other, and a ceramic film 230 is interposed between them.

[0027] The ceramic film 230 is an insulating film formed so as to cover the surface of the base plate 200. For example, an alumina film formed by thermal spraying, an oxide coating formed by anodizing, or the like can be used as the ceramic film 230. By covering the surface of the base plate 200 with the ceramic film 230, the dielectric strength of the base plate 200 is increased.

[0028] The ceramic film 230 covers not only the surface 210 of the base plate 200 but also the side surfaces connected to the surface 210. Of the surfaces of the base plate 200, only the surface 220 opposite the surface 210 is not covered with the ceramic film 230. Instead of this embodiment, a configuration in which only the surface 210 is covered with the ceramic film 230 may be used.

[0029] Of the ceramic film 230, the portion covering the surface 210 is also particularly referred to as "ceramic film 231" hereinafter. The outer surface of the ceramic film 231 is the surface to be bonded to the dielectric substrate 100 via the bonding layer 300. This surface is also referred to as "bonded surface S" hereinafter.

[0030] As described above, in this embodiment, at least the portion (surface 210) of the base plate 200 facing the bonding layer 300 is covered with the ceramic film 231, and the surface of the ceramic film 231 serves as the surface S to be bonded.

[0031] A coolant flow path 250 for flowing a coolant is formed inside the base plate 200. When a process such as etching is performed in the semiconductor manufacturing apparatus, a coolant is supplied to the coolant flow path 250 from the outside, thereby cooling the base plate 200. Heat generated in the substrate W during the process is transferred to the coolant via 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.

[0032] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and bonds the two together. The bonding layer 300 is formed by curing an adhesive made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 may be formed by curing another type of adhesive. In any case, it is preferable to use a material with as high a thermal conductivity as possible as the material for the bonding layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[0033] In this embodiment, the bonding strength between the bonding layer 300 and the bonded surface S is increased by devising a shape of the bonded surface S of the ceramic film 231. Fig. 2 shows a schematic cross-sectional shape of the bonded surface S and its neighboring portion of the ceramic film 231. Since the ceramic film 231 of this embodiment is a film formed by thermal spraying, numerous projections and recesses are formed on the bonded surface S. The bonded surface S is formed so as to satisfy at least one of the following first and second conditions. First condition: arithmetic mean height (Sa) ≦ 1.5 μm Second condition: root mean square height (Sq) ≦ 2.0 μm

[0034] The "arithmetic mean height (Sa)" in the first condition is the arithmetic mean height (Ra) extended from a line to a surface. The arithmetic mean height (Sa) can be calculated as the absolute average value of the height differences at each position of the bonded surface S with respect to the average surface of the bonded surfaces S. The "root mean square height (Sq)" in the second condition can be calculated as the standard deviation of the height (distance) at each position of the bonded surface S with respect to the average surface of the bonded surfaces S. The definitions and measurement methods of the arithmetic mean height (Sa) and root mean square height (Sq) mentioned above can be as specified in ISO25178.

[0035] The above first and second conditions both stipulate that the bonded surface S must be a relatively smooth surface. The bonded surface S may satisfy both the first and second conditions, or may satisfy only one of the first and second conditions.

[0036] The thermal resistance of the bonding layer 300 is calculated by dividing the thickness (m) of the bonding layer 300 by the thermal conductivity (W / mK). If the bonding surface S is smooth enough to satisfy at least one of the first and second conditions, the thickness of the bonding layer 300 directly above it will be generally uniform throughout, and as a result, the thermal resistance of the bonding layer 300 will also be generally uniform. This allows the in-plane temperature distribution of the substrate W during processing to be uniform.

[0037] The bonded surface S is further formed so as to satisfy at least one of the following third and fourth conditions. Third condition: Maximum valley depth (Sv) ≥ 20.0 μm Fourth condition: Maximum height (Sz) ≧ 20.0 μm

[0038] The third condition, "maximum valley depth (Sv)," can be calculated as the absolute value of the minimum height at each position of the bonded surface S relative to the average plane of the bonded surfaces S. The fourth condition, "maximum height (Sz)," can be calculated as the distance from the highest point to the lowest point among each position of the bonded surface S (the distance along the direction perpendicular to the average plane of the bonded surfaces S). The definitions and measurement methods of the above maximum valley depth (Sv) and maximum height (Sz) can be as specified in ISO25178.

[0039] The third and fourth conditions above are both conditions that stipulate that relatively deep recesses are formed on the bonded surface S. In the example of Fig. 2, such recesses are formed at the positions indicated by the arrows on the bonded surface S. In view of the bonded surface S satisfying the first or second condition, in many cases, multiple recesses will be scattered and spaced apart from each other.

[0040] When a recess is formed on the joining surface S to such an extent that at least one of the third and fourth conditions is satisfied, the uncured adhesive enters the recess and then cures when the dielectric substrate 100 and the base plate 200 are joined. This increases the so-called "anchor effect," and therefore increases the bonding strength between the bonding layer 300 and the joining surface S.

[0041] In this manner, in the electrostatic chuck 10 according to this embodiment, the shape of the joining surface S of the ceramic film 231 is designed to satisfy the conditions described above, thereby suppressing the variation in the thickness of the joining layer 300 while sufficiently increasing the bonding strength between the joining layer 300 and the joining surface S due to the anchor effect.

[0042] If a large thermal stress is applied to the bonding layer 300 or a portion nearby during processing of the substrate W, there is a concern that the bonding layer 300 may peel off locally at the interface on either the dielectric substrate 100 side or the ceramic film 231 side. FIG. 3(A) shows a schematic example of a case in which the bonding layer 300 peels off at the interface on the ceramic film 231 side. In this case, a minute gap G1 is formed between the bonding layer 300 and the ceramic film 231, and a part of the bonded surface S is exposed to the outside through the gap G1. As a result, there is a possibility that dielectric breakdown may occur between the part and a surrounding member (for example, a part of a semiconductor manufacturing device).

[0043] Therefore, in the electrostatic chuck according to the present embodiment, the bonding surface S is formed so as to satisfy the above-mentioned conditions, thereby increasing the bonding strength between the bonding layer 300 and the bonding surface S. When a large thermal stress is applied to the bonding layer 300 or its neighboring parts, the bonding layer 300 of the present embodiment peels off at the interface on the dielectric substrate 100 side or breaks inside the bonding layer 300 before peeling off at the interface on the ceramic film 231 side. FIG. 3B shows a schematic example of a case where the bonding layer 300 peels off at the interface on the dielectric substrate 100 side. In this case, a minute gap G2 is formed between the bonding layer 300 and the dielectric substrate 100, but the bonding surface S of the ceramic film 231 is entirely covered with the bonding layer 300. Even when the bonding layer 300 is broken inside, the same state is obtained, so that the bonding surface S of the ceramic film 231 is not exposed to the outside due to peeling of the bonding layer 300. Therefore, the occurrence of dielectric breakdown in the vicinity of the bonding layer 300, specifically, dielectric breakdown through the exposed portion of the ceramic film 231, can be sufficiently suppressed.

[0044] When the electrostatic chuck 10 is attached to a semiconductor manufacturing apparatus, the ceramic film 230 is covered from the outside with other structural members (e.g., a focus ring, etc.) except for the ceramic film 231. Therefore, the possibility of dielectric breakdown occurring through the ceramic film 231 is low.

[0045] The larger the maximum valley depth (Sv) of the third condition and the maximum height (Sz) of the fourth condition, the greater the bonding strength between the bonding layer 300 and the bonded surface S due to the anchor effect. However, if these values ​​are made too large, the recesses in the bonded surface S become deeper and the porosity of the ceramic film 230 increases, so that dielectric breakdown through the ceramic film 230 may be more likely to occur. There is also a concern about leakage of helium gas through the ceramic film 230.

[0046] For this reason, it is preferable that the bonded surface S is formed so as to further satisfy at least one of the following fifth and sixth conditions. Fifth condition: Maximum valley depth (Sv) ≦ 100.0 μm Condition 6: Maximum height (Sz) ≦ 100.0 μm

[0047] If the bonded surface S is formed as described above, the recess will not be too deep, so that the occurrence of dielectric breakdown through the ceramic film 230 can be sufficiently suppressed.

[0048] The parameters of the arithmetic mean height (Sa) in the first condition, the root mean square height (Sq) in the second condition, the maximum valley depth (Sv) in the third condition, and the maximum height (Sz) in the fourth condition are all obtained by measuring the entire predetermined area of ​​the welded surface S as a "surface" using a roughness measuring device. The above "predetermined area" is set to 350,000 μm 2 It is preferable to measure an area having the above-mentioned size. By measuring the above-mentioned parameters for such an area and setting the shape of the joining surface S to satisfy the first condition, it is possible to sufficiently suppress the occurrence of dielectric breakdown without being affected by measurement errors.

[0049] In the technical field of forming ceramic films by thermal spraying, it is known that the porosity of the ceramic film changes depending on various film formation conditions. For example, the porosity of the formed ceramic film changes depending on the thermal spraying method, such as high-velocity flame spraying or plasma spraying, the particle size of the spraying material, and the like. By appropriately selecting such film formation conditions, it is possible to form a ceramic film 231 that satisfies the third condition, the fourth condition, the fifth condition, and the sixth condition. Thereafter, by performing polishing or the like on the bonded surface S as necessary, it is possible to form a shape that satisfies the first condition and the second condition.

[0050] The present inventors prepared a plurality of samples of the electrostatic chuck 10, each having a different shape of the joining surface S, and evaluated the bonding strength between the joining layer 300 and the joining surface S for each sample. The table in FIG. 4 shows a list of the evaluation results.

[0051] In all of Samples No. 1 to 8, an alumina film formed by thermal spraying was used as the ceramic film 230. The thermal spraying conditions were changed for each sample so that the surface shape of each ceramic film 230 was different. In Sample No. 9, an oxide coating (anodic oxide layer) formed by anodizing was used as the ceramic film 230.

[0052] The thickness of each ceramic film 230 was 125 μm for sample No. 1, 330 μm for samples No. 2 to 6, 200 μm for samples No. 7 and 8, and 300 μm for sample No. 9.

[0053] In the "Sa" column of FIG. 4, the results of measuring the arithmetic mean height (Sa) of the bonded surfaces S before bonding are shown in μm units. The "Sq" column shows the results of measuring the root mean square height (Sq) of the bonded surfaces S before bonding are shown in μm units. The "Sv" column shows the results of measuring the maximum valley depth (Sv) of the bonded surfaces S before bonding are shown in μm units. The "Sz" column shows the results of measuring the maximum valley depth (Sv) of the bonded surfaces S before bonding are shown in μm units. These parameters were measured by observing the bonded surfaces S of each sample at a magnification of 20 times using a laser microscope. The area of ​​the measured region was 378,449 μm for samples No. 1 to 4 and 6. 2 , and 375375μm for sample No.5. 2 , and 375291 μm for samples No. 7 to 9. 2 It was decided.

[0054] 4, samples No. 1 to 4 and 6 to 9 satisfy at least one of the first and second conditions described above, and therefore the bonded surface S is sufficiently smooth. Therefore, compared to sample No. 5 which does not satisfy the first and second conditions, the variation in thickness of the bonding layer 300 (i.e., the variation in thermal resistance) can be suppressed.

[0055] The inventors performed a thermal cycle test on each of the samples No. 1 to No. 9 shown in FIG. 4 (after bonding). The thermal cycle test was performed for 10 cycles between -60°C and 25°C. In the visual inspection immediately after the thermal cycle test, no partial peeling was observed in any of the samples No. 1 and No. 5 to No. 9. Partial peeling was observed in the other samples. After the visual inspection, a part of each sample was processed to a predetermined size, and a shear force was applied to break it, and the fracture surface was observed. The size after processing was 50 mm x 10 mm x 5 mm.

[0056] In the samples No. 1, 5, and 7, no fracture occurred at the interface between the bonding layer 300 and the bonded surface S, nor at the interface between the bonding layer 300 and the surface 120, but fracture occurred almost entirely inside the bonding layer 300. In other words, a so-called "cohesive failure" occurred. Therefore, the bonding strength between the bonding layer 300 and the bonded surface S of these samples was evaluated as "Excellent".

[0057] In samples No. 6, 8, and 9, there were some parts that had undergone cohesive failure as described above, and some parts that had broken at the interface between the bonding layer 300 and the surface 120, as in the example of Fig. 3(B). The entire surface S to be bonded remained covered with the bonding layer 300. Therefore, for these samples, the bonding strength between the bonding layer 300 and the surface S to be bonded was evaluated as "good."

[0058] Samples No. 1 and 5 to 9 satisfied at least one of the third and fourth conditions described above. The bonding strengths of these samples were evaluated as "good" or "excellent" as described above. However, sample No. 5 did not satisfy the fifth and sixth conditions described above. For this reason, the recesses formed in the ceramic film 230 were too deep, and therefore it is possible that dielectric breakdown through the ceramic film 230 cannot be sufficiently suppressed.

[0059] In samples No. 2 to 4, as shown in the example of Fig. 3(A), the interface between the bonding layer 300 and the bonded surface S was broken, and the bonded surface S was exposed. Therefore, for these samples, the bonding strength between the bonding layer 300 and the bonded surface S was evaluated as "x". Samples No. 2 to 4 did not satisfy either the third or fourth condition described above.

[0060] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0061] 10: Electrostatic chuck 100: Dielectric substrate 200: Base plate 210: Face 230, 231: Ceramic membrane 300: Bonding layer S: Surface to be joined

Claims

1. A dielectric substrate; A base plate formed of a metal material; a bonding layer that bonds the dielectric substrate and the base plate, At least a portion of the base plate facing the bonding layer is covered with a ceramic film, and a surface of the ceramic film serves as a bonding surface; The surface to be joined is First condition: arithmetic mean height (Sa)≦1.5 μm Second condition: root mean square height (Sq)≦2.0 μm At least one of the first and second conditions is satisfied, and Third condition: maximum valley depth (Sv) ≧ 20.0 μm Fourth condition: maximum height (Sz) ≧ 20.0 μm An electrostatic chuck that satisfies at least one of the above third and fourth conditions.

2. The surface to be joined is Fifth condition: maximum valley depth (Sv)≦100.0 μm Sixth condition: maximum height (Sz)≦100.0 μm 2. The electrostatic chuck according to claim 1, which satisfies at least one of the above fifth and sixth conditions.

3. 2. The electrostatic chuck according to claim 1, wherein the ceramic film is a film formed by thermal spraying.

4. The arithmetic mean height (Sa) under the first condition, The maximum valley depth (Sv) under the second condition, The root mean square height (Sq) under the third condition, and The maximum height (Sz) in the fourth condition is, Of the surfaces to be joined, 350,000 μm ２ 2. The electrostatic chuck according to claim 1, wherein the value is obtained by measuring an entire area having an area of ​​at least 20 mm.

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