Holding device and electrostatic chuck

Abstract

[Problem] To provide a technique for reducing the thermal resistance of a bonding layer. [Solution] The retaining device is characterized by satisfying at least one of the following conditions (A) to (C). Condition (A): It contains filler that contacts a retaining member or a base member. Condition (B): When the ratio of the total cross-sectional area of ​​the filler occupying a range of 1 μm or less from the interface with the retaining member and the interface with the base member in the bonding layer is set as a first ratio and a second ratio, and the ratio of the total cross-sectional area of ​​the filler occupying a range of 30% or less of the thickness of the bonding layer from the center of the bonding layer towards the retaining member and towards the base member in the thickness direction is set as a third ratio, at least one of the value obtained by dividing the first ratio by the third ratio and the value obtained by dividing the second ratio by the third ratio is 0.5 or more. Condition (C): The filler with an aspect ratio of 1.4 or more is more numerous than the filler with an aspect ratio of less than 1.4.

Description

Technical Field

[0001] The present invention relates to a holding device and an electrostatic chuck. Prior Art

[0002] There is known a holding member that holds an object by electrostatic attraction. For example, Patent Document 1 discloses an electrostatic chuck that includes such a holding member, a base member, and a bonding layer that bonds the holding member and the base member. This bonding layer includes a first resin layer containing a filler and a second resin layer not containing a filler, and the second resin layer is disposed between the first resin layer and the holding member and between the first resin layer and the base member. [Prior Art Documents] [Patent Documents]

[0003] [Patent Document 1] Japanese Patent No. 6321522 Summary of the Invention

[0004] [Problems to be Solved by the Invention]

[0005] In the electrostatic chuck described in Patent Document 1, a second resin layer having a lower thermal conductivity than the first resin layer due to not containing a filler is present at the interface with the holding member and the interface with the base member in the bonding layer, so that the thermal resistance of the bonding layer becomes large. Therefore, there is room for improvement in reducing the thermal resistance of the bonding layer.

[0006] The present invention has been completed to solve at least a part of the above problems, and an object thereof is to provide a technique for reducing the thermal resistance of a bonding layer. [Means for Solving the Problems]

[0007] The present invention has been made to solve at least a part of the above problems and can be realized in the following form. (1) According to one aspect of the present invention, there is provided a holding device including: a holding member having a holding surface for holding an object; a base member disposed on a side opposite to the side of the holding surface in the holding member; and a bonding layer that bonds the holding member and the base member and includes a plurality of fillers, wherein the holding device is characterized in that: at least one of the following conditions (A) to (C) is satisfied: Condition (A): The aforementioned filler includes at least one of a first filler in contact with the aforementioned holding member and a second filler in contact with the aforementioned base member. Condition (B): Let the ratio of the total cross-sectional area of the aforementioned filler occupying the range within 1 μm from the interface with the aforementioned holding member in the aforementioned bonding layer be the first ratio; let the ratio of the total cross-sectional area of the aforementioned filler occupying the range within 1 μm from the interface with the aforementioned base member in the aforementioned bonding layer be the second ratio; when the ratio of the total cross-sectional area of the aforementioned filler occupying the range within 30% of the thickness of the aforementioned bonding layer from the center in the thickness direction of the aforementioned bonding layer toward the aforementioned holding member side and the range within 30% of the thickness of the aforementioned bonding layer from the center toward the aforementioned base member side is the third ratio, at least one of the value obtained by dividing the aforementioned first ratio by the aforementioned third ratio and the value obtained by dividing the aforementioned second ratio by the aforementioned third ratio is 0.5 or more. Condition (C): Among the aforementioned fillers, the number of the aforementioned fillers with an aspect ratio of 1.4 or more is more than the number of the aforementioned fillers with an aspect ratio less than 1.4.

[0008] According to this configuration, the holding device satisfies at least one of conditions (A) to (C). In the case of satisfying condition (A), since the filler with a relatively high thermal conductivity is in contact with at least one of the holding member and the base member, the thermal resistance at at least one of the interface between the bonding layer and the holding member and the interface between the bonding layer and the base member can be reduced. In the case of satisfying condition (B), in at least one of the range within 1 μm from the interface with the holding member in the bonding layer and the range within 1 μm from the interface with the base member in the bonding layer, there are more fillers, so the thermal resistance near at least one of the interface between the bonding layer and the holding member and the interface between the bonding layer and the base member can be reduced. In the case of satisfying condition (C), since the number of fillers with an aspect ratio of 1.4 or more in the filler included in the bonding layer is more than the number of fillers with an aspect ratio less than 1.4, heat can be transferred in the thickness direction of the bonding layer with fewer fillers, so flexibility can be maintained and the thermal resistance of the bonding layer can be reduced. Thus, by satisfying at least one of conditions (A) to (C), the thermal resistance of the bonding layer can be reduced.

[0009] (2) In the holding device of the above-described form, it is also possible that the aforementioned holding device satisfies at least the aforementioned condition (A), and at least one of the first filler and the second filler included in the aforementioned bonding layer contains a large-diameter filler having a particle diameter larger than the average particle diameter of the aforementioned filler. According to this configuration, since at least one of the first filler and the second filler included in the bonding layer contains a large-diameter filler, heat can be transferred from the interface in the thickness direction of the bonding layer. As a result, the thermal resistance at the interface can be further reduced.

[0010] (3) In the holding device of the above form, the holding device satisfies at least the above condition (A), and at least one of the first filler and the second filler included in the bonding layer may also contain a small-diameter filler having a particle diameter smaller than the above average particle diameter. According to this configuration, since at least one of the first filler and the second filler included in the bonding layer contains not only a large-diameter filler but also a small-diameter filler, the number of fillers in contact with the holding member or the base member is large, so heat can be more easily transferred from the interface in the thickness direction of the bonding layer.

[0011] (4) In the holding device of the above form, it is also possible that the holding device satisfies at least the above condition (A), and for at least one of the first filler and the second filler included in the bonding layer, the total cross-sectional area of the large-diameter fillers is larger than the total cross-sectional area of the small-diameter fillers. According to this configuration, for at least one of the first filler and the second filler included in the bonding layer, the amount of the large-diameter filler is guaranteed to a certain extent relative to the amount of the small-diameter filler, so the effect of reducing the thermal resistance of the interface caused by the large-diameter filler can be guaranteed.

[0012] (5) In the holding device of the above form, it is also possible that the holding device satisfies at least the above condition (A), and at least one of the first filler and the second filler included in the bonding layer contains the above filler having an aspect ratio of 1.4 or more. According to this configuration, since at least one of the first filler and the second filler included in the bonding layer contains a filler having an aspect ratio of 1.4 or more, heat can be easily transferred from the interface in the thickness direction of the bonding layer. As a result, the thermal resistance of the interface can be further reduced.

[0013] (6) In the holding device of the above form, it is also possible that the holding device satisfies at least the above condition (A), and at least one of the first filler and the second filler included in the bonding layer contains the above filler having an aspect ratio of less than 1.4. According to this configuration, since at least one of the first filler and the second filler included in the bonding layer contains not only a filler having an aspect ratio of 1.4 or more but also a filler having an aspect ratio of less than 1.4, the number of fillers in contact with the holding member or the base member is large, so heat can be more easily transferred from the interface in the thickness direction of the bonding layer.

[0014] (7) In the holding device of the above-described form, it is also possible that the above-described holding device satisfies at least the above-described condition (A). For at least one of the first filler and the second filler included in the above-described bonding layer, the sum of the cross-sectional areas of the above-described fillers having an aspect ratio of 1.4 or more is greater than the sum of the cross-sectional areas of the above-described fillers having an aspect ratio less than 1.4. According to this configuration, for at least one of the first filler and the second filler included in the bonding layer, the amount of the filler having an aspect ratio of 1.4 or more is guaranteed to a certain extent with respect to the amount of the filler having an aspect ratio less than 1.4. Therefore, it is possible to guarantee a reduction in the thermal resistance of the interface caused by the filler having an aspect ratio of 1.4 or more.

[0015] (8) In the holding device of the above-described form, it is also possible that the above-described holding device satisfies at least the above-described condition (A); at least one of the portion of the above-described holding member that is bonded to the above-described bonding layer and the portion of the above-described base member that is bonded to the above-described bonding layer is formed with a recess that is recessed deeper than the above-described average particle diameter; the depth of the above-described recess is greater than the average particle diameter of the above-described filler, and the above-described recess is filled with the above-described bonding layer; a large-diameter filler having a particle diameter larger than the average particle diameter of the above-described filler is in contact with the surface that defines the above-described recess. According to this configuration, since the formation of the recess results in an enlarged surface area, it is possible to reduce the thermal resistance of at least one of the interface between the holding member and the bonding layer and the interface between the base member and the bonding layer. Further, since a large-diameter filler having a particle diameter larger than the average particle diameter of the filler is in contact with the surface that defines the recess, it is possible to further reduce the thermal resistance of this interface.

[0016] (9) In the holding device of the above-described form, it is also possible that the above-described holding device satisfies at least the above-described condition (A); at least one of the portion of the above-described holding member that is bonded to the above-described bonding layer and the portion of the above-described base member that is bonded to the above-described bonding layer is formed with a recess that is recessed deeper than the above-described average particle diameter; the depth of the above-described recess is greater than the above-described average particle diameter, and the above-described recess is filled with the above-described bonding layer; the above-described filler having an aspect ratio of 1.4 or more is in contact with the surface that defines the above-described recess. According to this configuration, since the formation of the recess results in an enlarged surface area, it is possible to reduce the thermal resistance of at least one of the interface between the holding member and the bonding layer and the interface between the base member and the bonding layer. Further, since the filler having an aspect ratio of 1.4 or more is in contact with the surface that defines the recess, it is possible to further reduce the thermal resistance of this interface.

[0017] (10) According to another aspect of the present invention, an electrostatic chuck is provided. The electrostatic chuck is characterized by including: a holding device as described in any one of claims 1 to 9; and an electrostatic electrode that generates an electrostatic attraction force on the aforementioned holding surface. According to this configuration, by supplying power to the electrostatic electrode, an electrostatic attraction force (adsorption force) is generated, and an object can be held on the side of the holding surface by this electrostatic attraction force. Also, since it includes a holding device that satisfies at least one of conditions (A) to (C), an electrostatic chuck that reduces the thermal resistance of the bonding layer can be provided.

[0018] In addition, the present invention can be implemented in various aspects. For example, it can be implemented in the form of a holding member, an electrostatic chuck having a holding member and an electrostatic electrode that generates an electrostatic attraction force on the holding surface of the holding member, a vacuum chuck, a ceramic heater, a semiconductor manufacturing device, parts including these, and manufacturing methods of these. Brief Explanation of Drawings

[0019] FIG. 1 is an explanatory diagram schematically showing the cross-sectional configuration of the electrostatic chuck according to the first embodiment. FIG. 2 is an enlarged view of the cross-sectional configuration of the bonding layer. FIG. 3 is an explanatory diagram after applying hatching to a part of each of the fillers. FIG. 4 is an explanatory diagram showing each range of the cross-sectional configuration of the bonding layer. FIG. 5 is an enlarged view of the cross-sectional configuration of the holding device according to the second embodiment. Embodiments

[0020] [Modes for Carrying Out the Invention]

[0021] <First Embodiment> FIG. 1 is an explanatory diagram schematically showing the cross-sectional configuration of the electrostatic chuck 1 according to the first embodiment. The electrostatic chuck 1 is a device that adsorbs and holds an object, that is, a semiconductor wafer W, by electrostatic attraction. The arrow shown in FIG. 1 indicates the direction in which the semiconductor wafer W is adsorbed to the electrostatic chuck 1. The electrostatic chuck 1 is used, for example, to fix the semiconductor wafer W in a vacuum chamber of a semiconductor manufacturing device. The electrostatic chuck 1 includes: a holding member 10, a base member 20, and a bonding layer 30. The holding member 10, the base member 20, and the bonding layer 30 among the members constituting the electrostatic chuck 1 are collectively referred to as a holding device H.

[0022] The holding member 10 is a disk-shaped member that holds an object, i.e., a semiconductor wafer W, and is formed of alumina, aluminum nitride, or the like. The holding member 10 has a holding surface 10f. The holding surface 10f is a circular surface on the side that holds the semiconductor wafer W.

[0023] The electrostatic electrode 12 is disposed inside the holding member 10. The electrostatic electrode 12 is a disk-shaped member formed of a conductive material such as tungsten or molybdenum. The passage 14 is connected to the electrostatic electrode 12 inside the holding member 10. The passage 14 is a rod-shaped member formed of the same material as the electrostatic electrode 12.

[0024] The base member 20 is a disk-shaped member disposed on the side of the holding member 10 opposite to the holding surface 10f and is formed of aluminum, an aluminum alloy, or the like. Inside the base member 20, a refrigerant flow path 22 is disposed. The refrigerant flow path 22 is a flow path through which a cooling medium (e.g., a fluorinated liquid, pure water, etc.) flows.

[0025] The bonding layer 30 is disposed between the holding member 10 and the base member 20 and is a resin layer R (illustrated in FIGS. 2 and later) that bonds the holding member 10 and the base member 20 and includes a plurality of fillers F (illustrated in FIGS. 2 and later). Details will be described later.

[0026] Inside the electrostatic chuck 1, a through hole 40 is formed that penetrates the base member 20 and the bonding layer 30 and reaches the inside of the holding member 10. A cylindrical insulating member 42 is inserted into the through hole 40. Further, on the bottom surface of the through hole 40 located inside the holding member 10, a metallization layer 44 connected to the passage 14 is disposed. The metallization layer 44 is a plate-shaped member formed of the same material as the electrostatic electrode 12 or the passage 14. The connection terminal 46 is connected to the metallization layer 44 and is also connected to the terminal metal member 48. An external power source (not shown) is connected to the terminal metal member 48. That is, the electrostatic electrode 12 is supplied with power from an external power source (not shown) via the passage 14, the metallization layer 44, the connection terminal 46, and the terminal metal member 48, thereby generating an electrostatic attraction force on the holding surface 10f. By this electrostatic attraction force, the semiconductor wafer W is adsorbed toward the holding surface 10f and held on the holding surface 10f.

[0027] FIG. 2 is an enlarged view showing an enlarged cross-sectional structure of the bonding layer 30. As described above, the bonding layer 30 is a resin layer R containing a plurality of fillers F. In FIG. 2, the portion other than the filler F in the bonding layer 30 represents the resin layer R. The thermal conductivity of the filler F is higher than that of the resin layer R. The holding device H (holding member 10, base member 20, and bonding layer 30) satisfies the following condition (A). Condition (A): The plurality of fillers F includes at least one of a first filler F1 in contact with the holding member 10 and a second filler F2 in contact with the base member 20. In addition, when photographing each part of the bonding layer 30 using a scanning electron microscope (SEM), if a part satisfying condition (A) can be photographed at one part, the bonding layer 30 satisfies condition (A).

[0028] Regarding condition (A), in the present embodiment, the plurality of fillers F included in the bonding layer 30 includes both a first filler F1 in contact with the holding member 10 and a second filler F2 in contact with the base member 20. Here, as long as a part of the filler F is contained within a range R1 of 0.5 μm or less starting from the interface BD1 between the holding member 10 and the bonding layer 30, or within a range R2 of 0.5 μm or less starting from the interface BD2 between the base member 20 and the bonding layer 30, such a filler F is defined as the first filler F1 or the second filler F2.

[0029] The first filler F1 includes large-diameter fillers having a diameter larger than the average diameter of the filler F, that is, the first fillers F1a, F1b, and F1c. The second filler F2 also includes large-diameter fillers having a diameter larger than the average diameter of the filler F, that is, the second fillers F2a, F2c, F2e, and F2g. Furthermore, in the present embodiment, each of the first filler F1 and the second filler F2 also includes small-diameter fillers having a diameter smaller than the average diameter of the filler F, that is, the first filler F1d or the second fillers F2b, F2d, and F2f. Here, the so-called average diameter refers to the median diameter of the diameters when, after binarizing the cross-sectional image of the bonding layer 30 photographed using SEM, the area of each filler F is approximated by a true circle (πr2) and its diameter (2r) is regarded as the diameter of each filler F. More specifically, using a cross-sectional image obtained by photographing the bonding layer 30 in such a way as to include at least 500 or more fillers F, the median diameter of the diameters of all the fillers F reflected in the cross-sectional image corresponds to the average diameter.

[0030] FIG. 3 is an explanatory diagram in which hatching is applied to a part of each of the first filler F1 and the second filler F2 shown in FIG. 2. The sum of the cross-sectional areas of the large-diameter fillers in the first filler F1 is larger than the sum of the cross-sectional areas of the small-diameter fillers. In other words, the sum of the cross-sectional areas of the first filler F1 with a particle diameter larger than the average particle diameter is greater than the sum of the cross-sectional areas of the first filler F1 with a particle diameter smaller than the average particle diameter. Here, when explaining with FIG. 3, the sum of the cross-sectional areas of the large-diameter fillers (the first filler F1 with a particle diameter larger than the average particle diameter) in the first filler F1 does not refer to the sum of the cross-sectional areas of the portions included in the range R1 in the first fillers F1a, F1b, and F1c, but refers to the sum of the overall cross-sectional areas (hatched in the first fillers F1a, F1b, and F1c in FIG. 3). Similarly, when explaining with FIG. 3, the sum of the cross-sectional areas of the small-diameter fillers (the first filler F1 with a particle diameter larger than the average particle diameter) in the first filler F1 does not refer to the sum of the cross-sectional areas of the portions included in the range R2 in the first filler F1d, but refers to the sum of the overall cross-sectional areas (hatched in the first filler F1d in FIG. 3).

[0031] Also, similar to the first filler F1, the sum of the cross-sectional areas of the large-diameter fillers in the second filler F2 is larger than the sum of the cross-sectional areas of the small-diameter fillers. When explaining with FIG. 3, the sum of the overall cross-sectional areas (hatched in the second fillers F2a, F2c, F2e, and F2g in FIG. 3) of the second fillers F2a, F2c, F2e, and F2g is larger than the sum of the overall cross-sectional areas (hatched in the second fillers F2b, F2d, and F2f in FIG. 3) of the second fillers F2b, F2d, and F2f.

[0032] In addition to satisfying the above condition (A), the holding device H also satisfies the following condition (B). In addition, the range Rg1, the range Rg2, the center O, the range Ro1, and the range Ro2 regarding the following condition (B) are as shown in FIG. 4. Condition (B): In the bonding layer 30, in the range Rg1 within 1 μm from the interface BD1 with the holding member 10, the ratio of the total cross-sectional area of the filler F in the range Rg1 is set as the first ratio; in the bonding layer 30, in the range Rg2 within 1 μm from the interface BD2 with the base member 20, the ratio of the total cross-sectional area of the filler F in the range Rg2 is set as the second ratio; in the bonding layer 30, in the range Ro1 within 30% of the thickness of the bonding layer 30 from the center O in the thickness direction of the bonding layer 30 toward the holding member 10 side and the range Ro2 within 30% of the thickness of the bonding layer 30 from the center O toward the base member 20 side, when the ratio of the total cross-sectional area of the filler F in the ranges Ro1 and Ro2 is set as the third ratio; at least one of the value obtained by dividing the first ratio by the third ratio and the value obtained by dividing the second ratio by the third ratio is 0.5 or more. In addition, when photographing each part of the bonding layer 30 with an SEM, as long as one part satisfying the condition (B) can be photographed, the bonding layer 30 satisfies the condition (B). At this time, the value obtained by dividing the first ratio, which is the criterion for determining whether the condition (B) is satisfied, by the third ratio and the value obtained by dividing the second ratio by the third ratio are values calculated using the first to third ratios calculated within the same cross-sectional image.

[0033] In the condition (B), in the present embodiment, both the value obtained by dividing the first ratio by the third ratio and the value obtained by dividing the second ratio by the third ratio are 0.5 or more. Here, the ratio of the total cross-sectional area of the filler F in the range Rg1 (the first ratio), when explained with reference to FIG. 4, refers to the ratio of the cross-sectional area of the portions of the first fillers F1a to F1d included in the range Rg1 (hatched in the first fillers F1a to F1d in FIG. 4) to the total cross-sectional area of the range Rg1. Similarly, the ratio of the total cross-sectional area of the filler F in the range Rg2, when explained with reference to FIG. 4, refers to the ratio of the area of the portions of the second fillers F2a to F2g included in the range Rg2 (hatched in the second fillers F2a to F2g in FIG. 4) to the total cross-sectional area of the range Rg2.

[0034] The ratio of the total cross-sectional area of the filler F in the ranges Ro1 and Ro2 (the third ratio) refers to the ratio of the sum of the cross-sectional areas of the portions of each filler F included in the ranges Ro1 and Ro2 (hatched in the fillers F within the ranges Ro1 and Ro2 in FIG. 4) to the sum of the cross-sectional areas of the range Ro1 and the range Ro2.

[0035] The holding device H satisfies the following condition (C) in addition to satisfying the above conditions (A) and (B). In addition, the aspect ratio of each filler F is obtained by binarizing the cross-sectional image of the bonding layer 30 obtained by SEM photography, and then performing elliptical approximation on each filler F by fitting using the least squares method, and then dividing the major axis of the ellipse by the minor axis. Condition (C): The number of fillers F with an aspect ratio of 1.4 or more in the filler F is greater than the number of fillers F with an aspect ratio less than 1.4. In addition, when photographing each part of the bonding layer 30 with SEM, as long as one part satisfying condition (C) can be photographed, the bonding layer 30 satisfies condition (C). More specifically, in the cross-sectional image of the bonding layer 30 photographed in such a way that it includes at least 500 or more fillers F, as long as one cross-sectional image satisfying condition (C) can be confirmed, the bonding layer 30 satisfies condition (C).

[0036] Regarding condition (C), in the present embodiment, each of the first filler F1 (the filler F in contact with the holding member 10) and the second filler F2 (the filler F in contact with the base member 20) also includes a filler F with an aspect ratio of 1.4 or more. Also, each of the first filler F1 and the second filler F2 also includes a filler F with an aspect ratio less than 1.4. Also, in the first filler F1, the total cross-sectional area of the fillers F with an aspect ratio of 1.4 or more is greater than the total cross-sectional area of the fillers F with an aspect ratio less than 1.4. Similarly, in the second filler F2, the total cross-sectional area of the fillers F with an aspect ratio of 1.4 or more is greater than the total cross-sectional area of the fillers F with an aspect ratio less than 1.4. Here, the total cross-sectional area means, as in the case of the above-mentioned large-diameter fillers and small-diameter fillers, not the sum of the cross-sectional areas of the parts of each filler F included in the ranges R1 and R2, but the sum of the overall cross-sectional areas of each filler F.

[0037] In the electrostatic chuck 1, the resin material (the material that forms the basis of the bonding layer 30) contains the filler F such that the filler F having an aspect ratio of 1.4 or more is more than the filler F having an aspect ratio of less than 1.4, and then the holding device H satisfies the condition (C). When the electrostatic chuck 1 is manufactured, after such a resin material is applied to the surface of the base member 20 and then thermally cured to form the bonding layer 30, the holding member 10 is placed on the surface on the side opposite to the base member 20 in the bonding layer 30. In this manufacturing step, when the resin material is in a semi-cured state before being completely cured into the bonding layer 30, a load is applied in the thickness direction so that the filler F is easily arranged at the end side in the thickness direction of the resin material (bonding layer 30) (near the interface with the holding member 10 or near the interface with the base member 20). Then, by completely curing in the state where the load is applied, the resin material becomes the bonding layer 30. By applying the load during semi-curing in this way, in particular, large-diameter fillers or fillers F having an aspect ratio of 1.4 or more are easily arranged at the end side in the thickness direction of the resin material (bonding layer 30). That is, by applying the load during semi-curing, the holding device H easily satisfies the conditions (A) and (B).

[0038] As described above, the holding device H (holding member 10, base member 20, and bonding layer 30) included in the electrostatic chuck 1 of the present embodiment satisfies each of the conditions (A) to (C). In the case of satisfying the condition (A), since the first filler F1 and the second filler F2 among the fillers F having a higher thermal conductivity (compared with the resin layer R) are in contact with the holding member 10 and the base member 20, the thermal resistances of the interface BD1 (see FIGS. 2 to 4) between the bonding layer 30 and the holding member 10 and the interface BD2 (see FIGS. 2 to 4) between the bonding layer 30 and the base member 20 can both be reduced. In the case of satisfying the condition (B), the ranges Rg1 within 1 μm starting from the interface BD1 and Rg2 within 1 μm starting from the interface BD2 both contain a relatively large amount of the filler F (the first ratio / the third ratio ≥ 0.5, and the second ratio / the third ratio ≥ 0.5), so the thermal resistance near either the interface BD1 or the interface BD2 can also be reduced. In the case of satisfying the condition (C), since the fillers F having an aspect ratio of 1.4 or more in the filler F included in the bonding layer 30 are more than the fillers F having an aspect ratio of less than 1.4, heat can be transferred in the thickness direction of the bonding layer 30 with a smaller amount of the filler F, so flexibility can be maintained and the thermal resistance of the bonding layer 30 can be reduced. Thus, by the holding device H satisfying each of the conditions (A) to (C), the thermal resistance of the bonding layer 30 can be reduced.

[0039] Also, in the holding device H included in the present embodiment, the first filler F1 and the second filler F2 include large-diameter fillers having a particle diameter larger than the average particle diameter of the filler F, that is, the first fillers F1a, F1b, F1c and the second fillers F2a, F2c, F2e, F2g. Therefore, heat can be easily transferred from the interfaces BD1 and BD2 in the thickness direction of the bonding layer 30. As a result, the thermal resistance of the interfaces BD1 and BD2 can be further reduced.

[0040] Also, in the holding device H included in the present embodiment, in the first filler F1 and the second filler F2, in addition to including large-diameter fillers, small-diameter fillers having a particle diameter smaller than the average particle diameter of the filler F are also included, that is, the first filler F1d and the second fillers F2b, F2d, F2f. Therefore, since the number of the fillers F in contact with the holding member 10 and the base member 20 is large, heat can be more easily transferred from the interfaces BD1 and BD2 in the thickness direction of the bonding layer 30.

[0041] Also, in the holding device H included in the present embodiment, in the first filler F1, the total cross-sectional area of the large-diameter fillers (corresponding to F1a, F1b, F1c in FIG. 2) is larger than the total cross-sectional area of the small-diameter fillers (corresponding to F1d in FIG. 2). Also, in the second filler F2, the total cross-sectional area of the large-diameter fillers (corresponding to F2a, F2c, F2e, F2g in FIG. 2) is larger than the total cross-sectional area of the small-diameter fillers (corresponding to F2b, F2d, F2f in FIG. 2). Therefore, in the first filler F1 and the second filler F2, the amount of the large-diameter fillers is guaranteed to a certain extent with respect to the amount of the small-diameter fillers, so that the effect of reducing the thermal resistance of the interfaces BD1 and BD2 caused by the large-diameter fillers can be guaranteed.

[0042] Also, in the holding device H included in the present embodiment, the fillers F having an aspect ratio of 1.4 or more are included in the first filler F1 and the second filler F2. Therefore, heat can be easily transferred from the interfaces BD1 and BD2 in the thickness direction of the bonding layer 30. As a result, the thermal resistance of the interfaces BD1 and BD2 can be further reduced.

[0043] Also, in the holding device H included in the present embodiment, in the first filler F1 and the second filler F2, in addition to including the fillers F having an aspect ratio of 1.4 or more, fillers F having an aspect ratio of less than 1.4 are also included. Therefore, since the number of the fillers F in contact with the holding member 10 and the base member 20 is large, heat can be more easily transferred from the interfaces BD1 and BD2 in the thickness direction of the bonding layer 30.

[0044] Further, in the holding device H included in the present embodiment, in the first filler F1 and the second filler F2, the total cross-sectional area of the fillers F having an aspect ratio of 1.4 or more is greater than the total cross-sectional area of the fillers F having an aspect ratio of less than 1.4. Therefore, in the first filler F1 and the second filler F2, since the amount of the fillers having an aspect ratio of 1.4 or more is ensured to a certain extent with respect to the amount of the fillers having an aspect ratio of less than 1.4, the effect of reducing the thermal resistance of the interfaces BD1 and BD2 caused by the fillers having an aspect ratio of 1.4 or more can be ensured.

[0045] Further, in the electrostatic chuck 1 of the present embodiment, by supplying power to the electrostatic electrode 12, an electrostatic attraction force (adsorption force) is generated, and the semiconductor wafer W can be held on the side of the holding surface 10f by this electrostatic attraction force. Further, since the holding device H that satisfies each of the conditions (A) to (C) is provided, an electrostatic chuck 1 with a reduced thermal resistance of the bonding layer 30 can be provided.

[0046] <Second Embodiment> FIG. 5 is an explanatory diagram showing the base member 20a and the bonding layer 30 in the holding device Ha of the second embodiment. The holding device Ha of the second embodiment is the same as the holding device H of the first embodiment except that it includes a base member 20a different from the base member 20. That is, the holding device Ha of the second embodiment is also configured to be included in the electrostatic chuck 1 in the same manner as the holding device H of the first embodiment. In the description of the second embodiment, the same reference numerals are given to the same configurations as those in the first embodiment, and the previous description is referred to. In addition, in FIGS. 1 to 4, the base member 20 is hatched, but in FIG. 5, for convenience of illustration, the base member 20 is not hatched. Further, in FIG. 5, for convenience of illustration, the filler F is shown as a circle.

[0047] In the portion of the base member 20a that is joined to the bonding layer 30, a recessed portion 20D that is recessed deeper than the average particle diameter of the filler F is formed. The recessed portion 20D is formed by laser processing or the like. Further, the depth DP of the recessed portion 20D is larger than the average particle diameter of the filler F, and the recessed portion 20D is filled with the bonding layer 30. Furthermore, a large-diameter filler FL having a particle diameter larger than the average particle diameter of the filler F is in contact with the surface 20DS that defines the recessed portion 20D. Here, as long as a part of the filler F is included in the range Ra of 0.5 μm or less from the surface 20DS, such a filler F is regarded as being in contact with the surface 20DS. In addition, in the recessed portion 20D, since the surface 20DS is regarded as the interface BD2, the range Rg2 (see FIG. 4) is specified as the range of 1 μm or less from the surface 20DS.

[0048] According to the holding device Ha of the second embodiment described above, similar to the first embodiment, the thermal resistance of the bonding layer 30 can be reduced. Also, in the holding device Ha of the second embodiment, since the formation of the recessed portion 20D enlarges the surface area, the thermal resistance of the interface BD2 between the base member 20a and the bonding layer 30 can be reduced. Further, since the large-diameter filler FL having a particle diameter larger than the average particle diameter of the filler F contacts the surface 20DS defining the recessed portion 20D, the thermal resistance of the interface BD2 can be further reduced.

[0049] <Modifications of this embodiment> The present invention is not limited to the above-described embodiments, and can be implemented in various forms without departing from the gist thereof. For example, the following modifications can be made.

[0050] In the above-described embodiment, a plurality of heater electrodes formed of a conductive material such as tungsten or molybdenum may be further provided inside the holding member 10. In this case, when the holding member 10 holds an object, the object can be heated by supplying power from an external power source to heat the heater electrodes.

[0051] In the above-described embodiments, the holding devices H and Ha satisfy each of the conditions (A) to (C), but are not limited thereto. The holding devices H and Ha only need to satisfy at least one of the conditions (A) to (C).

[0052] In the above-described embodiment, the condition (A) is satisfied by the plurality of fillers F included in the bonding layer 30 each containing the first filler F1 (the filler F in contact with the holding member 10) and the second filler F2 (the filler F in contact with the base member 20), but is not limited thereto. It is also possible that the condition (A) is satisfied by the plurality of fillers F included in the bonding layer 30 containing only one of the first filler F1 and the second filler F2.

[0053] In the above-described embodiment, both the first filler F1 and the second filler F2 contain large-diameter fillers and small-diameter fillers, but are not limited thereto. Each of the first filler F1 and the second filler F2 may contain only one of the large-diameter fillers and the small-diameter fillers.

[0054] In the above-described embodiments, the total cross-sectional area of the large-diameter fillers is greater than the total cross-sectional area of the small-diameter fillers for both the first filler F1 and the second filler F2, but it is not limited thereto. It may also be the case that only one of the first filler F1 and the second filler F2 has the total cross-sectional area of the large-diameter fillers greater than the total cross-sectional area of the small-diameter fillers. Alternatively, for both the first filler F1 and the second filler F2, the total cross-sectional area of the large-diameter fillers may be less than the total cross-sectional area of the small-diameter fillers.

[0055] In the above-described embodiments, condition (B) is satisfied because both the value obtained by dividing the first ratio by the third ratio and the value obtained by dividing the second ratio by the third ratio are 0.5 or more, but it is not limited thereto. Condition (B) may be satisfied by making only one of the value obtained by dividing the first ratio by the third ratio and the value obtained by dividing the second ratio by the third ratio 0.5 or more.

[0056] In the above-described embodiments, both the first filler F1 and the second filler F2 contain the filler F having an aspect ratio of 1.4 or more and the filler F having an aspect ratio less than 1.4, but it is not limited thereto. Each of the first filler F1 and the second filler F2 may also contain only one of the filler F having an aspect ratio of 1.4 or more and the filler F having an aspect ratio less than 1.4.

[0057] In the above-described embodiments, for both the first filler F1 and the second filler F2, the total cross-sectional area of the filler F having an aspect ratio of 1.4 or more is greater than the total cross-sectional area of the filler F having an aspect ratio less than 1.4, but it is not limited thereto. It may also be the case that only one of the first filler F1 and the second filler F2 has the total cross-sectional area of the filler F having an aspect ratio of 1.4 or more greater than the total cross-sectional area of the filler F having an aspect ratio less than 1.4. Alternatively, for both the first filler F1 and the second filler F2, the total cross-sectional area of the filler F having an aspect ratio of 1.4 or more may be less than the total cross-sectional area of the filler F having an aspect ratio less than 1.4.

[0058] In the second embodiment, although the recessed portion 20D is formed in the portion of the base member 20a that is joined to the joining layer 30, it is not limited thereto. The same recessed portion may also be formed in the portion of the holding member 10 that is joined to the joining layer 30. Also in this form, when the large-diameter filler FL having a particle diameter larger than the average particle diameter of the filler F is in contact with the surface defining the recessed portion, the thermal resistance of the interface BD1 (see FIG. 2 etc.) can be further reduced. Further, the filler in contact with the surface defining the recessed portion 20D or the surface defining the recessed portion formed in the holding member 10 may be the filler F having an aspect ratio of 1.4 or more, instead of the large-diameter filler FL, or may be such that in addition to the contact with the large-diameter filler FL, the filler F having an aspect ratio of 1.4 or more is also in contact. Also in this form, the thermal resistance of the interfaces BD1, BD2 (see FIG. 2 etc.) can be further reduced.

[0059] As described above, the present aspect has been described based on the embodiments and modification examples. However, the embodiments of the above aspect are for making the present aspect easy to understand and do not limit the present aspect. The present aspect can be changed and improved without departing from its gist and the scope of the patent application, and the equivalents thereof are also included in the present aspect. Further, if the technical feature is not necessary to be described in this specification, it can be appropriately deleted.

[0060] The present invention can also be implemented in the following forms. [Application Example 1] A holding device, comprising: A holding member having a holding surface for holding an object; A base member disposed on the side opposite to the side of the holding surface in the holding member; and A joining layer that joins the holding member and the base member and includes a plurality of fillers, The holding device is characterized in that: At least one of the following conditions (A) to (C) is satisfied: Condition (A): The filler includes at least one of a first filler in contact with the holding member and a second filler in contact with the base member; Condition (B): The ratio of the total cross-sectional area of the aforementioned filler occupying a range of 1 μm or less from the interface with the aforementioned holding member 10 in the aforementioned bonding layer 30 is defined as the first ratio; the ratio of the total cross-sectional area of the aforementioned filler occupying a range of 1 μm or less from the interface with the aforementioned base member in the aforementioned bonding layer is defined as the second ratio; when the ratio of the total cross-sectional area of the aforementioned filler occupying a range of 30% or less of the thickness of the aforementioned bonding layer from the center in the thickness direction of the aforementioned bonding layer toward the aforementioned holding member side and a range of 30% or less of the thickness of the aforementioned bonding layer from the center toward the aforementioned base member side is defined as the third ratio, at least one of the value obtained by dividing the aforementioned first ratio by the aforementioned third ratio and the value obtained by dividing the aforementioned second ratio by the aforementioned third ratio is 0.5 or more. Condition (C): Among the aforementioned fillers, the number of the aforementioned fillers with an aspect ratio of 1.4 or more is greater than the number of the aforementioned fillers with an aspect ratio less than 1.4. [Application Example 2] The holding device as in Application Example 1, wherein the aforementioned holding device satisfies at least the aforementioned Condition (A), at least one of the aforementioned first filler and the aforementioned second filler included in the aforementioned bonding layer contains a large-diameter filler having a particle diameter larger than the average particle diameter of the aforementioned filler. [Application Example 3] The holding device as in Application Example 1 or Application Example 2, wherein the aforementioned holding device satisfies at least the aforementioned Condition (A), at least one of the aforementioned first filler and the aforementioned second filler included in the aforementioned bonding layer contains a small-diameter filler having a particle diameter smaller than the aforementioned average particle diameter. [Application Example 4] The holding device as in any one of Application Examples 1 to 3, wherein the aforementioned holding device satisfies at least the aforementioned Condition (A), in at least one of the aforementioned first filler and the aforementioned second filler included in the aforementioned bonding layer, the total cross-sectional area of the aforementioned large-diameter filler is larger than the total cross-sectional area of the aforementioned small-diameter filler. [Application Example 5] The holding device as in any one of Application Examples 1 to 4, wherein the aforementioned holding device satisfies at least the aforementioned Condition (A), at least one of the aforementioned first filler and the aforementioned second filler included in the aforementioned bonding layer contains the aforementioned filler with an aspect ratio of 1.4 or more. [Application Example 6] The holding device as in any one of Application Examples 1 to 5, wherein the aforementioned holding device satisfies at least the aforementioned Condition (A), At least one of the aforementioned first filler and the aforementioned second filler included in the aforementioned bonding layer contains the aforementioned filler having an aspect ratio of less than 1.4. [Application Example 7] A holding device as in any one of Application Examples 1 to 6, wherein the aforementioned holding device satisfies at least the aforementioned condition (A), in at least one of the aforementioned first filler and the aforementioned second filler included in the aforementioned bonding layer, the total cross-sectional area of the aforementioned filler having an aspect ratio of 1.4 or more is greater than the total cross-sectional area of the aforementioned filler having an aspect ratio of less than 1.4. [Application Example 8] A holding device as in any one of Application Examples 1 to 7, wherein the aforementioned holding device satisfies at least the aforementioned condition (A), at least one of the portion of the aforementioned holding member that is joined to the aforementioned bonding layer and the portion of the aforementioned base member that is joined to the aforementioned bonding layer is formed with a recess that is deeper than the average particle diameter of the aforementioned filler, the depth of the aforementioned recess is greater than the aforementioned average particle diameter, and the aforementioned recess is filled with the aforementioned bonding layer, a large-diameter filler having a particle diameter larger than the average particle diameter of the aforementioned filler is in surface contact with the surface defining the aforementioned recess. [Application Example 9] A holding device as in any one of Application Examples 1 to 8, wherein the aforementioned holding device satisfies at least the aforementioned condition (A), at least one of the portion of the aforementioned holding member that is joined to the aforementioned bonding layer and the portion of the aforementioned base member that is joined to the aforementioned bonding layer is formed with a recess that is deeper than the average particle diameter of the aforementioned filler, the depth of the aforementioned recess is greater than the aforementioned average particle diameter, and the aforementioned recess is filled with the aforementioned bonding layer, the aforementioned filler having an aspect ratio of 1.4 or more is in surface contact with the surface defining the aforementioned recess. [Application Example 10] An electrostatic chuck, characterized by comprising: a holding device as in any one of Application Examples 1 to 9; and an electrostatic electrode that generates an electrostatic attraction force on the aforementioned holding surface.

[0061] 1: Electrostatic chuck 10: Holding member 10f: Holding surface 12: Electrostatic electrode 14: Passage 20, 20a: Base member 20D: Recess 20DS: Surface 22: Refrigerant flow path 30: Bonding layer 40: Through-hole 42: Insulating member 44: Metallization layer 46: Connection terminal 48: Terminal metal part F: Filler F1: First filler F2: Second filler H, Ha: Holding device

Claims

1. A retaining device, characterized in that it comprises: a retaining member having a retaining surface for retaining an object; a base member disposed on the side of the retaining member opposite to the retaining surface; and a bonding layer for bonding the retaining member to the base member, and comprising a plurality of fillers, wherein the retaining device satisfies at least one of the following conditions (A) to (C): Condition (A): The fillers comprise at least one of a first filler in contact with the retaining member and a second filler in contact with the base member; Condition (B): The proportion of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned retaining member is set as the first proportion; the proportion of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned base member is set as the second proportion; when the proportion of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the thickness direction of the aforementioned bonding layer toward the aforementioned retaining member and within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the aforementioned bonding layer toward the aforementioned base member is set as the third proportion, at least one of the value obtained by dividing the aforementioned first proportion by the aforementioned third proportion and the value obtained by dividing the aforementioned second proportion by the aforementioned third proportion is 0.5 or more; Condition (C): The aforementioned fillers with an aspect ratio of 1.4 or more are more numerous than the aforementioned fillers with an aspect ratio of less than 1.

4.

2. The holding device as claimed in claim 1, wherein, The aforementioned retaining device at least satisfies the aforementioned condition (A), wherein at least one of the aforementioned first packing and the aforementioned second packing contained in the aforementioned bonding layer is a large-diameter packing with a particle size larger than the average particle size of the aforementioned packing.

3. The retaining device as claimed in claim 2, wherein, The aforementioned retaining device at least satisfies the aforementioned condition (A), wherein at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer contains a small-diameter packing with a particle size smaller than the aforementioned average particle size.

4. The retaining device as described in claim 3, wherein, The aforementioned retaining device at least satisfies the aforementioned condition (A), wherein, in at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned joint layer, the sum of the cross-sectional areas of the aforementioned large-diameter packing is greater than the sum of the cross-sectional areas of the aforementioned small-diameter packing.

5. The retaining device as claimed in claim 1, wherein, The aforementioned retaining device at least satisfies the aforementioned condition (A), wherein at least one of the aforementioned first filler and the aforementioned second filler included in the aforementioned bonding layer contains the aforementioned filler with an aspect ratio of 1.4 or more.

6. The retaining device of claim 5, wherein the retaining device at least satisfies the aforementioned condition (A), and at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer contains the aforementioned packing with an aspect ratio of less than 1.

4.

7. The retaining device of claim 6, wherein the retaining device at least satisfies the aforementioned condition (A), wherein, in at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer, the sum of the cross-sectional areas of the aforementioned packings with an aspect ratio of 1.4 or more is greater than the sum of the cross-sectional areas of the aforementioned packings with an aspect ratio of less than 1.

4.

8. The retaining device of claim 1, wherein the retaining device satisfies at least the aforementioned condition (A), wherein at least one of the portion of the retaining member that engages with the aforementioned bonding layer and the portion of the base member that engages with the aforementioned bonding layer is formed with a recess that is deeper than the average particle size of the aforementioned filler, the depth of the recess is greater than the aforementioned average particle size, and the recess is filled by the aforementioned bonding layer, and the large-diameter filler with a particle size greater than the average particle size of the aforementioned filler is in contact with the surface defining the recess.

9. The retaining device of claim 1, wherein the retaining device at least satisfies the aforementioned condition (A), wherein at least one of the portion of the retaining member that engages with the aforementioned bonding layer and the portion of the base member that engages with the aforementioned bonding layer is formed with a recess that is deeper than the average particle size of the aforementioned filler, the depth of the recess is greater than the aforementioned average particle size, and the recess is filled by the aforementioned bonding layer, and the aforementioned filler with an aspect ratio of 1.4 or more is in contact with the surface defining the recess.

10. A retaining device, characterized in that it comprises: a retaining member having a retaining surface for retaining an object; a base member disposed on the side of the retaining member opposite to the retaining surface; and a bonding layer for bonding the retaining member to the base member, and comprising a plurality of fillers, wherein the retaining device satisfies at least one of the following conditions (A) to (C): Condition (A): The fillers comprise at least one of a first filler in contact with the retaining member and a second filler in contact with the base member; Condition (B): The first proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned retaining member; the second proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned base member; the third proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the thickness direction of the aforementioned bonding layer toward the aforementioned retaining member and within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the aforementioned bonding layer toward the aforementioned base member, wherein at least one of the value obtained by dividing the aforementioned first proportion by the aforementioned third proportion and the value obtained by dividing the aforementioned second proportion by the aforementioned third proportion is 0.5 or more; Condition (C): The number of aforementioned fillers with an aspect ratio of 1.4 or more is greater than the number of aforementioned fillers with an aspect ratio of less than 1.4; At least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer is a large-diameter packing with a particle size larger than the average particle size of the aforementioned packing; at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer is a small-diameter packing with a particle size smaller than the aforementioned average particle size; in at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer, the sum of the cross-sectional areas of the aforementioned large-diameter packing is larger than the sum of the cross-sectional areas of the aforementioned small-diameter packing.

11. A retaining device, characterized in that it comprises: a retaining member having a retaining surface for retaining an object; a base member disposed on the side of the retaining member opposite to the retaining surface; and a bonding layer for bonding the retaining member to the base member, and comprising a plurality of fillers, wherein the retaining device satisfies at least one of the following conditions (A) to (C): Condition (A): The fillers comprise at least one of a first filler in contact with the retaining member and a second filler in contact with the base member; Condition (B): The first proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned retaining member; the second proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned base member; the third proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the thickness direction of the aforementioned bonding layer toward the aforementioned retaining member and within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the aforementioned bonding layer toward the aforementioned base member, wherein at least one of the value obtained by dividing the aforementioned first proportion by the aforementioned third proportion and the value obtained by dividing the aforementioned second proportion by the aforementioned third proportion is 0.5 or more; Condition (C): The number of aforementioned fillers with an aspect ratio of 1.4 or more is greater than the number of aforementioned fillers with an aspect ratio of less than 1.4; At least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer contains the aforementioned packing with an aspect ratio of 1.4 or more; at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer contains the aforementioned packing with an aspect ratio of less than 1.4; in at least one of the aforementioned first packing and the aforementioned second packing included in the aforementioned bonding layer, the sum of the cross-sectional areas of the aforementioned packings with an aspect ratio of 1.4 or more is greater than the sum of the cross-sectional areas of the aforementioned packings with an aspect ratio of less than 1.

4.

12. A retaining device, characterized in that it comprises: a retaining member having a retaining surface for retaining an object; a base member disposed on the side of the retaining member opposite to the retaining surface; and a bonding layer for bonding the retaining member to the base member, and comprising a plurality of fillers, wherein the retaining device satisfies at least one of the following conditions (A) to (C): Condition (A): The fillers comprise at least one of a first filler in contact with the retaining member and a second filler in contact with the base member; Condition (B): The first proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned retaining member; the second proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned base member; the third proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the thickness direction of the aforementioned bonding layer toward the aforementioned retaining member and within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the aforementioned bonding layer toward the aforementioned base member, wherein at least one of the value obtained by dividing the aforementioned first proportion by the aforementioned third proportion and the value obtained by dividing the aforementioned second proportion by the aforementioned third proportion is 0.5 or more; Condition (C): The number of aforementioned fillers with an aspect ratio of 1.4 or more is greater than the number of aforementioned fillers with an aspect ratio of less than 1.4; At least one of the portion of the aforementioned retaining member that is joined to the aforementioned bonding layer and the portion of the aforementioned base member that is joined to the aforementioned bonding layer is formed with a recessed portion that is deeper than the average particle size of the aforementioned filler. The depth of the recessed portion is greater than the average particle size, and the recessed portion is filled by the aforementioned bonding layer. The large-diameter filler with a particle size greater than the average particle size of the aforementioned filler is in contact with the surface that defines the recessed portion.

13. A retaining device, characterized in that it comprises: a retaining member having a retaining surface for retaining an object; a base member disposed on the side of the retaining member opposite to the retaining surface; and a bonding layer for bonding the retaining member to the base member, and comprising a plurality of fillers, wherein the retaining device satisfies at least one of the following conditions (A) to (C): Condition (A): The fillers comprise at least one of a first filler in contact with the retaining member and a second filler in contact with the base member; Condition (B): The first proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned retaining member; the second proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 1 μm or less from the interface with the aforementioned base member; the third proportion is defined as the ratio of the total cross-sectional area of ​​the aforementioned fillers in the aforementioned bonding layer within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the thickness direction of the aforementioned bonding layer toward the aforementioned retaining member and within a range of 30% or less of the thickness of the aforementioned bonding layer from the center of the aforementioned bonding layer toward the aforementioned base member, wherein at least one of the value obtained by dividing the aforementioned first proportion by the aforementioned third proportion and the value obtained by dividing the aforementioned second proportion by the aforementioned third proportion is 0.5 or more; Condition (C): The number of aforementioned fillers with an aspect ratio of 1.4 or more is greater than the number of aforementioned fillers with an aspect ratio of less than 1.4; At least one of the portion of the aforementioned retaining member that is joined to the aforementioned bonding layer and the portion of the aforementioned base member that is joined to the aforementioned bonding layer is formed with a recess that is deeper than the average particle size of the aforementioned filler. The depth of the recess is greater than the average particle size, and the recess is filled by the aforementioned bonding layer. The aforementioned filler with an aspect ratio of 1.4 or more is in contact with the surface that defines the recess.

14. An electrostatic chuck, characterized by comprising: a holding device as described in any one of claims 1 to 13; and an electrostatic electrode that generates electrostatic attraction on the holding surface.

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