Retention device

Abstract

To provide a holding device capable of improving a withstanding voltage.SOLUTION: An electrostatic chuck 1 holds a semiconductor wafer W on a holding surface 11 of a plate-like member 10, and comprises: the plate-like member 10 having first through-holes 15; a base member 20 having second through-holes 25 communicating with the first through-holes 15; and a bonding layer 40 arranged between a lower surface 12 of the plate-like member 10 and an upper surface 21 of the base member 20, bonding between the plate-like member 10 and the base member 20. The bonding layer 40 is formed with third through-holes 45 connecting between the first through-holes 15 and the second through-holes 25, respectively. Annular convex parts 34 that protrudes at least into the third through-holes 45, respectively, are formed in the lower surface 12 integrally with the plate-like member 10 so as to each surround an opening of the first through-hole 15.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present disclosure relates to a holding device for holding an object.

Background Art

[0002] For example, as a holding device for holding a semiconductor wafer, there is known a holding device including a first member, a second member, and a bonding layer for bonding the first member and the second member, and through holes (such as lift pin holes and gas holes) penetrating in the thickness direction are formed therein. In such a holding device, an insulating member is provided in the through holes so that abnormal discharge does not occur between the semiconductor wafer and the metal portion of the holding device. For example, in the placement table (holding device) described in Patent Document 1, a sleeve is disposed in the through hole and fixed with an adhesive. Further, in the member for a semiconductor manufacturing apparatus (holding device) described in Patent Document 2, an insulating tube bonded with an adhesive on the back surface of a plate (first member) is disposed in the through hole of a cooling substrate (second member).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described holding device, since an adhesive is used for joining the sleeve and the insulating tube, if the adhesive deteriorates, gaps may occur or the adhesive may be damaged, which may become a leakage path and abnormal discharge may occur. In recent years, in order to increase the etching depth of the semiconductor wafer or increase the processing speed, etc., the holding device is increasingly used in a high-power region (under a high-voltage plasma environment) or at a high temperature (250 ° C or higher), and the adhesive is likely to deteriorate. Therefore, in the holding device as described above, the possibility of abnormal discharge occurring between the semiconductor wafer and the metal portion of the holding device is increasing, and an improvement in the withstand voltage (insulation) of the holding device is desired.

[0005] Therefore, the present disclosure has been made to solve the above-described problems, and an object thereof is to provide a holding device capable of improving the withstand voltage.

Means for Solving the Problems

[0006] The present invention has been made to solve at least a part of the above-described problems and can be realized in the following forms. A first member including a first surface, a second surface provided on the side opposite to the first surface, and a first through hole penetrating the first surface and the second surface, a third surface, a fourth surface provided on the side opposite to the third surface, and a second through hole penetrating the third surface and the fourth surface and communicating with the first through hole. A second member, and a bonding layer disposed between the second surface of the first member and the third surface of the second member for bonding the first member and the second member. In the holding device for holding an object on the first surface of the first member, a third through hole for communicating the first through hole and the second through hole is formed in the bonding layer, and on the second surface, at least the first An annular convex portion protruding to a depth of 1 / 4 of the second through hole is integrally formed with the first member so as to surround the opening of the through hole. , a gap of 0.1 mm to 2.0 mm is formed between the convex portion and the second through hole along a direction orthogonal to the depth direction of the second through hole A holding device characterized by that. In addition, the present invention can also be realized in the following forms. One form of the present disclosure made to solve the above problems is A first member including a first surface, a second surface provided on the side opposite to the first surface, and a first through hole penetrating the first surface and the second surface, A second member including a third surface, a fourth surface provided on the side opposite to the third surface, and a second through hole penetrating the third surface and the fourth surface and communicating with the first through hole, A bonding layer disposed between the second surface of the first member and the third surface of the second member for bonding the first member and the second member, In a holding device for holding an object on the first surface of the first member, A third through hole for communicating the first through hole and the second through hole is formed in the bonding layer, An annular convex portion protruding at least into the third through hole is integrally formed with the first member so as to surround the opening of the first through hole on the second surface.

[0007] In this holding device, on the second surface, a convex portion integrally formed with the first member around the first through hole is arranged so as to cover at least a part of the bonding layer. Therefore, the creepage distance between the object and the second member (when made of metal) or the bonding layer (when using a metal bonding material) is increased by the convex portion. Accordingly, the occurrence of abnormal discharge between the object and the second member (when made of metal) or the bonding layer (when using a metal bonding material) can be prevented. Further, since the bonding layer is covered by the convex portion, the bonding layer is not directly exposed to the plasma environment, so that deterioration of the bonding layer can be prevented. As a result, the withstand voltage (insulation property) in the holding device can be improved.

[0008] In the above-described holding device, It is preferable that a gap is formed between the convex portion and the second through hole.

[0009] Here, when there is a difference in thermal expansion between the material forming the first member and the material forming the second member, when the temperature of the holding device rises / falls, the convex portion may be damaged by contacting the second member due to the difference in thermal expansion.

[0010] Therefore, by providing a gap between the convex portion and the second through hole, damage to the convex portion can be reliably prevented. As a result, abnormal discharge between the object and the second member (in the case of a metal) or the bonding layer (in the case of a metal bonding material) can be reliably prevented by the convex portion.

[0011] Also, in the holding device described above, it is preferable that the convex portion is in contact with the bonding layer.

[0012] Here, since heat transfer between the second member through the bonding layer does not occur in the first through hole, a temperature difference is likely to be locally larger near the first through hole on the first surface of the first member than in other portions, and it is likely to become a temperature singularity.

[0013] Therefore, by bringing the convex portion protruding so as to surround the opening of the first through hole into contact with the bonding layer, heat transfer between the first member and the second member occurs through the bonding layer and the convex portion, so heat transfer near the first through hole is promoted. Accordingly, it is possible to suppress the occurrence of a temperature singularity near the first through hole on the first surface, and it is possible to ensure the heat uniformity on the first surface.

Effect of the Invention

[0014] According to the present disclosure, it is possible to provide a holding device capable of improving the withstand voltage (insulation).

Brief Description of the Drawings

[0015]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Embodiments for Carrying Out the Invention

[0016] The holding device according to the embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, as the holding device, for example, an electrostatic chuck used in a semiconductor manufacturing apparatus such as a film forming apparatus (CVD film forming apparatus, sputtering film forming apparatus, etc.) or an etching apparatus (plasma etching apparatus, etc.) will be exemplified and described.

[0017] Therefore, the electrostatic chuck 1 of this embodiment will be described with reference to FIGS. 1 to 4. The electrostatic chuck 1 of this embodiment is a device that adsorbs and holds a semiconductor wafer W (object) by electrostatic attraction, and is used, for example, to fix the semiconductor wafer W in a vacuum chamber of a semiconductor manufacturing apparatus. As shown in FIG. 1, the electrostatic chuck 1 includes a plate-like member 10, a base member 20, and a bonding layer 40 that joins the plate-like member 10 and the base member 20. Note that the plate-like member 10 is an example of the "first member" of the present disclosure, and the base member 20 is an example of the "second member" of the present disclosure.

[0018] In the following description, for convenience of explanation, the XYZ axes are defined as shown in FIG. 1. Here, the Z axis is the axis in the axial direction (vertical direction in FIG. 1) of the electrostatic chuck 1, and the X axis and the Y axis are the axes in the radial direction of the electrostatic chuck 1.

[0019] As shown in FIG. 1, the plate-like member 10 is a disc-shaped member made of ceramics. Various ceramics can be used as the ceramics, but from the viewpoints of strength, wear resistance, plasma resistance, etc., for example, ceramics mainly composed of aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN) are preferably used. Here, the main component means the component with the highest content ratio (for example, the component with a volume content ratio of 90 vol% or more). The diameter of the plate-like member 10 is, for example, about 150 to 350 mm, and the thickness of the plate-like member 10 is, for example, about 2 to 6 mm.

[0020] As shown in FIGS. 1 and 2, the plate-like member 10 includes a holding surface 11 for holding the semiconductor wafer W and a lower surface 12 provided on the side opposite to the holding surface 11 in the thickness direction (the direction coinciding with the Z-axis direction, the vertical direction) of the plate-like member 10. Then, cylindrical first through holes 15a and 15b (hereinafter, may also be referred to as "first through holes 15") penetrating in the thickness direction (Z-axis direction, the vertical direction in FIG. 2) between the holding surface 11 and the lower surface 12 are formed. Note that the holding surface 11 is an example of the "first surface" of the present disclosure, and the lower surface 12 is an example of the "second surface" of the present disclosure.

[0021] The holding surface 11 of the plate-like member 10 has an uneven shape. Specifically, as shown in FIGS. 2 and 3, an annular convex seal band 16 is formed near the outer edge of the holding surface 11, and a plurality of independent columnar convex portions 17 are formed inside the seal band 16. The shape of the cross section (XZ cross section) of the seal band 16 is substantially rectangular as shown in FIG. 2. The height (dimension in the Z-axis direction) of the seal band 16 is, for example, about 10 μm to 20 μm. Also, the width (dimension in the X-axis direction) of the seal band 16 is, for example, about 0.5 mm to 5.0 mm.

[0022] As shown in Fig. 3, each convex portion 17 is substantially circular when viewed in the Z-axis direction (plan view) and is arranged at substantially equal intervals. Also, as shown in Fig. 2, the shape of the cross-section (XZ cross-section) of each convex portion 17 is substantially rectangular. The height of the convex portion 17 is substantially the same as the height of the seal band 16, for example, about 10 to 20 μm. Also, the width of the convex portion 17 (the maximum diameter of the convex portion 17 when viewed in the Z-axis direction) is, for example, about 0.5 to 1.5 mm. Note that, inside the seal band 16 on the holding surface 11 of the plate-like member 10, the portion where the convex portion 17 is not formed is a concave portion 18.

[0023] Then, the semiconductor wafer W is supported by the seal band 16 and the plurality of convex portions 17 on the holding surface 11 of the plate-like member 10 and is held by the electrostatic chuck 1. In a state where the semiconductor wafer W is held by the electrostatic chuck 1, a space S exists between the surface (lower surface) of the semiconductor wafer W and the holding surface 11 of the plate-like member 10 (specifically, the concave portion 18 of the holding surface 11) (see Fig. 2). An inert gas (for example, helium gas) is supplied to this space S through a gas hole 30b described later.

[0024] Also, as shown in Figs. 2 and 4, an annular convex portion 34 protruding in the Z-axis direction is provided on the lower surface 12 of the plate-like member 10 so as to surround the opening of the first through-hole 15. This annular convex portion 34 is made of ceramics like the plate-like member 10 and is integrally formed with the plate-like member 10. That is, the annular convex portion 34 may be integrally formed by co-firing with the plate-like member 10, or may be integrally formed with the plate-like member 10 by diffusion bonding. Alternatively, after manufacturing a thick plate-like member 10, the annular convex portion 34 may be formed by machining such as polishing (scraping off portions other than the portion that becomes the annular convex portion 34). Note that the inner diameter of the annular convex portion 34 and the inner diameter of the first through-hole 15 are the same diameter, and the annular convex portion 34 is coaxial with the first through-hole 15.

[0025] The inner diameter of the annular convex portion 34 may be larger than the inner diameter of the first through hole 15. However, by making the inner diameter of the annular convex portion 34 the same as that of the first through hole 15, the outer diameter of the annular convex portion 34 can be minimized, and thus the diameter of the second through hole 25 described later can be reduced. As a result, the area that is likely to become a temperature singularity point on the holding surface 11 can be reduced.

[0026] Here, the annular convex portion 34 only needs to extend in the Z-axis direction so as to cover at least the bonding layer 40. That is, the tip of the annular convex portion 34 only needs to be disposed within the third through hole 45 of the bonding layer 40 described later. In the present embodiment, the annular convex portion 34 protrudes to the middle of the second through hole 25 described later (about 1 / 4 of the depth of the hole). The length (dimension in the Z-axis direction) of the annular convex portion 34 is preferably, for example, 3 mm or more (the length at which the tip of the annular convex portion 34 is located within the second through hole 25). This is because the bonding layer 40 can be reliably covered by the annular convex portion 34.

[0027] As shown in FIG. 1, the base member 20 has a columnar shape. Specifically, two cylinders with different diameters are stacked such that the lower cylindrical surface portion with a smaller diameter is placed on the upper surface portion of the larger-diameter cylindrical shape, and are formed into a stepped columnar shape with a common central axis Ca. This base member 20 is often formed of a metal (for example, aluminum or an aluminum alloy), but may also be formed of a material other than metal (for example, ceramics).

[0028] As shown in FIGS. 1 and 2, the base member 20 includes an upper surface 21 and a lower surface 22 provided on the side opposite to the upper surface 21 in the direction of the central axis Ca (see FIG. 2) of the base member 20 (plate-like member 10) (that is, in the Z-axis direction). The upper surface 21 is an example of the "third surface" of the present disclosure, and the lower surface 22 is an example of the "fourth surface" of the present disclosure.

[0029] The diameter of the upper portion of the base member 20 is, for example, about 150 mm to 300 mm, and the diameter of the lower portion is, for example, about 180 mm to 350 mm. The thickness (dimension in the Z-axis direction) of the base member 20 is, for example, about 20 mm to 50 mm.

[0030] Also, as shown in FIG. 2, a refrigerant flow path 23 for flowing a refrigerant (for example, a fluorine-based inert liquid, water, etc.) is formed in the base member 20. The refrigerant flow path 23 is connected to a supply port and a discharge port (not shown) provided on the lower surface 22 of the base member 20. The refrigerant supplied to the base member 20 from the supply port flows through the refrigerant flow path 23 and is discharged from the discharge port to the outside of the base member 20. In this way, by flowing the refrigerant in the refrigerant flow path 23 of the base member 20, the base member 20 is cooled, and thereby, the plate-like member 10 is cooled through the bonding layer 40.

[0031] Then, cylindrical second through holes 25a and 25b (hereinafter, may also be referred to as "second through holes 25") penetrating in the thickness direction (Z-axis direction, vertical direction in FIG. 2) between the upper surface 21 and the lower surface 22 are formed in the base member 20. The second through holes 25a and 25b are coaxial with the first through holes 15a and 15b, and the diameters of the second through holes 25a and 25b are larger than the outer diameter of the annular convex portion 34. That is, a gap 35 (see FIG. 4) is formed between the base member 20 (second through holes 25) and the annular convex portion 34.

[0032] The bonding layer 40 is disposed between the lower surface 12 of the plate-like member 10 and the upper surface 21 of the base member 20, and bonds the plate-like member 10 and the base member 20. Through this bonding layer 40, the lower surface 12 of the plate-like member 10 and the upper surface 21 of the base member 20 are thermally connected. The thickness (dimension in the Z-axis direction) of the bonding layer 40 is, for example, about 0.1 to 1.0 mm.

[0033] The bonding layer 40 is composed of, for example, a resin adhesive such as a silicone-based resin, an acrylic-based resin, or an epoxy-based resin, or a metal bonding material mainly composed of a metal material. As the bonding layer 40, a resin adhesive is generally often used. However, when the electrostatic chuck 1 is used at a high temperature (for example, 250 °C or higher), there is a risk of poor bonding due to insufficient heat resistance in the resin adhesive, so a metal bonding material is used. As the metal bonding material, for example, a metal adhesive that bonds using metal powder or metal foil, a metal mesh composed of metal fibers, porous materials, a mesh structure, etc. and a brazing material, or a structure composed of a plurality of columnar metal pieces and a brazing material can be used. As the metal for forming the metal adhesive, metal mesh, or metal pieces, titanium, nickel, aluminum, copper, brass, alloys thereof, or stainless steel can be used.

[0034] As shown in FIG. 2, third through holes 45a and 45b in which the annular convex portions 34 are arranged are formed in this bonding layer 40. That is, cylindrical third through holes 45a and 45b (hereinafter, may also be referred to as "third through holes 45") are formed between the first through holes 15a and 15b and the second through holes 25a and 25b. The third through holes 45a and 45b are coaxial with the first through holes 15a and 15b and the second through holes 25a and 25b, and the first through holes 15a and 15b, the third through holes 45a and 45b, and the second through holes 25a and 25b are arranged in series in the Z-axis direction (the axial direction of the electrostatic chuck 1).

[0035] Then, as shown in FIG. 2, a lift pin insertion hole 30a that penetrates the electrostatic chuck 1 in the Z-axis direction is formed by the first through hole 15a, the inside (hole) of the annular convex portion 34, and the second through hole 25a. A lift pin 60 that pushes up the semiconductor wafer W from the holding surface 11 is inserted into the lift pin insertion hole 30a from the lower surface 22 side of the base member 20. The lift pin 60 has a cylindrical shape (round bar shape) and moves in the Z-axis direction within the lift pin insertion hole 30a. When the lift pin 60 moves to one side in the Z-axis direction (the upper side in FIG. 2) and the tip (upper end) of the lift pin 60 protrudes outside from the holding surface 11 of the plate-like member 10, the semiconductor wafer W placed on the holding surface 11 is separated from the holding surface 11 (the semiconductor wafer W is lifted by the lift pin 60).

[0036] In the electrostatic chuck 1 of the present embodiment, three lift pin insertion holes 30a are formed, and lift pins 60 are inserted into each of the lift pin insertion holes 30a. The three lift pin insertion holes 30a are formed at equal intervals in the circumferential direction of the electrostatic chuck 1 (see FIG. 3).

[0037] Also, a gas hole 30b that penetrates the electrostatic chuck 1 in the Z-axis direction is formed by the first through hole 15b, the inside (hole) of the annular convex portion 34, and the second through hole 25b. This gas hole 30b is a gas flow path through which an inert gas (for example, helium gas) flows. Thereby, by supplying the inert gas into the gas hole 30b from the lower surface 22 side of the base member 20, the space S between the lower surface of the semiconductor wafer W and the holding surface 11 (recess 18) of the plate-like member 10 can be filled with this inert gas. In the following description, the lift pin insertion hole 30a and the gas hole 30b may be simply referred to as "through hole 30".

[0038] Here, the configuration within the through hole 30 will be described with reference to FIG. 4. As shown in FIG. 4, an annular convex portion 34 integrally formed with the plate-like member 10 is formed within the through hole 30. This annular convex portion 34 extends from the lower surface 12 of the plate-like member 10 toward the lower surface 22 side of the base member 20, and the tip thereof is positioned within the second through hole 25 formed in the base member 20. In this embodiment, the annular convex portion 34 extends to a depth position about 1 / 4 of the second through hole 25. Thereby, the inner peripheral surface of the third through hole 45 of the bonding layer 40 is covered by the annular convex portion 34. And a gap 35 is formed between the annular convex portion 34 and the second through hole 25.

[0039] As such an electrostatic chuck 1, the following three examples (First to Third Examples) can be given depending on the combination of materials forming the base member 20 and the bonding layer 40.

[0040] <First Example> First, the First Example will be described. In the First Example, the base member 20 is made of metal, and the bonding layer 40 is composed of a resin adhesive. That is, in the electrostatic chuck 1 of the First Example, as shown in FIG. 5, a ceramic plate-like member 10 and a metal base member 20a are joined by a bonding layer 40a composed of a resin adhesive.

[0041] In such an electrostatic chuck 1 of the First Example, when the electrostatic chuck 1 is used in a high-power region (under a high-voltage plasma environment), abnormal discharge may occur between the semiconductor wafer W and the base member 20.

[0042] However, in the electrostatic chuck 1 of the first embodiment, an annular convex portion 34 integrally formed with the plate-like member 10 is provided on the lower surface 12 of the plate-like member 10 so as to surround the opening of the first through-hole 15. And the annular convex portion 34 is provided up to a depth position about 1 / 4 of the second through-hole 25. Therefore, the creeping distance between the semiconductor wafer W and the base member 20 can be increased by the annular convex portion 34. As a result, the withstand voltage between the semiconductor wafer W and the base member 20 is improved, so that the occurrence of abnormal discharge between the semiconductor wafer W and the base member 20 can be prevented.

[0043] Also, since the bonding layer 40 (the inner peripheral surface of the third through-hole 45) is covered by the annular convex portion 34, the bonding layer 40 is not directly exposed to the plasma environment (the plasma entering the first through-hole 15). As a result, the plasma does not come into contact with the bonding layer 40, so that the deterioration of the bonding layer 40 can be prevented.

[0044] And in the electrostatic chuck 1 of the first embodiment, since there is a thermal expansion difference between the plate-like member 10 and the base member 20a, when the temperature rises / falls during the use of the electrostatic chuck 1, the annular convex portion 34 may be damaged by contacting the base member 20a due to the thermal expansion difference.

[0045] Therefore, a gap 35 is formed between the annular convex portion 34 and the second through-hole 25. As the gap 35, it may be set to such an extent that the annular convex portion 34 does not contact the base member 20 even due to the thermal expansion difference between the plate-like member 10 and the base member 20 (for example, about 0.1 to 2.0 mm). By providing such a gap 35, damage to the annular convex portion 34 can be surely prevented. As a result, the occurrence of abnormal discharge between the semiconductor wafer W and the base member 20 can be surely prevented by the annular convex portion 34.

[0046] <Second Embodiment> Next, a second embodiment will be described. In the second embodiment, the base member 20 is formed of ceramics, and the bonding layer 40 is composed of a metal bonding material. That is, in the electrostatic chuck 1 of the second embodiment, as shown in FIG. 6, a plate-shaped member 10 made of ceramics and a base member 20b made of ceramics are bonded by a bonding layer 40b composed of a metal bonding material.

[0047] Such an electrostatic chuck 1 of the second embodiment is suitable for use at a high temperature (for example, 250° C. or higher) where the heat resistance of the resin adhesive is insufficient. And in the second embodiment, since the bonding layer 40b is composed of a metal bonding material, the creepage distance is shorter than that of the first embodiment (there is a risk of abnormal discharge occurring between the semiconductor wafer W and the bonding layer 40b).

[0048] However, also in the electrostatic chuck 1 of the second embodiment, an annular convex portion 34 integrally formed with the plate-shaped member 10 is provided on the lower surface 12 of the plate-shaped member 10 so as to surround the opening of the first through hole 15. Therefore, the creepage distance between the semiconductor wafer W and the bonding layer 40b can be increased by the annular convex portion 34. As a result, the withstand voltage between the semiconductor wafer W and the bonding layer 40b is improved, so that the occurrence of abnormal discharge between the semiconductor wafer W and the bonding layer 40b can be prevented. In the second embodiment, the length (dimension in the Z-axis direction) of the annular convex portion 34 may be shorter than that of the first embodiment because the base member 20b is not made of metal.

[0049] Also, in the second embodiment, since the bonding layer 40b is covered by the annular convex portion 34, the bonding layer 40b is not directly exposed to the plasma environment (plasma that enters the through hole 30). Therefore, deterioration of the bonding layer 40b can also be prevented.

[0050] And in the electrostatic chuck 1 of the second embodiment, since the thermal expansion difference between the plate-shaped member 10 and the base member 20b is small, the gap 35 provided between the annular convex portion 34 and the second through hole 25 may be smaller than that of the first embodiment (for example, about 0.1 to 2.0 mm).

[0051] <Third Embodiment> Finally, the third embodiment will be described. In the third embodiment, the base member 20 is made of metal, and the bonding layer 40 is composed of a metal bonding material. That is, in the electrostatic chuck 1 of the third embodiment, as shown in FIG. 7, the ceramic plate-like member 10 and the metal base member 20a are joined by a bonding layer 40b composed of a metal bonding material.

[0052] Such an electrostatic chuck 1 of the third embodiment is also suitable for use at high temperatures (for example, 250°C or higher) where the heat resistance of the resin adhesive is insufficient, similar to the second embodiment. And in the third embodiment as well, since the bonding layer 40b composed of a metal bonding material is used, the creepage distance becomes shorter than that of the first embodiment (there is a risk of abnormal discharge occurring between the semiconductor wafer W and the bonding layer 40).

[0053] However, in the electrostatic chuck 1 of the third embodiment as well, an annular convex portion 34 integrally formed with the plate-like member 10 is provided on the lower surface 12 of the plate-like member 10 so as to surround the opening of the first through hole 15. Therefore, the creepage distance between the semiconductor wafer W and the bonding layer 40b can be increased by the annular convex portion 34. As a result, the withstand voltage between the semiconductor wafer W and the bonding layer 40b is improved, and the occurrence of abnormal discharge between the semiconductor wafer W and the bonding layer 40 can be prevented. Note that in the third embodiment, the length (dimension in the Z-axis direction) of the annular convex portion 34 is the same as that of the first embodiment.

[0054] Also, in the third embodiment as well, since the bonding layer 40b is covered by the annular convex portion 34, the bonding layer 40b is not directly exposed to the plasma environment (plasma that enters the through hole 30). Therefore, deterioration of the bonding layer 40b can also be prevented.

[0055] And in the third embodiment, since there is a difference in thermal expansion between the plate-like member 10 and the base member 20, a gap 35 (for example, about 0.1 to 2.0 mm) equivalent to that in the first embodiment is provided between the annular convex portion 34 and the second through-hole 25. Thereby, damage to the annular convex portion 34 can be reliably prevented, and the annular convex portion 34 can reliably prevent the occurrence of abnormal discharge between the semiconductor wafer W and the bonding layer 40b.

[0056] <Modification> Subsequently, the modification will be described with reference to FIG. 8. The modification has the same basic structure as the above-described embodiment, but the diameter of the third through-hole 45 of the bonding layer 40 is smaller than that in the above-described embodiment. That is, in the modification, as shown in FIG. 8, the annular convex portion 34 (the outer peripheral surface thereof) and the bonding layer 40 (the inner peripheral surface of the third through-hole 45) are in contact with each other.

[0057] Here, heat transfer between the base member 20 through the bonding layer 40 does not occur in the first through-hole 15. Therefore, the vicinity of the first through-hole 15 on the holding surface 11 of the plate-like member 10 is likely to have a locally large temperature difference compared to other portions and become a temperature singularity.

[0058] Therefore, by bringing the annular convex portion 34 protruding so as to surround the opening of the first through-hole 15 into contact with the bonding layer 40, heat transfer between the plate-like member 10 and the base member 20 occurs through the bonding layer 40 and the annular convex portion 34. Thereby, heat transfer in the vicinity of the first through-hole 15 is promoted. Therefore, it is possible to suppress the occurrence of a temperature singularity in the vicinity of the first through-hole 15 on the holding surface 11, and it is possible to ensure the heat uniformity on the holding surface 11.

[0059] As described above, according to the electrostatic chuck 1 of the present embodiment, on the lower surface 12 of the plate-like member 10, the annular convex portion 34 integrally formed with the plate-like member 10 around the first through-hole 15 is provided so as to cover at least a part of the bonding layer 40. Therefore, the annular convex portion 34 can increase the creepage distance between the semiconductor wafer W and the base member 20b (Example 1) or the bonding layer 40b (Examples 2 and 3).

[0060] Therefore, it is possible to prevent the occurrence of abnormal discharge between the semiconductor wafer W and the base member 20b (Example 1) or the bonding layer 40b (Examples 2 and 3). Further, since the bonding layer 40 is covered by the annular convex portion 34, the bonding layer 40 is not directly exposed to the plasma environment, so that deterioration of the bonding layer 40 can be prevented. From these facts, the breakdown voltage (insulativity) of the electrostatic chuck 1 can be improved.

[0061] Note that the above-described embodiments are merely examples and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible without departing from the gist of the present disclosure. For example, in the above-described embodiments, the case where the present disclosure is applied to an electrostatic chuck is illustrated. However, the present disclosure can be applied not only to an electrostatic chuck but also to all holding devices that hold an object on a holding surface.

[0062] Further, in the above-described embodiments, the case where the annular convex portion 34 is provided up to the middle of the second through-hole 25 is illustrated. However, as shown in FIG. 9, the annular convex portion 34 may be provided over the entire area of the second through-hole 25 (so as not to protrude from the base member 20 up to the lower surface 22 of the base member 20). Thereby, the breakdown voltage of the electrostatic chuck 1 can be further improved. Note that when the annular convex portion 34 is provided over the entire area of the second through-hole 25, the annular convex portion 34 becomes long and there is a risk of damaging the annular convex portion 34 during the manufacture of the electrostatic chuck 1. Therefore, instead of providing the annular convex portion 34 over the entire area of the second through-hole 25, as shown in FIG. 10, an insulating sleeve 36 or the like formed of a separate member can be joined to the annular convex portion 34 provided up to the middle of the second through-hole 25. Thereby, it is possible to prevent the annular convex portion 34 from being damaged during manufacture and further improve the breakdown voltage of the electrostatic chuck 1.

[0063] Further, in the above-described embodiments, the case where the annular convex portion 34 extends up to the base member 20 (inside the second through-hole 25) is illustrated. However, even in a form in which the annular convex portion 34 extends up to the middle of the bonding layer 40, that is, the tip of the annular convex portion 34 is located inside the third layer through-hole 45, the above-described effects can be obtained.

[0064] Further, the tip corner of the annular convex portion 34 may be formed into an R shape or a tapered shape, or a step may be provided in the annular convex portion 34 (changing the thickness of the annular convex portion 34). By doing so, the creepage distance between the semiconductor wafer W and the bonding layer 40b or the base member 20a made of metal becomes longer, and the breakdown voltage can be further improved.

Explanation of Signs

[0065] 1 Electrostatic chuck 10 Plate-like member 11 Holding surface 12 Lower surface 15 First through-hole 20 Base member 21 Upper surface 22 Lower surface 25 Second through-hole 30 Through-hole 34 Annular convex portion 35 Gap 40 Bonding layer 45 Third through-hole W Semiconductor wafer

Claims

1. a first member including a first surface, a second surface provided on the side opposite to the first surface, and a first through hole penetrating the first surface and the second surface; a second member including a third surface, a fourth surface provided on the side opposite to the third surface, and a second through hole penetrating the third surface and the fourth surface and communicating with the first through hole; a bonding layer disposed between the second surface of the first member and the third surface of the second member for bonding the first member and the second member; a holding device for holding an object on the first surface of the first member, wherein a third through hole for communicating the first through hole and the second through hole is formed in the bonding layer; an annular convex portion protruding at least to a depth of 1 / 4 of the second through hole is integrally formed with the first member so as to surround an opening of the first through hole on the second surface; a gap of 0.1 mm to 2.0 mm is formed between the convex portion and the second through hole along a direction perpendicular to the depth direction of the second through hole The holding device is characterized by the above.

2. The holding device according to claim 1, wherein the convex portion is in contact with the bonding layer The holding device is characterized by the above.

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