JP7587396B2 - Retaining device - Google Patents

Description

This disclosure relates to a holding device for holding an object.

As a holding device, for example, an electrostatic chuck described in Patent Document 1 is known. This electrostatic chuck has a ceramic plate (plate-shaped member) that holds an object on its surface (holding surface) and a metal base member bonded to the ceramic plate, and an internal electrode such as a chuck electrode or a heater electrode is disposed inside the ceramic plate. This electrostatic chuck also has a configuration for supplying power to the internal electrode. That is, inside the base member, a terminal through hole is formed that opens on the surface of the base member that faces the ceramic plate (hereinafter referred to as the "upper surface"), and a columnar electrode terminal is disposed in the terminal through hole. Also, an electrode pad (terminal pad) that is conductive to the internal electrode is disposed in a predetermined area of the surface of the ceramic plate that faces the base member (hereinafter referred to as the "lower surface").

Here, if the creeping distance from the electrode pad to the base member along the lower surface of the ceramic plate is short, there is a risk of a short circuit occurring between the electrode pad and the base member. In order to increase the creeping distance, in this electrostatic chuck, at least one of a recess recessed toward the internal electrode from the position where the electrode pad is arranged in the thickness direction and a protrusion protruding away from the internal electrode from the position where the electrode pad is arranged in the thickness direction is continuously formed in the first region (region overlapping the terminal through hole as viewed in the thickness direction of the ceramic plate) on the second surface (surface facing the base member) of the ceramic plate so as to surround the electrode pad as viewed in the thickness direction. As a result, in this electrostatic chuck, the creeping distance from the electrode pad to the base member along the second surface of the ceramic plate is increased, thereby suppressing the occurrence of a short circuit between the electrode pad and the base member.

JP 2018-101711 A

However, in the above electrostatic chuck, the thickness of the ceramic plate is reduced in the area where the recess is formed, and if an internal electrode is placed near the recess, the distance between the bottom of the hole and the internal electrode is shortened, which may cause insulation breakdown. In addition, the volume of the ceramic plate is reduced in the area where the recess is formed, which may cause poor heat transfer and result in the holding surface becoming locally hot in the area directly above the recess, making it difficult to uniformly control the temperature of the holding surface, which may reduce the thermal uniformity of the holding surface.

The present disclosure has been made to solve the above-mentioned problems, and aims to provide a holding device that can improve the insulation between the terminal pad and the base member by increasing the creepage distance from the terminal pad to the base member, and can also improve the thermal uniformity on the holding surface.

In order to solve the above problems, one aspect of the present disclosure is to
a plate-like member including a first surface, a second surface provided on an opposite side to the first surface in a first direction, an internal electrode provided therein, and a terminal pad electrically connected to the internal electrode;
an electrode terminal joined to the terminal pad;
an insulating member covering an outer circumferential surface of the electrode terminal;
a metal base member having through holes in which the electrode terminals and the insulating members are disposed and joined to the second surface of the plate-like member;
A holding device for holding an object on the first surface of the plate-like member,
the second surface of the plate-like member is formed with a bottomed hole recessed toward the first surface and in which the terminal pad is disposed;
a cavity is formed in a bottom or an opening side surface of the bottomed hole, the cavity extending outward from the opening side surface of the bottomed hole in a second direction perpendicular to the first direction ,
The maximum dimension of the hollow portion in the first direction is equal to or less than half the dimension of the bottomed hole in the first direction .

In this holding device, a cavity is formed in the bottom or opening side of the bottomed hole in which the terminal pad is placed, which extends outward from the opening side (i.e., the inner peripheral surface) of the bottomed hole in a second direction (radial direction) perpendicular to the first direction (axial direction), making it possible to lengthen the creepage distance from the terminal pad to the base member. This makes it possible to improve the insulation between the terminal pad and the base member.

In addition, because the cavity is formed to expand outward in the second direction (radial direction), the thickness of the plate-shaped member does not decrease in the area where the bottomed holes are arranged, as in conventional devices. This makes it possible to prevent dielectric breakdown from occurring between the internal electrode (which is arranged closest to the terminal pad, such as a heater electrode or a conductive layer that is a land pattern for supplying an electrode to the heater electrode) and the terminal pad.

Here, on the first surface (holding surface), the area where the bottomed holes are located (the position directly above the bottomed holes) is more likely to become hotter because its volume is smaller than other areas. If the thickness (volume) of the plate-like member is reduced in the area where the bottomed holes are located, as in conventional devices, temperature singularities that cause localized high temperatures are very likely to occur in the area where the bottomed holes are located on the first surface.

In contrast, in this holding device, the cavity is formed to expand outward in the second direction (radial direction), so the thickness (volume) of the plate-shaped member does not decrease in the area where the bottomed holes are arranged. Therefore, in the area where the bottomed holes are arranged, deterioration of heat transfer due to a decrease in the volume of the plate-shaped member does not occur. Therefore, it is possible to suppress the occurrence of temperature singularities on the first surface (holding surface) that cause localized high temperatures, and to improve thermal uniformity on the first surface.

Here, if the maximum dimension of the cavity in the first direction (axial direction) is increased, the creepage distance from the terminal pad to the base member can be increased, but the volumetric reduction of the plate-like member around the bottomed hole will be large. If the volumetric reduction of the plate-like member around the bottomed hole becomes large, heat transfer will deteriorate, and there is a risk of temperature singularities occurring on the first surface (holding surface) where the temperature becomes locally high.

Thus, by specifying the maximum dimension of the cavity in the first direction in this manner, it is possible to ensure the required creepage distance (that does not cause a short circuit) while suppressing the volumetric reduction of the plate-like member around the bottomed hole, thereby preventing the occurrence of temperature singularities that cause localized high temperatures around the bottomed hole, and improving thermal uniformity on the first surface.

In the above-mentioned holding device,
It is preferable that the cavity includes a surface on which the terminal pads are arranged in the first direction.

By forming the cavity at the bottom of the bottomed hole in this way, the creepage distance from the terminal pad to the side of the opening is extended compared to when the cavity is formed on the side of the opening of the bottomed hole, thereby further improving the insulation between the terminal pad and the base member.

In the above-mentioned holding device,
It is preferable that the hollow portion has a tapered portion formed in the bottom portion , the dimension of which in the second direction gradually increases from the opening of the bottomed hole toward the bottom portion.

By doing this, the volumetric reduction of the plate-like member around the bottomed holes can be further suppressed, and the temperature gradient becomes gentler, so that it is possible to reliably prevent the occurrence of temperature singularities around the bottomed holes where the temperature becomes locally high, and the thermal uniformity on the first surface can be further improved.

In addition, when filling the bottomed holes and the hollow portion with adhesive (such as silicone-based resin), the adhesive can be filled smoothly and without gaps into the hollow portion. This increases the thermal conductivity of the hollow portion, making it possible to more reliably prevent the occurrence of temperature singularities that cause localized high temperatures around the bottomed holes, and effectively suppresses the decrease in thermal uniformity on the first surface caused by the provision of the hollow portion.

According to the present disclosure, it is possible to provide a holding device that can improve the insulation between the terminal pad and the base member by increasing the creepage distance from the terminal pad to the base member, and can also improve the thermal uniformity on the holding surface.

FIG. 1 is a schematic perspective view of an electrostatic chuck according to a first embodiment. 1 is a schematic configuration diagram of an electrostatic chuck according to a first embodiment of the present invention taken along an XZ cross section; FIG. 3 is an enlarged view of the vicinity of the cavity (part X1 in FIG. 2). FIG. 2 is an enlarged view of the vicinity of a cavity in an electrostatic chuck having a conductive layer. FIG. 11 is an enlarged view of the vicinity of a cavity in an electrostatic chuck according to a second embodiment.

[First embodiment]
A holding device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, an electrostatic chuck 1 that holds an object, that is, a semiconductor wafer W, will be described as an example. The electrostatic chuck 1 of this embodiment will be described with reference to FIGS. 1 to 3.

The electrostatic chuck 1 of this embodiment is a device that attracts 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 device. As shown in FIG. 1, the electrostatic chuck 1 has a plate-shaped member 10, a base member 20, and a bonding layer 40 that bonds the plate-shaped member 10 and the base member 20.

For ease of explanation, in the following description, the X, Y and Z axes are defined as shown in FIG. 1. Here, the Z axis is the axis in the axial direction of the electrostatic chuck 1 (the vertical direction in FIG. 1), and the X and Y axes are the axes in the radial direction of the electrostatic chuck 1. The Z axis direction is an example of the "first direction" of the present disclosure, and the radial directions (X axis direction and Y axis direction) are an example of the "second direction" of the present disclosure.

The plate-like member 10 is a disk-like member as shown in Fig. 1, and may be made of ceramics. Various ceramics may be used as the ceramics, but from the viewpoints of strength, wear resistance, plasma resistance, etc., it is preferable to use ceramics whose main component is, for example, aluminum oxide (alumina, _Al2O3 ) or aluminum nitride (AlN). Note that the main component here means the component with the highest content (for example, _a component with a volume content of 90 vol% or more).

The diameter of the plate-shaped member 10 is, for example, about 150 to 300 mm at the upper portion and about 180 to 350 mm at the lower portion. The thickness of the plate-shaped member 10 is, for example, about 2 to 6 mm. The thermal conductivity of the plate-shaped member 10 is preferably within the range of 10 to 50 W/mK (more preferably, 18 to 30 W/mK).

As shown in Figures 1 and 2, the plate-like member 10 has a holding surface 11 that holds a semiconductor wafer W, and a bottom surface 12 that is provided on the opposite side of the holding surface 11 in the thickness direction of the plate-like member 10 (the direction that coincides with the Z-axis direction, the up-down direction). Note that the holding surface 11 is an example of a "first surface" in this disclosure, and the bottom surface 12 is an example of a "second surface" in this disclosure.

As shown in Figs. 2 and 3, a chuck electrode 13 made of a conductive material (e.g., tungsten, molybdenum, etc.) is provided inside the plate-like member 10. The shape of the chuck electrode 13 as viewed in the Z-axis direction is, for example, substantially circular. When a voltage is applied to the chuck electrode 13 from a power source (not shown), an electrostatic force is generated, and the wafer W is attracted and fixed to the holding surface 11 of the plate-like member 10 by this electrostatic force.

As shown in FIG. 2, a heater electrode 14 is provided inside the plate-like member 10 and is made of a resistive heating element made of a conductive material (e.g., tungsten, molybdenum, etc.). The shape of the heater electrode 14 when viewed in the Z-axis direction is, for example, approximately spiral.

The heater electrode 14 has a line width of, for example, about 0.1 to 10 mm, and a thickness (dimension in the Z-axis direction) of, for example, about 0.02 to 3 mm. When a voltage is applied to the heater electrode 14 from a power source (not shown), the heater electrode 14 generates heat, which heats the holding surface 11, thereby heating the semiconductor wafer W held by the holding surface 11.

A bottomed hole 15 is formed on the lower surface 12 of the plate-like member 10. This bottomed hole 15 is a circular recess, and when viewed in the Z-axis direction, the area overlapping with the through hole 25 of the base member 20 described later has a shape recessed toward the holding surface 11 side. The diameter of the bottomed hole 15 is, for example, 7 to 8 mm. A terminal pad 30 is disposed on the bottom 15b of this bottomed hole 15. The shape of the terminal pad 30 when viewed in the Z-axis direction is, for example, approximately circular. In this embodiment, for example, as shown in FIG. 2, one terminal pad 30 is electrically connected to the chuck electrode 13 through the via 31, and the other terminal pad 30 is electrically connected to the heater electrode 14 through the via 31. The terminal pad 30 and the via 31 are formed of a conductive material (for example, tungsten, molybdenum, etc.). Note that the entire terminal pad 30 in the thickness direction (Z-axis direction) is exposed from the plate-like member 10 as shown in FIGS. 2 and 3. However, as long as the underside of the terminal pad 30 is exposed from the plate-like member 10, a part or the entirety of the terminal pad 30 in the thickness direction may be embedded in the plate-like member 10.

A hollow portion 16 is formed in the bottom 15b of the bottomed hole 15. That is, the hollow portion 16 includes the surface on which the terminal pad 30 is arranged in the Z-axis direction. This hollow portion 16 is an annular space that expands radially outward from the inner peripheral surface 15a of the bottomed hole 15, and has a tapered portion 16a whose radial dimension gradually increases from the opening of the bottomed hole 15 to the bottom 15b. That is, the hollow portion 16 is an annular space with a triangular cross section. The diameter of the hollow portion 16 is, for example, 9 to 10 mm. By forming such a hollow portion 16, it is possible to increase the creepage distance CD from the terminal pad 30 to the base member 20.

As shown in Fig. 1, the base member 20 is cylindrical, more specifically, a stepped cylinder formed by stacking two cylinders of different diameters coaxially (with a common central axis) with the lower surface of the smaller diameter cylinder placed on the upper surface of the larger diameter cylinder. This base member 20 is preferably made of a metal (e.g., aluminum or an aluminum alloy), but may be made of a material other than metal.

As shown in Figs. 1 and 2, the base member 20 has an upper surface 21 and a lower surface 22 provided on the opposite side of the upper surface 21 in the Z-axis direction of the base member 20 (plate-like member 10). The upper surface 21 is an example of a "third surface" in the present disclosure, and the lower surface 22 is an example of a "fourth surface" in the present disclosure.

The diameter of the base member 20 is, for example, about 150 mm to 300 mm at the upper stage and about 180 mm to 350 mm at the lower stage. The thickness of the base member 20 (dimension in the Z-axis direction) is, for example, about 20 mm to 50 mm. The thermal conductivity of the base member 20 (assumed to be aluminum) is greater than that of the plate-like member 10, and is desirably within the range of 180 to 250 W/mK (preferably about 230 W/mK).

As shown in FIG. 2, the base member 20 is formed with a refrigerant flow path 23 for flowing a refrigerant (e.g., a fluorine-based inert liquid, water, etc.). 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, and 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, the base member 20 is cooled by flowing the refrigerant through the refrigerant flow path 23 of the base member 20, and the plate-like member 10 is thereby cooled via the bonding layer 40.

The base member 20 has a cylindrical through-hole 25 that penetrates between the upper surface 21 and the lower surface 22 in the thickness direction (Z-axis direction, vertical direction in FIG. 2). An electrode terminal 35 and an insulating member 36 are disposed in the through-hole 25.

Here, the electrode terminal 35 is a columnar terminal extending in the Z-axis direction, and in this embodiment, for example, has a circular cross-sectional shape (cross-sectional shape parallel to the surface direction). The upper end of the electrode terminal 35 reaches the terminal pad 30, and the electrode terminal 35 is joined to the terminal pad 30 by, for example, a metal brazing material.

The insulating member 36 provides insulation between the base member 20 and the electrode terminal 35. This insulating member 36 continuously surrounds the electrode terminal 35 so as to be interposed between the electrode terminal 35 and the surface of the through hole 25. The insulating member 36 is made of an insulating material such as resin or ceramics. In this embodiment, the thermal conductivity of the insulating member 36 is lower than the thermal conductivity of the plate-shaped member 10 (i.e., the thermal conductivity of the plate-shaped member 10 is higher than the thermal conductivity of the insulating member 36).

Adhesive 70 is filled around the insulating member 36, specifically between the insulating member 36 and the electrode terminal 35, between the insulating member 36 and the plate-like member 10, between the insulating member 36 and the base member 20, and in the cavity 16 (see FIG. 3). The adhesive 70 is made of, for example, a silicone resin, an acrylic resin, an epoxy resin, or other adhesive, and bonds the insulating member 36 to the electrode terminal 35, the plate-like member 10, and the base member 20.

As shown in Figs. 1 and 2, the bonding layer 40 is disposed between the lower surface 12 of the plate-shaped member 10 and the upper surface 21 of the base member 20, and bonds the plate-shaped member 10 and the base member 20. The lower surface 12 of the plate-shaped member 10 and the upper surface 21 of the base member 20 are thermally connected via this bonding layer 40.

The bonding layer 40 is made of an adhesive such as silicone resin, acrylic resin, or epoxy resin. The thickness (dimension in the Z-axis direction) of the bonding layer 40 is, for example, about 0.1 to 1.0 mm. The thermal conductivity of the bonding layer 40 is, for example, 1.0 W/mK. The thermal conductivity of the bonding layer 40 (assuming silicone resin) is preferably in the range of 0.1 to 2.0 W/mK (preferably 0.5 to 1.5 W/mK).

As shown in FIG. 3, the bonding layer 40 has a through hole 45 formed therein, which penetrates the bonding layer 40 in the Z-axis direction. The through hole 45 connects the through hole 25 of the base member 20 to the bottomed hole 15. In other words, the through hole 25 formed in the base member 20 and the bottomed hole 15 formed in the plate-like member 10 form an integrated hole that communicates with each other via the through hole 45 formed in the bonding layer 40.

In the electrostatic chuck 1 having the above-mentioned configuration, the bottom 15b of the bottomed hole 15 has a cavity 16 that expands in the radial direction, so that the creepage distance CD from the position where the terminal pad 30 is arranged to the base member 20 can be increased. As a result, according to the electrostatic chuck 1 of this embodiment, the occurrence of a short circuit between the terminal pad 30 and the base member 20 can be suppressed, and the insulation between the terminal pad 30 and the base member 20 can be improved. This makes it possible to prevent the occurrence of dielectric breakdown in the electrostatic chuck 1.

The cavity 16 provided to lengthen the creepage distance CD is provided in the radial direction, not the Z-axis direction as in the conventional device, so the thickness (volume) of the plate-shaped member 10 does not decrease. That is, the distance between the bottom 15b of the bottomed hole 15 and the internal electrode (heater electrode 14 in this embodiment) closest to the terminal pad 30 does not change (does not shorten). Therefore, it is possible to suppress the occurrence of a short circuit between the terminal pad 30 and the internal electrode (heater electrode 14 in this embodiment), and it is possible to prevent the occurrence of dielectric breakdown in the electrostatic chuck 1.

In this embodiment, in order to achieve uniform heating of the holding surface 11, the conductive layer, which is a land pattern serving as a power supply path to the heater electrode 14, is not provided. However, as shown in FIG. 4, when the conductive layer 60 is provided, the conductive layer 60 becomes the internal electrode closest to the bottom 15b of the bottomed hole 15 and the terminal pad 30. In this case, the terminal pad 30 and the conductive layer 60 are electrically connected through the via 31, and the conductive layer 60 and the heater electrode 14 are electrically connected through the via 32. In this way, when the conductive layer 60 is provided, the thickness of the plate-shaped member 10 does not decrease even if the cavity 16 is provided, so the distance between the bottom 15b of the bottomed hole 15 and the conductive layer 60 does not change (does not become shorter), and therefore the occurrence of a short circuit between the terminal pad 30 and the conductive layer 60 can be suppressed. The conductive layer 60 is formed of a conductive material (e.g., tungsten, molybdenum, etc.).

Here, the area of the holding surface 11 where the bottomed holes 15 are arranged (the position directly above the bottomed holes 15) is more likely to become hotter than other areas. This is because the area where the bottomed holes 15 are arranged has poorer heat transfer and is more difficult to cool due to the presence of the through holes 25 and through holes 45. If the thickness of the plate-like member 10 is further reduced in the area where the bottomed holes 15 are arranged, as in the conventional device, temperature singularities that cause localized high temperatures are very likely to occur in the area where the bottomed holes 15 are arranged on the holding surface 11.

However, in the electrostatic chuck 1 of this embodiment, the cavity 16 is formed to expand radially outward, so the thickness of the plate-shaped member 10 does not decrease in the area where the bottomed holes 15 are arranged. Therefore, in the holding surface 11, in the area where the bottomed holes 15 are arranged, deterioration of heat transfer due to a reduction in the volume of the plate-shaped member 10 does not occur. Therefore, in the holding surface 11, it is possible to suppress the occurrence of temperature singularities that become locally high temperatures near the area where the bottomed holes 15 are arranged, and the thermal uniformity in the holding surface 11 can be improved.

The hollow portion 16 has a tapered portion 16a in which the radial dimension gradually increases from the opening of the bottomed hole 15 toward the bottom portion 15b, so that the volume reduction of the plate-like member 10 around the bottomed hole 15 can be further suppressed. This makes it possible to reliably prevent the occurrence of temperature singularities in the vicinity of the bottomed hole 15 on the holding surface 11 where the temperature becomes locally high, and further improves the thermal uniformity on the holding surface 11.

In addition, because the hollow portion 16 has a tapered portion 16a, the adhesive 70 that bonds the insulating member 36 to the electrode terminal 35, the plate-like member 10, and the base member 20 can be smoothly filled into the hollow portion 16 without any gaps. This increases the thermal conductivity of the hollow portion 16, making it possible to more reliably prevent the occurrence of temperature singularities around the bottomed holes 15 on the holding surface 11 where the temperature becomes locally high, and effectively suppresses the decrease in thermal uniformity on the holding surface 11 caused by the provision of the hollow portion 16.

In addition, if the maximum dimension of the cavity 16 in the Z-axis direction or radial direction is increased, the creepage distance CD from the terminal pad 30 to the base member 20 becomes longer, while the volume reduction of the plate-like member 10 around the bottomed hole 15 becomes greater. If the volume reduction of the plate-like member 10 around the bottomed hole 15 becomes greater, heat transfer deteriorates, and there is a risk of temperature singularities occurring on the holding surface 11 where the temperature becomes locally high.

Therefore, it is preferable that the maximum dimension of the cavity 16 in the Z-axis direction is 1/2 or less of the dimension of the bottomed hole 15 in the Z-axis direction. Also, it is preferable that the radial dimension of the bottomed hole 15 is 1/2 or more and 1 or less of the maximum radial dimension of the cavity 16. By specifying the maximum dimension of the cavity 16 in the Z-axis direction and the radial dimension of the bottomed hole 15 in this way, it is possible to ensure the required creepage distance (that does not cause a short circuit) while suppressing the volume reduction of the plate-like member 10 around the bottomed hole 15, and to prevent the occurrence of temperature singularities where the temperature becomes locally high around the bottomed hole 15 on the holding surface 11, thereby improving the thermal uniformity on the holding surface 11.

As described above, according to the electrostatic chuck 1 of this embodiment, a cavity 16 is formed in the bottom 15b of the bottomed hole 15, which extends radially outward beyond the inner peripheral surface 15a of the bottomed hole 15. Therefore, in the area where the bottomed hole 15 is arranged, the creepage distance CD from the terminal pad 30 to the base member 20 can be increased without reducing the thickness of the plate-like member 10. This improves the insulation between the terminal pad 30 and the base member 20 and between the terminal pad 30 and the internal electrode, and also improves the thermal uniformity on the holding surface 11.

[Second embodiment]
Next, a second embodiment will be described. In the second embodiment, the position of the cavity is different from that of the first embodiment. That is, in the second embodiment, the cavity 116 is provided not in the bottom 15b of the bottomed hole 15 but in the inner circumferential surface 15a which is the opening side surface of the bottomed hole 15. Therefore, the same reference numerals are used for the same configuration as in the first embodiment, and the description is omitted as appropriate, and the differences from the first embodiment will be mainly described.

As shown in FIG. 5, in the electrostatic chuck of this embodiment, a cavity 116 that extends radially outward is formed on the inner circumferential surface 15a of the bottomed hole 15. This cavity 116 is an annular space that extends radially outward beyond the inner circumferential surface 15a of the bottomed hole 15. The cavity 116 has a tapered portion 16a. The cavity 116 is filled with adhesive 70.

Even when such a cavity 116 is formed, the creepage distance CD from the terminal pad 30 to the base member 20 can be increased. As a result, even in the electrostatic chuck of this embodiment, the occurrence of a short circuit between the terminal pad 30 and the base member 20 can be suppressed, and the insulation between the terminal pad 30 and the base member 20 can be improved.

The cavity 116 provided to lengthen the creepage distance CD is provided in the radial direction, not the Z-axis direction as in conventional devices, so the thickness (volume) of the plate-shaped member 10 does not decrease. That is, the distance between the bottom 15b of the bottomed hole 15 and the internal electrode (heater electrode 14 in this embodiment) closest to the terminal pad 30 does not change (does not shorten). Therefore, it is possible to suppress the occurrence of a short circuit between the terminal pad 30 and the internal electrode (heater electrode 14 in this embodiment). In this way, this embodiment also makes it possible to prevent the occurrence of dielectric breakdown in the electrostatic chuck.

In addition, because the hollow portion 116 has a tapered portion 16a, the volumetric reduction of the plate-like member 10 around the bottomed hole 15 can be further suppressed. As a result, the temperature gradient becomes gentle around the bottomed hole 15 on the holding surface 11, so the occurrence of temperature singularities that cause localized high temperatures can be reliably prevented, and the thermal uniformity on the holding surface 11 can be further improved.

Furthermore, because the hollow portion 116 has a tapered portion 16a, the adhesive 70 can be smoothly filled into the hollow portion 116 without any gaps. This increases the thermal conductivity of the hollow portion 16, making it possible to more reliably prevent the occurrence of temperature singularities around the bottomed holes 15 on the holding surface 11 where the temperature becomes locally high, and effectively suppresses the decrease in thermal uniformity on the holding surface 11 caused by the provision of the hollow portion 116.

As described above, according to the electrostatic chuck of this embodiment, a cavity 116 is formed on the inner peripheral surface 15a of the bottomed hole 15, which extends radially outward beyond the inner peripheral surface 15a of the bottomed hole 15. Therefore, in the area where the bottomed hole 15 is arranged, the creepage distance CD from the terminal pad 30 to the base member 20 can be increased without reducing the thickness of the plate-like member 10. This improves the insulation between the terminal pad 30 and the base member 20 and between the terminal pad 30 and the internal electrode, and also improves the thermal uniformity on the holding surface 11.

The above embodiments are merely examples and do not limit the present disclosure in any way. Needless to say, various improvements and modifications are possible without departing from the spirit of the present disclosure. For example, the above embodiments illustrate the application of the present disclosure to an electrostatic chuck, but the present disclosure is not limited to electrostatic chucks and can be applied to any holding device that holds an object on its surface.

In the above embodiment, the hollow portion 16, 116 is provided with a tapered portion 16a, but the hollow portion 16, 116 does not have to have a tapered portion 16a. In other words, the hollow portion 16, 116 may be a lateral hole (an annular space with a rectangular cross section) that extends radially outward from the inner circumferential surface 15a.

Reference Signs List 1 electrostatic chuck 10 plate-like member 11 holding surface 12 lower surface 13 chuck electrode 14 heater electrode 15 bottomed hole 15a inner circumferential surface 15b bottom portion 16 cavity portion 16a tapered portion 20 base member 25 through hole 30 terminal pad 35 electrode terminal 36 insulating member 116 cavity portion CD creepage distance W semiconductor wafer

Claims (3)

a plate-like member including a first surface, a second surface provided on an opposite side to the first surface in a first direction, an internal electrode provided therein, and a terminal pad electrically connected to the internal electrode;
an electrode terminal joined to the terminal pad;
an insulating member covering an outer circumferential surface of the electrode terminal;
a metal base member having through holes in which the electrode terminals and the insulating members are disposed and joined to the second surface of the plate-like member;
A holding device for holding an object on the first surface of the plate-like member,
the second surface of the plate-like member is formed with a bottomed hole recessed toward the first surface and in which the terminal pad is disposed;
a cavity is formed in a bottom or an opening side surface of the bottomed hole, the cavity extending outward from the opening side surface of the bottomed hole in a second direction perpendicular to the first direction ,
The maximum dimension of the hollow portion in the first direction is equal to or less than half the dimension of the bottomed hole in the first direction.
A holding device characterized in that 2. The holding device according to claim 1 ,
A holding device, characterized in that the cavity includes a surface on which the terminal pads are arranged in the first direction. The holding device according to claim 1 or 2,
A holding device characterized in that the cavity has a tapered portion formed in the bottom portion, the dimension in the second direction gradually increasing from the opening of the bottomed hole toward the bottom portion.

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