Retention device and electrostatic chuck

Abstract

To provide a retainer which enables improvement of thermal uniformity on a retaining surface, and to provide an electrostatic chuck.SOLUTION: An electrostatic chuck 1 has: a plate-like member 10 which includes a retaining surface 11 and a lower surface 12 provided at the opposite side of the retaining surface 11 and in which a flange gas passage 40a, including a first upper tunnel 44 and a lower tunnel 42 extending in an XY direction and a vertical hole 43 connecting the first upper tunnel 44 with the lower tunnel 42 and extending in a Z axis direction, is formed between the retaining surface 11 and the lower surface 12; a base member 20 including an upper surface 21 and a lower surface 22 provided at the opposite side of the upper surface 21; and a joint layer 30 which is disposed between the lower surface 12 and the upper surface 21 to join the plate-like member 10 to the base member 20. The electrostatic chuck 1 retains a semiconductor wafer W on the retaining surface 11. In the joint layer 30, a first area R1 and a second area R2 having heat conductivity lower than that of the first area R1 are formed. The second area R2 is formed at a position which overlaps with the vertical hole 43 when viewed in the Z axis direction.SELECTED DRAWING: Figure 3

Description

Technical Field

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

Background Art

[0002] As a device for holding an object, for example, a holding device having a ceramic plate (plate-like member) for holding an object, a base plate (base member), and an adhesive layer (bonding layer) for bonding the ceramic plate and the base plate is known (see Patent Document 1). In this type of holding device, uniform heat distribution on the holding surface is required. Therefore, in the holding device described in Patent Document 1, at least one space that does not penetrate the adhesive layer in the thickness direction is formed inside the adhesive layer to ensure uniform heat distribution on the holding surface.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Here, in the holding device, in order to supply gas to the upper surface of the plate-like member, a gas passage composed of a vertical hole and a horizontal hole may be provided inside the plate-like member. In such a holding device having a gas passage, in a region above a portion where a vertical hole connecting a plurality of horizontal holes exists on the holding surface, a temperature singularity where the temperature is lower than other regions is likely to be formed due to the gas flowing in the gas passage colliding with the inner surface of the flow path.

[0005] In the above-described holding device, by forming a space that does not penetrate in the thickness direction inside the adhesive layer, the isothermal property on the holding surface is ensured. However, there is no disclosure regarding the case where a gas passage is provided in the ceramic plate (plate-like member). Therefore, when a gas passage is provided in the plate-like member, there is a possibility that the isothermal property on the holding surface cannot be sufficiently improved.

[0006] Therefore, the present disclosure has been made to solve the above-described problems, and an object thereof is to provide a holding device and an electrostatic chuck that can improve the isothermal property on the holding surface.

Means for Solving the Problems

[0007] One aspect of the present disclosure made to solve the above problems is a plate-like member having a first surface and a second surface provided on the side opposite to the first surface, and a gas passage is formed between the first surface and the second surface, a base member having a third surface and a fourth surface provided on the side opposite to the third surface, a bonding layer disposed between the second surface and the third surface for bonding the plate-like member and the base member, and in a holding device that holds an object on the first surface of the plate-like member, the gas passage includes a first horizontal hole and a second horizontal hole that extend in the plane direction and are arranged at different heights in the thickness direction, and a vertical hole that connects the first horizontal hole and the second horizontal hole and extends in the thickness direction, in the bonding layer, a first region and a second region having a lower thermal conductivity than the first region are formed, and the second region is formed at a position overlapping the vertical hole when viewed in the thickness direction.

[0008] In this way, by forming the first region and the second region having a lower thermal conductivity than the first region in the bonding layer, in the second region, heat transfer between the plate-like member and the base member (heat extraction from the plate-like member to the base member) is suppressed compared to the first region. Then, by forming the second region in the bonding layer at a position overlapping the vertical hole in the thickness direction view, heat extraction to the base member can be restricted in the vicinity above the vertical hole on the first surface, so that the temperature difference from other regions becomes smaller. Therefore, it is possible to prevent the formation of a temperature singularity point in the vicinity above the vertical hole on the first surface, and thus the heat uniformity on the first surface can be improved.

[0009] In the holding device described above, the second region is preferably a space.

[0010] In this way, by forming the second region in the bonding layer as a space, a region having a lower thermal conductivity than the first region can be easily provided. And in the vicinity above the vertical hole on the first surface, the temperature difference from other regions becomes smaller, so that a temperature singularity point is not formed on the first surface, and the heat uniformity on the first surface can be improved.

[0011] In the holding device described above, the space is preferably a through hole penetrating the bonding layer in the thickness direction.

[0012] By making the space formed as the second region in the bonding layer a through hole in this way, a region having a lower thermal conductivity can be provided very easily, and it is possible to surely prevent the space from being filled during bonding. Therefore, the thermal conductivity in the second region can be surely made smaller than that in the first region. As a result, in the vicinity above the vertical hole on the first surface, the temperature difference from other regions can be further reduced, and the heat uniformity on the first surface can be further improved.

[0013] Even if the space as the second region is a through-hole, since both the plate-like member and the base member are hard members, the plate-like member and the base member do not come into contact with each other at the portion of the through-hole, and no problem regarding insulation occurs.

[0014] In the above-described holding device, The through-hole is preferably arranged coaxially with the vertical hole, and its diameter is preferably 3.5 times or less the diameter of the vertical hole.

[0015] As the diameter of the through-hole increases, the region where heat transfer between the plate-like member and the base member is restricted becomes larger. Therefore, in the vicinity of the upper part of the vertical hole on the first surface, the temperature difference from other regions becomes smaller. However, if the diameter of the through-hole becomes too large, there is a possibility that it will become hotter than other regions and the temperature difference from other regions will become large.

[0016] Therefore, by setting the diameter of the through-hole to 3.5 times or less the diameter of the vertical hole in this way, it is possible to surely reduce the temperature difference from other regions in the vicinity of the upper part of the vertical hole on the first surface. As a result, a temperature singularity is not formed on the first surface, and the heat uniformity on the first surface can be improved.

[0017] Note that the diameter of the through-hole is preferably about 0.8 times to 3.4 times, more preferably about 1.5 times to 3.2 times, the diameter of the vertical hole. By doing so, the temperature difference from other regions can be made smaller in the vicinity of the upper part of the vertical hole on the first surface, so that the heat uniformity on the first surface can be further improved.

[0018] In any of the above-described holding devices, The plate-like member is provided with a heating resistor inside, The heating resistor is preferably arranged in a plane intersecting the vertical hole.

[0019] When a heating resistor is provided inside a plate-shaped member, if the heating resistor is arranged in a plane intersecting the vertical hole, the heating resistor cannot be arranged near the portion where the vertical hole is formed. Therefore, in the vicinity of the upper part of the vertical hole on the first surface, the temperature difference from other regions becomes even larger.

[0020] Therefore, when the heating resistor is arranged in a plane intersecting the vertical hole, by forming the second region at a position overlapping the vertical hole in the thickness direction view of the bonding layer in this way, the temperature difference from other regions can be reduced in the vicinity of the upper part of the vertical hole on the first surface. Therefore, even when the heating resistor is arranged in a plane intersecting the vertical hole, the heat uniformity on the first surface can be improved.

[0021] In any of the above holding devices, the plate-shaped member is provided with a flange portion protruding outward, it is preferable that the vertical hole is a part of a passage for supplying an inert gas to the flange portion in the gas passage.

[0022] When the vertical hole constituting the gas passage is a part of the gas passage for supplying an inert gas to the flange portion of the plate-shaped member, the heating resistor is often arranged in a plane intersecting the vertical hole. Therefore, by forming the second region at a position overlapping the vertical hole in the thickness direction view of the bonding layer in this way, the temperature difference from other regions can be reduced in the vicinity of the upper part of the vertical hole on the first surface. Therefore, the heat uniformity on the first surface can be improved.

[0023] Another form of the present disclosure made to solve the above problems is provided in any of the above holding devices, it is preferable that the plate-shaped member is an electrostatic chuck having an electrostatic electrode that generates an electrostatic attraction force for fixing an object to the first surface.

[0024] According to such an electrostatic chuck, since the isothermal property on the first surface of the plate-like member is improved, the temperature of the object held on the first surface can be maintained uniformly. As a result, various processes performed on the object can be carried out with high precision.

Advantages of the Invention

[0025] According to the present disclosure, it is possible to provide a holding device and an electrostatic chuck that can improve the isothermal property on the holding surface.

Brief Description of the Drawings

[0026]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0027] The holding device and the electrostatic chuck according to the embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, 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.

[0028] Therefore, the electrostatic chuck 1 of the present embodiment will be described with reference to FIGS. 1 to 4. The electrostatic chuck 1 of the present 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 30 that bonds the plate-like member 10 and the base member 20.

[0029] 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 (the vertical direction in FIG. 1) of the electrostatic chuck 1, and the Z-axis direction is an example of the "thickness direction" of the present disclosure. The X axis and the Y axis are the axes in the radial direction of the electrostatic chuck 1. Further, the "plane direction" of the present disclosure means the direction of the XY plane that extends perpendicular to the Z-axis direction.

[0030] As shown in FIG. 1, the plate-like member 10 is a disc-shaped member, and includes a holding surface 11 that holds the semiconductor wafer W on the upper surface and a lower surface 12 that is provided on the side opposite to the holding surface 11 in the thickness direction (Z-axis direction) of the plate-like member 10. The plate-like member 10 has a mounting portion 110 formed in the central portion and a flange portion 120 that projects radially outward from the mounting portion 110. The upper surface of the mounting portion 110 is the holding surface 11, and the semiconductor wafer W is fixed to the mounting portion 110. Further, an annular ring (focus ring) is arranged on the upper surface 121 of the flange portion 120. The diameter of such a plate-like member 10 is, for example, about 50 to 500 mm (usually about 200 mm to 350 mm), and the thickness of the plate-like member 10 is, for example, about 1 to 10 mm. 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.

[0031] The plate-shaped member 10 is formed of ceramics. Although various ceramics are used as the ceramics, 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).

[0032] And the plate-shaped member 10 is provided with a chuck electrode 13 inside. The chuck electrode 13 has, for example, a substantially disc shape when viewed in the Z-axis direction and is formed of a conductive material (for example, tungsten, molybdenum, etc.). By supplying power from a power source (not shown) to this chuck electrode 13, an electrostatic attraction force (adsorption force) is generated, and the semiconductor wafer W is adsorbed and fixed to the holding surface 11 of the plate-shaped member 10 by this electrostatic attraction force.

[0033] Also, the plate-shaped member 10 is provided with a heater electrode 14 inside. The heater electrode 14 constitutes a pattern that extends, for example, in a substantially spiral shape when viewed in the Z-axis direction and is formed of a conductive material (for example, tungsten, molybdenum, platinum, etc.). By supplying power from a power source (not shown) to this heater electrode 14 and causing the heater electrode 14 to generate heat, the holding surface 11 and thus the semiconductor wafer W are heated.

[0034] Here, in order to make the surface temperature of the semiconductor wafer W held on the holding surface 11 uniform, a gas passage 40 for supplying an inert gas (for example, helium gas, etc.) is formed inside the plate-shaped member 10 in the minute gap between the semiconductor wafer W and the holding surface 11 and in the minute gap between the annular ring held on the upper surface of the flange portion 120 and the upper surface 121 of the flange portion 120. The gas passage 40 includes a gas passage 40a for the flange portion that supplies an inert gas to the upper surface 121 of the flange portion 120 and a gas passage 40b for the mounting portion that supplies an inert gas to the holding surface 11.

[0035] As shown in FIGS. 2 and 3, the flange portion gas passage 40a includes a plurality of flange portion gas holes 41, a lower tunnel 42, a vertical hole 43, a first upper tunnel 44, and a gas introduction passage 45. The flange portion gas holes 41 extend in the Z-axis direction and open to the upper surface 121 of the flange portion 120. In this embodiment, eight flange portion gas holes 41 are formed at substantially equal intervals on the upper surface 121. The lower tunnel 42 is disposed on the lower surface 12 side of the plate-like member 10 and is composed of a plurality (eight in this embodiment) of passages that extend in the XY-plane direction and communicate the flange portion gas holes 41 with the vertical hole 43. The vertical hole 43 extends in the Z-axis direction without penetrating the plate-like member 10 and communicates the lower tunnel 42 with the first upper tunnel 44. The first upper tunnel 44 is disposed on the holding surface 11 side of the plate-like member 10 and is a passage that extends in the XY-plane direction and communicates the vertical hole 43 with the gas introduction passage 45, and includes an annular passage 44a, a communication passage 44b that communicates the annular passage 44a with the vertical hole 43, and a communication passage 44c that communicates the annular passage 44a with the gas introduction passage 45. Note that the lower tunnel 42 and the first upper tunnel 44 (communication passage 44b) are examples of the "first horizontal hole" and the "second horizontal hole" of the present disclosure.

[0036] Accordingly, in the flange portion gas passage 40a, when an inert gas is supplied to the gas introduction passage 45, the inert gas flows from the communication passage 44c into the annular passage 44a, branches from the annular passage 44a into each communication passage 44b, and then flows into each vertical hole 43. Then, the inert gas flowing into each vertical hole 43 is supplied from each flange portion gas hole 41 to the upper surface 121 of the flange portion 120 through the lower tunnel 42.

[0037] As shown in FIGS. 2 and 3, the placement portion gas passage 40b includes a plurality of placement portion gas holes 51, a second upper tunnel 54, and a gas introduction passage 55. The placement portion gas holes 51 extend in the Z-axis direction and open to the holding surface 11. In this embodiment, eight placement portion gas holes 51 are formed at substantially equal intervals on the holding surface 11. The second upper tunnel 54 is disposed on the holding surface 11 side (the same surface as the first upper tunnel 44) of the plate-like member 10 and is a passage that extends in the XY-plane direction and communicates the placement portion gas holes 51 with the gas introduction passage 55, and includes an annular passage 54a, a communication passage 54b that communicates the annular passage 54a with the placement portion gas holes 51, and a communication passage 54c that communicates the annular passage 54a with the gas introduction passage 55.

[0038] Accordingly, in the gas passage 40b for the mounting portion, when an inert gas is supplied to the gas introduction passage 55, the inert gas flows from the communication passage 54c to the annular passage 54a, branches from the annular passage 54a to each communication passage 54b, and is supplied from each mounting portion gas hole 51 to the holding surface 11.

[0039] Note that the gas passage 40 only needs to be arranged so as not to interfere with other components provided inside the plate-like member 10, and its arrangement and number are not limited to those illustrated and can be changed as appropriate.

[0040] As shown in FIGS. 1 and 3, 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 thickness direction of the base member 20 (i.e., the Z-axis direction), and is formed in a cylindrical shape. The upper surface 21 is an example of the "third surface" of the present disclosure, and the lower surface 12 is an example of the "fourth surface" of the present disclosure. This base member 20 is preferably formed of a metal (e.g., aluminum or an aluminum alloy), but may be other than a metal (e.g., ceramics). Note that the base member 20 of the present embodiment is made of metal. The diameter of the base member 20 is, for example, about 220 mm to 550 mm (usually about 220 mm to 350 mm), and the thickness of the base member 20 (dimension in the Z-axis direction) is, for example, about 20 mm to 40 mm.

[0041] As shown in FIG. 3, a refrigerant flow path 23 for flowing a refrigerant (e.g., a fluorine-based inert liquid or water) is formed in the base member 20. By flowing the refrigerant in the refrigerant flow path 23, the base member 20 is cooled, and thereby the plate-like member 10 is cooled via the bonding layer 30.

[0042] In addition, through holes 26a and 26b that extend in the Z-axis direction, penetrate the base member 20, and open to the upper surface 21 and the lower surface 22 are formed in the base member 20. In a view from the Z-axis direction, the through hole 26a is arranged at a position overlapping (coaxial) with the gas introduction passage 45, and the through hole 26b is arranged at a position overlapping (coaxial) with the gas introduction passage 55.

[0043] As shown in FIGS. 1 and 3, the bonding layer 30 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 30, the lower surface 12 of the plate-like member 10 and the upper surface 21 of the base member 20 are thermally connected. The bonding layer 30 is composed of an adhesive such as a silicone-based resin, an acrylic-based resin, or an epoxy-based resin. Note that the thickness (dimension in the Z-axis direction) of the bonding layer 30 is, for example, about 0.1 to 1.0 mm.

[0044] A communication hole 36a that communicates the gas introduction path 45 and the through hole 26a is formed in the bonding layer 30. The communication hole 36a is arranged coaxially with the gas introduction path 45 and the through hole 26a. And the communication hole 36a has an inner diameter larger than those of the gas introduction path 45 and the through hole 26a, and an O-ring 37 for protecting the bonding layer 30 is arranged in the communication hole 36a. By this O-ring 37, plasma, process gas, etc. that enter the electrostatic chuck 1 through the flange portion gas passage 40a are prevented from contacting the bonding layer 30, and the bonding layer 30 is prevented from being corroded.

[0045] Also, a communication hole 36b that communicates the gas introduction path 55 and the through hole 26b is formed in the bonding layer 30. The communication hole 36b is arranged coaxially with the gas introduction path 55 and the through hole 26b. And the communication hole 36b has an inner diameter larger than those of the gas introduction path 55 and the through hole 26b, and an O-ring 37 for protecting the bonding layer 30 is arranged in the communication hole 36b. By this O-ring 37, plasma, process gas, etc. that enter the electrostatic chuck 1 through the mounting portion gas passage 40b are prevented from contacting the bonding layer 30, and the bonding layer 30 is prevented from being corroded.

[0046] Then, as shown in FIGS. 3 and 4, the bonding layer 30 is formed with a first region R1 and a second region R2 having a lower thermal conductivity than the first region R1. The second region R2 is disposed at a position overlapping each vertical hole 43 when viewed in the Z-axis direction. In the present embodiment, the second region R2 is a through hole 31 (space) penetrating the bonding layer 30 in the Z-axis direction, and eight through holes 31 are provided in a concentric circular shape. The through holes 31 are coaxially arranged with the vertical holes 43, and the diameter thereof is 3.5 times or less the diameter of the vertical holes 43. Note that the first region R1 is the portion of the bonding layer 30 excluding the through holes 31 and the communication holes 36a and 36b.

[0047] In such an electrostatic chuck 1 of the present embodiment, the inert gas supplied to the gas introduction paths 45 and 55 from the outside (the lower surface 22 side of the base member 20) flows into the respective gas holes 41 and 51 through the gas passages 40a and 40b in the electrostatic chuck 1, and is supplied from the flange gas hole 41 to the upper surface 121 of the flange portion 120 and from the mounting portion gas hole 51 to the holding surface 11.

[0048] Here, on the holding surface 11, in the upper portion 11a where the vertical hole 43 exists, the inert gas flowing in the gas passage 40a for the flange portion collides with the inner surface of the passage, and thus a temperature singularity where the temperature is lower than other regions is likely to be formed. And since the vertical hole 43 is connected to the plurality of horizontal holes of the lower tunnel 42 and the first upper tunnel 44, the collision of the inert gas against the inner surface of the passage is more frequent than in other passages. As a result, compared with a vertical hole connected to one horizontal hole, the vertical hole 43 connected to a plurality of horizontal holes is more likely to form a temperature singularity where the temperature is lower than other regions. Further, since the heater electrode 14 is disposed in the plane intersecting the vertical hole 43, the heater electrode 14 does not exist in the vicinity of the portion where the vertical hole 43 is formed. Therefore, on the holding surface 11, in the upper portion 11a of the vertical hole 43, the temperature difference from other regions becomes even larger. Therefore, there is a possibility that the heat uniformity on the holding surface 11 may deteriorate.

[0049] Therefore, in the electrostatic chuck 1 of the present embodiment, in the bonding layer 30, by providing the through holes 31 at positions overlapping with the respective vertical holes 43 in the Z-axis direction view, a first region R1 (the portion excluding the through holes 31 and the communication holes 36a and 36b) and a second region R2 (the portion of the through holes 31) having a lower thermal conductivity than the first region R1 are formed. Thereby, in the second region R2 where the through holes 31 exist, the heat transfer (heat drawing from the plate-like member 10 to the base member 20) between the plate-like member 10 and the base member 20 is suppressed as compared with the first region R1. And since the through holes 31 which are the second region R2 in the bonding layer 30 are arranged at positions overlapping with the vertical holes 43 in the Z-axis direction view, in the upper portion 11a of the vertical holes 43 on the holding surface 11, the heat drawing to the base member 20 is restricted, so that the temperature difference from other regions becomes small. Therefore, since it is possible to prevent the formation of temperature singularities in the upper portion 11a of the vertical holes 43 on the holding surface 11, the heat uniformity on the holding surface 11 can be improved.

[0050] And since the through holes 31 are formed as the second region R2 having a lower thermal conductivity than the first region R1 in the bonding layer 30, the second region R2 having a lower thermal conductivity can be provided very easily. Note that the second region R2 in the bonding layer 30 may be a hole instead of the through hole 31, but in the case of a blind hole, there is a possibility that the blind hole may be filled when the plate-like member 10 and the base member 20 are joined. Therefore, it is preferable to form the second region R2 by providing the through holes 31 instead of the blind holes in the bonding layer 30. Even if the through holes 31 are provided in the bonding layer 30, since both the plate-like member 10 and the base member 20 are hard members, the plate-like member 10 and the base member 20 do not come into contact with each other in the portion of the through holes 31, and no problem regarding insulation occurs.

[0051] Here, as the diameter of the through hole 31 provided as the second region R2 of the bonding layer 30 increases, the region where heat transfer between the plate-like member 10 and the base member 20 is restricted becomes larger. Therefore, in the upper portion 11a of the vertical hole 43 on the holding surface 11, the temperature difference from other regions becomes smaller. However, if the diameter of the through hole 31 becomes too large, there is a risk that it will become hotter than other regions and the temperature difference from other regions will become large.

[0052] Therefore, an evaluation was conducted on the relationship between the diameter of the through hole 31 and the temperature distribution on the holding surface 11. Specifically, with the diameter of the vertical hole 43 set to 1.6 mm, the diameter of the through hole 31 was changed and the temperature distribution on the holding surface 11 was evaluated. The results are shown in FIG. 5. FIG. 5 is a graph showing the relationship between the diameter of the through hole 31 and the temperature difference ΔT of the holding surface 11. The "temperature difference ΔT of the holding surface 11" is the temperature difference between the central position of the upper portion 11a of the vertical hole 43 (the portion corresponding to the second region R2 (through hole 31)) on the holding surface 11 and other positions (the positions corresponding to the first region R1). That is, the smaller the temperature difference ΔT of this holding surface 11, the better the heat uniformity of the holding surface 11.

[0053] As can be seen from FIG. 5, when the through hole 31 is provided and its diameter is increased, until the diameter of the through hole 31 reaches 4.0 mm, the temperature difference ΔT of the holding surface 11 becomes smaller. And when the diameter of the through hole 31 exceeds 4.0 mm, as the diameter increases, the temperature difference ΔT of the holding surface 11 increases. When the diameter of the through hole 31 exceeds 5.6 mm (about 3.5 times the diameter of the vertical hole 43), the temperature difference ΔT of the holding surface 11 becomes larger than when there is no through hole 31. That is, when the diameter of the through hole 31 exceeds 5.6 mm (about 3.5 times the diameter of the vertical hole 43), the heat uniformity on the holding surface 11 is deteriorated.

[0054] By setting the diameter of the through hole 31 to be 1.4 mm to 5.5 mm (about 0.87 times to 3.4 times the diameter of the vertical hole 43), the temperature difference ΔT of the holding surface 11 can be made 2.0°C or less. Further, by setting the diameter of the through hole 31 to be 2.4 mm to 5.2 mm (about 1.5 times to 3.2 times the diameter of the vertical hole 43), the temperature difference ΔT of the holding surface 11 can be made 1.5°C or less.

[0055] Therefore, in the electrostatic chuck 1 of the present embodiment, the diameter of the through hole 31 is set to be 3.5 times or less the diameter of the vertical hole 43. By providing such a through hole 31 at a position overlapping the vertical hole 43 in the Z-axis direction view in the bonding layer 30, the temperature difference ΔT of the holding surface 11 can be reduced, so that the heat uniformity of the holding surface 11 can be improved.

[0056] And the diameter of the through hole 31 is preferably set to be about 0.8 times to 3.4 times the diameter of the vertical hole 43, more preferably about 1.5 times to 3.2 times. By doing so, the temperature difference ΔT of the holding surface 11 can be made smaller, so that the heat uniformity of the holding surface 11 can be further improved.

[0057] As described above, according to the electrostatic chuck 1 of the present embodiment, in the bonding layer 30, a through hole 31 is provided at a position overlapping the vertical hole 43 which is a part of the flange portion gas passage 40a in the Z-axis direction view. In this through hole 31 portion, heat transfer (heat extraction from the plate-like member 10 to the base member 20) between the plate-like member 10 and the base member 20 is suppressed. Therefore, in the vicinity above the vertical hole 43 on the holding surface 11, heat extraction to the base member 20 is restricted, so that the temperature difference of the holding surface 11 becomes smaller. Thereby, the heat uniformity of the holding surface 11 can be improved. As a result, the temperature of the semiconductor wafer W held on the holding surface 11 can be maintained uniformly, so that various processes performed on the semiconductor wafer W can be accurately performed.

[0058] Note that the above embodiments are merely illustrative and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications can be made without departing from the gist of the present disclosure. For example, in the above 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 electrostatic chucks but also to all holding devices that hold an object on the surface.

[0059] Also, in the above embodiments, nothing is arranged in the through-hole 31 of the bonding layer 30. However, a thermometer such as a thermistor may be arranged in the through-hole 31 so as to be connected to the plate-like member 10.

Description of Reference Numerals

[0060] 1 Electrostatic chuck 10 Plate-like member 20 Base member 30 Bonding layer 31 Through-hole 40 Gas passage 40a Gas passage for flange portion 40b Gas passage for mounting portion 41 Flange portion gas hole 42 Lower tunnel 43 Vertical hole 44 First upper tunnel 45 Gas introduction path 51 Mounting portion gas hole 54 Second upper tunnel 55 Gas introduction path 110 Mounting portion 120 Flange portion R1 First region R2 Second region W Semiconductor wafer

Claims

1. A plate-like member including a first surface and a second surface provided on the side opposite to the first surface, with a gas passage formed between the first surface and the second surface; A base member including a third surface and a fourth surface provided on the side opposite to the third surface; A bonding layer disposed between the second surface and the third surface for bonding the plate-like member and the base member; and A holding device for holding an object on the first surface of the plate-like member, wherein the gas passage includes a first lateral hole and a second lateral hole that extend in the planar direction and are arranged at different heights in the thickness direction, and a vertical hole that connects the first lateral hole and the second lateral hole and extends in the thickness direction; the bonding layer is formed with a first region and a second region having a lower thermal conductivity than the first region, and the second region is formed at a position overlapping the vertical hole in a view in the thickness direction. The holding device is characterized by the above.

2. The holding device according to Claim 1, wherein the second region is a space. The holding device is characterized by the above.

3. The holding device according to Claim 2, wherein the space is a through hole penetrating the bonding layer in the thickness direction. The holding device is characterized by the above.

4. The holding device according to Claim 3, wherein the through hole is arranged coaxially with the vertical hole, and its diameter is 3.5 times or less the diameter of the vertical hole. The holding device is characterized by the above.

5. The holding device according to Claim 1 or Claim 3, wherein the plate-like member includes a heating resistor inside, and the heating resistor is arranged in a plane intersecting the vertical hole. The holding device is characterized by the above.

6. The holding device according to Claim 1 or Claim 3, wherein the plate-like member includes a flange portion protruding outward, and the vertical hole is a part of a passage for supplying an inert gas to the flange portion in the gas passage. The holding device is characterized by the above.

7. Comprising the holding device according to Claim 1 or Claim 3, wherein the plate-like member has an electrostatic electrode for generating an electrostatic attraction force for fixing an object to the first surface. The electrostatic chuck is characterized by the above.

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