Holding device

Abstract

To suppress displacement of a terminal for energization and bonding failure when a plurality of ceramics are bonded.SOLUTION: A holding device for holding an object includes a first ceramic layer formed of ceramic, a plate-shaped electrode disposed inside the first ceramic layer, a plate-shaped second ceramic layer disposed on the first ceramic layer and formed of ceramic, and an intermediate layer disposed between the first ceramic layer and the second ceramic layer, wherein a thickness of the second ceramic layer in a stacking direction of the first ceramic layer, the intermediate layer, and the second ceramic layer is greater than a thickness of a portion of the first ceramic layer between the electrode and the intermediate layer, It is larger than the thickness of the intermediate layer.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a retaining device. [Background technology]

[0002] Holding devices such as electrostatic chucks that attract and hold semiconductor wafers are known (see, for example, Patent Document 1). The electrostatic chuck described in Patent Document 1 is formed by bonding together a first ceramic body incorporating a heater electrode and a second ceramic body incorporating a chuck electrode. The second ceramic body attracts and holds the wafer on the surface opposite to the surface bonded to the first ceramic body. The first ceramic body is made up of a stack of sintered bodies of multiple green sheets. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-67767 Summary of the Invention [Problem to be solved by the invention]

[0004] In the electrostatic chuck described in Patent Document 1, the terminal for applying current to the chuck electrode built into the second ceramic needs to be taken out from the chuck electrode built into the first ceramic. In this case, there is a risk of misalignment between the terminal on the second ceramic side and the terminal on the first ceramic side, or poor bonding between the first ceramic and the second ceramic. In addition, because high-voltage power is supplied to the terminal, there is a risk of damage or wear to the ceramic near the terminal.

[0005] The present invention has been made to solve at least part of the above-mentioned problems, and aims to suppress misalignment of current-carrying terminals and poor bonding when bonding multiple ceramic pieces. [Means for solving the problem]

[0006] The present invention has been made to solve at least part of the above-mentioned problems, and can be realized in the following forms.

[0007] (1) According to one aspect of the present invention, there is provided a holding device for holding an object, the holding device including: a first ceramic layer made of ceramic; a plate-shaped electrode disposed inside the first ceramic layer; a plate-shaped second ceramic layer formed of ceramic and disposed on the first ceramic layer; and an intermediate layer disposed between the first and second ceramic layers, wherein the thickness of the second ceramic layer in a stacking direction of the first ceramic layer, the intermediate layer, and the second ceramic layer is greater than the thickness of a portion of the first ceramic layer between the electrode and the intermediate layer and greater than the thickness of the intermediate layer.

[0008] According to this configuration, the holding device is formed by integrally stacking the first ceramic layer, the intermediate layer, and the second ceramic layer. Therefore, in this configuration, when the first ceramic layer and the second ceramic layer are subsequently bonded, there is no need to align the terminals of the first ceramic layer with the terminals of the second ceramic layer. As a result, misalignment between the object held on the second ceramic layer and the electrodes disposed inside the first ceramic layer does not occur, thereby suppressing poor bonding between the first ceramic layer and the second ceramic layer. Furthermore, since there are no terminals in this configuration, damage and wear of the first ceramic layer and the second ceramic layer near the terminals are suppressed. Furthermore, the electrodes are disposed within the first ceramic layer with good flatness. Furthermore, in the stacking direction, the thickness of the second ceramic layer is greater than the thickness of the portion of the first ceramic layer between the electrodes and the intermediate layer and is also greater than the thickness of the intermediate layer. In other words, the second ceramic layer is thickest on the side of the object being held relative to the electrodes in the holding device, improving the dechucking performance of the object.

[0009] (2) In the holding device of the above aspect, the porosity of the second ceramic layer may be smaller than the porosity of the first ceramic layer. With this configuration, the porosity of the second ceramic layer, where the surface for holding the object is exposed, is smaller than the porosity of the first ceramic layer, thereby improving the voltage resistance of the holding device and the particle resistance of the second ceramic layer.

[0010] (3) In the holding device of the above aspect, the porosity of the second ceramic layer may be smaller than the porosity of the intermediate layer. With this configuration, even if the opposing surfaces of the first and second ceramic layers are slightly uneven, the intermediate layer with its high porosity functions as a stress relief layer, thereby improving the bond between the first and second ceramic layers.

[0011] (4) In the holding device of the above aspect, the intermediate layer may be made of ceramic. According to this configuration, in addition to the first and second ceramic layers, the intermediate layer is also made of ceramic, which makes the entire holding device less susceptible to deterioration due to plasma irradiation.

[0012] (5) In the holding device of the above aspect, the first ceramic layer, the intermediate layer, and the second ceramic layer may each have the same main component. With this configuration, the first ceramic layer, intermediate layer, and second ceramic layer are formed from the same material as the main component, and the similar compositions of the materials forming these three layers reduce the difference in thermal expansion when the three layers are sintered together.

[0013] The present invention can be realized in various forms, for example, a holding device, an electrostatic chuck, a system including these, a method for manufacturing a holding device, a method for manufacturing an electrostatic chuck, etc. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic perspective view of a holding device according to an embodiment of the present invention; [Figure 2]FIG. 2 is a schematic cross-sectional view of a holding device. [Figure 3] FIG. 2 is an explanatory diagram of a cross-sectional photograph of a first ceramic layer, an intermediate layer, and a second ceramic layer. DETAILED DESCRIPTION OF THE INVENTION

[0015] <Embodiment> FIG. 1 is a schematic perspective view of a holding device 1 according to one embodiment of the present invention. FIG. 2 is a schematic cross-sectional view of the holding device 1. FIG. 1 shows the holding device 1 and a wafer (object) W that is attracted and held by the holding device 1. The holding device 1 of this embodiment is an electrostatic chuck that attracts and holds the wafer W using electrostatic attraction. The holding device 1 is used, for example, in semiconductor wafer transport, exposure, film formation processes such as CVD (Chemical Vapor Deposition), and microfabrication such as shaping, etching, and dicing.

[0016] The holding device 1 shown in FIG. 1 is formed by stacking a first ceramic layer 10, an intermediate layer 30, and a second ceramic layer 20 in this order from bottom to top along the stacking direction (Z-axis direction). The Cartesian coordinate system CS shown in FIG. 1 is composed of a Z-axis parallel to the stacking direction and X- and Y-axes perpendicular to each other in a plane direction perpendicular to the Z-axis. The Cartesian coordinate system CS shown in FIG. 1 corresponds to the Cartesian coordinate system CS shown in FIG. 2 and subsequent figures. In FIGS. 1 and 2, the arrangement of each part is shown schematically, and the dimensional ratios of each part are not accurately shown.

[0017] As shown in Figure 2, the holding device 1 includes a first ceramic layer 10 made of ceramic, a disk-shaped chuck electrode (electrode) 40 arranged inside the first ceramic layer 10, a plate-shaped second ceramic layer 20 made of ceramic, and an intermediate layer 30 arranged between the first ceramic layer 10 and the second ceramic layer 20.

[0018] The first ceramic layer 10 of this embodiment is formed of ceramics containing aluminum oxide (alumina, Al2O3) as its main component. In this specification, the term "main component" refers to a component with a content of 90 wt% or more. As shown in FIGS. 1 and 2, the first ceramic layer 10 is formed by combining two disk-shaped portions, an upper portion 11 and a lower portion 12, with different areas along the stacking direction. As shown in FIG. 2, the upper portion 11 is located on the positive side of the Z-axis in the first ceramic layer 10 and is in contact with the intermediate layer 30. In the planar direction, the area of ​​the upper portion 11 is smaller than the area of ​​the lower portion 12.

[0019] The chuck electrode 40 of this embodiment is made of a conductive material (e.g., tungsten, molybdenum, etc.). As shown in FIG. 2, the chuck electrode 40 is embedded in the upper portion 11 of the first ceramic layer 10. The chuck electrode 40 has a disk shape extending in the planar direction about a central axis OL1. The chuck electrode 40 generates an electrostatic attraction force (attraction force) when power is supplied from a power source (not shown). The electrostatic attraction force attracts and fixes the wafer W to the mounting surface 21 of the second ceramic layer 20.

[0020] 2, the lower portion 12 of the first ceramic layer 10 includes a heater electrode 13, a power line 14, and a tunnel 15. The heater electrode 13 has a pattern that extends, for example, in a substantially spiral shape in the surface direction, and is made of a conductive material (for example, tungsten, molybdenum, platinum, etc.). Power is supplied to the heater electrode 13 via the power line 14 connected to a power source (not shown), and the heater electrode 13 generates heat to heat the wafer W held on the mounting surface 21.

[0021] The tunnel 15 is an annular cavity formed along the circumferential direction of the central axis OL1, which is parallel to the stacking direction. The tunnel 15 is connected to a through-hole (not shown) that penetrates along the stacking direction. The through-hole includes a hole that penetrates the lower portion 12 on the negative Z-axis side of the tunnel 15, and a hole that penetrates the first ceramic layer 10, the intermediate layer 30, and the second ceramic layer 20 on the positive Z-axis side. An inert gas (e.g., helium gas) is supplied from outside the holding device 1 to the mounting surface 21 of the second ceramic layer 20 through the through-hole and the tunnel 15. The supplied inert gas is supplied between the mounting surface 21 and the wafer W held on the mounting surface 21, thereby uniforming the in-plane temperature of the wafer W. The surface of the lower portion 12 on the negative Z-axis side is bonded to, for example, a metal base.

[0022] The second ceramic layer 20 has a disk shape in the planar direction with the same area as the upper portion 11 of the first ceramic layer 10. In this embodiment, the second ceramic layer 20 is formed from the same material as the first ceramic layer 10, that is, ceramics containing alumina as the main component.

[0023] The intermediate layer 30 has a disk shape in the planar direction with the same area as the upper portion 11 of the first ceramic layer 10 and the second ceramic layer 20. The intermediate layer 30 is formed of a sintered body of a material in which a binder and a solvent are added to alumina powder. The main component of the intermediate layer 30 is ceramic alumina. Examples of binders that can be used include Ethocel resin and butyral resin. Examples of solvents that can be used include butyl carbitol, butyl carbitol acetate, terpineol, and Texanol. In this embodiment, the retaining device 1 is manufactured by disposing the intermediate layer 30, which functions as an adhesive, between the first ceramic layer 10 and the second ceramic layer 20 and sintering it.

[0024] The diameter in the planar direction of the upper portion 11 of the first ceramic layer 10, the intermediate layer 30, and the second ceramic layer 20 may be, for example, about 50 mm to 500 mm, and is usually 200 mm to 350 mm. The diameter in the planar direction of the lower portion 12 of the first ceramic layer 10 may be, for example, about 220 mm to 550 mm, and is usually 220 mm to 350 mm.

[0025] In this embodiment, the first ceramic layer 10 is formed so that the thickness t10u of the first ceramic layer 10 along the stacking direction from the surface of the chuck electrode 40 on the positive side of the Z axis to the intermediate layer 30 is 1 μm or more and 150 μm or less. The intermediate layer 30 is formed so that the thickness t30 of the intermediate layer 30 along the stacking direction is 1 μm or more and 50 μm or less. The second ceramic layer 20 is formed so that the thickness t20 of the second ceramic layer 20 along the stacking direction is 150 μm or more and 350 μm or less. In particular, in this embodiment, the holding device 1 is formed so that the thickness t20 of the second ceramic layer 20 is greater than the thickness t10u of the first ceramic layer 10 and greater than the thickness t30 of the intermediate layer 30.

[0026] FIG. 3 is an explanatory diagram of the porosity of each layer. FIG. 3 shows a portion of an enlarged photograph of the cross section of the first ceramic layer 10, the intermediate layer 30, and the second ceramic layer 20 taken with an SEM (Scanning Electron Microscope). As shown in FIG. 3, a plurality of pores P are present in the intermediate layer 30 and the first ceramic layer 10. On the other hand, no pores P are present in the second ceramic layer 20. Furthermore, the proportion of the area occupied by the pores P in the first ceramic layer 10 is greater than the proportion of the area occupied by the pores P present in the intermediate layer 30. In other words, in this embodiment, the porosity of the second ceramic layer 20 is smaller than that of the first ceramic layer 10. Furthermore, the porosity of the second ceramic layer 20 is smaller than that of the intermediate layer 30. That is, the second ceramic layer 20 is formed denser than both the first ceramic layer 10 and the intermediate layer 30. In this embodiment, the porosity of the second ceramic layer 20 is 1% or less. The porosity of the first ceramic layer 10 is 5% or less, and the porosity of the intermediate layer 30 is 10% or less.

[0027] As described above, the holding device 1 of this embodiment includes the first ceramic layer 10 made of ceramic, the disk-shaped chuck electrode 40 disposed inside the first ceramic layer 10, the plate-shaped second ceramic layer 20 made of ceramic, and the intermediate layer 30 disposed between the first ceramic layer 10 and the second ceramic layer 20. The holding device 1 is formed so that the thickness t20 of the second ceramic layer 20 is greater than the thickness t10u of the first ceramic layer 10 along the stacking direction from the surface of the chuck electrode 40 on the positive side of the Z axis to the intermediate layer 30, and is also greater than the thickness t30 of the intermediate layer 30. The holding device 1 of this embodiment is formed by integrally stacking the first ceramic layer 10, the intermediate layer 30, and the second ceramic layer 20. Therefore, in this embodiment, when the first ceramic layer 10 and the second ceramic layer 20 are subsequently bonded, there is no need to align the terminals of the first ceramic layer 10 and the terminals of the second ceramic layer 20. As a result, misalignment between the wafer W held on the second ceramic layer 20 and the chuck electrode 40 disposed inside the first ceramic layer 10 does not occur, suppressing poor bonding between the first ceramic layer 10 and the second ceramic layer 20. Furthermore, since the holding device 1 of this embodiment does not have terminals, damage and wear to the first ceramic layer 10 and the second ceramic layer 20 near the terminals are suppressed. Furthermore, the electrodes are disposed within the first ceramic layer 10 with good flatness. The chuck electrode 40 is disposed within the first ceramic layer 10 with good flatness. Furthermore, in the stacking direction, the thickness t20 of the second ceramic layer 20 is greater than the thickness t10u of the portion of the first ceramic layer 10 between the chuck electrode 40 and the intermediate layer 30 and is also greater than the thickness t30 of the intermediate layer 30. That is, the thickness t20 of the second ceramic layer 20 is greatest on the side of the wafer W held by the holding device 1 relative to the chuck electrode 40, thereby improving the dechucking performance of the wafer W.

[0028] Furthermore, the porosity of the second ceramic layer 20 in this embodiment is smaller than the porosity of the first ceramic layer 10. In this embodiment, the porosity of the second ceramic layer 20, where the mounting surface 21 that holds the wafer W is exposed, is smaller than the porosity of the first ceramic layer 10. As a result, the voltage resistance of the holding device 1 is improved, and the particle resistance of the second ceramic layer 20 is improved.

[0029] Furthermore, in this embodiment, the porosity of the second ceramic layer 20 is smaller than the porosity of the intermediate layer 30. Therefore, even if there are some irregularities on the surfaces of the first ceramic layer 10 and the second ceramic layer 20 facing each other, the intermediate layer 30, which has a large porosity, functions as a stress relief layer. This improves the bonding strength between the first ceramic layer 10 and the second ceramic layer 20.

[0030] In addition, the intermediate layer 30 in this embodiment is made of alumina, a ceramic material. In this embodiment, in addition to the first ceramic layer 10 and the second ceramic layer 20, the intermediate layer 30 is also made of ceramic. Therefore, the entire holding device 1 is less susceptible to deterioration due to plasma irradiation.

[0031] In addition, the main component of the intermediate layer 30 in this embodiment is alumina. In this embodiment, the three layers, i.e., the first ceramic layer 10, the intermediate layer 30, and the second ceramic layer 20, are formed using the same ceramic as the main component. Therefore, the compositions of the materials forming these three layers are very similar, which reduces the difference in thermal expansion when the three layers are sintered together.

[0032] <Modification of this embodiment> The present invention is not limited to the above-described embodiment, and can be embodied in various forms without departing from the spirit of the invention. For example, the following modifications are also possible.

[0033] In the above embodiment, an example of the holding device 1 for holding a wafer W as an object has been described. However, the holding device 1 is deformable in the stacking direction within a range in which the thickness t20 of the second ceramic layer 20 is greater than the thickness t10u of the portion of the first ceramic layer 10 between the chuck electrode 40 and the intermediate layer 30 and greater than the thickness t30 of the intermediate layer 30. The thickness t10u of the first ceramic layer 10 may be less than 1 μm or greater than 150 μm. The thickness t30 of the intermediate layer 30 may be less than 1 μm or greater than 50 μm. The thickness t20 of the second ceramic layer 20 may be less than 150 μm or greater than 350 μm. The diameters of the first ceramic layer 10, the intermediate layer 30, and the second ceramic layer 20 in the planar direction are also deformable in the same manner as the thicknesses.

[0034] In the above embodiment, the porosity of the second ceramic layer 20 was smaller than the porosity of the first ceramic layer 10 and the porosity of the intermediate layer 30, but it may be equal to or greater than the porosity of the first ceramic layer 10 or the porosity of the intermediate layer 30.

[0035] In the above embodiment, the first ceramic layer 10, the second ceramic layer 20, and the intermediate layer 30 are formed of ceramics containing alumina as a main component. However, the materials forming the first ceramic layer 10, the second ceramic layer 20, and the intermediate layer 30 can be modified. For example, the first ceramic layer 10, the second ceramic layer 20, and the intermediate layer 30 may each be formed of a different ceramic as a main component. The first ceramic layer 10 and the second ceramic layer 20 may be formed of ceramic, and the intermediate layer 30 may not contain ceramic. The first ceramic layer 10, the second ceramic layer 20, and the intermediate layer 30 may be formed of ceramics containing aluminum nitride (AlN) as a main component. It is more preferable that the first ceramic layer 10, the second ceramic layer 20, and the intermediate layer 30 contain at least 99 wt% of the same ceramic as a main component.

[0036] This aspect has been described above based on embodiments and modifications. However, the above-described embodiments are intended to facilitate understanding of this aspect and are not intended to limit this aspect. This aspect may be modified or improved without departing from the spirit and scope of the claims, and equivalents thereof are included in this aspect. Furthermore, if a technical feature is not described as essential in this specification, it may be deleted as appropriate.

[0037] The present invention can also be realized in the following forms. [Application example 1] A holding device for holding an object, a first ceramic layer formed of ceramic; a plate-shaped electrode disposed inside the first ceramic layer; a plate-shaped second ceramic layer formed of ceramic and disposed on the first ceramic layer; an intermediate layer disposed between the first ceramic layer and the second ceramic layer; In the stacking direction of the first ceramic layer, the intermediate layer, and the second ceramic layer, the thickness of the second ceramic layer is greater than the thickness of a portion of the first ceramic layer between the electrode and the intermediate layer, and is greater than the thickness of the intermediate layer; A holding device characterized by: [Application example 2] The holding device according to Application Example 1, The porosity of the second ceramic layer is smaller than the porosity of the first ceramic layer. A holding device characterized by: [Application example 3] The holding device according to Application Example 1 or Application Example 2, The porosity of the second ceramic layer is smaller than the porosity of the intermediate layer. A holding device characterized by: [Application example 4] The holding device according to any one of Application Examples 1 to 3, The intermediate layer is made of ceramic. A holding device characterized by: [Application example 5] The holding device according to any one of Application Examples 1 to 4, The first ceramic layer, the intermediate layer, and the second ceramic layer each have the same main component. A holding device characterized by: [Explanation of symbols]

[0038] 1...Holding device 10...First ceramic layer 11...Top of the first ceramic layer 12...Bottom of the first ceramic layer 13...Heater electrode 14...Power lines 15...Tunnel 20...Second ceramic layer 21...Placement surface 30...Middle class 40...Chuck electrode CS...Cartesian coordinate system OL1…Center axis P…Pore W...wafer (object)

Claims

1. A holding device for holding an object, a first ceramic layer formed of ceramic; a plate-shaped electrode disposed inside the first ceramic layer; a plate-shaped second ceramic layer formed of ceramic and disposed on the first ceramic layer; an intermediate layer disposed between the first ceramic layer and the second ceramic layer; In the stacking direction of the first ceramic layer, the intermediate layer, and the second ceramic layer, the thickness of the second ceramic layer is greater than the thickness of a portion of the first ceramic layer between the electrode and the intermediate layer, and is greater than the thickness of the intermediate layer; A holding device characterized by:

2. 2. The holding device of claim 1, the porosity of the second ceramic layer is less than the porosity of the first ceramic layer; A holding device characterized by:

3. 2. The holding device of claim 1, the porosity of the second ceramic layer is less than the porosity of the intermediate layer; A holding device characterized by:

4. A holding device according to any one of claims 1 to 3, The intermediate layer is made of ceramic. A holding device characterized by:

5. 5. The holding device according to claim 4, the first ceramic layer, the intermediate layer, and the second ceramic layer each have the same main component; A holding device characterized by:

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