Holding device

Abstract

To provide a holding device capable of improving a processing speed in an outer peripheral area of a target to be held.SOLUTION: In an electrostatic chuck 1 comprising a tabular member 10, a base member 20 and a junction layer 30 joining the tabular member 10 and the base member 20, the tabular member 10 includes an inside part 10a in a central part in a surface direction and an outside part 10b in an outer peripheral part in the surface direction. The junction layer 30 includes a first junction layer 30a, which is disposed between the inside part 10a of the tabular member 10 and the base member 20, and a second junction layer 30b which is disposed between the outside part 10b of the tabular member 10 and the base member 20. A total value of thermal resistance in the outside part 10b of the tabular member 10 and thermal resistance in the second junction layer 30b is smaller than a total value of thermal resistance in the inside part 10a of the tabular member 10 and thermal resistance in the first junction layer 30a.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] In semiconductor manufacturing processes, electrostatic chucks (holding devices) are used to hold semiconductor wafers. Such electrostatic chucks have a ceramic member (plate-shaped member) that holds a semiconductor wafer (object) on its mounting surface, and a chuck electrode is provided inside the ceramic member. A voltage is applied to the chuck electrode to generate an electrostatic attractive force, thereby attracting and holding the semiconductor wafer (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6806051 [Patent Document 2] Patent No. 6894000 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the electrostatic chuck described above, the diameter of the plate-shaped member is slightly (by a few mm) smaller than the diameter of the semiconductor wafer so as to prevent the plate-shaped member from wearing out during various processes on the semiconductor wafer it holds. Also, the chuck electrode provided inside the plate-shaped member is positioned only to a position slightly recessed (inward) from the outermost periphery of the plate-shaped member to ensure insulation.

[0005] Therefore, the clamping force of the semiconductor wafer held by the electrostatic chuck is weaker at the outer periphery than at the inner (center) part. As a result, during various processes, the outer periphery of the semiconductor wafer, which has a weak clamping force, is poorly dissipated, causing it to become too hot, which can reduce the processing speed (e.g., etching rate) of the semiconductor wafer.

[0006] Moreover, in recent years, a high bias voltage has been increasingly applied to electrostatic chucks (they are used at high power), and the amount of heat input to the semiconductor wafer has increased. As a result, the temperature often rises sharply in the outer peripheral region where the clamping force of the target object tends to be weak, resulting in a significant decrease in processing speed in the outer peripheral region of the semiconductor wafer.

[0007] Therefore, the present disclosure has been made to solve the above-mentioned problems, and aims to provide a holding device that can improve the processing speed in the outer peripheral area of ​​the object being held. [Means for solving the problem]

[0008] In order to solve the above problems, one aspect of the present disclosure is to A holding device including a plate-shaped member, a base member, and a bonding layer that bonds the plate-shaped member and the base member, the plate-like member has an inner portion at a center portion in a surface direction and an outer portion at an outer periphery in a surface direction, the bonding layer includes a first bonding layer disposed between an inner portion of the plate-like member and the base member, and a second bonding layer disposed between an outer portion of the plate-like member and the base member, The sum of the thermal resistance of the outer portion of the plate-shaped member and the thermal resistance of the second bonding layer is smaller than the sum of the thermal resistance of the inner portion of the plate-shaped member and the thermal resistance of the first bonding layer.

[0009] In this holding device, the sum of the thermal resistance of the outer portion of the plate-shaped member and the thermal resistance of the second bonding layer is smaller than the sum of the thermal resistance of the inner portion of the plate-shaped member and the thermal resistance of the first bonding layer, making it easier to lower the temperature of the outer portion of the plate-shaped member. As a result, the temperature of the outer portion of the plate-shaped member where the focus ring is located can be controlled to be lower than the temperature of the inner portion of the plate-shaped member where the object is placed.

[0010] Here, the plasma dry etching process includes an etching process and a deposition process, and the process can be controlled by changing the gas species, for example.

[0011] The gas used in the etching process may include, for example, CF4, C2F6, or C4F8, or a mixture of Ar, He, N2, and other gases that function as carrier gases. The etching process gas in the plasma becomes radicals, and as the temperature increases, the reaction progresses and the radicals are consumed, making them more likely to be transported to the higher temperature side. By controlling the temperature of the target object higher than the temperature of the focus ring during the etching process, the radicals are more likely to be transported to the target object, resulting in a localized improvement in the etching rate at the outermost periphery (edge) of the target object.

[0012] In contrast, the gas used in the deposition process may include, for example, CHF3, CH2F2, or CH3F, or a mixed gas combining Ar, He, N2, or other gases that function as carrier gases. The deposition process generates reaction products to control the etching rate; the greater the deposition, the more difficult it is to etch during the etching process. The deposition process gas in the plasma becomes radicals, and the lower the temperature, the more reaction products are generated and deposited, and the more easily the radicals are transported. By controlling the temperature of the focus ring lower than the temperature of the target during the deposition process, radicals are more easily transported toward the focus ring, which results in less localized deposition at the outermost periphery (edge) of the target. As a result, the etching rate during the etching process is improved.

[0013] Therefore, with this holding device, the temperature of the outer part of the plate-shaped member can be controlled to be lower than the temperature of the inner part of the plate-shaped member, thereby improving the processing speed (e.g., etching rate) at the outermost peripheral region (edge) of the object being held.

[0014] In the above-mentioned holding device, an inner portion of the plate-shaped member and an outer portion of the plate-shaped member are formed of different materials; The thermal resistance of the outer portion of the plate-shaped member is preferably smaller than the thermal resistance of the inner portion of the plate-shaped member.

[0015] In this way, by forming the inner and outer portions of the plate-shaped member from different materials, it is possible to form, for example, the outer portion from a material with a higher thermal conductivity than the inner portion. This allows the thermal resistance of the outer portion of the plate-shaped member to be further reduced compared to the thermal resistance of the inner portion of the plate-shaped member. Therefore, the temperature of the outer portion of the plate-shaped member where the focus ring is disposed can be further reduced, thereby further improving the processing speed (e.g., etching rate) at the outermost peripheral region (edge) of the held object.

[0016] In addition, in any of the above-mentioned holding devices, It is preferable that the bonding surface between the inner portion of the plate-shaped member and the first bonding layer is positioned at a different position from the bonding surface between the outer portion of the plate-shaped member and the second bonding layer in a direction perpendicular to the surface direction of the bonding surface.

[0017] In this way, by disposing the bonding surface between the inner portion of the plate-shaped member and the first bonding layer and the bonding surface between the outer portion of the plate-shaped member and the second bonding layer at different positions in the direction perpendicular to the plane of the bonding surfaces, the position of the focus ring mounting surface (the upper surface of the outer portion of the plate-shaped member) can be adjusted as desired, and the position of the focus ring can be freely changed.

[0018] As a result, the temperature of the outer portion of the plate-like member on which the focus ring is disposed can be controlled to a desired temperature, which in turn controls the movement of the etching process gas in the plasma, facilitating the transport of radicals to the outermost peripheral region of the target, thereby improving the processing speed (e.g., etching rate) at the outermost peripheral region (edge) of the target being held.

[0019] In addition, in any of the above-mentioned holding devices, The outer portion of the plate-like member preferably has an electrode therein.

[0020] In this way, by providing an electrode (at least one of an electrode connected to a DC power supply or an AC power supply) on the outer side of the plate-like member, the chucking electrode connected to the DC power supply can improve the chucking force of the focus ring, thereby improving the heat dissipation of the focus ring and preventing a sudden rise in temperature at the outermost edge of the held object. Furthermore, by applying a high or low frequency to the electrode connected to the AC power supply, the plasma can be controlled and transported to the outermost edge of the held object. This further improves the processing speed at the outermost edge of the held object.

[0021] In addition, in any of the above-mentioned holding devices, The thickness of the inner portion of the plate-like member is preferably greater than the thickness of the outer portion of the plate-like member.

[0022] By making the outer portion of the plate-shaped member thinner than the inner portion, it is possible to reduce the loss of electrical energy due to the dielectric loss tangent in the outer portion of the plate-shaped member when a high-frequency voltage is applied to the holding device. Therefore, by being able to apply a bias voltage to the outermost peripheral region more efficiently, it is possible to increase the etching efficiency of ions in the plasma, and it is possible to further improve the processing speed (e.g., etching rate) in the outermost peripheral region (edge) of the held object. [Effects of the Invention]

[0023] According to the present disclosure, it is possible to provide a holding device that can improve the processing speed in the outer peripheral area of ​​the object being held. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a schematic perspective view of an electrostatic chuck according to an embodiment; [Figure 2] 1 is a schematic configuration diagram of an XZ cross section of an electrostatic chuck according to an embodiment. [Figure 3] 1A to 1C are diagrams showing specific examples of each member in an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0025] A holding device according to an embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, the holding device will be described by taking as an example an electrostatic chuck used in semiconductor manufacturing equipment such as an etching device (such as a plasma etching device) or a film forming device (such as a CVD film forming device or a sputtering film forming device).

[0026] 1 to 3, an electrostatic chuck 1 according to this embodiment will be described. The electrostatic chuck 1 according to 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 FIGS. 1 and 2, 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 together.

[0027] In the following description, for convenience of explanation, 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 is an example of the "thickness direction" in the present disclosure. The X and Y axes are axes in the radial direction of the electrostatic chuck 1, and the direction of the XY plane is an example of the "plane direction" in the present disclosure.

[0028] As shown in FIG. 1 , the plate-shaped member 10 is a disk-shaped member made of ceramics. Specifically, the plate-shaped member 10 has an inner portion 10a at the center in the XY plane direction (surface direction) and an outer portion 10b at the periphery in the XY plane direction (surface direction). A semiconductor wafer W is placed on an upper surface 11a of the inner portion 10a of the plate-shaped member 10, and an annular member (focus ring FR) surrounding the semiconductor wafer W is disposed on an upper surface 11b of the outer portion 10b of the plate-shaped member 10. Note that, although the present embodiment illustrates the plate-shaped member 10 in which the inner portion 10a and the outer portion 10b are separated from each other (separate structure), the plate-shaped member 10 may also be one in which the inner portion 10a and the outer portion 10b are connected to each other (integral structure).

[0029] Although various ceramics can be used as the ceramics forming the plate-like member 10, it is preferable to use ceramics whose main component is, for example, aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN) from the viewpoints of strength, wear resistance, plasma resistance, etc. The main component here means the component with the highest content (for example, a component with a volume content of 90 vol% or more).

[0030] As shown in Figures 1 and 2, the inner portion 10a of the plate-like member 10 is disk-shaped and includes an upper surface 11a, which is a holding surface for holding a semiconductor wafer W, and a lower surface 12a, which is provided on the opposite side of the upper surface 11a in the Z-axis direction. The diameter of the inner portion 10a is, for example, about 150 mm to 300 mm. The thickness of the inner portion 10a is, for example, about 1 mm to 10 mm. The thermal conductivity of the inner portion 10a is preferably in the range of 10 W / mK to 50 W / mK.

[0031] 2, the inner portion 10a of the plate-like member 10 includes a chuck electrode 50. The chuck electrode 50 has, for example, a substantially circular shape when viewed in the Z-axis direction, and is made of a conductive material (for example, tungsten or molybdenum). When a voltage is applied to the chuck electrode 50, an electrostatic attraction force (adsorption force) is generated, and the semiconductor wafer W is attracted and fixed to the upper surface 11a by this electrostatic attraction force.

[0032] 1 and 2, the outer portion 10b of the plate-shaped member 10 has an annular shape and includes an upper surface 11b on which the focus ring FR is disposed, and a lower surface 12b provided on the opposite side of the upper surface 11b in the Z-axis direction. The outer portion 10b is disposed lower than the inner portion 10a in the Z-axis direction. In other words, the lower surface 12b, which serves as the bonding surface between the inner portion 10a and the bonding layer 30 (second bonding layer 30b), is disposed at a different position (lower in the Z-axis direction) from the lower surface 12a, which serves as the bonding surface between the outer portion 10b and the bonding layer 30 (first bonding layer 30a).

[0033] The outer diameter of the outer portion 10b is, for example, about 180 mm to 400 mm. The thickness of the outer portion 10b is, for example, about 1 mm to 10 mm. In other words, the thickness of the outer portion 10b of the plate-shaped member 10 is smaller (thinner) than the thickness of the inner portion 10a of the plate-shaped member 10. The thermal conductivity of the outer portion 10b is preferably within a range of 10 W / mK to 50 W / mK.

[0034] 2, the outer portion 10b of the plate-like member 10 includes a chuck electrode 51 therein. The chuck electrode 51 has, for example, a substantially annular shape when viewed in the Z-axis direction, and is made of a conductive material (for example, tungsten or molybdenum). When a voltage is applied to the chuck electrode 51, an electrostatic attraction force (adsorption force) is generated, and the focus ring FR is attracted and fixed to the upper surface 11b by this electrostatic attraction force.

[0035] In this embodiment, the outer portion 10b of the plate-shaped member 10 is separated from the inner portion 10a of the plate-shaped member 10 (separate structure), but they may be connected (integral structure). The material forming the outer portion 10b of the plate-shaped member 10 may be the same as the material forming the inner portion 10a (for example, both are alumina), or may be different (for example, the outer portion 10b is aluminum nitride and the inner portion 10a is alumina).

[0036] 1, the base member 20 is disposed on the underside of the plate-shaped member 10. The base member 20 is formed, for example, in a cylindrical shape, and in this embodiment, the portion that is joined to the inner portion 10a of the plate-shaped member 10 is convex. The base member 20 is formed, for example, from a metal (for example, aluminum or an aluminum alloy), but may also be formed from a material other than a metal (for example, ceramics or a metal-ceramic composite material).

[0037] 1 and 2, the base member 20 has an upper surface 21a to which the inner portion 10a is joined, an upper surface 21b to which the outer portion 10b is joined, and a lower surface 22 provided on the opposite side of the upper surfaces 21a and 21b in the Z-axis direction. The upper surfaces 21a and 21b of the base member 20 are thermally connected to the lower surface 12a of the inner portion 10a of the plate-shaped member 10 and the lower surface 12b of the outer portion 10b of the plate-shaped member 10 via bonding layers 30 (30a, 30b).

[0038] The diameter of the base member 20 is, for example, about 180 mm to 400 mm. The thickness (dimension in the Z-axis direction) of the base member 20 is, for example, about 20 mm to 50 mm. The thermal conductivity of the base member 20 (assumed to be aluminum) is preferably within the range of 160 W / mK to 250 W / mK (preferably, about 230 W / mK).

[0039] A coolant flow path 23 for flowing a coolant (e.g., a fluorine-based inert liquid, water, etc.) is formed in the base member 20. By flowing a coolant through this coolant flow path 23, the base member 20 is cooled, and the plate-like member 10 is cooled via the bonding layer 30. This cools the semiconductor wafer W whose temperature has risen during various processes, and heat is removed from the semiconductor wafer W.

[0040] 1 and 2, the bonding layer 30 is disposed between the plate-shaped member 10 and the base member 20, and bonds the plate-shaped member 10 and the base member 20. The bonding layer 30 has a first bonding layer 30a disposed between the inner portion 10a of the plate-shaped member 10 and the base member 20, and a second bonding layer 30b disposed between the outer portion 10b of the plate-shaped member 10 and the base member 20.

[0041] 2, the first bonding layer 30a is disposed between the lower surface 12a of the inner portion 10a of the plate-shaped member 10 and the upper surface 21a of the base member 20, and bonds the inner portion 10a and the base member 20 in a heat-transferable manner. This first bonding layer 30a is made of a resin adhesive such as a silicone resin, an acrylic resin, or an epoxy resin.

[0042] The thickness (dimension in the Z-axis direction) of this first bonding layer 30a is, for example, about 0.05 mm to 0.5 mm. The thermal conductivity of the first bonding layer 30a is preferably in the range of, for example, 0.1 W / mK to 2.0 W / mK (preferably, 0.5 W / mK to 1.5 W / mK).

[0043] 2, the second bonding layer 30b is disposed between the lower surface 12b of the outer portion 10b of the plate-shaped member 10 and the upper surface 21b of the base member 20, and bonds the outer portion 10b of the plate-shaped member 10 to the base member 20 in a heat-transferable manner. This second bonding layer 30b is made of, for example, a resin adhesive such as a silicone-based resin, an acrylic-based resin, or an epoxy-based resin, or a metal bonding material whose main component is a metal material.

[0044] Examples of metal bonding materials that can be used include metal adhesives that use metal powder or metal foil for bonding, materials composed of metal fibers, porous materials, metal meshes such as mesh structures, and brazing material, and materials composed of multiple columnar metal pieces and brazing material, etc. Metals that can be used to form the metal adhesives, metal meshes, or metal pieces include aluminum alloys, indium, titanium, nickel, copper, brass, alloys of these, and stainless steel.

[0045] The thickness (dimension in the Z-axis direction) of the second bonding layer 30b is, for example, about 0.05 mm to 0.5 mm. The thermal conductivity of the second bonding layer 30b is preferably within a range of, for example, 100 W / mK to 200 W / mK (preferably, 150 W / mK to 180 W / mK).

[0046] The sum of the thermal resistance of the outer portion 10b of the plate-shaped member 10 and the thermal resistance of the second bonding layer 30b is smaller than the sum of the thermal resistance of the inner portion 10a of the plate-shaped member 10 and the thermal resistance of the first bonding layer 30a. Note that thermal resistance is defined as the thickness of a member divided by the thermal conductivity of the member. This thermal resistance can be reduced by reducing the thickness or increasing the thermal conductivity.

[0047] When the electrostatic chuck 1 having such a configuration is used, various processes are performed on the semiconductor wafer W while the semiconductor wafer W is held on the upper surface 11 a of the plate-shaped member 10 and the focus ring FR is held on the upper surface 11 b of the outer portion 10 b of the plate-shaped member 10. For example, in recent years, etching processes on semiconductor wafers W have increasingly been performed at high power, increasing the amount of heat input to the semiconductor wafer W. As a result, the temperature often rises sharply in the outer peripheral region of the semiconductor wafer W, where the attracting force of the semiconductor wafer W is likely to be weak, which may result in a decrease in the etching rate (processing speed) in the outer peripheral region of the semiconductor wafer W.

[0048] Therefore, in the electrostatic chuck 1 of this embodiment, the sum of the thermal resistance of the outer portion 10b of the plate-shaped member 10 and the thermal resistance of the second bonding layer 30b is set smaller than the sum of the thermal resistance of the inner portion 10a of the plate-shaped member 10 and the thermal resistance of the first bonding layer 30a. Examples (Examples 1 to 5) of such combinations of the outer portion 10b and the second bonding layer 30b and the inner portion 10a and the first bonding layer 30a are shown in FIG.

[0049] 3, the inner portion 10a of the plate-shaped member 10 and the first bonding layer 30a are made the same on the side where the semiconductor wafer W is placed, while the material of the outer portion 10b of the plate-shaped member 10 or the second bonding layer 30b is changed on the side where the focus ring FR is placed. Therefore, the components in the specific combination examples of Examples 1 to 5 will be described separately for the component on the focus ring FR placement side and the component on the semiconductor wafer W placement side.

[0050] First, the components on the side where the focus ring FR is mounted will be described. In all of Examples 1 to 5, the inner portion 10a of the plate-shaped member 10 is made of alumina, and has a thermal conductivity of 32 W / mK, a thickness of 1.5 mm, and a thermal resistance of 4.7×10 -5 m 2 The first bonding layer 30a is made of silicone resin, and has a thermal conductivity of 1 W / mK, a thickness of 0.1 mm, and a thermal resistance of 1.0×10 -4 m 2The total thermal resistance of the inner portion 10a and the first bonding layer 30a is 1.5×10 -4 m 2 It is K / W.

[0051] Next, a description will be given of the member on the side where the semiconductor wafer W is placed. In Example 1, the outer portion 10b of the plate-like member 10 is made of alumina, and has a thermal conductivity of 32 W / mK, a thickness of 1 mm, and a thermal resistance of 3.1×10 -5 m 2 The second bonding layer 30b is made of silicone resin, and has a thermal conductivity of 1 W / mK, a thickness of 0.1 mm, and a thermal resistance of 1.0×10 -4 m 2 The total thermal resistance of the outer portion 10b and the second bonding layer 30b is 1.3×10 -4 m 2 It is K / W.

[0052] In Example 2, the outer portion 10b of the plate-like member 10 is made of alumina, and has a thermal conductivity of 32 W / mK, a thickness of 1 mm, and a thermal resistance of 3.1×10 -5 m 2 The second bonding layer 30b is made of silicone resin, and has a thermal conductivity of 1.4 W / mK, a thickness of 0.1 mm, and a thermal resistance of 7.1×10 -5 m 2 The total thermal resistance of the outer portion 10b and the second bonding layer 30b is 1.0×10 -4 m 2 K / W. In other words, the total value of the thermal resistance in the second embodiment is smaller than that in the first embodiment.

[0053] In Example 3, the outer portion 10b of the plate-like member 10 is made of alumina, and has a thermal conductivity of 32 W / mK, a thickness of 1 mm, and a thermal resistance of 3.1×10 -5 m 2 The second bonding layer 30b is made of silicone resin, and has a thermal conductivity of 1.4 W / mK, a thickness of 0.07 mm, and a thermal resistance of 5.0×10 -5 m 2The total thermal resistance of the outer portion 10b and the second bonding layer 30b is 8.1×10 -5 m 2 K / W. In other words, in the third embodiment, the total value of the thermal resistance is even smaller than in the second embodiment.

[0054] In Example 4, the outer portion 10b of the plate-like member 10 is made of aluminum nitride, and has a thermal conductivity of 170 W / mK, a thickness of 1 mm, and a thermal resistance of 5.9×10 -6 m 2 The second bonding layer 30b is made of silicone resin, and has a thermal conductivity of 1.4 W / mK, a thickness of 0.07 mm, and a thermal resistance of 5.0×10 -5 m 2 The total thermal resistance of the outer portion 10b and the second bonding layer 30b is 5.6×10 -5 m 2 K / W. In other words, in the fourth embodiment, the total value of the thermal resistance is even smaller than in the third embodiment.

[0055] In Example 5, the outer portion 10b of the plate-like member 10 is made of alumina, and has a thermal conductivity of 32 W / mK, a thickness of 1 mm, and a thermal resistance of 3.1×10 -5 m 2 The second bonding layer 30b is made of an aluminum alloy, and has a thermal conductivity of 170 W / mK, a thickness of 0.3 mm, and a thermal resistance of 1.8×10 -6 m 2 The total thermal resistance of the outer portion 10b and the second bonding layer 30b is 3.3×10 -5 m 2 K / W. In other words, in the fifth embodiment, the total value of the thermal resistance is even smaller than in the fourth embodiment.

[0056] As illustrated in Examples 1 to 5, the sum of the thermal resistance of the outer portion 10b of the plate-shaped member 10 and the thermal resistance of the second bonding layer 30b (the side where the focus ring FR is placed) is smaller than the sum of the thermal resistance of the inner portion 10a of the plate-shaped member 10 and the thermal resistance of the first bonding layer 30a (the side where the semiconductor wafer W is placed). This makes it easier to lower the temperature of the outer portion 10b of the plate-shaped member 10. This makes it possible to control the temperature of the outer portion 10b of the plate-shaped member 10, where the focus ring FR is placed, to be lower than the temperature of the inner portion 10a of the plate-shaped member 10, where the semiconductor wafer W is placed.

[0057] During the etching process of the semiconductor wafer W, the etching rate of the outermost peripheral region (edge) of the semiconductor wafer W can be locally improved by controlling the temperature of the semiconductor wafer W higher than the temperature of the focus ring FR. This is because the etching process gas in the plasma becomes radicals, and as the temperature increases, the reaction progresses and the radicals are consumed, making them more likely to be transported to the higher temperature side. On the other hand, during the deposition process, by controlling the temperature of the focus ring FR lower than the temperature of the semiconductor wafer W, deposition is less likely to be locally generated and accumulated in the outermost peripheral region (edge) of the semiconductor wafer W. This is because as the temperature decreases, reaction products are more likely to be generated and accumulated, making it easier for radicals to be transported to the lower temperature side. As a result, the etching rate can be improved during the etching process.

[0058] Therefore, according to Examples 1 to 5, the temperature of the outer portion 10b of the plate-shaped member 10 on which the focus ring FR is placed can be controlled to be lower than the temperature of the inner portion 10a of the plate-shaped member 10 on which the semiconductor wafer W is placed, thereby improving the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W.

[0059] Furthermore, in the electrostatic chuck 1 of this embodiment (Examples 1 to 5), the bonding surface between the inner portion 10a of the plate-shaped member 10 and the first bonding layer 30a (the lower surface 12a of the inner portion 10a) is positioned at a different position in the Z-axis direction from the bonding surface between the outer portion 10b of the plate-shaped member 10 and the second bonding layer 30b (the lower surface 12b of the outer portion 10b).

[0060] This allows the position (height position) of the outer portion 10b of the plate-shaped member 10 in the Z-axis direction to be freely set, and therefore the position of the mounting surface of the focus ring FR (the upper surface 11b of the outer portion 10b of the plate-shaped member 10) can be freely adjusted. Therefore, the position of the focus ring FR can be freely changed. Therefore, the temperature of the outer portion 10b of the plate-shaped member 10 on which the focus ring FR is placed can be controlled to a desired temperature. This allows the movement of radicals in the plasma to be controlled, which makes it easier for the radicals to be transported to the outermost peripheral region of the semiconductor wafer W, thereby improving the etching rate at the outermost peripheral region (edge) of the semiconductor wafer W.

[0061] Furthermore, in the electrostatic chuck 1 (Examples 1 to 5) of this embodiment, the chuck electrode 51 is disposed on the outer portion 10b of the plate-like member 10. This improves the chucking force of the focus ring FR. This improves the heat dissipation capability of the focus ring FR, thereby preventing a sudden rise in temperature at the outermost peripheral region (edge) of the semiconductor wafer W. This prevents a decrease in the etching rate at the outermost peripheral region (edge) of the semiconductor wafer W.

[0062] Furthermore, in the electrostatic chuck 1 of this embodiment (Examples 1 to 5), the outer portion 10b of the plate-shaped member 10 is thinner than the inner portion 10a. Therefore, when a high-frequency voltage is applied to the electrostatic chuck 1, the loss of electrical energy due to the dielectric loss tangent can be reduced in the outer portion 10b of the plate-shaped member 10. This makes it easier for radicals in the plasma to move to the outermost peripheral region of the semiconductor wafer W, thereby further improving the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W.

[0063] In addition, as in Example 4, the inner portion 10a and the outer portion 10b of the plate-shaped member 10 are formed from different materials, and the outer portion 10b is formed from a material having a higher thermal conductivity than the inner portion 10a, thereby making the thermal resistance of the outer portion 10b of the plate-shaped member 10 even smaller than those of Examples 1 to 3. Therefore, according to Example 4, the temperature of the outer portion 10b of the plate-shaped member 10 where the focus ring FR is disposed can be further reduced, thereby further improving the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W.

[0064] Here, even when the inner portion 10a and the outer portion 10b of the plate-shaped member 10 are formed of the same alumina as in Examples 1 to 3, by using low-purity alumina for the inner portion 10a and high-purity alumina for the outer portion 10b, the thermal conductivity of the outer portion 10b can be made higher than that of the inner portion 10a. Low-purity alumina can be produced by sintering using a sintering aid such as glass. Alternatively, the thermal conductivity of the outer portion 10b can be made higher than that of the inner portion 10a by densifying the outer portion 10b (e.g., by sintering the outer portion at a higher temperature). This measure also reduces the temperature of the outer portion 10b of the plate-shaped member 10 where the focus ring FR is disposed, thereby improving the etching rate at the outermost peripheral region (edge) of the semiconductor wafer W.

[0065] The interfacial thermal resistance (between the plate-shaped member 10 and the bonding layer 30 / between the bonding layer 30 and the base member 20) is also smaller on the side where the focus ring FR is placed (the outer portion 10b side) than on the side where the semiconductor wafer W is placed (the inner portion 10a side). This also contributes to making the sum of the thermal resistance of the outer portion 10b of the plate-shaped member 10 and the thermal resistance of the second bonding layer 30b smaller than the sum of the thermal resistance of the inner portion 10a of the plate-shaped member 10 and the thermal resistance of the first bonding layer 30a.

[0066] Furthermore, by forming the second bonding layer 30b from a metal bonding material (aluminum alloy) as in Example 5, the sum of the thermal resistance of the outer portion 10b of the plate-shaped member 10 and the thermal resistance of the second bonding layer 30b (on the side where the focus ring FR is placed) can be made even smaller than the sum of the thermal resistance of the inner portion 10a of the plate-shaped member 10 and the thermal resistance of the first bonding layer 30a (on the side where the semiconductor wafer W is placed) compared to Examples 1 to 4. Therefore, the temperature of the outer portion 10b of the plate-shaped member 10 where the focus ring FR is placed can be further reduced, thereby further improving the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W.

[0067] As described above, according to the electrostatic chuck 1 of the present embodiment, the sum of the thermal resistance of the outer portion 10b of the plate-shaped member 10 and the thermal resistance of the second bonding layer 30b is smaller than the sum of the thermal resistance of the inner portion 10a of the plate-shaped member 10 and the thermal resistance of the first bonding layer 30a, so that the temperature of the outer portion 10b of the plate-shaped member 10 can be reduced. Therefore, the temperature of the outer portion 10b of the plate-shaped member 10 on which the focus ring FR is disposed can be controlled to be lower than the temperature of the inner portion 10a of the plate-shaped member 10 on which the semiconductor wafer W is placed. Therefore, the etching rate of the outermost peripheral region (edge) of the semiconductor wafer W held can be improved.

[0068] The above-described embodiment is merely illustrative and does not limit the present disclosure in any way. Naturally, various improvements and modifications are possible within the spirit and scope of the present disclosure. For example, in the above-described embodiment, the electrode provided inside the outer portion 10b of the plate-shaped member 10 is the chuck electrode 51. However, the internal electrode is not limited to the chuck electrode and may be, for example, a radio-frequency electrode. By providing a radio-frequency electrode, radicals in the plasma can be transported to the outermost peripheral region of the semiconductor wafer W, thereby further improving the etching rate at the outermost peripheral region (edge) of the semiconductor wafer W. [Explanation of symbols]

[0069] 1. Electrostatic chuck 10 Plate-shaped member 10a Medial part 10b Outer part 20 Base member 30 Bonding layer 30a 1st bonding layer 30b 2nd bonding layer 50 Chuck electrode 51 Chuck electrode FR focus ring W Semiconductor wafer

Claims

1. A holding device including a plate-shaped member, a base member, and a bonding layer that bonds the plate-shaped member and the base member, the plate-like member has an inner portion at a center portion in a surface direction and an outer portion at an outer periphery in a surface direction, the bonding layer includes a first bonding layer disposed between an inner portion of the plate-like member and the base member, and a second bonding layer disposed between an outer portion of the plate-like member and the base member, The sum of the thermal resistance of the outer portion of the plate-shaped member and the thermal resistance of the second bonding layer is smaller than the sum of the thermal resistance of the inner portion of the plate-shaped member and the thermal resistance of the first bonding layer. A holding device characterized by:

2. 2. The holding device according to claim 1, an inner portion of the plate-shaped member and an outer portion of the plate-shaped member are formed of different materials; The thermal resistance of the outer portion of the plate-shaped member is smaller than the thermal resistance of the inner portion of the plate-shaped member. A holding device characterized by:

3. 2. The holding device according to claim 1, The bonding surface between the inner portion of the plate-like member and the first bonding layer is disposed at a position different from the bonding surface between the outer portion of the plate-like member and the second bonding layer in a direction perpendicular to the planar direction of the bonding surface. A holding device characterized by:

4. 2. The holding device according to claim 1, The outer portion of the plate-like member has an electrode therein. A holding device characterized by:

5. 2. The holding device according to claim 1, The thickness of the inner portion of the plate-like member is greater than the thickness of the outer portion of the plate-like member. A holding device characterized by:

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