Retention device

Abstract

Providing a holding device capable of improving the processing speed in the outer peripheral region of an object to be held. 【Solution means】In an electrostatic chuck 1 including a plate member 10, a base member 20, and a bonding layer 30 that bonds the plate member 10 and the base member 20, the plate member 10 has an inner portion 10a at the central portion in the plane direction and an outer portion 10b at the outer peripheral portion in the plane direction. The bonding layer 30 has a first bonding layer 30a disposed between the inner portion 10a of the plate member 10 and the base member 20, and a second bonding layer 30b disposed between the outer portion 10b of the plate member 10 and the base 20. The total value of the thermal resistance of the outer portion 10b of the plate member 10 and the thermal resistance of the second bonding layer 30b is smaller than the total value of the thermal resistance of the inner portion 10a of the plate member 10 and the thermal resistance of the first bonding layer 30a.

Description

Technical Field

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

Background Art

[0002] In semiconductor manufacturing processes, an electrostatic chuck (holding device) is used to hold a semiconductor wafer. Such an electrostatic chuck has a ceramic member (plate-like member) that holds a semiconductor wafer (object) on a mounting surface, and a chuck electrode is provided inside the ceramic member. Then, by applying a voltage to the chuck electrode to generate an electrostatic attraction force, the semiconductor wafer is adsorbed and held (see Patent Documents 1 and 2).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, in the above-described electrostatic chuck, the diameter of the plate-like member is slightly smaller (by about several millimeters) than the diameter of the semiconductor wafer so that the plate-like member does not wear during various processings on the held semiconductor wafer. Further, the chuck electrode provided inside the plate-like member is arranged only up to a position slightly withdrawn (inside) from the outermost periphery of the plate-like member in order to ensure insulation.

[0005] Therefore, the adsorption force of the semiconductor wafer held by the electrostatic chuck is weaker at the outer peripheral portion than at the inner side (central portion). As a result, during various processings, the heat dissipation of the outer peripheral region of the semiconductor wafer with a low adsorption force deteriorates, leading to a high temperature, and there is a risk that the processing speed (e.g., etching rate, etc.) for the semiconductor wafer may decrease.

[0006] In recent years, moreover, a high bias voltage has been increasingly applied to the electrostatic chuck (used at high power), and since the amount of heat input to the semiconductor wafer has increased, the temperature often rises rapidly in the outer peripheral region where the adsorption force of the object is likely to be low, and the decrease in the processing speed becomes remarkable in the outer peripheral region of the semiconductor wafer.

[0007] Therefore, the present disclosure has been made to solve the above-described problems, and an object thereof is to provide a holding device capable of improving the processing speed in the outer peripheral region of an object to be held.

Means for Solving the Problem

[0008] One aspect of the present disclosure made to solve the above problems is In a holding device including a plate-like member, a base member, and a bonding layer that bonds the plate-like member and the base member, The plate-like member has an inner portion at the central portion in the plane direction and an outer portion at the outer peripheral portion in the plane direction, The bonding layer has a first bonding layer disposed between the inner portion of the plate-like member and the base member and a second bonding layer disposed between the outer portion of the plate-like member and the base portion, It is characterized in that the total value of the thermal resistance of the outer portion of the plate-like member and the thermal resistance of the second bonding layer is smaller than the total value of the thermal resistance of the inner portion of the plate-like member and the thermal resistance of the first bonding layer.

[0009] In this holding device, since the total value of the thermal resistance of the outer portion of the plate-like member and the thermal resistance of the second bonding layer is smaller than the total value of the thermal resistance of the inner portion of the plate-like member and the thermal resistance of the first bonding layer, it becomes easier to lower the temperature of the outer portion of the plate-like member. Therefore, the temperature of the outer portion of the plate-like member where the focus ring is disposed can be controlled to be lower than the temperature of the inner portion of the plate-like member on which the object is placed.

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

[0011] The gas used in the etching process may contain gases such as CF4, C2F6, C4F8, etc., or may be a mixed gas combined with Ar, He, N2, etc. that function as carrier gases. The etching process gas in the plasma becomes radicals, and the reaction proceeds more as the temperature rises and the radicals are consumed, so it has the property of being easily transported to the high-temperature side. By controlling the temperature of the object to be higher than the temperature of the focus ring during the etching process, the radicals are more easily transported to the object side, and as a result, the etching rate of the outermost peripheral region (edge) of the object is locally improved.

[0012] In contrast, the gas used in the deposition process may include gases such as CHF3, CH2F2, CH3F, etc., or may be a mixed gas combined with Ar, He, N2, etc. that functions as a carrier gas. The deposition process is a process of generating reaction products to control the etching rate. The more deposition there is, the more difficult it is to be etched during the etching process. The deposition process gas in the plasma becomes radicals, and the lower the temperature, the more the reaction products are generated and deposited, and the easier it is for the radicals to be transported. By controlling the temperature of the focus ring to be lower than the temperature of the object during the deposition process, the radicals are more easily transported to the focus ring side. As a result, it becomes difficult for deposition to be generated and deposited locally in the outermost peripheral region (edge) of the object. As a result, the etching rate is improved during the etching process.

[0013] Therefore, according to this holding device, by controlling the temperature of the outer part of the plate-like member to be lower than the temperature of the inner part of the plate-like member, the processing speed (for example, the etching rate) in the outermost peripheral region (edge) of the object to be held can be improved.

[0014] In the holding device described above, The inner part and the outer part of the plate-like member are formed of different members, It is preferable that the thermal resistance of the outer part of the plate-like member is smaller than the thermal resistance of the inner part of the plate-like member.

[0015] In this way, by forming the inner part and the outer part of the plate-like member of different members respectively, for example, the outer part can be formed of a material with a higher thermal conductivity than the inner part. Thereby, the thermal resistance of the outer part of the plate-like member can be made even smaller than the thermal resistance of the inner part of the plate-like member. Therefore, since the temperature of the outer part of the plate-like member where the focus ring is arranged can be further lowered, the processing speed (for example, the etching rate) in the outermost peripheral region (edge) of the object to be held can be further improved.

[0016] Also, in any of the holding devices described above, It is preferable that the joint surface between the inner part of the plate-like member and the first joint layer is arranged at a position different from the joint surface between the outer part of the plate-like member and the second joint layer in a direction orthogonal to the plane direction of the joint surface.

[0017] In this way, by arranging the joint surface between the inner part of the plate-like member and the first joint layer and the joint surface between the outer part of the plate-like member and the second joint layer at different positions in a direction orthogonal to the plane direction of the joint surface, the position of the mounting surface of the focus ring (the upper surface of the outer part of the plate-like member) can be arbitrarily adjusted. Therefore, the arrangement position of the focus ring can be freely changed.

[0018] As a result, the temperature of the outer part of the plate-like member on which the focus ring is arranged can be controlled to a desired temperature. Thereby, since the movement of the etching process gas in the plasma can be controlled, it becomes easier to transport radicals to the outermost peripheral region of the object, and the processing speed (for example, etching rate) in the outermost peripheral region (edge) of the object to be held can be improved.

[0019] Also, in any of the holding devices described above, It is preferable that the outer part of the plate-like member is provided with an electrode inside thereof.

[0020] In this way, by providing an electrode (at least one of the electrodes connected to a DC power source or an AC power source) on the outer part of the plate-like member, the adsorption force of the focus ring can be improved by the chuck electrode connected to the DC power source, so that the heat dissipation property of the focus ring is improved. As a result, a rapid rise in temperature in the outermost peripheral region (edge) of the object to be held can be prevented. Also, by applying a high frequency or a low frequency to the electrode connected to the AC power source, the plasma can be controlled and transported to the outermost peripheral region of the object. Therefore, the processing speed in the outermost peripheral region (edge) of the object to be held can be further improved.

[0021] Also, in any of the holding devices described above, It is preferable that the thickness of the inner part of the plate-like member is larger than the thickness of the outer part of the plate-like member.

[0022] In this way, by making the outer part of the plate-like member thinner than the inner part in the plate-like member, when a high-frequency voltage is applied to the holding device, the loss of electrical energy due to the dielectric tangent can be reduced in the outer part of the plate-like member. Therefore, since the bias voltage in the outermost peripheral region can be applied more efficiently, the etching efficiency by ions in the plasma can be increased, so that the processing speed (for example, etching rate) in the outermost peripheral region (edge) of the object to be held can be further improved.

Advantages of the Invention

[0023] According to the present disclosure, it is possible to provide a holding device capable of improving the processing speed in the outer peripheral region of the object to be held.

Brief Description of the Drawings

[0024]

Figure 1

Figure 2

Figure 3

Modes for Carrying Out the Invention

[0025] The holding device according to the embodiment of the present disclosure will be described in detail with reference to the drawings. In this embodiment, as the holding device, for example, an electrostatic chuck used in a semiconductor manufacturing device 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) will be exemplified and described.

[0026] Therefore, the electrostatic chuck 1 of the present embodiment will be described with reference to FIGS. 1 to 3. 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 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.

[0027] In the following description, for convenience of explanation, the XYZ axes are defined as shown in FIG. 1. Here, the Z axis is the axis in the axial direction (vertical direction in FIG. 1) of the electrostatic chuck 1, and 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, and the direction of the XY plane is an example of the "plane direction" of the present disclosure.

[0028] As shown in FIG. 1, the plate-like member 10 is a disc-shaped member formed of ceramics. Specifically, the plate-like member 10 has an inner portion 10a at the center in the XY plane direction (plane direction) and an outer portion 10b at the outer periphery in the XY plane direction (plane direction). The semiconductor wafer W is placed on the upper surface 11a of the inner portion 10a of the plate-like member 10, and an annular member (focus ring FR) surrounding the semiconductor wafer W is disposed on the upper surface 11b of the outer portion 10b of the plate-like member 10. In the present embodiment, as the plate-like member 10, an example in which the inner portion 10a and the outer portion 10b are separated (separate structure) is illustrated, but the plate-like member 10 may be one in which the inner portion 10a and the outer portion 10b are connected (integral structure).

[0029] Note that various ceramics are used as the ceramics forming the plate-like member 10, but from the viewpoints of strength, wear resistance, plasma resistance, etc., for example, ceramics mainly composed of aluminum oxide (alumina, Al2O3) or aluminum nitride (AlN) are preferably used. Here, the main component means the component having the highest content ratio (for example, a component having a volume content ratio of 90 vol% or more).

[0030] As shown in FIGS. 1 and 2, the inner portion 10a of the plate-like member 10 is disk-shaped and has an upper surface 11a which is a holding surface for holding the semiconductor wafer W, and a lower surface 12a provided on the side opposite to 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. Also, the thickness of the inner portion 10a is, for example, about 1 mm to 10 mm. Note that the thermal conductivity of the inner portion 10a is desirably in the range of 10 W / mK to 50 W / mK.

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

[0032] As shown in FIGS. 1 and 2, the outer portion 10b of the plate-like member 10 is annular and has an upper surface 11b on which the focus ring FR is disposed, and a lower surface 12b provided on the side opposite to the upper surface 11b in the Z-axis direction. This outer portion 10b is disposed below the inner portion 10a in the Z-axis direction. That is, the lower surface 12b which is the joint surface of the inner portion 10a and the bonding layer 30 (second bonding layer 30b) is disposed at a different position (lower side in the Z-axis direction) from the lower surface 12a which is the joint surface of the outer portion 10b and the bonding layer 30 (first bonding layer 30a).

[0033] Also, the outer diameter of the outer portion 10b is, for example, about 180 mm to 400 mm. Also, the thickness of the outer portion 10b is, for example, about 1 mm to 10 mm. That is, the thickness of the outer portion 10b of the plate-like member 10 is smaller (thinner) than the thickness of the inner portion 10a of the plate-like member 10. Note that the thermal conductivity of the outer portion 10b is desirably in the range of 10 W / mK to 50 W / mK.

[0034] As shown in FIG. 2, the outer portion 10b of such a plate-like member 10 is provided with a chuck electrode 51 inside thereof. The chuck electrode 51 has, for example, a substantially annular shape when viewed in the Z-axis direction, and is formed of a conductive material (for example, tungsten, molybdenum, etc.). When a voltage is applied to the chuck electrode 51, an electrostatic attraction force (adsorption force) is generated, and the focus ring FR is adsorbed and fixed to the upper surface 11b by this electrostatic attraction force.

[0035] In addition, in the present embodiment, the outer portion 10b of the plate-like member 10 is separated from the inner portion 10a of the plate-like member 10 (separate structure), but may be connected (integral structure). Further, the material forming the outer portion 10b of the plate-like 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] As shown in FIG. 1, the base member 20 is disposed on the lower surface side of the plate-like member 10. The base member 20 is formed, for example, in a columnar shape, and in the present embodiment, the portion joined to the inner portion 10a of the plate-like member 10 is convex. Such a base member 20 is formed of, for example, a metal (for example, aluminum, aluminum alloy, etc.), but may be other than a metal (for example, ceramics, metal-ceramics composite material, etc.).

[0037] Then, as shown in FIGS. 1 and 2, the base member 20 includes an upper surface 21a to which the inner portion 10a is joined and an upper surface 21b to which the outer portion 10b is joined on the upper surface side, and a lower surface 22 provided on the side opposite to 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-like member 10 and the lower surface 12b of the outer portion 10b of the plate-like member 10 via joining layers 30 (30a, 30b).

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

[0039] In such a base member 20, a refrigerant flow path 23 for flowing a refrigerant (for example, a fluorine-based inert liquid, water, etc.) is formed. By flowing the refrigerant in this refrigerant flow path 23, the base member 20 is cooled, and the plate-like member 10 is cooled through the bonding layer 30. Thereby, the semiconductor wafer W whose temperature has risen during various processings is cooled, and heat extraction (heat removal) from the semiconductor wafer W is performed.

[0040] As shown in FIGS. 1 and 2, the bonding layer 30 is disposed between the plate-like member 10 and the base member 20, and joins the plate-like member 10 and the base member 20. This bonding layer 30 has a first bonding layer 30a disposed between the inner portion 10a of the plate-like member 10 and the base member 20, and a second bonding layer 30b disposed between the outer portion 10b of the plate-like member 10 and the base member 20.

[0041] As shown in FIG. 2, the first bonding layer 30a is disposed between the lower surface 12a of the inner portion 10a of the plate-like member 10 and the upper surface 21a of the base member 20, and joins the inner portion 10a and the base member 20 so as to be thermally conductive. This first bonding layer 30a is constituted by a resin adhesive such as a silicone-based resin, an acrylic-based resin, or an epoxy-based resin, for example.

[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 desirably within 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] As shown in Fig. 2, the second bonding layer 30b is disposed between the lower surface 12b of the outer portion 10b of the plate-like member 10 and the upper surface 21b of the base member 20, and thermally joins the outer portion 10b of the plate-like member 10 and the base member 20. The second bonding layer 30b is composed of, for example, a resin adhesive such as a silicone-based resin, an acrylic-based resin, an epoxy-based resin, or a metal bonding material mainly composed of a metal material.

[0044] As the metal bonding material, for example, a metal adhesive that joins using metal powder or metal foil, a metal mesh composed of metal fibers, porous materials, mesh structures, etc. and a brazing material, or a material composed of a plurality of columnar metal pieces and a brazing material can be used. As the metal for forming the metal adhesive, metal mesh, or metal pieces, an aluminum alloy, indium, titanium, nickel, copper, brass, these alloys, or stainless steel can be used.

[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. Also, the thermal conductivity of the second bonding layer 30b is desirably in the range of, for example, 100 W / mK to 200 W / mK (preferably 150 W / mK to 180 W / mK).

[0046] And the total value of the thermal resistance of the outer portion 10b of the plate-like member 10 and the thermal resistance of the second bonding layer 30b is smaller than the total value of the thermal resistance of the inner portion 10a of the plate-like member 10 and the thermal resistance of the first bonding layer 30a. Note that the thermal resistance is defined as the thickness of the member / the thermal conductivity of the member. To reduce this thermal resistance, the thickness can be made thinner or the thermal conductivity can be increased.

[0047] When using the electrostatic chuck 1 having such a configuration, the semiconductor wafer W is held on the upper surface 11a of the plate-like member 10, and various processings are performed on the semiconductor wafer W while the focus ring FR is held on the upper surface 11b of the outer portion 10b of the plate-like member 10. For example, in the etching process for the semiconductor wafer W, in recent years, it has been increasingly used at high power, and the amount of heat input to the semiconductor wafer W has increased. Therefore, the temperature often rises rapidly in the outer peripheral region where the adsorption force of the semiconductor wafer W is likely to be low, and there is a possibility that the etching rate (processing speed) decreases in the outer peripheral region of the semiconductor wafer W.

[0048] Therefore, in the electrostatic chuck 1 of the present embodiment, the total value of the thermal resistance of the outer portion 10b of the plate-like member 10 and the thermal resistance of the second bonding layer 30b is made smaller than the total value of the thermal resistance of the inner portion 10a of the plate-like member 10 and the thermal resistance of the first bonding layer 30a. Examples of combinations (Examples 1 to 5) of such an outer portion 10b and the second bonding layer 30b and an inner portion 10a and the first bonding layer 30a are shown in FIG. 3.

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

[0050] First, the members on the focus ring FR mounting side will be described. In all of Examples 1 to 5, the inner portion 10a of the plate-like member 10 is formed of alumina, its thermal conductivity is 32 W / mK, its thickness is 1.5 mm, and its thermal resistance is 4.7×10 -5 m 2 K / W. Further, the first bonding layer 30a is formed of a silicone resin, its thermal conductivity is 1 W / mK, its thickness is 0.1 mm, and its thermal resistance is 1.0×10 -4 m 2It is K / W. And the total value of the thermal resistance between the inner part 10a and the first bonding layer 30a is 1.5×10 -4 m 2 K / W.

[0051] Next, the members on the semiconductor wafer W mounting side will be described. In Example 1, the outer part 10b of the plate-like member 10 is formed of alumina, its thermal conductivity is 32 W / mK, its thickness is 1 mm, and its thermal resistance is 3.1×10 -5 m 2 K / W. Also, the second bonding layer 30b is formed of silicone resin, its thermal conductivity is 1 W / mK, its thickness is 0.1 mm, and its thermal resistance is 1.0×10 -4 m 2 K / W. And the total value of the thermal resistance between the outer part 10b and the second bonding layer 30b is 1.3×10 -4 m 2 K / W.

[0052] In Example 2, the outer part 10b of the plate-like member 10 is formed of alumina, its thermal conductivity is 32 W / mK, its thickness is 1 mm, and its thermal resistance is 3.1×10 -5 m 2 K / W. Also, the second bonding layer 30b is formed of silicone resin, its thermal conductivity is 1.4 W / mK, its thickness is 0.1 mm, and its thermal resistance is 7.1×10 -5 m 2 K / W. And the total value of the thermal resistance between the outer part 10b and the second bonding layer 30b is 1.0×10 -4 m 2 K / W. That is, in the second embodiment, the total value of the thermal resistance is smaller than that in the first embodiment.

[0053] In Example 3, the outer part 10b of the plate-like member 10 is formed of alumina, its thermal conductivity is 32 W / mK, its thickness is 1 mm, and its thermal resistance is 3.1×10 -5 m 2 K / W. Also, the second bonding layer 30b is formed of silicone resin, its thermal conductivity is 1.4 W / mK, its thickness is 0.07 mm, and its thermal resistance is 5.0×10 -5 m 2It is K / W. And the total value of the thermal resistance between the outer part 10b and the second bonding layer 30b is 8.1×10 -5 m 2 K / W. That is, in the third embodiment, the total value of the thermal resistance is even smaller than that in the second embodiment.

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

[0055] In Example 5, the outer part 10b of the plate-like member 10 is formed of alumina, its thermal conductivity is 32 W / mK, the thickness is 1 mm, and the thermal resistance is 3.1×10 -5 m 2 K / W. Also, the second bonding layer 30b is formed of an aluminum alloy, its thermal conductivity is 170 W / mK, the thickness is 0.3 mm, and the thermal resistance is 1.8×10 -6 m 2 K / W. And the total value of the thermal resistance between the outer part 10b and the second bonding layer 30b is 3.3×10 -5 m 2 K / W. That is, in the fifth embodiment, the total value of the thermal resistance is even smaller than that in the fourth embodiment.

[0056] As exemplified in Examples 1 to 5, the total value of the thermal resistance of the outer portion 10b of the plate-like 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 total value of the thermal resistance of the inner portion 10a of the plate-like member 10 and the thermal resistance of the first bonding layer 30a (the side where the semiconductor wafer W is placed). Therefore, it becomes easier to lower the temperature of the outer portion 10b of the plate-like member 10. As a result, the temperature of the outer portion 10b of the plate-like member 10 where the focus ring FR is disposed can be controlled to be lower than the temperature of the inner portion 10a of the plate-like member 10 on which the semiconductor wafer W is placed.

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

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

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

[0060] Thereby, since the arrangement position (height position) of the outer portion 10b of the plate-like member 10 in the Z-axis direction can be freely set, the position of the mounting surface of the focus ring FR (the upper surface 11b of the outer portion 10b of the plate-like member 10) can be arbitrarily adjusted. Therefore, the arrangement position of the focus ring FR can be freely changed. Accordingly, the temperature of the outer portion 10b of the plate-like member 10 on which the focus ring FR is arranged can be controlled to a desired temperature. Thereby, since the movement of radicals in the plasma can be controlled, the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W can be improved by making it easier for the radicals to be transported to the outermost peripheral region of the semiconductor wafer W.

[0061] Further, in the electrostatic chuck 1 (Examples 1 to 5) of the present embodiment, the chuck electrode 51 is arranged on the outer portion 10b of the plate-like member 10. Therefore, the adsorption force of the focus ring FR can be improved. Thereby, since the heat removal property of the focus ring FR is improved, a rapid increase in temperature in the outermost peripheral region (edge) of the semiconductor wafer W can be prevented. Accordingly, a decrease in the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W can be prevented.

[0062] Furthermore, in the electrostatic chuck 1 (Examples 1 to 5) of the present embodiment, the outer portion 10b of the plate-like member 10 is made 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-like member 10. Thereby, since radicals in the plasma can be easily moved to the outermost peripheral region of the semiconductor wafer W, the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W can be further improved.

[0063] Then, as in Example 4, in the plate-like member 10, the inner portion 10a and the outer portion 10b are formed of different materials, and the outer portion 10b is formed of a material having a higher thermal conductivity than the inner portion 10a. Thus, the thermal resistance of the outer portion 10b of the plate-like member 10 and the thermal resistance of the inner portion 10a of the plate-like member 10 can be made even smaller than in Examples 1 to 3. Therefore, according to Example 4, since the temperature of the outer portion 10b of the plate-like member 10 on which the focus ring FR is disposed can be further lowered, the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W can be further improved.

[0064] Here, even when the inner portion 10a and the outer portion 10b in the plate-like 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 the thermal conductivity of the inner portion 10a. The low-purity alumina can be produced by sintering using a sintering aid such as glass. Alternatively, by making the outer portion 10b dense (for example, sintering the outer portion at a higher temperature), the thermal conductivity of the outer portion 10b can also be made higher than the thermal conductivity of the inner portion 10a. By such measures as well, since the temperature of the outer portion 10b of the plate-like member 10 on which the focus ring FR is disposed can be lowered, the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W can be improved.

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

[0066] Also, by forming the second bonding layer 30b with a metal bonding material (aluminum alloy) as in Example 5, the total value of the thermal resistance of the outer portion 10b of the plate-like member 10 and the thermal resistance of the second bonding layer 30b (on the focus ring FR placement side) can be made smaller than the total value of the thermal resistance of the inner portion 10a of the plate-like member 10 and the thermal resistance of the first bonding layer 30a (on the semiconductor wafer W placement side). Therefore, the temperature of the outer portion 10b of the plate-like member 10 where the focus ring FR is disposed can be further lowered, and thus the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W can be further improved.

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

[0068] Note that the above embodiments are merely examples and do not limit the present disclosure in any way. It goes without saying that various improvements and modifications are possible without departing from the gist thereof. For example, in the above embodiment, the case where the electrode provided inside the outer portion 10b of the plate-like member 10 is the chuck electrode 51 is exemplified, but the internal electrode is not limited to the chuck electrode and may be, for example, a high-frequency electrode or the like. By providing a high-frequency electrode, radicals in the plasma can be transported to the outermost peripheral region of the semiconductor wafer W, so that the etching rate in the outermost peripheral region (edge) of the semiconductor wafer W can be further improved.

Description of Reference Numerals

[0069] 1 Electrostatic chuck 10 Plate-like member 10a Inner part 10b Outer part 20 Base member 30 Bonding layer 30a First bonding layer 30b Second bonding layer 50 Chuck electrode 51 Chuck electrode FR Focus ring W Semiconductor wafer

Claims

1. A holding device including a plate-like member, a base member, and a bonding layer that bonds the plate-like member and the base member, the plate-like member has an inner portion in which a semiconductor wafer is disposed at a center in a surface direction, and an outer portion in which a focus ring is disposed at an outer periphery in the 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, a 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 a sum of the thermal resistance of the inner portion of the plate-shaped member and the thermal resistance of the first bonding layer; The thermal conductivity of the second bonding layer is greater than the thermal conductivity of the first bonding layer. A holding device characterized in that

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

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 perpendicular to the surface direction of the bonding surface. a bonding surface between the outer portion of the plate-like member and the second bonding layer in a direction different from the ... A holding device characterized in that

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 in that

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 in that

6. 2. The holding device according to claim 1, The thickness of the first bonding layer is greater than the thickness of the second bonding layer. A holding device characterized in that

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