Electrostatic chuck

Abstract

To provide an electrostatic chuck capable of uniformly approximating an in-plane temperature distribution of a substrate in a processing.SOLUTION: An electrostatic chuck 10 comprises: a heater unit 300 that is generated by receiving a supply of a power from an external part; a base plate 200 that supports the heater unit 300; and a joint layer 420 that joints between the heater unit 300 and the base plate 200. A surface 210 (a jointed surface) that is a part jointed to the heater unit 300 from a front surface of the base plate 200 includes: a first part 211 at a center side; and a second part 212 on an outer peripheral side. The electrostatic chuck 10 includes a heat transmission suppression structure that suppresses a heat transmission via the second part 212 from the heater unit 300 than a heat transmission via the first part 211 from the heater unit 300.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an electrostatic chuck. [Background technology]

[0002] For example, in a semiconductor manufacturing apparatus such as an etching apparatus, an electrostatic chuck is provided as a device for attracting and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes a dielectric substrate provided with an attracting electrode and a base plate supporting the dielectric substrate, which are joined together. When a voltage is applied to the attracting electrode, an electrostatic force is generated, and the substrate placed on the dielectric substrate is attracted and held. When the substrate is being processed in the semiconductor manufacturing apparatus, the dielectric substrate is cooled by the base plate. This allows the temperature of the substrate placed on the dielectric substrate to be maintained at an appropriate temperature.

[0003] During the processing of a substrate, it is required to make the temperature distribution in the surface of the substrate as uniform as possible. In order to adjust the temperature distribution in the surface of the substrate with high accuracy, electrostatic chucks equipped with heaters have been developed in recent years and have already been put to practical use. The heater may be provided inside the dielectric substrate, or may be provided between the dielectric substrate and the base plate in a unitized state, as described in, for example, Patent Document 1 below. Considering that the dielectric substrate with a built-in heater can be regarded as a "heater unit" in its entirety, in either of the above cases, it can be said that the base plate is joined to the heater unit. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-197485 Summary of the Invention [Problem to be solved by the invention]

[0005] It is difficult to make the heat generation amount in each part of the heater unit uniform throughout. The heat generation amount of the heater unit tends to be smaller in the outer periphery than in the center. As a result, the temperature of the substrate during processing may become lower in the outer periphery.

[0006] The present invention has been made in view of the above problems, and an object of the present invention is to provide an electrostatic chuck that can make the in-plane temperature distribution of a substrate during processing more uniform. [Means for solving the problem]

[0007] In order to solve the above problems, an electrostatic chuck according to the present invention includes a heater unit that generates heat by receiving power from an external source, a base plate that supports the heater unit, and a bonding layer that bonds the heater unit and the base plate. A bonding surface of the base plate that is a portion that is bonded to the heater unit has a first portion on the central side and a second portion on the outer periphery side. The electrostatic chuck has a heat transfer suppressing structure that suppresses heat transfer from the heater unit via the second portion more than heat transfer from the heater unit via the first portion.

[0008] The portion of the heater unit directly above the first portion (center side) generates less heat than the portion directly above the second portion (outer periphery side). Therefore, in the electrostatic chuck having the above configuration, the heat transfer suppression structure suppresses heat transfer from the outer periphery of the heater unit, which generates less heat, to the base plate (i.e., heat transfer via the second portion) more than heat transfer from the center, which generates more heat, to the base plate (i.e., heat transfer via the first portion). Since the heat transfer to the base plate is adjusted according to the heat generation of each portion of the heater unit, the temperature distribution within the surface of the substrate can be made uniform. Effect of the Invention

[0009] According to the present invention, it is possible to provide an electrostatic chuck that can make the in-plane temperature distribution of a substrate during processing closer to uniform. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of an electrostatic chuck according to an embodiment of the present invention. [Diagram 2] 2 is an enlarged view showing the configuration of part A in FIG. 1. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. In order to facilitate understanding of the description, the same components in each drawing are denoted by the same reference numerals as much as possible, and duplicated description will be omitted.

[0012] The electrostatic chuck 10 according to this embodiment is configured to electrostatically attract and hold a substrate W to be processed inside a semiconductor manufacturing apparatus (not shown), such as an etching apparatus. The substrate W is, for example, a silicon wafer. The electrostatic chuck 10 may be used in an apparatus other than a semiconductor manufacturing apparatus.

[0013] 1 shows, in a schematic cross-sectional view, the configuration of an electrostatic chuck 10 in a state in which the electrostatic chuck 10 attracts and holds a substrate W. The electrostatic chuck 10 includes a dielectric substrate 100, a base plate 200, and a heater unit 300.

[0014] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment.

[0015] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is mounted. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "bonded surface" that is bonded to the heater unit 300 via a bonding layer 410. The viewpoint when the electrostatic chuck 10 is viewed from the side of the surface 110 along a direction perpendicular to the surface 110 will hereinafter be referred to as a "top view".

[0016] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin flat layer made of a metal material such as tungsten, and is embedded in the dielectric substrate 100 in a state parallel to the surface 110. The material of the adsorption electrode 130 may be tungsten, molybdenum, platinum, palladium, or the like. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply path (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. As the configuration of the power supply path, various known configurations can be adopted. The adsorption electrode 130 may be provided as a so-called "monopolar" electrode, as in this embodiment, or may be provided as two so-called "bipolar" electrodes.

[0017] As shown in Fig. 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When a process such as etching is performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP through a gas hole (not shown). By providing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between them is adjusted, and the temperature of the substrate W is thereby maintained at an appropriate temperature. The temperature adjustment gas supplied to the space SP may be a type of gas other than helium.

[0018] A seal ring 111, dots 112, etc. are provided on a surface 110 that is a mounting surface, and the above-mentioned space SP is formed around these.

[0019] The seal ring 111 is a wall that divides the space SP at the outermost position. The upper end surface of the seal ring 111 forms part of the surface 110 and abuts against the substrate W. Note that a plurality of seal rings 111 may be provided to divide the space SP. With this configuration, it is possible to individually adjust the pressure of the helium gas in each space SP and make the surface temperature distribution of the substrate W during processing more uniform.

[0020] 1, the portion marked with the reference symbol "116" is the bottom surface of the space SP. Hereinafter, this portion will also be referred to as the "bottom surface 116." The seal ring 111, together with the dots 112 described below, is formed by digging down a part of the surface 110 to the position of the bottom surface 116.

[0021] The dots 112 are circular protrusions protruding from the bottom surface 116. A plurality of dots 112 are provided and are distributed approximately evenly on the mounting surface of the dielectric substrate 100. The upper end of each dot 112 forms part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, bending of the substrate W is suppressed.

[0022] The base plate 200 is a substantially disk-shaped member that supports the dielectric substrate 100 and the heater unit 300. The base plate 200 is formed of a metal material such as aluminum. The upper surface 210 of the base plate 200 in FIG. 1 is a "bonded surface" that is bonded to the heater unit 300 via a bonding layer 420.

[0023] A coolant flow path 250 for flowing a coolant is formed inside the base plate 200. When a process such as etching is performed in the semiconductor manufacturing apparatus, a coolant is supplied to the coolant flow path 250 from the outside, thereby cooling the base plate 200. Heat generated in the substrate W during the process is transferred to the coolant via the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the coolant.

[0024] An insulating film 230 is formed on the surface of the base plate 200 that is exposed to the outside. For example, an alumina film formed by thermal spraying can be used as the insulating film 230. By covering the surface of the base plate 200 with the insulating film 230, the dielectric strength voltage of the base plate 200 is increased. The insulating film 230 is formed so as to cover not only the surface of the base plate 200 that is exposed to the outside, but also a part of the surface 210 that is the surface to be joined. This will be described later.

[0025] The heater unit 300 generates heat when power is supplied from the outside, and heats the dielectric substrate 100. A heat generating portion (not shown) made of a linearly routed conductor is embedded inside the heater unit 300. The heat generating portion is sandwiched from above and below in FIG. 1 by sheet-like insulating material such as polyimide.

[0026] When power is supplied to the heater unit from the outside, Joule heat is generated in the heat generating portion, increasing the temperature of the entire heater unit 300. A terminal (not shown) for receiving power from the outside protrudes from the heater unit 300 toward the base plate 200, and is housed inside a through hole (not shown) formed in the base plate 200.

[0027] The heater unit 300 may be provided with a plurality of heat generating parts, and the heat generation amount of each heat generating part may be individually adjusted. By individually adjusting the heat generation amount of each part, the in-plane temperature distribution of the substrate W during processing can be made closer to uniform.

[0028] The heater unit 300 is sandwiched between the dielectric substrate 100 and the base plate 200 and is bonded to each of them. The heater unit 300 and the dielectric substrate 100 are bonded via a bonding layer 410, and the heater unit 300 and the base plate 200 are bonded via a bonding layer 420. The bonding layers 410 and 420 are layers formed by, for example, hardening a silicone adhesive. A plurality of particulate fillers (fillers) for increasing thermal conductivity are disposed inside each of the bonding layers. For example, particles mainly composed of alumina can be used as the filler.

[0029] The surface 210, which is the surface to be joined of the base plate 200, and the configuration in the vicinity thereof will be further described. Fig. 2 shows an enlarged view of the configuration of part A in Fig. 1. As shown in Fig. 2, the surface 210 is not entirely flat, but has a step near the outer periphery (the position of the dotted line DL). Such a step is formed so as to be continuous around the entire periphery of the surface 210.

[0030] Of the surface 210, a portion on the central side of the dotted line DL in Fig. 2 (left side in Fig. 2) is also referred to below as a "first portion 211." Of the surface 210, a portion on the outer periphery side of the dotted line DL in Fig. 2 (right side in Fig. 2) is also referred to below as a "second portion 212." In this way, the surface 210 of this embodiment is a joined surface that is a portion of the surface of the base plate 200 that is joined to the heater unit 300, and has the first portion 211 on the central side and the second portion 212 on the outer periphery side.

[0031] Since the surface 210 has the above-described step, the distance D2 from the second portion 212 to the heater unit 300 is longer than the distance D1 from the first portion 211 to the heater unit 300. As a result, the portion of the bonding layer 420 covering the area directly above the second portion 212 is thicker than the portion of the bonding layer 420 covering the area directly above the first portion 211.

[0032] The advantages of such a configuration will be described below. Due to its structure, it is difficult for the heater unit 300 to uniformize the amount of heat generated in each part. This is because the linear heat generating parts embedded inside the heater unit 300 cannot be routed evenly to the outer circumferential end. For this reason, the amount of heat generated by the heater unit 300 tends to be smaller in the outer circumferential part than in the central part. When the temperature of the substrate W during processing is adjusted using such a heater unit 300, the temperature of the substrate W may become lower in the outer circumferential part.

[0033] Therefore, in the electrostatic chuck 10 according to the present embodiment, as described above, the distance D2 from the second portion 212 to the heater unit 300 is longer than the distance D1 from the first portion 211 to the heater unit 300. In such a configuration, heat transfer from the outer periphery of the heater unit 300, which generates less heat, to the base plate 200 (i.e., heat transfer via the second portion 212) is suppressed more than heat transfer from the center, which generates more heat, to the base plate 200 (i.e., heat transfer via the first portion 211). Since the heat transfer to the base plate 200 is adjusted in accordance with the heat generation amount of each portion of the heater unit 300, the in-plane temperature distribution of the substrate W during processing can be made more uniform than in the past.

[0034] The above-described structure, i.e., the structure in which the distance D2 from the second portion 212 to the heater unit 300 is longer than the distance D1 from the first portion 211 to the heater unit 300, is a structure that suppresses heat transfer from the heater unit 300 via the second portion 212 more than heat transfer from the heater unit 300 via the first portion 211, and corresponds to the "heat transfer suppression structure" of this embodiment.

[0035] 2, in this embodiment, the insulating film 230 covering the surface of the base plate 200 also covers the entire second portion 212, but does not cover the first portion 211. Since the thermal conductivity of the insulating film 230 is relatively small, the heat transfer from the heater unit 300 via the second portion 212 is further suppressed by the insulating film 230. The portion of the insulating film 230 covering the second portion 212 corresponds to the "heat transfer suppressing film" of this embodiment. In addition, a configuration in which the second portion 212 is covered with the insulating film 230 and the first portion 211 is not covered with the insulating film 230 also corresponds to the "heat transfer suppressing structure" of this embodiment.

[0036] Only one of the two heat transfer suppression structures described above may be employed. For example, a configuration may be adopted in which a step is provided on the surface 210 as in the present embodiment, and no part of the surface 210 is covered with the insulating film 230. Alternatively, a configuration may be adopted in which the entire surface 210 is a flat surface, and only the second part 212 on the outer periphery side is covered with the insulating film 230.

[0037] The heat transfer suppression film may be the insulating film 230 formed by thermal spraying as in this embodiment, but may also be another type of film.

[0038] The heater unit 300 may be provided separately from the dielectric substrate 100 as in this embodiment, or may be integrated with the dielectric substrate 100. For example, a linear heat generating portion may be embedded inside the dielectric substrate 100, and the dielectric substrate 100 may be joined to a base plate 200. In this case, the base plate 200 may also employ a heat transfer suppression structure similar to that described above.

[0039] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Any design modifications made by a person skilled in the art to these specific examples are also included within the scope of the present disclosure as long as they have the features of the present disclosure. The elements of each of the above-mentioned specific examples and their arrangements, conditions, shapes, etc. are not limited to those exemplified and can be changed as appropriate. The combination of each of the elements of each of the above-mentioned specific examples can be changed as appropriate as long as no technical contradiction occurs. [Explanation of symbols]

[0040] 10: Electrostatic chuck 200: Base plate 210: Face 211: Part 1 212:Second part 230: Insulating film 300: Heater unit 420: Bonding layer

Claims

1. A heater unit that generates heat by receiving power from an external source; A base plate supporting the heater unit; a bonding layer that bonds the heater unit and the base plate, a joining surface of the base plate which is a portion to be joined to the heater unit has a first portion on a central side and a second portion on an outer circumferential side, Heat transfer from the heater unit through the second portion, an electrostatic chuck having a heat transfer suppression structure that suppresses heat transfer from the heater unit to a level greater than that via the first portion;

2. The heat transfer suppression structure includes: The distance from the second portion to the heater unit is 2. The electrostatic chuck according to claim 1, wherein the distance between the first portion and the heater unit is longer than the distance between the first portion and the heater unit.

3. The heat transfer suppression structure includes:

2. The electrostatic chuck according to claim 1, wherein the second portion is covered with a heat transfer suppressing film.

4. 4. The electrostatic chuck according to claim 3, wherein the heat transfer suppressing film is a film formed by thermal spraying.

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