Electrostatic chuck

Abstract

To provide an electrostatic chuck that can keep the temperature of a substrate suitably during a process.SOLUTION: An electrostatic chuck 10 includes a dielectric substrate 100 having a placement surface, an adsorption electrode 130 provided inside the dielectric substrate 100, and a base plate 200 that supports the dielectric substrate 100. The dielectric substrate 100 includes a first part 101 that is a part more on the placement surface side than the adsorption electrode 130, and a second part 102 that is a part more on the base plate 200 side than the adsorption electrode 130. The second part 102 is thicker than the first part 101. The thermal conductivity of the second part 102 is higher than that of the first part 101.SELECTED DRAWING: Figure 1

Description

[Technical field]

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

[0002] For example, in semiconductor manufacturing equipment such as an etching device, 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 having an attracting electrode provided therein, and a base plate for 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. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6993835 Summary of the Invention [Problem to be solved by the invention]

[0004] The portion of the dielectric substrate closer to the mounting surface than the chucking electrode is the portion that generates the electrostatic force and contributes directly to the chucking of the substrate. This portion is also referred to as the "first portion" below. The portion of the dielectric substrate closer to the base plate than the chucking electrode is the portion that supports the first portion and does not contribute directly to the chucking of the substrate. This portion is also referred to as the "second portion" below.

[0005] In this way, the first and second parts sandwiching the chucking electrode have different roles. Therefore, it may not be appropriate to form the entire dielectric substrate from the same material. For example, since the second part is relatively thick, if a material with the same thermal conductivity as the first part is used, heat may be trapped and the temperature of the substrate may rise.

[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 capable of maintaining an appropriate temperature of a substrate during processing. [Means for solving the problem]

[0007] In order to solve the above problems, an electrostatic chuck according to the present invention includes a dielectric substrate having a mounting surface on which an object to be attracted is placed, an attraction electrode provided inside the dielectric substrate, and a base plate supporting the dielectric substrate. The dielectric substrate has a first portion which is closer to the mounting surface than the attraction electrode, and a second portion which is closer to the base plate than the attraction electrode. The second portion is thicker than the first portion, and the thermal conductivity of the second portion is higher than the thermal conductivity of the first portion.

[0008] Since the first portion is a portion that directly contributes to the adhesion of the substrate, it is preferable to use an appropriate material that takes into consideration the workability of the dots, the detachment response, etc. On the other hand, since the second portion is a portion for supporting the first portion and is relatively thick, it is preferable to use an appropriate material that takes into consideration the thermal conductivity so as not to trap heat.

[0009] Therefore, in the electrostatic chuck having the above-mentioned configuration, the thermal conductivity of the dielectric substrate is not uniform throughout, but is different in each portion. Specifically, the thermal conductivity of the second portion is made higher than that of the first portion. With this configuration, it is possible to use an appropriate material for the first portion in consideration of the detachment response, etc., while using an appropriate material for the second portion to facilitate the release of heat to the base plate side. As a result, the temperature of the substrate during processing can be maintained at an appropriate temperature. Effect of the Invention

[0010] According to the present invention, it is possible to provide an electrostatic chuck capable of maintaining an appropriate temperature of a substrate during processing. [Brief description of the drawings]

[0011] [Figure 1]1 is a cross-sectional view illustrating a schematic configuration of an electrostatic chuck according to an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] 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.

[0013] 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 to be attracted is, for example, a silicon wafer. The electrostatic chuck 10 may be used in an apparatus other than a semiconductor manufacturing apparatus.

[0014] 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 and a base plate 200.

[0015] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 is made of, for example, high-purity aluminum oxide (Al 2 O 3 ), 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, etc. required for the dielectric substrate 100 in the semiconductor manufacturing equipment.

[0016] Although the dielectric substrate 100 is entirely made of ceramic, it is not made of a single material, but is made of different materials in different locations, as will be described later.

[0017] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "joined surface" that is joined to the base plate 200 via a joining layer 300. 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".

[0018] 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 arranged parallel to the surface 110. The material of the adsorption electrode 130 may be molybdenum, platinum, palladium, or the like, in addition to tungsten. 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.

[0019] 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.

[0020] A seal ring 111 and dots 112 are provided on a surface 110 serving as a mounting surface, and the above-mentioned space SP is formed around these.

[0021] The seal ring 111 is a wall that divides the space SP at the outermost position. The upper end 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.

[0022] 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.

[0023] 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.

[0024] The base plate 200 is a substantially disk-shaped member that supports the dielectric substrate 100. 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 dielectric substrate 100 via a bonding layer 300.

[0025] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and bonds the two together. The bonding layer 300 is formed by curing an adhesive made of an insulating material. In this embodiment, a silicone adhesive is used as the adhesive. However, the bonding layer 300 may be formed by curing another type of adhesive. In any case, it is preferable to use a material with as high a thermal conductivity as possible as the material for the bonding layer 300 so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[0026] An insulating film may be formed on the surface of the base plate 200. For example, an alumina film formed by thermal spraying can be used as the insulating film. By covering the surface of the base plate 200 with the insulating film, the dielectric strength of the base plate 200 can be increased.

[0027] A coolant flow path 250 for passing 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.

[0028] A specific configuration of the dielectric substrate 100 will be described. A portion of the dielectric substrate 100 closer to the surface 110 than the attraction electrode 130 is hereinafter also referred to as a "first portion 101." Also, a portion of the dielectric substrate 100 closer to the base plate 200 than the attraction electrode 130 is hereinafter also referred to as a "second portion 102."

[0029] The first portion 101 is a portion that generates an electrostatic force between itself and the substrate W, and is a portion that directly contributes to the adsorption of the substrate W. The thickness T1 of the first portion 101 is relatively thin for the purposes of generating a large electrostatic force and reducing impedance when plasma is generated.

[0030] The second portion 102 is a portion that supports the first portion 101 and does not directly contribute to adsorption of the substrate W. The thickness T2 of the second portion 102 is greater than the thickness T1 of the first portion 101 for the purpose of ensuring the strength of the dielectric substrate 100, etc.

[0031] In this embodiment, the second portion 102 and the first portion 101 are formed of different materials so that the thermal conductivity of the second portion 102 is higher than that of the first portion 101. For example, the thermal conductivity of the second portion 102 can be increased by making the titanium content per unit volume in the second portion 102 higher than the titanium content per unit volume in the first portion 101. Titanium can be, for example, titania (TiO 2 ), or may be added as another titanium compound or as metallic titanium. In either case, it is sufficient that the titanium content (the number of Ti atoms) per unit volume in the second portion 102 is greater than the titanium content (the number of Ti atoms) per unit volume in the first portion 101.

[0032] The dielectric substrate 100 having such a configuration can be manufactured, for example, by stacking green sheets and processing and firing the resulting laminate in the same manner as conventional dielectric substrates. At this time, the green sheet laminated on the portion closer to the surface 110 than the attraction electrode 130 and the green sheet laminated on the portion closer to the base plate 200 than the attraction electrode 130 may be made of different materials.

[0033] The reason for adopting such a configuration will be explained. As described above, the first portion 101 is a portion that directly contributes to the adsorption of the substrate W, and the second portion 102 is a portion that supports the first portion 101. In this manner, the first portion 101 and the second portion 102 that sandwich the adsorption electrode 130 have different roles from each other. Therefore, if the entire dielectric substrate 100 is made of the same material, there may be cases where each of the portions cannot adequately perform their respective roles. For example, since the second portion 102 is relatively thick, if a material with the same thermal conductivity as the first portion 101 is used, heat may be trapped, and the temperature of the substrate W may increase during processing.

[0034] Therefore, in this embodiment, the thermal conductivity of the dielectric substrate 100 is not uniform throughout, but is varied in each portion. Specifically, the thermal conductivity of the second portion 102 is made higher than that of the first portion 101. With this configuration, it is possible to use an appropriate material for the first portion 101 in consideration of the detachment response of the substrate W, and to use an appropriate material for the second portion 102 in order to facilitate the release of heat to the base plate 200 side. As a result, the temperature of the substrate W during processing can be maintained at an appropriate temperature.

[0035] The first portion 101 and the second portion 102 may be different from each other in physical properties other than thermal conductivity as a result of being formed from appropriate materials according to their respective roles. However, in consideration of the durability of the dielectric substrate 100 in a semiconductor manufacturing device, it is preferable that the first portion 101 and the second portion 102 are both formed from ceramics as in this embodiment.

[0036] 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]

[0037] 10: Electrostatic chuck 100: Dielectric substrate 101: Part 1 102:Second part 110: Face 130: Adsorption electrode 200: Base plate W: Substrate

Claims

1. a dielectric substrate having a mounting surface on which an object to be attached is placed; an adsorption electrode provided inside the dielectric substrate; a base plate supporting the dielectric substrate; The dielectric substrate is a first portion that is a portion closer to the placement surface than the chucking electrode; a second portion that is a portion closer to the base plate than the attraction electrode; The second portion is thicker than the first portion; The second portion has a higher thermal conductivity than the first portion.

2. 2. The electrostatic chuck according to claim 1, wherein the first portion and the second portion are both made of ceramic.

3. 3. The electrostatic chuck of claim 2, wherein the second portion has a titanium content per unit volume greater than the first portion has a titanium content per unit volume.

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