Electrostatic chuck

Abstract

To provide an electrostatic chuck that can prevent a variation in the in-plane temperature distribution of a substrate during processing.SOLUTION: An electrostatic chuck 10 comprises a dielectric substrate 100, an attraction electrode 130 provided inside the dielectric substrate 100, and an RF electrode 140 provided inside the dielectric substrate 100. In a top view, the RF electrode 140 is provided within a range where its outer peripheral side end is located inside an outer peripheral side end of the attraction electrode 130.SELECTED DRAWING: Figure 2

Description

[Technical Field]

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

[0002] Semiconductor manufacturing equipment, such as an etching apparatus, is equipped with an electrostatic chuck 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 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, attracting and holding a substrate placed on the dielectric substrate. The attracting electrode may be formed on the surface of the dielectric substrate facing the base plate, but is often provided inside the dielectric substrate.

[0003] As described in Patent Document 1 below, an RF electrode may be built into the dielectric substrate in addition to the chucking electrode. The RF electrode functions as one of a pair of opposing electrodes for generating plasma in semiconductor manufacturing equipment. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-119654 Summary of the Invention [Problem to be solved by the invention]

[0005] When a substrate is being processed, such as during etching, Joule heat is generated in the RF electrodes, which can raise the temperature of surrounding components. In other words, the RF electrodes can become a heat source during processing. However, no specific consideration has been given to how to position the RF electrodes, which are heat sources, in order to suppress variations in the in-plane temperature distribution of the substrate during processing.

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

[0007] In order to achieve the above object, 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 an RF electrode provided inside the dielectric substrate, wherein, when viewed from a direction perpendicular to the mounting surface, the RF electrode is provided in a range in which its outer peripheral end is located inside the outer peripheral end of the attraction electrode.

[0008] It is known that the temperature of a substrate, particularly its outer periphery, tends to rise during processing such as etching. Therefore, in the electrostatic chuck having the above configuration, the RF electrode, which is a heat source, is positioned so that its outer periphery edge is located inside the outer periphery edge of the attracting electrode, thereby suppressing the temperature rise in the outer periphery of the substrate. This makes it possible to suppress the variation in the in-plane temperature distribution of the substrate during processing more than ever before. [Effects of the Invention]

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

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

[0011] Hereinafter, the present embodiment will be described with reference to the accompanying drawings. To facilitate understanding of the description, the same components in the drawings will be denoted by the same reference numerals as much as possible, and duplicated descriptions 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 to be attracted is, for example, a silicon wafer. The electrostatic chuck 10 may also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0013] 1 is a schematic cross-sectional view showing the configuration of an electrostatic chuck 10 in a state where the electrostatic chuck 10 attracts and holds a substrate W. The electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200.

[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 also contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set taking into consideration the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment. The diameter of the dielectric substrate 100 is, for example, 290 to 300 mm. The thickness of the dielectric substrate 100 is, for example, 0.5 to 3.0 mm.

[0015] 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 "bonded surface" that is bonded to the base plate 200 via a bonding 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 also be referred to as a "top view."

[0016] An adsorption electrode 130 is embedded within the dielectric substrate 100. The adsorption electrode 130 is a thin, flat layer made of a metal material such as tungsten, and is disposed parallel to the surface 110. The adsorption electrode 130 may be made of tungsten or other materials such as molybdenum, platinum, or palladium. When a voltage is applied to the adsorption electrode 130 from the outside via a power supply line (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. Various known configurations can be employed for the power supply line. As in this embodiment, only one adsorption electrode 130 may be provided as a so-called "monopolar" electrode, or two may be provided as so-called "bipolar" electrodes. The depth at which the adsorption electrode 130 is disposed, i.e., the distance from a bottom surface 116 (described below) to the adsorption electrode 130, is, for example, 0.1 to 0.5 mm.

[0017] In addition to the above-described attracting electrode 130, an RF electrode 140 is also embedded inside the dielectric substrate 100. The RF electrode 140 is provided as one of a pair of opposing electrodes for generating plasma in the semiconductor manufacturing equipment. The other opposing electrode is provided at a position above the electrostatic chuck 10 in the semiconductor manufacturing equipment. When a high-frequency AC voltage is applied between these opposing electrodes, plasma is generated above the substrate W, and is used for processing the substrate W, such as film formation and etching.

[0018] Like the chucking electrode 130, the RF electrode 140 is a thin, flat layer made of a metal material such as tungsten. Other materials that may be used for the RF electrode 140 include molybdenum, platinum, and palladium, in addition to tungsten. The RF electrode 140 is embedded in a position closer to the surface 120 than the chucking electrode 130. Like the chucking electrode 130, the RF electrode 140 is disposed parallel to the surface 110. The RF electrode 140 is a single electrode that is substantially circular in top view. The center of the RF electrode 140 coincides with the center of the dielectric substrate 100 in top view. The distance from the chucking electrode 130 to the RF electrode 140 is, for example, 0.2 to 2 mm. The distance from the RF electrode 140 to the surface 120 is, for example, 0.1 to 2.5 mm.

[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 equipment, helium gas for temperature adjustment is supplied to the space SP from the outside 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, thereby maintaining the temperature of the substrate W at an appropriate temperature. Note that the temperature adjustment gas supplied to the space SP may be a gas other than helium.

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

[0021] The seal ring 111 is a wall that partitions the space SP at the outermost position. The seal ring 111 is an annular protrusion formed on the surface 110. The tip (the upper end in FIG. 1) of the seal ring 111 is part of the surface 110 and abuts against the substrate W. The tip of the seal ring 111 can be said to be the outermost part of the surface 110, which is the mounting surface.

[0022] It should be noted that a plurality of seal rings 111 may be provided to divide the space SP. With such a configuration, the pressure of the helium gas in each space SP can be adjusted individually, and the surface temperature distribution of the substrate W during processing can be made more uniform.

[0023] 1, the portion marked with the reference numeral "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 portion of the surface 110 to the position of the bottom surface 116.

[0024] The dots 112 are circular protrusions that protrude 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 tip of each dot 112 forms part of the surface 110 and comes into contact with the substrate W. By providing a plurality of such dots 112, bending of the substrate W is suppressed.

[0025] 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 base plate 200 is bonded to the surface 120 of the dielectric substrate 100 via a bonding layer 300. The surface 210 of the base plate 200, which is on the upper side in FIG. 1, is the "bonded surface" that is bonded to the dielectric substrate 100.

[0026] The bonding layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200, and bonds them 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 either 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 as to reduce the thermal resistance between the dielectric substrate 100 and the base plate 200.

[0027] 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 an insulating film, the dielectric strength of the base plate 200 can be increased.

[0028] The base plate 200 has a support portion 201 and a flange portion 202. The support portion 201 is the upper portion of the base plate 200 in FIG. 1 and is a substantially cylindrical portion that directly supports the dielectric substrate 100 from below. The diameter of the support portion 201, i.e., the diameter of the surface 210, may be the same as the diameter of the dielectric substrate 100, or may be slightly smaller than the diameter of the dielectric substrate 100. The diameter of the support portion 201 is, for example, 290 to 300 mm. The thickness of the support portion 201, i.e., the amount of protrusion of the support portion 201 toward the upper side in FIG. 1 (the amount of protrusion from the flange portion 202), is, for example, 3 to 15 mm.

[0029] The flange 202 is the lower part of the base plate 200 in FIG. 1. The flange 202 is substantially cylindrical, and its central axis coincides with the central axis of the support portion 201. The diameter of the flange 202 is larger than the diameter of the support portion 201. The amount of protrusion of the flange 202 from the outer surface of the support portion 201 (i.e., the amount of protrusion in the radial direction) is, for example, 20 to 30 mm. The thickness of the flange 202 is, for example, 25 to 40 mm. The overall thickness of the base plate 200, including the support portion 201 and the flange 202, is, for example, 30 to 40 mm.

[0030] When processing a substrate W in a semiconductor manufacturing apparatus, a focus ring (not shown) is installed on the upper surface 203 of the flange portion 202. The focus ring is an annular, plate-shaped member made of an insulating material such as quartz, and is installed for the purpose of adjusting the distribution of plasma during processing. The dielectric substrate 100 and the support portion 201 are substantially entirely surrounded by the focus ring from the outer periphery.

[0031] 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 equipment, 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.

[0032] Incidentally, it is known that during processing such as etching, the temperature of the substrate W tends to rise, particularly at the outer periphery. Therefore, in the electrostatic chuck 10 of this embodiment, various improvements described below have been made to suppress the above-mentioned local temperature rise and to make the in-plane temperature distribution of the substrate W during processing as uniform as possible.

[0033] 1, the coolant flow path 250 is routed not only in the portion of the base plate 200 directly below the substrate W, but also in a portion outside the portion directly below the substrate W. The coolant passing through the outer portion cools a focus ring (not shown) and the like located directly above the upper surface 203, and the outer peripheral portion of the substrate W is also cooled through these.

[0034] In this embodiment, the diameter of the flange 202 is relatively large. By enlarging the flange 202 and forming a coolant flow path 250 that extends over substantially the entire flange 202, and then circulating the coolant, it is possible to suppress a temperature rise in the outer peripheral portion of the substrate W.

[0035] 2 is an enlarged detailed view of the outer circumferential edge of the dielectric substrate 100 and the surrounding area of the electrostatic chuck 10 shown in FIG. 2. A dotted line DL1 in FIG. 2 indicates the position of the outer circumferential edge of the chucking electrode 130. A dotted line DL2 indicates the position of the outer circumferential edge of the RF electrode 140. Note that the "outer circumferential edge" of the chucking electrode 130 refers to the portion where the chucking electrode 130 overlaps with the smallest circle among the circles that encompass the entire chucking electrode 130 in a top view. The "outer circumferential edge" of the RF electrode 140 is defined in the same way.

[0036] To prevent dielectric breakdown, the distance from the outer peripheral end (dotted line DL1) of the chucking electrode 130 to the outer surface of the dielectric substrate 100 is preferably about 0.1 mm to 3 mm. Furthermore, the distance from the outer peripheral end (dotted line DL2) of the RF electrode 140 to the outer surface of the dielectric substrate 100 is preferably about 0.1 mm to 5 mm. In a range that satisfies the above conditions, the diameter of the outer peripheral end of the RF electrode 140 is preferably smaller than the diameter of the outer peripheral end of the chucking electrode 130. In other words, the RF electrode 140 is preferably provided in a range where its outer peripheral end (dotted line DL1) is inside the outer peripheral end (dotted line DL2) of the chucking electrode 130 in a top view.

[0037] When the substrate W is being processed, Joule heat is generated in the RF electrode 140, which may increase the temperature of surrounding components. In other words, the RF electrode 140 can become a heat source during processing. Therefore, in this embodiment, as described above, the RF electrode 140 is placed within a range in which its outer circumferential end is located inside the outer circumferential end of the attraction electrode 130. By placing the RF electrode 140, which is a heat source, within the above range, it is possible to suppress a temperature rise in the outer circumferential portion of the substrate W. This makes it possible to suppress variations in the in-plane temperature distribution of the substrate W during processing more than in the past.

[0038] The diameter of the outer peripheral end of the chucking electrode 130 is larger than the diameter of the inner peripheral side of the seal ring 111 and smaller than the diameter of the outer peripheral side of the seal ring 111. Therefore, a part of the seal ring 111 overlaps with the chucking electrode 130 in a top view. When the seal ring 111 and the chucking electrode 130 overlap each other in a top view, the chucking force on the seal ring 111 increases, and the seal ring 111 and the substrate W are tightly attached with a strong force. This reduces the thermal resistance between the seal ring 111 and the substrate W, making it possible to suppress a temperature rise of the substrate W directly above the seal ring 111. As a result, it is possible to further suppress variations in the in-plane temperature distribution of the substrate W during processing.

[0039] The entire seal ring 111, not just a part of it, may overlap with the chucking electrode 130 in top view. In this case, the diameter of the outer periphery of the seal ring 111 may be made smaller than the diameter of the dielectric substrate 100 and also smaller than the diameter of the outer periphery end of the chucking electrode 130.

[0040] The present embodiment has been described above with reference to specific examples. However, the present disclosure is not limited to these specific examples. Design modifications to these specific examples made by a person skilled in the art as appropriate are also included within the scope of the present disclosure as long as they comprise the features of the present disclosure. The elements of the above-described specific examples, as well as their arrangement, conditions, shape, etc., are not limited to those exemplified and can be modified as appropriate. The elements of the above-described specific examples can be combined in various ways as appropriate, as long as no technical contradictions arise. [Explanation of symbols]

[0041] 10: Electrostatic chuck 100: Dielectric substrate 110: Face 111: Seal ring 130: Adsorption electrode 140:RF electrode

Claims

1. a dielectric substrate having a mounting surface on which an object to be attracted is placed; an adsorption electrode provided inside the dielectric substrate; an RF electrode provided inside the dielectric substrate; When viewed from a direction perpendicular to the placement surface, The electrostatic chuck is characterized in that the RF electrode is provided in a range in which its outer peripheral end is located inside the outer peripheral end of the attraction electrode.

2. a seal ring, which is an annular protrusion whose tip forms part of the mounting surface, is formed on the dielectric substrate; When viewed from a direction perpendicular to the placement surface, 2. The electrostatic chuck according to claim 1, wherein at least a portion of said seal ring overlaps with said attracting electrode.

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