Electrostatic chuck

Abstract

To provide an electrostatic chuck capable of suppressing the occurrence of discharge in a gas groove.SOLUTION: An electrostatic chuck 10 includes a first portion 101 including a surface 110 on which a substrate W is placed, a second portion 102 protruding further outward from the outer peripheral edge of the first portion 101 and being thinner than the first portion 101, an internal electrode 140 provided inside the second portion 102, and a gas groove 181 formed on a surface 180 of the second portion 102. In a top view, the gas groove 181 is formed at a position that does not overlap the internal electrode 140.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] For example, semiconductor manufacturing equipment such as etching equipment 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 on which an attracting electrode is provided. When a voltage is applied to the attracting electrode, an electrostatic force is generated, attracting and holding the substrate placed on the dielectric substrate.

[0003] During substrate processing, an annular member called a focus ring or the like is arranged around the substrate. For example, as described in Patent Document 1 below, a dielectric substrate may be provided with a flange portion on which such an annular member is placed. The portion of the dielectric substrate on which a substrate to be processed, such as a silicon wafer, is placed is hereinafter also referred to as the "first portion." The flange portion provided on the dielectric substrate is hereinafter also referred to as the "second portion." The second portion (flange portion) protrudes further outward from the outer circumferential edge of the first portion and is thinner than the first portion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-281680 Summary of the Invention [Problem to be solved by the invention]

[0005] The inventors have been studying the possibility of supplying an inert gas between the second portion and the annular member to adjust the temperature of the annular member. In this case, it is preferable to form gas grooves on the surface of the second portion to quickly guide the inert gas to each part. However, the second portion is relatively thin. Therefore, if gas grooves are formed on the surface of the second portion, the internal electrode provided inside the second portion may be exposed on the inner surface of the gas groove, which may cause problems such as discharge.

[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 the occurrence of discharge in the gas grooves. [Means for solving the problem]

[0007] In order to solve the above problems, the electrostatic chuck according to the present invention includes a first portion including a mounting surface on which an object to be attracted is placed, a second portion protruding from an outer peripheral edge of the first portion toward the outer periphery and thinner than the first portion, an internal electrode provided inside the second portion, and a gas groove formed in the surface of the second portion facing the mounting surface. When viewed from a direction perpendicular to the mounting surface, the gas groove is formed at a position that does not overlap with the internal electrode.

[0008] Since the gas grooves are formed at positions that do not overlap with the internal electrodes when viewed from above, the internal electrodes are not exposed at the inner surfaces of the gas grooves, thereby making it possible to suppress the occurrence of discharge in the gas grooves. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an electrostatic chuck that can suppress the occurrence of discharge in the gas grooves. [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]5A and 5B are diagrams for explaining the positional relationship between gas grooves and internal electrodes, etc. FIG. [Figure 3] FIG. 10 is a diagram for explaining the position of a gas groove. 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 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 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] The dielectric substrate 100 has a first portion 101 and a second portion 102. The first portion 101 is a generally cylindrical portion that extends from a surface 110 downward in Fig. 1 to a surface 120. Such a first portion 101 can be said to be a portion of the dielectric substrate 100 that includes the surface 110, which is the mounting surface.

[0017] The second portion 102 is an annular portion that protrudes further outward from the outer peripheral edge of the first portion 101, and is also referred to as the "flange" of the dielectric substrate 100. In FIG. 1, the boundary between the first portion 101 and the second portion 102 is indicated by a dotted line DL01. The second portion 102 is thinner than the first portion 101. That is, the dimension of the second portion 102 in a direction perpendicular to the surface 110 (the vertical direction in FIG. 1) is smaller than the dimension of the first portion 101 in the same direction. The surface 120 mentioned above is the lowermost surface of the first portion 101 in FIG. 1 and is also the lowermost surface of the second portion 102. The uppermost surface 180 of the second portion 102 is located lower than the surface 110 in FIG. 1. The surface 180 can be said to be the surface of the second portion 102 on the mounting surface side.

[0018] When a substrate W is processed in a semiconductor manufacturing apparatus, an annular member RE, such as a focus ring, is arranged around the substrate W. A surface 180 of the second portion 102 supports the annular member RE from below. The surface 180 is parallel to the surface 110. The surface 180 may support the entire annular member RE from below, as in the example of FIG. 1, or may support only a portion of the annular member RE.

[0019] An attraction electrode 130 is provided inside the first portion 101 of the dielectric substrate 100. The attraction electrode 130 is a thin, flat layer made of a metal material such as tungsten, and is disposed parallel to the surface 110. The attraction electrode 130 may be made of molybdenum, platinum, palladium, or the like, in addition to tungsten. When a voltage is applied to the attraction 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 attracting and holding the substrate W. The power supply path may be configured in any of various well-known ways. The attraction electrode 130 may be provided as a single so-called "monopolar" electrode as in this embodiment, or as two so-called "bipolar" electrodes.

[0020] An internal electrode 140 is provided inside the second portion 102 of the dielectric substrate 100. The internal electrode 140 is a thin, flat layer made of the same material as the chucking electrode 130, and is disposed parallel to the surface 180. When a voltage is applied to the internal electrode 140 from the outside via a power supply path (not shown), an electrostatic force is generated between the surface 180 and the annular member RE, thereby attracting and holding the annular member RE. Various known configurations can be used as the configuration of the power supply path connected to the internal electrode 140. The specific configuration of the internal electrode 140 will be described later.

[0021] In this embodiment, a part of the internal electrode 140 extends beyond the dotted line DL01 into the inner first portion 101. In other words, the internal electrode 140 is provided in a range that spans both the first portion 101 and the second portion 102. Alternatively, the entire internal electrode 140 may be provided only in the second portion 102.

[0022] In addition to the above-described chucking electrode 130 and internal electrode 140, an RF electrode for generating plasma and attracting it toward the substrate W may be provided inside the dielectric substrate 100. The chucking electrode 130 and internal electrode 140 may also be used as the above-described RF electrode.

[0023] 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 to the space SP from the outside through a first gas hole 150 described below. 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 type of gas other than helium.

[0024] 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.

[0025] 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 multiple 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.

[0026] 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.

[0027] 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 upper end 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.

[0028] A first gas hole 150 is formed in the first portion 101 of the dielectric substrate 100. The first gas hole 150 is a circular through-hole formed to extend in a direction perpendicular to the surface 110, which is the mounting surface. The end of the first gas hole 150 on the surface 110 side is connected to the space SP. The first gas hole 150 is part of a flow path for supplying helium gas toward the space SP. A plurality of first gas holes 150 are formed in the first portion 101, but only one of them is shown in FIG. 1.

[0029] The portion of the first gas hole 150 on the surface 120 side has a larger diameter than the portion on the surface 110 side. Hereinafter, this expanded diameter portion will also be referred to as the "expanded diameter portion 151." A first ventilation member 400 is disposed inside the expanded diameter portion 151. The first ventilation member 400 is a substantially cylindrical member made of an insulating material and has gas permeability. In this embodiment, porous alumina is used as the material for the first ventilation member 400. The first ventilation member 400 is provided to prevent discharge (dielectric breakdown) from the substrate W through the first gas hole 150 to the base plate 200. The first ventilation member 400 may be a member having a plurality of ventilation holes extending linearly from one end to the other end, or may be a member having a mesh-like flow path.

[0030] Second gas holes 160 are formed in the second portion 102 of the dielectric substrate 100. The second gas holes 160 are circular through-holes extending in a direction perpendicular to the surface 110 and the surface 180. The second gas holes 160 are part of a flow path for supplying helium gas toward a gap (not shown) between the surface 180 and the annular member RE. By providing helium gas between the surface 180 and the annular member RE, the thermal resistance between them is adjusted, thereby maintaining the temperature of the annular member RE at an appropriate temperature. A plurality of second gas holes 160 are formed in the second portion 102, and are arranged in a ring shape when viewed from above, although only two of them are shown in FIG. 1 . The gas supplied through the second gas holes 160 may be a different type of gas from the gas supplied through the first gas holes 150.

[0031] Gas grooves 181 are formed in surface 180. Gas grooves 181 are formed to quickly guide gas supplied through second gas holes 160 to each portion along surface 180. The ends of second gas holes 160 on the surface 180 side open at the bottom surface of gas groove 181. As shown in FIG. 2, gas groove 181 is formed to extend along an arc that passes through each position of the multiple second gas holes 160 arranged in an annular shape.

[0032] As shown in FIG. 1 , the portion of the second gas hole 160 on the surface 120 side has a larger diameter than the portion on the surface 180 side. Hereinafter, this expanded diameter portion will also be referred to as the "expanded diameter portion 161." A second ventilation member 500 is disposed inside the expanded diameter portion 161. The second ventilation member 500 is a substantially cylindrical member made of an insulating material and has gas permeability. In this embodiment, porous alumina is used as the material for the second ventilation member 500. The second ventilation member 500 is provided to prevent discharge that would reach the base plate 200 through the second gas hole 160. The second ventilation member 500 may be a member formed with a plurality of ventilation holes extending linearly from one end to the other end, or may be a member formed with a mesh-like flow path.

[0033] 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. The outer shape of the surface 210 in a top view is generally the same as the outer shape of the second portion 102 in a top view.

[0034] 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.

[0035] 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.

[0036] A coolant flow path 240 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 240 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 then discharged to the outside together with the coolant. The coolant is supplied to and discharged from the coolant flow path 240 through an opening (not shown) formed on the surface 220 of the base plate 200 opposite the surface 210. The coolant flow path 240 is formed to pass not only through the area overlapping with the first portion 101 in top view, but also through the area overlapping with the second portion 102. Therefore, not only the substrate W but also the annular member RE are cooled by the coolant passing through the coolant flow path 240.

[0037] Gas holes 251 are formed in the surface 210 of the base plate 200 at positions that overlap with the expanded diameter portions 151 in a top view. The shape of the gas holes 251 in a top view is the same circular shape as the shape of the expanded diameter portions 151 in a top view. The gas holes 251 are formed to extend from the surface 210 to a predetermined depth in a direction perpendicular to the surface 210.

[0038] An opening 301 is formed in the bonding layer 300 at a position between the expanded diameter portion 151 and the gas hole 251. An end of the gas hole 251 on the surface 210 side is connected to the expanded diameter portion 151 of the first gas hole 150 through the opening 301. An end of the gas hole 251 on the opposite side to the above end is connected to a distribution flow path 271 formed inside the base plate 200.

[0039] The distribution flow path 271 is a flow path formed to distribute helium gas supplied from the outside to each of the multiple gas holes 251. The distribution flow path 271 is routed along a path that passes directly below all of the gas holes 251. A configuration may be adopted in which multiple distribution flow paths 271 are formed and the supply of helium gas to the gas holes 251 is divided into multiple systems. With such a configuration, for example, the pressure of the helium gas supplied to the gas holes 251 on the central side and the pressure of the helium gas supplied to the gas holes 251 on the outer periphery side can be made different from each other.

[0040] An air-permeable member 610 is disposed inside the gas hole 251. The air-permeable member 610 is a substantially cylindrical member that is air-permeable. In this embodiment, porous alumina is used as the air-permeable member 610. The air-permeable member 610 may be a member in which a plurality of air holes extending linearly from one end to the other end are formed, or may be a member in which a mesh-like flow path is formed.

[0041] Gas holes 261 are formed in the surface 210 of the base plate 200 at positions that overlap with the expanded diameter portions 161 in a top view. The shape of the gas holes 261 in a top view is the same circular shape as the shape of the expanded diameter portions 161 in a top view. The gas holes 261 are formed to extend from the surface 210 to a predetermined depth in a direction perpendicular to the surface 210.

[0042] An opening 302 is formed in the bonding layer 300 at a position between the expanded diameter portion 161 and the gas hole 261. An end of the gas hole 261 on the surface 210 side is connected to the expanded diameter portion 161 of the second gas hole 160 through the opening 302. An end of the gas hole 261 on the opposite side to the above end is connected to a distribution flow path 272 formed inside the base plate 200.

[0043] The distribution flow path 272 is a flow path formed to distribute helium gas supplied from the outside to each of the multiple gas holes 261. The distribution flow path 272 is routed along a path that passes directly below all of the gas holes 261. A configuration may be adopted in which multiple distribution flow paths 272 are formed, and the supply of helium gas to the gas holes 261 is divided into multiple systems. With such a configuration, for example, the pressure of the helium gas supplied to the gas holes 261 on the central side and the pressure of the helium gas supplied to the gas holes 261 on the outer periphery side can be made different from each other. The distribution flow path 272 may be connected to the distribution flow path 271.

[0044] An air-permeable member 620 is disposed inside the gas hole 261. The air-permeable member 620 is a substantially cylindrical member that is air-permeable. In this embodiment, porous alumina is used as the air-permeable member 620. The air-permeable member 620 may be a member in which a plurality of air holes extending linearly from one end to the other end are formed, or may be a member in which a mesh-like flow path is formed.

[0045] 2, the arrangement of the internal electrodes 140, gas grooves 181, etc. is schematically depicted in a top view. In the figure, the circular dotted line labeled "DL11" represents the outline of the second portion 102. Furthermore, the circular dotted line labeled "DL12" represents the outline of the first portion 101. The region between DL11 and DL12 corresponds to the second portion 102.

[0046] 2, in this embodiment, a total of four second gas holes 160 are provided in the second portion 102. These four second gas holes 160 are arranged in a ring shape at equal intervals when viewed from above. The distance from the center of the dielectric substrate 100 to the center of each second gas hole 160 is the same for each second gas hole 160.

[0047] A total of four gas grooves 181 are provided, one for each second gas hole 160. As described above, the gas grooves 181 are formed to extend along an arc that passes through the positions of the multiple second gas holes 160 arranged in an annular shape. The second gas holes 160 are open at the bottom surface of the gas grooves 181.

[0048] Two internal electrodes 140 are provided as so-called "bipolar" electrodes, and are arranged side by side in Fig. 2. Alternatively, only one internal electrode 140 may be provided as a so-called "unipolar" electrode.

[0049] 2, the gas grooves 181 of this embodiment are formed in a position that does not overlap any of the internal electrodes 140 in top view. In other words, the internal electrodes 140 of this embodiment are formed in a position that does not overlap any of the gas grooves 181.

[0050] The second portion 102 is a relatively thin portion. Therefore, if the gas groove 181 were formed at a position overlapping the internal electrode 140 in a top view, the internal electrode 140 would be exposed on the inner surface of the gas groove 181, which could result in problems such as discharge. Therefore, in this embodiment, the gas groove 181 is formed at a position that does not overlap any of the internal electrodes 140, as described above. Even if the gas groove 181 is formed deep, the internal electrode 140 is not exposed on the inner surface, and the distance from the inner surface of the gas groove 181 to the internal electrode 140 is not too small, so that the occurrence of discharge in the gas groove 181 can be sufficiently suppressed.

[0051] Each internal electrode 140 has a first electrode portion 141 , a second electrode portion 142 , and a connection electrode portion 143 .

[0052] First electrode portion 141 is a portion formed to extend in an arc shape at a position outside gas groove 181 in top view. The center of curvature of first electrode portion 141 is at the same position as the center of curvature of gas groove 181 and the center of first portion 101. The portion of first electrode portion 141 near second gas hole 160 is notched in an arc shape. This ensures an insulation distance from the inner surface of second gas hole 160 to first electrode portion 141, preventing insulation breakdown between them.

[0053] The second electrode portion 142 is a portion that is formed to extend in an arc shape at a position that is more inward than the gas groove 181 in a top view. Therefore, the second electrode portion 142 is located more inward than the first electrode portion 141. The center of curvature of the second electrode portion 142 is at the same position as the center of curvature of the gas groove 181 and also at the same position as the center of the first portion 101. Note that the portion of the second electrode portion 142 near the second gas hole 160 is notched out in an arc shape. This ensures an insulation distance from the inner surface of the second gas hole 160 to the second electrode portion 142, preventing insulation breakdown between them.

[0054] The connection electrode portion 143 is a portion that connects the first electrode portion 141 and the second electrode portion 142. A total of three connection electrode portions 143 are provided between the pair of first electrode portion 141 and second electrode portion 142. The number of connection electrode portions 143 may be different from this. The connection electrode portions 143 are provided at positions where the gas grooves 181 are not formed when viewed from above. Therefore, it can be said that the gas grooves 181 are formed between the first electrode portion 141 and the second electrode portion 142 and at positions that do not overlap with the connection electrode portions 143.

[0055] In this configuration, the gas grooves 181 are formed to extend over almost the entire circumference, enabling uniform gas supply over a wide area, while eliminating the need to divide the internal electrode 140 by the gas grooves 181. In other words, it is not necessary to provide multiple internal electrodes 140 of the same polarity (specifically, inner and outer) to avoid interference with the gas grooves 181. This simplifies the configuration of the electrical path for supplying power to the internal electrode 140.

[0056] 3, the gas grooves 181 formed on the surface 180 of the second portion 102 are schematically illustrated in a top view. In the figure, a circular dotted line labeled "DL21" indicates the center position in the radial direction (which can also be considered as the width direction) of the annular second portion 102. In addition, in the figure, a circular dotted line labeled "DL22" indicates the center position in the radial direction (which can also be considered as the width direction) of the arc-shaped gas groove 181.

[0057] In this embodiment, the diameter of the dotted line DL21 is larger than the diameter of the dotted line DL22. That is, the gas groove 181 in this embodiment is formed at a position that is more inward than the radial center of the second portion 102 in top view.

[0058] Forming the gas groove 181 at such a position makes it possible to ensure a long distance from the gas groove 181 to the outer circumferential edge of the second portion 102. This makes it possible to reduce the flow rate of gas leaking from the outer circumferential edge of the second portion 102 to the outside.

[0059] 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]

[0060] 10: Electrostatic chuck 100: Dielectric substrate 101: Part 1 102:Second part 110: Face 140: Internal electrode 141:First electrode part 142:Second electrode part 143: Connection electrode part 180: Face 181: Gas groove W: Substrate

Claims

1. a first portion including a placement surface on which an object to be attracted is placed; a second portion that protrudes further outward from the outer peripheral end of the first portion and is thinner than the first portion; an internal electrode provided inside the second portion; a gas groove formed in a surface of the second portion on the side of the mounting surface, When viewed from a direction perpendicular to the placement surface, The electrostatic chuck is characterized in that the gas groove is formed at a position where it does not overlap with the internal electrode.

2. When viewed from a direction perpendicular to the placement surface, The internal electrode is a first electrode portion extending in an arc shape; a second electrode portion extending in an arc shape and disposed more inward than the first electrode portion; a connection electrode portion connecting the first electrode portion and the second electrode portion, 2. The electrostatic chuck according to claim 1, wherein the gas groove is formed between the first electrode portion and the second electrode portion and at a position not overlapping with the connection electrode portion.

3. When viewed from a direction perpendicular to the placement surface, The gas groove is 2. The electrostatic chuck according to claim 1, wherein the second portion is formed at a position more inward than a center in a radial direction of the second portion.

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