Electrostatic chuck

Abstract

To provide an electrostatic chuck that facilitates the realization of a complex internal structure of a base plate.SOLUTION: An electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200 bonded to the dielectric substrate 100. The base plate 200 has: a first portion 201 that is a portion on the dielectric substrate 100 side; and a second portion 202 that is a portion adjacent to the first portion 201 from the opposite side of the dielectric substrate 100 and has an outer shape larger than the outer shape of the first portion 201 as viewed from above. The base plate 200 is configured by bonding a plurality of members. A bonding boundary B1 closest to the dielectric substrate 100 is located at the second portion 202.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 an etching apparatus is provided 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 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, attracting and holding a substrate placed on the dielectric substrate.

[0003] As described in Patent Document 1 below, a refrigerant flow path and the like for passing a refrigerant are formed inside the base plate. To facilitate the formation of the refrigerant flow path and the like, the base plate is generally configured by joining multiple members. For example, if a groove is formed on the surface of one member and another member is joined to cover the surface, a flow path along the groove can be easily formed inside the base plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-35447 Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to the above-mentioned coolant flow paths, the base plate also has supply flow paths formed therein for guiding gas to the mounting surface of the dielectric substrate. A porous member may also be disposed inside the supply flow paths to prevent discharge. Thus, the internal structure of the base plate near the dielectric substrate is often relatively complex.

[0006] As described above, the base plate is generally configured by joining a plurality of members together. In order to realize such a complex internal structure, there is room for further improvement in conventional electrostatic chucks in terms of the position of the joining boundary between the members in the base plate.

[0007] 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 easily realize a complex internal structure of a base plate. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention provides an electrostatic chuck comprising a dielectric substrate having a mounting surface on which an object to be attracted is placed, and a base plate joined to the dielectric substrate. The base plate has a first portion that faces the dielectric substrate, and a second portion that is adjacent to the first portion on the opposite side of the dielectric substrate from the mounting surface and has an outer shape larger than that of the first portion when viewed perpendicularly to the mounting surface. The base plate is formed by joining multiple members, and the joining boundary closest to the dielectric substrate is located in the second portion.

[0009] In the electrostatic chuck having the above configuration, the base plate is formed by joining multiple members, and the joining boundary closest to the dielectric substrate is located in the second portion, not the first portion. Because the member closest to the dielectric substrate is thicker than when the joining boundary is located in the first portion, it is possible to simplify, for example, the task of arranging a porous member in a gas supply flow path. This allows for the base plate to have a complex internal structure. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide an electrostatic chuck that can easily realize a complex internal structure of the base plate. [Brief explanation of the drawings]

[0011] [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 a diagram schematically illustrating the configuration of distribution channels and the like inside the base plate. DETAILED DESCRIPTION OF THE INVENTION

[0012] 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.

[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 also be used in apparatuses other than semiconductor manufacturing apparatuses.

[0014] 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.

[0015] 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.

[0016] 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."

[0017] 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.

[0018] 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 via a supply flow path 140, which will be described later. 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] A supply flow path 140 is formed in the dielectric substrate 100. The supply flow path 140 is a through-hole formed to extend in a direction perpendicular to the surface 110, which is the mounting surface. The end of the supply flow path 140 on the surface 110 side is connected to the space SP. The supply flow path 140 is part of a flow path for supplying helium gas toward the space SP. A plurality of supply flow paths 140 are formed in the dielectric substrate 100, but only one of them is shown in FIG. 1.

[0025] 1, the portion of supply flow path 140 on the surface 120 side has a larger diameter than the portion on the surface 110 side, and a porous member 160 is disposed inside the portion. Porous member 160 is a porous body made of alumina, for example, and is entirely breathable. By disposing such a porous member 160 inside supply flow path 140, it is possible to ensure the flow of helium gas through porous member 160 while suppressing the occurrence of dielectric breakdown in the path through supply flow path 140.

[0026] 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.

[0027] 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.

[0028] 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.

[0029] The base plate 200 has a first portion 201 and a second portion 202. The first portion 201 is a portion of the base plate 200 on the dielectric substrate 100 side (upper side in FIG. 1) and is a substantially cylindrical portion that directly supports the dielectric substrate 100 from below. The diameter of the first 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 first portion 201 is, for example, 290 to 300 mm. The thickness of the first portion 201, i.e., the amount of protrusion of the first portion 201 toward the upper side in FIG. 1 (the amount of protrusion from the second portion 202), is, for example, 3 to 15 mm.

[0030] The second portion 202 is a portion of the base plate 200 adjacent to the first portion 201 from the side opposite to the dielectric substrate 100 (the lower side in FIG. 1 ). In this embodiment, the entire base plate 200 excluding the first portion 201 constitutes the second portion 202. The second portion 202 is substantially cylindrical in shape, and its central axis coincides with the central axis of the first portion 201. The thickness of the second portion 202 is, for example, 25 to 40 mm. The diameter of the second portion 202 is larger than the diameter of the first portion 201. The amount of protrusion of the second portion 202 from the outer surface of the first portion 201 (i.e., the amount of protrusion in the radial direction) is, for example, 20 to 30 mm. Therefore, the outer shape of the first portion 201 when viewed from above is larger than the outer shape of the second portion 202 when viewed from above.

[0031] When processing the substrate W in the semiconductor manufacturing equipment, a focus ring (not shown) is installed on the upper surface 203 of the second 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 first portion 201 are substantially entirely surrounded by the focus ring from the outer periphery.

[0032] A coolant flow path 270 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 270 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.

[0033] 1, the coolant flow path 270 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 second portion 202 is relatively large. By enlarging the second portion 202 and forming the coolant flow path 270 so as to extend over substantially the entire second portion 202, and then circulating the coolant, it is possible to suppress a temperature rise in the outer peripheral portion of the substrate W.

[0035] A supply flow path 240 is formed in the base plate 200. The supply flow path 240 is a hole formed to extend in a direction perpendicular to the surface 110, which is the mounting surface, and extends from the surface 210 to a distribution flow path 250, which will be described later. The supply flow paths 240 are formed at positions that overlap with the supply flow paths 140 in a top view, and are connected to the supply flow paths 140 via through holes 310 formed in the bonding layer 300. The supply flow paths 240, together with the supply flow paths 140 of the dielectric substrate 100, form part of a flow path for supplying helium gas toward the space SP on the mounting surface side.

[0036] 1, the portion of supply flow path 240 on the surface 210 side has a larger diameter than the portion on the distribution flow path 250 side, and a porous member 260 is disposed inside the portion. Porous member 260 is a porous body made of alumina, for example, and is entirely breathable. By disposing such porous member 260 inside supply flow path 240, it is possible to ensure the flow of helium gas in supply flow path 240 while suppressing the occurrence of dielectric breakdown in the path through supply flow path 240.

[0037] Distribution channels 250 are formed inside the base plate 200. The distribution channels 250 are channels for distributing helium gas to each of the supply channels 240. The distribution channels 250 are routed parallel to the surface 210 and connected to the lower ends of each of the supply channels 240.

[0038] 2 schematically illustrates the configuration of distribution channels 250 inside base plate 200, supply channels 240 connected thereto, and the like. Arrows in FIG. 2 indicate the flow of helium gas. The portion marked with the reference symbol "251" in FIG. 2 indicates a channel for helium gas formed in base plate 200 to guide helium gas supplied from the outside to distribution channels 250. This channel will also be referred to as "channel 251" below. One end of channel 251 is connected to distribution channel 250. The other end of channel 251 opens at surface 220 of base plate 200, which is opposite surface 210.

[0039] 2, in this embodiment, the multiple supply channels 240 are arranged in a circular pattern when viewed from above. The distribution channels 250 are routed in a circular pattern so as to pass directly below each of the supply channels 240 when viewed from above. The lower ends of each of the supply channels 240 are connected to the distribution channels 250. Therefore, helium gas supplied from the outside is supplied to the distribution channels 250 through the channels 251 and distributed from the distribution channels 250 to each of the supply channels 240. The helium gas is then supplied from each of the supply channels 240 to the space SP through the supply channels 140 located directly above it. By forming the distribution channels 250 inside the base plate 200, the number of parts (i.e., channels 251) that receive helium gas supplied from the outside can be reduced.

[0040] As described above, the base plate 200 has a relatively complicated internal structure, with the refrigerant flow paths 270, distribution flow paths 250, and supply flow paths 240 formed therein. Furthermore, since a porous member 260 is disposed in each supply flow path 240, the internal structure of the base plate 200 on the dielectric substrate 100 side becomes even more complicated.

[0041] In order to facilitate the formation of the refrigerant flow paths 270 and the like, the base plate 200 of this embodiment is formed by joining a plurality of members. Specifically, the base plate 200 is formed by joining together three members consisting of a first member C1, a second member C2, and a third member C3 into an integrated unit. The members are joined by welding, but may also be joined by methods such as brazing or fastening. The number of members constituting the base plate 200 may be four or more, or may be two.

[0042] The first member C1, the second member C2, and the third member C3 are arranged in this order along a direction perpendicular to the surface 110, which is the mounting surface. The first member C1 is the part of the members constituting the base plate 200 that is closest to the dielectric substrate 100. The surface 210 mentioned above is a part of the first member C1. The third member C3 is the part of the members constituting the base plate 200 that is on the opposite side from the dielectric substrate 100. The surface 220 mentioned above is a part of the third member C3. The second member C2 is a member that is between the first member C1 and the third member C3.

[0043] A joint boundary B1 between the first member C1 and the second member C2 is parallel to the surface 110 and the surface 210. A joint boundary B2 between the second member C2 and the third member C3 is also parallel to the surface 110 and the surface 210.

[0044] Of the multiple bonded boundaries, the bonded boundary B1 is the bonded boundary closest to the dielectric substrate 100. The first member C1 is a member located closer to the dielectric substrate 100 than the bonded boundary B1. The second member C2 is a member joined to the first member C1 across the bonded boundary B1.

[0045] 1, in this embodiment, the distribution channels 250 and the supply channels 240 are both entirely formed in the first member C1. The distribution channels 250 are annular grooves that are formed in advance along the surface of the first member C1 that will become the joining boundary B1 before the respective members are joined. In this way, by forming the grooves in advance in the surface of the first member C1 and then joining the second member C2 so as to cover the surface, the distribution channels 250 that follow the grooves can be easily formed inside the base plate 200. Note that the grooves that will become the distribution channels 250 may be formed in the surface of the second member C2 that will become the joining boundary B1, rather than in the surface of the first member C1.

[0046] 1, the coolant flow path 270 in this embodiment is entirely formed in the second member C2. The coolant flow path 270 is a groove that is formed in advance along the surface of the second member C2 that will become the joining boundary B2 before the respective members are joined. In this way, by forming the groove in advance on the surface of the second member C2 and then joining the third member C3 so as to cover this surface, the coolant flow path 270 that follows the groove can be easily formed inside the base plate 200. Note that the groove that becomes the coolant flow path 270 may also be formed on the surface of the second member C2 that will become the joining boundary B1.

[0047] However, if the bonding boundary B1 closest to the dielectric substrate 100 is located in the first portion 201, the first member C1 would be thinner than in this embodiment. As a result, it would be necessary to arrange each porous member 260 so that it spans both the first portion 201 and the second portion 202. For example, the porous members 260 are inserted into the recesses of the second member C2, and the first member C1 is bonded to the second member C2 so that each porous member 260 protrudes from the surface of the second member C2 and covers that surface. In this case, the porous members 260 protruding from the surface of the second member C2 must be aligned to fit into the recesses of the first portion 201 during bonding. However, the porous members 260 are very small and fragile, and there are a large number of them. Therefore, it is very difficult to perform the above-described alignment and other tasks without damaging the porous members 260.

[0048] Therefore, the base plate 200 of this embodiment is configured such that the bond boundary B1 closest to the dielectric substrate 100 is located in the second portion 202, not the first portion 201. In other words, the first portion 201 and a portion of the second portion 202 are integrated into a single member (first member C1) without a bond boundary. In this configuration, the first member C1 closest to the dielectric substrate 100 is thicker than when the bond boundary B1 is located in the first portion 201. This makes it possible to position the entire porous member 260 inside the first portion 201, as in this embodiment. Since there is no risk of damaging the porous member 260 when bonding the first member C1 and the second member C2, the above-described alignment and bonding operations can be easily performed. This makes it possible to easily realize a complex internal structure of the base plate 200.

[0049] 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]

[0050] 10: Electrostatic chuck 100: Dielectric substrate 110: Face 200: Base plate 201: Part 1 202:Second part C1: First member C2: Second member B1: Junction boundary 240: Supply channel 250: Distribution channel 260: Porous material

Claims

1. a dielectric substrate having a mounting surface on which an object to be attracted is placed; a base plate joined to the dielectric substrate, The base plate is a first portion that is a portion on the dielectric substrate side; a second portion that is adjacent to the first portion on the opposite side of the dielectric substrate and has an outer shape larger than that of the first portion when viewed in a direction perpendicular to the mounting surface; The base plate is An electrostatic chuck, which is formed by joining a plurality of members together, and the joining boundary closest to the dielectric substrate is located in the second portion.

2. Among the plurality of members constituting the base plate, a first member is a member located closer to the dielectric substrate than the junction boundary; When the member joined to the first member across the joint boundary is a second member, a supply flow path for supplying gas to the placement surface side is formed in the first member so as to extend in a direction perpendicular to the placement surface; 2. The electrostatic chuck according to claim 1, wherein a porous member is disposed inside the supply flow path.

3. A plurality of the supply channels are formed, The base plate includes:

3. The electrostatic chuck according to claim 2, further comprising a distribution passage for distributing gas to the plurality of supply passages.

4. 4. The electrostatic chuck according to claim 3, wherein the distribution flow path is a groove formed in either the first member or the second member so as to extend along the bonded boundary.

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