Electrostatic Chuck

Abstract

An electrostatic chuck capable of suppressing variations in the in-plane temperature distribution of a substrate during processing. [Solution] An electrostatic chuck 10 includes a dielectric substrate 100 and a base plate 200 supporting the dielectric substrate 100. The base plate 200 is formed with a coolant flow path 260 through which a coolant passes, and a through hole 230. In top view, the coolant flow path 260 has a branching portion 263 at which the coolant flow path 260 branches into a first flow path 261 and a second flow path 262, and a junction portion 264 at which the first flow path 261 and the second flow path 262 join again. The through hole 230 is formed to penetrate a portion of the base plate 200 between the first flow path 261 and the second flow path 262.

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 provided with an attracting electrode 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.

[0003] During processing such as etching, it is necessary to maintain the temperature of the substrate at an appropriate temperature. For this reason, as described in Patent Document 1 below, a coolant flow path for passing a coolant is formed inside the base plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-028960 Summary of the Invention [Problem to be solved by the invention]

[0005] In addition to the above-mentioned coolant flow paths, the base plate is also formed with a plurality of through holes. Examples of such through holes include holes for passing lift pins through, holes for supplying an inert gas such as helium gas to the substrate side, etc. The coolant flow paths need to be routed along a path that avoids such through holes.

[0006] For example, when the coolant flow path is routed along a path that passes between a pair of adjacent through holes, it is necessary to locally narrow the width of the coolant flow path. However, in that portion, the flow speed of the coolant increases locally, and the cooling performance increases, which may cause a decrease in the temperature of the substrate directly above. As a result, the temperature distribution on the substrate may become uneven.

[0007] 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 suppressing variations in the in-plane temperature distribution of a substrate during processing. [Means for solving the problem]

[0008] 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, and a base plate supporting the dielectric substrate. The base plate is formed with a coolant flow path through which a coolant passes, and a through hole extending in a direction perpendicular to the mounting surface. When viewed from a direction perpendicular to the mounting surface, the coolant flow path has a branching portion where the coolant flow path branches into a first flow path and a second flow path, and a junction portion where the first flow path and the second flow path join again. The through hole is formed to penetrate a portion of the base plate between the first flow path and the second flow path.

[0009] In an electrostatic chuck having such a configuration, the coolant flow path branches into a first flow path and a second flow path near the through hole. Therefore, even if one of the first flow paths is narrowed to avoid interference with the through hole, the coolant passes through not only the first flow path but also the second flow path, so that a local increase in flow velocity in the first flow path is suppressed. As a result, the cooling performance in each part of the coolant flow path remains approximately uniform, so that the variation in the in-plane temperature distribution of the substrate during processing is suppressed. Effect of the Invention

[0010] According to the present invention, it is possible to provide an electrostatic chuck capable of suppressing variations in the in-plane temperature distribution 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. [Diagram 2] 5A and 5B are diagrams illustrating a configuration of a coolant flow path formed in a base plate. [Diagram 3] 3 is an enlarged view showing the configuration of a portion of the refrigerant flow path in FIG. 2 near a through hole. [Figure 4] 3 is an enlarged view showing the configuration of a portion of the refrigerant flow path in FIG. 2 near a through hole. 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, a base plate 200, and a heater unit 300.

[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 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.

[0016] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is mounted. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "bonded surface" that is bonded to the heater unit 300 via a bonding layer 410. The viewpoint when the electrostatic chuck 10 is viewed from the side of the surface 110 along a direction perpendicular to the surface 110 will hereinafter be referred to as a "top view".

[0017] 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 disposed 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, an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. Two adsorption electrodes 130 may be provided as so-called "bipolar" electrodes, or only one may be provided as a so-called "monopolar" electrode.

[0018] A power supply terminal 132 is embedded in the surface 120 of the dielectric substrate 100. The power supply terminal 132 is a terminal for receiving a voltage to be applied to the chucking electrode 130 from the outside. The power supply terminal 132 has a circular shape when viewed from above. The power supply terminal 132 and the chucking electrode 130 are electrically connected by a via 131. The via 131 is a long and narrow hole filled with a conductor. One end of a bus bar 13, which is a rod-shaped conductive member, is connected to the power supply terminal 132. A voltage is applied to the chucking electrode 130 from the outside via the bus bar 13. The bus bar 13 is drawn out to the outside through a through hole 306 formed in the heater unit 300 and a through hole 240 formed in the base plate. The configuration of the electric path for applying a voltage to the chucking electrode 130 may be different from that described above.

[0019] 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 the gas hole 114. 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 which is 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] Gas holes 114 are formed in the dielectric substrate 100. The gas holes 114 are holes for supplying helium gas to the space SP, and are circular through-holes formed to extend perpendicularly to the surface 110. A plurality of gas holes 114 are formed, but only one of them is shown in FIG. 1. Helium gas supplied from the outside passes through gas hole 214 formed in the base plate 200 and through-hole 305 formed in the heater unit 300, and is then supplied to the space SP through each of the gas holes 114.

[0025] A porous body made of, for example, alumina may be disposed inside the gas hole 114. With such a configuration, it is possible to suppress the occurrence of dielectric breakdown in the path through the gas hole 114 while ensuring the flow of gas through the gas hole 114.

[0026] The base plate 200 is a substantially disk-shaped member that supports the dielectric substrate 100 and the heater unit 300. The base plate 200 is formed of a metal material such as aluminum. The upper surface 210 of the base plate 200 in FIG. 1 is a "bonded surface" that is bonded to the heater unit 300 via a bonding layer 420.

[0027] A coolant flow path 260 for flowing a coolant is formed inside the base plate 200. When a process such as etching is performed in the semiconductor manufacturing apparatus, a coolant is supplied to the coolant flow path 260 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. The coolant is supplied to and discharged from the coolant flow path 260 via openings 266, 267 (not shown in FIG. 1, see FIG. 2) formed in the surface 220 of the base plate 200 opposite to the surface 210.

[0028] Fig. 2 shows a schematic top view of the configuration of the coolant flow path 260 formed inside the base plate 200. Note that the configuration of the coolant flow path 260 shown in Fig. 2 is schematic and differs in part from the actual configuration. The configuration of this part will be described later with reference to Fig. 3 etc.

[0029] As described above, the openings 266, 267 are provided in the surface 220 of the base plate 200. The coolant flow path 260 connects between the openings 266 and 267, and is formed along a path that passes through substantially the entire base plate 200 in a top view.

[0030] Both of the openings 266 and 267 are circular openings when viewed from above, and are formed to extend perpendicularly to the surface 220 from the surface 220 toward the coolant flow path 260. In this embodiment, a coolant is supplied from the outside to the opening 266. The coolant that has passed through the coolant flow path 260 and is used to cool the substrate W is discharged from the opening 267 to the outside.

[0031] Returning to FIG. 1, the description will be continued. A through hole 240 is formed in a portion of the base plate 200 that overlaps with the power supply terminal 132 in a top view. The through hole 240 is a circular through hole formed to extend vertically from the surface 210 toward the surface 220. As described above, the bus bar 13 for applying a voltage to the chucking electrode 130 is disposed inside the through hole 240. A circular opening that is the upper end of the through hole 240 is formed in the surface 210 of the base plate 200 on the dielectric substrate 100 side.

[0032] Gas holes 214 are formed in the base plate 200 at portions that overlap with the gas holes 114 in a top view. The gas holes 214 are circular through holes formed to extend vertically from the surface 210 toward the surface 220. As described above, the gas holes 214 form part of a path for supplying helium gas to the space SP. A plurality of gas holes 214 are formed in addition to the gas holes 114. A plurality of circular openings that are the upper ends of the gas holes 214 are formed in the surface 210 of the base plate 200 on the dielectric substrate 100 side.

[0033] A through hole 230 is formed in the base plate 200. The through hole 230 is a circular through hole formed to extend vertically from the surface 210 to the surface 220. The through hole 230 is a through hole for accommodating a power supply terminal 390 provided in the heater unit 300 described below and a power supply member connected thereto. A plurality of through holes 230 are formed, but only one of them is shown in FIG.

[0034] 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.

[0035] The heater unit 300 generates heat when power is supplied from the outside, and heats the dielectric substrate 100. A heat generating portion (not shown), which is a conductor that is wired, is provided inside the heater unit 300. When a current is supplied to the heat generating portion from the outside, Joule heat is generated in the heat generating portion. A plurality of heat generating portions are arranged, and the heat generation amount of each heat generating portion can be adjusted individually. By individually adjusting the heat generation amount of each portion, the in-plane temperature distribution of the substrate W during processing can be made closer to uniform.

[0036] The heater unit 300 is sandwiched between the dielectric substrate 100 and the base plate 200 and bonded to each of them. The heater unit 300 and the dielectric substrate 100 are bonded via a bonding layer 410, and the heater unit 300 and the base plate 200 are bonded via a bonding layer 420. The bonding layers 410 and 420 are layers formed by, for example, hardening a silicone adhesive. A plurality of particulate fillers (fillers) for increasing thermal conductivity are disposed inside each of the bonding layers. For example, particles mainly composed of alumina can be used as the filler.

[0037] The heater unit 300 is provided with a power supply terminal 390. The power supply terminal 390 is a terminal for receiving an electric current supplied to the heat generating portion from the outside. The power supply terminal 390 is formed as a long and thin rod-shaped plug, and protrudes from the heater unit 300 toward the base plate 200. A plurality of power supply terminals 390 are provided, but only one of them is shown in FIG. 1. Each power supply terminal 390 is accommodated inside a through hole 230 formed in the base plate 200. In other words, power is supplied to the heater unit 300 through the through hole 230.

[0038] A through hole 306 is formed in a portion of the heater unit 300 that overlaps with the power supply terminal 132 in a top view. The through hole 306 is a circular through hole formed to extend in a direction perpendicular to the surface 210. As described above, the bus bar 13 for applying a voltage to the chucking electrode 130 is disposed inside the through hole 306.

[0039] In the heater unit 300, a through hole 305 is formed in a portion that overlaps with the gas hole 114 in a top view. The through hole 305 is a circular through hole formed to extend in a direction perpendicular to the surface 210. As described above, the through hole 305 is a part of a path for supplying helium gas to the space SP. A plurality of through holes 305 are formed, along with the gas holes 114 and the gas holes 214.

[0040] In addition, the heater for heating the dielectric substrate 100 may be unitized as a heater unit 300 as in this embodiment and placed outside the dielectric substrate 100, but part or all of it may be built into the dielectric substrate 100.

[0041] The electrostatic chuck 10 has a plurality of lift pin holes for passing lift pins provided in a semiconductor manufacturing apparatus, but these are not shown in Fig. 1. The lift pin holes are circular through holes formed to vertically penetrate the entire electrostatic chuck 10, similar to the gas holes 114, the through holes 305, and the gas holes 214. A plurality of circular openings, which are the upper ends of the lift pin holes, are formed on the surface 210 of the base plate 200 facing the dielectric substrate 100.

[0042] As described above, the base plate 200 has a plurality of through holes formed therein, which extend in a direction perpendicular to the surface 110 (mounting surface). Such through holes include, for example, the through holes 230 and 240 and the gas hole 214 shown in FIG. 1, and lift pin holes (not shown). In addition, through holes may be formed in the base plate 200 so that the temperature of the dielectric substrate 100 can be measured from the surface 120 side. Although the through holes 230 and the like are not shown in FIG. 2, the coolant flow path 260 needs to be routed along a path that avoids the through holes 230 and the like when viewed from above.

[0043] For example, when the coolant flow path 260 is routed along a path passing between a pair of adjacent through holes 230, it is necessary to locally narrow the width of the coolant flow path 260. However, in that portion, the flow speed of the coolant increases locally, and the cooling performance increases, which may cause a temperature drop of the substrate W directly above it. As a result, the in-plane temperature distribution of the substrate W may vary.

[0044] Therefore, in the electrostatic chuck 10 according to this embodiment, the configuration of the coolant flow passage 260 in the vicinity of the through hole 230 and the like is devised to solve the above problem.

[0045] 3, through holes 230 formed in base plate 200 and coolant flow paths 260 routed in the vicinity thereof are illustrated in a top view. In this portion, a pair of through holes 230 are formed in positions close to each other. Of these, one of the through holes 230 is also referred to as a "first through hole 231" below. The other through hole 230 is also referred to as a "second through hole 232" below.

[0046] The arrows shown in Fig. 3 indicate the direction in which the refrigerant flows in the refrigerant flow path 260. In the example of Fig. 3, the refrigerant flow path 260 branches into two flow paths along the way, and merges again downstream to form a single flow path. One of the two branched flow paths is hereinafter also referred to as a "first flow path 261," and the other is hereinafter also referred to as a "second flow path 262."

[0047] A portion of refrigerant flow path 260 that is upstream of first through hole 231 and second through hole 232 along the direction in which the refrigerant flows and that branches into first flow path 261 and second flow path 262 is also referred to below as "branching section 263." A portion downstream of branching section 263 where first flow path 261 and second flow path 262 merge again is also referred to below as "merging section 264."

[0048] The first flow path 261 extends between the first through hole 231 and the second through hole 232 in a top view. The second flow path 262 extends to sandwich the first through hole 231 between the first flow path 261 in a top view. In other words, the first through hole 231 is formed to pass through a portion of the base plate 200 between the first flow path 261 and the second flow path 262 in a top view. The second through hole 232 is formed at a position opposite the first through hole 231 with the first flow path 261 in between.

[0049] The width of the first flow path 261 is narrower, particularly in the central portion (the central portion along the flow direction), than the width of the portion of the refrigerant flow path 260 upstream of the branching portion 263 and the width of the portion downstream of the merging portion 264. The dotted line DL shown in FIG. 3 represents the shape of the first flow path 261 when the first flow path 261 passes between the first through hole 231 and the second through hole 232 without narrowing the width of the first flow path 261 as described above. The width of the first flow path 261 may be locally narrowed in the middle as in this embodiment, but may be uniformly narrowed throughout the first flow path 261. In either case, it is sufficient that the width of at least a portion of the first flow path 261 is narrower than the width of the refrigerant flow path 260 upstream of the branching portion 263. In other words, the portion of the refrigerant flow path 260 where the width is locally narrowed may be a part or the entire first flow path 261.

[0050] In this embodiment, the first through hole 231 and the second through hole 232 are close to each other. Therefore, if the coolant flow path 260 is routed along a path that passes between the two, there is a high possibility that the coolant flow path 260 and the first through hole 231 will interfere with each other, as shown by the dotted line DL. For this reason, it is necessary to locally narrow the width of the coolant flow path 260 between the first through hole 231 and the second through hole 232, as in the first flow path 261 in this embodiment. As a result, as described above, the flow rate of the coolant increases locally, which may cause a problem that the in-plane temperature distribution of the substrate W varies.

[0051] 3, in this embodiment, in addition to the first flow path 261 passing between the first through hole 231 and the second through hole 232, a second flow path 262 is provided to bypass the first through hole 231. In this configuration, even if one of the first flow paths 261 is narrowed to avoid interference with the first through hole 231, etc., the coolant passes through not only the first flow path 261 but also the second flow path 262, so that a local increase in flow rate in the first flow path 261 is suppressed. As a result, the cooling performance in each part of the coolant flow path 260 remains approximately uniform, so that the variation in the in-plane temperature distribution of the substrate W during processing can be suppressed.

[0052] In this embodiment, since a pair of through holes (first through hole 231 and second through hole 232) formed in base plate 200 are close to each other, it is necessary to make the width of first flow path 261 passing between them narrower than the width of other parts. If temperature adjustment by heater unit 300 is performed more precisely in the future and the number of heat generating parts provided in heater unit 300 increases, it is considered that the need to locally narrow the width of coolant flow path 260 as described above will become even higher. Even in such a case, if a configuration similar to that of FIG. 3 is applied to each of the parts where the width of coolant flow path 260 is locally narrowed, it is possible to suppress a local increase in the flow speed of the coolant and suppress variations in the in-plane temperature distribution of substrate W.

[0053] The need to locally narrow the width of refrigerant flow path 260 may also arise in a portion other than between first through hole 231 and second through hole 232. For example, as in the example of Fig. 4, when through hole 230 is provided at a position close to outer peripheral surface 201 of base plate 200 and refrigerant flow path 260 is routed to pass between through hole 230 and outer peripheral surface 201, it is necessary to narrow the width of refrigerant flow path 260 in that portion.

[0054] 4, the refrigerant flow path 260 is branched into a first flow path 261 that passes between the through hole 230 and the outer peripheral surface 201, and a second flow path 262 that passes through a portion on the inner peripheral side of the through hole 230, in top view. In this example, the first flow path 261 is also locally narrowed in the middle. The through hole 230 is formed so as to penetrate the portion of the base plate 200 between the first flow path 261 and the second flow path 262. With this configuration, the same effect as that described with reference to FIG. 3 is achieved.

[0055] In this embodiment, the first flow path 261 and the second flow path 262 are provided so as to avoid interference with the through hole 230 for arranging the power supply terminal 390 (i.e., the through hole 230 for supplying power to the heater unit 300). However, the through holes in the base plate 200 near the first flow path 261 and the second flow path 262 may be holes different from those described above. For example, the first flow path 261 and the second flow path 262 may be provided so as to avoid interference with the through hole 240 and the gas hole 214 shown in FIG. 1, a lift pin hole (not shown), a through hole (not shown) for measuring the temperature of the dielectric substrate 100 from the surface 120 side, and the like.

[0056] 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]

[0057] 10: Electrostatic chuck 100: Dielectric substrate 110: Face 200: Base plate 230:Through hole 231: First through hole 232: Second through hole 260: Coolant flow path 261: First flow path 262: Second flow path 263: Branch 264: Junction W: Substrate

Claims

[Claim 1] a dielectric substrate having a mounting surface on which an object to be attached is placed; a base plate supporting the dielectric substrate; The base plate includes: a refrigerant flow path through which the refrigerant passes; A through hole extending in a direction perpendicular to the mounting surface is formed, When viewed from a direction perpendicular to the placement surface, The refrigerant flow path is a branching portion which branches into a first flow path and a second flow path; a junction portion where the first flow path and the second flow path join again, The through hole is formed to penetrate a portion of the base plate between the first flow path and the second flow path, When viewed from a direction perpendicular to the placement surface, The through hole is a first through hole formed to penetrate a portion between the first flow path and the second flow path; a second through hole formed at a position opposite to the first through hole across the first flow path, The width of the refrigerant flow path is locally narrowed in the first flow path, Further comprising a heater for heating the dielectric substrate, An electrostatic chuck, wherein power is supplied to the heater through each of the first through hole and the second through hole.

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