Electrostatic chuck

Abstract

To provide an electrostatic chuck capable of suppressing variations in the in-plane temperature of a substrate during processing.SOLUTION: An electrostatic chuck 10 comprises a dielectric substrate 100 having a mounting surface, and a base plate 200 bonded to the dielectric substrate 100, where a refrigerant flow path 400 through which refrigerant flows is formed internally. A refrigerant flow path 400 includes a first flow path 410 and a second flow path 420 connected in series with each other. The second flow path 420 is formed in a position closer to the dielectric substrate 100 than first flow path 410, in a direction perpendicular to the mounting surface.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] It is necessary to maintain the temperature of the substrate at an appropriate temperature during processing such as etching, etc. 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] Japanese Patent Application Publication No. 2020-161597 Summary of the Invention [Problem to be solved by the invention]

[0005] In the electrostatic chuck described in Patent Document 1, the routing path of the coolant flow path is devised so as to make the in-plane temperature distribution of the substrate uniform during processing. However, there is room for further improvement in the configuration of the coolant flow path in conventional electrostatic chucks to make the in-plane temperature distribution uniform.

[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 temperature within the surface of a substrate during processing. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention provides an electrostatic chuck including 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 and having a coolant flow path formed therein through which a coolant flows. The coolant flow path includes a first flow path and a second flow path connected to each other in series. The second flow path is formed closer to the dielectric substrate than the first flow path in a direction perpendicular to the mounting surface.

[0008] The second flow path is located closer to the cooling target than the first flow path, allowing for more efficient cooling of the cooling target. This means that cooling performance can be locally enhanced in the area of ​​the second flow path. The "cooling target" here refers to, for example, a substrate such as a silicon wafer, or an annular member that surrounds the substrate. By locating the second flow path directly below a portion of the cooling target that is relatively prone to temperature rise, it is possible to suppress temperature variations within the substrate during processing. [Effects of the Invention]

[0009] According to the present invention, it is possible to provide an electrostatic chuck that can suppress variations in the temperature of a substrate within its surface 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] 5A and 5B are diagrams illustrating the configuration of a coolant flow path formed in a base plate. [Figure 3] FIG. 3 is an enlarged cross-sectional view showing a configuration of a part of a refrigerant flow path. 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] An attraction electrode 130 is embedded inside 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 a material other than tungsten, such as molybdenum, platinum, or palladium. 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] The dielectric substrate 100 of this embodiment is provided with a flange 150. The flange 150 is a portion that protrudes further outward than the surface 110, which is the mounting surface. In a top view, the flange 150 surrounds the entire surface 110 from the outside. The surface of the flange 150 facing the substrate W (the upper surface in FIG. 1 ) is located closer to the base plate 200 than the surface 110 (the lower side in FIG. 1 ). When processing the substrate W, an annular member (not shown), such as a "focus ring," is placed on the flange 150. Alternatively, the dielectric substrate 100 may not be provided with the flange 150, and the annular member may be placed directly on the base plate 200.

[0023] 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. An 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.

[0024] 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.

[0025] 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.

[0026] A coolant flow path 400 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 400 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 400 through openings 401 and 402 (not shown in FIG. 1 , see FIG. 2 ) formed on the surface 220 of the base plate 200 opposite the surface 210. The coolant flow path 400 is formed so as to pass not only through an area overlapping with the surface 110 in top view, but also through a portion outer than the surface 110. Therefore, not only the substrate W but also the above-mentioned annular member are cooled by the coolant passing through the coolant flow path 400.

[0027] The configuration of the coolant flow path 400 will be described. FIG. 2 shows a schematic top view of the coolant flow path 400 formed inside the base plate 200. As described above, openings 401 and 402 are provided in the surface 220 of the base plate 200. The coolant flow path 400 connects the openings 401 and 402 and is formed to extend along a path that passes through substantially the entire base plate 200 in a top view. Both openings 401 and 402 are circular in a top view and are formed to extend perpendicularly from the surface 220 toward the coolant flow path 400. The internal spaces of the openings 401 and 402 can also be considered part of the coolant flow path 400. In this embodiment, a coolant is supplied from the outside to the opening 401. The coolant that has passed through the coolant flow path 400 and is used to cool the substrate W is discharged to the outside through the opening 402. The flow direction of the coolant in the coolant flow path 400 may be opposite to that described above.

[0028] Coolant flow path 400 includes a first flow path 410 and a second flow path 420. First flow path 410 and second flow path 420 are connected to each other in series, and are formed so that the entirety of these flow paths extends in a spiral shape when viewed from above.

[0029] First flow path 410 is a downstream portion of refrigerant flow path 400 in the direction of refrigerant flow, and is formed to extend upstream from opening 402. Second flow path 420 is an upstream portion of refrigerant flow path 400 in the direction of refrigerant flow, and is formed to extend downstream from opening 401. First flow path 410 and second flow path 420 are connected in series via a connecting flow path 415, which will be described later.

[0030] The second flow path 420 is located at the outermost position of the spiral refrigerant flow path 400, and extends in the circumferential direction (i.e., in an arc shape) at that position. That is, the second flow path 420 is formed at a position that is more outer than the first flow path 410 in a top view. As shown in Fig. 1, the second flow path 420 is formed at a position directly below the outermost portion of the substrate W. In a top view, a portion of the second flow path 420 overlaps with the surface 110, and another portion of the second flow path 420 overlaps with the flange portion 150.

[0031] As shown in FIG. 1, in this embodiment, the second flow path 420 is formed at a position closer to the dielectric substrate 100 (i.e., the upper side in FIG. 1) than the first flow path 410 in a direction perpendicular to the mounting surface.

[0032] Note that the "position" of the first flow path 410 and the second flow path 420 in the above means the position of the part of the first flow path 410, etc. that is closest to the surface 210 (the upper position in FIG. 1). Therefore, the positional relationship between the first flow path 410 and the second flow path 420 as described above can be rephrased as the distance from the second flow path 420 to the surface 210 being shorter than the distance from the first flow path 410 to the surface 210.

[0033] The connecting flow path 415 is a portion that connects the first flow path 410 and the second flow path 420. In Fig. 2, the boundary between the first flow path 410 and the connecting flow path 415 and the boundary between the second flow path 420 and the connecting flow path 415 are each indicated by a dotted line.

[0034] 3 is a schematic cross-section of the portion of the base plate 200 where the connecting flow path 415 is provided and its vicinity, taken perpendicularly to the surface 110. In FIG. 3, as in FIG. 2, the boundary between the first flow path 410 and the connecting flow path 415 and the boundary between the second flow path 420 and the connecting flow path 415 are indicated by dotted lines.

[0035] 3, the connection flow path 415 extends in a direction inclined with respect to the mounting surface. As a result, the connection flow path 415 smoothly connects the first flow path 410 and the second flow path 420, which are located at different heights as described above. The phrase "extending in a direction inclined" above means that the angle between the direction in which the refrigerant flows through the connection flow path 415 and the mounting surface is greater than 0 degrees and less than 90 degrees. By forming the connection flow path 415 in this manner, the flow path resistance in the entire refrigerant flow path 400 can be suppressed, and the load on the refrigerant supply device can be reduced.

[0036] The effect of arranging the second flow path 420 at a position closer to the dielectric substrate 100 than the first flow path 410 will be described. It is known that when a substrate W is being processed in a semiconductor manufacturing device, the temperature of the outer peripheral portion of the substrate W is likely to rise locally. However, a local temperature rise in the substrate W is undesirable because it can cause processes such as etching to be performed non-uniformly. Therefore, the coolant flow path 400 needs to be formed so that the in-plane temperature distribution of the substrate W during processing is as uniform as possible.

[0037] Therefore, in this embodiment, the second flow path 420 is disposed in a position directly below a portion of the cooling target where a local temperature rise is likely to occur. Since the second flow path 420 is located closer to the cooling target than the first flow path 410, cooling by the second flow path 420 can be performed efficiently.

[0038] The "cooling target" here refers to, for example, the substrate W or a ring-shaped member (not shown) that is arranged to surround the substrate W. By arranging the second flow path 420 in a position directly below a portion of the cooling target that is relatively prone to temperature rise, it is possible to suppress variations in the in-plane temperature of the substrate W during processing.

[0039] The dimension of the refrigerant flow path 400 along a direction perpendicular to the direction in which the refrigerant flows through the refrigerant flow path 400 and parallel to the mounting surface (surface 110) will hereinafter also be referred to as the "width dimension" of the refrigerant flow path 400.

[0040] 2, the first flow path 410 and the second flow path 420 also differ from each other in width. Specifically, the width W2 of the second flow path 420 is larger than the width W1 of the first flow path 410. In the connecting flow path 415, the width of the refrigerant flow path 400 smoothly changes from W1 to W2 as it moves from the first flow path 410 side to the second flow path 420 side.

[0041] The dimension of refrigerant flow path 400 along the direction perpendicular to the mounting surface (surface 110) is also referred to below as the "height dimension" of refrigerant flow path 400. As shown in FIG. 3, first flow path 410 and second flow path 420 differ from each other not only in width dimension but also in height dimension. Specifically, height dimension H2 of second flow path 420 is smaller than height dimension H1 of first flow path 410. In connection flow path 415, the height dimension of refrigerant flow path 400 smoothly changes from H1 to H2 as it moves from the first flow path 410 side to the second flow path 420 side.

[0042] As described above, the connecting flow path 415 also serves as a part that smoothly connects the first flow path 410 and the second flow path 420, which are different from each other in both width and height dimensions.

[0043] 1, in the first flow path 410, the width dimension (W1) of the refrigerant flow path 400 is smaller than the height dimension (H1). On the other hand, in the second flow path 420, the width dimension (W2) of the refrigerant flow path 400 is larger than the height dimension (H2). The part of the refrigerant flow path 400 where the width dimension is larger than the height dimension is also referred to as the "flat portion" below. In this embodiment, the entire second flow path 420 corresponds to the flat portion.

[0044] In this embodiment, the second flow path 420 is disposed directly below the area where a local temperature rise is likely to occur, and the second flow path 420 is further formed as a flat section. In the flat section, the height dimension of the coolant flow path 400 is reduced, resulting in a higher flow rate of the coolant, allowing the area directly above the flat section to be efficiently cooled. Furthermore, most of the coolant passing through the flat section passes near the cooling target located above, enabling even more efficient cooling. As a result, it is possible to sufficiently suppress in-plane temperature variations of the substrate W during processing.

[0045] In areas where relatively high cooling performance is required, such as directly below the outer periphery of the substrate W, it is possible to increase the flow rate of the coolant and improve cooling performance by sufficiently reducing the width of the coolant flow path 400 in those areas, rather than by providing a flat portion as described above. However, such a configuration would increase the overall length of the coolant flow path 400, resulting in increased flow path resistance and potentially increasing the load on a coolant supply device (not shown). On the other hand, when improving cooling performance by providing a flat portion in part of the coolant flow path 400, as in this embodiment, there is no need to increase the overall length of the coolant flow path 400, and therefore the above-mentioned problem does not occur.

[0046] The smaller the ratio of the height dimension to the width dimension of the refrigerant flow path 400, the more the cooling performance of the refrigerant flow path 400 can be improved. Experiments conducted by the present inventors have confirmed that if the flat portion is formed so that the width dimension of the refrigerant flow path 400 is five times or more the height dimension, the cooling performance of that portion can be sufficiently improved. If the width dimension of the refrigerant flow path 400 is six times or more the height dimension, the cooling performance can be further improved.

[0047] The flat portion can be provided in any part of the refrigerant flow path 400. As described above, in this embodiment, the entire second flow path 420 of the refrigerant flow path 400, i.e., the entire portion extending in the circumferential direction at the outermost position of the refrigerant flow path 400, is configured to be a flat portion. With this configuration, the outermost portion of the substrate W and an annular member or the like placed further outside can be efficiently cooled. As a result, the in-plane temperature distribution of the substrate W can be made uniform.

[0048] The flat portion may be formed as only a part of the refrigerant flow path 400, or may be formed as the entire refrigerant flow path 400. In other words, the entire refrigerant flow path 400 may be formed so that the width dimension is greater than the height dimension.

[0049] In order to facilitate the formation of the relatively complicated refrigerant flow path 400, the base plate 200 of this embodiment is formed by joining multiple members. Specifically, the base plate 200 is formed by joining two members, a first member 201 and a second member 202, together into one 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 three or more.

[0050] As shown in FIG. 1 , the first member 201 and the second member 202 are arranged in this order along a direction perpendicular to the surface 110, which is the mounting surface. The second member 202 is a member arranged on the dielectric substrate 100 side, and the first member 201 is a member arranged on the opposite side. The surface 210 mentioned above is a part of the second member 202, and the surface 220 is a part of the first member 201. The bonding boundary B between the first member 201 and the second member 202 is parallel to the surface 210 and the surface 220. In this way, the base plate 200 of this embodiment is formed by bonding the first member 201 and the second member 202, which is closer to the dielectric substrate 100 than the first member 201.

[0051] 1 and 3, the first flow path 410 in this embodiment is entirely formed in the first member 201. The first flow path 410 is a groove that is formed in advance in a surface 211 of the first member 201 that faces the second member 202 before the first member 201 and the second member 202 are joined. The surface 211 is a surface that becomes the joining boundary B after joining. In the portion of the connection flow path 415, the groove in the surface 211 as described above is formed to gradually become shallower from the first flow path 410 side toward the second flow path 420 side.

[0052] Moreover, the entire second flow path 420 in this embodiment is formed in the second member 202. The second flow path 420 is a groove that is formed in advance in the surface 212 of the second member 202 that faces the first member 201 before the first member 201 and the second member 202 are joined. The surface 212 is a surface that becomes the joining boundary B after joining. In the portion of the connection flow path 415, the groove in the surface 212 as described above is formed so as to become gradually deeper from the first flow path 410 side toward the second flow path 420 side.

[0053] In this way, the base plate 200 is formed by joining together members each having a groove formed therein in advance, which makes it possible to easily form the refrigerant flow path 400 having a relatively complex shape inside the base plate 200.

[0054] In the above, an example has been described in which the second flow path 420 is formed at a position closer to the dielectric substrate 100 than the first flow path 410, and the second flow path 420 has a flat portion. Instead of this, a mode may be adopted in which the refrigerant flow path 400 does not have a flat portion, that is, a mode may be adopted in which the second flow path 420 is formed at a position closer to the dielectric substrate 100 than the first flow path 410, and the width dimension of the refrigerant flow path 400 as a whole is smaller than the height dimension.

[0055] 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]

[0056] 10: Electrostatic chuck 100: Dielectric substrate 110: Face 200: Base plate 201: First member 202: Second member 400: Coolant flow path 410: First flow path 415: Connecting channel 420: Second flow path W: Substrate

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 and having a coolant flow path formed therein through which a coolant passes; the refrigerant flow path includes a first flow path and a second flow path connected in series to each other, The second flow path is An electrostatic chuck, characterized in that the electrostatic chuck is formed at a position closer to the dielectric substrate than the first flow path in a direction perpendicular to the mounting surface.

2. When viewed from a direction perpendicular to the placement surface, 2. The electrostatic chuck according to claim 1, wherein the second flow passage is formed at a position closer to the outer periphery than the first flow passage.

3. 2. The electrostatic chuck according to claim 1, wherein a portion of the coolant flow path that connects the first flow path and the second flow path extends in a direction inclined with respect to the mounting surface.

4. 2. The electrostatic chuck according to claim 1, wherein the second flow path has a width dimension greater than a height dimension.

5. 5. The electrostatic chuck according to claim 4, wherein the width of the second flow path is at least five times the height of the second flow path.

6. the base plate is configured by joining a first member and a second member that is closer to the dielectric substrate than the first member, the first flow path is formed in the first member, 2. The electrostatic chuck according to claim 1, wherein the second flow path is formed in the second member.

7. the first flow path is a groove formed on a surface of the first member that faces the second member, 7. The electrostatic chuck according to claim 6, wherein the second flow path is a groove formed in a surface of the second member facing the first member.

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