Electrostatic chuck

Abstract

To provide an electrostatic chuck in which an in-plane temperature distribution of a substrate during a process can be set as a more uniform distribution than that in the prior art.SOLUTION: An electrostatic chuck 10 includes a dielectric substrate 100 including a surface 110 serving as a placement surface, and a base plate 200 which is joined to the dielectric substrate 100 and which has formed therein a coolant flow path 250 through which a coolant flows. In top view, the base plate 200 includes a first part P1 that is a part overlapped with an edge E on an outer circumferential side of the surface 110, and a second part P2 that is a part on the further outer circumferential side relative to the first part P1, and the coolant flow path 250 is formed in each of the first part P1 and the second part P2. The coolant flow path 250 is formed such that the cooling performance for the first part P1 is set to be higher than the cooling performance for the second part P2.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] 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. Heat from the substrate is transferred to the coolant through the dielectric substrate and the base plate, and is discharged to the outside together with the coolant. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-151055 Summary of the Invention [Problem to be solved by the invention]

[0005] During processes such as etching, the temperature of the substrate tends to rise, particularly in the outer periphery. To suppress this temperature rise in the outer periphery and to make the in-plane temperature distribution of the substrate as uniform as possible, optimal routing of the coolant flow path in the base plate has been studied. However, previous studies have mainly focused on routing the coolant flow path within the area that overlaps with the substrate in a top view, and there is still room for improvement in routing the coolant flow path in other areas.

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

[0007] In order to solve the above problems, the present invention provides an electrostatic chuck that includes 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 passes. When viewed from a direction perpendicular to the mounting surface, the base plate has a first portion that overlaps with an outer peripheral edge of the mounting surface and a second portion that is further outer than the first portion, and the coolant flow path is formed in each of the first and second portions. The coolant flow path is formed so that the cooling performance for the first portion is higher than the cooling performance for the second portion.

[0008] In the electrostatic chuck having the above configuration, the coolant flow passage is formed not only in the portion of the base plate directly below the substrate but also in a second portion located further outward. By forming the coolant flow passage in such a range, it is possible to suppress temperature rise in the outer peripheral portion of the substrate. Furthermore, in the electrostatic chuck having the above configuration, the coolant flow passage is formed so that the cooling performance for the first portion is higher than that for the second portion. By providing a difference in cooling performance between the first portion and the second portion, it is possible to sufficiently suppress temperature rise in the outer peripheral portion of the substrate while preventing components (e.g., a focus ring) located further outward from the outer peripheral portion of the substrate from being excessively cooled. This allows the in-plane temperature distribution of the substrate during processing to be more uniform than conventional methods. [Effects of the Invention]

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

[0010] [Figure 1] 1 is a cross-sectional view schematically showing the configuration of an electrostatic chuck according to a first embodiment. [Figure 2] 3A and 3B are diagrams illustrating a configuration of a coolant flow path formed in a base plate of the first embodiment. [Figure 3] FIG. 10 is a cross-sectional view schematically showing the configuration of an electrostatic chuck according to a second embodiment. [Figure 4] 10A and 10B are diagrams illustrating the configuration of a coolant flow path formed in a base plate according to a third embodiment. 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] A first embodiment will be described. An 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 object to be attracted, that is, the substrate W, is, for example, a silicon wafer. The electrostatic chuck 10 may also be used in apparatuses other than semiconductor manufacturing apparatuses.

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

[0014] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 contains, for example, high-purity aluminum oxide (Al2O3), but may also contain other materials. The purity, type, and additives of the ceramics in the dielectric substrate 100 can be appropriately set taking into consideration the plasma resistance and other properties required of the dielectric substrate 100 in semiconductor manufacturing equipment. The diameter of the dielectric substrate 100 is, for example, 290 to 300 mm. The thickness of the dielectric substrate 100 is, for example, 0.5 to 3.0 mm.

[0015] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "bonded surface" that is bonded to the base plate 200 via a bonding layer 300. The viewpoint when the electrostatic chuck 10 is viewed from the side of the surface 110 along a direction perpendicular to the surface 110 will hereinafter also be referred to as a "top view."

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

[0017] 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 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.

[0023] 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.

[0024] 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. The thickness of the insulating film is, for example, 1 mm or less.

[0025] The base plate 200 has a support portion 201 and a flange portion 202. The support portion 201 is the upper portion of the base plate 200 in FIG. 1 and is a substantially cylindrical portion that directly supports the dielectric substrate 100 from below. The diameter of the support portion 201, i.e., the diameter of the surface 210, may be the same as the diameter of the dielectric substrate 100, or may be slightly smaller than the diameter of the dielectric substrate 100. The diameter of the support portion 201 is, for example, 290 to 300 mm. The thickness of the support portion 201, i.e., the amount of protrusion of the support portion 201 toward the upper side in FIG. 1 (the amount of protrusion from the flange portion 202), is, for example, 3 to 15 mm.

[0026] The flange 202 is the lower part of the base plate 200 in FIG. 1. The flange 202 is substantially cylindrical, and its central axis coincides with the central axis of the support portion 201. The diameter of the flange 202 is larger than the diameter of the support portion 201. The amount of protrusion of the flange 202 from the outer surface of the support portion 201 (i.e., the amount of protrusion in the radial direction) is, for example, 20 to 30 mm. The thickness of the flange 202 is, for example, 25 to 40 mm. The overall thickness of the base plate 200, including the support portion 201 and the flange 202, is, for example, 30 to 40 mm.

[0027] When processing a substrate W in a semiconductor manufacturing apparatus, a focus ring (not shown) is installed on the upper surface 203 of the flange portion 202. The focus ring is an annular, plate-shaped member made of an insulating material such as quartz, and is installed for the purpose of adjusting the distribution of plasma during processing. The dielectric substrate 100 and the support portion 201 are substantially entirely surrounded by the focus ring from the outer periphery.

[0028] A coolant flow path 250 for passing a coolant is formed inside the base plate 200. When a process such as etching is performed in the semiconductor manufacturing equipment, a coolant is supplied to the coolant flow path 250 from the outside, thereby cooling the base plate 200. Heat generated in the substrate W during the process is transferred to the coolant via the helium gas in the space SP, the dielectric substrate 100, and the base plate 200, and is discharged to the outside together with the coolant. The coolant is supplied to and discharged from the coolant flow path 250 through openings 255 and 256 (not shown in FIG. 1, see FIG. 2) formed in the surface 220 of the base plate 200 opposite the surface 210.

[0029] For ease of explanation, the outer peripheral edge of surface 110, which is the mounting surface, will hereinafter also be referred to as "edge E." Edge E has a circular ridgeline when viewed from above, but a portion of the ridgeline (for example, the orientation flat portion) may be a ridgeline that is not circular.

[0030] A portion of the base plate 200 that overlaps with the end E in a top view is also referred to below as a "first portion P1." The first portion P1 is, for example, a portion that has a certain width that encompasses the entire end E in a top view, but the method for determining the width is not particularly limited.

[0031] A portion of the base plate 200 that is further outwardly disposed than the first portion P1 in a top view is hereinafter also referred to as a "second portion P2." The second portion P2 refers to the entire portion of the base plate 200 that is adjacent to the first portion P1 from the outer periphery and is further outwardly disposed than the first portion P1.

[0032] Incidentally, it is known that during processing such as etching, the temperature of the substrate W tends to increase, particularly at the outer periphery. The electrostatic chuck 10 of this embodiment has been improved in various ways, as described below, to suppress such local temperature increases and to make the in-plane temperature distribution of the substrate W during processing as uniform as possible.

[0033] 1, coolant flow path 250 is routed not only through first portion P1 and its interior, but also through outer second portion P2 of base plate 200. In other words, coolant flow path 250 is formed so as to extend to second portion P2, which is outer than the portion directly below substrate W and support portion 201 (i.e., first portion P1, etc.). The coolant passing through coolant flow path 250 in second portion P2 cools a focus ring (not shown) located directly above second portion P2, and also cools the outer peripheral portion of substrate W via the focus ring.

[0034] In this embodiment, the diameter of the flange 202 is relatively large, and accordingly, the second portion P2 is also large. By enlarging the second portion P2 and forming the coolant flow path 250 so as to extend over substantially the entire second portion P2, it is possible to suppress a temperature rise in the outer peripheral portion of the substrate W.

[0035] 2 is a schematic top view of the configuration of coolant flow path 250 formed inside base plate 200. As described above, openings 255 and 256 are provided in surface 220 of base plate 200. Coolant flow path 250 is formed along a path connecting openings 255 and 256. For example, opening 255 is used as an inlet for the coolant, and opening 256 is used as an outlet for the coolant. The circular dotted line shown in FIG. 2 represents end E on the outer circumferential side of surface 110, which is the mounting surface.

[0036] In this embodiment, an opening 255 is formed in a position near the outer peripheral end of base plate 200, and an opening 256 is formed in a position at the center of base plate 200. Coolant flow path 250 connects openings 255 and 256 in a spiral shape and is routed along a path that passes through substantially the entire base plate 200.

[0037] Of the refrigerant flow path 250, the portion routed in the first portion P1 (i.e., directly below the end E) is hereinafter also referred to as "refrigerant flow path 251." As shown in Fig. 2, the refrigerant flow path 251 is routed so as to extend in an arc shape along the end E in top view.

[0038] 1, the width W1 of the refrigerant flow path 251 in the first portion P1 is narrower than the width W2 of the refrigerant flow path 250 in the second portion P2. The width of the refrigerant flow path 250 in the portion more inward than the first portion P1 is the same as the width W2 of the refrigerant flow path 250 in the second portion P2, but may be a different size. Note that the "width" of the refrigerant flow path 250 here refers to the dimension of the refrigerant flow path 250 in a direction perpendicular to the direction of the refrigerant flow when viewed from above.

[0039] In this configuration, the flow rate of the refrigerant flowing through the refrigerant flow path 251 is faster than the flow rate of the refrigerant flowing through other portions of the refrigerant flow path 250. As the flow rate increases, the heat transfer coefficient in the refrigerant flow path 251 increases, and the first portion P1 is cooled more efficiently than the second portion P2. In other words, in the refrigerant flow path 250 of this embodiment, the width of the refrigerant flow path 251 directly below the end E is narrowed, and as a result, the cooling performance for the first portion P1 is higher than the cooling performance for the second portion P2.

[0040] By providing a difference in cooling performance between the first portion P1 and the second portion P2, it is possible to sufficiently suppress a temperature rise in the outer peripheral portion of the substrate W, while preventing components such as a focus ring disposed further outward than the outer peripheral portion of the substrate W from being cooled more than necessary. This makes it possible to achieve a more uniform in-plane temperature distribution of the substrate W during processing than in the past.

[0041] The second embodiment will be described below. The differences from the first embodiment will be mainly described below, and the description of the commonalities with the first embodiment will be omitted as appropriate.

[0042] 3 shows the configuration of the electrostatic chuck 10 according to this embodiment in a cross-sectional view similar to that of FIG. 1. In this embodiment, as in the first embodiment, a coolant flow path 250 is formed inside the base plate 200, and a part of the coolant flow path 250 (coolant flow path 251) is routed so as to pass through a first portion P1 directly below the end E. In this embodiment, the width of the coolant flow path 250, including the coolant flow path 251, is uniform throughout.

[0043] The distance between refrigerant flow path 250 and surface 110, which is a distance along a direction perpendicular to surface 110 serving as the mounting surface, is hereinafter also referred to as the "refrigerant distance." The refrigerant distance is defined for each portion of refrigerant flow path 250 and can be considered an index representing the height position of refrigerant flow path 250. As shown in FIG. 3, in this embodiment, refrigerant flow path 250 is routed so that the refrigerant distance (H1) in first portion P1 is smaller than the refrigerant distance (H2) in second portion P2. In other words, in first portion P1, refrigerant flow path 250 is located at a higher position than other portions, and is routed so as to pass through a position close to surface 110 serving as the mounting surface. The refrigerant distance of refrigerant flow path 250 in the portion inside first portion P1 is the same as the refrigerant distance (H2) in second portion P2, but may be a different distance.

[0044] In this configuration, the thermal resistance between the refrigerant flow path 251 and the surface 110 in the first portion P1 is smaller than the thermal resistance between the refrigerant flow path 250 and the surface 110 in the second portion P2. As a result, the first portion P1 is cooled more efficiently than the second portion P2. In other words, in the refrigerant flow path 250 of this embodiment, the refrigerant distance directly below the end E is reduced, and as a result, the cooling performance for the first portion P1 is higher than the cooling performance for the second portion P2. Even with this configuration, it is possible to achieve the same effects as those described in the first embodiment.

[0045] The third embodiment will be described below. Differences from the first embodiment will be mainly described below, and descriptions of commonalities with the first embodiment will be omitted as appropriate.

[0046] 4 shows the configuration of the refrigerant flow path 250 formed in the base plate 200 of this embodiment in the same manner as in FIG. 2. In this embodiment, as in the first embodiment, the refrigerant flow path 250 is formed inside the base plate 200, and a part of it (refrigerant flow path 251) is routed so as to pass through the first portion P1 directly below the end E. The width of the refrigerant flow path 250 in this embodiment is uniform throughout, including the refrigerant flow path 251. Furthermore, the refrigerant distance in this embodiment is also uniform throughout, including the refrigerant flow path 251.

[0047] 4, in this embodiment, opening 255, which serves as an inlet for the refrigerant into refrigerant channel 250, is formed at a position overlapping end E in top view. In other words, one end (inlet side) of refrigerant channel 250 is disposed at a position overlapping end E in top view.

[0048] In top view, refrigerant flow path 250 extends in an arc shape from opening 255 along end E and is routed so as to pass through first portion P1. That is, the portion extending in an arc shape from opening 255 as described above constitutes refrigerant flow path 251 in this embodiment. As is clear from FIG. 4 , the refrigerant supplied to opening 255 first passes through refrigerant flow path 251 located immediately below end E and cools first portion P1. Then, the refrigerant passes through second portion P2 located outside end E and cools second portion P2. Then, the refrigerant passes through a portion inside end E and cools that portion. Finally, the refrigerant is discharged to the outside through opening 256. As the refrigerant passes through the above-described path, its temperature gradually increases.

[0049] The first portion P1 is cooled with relatively high efficiency because a low-temperature refrigerant passes through it first. On the other hand, the second portion P2 is cooled with relatively low efficiency because the refrigerant passes through it after passing through the first portion P1 and raising its temperature. That is, in the refrigerant flow path 250 of this embodiment, the inlet end portion connected to the opening 255 is located directly below the end portion E, and as a result, the cooling performance for the first portion P1 is higher than the cooling performance for the second portion P2. Even with this configuration, the same effects as those described in the first embodiment can be achieved.

[0050] Note that only one end of the refrigerant flow path 250 may be arranged at a position overlapping with the end E in a top view, or both ends may be arranged. In other words, both openings 255 and 256 may be arranged at a position directly below the end E. In such a configuration, regardless of which of the openings 255 and 256 is used as the refrigerant inlet, the first portion P1 can be cooled with high efficiency.

[0051] The configuration of the refrigerant flow paths 250 for making the cooling performance for the first portion P1 higher than the cooling performance for the second portion P2 is not limited to the example described above, and various other configurations can be adopted. For example, the distance between adjacent refrigerant flow paths 250 in a top view, i.e., the spacing between the refrigerant flow paths 250, may be varied depending on the location. Specifically, the spacing between the refrigerant flow paths 250 in the first portion P1 may be narrower than the spacing between the refrigerant flow paths 250 in the second portion P2. Even in such a configuration, the same effects as those of the above-described embodiments can be achieved.

[0052] 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]

[0053] 10: Electrostatic chuck 100: Dielectric substrate 110: Face E: End 200: Base plate 250, 251: refrigerant flow path P1: 1st part P2: 2nd part

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 base plate is a first portion that overlaps with an outer peripheral end of the placement surface when viewed from a direction perpendicular to the placement surface; a second portion that is a portion further outwardly than the first portion, the refrigerant flow path is formed in each of the first portion and the second portion, The refrigerant flow path is An electrostatic chuck, characterized in that the electrostatic chuck is formed so that the cooling performance for the first portion is higher than the cooling performance for the second portion.

2. 2. The electrostatic chuck according to claim 1, wherein a width of the coolant flow passage in the first portion is narrower than a width of the coolant flow passage in the second portion.

3. When a refrigerant distance is a distance along a direction perpendicular to the mounting surface between the refrigerant flow path and the mounting surface, 2. The electrostatic chuck of claim 1, wherein the coolant distance in the first portion is smaller than the coolant distance in the second portion.

4. When viewed from a direction perpendicular to the placement surface, 2. The electrostatic chuck according to claim 1, wherein at least one end of the coolant flow path is disposed at a position overlapping an outer peripheral end of the mounting surface.

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