Electrostatic Chuck

Abstract

An electrostatic chuck capable of achieving a more uniform in-plane temperature distribution of a substrate during processing than ever before. [Solution] An electrostatic chuck 10 includes a dielectric substrate 100 having a surface 110 that is a mounting surface, and a base plate 200 that is joined to the dielectric substrate 100 and has a coolant flow path 250 formed therein through which a coolant passes. In a top view, the base plate 200 has a first portion P1 that is a portion that overlaps with an end E on the outer periphery side of the surface 110, and a second portion P2 that is a portion further on the outer periphery side than the first portion P1, and the coolant flow path 250 is formed in each of the first portion P1 and the second portion P2. The coolant flow path 250 is formed so that the cooling performance for the first portion P1 is higher than the cooling performance for the second portion P2.

Description

[Technical field]

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

[0002] For example, in a semiconductor manufacturing device 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 the following Patent Document 1, 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] JP 2011-151055 A Summary of the Invention [Problem to be solved by the invention]

[0005] During processing such as etching, the temperature of the substrate tends to rise, particularly in the outer peripheral portion. In order to suppress such a temperature rise in the outer peripheral portion and to make the in-plane temperature distribution of the substrate as uniform as possible, optimal layout of the coolant flow path in the base plate has been studied. However, what has been studied so far has been mainly the layout of the coolant flow path within the range that overlaps with the substrate in a top view, and there is still room for improvement in the layout of the coolant flow path in other portions.

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

[0007] 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 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 circumferential end of the mounting surface and a second portion that is further outer circumferential 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 under the substrate but also in the second portion outside the portion. By forming the coolant flow passage in such a range, it is possible to suppress the temperature rise of the outer peripheral portion of the substrate. In addition, 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 the cooling performance for the second portion. By making a difference in cooling performance between the first portion and the second portion, it is possible to prevent the members (e.g., focus ring, etc.) arranged further outside the outer peripheral portion of the substrate from being cooled more than necessary while sufficiently suppressing the temperature rise of the outer peripheral portion of the substrate. This makes it possible to make the in-plane temperature distribution of the substrate during processing more uniform than in the past. Effect 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 in the past. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view illustrating a schematic configuration of an electrostatic chuck according to a first embodiment. [Diagram 2] 3A and 3B are diagrams illustrating a configuration of a coolant flow path formed in a base plate of the first embodiment. [Diagram 3] FIG. 11 is a cross-sectional view illustrating a schematic configuration of an electrostatic chuck according to a second embodiment. [Figure 4] 13A and 13B are diagrams illustrating the configuration of a coolant flow path formed in a base plate of a third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] 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.

[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 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.

[0013] 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 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 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 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 "joined surface" that is joined to the base plate 200 via a joining 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 be referred to as a "top view".

[0016] 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 arranged parallel to the surface 110. The material of the adsorption electrode 130 may be tungsten, molybdenum, platinum, palladium, or the like. When a voltage is applied to the adsorption electrode 130 from the outside through a power supply path (not shown), an electrostatic force is generated between the surface 110 and the substrate W, thereby adsorbing and holding the substrate W. As the configuration of the power supply path, various known configurations can be adopted. The adsorption electrode 130 may be provided as a single so-called "monopolar" electrode as in this embodiment, or may be provided as two so-called "bipolar" electrodes. The depth at which the adsorption electrode 130 is arranged, 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 apparatus, helium gas for temperature adjustment is supplied from the outside to the space SP 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, 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.

[0018] A seal ring 111 and dots 112 are provided on a surface 110 serving as a mounting surface, and the above-mentioned 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 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.

[0020] 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.

[0021] 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.

[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. Of the base plate 200, a surface 210 on the upper side in FIG. 1 is a "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 the two 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 any 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 that the thermal resistance between the dielectric substrate 100 and the base plate 200 is small.

[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 the 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 an 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 portion 202 is a portion of the base plate 200 on the lower side in FIG. 1. The flange portion 202 is substantially cylindrical in shape, and its central axis coincides with the central axis of the support portion 201. The diameter of the flange portion 202 is larger than the diameter of the support portion 201. The amount of protrusion of the flange portion 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 portion 202 is, for example, 25 to 40 mm. The overall thickness of the base plate 200, including the support portion 201 and the flange portion 202, is, for example, 30 to 40 mm.

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

[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 apparatus, 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 via openings 255, 256 (not shown in FIG. 1, see FIG. 2) formed in the surface 220 of the base plate 200 opposite to the surface 210.

[0029] For ease of explanation, the edge portion on the outer periphery of surface 110, which is the mounting surface, is also referred to as "edge E" below. Edge E has a circular ridgeline when viewed from above, but a part of it (e.g., the orientation flat portion) may have a ridgeline that is not circular.

[0030] A portion of the base plate 200 that overlaps with the end E in top view is also referred to as the "first portion P1" below. The first portion P1 is, for example, a portion having a certain width that encompasses the entire end E in 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 spaced from the first portion P1 in a top view is hereinafter also referred to as a "second portion P2." The second portion P2 is a portion of the base plate 200 that is adjacent to the first portion P1 from the outer periphery side and is the entire portion that is further outwardly spaced from 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. In the electrostatic chuck 10 of the present embodiment, various improvements described below have been made 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 in first portion P1 and its inside of base plate 200, but also in second portion P2 on the outside. That is, coolant flow path 250 is formed so as to extend to second portion P2 that is outside the portion (i.e., first portion P1, etc.) directly below substrate W and support portion 201. A focus ring (not shown) directly above second portion P2 is cooled by the coolant passing through coolant flow path 250 in second portion P2, and an outer peripheral portion of substrate W is also cooled via the focus ring.

[0034] In this embodiment, the diameter of the flange 202 is relatively large, and therefore the second portion P2 is also large. By making the second portion P2 large 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, the configuration of the coolant flow path 250 formed inside the base plate 200 is depicted in a top view. As described above, the openings 255 and 256 are provided in the surface 220 of the base plate 200. The coolant flow path 250 is formed along a path connecting the openings 255 and 256. For example, the opening 255 is used as an inlet for the coolant, and the opening 256 is used as an outlet for the coolant. The circular dotted line shown in FIG. 2 represents the end E on the outer circumferential side of the surface 110, which is the mounting surface.

[0036] In this embodiment, an opening 255 is formed in a position near the outer circumferential 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, width W1 of refrigerant flow path 251 in first portion P1 is narrower than width W2 of refrigerant flow path 250 in second portion P2. The width of refrigerant flow path 250 in a portion inside first portion P1 is the same as width W2 of refrigerant flow path 250 in second portion P2, but may be a different size. Note that the "width" of refrigerant flow path 250 here refers to the dimension of refrigerant flow path 250 along a direction perpendicular to the direction of refrigerant flow in top view.

[0039] In such a 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 parts of the refrigerant flow path 250. As the flow rate increases, the heat transfer coefficient in the refrigerant flow path 251 increases, so that 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, as a result of narrowing the width of the refrigerant flow path 251 directly below the end E, 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 outside the outer peripheral portion of the substrate W from being cooled more than necessary. This makes it possible to make the in-plane temperature distribution of the substrate W during processing more uniform than in the past.

[0041] A second embodiment will be described below. In the following, differences from the first embodiment will be mainly described, and descriptions of commonalities with the first embodiment will be omitted as appropriate.

[0042] Fig. 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 the refrigerant flow path 250 and the surface 110, which is a distance along a direction perpendicular to the surface 110 that is the mounting surface, is also referred to as the "refrigerant distance" below. The refrigerant distance is defined in each part of the refrigerant flow path 250, and can be said to be an index that indicates the height position of the refrigerant flow path 250. As shown in FIG. 3, in this embodiment, the refrigerant flow path 250 is routed so that the refrigerant distance (H1) in the first part P1 is smaller than the refrigerant distance (H2) in the second part P2. In other words, in the first part P1, the refrigerant flow path 250 is located at a higher position than other parts, and the refrigerant flow path 250 is routed so as to pass through a position close to the surface 110 that is the mounting surface. The refrigerant distance of the refrigerant flow path 250 in the part inside the first part P1 is the same as the refrigerant distance (H2) in the second part P2, but may be a different distance.

[0044] In such a 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. That is, 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 in such a configuration, it is possible to achieve the same effects as those described in the first embodiment.

[0045] A third embodiment will be described below. In the following, differences from the first embodiment will be mainly described, 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 a manner similar to that of 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 (the 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, an opening 255 serving as an inlet for the refrigerant to the refrigerant flow path 250 is formed at a position overlapping with the end E in top view. That is, an end on one side (the inlet side) of the refrigerant flow path 250 is disposed at a position overlapping with the end E in top view.

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

[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 increasing its temperature. That is, in the refrigerant flow path 250 of this embodiment, the inlet side end portion connected to the opening 255 is disposed 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 such a configuration, it is possible to achieve the same effects as those described in the first embodiment.

[0050] Incidentally, 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, 256 may be arranged at a position directly below the end E. In such a configuration, the first portion P1 can be cooled with high efficiency regardless of which of the openings 255, 256 is used as the inlet for the refrigerant.

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

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

Claims

1. a dielectric substrate having a mounting surface on which an object to be attached 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 on a further outer circumferential side than the first portion, The coolant flow path is formed in each of the first portion and the second portion, The refrigerant flow path is The cooling performance for the first portion is formed to be higher than the cooling performance for the second portion, 4. An electrostatic chuck comprising: a cooling medium passage having a width narrower in the first portion than in the second portion.

2. 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 on a further outer circumferential side than the first portion; a third portion that is a portion on the inner circumferential side of the first portion, the coolant flow path is formed in each of the first portion, the second portion, and the third portion, The refrigerant flow path is The cooling performance for the first portion is formed to be higher than the cooling performance for the second portion, When a refrigerant distance is a distance along a direction perpendicular to the mounting surface between the refrigerant flow path and the mounting surface, the refrigerant distance in the first portion is smaller than the refrigerant distance in the second portion; 4. An electrostatic chuck comprising: a first portion having a coolant distance that is smaller than a second ...

3. An electrostatic chuck as described in claim 2, characterized in that the refrigerant distance in the second portion and the refrigerant distance in the third portion are equal to each other.

4. 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 on a further outer circumferential side than the first portion, The coolant flow path is formed in each of the first portion and the second portion, The refrigerant flow path is The cooling performance for the first portion is formed to be higher than the cooling performance for the second portion, When viewed from a direction perpendicular to the placement surface, an electrostatic chuck, characterized in that at least one end of the coolant flow path is disposed at a position overlapping an outer circumferential end of the mounting surface;

5. When viewed from a direction perpendicular to the placement surface, 5. The electrostatic chuck according to claim 4, wherein a portion of the coolant flow passage connected to the one end is formed so as to extend in an arc shape along an outer peripheral end of the mounting surface.

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