Electrostatic chuck

Abstract

To provide an electrostatic chuck, which can efficiently cool a base plate.SOLUTION: An electrostatic chuck 10 comprises a dielectric substrate 100, and a base plate 200 bonded to the dielectric substrate 100 and having a refrigerant flow path 400 inside through which refrigerant passes. In the vicinity of at least one end of the refrigerant flow path 400, a curved section 401 is formed in which the flow direction of the refrigerant changes more than 90 degrees.SELECTED DRAWING: Figure 2

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] A low-temperature coolant is supplied from the outside to one end of the coolant flow path. Heat from the substrate is transferred to the coolant through the dielectric substrate and the base plate. The coolant gradually increases in temperature as it flows through the coolant flow path, and is discharged to the outside from the other end of the coolant flow path. It is preferable that the coolant cools the base plate as efficiently as possible throughout the entire coolant flow path from the upstream side to the downstream side.

[0006] 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 efficiently cooling a base plate. [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. A curved portion is formed near at least one end of the coolant flow path, at which the flow direction of the coolant changes by an angle greater than 90 degrees.

[0008] When the end of the refrigerant flow path where the curved portion is formed is used as the refrigerant inlet, the refrigerant becomes turbulent at the curved portion immediately after being supplied from the outside and continues to flow downstream. The turbulent flow increases the heat transfer coefficient, allowing the refrigerant to efficiently cool each part.

[0009] Furthermore, regardless of whether a curved portion is formed on the inlet side of the refrigerant flow path, the refrigerant reaches the vicinity of the outlet end of the refrigerant flow path with its temperature having increased by absorbing heat from each part. This reduces the cooling efficiency in that part. If such an increase in the refrigerant temperature on the outlet side is a problem, the end where the curved portion is formed can be used as the refrigerant outlet. In this case, the flow speed of the refrigerant increases locally in the curved portion, and new turbulence is generated, increasing the heat transfer coefficient in that part. This increases the cooling efficiency in the vicinity of the downstream end. Effect of the Invention

[0010] According to the present invention, it is possible to provide an electrostatic chuck capable of efficiently cooling a base plate. [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] 11A and 11B are diagrams for explaining the shape of a curved portion. 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 and a base plate 200.

[0015] The dielectric substrate 100 is a substantially disk-shaped member made of a sintered ceramic body. The dielectric substrate 100 is made of, for example, high-purity aluminum oxide (Al 2 O 3 ), 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, etc. required for the dielectric substrate 100 in the semiconductor manufacturing equipment.

[0016] 1 of the dielectric substrate 100 is a "mounting surface" on which the substrate W is placed. Also, a lower surface 120 of the dielectric substrate 100 in FIG. 1 is a "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".

[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 arranged 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 via 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 so-called "monopolar" electrode as in this embodiment, or may be provided as two so-called "bipolar" electrodes.

[0018] 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.

[0019] 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.

[0020] 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.

[0021] 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.

[0022] 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.

[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. The 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 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.

[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 the 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 apparatus, 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 discharged to the outside together with the coolant. The coolant is supplied to and discharged from the coolant flow path 400 via openings 251, 252 (not shown in FIG. 1, see FIG. 2) formed in the surface 220 of the base plate 200 opposite to the surface 210.

[0027] The configuration of the refrigerant flow path 400 will be described with reference mainly to Fig. 2. Fig. 2 shows a schematic top view of the configuration of the refrigerant flow path 400 formed inside the base plate 200. As described above, openings 251 and 252 are provided on the surface 220 of the base plate 200. The refrigerant flow path 400 connects between the openings 251 and 252, and is formed along a path that passes through substantially the entire base plate 200 in the top view.

[0028] Both of the openings 251 and 252 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 400. In this embodiment, a coolant is supplied from the outside to the opening 251. The coolant that has passed through the coolant flow path 400 and is used to cool the substrate W is discharged from the opening 252 to the outside.

[0029] Coolant flow path 400 is formed at the same height position throughout (specifically, the portion between openings 251 and 252). Note that the "height position" refers to the position in the direction perpendicular to surface 110, which is the mounting surface. Since the distance from coolant flow path 400 to surface 110 is uniform throughout, cooling by the coolant can be performed uniformly in each portion.

[0030] 2, the refrigerant flow path 400 is formed as a flow path that extends in a generally spiral shape. However, a curved portion 401 where the flow direction of the refrigerant changes significantly is formed in a position of the refrigerant flow path 400 near the opening 251, i.e., a position near one end of the refrigerant flow path 400. In this embodiment, the curved portion 401 is formed so that the flow direction of the refrigerant changes by 180 degrees.

[0031] Similarly, a curved portion 402 where the flow direction of the refrigerant changes significantly is formed in a position of the refrigerant flow path 400 near the opening 252, i.e., near the other end of the refrigerant flow path 400. In this embodiment, the curved portion 402 is formed so that the flow direction of the refrigerant changes by 180 degrees.

[0032] In the case where the curved portion 401 is formed near the opening 251 which is the inlet of the refrigerant as in this embodiment, the refrigerant becomes turbulent at the curved portion 401 immediately after being supplied from the outside through the opening 251, and flows downstream while maintaining the turbulent flow. The generation of turbulence increases the heat transfer coefficient, so that the refrigerant can efficiently and uniformly cool each part.

[0033] In order to achieve this effect, it is sufficient that curved portion 401 is formed so that the flow direction of the refrigerant changes by at least 90 degrees or more.

[0034] 3 is a schematic top view of the configuration of curved portion 401 and its surroundings in refrigerant flow path 400. Point P0 shown in the figure is the end of refrigerant flow path 400 closest to opening 251 and is the center in the width direction. Point P1 is a point that is a distance L away from point P0 along the direction in which the refrigerant flows.

[0035] The above-mentioned "distance L" is a distance that satisfies the relationship L = 5 × W, where "W" is the width of the refrigerant flow path 400 in a top view. In cases where the value of W varies with position, a specific value within the range of variation is set as the representative value of W, and this is used to calculate the above-mentioned L (= 5 × representative value). As the "representative value", for example, any of the maximum, minimum, or average value of the flow path width of each portion within a predetermined range of the refrigerant flow path 400 that can be sufficiently included within the range of distance L from point P0 may be used.

[0036] It is preferable that the curved portion 401 is formed so that the flow direction of the refrigerant changes by at least 90 degrees in the range from point P0 to point P1 in the refrigerant flow path 400. More preferably, the change in the flow direction of the refrigerant in the same range may be 135 degrees or more, or 180 degrees or more.

[0037] The refrigerant, which has absorbed heat from each part of the base plate 200 and has increased in temperature, reaches the vicinity of the outlet end (opening 252) of the refrigerant flow path 400. This reduces the cooling efficiency at this portion. When such an increase in the refrigerant temperature at the outlet side becomes a problem, as in this embodiment, a curved portion 402 may be formed at a position near the outlet end (opening 252) of the refrigerant flow path 400. In this case, the flow speed of the refrigerant increases locally at the curved portion 402, and further turbulence is newly generated, so that the heat transfer coefficient at this portion increases. This increases the cooling efficiency near the downstream end, so that the cooling efficiency of each part of the refrigerant flow path 400 can be made closer to uniform.

[0038] Similarly to curved portion 401, curved portion 402 is preferably formed so that the flow direction of the refrigerant changes by at least 90 degrees within a range of distance L (=5×W) from the end on the opening 252 side. More preferably, the change in the flow direction of the refrigerant within the same range may be 135 degrees or more, or 180 degrees or more.

[0039] The coolant flow path 400 may have both curved portions 401 and 402 as in this embodiment, or may have only one of them. In either case where the end of the coolant flow path 400 where the curved portion is formed is used as the coolant inlet or outlet, as described above, the base plate 200 can be cooled efficiently and uniformly.

[0040] The curved portions 401, 402 may be formed, for example, such that the flow direction of the refrigerant when viewed from a direction parallel to the mounting surface (surface 110) changes by more than 90 degrees. In that case, however, the distance from the refrigerant flow path 400 to the surface 110 changes from place to place, and there is a possibility that cooling by the refrigerant will not be performed efficiently in some places. Therefore, it is preferable that the curved portions 401, 402 are formed, as in this embodiment, such that the flow direction of the refrigerant when viewed from a direction perpendicular to the mounting surface (surface 110) changes by more than 90 degrees.

[0041] 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]

[0042] 10: Electrostatic chuck 100: Dielectric substrate 110: Face 200: Base plate 400: Coolant flow path 401, 402: Curved section W: Substrate

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 electrostatic chuck is characterized in that a curved portion is formed near at least one end of the coolant flow passage, where the flow direction of the coolant changes by an angle greater than 90 degrees.

2. 2. The electrostatic chuck according to claim 1, wherein the curved portion is formed so that a flow direction of the coolant changes by an angle greater than 90 degrees when viewed from a direction perpendicular to the mounting surface.

3. 2. The electrostatic chuck according to claim 1, wherein the curved portion is formed near one end of the coolant flow passage and near the other end of the coolant flow passage.

4. 2. The electrostatic chuck according to claim 1, wherein the entire coolant flow passage is formed at the same height position.

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