Electrostatic chuck

Abstract

To provide an electrostatic chuck which can be efficiently cooled with a refrigerant.SOLUTION: An electrostatic chuck 10 includes: a dielectric substrate 100; a base plate 200 joined to the dielectric substrate 100, the base plate being formed in a refrigerant flow passage 250 in which a refrigerant flows; and a heat insulation member 400 for covering the inner surface of the edge part in one side of the refrigerant flow passage 250.SELECTED DRAWING: Figure 1

Description

Technical Field

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

Background Art

[0002] For example, in a semiconductor manufacturing apparatus such as an etching apparatus, an electrostatic chuck is provided as a device for adsorbing and holding a substrate such as a silicon wafer to be processed. The electrostatic chuck includes a dielectric substrate provided with an adsorption electrode and a base plate for supporting the dielectric substrate, and these are joined to each other. When a voltage is applied to the adsorption electrode, an electrostatic force is generated, and the substrate placed on the dielectric substrate is adsorbed 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 refrigerant flow path for passing refrigerant is formed inside the base plate. A low-temperature refrigerant is supplied from the outside to one end of the refrigerant flow path. The heat from the substrate is transmitted to the refrigerant through the dielectric substrate and the base plate. The refrigerant gradually increases its temperature while flowing through the refrigerant flow path, and is discharged to the outside from the other end of the refrigerant flow path.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In many cases, both the end portion on the inlet side and the end portion on the outlet side of the refrigerant flow path are formed as flow paths that lead to openings at positions relatively far from the dielectric substrate in the base plate (in many cases, the bottom surface of the base plate). At the inlet portion of the refrigerant flow path, since the low-temperature refrigerant is supplied from the outside as described above, the temperature difference between the base plate and the refrigerant becomes the largest.

[0006] Therefore, immediately after the refrigerant is supplied from an inlet on the bottom surface of the base plate or the like, its temperature rises relatively significantly. The refrigerant that has reached the temperature after rising at the inlet will reach the portion of the refrigerant flow path deeper than the inlet, that is, the portion close to the dielectric substrate and that can significantly contribute to cooling. Such an increase in the refrigerant temperature is not preferable from the viewpoint of cooling efficiency.

[0007] The present invention has been made in view of such problems, and an object thereof is to provide an electrostatic chuck capable of efficiently performing cooling with a refrigerant.

Means for Solving the Problems

[0008] In order to solve the above problems, an electrostatic chuck according to the present invention includes a dielectric substrate, a base plate joined to the dielectric substrate and having a refrigerant flow path through which a refrigerant passes formed therein, and a heat insulating member covering an inner surface of one end portion of the refrigerant flow path.

[0009] In the electrostatic chuck having such a configuration, when the refrigerant is supplied from the above "one end portion" of the refrigerant flow path, heat transfer between the low-temperature refrigerant immediately after being supplied from the outside and the base plate is suppressed by the heat insulating member. The refrigerant reaches the portion deeper in the refrigerant flow path with almost no increase in its temperature. Therefore, it becomes possible to cool the substrate or the like more efficiently with the low-temperature refrigerant than before.

Effects of the Invention

[0010] According to the present invention, it is possible to provide an electrostatic chuck capable of efficiently performing cooling with a refrigerant.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Embodiment for Carrying Out the Invention

[0012] Hereinafter, this embodiment will be described with reference to the accompanying drawings. For ease of understanding the description, the same reference numerals are given to the same components in each drawing as much as possible, and duplicate descriptions are omitted.

[0013] The electrostatic chuck 10 according to this embodiment adsorbs and holds a substrate W to be processed by electrostatic force inside a semiconductor manufacturing apparatus (not shown) such as an etching apparatus. The substrate W to be adsorbed is, for example, a silicon wafer. The electrostatic chuck 10 may be used in an apparatus other than a semiconductor manufacturing apparatus.

[0014] FIG. 1 shows a schematic cross-sectional view of the configuration of the electrostatic chuck 10 in a state where the substrate W is adsorbed and held. 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 ceramic sintered body. The dielectric substrate 100 is made of, for example, high-purity aluminum oxide (Al 2 O 3 ) and may contain other materials. The purity, type, additives, etc. of the ceramics in the dielectric substrate 100 can be appropriately set in consideration of the plasma resistance required for the dielectric substrate 100 in a semiconductor manufacturing apparatus.

[0016] Of the dielectric substrate 100, the upper surface 110 in FIG. 1 is the "placement surface" on which the substrate W is placed. Also, the lower surface 120 of the dielectric substrate 100 in FIG. 1 is the "surface to be joined" that is joined to the base plate 200 via the joining layer 300. Along the direction perpendicular to the surface 110, the viewpoint when looking at the electrostatic chuck 10 from the surface 110 side will also be hereinafter referred to as "top view".

[0017] An adsorption electrode 130 is embedded inside the dielectric substrate 100. The adsorption electrode 130 is a thin flat plate-like layer formed of a metal material such as tungsten, for example, and is arranged parallel to the surface 110. As the material of the adsorption electrode 130, in addition to tungsten, molybdenum, platinum, palladium, etc. may also be used. 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, and thereby the substrate W is adsorbed and held. As the configuration of the above power supply path, various known configurations can be adopted. The adsorption electrode 130 may be provided only one as a so-called "monopole" electrode as in this embodiment, or two may be provided as a so-called "bipolar" electrode.

[0018] As shown in FIG. 1, a space SP is formed between the dielectric substrate 100 and the substrate W. When processes such as etching are performed in the semiconductor manufacturing apparatus, helium gas for temperature adjustment is supplied to the space SP from the outside through a gas hole (not shown). By interposing helium gas between the dielectric substrate 100 and the substrate W, the thermal resistance between the two is adjusted, and thereby the temperature of the substrate W is maintained at an appropriate temperature. Note that the gas for temperature adjustment supplied to the space SP may be a gas of a type different from helium.

[0019] A seal ring 111 and dots 112 are provided on the surface 110 which is the placement surface, and the above space SP is formed around these.

[0020] The seal ring 111 is a wall that partitions the space SP at the outermost peripheral position. The upper end of the seal ring 111 forms a part of the surface 110 and abuts against the substrate W. Incidentally, a plurality of seal rings 111 may be provided so as to divide the space SP. With such a configuration, it becomes possible to individually adjust the pressure of the helium gas in each space SP and to make the surface temperature distribution of the substrate W during processing closer to uniform.

[0021] In FIG. 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 is formed as a result of digging down a part of the surface 110 to the position of the bottom surface 116 together with the dot 112 described below.

[0022] The dot 112 is a circular protrusion protruding from the bottom surface 116. A plurality of dots 112 are provided and are arranged substantially evenly and dispersedly on the mounting surface of the dielectric substrate 100. The upper end of each dot 112 forms a part of the surface 110 and abuts against the substrate W. By providing a plurality of such dots 112, the deflection 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, for example. Among the base plate 200, the upper surface 210 in FIG. 1 is a "surface to be joined" that is joined to the dielectric substrate 100 via the joining layer 300.

[0024] The joining layer 300 is a layer provided between the dielectric substrate 100 and the base plate 200 and joins the two. The joining layer 300 is obtained by curing an adhesive made of an insulating material. In the present embodiment, a silicone adhesive is used as the adhesive. However, the joining layer 300 may be obtained by curing another type of adhesive. In any case, as the material of the joining layer 300, it is preferable to use a material having as high a thermal conductivity as possible so that the thermal resistance between the dielectric substrate 100 and the base plate 200 is reduced.

[0025] An insulating film may be formed on the surface of the base plate 200. As the insulating film, for example, an alumina film formed by thermal spraying can be used. By covering the surface of the base plate 200 with the insulating film, the dielectric breakdown voltage of the base plate 200 can be increased.

[0026] Inside the base plate 200, a refrigerant flow path 250 for passing a refrigerant is formed. The refrigerant flow path 250 is formed, for example, as a spiral flow path along a path passing through substantially the entire surface 210 in a top view. When a process such as etching is performed in the semiconductor manufacturing apparatus, the refrigerant is supplied from the outside to the refrigerant flow path 250, and thereby the base plate 200 is cooled. The heat generated in the substrate W during the process is transmitted to the refrigerant through 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 refrigerant. The refrigerant flow path 250 may be formed as a flow path along a single path, but may also be formed as a flow path along a path that branches into a plurality of paths in the middle and then merges again. Further, it may be formed as a plurality of mutually separated flow paths.

[0027] Most of the refrigerant flow path 250 extends along a direction parallel to the surface 210 at a height position near the surface 210. Both ends of the refrigerant flow path 250, that is, the respective ends on the inlet side and the outlet side, extend along a direction perpendicular to the surface 210 and open on the surface 220 opposite to the surface 210. Each of the pair of openings formed on the surface 220 as the inlet or outlet of the refrigerant flow path 250 is hereinafter also referred to as "opening 251".

[0028] The end of the refrigerant flow path 250 connected to the opening 251 can also be referred to as a recess 260 formed on the surface of the base plate 200 (surface 220 in this embodiment). The recess 260 of this embodiment is a cylindrical recess, and its central axis is perpendicular to the surface 220. In FIG. 1, only one of the pair of recesses 260 of the refrigerant flow path 250 is shown.

[0029] As shown in FIG. 2, a pair of recesses 260 are formed at positions close to each other on the surface 220. Such an embodiment is merely an example. The positions of the respective recesses 260 may be appropriately changed according to the path along which the refrigerant flow path 250 is routed. Also, one or both of the recesses 260 may be formed in a portion other than the surface 220 (for example, the side surface of the base plate 200, etc.).

[0030] In the present embodiment, a heat insulating member 400 is disposed inside each of the recesses 260. As shown in FIG. 3, the heat insulating member 400 is a cylindrical member, and a through hole 410 is formed along its central axis. The outer diameter of the heat insulating member 400 is approximately equal to the inner diameter of the recess 260. Also, the length of the heat insulating member 400 is approximately equal to the depth of the recess 260. The internal space of the through hole 410 forms part of the refrigerant flow path 250. Such a heat insulating member 400 can be said to be a member that covers the inner surface of the recess 260 (that is, the end portion of the refrigerant flow path 250) in the refrigerant flow path 250. The heat insulating member 400 may be press-fitted inside the recess 260, or may be adhered to the inner surface of the recess 260.

[0031] In the present embodiment, the entire inner surface of the recess 260 is covered by the heat insulating member 400. In the portion of the refrigerant flow path 250 other than the recess 260, the inner surface thereof is not covered by the heat insulating member 400, and the metal surface of the base plate 200 is exposed to the space through which the refrigerant passes.

[0032] As the material of the heat insulating member 400, a material having a lower thermal conductivity than the metal base plate 200 is used. As such a material, for example, resin materials such as PEEK (Poly Ether Ether Ketone), PEI (Poly Ether Imide), and PI (Poly Imide) are suitable.

[0033] Thus, in the present embodiment, the inner surfaces of the end portions on one side and the other side of the refrigerant flow path 250 are each covered by the heat insulating member 400.

[0034] Describe the advantages of such a configuration. In a general electrostatic chuck, the end portion on the inlet side of the refrigerant flow path is often formed as a flow path that leads to the opening 251 at a position relatively far from the dielectric substrate 100 in the base plate 200 (surface 220 in this embodiment), similar to this embodiment. At the inlet portion of the refrigerant flow path 250, since low-temperature refrigerant is supplied from the outside, the temperature difference between the base plate 200 and the refrigerant becomes the largest.

[0035] Therefore, immediately after the refrigerant is supplied from the inlet on the surface 220 of the base plate 200 or the like, its temperature is relatively greatly increased by heat transfer from the base plate 200. In the portion of the refrigerant flow path 250 deeper than the inlet, that is, the portion close to the dielectric substrate 100 and capable of greatly contributing to cooling (the portion extending parallel to the surface 210 in this embodiment), the refrigerant after the temperature has risen at the inlet will reach. Such an increase in refrigerant temperature is not preferable from the viewpoint of cooling efficiency.

[0036] Therefore, in this embodiment, as described above, the inner surface of the end portion (recess 260) of the refrigerant flow path 250 is covered with the heat insulating member 400. The refrigerant supplied from one opening 251 to the refrigerant flow path 250 first flows through the through hole 410 of the heat insulating member 400 toward the surface 210 side. At this time, the heat transfer between the low-temperature refrigerant immediately after being supplied from the outside and the base plate 200 is suppressed by the heat insulating member 400. For this reason, the refrigerant reaches the deep portion of the refrigerant flow path 250 with almost no increase in its temperature, and while passing through the vicinity of the surface 210 while remaining at the initial low temperature, it is used for cooling the substrate W. Therefore, in this embodiment, it is possible to cool the substrate W or the like more efficiently with low-temperature refrigerant than before.

[0037] The heat insulation member 400 may be disposed only in the recess 260 that serves as the refrigerant inlet among the pair of recesses 260 provided in the base plate 200. However, if the heat insulation member 400 is disposed in both of the pair of recesses 260 as in the present embodiment, even when the refrigerant is supplied from either recess 260, it is possible to enhance the cooling efficiency of the substrate W or the like as described above.

[0038] In the present embodiment, by disposing the heat insulation member 400 formed in a cylindrical shape in advance inside the recess 260, the inner surface of the end portion of the refrigerant flow path 250 is covered with the heat insulation member 400. Instead of such a mode, the heat insulation member 400 may be formed by, for example, forming a film on the inner surface of the recess 260, or applying a liquid material that becomes the heat insulation member 400 and curing it.

[0039] As described above, the present embodiment has been described with reference to specific examples. However, the present disclosure is not limited to these specific examples. Those obtained by appropriately making design changes by those skilled in the art to these specific examples are also included in the scope of the present disclosure as long as they have the features of the present disclosure. Each element included in each of the above-described specific examples and its arrangement, conditions, shape, etc. are not limited to those illustrated and can be changed as appropriate. Each element included in each of the above-described specific examples can be combined as appropriate as long as no technical contradiction occurs.

Description of Reference Numerals

[0040] 10: Electrostatic chuck 100: Dielectric substrate 200: Base plate 250: Refrigerant flow path 260: Recess 400: Heat insulation member

Claims

1. A dielectric substrate, a base plate joined to the dielectric substrate and having a refrigerant flow path through which refrigerant passes formed therein, and a heat insulating member covering an inner surface of one end portion of the refrigerant flow path, wherein the electrostatic chuck is characterized by comprising these components.

2. The electrostatic chuck according to claim 1, further comprising a heat insulating member covering an inner surface of the other end portion of the refrigerant flow path.

3. The base plate is formed of metal, and the heat insulating member is formed of resin, wherein the electrostatic chuck is characterized by these features according to claim 1.

4. The heat insulating member is a cylindrical member and is disposed inside a recess formed in the base plate, wherein the electrostatic chuck is characterized by this configuration according to claim 1.

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