Electrostatic chuck, substrate holding device

Abstract

To provide an electrostatic chuck with two types of ceramic substrates stacked in a simple manner.SOLUTION: The electrostatic chuck has a first substrate, a second substrate laminated on the first substrate via a first adhesive layer, and an electrostatic electrode built into the second substrate, and the first substrate is aluminum oxide ceramics, and the second substrate is aluminum oxide ceramics with a higher purity of aluminum oxide than the first substrate.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to an electrostatic chuck and a substrate fixing device. [Background technology]

[0002] 2. Description of the Related Art Conventionally, film formation apparatuses (eg, CVD apparatuses, PVD apparatuses, etc.) and plasma etching apparatuses used in manufacturing semiconductor devices such as ICs and LSIs have a stage for precisely holding a wafer within a vacuum processing chamber.

[0003] As such a stage, for example, a substrate fixing device has been proposed that attracts and holds a wafer, which is an object to be attracted, by an electrostatic chuck mounted on a base plate.

[0004] One example of an electrostatic chuck mounted on a substrate fixing device is one in which two types of ceramic substrates are stacked together, the two substrates being integrally formed by, for example, high-temperature fusion. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 10-107133 Summary of the Invention [Problem to be solved by the invention]

[0006] However, high-temperature fusion requires that it be performed in a high-temperature environment of 1000°C or higher, that the members to be fused must be subjected to surface activation treatment, and that the surface roughness must be made extremely small, so it is not a simple lamination method.

[0007] The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide an electrostatic chuck in which two types of ceramic base bodies are laminated by a simple method. [Means for solving the problem]

[0008] The electrostatic chuck has a first base, a second base stacked on the first base via a first adhesive layer, and an electrostatic electrode built into the second base, wherein the first base is made of aluminum oxide ceramics and the second base is made of aluminum oxide ceramics having a higher aluminum oxide purity than the first base. Effect of the Invention

[0009] According to the disclosed technique, it is possible to provide an electrostatic chuck in which two types of ceramic base bodies are laminated by a simple method. [Brief description of the drawings]

[0010] [Figure 1] 1 is a cross-sectional view illustrating a simplified example of a substrate fixing device according to a first embodiment. [Diagram 2] 1 is a cross-sectional view illustrating, in a simplified form, a substrate fixing device according to a first modified example of the first embodiment. [Diagram 3] 11 is a cross-sectional view illustrating, in a simplified form, a substrate fixing device according to a second modified example of the first embodiment. FIG. [Figure 4] 11 is a cross-sectional view illustrating, in a simplified form, a substrate fixing device according to a third modified example of the first embodiment. FIG. [Diagram 5] 13 is a cross-sectional view illustrating, in a simplified form, a substrate fixing device according to a fourth modified example of the first embodiment. FIG. [Figure 6] 13 is a cross-sectional view illustrating in a simplified form a substrate fixing device according to a fifth modified example of the first embodiment. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, the same components are denoted by the same reference numerals, and duplicated explanations may be omitted.

[0012] First embodiment [Structure of the substrate holding device] Fig. 1 is a cross-sectional view illustrating a substrate fixing device according to a first embodiment in a simplified manner. Referring to Fig. 1, the substrate fixing device 1 has a base plate 10, an adhesive layer 20, and an electrostatic chuck 30 as main components.

[0013] The base plate 10 is a member for mounting the electrostatic chuck 30. The thickness of the base plate 10 may be, for example, about 20 mm or more and 50 mm or less. The base plate 10 may be formed from a metal such as aluminum, copper, titanium, or the like. Among these, it is preferable to use aluminum, which is inexpensive and easy to process.

[0014] The base plate 10 can also be used as an electrode for controlling plasma. By supplying a predetermined high-frequency power to the base plate 10, the energy for causing ions in the generated plasma state to collide with the wafer attracted to the electrostatic chuck 30 can be controlled, and the etching process can be performed effectively.

[0015] A flow path 15 may be provided inside the base plate 10. The flow path 15 has a cooling medium inlet 15a at one end and a cooling medium outlet 15b at the other end. The flow path 15 is connected to a cooling medium control device (not shown) provided outside the substrate fixing device 1. The cooling medium control device (not shown) introduces a cooling medium from the cooling medium inlet 15a to the flow path 15 and discharges the cooling medium from the cooling medium outlet 15b. The cooling medium is circulated through the flow path 15 to cool the base plate 10, thereby cooling the wafer adsorbed on the electrostatic chuck 30. For example, water or Galden can be used as the cooling medium. In addition to the flow path 15, the base plate 10 may be provided with a gas path or the like for introducing an inert gas to cool the wafer adsorbed on the electrostatic chuck 30.

[0016] The electrostatic chuck 30 is mounted on the base plate 10 via an adhesive layer 20. For example, a silicone-based resin can be used as the adhesive layer 20. An epoxy-based resin or an acrylic-based resin may also be used as the adhesive layer 20. The adhesive layer 20 is preferably thick. By making the adhesive layer 20 thicker, it is possible to obtain an effect of reducing stress caused by a difference in thermal expansion with the metal base plate.

[0017] The adhesive layer 20 may have a laminated structure in which a plurality of adhesive layers are laminated. For example, by making the adhesive layer 20 have a two-layer structure in which an adhesive with high thermal conductivity and an adhesive with low elasticity are combined, it is possible to obtain an effect of further reducing stress caused by the difference in thermal expansion with the metal base plate.

[0018] The electrostatic chuck 30 is a part that attracts and holds a wafer, which is an object to be attracted. The planar shape of the electrostatic chuck 30 may be, for example, circular. The diameter of the wafer, which is an object to be attracted to the electrostatic chuck 30, may be, for example, about 8, 12, or 18 inches. The electrostatic chuck 30 is, for example, a Coulomb force type electrostatic chuck. However, the electrostatic chuck 30 may be a Johnsen-Rahbek type electrostatic chuck.

[0019] The electrostatic chuck 30 has a first base 31, a second base 34 laminated on the first base 31 via an adhesive layer 33, and an electrostatic electrode 35 built into the second base 34.

[0020] The first substrate 31 is a dielectric material. Specifically, the first substrate 31 is aluminum oxide ceramics. In the first substrate 31, the purity of the aluminum oxide is, for example, 80 weight percent or more and 97 weight percent or less. The thickness of the first substrate 31 is, for example, about 2 to 10 mm.

[0021] The first base 31 may have a built-in conductor 32. The conductor 32 is, for example, a heating element. The heating element generates heat when a voltage is applied from outside the substrate fixing device 1, and heats the mounting surface 34a of the second base 34 described below to a predetermined temperature. The heating element can heat the mounting surface 34a of the second base 34 to a temperature of, for example, about 250°C to 300°C. Examples of the material for the heating element include tungsten (W) and molybdenum (Mo). The heating element can be, for example, in a concentric pattern. The conductor 32 may be a single-layer wiring or a multi-layer wiring.

[0022] The adhesive layer 33 may be made of, for example, a silicone-based resin. The adhesive layer 33 may be made of, for example, an epoxy-based resin or an acrylic-based resin. The adhesive layer 33 may be made of the same material as the adhesive layer 20, or may be made of a different material. The thickness of the adhesive layer 33 may be thinner than the thickness of the adhesive layer 20. This is because the upper and lower surfaces of the adhesive layer 33 are both ceramic substrates and have approximately the same thermal expansion coefficient, so there is no need to increase the thickness to reduce stress. The thickness of the adhesive layer 33 may be, for example, 0.1 mm or more and 2 mm or less.

[0023] The second substrate 34 is a dielectric material. Specifically, the second substrate 34 is an aluminum oxide ceramic having a higher purity of aluminum oxide than the first substrate 31. In the second substrate 34, the purity of the aluminum oxide is preferably 97 weight percent, more preferably 98 weight percent or more, and even more preferably 99 weight percent or more. The thickness of the second substrate 34 is, for example, about 1 to 5 mm.

[0024] By making the purity of aluminum oxide 97 weight percent or more, it is possible to improve plasma resistance. Note that a purity of 97% or more means that it is formed without adding a sintering aid. Also, a purity of 97% or more means that it may contain unintended impurities during the manufacturing process, etc.

[0025] The electrostatic electrode 35 is a thin-film electrode, and is built into the second base 34. The electrostatic electrode 35 is connected to a power source provided outside the substrate fixing device 1, and when a predetermined voltage is applied from the power source, an electrostatic adsorption force is generated between the electrostatic electrode 35 and the wafer. This allows the wafer to be adsorbed and held on the mounting surface 34a of the second base 34 of the electrostatic chuck 30. The adsorption and holding force becomes stronger as the voltage applied to the electrostatic electrode 35 becomes higher. The electrostatic electrode 35 may be unipolar or bipolar. The electrostatic electrode 35 may be made of, for example, tungsten, molybdenum, or the like.

[0026] To manufacture the substrate fixing device 1, first, the electrostatic chuck 30 is fabricated. Specifically, a first base 31 incorporating a conductor 32 and a second base 34 incorporating an electrostatic electrode 35 are separately prepared. Then, the second base 34 is laminated on the first base 31 via an uncured adhesive layer 33. Thereafter, the adhesive layer 33 is cured. The temperature for curing the adhesive layer 33 is, for example, about 100°C.

[0027] The first base 31 can be produced by a known manufacturing method including, for example, a step of processing a via in a green sheet, a step of filling the via with a conductive paste, a step of forming a pattern that will become the conductor 32, a step of stacking and firing other green sheets, a step of flattening the surface, etc. The second base 34 can be produced by a known manufacturing method including, for example, a step of processing a via in a green sheet, a step of filling the via with a conductive paste, a step of forming a pattern that will become the electrostatic electrode 35, a step of stacking and firing other green sheets, a step of flattening the surface, etc.

[0028] Next, the base plate 10 having the flow path 15 and the like formed thereon is prepared. Then, the first base 31 side of the electrostatic chuck 30 is laminated on the base plate 10 via the uncured adhesive layer 20. Thereafter, the adhesive layer 20 is cured. The temperature for curing the adhesive layer 20 is, for example, about 100° C. With the above steps, the substrate fixing device 1 is completed.

[0029] Thus, the electrostatic chuck 30 has a structure in which the first base 31, which is an aluminum oxide ceramic, and the second base 34, which is also an aluminum oxide ceramic having a higher aluminum oxide purity than the first base 31, are laminated via the adhesive layer 33. By providing the adhesive layer 33, the two types of bases can be easily laminated without using a special method such as high-temperature fusion.

[0030] For example, high-temperature fusion must be performed in a high-temperature environment of 1000° C. or higher, but the hardening of adhesive layer 33 can be performed at about 100° C. Also, high-temperature fusion requires surface activation treatment of the members to be fused and extremely small surface roughness, but when adhesive layer 33 is used, such steps are not necessary.

[0031] Furthermore, by making the purity of aluminum oxide in the second substrate 34 that holds the wafer by suction equal to or greater than 97 weight percent, the plasma resistance of the second substrate 34 can be improved.

[0032] On the other hand, if the second base 34 having high purity aluminum oxide is made thick and the conductors are laminated in multiple layers, there is a high possibility that peeling or cracking will occur in the conductor. For example, if the second base 34 is made thick and the conductor 32 is built into the second base 34 in addition to the electrostatic electrode 35, there is a high possibility that peeling or cracking will occur in the electrostatic electrode 35 and the conductor 32 after firing. Therefore, in the substrate fixing device 1, the second base 34 having high purity aluminum oxide is not made thicker than necessary, and only the electrostatic electrode 35 is built into it. This makes it possible to reduce peeling and cracking of the electrostatic electrode 35 without performing high-cost processing such as HIP processing.

[0033] Furthermore, in the substrate fixing device 1, the purity of aluminum oxide in the first base 31 that does not suction-hold a wafer is made lower than that of the second base 34, and the conductor 32 is formed on the first base 31. By forming the conductor 32 on the first base 31 having a relatively low purity of aluminum oxide, peeling and cracks of the conductor 32 can be reduced without performing costly processing such as HIP processing. Furthermore, the first base 31 having a relatively low purity of aluminum oxide can be made thicker to form the conductor 32 in multiple layers.

[0034] Modification of the First Embodiment In the modified example of the first embodiment, an example of a substrate fixing device equipped with a sealant is shown. Note that in the modified example of the first embodiment, the description of the same components as those in the already described embodiment may be omitted.

[0035] 2 is a simplified cross-sectional view illustrating a substrate fixing device according to Modification 1 of the first embodiment. As shown in FIG. 2, the substrate fixing device 1A is different from the substrate fixing device 1 in that it has a sealant 38.

[0036] In the substrate fixing device 1A, an annular gap where the adhesive layer 33 is not present is formed in a region where the outer periphery of the upper surface of the first base 31 and the outer periphery of the lower surface of the second base 34 face each other, and a sealant 38 is disposed in the gap. The upper surface of the sealant 38 is in close contact with the lower surface of the second base 34, and the lower surface of the sealant 38 is in close contact with the upper surface of the first base 31. For example, an O-ring or the like can be used as the sealant 38. A resin having higher plasma resistance than the adhesive layer 33 may be used as the sealant 38.

[0037] In this manner, by arranging the sealant 38 so that the adhesive layer 33 is not exposed to the outside of the substrate fixing device 1, the adhesive layer 33 can be airtightly isolated from the plasma, thereby suppressing deterioration of the adhesive layer 33.

[0038] 3 is a cross-sectional view illustrating a simplified example of a substrate fixing device according to Modification 2 of the first embodiment. As shown in FIG. 3, the substrate fixing device 1B is different from the substrate fixing device 1A in that an annular groove 31x recessed in a direction away from the second base 34 is provided on the outer periphery of the upper surface of the first base 31. In the substrate fixing device 1B, an annular gap in which the adhesive layer 33 does not exist is formed in an area where the groove 31x faces the outer periphery of the second base 34, and a sealant 38 is disposed in this gap. The groove 31x can be formed by, for example, blast processing. The depth of the groove 31x can be, for example, 0.1 mm or more and 2.0 mm or less.

[0039] In this way, by providing the groove 31x in which the sealant 38 is disposed on the outer periphery of the first base 31, the thickness of the adhesive layer 33 can be reduced even if the sealant 38 has the same thickness as that of the substrate fixing device 1A. Furthermore, since the thickness of the adhesive layer 33 can be reduced, the variety of adhesive material selection for the adhesive layer 33 is expanded, and the amount of adhesive used can be reduced, thereby reducing material costs.

[0040] FIG. 4 is a cross-sectional view illustrating a substrate fixing device according to Modification 3 of the first embodiment in a simplified manner. As shown in FIG. 4, the substrate fixing device 1C is different from the substrate fixing device 1A in that an annular groove 34x recessed in a direction away from the first base 31 is provided on the outer periphery of the lower surface of the second base 34. In the substrate fixing device 1C, an annular gap in which the adhesive layer 33 does not exist is formed in an area where the groove 34x faces the outer periphery of the first base 31, and a sealant 38 is disposed in this gap. The groove 34x can be formed by, for example, blast processing. The depth of the groove 34x can be, for example, 0.1 mm or more and 2.0 mm or less.

[0041] In this way, even if the groove 34x in which the sealant 38 is disposed is provided on the outer periphery of the second base 34, the same effect as in the case of the substrate fixing device 1B can be achieved. Note that the second base 34 is harder than the first base 31 because the purity of aluminum oxide is higher than that of the first base 31. Therefore, it is easier to form the groove 31x than to form the groove 34x.

[0042] Fig. 5 is a cross-sectional view illustrating a simplified example of a substrate fixing device according to Modification 4 of the first embodiment. As shown in Fig. 5, the substrate fixing device 1D is different from the substrate fixing device 1A in that an annular groove 31x recessed in a direction away from the second substrate 34 is provided on the outer periphery of the upper surface of the first substrate 31, and an annular groove 34x recessed in a direction away from the first substrate 31 is provided on the outer periphery of the lower surface of the second substrate 34. In the substrate fixing device 1D, an annular gap in which the adhesive layer 33 does not exist is formed in the region where the groove 31x and the groove 34x face each other, and a sealant 38 is disposed in this gap.

[0043] In this manner, grooves 31x and 34x for disposing the sealant 38 may be provided on the outer periphery of the first base 31 and the second base 34. This allows the thickness of the adhesive layer 33 to be further reduced even if the sealant 38 has the same thickness as that of the substrate fixing devices 1B and 1C. Furthermore, since the amount of adhesive used is further reduced, the material cost can be further reduced.

[0044] 6 is a simplified cross-sectional view illustrating a substrate fixing device according to Modification 5 of the first embodiment. As shown in FIG. 6, the substrate fixing device 1E is different from the substrate fixing device 1 in that it has a seal material 40.

[0045] In the substrate fixing device 1E, an annular gap where no adhesive layer 20 exists is formed in a region where the outer periphery of the lower surface of the first base 31 and the outer periphery of the upper surface of the base plate 10 face each other, and a sealant 40 is disposed in this gap. The upper surface of the sealant 40 is in close contact with the lower surface of the first base 31, and the lower surface of the sealant 40 is in close contact with the upper surface of the base plate 10. For example, an O-ring or the like can be used as the sealant 40. A resin having higher plasma resistance than the adhesive layer 20 may be used as the sealant 40.

[0046] In this manner, by arranging the sealant 40 so that the adhesive layer 20 is not exposed to the outside of the substrate fixing device 1E, the adhesive layer 20 can be airtightly isolated from the plasma, thereby suppressing deterioration of the adhesive layer 20.

[0047] It is not necessary to provide grooves in the first substrate 31 and the base plate 10 in the region where the seal material 40 is disposed. As described above, the thicker the adhesive layer 20, the greater the effect of reducing stress caused by the difference in thermal expansion between the metal base plate 10 and the ceramic first substrate 31. Therefore, there is little technical significance in providing grooves to thin the adhesive layer 20. That is, as shown in FIG. 6, on the surface of the first substrate 31 facing the base plate 10, the outer periphery and the center are on the same plane. Also, on the surface of the base plate 10 facing the first substrate 31, the outer periphery and the center are on the same plane.

[0048] Although the preferred embodiments have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions can be made to the above-described embodiments without departing from the scope of the claims.

[0049] For example, the substrate fixing devices 1, 1A, 1B, 1C, and 1D may also be provided with the sealant 40, similar to the substrate fixing device 1E.

[0050] Furthermore, examples of objects to be attracted by the substrate fixing device according to the present invention include glass substrates used in the manufacturing process of liquid crystal panels and the like, in addition to semiconductor wafers (silicon wafers and the like). [Explanation of symbols]

[0051] 1, 1A, 1B, 1C, 1D, 1E Board fixing device 10 Base plate 15 Flow Path 15a Cooling medium introduction part 15b Coolant discharge section 20 Adhesive layer 30 Electrostatic Chuck 31 First base 31x,34x groove 32 Conductors 33 Adhesive layer 34 Second Base 34a Placement surface 35 Electrostatic Electrode 38,40 Sealing material

Claims

1. A first substrate; a second substrate laminated on the first substrate via a first adhesive layer; an electrostatic electrode incorporated in the second substrate; the first substrate is an aluminum oxide ceramic; The second substrate is made of aluminum oxide ceramics having a higher purity of aluminum oxide than the first substrate.

2. The electrostatic chuck of claim 1 , wherein the first base has an internal conductor.

3. a first annular gap is formed in a region where an outer periphery of the first base and an outer periphery of the second base face each other, and the first adhesive layer is not present; The electrostatic chuck of claim 1 , further comprising a first sealant disposed in the first gap.

4. a first annular groove recessed in a direction away from the second base is provided on an outer periphery of the first base, a first annular gap is formed in a region where the first groove and an outer periphery of the second base are opposed to each other, and the first adhesive layer is not present; The electrostatic chuck of claim 1 , further comprising a first sealant disposed in the first gap.

5. a second annular groove recessed in a direction away from the first base is provided on an outer periphery of the second base, a first annular gap is formed in a region where the second groove and an outer periphery of the first base are opposed to each other, and the first adhesive layer is not present; The electrostatic chuck of claim 1 , further comprising a first sealant disposed in the first gap.

6. a first annular groove recessed in a direction away from the second base is provided on an outer periphery of the first base, a second annular groove recessed in a direction away from the first base is provided on an outer periphery of the second base, a first annular gap is formed in a region where the first groove and the second groove face each other, and the first adhesive layer is not present; The electrostatic chuck of claim 1 , further comprising a first sealant disposed in the first gap.

7. A base plate; A substrate fixing device comprising: the electrostatic chuck according to claim 1 , which is mounted on the base plate via a second adhesive layer.

8. The substrate fixing device according to claim 7 , wherein the second adhesive layer is thicker than the first adhesive layer.

9. a ring-shaped second gap is formed in a region where an outer periphery of the first substrate and an outer periphery of the base plate face each other, and the second adhesive layer is not present; The substrate fixing device according to claim 7 , wherein a second sealant is disposed in the second gap.

10. an outer periphery and a central portion of the first base on a surface facing the base plate are on the same plane; The substrate fixing device according to claim 7 , wherein an outer periphery and a central portion of the surface of the base plate facing the first base are on the same plane.

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