Electrostatic chuck and substrate fixing device
By using a combination of alumina ceramic matrix and an adhesive layer, the complexity and cost problems of the high-temperature fusion process of ceramic electrostatic suction cups are solved, and the production of low-cost and low-temperature cured electrostatic suction cups is achieved, and plasma resistance is improved.
Patent Information
- Application Number
- CN202410918726.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2023-07-12
- Filing Date
- 2024-07-10
- Publication Date
- 2025-01-14
AI Technical Summary
In the prior art, electrostatic suction cups made of stacked ceramics need to be fused at high temperature under high temperature environments and require surface activation to reduce surface roughness, which is complex and costly.
Using the first and second substrates made of alumina ceramics, the high temperature fusion is avoided by embedded conductors and electrostatic electrodes therein and using silicon-based resin or epoxy resin as the adhesive layer, stacking and curing to form an electrostatic suction cup, The curing temperature can reach 100℃.
It realizes simple and low-cost stacking of ceramic electrostatic suction cups, improves plasma resistance, and reduces the need for surface treatment during high-temperature fusion and reduces production costs.
Smart Images
Figure CN119314933A_ABST
Abstract
Description
Technical Field
[0001] The present disclosure relates to an electrostatic chuck and a substrate fixing device. Background Art
[0002] In the related art, a film forming apparatus (eg, a CVD apparatus, a PVD apparatus, etc.) or a plasma etching apparatus used in the manufacture of semiconductor devices such as ICs and LSIs has a stage for accurately holding a wafer in a vacuum processing chamber.
[0003] As such a stage portion, for example, there is proposed a substrate holding device that absorbs and holds a wafer as a target object to be absorbed by an electrostatic chuck mounted on a base plate.
[0004] As an example of an electrostatic chuck mounted on a substrate holding device, there is an electrostatic chuck in which two bases made of ceramics are stacked and formed integrally by, for example, high-temperature fusion.
[0005] Citation List
[0006] Patent Literature
[0007] Patent Document 1: JPH10-107133A Summary of the invention
[0008] However, high-temperature fusion is not a simple stacking method because it needs to be performed in a high-temperature environment of 1000° C. or more to perform surface activation treatment on the members to be fused and to minimize the surface roughness.
[0009] The present disclosure has been made in view of the above circumstances, and an object thereof is to provide an electrostatic chuck that stacks two substrates made of ceramics in a simple manner.
[0010] An electrostatic chuck according to the present disclosure comprises:
[0011] a first matrix;
[0012] a first adhesive layer;
[0013] a second substrate stacked on the first substrate with the first adhesive layer interposed between the first substrate and the second substrate; and
[0014] an electrostatic electrode embedded in the second matrix,
[0015] Wherein, the first substrate is made of alumina ceramics, and
[0016] The second substrate is made of alumina ceramic having a higher alumina purity than that of the first substrate.
[0017] According to the present disclosure, it is possible to provide an electrostatic chuck in which two bases made of ceramics are stacked in a simple manner. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] Figure 1 is a cross-sectional view that simplifies and illustrates the substrate fixing device according to the first embodiment.
[0019] Figure 2 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 1 of the first embodiment.
[0020] Figure 3 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 2 of the first embodiment.
[0021] Figure 4 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 3 of the first embodiment.
[0022] Figure 5 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 4 of the first embodiment.
[0023] Figure 6 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 5 of the first embodiment. DETAILED DESCRIPTION
[0024] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. It should be noted that in the various drawings, the same reference numerals are used to identify parts having the same configuration, and repeated descriptions may be omitted.
[0025] <First Embodiment>
[0026] [Structure of substrate fixing device]
[0027] Figure 1 1 is a cross-sectional view that simplifies and illustrates the substrate fixing device according to the first embodiment. Figure 1 , the substrate fixing device 1 has a base plate 10, an adhesive layer 20 and an electrostatic chuck 30 as main constituent elements.
[0028] The base plate 10 is a member for mounting the electrostatic chuck 30. The thickness of the base plate 10 may be, for example, greater than or equal to about 20 mm and less than or equal to 50 mm. The base plate 10 may be made of a metal such as aluminum, copper, or titanium. Among these metals, aluminum, which is inexpensive and easy to process, is preferably used.
[0029] The base plate 10 may also be used as an electrode for controlling plasma, etc. 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, thereby efficiently performing etching processing.
[0030] A flow channel 15 is provided in the base plate 10. One end of the flow channel 15 has a cooling medium introduction portion 15a, and the other end of the flow channel 15 has a cooling medium discharge portion 15b. The flow channel 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 the cooling medium from the cooling medium introduction portion 15a into the flow channel 15, and discharges the cooling medium from the cooling medium discharge portion 15b. By circulating the cooling medium in the flow channel 15 to cool the base plate 10, the chip adsorbed on the electrostatic chuck 30 can be cooled. As the cooling medium, for example, water or a heat transfer liquid (Galden) can be used. In addition to the flow channel 15, the base plate 10 may also be provided with a gas channel for introducing an inert gas to cool the chip adsorbed on the electrostatic chuck 30, etc.
[0031] The electrostatic chuck 30 is mounted on the base plate 10, and the adhesive layer 20 is interposed between the electrostatic chuck 30 and the base plate 10. As the adhesive layer 20, for example, a silicone-based resin can be used. As the adhesive layer 20, an epoxy resin or an acrylic resin can also be used. The thickness of the adhesive layer 20 is preferably thick. By increasing the thickness of the adhesive layer 20, the effect of reducing the stress caused by the thermal expansion difference with the metal base plate is obtained.
[0032] The adhesive layer 20 may have a layered structure in which a plurality of adhesive layers are stacked. For example, when the adhesive layer 20 is composed of a two-layer structure of an adhesive having high thermal conductivity and an adhesive having a low elastic modulus, the effect of further reducing stress caused by the thermal expansion difference with the metal base plate is obtained.
[0033] The electrostatic chuck 30 is a component that adsorbs and holds a wafer as a target object to be adsorbed. The planar shape of the electrostatic chuck 30 may be, for example, circular. The diameter of the wafer as a target object to be adsorbed by the electrostatic chuck 30 may be, for example, 8 inches, 12 inches, or 18 inches. The electrostatic chuck 30 is, for example, a Coulomb force type electrostatic chuck. However, the electrostatic chuck 30 may also be a Johnson-Rahbek type electrostatic chuck.
[0034] The electrostatic chuck 30 has: a first base 31 ; a second base 34 stacked on the first base 31 with an adhesive layer 33 interposed therebetween; and an electrostatic electrode 35 buried in the second base 34 .
[0035] The first substrate 31 is a dielectric body. Specifically, the first substrate 31 is made of alumina ceramics. In the first substrate 31, the purity of alumina is, for example, 80 wt % or more and 97 wt % or less. The thickness of the substrate 31 is, for example, about 2 mm to 10 mm.
[0036] The conductor 32 can be embedded in the first substrate 31. The conductor 32 is, for example, a heating element. The heating element (heating element) generates heat by applying a voltage from the outside of the substrate fixing device 1, and heats so that the placement surface 34a of the second substrate 34 described below reaches a predetermined temperature. The heating element can heat the placement surface 34a of the second substrate 34 to a temperature of, for example, about 250°C to 300°C. As a material for the heating element, for example, tungsten (W), molybdenum (Mo) etc. can be used. For example, the heating element can be patterned into a concentric circle shape. It should be noted that the conductor 32 can be a single-layer wiring or a multi-layer wiring.
[0037] As the adhesive layer 33, for example, a silicon-based resin can be used. As the adhesive layer 33, an epoxy resin or an acrylic resin can also be used. The adhesive layer 33 can be made of the same or different material as the adhesive layer 20. The thickness of the adhesive layer 33 can be less than the thickness of the adhesive layer 20. This is because the upper and lower sides of the adhesive layer 33 are both ceramic substrates, and the thermal expansion coefficients are roughly the same, so there is no need to increase the thickness for the effect of reducing stress. The thickness of the adhesive layer 33 can be set to, for example, greater than or equal to 0.1 mm and less than or equal to 2 mm.
[0038] The second substrate 34 is a dielectric body. Specifically, the second substrate 34 is made of alumina ceramics having a higher purity of alumina than that of the first substrate 31. In the second substrate 34, the purity of alumina is preferably 97% by weight, more preferably 98% by weight or more, and even more preferably 99% by weight or more. The thickness of the second substrate 34 is, for example, about 1 mm to 5 mm. The difference in purity of alumina between the first substrate 31 and the second substrate 34 is preferably 3% to 5%.
[0039] By setting the purity of aluminum oxide to 97% by weight or more, plasma resistance can be improved. It should be noted that a purity of 97% or more means that no sintering aid is added. In addition, a purity of 97% or more means that undesirable impurities may be included during the manufacturing process, etc.
[0040] The electrostatic electrode 35 is a thin film electrode and is buried in the second substrate 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 adsorption force is generated between the electrostatic electrode and the wafer by static electricity. This can adsorb and hold the wafer on the placement surface 34a of the second substrate 34 of the electrostatic chuck 30. The higher the voltage applied to the electrostatic electrode 35, the stronger the adsorption holding force. The electrostatic electrode 35 may have a monopolar shape or a bipolar shape. As the material of the electrostatic electrode 35, for example, tungsten, molybdenum, etc. may be used.
[0041] In order to manufacture the substrate holding device (substrate fixing device) 1, first, the electrostatic chuck 30 is manufactured. Specifically, a first substrate 31 in which a conductor 32 is embedded and a second substrate 34 in which an electrostatic electrode 35 is embedded are prepared separately. Then, the second substrate 34 is stacked on the first substrate 31, and an uncured adhesive layer 33 is interposed between the second substrate 34 and the first substrate 31. Then, the adhesive layer 33 is cured. The temperature when the adhesive layer 33 is cured is, for example, about 100°C.
[0042] It should be noted that the first substrate 31 can be manufactured by a known manufacturing method, including, for example, a process of machining a through hole in a green sheet, a process of filling the through hole with a conductive paste, a process of forming a pattern to become the conductor 32, a process of stacking and firing another green sheet, a surface flattening process, etc. In addition, the second substrate 34 can be manufactured by a known manufacturing method, including, for example, a process of machining a through hole in a green sheet, a process of filling the through hole with a conductive paste, a process of forming a pattern to become the electrostatic electrode 35, a process of stacking and firing another green sheet, a surface flattening process, etc.
[0043] Next, a base plate 10 having a flow channel 15 and the like formed in advance is prepared. Then, the first base 31 of the electrostatic chuck 30 is stacked on the base plate 10, and an uncured adhesive layer 20 is interposed between the first base 31 and the base plate 10. Then, the adhesive layer 20 is cured. The temperature when curing the adhesive layer 20 is, for example, about 100° C. As a result, the substrate fixing device 1 is completed.
[0044] In this way, the electrostatic chuck 30 has a structure in which a first substrate 31 and a second substrate 34 are stacked and an adhesive layer 33 is interposed between the first substrate 31 and the second substrate 34, wherein the first substrate 31 is made of alumina ceramic and the second substrate 34 is made of alumina ceramic having a higher alumina purity than that of the first substrate 31. By providing the adhesive layer 33, the two substrates can be easily stacked without using a special method such as high-temperature fusion.
[0045] For example, high temperature fusion needs to be performed in a high temperature environment of 1000° C. or more, but curing of the adhesive layer 33 can be performed at about 100° C. In addition, in order to perform high temperature fusion, it is necessary to perform surface activation treatment on the member to be fused or to minimize the surface roughness. However, when the adhesive layer 33 is used, these treatments are not required.
[0046] In addition, by setting the purity of aluminum oxide in the second base 34 that absorbs and holds the wafer to 97 wt % or more, the plasma resistance of the second base 34 can be improved.
[0047] On the other hand, if the second substrate 34 with high-purity alumina is made thicker and the conductors are stacked in multiple layers, the risk of peeling or cracking in the conductors increases. For example, if the second substrate 34 is made thicker and the conductors 32 other than the electrostatic electrodes 35 are buried in the second substrate 34, the risk of peeling or cracking in the electrostatic electrodes 35 or the conductors 32 after firing increases. Therefore, in the substrate fixing device 1, the second substrate 34 with high-purity alumina is not made thicker than necessary and has only the electrostatic electrodes 35 buried therein. This can reduce peeling and cracking of the electrostatic electrodes 35 without the need for expensive treatments such as HIP (hot isostatic pressing) treatment.
[0048] In addition, in the substrate holding device 1, the purity of aluminum oxide in the first base 31 that does not absorb and hold the wafer is made lower than the purity of aluminum oxide in the second base 34, and the conductor 32 is formed in the first base 31. By forming the conductor 32 in the first base 31 in which the purity of aluminum oxide is relatively low, it is possible to reduce peeling and cracking of the conductor 32 without performing expensive treatments such as HIP treatment. In addition, the first base 31 in which the purity of aluminum oxide is relatively low can be made thicker, and the conductor 32 can be formed in multiple layers.
[0049] <Modification of First Embodiment>
[0050] In the modification of the first embodiment, an example of a substrate fixing device provided with a sealing member is shown. It should be noted that in the modification of the first embodiment, description of the same constituent parts as those of the embodiment already described may be omitted.
[0051] Figure 2 1 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 1 of the first embodiment. Figure 2 As shown, the substrate holding device (substrate fixing device) 1A is different from the substrate holding device 1 in that the substrate holding device 1A has a sealing member 38 .
[0052] In the substrate fixing device 1A, an annular space in which the adhesive layer 33 does not exist is formed in a region where the outer peripheral portion of the upper surface of the first base 31 and the outer peripheral portion of the lower surface of the second base 34 face each other, and a sealing member 38 is arranged in the space. The upper surface of the sealing member 38 is in close contact with the lower surface of the second base 34, and the lower surface of the sealing member 38 is in close contact with the upper surface of the first base 31. As the sealing member 38, for example, an O-ring or the like can be used. As the sealing member 38, a resin having higher plasma resistance than that of the adhesive layer 33 can be used.
[0053] In this way, by arranging the sealing member 38 so that the adhesive layer 33 is not exposed to the outside of the substrate fixing device 1A, the adhesive layer 33 can be hermetically isolated from the plasma, and thus deterioration of the adhesive layer 33 can be suppressed.
[0054] Figure 3 2 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to a modification 2 of the first embodiment. Figure 3 As shown, the substrate holding device (substrate holding device) 1B is different from the substrate holding device 1A in that the substrate holding device 1B is provided with an annular groove 31x recessed in a direction away from the second substrate 34 on the outer periphery of the upper surface of the first substrate 31. In the substrate holding device 1B, an annular space in which the adhesive layer 33 is not present is formed in the area where the groove 31x and the outer periphery of the second substrate 34 face each other, and the sealing member 38 is arranged in the space. The groove 31x can be formed by sandblasting, for example. The depth of the groove 31x can be set to, for example, 0.1 mm or more and 2.0 mm or less.
[0055] In this way, by providing the groove 31x for arranging the sealing member 38 on the outer periphery of the first base 31, even if the sealing member 38 having the same thickness as the sealing member in the substrate fixing device 1A is used, the thickness of the adhesive layer 33 can be reduced. In addition, since the thickness of the adhesive layer 33 can be reduced, the variation of the material selection of the adhesive constituting the adhesive layer 33 can be expanded, the amount of adhesive used can be reduced, and thus the material cost can be reduced.
[0056] Figure 4 2 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 3 of the first embodiment. Figure 4 As shown, the substrate holding device (substrate holding device) 1C is different from the substrate holding device 1A in that the substrate holding device 1C is provided with an annular groove 34x recessed in a direction away from the first substrate 31 on the outer periphery of the lower surface of the second substrate 34. In the substrate holding device 1C, an annular space in which the adhesive layer 33 is not present is formed in the area where the groove 34x and the outer periphery of the first substrate 31 face each other, and the sealing member 38 is arranged in the space. The groove 34x can be formed by sandblasting, for example. The depth of the groove 34x can be set to, for example, 0.1 mm or more and 2.0 mm or less.
[0057] In this way, even when the groove 34x for arranging the sealing member 38 is provided on the outer peripheral portion of the second base 34, an effect similar to that of the substrate fixing device 1B can be achieved. It should be noted that the second base 34 is harder than the first base 31 because the purity of the aluminum oxide of the second base 34 is higher than the purity of the aluminum oxide of the first base 31. Therefore, it is easier to form the groove 31x than to form the groove 34x.
[0058] Figure 5 1 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to Modification 4 of the first embodiment. Figure 5 As shown, the substrate fixing device 1D is different from the substrate fixing device 1A in that, in the substrate fixing device 1D, an annular groove 31x recessed in a direction away from the second substrate 34 is provided on the outer peripheral portion 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 peripheral portion of the lower surface of the second substrate 34. In the substrate fixing device 1D, an annular space in which the adhesive layer 33 does not exist is formed in a region where the grooves 31x and 34x face each other, and a sealing member 38 is arranged in the space.
[0059] In this way, the grooves 31x and 34x for arranging the sealing member 38 can be provided on the outer peripheral portion of the first base 31 and the outer peripheral portion of the second base 34. As a result, even when the sealing member 38 having the same thickness as the sealing member in the substrate fixing devices 1B and 1C is used, the thickness of the adhesive layer 33 can be further reduced. In addition, since the amount of adhesive used can be further reduced, the material cost can be further reduced.
[0060] Figure 6 2 is a cross-sectional view that simplifies and illustrates a substrate fixing device according to a modification 5 of the first embodiment. Figure 6 As shown, the substrate holding device 1E is different from the substrate holding device 1 in that the substrate holding device 1E has a sealing member 40 .
[0061] In the substrate fixing device 1E, an annular space in which the adhesive layer 20 is not present 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 bottom plate 10 face each other, and a sealing member 40 is arranged in the space. The upper surface of the sealing member 40 is in close contact with the lower surface of the first base 31, and the lower surface of the sealing member 40 is in close contact with the upper surface of the bottom plate 10. As the sealing member 40, for example, an O-ring or the like can be used. As the sealing member 40, a resin having higher plasma resistance than that of the adhesive layer 20 can be used.
[0062] In this way, by arranging the sealing member 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 hermetically isolated from the plasma, and thus the degradation of the adhesive layer 20 can be suppressed.
[0063] It should be noted that there is no need to provide grooves on the first substrate 31 and the bottom plate 10 in the area where the sealing member 40 is arranged. Specifically, as described above, the thicker the adhesive layer 20 is, the greater the effect of reducing the stress caused by the difference in thermal expansion between the metal bottom plate 10 and the first substrate 31 made of ceramic. Therefore, there is little technical significance in making the adhesive layer 20 thinner by providing grooves. That is, as Figure 6 As shown, on the surface of the first substrate 31 facing the bottom plate 10, the outer periphery and the center of the first substrate 31 are on the same plane. In addition, on the surface of the bottom plate 10 facing the first substrate 31, the outer periphery and the center of the bottom plate 10 are on the same plane. When the thickness of the adhesive layer 20 is smaller than the thickness of the sealing member 40 in consideration of restrictions on the O-ring, etc., the groove for the sealing member 40 may be formed on the bottom plate 10 or the first substrate 31.
[0064] Although the preferred embodiments and the like have been described in detail, the present invention is not limited to the above-described embodiments and the like, and various changes and substitutions may be made to the above-described embodiments and the like without departing from the scope defined in the claims.
[0065] For example, in the substrate holding devices 1 , 1A, 1B, 1C, and 1D, the sealing member 40 may be provided in the same or similar manner as that of the substrate holding device 1E.
[0066] In addition, as a target object to be sucked by the substrate fixing device of the present invention, in addition to semiconductor wafers (silicon wafers, etc.), glass substrates used in the manufacturing process of liquid crystal panels, etc. can be exemplified.
Claims
1. An electrostatic chuck, comprising: a first matrix; a first adhesive layer; a second substrate stacked on the first substrate with the first adhesive layer interposed between the first substrate and the second substrate; and an electrostatic electrode embedded in the second matrix, Wherein, the first substrate is made of alumina ceramics, and The second substrate is made of alumina ceramic having a higher alumina purity than that of the first substrate.
2. The electrostatic chuck according to claim 1, comprising: A conductor is embedded in the first matrix.
3. The electrostatic chuck according to claim 1, comprising: a first sealing member, wherein an annular first space where the first adhesive layer does not exist is formed in a region where the outer periphery of the first substrate and the outer periphery of the second substrate face each other, and The first sealing member is arranged in the first space.
4. The electrostatic chuck according to claim 1, comprising: a first sealing member, A first annular groove is provided on the outer periphery of the first substrate and is recessed in a direction away from the second substrate. An annular first space where the first adhesive layer does not exist is formed in a region where the first groove and the outer peripheral portion of the second base body face each other, and The first sealing member is arranged in the first space.
5. The electrostatic chuck according to claim 1, comprising: a first sealing member, A second annular groove is provided on the outer periphery of the second substrate and is recessed in a direction away from the first substrate. An annular first space where the first adhesive layer does not exist is formed in a region where the second groove and the outer peripheral portion of the first base face each other, and The first sealing member is arranged in the first space.
6. The electrostatic chuck according to claim 1, comprising: a first sealing member, A first annular groove is provided on the outer periphery of the first substrate and is recessed in a direction away from the second substrate. A second annular groove is provided on the outer periphery of the second base body and is recessed in a direction away from the first base body. An annular first space where the first adhesive layer does not exist is formed in a region where the first groove and the second groove face each other, and The first sealing member is arranged in the first space.
7. A substrate fixing device, comprising: Base plate; a second adhesive layer; as well as The electrostatic chuck according to any one of claims 1 to 6, wherein the electrostatic chuck is mounted on the base plate, and the second adhesive layer is interposed between the electrostatic chuck and the base plate.
8. The substrate fixing device according to claim 7, wherein: The second adhesive layer is thicker than the first adhesive layer.
9. The substrate fixing device according to claim 7, comprising: a second sealing member, wherein an annular second space where the second adhesive layer does not exist is formed in a region where the outer periphery of the first base body and the outer periphery of the bottom plate face each other, and The second sealing member is arranged in the second space.
10. The substrate fixing device according to claim 7, wherein: On the surface of the first substrate facing the bottom plate, the outer peripheral portion and the central portion of the first substrate are on the same plane, and On the surface of the bottom plate facing the first base body, the outer peripheral portion and the central portion of the bottom plate are on the same plane.