Substrate holding device

Abstract

To provide a substrate holding device with a structure that prevents the adhesive layer from deteriorating and heat from escaping to a base plate side.SOLUTION: The substrate holding device has a base plate, an adhesive layer on the base plate, an insulating layer on the adhesive layer, and an electrostatic chuck on the insulating layer. The electrostatic chuck has a base and electrostatic electrodes built into the base, and the insulating layer has a lower thermal conductivity than the base and adhesive layer.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to 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 via an adhesive layer. One example of the substrate fixing device is one that has a structure provided with a heating element for adjusting the temperature of the wafer. In the substrate fixing device, a heat insulating layer may be provided on the base plate. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Special Publication No. 2013-511162 Summary of the Invention [Problem to be solved by the invention]

[0005] In the substrate fixing device having the above-mentioned structure, it is required to prevent the adhesive layer from deteriorating and to make it difficult for heat to escape to the base plate side.

[0006] The present invention has been made in consideration of the above-mentioned points, and has an object to provide a substrate fixing device having a structure in which the adhesive layer is less likely to deteriorate and heat is less likely to escape to the base plate side. [Means for solving the problem]

[0007] This substrate fixing device has a base plate, an adhesive layer provided on the base plate, an insulating layer provided on the adhesive layer, and an electrostatic chuck provided on the insulating layer, the electrostatic chuck having a base and an electrostatic electrode built into the base, and the insulating layer has a lower thermal conductivity than the base and the adhesive layer. Effect of the Invention

[0008] According to the disclosed technique, it is possible to provide a substrate fixing device having a structure in which the adhesive layer is less likely to deteriorate and heat is less likely to escape to the base plate side. [Brief description of the drawings]

[0009] [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 a simplified example of a substrate fixing device according to a second embodiment. FIG. [Figure 4] FIG. 13 is a diagram showing a simulation result. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] 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.

[0011] First embodiment [Structure of the substrate fixing 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, as main components, a base plate 10, an adhesive layer 20, a heat insulating layer 30, and an electrostatic chuck 50.

[0012] The base plate 10 is a member for mounting the electrostatic chuck 50. 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.

[0013] 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 50 can be controlled, and the etching process can be performed effectively.

[0014] 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 50. 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 50.

[0015] The electrostatic chuck 50 is mounted on the base plate 10 via an adhesive layer 20 and a heat insulating layer 30. The adhesive layer 20 and the heat insulating layer 30 are provided on the base plate 10, and the electrostatic chuck 50 is provided on the heat insulating layer 30. The adhesive layer 20 and the heat insulating layer 30 will be described later.

[0016] The electrostatic chuck 50 is a part that attracts and holds a wafer, which is an object to be attracted. The planar shape of the electrostatic chuck 50 may be, for example, circular. The diameter of the wafer, which is an object to be attracted to the electrostatic chuck 50, may be, for example, about 8, 12, or 18 inches. The electrostatic chuck 50 has at least a base 51 and an electrostatic electrode 52. In the example of FIG. 1, the electrostatic chuck 50 further has a heating element 53. The electrostatic chuck 50 is, for example, a Johnsen-Rahbek type electrostatic chuck. However, the electrostatic chuck 50 may be a Coulomb force type electrostatic chuck.

[0017] The base 51 is a dielectric material, and may be made of ceramics such as aluminum oxide (Al2O3) or aluminum nitride (AlN). The thickness of the base 51 may be, for example, about 1 to 10 mm, and the relative dielectric constant (1 kHz) of the base 51 may be, for example, about 9 to 10.

[0018] The electrostatic electrode 52 is a thin-film electrode, and is built into the base 51. The electrostatic electrode 52 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 52 and the wafer. This allows the wafer to be adsorbed and held on the mounting surface 51a of the base 51 of the electrostatic chuck 50. The adsorption and holding force becomes stronger as the voltage applied to the electrostatic electrode 52 becomes higher. The electrostatic electrode 52 may be of either a monopolar or bipolar shape. Examples of materials that can be used for the electrostatic electrode 52 include tungsten (W) and molybdenum (Mo).

[0019] The heating element 53 is built into the base 51 on a side closer to the base plate 10 than the electrostatic electrode 52. The heating element 53 generates heat when a voltage is applied from outside the substrate fixing device 1, and heats the mounting surface 51a of the base 51 to a predetermined temperature. The heating element 53 can heat the mounting surface 51a of the base 51 to a temperature of, for example, about 250°C or higher and 400°C or lower. The heating element 53 can be made of, for example, tungsten, molybdenum, or the like. The heating element 53 can be formed in, for example, a concentric circular pattern.

[0020] The adhesive layer 20 is provided on the base plate 10. The adhesive layer 20 has, for example, a single-layer structure. The adhesive layer 20 preferably has a thermal conductivity of 2 W / mK or more. For example, a silicone adhesive can be used as the material for the adhesive layer 20. The adhesive layer 20 preferably has a thickness equal to or greater than the thickness of the heat insulating layer 30. The adhesive layer 20 may have a thickness of, for example, 0.1 mm or more and 3.0 mm or less.

[0021] The adhesive layer 20 may have a laminated structure. In the example of FIG. 1, the adhesive layer 20 has a laminated structure in which a second adhesive layer 22 is laminated on a first adhesive layer 21. For example, by forming the second adhesive layer 22 from an adhesive with a high thermal conductivity and forming the first adhesive layer 21 from an adhesive with a low elastic modulus, it is possible to obtain an effect of reducing stress caused by the difference in thermal expansion between the metal base plate 10 and the ceramic substrate 51. For example, a silicone adhesive or an epoxy adhesive can be used as the material of the first adhesive layer 21. For example, a silicone adhesive or an epoxy adhesive can be used as the material of the second adhesive layer 22.

[0022] The heat insulating layer 30 is provided on the adhesive layer 20. The heat insulating layer 30 has a lower thermal conductivity than the base 51 and adhesive layer 20 constituting the electrostatic chuck 50. The thickness of the heat insulating layer 30 can be, for example, 0.1 mm or more and 2.0 mm or less. By providing the heat insulating layer 30 on the electrostatic chuck 50 side of the adhesive layer 20, it is possible to suppress the heat generated by the heating element 53 from being transferred to the adhesive layer 20. This makes it difficult for the adhesive layer 20 to lose weight due to deterioration or decomposition of the adhesive layer 20, and it is possible to suppress the base 51 from peeling off from the base plate 10.

[0023] The thickness and thermal conductivity of the heat insulating layer 30 can be determined taking into consideration an increase in the thermal resistance of the heat insulating layer 30. Details will be shown in a simulation described later, but for example, when the temperature near the mounting surface 51a of the base 51 is 250°C, if it is desired to suppress the temperature applied to the adhesive layer 20 to 180°C or less, if the thickness of the heat insulating layer 30 is 1 mm, the thermal conductivity can be 1 W / mK or less. Also, if the thickness of the heat insulating layer 30 is 0.1 mm, the thermal conductivity can be 0.1 W / mK or less.

[0024] If the heat insulating layer 30 is not provided, when the temperature in the vicinity of the mounting surface 51a of the base 51 becomes high, 250° C. or more and 400° C. or less, the adhesive layer 20 also becomes high at a similar temperature. Therefore, the weight of the adhesive layer 20 decreases, and the adhesive layer 20 is destroyed, and the likelihood that the base 51 will peel off from the base plate 10 increases.

[0025] The adhesive layer 20 preferably has a weight loss rate of 0 to 0.1% at 250°C obtained by TGDTA measurement. In other words, the material, thickness, and thermal conductivity of the heat insulating layer 30 are preferably selected so that the weight loss rate of the adhesive layer 20 obtained by TGDTA measurement is 0 to 0.1% at 250°C. Since the adhesive layer 20 is less likely to be broken, the substrate 51 can be prevented from peeling off from the base plate 10. The TGDTA measurement is a method for simultaneously analyzing thermogravimetry and differential heat, and can simultaneously measure the weight change and endothermic and exothermic reactions associated with changing the temperature of a sample.

[0026] For example, a silicone-based or epoxy-based insulating resin containing a filler can be used as the material of the heat insulating layer 30. The above-mentioned thermal conductivity can be achieved by adjusting the composition of the material and the type and content of the filler.

[0027] Moreover, by providing the heat insulating layer 30, it is possible to prevent the heat generated by the heating element 53 from escaping to the base plate 10 side. Moreover, by making the adhesive layer 20 thicker, it is possible to further prevent the heat generated by the heating element 53 from escaping to the base plate 10 side.

[0028] First Modification of the First Embodiment In the first modification of the first embodiment, an example of a substrate fixing device having a sealant is shown. Note that in the first modification of the first embodiment, the description of the same components as those in the already described embodiment may be omitted.

[0029] 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 seal material 60.

[0030] In the substrate fixing device 1A, the adhesive layer 20 and the heat insulating layer 30 are arranged so as to expose the outer periphery of the base plate 10 in an annular shape. A sealant 60 is arranged on the annularly exposed area of ​​the outer periphery of the base plate 10 to cover the outer periphery of the adhesive layer 20 and the heat insulating layer 30. The upper surface of the sealant 60 is in close contact with the lower surface of the substrate 51, and the lower surface of the sealant 60 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 60. A resin having higher plasma resistance than the adhesive layer 20 and the heat insulating layer 30 may be used as the sealant 60.

[0031] In this manner, by disposing the sealant 60 so that the adhesive layer 20 and the heat insulating layer 30 are not exposed to the outside of the substrate fixing device 1A, the adhesive layer 20 and the heat insulating layer 30 can be airtightly isolated from the plasma during plasma etching, etc. Therefore, deterioration of the adhesive layer 20 and the heat insulating layer 30 can be suppressed.

[0032] Second Embodiment In the second embodiment, an example of a substrate fixing device in which a heating element is disposed under an electrostatic chuck is shown. Note that in the second embodiment, the description of the same components as those in the already described embodiments may be omitted.

[0033] 3 is a simplified cross-sectional view illustrating a substrate fixing device according to a second embodiment. As shown in FIG. 3, the substrate fixing device 2 is mainly different from the substrate fixing device 1 in that the substrate fixing device 2 has a heat generating part 40.

[0034] In the substrate fixing device 2, the electrostatic chuck 50A does not include a built-in heating element, unlike the electrostatic chuck 50. In the substrate fixing device 2, the heating part 40 is disposed below the electrostatic chuck 50A.

[0035] Heat generating section 40 has an insulating resin layer 41 provided between base 51 of electrostatic chuck 50A and heat insulating layer 30, and a heat generating element 42 built into insulating resin layer 41. In heat generating section 40, the periphery of heat generating element 42 is covered with insulating resin layer 41 to be protected from the outside.

[0036] For example, epoxy resin or bismaleimide triazine resin having high thermal conductivity and high heat resistance can be used as the insulating resin layer 41. The thermal conductivity of the insulating resin layer 41 is preferably 3 W / mK or more. The thermal conductivity of the insulating resin layer 41 can be improved by adding a filler such as alumina or aluminum nitride to the insulating resin layer 41. The glass transition temperature (Tg) of the insulating resin layer 41 is preferably 250° C. or more. The thickness of the insulating resin layer 41 is preferably about 100 to 150 μm, and the thickness variation of the insulating resin layer 41 is preferably ±10% or less.

[0037] The heating element 42 generates heat by applying a voltage from outside the substrate fixing device 2, and heats the mounting surface 51a of the base 51 to a predetermined temperature. The heating element 42 can heat the mounting surface 51a of the base 51 to a temperature of, for example, 250°C or higher and 400°C or lower. The material of the heating element 42 can be, for example, copper (Cu), tungsten (W), nickel (Ni), aluminum (Al), constantan (Cu / Ni / Mn / Fe alloy), geranine (Cu / Mn / Sn alloy), manganin (Cu / Mn / Ni alloy), etc. The heating element 42 can be formed, for example, in a concentric pattern.

[0038] In order to improve the adhesion between the heating element 42 and the insulating resin layer 41 at high temperatures, it is preferable that at least one surface (either the upper or lower surface or both) of the heating element 42 is roughened. Of course, both the upper and lower surfaces of the heating element 42 may be roughened. In this case, different roughening methods may be used for the upper and lower surfaces of the heating element 42. The roughening method is not particularly limited, but examples thereof include an etching method, a method using a coupling agent-based surface modification technique, and a method using dot processing with a UV-YAG laser having a wavelength of 355 nm or less.

[0039] The heat insulating layer 30 has a lower thermal conductivity than the base 51, the adhesive layer 20, and the insulating resin layer 41. This makes it possible to suppress the heat generated by the heating element 42 from being transferred to the adhesive layer 20, as in the first embodiment. It also makes it possible to suppress the heat generated by the heating element 42 from escaping to the base plate 10. Furthermore, by making the adhesive layer 20 thicker, it is possible to further suppress the heat generated by the heating element 42 from escaping to the base plate 10.

[0040] <simulation> A simulation was performed on the conditions of the insulating layer 30 so that the maximum temperature at the top of the adhesive layer 20 would be 180°C or less when the substrate fixing device 1 was operated so that the temperature of the mounting surface 51a of the base 51 was 250°C and the cooling temperature of the cooling medium in the flow path 15 was 70°C.

[0041] Specifically, the simulation was performed for the case where the heat insulating layer 30 was not provided, and for the cases where the thickness of the heat insulating layer 30 was 1.0 mm and the thermal conductivity of the heat insulating layer 30 was 2 W / mK, 1 W / mK, and 0.5 W / mK. In the simulation, the maximum temperature of the adhesive layer 20 and the increase in the thermal resistance of the heat insulating layer 30 were calculated. For reference, the output required to raise the temperature of the mounting surface 51a of the base 51 to 250°C was also obtained.

[0042] [Table 1] The results are shown in Figure 4 and Table 1. Note that Figure 4 shows the cross-sectional temperature of the electrostatic chuck, the temperature distribution of the insulating layer, and the temperature distribution of the adhesive layer when the conditions of the insulating layer are changed. As shown in Figure 4 and Table 1, the simulation showed that when the insulating layer 30 is not present, the maximum temperature at the top of the adhesive layer 20 is 230°C. It was also found that when the insulating layer 30 is 1.0 mm thick and has a thermal conductivity of 1 W / mK, the maximum temperature at the top of the adhesive layer 20 is 180°C, which is 50°C lower than when the insulating layer 30 is not present. In addition, at this time, the increase in thermal resistance of the insulating layer 30 is 0.001 m 2 It was K / W.

[0043] Here, the simulation was performed for a case where the thickness of the insulating layer 30 was 1.0 mm, but the calculated increase in thermal resistance of the insulating layer 30 (0.001 mm 2 By using the above-mentioned ratio (K / W), it is possible to obtain the thermal conductivity required to make the maximum temperature of the upper part of the adhesive layer 20 180° C. even when the thickness of the insulating layer 30 is other than 1.0 mm. For example, if the thickness of the insulating layer 30 is 0.1 mm, then 0.1 [mm] / 0.001 [m 2 When the thermal conductivity of the insulating layer 30 is 0.1 [W / mK], the maximum temperature at the top of the adhesive layer 20 is 180°C.

[0044] Thus, the thickness of the insulating layer 30 and the thermal conductivity of the insulating layer 30 are such that the increase in thermal resistance of the insulating layer 30 is 2 K / W or less. As a result, even if the temperature in the vicinity of the mounting surface 51a of the substrate 51 reaches 250° C., the temperature applied to the adhesive layer 20 can be suppressed to 180° C. or less. As a result, the adhesive layer 20 is less likely to lose weight due to deterioration or decomposition of the adhesive layer 20, and the substrate 51 can be prevented from peeling off from the base plate 10.

[0045] Also, when the temperature in the vicinity of the mounting surface 51a of the base 51 is set to 400° C. or the like, the thickness and thermal conductivity required for the heat insulating layer 30 can be found by a method similar to that described above.

[0046] Although preferred embodiments have been described above in detail, 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.

[0047] For example, 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, etc., in addition to semiconductor wafers (silicon wafers, etc.). [Explanation of symbols]

[0048] 1,1A,2 Board fixing device 10 Base plate 15 Flow Path 15a Cooling medium introduction part 15b Coolant discharge section 20 Adhesive layer 21 1st adhesive layer 22 Second adhesive layer 30 Thermal insulation layer 40 Heating Part 41 Insulating resin layer 42,53 Heating element 50,50A electrostatic chuck 51 Base 51a Placement surface 52 Electrostatic Electrode 60 Sealing material

Claims

1. A base plate; an adhesive layer provided on the base plate; A heat insulating layer provided on the adhesive layer; an electrostatic chuck provided on the thermal insulation layer; The electrostatic chuck includes a base and an electrostatic electrode built into the base, The heat insulating layer has a lower thermal conductivity than the base and the adhesive layer.

2. The substrate fixing device according to claim 1 , wherein the adhesive layer has a thickness equal to or greater than the thickness of the heat insulating layer.

3. The substrate fixing device according to claim 1 , further comprising a heating element built into the base.

4. an insulating resin layer provided between the base and the heat insulating layer; A heating element is embedded in the insulating resin layer, The substrate fixing device according to claim 1 , wherein the heat insulating layer has a lower thermal conductivity than the insulating resin layer.

5. The substrate fixing device according to claim 1 , wherein the adhesive layer has a laminated structure in which a second adhesive layer is laminated on a first adhesive layer.

6. the adhesive layer and the heat insulating layer are arranged to expose an outer periphery of the base plate in an annular shape; The substrate fixing device according to claim 1 , wherein a sealant is disposed on the annular exposed area of ​​the outer periphery of the base plate, the sealant covering the outer periphery of the adhesive layer and the heat insulating layer.

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