substrate fixing device

Abstract

To provide a substrate fixing device that can improve temperature uniformity on the substrate mounting surface. [Solution] The substrate fixing device comprises a base plate having a first adhesive surface, a substrate mounting surface on which a substrate is placed, and a second adhesive surface opposite to the substrate mounting surface, and an electrostatic chuck that adsorbs and holds the substrate, and an adhesive layer that adheres the first adhesive surface of the base plate and the second adhesive surface of the electrostatic chuck, wherein the electrostatic chuck comprises a substrate having a third adhesive surface that constitutes a part of the second adhesive surface and has a recess, an electronic component housed in the recess, and a resin layer having a fourth adhesive surface that seals the electronic component within the recess and constitutes another part of the second adhesive surface, and the temperature corresponding to the extreme value of the loss tangent of the resin layer in the temperature range of -150°C to 250°C is -70°C or lower.

Description

Technical Field

[0001] The present disclosure relates to a substrate fixing device. Background Art

[0002] Conventionally, film forming apparatuses and plasma etching apparatuses used for manufacturing semiconductor devices include a stage for accurately holding a substrate such as a silicon wafer in a vacuum processing chamber. As such a stage, for example, a substrate fixing device that suction-holds a substrate by an electrostatic chuck mounted on a base plate has been proposed.

[0003] The substrate fixing device includes a base plate, an electrostatic chuck mounted on the base plate, and an adhesive layer that bonds the base plate and the electrostatic chuck together. The electrostatic chuck incorporates an electrode for suctioning the substrate and a heating element for controlling the temperature of the substrate that is the suction target. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2024-030799 Patent Document 2 Japanese Unexamined Patent Publication No. 2023-071003 Summary of the Invention Problems to be Solved by the Invention

[0005] In a substrate fixing device, variation in heat generation density may occur on the substrate mounting surface of the electrostatic chuck that suctions the substrate. Such variation in heat generation density causes temperature variation in the substrate. Variation in substrate temperature causes variation in etching rate, for example, in a plasma etching apparatus, and thus becomes a factor that reduces the yield of semiconductor elements. Therefore, improvement of temperature uniformity on the substrate mounting surface of the electrostatic chuck is demanded.

[0006] This disclosure aims to provide a substrate fixing device that can improve temperature uniformity on the substrate mounting surface. [Means for solving the problem]

[0007] According to one embodiment of the present disclosure, a substrate fixing device is provided, comprising: a base plate having a first adhesive surface; a substrate mounting surface on which a substrate is placed; a second adhesive surface opposite to the substrate mounting surface, and an electrostatic chuck for adsorbing and holding the substrate; and an adhesive layer for bonding the first adhesive surface of the base plate and the second adhesive surface of the electrostatic chuck, wherein the electrostatic chuck comprises a substrate having a third adhesive surface that constitutes a part of the second adhesive surface and has a recess; an electronic component housed in the recess; and a resin layer that seals the electronic component within the recess and has a fourth adhesive surface that constitutes another part of the second adhesive surface, and the temperature corresponding to the extreme value of the loss tangent of the resin layer in a temperature range of -150°C to 250°C is -70°C or lower. [Effects of the Invention]

[0008] According to this disclosure, it is possible to improve the uniformity of temperature on the substrate mounting surface. [Brief explanation of the drawing]

[0009] [Figure 1] This is a cross-sectional view illustrating a substrate fixing device according to an embodiment. [Figure 2] This figure shows the relationship between the measured temperature and the loss tangent. [Modes for carrying out the invention]

[0010] The inventors of the present invention conducted intensive research to investigate the cause of variations in heat generation density on the substrate mounting surface of conventional substrate fixing devices. As a result, it became clear that when a substrate fixing device is used in a low-temperature environment of -40°C or below, cracks may occur in the resin layer, where an electrostatic chuck has a recess for housing electronic components used for temperature control, etc., and the recess is filled with a resin layer. It also became clear that cracks in the resin layer reduce the uniformity of the temperature transfer characteristics, causing variations in heat generation density. Furthermore, it became clear that the cause of cracks in the resin layer is that the elastic modulus of the resin layer increases rapidly in low-temperature environments of -40°C or below, and a large stress acts on the resin layer when the electrostatic chuck thermally shrinks. Based on these findings, the inventors of the present invention conducted further intensive research to reduce the stress acting on the resin layer in low-temperature environments and came up with the following embodiment.

[0011] Embodiments of this disclosure will be described in detail below with reference to the accompanying drawings. In this specification and the drawings, components having substantially the same functional configuration will be denoted by the same reference numerals to avoid redundant descriptions.

[0012] The embodiment relates to a substrate fixing device. Figure 1 is a cross-sectional view illustrating a substrate fixing device according to the embodiment.

[0013] As shown in Figure 1, the substrate fixing device 10 includes a base plate 20, an electrostatic chuck 30, and an adhesive layer 50. The base plate 20 is a base member for mounting the electrostatic chuck 30. The electrostatic chuck 30 is the part that adsorbs and holds the substrate W, which is the object to be adsorbed. The electrostatic chuck 30 is, for example, a temperature control device that adjusts the temperature of the substrate W. The substrate W is, for example, a silicon wafer.

[0014] The base plate 20 is formed, for example, in the shape of a circular plate. The planar shape of the base plate 20 is, for example, circular. The diameter of the base plate 20 is, for example, about 200 mm to 300 mm. The thickness of the base plate 20 is, for example, about 20 mm to 50 mm.

[0015] Examples of materials for the base plate 20 include metallic materials such as aluminum and cemented carbide, as well as composite materials of these metallic materials and ceramic materials. The base plate 20 can also be used, for example, as an electrode for controlling the plasma. For example, by supplying a predetermined high-frequency power to the base plate 20, the energy for causing ions in the generated plasma state to collide with the substrate W adsorbed on the electrostatic chuck 30 can be controlled, thereby effectively performing the etching process.

[0016] The base plate 20 has a first bonding surface 20A (here, the top surface). The first bonding surface 20A is the surface that is bonded to the adhesive layer 50. The first bonding surface 20A faces the electrostatic chuck 30. Here, "facing" in this disclosure includes both cases where a member other than the two parts is interposed between the two parts and cases where nothing is interposed between the two parts.

[0017] A cooling passage 21 is provided inside the base plate 20. The cooling passage 21 has an introduction section 22 at one end and a discharge section 23 at the other end. The cooling passage 21 is connected to a cooling medium control device (not shown) provided outside the substrate fixing device 10. The cooling medium control device introduces a cooling medium into the cooling passage 21 from the introduction section 22 and discharges the cooling medium from the discharge section 23. By circulating the cooling medium in the cooling passage 21 and cooling the base plate 20, the substrate W adsorbed on the electrostatic chuck 30 can be cooled. As the cooling medium, for example, water or a fluorine-based fluid can be used. In addition to the cooling passage 21, the base plate 20 may also be provided with a gas passage for introducing an inert gas to cool the substrate W adsorbed on the electrostatic chuck 30.

[0018] The electrostatic chuck 30 is formed in, for example, a circular plate shape. The planar shape of the electrostatic chuck 30 is, for example, circular. The diameter of the electrostatic chuck 30 may, for example, be equal to the diameter of the base plate 20 or may be larger than the diameter of the base plate 20. In the present embodiment, the diameter of the electrostatic chuck 30 is equal to the diameter of the base plate 20. The diameter of the electrostatic chuck 30 is, for example, approximately 200 mm to 300 mm. The thickness of the electrostatic chuck 30 is, for example, approximately 1 mm to 10 mm.

[0019] The electrostatic chuck 30 includes, for example, a base body 31, an electrostatic electrode 32 and a heating element 33 embedded in the base body 31, an electronic component 34, and a resin layer 40. The electrostatic chuck 30 has a substrate placement surface 30A (the upper surface in this example) on which a substrate W is placed, and a second adhesive surface 30B (the lower surface in this example) opposite to the substrate placement surface 30A. The substrate placement surface 30A and the second adhesive surface 30B are provided on opposite sides of each other in the thickness direction of the electrostatic chuck 30 (the vertical direction in the drawings). For example, the substrate placement surface 30A and the second adhesive surface 30B are parallel to each other. The electrostatic chuck 30 is, for example, a Johnsen-Rahbek type electrostatic chuck. Note that the electrostatic chuck 30 may alternatively be a Coulomb force type electrostatic chuck.

[0020] Examples of the material of the base body 31 include insulating materials. Specific examples of the material of the base body 31 include ceramics such as alumina, aluminum nitride, and silicon nitride, and organic materials such as silicone resin and polyimide resin. Ceramics are preferable as the material of the base body 31 in terms of easy availability, easy processability, and relatively high resistance to plasma and the like. In particular, when the material of the base body 31 is aluminum nitride, its thermal conductivity is as high as approximately 15 W / (m·K) to 250 W / (m·K), which is preferable for reducing the in-plane temperature difference of the substrate W adsorbed to the electrostatic chuck 30.

[0021] The base body 31 has a third adhesive surface 31B that forms part of a second adhesive surface 30B. A plurality of recesses 35 are provided on the third adhesive surface 31B. Each recess 35 is formed so as to be recessed from the third adhesive surface 31B toward the substrate mounting surface 30A. The depth of each recess 35 is, for example, approximately 800 μm to 1000 μm. The planar shape of each recess 35 may be any shape and any size. The planar shape of each recess 35 is, for example, circular or elliptical.

[0022] The electrostatic electrode 32 is an electrode for adsorbing a substrate W. The electrostatic electrode 32 is an electrode formed in a thin film shape. The electrostatic electrode 32 is embedded in the base body 31. The electrostatic electrode 32 is embedded, for example, in a portion located near the substrate mounting surface 30A in the thickness direction of the base body 31. The electrostatic electrode 32 is disposed, for example, on a plane parallel to the substrate mounting surface 30A. The electrostatic electrode 32 is electrically connected to an adsorption power supply (not shown) provided outside the substrate fixing apparatus 10. When a predetermined voltage is applied from the adsorption power supply, the electrostatic electrode 32 generates an adsorption force due to static electricity between itself and the substrate W mounted on the substrate mounting surface 30A. Thereby, the substrate W can be adsorbed and held on the substrate mounting surface 30A. The adsorption holding force of the electrostatic chuck 30 increases as the voltage applied to the electrostatic electrode 32 increases. The electrostatic electrode 32 may have a unipolar shape or a bipolar shape. Examples of materials for the electrostatic electrode 32 include tungsten (W) and molybdenum (Mo). Although each drawing shows one electrostatic electrode 32, it actually includes a plurality of electrodes arranged on the same plane.

[0023] Multiple heating elements 33 are used to heat the substrate W. The multiple heating elements 33 are embedded in the base body 31. The multiple heating elements 33 are embedded, for example, between the electrostatic electrode 32 and the second bonding surface 30B in the thickness direction of the base body 31. The multiple heating elements 33 are arranged, for example, on a plane parallel to the substrate mounting surface 30A. Each heating element 33 is electrically insulated from the electrostatic electrode 32. Examples of materials for the heating elements 33 include copper (Cu), tungsten, nickel (Ni), and constantan (an alloy of Cu, Ni, Mn, and Fe). The thickness of the heating elements 33 is, for example, about 20 μm to 100 μm. The multiple heating elements 33 are arranged, for example, in a concentric circular pattern.

[0024] Multiple heating elements 33 are electrically connected to a heating power supply (not shown) located outside the substrate fixing device 10. The multiple heating elements 33 generate heat in accordance with the voltage applied from the heating power supply. The multiple heating elements 33 heat the substrate mounting surface 30A to a predetermined temperature. The heating elements 33 can, for example, heat the substrate mounting surface 30A to a temperature of approximately 250°C to 300°C.

[0025] The electronic component 34 is housed in the recess 35. The electronic component 34 is located on the bottom surface of the recess 35. The electronic component 34 is electrically connected to, for example, the electrostatic electrode 32 or the heating element 33. The electronic component 34 is an electronic component used, for example, for temperature control of the substrate mounting surface 30A. Examples of electronic components 34 include diodes, capacitors, and thermistors.

[0026] The resin layer 40 is provided within the recesses 35. The resin layer 40 is formed to seal, for example, the electronic components 34 housed in each recess 35, and fills the recesses 35. The resin layer 40 has a fourth adhesive surface 40B which constitutes another part of the second adhesive surface 30B. The second adhesive surface 30B of the electrostatic chuck 30 has a third adhesive surface 31B of the substrate 31 and a fourth adhesive surface 40B of the resin layer 40. For example, the fourth adhesive surface 40B is flush with the third adhesive surface 31B. Examples of materials for the resin layer 40 include silicone resin. The temperature corresponding to the extreme value of the loss tangent of the resin layer 40 in the temperature range of -150°C to 250°C is -70°C or lower, preferably -100°C or lower. The resin layer 40 may contain fillers such as alumina or aluminum nitride.

[0027] The adhesive layer 50 adheres the electrostatic chuck 30 to the base plate 20. The adhesive layer 50 conducts heat from the electrostatic chuck 30 to the base plate 20, for example. In other words, the adhesive layer 50 functions as an adhesive that bonds the base plate 20 and the electrostatic chuck 30, as well as a heat conductive member.

[0028] The adhesive layer 50 has a first layer 51, a second layer 52, and a third layer 53. The first layer 51 is located between the second layer 52 and the third layer 53. The second layer 52 is located between the first layer 51 and the base plate 20, and the third layer is located between the first layer 51 and the electrostatic chuck 30. For example, the first layer 51 is thicker than each of the second layer 52 and the third layer 53. For example, in the adhesive layer 50, the first layer 51 functions as the main adhesive layer, and the second layer 52 and the third layer 53 function as adhesive auxiliary layers.

[0029] The material for the first layer 51 is preferably a material with high thermal conductivity. Examples of materials for the first layer 51 include silicone adhesives. The first layer 51 may contain fillers such as alumina or aluminum nitride. The second layer 52 and the third layer 53 include, for example, surface modifiers, coupling agents, or resinous substances that readily interact with the first layer 51. For example, the second layer 52 is applied to the first bonding surface 20A, and the third layer 53 is applied to the second bonding surface 30B.

[0030] In the substrate fixing device 10, as described above, the temperature corresponding to the extreme value of the loss tangent of the resin layer 40 in the temperature range of -150°C to 250°C is -70°C or lower. Therefore, even if the substrate fixing device 10 is used in a low-temperature environment of -40°C or lower and undergoes thermal shrinkage, the elastic modulus of the resin layer 40 does not increase significantly, and the stress acting on the resin layer 40 does not become large enough to cause cracks in the resin layer 40. Consequently, the substrate fixing device 10 can reduce the occurrence of cracks and improve the temperature uniformity on the substrate mounting surface 30A.

[0031] Here, we will describe the experiment conducted by the present inventor. In this experiment, test specimens were prepared using two types of adhesives (adhesive A and adhesive B), and their loss tangents were measured. The results are shown in Figure 2. Both adhesive A and adhesive B are silicone resins, but at least the side chain structure differs between adhesive A and adhesive B. The loss tangent was measured by dynamic mechanical analysis (DMA). Figure 2 shows the relationship between the measurement temperature and the loss tangent.

[0032] The measurement conditions for the loss tangent are as follows:

[0033] Measurement device: DMA6100 (manufactured by Hitachi High-Tech Science) Measurement temperature range: -150℃ to 250℃ Heating rate: 5°C / min Measurement mode: Tensile Measurement frequency: 1Hz Specimen shape: Strip shape Specimen dimensions: Length 15mm x Width 15mm x Thickness 0.1mm~1mm Distortion amplitude: 10 μm

[0034] In DMA, the complex modulus of elasticity (G) is expressed by the following equation (1). * The storage modulus (G') and loss modulus (G") were measured.

[0035] G * =G'+G"i ··· (1) Here, the storage modulus (G') is a value that indicates the hardness of the viscoelastic material, and the loss modulus (G") is a value that indicates the viscosity of the viscoelastic material.

[0036] Furthermore, in DMA, the loss tangent tanδ, expressed by the following equation (2), was calculated from the storage modulus (G') and loss modulus (G"). The loss tangent tanδ is a value that indicates the degree of viscosity contribution to the viscoelastic material. The temperature corresponding to the extreme value of the loss tangent tanδ is also called the glass transition temperature (Tg).

[0037] tanδ = G" / G' ··· (2)

[0038] As shown in Figure 2, the measurement data obtained from the test specimens indicates that for adhesive A, the temperature corresponding to the extreme value of the loss tangent tanδ is approximately -120°C (below -70°C), and for adhesive B, the temperature corresponding to the extreme value of the loss tangent tanδ is approximately -50°C. In the above embodiment, adhesive A can be used for the resin layer 40.

[0039] The inventors of this application calculated by simulation the stress acting on the resin layer 40 when adhesive A is used in the resin layer 40, at temperatures of -60°C, -80°C, and -100°C of the substrate 31. For comparison, the inventors also calculated by simulation the stress acting on the resin layer when adhesive B is used instead of the resin layer 40 using adhesive A, at temperatures of -60°C, -80°C, and -100°C of the substrate 31. The results are shown in Table 1.

[0040] [Table 1]

[0041] As shown in Table 1, in the embodiment using adhesive A, the stress acting on the resin layer 40 was found to be approximately 0.4% to 0.6% of the stress acting on the resin layer in the reference example using adhesive B. In other words, it was confirmed that the stress ratio was extremely small, approximately 0.4% to 0.6%.

[0042] Furthermore, the first layer 51 may be formed from the same type of adhesive as the resin layer 40. That is, the temperature corresponding to the extreme value of the loss tangent of the first layer 51 in the temperature range of -150°C to 250°C may be -70°C or lower.

[0043] The fourth adhesive surface 40B of the resin layer 40 does not have to be flush with the third adhesive surface 31B of the substrate 31. For example, the fourth adhesive surface 40B may have a convex shape that bulges out from the third adhesive surface 31B toward the first adhesive surface 20A.

[0044] Although preferred embodiments have been described in detail above, this disclosure is not limited to the embodiments described above, and various modifications and substitutions can be made to the embodiments described above without departing from the scope of the claims. [Explanation of Symbols]

[0045] 10 Board fixing device 20 base plates 20A 1st adhesive surface 30 Electrostatic Chuck 30A Substrate mounting surface 30B 2nd adhesive surface 31 Base 31B 3rd adhesive surface 32 electrostatic electrodes 33 Heating element 34 Electronic Components 35 recess 40 resin layer 40B 4th adhesive surface 50 Adhesive layer

Claims

1. A base plate having a first adhesive surface, An electrostatic chuck having a substrate mounting surface on which the substrate is placed, and a second adhesive surface opposite to the substrate mounting surface, which holds the substrate by adsorption, An adhesive layer that bonds the first adhesive surface of the base plate and the second adhesive surface of the electrostatic chuck, It has, The electrostatic chuck is, A base having a third adhesive surface that constitutes a part of the second adhesive surface and has a recess, The electronic component housed in the recess, A resin layer having a fourth adhesive surface that seals the electronic component within the recess and constitutes another part of the second adhesive surface, It has, A substrate fixing device in which the temperature corresponding to the extreme value of the loss tangent of the resin layer in the temperature range of -150°C to 250°C is -70°C or lower.

2. The substrate fixing device according to claim 1, wherein the temperature corresponding to the extreme value of the loss tangent of the resin layer in a temperature range of -150°C to 250°C is -100°C or lower.

3. The substrate fixing apparatus according to claim 1 or 2, wherein the adhesive layer has a layer whose temperature corresponding to the extreme value of the loss tangent in a temperature range of -150°C to 250°C is -70°C or lower.

4. The substrate fixing apparatus according to claim 1 or 2, wherein the resin layer contains a filler.

5. The electrostatic chuck is built into the substrate and has electrodes for adsorbing the substrate, The substrate fixing device according to claim 1 or 2, wherein the electronic component is electrically connected to the electrode.

6. The electrostatic chuck is built into the substrate and has a heating element that heats the substrate, The substrate fixing device according to claim 1 or 2, wherein the electronic component is electrically connected to the heating element.

7. The substrate fixing device according to claim 1 or 2, wherein the base plate has a cooling passage through which a cooling medium flows.

8. The substrate fixing device according to claim 1 or 2, wherein the third adhesive surface and the fourth adhesive surface are flush.

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