Method for manufacturing an electrostatic chuck

Abstract

To provide an electrostatic chuck with further improved heat soaking property.SOLUTION: An electrostatic chuck includes a substrate having a mounting surface on which an object to be adsorbed is mounted, a heat diffusion layer directly formed on the back surface of the substrate, which is located on the side opposite to the mounting surface of the substrate, an insulating layer arranged so as to be in contact with the heat diffusion layer on the opposite side of the heat diffusion layer from the substrate, and a heating element built into the insulating layer, and the heat diffusion layer is formed of a material having a higher thermal conductivity than the insulating layer.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a manufacturing method of an electrostatic chuck. of Manufacturing method to Related to.

Background Art

[0002] Conventionally, a film forming apparatus (for example, a CVD apparatus or a PVD apparatus) and a plasma etching apparatus used when manufacturing semiconductor devices such as ICs and LSIs have a stage for accurately holding a wafer in a vacuum processing chamber.

[0003] As such a stage, for example, a substrate fixing device that adsorbs and holds a wafer, which is an object to be adsorbed, by an electrostatic chuck mounted on a base plate has been proposed. The electrostatic chuck includes, for example, a heating element and a metal layer that equalizes the heat from the heating element.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in recent years, further improvement in heat uniformity has been demanded for electrostatic chucks, and it has been difficult to satisfy the requirement for improving heat uniformity with the conventional structure.

[0006] The present invention has been made in view of the above points, and an object thereof is to provide an electrostatic chuck with further improved heat uniformity. Manufacturing method of To provide.

Means for Solving the Problems

[0007] This electrostatic chuck Manufacturing method of Is, A step of directly forming a thermally diffused layer with a uniform film thickness on one surface of a substrate; a step of directly disposing a first insulating resin film on the surface of the thermally diffused layer opposite to the substrate; a step of disposing a metal foil on the first insulating resin film; a step of patterning the metal foil to form a heating element; a step of disposing a second insulating resin film covering the heating element on the first insulating resin film; and a step of curing the first insulating resin film and the second insulating resin film to form an insulating layer directly bonded to the thermally diffused layer, wherein the thermally diffused layer is formed of a material having a higher thermal conductivity than the insulating layer .

Effects of the Invention

[0008] According to the disclosed technology, an electrostatic chuck with further improved heat uniformity Manufacturing method of can be provided.

Brief Description of the Drawings

[0009]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0010] Hereinafter, embodiments for carrying out the invention will be described with reference to the drawings. In each drawing, the same reference numerals are assigned to the same components, and redundant descriptions may be omitted.

[0011] [Structure of Substrate Fixing Device] FIG. 1 is a cross-sectional view schematically illustrating the substrate fixing device according to the present embodiment. Referring to FIG. 1, the substrate fixing device 1 has, as main components, a base plate 10, an adhesive layer 20, and an electrostatic chuck 30.

[0012] The base plate 10 is a member for mounting the electrostatic chuck 30. The thickness of the base plate 10 can be, for example, about 20 to 50 mm. The base plate 10 is formed of, for example, aluminum and can also be used as an electrode or the like for controlling plasma. By supplying a predetermined high-frequency power to the base plate 10, the energy for causing ions or the like in the generated plasma state to collide with the wafer adsorbed on the electrostatic chuck 30 can be controlled, and the etching process can be effectively performed.

[0013] Inside the base plate 10, a water channel 15 is provided. The water channel 15 is provided with a cooling water introduction part 15a at one end and a cooling water discharge part 15b at the other end. The water channel 15 is connected to a cooling water control device (not shown) provided outside the substrate fixing device 1. The cooling water control device (not shown) introduces cooling water into the water channel 15 from the cooling water introduction part 15a and discharges the cooling water from the cooling water discharge part 15b. By circulating the cooling water in the water channel 15 to cool the base plate 10, the wafer adsorbed on the electrostatic chuck 30 can be cooled. In addition to the water channel 15, the base plate 10 may be provided with a gas path or the like for introducing an inert gas for cooling the wafer adsorbed on the electrostatic chuck 30.

[0014] The electrostatic chuck 30 is a part for adsorbing and holding a wafer as an object to be adsorbed. The planar shape of the electrostatic chuck 30 can be, for example, circular. The diameter of the wafer, which is the object to be adsorbed by the electrostatic chuck 30, can be, for example, about 8, 12, or 18 inches.

[0015] The electrostatic chuck 30 is mounted on one surface of the base plate 10 via an adhesive layer 20. As the adhesive layer 20, for example, a silicone-based adhesive can be used. The thickness of the adhesive layer 20 can be, for example, about 2 mm. The thermal conductivity of the adhesive layer 20 is preferably 2 W / mK or more. The adhesive layer 20 may have a laminated structure in which a plurality of adhesive layers are laminated. For example, by forming the adhesive layer 20 into a two-layer structure combining an adhesive with a high thermal conductivity and an adhesive with a low elastic modulus, an effect of reducing stress caused by the difference in thermal expansion from the aluminum base plate can be obtained.

[0016] The electrostatic chuck 30 has a base body 31, an electrostatic electrode 32, a heat diffusion layer 33, an insulating layer 34, and a heating element 35. The electrostatic chuck 30 is, for example, a Johnsen-Rahbek type electrostatic chuck. However, the electrostatic chuck 30 may be a Coulomb force type electrostatic chuck.

[0017] The base body 31 is a dielectric and has a placement surface 31a on which the object to be adsorbed is placed. As the base body 31, for example, ceramics such as aluminum oxide (Al2O3) and aluminum nitride (AlN) can be used. The thickness of the base body 31 can be, for example, about 1 to 10 mm, and the relative permittivity (1 kHz) of the base body 31 can be, for example, about 9 to 10.

[0018] The electrostatic electrode 32 is a thin-film electrode and is built into the base body 31. The electrostatic electrode 32 is connected to a power source provided outside the substrate fixing device 1. When a predetermined voltage is applied from the power source, an electrostatic adsorption force is generated between the electrostatic electrode 32 and the wafer. Thereby, the wafer can be adsorbed and held on the placement surface 31a of the base body 31 of the electrostatic chuck 30. The adsorption and holding force becomes stronger as the voltage applied to the electrostatic electrode 32 is higher. The electrostatic electrode 32 may have a single-pole shape or a bipolar shape. As the material of the electrostatic electrode 32, for example, tungsten, molybdenum, etc. can be used.

[0019] The heat diffusion layer 33 is directly formed on the back surface of the base body 31, which is located on the side opposite to the placement surface 31a of the base body 31. That is, the heat diffusion layer 33 is in contact with the back surface of the base body 31 without an adhesive layer or the like in between. The heat diffusion layer 33 is a layer that equalizes and diffuses the heat generated by the heating element 35, and is formed of a material having a higher thermal conductivity than the insulating layer 34. The thermal conductivity of the heat diffusion layer 33 is preferably 400 W / m·k or more. Examples of materials that can achieve such a thermal conductivity include metals such as copper (Cu), copper alloys, silver (Ag), silver alloys, and carbon nanotubes.

[0020] The heat diffusion layer 33 is preferably formed over the entire back surface of the base body 31. That is, the heat diffusion layer 33 is preferably formed in a solid state on the back surface of the base body 31, and preferably does not have patterning or openings. By doing so, the heat diffusion layer 33 can fully exhibit the effect of improving the heat uniformity. The thickness of the heat diffusion layer 33 can be, for example, about several nm to several 100 μm. The lower surface of the heat diffusion layer 33 is in contact with the upper surface of the insulating layer 34.

[0021] In a conventional electrostatic chuck, a metal layer or the like that functions as a heat diffusion layer was fixed to a substrate via an adhesive layer, or the metal layer was patterned into a predetermined shape, and sufficient heat uniformity could not be achieved.

[0022] The insulating layer 34 is disposed on the side opposite to the substrate 31 of the heat diffusion layer 33 so as to be in contact with the heat diffusion layer 33. The insulating layer 34 is a layer that insulates the heat diffusion layer 33 and the heating element 35. As the insulating layer 34, for example, an epoxy resin or a bismaleimide triazine resin having high thermal conductivity and high heat resistance can be used. The thermal conductivity of the insulating layer 34 is preferably 3 W / mK or more. By incorporating a filler such as alumina or aluminum nitride into the insulating layer 34, the thermal conductivity of the insulating layer 34 can be improved. Further, the glass transition temperature (Tg) of the insulating layer 34 is preferably 250°C or more. Further, the thickness of the insulating layer 34 is preferably about 100 to 150 μm, and the thickness variation of the insulating layer 34 is preferably ±10% or less.

[0023] The heating element 35 is built in the insulating layer 34. The periphery of the heating element 35 is covered with the insulating layer 34 and protected from the outside. The heating element 35 generates heat by applying a voltage from outside the substrate fixing device 1 and heats the mounting surface 31a of the substrate 31 to a predetermined temperature. The heating element 35 can heat the mounting surface 31a of the substrate 31 to about 250°C to 300°C, for example. As the material of the heating element 35, for example, copper (Cu), tungsten (W), nickel (Ni), constantan (an alloy of Cu / Ni / Mn / Fe), etc. can be used. The thickness of the heating element 35 can be, for example, about 20 to 100 μm. The heating element 35 can be, for example, a concentric pattern.

[0024] In order to improve the adhesion between the heating element 35 and the insulating layer 34 at high temperatures, it is preferable that at least one surface (one or both of the upper and lower surfaces) of the heating element 35 is roughened. Of course, both the upper and lower surfaces of the heating element 35 may be roughened. In this case, different roughening methods may be used for the upper and lower surfaces of the heating element 35. The roughening method is not particularly limited, and examples thereof include a method by etching, a method using a coupling agent-based surface modification technique, a method using dot processing with a UV-YAG laser having a wavelength of 355 nm or less, and the like.

[0025] [Method for manufacturing a substrate fixing device] Figs. 2 to 4 are diagrams illustrating the manufacturing process of the substrate fixing device according to the present embodiment. With reference to Figs. 2 to 4, the manufacturing process of the substrate fixing device 1 will be described centering on the formation process of the electrostatic chuck. Note that Figs. 2(a) to 4(a) are drawn in a state where the up and down are reversed compared to Fig. 1.

[0026] First, in the process shown in Fig. 2(a), a substrate 31 incorporating an electrostatic electrode 32 is produced by a well-known manufacturing method including a process of performing via processing on a green sheet, a process of filling the via with a conductive paste, a process of forming a pattern serving as an electrostatic electrode, a process of laminating and firing another green sheet, a process of planarizing the surface, and the like.

[0027] Next, in the process shown in Fig. 2(b), a thermal diffusion layer 33 is directly formed on one surface of the substrate 31. The thermal diffusion layer 33 can be directly formed on one surface of the substrate 31 by using a metal such as copper or silver and by a method such as sputtering, electroless plating, or spray coating. The thermal diffusion layer 33 is preferably formed over the entire surface of one surface of the substrate 31. When the thermal diffusion layer 33 is formed by sputtering, the thickness of the thermal diffusion layer 33 is about 10 nm or more and 500 nm or less. Since the thermal diffusion layer 33 formed by sputtering has a uniform film thickness, it has a high effect of improving heat uniformity. Here, the uniform film thickness means a case where the difference between the thickest part and the thinnest part of the thermal diffusion layer 33 is 10% or less.

[0028] Before forming the heat diffusion layer 33, it is preferable to perform a surface treatment on the substrate 31. The surface treatment is, for example, cleaning and reverse sputtering treatment. For example, the cleaning is performed by immersing in pure water and ultrasonic cleaning, followed by replacement with IPA and then vacuum drying. Further, for example, immediately before sputtering, after removing dirt such as carbon on one surface of the substrate 31 by reverse sputtering using Ar gas, the sputtering process is performed.

[0029] Next, in the process shown in FIG. 2(c), the insulating resin film 341 is directly disposed on the surface of the heat diffusion layer 33 opposite to the substrate 31 (the upper surface in FIG. 2(c)). The insulating resin film 341 is suitable in that it can suppress the entrapment of voids when laminated in a vacuum. The insulating resin film 341 is kept in a semi-cured state (B-stage) without being cured. Due to the adhesive force of the insulating resin film 341 in the semi-cured state, the insulating resin film 341 is temporarily fixed on the heat diffusion layer 33.

[0030] As the insulating resin film 341, for example, an epoxy resin or a bismaleimide triazine resin having high thermal conductivity and high heat resistance can be used. The thermal conductivity of the insulating resin film 341 is preferably 3 W / mK or more. By incorporating fillers such as alumina or aluminum nitride into the insulating resin film 341, the thermal conductivity of the insulating resin film 341 can be improved. Also, the glass transition temperature of the insulating resin film 341 is preferably 250°C or more. Also, from the viewpoint of enhancing the heat conduction performance (increasing the heat conduction speed), the thickness of the insulating resin film 341 is preferably 60 μm or less, and the thickness variation of the insulating resin film 341 is preferably ±10% or less.

[0031] Next, in the process shown in Fig. 3(a), a metal foil 351 is disposed on the insulating resin film 341. Since the metal foil 351 is the layer that finally becomes the heating element 35, the material of the metal foil 351 is the same as the material of the heating element 35 already exemplified. Considering the wiring formability by etching, the thickness of the metal foil 351 is preferably 100 μm or less. The metal foil 351 is temporarily fixed on the insulating resin film 341 by the adhesive force of the insulating resin film 341 in a semi-cured state.

[0032] Note that before disposing on the insulating resin film 341, it is preferable to roughen at least one surface (one or both of the upper and lower surfaces) of the metal foil 351. Of course, both the upper and lower surfaces of the metal foil 351 may be roughened. In this case, different roughening methods may be used for the upper and lower surfaces of the metal foil 351. The roughening method is not particularly limited, and examples thereof include a method by etching, a method using a coupling agent-based surface modification technique, a method using dot processing with a UV-YAG laser having a wavelength of 355 nm or less, and the like.

[0033] Also, in the method using dot processing, the necessary area of the metal foil 351 can be selectively roughened. Therefore, in the method using dot processing, it is not necessary to roughen the entire area of the metal foil 351, and it is sufficient to roughen at least the area to be left as the heating element 35 (that is, it is not necessary to roughen the area to be removed by etching).

[0034] Next, in the process shown in Fig. 3(b), the metal foil 351 is patterned to form the heating element 35. The heating element 35 can be, for example, a concentric pattern. Specifically, for example, a resist is formed on the entire surface of the metal foil 351, the resist is exposed and developed, and a resist pattern is formed that covers only the portion to be left as the heating element 35. Next, the metal foil 351 in the portion not covered by the resist pattern is removed by etching. For example, when the material of the metal foil 351 is copper, a cupric chloride etching solution, a ferric chloride etching solution, or the like can be used as the etching solution for removing the metal foil 351.

[0035] Thereafter, by peeling the resist pattern with a stripping solution, the heating element 35 is formed at a predetermined position on the insulating resin film 341 (photolithography method). By forming the heating element 35 by the photolithography method, it becomes possible to reduce the variation in the dimensional variation in the width direction of the heating element 35, and the heat generation distribution can be improved. In addition, the cross-sectional shape of the heating element 35 formed by etching can be, for example, a substantially trapezoidal shape. In this case, the difference in wiring width between the surface in contact with the insulating resin film 341 and the opposite surface can be, for example, about 10 to 50 μm. By making the cross-sectional shape of the heating element 35 a simple substantially trapezoidal shape, the heat generation distribution can be improved.

[0036] Next, in the process shown in FIG. 3(c), an insulating resin film 342 that covers the heating element 35 is disposed on the insulating resin film 341. The insulating resin film 342 is suitable in that it can suppress the entrainment of voids when laminated in a vacuum. The material of the insulating resin film 342 can be, for example, the same as that of the insulating resin film 341. However, the thickness of the insulating resin film 341 can be appropriately determined within a range that can cover the heating element 35, and it is not necessarily the same thickness as the insulating resin film 341.

[0037] Next, in the process shown in FIG. 4(a), while pressing the insulating resin films 341 and 342 toward the substrate 31 side, the insulating resin films 341 and 342 are heated to a temperature equal to or higher than the curing temperature and cured. As a result, the insulating resin films 341 and 342 are integrated to form the insulating layer 34, and the insulating layer 34 directly joined to the heat diffusion layer 33 is formed. In addition, the periphery of the heating element 35 is covered with the insulating layer 34. Considering the stress when returning to room temperature, the heating temperature of the insulating resin films 341 and 342 is preferably 200° C. or lower. Thus, the electrostatic chuck 30 is completed.

[0038] By heating and curing while pressing the insulating resin films 341 and 342 against the substrate 31 side, unevenness on the upper surface of the insulating layer 34 (the surface not in contact with the electrostatic chuck 30) due to the presence or absence of the heating element 35 can be reduced and flattened. The unevenness on the upper surface of the insulating layer 34 is preferably 7 μm or less. By setting the unevenness on the upper surface of the insulating layer 34 to 7 μm or less, it is possible to prevent air bubbles from being entrapped between the insulating layer 34 and the adhesive layer 20 in the next process. That is, it is possible to prevent a decrease in the adhesiveness between the insulating layer 34 and the adhesive layer 20.

[0039] Next, in the process shown in FIG. 4(b), a base plate 10 in which a water channel 15 or the like has been formed in advance is prepared, and an adhesive layer 20 (uncured) is formed on the base plate 10. Then, the electrostatic chuck 30 shown in FIG. 4(a) is turned upside down and placed on the base plate 10 via the adhesive layer 20, and the adhesive layer 20 is cured. Thereby, the substrate fixing device 1 in which the electrostatic chuck 30 is laminated on the base plate 10 via the adhesive layer 20 is completed.

[0040] In this way, in the electrostatic chuck 30, since the heat diffusion layer 33 is directly formed on the back surface of the substrate 31, the heat generated by the heating element 35 can be easily transmitted to the substrate 31 uniformly. That is, in the electrostatic chuck 30, it is possible to further improve the heat uniformity compared to the conventional structure in which an adhesive layer or the like is interposed between the substrate and a metal layer or the like.

[0041] Also, by forming the heat diffusion layer 33 over the entire back surface of the substrate 31, the heat generated by the heating element 35 can be uniformly diffused over the entire substrate 31. Further, by setting the thermal conductivity of the heat diffusion layer 33 to 400 W / m·k or more, heat can be quickly diffused in the horizontal direction of the substrate 31. And the heat uniformly diffused by the heat diffusion layer 33 can uniformly heat the substrate 31.

[0042] In addition, the heat diffusion layer 33 directly formed on the back surface of the substrate 31 has a uniform film thickness, unlike the case where a metal foil is attached. Therefore, the effect of improving the heat uniformity is high.

[0043] In addition, the insulating layer 34 incorporating the heating element 35 is arranged in contact with the heat diffusion layer 33, so that the heat generated by the heating element 35 can be efficiently transmitted to the heat diffusion layer 33.

[0044] As described above, the preferred embodiments have been described in detail. However, 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 described in the claims.

[0045] For example, examples of the object to be adsorbed by the substrate fixing device according to the present invention include glass substrates and the like used in the manufacturing process of liquid crystal panels and the like, in addition to semiconductor wafers (such as silicon wafers).

Explanation of Reference Numerals

[0046] 1 Substrate fixing device 10 Base plate 15 Water channel 15a Cooling water inlet 15b Cooling water outlet 20 Adhesive layer 30 Electrostatic chuck 31 Substrate 31a Mounting surface 32 Electrostatic electrode 33 Heat diffusion layer 34 Insulating layer 35 Heating element 341, 342 Insulating resin film 351 Metal foil

Claims

【Claim 1】 A step of directly forming a heat diffusion layer with a uniform film thickness on one surface of a substrate; A step of directly disposing a first insulating resin film on the surface of the heat diffusion layer opposite to the substrate; A step of disposing a metal foil on the first insulating resin film; A step of patterning the metal foil to form a heating element; A step of disposing a second insulating resin film covering the heating element on the first insulating resin film; A step of curing the first insulating resin film and the second insulating resin film to form an insulating layer directly joined to the heat diffusion layer; and The heat diffusion layer is formed of a material having a higher thermal conductivity than the insulating layer, a method for manufacturing an electrostatic chuck.

Images