Electrostatic chuck, substrate holding device, and method for manufacturing substrate holding device

Abstract

The present application relates to an electrostatic chuck, a substrate fixing device, and a manufacturing method of a substrate fixing device, the electrostatic chuck including: a plurality of ceramic substrates each having a step formed at a peripheral portion of one surface, the ceramic substrates being arranged adjacent to each other with the steps facing each other; electrodes each embedded in each of the plurality of ceramic substrates; and a filling portion filling a groove portion formed by the facing steps of the adjacent ceramic substrates.

Description

Technical Field

[0001] This invention relates to an electrostatic chuck, a substrate fixing device, and a method for manufacturing the substrate fixing device. Background Technology

[0002] In existing technologies, substrate holding devices with electrostatic chucks are used, for example, to hold wafers during etching. The substrate holding device is constructed by bonding an electrostatic chuck, consisting of a ceramic substrate with embedded electrodes, to a metal base plate. Typically, a flexible silicone-based adhesive is used as the adhesive to bond the electrostatic chuck to the base plate to maintain thermal conductivity and absorb the difference in thermal expansion between the base plate and the electrostatic chuck.

[0003] A substrate holding device can attract wafers to an electrostatic chuck by applying a voltage to electrodes embedded in a ceramic substrate and using the electrostatic force generated by the voltage. When fixing larger wafers, a substrate holding device can be constructed by bonding an electrostatic chuck composed of multiple ceramic substrates to a base plate. Specifically, for example, a substrate holding device with a 500mm × 500mm electrostatic chuck is constructed by arranging four ceramic substrates, each with a size of 250mm × 250mm, side by side and bonding the ceramic substrates to a base plate to attract large-scale wafers.

[0004] Citation List

[0005] Patent documents

[0006] Patent Document 1: JP-A-2003-051433

[0007] Patent Document 2: JP-A-2017-050468

[0008] Patent Document 3: JP-A-H07-335731 Summary of the Invention

[0009] However, when an electrostatic chuck composed of multiple ceramic substrates is bonded to a base plate, adhesive components seep to the surface of the ceramic substrates due to the adhesion between adjacent ceramic substrates. Specifically, when an electrostatic chuck composed of multiple ceramic substrates is bonded to a base plate using a silicone resin-based adhesive (hereinafter referred to as "silicone adhesive"), the silicone adhesive is also introduced between adjacent ceramic substrates. When the substrate fixing device is used in this state, the silicone oil included in the silicone adhesive seeps to the surface of the ceramic substrate that serves as the adsorption surface, causing stains to form near the boundaries of adjacent ceramic substrates. As a result, in some cases, the stains transfer to the adsorption object, such as a wafer adsorbed onto the electrostatic chuck, causing contamination of the adsorption object.

[0010] Therefore, it was also considered to bond multiple ceramic substrates to the base plate with spacing, and to remove the adhesive between adjacent ceramic substrates. However, when multiple ceramic substrates are arranged with spacing, the temperature of the adsorption surface of the electrostatic chuck is uneven, which impairs the heat homogenization performance of maintaining a uniform temperature across the entire adsorbed object.

[0011] A non-limiting aspect of this disclosure is to provide an electrostatic chuck, a substrate fixing device, and a method for manufacturing the substrate fixing device that can prevent the adsorbed object from being contaminated without compromising heat distribution performance.

[0012] According to one aspect of this disclosure, an electrostatic chuck is provided, comprising:

[0013] Multiple ceramic substrates, each having a step formed at the periphery of a surface, are arranged adjacent to each other with the steps facing each other.

[0014] Electrodes, each embedded in each of a plurality of ceramic substrates; and

[0015] The filling portion is filled by a groove formed by the facing steps of an adjacent ceramic substrate.

[0016] According to one aspect of the electrostatic chuck, substrate fixing device, and method for manufacturing the substrate fixing device disclosed herein, it is possible to prevent the adsorbed object from being contaminated without compromising heat dissipation performance. Attached Figure Description

[0017] Figure 1 This is a perspective view showing the structure of the substrate fixing device according to an embodiment.

[0018] Figure 2 This is a schematic diagram showing a cross-section of the substrate fixing device according to an embodiment.

[0019] Figure 3This is a flowchart illustrating a method for manufacturing a substrate fixing device according to an embodiment.

[0020] Figure 4 An example of a ceramic substrate is shown.

[0021] Figure 5 An example of the step formation process is shown.

[0022] Figure 6 An example of the bonding process is shown.

[0023] Figure 7 An example of the alumina spraying process is shown.

[0024] Figure 8 An example of the polishing process is shown.

[0025] Figure 9 An example of temperature variation in an electrostatic chuck is shown. Detailed Implementation

[0026] Hereinafter, an embodiment of the electrostatic chuck, substrate fixing device, and method for manufacturing the substrate fixing device of this disclosure will be described in detail with reference to the accompanying drawings. It should be noted that the present invention is not limited to this embodiment.

[0027] Figure 1 This is a perspective view showing the structure of the substrate fixing device 100 according to an embodiment. Figure 1 The substrate fixing device 100 shown has a structure in which the electrostatic chuck 120 is bonded to the base plate 110.

[0028] For example, the base plate 110 is a square component made of a metal such as aluminum. The base plate 110 is a base component for fixing the electrostatic chuck 120. The base plate 110 is attached to a semiconductor manufacturing apparatus, for example, and enables the substrate holding device 100 to function as a semiconductor holding device configured to hold a wafer.

[0029] The electrostatic chuck 120 has multiple ( ) arranged side by side. Figure 1 The electrostatic chuck 120 consists of four ceramic substrates and is configured to attract objects such as wafers to the surface of the ceramic substrates using electrostatic force. For example, the electrostatic chuck 120 is bonded to the base plate 110 using a silicone adhesive. The multiple ceramic substrates constituting the electrostatic chuck 120 are arranged adjacent to each other, and an alumina coating is formed at the boundaries of the adjacent ceramic substrates.

[0030] Figure 2 It shows along Figure 1 A schematic diagram of the cross-section taken by line II. (See diagram.) Figure 2 As shown, the substrate fixing device 100 is constructed by bonding the electrostatic chuck 120 to the base plate 110 via the adhesive layer 130.

[0031] The base plate 110 is a metal component with a thickness of approximately 20 mm to 50 mm, and a cooling water channel 111 is formed therein, serving as a flow path for cooling water. The base plate 110 is configured to cool the electrostatic chuck 120 by introducing cooling water from outside the substrate holder 100 into the cooling water channel 111. The electrostatic chuck 120 is cooled, thereby cooling the adsorbed object, such as a wafer, adsorbed onto the electrostatic chuck 120.

[0032] Note that the base plate 110 may have a cooling gas passage that serves as a flow path for cooling gas, instead of a cooling water passage 111. For example, the base plate 110 may have a coolant passage through which coolants such as cooling water and cooling gas pass.

[0033] Furthermore, the base plate 110 can be integrated with a heater configured to heat the electrostatic chuck 120 via heating electrodes. Thus, the base plate 110 can control the temperature of the electrostatic chuck 120 through heating from the heater and cooling from the coolant channel, and can heat the adsorbed object adsorbed onto the electrostatic chuck 120 to a desired temperature.

[0034] The electrostatic chuck 120 has multiple ceramic substrates including ceramic substrates 121a and 121b, and a coating section 123. Corresponding electrodes 122a and 122b are embedded in each of the ceramic substrates 121a and 121b, respectively.

[0035] For example, ceramic substrates 121a and 121b are each formed by sintering a green sheet prepared using alumina. At this time, by stacking and sintering the green sheet and electrodes 122a and 122b, ceramic substrates 121a and 121b with embedded electrodes 122a and 122b are formed. The thickness of each of the ceramic substrates 121a and 121b is, for example, about 3 mm to 7 mm, and preferably 4 mm to 5 mm.

[0036] Ceramic substrates 121a and 121b are bonded to the base plate 110 in an adjacent state. Specifically, the lower surfaces of ceramic substrates 121a and 121b are bonded to the upper surface of the base plate 110 via an adhesive layer 130. A step is formed at the periphery of the upper surface of each of the ceramic substrates 121a and 121b, and the steps of the ceramic substrates 121a and 121b face each other to form a groove at the boundary of the ceramic substrates 121a and 121b. A coating portion 123 is formed in the groove.

[0037] Electrodes 122a and 122b are each embedded in one of the ceramic substrates 121a and 121b (electrodes 122a and 122b are embedded in one corresponding one of the ceramic substrates 121a and 121b), and generate electrostatic force when a voltage is applied, thereby adsorbing the object onto the upper surface of the ceramic substrates 121a and 121b. The electrodes 122a and 122b of the ceramic substrates 121a and 121b are single electrodes with the same polarity. Therefore, for example, insulating substrates such as glass substrates can be adsorbed. However, the electrodes 122a and 122b of adjacent ceramic substrates 121a and 121b can also be configured as dipole electrodes with different polarities.

[0038] The sprayed portion 123 is formed, for example, by spraying alumina into a groove formed by the steps facing the periphery of the upper surfaces of the ceramic substrates 121a and 121b. The sprayed portion 123 can also be formed, for example, by spraying yttrium oxide instead of alumina. If the ceramic substrates 121a and 121b are formed of oxides or nitrides other than alumina, the sprayed portion 123 can also be formed by spraying an oxide or nitride of the same material as the ceramic substrates 121a and 121b.

[0039] Since the groove where the coating portion 123 is formed has a cross-sectional shape with a depth of 0.2 mm to 1 mm and a width of 1 mm to 2 mm from the upper surfaces of the ceramic substrates 121a and 121b, the coating portion 123 also has a cross-sectional shape with a thickness of 0.2 mm to 1 mm and a width of 1 mm to 2 mm. Because the side ends of the electrodes 122a and 122b are located 1 mm to 2 mm inside the side surfaces of the ceramic substrates 121a and 121b, the coating portion 123 does not overlap with the electrodes 122a and 122b when viewed from above. Because the upper surfaces of the electrodes 122a and 122b are located at a depth of 0.6 mm to 1.5 mm from the upper surfaces of the ceramic substrates 121a and 121b, the coating portion 123 does not overlap with the electrodes 122a and 122b when viewed from the side.

[0040] The spraying section 123 seals the upper surface of the adjacent side surfaces of the ceramic substrates 121a and 121b, thereby preventing adhesive components from seeping from the adhesive layer 130 to the upper surfaces of the ceramic substrates 121a and 121b. Specifically, the spraying section 123 prevents adhesive components from seeping into the adsorption surface of the electrostatic chuck 120, thereby preventing the adsorbed object adsorbed on the adsorption surface from being contaminated.

[0041] The adhesive layer 130 is a layer of silicone resin-based adhesive (silicone adhesive) that bonds the lower surface of the electrostatic chuck 120 to the upper surface of the base plate 110. Specifically, the adhesive layer 130 bonds the lower surfaces of a plurality of ceramic substrates, including ceramic substrates 121a and 121b, to the upper surface of the base plate 110. The silicone adhesive forming the adhesive layer 130 is also attached to the facing side surfaces of adjacent ceramic substrates 121a and 121b. However, since the spraying portion 123 is formed above the facing side surfaces of adjacent ceramic substrates 121a and 121b, the adhesive components do not seep from the adhesive attached to the facing side surfaces of ceramic substrates 121a and 121b to the upper surface of ceramic substrates 121a and 121b.

[0042] Subsequently, referring to Figure 3 The flowchart shown describes the manufacturing method of the substrate fixing device 100 with the above-described structure.

[0043] First, a plurality of ceramic substrates 121 constituting the electrostatic chuck 120 are prepared (step S101). Specifically, a plurality of green sheets with alumina as the main material are prepared, and an electrode 122 is formed on one surface of the green sheets. For example, the electrode 122 can be formed by screen printing metal paste on the surface of the green sheets. Then, the plurality of green sheets are stacked and sintered to prepare the ceramic substrate 121.

[0044] For example, such as Figure 4 As shown, a layer of electrode 122 is formed in the ceramic substrate 121. The thickness of the ceramic substrate 121 is, for example, about 3 mm to 7 mm, and preferably 4 mm to 5 mm. For example, the electrode 122 is formed at a depth of 0.8 mm to 1.7 mm from the upper surface of the ceramic substrate 121. During the polishing process described later, since the upper surface of the ceramic substrate 121 is polished together with the spraying part 123, the electrode 122 is more durable than that of the electrode 122 when the substrate fixing device 100 is completed. Figure 4 The electrode 122 shown is formed at a location deeper than the upper surface of the ceramic substrate 121. Furthermore, for example, the side end of the electrode 122 is located 1 mm to 2 mm inside the side surface of the ceramic substrate 121.

[0045] When fabricating multiple (e.g., four) ceramic substrates 121, a step is formed at the periphery of one surface of each of the ceramic substrates 121 (step S102). Specifically, for example, as Figure 5As shown, when viewed from above and the side, a step 125 with dimensions that do not overlap with the electrode 122 is formed on one side of the upper surface of the ceramic substrate 121. Specifically, the depth of the step 125 is, for example, 0.4 mm to 1.2 mm, and the width of the bottom surface of the step 125 is, for example, 0.5 mm to 1 mm. The step 125 is formed above the side surface of the ceramic substrate 121, which is adjacent to another ceramic substrate 121 when the ceramic substrate 121 is bonded to the base plate 110. Therefore, for example, when both side surfaces of the ceramic substrate 121 are adjacent to other ceramic substrates 121, steps 125 are formed above each of the two side surfaces.

[0046] The plurality of ceramic substrates 121, each having a step 125, are bonded to the base plate 110 using an organosilicon adhesive (step S103). Specifically, for example, as... Figure 6 As shown, ceramic substrates 121a and 121b are bonded side-by-side to the upper surface of the base plate 110 using a silicone adhesive. The silicone adhesive used for bonding forms an adhesive layer 130 between the base plate 110 and the ceramic substrates 121a and 121b.

[0047] Adjacent ceramic substrates 121a and 121b are arranged such that steps 125 formed at the periphery of the upper surfaces of ceramic substrates 121a and 121b face each other, and adjacent ceramic substrates 121a and 121b are bonded to the base plate 110, and grooves 126 are formed by the facing steps 125 of ceramic substrates 121a and 121b. Specifically, when multiple ceramic substrates 121 are bonded to the base plate 110, grooves 126 are formed at the boundary of adjacent ceramic substrates 121. Since the groove is formed by the facing steps 125, the depth of the groove is the same as the depth of the steps 125, for example, 0.4 mm to 1.2 mm, and the width of the bottom surface of the groove is twice the width of the bottom surface of the steps 125, for example, 1 mm to 2 mm.

[0048] When multiple ceramic substrates 121 are bonded to the base plate 110, the silicone adhesive that has leaked from the adhesive layer 130 to the bottom surface of the groove 126 is removed (step S104). Specifically, when the ceramic substrates 121 are bonded to the base plate 110, some silicone adhesive adheres to the side surface of the ceramic substrates 121 and is squeezed by the side surface of adjacent ceramic substrates 121, causing the silicone adhesive to leak to the bottom surface of the groove 126. The silicone adhesive that has leaked to the bottom surface of the groove 126 is removed. At the same time, the silicone adhesive that has leaked from the lower surface of the ceramic substrates 121 to the outer periphery of the upper surface of the base plate 110 is also removed.

[0049] Then, an alumina spraying process is performed, in which molten alumina particles are sprayed into the tank 126 (step S105). Specifically, molten and softened alumina particles are sprayed into the tank 126 and then cooled and solidified to form an alumina spraying process. Figure 7 The spraying section 123 is shown. The spraying section 123 seals the boundary between adjacent ceramic substrates 121a and 121b near the upper surfaces of the ceramic substrates 121a and 121b. Therefore, the spraying section 123 prevents the components of the silicone adhesive adhering to the side surfaces of the ceramic substrates 121a and 121b from seeping to the upper surfaces of the ceramic substrates 121a and 121b.

[0050] It should be noted that the material to be sprayed is not limited to alumina. For example, when yttrium oxide is sprayed to form the sprayed portion 123, the plasma resistance of the sprayed portion 123 can be improved. Specifically, when the substrate holder 100 is used for plasma etching of a wafer, for example, the ceramic substrate 121 and the sprayed portion 123 are exposed to the plasma. When the sprayed portion 123 is formed by spraying yttrium oxide, corrosion of the sprayed portion 123 due to plasma can be suppressed. In addition, when the ceramic substrate 121 is formed of an oxide or nitride other than alumina, the sprayed portion 123 can also be formed by spraying an oxide or nitride of the same material as the ceramic substrate 121. In this way, the temperature difference between the ceramic substrate 121 and the sprayed portion 123 can be reduced, and the reduction in the heat dissipation performance of the electrostatic chuck 120 having the ceramic substrate 121 and the sprayed portion 123 can be suppressed.

[0051] After performing alumina spraying, the surface of the sprayed section 123 is polished together with the upper surface of the ceramic substrate 121 (step S106). Specifically, for example, as... Figure 8 As shown, the portion P, which has a thickness of, for example, 0.2 mm, at a distance from the upper surfaces of the ceramic substrates 121a and 121b, is polished so that the upper surface of the spraying portion 123 becomes flush with the upper surfaces of the ceramic substrates 121a and 121b. Specifically, the upper surfaces of the plurality of ceramic substrates 121 are flush with the upper surfaces of the spraying portion 123, making the adsorption surface of the electrostatic chuck 120 a continuous plane. Since the upper part of the spraying portion 123 is polished together with the upper part of the ceramic substrates 121, the thickness of the polished spraying portion 123 becomes, for example, 0.2 mm to 1 mm.

[0052] Then, as needed, embossing or groove formation is performed on the adsorption surface of the electrostatic chuck 120 (i.e., the upper surface of the ceramic substrate 121 and the spraying portion 123) to complete the substrate fixing device 100 with the electrostatic chuck 120. Since the substrate fixing device 100 has multiple electrostatic chucks 120 with ceramic substrates 121 arranged side-by-side, the substrate fixing device can adsorb and fix a relatively large number of adsorption objects. Furthermore, the spraying portion 123 is formed at the boundary of the multiple ceramic substrates 121, preventing the components of the silicone adhesive used to bond the ceramic substrates 121 to the base plate 110 from seeping onto the adsorption surface of the electrostatic chuck 120. As a result, stains are prevented from forming on the adsorption surface of the electrostatic chuck 120, thereby preventing contamination of the adsorption object.

[0053] Furthermore, since the sprayed portion 123 is formed at the boundaries of the plurality of ceramic substrates constituting the electrostatic chuck 120, the temperature of the adsorption surface of the electrostatic chuck 120 can be made uniform, thereby preventing a decrease in heat uniformity. Specifically, when the substrate fixing device 100 having the sprayed portion 123 formed by alumina spraying is placed on a hot plate at 60°C, a specific example of the temperature change of the ceramic substrate 121 and the sprayed portion 123 is as follows: Figure 9 As shown.

[0054] like Figure 9 As shown, after the substrate fixing device 100 is mounted on a hot plate at 60°C, the temperature difference between the ceramic substrate 121 and the spraying section 123 remains within the range of 0.1°C to 0.4°C over a period of time. Specifically, the temperature difference between the ceramic substrate 121 and the spraying section 123 constituting the electrostatic chuck 120 is small, and the temperature of the adsorption surface is uniform. Therefore, the adsorbed object adsorbed on the adsorption surface can be heated uniformly, thereby suppressing the reduction of heat uniformity performance.

[0055] As described above, according to this embodiment, for an electrostatic chuck formed by arranging multiple ceramic substrates side by side, the spraying section is formed by spraying alumina onto the boundaries of adjacent ceramic substrates. Therefore, the boundaries of adjacent ceramic substrates on the adsorption surface of the electrostatic chuck are sealed, preventing the silicone adhesive from seeping into the adsorption surface of the chuck and thus preventing contamination of the adsorbed object when the chuck is bonded to the base plate using silicone adhesive. Furthermore, since the ceramic substrates and the spraying section constitute the adsorption surface of the electrostatic chuck, the temperature of the adsorption surface becomes uniform, thereby suppressing a decrease in heat dissipation performance. In other words, contamination of the adsorbed object can be prevented without reducing heat dissipation performance.

[0056] In the above embodiment, the sprayed portion 123 is formed at the boundary of the adjacent ceramic substrate 121. However, the boundary of the ceramic substrate 121 can also be filled by PVD (physical vapor deposition) or resin filling instead of spraying. Specifically, the boundary of the adjacent ceramic substrate 121 can be filled with, for example, yttrium oxide by PVD or epoxy resin. In this way, by spraying, PVD, or resin filling to form a filling portion at the boundary of the adjacent ceramic substrate 121, the components of the silicone adhesive will not seep into the adsorption surface of the electrostatic chuck 120, and thus, contamination of the adsorbed object can be prevented.

[0057] Furthermore, in this embodiment, square ceramic substrates 121 are arranged side by side to form an electrostatic chuck 120 with a square adsorption surface. However, the shape of the electrostatic chuck 120 is not limited to this. Specifically, fan-shaped ceramic substrates can be arranged side by side to form an electrostatic chuck with a circular adsorption surface. In the same case, a step is formed at the periphery corresponding to the fan-shaped radius of each ceramic substrate, and the groove formed by the facing steps of adjacent ceramic substrates can be formed by, for example, alumina spraying.

Claims

1. An electrostatic chuck, comprising: Multiple ceramic substrates, each having a step formed at the periphery of a surface, are arranged adjacent to each other with the steps facing each other. Electrodes, each embedded in each of the plurality of ceramic substrates; as well as The filling portion fills the groove formed by the steps facing the adjacent ceramic substrate. The filling portion is formed in a position where it does not overlap with the electrode when viewed from above and the side.

2. The electrostatic chuck according to claim 1, wherein, The filling portion is formed by spraying oxides or nitrides into the groove.

3. The electrostatic chuck according to claim 1, wherein, Each of the plurality of ceramic substrates is a ceramic substrate formed of alumina, and The filling portion is formed by spraying aluminum oxide.

4. The electrostatic chuck according to claim 1, wherein, The filling portion is formed by spraying yttrium oxide.

5. A substrate fixing device, comprising: Base plate; Multiple ceramic substrates, each having a step formed at the periphery of one surface, are arranged adjacent to each other on a base plate with the steps facing each other, and the ceramic substrates are bonded to the base plate using an adhesive. Electrodes, each embedded in each of the plurality of ceramic substrates; as well as The filling portion fills the groove formed by the steps facing the adjacent ceramic substrate. The filling portion is formed in a position where it does not overlap with the electrode when viewed from above and the side.

6. A method for manufacturing a substrate fixing device, the method comprising: Multiple ceramic substrates, each having a step formed at the periphery of a surface and each having an electrode embedded therein, are arranged adjacent to each other on a base plate with the steps facing each other. as well as The groove formed by the steps facing the adjacent ceramic substrate is filled to form a filling portion. The filling portion is formed in a position where it does not overlap with the electrode when viewed from above and the side.

7. The manufacturing method according to claim 6, wherein, The filling includes spraying oxides or nitrides into the groove.

8. The manufacturing method according to claim 7, further comprising: The surface of the sprayed portion formed by the spraying and one surface of each of the plurality of ceramic substrates are polished.

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