Electrostatic chuck member, electrostatic chuck device, and method for manufacturing an electrostatic chuck member

Abstract

To provide an electrostatic chuck component that enables an electrostatic chuck device with good heat uniformity. To provide an electrostatic chuck device having such an electrostatic chuck component and having good heat uniformity. Furthermore, to provide a method for manufacturing such an electrostatic chuck component that enables easy production. [Solution] An electrostatic chuck member comprising a base body whose upper surface is a mounting surface on which a plate-shaped sample is placed, and an electrostatic adsorption electrode provided on the base body on the surface opposite to the mounting surface or inside the base body, wherein the base body has an annular projection that protrudes upward along the edge of the upper surface and is provided in a closed annular shape, and a plurality of projections that protrude upward in the region inside the annular projection, the annular projection having a first projection that is arc-shaped in a plan view and a second projection that is chord-shaped and continuous with both ends of the first projection, and the upper surface of the annular projection is radially flat.

Description

Technical Field

[0001] The present invention relates to an electrostatic chuck member, an electrostatic chuck device, and a method for manufacturing the electrostatic chuck member.

Background Art

[0002] In semiconductor manufacturing apparatuses that perform plasma processes, electrostatic chuck devices are used that allow a plate-shaped sample (wafer) to be easily attached and fixed to a sample stage, and can maintain the wafer at a desired temperature. The electrostatic chuck device includes an electrostatic chuck member (a plate-shaped ceramic body) having a base body whose one main surface is a mounting surface for placing a wafer, and an electrostatic adsorption electrode that generates an electrostatic force (Coulomb force) between the electrode and the wafer placed on the mounting surface (for example, see Patent Document 1). The base body is usually made of a ceramic sintered body as a forming material.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0004] In recent years, devices using semiconductors have tended to be highly integrated. Therefore, fine wiring processing technology and three-dimensional mounting technology are required during device manufacturing. In implementing such processing technologies, semiconductor manufacturing apparatuses are required to reduce the in-plane temperature distribution (temperature difference) of the wafer.

[0005] However, in the prior art, the in-plane temperature difference of the wafer may not be reduced to a desired range, and improvements have been demanded.

[0006] In this specification, the degree of temperature difference across the surface of a wafer held by an electrostatic chuck during plasma processing may be referred to as "temperature uniformity." Furthermore, a small temperature difference across the surface of a wafer during plasma processing may be described as "good temperature uniformity."

[0007] The present invention has been made in view of these circumstances, and aims to provide an electrostatic chuck member that can be used in an electrostatic chuck device with good heat uniformity. It also aims to provide an electrostatic chuck device having such an electrostatic chuck member and having good heat uniformity. Furthermore, it also aims to provide a method for manufacturing such an electrostatic chuck member that can be easily manufactured. [Means for solving the problem]

[0008] In electrostatic chuck devices, a configuration is known in which a closed annular projection (seal band) is provided on the periphery of the base body in a plan view, and the wafer is supported by adsorption onto the upper surface of the annular projection. In such an electrostatic chuck device, by supplying and flowing a pressurized gaseous coolant (e.g., helium) into the space surrounded by the annular projection, the coolant cools the wafer, reducing the in-plane temperature difference of the wafer and making it possible to maintain a desired temperature. In order to make close contact with the lower surface of the wafer, the upper surface of the annular projection is required to conform to the shape of the lower surface of the wafer and have as little change in radial height as possible. In the following description, a shape that suppresses change in radial height may be referred to as flat.

[0009] The upper surface of an annular protrusion is usually processed using grinding with a grinding wheel to create a shape that suppresses radial height changes, such as a flat surface. However, grinding with a grinding wheel makes it difficult to make the center and ends of the upper surface of the annular protrusion flat, and for example, the outer edge of the upper surface may be higher than the center of the surface.

[0010] When a wafer is attached to an annular protrusion of this shape, the contact area between the annular protrusion and the wafer becomes smaller compared to a flat annular protrusion, and the force with which the electrostatic chuck device holds the wafer becomes relatively smaller. In that case, the force with which the pressurized refrigerant lifts the wafer may exceed the force with which it holds the wafer, potentially causing the wafer and the annular protrusion to separate and the refrigerant to leak out.

[0011] Furthermore, the annular protrusion may not be a perfect ring in plan view, but rather have a shape consisting of a superior arc portion and a chord portion in plan view. Such shapes are also used in the wafers being processed, and the chord portion is known as an orientation flat. When the annular protrusion has an orientation flat shape, it becomes even more difficult to perform the same polishing process on both the superior arc portion and the chord portion.

[0012] Based on the above findings, the inventors conducted diligent studies and discovered that by devising a manufacturing method, they were able to create an annular protrusion with a shape that suppresses changes in radial height on the upper surface, thereby suppressing refrigerant leakage that occurs at the periphery of the electrostatic chuck member, and thus completed the present invention.

[0013] To solve the above problems, one aspect of the present invention includes the following aspects.

[0014] [1] An electrostatic chuck member comprising a base body whose upper surface is a mounting surface on which a plate-shaped sample is placed, and an electrostatic adsorption electrode provided on the base body on the surface opposite to the mounting surface or inside the base body, wherein the base body has an annular projection that protrudes upward along the edge of the upper surface and is provided in a closed annular shape, and a plurality of projections that protrude upward in the region inside the annular projection, wherein the annular projection has a first projection that is arc-shaped in a plan view and a second projection that is chord-shaped and continuous with both ends of the first projection, and the upper surface of the annular projection is radially flat.

[0015] [2] The electrostatic chuck member according to [1], wherein the annular protrusion is flat over the entire circumference in the circumferential direction.

[0016] [3] The electrostatic chuck member according to [1] or [2], wherein the width of the annular projection is 0.1 mm or more and 4.0 mm or less.

[0017] [4] An electrostatic chuck member according to any one of [1] to [3], having a first suction portion having the aforementioned mounting surface and a second suction portion formed in a closed annular shape on the outside of the first suction portion in a plan view, wherein the annular protrusion is provided on the outer edge of the first suction portion.

[0018] An electrostatic chuck device comprising an electrostatic chuck member as described in any one of items [5], [1] to [4].

[0019] [6] The electrostatic chuck device according to [5], wherein the substrate has a concave shape in the thickness direction of the substrate, with the height gradually increasing from the center of the mounting surface toward the outer circumference of the mounting surface.

[0020] [7] The electrostatic chuck device according to [5], wherein the substrate has a convex shape in the thickness direction of the substrate, with the height gradually decreasing from the center of the mounting surface toward the outer circumference of the mounting surface.

[0021] [8] A method for manufacturing an electrostatic chuck member, comprising the steps of: flattening one surface of a dielectric substrate that is circular in plan view and equipped with electrostatic adsorption electrodes; grinding the side of one surface of the dielectric substrate from the periphery to form the flattened first surface and a second surface concentric with the first surface; and processing the first surface to form an annular projection that protrudes upward along the edge of the first surface and is provided in a closed annular shape, and a plurality of projections that protrude upward in the region inside the annular projection. [Effects of the Invention]

[0022] According to the present invention, it is possible to provide an electrostatic chuck member that enables an electrostatic chuck device with good heat uniformity. Furthermore, it is possible to provide an electrostatic chuck device having such an electrostatic chuck member and having good heat uniformity. Moreover, it is possible to provide a method for manufacturing such an electrostatic chuck member that enables easy production of the electrostatic chuck member. Brief Description of the Drawings

[0023] [Figure 1] Figure 1 is a schematic cross-sectional view showing the electrostatic chuck device 1A of the present embodiment. [Figure 2] Figure 2 is a plan view of the electrostatic chuck member 2. [Figure 3] Figure 3 is an enlarged cross-sectional view showing the configuration of the peripheral edge portion of the electrostatic chuck member 2. [Figure 4] Figure 4 is a process diagram showing the manufacturing method of the electrostatic chuck member 2. [Figure 5] Figure 5 is a schematic cross-sectional view showing an electrostatic chuck device 1B of a modified example. [Figure 6] Figure 6 is a schematic cross-sectional view showing an electrostatic chuck device 1C of a modified example. [Figure 7] Figure 7 is an explanatory diagram of the test specimen 2X produced in Example 1 and Comparative Example 1. [Figure 8] Figure 8 is an explanatory diagram for explaining the measurement positions on the upper surface of the test specimen 2X. [Figure 9] Figure 9 is a graph showing the measurement results of the test specimen of Example 1. [Figure 10] Figure 10 is a graph showing the measurement results of the test specimen of Comparative Example 1. Modes for Carrying Out the Invention

[0024] Hereinafter, the electrostatic chuck member, the electrostatic chuck device, and the manufacturing method of the electrostatic chuck member according to the present embodiment will be described with reference to Figures 1 to 6. Note that in all the following drawings, the dimensions, ratios, and the like of each component are appropriately varied to make the drawings easier to view.

[0025] <<Electrostatic Chuck Member, Electrostatic Chuck Device>> Figure 1 is a schematic cross-sectional view of the electrostatic chuck device 1A of this embodiment, and is a cross-sectional view taken in a cross-section passing through the center of the circular electrostatic chuck member 2 in plan view. The electrostatic chuck device 1A comprises the electrostatic chuck member 2, a base 3, and a bonding layer 4. The electrostatic chuck member 2 and the base 3 are stacked on top of each other via the bonding layer 4.

[0026] In this specification, the side on which the electrostatic chuck member 2 is positioned relative to the base 3 may be referred to as "upper," and the opposite side as "lower." Furthermore, in the following description, the vertical direction will be used as the stacking direction when describing the parts of the electrostatic chuck device 1A. However, the vertical direction here is merely used for the sake of simplicity in explanation and does not limit the orientation of the electrostatic chuck device 1A when it is in use.

[0027] <Electrostatic Chuck Components> The electrostatic chuck member 2 comprises a base body 11 and electrostatic adsorption electrodes 13. The electrostatic chuck member 2 has a first adsorption portion 21 that adsorbs and holds the wafer W on its upper surface, and a second adsorption portion 22 that adsorbs and holds the focus ring FR on its upper surface.

[0028] The first suction portion 21 is formed in a cylindrical shape, and its upper surface is provided with a plurality of upwardly projecting protrusions 211. In addition, a closed annular projection 212 is provided along the edge of the upper surface of the first suction portion 21. In this specification, "plan view" refers to the field of view seen from the thickness direction of the electrostatic chuck member 2.

[0029] The electrostatic chuck device 1A supports the wafer W with the tips (upper surfaces) of the multiple protrusions 211 and the upper surface of the annular protrusion 212. In other words, in the electrostatic chuck device 1A, the virtual surface connecting the upper surface of the annular protrusion 212 and the upper surfaces of the multiple protrusions 211 corresponds to the mounting surface 21a of the wafer W.

[0030] When a wafer W is placed on the mounting surface 21a, the space on the lower surface of the wafer W, surrounded by the multiple protrusions 211 and the annular protrusion 212, functions as a flow channel 21x for the cooling gas to flow. The electrostatic chuck device 1A is provided with a gas supply hole (not shown) that penetrates the electrostatic chuck device 1A in the thickness direction, and cooling gas is supplied from the gas supply hole to the flow channel 21x. The cooling gas flowing through the flow channel 21x cools the wafer W, which is heated during plasma processing.

[0031] The second suction portion 22 is a concentric cylindrical shape with a larger radius than the first suction portion 21, and is integrally formed with the first suction portion 21. The upper surface 22a of the second suction portion 22 is exposed in a plan view, surrounding the periphery of the first suction portion 21. The upper surface 22a corresponds to the mounting surface that holds the focus ring FR by suction.

[0032] An annular groove 22x is formed on the upper surface 22a in plan view. When the focus ring FR is placed on the upper surface 22a, the space surrounded by the lower surface of the focus ring FR and the groove 22x functions as a flow path for the cooling gas. The electrostatic chuck device 1A is provided with a gas supply hole (not shown) that penetrates the electrostatic chuck device 1A in the thickness direction, and cooling gas is supplied from the gas supply hole to the flow path (groove 22x). The cooling gas flowing through the flow path cools the focus ring FR, which is heated during plasma processing.

[0033] (Dielectric substrate) The substrate 11 is made of ceramics that includes an insulating material and a conductive material, has sufficient mechanical strength, and is resistant to corrosive gases and their plasmas.

[0034] The ceramics that make up the substrate 11 include aluminum oxide (Al2O3) and aluminum nitride (AlN) as the main components, which are insulating materials. "Main component" refers to a component that accounts for 50% or more of the total volume.

[0035] The conductive material is not particularly limited as long as it is a material that can be used for the substrate 11. For example, at least one selected from the group consisting of SiC, TiO2, TiN, TiC, W, WC, MoC, Mo2C, TaC, TaN, NbC, VC, and C can be used.

[0036] The ceramic material constituting the substrate 11 is preferably an aluminum oxide (Al2O3)-silicon carbide (SiC) composite sintered body. In particular, from the viewpoint of dielectric properties at high temperatures, high corrosion resistance, plasma resistance, and heat resistance, an Al2O3-SiC composite sintered body is preferred as the material constituting the substrate 11.

[0037] (Electrodes for electrostatic adsorption) The electrostatic adsorption electrode 13 is positioned inside the substrate 11. The electrostatic adsorption electrode 13 extends along the mounting surface 21a of the substrate 11. When a voltage is applied, the electrostatic adsorption electrode 13 generates an electrostatic adsorption force to hold the wafer W on the mounting surface 21a.

[0038] In Figure 1, the electrostatic adsorption electrode 13 is provided inside the base body 11, but the electrostatic adsorption electrode 13 may also be provided on the surface of the base body 11 opposite to the mounting surface (i.e., the lower surface 2a of the electrostatic chuck member 2). Also, in Figure 1, the electrostatic adsorption electrode 13 is shown as a unipolar type, but the electrostatic adsorption electrode 13 may also be a bipolar type.

[0039] The adsorption electrode 15 is positioned inside the substrate 11. The adsorption electrode 15 extends in an annular shape in plan view along the upper surface 22a of the second adsorption portion 22. When a voltage is applied, the adsorption electrode 15 generates an electrostatic adsorption force to hold the wafer W on the upper surface 22a.

[0040] In Figure 1, the adsorption electrode 15 is provided inside the substrate 11, but the adsorption electrode 15 may also be provided on the surface of the substrate 11 opposite to the mounting surface (i.e., the lower surface 2a of the electrostatic chuck member 2). Also, although Figure 1 shows the adsorption electrode 15 as a unipolar type, the adsorption electrode 15 may also be a bipolar type.

[0041] The electrostatic adsorption electrode 13 and the adsorption electrode 15 are each connected to a power supply terminal (not shown) for applying a DC voltage to the electrostatic adsorption electrode 13 and the adsorption electrode 15, respectively.

[0042] The electrostatic adsorption electrodes 13 and 15 are composed of a composite material of an insulating material and a conductive material. The insulating material contained in the electrostatic adsorption electrodes 13 and 15 is not particularly limited, but is preferably at least one selected from the group consisting of aluminum oxide (Al2O3), aluminum nitride (AlN), silicon nitride (Si3N4), yttrium(III) oxide (Y2O3), yttrium aluminum garnet (YAG), and SmAlO3.

[0043] The conductive material contained in the electrostatic adsorption electrode 13 is preferably at least one selected from the group consisting of molybdenum carbide (Mo2C), molybdenum (Mo), tungsten carbide (WC), tungsten (W), tantalum carbide (TaC), tantalum (Ta), silicon carbide (SiC), carbon black, carbon nanotubes, and carbon nanofibers.

[0044] The thickness of the electrostatic chuck member 2 is preferably 0.5 mm or more and 5 mm or less. When the thickness of the electrostatic chuck member 2 is 0.5 mm or more, the dielectric strength of the electrostatic chuck member 2 is increased. Also, when the thickness of the electrostatic chuck member 2 is 5 mm or less, the heat capacity of the electrostatic chuck member 2 is reduced, making it easier to maintain a uniform temperature of the plate-shaped sample being processed during plasma processing.

[0045] <Base> The base 3 is a disc-shaped member in plan view and supports the electrostatic chuck member 2 from below (the other side in the stacking direction). The upper surface (support surface) 3a of the base 3 faces the lower surface 2a of the electrostatic chuck member 2 in the vertical direction (stacking direction) via the bonding layer 4. The base 3 supports the electrostatic chuck member 2 at its support surface 3a.

[0046] A flow path 3f for circulating a refrigerant may be provided inside the base 3. The refrigerant flowing through the flow path 3f may be a fluorine-based inert liquid, water, He gas, N2 gas, etc. The flow path 3f extends along the support surface 3a. The refrigerant in the flow path 3f cools the entire base 3 and also cools the electrostatic chuck member 2 via the support surface 3a. In other words, the base 3 functions as a temperature control member for the electrostatic chuck member 2.

[0047] The base 3 is connected to an external high-frequency power supply 5 via a matching circuit (not shown) and also serves as an internal electrode for plasma generation.

[0048] The material of the base 3 is not limited as long as it is a metal with excellent thermal conductivity, electrical conductivity, and workability, or a composite material containing such metals, or a ceramic with high thermal conductivity, a conductive ceramic, or a metal-ceramic composite material (MMC: Metal Matrix Composition), etc. For example, aluminum (Al), aluminum alloys, copper (Cu), copper alloys, stainless steel (SUS), and ceramics composed of a high thermal conductivity material and a conductive material are preferably used. The ceramic may, for example, have a volume ratio of high thermal conductivity material to conductive material of 10:90 to 90:10, and may be composed of AlN and TiN, AlN and Mo, or AlN, TiN, and Mo. Preferably, at least the surface of the base 3 that is exposed to the plasma is anodized or has an insulating film such as alumina deposited on it.

[0049] The thermal expansion coefficient of the base 3 is preferably close to that of the electrostatic chuck member 2. Ideally, there should be no difference in thermal expansion coefficient between the base 3 and the electrostatic chuck member 2. By using a base 3 with such a configuration, it is possible to suppress changes in the shape of the electrostatic chuck member 2 (upward or downward bending) when the electrostatic chuck member 2 changes temperature.

[0050] <Joining layer> The bonding layer 4 can be made of known bonding materials and may be formed of organic adhesives such as polyimide resin, acrylic resin, silicone resin, and epoxy resin. These organic adhesives have heat resistance and insulating properties after bonding and curing.

[0051] The bonding layer 4 may be formed from an organic adhesive, specifically a silicone adhesive. Silicone adhesives have a low glass transition temperature, a high heat resistance temperature, and rubber elasticity. This silicone adhesive may also contain insulating ceramic powder (such as aluminum oxide or aluminum nitride) as a thermally conductive filler.

[0052] When an organic adhesive is used as the material for the bonding layer 4, even if there is a difference between the thermal expansion coefficient of the base 3 and the thermal expansion coefficient of the electrostatic chuck member 2, the difference in the amount of thermal expansion can be buffered.

[0053] If the bonding layer 4 using an organic adhesive contains a resin and a filler, the filler may include spherical filler 1 and spherical filler 2 with different primary particle sizes. The bonding layer 4 preferably has a thermal conductivity of 3.0 W / (m·K) or higher. A thermal conductivity of 3.0 W / (m·K) or higher makes it easier to transfer heat from the temperature-controlled base member to the electrostatic chuck device, allowing the temperature of the sample on the electrostatic chuck device to be kept constant. More preferably, the thermal conductivity of the bonding layer is 4.0 W / (m·K) or higher. The thermal conductivity of the bonding layer is measured by methods such as the laser flash method.

[0054] The bonding layer 4 preferably has a uniform thickness and low variation in thermal conductivity. Specifically, it is preferable that the difference between the minimum and maximum values ​​of the thermal conductivity of the bonding layer 4, measured at three arbitrary points on the bonding layer 4, is 0.3 W / (m·K) or less. However, the difference between the minimum and maximum values ​​may be 0.2 W / (m·K) or less, or 0.1 W / (m·K) or less.

[0055] One method for sampling the bonding layer is to cut the electrostatic chuck member body and sample directly from the cross-section.

[0056] As for the resin used in the bonding layer 4, acrylic resin may be used, from the viewpoint of making it easier to adjust the thickness of the bonding layer uniformly.

[0057] The materials of filler 1 and filler 2 contained in the filler are not particularly limited as long as they have high thermal conductivity and a thermal conductivity of 180 W / (m·K) or higher. If the material has a thermal conductivity of less than 180 W / (m·K), it will be difficult to achieve high thermal conductivity when mixed with the organic adhesive before curing to form a bonding layer. Examples of high thermal conductivity filler materials include ceramic powders such as aluminum nitride (AlN) and metal powders such as aluminum (Al).

[0058] Furthermore, in addition to being formed from a homogeneous material, the filler may also have a coating layer on its surface made of a material different from the material constituting the filler particles. By appropriately selecting the material constituting the coating layer, it is possible to improve the water resistance of the filler or to improve the compatibility between the filler and the resin, thereby increasing the flexibility of the joint 4. For example, when using aluminum nitride powder as the filler, a coating layer containing silicon dioxide (SiO2), aluminum oxide (Al2O3), or aluminum phosphate (AlPO4) may be provided on the surface of the aluminum nitride particles constituting the filler.

[0059] Surface-coated AlN particles, in which a coating layer of SiO2 is formed on the surface of the AlN particles, have superior water resistance compared to simple AlN particles without a surface coating. Therefore, the durability of the bonding layer 4 can be ensured, and the durability of the electrostatic chuck device 1 can be dramatically improved.

[0060] AlN particles without a surface coating are hydrolyzed by, for example, water in the atmosphere, as shown in the chemical reaction equation (a) below, producing aluminum hydroxide (Al(OH)3) and ammonia (NH3). This aluminum hydroxide (Al(OH)3) reduces the thermal conductivity of the AlN particles. AlN+3H2O→Al(OH)3+NH3···(a)

[0061] On the other hand, in surface-coated AlN particles, the surface of the AlN particles is coated with a coating layer made of SiO2, which has excellent water resistance. As a result, the AlN particles are not hydrolyzed by water in the atmosphere, and the thermal conductivity of the AlN particles does not decrease. Therefore, the durability of the bonding layer 4 is improved, and it does not become a source of contamination for plate-shaped samples such as semiconductor wafers.

[0062] The surface-coated AlN particles can achieve a strong bond between the silicon (Si) in the coating layer and the resin, thereby improving the elongation of the bonding layer 4. This reduces thermal stress caused by the difference between the thermal expansion coefficients of the substrate 11 of the electrostatic chuck member 2 and the base 3, allowing for a precise and strong bond between the electrostatic chuck member 2 and the base 3. Furthermore, it provides sufficient resistance to thermal cycling loads during use, improving the durability of the electrostatic chuck device.

[0063] The thickness of the coating layer of the surface-coated AlN particles is preferably 0.005 μm or more and 0.05 μm or less, and more preferably 0.005 μm or more and 0.03 μm or less.

[0064] If the thickness of the coating layer is 0.005 μm or more, the water resistance (moisture resistance) of the AlN particles can be fully exhibited. On the other hand, if the thickness of the coating layer is 0.05 μm or less, the thermal conductivity of the surface-coated AlN particles will not decrease, and consequently, the thermal conductivity between the plate-shaped sample placed on the mounting surface 11a of the mounting plate 11 and the base 3 will not decrease. Therefore, the temperature of the plate-shaped sample during processing can be maintained at a preferred constant temperature.

[0065] The primary particle size of filler 1 is between 2 μm and less than 15 μm, and the primary particle size of filler 2 is between 15 μm and 50 μm. This size distribution of filler 1 and filler 2 makes it easier for the smaller filler particles of filler 1 to fill the gaps between the larger filler particles of filler 2 when mixed with the resin. This makes it easier to achieve a high particle filling rate while maintaining adhesive performance as a bonding layer, and to impart high thermal conductivity to the bonding layer.

[0066] Note that the "primary particle diameter of the filler" contained in the bonding layer 4 refers to the diameter of the spherical particles. If the spherical particles are not perfectly spherical, it refers to the diameter of the circumscribed circle of the filler with the largest diameter. The primary particle diameter of the filler can be measured using a scanning electron microscope (SEM) or the like.

[0067] Regarding the shape of the filler in the bonding layer 4, it is preferable that the filler be perfectly spherical from the viewpoint of improving the thermal conductivity of the bonding layer 4 by high-density filling of the filler, but the sphericity of the filler is not limited to this. For example, the sphericity of the filler may be 0.5 or more, 0.6 or more, 0.7 or more, or 0.8 or more.

[0068] The sphericity of a filler is the value obtained by dividing the circumference of a circle with the same area as the projected area of ​​the particle image by the perimeter of that particle image. A perfect circle has a sphericity of 1, and it decreases as the shape deviates from a sphere.

[0069] The average sphericity of the filler is preferably 0.7 or higher, and more preferably 0.8 or higher. The average sphericity of the filler is obtained by measuring the sphericity of a predetermined number of fillers, for example, 200 or 100, and taking a weighted average of these measurements.

[0070] The filler content in the bonding layer 4 is preferably 50% by volume or more. A filler content of 50% by volume or more makes it easier to impart high thermal conductivity to the bonding layer 4. Consequently, the thermal conductivity between the plate-shaped sample placed on the mounting surface 11a of the mounting plate 11 and the base 3 does not decrease, and the temperature of the plate-shaped sample during processing can be maintained at a preferred constant temperature.

[0071] The filler content is more preferably 60% by volume or more, and even more preferably 70% by volume or more. On the other hand, the filler content is preferably 90% by volume or less, more preferably 85% by volume or less, and even more preferably 80% by volume or less. Adhesion performance can be ensured if the filler content is 90% by volume or less. The filler content in the bonding layer 4 can be determined by removing the electrostatic chuck member from the electrostatic chuck device, cutting the electrostatic chuck member, and measuring the density of a sample obtained from the cross-section. The density of the sampled sample can be measured using a method such as liquid weighing.

[0072] The content of filler 1 should be between 10% and 50% by volume relative to the total volume of filler 1 and filler 2. The content of filler 2 should be between 50% and 90% by volume relative to the total volume of filler 1 and filler 2. When the content of filler 1 is 10% or more by volume, a sufficient amount of filler 1 can fill the gaps between filler 2 particles, making it easier to achieve a high particle packing density. When the content of filler 1 is 50% or less by volume, filler 1 is less likely to overflow from the gaps between filler 2 particles, making it easier to maintain a good dispersion state within the bonding layer 4.

[0073] To improve the dispersibility of the filler within the bonding layer 4, a dispersant may be included in the bonding layer 4. The inclusion of a dispersant can suppress localized non-uniformity of the filler within the bonding layer 4. This makes it easier to achieve a uniform thickness in the bonding layer 4 and suppresses variations in thermal conductivity.

[0074] For example, the dispersant can be at least one of phosphonic acid, carboxylic acid, polycarboxylic acid, phosphoric acid, polyphosphate, or salts thereof, or a silane coupling agent or polyvinylpyrrolidone. It is preferable to add the dispersant in an amount of more than 0.0% and up to 5.0% by mass relative to the entire bonding layer 4.

[0075] The thickness of the bonding layer 4 is preferably 50 μm or more and 300 μm or less, and preferably 60 μm or more and 200 μm or less. If the thickness of the bonding layer 4 is 50 μm or more, the thermal conductivity between the electrostatic chuck member 2 and the base 3 will be good, and thermal stress relaxation will be sufficient. On the other hand, if the thickness of the bonding layer 4 is 300 μm or less, sufficient thermal conductivity between the electrostatic chuck member 2 and the base 3 can be ensured, and plasma permeability will also be improved.

[0076] In the bonding layer 4, the variation in thickness in the direction perpendicular to the bonding surfaces within the bonding surface with the electrostatic chuck member 2 and the bonding surface with the base 3 is expressed as the difference between the maximum and minimum values ​​of its thickness. The difference between the maximum and minimum values ​​of the thickness in the direction perpendicular to the bonding surfaces within the bonding surface with the electrostatic chuck member 2 and the bonding surface with the base 3 of the bonding layer 4 is 10 μm or less. Furthermore, the smaller the difference, the better, with 5 μm or less being more preferable, and ideally 0 μm being preferable. The thickness of the bonding layer 4 can be measured using, for example, a micrometer before bonding, or measured using, for example, an optical microscope while observing the cross-section, after bonding.

[0077] The bonding layer 4 may have a laminated structure in which a first layer containing a filler is sandwiched between a second layer made only of resin without a filler. In this configuration, the first layer has high thermal conductivity, and the second layer without a filler has adhesive properties, allowing the bonding layer 4 as a whole to exhibit higher thermal conductivity and better adhesion.

[0078] The thickness of the pair of second layers is preferably 5% to 30% of the thickness of the bonding layer 4, and more preferably 10% to 20%. This thickness range allows for maintaining adhesion while suppressing a decrease in thermal conductivity.

[0079] The combined thickness of the pair of second layers may be 2 μm or more and 60 μm or less, 4 μm or more and 40 μm or less, 6 μm or more and 30 μm or less, or 8 μm or more and 20 μm or less. The pair of second layers may both have the same thickness or have different thicknesses.

[0080] The thickness of the first layer may be 50 μm or more and 270 μm or less, 70 μm or more and 200 μm or less, or 80 μm or more and 150 μm or less.

[0081] The bonding layer 4 may also contain spherical filler 3 in addition to filler 1 and filler 2.

[0082] The primary particle size of filler 3 is preferably 0.05 μm or more and less than 2 μm. Being within this primary particle size range indicates that filler 3 has a smaller particle size than fillers 1 and 2. This size makes it easier for filler 3 to fill the gaps between fillers 2, thus making it easier to increase the particle filling rate of the bonding layer.

[0083] Filler 3 is not particularly limited, but is preferably one with a thermal conductivity of 30 W / (m·K) or higher. Having a thermal conductivity of 30 W / (m·K) or higher in filler 3 prevents a decrease in the thermal conductivity of the bonding layer. Examples of materials used for filler 3 include Al2O3 and AlN. Similar to fillers 1 and 2, filler 3 may have a coating layer on its surface made of a material different from the material constituting the particle body of filler 3.

[0084] Furthermore, the material of the bonding layer 4 may be a metal brazing material or a ceramic.

[0085] When a metal brazing material is used as the material for the bonding layer 4, heat is more easily transferred from the electrostatic chuck member 2 to the base 3 compared to when the bonding layer 4 is formed with an organic adhesive, making cooling (temperature control) by the base 3 easier. When ceramics are used as the material for the bonding layer 4, the base 3 and the electrostatic chuck member 2 can be connected by diffusion bonding.

[0086] The base 3, bonding layer 4, and materials described above are merely examples; any base and bonding layer used in known electrostatic chuck devices can be appropriately adopted.

[0087] Furthermore, the electrostatic chuck device 1A may appropriately adopt known configurations as those of an electrostatic chuck device, as long as they do not impair the effects of the invention.

[0088] Figure 2 is a plan view of the electrostatic chuck member 2. The annular protrusion 212 of the electrostatic chuck member 2 has, in plan view, an arc-shaped curved surface portion (first protrusion) 212x and a chordal orientation flat portion (second protrusion) 212y that is continuous with both ends of the curved surface portion 212x.

[0089] Figure 3 is an enlarged cross-sectional view showing the configuration of the peripheral edge of the electrostatic chuck member 2. Figure 3 is an enlarged view of the same cross-section as Figure 1, and shows the peripheral structure of the annular protrusion 212.

[0090] (a) Width of the annular protrusion 212 The annular projection 212 is formed with the same width throughout its entire circumferential range, including the curved surface portion 212x and the orientation flat portion 212y. The width WA of the annular projection 212 refers to the radial length of the annular projection 212 in a plan view.

[0091] The width WA of the annular projection 212 is 0.1 mm or more and 4.0 mm or less. The width WA of the annular projection 212 may be 0.5 mm or more, 1.0 mm or more, or 1.5 mm or more. Also, the width WA of the annular projection 212 may be 3.5 mm or less, 3.0 mm or less, 2.5 mm or less, or 2.0 mm or less.

[0092] The upper and lower limits of the width WA of the annular protrusion 212 can be arbitrarily combined. For example, the width WA may be 0.3 mm or more and 4.0 mm or less, or 0.5 mm or more and 2.0 mm or less.

[0093] By setting the width of the annular protrusion 212 to 4.0 mm or less, the flow path C can be formed relatively widely, allowing the cooling of the wafer W by the cooling gas to effectively extend to the peripheral area of ​​the wafer W. As a result, the electrostatic chuck device 1A can suitably control the temperature up to the peripheral edge of the wafer W, and it is expected that the plasma processing (etching) state at the peripheral area of ​​the wafer W will stabilize and the yield will improve.

[0094] Furthermore, by setting the width WA of the annular protrusion 212 to 0.1 mm or more, it becomes possible to adsorb the wafer W onto the mounting surface 21a and seal the cooling gas in the flow path C. For example, the width WA of the annular protrusion 212 can be 2 mm.

[0095] (b) Upper surface 212a of the annular protrusion 212 The upper surface 212a of the annular projection 212 is machined to be a radially flat surface. Here, the fact that the upper surface 212a is "radially flat" can be confirmed by the following method.

[0096] First, in this invention, "flat" means that the upper surface 212a has a shape that suppresses changes in radial height. More specifically, in a cross-section with the same field of view as in Figures 1 and 3, when a virtual line is assumed to connect the center in the width direction of the upper surface of the annular protrusion 212 to the upper surfaces of the multiple protrusions 211, whether or not it is flat is determined by the relative position between this virtual line and the outer edge of the annular protrusion 212 (the part enclosed by the symbol α in Figure 3).

[0097] As will be explained in more detail later, during the manufacturing of the electrostatic chuck member 2, before forming the upper surfaces of the multiple protrusions 211 and the upper surface 212a of the annular protrusion 212, a continuous surface with suppressed height changes is formed by machining, which will later become the mounting surface. On the other hand, the outer edge α of the electrostatic chuck member 2 was not in a stable state during machining and was prone to height changes relative to the above continuous surface. Therefore, in this embodiment, a virtual line is assumed to connect the upper surfaces of the multiple protrusions 211 and the center of the upper surface 212a of the annular protrusion 212, and the upper surface 212a is judged to be "flat" if the height of this virtual line matches that of the outer edge α.

[0098] If the displacement of the outer edge α relative to the above-mentioned imaginary line is within ±2 μm (with vertically upward being positive), preferably within ±1 μm, then the shape of the upper surface 212a suppresses radial height changes and can be judged to be flat.

[0099] On the other hand, if the outer edge α of the upper surface 212a is located above or below the above-mentioned imaginary line, it can be determined that the shape of the outer edge α deviates from the setting of the mounting surface. In this state, it is determined that the upper surface 212a is "not flat".

[0100] In the electrostatic chuck member 2, the upper surface 212a of the annular projection 212 is flat in both the curved surface 212x and the orientation flat portion 212y. Furthermore, the upper surface 212a is flat over the entire circumference of the annular projection 212 in the circumferential direction.

[0101] <Method for manufacturing electrostatic chuck components> The electrostatic chuck member 2 described above can be suitably manufactured by the manufacturing method shown in Figure 4. Figure 4 is a process diagram showing the manufacturing method of the electrostatic chuck member 2.

[0102] Conventionally, the electrostatic chuck member 2 was manufactured by roughly machining a disc-shaped dielectric substrate to create a convex shape with portions corresponding to the first and second adsorption portions, and then polishing the upper surface with a rotating grinding wheel to flatten the upper surface 211a of the convex portion 211 and the upper surface 212a of the annular convex portion 212. At this time, there was a problem that the contact area between the interior of the upper surface and the rotating grinding wheel differed at the peripheral edge of the upper surface of the dielectric substrate, making it difficult to maintain a consistent polishing state. Therefore, in electrostatic chuck devices employing the conventional processing method, the outer edge α of the annular convex portion of the electrostatic chuck member tended to bend upward due to insufficient polishing, or sag downward due to excessive polishing.

[0103] Furthermore, if the annular protrusion of the electrostatic chuck member has a curved surface portion 212x and an orientation flat portion 212y, as in the annular protrusion 212 of this embodiment, it becomes necessary to change the processing conditions for the curved surface portion 212x and the orientation flat portion 212y, making it difficult to make the upper surface flat.

[0104] In response to these challenges, the inventors investigated and found that the top surface could be easily made flat by the manufacturing method described below.

[0105] First, as shown in Figure 4(a), one surface 200a of the dielectric substrate 200, which is circular in plan view and equipped with electrostatic adsorption electrodes, is flattened (flattening process). As a result, one surface of the dielectric substrate 200 becomes a flat surface 200b.

[0106] In the formed flat surface 200b, the inner circumference (indicated by symbol X1) undergoes stable machining and becomes a flat surface, but the peripheral edge (indicated by symbol X2) undergoes unstable machining and is prone to under-polishing or over-polishing.

[0107] Next, as shown in Figure 4(b), one side of the dielectric substrate 200 (the flat surface 200b) is ground from the periphery to form a first surface 201 and a second surface 202 that is concentric with the first surface 201 (process of forming the first and second surfaces). The first surface 201 is a part of the flat surface 200b and is a flattened surface. The second surface 202 is the surface formed by this process.

[0108] In this process, the peripheral edge X2 shown in Figure 4(a) is ground away. Therefore, the formed first surface 201 consists only of the inner circumference indicated by the reference numeral X1 in Figure 4(a), and is uniformly flat from the inner circumference to the peripheral edge.

[0109] Next, as shown in Figure 4(c), the first surface 201 is processed to form an annular projection 212 that protrudes upward along the edge of the first surface 201 and is provided in a closed annular shape, and a plurality of projections 211 that protrude upward in the region inside the annular projection 212.

[0110] In this process, the protrusions 211 and the annular protrusions 212 can be formed by machining the first surface 201, such as by blasting. In addition, the grooves 22x can be formed by machining the second surface 202.

[0111] By carrying out the manufacturing method of the electrostatic chuck member of this embodiment as described above, an electrostatic chuck member having a flat annular protrusion on its upper surface can be easily manufactured.

[0112] With an electrostatic chuck component configured as described above, it is possible to create an electrostatic chuck device with good heat uniformity.

[0113] Furthermore, an electrostatic chuck device with the above-described configuration has good heat uniformity due to the presence of the aforementioned electrostatic chuck member.

[0114] (modified version) Figures 5 and 6 are schematic cross-sectional views showing modified examples of this embodiment, and correspond to Figure 1.

[0115] In the electrostatic chuck device 1B shown in Figure 5, the cross-sectional shape of the base body 11 in the thickness direction is concave, with the height gradually increasing from the center 215 of the mounting surface 21a toward the outer circumference (annular protrusion 212) of the mounting surface 21a. The cross-sectional shape of the base body 11 may be a curved concave, or it may be a V-shape with the center 215 being the lowest point and inclined toward the center 215.

[0116] In the electrostatic chuck device 1C shown in Figure 6, the cross-sectional shape of the base body 11 in the thickness direction is convex, with the height gradually increasing from the center 215 of the mounting surface 21a toward the outer circumference (annular protrusion 212) of the mounting surface 21a.

[0117] For example, if there is a difference in thermal expansion coefficient between the electrostatic chuck member 2 and the base 3, the difference in thermal expansion between the two may cause the electrostatic chuck member 2 to deform into a convex or concave shape during use of the electrostatic chuck device. Also, when fastening the electrostatic chuck device to an installation location, the stress received by the electrostatic chuck device from the fastener may cause the entire electrostatic chuck device to deform upward into a convex shape. Furthermore, if the material of the bonding layer is an organic adhesive, the bonding layer may harden due to aging, causing the electrostatic chuck member to deform into a convex shape.

[0118] As described above, the electrostatic chuck devices 1B and 1C can counteract the deformation of the electrostatic chuck member 2, which is deformed due to various causes.

[0119] In these electrostatic chuck devices 1B and 1C as well, the flat upper surface of the annular projection 212 results in an electrostatic chuck member and electrostatic chuck device with good heat uniformity, similar to the electrostatic chuck device 1A described above.

[0120] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention. [Examples]

[0121] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0122] (Example 1) In Example 1, a dielectric substrate was processed using the method shown in Figures 4(a) and 4(b) to produce a test specimen corresponding to the electrostatic chuck member before dot formation. Specifically, one surface of the dielectric substrate (without electrostatic adsorption electrodes; circular in plan view; 350 mm in diameter) was flattened, and then the side of the dielectric substrate was ground from the periphery to form a flattened first surface and a second surface concentric with the first surface.

[0123] (Comparative Example 1) In Comparative Example 1, a dielectric substrate was processed to form a first surface and a second surface concentric with the first surface. Then, the first surface was flattened to produce a test specimen corresponding to the electrostatic chuck member before dot formation.

[0124] Figure 7 is an explanatory diagram of the test specimens 2X prepared in Example 1 and Comparative Example 1. There were no significant external differences between the test specimens of Example 1 and Comparative Example 1. Both test specimens are disc-shaped members having a portion 21X corresponding to the first adsorption portion and a portion 22X corresponding to the second adsorption portion. In addition, a plane X corresponding to the orientation flat portion 212y of the annular protrusion 212 described above was formed on the side surface of portion 21X.

[0125] For the fabricated test specimen 2X, the change in surface height in the vertical direction was measured radially in section 21X to confirm the shape of the outer edge. The above change in surface height was measured using a surface roughness / contour shape combined measuring instrument (product name: SURFCOM NEX, manufactured by Tokyo Seimitsu Co., Ltd.). The outer edge is where an annular protrusion is formed by processing. The radial width of the annular protrusion was set to 4 mm.

[0126] Figure 8 is an explanatory diagram illustrating the measurement locations on the upper surface of test specimen 2X. The change in surface height in the vertical direction was measured in six directions (A to F) passing through the center P of part 21X of test specimen 2X. The angle between adjacent measurement directions was 60°.

[0127] The measurement results are shown in Figures 9 and 10. Figure 9 is a graph showing the measurement results of the test specimen of Example 1, and Figure 10 is a graph showing the measurement results of the test specimen of Comparative Example 1. In Figures 9 and 10, the area corresponding to the formation position of the annular protrusion (a range of 4 mm from the outer edge of the first surface) is enclosed by a dashed line.

[0128] As shown in Figure 9, in the test specimen of Example 1, there was no change in the surface height in the vertical direction from radially to the outer circumference in any of the directions A to F. Furthermore, there was no difference between direction A, where a flat surface X is formed on the side surface, and directions B to F, where the side surface is curved.

[0129] When an annular protrusion is formed on a dielectric substrate with the outer edge of the first surface having this shape by the machining shown in Figure 4(c), the upper surface of the annular protrusion becomes radially flat. Therefore, if an electrostatic chuck device is manufactured using the resulting electrostatic chuck member, it will have excellent heat uniformity.

[0130] In contrast, as shown in Figure 10, the surface height in the vertical direction varied at the outer edge of the specimen of Comparative Example 1 in all directions from A to F.

[0131] When an annular protrusion is formed on a dielectric substrate with the outer edge of the first surface having this shape by the machining shown in Figure 4(c), the upper surface of the annular protrusion is not radially flat. Therefore, even if an electrostatic chuck device is manufactured using the obtained electrostatic chuck member, the uniform heat distribution is considered to be lower than that of Example 1.

[0132] From the above results, it has been confirmed that the present invention is useful. [Explanation of Symbols]

[0133] 1A, 1B, 1C... Electrostatic chuck device, 2... Electrostatic chuck member, 11... Substrate, 13... Electrostatic adsorption electrode, 212... Annular protrusion, 21... First adsorption part, 21a... Mounting surface, 21a, 22a, 211a, 212a... Top surface, 21X, 22X... Part, 22... Second adsorption part, 200... Dielectric substrate, 200a... One surface, 200b... Flat surface, 201... First surface, 202... Second surface, 211... Protrusion, 212x... Curved surface (first protrusion), 212y... Orientation flat (second protrusion), 215, P... Center, WA... Width, X... Plane

Claims

1. A base whose upper surface is a mounting surface on which a plate-shaped sample is placed, The substrate comprises an electrostatic adsorption electrode provided on the surface opposite to the mounting surface or inside the substrate, The base has an annular projection that protrudes upward along the edge of the upper surface and is provided in a closed annular shape, The annular projection has a plurality of projections that protrude upward in the inner region of the annular projection, The aforementioned annular protrusion has a first protrusion that is arc-shaped in plan view, It has a chordal second protrusion that is continuous with both ends of the first protrusion, An electrostatic chuck member in which the upper surface of the annular protrusion is flat in the radial direction.

2. The electrostatic chuck member according to claim 1, wherein the annular protrusion is flat over its entire circumference in the circumferential direction.

3. The electrostatic chuck member according to claim 1 or 2, wherein the width of the annular projection is 0.1 mm or more and 4.0 mm or less.

4. The first suction part having the mounting surface, It has a second adsorption portion formed in a closed annular shape on the outside of the first adsorption portion in a plan view, The electrostatic chuck member according to claim 1 or 2, wherein the annular projection is provided on the outer edge of the first suction portion.

5. An electrostatic chuck device comprising the electrostatic chuck member according to claim 1 or 2.

6. The electrostatic chuck device according to claim 5, wherein the substrate has a concave shape in the thickness direction of the substrate, with the height gradually increasing from the center of the mounting surface toward the outer circumference of the mounting surface.

7. The electrostatic chuck device according to claim 5, wherein the substrate has a convex shape in the thickness direction of the substrate, with the height gradually decreasing from the center of the mounting surface toward the outer circumference of the mounting surface.

8. A dielectric substrate that is circular in plan view and equipped with electrostatic adsorption electrodes, comprising the steps of flattening one surface of the dielectric substrate, A step of grinding one side of the dielectric substrate from the periphery to form the flattened first surface and a second surface concentric with the first surface, A method for manufacturing an electrostatic chuck member, comprising the steps of: processing the first surface to form an annular projection that protrudes upward along the edge of the first surface and is provided in a closed annular shape; and a plurality of projections that protrude upward in the region inside the annular projection.

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