Electrostatic Chuck Having a Composite Buffer Layer Structure

Abstract

The present invention relates to an electrostatic chuck capable of improving durability and reliability in high-temperature environments by increasing the adhesion strength between a metal base layer and a ceramic coating layer. The electrostatic chuck of the present invention comprises a base layer made of a metal material; a coating layer made of a ceramic material disposed on top of the base layer; and a plurality of buffer layers stacked between the base layer and the coating layer, wherein the buffer layer is characterized by comprising a metal-based region containing a metal component corresponding to the base layer and a ceramic-based region containing a ceramic component corresponding to the coating layer.

Description

Technology Field

[0001] The present invention relates to an electrostatic chuck, and more specifically, to an electrostatic chuck capable of improving the adhesion between a metal base layer and a ceramic insulating layer. The present invention is supported by the following national R&D project. Project No.: 2410014276 Project No.: 20032589 Ministry: Ministry of Trade, Industry and Energy Project Management Agency: Korea Institute of Industrial Technology Planning and Evaluation Research Project Name: Materials and Components Technology Development Project Project Title: Development of Temperature-Controlled Electrostatic Chuck Technology for 8th Generation Downward Deposition Sputter Equipment Contribution Rate: 1 / 1 Project Performing Agency: TTS Co., Ltd. Research Period: 2025. 01. 01. ~ 2025. 12. 13. Background Technology

[0002] In structures where a ceramic thermal spray coating layer is laminated onto a metal base, such as in an electrostatic chuck, there is a problem where cracking, peeling, or detachment of the ceramic coating layer occurs during the process due to the difference in the coefficient of thermal expansion between the metal layer and the ceramic coating layer.

[0003] In other words, a base composed of metal materials such as aluminum or stainless steel has a relatively higher coefficient of thermal expansion compared to the ceramic coating layer, so repetitive thermal stress may concentrate at the adhesive interface during plasma processing or thermal cycling, potentially causing the coating layer to peel off.

[0004] In order to mitigate such problems, a technique has been proposed in the past to buffer the difference in the coefficient of thermal expansion between the two materials by inserting a single buffer layer (adhesive layer) composed of a Ni-Al alloy between a metal base (10) and a ceramic thermal spray coating layer (20), as shown in FIG. 1.

[0005] However, conventional single-buffer layer structures alone make it difficult to sufficiently disperse thermal stress at the interface caused by differences in thermal expansion coefficients, and in electrostatic chuck processes requiring the maintenance of high and ultra-high temperatures, there were still problems such as cracking, peeling, or reduced adhesion of the ceramic coating layer. Prior art literature

[0006] Korean Patent Publication No. 10-0872541 (December 1, 2008) The problem to be solved

[0007] The technical problem to be solved by the present invention is to provide an electrostatic chuck structure capable of resolving the problem of reduced interfacial adhesion occurring between a metal base layer and a ceramic coating layer, and improving the reliability of bonding between the two layers. means of solving the problem

[0008] The electrostatic chuck of the present invention for solving the above-mentioned technical problem comprises: a base layer made of a metal material; a coating layer made of a ceramic material disposed on top of the base layer; and a plurality of buffer layers stacked between the base layer and the coating layer, wherein the buffer layer comprises a metal-based region containing a metal component corresponding to the base layer and a ceramic-based region containing a ceramic component corresponding to the coating layer.

[0009] Here, the buffer layer may be composed of a composite buffer layer in which a metal-based region and a ceramic-based region are sequentially stacked.

[0010] In addition, multiple buffer layers may have different compositional ratios of metal components and ceramic components.

[0011] Specifically, multiple buffer layers can be configured such that the ratio of metal components to ceramic components differs from bottom to top.

[0012] At this time, multiple buffer layers can be configured such that the proportion of metal components decreases from the bottom to the top.

[0013] In addition, multiple buffer layers can be configured such that the proportion of ceramic components increases from the bottom to the top.

[0014] Here, the metallic region may include aluminum (Al) and nickel (Ni).

[0015] In addition, the ceramic region may contain aluminum oxide (Al2O₃). Effects of the invention

[0016] According to the present invention, by stacking and forming a plurality of buffer layers between a metal base layer and a ceramic thermal spray coating layer of an electrostatic chuck, the difference in the coefficient of thermal expansion between the two layers can be mitigated stepwise. Accordingly, the problem of thermal stress concentration that occurred in conventional single-buffer-layer structures is effectively resolved, and the thermal bonding stability of the entire structure is improved.

[0017] In particular, by forming a composite buffer layer with a multilayer structure including a metallic region composed of an aluminum-nickel (Al-Ni) alloy and a ceramic region composed of aluminum oxide (Al2O₃), and applying a gradient structure that gradually changes the metal-ceramic composition ratio of each composite buffer layer, thermal properties are gradually and naturally transferred from the lower metallic region to the upper ceramic region, thereby significantly reducing delamination and cracking occurring at the interface of the thermal spray coating layer.

[0018] In addition, since each of the multiple buffer layers can be formed such that the ratio of metal components to ceramic components changes continuously from bottom to top, thermal stability and interfacial reliability that are difficult to secure with a conventional single adhesive layer can be provided. Accordingly, the adhesion of the thermal spray coating layer is stably maintained even in high-temperature or repetitive thermal cycling environments, thereby ensuring the durability and reliability of the electrostatic chuck.

[0019] In addition, the buffer layer placed on top contains ceramic components, so it has high chemical and microstructural affinity with the upper ceramic thermal spray coating layer, which further improves interfacial bonding strength and has the effect of preventing a decrease in adhesion strength even in high-temperature processes.

[0020] In addition, unlike conventional discrete stacked structures consisting of a metal layer, an alloy layer (adhesive layer), and a single ceramic layer, the gradient buffer layer structure of the present invention, in which the compositional ratio between metal and ceramic gradually changes, can operate stably under various temperature conditions through a multilayer buffer layer structure in which the composition changes stepwise, and can provide suitable structural performance for various semiconductor process equipment requiring high heat resistance and high reliability. Brief explanation of the drawing

[0021] FIG. 1 is a cross-sectional view illustrating a ceramic thermal spray coating layer bonding structure using a conventional single adhesive layer. FIG. 2 is a cross-sectional view illustrating a ceramic thermal spray coating layer bonding structure using a plurality of buffer layers according to an embodiment of the present invention. Specific details for implementing the invention

[0022] The following examples are provided to more fully explain the invention to those skilled in the art and may be modified into various other forms of embodiments.

[0023] The terms used herein are for describing specific embodiments and are not intended to limit the invention. Additionally, the singular form in this specification may include the plural form unless the context clearly indicates otherwise.

[0024] In the description of the embodiments, the reference for "upper" or "lower" shall, in principle, be based on the drawings. The drawings are intended merely to facilitate understanding of the concept of the present invention and should not be interpreted as limiting the scope of the present invention. Furthermore, relative thicknesses, lengths, or relative sizes in the drawings may be exaggerated for convenience and clarity of explanation.

[0025] The electrostatic chuck (ESC) of the present invention is a device for stably fixing various substrates, such as semiconductor wafers, display panels, and glass substrates, using electrostatic force. By maintaining the substrate in a non-contact manner under special process conditions, such as a vacuum or plasma environment, it enables high-precision processes such as etching, deposition, and ion implantation.

[0026] The present invention provides a multilayer buffer layer (adhesive layer) structure to improve the problems of thermal stress concentration and interfacial delamination caused by the difference in the coefficient of thermal expansion occurring between the metal base layer and the ceramic thermal spray coating layer of an electrostatic chuck. The buffer layer is arranged in a form in which a plurality of individual buffer layers are sequentially stacked between the metal base layer and the ceramic coating layer, and each buffer layer may be formed as a composite structure comprising a metal-based region containing a metal component and a ceramic-based region containing a ceramic component.

[0027] In addition, each buffer layer is configured such that the ratio of metal components to ceramic components differs from layer to layer, forming a compositional gradient structure in which the metal component gradually decreases and the ceramic component gradually increases from the lower layer to the upper layer. Due to this multilayer buffer layer structure, the difference in the coefficient of thermal expansion between the metal layer and the ceramic layer is gradually mitigated, thereby suppressing delamination or cracking of the ceramic thermal spray coating layer and ensuring excellent thermal stability even in high-temperature environments.

[0028] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the attached drawings.

[0029] FIG. 2 is a cross-sectional view showing a multilayer buffer layer structure interposed between a metal base layer and a ceramic coating layer in an electrostatic chuck according to an embodiment of the present invention.

[0030] Referring to FIG. 2, the electrostatic chuck (400) includes a base layer (100) made of a metal material, a coating layer (300) made of a ceramic material placed on top of the base layer (100), and a plurality of buffer layers (200) stacked between the base layer (100) and the coating layer (300).

[0031] The base layer (100) can be composed of various metal materials such as aluminum (Al), stainless steel (SUS), copper (Cu), molybdenum (Mo), and tungsten (W), but in the embodiment, a form using aluminum (Al) is exemplified.

[0032] The coating layer (300) is a ceramic insulating layer that insulates and protects an electrode (not shown) embedded inside an electrostatic chuck, and is made of aluminum oxide (Al2O₃), yttria (Y2O₃), aluminum nitride (AlN), and titanium oxide (TiO₂). 2) Ceramic materials such as zirconium oxide (ZrO2) may be applied. The coating layer (300) in the embodiment may use aluminum oxide (Al2O₃) material and may be formed through an atmospheric plasma spray (APS) process. This coating layer (300) performs the functions of insulating the electrode and protecting the electrostatic chuck, while also performing the function of controlling heat transfer characteristics.

[0033] Meanwhile, if a ceramic coating layer (300) is formed directly on a metal base layer (100), the coating layer may peel off or crack during a high-temperature plasma process due to the large difference in the coefficient of thermal expansion between the metal and the ceramic. Conventionally, to mitigate this problem, a method of attachment was used by interposing a single adhesive layer (buffer layer) having an intermediate coefficient of thermal expansion (see FIG. 1), but this single adhesive layer structure alone was insufficient to sufficiently relieve thermal stress, and there was a limitation in that repeated reduction of adhesion and interfacial peeling occurred in a high-temperature environment.

[0034] Accordingly, in the present invention, a buffer layer disposed between a metal base layer (100) and a ceramic coating layer (300) is composed of a plurality of buffer layers (200) having different thermal expansion characteristics, and a multilayer gradient structure is adopted in which the ratio of the metal component and the ceramic component of each buffer layer is gradually changed layer by layer. With this configuration, peeling and cracking occurring at the interface of the coating layer (300) can be effectively suppressed, and improved durability and stability can be secured even in a high-temperature plasma environment.

[0035] The embodiment illustrated in FIG. 2 shows an example in which a buffer layer composed of three layers is laminated between a metal base layer and a ceramic coating layer.

[0036] Referring to FIG. 2, the multilayer buffer layer structure of the present invention is described more specifically as follows: between the metal base layer (100) and the ceramic coating layer (300), a first buffer layer (210), a second buffer layer (220), and a third buffer layer (230) are sequentially stacked to form a structure.

[0037] Each buffer layer (210, 220, 230) is composed of a composite buffer layer containing a metal component and a ceramic component, and the metal component and the ceramic component included in each buffer layer (210, 220, 230) may be formed to have different compositional ratios. Additionally, the plurality of buffer layers (210, 220, 230) may be formed such that the ratio of the metal component and the ceramic component differs from bottom to top.

[0038] Each buffer layer (210, 220, 230) is composed of a metal-based region (212, 222, 232) containing a metal component and a ceramic-based region (214, 224, 234) containing a ceramic component, and the ceramic-based region (214, 224, 234) can be formed on the metal-based region (212, 222, 232).

[0039] The metallic regions (212, 222, 232) may include a metallic component corresponding to the base layer (100). In the embodiment, an Al-Ni alloy including an aluminum (Al) component and a nickel (Ni) component corresponding to the base layer (100) may be applied.

[0040] The ceramic region (214, 224, 234) may include a ceramic component corresponding to the coating layer (300). In the embodiment, aluminum oxide (Al2O₃) corresponding to the coating layer (300) may be included as the ceramic component.

[0041] Specifically, the first buffer layer (210) is a layer adjacent to the metal base layer (100) and is a metal-ceramic composite layer composed of about 75% Al-Ni alloy and about 25% aluminum oxide (Al2O₃). The first buffer layer (210) is composed of a metal-based region (212) containing a metal component corresponding to the base layer (100) and a ceramic-based region (214) containing a ceramic component corresponding to the coating layer (300), wherein the metal-based region (212) is first deposited on the base layer (100) and the ceramic-based region (214) is formed thereon.

[0042] A second buffer layer (220) is laminated on top of the first buffer layer (210). The second buffer layer (220) is a metal-ceramic composite layer composed of approximately 50% Al-Ni alloy and approximately 50% aluminum oxide (Al2O₃), and has a structure in which a metal-based region (222) and a ceramic-based region (224) are laminated sequentially.

[0043] Additionally, a third buffer layer (230) is disposed on top of the second buffer layer (220). The third buffer layer (230) is composed of approximately 25% Al-Ni alloy and approximately 75% aluminum oxide (Al2O₃), and a metallic region (232) and a ceramic region (234) are formed sequentially.

[0044] In this way, each buffer layer (210, 220, 230) forms a gradient layer with a composition ratio set in stages such that the proportion of the metal component decreases and the proportion of the ceramic component increases from the bottom to the top. Accordingly, the difference in the coefficient of thermal expansion occurring between the metal base layer (100) and the ceramic coating layer (300) is continuously mitigated, so that the thermal stress distribution can be naturally dispersed.

[0045] The configuration of the present invention can effectively suppress peeling and cracking of the ceramic coating layer, which frequently occurred in conventional single-buffer layer structures, and can effectively contribute to maintaining the adhesion of the ceramic coating layer stably even in high-temperature or repetitive thermal cycling environments. In addition, there is an advantage in that the mechanical stability of the electrostatic chuck is improved by reducing structural warping and deformation of the coating layer due to the stepwise relief of thermal stress.

[0046] In the embodiment of FIG. 2, a plurality of buffer layers are described as being formed in a three-layer structure, but the same method can be applied even when a plurality of buffer layers are formed in an n-layer structure.

[0047] That is, in an electrostatic chuck (400) structure in which a plurality of buffer layers (first buffer layer, second buffer layer, nth buffer layer) are stacked in an n-layer structure between a metal base layer (100) and a ceramic thermal spray coating layer (300), the plurality of buffer layers (200) can be formed such that a different composition ratio is applied to each of the n-layer buffer layers, so that the proportion of the metal component (Al-Ni) gradually decreases and the proportion of the ceramic component (Al2O₃) gradually increases from the buffer layer adjacent to the metal base layer (100) to the buffer layer adjacent to the ceramic coating layer (300).

[0048] As such, the present invention forms a multilayer buffer layer composed of a composite Ni-based alloy and Al2O₃ ceramic, and forms a gradient structure in which the composition ratio of each buffer layer is varied stepwise such that the proportion of the Ni-based alloy in the buffer layer closer to the lower metal base layer is high, and the proportion of Al2O₃ in the buffer layer closer to the upper ceramic coating layer is high. This allows for the effective stepwise dispersion of thermal stress generated between the metal-ceramic interface, thereby suppressing cracking and peeling of the ceramic coating layer and improving the adhesion and durability of the coating layer even in high-temperature environments. This multilayer buffer layer stacking structure of the present invention can be applied to various semiconductor process equipment requiring high heat resistance and high reliability, in addition to electrostatic chucks.

[0049] As described in the embodiment of FIG. 2 above, the present invention comprises a plurality of buffer layers (200) stacked between a base layer (100) and a coating layer (300), which are configured as mixed layers in which a Ni-based alloy component (Ni-Al, NiCrAl, etc.) and a ceramic component (Al2O₃) are mixed. In the lowest buffer layer closest to the metal base layer (100), the Ni-based alloy content is relatively high (e.g., Ni-Al 75%, Al2O₃ 25%), and as it goes upward, the content of the ceramic component (Al2O₃) gradually increases, so that in the middle layer, the ratio of both components is maintained at a similar level (e.g., Ni-Al 50%, Al2O₃ 50%), and in the uppermost buffer layer, the ceramic component is dominant (e.g., Ni-Al 25%, Al2O₃ 75%).

[0050] As configured in this way, the high thermal expansion coefficient (approx. 23×10) of the metal base layer (100) -6 / K) and the low coefficient of thermal expansion (approx. 8×10) of the ceramic coating layer (300) -6The thermal properties between / K) can be dispersed and mitigated stepwise and continuously by changing the metal-ceramic component composition ratio of the multiple buffer layers (200). Accordingly, even in high temperature and ultra-high temperature process environments (e.g., in the range of about 80°C to about 900°C), thermal stress concentrated at the metal-ceramic interface can be effectively mitigated, thereby stably maintaining the adhesion of the ceramic thermal spray coating layer and significantly reducing interfacial delamination or cracking of the coating layer. In particular, the Al2O₃ component included in the top buffer layer has high chemical and microstructural affinity with the thermal spray coating layer (300), which has the effect of further improving interfacial adhesion.

[0051] The above description is merely an illustrative explanation of the technical concept of the present invention, and those skilled in the art to which the present invention pertains will be able to make various modifications and variations within the scope of the essential characteristics of the present invention. Explanation of the symbols

[0052] 100: Base layer 200: Buffer layer 210: First buffer layer 212,222,232: Metallic region 214,224,234: Ceramic-based region 220: Second buffer layer 230: Third buffer layer 300: Coating layer 400: Electrostatic Chuck

Claims

Claim 1 An electrostatic chuck comprising: a base layer made of a metal material; a coating layer made of a ceramic material disposed on top of the base layer; and a plurality of buffer layers stacked between the base layer and the coating layer, wherein the buffer layer comprises a metal-based region containing a metal component corresponding to the base layer and a ceramic-based region containing a ceramic component corresponding to the coating layer, and wherein the metal-based region and the ceramic-based region are sequentially stacked to form a composite buffer layer. Claim 2 delete Claim 3 In claim 1, the electrostatic chuck having a plurality of buffer layers having different compositional ratios of metal components and ceramic components. Claim 4 An electrostatic chuck according to claim 1, wherein the plurality of buffer layers are configured such that the ratio of metal components to ceramic components differs from bottom to top. Claim 5 An electrostatic chuck according to claim 1, wherein the plurality of buffer layers are configured such that the proportion of metal components decreases from the bottom to the top. Claim 6 An electrostatic chuck according to claim 1, wherein the plurality of buffer layers are configured such that the proportion of ceramic components increases from the bottom to the top. Claim 7 In claim 1, the electrostatic chuck, wherein the metal region comprises aluminum (Al) and nickel (Ni). Claim 8 An electrostatic chuck according to claim 1, wherein the ceramic region comprises aluminum oxide (Al2O₃).

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