Low-porosity coating for electrostatic chuck and preparation method

Abstract

The invention discloses a low-porosity coating for an electrostatic chuck and a preparation method, and belongs to the technical field of electrostatic chucks, the low-porosity coating comprises a first coating arranged on a metal substrate and a second coating arranged on the first coating, the first coating is a ceramic layer which is arranged on the metal base material through a thermal spraying method and has no appearance damage; the second coating is a low-porosity ceramic layer arranged on the first coating through an atomic layer deposition method. According to the method, the compact ceramic coating can be uniformly deposited on the surface of the thermal spraying coating through atomic layer deposition, and pits in the surface of the coating and internal pores and microcracks are greatly reduced; the insulating property of the low-porosity ceramic coating can be remarkably improved, the risk of charge leakage is reduced, the clamping force and stability of the electrostatic chuck are improved, and the electrostatic chuck can still work reliably under the vacuum environment and the high-voltage condition.

Description

Technical Field

[0001] The invention relates to the technical field of electrostatic chucks, and in particular to a low-porosity coating for an electrostatic chuck and a preparation method thereof. Background Art

[0002] In the semiconductor manufacturing process, the electrostatic chuck (ESC) is an important device for fixing and positioning silicon wafers. In order to ensure the stability and accuracy of silicon wafers during processing, the surface of the electrostatic chuck exposed to the rigorous semiconductor manufacturing and processing environment is usually a high-performance ceramic layer. Thermal spraying technology is a surface treatment method widely used in the industrial field. In the manufacture of some electrostatic chucks, thermal spraying technology is used to form a ceramic coating with good electrical insulation and corrosion resistance. Although thermal spraying technology provides an efficient, economical and high-performance solution for the surface treatment of electrostatic chucks, in practical applications, the rapid cooling of ceramic particles during thermal spraying and the complexity of the spraying process lead to the formation of a large number of pores inside the coating. These pores are usually interconnected to form a channel network from the surface to the substrate. Studies have shown that the pores of the coating not only affect the electrical properties of the coating, but may also become a stress concentration area that affects the mechanical strength, wear resistance and corrosion resistance of the coating on the surface of the device. The interface bonding between the high-porosity ceramic layer and the substrate is usually poor, and this lack of adhesion may even cause cracks and peeling, resulting in device failure.

[0003] In the prior art, in order to reduce the porosity of the coating, the prior art uses boron nitride-silicate sealants to fill the pores in the coating. U.S. Patent US20090087642A1 uses in-situ precipitation technology to form compatible solid compounds in the interconnected pores of thermal sprayed or sintered objects. Although these methods have certain effects, they still face many challenges, such as the risk that the sealant does not meet the requirements of the use environment and product performance requirements, which is not allowed in semiconductor manufacturing equipment. Chinese patent CN118086815A uses a more advanced suspension plasma spraying (Suspension Plasma Spraying, SPS) process to prepare a low-porosity ceramic spraying layer, but its high cost and complexity limit its application in large-scale production. In addition, appropriate heat treatment can also significantly improve the performance of ceramic coatings prepared by thermal spraying, making it more suitable for high-demand applications, but the temperature, time and atmosphere control requirements during the treatment process are strict, and any deviation may introduce new defects and problems, resulting in unstable coating quality. The aerosol deposition layer is formed on the spray coating to provide plasma resistance, but it requires sandblasting to ensure good adhesion between the aerosol deposition layer and the spray coating, which increases the manufacturing cost and time. Other methods that protect the coating include chemical vapor deposition (CVD) and physical vapor deposition (PVD), but these two methods cannot fill the fine pits and cracks formed on the surface of the first coating layer, and the overall performance of the equipment cannot be significantly improved. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a low-porosity coating for an electrostatic chuck and a preparation method thereof, which can charge new energy batteries and quickly replace batteries, is easy to use, and avoids the charging head and charging cable being placed randomly.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] On one hand, the present invention discloses a low-porosity coating for an electrostatic chuck, wherein the low-porosity coating comprises a first coating disposed on a metal substrate, and a second coating disposed on the first coating, wherein the first coating is a ceramic layer without appearance damage disposed on the metal substrate by a thermal spraying method, and the second coating is a low-porosity ceramic layer disposed on the first coating by an atomic layer deposition method.

[0007] Preferably, the metal substrate is a metal material or a metal-based composite material.

[0008] Preferably, the preparation material of the first coating is: any one or two of Al2O3, AlN, ZrO2, SiC, TiO2, Y2O3, YF3, YOF, YAP, YAM, Gd2O3, Er2O3, Sm2O3, or a mixture of two or more to ensure that the coating is free of crack damage.

[0009] Preferably, the first coating layer includes an upper layer, a lower layer and a metal layer arranged between the upper layer and the lower layer, the lower layer is arranged on the metal substrate, and the preparation material of the metal layer includes W or Mo.

[0010] Preferably, the preparation material of the second coating includes at least one of Al2O3, AlN, ZrO2, Y2O3, Gd2O3, Er2O3, and Sm2O3.

[0011] Preferably, the overall porosity of the first coating is less than or equal to 4%, the total thickness is 50 to 900 μm, the surface roughness is 5 to 7 μm, and the first coating is ground and polished after the thermal spraying process is completed. The surface roughness Ra after grinding and polishing is ≤ 0.2 μm to ensure the surface flatness of the coating.

[0012] Preferably, the second coating has a porosity of less than or equal to 1%, a thickness of 0.1 to 50 μm, and a surface roughness Ra ≤ 0.2 μm.

[0013] Preferably, the thermal spraying method is any one of atmospheric plasma spraying, flame spraying, high energy plasma spraying and vacuum plasma spraying.

[0014] Another aspect of the present invention discloses a method for preparing the low-porosity coating for an electrostatic chuck as described above, the preparation method comprising:

[0015] S1: Substrate surface pretreatment: sandblast the surface of the metal substrate to produce surface roughness, use a roughness meter to confirm that the surface roughness Ra is 5-7 μm, and use pure water and isopropanol to clean the substrate surface and airway ultrasonically for 30 minutes;

[0016] S2: Preparation of the first coating: preparing a lower layer, a metal layer and an upper layer on the surface of the metal substrate by an atmospheric plasma thermal spraying method, wherein the thickness of the lower layer is 25 to 550 μm, the thickness of the metal layer is 10 to 30 μm, and the thickness of the upper layer is 15 to 320 μm;

[0017] S3: Mechanical grinding of the first coating: The surface of the first coating is ground using a grinder, and the flushing material is pure water to ensure that the surface of the first coating is clean and flat, and the surface roughness of the upper layer is Ra≤0.2μm;

[0018] S4: Preparation of the second coating: preparing the second coating on the upper surface by atomic layer deposition, the thickness of the second coating is 0.1-50 μm, and the surface roughness Ra ≤ 0.2 μm;

[0019] S5: Coating inspection: Use a scanning electron microscope to take SEM pictures, and observe that there are no obvious pits and protrusions on the surface of the overall coating. The atomic layer deposition method fills the surface of the coating and cracks and pores of a certain depth. Perform a porosity analysis on the coating to obtain the porosity of the first coating and the second coating to determine whether it meets the requirements.

[0020] The above technical solution has the following beneficial effects:

[0021] 1. Atomic layer deposition can evenly deposit on the surface of thermal spray coating to form a dense ceramic coating, greatly reducing the pits on the coating surface and the pores and microcracks inside;

[0022] 2. The insulation of the low-porosity ceramic coating can be significantly improved, the risk of charge leakage is reduced, the clamping force and stability of the electrostatic chuck are improved, and the electrostatic chuck can still work reliably under vacuum environment and high voltage conditions;

[0023] 3. The smoother second coating surface reduces the need for grinding, fills the pores and defects on the surface, reduces the generation of concentrated electric field areas, and reduces the risk of electrostatic chuck failure caused by arc discharge;

[0024] 4. High-precision control of the process for preparing the second coating can make the interface between the second coating and the first coating more tightly bonded. Good interlayer bonding strength improves the overall durability of the coating and reduces the problem of coating peeling or damage during use;

[0025] 5. Compared with the previous high-cost and complex processes, by optimizing the coating preparation process and using a process different from thermal spraying to prepare the double-layer covering layer, the manufacturing process is simplified, the environmental impact and process difficulty are greatly reduced, and the use of low-porosity coatings and multi-layer structures also eliminates the problem of sealant inapplicability, ensuring the reliability of the coating in a high-demand environment;

[0026] 6. Optimizing coating surface treatment and interlayer bonding measures through ALD technology can improve the adhesion and overall flatness of the coating, reduce surface defects, and improve the performance of the electrostatic chuck. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic structural diagram of a low-porosity coating for an electrostatic chuck of the present invention;

[0028] Figure 2 It is a schematic diagram of the detailed cross-sectional structure of the low-porosity coating of the present invention;

[0029] Figure 3 It is a schematic diagram of the detailed cross-sectional structure of the low-porosity coating with pores and cracks of the present invention;

[0030] Figure 4 This is a schematic diagram of the detailed cross-sectional structure of the second coating of the present invention. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Example 1

[0033] The technical problem to be solved by the present invention is that the overall performance and reliability of a thermal spray electrostatic chuck are closely related to the porosity of the thermal spray coating. The present invention aims to improve the inherent impedance of the composite coating by designing a low-porosity coating and a preparation method, preparing the coating by ALD technology, and performing crack and pore filling treatment on the surface of the thermal spray coating, thereby solving the problems of electrostatic chuck performance degradation, poor long-term stability, complex preparation process, and introduction of new pollution caused by high porosity in the prior art, so as to improve the overall performance and production efficiency of the electrostatic chuck.

[0034] refer to Figure 1 , Figure 2 The present application provides a low-porosity coating for an electrostatic chuck, the low-porosity coating comprising a first coating disposed on a metal substrate 1, and a second coating 5 disposed on the first coating, the first coating being a ceramic layer without appearance damage disposed on the metal substrate 1 by a thermal spraying method, and may be crystalline or a mixture of crystalline and amorphous, the second coating 5 being a low-porosity ceramic layer disposed on the first coating by an atomic layer deposition method;

[0035] The metal substrate 1 is a metal material or a metal-based composite material. One of the metals or metal-based composite materials is selected as the substrate material. The metal material or metal-based composite material includes but is not limited to titanium (Ti), aluminum (Al), stainless steel, etc. The selection of the metal substrate 1 should take into account its thermal expansion coefficient matching with the coating material, mechanical strength, heat resistance and chemical corrosion resistance to ensure that the substrate maintains stability under high temperature and harsh environment, and forms good adhesion with the coating;

[0036] The preparation material of the first coating is: any one or two of Al2O3, AlN, ZrO2, SiC, TiO2, Y2O3, YF3, YOF, YAP, YAM, Gd2O3, Er2O3, Sm2O3, or a mixture of two or more of them, so as to ensure that the coating has no crack damage;

[0037] The first coating layer includes an upper layer 4, a lower layer 2 and a metal layer 3 arranged between the upper layer 4 and the lower layer 2, the lower layer 2 is arranged on the metal substrate 1, the preparation material of the metal layer 3 includes W or Mo, and the preparation materials of the upper layer 4 and the lower layer 2 are: any one or two of Al2O3, AlN, ZrO2, SiC, TiO2, Y2O3, YF3, YOF, YAP, YAM, Gd2O3, Er2O3, Sm2O3, and a mixture of two or more thereof;

[0038] The preparation material of the second coating layer 5 includes at least one of Al2O3, AlN, ZrO2, Y2O3, Gd2O3, Er2O3, and Sm2O3;

[0039] The first coating includes a single ceramic layer and a plurality of superimposed coatings prepared by the same thermal spraying process but with different materials, wherein it is ensured that the coating material at the contact surface between the first coating and the second coating 5 and the second coating 5 material will not chemically react under the ALD technical conditions, the overall porosity of the first coating is less than or equal to 4%, the total thickness is 50-900 μm, the surface roughness is 5-7 μm, and the first coating is ground and polished after the thermal spraying process is completed, and the surface roughness Ra after grinding and polishing is ≤0.2 μm to ensure the surface flatness of the coating, that is, the upper layer 4 is ground and polished;

[0040] In other implementations of this embodiment, the overall porosity of the first coating is 3%, the total thickness is 50 μm or 900 μm, or 450 μm, the surface roughness is 5 μm or 7 μm, or 6 μm, and the first coating is ground and polished after the thermal spraying process, and the surface roughness Ra after grinding and polishing is 0.15 μm;

[0041] The second coating 5 has a porosity of less than or equal to 1%, a thickness of 0.1 to 50 μm, and a surface roughness of Ra ≤ 0.2 μm. The second coating 5 is a low-porosity ceramic coating, which is a low-porosity ceramic coating applied on the first coating by atomic layer deposition. The thickness of the coating is precisely controlled to be 0.1 to 50 μm, and the coating roughness Ra ≤ 0.2 μm, and no subsequent grinding and polishing is required to achieve the best functional effect;

[0042] In other implementations of this embodiment, the second coating 5 has a porosity of 0.5%, a thickness of 0.1 μm or 50 μm, or 25 μm, and a surface roughness Ra of 0.1 μm. The second coating 5 is formed by a low-porosity ceramic coating, which is a low-porosity ceramic coating applied on the first coating by atomic layer deposition, without subsequent grinding and polishing, to achieve the best functional effect;

[0043] refer to Figure 3 , Figure 4 The second coating 5 can well cover the tiny pores, cracks and pits on the coating surface to a certain extent, further enhancing the insulation performance of the overall coating and the adhesion between the coating and the first coating;

[0044] The thermal spraying method is any one of atmospheric plasma spraying, flame spraying, high energy plasma spraying and vacuum plasma spraying.

[0045] Example 2

[0046] Another aspect of the present invention discloses a method for preparing the low-porosity coating for an electrostatic chuck as described above, the preparation method comprising:

[0047] S1: Substrate surface pretreatment: sandblast the surface of the metal substrate 1 to obtain surface roughness, and use a roughness meter to confirm that the surface roughness Ra is 5-7 μm, and use pure water and isopropanol to clean the substrate surface and airway ultrasonically for 30 minutes;

[0048] The metal substrate 1 after surface cleaning must undergo strict surface pretreatment before coating treatment to ensure that the surface of the substrate is uniform and free of residual impurities, forming a clean surface with a roughness of 5 to 7 μm. Treatment methods include but are not limited to the following: sandblasting, mechanical grinding, chemical cleaning, laser treatment, plasma treatment;

[0049] S2: Preparation of the first coating: preparing a lower layer 2, a metal layer 3 and an upper layer 4 on the surface of the metal substrate 1 by an atmospheric plasma thermal spraying method, wherein the thickness of the lower layer 2 is 25 to 550 μm, the thickness of the metal layer 3 is 10 to 30 μm, and the thickness of the upper layer 4 is 15 to 320 μm;

[0050] In other implementations of this embodiment, the thickness of the lower layer 2 is 25 μm or 550 μm, the thickness of the metal layer 3 is 10 μm or 30 μm, and the thickness of the upper layer 4 is 15 μm or 320 μm. In addition, the thickness of the lower layer 2 can also be 320 μm, the thickness of the metal layer 3 can also be 20 μm, and the thickness of the upper layer 4 can also be 250 μm.

[0051] S3: Mechanical grinding of the first coating: The surface of the formed first coating is ground using a grinder, and the flushing material is pure water to ensure that the surface of the first coating is clean and flat, and the surface roughness of the upper layer 4 is Ra≤0.2μm;

[0052] S4: Preparation of the second coating 5: preparing the second coating 5 on the surface of the upper layer 4 by atomic layer deposition, the thickness of the second coating 5 is 0.1-50 μm, and the surface roughness Ra is ≤ 0.2 μm;

[0053] S5: Coating inspection: Use a scanning electron microscope to take SEM pictures, and observe that there are no obvious pits or protrusions on the surface of the overall coating. The atomic layer deposition method fills the surface of the coating and cracks and pores of a certain depth. The porosity of the coating is analyzed by Image software to obtain the porosity of the first coating and the second coating 5 to determine whether it meets the requirements. The coating is prepared by the method of the present application, and the porosities of the first coating and the second coating 5 are 2.98% and 0.4%, respectively.

[0054] The low-porosity coating and the preparation method thereof in the present technical solution have the following advantages:

[0055] 1. Atomic layer deposition can evenly deposit on the surface of thermal spray coating to form a dense ceramic coating, greatly reducing the pits on the coating surface and the pores and microcracks inside;

[0056] 2. The insulation of the low-porosity ceramic coating can be significantly improved, the risk of charge leakage is reduced, the clamping force and stability of the electrostatic chuck are improved, and the electrostatic chuck can still work reliably under vacuum environment and high voltage conditions;

[0057] 3. The smoother second coating 5 surface reduces the need for grinding, fills the pores and defects on the surface, reduces the generation of electric field concentration areas, and reduces the risk of electrostatic chuck failure caused by arc discharge;

[0058] 4. High-precision control of the process for preparing the second coating 5 can make the interface between the second coating 5 and the first coating more tightly bonded, and good interlayer bonding strength improves the overall durability of the coating and reduces the problem of coating peeling or damage during use;

[0059] 5. Compared with the previous high-cost and complex processes, by optimizing the coating preparation process and using a process different from thermal spraying to prepare the double-layer covering layer, the manufacturing process is simplified, the environmental impact and process difficulty are greatly reduced, and the use of low-porosity coatings and multi-layer structures also eliminates the problem of sealant inapplicability, ensuring the reliability of the coating in a high-demand environment;

[0060] 6. Optimizing coating surface treatment and interlayer bonding measures through atomic layer deposition technology can improve coating adhesion and overall flatness, reduce surface defects, and improve electrostatic chuck performance.

[0061] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A low porosity coating for an electrostatic chuck, characterized in that: The low-porosity coating includes a first coating disposed on a metal substrate, and a second coating disposed on the first coating, wherein the first coating is a ceramic layer without appearance damage disposed on the metal substrate by a thermal spraying method, and the second coating is a low-porosity ceramic layer disposed on the first coating by an atomic layer deposition method.

2. A low porosity coating for an electrostatic chuck according to claim 1, characterized in that: The metal substrate is a metal material or a metal-based composite material.

3. A low porosity coating for an electrostatic chuck according to claim 1, characterized in that: The preparation material of the first coating is: any one or two of Al2O3, AlN, ZrO2, SiC, TiO2, Y2O3, YF3, YOF, YAP, YAM, Gd2O3, Er2O3, Sm2O3, or a mixture of two or more to ensure that the coating is free of crack damage.

4. A low porosity coating for an electrostatic chuck according to claim 3, characterized in that: The first coating layer includes an upper layer, a lower layer and a metal layer disposed between the upper layer and the lower layer. The lower layer is disposed on the metal substrate. The preparation material of the metal layer includes W or Mo.

5. The low porosity coating for an electrostatic chuck according to claim 1, characterized in that: The preparation material of the second coating layer includes at least one of Al2O3, AlN, ZrO2, Y2O3, Gd2O3, Er2O3, and Sm2O3.

6. A low porosity coating for an electrostatic chuck according to claim 1, characterized in that: The overall porosity of the first coating is less than or equal to 4%, the total thickness is 50 to 900 μm, the surface roughness is 5 to 7 μm, and the first coating is ground and polished after the thermal spraying process is completed. The surface roughness Ra after grinding and polishing is ≤ 0.2 μm to ensure the surface flatness of the coating.

7. A low porosity coating for an electrostatic chuck according to claim 1, characterized in that: The porosity of the second coating is less than or equal to 1%, the thickness is 0.1-50 μm, and the surface roughness Ra is less than or equal to 0.2 μm.

8. The low porosity coating for an electrostatic chuck according to claim 1, characterized in that: The thermal spraying method is any one of atmospheric plasma spraying, flame spraying, high energy plasma spraying and vacuum plasma spraying.

9. A method for preparing a low-porosity coating for an electrostatic chuck according to any one of claims 1 to 8, characterized in that: The preparation method comprises: S1: Substrate surface pretreatment: sandblast the surface of the metal substrate to produce surface roughness, use a roughness meter to confirm that the surface roughness Ra is 5-7 μm, and use pure water and isopropanol to clean the substrate surface and airway ultrasonically for 30 minutes; S2: Preparation of the first coating: preparing a lower layer, a metal layer and an upper layer on the surface of the metal substrate by an atmospheric plasma thermal spraying method, wherein the thickness of the lower layer is 25 to 550 μm, the thickness of the metal layer is 10 to 30 μm, and the thickness of the upper layer is 15 to 320 μm; S3: Mechanical grinding of the first coating: The surface of the first coating is ground using a grinder, and the flushing material is pure water to ensure that the surface of the first coating is clean and flat, and the surface roughness of the upper layer is Ra≤0.2μm; S4: Preparation of the second coating: preparing the second coating on the upper surface by atomic layer deposition, the thickness of the second coating is 0.1-50 μm, and the surface roughness Ra ≤ 0.2 μm; S5: Coating inspection: Use a scanning electron microscope to take SEM pictures, and observe that there are no obvious pits and protrusions on the surface of the overall coating. The atomic layer deposition method fills the surface of the coating and cracks and pores of a certain depth. Perform a porosity analysis on the coating to obtain the porosity of the first coating and the second coating to determine whether it meets the requirements.

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