Plasma etching resistant nanostructured composite ceramic coating and method of making

Abstract

The application discloses a kind of nanostructure composite ceramic coating resistant to plasma etching and preparation method thereof, belong to the surface protection technical field in the process of semiconductor device manufacturing, composite ceramic coating includes the surface protection layer and the primer layer sequentially deposited on substrate using vacuum cold spraying method, the primer layer material is oxide ceramic, the surface protection layer material is high stability rare earth ceramic, the thickness of primer layer is 0.2~20 μm, grain size is 10~200nm, the thickness of surface protection layer is 1~10 μm, grain size is 10~50 nm.The application is by first using the method of vacuum cold spraying on substrate surface to make a layer of oxide ceramic coating as primer layer after heat treatment, to ensure that coating has higher bonding force, prevent subsequent coating from falling off, when making high stability rare earth ceramic, select powder with smaller particle size to make, to ensure that coating has certain etching resistance.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of surface protection in semiconductor device manufacturing process, and particularly relates to a nano-structured composite ceramic coating resistant to plasma etching and a preparation method thereof. BACKGROUND

[0002] With the continuous development of semiconductor manufacturing process towards higher precision and smaller feature size, as the core means of pattern transfer, the process environment of plasma etching technology is developing towards higher energy density, higher frequency and stronger reactivity. In advanced processes (such as 5nm and below), in order to meet the high standard requirements of etching selectivity, pattern fidelity and device cleanliness, the protection performance of the internal structure of the etching chamber has become one of the key factors affecting the performance of the equipment and the yield of the device. Especially under the condition of fluorine-containing etching gas represented by CF4 and CHF3, the plasma has a strong corrosion and sputtering effect on the surface material of the equipment, which easily leads to the erosion and degradation of the materials of the key components such as the chamber lining, and then causes the micro-particle pollution. This pollution will deposit on the wafer surface, resulting in a decrease in yield. In addition, the frequent replacement and maintenance of equipment components also cause production interruption and cost increase.

[0003] In order to improve the service life and process stability of the equipment in the plasma etching environment, thermal spraying technology (such as atmospheric plasma spraying) is widely used to deposit a ceramic protective layer with controllable thickness on the surface of the equipment component. At present, the thermal spraying coating using Y2O3 or Al2O3 as the base has achieved effective blocking of high temperature and strong corrosive plasma to some extent, and therefore has been widely used in large-size (such as 8 inches and above) semiconductor etching equipment. However, the ceramic coating prepared by the traditional thermal spraying process generally has defect structures such as micropores and cracks. Under the long-term bombardment of high-power plasma, these structures easily induce particle peeling, leading to wafer surface pollution and process instability, and affecting the chip yield. In order to improve the etching protection effect, the thickness of the coating often needs to be increased to hundreds of microns, resulting in a significant increase in the cost of coating preparation, and also limiting its further application in higher-order processes.

[0004] In recent years, more and more researches have focused on building high-density nano-structured coatings to enhance the corrosion resistance and impact resistance in the face of high-energy plasma environment. The dense structure not only helps to shield the erosion path of high-energy ions in the plasma, but also significantly reduces the risk of particle generation and interface crack propagation. In addition, the nano-scale structure regulation can effectively optimize the stress distribution and interface bonding strength inside the coating, induce uniform etching of the coating surface, and reduce the generation of particle pollutants, improving the reliability while taking into account the thickness control and insulation performance.

[0005] Therefore, it is urgent to develop a composite ceramic nano coating system with high density, excellent electrical insulation and strong plasma etching resistance, and a new type of preparation process suitable for low temperature and high coverage deposition, to meet the higher requirements of advanced semiconductor manufacturing equipment on the protection performance of structural parts, and to improve the operation stability and process yield of the whole machine. SUMMARY

[0006] To solve the above problems, the present application provides a nano-structured composite ceramic coating resistant to plasma etching and a preparation method, aiming to solve the problems of poor etching resistance, insufficient coating density, weak adhesion to the substrate, poor thermal stability and high cost of thick coating of the existing plasma protective coating in the semiconductor manufacturing process. The present application uses a vacuum cold spraying method to prepare a composite ceramic coating with a primer layer, an intermediate transition layer and a surface protective layer on the substrate. By controlling the process parameters, coating thickness and other parameters of each coating, a protective coating with good plasma etching resistance and a thickness not higher than 50 μm is prepared. The coating structure is reasonable, the material system is stable, the preparation process is controllable, and the coating can provide excellent protection performance in high-energy environments such as plasma etching, prolong the service life of the device, and improve the process window and integration reliability.

[0007] To achieve the above purpose, the present application first provides a nano-structured composite ceramic coating resistant to plasma etching, which comprises a primer layer and a surface protective layer deposited on a substrate in sequence by a vacuum cold spraying method. The primer layer material is an oxide ceramic, and the surface protective layer material is a high-stability rare earth ceramic. The thickness of the primer layer is 0.2-20 μm, the grain size is 10-200 nm, and the coating porosity is <2%. The thickness of the surface protective layer is 1-10 μm, the grain size is 10-50 nm, and the coating porosity is <1%.

[0008] In an embodiment of the present application, an intermediate transition layer is further provided between the primer layer and the surface protective layer, and the intermediate transition layer is a composite of oxide ceramic and high-stability rare earth ceramic. The thickness of the intermediate transition layer is 0.2-20 μm, the grain size is in the range of 10-200 nm, and the coating porosity is <2%.

[0009] In an embodiment of the present application, the primer layer material is aluminum oxide or yttrium oxide, the primer layer thickness is preferably 1-15 μm, further preferably 2-10 μm, the grain size is controlled in the range of 10-200 nm, preferably 50-150 nm, and the coating porosity is <2%.

[0010] In an embodiment of the present application, the surface protective layer material includes at least one of yttrium oxide, yttrium fluoride, yttrium oxyfluoride or yttrium aluminum garnet, the surface layer thickness is 1-10 μm, the grain size is controlled in the range of 10-50 nm, and the coating porosity is <1%.

[0011] In one embodiment of the present application, the intermediate transition layer material is a mixture of the primer layer material and the surface protective layer material, i.e. a mixture of oxide ceramic and high-stability rare earth ceramic, the mass ratio of the oxide ceramic and the high-stability rare earth ceramic being 7:3 to 3:7, the thickness of the intermediate transition layer being 0.2 to 20 μm, preferably 1 to 15 μm, further preferably 2 to 10 μm, the grain size range being 10 to 200 nm, preferably 50 to 150 nm, and the coating porosity being < 2%.

[0012] In one embodiment of the present application, the intermediate transition layer material is a composite of the primer layer material and the surface protective layer material, the composite being high-stability rare earth ceramic coated oxide ceramic, the particle size of the composite being 0.1 to 5 μm.

[0013] In the present application, the primer layer is selected from oxide ceramic materials, such as alumina or yttria, and is mainly used to improve the adhesion between the coating and the substrate and to inhibit the interface stress concentration. The intermediate layer is a mixed zone of the primer layer and the surface layer material, adopts a gradient structure design, and is used to realize the transition between materials, release the interface stress, and further improve the overall stability of the coating structure. The surface layer is a functional protective layer directly exposed to the plasma environment, and the material is selected from high-stability rare earth ceramics, such as yttria, yttrium fluoride, yttrium oxyfluoride, or yttrium aluminum garnet, and has high plasma stability and low etching rate.

[0014] In one embodiment of the present application, the substrate includes but is not limited to any one of ceramic, metal, glass, and polymer plastic.

[0015] The present application also discloses a preparation method of the above-mentioned plasma-etching-resistant nano-structured composite ceramic coating.

[0016] (1) The surface of the substrate is subjected to mechanical polishing treatment, so that the surface roughness Ra is < 0.2 μm;

[0017] (2) An oxide ceramic powder with a powder particle size of 0.1 to 5 μm is selected, and a primer layer is prepared on the substrate by vacuum cold spraying, and the primer layer is subjected to heat treatment;

[0018] (3) An intermediate transition layer is prepared on the primer layer obtained in step (2) by vacuum cold spraying, the particle size range of the transition layer powder being 0.1 to 5 μm, and the transition layer is subjected to heat treatment after being prepared;

[0019] (4) A surface protective layer is prepared on the surface of the heat-treated transition layer obtained in step (3), the particle size range of the surface protective layer powder being 0.2 to 2 μm, and the surface protective layer is subjected to heat treatment after being prepared.

[0020] In one embodiment of the present application, the powder particle size in step (2) is preferably 0.2-3 μm, further preferably 0.5-2 μm, the thickness of the primer layer is 0.2-20 μm, the vacuum cold spraying process uses nitrogen or compressed air as the working gas, the gas flow rate is 5-50 L / min, the spraying distance is 3-20 mm, and the powder feeding rate is 0.1-5 g / min.

[0021] In one embodiment of the present application, the gas flow rate in the vacuum cold spraying process in step (2) is preferably 10-30 L / min, the spraying distance is preferably 5-15 mm, and the powder feeding rate is preferably 0.5-2 g / min.

[0022] In one embodiment of the present application, the heat treatment in step (2) is performed at a temperature of 400-1000 ℃, preferably 600-800 ℃, for a time period of 1-10 h, preferably 2-6 h.

[0023] In one embodiment of the present application, the powder particle size in step (3) is preferably 0.2-2 μm, the thickness of the intermediate transition layer is 0.2-20 μm, the intermediate transition layer material is a mixture of the primer layer material and the surface protection layer material, i.e. a mixture of oxide ceramic and high-stability rare earth ceramic, the mass ratio of the oxide ceramic and the high-stability rare earth ceramic is 7:3-3:7, and the mixture is prepared by mechanical mixing.

[0024] In one embodiment of the present application, the vacuum cold spraying process in step (3) uses nitrogen or compressed air as the working gas, the gas flow rate is 5-50 L / min, the spraying distance is 3-20 mm, and the powder feeding rate is 0.1-5 g / min.

[0025] In one embodiment of the present application, the gas flow rate in the vacuum cold spraying process in step (3) is preferably 10-30 L / min, the spraying distance is preferably 5-15 mm, and the powder feeding rate is preferably 0.5-2 g / min.

[0026] In one embodiment of the present application, the heat treatment in step (3) is performed at a temperature of 400-1000 ℃, preferably 600-800 ℃, for a time period of 1-10 h, preferably 2-6 h.

[0027] In one embodiment of the present application, the powder particle size in step (4) is preferably 0.3-1 μm, the thickness of the surface protection layer is 1-10 μm, the vacuum cold spraying process uses nitrogen or compressed air as the working gas, the gas flow rate is 5-50 L / min, the spraying distance is 3-20 mm, and the powder feeding rate is 0.1-5 g / min.

[0028] In one embodiment of the present application, the gas flow rate in the vacuum cold spraying process of step (4) is preferably 10-20 L / min, the spraying distance is preferably 5-10 mm, and the powder feeding rate is preferably 0.5-2 g / min.

[0029] In one embodiment of the present application, the heat treatment in step (3) is performed at a temperature of 400-1000 ℃, preferably 600-800 ℃, for a time period of 1-10 h, preferably 1-3 h.

[0030] The present application also provides a use of the nanostructured composite ceramic coating described above in a semiconductor device.

[0031] In one embodiment of the present application, the use includes use as a plasma etching protective coating.

[0032] Advantages:

[0033] (1) The present application uses the vacuum cold spraying process to first deposit an oxide ceramic layer with slightly larger porosity and larger grain size on the substrate, and then deposits a high-stability rare earth ceramic layer with smaller porosity and smaller grain size on the surface of the oxide ceramic layer. The larger-grain oxide ceramic bottom layer can increase the bonding strength between the coating and the substrate, prevent the coating from falling off, and also help to increase the etching resistance of the coating. The smaller-grain rare earth ceramic surface layer can further increase the etching resistance of the coating.

[0034] (2) In order to further improve the bonding force between the coatings, the present application further increases an intermediate transition layer between the bottom layer and the surface protective coating. The transition layer is made of a mixture of the bottom layer powder and the surface protective coating powder. The production of the transition layer further increases the bonding force between the bottom layer and the surface protective layer, and also further improves the etching resistance of the composite coating, so that the coating can achieve good etching resistance at a very low thickness, greatly reducing the preparation cost of the etching-resistant coating.

[0035] (3) The present application first uses the vacuum cold spraying method to produce an oxide ceramic coating on the surface of the substrate as a bottom layer. The bottom layer is heat-treated for a long time after production to ensure that the coating has high bonding force and prevents the subsequent coating from falling off. A high-stability rare earth ceramic is then produced on the surface of the coating. In the production of the high-stability rare earth ceramic, a powder with a smaller particle size is used. Even if the grain size increases to a certain extent during subsequent heat treatment, the coating can still have certain etching resistance.

[0036] (4) The present application selects the powder with the particle size of 0.1-5 um to carry out vacuum cold spraying when the base layer and the intermediate transition layer are made, the thickness of the intermediate layer and the transition layer is not higher than 20 um, the powder particle size of the surface protective coating is selected to be 0.2-2 um, the thickness of the surface protective layer is not higher than 10 um, the adhesion between the coatings is further adjusted by further adjusting the material particle size and the coating thickness, and the etching resistance of the composite coating is further improved.

[0037] (5) The three-layer structure of the present application provides good stress distribution and interface matching performance for the coating, the composite design effectively inhibits crack initiation and propagation; the nanocrystalline grain refinement significantly improves the density, thermal shock resistance and micro stability of the coating, effectively reduces the formation of particulate pollutants; the vacuum cold spraying process is low-temperature and non-melting, avoids material structure degradation, and is suitable for heat-sensitive substrates and high-precision requirements; the material system is flexible and adjustable, suitable for protective requirements in different process environments, and has industrial application potential.

[0038] (6) The present application constructs a nano-structured plasma protection composite ceramic coating system, and proposes an efficient, low-loss and controllable preparation method, which provides a new material solution for plasma etching protection in semiconductor device manufacturing. BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 Figure 1 is the coating surface morphology of the three-layer structure composite coating after etching of Example 1;

[0040] Figure 2 Figure 2 is the coating surface morphology of the yttrium oxide coating after etching of Comparative Example 1;

[0041] Figure 3 Figure 3 is a coating structure of a nano-structured plasma protection composite coating, wherein 1 is a substrate, 2 is a composite coating, 21 is a base layer, 22 is an intermediate transition layer, and 23 is a surface protective layer. DETAILED DESCRIPTION

[0042] The present application will be described in detail below with specific embodiments. The following examples will help those skilled in the art to further understand the present application, but do not limit the present application in any form. It should be pointed out that, for those skilled in the art, without departing from the concept of the present application, a number of changes and improvements can be made. These all belong to the protection scope of the present application.

[0043] The nano-structured composite ceramic coating for plasma etching provided by the embodiments of the present application is suitable for surface protection of the inner wall parts of the semiconductor etching equipment chamber.

[0044] The coating thickness involved in the examples and comparative examples of the present application is observed by scanning electron microscope (SEM) on the cross section of the coating, 10 measurement points are selected at different positions of the coating by cross section sample preparation, and data reading and statistics are carried out by combining image analysis software to obtain the average thickness of each layer of the coating. The porosity is obtained by acquiring the SEM image of the cross section of the coating, the pore area is identified and quantified by image gray threshold segmentation method, and the average porosity is determined by calculating the area ratio of black and white pixels. The grain size and coating bonding strength are tested on three samples, and the average value of the results of the three samples is taken.

[0045] Example 1

[0046] A nano-structured composite ceramic coating 2 resistant to plasma etching, comprising a primer layer 21, an intermediate transition layer 22 and a surface protective layer 23 prepared in sequence on the surface of an alumina substrate 1 by vacuum cold spraying method, the material of the primer layer 21 is alumina, the coating thickness is 5 μm, the grain size is 120 nm, the intermediate transition layer 22 is a mixture of alumina and yttrium oxide, the ratio of the two is 1:1, the thickness of the intermediate transition layer 22 is 5 μm, the grain size is 120 nm, the material of the surface protective layer 23 is yttrium oxide, the thickness of the surface protective layer is 5 μm, and the grain size is 40 nm.

[0047] A preparation method of a nano-structured composite ceramic coating resistant to plasma etching, comprising the following steps:

[0048] (1) Alumina powder with a particle size D50 of 1.2 μm is selected, and a primer layer with a thickness of 5 μm is prepared by vacuum cold spraying method, nitrogen is used as working gas during vacuum cold spraying preparation, the gas flow is 25 L / min, the spraying distance is 10 mm, the powder feeding rate is 2 g / min, and after the primer layer is prepared, it is subjected to heat treatment, the heat treatment temperature is 800 ℃, and the time is 5 h;

[0049] (2) The alumina powder with a particle size D50 of 1.2 μm and the yttrium oxide powder with a particle size D50 of 0.8 μm are mixed by using a drum ball milling method, after ball milling for 1 h, an intermediate transition layer with a thickness of 5 μm is prepared by vacuum cold spraying method, nitrogen is used as working gas during vacuum cold spraying preparation, the gas flow is 25 L / min, the spraying distance is 10 mm, the powder feeding rate is 2 g / min, and after the primer layer is prepared, it is subjected to heat treatment, the heat treatment temperature is 800 ℃, and the time is 5 h;

[0050] (3) The yttria powder with a particle size D50 of 0.8 μm is selected, and a surface protective layer with a thickness of 5 μm is prepared by vacuum cold spraying, in which nitrogen is used as the working gas, the gas flow rate is 15 L / min, the spraying distance is 8 mm, and the powder feeding rate is 1.2 g / min. After the preparation of the base layer, heat treatment is performed, the heat treatment temperature is 600 ℃, and the time is 2 h.

[0051] Through characterization analysis, the results show that the overall thickness of the composite coating is 15 μm, the porosity of the base layer and the transition layer is 1.2%, the grain size is 120 nm, the porosity of the surface protective layer is 0.5%, the grain size is 40 nm, and the coating bonding strength is 22 MPa; under the CF4 / O2 atmosphere, etching for 8 hours, as shown in FIG. 2, there are etching pits on the surface of the composite coating, no obvious structure degradation, and the etching rate is about 2.1 nm / min. Figure 1

[0052] Example 2

[0053] A nano-structured composite ceramic coating resistant to plasma etching, comprising a base layer, an intermediate transition layer and a surface protective layer prepared on the surface of a quartz glass substrate by vacuum cold spraying, wherein the base layer is made of aluminum oxide with a thickness of 0.5 μm and a grain size of 50 nm; the intermediate transition layer is a mixture of aluminum oxide and yttrium oxide with a mass ratio of 7:3, a thickness of 1 μm and a grain size of 50 nm; and the surface protective layer is yttria with a thickness of 0.5 μm and a grain size of 30 nm.

[0054] The preparation method of the composite ceramic coating comprises the following steps:

[0055] (1) The aluminum oxide powder with a particle size D50 of 0.3 μm is selected, and a base layer with a thickness of 0.5 μm is deposited on the surface of the aluminum oxide substrate by vacuum cold spraying, in which nitrogen is used as the working gas, the gas flow rate is 8 L / min, the spraying distance is 5 mm, the powder feeding rate is 0.5 g / min, and heat treatment is performed after spraying, the heat treatment temperature is 400 ℃, and the time is 3 h;

[0056] (2) The aluminum oxide powder with a particle size D50 of 0.3 μm and the yttrium fluoride powder with a particle size D50 of 0.5 μm are mixed in a mass ratio of 7:3 by a drum ball milling method for 1 h, and then a intermediate transition layer with a thickness of 1 μm is prepared by using the same process parameters as in step (1);

[0057] ​(3) YF3 powder with D50 of 0.5 μm was used to prepare the surface protective layer with a thickness of 1 μm by vacuum cold spraying, and the spraying conditions were as follows: nitrogen flow rate 10 L / min, spraying distance 10 mm, powder feeding rate 1.0 g / min, heat treatment temperature 400 ℃, and heat treatment time 1 h.

[0058] The prepared composite coating had a total thickness of 2.5 μm, a porosity of 0.9%, a grain size in the range of 30-50 nm, and a bonding strength of 23 MPa. After etching in a CF4 / O2 plasma atmosphere for 8 h, the etching rate was about 2.0 nm / min, and no obvious structure spalling occurred on the surface, as shown in FIG. 2. Figure 1

[0059] Example 3

[0060] A nanostructured composite ceramic coating resistant to plasma etching comprises a base layer, an intermediate transition layer, and a surface protective layer prepared on the surface of an alumina substrate by vacuum cold spraying in sequence, wherein the base layer is Y2O3, has a thickness of 15 μm, and a grain size of 150 nm; the intermediate transition layer is a mixture of Y2O3 and YOF, has a mass ratio of 4:6, a thickness of 18 μm, and a grain size of 150 nm; and the surface protective layer is YOF, has a thickness of 10 μm, and a grain size of 50 nm.

[0061] The preparation method of the composite ceramic coating comprises the following steps:

[0062] (1) Y2O3 powder with D50 of 2.3 μm was used to prepare the base layer with a thickness of 15 μm on the surface of an aluminum alloy substrate by vacuum cold spraying, and the spraying process used nitrogen as the working gas, the nitrogen flow rate was 35 L / min, the spraying distance was 15 mm, the powder feeding rate was 2.5 g / min, and heat treatment was performed after spraying, the heat treatment temperature was 800 ℃, and the heat treatment time was 6 h;

[0063] (2) Y2O3 powder with D50 of 2.3 μm and YOF powder with D50 of 0.8 μm were mixed in a mass ratio of 4:6 by a drum ball milling method for 1 h, and then an intermediate transition layer with a thickness of 18 μm was prepared by using the same process parameters as in step (1);

[0064] (3) YOF powder with D50 of 0.8 μm was used to prepare the surface protective layer with a thickness of 10 μm by vacuum cold spraying, and the spraying conditions were as follows: nitrogen flow rate 15 L / min, spraying distance 10 mm, powder feeding rate 1.0 g / min, heat treatment temperature 600 ℃, and heat treatment time 3 h.

[0065] ​The prepared composite coating has a total thickness of 43 μm, a porosity of 1.9% and a grain size of 150 nm in the base layer, a porosity of 0.8% and a grain size of 50 nm in the surface protective layer, and a bonding strength of 18 MPa. After etching in a CF4 / O2 plasma atmosphere for 8 hours, the etching rate is about 2.5 nm / min, and no obvious structure peeling occurs on the surface.

[0066] Example 4

[0067] Example 4 is different from Example 1 in that the base layer is an alumina coating with a thickness of 30 μm, the intermediate transition layer is an alumina / yttria coating (mass ratio 1:1) with a thickness of 30 μm, and the surface protective layer is yttria with a thickness of 15 μm.

[0068] The coating has a total thickness of 45 μm, a porosity of 1.8% and a grain size of 150 nm in the base layer, a porosity of 2.2% and a grain size of 130 nm in the intermediate transition layer, and a porosity of 1.4% and a grain size of 80 nm in the surface protective layer. The bonding strength of the composite coating is measured to be 12 MPa. After the plasma etching experiment (CF4 / O2 atmosphere, etching time 8 hours), the etching rate is 3.1 nm / min, and a small amount of cracks exist in the coating.

[0069] Comparative Example 1

[0070] Comparative Example 1 is different from Example 1 in that a vacuum cold spraying method is used to only prepare a surface protective yttria layer on the substrate.

[0071] High-purity yttria powder with a D50 particle size of 0.8 μm is directly used for spraying, and the coating is prepared by vacuum cold spraying technology. Nitrogen is used as the working gas, the gas flow is 15 L / min, the spraying distance is 8 mm, and the powder feeding rate is 1.2 g / min. The deposition thickness is 9 μm, the porosity of the coating is about 0.8%, the grain size is 80 nm, and the bonding strength is measured to be 9 MPa, which is lower than that of the composite sample (22 MPa). After the plasma etching experiment (CF4 / O2 atmosphere, etching time 8 hours), etching pits exist on the surface of the composite coating, the etching rate is 3.6 nm / min, as shown in Figure 2 , and it can be observed that part of the coating falls off.

[0072] Comparative Example 2

[0073] Comparative Example 2 is different from Example 1 in that the base layer is an alumina coating with a thickness of 10 μm, the intermediate transition layer is an alumina / yttria coating (mass ratio 1:1) with a thickness of 10 μm, and the surface protective layer is yttria with a thickness of 5 μm.

[0074] The coating is prepared without heat treatment after each layer of the coating is prepared.

[0075] The total thickness of the coating is 25 μm, the porosity of the base layer is 2.1%, and the grain size is 80 nm; the porosity of the intermediate transition layer is 2.3%, and the grain size is 80 nm; the porosity of the surface protective layer is 1.6%, and the grain size is 50 nm. The measured bonding strength of the composite coating is only 7 MPa, which is significantly lower than that of the coating prepared in Example 1 (22 MPa) under the relatively optimal preparation parameters. Before the plasma etching experiment, part of the coating of the composite coating falls off, and after the plasma etching experiment (CF4 / O2 atmosphere, etching time 8 hours), the range of coating falling off is expanded, and the etching rate is calculated to be 5.8 nm / min.

[0076] Comparative Example 3

[0077] Comparative Example 3 is different from Example 1 in that the particle size of the aluminum oxide powder in the base layer and the transition layer is 2.5 μm, and the particle size of the yttrium oxide powder in the transition layer and the surface protective layer is 2.2 μm. The thickness of the aluminum oxide is 5 μm, the intermediate transition layer is 5 μm, and the thickness of the surface protective layer is 2 μm.

[0078] The total thickness of the coating is 12 μm, the porosity of the base layer is 2.5%, and the grain size is 180 nm; the porosity of the intermediate transition layer is 2.8%, and the grain size is 150; the porosity of the surface protective layer is 1.8%, and the grain size is 120 nm, the bonding strength is only 3 MPa, the etching rate is as high as 12.5 nm / min, and the surface appears obvious peeling and structure collapse phenomenon.

[0079] The experimental data of Examples 1-4 and Comparative Examples 1-3 are shown in Table 1. As can be seen from Table 1, if only the vacuum cold spraying method is used to prepare the yttrium oxide coating, the plasma etching resistance of the 9 μm thick yttrium oxide coating is about 3.6 nm / min, the coating has a certain etching resistance, but the bonding strength of the coating is low, and the coating will fall off during etching. It is found that additional heat treatment of the yttrium oxide coating helps to increase the bonding strength of the coating, but at the same time, the grain size in the coating increases, which further reduces the etching resistance of the coating.

[0080] In order to further improve the easy peeling performance of the yttrium oxide coating, the structure of the base layer, the intermediate transition layer and the surface protective layer is designed for experiment, as in Comparative Example 2, it is found that only increasing the aluminum oxide as the base layer and increasing the transition layer structure cannot improve the bonding strength of the coating, nor can it increase the etching resistance of the coating, and the comprehensive performance of the coating has decreased significantly.

[0081] The application first uses a vacuum cold spraying method to make an oxide ceramic coating as a primer layer on the surface of the substrate, and then performs a long time heat treatment after the primer layer is made to ensure that the coating has high bonding strength and prevents the subsequent coating from falling off. Then, a high-stability rare earth ceramic is made on the surface of the coating. When the high-stability rare earth ceramic is made, a powder with a small particle size is selected for making, so that even if the grain size increases to a certain extent during subsequent heat treatment, the coating can still have certain etching resistance.

[0082] In order to further improve the bonding strength between the coatings, the application further adds an intermediate transition layer between the primer layer and the surface protective coating. The transition layer is made of a mixture of the primer layer powder and the surface protective coating powder. The preparation of the transition layer further increases the bonding strength between the primer layer and the surface protective layer, and further improves the etching resistance of the composite coating, so that the coating can achieve good etching resistance at very low thickness, greatly reducing the preparation cost of the etching-resistant coating.

[0083] The particle size of the powder material of the primer layer and the surface protective coating also has a great influence on the performance of the composite coating. As can be seen from the experimental data of Examples and Comparative Example 3, when the particle size of the powder used in the surface composite coating is greater than 1.5 μm, or even greater than 2 μm, the etching resistance of the bonding strength of the coating is significantly reduced, which cannot meet the requirements.

[0084] In addition, the thickness of each layer and the overall thickness of the coating will significantly affect the bonding strength and etching resistance of the composite coating. As can be seen from Example 1 and Example 4, when the thickness of the primer layer and the transition layer increases to more than 20 μm, and the thickness of the surface protective layer increases to more than 10 μm, the bonding strength between the coatings decreases. Compared with Example 1, although Example 4 also uses a three-layer structure, with the increase of the thickness of the composite coating, problems such as high porosity and coarse grains of the coating occur, resulting in that the bonding strength and etching resistance of the coating are significantly lower than those of Example 1, and cracks begin to appear in the coating of Example 4.

[0085] Table 1 Comparison of results of composite coatings of Examples and Comparative Examples

[0086]

[0087] The above examples are not intended to limit the scope of the application, and the described steps are not intended to limit the execution order. Those skilled in the art can make obvious improvements to the application based on existing common knowledge, which also falls within the protection scope defined by the claims of the application.

Claims

1. A nanostructured composite ceramic coating resistant to plasma etching, characterized in that, The method comprises a base layer, an intermediate transition layer, and a surface protective layer sequentially deposited on a substrate using a vacuum cold spraying method. The base layer is made of oxide ceramic, which may be alumina or yttrium oxide. The surface protective layer is made of highly stable rare earth ceramic, including at least one of yttrium oxide, yttrium fluoride, yttrium oxyfluoride, or yttrium aluminum garnet. The intermediate transition layer is a mixture of oxide ceramic and highly stable rare earth ceramic. The thickness of the base layer is 0.2–20 μm, the grain size is 10–200 nm, and the porosity is <2%. The thickness of the surface protective layer is 1–10 μm, the grain size is 10–50 nm, and the porosity is <1%. The thickness of the intermediate transition layer is 0.2–20 μm, the grain size is 10–200 nm, and the porosity is <2%. The preparation method of the nanostructured composite ceramic coating includes the following steps: (1) The surface of the substrate is mechanically polished to make its surface roughness Ra < 0.2 μm; (2) Select oxide ceramic powder with a particle size of 0.2~2.3 μm, use vacuum cold spraying to make a base layer on the substrate, and then heat treat it; (3) A vacuum cold spraying method is used to make an intermediate transition layer on the base layer obtained in step (2). The particle size range of the transition layer powder is 0.2~2 μm. After the transition layer is made, heat treatment is performed. (4) A surface protective layer is made on the surface of the heat-treated transition layer obtained in step (3). The particle size range of the surface protective layer powder is 0.3~0.8 μm. After the surface protective layer is made, heat treatment is performed.

2. The nanostructured composite ceramic coating according to claim 1, characterized in that, The thickness of the substrate is 2~10 μm, and the grain size is controlled at 50~150 nm.

3. The nanostructured composite ceramic coating according to claim 1, characterized in that, In the intermediate transition layer, the mass ratio of oxide ceramic and high-stability rare earth ceramic is 7:3 to 3:7, the thickness of the intermediate transition layer is 2 to 10 μm, and the grain size ranges from 50 to 150 nm.

4. The nanostructured composite ceramic coating according to claim 1, characterized in that, The substrate material includes any one of ceramics, metals, glass, and polymer plastics.

5. The method for preparing the nanostructured composite ceramic coating according to any one of claims 1 to 4, characterized in that, Includes the following steps: (1) The surface of the substrate is mechanically polished to make its surface roughness Ra < 0.2 μm; (2) Select oxide ceramic powder with a particle size of 0.2~2.3 μm, use vacuum cold spraying to make a base layer on the substrate, and then heat treat it; (3) A vacuum cold spraying method is used to make an intermediate transition layer on the base layer obtained in step (2). The particle size range of the transition layer powder is 0.2~2 μm. After the transition layer is made, heat treatment is performed. (4) A surface protective layer is made on the surface of the heat-treated transition layer obtained in step (3). The particle size range of the surface protective layer powder is 0.3~0.8 μm. After the surface protective layer is made, heat treatment is performed.

6. The preparation method according to claim 5, characterized in that, In step (2), the vacuum cold spraying process uses nitrogen or compressed air as the working gas, with a gas flow rate of 5~50 L / min, a spraying distance of 3~20 mm, a powder feeding rate of 0.1~5 g / min, a heat treatment temperature of 400~1000 ℃, and a treatment time of 1~10 h.

7. The preparation method according to claim 5, characterized in that, In step (3), the vacuum cold spraying process uses nitrogen or compressed air as the working gas, with a gas flow rate of 5~50 L / min, a spraying distance of 3~20 mm, a powder feeding rate of 0.1~5 g / min, a heat treatment temperature of 400~1000 ℃, and a treatment time of 1~10 h.

8. The preparation method according to claim 5, characterized in that, The thickness of the surface protective layer in step (4) is 1~10 μm. The vacuum cold spraying process uses nitrogen or compressed air as the working gas with a flow rate of 5~50 L / min, a spraying distance of 3~20 mm, a powder feeding rate of 0.1~5 g / min, a heat treatment temperature of 400~1000 ℃, and a treatment time of 1~10 h.

9. The application of the nanostructured composite ceramic coating according to any one of claims 1 to 4 as a plasma etching protective coating in semiconductor devices.

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