Method for preparing super-thick coating through dynamic compensation optimization chemical vapor deposition

Abstract

The invention discloses a method for preparing an ultra-thick coating through dynamic compensation optimization chemical vapor deposition, and belongs to the technical field of coating preparation. The method comprises the following steps: firstly, establishing a three-dimensional chemical vapor deposition model without a coating and with a predicted coating thickness, analyzing the change of the deposition rate on the surface of the substrate caused by the growth of the coating, and then regulating and controlling the deposition condition through fluid mechanics simulation to realize dynamic compensation regulation and control in the deposition process. According to the method, the surface deposition rate of the super-thick coating in the growth process is kept relatively stable, the problem that existing fluid mechanics simulation cannot be adapted to geometric distribution of a cavity in the later growth period of the super-thick coating and the initial condition deviation is large can be effectively solved, and the method can adapt to the regulation and control process of preparing different super-thick coatings through various chemical vapor deposition methods; the method is particularly suitable for batch production of multiple substrates, greatly saves experiment trial and error time and economic cost, improves the growth design efficiency of the super-thick coating, and has important application prospects.

Description

Technical Field

[0001] The invention belongs to the technical field of coating preparation, and in particular relates to a method for preparing an ultra-thick coating by dynamically compensating and optimizing chemical vapor deposition. Background Art

[0002] In recent years, with the needs of third-generation semiconductor production equipment and high-temperature protective coatings, high-temperature resistant and corrosion-resistant coatings such as SiC and TaC have received extensive attention and can be used in extreme temperatures, mechanical loads, heat flows, and chemical corrosion environments. Chemical vapor deposition (CVD) is a coating preparation technology with good substrate geometry adaptability, high surface coverage, and easy control of precursor ratio and coating thickness. It can deposit coatings with good uniformity, high crystallinity, and high density at lower temperatures, and has become one of the current mainstream coating preparation technologies.

[0003] With the expansion of application scenarios and service environments, thinner coatings can no longer meet the application of various scenarios. The application advantages of ultra-thick coatings in some service environments are more obvious and have received more and more widespread attention. However, unlike the deposition process of thinner coatings, the thickness change of ultra-thick coatings during the deposition process due to coating deposition is more obvious, which will have a certain impact on the geometric arrangement of the reaction chamber. In addition, in order to improve production efficiency, multiple substrates are usually deposited as much as possible at the same time in production. Therefore, this phenomenon will be more significant in multi-substrate deposition systems. The change in coating thickness will cause changes in the spacing between substrates and the spacing between substrates and walls, thereby affecting the flow field distribution, the deposition rate of the coating, etc. This will cause the deposition conditions on the surface during the initial growth stage of the coating to be significantly different from the surface in the later stage of coating growth, making it difficult to ensure the consistency of the coating growth environment, greatly reducing the quality and longitudinal uniformity of the grown coating.

[0004] The current thermal and flow field design of chemical vapor deposition is usually based on the substrate and chamber arrangement without coating thickness to guide the experiment. This strategy is suitable for the growth process of thinner coatings at the micron level, but when the grown coating is thicker and reaches the centimeter level, the coating thickness is close to that of a block, the geometric distribution of the deposition chamber has deviated from the initial conditions, and the flow field environment will change accordingly. The influence of the coating on the internal geometric distribution of the chamber cannot be ignored, especially in industrial mass production, this influence will become more significant. This will inevitably lead to differences in the deposition conditions of the early-grown coating and the later-grown coating, and then lead to differences in the microstructure. Ultimately, stress and cracks will inevitably appear, reducing the performance of the coating. Traditional flow field analysis methods can no longer meet the growth needs of ultra-thick coatings. Therefore, it is necessary to optimize the existing thermal and flow field design strategies to meet the needs of ultra-thick coating deposition and growth. Summary of the invention

[0005] In order to make up for the shortcomings of the existing chemical vapor deposition technology for preparing ultra-thick coatings, the present invention provides a method for preparing ultra-thick coatings by dynamically compensating and optimizing chemical vapor deposition. A simulation design is performed before depositing the ultra-thick coating, and dynamic compensation optimization guidance is provided for the actual production process of the ultra-thick coating. The deposition rate on the coating surface can be stably regulated, so that during the deposition of the ultra-thick coating, the surface deposition conditions do not change significantly with the change of the coating thickness, but are in a relatively stable state, thereby providing an effective means for high-quality deposition of the ultra-thick coating.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing an ultra-thick coating by dynamically compensating and optimizing chemical vapor deposition is provided, comprising the following steps:

[0008] 1) Establish simplified three-dimensional models of the thickness without coating and the thickness of the coating expected to be deposited by chemical vapor deposition equipment;

[0009] 2) Meshing the simplified three-dimensional model generated in step 1) to generate mesh files;

[0010] 3) importing the grid file obtained in step 2) into the simulation solution software of computational fluid dynamics, setting the physical model, then setting the corresponding boundary conditions, and then performing iterative solution to obtain the deposition rate without coating thickness and with the expected coating thickness respectively;

[0011] 4) comparing and analyzing the changes in the deposition rate when there is no coating thickness and when there is an expected coating thickness obtained in step 3), and correcting the boundary conditions with the expected coating thickness so that the deposition rate of the model growth surface with the expected coating thickness is close to the simulation result of the no coating thickness;

[0012] 5) In the actual deposition of the ultra-thick coating, the boundary condition without coating thickness is used as the initial parameter, and the boundary condition with the expected coating thickness after correction obtained in step 4) is used as the endpoint parameter. As the coating thickness increases, the boundary condition parameters of the deposition are adjusted from the initial parameters to the endpoint parameters in a linear manner to achieve dynamic compensation deposition of the ultra-thick coating.

[0013] According to the above scheme, in step 1), a simplified three-dimensional model is established using Spaceclaim software.

[0014] According to the above scheme, in the step 1), when establishing the simplified three-dimensional model, the relevant parameters include the inlet and outlet arrangement, the chamber size, the number of substrates, and the substrate placement method.

[0015] According to the above scheme, in the step 1), when the simplified three-dimensional model is established, the calculation and solution area only includes the fluid domain inside the cavity.

[0016] According to the above scheme, in step 2), Fluent Meshing software is used for meshing.

[0017] According to the above scheme, in step 3), the simulation solution software is Fluent.

[0018] According to the above scheme, in step 3), the physical model includes a flow model, a radiation model and a component transport model; preferably, the flow model adopts a standard k-ε turbulence model; the radiation model adopts a DO model; and the component transport model adopts a Species Transport finite velocity model.

[0019] According to the above scheme, in step 3), the boundary conditions include intake air flow rate, precursor ratio, intake air temperature, substrate rotation speed, inlet type, outlet type, wall temperature, and deposition pressure.

[0020] Preferably, the inlet type is a velocity inlet, and the outlet type is a pressure outlet.

[0021] According to the above scheme, in step 3), the iterative solution adopts the Coupled coupling algorithm.

[0022] According to the above scheme, in step 4), when the absolute value of the surface average deposition rate deviation of the system with coating thickness and the surface deposition rate of the model without coating thickness is more than 5%, the boundary conditions are adjusted to correct the surface average deposition rate deviation to an absolute value of <5%.

[0023] According to the above scheme, in the step 4), in correcting the boundary conditions with the expected coating thickness, one or more boundary conditions are selected for correction.

[0024] Provided is a method for preparing an ultra-thick coating by dynamically compensating and optimizing chemical vapor deposition, wherein the ultra-thick coating has a thickness of 1 to 4 mm.

[0025] According to the above scheme, the ultra-thick coating is dense, has good longitudinal uniformity, and has no cracks or delamination on the cross section.

[0026] The beneficial effects of the present invention are as follows:

[0027] 1. The present invention provides a method for preparing ultra-thick coatings by dynamically compensating and optimizing chemical vapor deposition, establishes a three-dimensional chemical vapor deposition model without coating and with expected coating thickness, analyzes the change in substrate surface deposition rate caused by coating growth, and then regulates deposition conditions through fluid mechanics simulation to achieve dynamic compensation regulation of the deposition process, so that the surface deposition rate of the ultra-thick coating remains relatively stable during the growth process. This can effectively solve the problem that the existing fluid mechanics simulation cannot adapt to the large deviation between the chamber geometric distribution and the initial conditions in the late growth stage of the ultra-thick coating, and can adapt to the regulation process of preparing different ultra-thick coatings by a variety of chemical vapor deposition methods, especially for the mass production of multiple substrates, greatly saving experimental trial and error time and economic costs, and improving the growth design efficiency of ultra-thick coatings. This method has important application prospects.

[0028] 2. The ultra-thick coating prepared by chemical vapor deposition using the method of the present invention is dense, has good longitudinal uniformity, has no cracks or delamination in the cross section, and has practical application value. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flowchart of a dynamic compensation simulation method for chemical vapor deposition of ultra-thick coatings in an example of the present invention.

[0030] Figure 2 This is a simplified schematic diagram of a three-dimensional model of a multi-piece ultra-thick silicon carbide coating deposition equipment in an example of the present invention, wherein the substrate thickness is 4 mm, (a) is a three-dimensional model without coating thickness, and (b) is a three-dimensional model after 3 mm thick coatings are deposited on the upper and lower surfaces of the substrate.

[0031] Figure 3 This is a cross-sectional SEM image of the ultra-thick silicon carbide coating obtained in an embodiment of the present invention.

[0032] Figure 4 This is a surface SEM image of the ultra-thick silicon carbide coating obtained in an embodiment of the present invention. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0034] The present invention aims to provide a dynamic compensation deposition strategy for an ultra-thick coating chemical vapor deposition process combined with fluid mechanics simulation to achieve stable and efficient deposition of the ultra-thick coating.

[0035] like Figure 1 As shown, an embodiment of the present invention provides a method for preparing an ultra-thick coating by dynamically compensating and optimizing chemical vapor deposition, comprising the following steps:

[0036] 1) Establish simplified three-dimensional models of the thickness without coating and the thickness of the coating expected to be deposited by chemical vapor deposition equipment;

[0037] 2) Meshing the simplified three-dimensional model generated in step 1) to generate mesh files;

[0038] 3) importing the grid file obtained in step 2) into the simulation solution software of computational fluid dynamics, setting the physical model, then setting the corresponding boundary conditions, and then performing iterative solution to obtain the deposition rate without coating thickness and with the expected coating thickness respectively;

[0039] 4) comparing and analyzing the changes in the deposition rate when there is no coating thickness and when there is an expected coating thickness obtained in step 3), and correcting the boundary conditions with the expected coating thickness so that the deposition rate of the model growth surface with the expected coating thickness is close to the simulation result of the no coating thickness;

[0040] 5) In the actual deposition of the ultra-thick coating, the boundary condition without coating thickness is used as the initial parameter, and the boundary condition with the expected coating thickness after correction obtained in step 4) is used as the endpoint parameter. As the coating thickness increases, the boundary condition parameters of the deposition are adjusted from the initial parameters to the endpoint parameters in a linear manner to achieve dynamic compensation deposition of the ultra-thick coating.

[0041] In one of the embodiments, in step 1), a simplified three-dimensional model is established using Spaceclaim software, and the calculation and solution area only includes the fluid domain inside the cavity.

[0042] In one of the embodiments, in the step 1), when establishing the simplified three-dimensional model, the relevant parameters include the inlet and outlet arrangement, the chamber size, the number of substrates, and the substrate placement method.

[0043] In one embodiment, in the step 2), Fluent Meshing software is used for meshing.

[0044] In one embodiment, in step 3), the simulation solution software is Fluent.

[0045] In one of the embodiments, in the step 3), the physical model includes a flow model, a radiation model and a component transport model; preferably, the flow model adopts a standard k-ε turbulence model; the radiation model adopts a DO model; and the component transport model adopts a Species Transport finite velocity model.

[0046] In one embodiment, in step 3), the boundary conditions include inlet flow rate, precursor ratio, inlet temperature, substrate rotation speed, inlet type, outlet type, wall temperature, and deposition pressure. Preferably, the inlet type is a velocity inlet, and the outlet type is a pressure outlet.

[0047] In one of the embodiments, in step 3), the iterative solution adopts a Coupled coupling algorithm.

[0048] In one embodiment, in step 4), when the absolute value of the surface average deposition rate deviation between the system with coating thickness and the surface deposition rate of the model without coating thickness is more than 5%, the surface average deposition rate deviation is corrected to an absolute value of less than 5%.

[0049] In one embodiment, in the step 4), in correcting the boundary conditions with the estimated coating thickness, one or more boundary conditions are selected for correction.

[0050] Example 1

[0051] A method for preparing an ultra-thick coating by dynamically compensating and optimizing chemical vapor deposition is provided, comprising the following steps:

[0052] First, use Spaceclaim software to establish three-dimensional simplified models without coating thickness and with expected coating thickness, and perform mesh division to generate mesh files. Import the generated mesh file into the solver Fluent, set the physical model including flow model, radiation model and component transport model, among which the flow model adopts the standard k-ε model, the flow state is turbulent, the radiation model adopts the DO model, and the component transport model adopts the Species Transport finite velocity model. Then set the boundary conditions: intake flow rate, precursor ratio, intake temperature, substrate rotation speed, inlet type, outlet type, wall temperature, deposition pressure, and use the Coupled coupling algorithm for iterative solution. In the initial calculation, the boundary conditions of no coating thickness and with expected coating thickness need to be consistent, so as to compare the changes in surface deposition rate caused by changes in coating thickness for the next step of regulation.

[0053] like Figure 2As shown in (a), this embodiment provides a high-temperature hot-wall chemical vapor deposition system for dynamically controlling the growth of SiC ultra-thick coatings. It is a multi-substrate reaction chamber. The simplified model only includes the fluid domain inside the chamber. The overall chamber height is 0.132m. There are three parallel gas inlets on the left with a diameter of 0.01m, and two parallel gas outlets on the right with a diameter of 0.02m. The substrate is a graphite substrate with a diameter of 0.1m and a substrate thickness of 0.004m. The inlet temperature is 353K, the wall temperature is 1573K, the deposition pressure is 10kPa, and the substrate rotates along the z-axis at a speed of 60rpm. The inlet gas flow rate is 0.255m / s, the molar ratio of the inlet mixed gas is H2:SiCl4:CH4=10:1:1, and the outlet is a pressure outlet. The convergence criteria for controlling the energy and mass conservation equations are 1e-6, and the convergence criteria for other monitoring values ​​are set to 1e-3. At the same time, speed monitoring points are set in the chamber and SiC deposition rate monitoring points are set on the substrate surface. The calculation is considered to have converged when the residual reaches the convergence criterion and the monitoring point values ​​no longer fluctuate significantly.

[0054] Figure 2 (b) is a simplified model after a 0.003m thick coating grows on the upper and lower surfaces of the substrate, and the calculation parameters are the same as above. Taking the upper surface of the uppermost substrate as the monitoring object, when the boundary conditions are the same, the average SiC deposition rate of the monitoring surface of the model with no coating thickness and the model with a 3mm thick coating differs by -10.5%, and the deposition rate is significantly slowed down. Therefore, it is necessary to adjust the deposition conditions of the model with a 0.003m coating thickness to reduce the degree of deviation in the deposition rate. In this example, the deposition rate is regulated by changing the deposition pressure. As shown in Table 1, when the deposition pressure increases from the initial 10kPa to 10.5kPa, the deviation from the average deposition rate of the monitoring surface without coating thickness is only -1.91%. Therefore, it can be judged that the regulation requirements are met. Therefore, during the deposition process, the deposition pressure is gradually increased at a rate of 100Pa every two hours, and the deposition is carried out for 10 hours. The ultra-thick coating obtained by deposition is as shown in FIG. Figure 3 , Figure 4 shown.

[0055] Figure 3 This is the SEM image of the cross section of the deposited ultra-thick SiC coating. There are no cracks or delamination on the cross section. The deposited coating is dense and has good longitudinal uniformity. Figure 4 This is the surface SEM image of the deposited ultra-thick SiC coating, which has a dense surface and uniform particles.

[0056] Table 1 shows the deviation between the average SiC deposition rate of the monitoring surface and the initial deposition rate of the non-thick coating after adjusting the deposition pressure in the embodiment. When the deposition pressure increases to 10.5 kPa, the absolute value of the deposition rate deviation is less than 5%.

[0057] Table 1. Deviation of the average SiC deposition rate on the monitoring surface after adjusting the deposition pressure in Example 1

[0058]

[0059] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A method for preparing ultra-thick coatings by dynamically compensating and optimizing chemical vapor deposition, characterized in that: The following steps are involved: 1) Establish simplified three-dimensional models of the thickness without coating and the thickness of the coating expected to be deposited by chemical vapor deposition equipment; 2) Meshing the simplified three-dimensional model generated in step 1) to generate mesh files; 3) importing the grid file obtained in step 2) into the simulation solution software of computational fluid dynamics, setting the physical model, then setting the corresponding boundary conditions, and then performing iterative solution to obtain the deposition rate without coating thickness and with the expected coating thickness respectively; 4) Comparing and analyzing the changes in the deposition rate when there is no coating thickness and when there is an expected coating thickness obtained in step 3), and correcting the boundary conditions with the expected coating thickness so that the surface deposition rate of the model with the expected coating thickness is close to the simulation result of the no coating thickness; 5) In the actual deposition of the ultra-thick coating, the boundary condition without coating thickness is used as the initial parameter, and the boundary condition with the expected coating thickness after correction obtained in step 4) is used as the endpoint parameter. As the coating thickness increases, the boundary condition parameters of the deposition are adjusted from the initial parameters to the endpoint parameters in a linear manner to achieve dynamic compensation deposition of the ultra-thick coating.

2. The method according to claim 1, characterized in that: In the step 1), when establishing the simplified three-dimensional model, the relevant parameters include the inlet and outlet arrangement, the chamber size, the number of substrates, and the substrate placement method.

3. The method according to claim 1, characterized in that In the step 1), when the simplified three-dimensional model is established, the calculation and solution area only includes the fluid domain inside the cavity.

4. The method according to claim 1, characterized in that: In the step 1), a simplified three-dimensional model is established using Spaceclaim software; in the step 2), a mesh is divided using Fluent Meshing software.

5. The method according to claim 1, characterized in that In the step 3), the physical model includes a flow model, a radiation model and a component transport model.

6. The method according to claim 1, characterized in that In the step 3), the boundary conditions include air flow rate, precursor ratio, air temperature, substrate rotation speed, inlet type, outlet type, wall temperature, and deposition pressure.

7. The method according to claim 1, characterized in that In the step 3), the simulation solution software is Fluent; the iterative solution adopts the Coupled coupling algorithm.

8. The method according to claim 1, characterized in that In the step 4), when the absolute value of the surface average deposition rate deviation between the system with coating thickness and the surface deposition rate of the model without coating thickness is more than 5%, the boundary conditions are adjusted to correct the surface average deposition rate deviation to an absolute value of less than 5%.

9. The method according to claim 1, characterized in that: In the step 4), in correcting the boundary conditions with the estimated coating thickness, one or more boundary conditions are selected for correction.

10. An ultra-thick coating prepared by the method for preparing an ultra-thick coating by dynamically compensated optimized chemical vapor deposition according to any one of claims 1 to 9, characterized in that: The thickness of the ultra-thick coating is 1 to 4 mm.

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