Modeling And Process Optimization Of Atomic Layer Deposition Equipment Based On Computational Fluid Dynamics

Atomic layer deposition(ALD)technology,as a bottom-up material surface modification method,has shown significant advantages in the field of ultra-thin film preparation.During the film preparation process,due to the self-limiting characteristics of the semi-reaction on the ALD surface,the films prepared have the advantages of precise and controllable thickness,high uniformity and high consistency.Therefore,ALD technology is also widely used in industrial production such as photovoltaics,packaging,and other applications that require high yields and large-scale deposition capabilities,as well as catalyst design and modification that require precise control of material surfaces.However,since the ALD growth process is a complex heat and mass transfer process with multiple chemical components interacting,how to select appropriate process parameters to maximize the production efficiency of atomic layer deposition has become a key issue in industrial applications.Computational fluid dynamics(CFD),as an effective computational simulation method,can simulate the complex growth process of atomic layer deposition in the reactor scale,and predict the deposition results by regulating the relevant process parameters.This work is dedicated to constructing a theoretical model of the atomic layer deposition process by using computational fluid dynamics method,and using relevant software to analyze two specific atomic layer deposition equipment,then optimize process parameters.This thesis includes the following two aspects:(1)By analyzing the chemical adsorption process of the precursor group on the substrate surface and the gas flow process in the reaction chamber of the Atomic Layer Deposition equipment,a heat and mass exchange model for the growth of the atomic layer deposition film coupled with the chemical reaction was constructed,combined with the gas mass transfer theory.A mathematical model combining fluid dynamics and chemical dynamics is established with the dynamic mesh method.Quantitative analysis of the effects of different process parameters on the deposition process in the space atomic layer deposition equipment has been conducted.In addition,the impact of the dragging effect caused by the movement of the substrate during the space atomic layer deposition process was studied.The good agreement between the simulation results and the experimental data proves the effectiveness of the dynamic model.In order to obtain a uniform film with a relatively high deposition rate as well as high utilization of precursors,the speed range of the substrate was optimized.This numerical model provides important guidance for the optimization of various deposition systems based on Atomic Layer Deposition and the design of a Space Atomic Layer Deposition systems.(2)Based on the effect of the sound field on the fluidization of single particles,a single particle motion model under the influence of plane sound waves is constructed,and the model is used to explore the effects of different parameters such as sound pressure level,sound frequency,particle size,particle density on the particles' movement under sound field.Secondly,based on the Euler-Lagrangian method,the Dense Discrete Phase Model(DDPM)and CFDDEM coupling methods are used to model and analyze the granular powder fluidized bed.Through the DDPM method,a fluidized process model of batch powder coating was constructed,and the effect of multiple parameters like gas speed,particle density and so on was explored to figure out particles fluidization procedure.The CFD-DEM under the EulerLagrangian framework,coupled with vibration,was used to construct another numerical model.The gas-solid interaction during the fluidization procedure of powders was analyzed,and the effect of vibration frequency on fluidization efficiency was further discussed.