Simulation Of Atomic Layer Deposition And The Research Of Steric Hindrance Effect

The saturation deposition of atomic layer deposition(ALD)has led to widespread adoption of this technology in the electronics industry,which places a high demand on the material thickness and purity.The mechanism of material growth is an important part of material science research.Computer simulation of ALD process can help people understand the mechanism that experimental methods can not obtain,which is very important for improving and optimizing the film growth process and the quality and the characteristic of the film.We introduce a Monte Carlo model based on random deposition and diffusion limited aggregation in order to study the morphological evolution of deposition of ALD nano-film,which is difficult to carry out by the experimental methods.The instantaneous evolution of morphology and the corresponding parameters are observed when employing a novel perspective,modeling the aggregation of nanoscale units.Despite simplifying the chemical details,the simulation results qualitatively describe experiments with bulky precursors,and the strong dependence of growth rate on steric hindrance is obtained.Moreover,the well know behavior that the delay before steady growth is accurately predicted and analyzed based solely on modeling.Through this work,the great influence of steric hindrance on the initial stage of ALD is described.In this paper,the computer simulation of atomic layer deposition has been systematically studied,the research can be summarized as the following aspects:(1)Based on the summary of the existing models,combined with the unique deposition characteristics of ALD,the deposition model for the amorphous ALD films was abstracted and established.The deposition process of the thin film was simulated by Monte Carlo method,and the changes of the morphology,growth rate,roughness and other parameters of the film with the number of growth cycles were analyzed.It was observed that the growth of the material from the formation of dendrite to the formation of the island and the final growth of the film,and the actual observed ALD process is basically the same.On this basis,the behavior of sedimentary particles during the growth of ALD was demonstrated and discussed,and the relationship between sediment particle behavior and ALD growth stage was studied.(2)The effects of pulse time and diffusion rate on the deposition of ALD thin films were investigated by adjusting the maximum number of deposition attempts and diffusion steps in the model.It is found that increasing the pulse duration of precursors before the saturated deposition of ALD can effectively increase the initial growth rate GPC of ALD.In addition,no significant effect of diffusion rate on ALD was observed in the simulation range herein.(3)Based on the above studies,the effect of steric hindrance on ALD was further studied by changing the steric hindrance coefficient.By changing and analyzing the simulation parameters,we explored the reasons for the delay before entering stable growth that occurs preponderantly in ALD deposition.Through the real-time topography of the film under the framework of OpenGL,the morphological evolution of the initial stage of ALD growth is visualized.It is found that the steric hindrance effect resulted in the decrease of ALD film growth rate and the increase of roughness.In addition,we also demonstrate that steric hindrance causes the slow growth of ALD in the early stage of ALD.It is found that the reuse of surface adsorption sites caused by the change of roughness in the initial stage of ALD is the main factor.