Numerical Calculation Study On The Growth Mechanism Of Nitride Films

The nitride film mainly refers to the third generation semiconductor thin film material of gallium nitride(GaN),aluminum nitride(AlN),and aluminum gallium nitride(AlGaN),they have high bandgap width,strong breakdown strength,high thermal conductivity,high pressureresistance and other characteristics.Therefore,nitride thin films have a broad application prospect in the preparation of new high-power semiconductor devices.Metal-organic Chemical Vapor Deposition is the key technology to produce nitride semiconductor films on a large scale.Due to the complexity of the process of growing nitride films by MOCVD,although some research results have been obtained,the current understanding of the process of using MOCVD to grow nitride film is still not clear.Therefore,further research is needed on the growth of nitride films by MOCVD.The research on the growth mechanism of the nitride film is helpful to understand the growth process of the nitride film and grow a high-quality nitride semiconductor film.The purpose of this study is to use the simulation software to build a MOCVD nitride film growth model to numerically simulate the growth process of the nitride film,and to study the changes in the concentration of the intermediate products and the spatial distribution of the intermediate products during the growth of different nitrides by various parameters of the reaction chamber,and the influence of these parameters on the growth rate and uniformity of the substrate film is considered.The related nitride growth mechanism is explored,and the growth conditions of the high-quality nitride film are finally obtained.The research results have important guiding significance for improving the quality of nitride films in actual growth.The main research contents of this paper are as follows:(1)A multiphysics coupled model of MOCVD reaction chamber was established.First,the physical model was set according to the actual state of the MOCVD reaction chamber.Based on the physical model,the governing equations were established,including the continuity equation,momentum equation,energy conservation equation,gas phase reaction rate equation,and surface reaction rate equation.The boundary conditions of the model were set to make the model meet the growth requirements,and the model was calculated and solved using the finite element method.(2)The chemical reaction model of related nitrides is described.This paper first discusses the general chemical reaction model of nitrides.Based on this,the chemical reaction models of gallium nitride,aluminum nitride and aluminum gallium nitrogen are established.The chemical reaction model of gallium nitride consists of gas phase reaction and surface reaction.The gas phase reaction includes thirteen chemical reactions,mainly pyrolysis reactions.The surface reaction consists of seven reactions.The chemical reaction of aluminum nitride is also composed of a gas phase reaction and a surface reaction.The gas-phase reaction contains ten chemical reactions,mainly adductive reactions.The surface reaction consists of six reactions.The chemical reaction model of aluminum gallium nitrogen is similar to that of aluminum nitride and gallium nitride.In the surface reaction,two metal atoms are incorporated into the substrate lattice.However,the probability of these two metal atoms merging into the crystal lattice is not equal because of their particular material properties,so the composition control is a common problem when growing aluminum gallium nitrogen films.(3)Based on the establishment of a multiphysics coupling model and related chemical reaction models,the growth processes of gallium nitride film,aluminum nitride film,and aluminum gallium nitride film in small-sized(2-inch)electromagnetically heated MOCVD reaction chambers were simulation.For the gallium nitride film,the relationship between the pyrolysis reaction and temperature,the radical reaction,and the changes in the concentration of the intermediate products of the reactants were mainly studied.For the aluminum nitride films,the effects of heating current and frequency,carrier gas composition,air inlet temperature,and boundary layer parasitic reactions on aluminum nitride films are mainly studied.Aiming at the problem of difficult to control the composition of aluminum gallium nitride film,the variation rule of aluminum composition at different temperatures,pressures,carrier gas composition,and V / III,and the change of growth rate and uniformity were studied.(4)Based on the study of a small(2-inch)MOCVD reaction chamber,a large(8-inch)MOCVD reaction chamber was preliminarily modeled and simulated in this paper.The growth of aluminum nitride films under the 8-inch reaction chamber was simulated,the effect of the height of the large-sized MOCVD reaction chamber on its growth was studied,and the changes in the concentration distribution of parasitic reaction products at different heights were analyzed.And the effects of changes in inlet temperature and pressure inside the reaction chamber on the growth rate of aluminum nitride films and intermediate products in large-sized MOCVD reactors were further studied.The relative growth of aluminum nitride films in 8-inch reaction chambers was summarized law.