Coupled Simulation Of Thermal Field And Flow Field Of Aln Grown By High Temperature MOCVD

The growth of AlN by high temperature MOCVD can not only increase the lateral mobility of Al atoms,but also make large particle pollutants away from the surface,thus reducing the surface defects and improving the quality of the films.The growth of AlN by high temperature MOCVD has opened up a new application field for deep submicron devices,and has played a key role in realizing deep ultraviolet devices,and has gradually become the mainstream direction of mass production technology in the industry.However,the simulation of AlN growth at high temperature MOCVD has not been reported yet.In this paper,a three-dimensional reaction chamber structure model and a chemical reaction model for simulation of MOCVD are built.The influence of operating pressure and susceptor rotating speed on the flow stability under high temperature is studied.The"pressure-rotating"map is drawn,and the characteristics and differences of the three critical flow regimes under different technological parameters are obtained.It is found that the maximum operating pressure can't exceed 240 Torr when the gas flow rate is 50 slm.Forced convection from top to bottom can suppress reverse natural convection,so buoyancy driven flow is highly influenced by the height of the reaction chamber.Compared with steady piston flow,rotation-induced flow usually generates vortex at the edge of the substrate and the wall of the reaction chamber.By reducing the pressure or increasing the flow rate of the gas,it is possible to avoid the vorticity generated by the large rotating speed of the susceptor.The above research provides a reference for setting the corresponding technology parameters.On this basis,a large number of single factor simulation tests are carried out for the main technology parameters.The effects of technology parameters on the coupled distribution of heat field and flow field inside the reactor and on the surface of the substrate are systematically studied.It is found that the increase of gas flow makes the high temperature layer thinner and effectively suppresses the effect of thermophoretic force.The rotating speed of the susceptor increases the axial suction effect of the pump,so that the gas flow is closer to the substrate,so that the distribution of the reaction gas is more reasonable on the surface.Under the condition of low pressure and high speed rotation,the flow field at low temperature can be maintained well when the susceptor temperature increases.The increase of operating pressure can restrain the rise of the high temperature boundary layer,but it will sometimes destroy the stability of the flow field.Orthogonal experiment is used to optimize the coupling distribution of thermal field and flow field on the substrate surface.Gas flow rate,operation pressure,susceptor temperature and susceptor rotation speed are selected as experimental factors,and each factor is selected with 4 different parameter levels.The test indexes are density distribution,pressure distribution and temperature distribution.According to the orthogonal test method,orthogonal test schedule L₁₆?4⁴?is designed,and 16 groups of experiments are carried out.According to the method of silicon wafer uniformity,the simulation results of 5 points on the substrate surface are analyzed by the range,matrix and variance.The optimal technology combination scheme is obtained as follows:susceptor speed 400 rpm,pressure 40 Torr,flow rate 50 slm,susceptor temperature 1550 K.