Optimal Design Of Vertical Showerhead GaN-MOCVD Reactor

MOCVD(Metal Organic Chemical Vapor Deposition) technique involves many aspects,mainly including thermodynamics,dynamics,fluid mechanics,physical chemistry,etc.,it is very difficult to research and the gas flow and temperature distribution in MOCVD reactor has the characteristics of complex with an observation, It is a valuable reference for MOCVD reaction chamber optimization design and GaN thin-film material production by CFD simulation on inner heat flow in reaction chamber, thus reduce the cost of industrial research.The paper focuses on two different models of vertical spray-type MOCVD reaction chamber to carry out the optimization of design work, using CFD to research GaN-MOCVD reaction chamber gas transport in the process of sedimentation model simulation,and let the part of conclusion compared with the experimental results. Research's purpose is to discuss the reaction chamber flow under different growth conditions, surface deposition, the substrate surface TMG uniformity and TMG utilization and so on.The main research content of The article is divided into two parts:For experimental small capacity of MOCVD equipment spray type vertical reaction chamber optimization design research, through debugging spray head height and the growth of the operating pressure to find a better process conditions. Study find that the higher the spray head height, the better deposition uniformity, the slower growth rate,the lower deposition degree on the wall, when the spray head reaches a certain height, the concentration of wall deposition remain unchanged. In addition through to change the fine-tuning pressure of the high spray type of reaction chamber,observe effects of pressure on GaN epitaxial growth, and put forward the optimal pressure range of growth. Found that decrease the pressure can promote the uniformity of film,when the pressure is bigger, the average growth rate is large, but the larger pressure is easy to cause the flow instability.Aiming at the bigger capacity for production-oriented MOCVD equipment vertical spray type reaction chamber optimization design research, first of all, study the influence of the interior flow field in the reaction.by pressure and rotating speed adjustment of graphite,use rotation speed with pressure of laminar flow graph to study the different parameters under the condition of three kinds of critical flow characteristics and differences,and get the conclusion that " improve the flow, expand the GaN film growth window". Then this paper introduce the reaction chamber optimization design of spray height,and find that when the reaction chamber spray height is lower,the uniformity of TMG deposition on the surface of the substrate has dramatically improved, this structure increase the uniformity but it may reduce the TMG utilization. The third section describes a on imports of optimization design that let TMG source release,it is conducive to improve the utilization rate of TMG, and deposition uniformity is affected by smaller at the same time.The purpose of this paper is to study flow field and concentration field of MOCVD reaction chamber deeply,and the related theory applied to the simulation, to guide production MOCVD technique, thus eventually produce TMG utilization rate as high as possible under the content uniformity of conditions and sidewall zero deposit of GaN epitaxial films.