Stability and process parameter optimization for a vertical rotating ZnO-MOCVD reaction chamber

Developing an understanding of the cavity stability underlying the metalorganic chemical vapor deposition (MOCVD) of ZnO is critical to the fabrication of oxide-based devices. Therefore, computational fluid dynamics (CFD) was used to study the process parameters (e.g., the growth temperature, total gas flow, chamber pressure, and substrate speed) of the MOCVD H-type reaction chamber for four states in the cavity: buoyancy-induced flow, plug flow, rotating-plug flow, and rotating flow. Based on these states, criteria for determining stable and unstable flows were determined. These can be presented on the pressure-rotation rate spectrum, which can be used to visualize the effects of specific process parameters on the flow stability. In order to obtain a good film deposition rate in the stable flow state of the cavity, a response surface model and genetic algorithm were also used to optimize the process parameters. The coefficient of variation of the optimized ZnO film was reduced to 2%, which greatly improved the film quality. This study provides a comprehensive insight into the transport phenomena of the MOCVD H-type reaction chamber, including coupled heat and mass transfer and chemical reactions, and presents the optimal combination of parameters to provide a useful reference for obtaining high-quality thin films.