Simulation of Chemically Reacting Flow in Plasma Native Oxide Cleaning Process

A plasma native oxide cleaning process is widely used on the semiconductor production line to remove oxide impurities on silicon surfaces of an wafer. In this study, a flow simulation with microwave plasma species has been conducted to analyze the flow characteristics in a showerhead that affect the batch uniformity in the process. In particular, the distributions of temperature and mass flow rate of the gas as well as the number density of hydrogen radicals at the showerhead hole outlets were compared for different showerhead designs by using computational fluid dynamics. The distribution of gas temperature at the hole outlets was found to be inversely proportional to one of gas mass flow rate by the simulation results. However, mass flow rate distribution for the total gas shows a different trend from one of hydrogen radicals in the showerhead hole outlets. The showerhead design with low temperature gradient also showed a more uniform mass flow rate profile at the hole outlets, which was validated by the simulation results.