Simulations for the effect of chamber geometry on oxygen plasma characteristics for very large plasma sources

Using an oxygen discharge model based on diffusion equations, we numerically investigate the effect of chamber geometry on plasma density profiles, especially for very large rectangular high-density plasma chambers. The calculation results show that uniformity of the ion and O-atom density profiles seriously deteriorates when the chamber length increases up to 2 m. We discuss the dependence of the plasma density profiles on the chamber geometry in terms of the relationship between particle generation in the volume and loss at the wall surface. The simulation results indicate that the surface loss at the top and bottom chamber walls dominates the loss at the side walls. The density profiles, therefore, vary, depending on the chamber length even at the same aspect ratio. The simulation results also predict that the uniformity of the density profiles could be significantly improved over the very large area if the plasma were properly confined by using magnetic multipole fields, along with choosing suitable wall materials that influence the particle loss at the surface.