Estimation of Carbon Fluxes Interchanging between Chamber Wall and Gas Phase in Fluorocarbon Plasmas

Abstract

We have evaluated carbon flux that contributes to the deposition of fluorocarbon film on the chamber wall in C4F8 and C4F8–H2 plasmas. The deposition flux was estimated from the deposition rate, carbon concentration, and weight density of the fluorocarbon film. In addition, the deposition carbon flux was compared with the carbon flux desorbed from the fluorocarbon film, which was roughly estimated by the inward diffusion fluxes of CF and CF2 having hollow-shaped density distributions. This is because the source of the inward diffusion fluxes is the production of CF and CF2 from the fluorocarbon film. In the case of pure C4F8 plasmas, the deposition carbon flux was on the order of <1014 cm-2s-1, which was much smaller than the desorption carbon flux on the order of 1015–1016 cm-2s-1. Accordingly, it is revealed that the carbon flux adsorbing to the chamber wall contributes negligibly to the growth of the fluorocarbon film, and mostly goes back to the gas phase. On the other hand, in C4F8–H2 plasmas, the deposition flux was on a comparable order to the desorption flux.