A global model for C4F8 plasmas coupling gas phase and wall surface reaction kinetics

Abstract

A global or zero-dimensional model for C4F8 plasmas is formulated by coupling gas phase and wall surface reaction kinetics. A set of surface reactions implements experimental findings and quantifies the effect of the fluorocarbon film formed on the reactor walls on the densities of species in the gas phase. The model allows the calculation of the pressure change after the ignition of the discharge and the effective sticking (surface loss) coefficients of the neutral species on the wall surface. The model is validated by comparison with experimental measurements, i.e. pressure rise and densities of F atoms, CF2 and CF radicals, in an inductively coupled plasma reactor. It is predicted that C4F8 is vastly dissociated and CF4 becomes the dominant species even at low power conditions. A net production of CF3 radical and a net consumption of CF2 radical at the reactor walls are predicted. A study on the contribution of each reaction to the production and consumption of the species shows that at least one surface reaction is among the major sinks or sources of CF4, CFx radicals and F.