Ion energy distribution in the sheath of radio frequency discharges.

The dynamics of ions in the sheath of an asymmetric glow discharge system was studied by analyzing the energy of ions, impinging on the cathode (smaller electrode). The ion energy distributions (IED) were found to exhibit characteristic series of peaks, the position of which depending clearly on process parameters such as bias-voltage or pressure. A model has been developped, showing that these structures in the IED are due to the high frequency modulation of the sheath potential combined with the generation of thermal ions in the sheath, e.g. by symmetric charge exchange. By fitting the theoretical peak positions to the experimentally measured ones, information about the spatial distribution of the electric field in the sheath is obtained.