Numerical model of hydrogen radiofrequency discharges: comparisons with experiments

Summary form only given. A simplified numerical model of radiofrequency discharges in hydrogen has been developed. The model is a one-dimensional, two-electron group, fluid model. The bulk electrons are described by three moments equations: continuity, momentum (drift-diffusion approximation) and energy. The electrons emitted by the electrodes and accelerated in the sheath are described by continuity and energy equations assuming a monoenergetic electron distribution. Only the two first moments are considered for the ions. In the model, only H/sub 2//sup +/ ions have been considered. In spite of this great simplification, the results obtained are quite satisfactory. In hydrogen discharge H/sub 2//sup +/ ions are created by direct electron impact ionization of H/sub 2/ molecules, then these ions are quite efficiently converted into H/sub 3//sup +/ ions. It´s generally admitted that the major ions in the discharge (under our conditions) are H/sub 3//sup +/ ions. H/sup +/ and H/sup -/ ions are considered to play a minor role in the electrical characteristic of the discharge. In order to have a simpler model (one ion) it was then necessary to take into account only H/sub 2//sup +/ ions created by electron impact ionization. If we consider that H/sup +/ ions are not too important (erected also by direct electron impact ionization) then, the global ion source term is correctly described in the discharge. We consider two situations: (1) Secondary electron emission regime. (2) Ohmic sheath heating.