Two-dimensional modelling of CH4-H-2 radio-frequency discharges for a-C : H deposition

A two-dimensional numerical code, previously developed for the modelling of alpha -Si:H deposition in a SiH4/H-2 radio frequency cylindrical PECVD rea ctor, has been modified in order to perform the modelling of CH4/H-2 mixtur es in the same experimental configuration. This model, which includes elect rical and chemical modules, takes into account the transport and the chemis try of the charged and neutral species. The results of the models have been compared to measurements. The calculated electrical power coupled to the p lasma and the self-bias voltages are compared to the experimental ones. The calculated radical densities are compared to those measured by threshold i onization mass spectroscopy at the substrate centre. Moreover, the calculat ed radial distribution of the deposition rate is compared to profilometry m easurements. Eventually, results obtained here in CH4/H-2 are compared with those previously obtained in SiH4/H-2 plasmas under similar experimental c onditions.