RF discharge modelling in a N2O/SiH4 mixture for SiO2deposition and comparison with experiment

Abstract

The present work concerns the experimental and theoreticalanalysis of the electrical behaviour and N2O/SiH4dissociation of a classical RF discharge used for SiO2 thin-filmdeposition. Electric and deposition rate measurements are undertaken at 0.5and 1 Torr gas pressures. The reactor modelling involves electrical,hydrodynamic and mass transfer models. The electrical model enables thecalculation of the electron impact dissociation rates required for the masstransfer model, while the gas velocities are determined by the hydrodynamicmodel. Only an electrical discharge model accounting for the negative-ionconversion reactions O-/SiH4 and NO-/SiH4allows good agreement between the measured and calculated power densitiesparticularly at 1 Torr. Furthermore, a simplified chemical scheme whichincludes 16 species (N2O, N2, O2, NO,NO2, N, O(3P), O(1D), SiH4, SiH3, SiH3O, H2SiO, H, H2, OH and H2O) is used in the mass transfer model. The corresponding results(deposition rates) are quite consistent with the measurements.