IMPROVEMENT OF THE SIO2 DEPOSITION BY 185-NM PHOTOLYSIS OF N2O AND SIH4 BY ADDITION OF NEOPENTANE

The modelling of the deposition of silicon oxide by photolysis at 185 nm of N2O and SiH4 is presented in this paper. OH and SiH3 gaseous radicals are essential for the deposition mechanism whereas the formation of NO from the reaction of O(1D) on N2O is undesirable. A low addition of neopentane modifies the O(1D) reaction route and increases the SiH4 dissociation and the OH generation: powder formation is avoided and N contamination in the film (which is due to NO) seems to be reduced. We have measured high initial deposition rates (25 +/- 5 angstrom/min) but the loss of transparency of the quartz window due to the deposition of an opaque layer reduces considerably the average deposition rates. The bulk electrical properties of the deposited silicon oxide are not affected by the addition of neopentane.