ANALYSIS AND MODELING OF A PULSED-PLASMA REACTOR FOR SILICON-NITRIDE DEPOSITION - REACTOR OPTIMIZATION

Numerical modelling of a RF pulsed plasma reactor for silicon nitride deposition from SiH4/NH3 mixture was carried out and a detailed treatm ent of both electrical and mass transfer phenomena performed. Starting from two-dimensional simulations of the concentration profiles, some a posteriori simplifications were made to shorten the calculation time . The resulting numerical procedure, which was much more rapid, was fo und to be very accurate. The homogeneous and heterogeneous chemical me chanisms selected were previously investigated for a continuous-wave p lasma; the good agreement achieved between calculation and experiment suggests that, on the whole, realistic choices were made. In the case of a pulsed-plasma reactor, good agreement was also found between calc ulation and experiment. It was shown that the use of a pulsed discharg e was necessary to obtain uniform thickness and composition over all s amples when using a low silane percentage in the gaseous mixture. An a ttempted reactor preoptimization was satisfactorily performed, in the light of the experimental correlation between electrical properties an d chemical bonding in the deposited films.