Plasma enhanced deposition of a-Si-H: comparison of two reactor arrangements

Abstract

Plasma deposition processes involve complex phenomena which render the design and optimization of industrial equipment difficult to perform. In the particular case of silane plasmas used to produce amorphous silicon, two flow arrangements were studied by numerical modeling of mass transport. The modeling of the first geometry, using inlet slit gas feed, showed a decrease of both silane concentration and deposition rate from inlet to outlet. The modeling of the second geometry, using a distributed gas feed by means of a porous electrode, showed more uniform concentration profiles and deposition rate. In large industrial plasma enhanced chemical vapor deposition machines, the choice of gas flow arrangement plays a particularly important role. However, this subject has seldom been treated in the literature [1,2], probably because an experimental approach would involve a high level of investment to build the necessary equipment. This paper suggests an alternative theoretical treatment, using modeling and numerical simulation. First, the principles and methods of a recently developed model [3,4] will be recalled. Then, numerical simulation will be used to compare two different gas flow arrangements and their consequences on the deposition rate profile.