Preparation and properties of PECVD silicon nitride films from SiH4 + NH3 and/or NF3 and SiF4 + NH3 gas mixtures

The structural and chemical properties of PECVD silicon nitride films from different gas sources are studied. The films deposited from SiH4/NH3/N2 gas mixtures present hydrogen atoms incorporated in their network as NH+ species giving rise to the formation of positive charge in the bulk of the film. Using NF3 or SiF4 as nitrogen or silicon sources respectively, produce the incorporation of fluorine atoms in the film improving its electrical characteristics. However, for high fluorine content, the films are unstable in air and water vapor atmospheres. The film stability is determined by the presence of the fluorine atoms which are incorporated in the form of -SiF, -SiF2, [-SiF2-]n, and -SiF3 radicals. (orig.)