Optical investigation of silicon nitride thin films deposited by r.f. magnetron sputtering

We prepared SiNx thin films by r.f. magnetron sputtering without intentional substrate heating with refractive index approximately 2.0. Several different deposition routines showed that sputtering pressure played the most dominant role in film oxygen incorporation, film packing density and resistance to oxidation. High sputtering pressure led to a porous structure of the film and post-depositional oxidation in the atmosphere. The film refractive index was directly dependent on the sputtering conditions indicating a correlation with film stoichiometry and microstructure, and could be looked as an indication of film stoichiometry if the film was highly packed and with low-level dopant or contamination.