Residual stress, composition, and optical properties of SiOxNy thin films deposited by dual ion beam sputtering

Silicon oxynitride thin films were deposited on various substrates by dual ion beam sputtering from a silicon target in an argon oxygen nitrogen mixture. The composition and density of the films were deduced from Rutherford backscattering spectroscopy and nuclear reaction analyses. The residual stress was determined by measurements of the radius of curvature of the silicon substrates. The refractive index, extinction coefficient, composition and residual stress were investigated as a function of oxygen flow rate and deposition rate. The composition of the deposited materials was found to vary from Si 3 N 4 to SiO 2 with increasing oxygen flow rate. The resulting films were dense, stable and insensitive to ambient moisture. A strong correlation between the compressive residual stress and the nitrogen content of the films was established. The origin of residual stress and its evolution with deposition parameters and composition of the films are discussed.