Modification of refractive index in silicon oxynitride films during deposition

Inhomogeneous thin films of SiO(x)N(y) have been deposited by laser ablation of a Si(3)N(4) sintered target in an oxygen gas environment. The high oxidation rate of silicon nitride has been used to control the film stoichiometry by varying the oxygen partial pressure. The refractive index of the deposited material was able to be tailored at any value from 1.47 (SiO(2)) to 2.3 (Si(3)N(4)) by this approach. In situ optical characterization of the growing layer on the film was performed using kinetic and spectroscopic ellipsometry. The effective medium approximation (EMA) was used to determine the composition and refractive index by considering a mixture of SiO(2). Si(3)N(4) and voids. The volumetric composition obtained by ellipsometry was compared to the results determined by AES and XPS characterization. The goal of this application is to show that reactive PLD can be used to produce high quality optical filters. (C) 2000 Elsevier Science B.V. All rights reserved.