Refractive Index Dispersion of Phosphosilicate Glass, Thermal Oxide and Silicon Nitride Films on Silicon

We present precise measurements of the refractive index dispersion in the range 0.6 to 1.5 microns of dielectric films commonly used to form optical waveguides on Si. These are thermal SiO sub 2 and phosphosilicate glass formed from several types of low pressure chemical vapor deposition and Si sub 3 N sub 4 formed by LPCVD. Mode refractive index measurements were made with absolute accuracies of 1x10 sup -4. We show that for samples >~ 3microns thick, the error in the film refractive index, determined by extrapolation of the mode refractive index data of the lowest two modes, is ~1x10 sup -4. Annealing studies of the phosphosilicate glass samples show that films containing 2 or more percent of P reached their equilibrium refractive indices after annealing at 800C, while undoped silica films require annealing at 1100C to reach equilibrium.