Optical properties of amorphous hydrogenated silicon nitride thin films

Abstract

This paper presents a study of the optical properties of amorphous hydrogenated silicon nitride $(a-Si3N4:H)$ films under deposition temperature influence. The films were deposited by low-frequency plasma-enhanced chemical vapor deposition at temperatures of 200, 300, and $400°C$ and 0.6-Torr pressure. The mixture gases were silane $(SiH4)$, ammonia $(NH3)$, and hydrogen $(H2)$. The optical properties of the films samples were obtained by means of the transmittance spectra and from spectroellipsometry measurements. Then, the optical parameters of the films were determined using the Swanepoel, Cauchy, and Sellmeier models. The refractive index dispersion curves were well fitted with both the Cauchy and the Sellmeier theoretical model. The equivalence between the parameters that characterize the two models is established.