Optical properties and local bonding configurations of hydrogenated amorphous silicon nitride thin films

We report on the optical properties and local bonding configurations of both as-deposited and postannealed hydrogenated amorphous silicon nitride a-SiNx :H thin films grown on crystalline Si substrates with x approximately 1.2±0.1. Ultraviolet optical reflection and infrared IR absorption measurements were applied to characterize the films. A method simply based on optical reflection spectra is proposed for accurate determination of the optical band gap, band tail, wavelength-dependent refractive index and extinction coefficient, as well as the film thickness, suggesting that the Tauc-Lorentz G. E. Jellison, Jr. and F. A. Modine, Appl. Phys. Lett. 69, 371 1996 ; 69, 2137 1996 model with the inclusion of Urbach tail is the optimal one to describe the optical response of a-SiNx :H films. The yielded optical parameters can be related well to the film microstructure as revealed by the IR absorption analysis. These results have implications for future deposition controlling and device applications. © 2006 American Institute of Physics. DOI: 10.1063/1.2356915