Optical and structural properties of silicon nitride thin films prepared by ion-assisted deposition

Silicon nitride (SiNx) films were prepared by ion-assisted deposition process. The films were analyzed by measurement of scanning electron microscopy (SEM), Fourier transform infrared spectrometry (FTIR), X-ray photoelectron spectrometry, spectrophotometer, and ellipsometer measurements. The effects of N-ion current density (J) on the structural and optical properties of SiNx thin films were investigated. The SEM studies revealed that films deposited at a higher value of J had highly condensed structure. FTIR analysis indicated an extremely low hydrogen content in the IAD films. It was found that the N/Si ratio of films increased when J increased. The optical constants and the optical band gap of films were determined. The stoichiometric Si3N4 thin film was obtained with a high refractive index of 2.073 (at a wavelength of 400 nm), an extinction coefficient less than 6 × 10−4, and an optical band gap of 4.57 eV.