ABSTRACT Excimer lamp deposited ultra-thin (< 250 angstrom) silicon dioxide and silicon oxynitride films were characterized using spectroscopic ellipsometry (SE) and Fourier transform infrared (FTIR) spectroscopy. SE analysis of the photo-deposited SiO2 films revealed no variation in the refractive index (n) of the films for deposition temperatures of 200 degree(s)C and 300 degree(s)C. Using a Bruggeman effective medium approximation (EMA), SE analysis was employed to determine both the silicon oxynitride layer thicknesses and compositions as a function of deposition temperatures and gas ratio, defined as (N2O/(N2O + NH3)). From this analysis the optical properties of the silicon oxynitride thin films were extracted. It was observed that the refractive index for the 200 degree(s)C and 300 degree(s)C series of samples decreased from n equals 1.81 to 1.46 and n equals 1.72 to 1.46 respectively as a function of increasing gas flow ratio. FTIR analysis revealed spectral features characteristic of Si-O, Si-N, Si-H and N-H bonding. The most significant feature in all recorded spectra was a mixed spectral absorption band ranging from 800 cm-1 to 1300 cm-1. Both the integrated band area and peak wavenumber of this absorption band was found to be sensitive to the degree of nitridation and layer thickness of the thin films. The N-H stretching bond density was calculated from the N-H peak at 3360 cm-1 using appropriate calibration factors. A slight decrease in the N-H bond density with increasing gas flow rate was observed. This variation in bond density was significantly less than that observed for PECVD silicon oxynitride films.
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