Physico-chemical, structural and physical properties of hydrogenated silicon oxinitride films elaborated by pulsed radiofrequency discharge

Films prepared by radiofrequency pulsed plasma enhanced chemical vapor deposition from a mixture of silane (SiH4) and nitrous oxide (N2O) were studied. Variation of operating conditions (flow rate, deposition temperature ...) resulted in films with chemical compositions changing from hydrogenated silicon oxynitride (SiOxNy:H) to silicon oxide (SiOx:H). Infrared and Rutherford backscattering spectroscopy studies of the as-deposited films revealed different SiOx arrangements disturbed by Si–N bonds and H–Si ≡ Si(3 − x)Ox clusters depending on the substrate temperature and the N2O/SiH4 ratio. For films obtained using low N2O/SiH4 rations and annealed at temperature higher than 1273 K, Raman spectroscopy and microscopy analyses revealed the presence of silicon nanocrystals embedded in a matrix containing Si, O, and N. Spectroscopic ellipsometry revealed the presence of silicon nanocrystals along with two other amorphous phases (SiOxNy and SiO2) in annealed samples. The electrical characteristics of annealed films obtained from capacitance–voltage measurements indicated a stable charge trapping in ultra-thin SiOxNy layers. These preliminary results suggest that Si-nc containing silicon oxynitride layers can be potential candidates to be used in the floating gate fabrication of memory devices.