A study of the radiation sensitivity of non-crystalline SiO2 films using spectroscopic ellipsometry

Dry thermal oxides were grown on Si substrates at temperatures from 900 degrees C to 1200 degrees C. Portions of these oxides were then annealed for 10 min at temperatures from 900 degrees C to 1125 degrees C. Spectroscopic ellipsometry was used to determine the density of these oxides, and to look for the existence of an interfacial layer. It was found that the oxide density depends on both the growth temperature and the anneal temperature. No evidence was found of an interfacial layer. The oxides were then irradiated with x-rays, and the radiation-induced shift of the flatband voltage was determined. It was found that the radiation response was related to the oxide density determined by spectroscopic ellipsometry. These results suggest that the macroscopic structure of the oxide influences the extent of charge trapping.