Dielectric relaxation in thermally grown SiO2films

An extensive investigation of the dielectric properties of thermally grown silicon dioxide films was performed in the temperature range from 400°C to 525°C. Principally, the variation of dissipation factor with frequency was observed at various applied peak fields and oxide thicknesses. In the temperature and frequency domain investigated, a large peak in the dissipation factor occurred. This peak corresponded to a massive capacitance dispersion with accompanying peaking of the loss factor at low frequencies. The phenomenon was apparently an ionic space-charge polarization. Theoretical developments based on this model were verified by experiment. The activation energy for the relaxation time was 10.1 ± 0.4 kcal/mole. Examination of the oxide thickness dependence indicated that the carriers were not uniformly distributed initially, but a fixed number was present at a particular temperature and this number was independent of thickness. Further investigation led to the conclusion that a reaction between the metal electrode and the SiO2produced positively charged oxygen vacancies which migrated through the oxide under the influence of an electric field. A mechanism for the production and migration of these vacancies is proposed which complies with the low activation energy as well as the observed temperature and electrode dependence.