Comparison of interface-state buildup in MOS capacitors subjected to penetrating and nonpenetrating radiation

Abstract

Metal‐SiO₂‐Si capacitors under positive bias were subjected to penetrating Co⁶⁰ γ and nonpenetrating 10.2‐eV uv radiation. High‐frequency 1‐MHz and quasistatic C‐V curves were recorded before and after irradiation, and interface‐state densities over the Si band gap were calculated from these curves by using the Terman, Berglund, and Castagne techniques. The nature and magnitude of the buildup of interface states were similar for both types of irradiation, demonstrating that the buildup is not related to the direct interaction of radiation at the interface or a structural modification of the SiO₂ layer, but to the production of electron‐hole pairs in the oxide and the subsequent transport of holes to the oxide‐semiconductor interface. The buildup of interface states under irradiation saturated at ∼5×10⁵ rad (SiO₂).