Charge transport studies in SiO2: Processing effects and implications for radiation hardening

Abstract

Charge transport studies have been performed on SiO2 films using an electron-beam injection technique. MOS capacitors incorporating oxides grown at 1000 and 1100°C were investigated, including units fabricated at Hughes Aircraft using radiation hardening procedures. A comparison of beam-induced current vs field characteristics is made for devices with differing processing histories. Additionally, experimental determinations of trapped positive charge vs collected charge were performed. Present findings indicate that holes are mobile in SiO2, that the schubweg model is insufficient for describing charge transport in SiO2 films, and that the electron-hole pair creation energy for SiO2 is ≤ 19 eV. Current vs field data can be qualitatively explained in terms of columnar and/or geminate recombination. Conclusions concerning the effects of processing on charge buildup are made and a qualitative model based on experimental findings is presented. Implications of this model for radiation hardening are discussed.