Effect of Heavy Ion irradiation and Electrical Stress on Ultra-Thin Gate Oxide SOI MOSFETs

An accelerated wear-out of ultra-thin gate oxides used in contemporary deep-submicron CMOS technologies is one of the effects observed in MOSFETs submitted to irradiation with high LET particles [1-5]. The damage introduced in the gate oxide by an impinging ion may in fact act as a seed for further degradation produced by electrons and holes injected at high fields during a subsequent electrical stress, eventually leading to a premature breakdown of the oxide. Synergy between radiation and electrical stresses is not limited to the oxide breakdown process, but it includes also an accelerated degradation of MOSFET parameters during high field stresses following irradiation with high LET ions, as reported in case of bulk CMOS transistors [6]. In parallel, radiation damage on deep-submicron SOI devices with ultra-thin gate oxides has been recently investigated after X-ray [7, 8] and proton exposure [9-11]. Yet, the reaction of irradiated SOI devices fabricated in a contemporary CMOS technology to subsequent accelerated electrical stresses is still a virgin chapter in the radiation effects field, at least for what concerns high LET particles. The contemporary presence of radiation and high electric fields is the living scenario for any component operating in a radiation harsh environments, and deserves attention from the radiation effects community to assess reliability issues in CMOS devices.