Correlation between Co-60 and X-ray radiation-induced charge buildup in silicon-on-insulator buried oxides

Large differences in charge buildup in SOI buried oxides are observed for X-ray and Co-60 irradiations of SIMOX and Unibond transistors. The Co-60 response is typically worse than the X-ray response. These results are consistent with expectations derived from previous work on the relative charge yield versus field in thick oxides. The effects of bias configuration and substrate type on charge buildup and hardness assurance issues are explored via experiments and simulation. The worst-case bias condition is found to be either the off-state or transmission gate configuration. Simulations of the buried oxide electric field in the various bias configurations are used to illustrate the factors that affect charge transport and trapping in the buried oxides. Hardness assurance implications are discussed.