Optimum laboratory radiation source for hardness assurance testing

Silicon-on-insulator (SOI) and bulk-silicon transistors were irradiated using X-ray, Co-60 gamma, and proton radiation sources. Co-60 gamma irradiation generates larger radiation-induced threshold voltage shifts (by a factor of two) in SOI buried oxides and in parasitic field oxides under low-field conditions than X-ray or proton irradiation. For all devices examined, the radiation-induced threshold voltage shifts generated by X-ray irradiation were equal to, within experimental uncertainty, the radiation-induced threshold voltage shifts generated by proton irradiation. The differences in threshold voltage shifts for the different radiation sources are attributed to differences in stopping power and consequently charge yield. The results suggest that for simulating proton-rich space environments, X-ray laboratory radiation sources are better suited for hardness assurance testing than Co-60 gamma radiation sources. Using Co-60 gamma sources for hardness assurance testing will result in more conservative estimates of device failure levels. Thus, our results do not preclude the use of Co-60 gamma radiation sources for hardness assurance testing for proton-rich environments. For electron-rich space environments, Co-60 gamma radiation sources may be better suited for hardness assurance testing.