TOTAL-DOSE HARDNESS ASSURANCE ISSUES FOR SOI MOSFETS

The top-gate, back-gate, and sidewall responses of SIMOX and ZMR SOI/MOS transistors to 10-keV X-ray and Co-60 irradiation are compared. For top-gate and sidewall insulators, Co-60 and 10-keV X-ray irradiations at matched dose rates lead to nearly identical responses. Back-gate response, on the other hand, depends strongly on radiation energy and buried insulator thickness. Different X-ray to Co-60 correlation factors can be observed for other technologies with different sidewall and buried insulator materials and thicknesses. It is demonstrated that it is not possible to define a generic set of worst-case radiation bias conditions for all SOI technologies, as back-gate radiation response can be a strong function of transistor drain bias during exposure. However, the magnitude of this effect can vary with material and device processing, and the detailed changes in Si island potential and insulator electric fields that cause this behavior are not yet understood. Postirradiation effects are also addressed briefly.