Radiation Hardened By Design Digital I/O for High SEE and TID Immunity

Level shifting radiation hardening by design input and output (I/O) pads on a 90 nm process using triple modular redundancy for single event effect (SEE) mitigation with high total ionizing dose (TID) immunity are described. The designs use annular NMOS transistors for both thin and thick gate transistors. SEE mitigation is experimentally demonstrated by heavy ion measurements with LET
_eff
up to 220 MeV-cm
²
/mg with no failures. Measurements of the I/O standby leakage current after TID irradiation to 2 Mrad(Si) show no standby current increase.