Comparison of conventional 60Co testing and very low dose-rate irradiation of metal-gate CMOS ICs

Data are presented for one family of Hi-Rel, rad-hard, metal-gate CMOS ICs which show a much greater tolerance to very low dose-rate ionizing radiation than that predicted by conventional-rate (approximately 106 rads(Si)/hr) 60Co testing. Data obtained using the conventional rate 60Co irradiations followed by either a 24 hour, high-temperature (1000C) or 65 day room temperature anneal are in good agreement with data obtained by exposing similar parts at a very low dose accumulation rate (5000 rads(Si)/day) for 200 consecutive days. The similarity between these findings and the rebound phenomena is described, and the implications of these findings for space and other low dose-rate applications is discussed. A simple test procedure for identifying low dose-rate annealing, or rebound, and its recovery time is proposed. Graphs of thresholds, output drive, and propagation delay versus low dose-rate and conventional-rate dose accumulation are included