ACCOUNTING FOR TIME-DEPENDENT EFFECTS ON CMOS TOTAL-DOSE RESPONSE IN-SPACE ENVIRONMENTS

Time-dependent charge buildup and annealing processes cause the ionizi ng radiation response of CMOS devices and circuits to depend strongly on the dose rate of the exposure. Oxide-trap charge annealing and inte rface-trap buildup in nMOS transistors can lead to positive threshold voltage shifts in a space environment, while negative threshold voltag e shifts are commonly observed after irradiations at typical laborator y dose rates [50-300 rad(Si)/s]. Thus, devices that pass laboratory te sting can fail at the low dose rates encountered in space due to posit ive nMOS transistor threshold-voltage shifts above preirradiation valu es, i.e. ''rebound''. We summarize how this issue can be addressed in total-dose hardness assurance test methods for space. An example of su ch a guideline is the revised U.S. military-standard ionizing-radiatio n-effects test method (MIL-STD 883D, Test Method 1019.4).