Publications Details
Predicting switched-bias response from steady-state irradiations
In actual circuit application, MOS transistor bias is generally not constant through radiation exposure. Nevertheless, the overwhelming majority of radiation effects studies and hardness assurance testing is performed at constant bias for simplicity and practicality. In the past 15 years, however, it has been shown that oxide- and interface-trap charge buildup and annealing during switched-bias exposures can differ quantitatively and qualitatively from that observed during steady-state exposures. This has made it difficult to develop predictive models of MOS circuit response for actual use conditions, and has introduced uncertainty into hardness assurance testing of MOS circuits. In this summary, defect growth and annealing rates are compared for steady-state and switched-biased irradiations of MOS transistors. A simple method is described to predict MOS oxide-trap charge, interface-trap charge, and mobility degradation during switched-bias exposures from steady-state ( on'' and off'') irradiations. Over a wide range of switching conditions for the devices examined, this method has provided predictions typically accurate to within better than 20%. The maximum error observed to data is less than 40%. This method should allow the total-dose radiation response of MOS circuits in real-use scenarios to be modeled with improved accuracy and flexibility. 9 refs., 3 figs.