SINGLE EVENT UPSET IN IRRADIATED 16K CMOS SRAMS

The single-event-upset (SEU) characteristics of a CMOS SRAM cell irradiated under conditions that simulate the total-dose degradation anticipated in space applications were experimentally and theoretically investigated. Simulations of SEU sensitivity utilizing a 2-D circuit/device simulator, with measured transistor threshold- voltage shifts and mobility degradations as inputs, are shown to be in good agreement with experimental data at high total dose. Both simulation and experiment show a strong SRAM cell SEU imbalance resulting in a more SEU-tolerant preferred state and a less tolerant nonpreferred state. The resulting cell imbalance causes an overall degradation in SEU immunity, which increases with increasing total dose and should be taken into account in SEU testing and part characterization.