Radiation Response of SNOS Nonvolatile Transistors

Data loss and permanent damage resulting from the irradiation of SNOS (polySilicon-Nitride-Oxide-Silicon) nonvolatile memory transistors fabricated with current SNLA EEPROM processing are examined. It is shown that these transistors can retain data for ten years after a 500 krad irradiation, and can be programmed and function properly following a 1300 Mrad irradiation. A new model is presented which yields a simple analytical solution that accurately predicts the radiation induced threshold voltage shifts of SNOS transistors for a wide range of initial threshold voltages and total doses.