Effects of Ionizing Radiation on Digital Single Event Transients in a 180-nm Fully Depleted SOI Process

Effects of ionizing radiation on single event transients are reported for Fully Depleted SOI (FDSOI) technology using experiments and simulations. Logic circuits, i.e. CMOS inverter chains, were irradiated with cobalt-60 gamma radiation. When charge is induced in the n-channel FET with laser-probing techniques, laser-induced transients widen with increased total dose. This is because radiation causes charge to be trapped in the buried oxide, and reduces the p-channel FET drive current. When the p-channel FET drive current is reduced, the time required to restore the output of the laser-probed FET back to its original condition is increased, i.e. the upset transient width is increased. A widening of the transient pulse is also observed when a positive bias is applied to the wafer without any exposure to radiation. This is because a positive wafer bias reproduces the shifts in FET threshold voltages that occur during total dose irradiation. Results were also verified with heavy ion testing and mixed mode simulations.