Total dose and RT annealing effects on startup current transient in antifuse FPGA

The startup current in an antifuse field programmable gate array (FPGA) device, A1280A, is investigated in the context of ionizing radiation effects. If properly measured, a radiation induced startup transient (RIST) can be identified after certain amount of irradiation. RIST increases with total dose (TID), and is strongly dependent on the dose rate. Room-temperature biased annealing for few days can reduce RIST to a very low level. A transistor-level mechanism is proposed to elucidate the origin of RIST. The ionization induced leakage in the NMOS diode is believed to be the root cause. The degradation of the ramping speed of the charge pump causes RIST when powering up the device. SPICE simulation was also performed to demonstrate the slow down of the ramping speed by the leakage in the NMOS diode. In typical low-dose-rate space environments, RIST is not the limiting factor for the total dose tolerance.