A low-power and in situ annealing mitigation technique for fast neutrons irradiation of integrated temperature sensing diodes

High doses of fast neutrons is detrimental to the performance of most common solid-state devices such as diodes and transistors. The ionizing effect is observed in particular for diodes used as simple integrated temperature sensors, or thermodiodes, when their junction voltage is measured at constant current bias. In this work, we present a low-power and in situ mitigation technique based on Silicon-on-Insulator (SOI) microhotplates to recover thermodiodes. The basic operating principle consists in annealing the temperature-sensitive diodes integrated on the membrane during or after their irradiation in order to restore similar sensing characteristics over time. We measured thermodiodes integrated to microhotplates during their irradiation by fast neutrons (23 MeV peak) with total doses about 2.97±0.08 kGy. The membrane annealing is taking place at 450 °C using 40 mW of electrical power. Thanks to the annealing, the diode keeps a total measurement error below 0.5 °C. In this harsh radiation environment and beside the good tolerance of the thermodiodes and the membrane materials to the total ionizing dose, the thermodiode located on the heating membrane keeps a constant sensitivity. The demonstrated resistance of microhotplates and the integrated thermodiodes to fast neutron radiations can extend their use in nuclear plants and for radiation detectors.