Recovery behaviour resulting from thermal annealing in n-MOSFETs irradiated by 20 MeV protons

The radiation damage of 20 MeV proton irradiated n-MOSFETs fabricated in a BiCMOS process is studied. From the input characteristics of the drain current, the activation energy of the voltage shift based on trapped-oxide charge (ΔVNot) and SiO2/Si interface traps (ΔVNit) for a total ionizing dose of 35 Mrad(Si) is calculated to be 0.40 and 0.26 eV, respectively. Also, the activation energy for the annealing of the density of radiation-induced interface traps (Nit) estimated from the base current of the bipolar mode operation corresponds to 0.27 eV. From the activation energy of the ohmic drain–source current recovery of 0.40 eV it can be concluded that the trapped-oxide charge is mainly responsible for the degradation of the transistor performance.