PHYSICALLY-BASED COMPARISON OF HOT-CARRIER-INDUCED AND IONIZING-RADIATION-INDUCED DEGRADATION IN BJTS

A physically based comparison between hot-carrier and ionizing radiati on stress in BJT's is presented, Although both types of stress lead to qualitatively similar changes in the current gain of the device, the physical mechanisms responsible for the degradation are quite differen t, In the case of hot-carrier stress the damage is localized near the emitter-base junction, which causes the excess base current to have an ideality factor of two, For ionizing radiation stress, the damage occ urs along all oxide-silicon interfaces, which causes the excess base c urrent to have an ideality factor between one and two for low total do ses of ionizing radiation, but an ideality factor of two for large tot al doses, The different physical mechanisms that apply for each type o f stress imply that improvement in resistance to one type of stress do es not necessarily imply improvement in resistance to the other type o f stress, Based on the physical model, implications for correlating an d comparing hot-carrier-induced and ionizing-radiation-induced damage are discussed.