Avalanche current induced hot carrier degradation in 200 GHz SiGe heterojunction bipolar transistors

SiGe heterojunction bipolar transistors (HBTs) have been investigated under accelerated avalanche stress conditions, where the base-emitter junction is forward biased, while the collector-base junction is reverse biased under avalanche conditions. The high energy avalanche carriers (hot carriers) introduce damage at Si-SiO₂ interfaces and degrade the characteristics of the SiGe HBTs. A new model has been developed to predict the damage at the Si-SiO₂ interface. The DC degradation of the base current is shown to correlate with the injected charge total and corresponding energy. The change of base current dependence on avalanche charges and applied voltage is shown, and a model is used to predict the parameter degradation within a typical digital switching application. The impact of this degradation mechanism to f_T has also been studied and found not to be significant.