Analysis and modeling of the long-term ageing rate of SiGe HBTs under mixed-mode stress

By means of long-term mixed-mode stress tests of high-speed SiGe HBTs an empirical ageing function for compact models was constructed. This ageing function models saturation of the aging rate as a function of stress time and stress current and is applicable for all relevant mixed-mode stress conditions of this HBT type. Additionally, 1000h stress tests on a high-voltage HBT revealed that not only saturation but even reversal of ageing rate is possible in the long run.