Mixed-mode stress degradation mechanisms in pnp SiGe HBTs

An investigation of the high-voltage/high-current mixed-mode (M-M) stress-induced damage mechanisms of pnp silicon-germanium (SiGe) heterojunction bipolar transistors (HBTs) is presented. Different accelerated stress methods, including mixed-mode stress, reverse emitter-base (EB) stress, and forward collector plus reverse EB stress, were applied to pnp SiGe HBTs from a state-of-the-art complementary-SiGe BiCMOS process technology platform. The operative damage mechanism from the M-M stress method is identified. Experimental evidence of collector current change due to the M-M stress, and the experimental proof of the type of hot carriers (electrons vs. holes) responsible for the observed M-M stress damage are presented.