Investigation on Base-Emitter Reverse Biasing: Light Emission, Junction Cross-Talk and Hot Carriers in Single-Polysilicon Quasi Self-Aligned Bipolar-Complementary Metal-Oxide Semiconductor Bipolar Transistors

In this paper we investigate, in single-polysilicon quasi self-aligned bipolar transistors of an advanced 0.5 µm planar bipolar-complementary metal-oxide semiconductor (BiCMOS) technology, the base-emitter junction characteristics in reverse bias conditions and its influence on the behaviour of other neighbouring junctions, i.e. collector and substrate. We will show, due to the high emitter and base doping, the non negligible presence of impact-ionization effects superimposed over the well known reverse tunnel current even at moderate reverse bias. The related light emission coming from the energetic carriers in the impact-ionization regime can influence the collector and even the substrate junctions. These investigations are confirmed by temperature measurements and the results suggest that attention should be paid also to these secondary, higher order, effects during device scaling-down in BiCMOS circuitry.