Parasitic bipolar transistor model using generated-hole-dependent base resistance

An accurate parasitic bipolar transistor model is indispensable for the evaluation of ESD immunity. Injected electrons are well known to modulate base resistance, but we found that it is not true during snapback because the electric field associated with injected electrons is compensated by the holes generated in the drain region. We therefore developed a new base resistance model that depends on generated holes as well as injected electrons. Here we show that this model can account for the Gummel plot and the snapback characteristics simultaneously. Furthermore, we developed analytical modes for prominent features of snapback characteristics and clarified the dependence of snapback characteristics on various parameters.