Validation on Duality in Impact-ionization Carrier Generation at the Onset of Snapback in Power MOSFETs

Abstract

Carrier generation due to impact ionization is an underlying physical mechanism in the snapback phenomenon. An exceedingly large amount of current during the snapback phenomenon is supplied from the two branches of carrier generation due to impact ionization; one originates from the surface channel current and the other from the source-junction injected current which tends to flow across a deeper location than the surface channel current. Device simulation for a power Laterally-Diffused MOSFET has revealed twin peaks of carrier generation rate distribution near the drain junction. This finding validates an incorporation of substrate current model equations in a common functional form to a MOSFET compact model, except for a distinct set of model parameters respectively; one for the shallow current and the other for the deep current.