POLYSILICON EMITTER RESISTANCE AND CARRIER TRANSPORT STUDIES.

Abstract

Narrow basewidths in high-performance bipolar transistors can only be achieved controllably with very shallow base-emitter junctions. The resulting degradation of current gain can be prevented by application of polysilicon as emitter contact and diffusion source. The mechanisms responsible for the improved emitter efficiency have received wide attention, especially the role of interface oxides. However, as higher current densities are expected in scaled bipolar devices, series resistances take on added importance. Experimental results are presented on the contact resistance associated with polysilicon emitters with and without intentional interface oxides. The amount of As doping is shown to be a dominant factor in the coupling between base current and emitter resistance.