Polysilicon emitter p-n-p transistors

Abstract

In-situ boron-doped polysilicon has been used to form the emitter in p-n-p transistors. Various polysilicon deposition conditions, interface preparation treatments prior to deposition, and post-deposition anneals were investigated. Unannealed devices lacking a deliberately grown interfacial oxide gave effective emitter Gummel numbers G/sub E/ of 7-9*10/sup -12/s cm/sup -4/ combined with emitter resistances R/sub E/ of approximately 8 mu Omega cm/sup 2/. Introduction of a chemically grown interfacial oxide increased G/sub E/ to 2*10/sup 14/s cm/sup -4/, but also raised R/sub E/ by a factor of three. Annealing at 900 degrees C following polysilicon deposition raised G/sub E/ values for transistors lacking deliberate interfacial oxide to approximately 6*10/sup 13/s cm/sup -4/, but had little effect of G/sub E/ for devices with interfacial oxide. Both types of annealed devices gave R/sub E/ values in the range 1-2 mu Omega cm/sup 2/.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>