Inherent and Stress-Induced Leakage in Heavily Doped Silicon Junctions

Abstract

Inherent leakage currents and leakage induced with reverse-bias stress are investigated in heavily doped emitter-base junctions of polysilicon self-aligned bipolar transistors and similar diodes. Inherent in the devices is a reverse leakage component found to have a perimeter trap-assisted tunneling component characteristic of the Si-SiO2 surface and evident at doping insufficient for significant band-to-band tunneling. The band-to-band phonon-assisted tunneling and avalanche leakage components are also identified. Introducing surface states through reverse-bias stress induces a Poole-Frenkel electric field enhanced generation/recombination surface leakage component. The induced and trap-assisted tunneling components are distinct. The induced component is found to saturate as available states, dependent on the peak electric field, are exhausted. Trapped charge accumulation after extensive stressing affects the electric field along the surface reducing the induced and trap-assisted tunneling leakage components. © 1988 IEEE.