Fluorine effects in n-p-n double-diffused polysilicon emitter bipolar transistors

We demonstrate that fluorine incorporation in the polysilicon emitter of n-p-n double-diffused bipolar transistors during BF/sub 2/ implantation at a dose of 1/spl times/10/sup 15/ cm/sup -2/ significantly alters the device electrical characteristics. In particular, tunneling emitter/base currents are observed at both forward and reverse voltages, due to excessive base dopant concentration at the junction. Fluorine-enhanced interfacial oxide break-up and epitaxial realignment of the poly-Si emitter are shown to be responsible for these results.