Matching NPN and PNP collector profiles for high-speed complementary bipolar technology presents a special challenge to epi processing. This paper describes a novel thin epi process that is designed to reduce the effect of boron autodoping and improve the NPN collector doping in the deep portion of the collector region. Summary evaluations of autodoping are presented for different H2 bake and HCl etch cycles, and for the use of intrinsic- and As-doped cap layers. An epitaxial technique, which introduces As dopant during the high temperature H2 bake, is described. This technique has proven very effective in suppressing the effects of boron autodoping and correcting the NPN collector profile.
Vladimir F. Drobny,
Kevin X. Bao,
"Novel thin epi process for high-speed CB-CMOS", Proc. SPIE 3506, Microelectronic Device Technology II, (4 September 1998); doi: 10.1117/12.323986; https://doi.org/10.1117/12.323986