A super self-aligned selectively grown SiGe base (SSSB) bipolar transistor fabricated by cold-wall type UHV/CVD technology

A novel selective epitaxial growth (SEG) technology for fabricating the intrinsic SiGe-base layer of a double poly-Si self-aligned bipolar transistor has been developed. Selectively grown Si and SiGe-alloy layers were obtained by using Si/sub 2/H/sub 6/+GeH/sub 4/+Cl/sub 2/+B/sub 2/H/sub 6/ gas system using cold-wall ultra-high vacuum (UHV)/CVD. We have optimized the growth conditions so that Si or SiGe grows selectively against Si/sub 3/N/sub 4/ both on single crystalline Si and on poly-Si of a structure consisting of a poly-Si layer overhanging the single crystalline Si substrate. The selective growth is maintained until the growth from the bottom Si and the top poly-Si coalesce. This selective growth permits a novel emitter-base self-aligned transistor which we call a super self-aligned selectively grown SiGe base (SSSB) HBT.<
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