A low-cost fully self-aligned SiGe BiCMOS technology using selective epitaxy and a lateral quasi-single-poly integration concept

We present a low-cost concept for a self-aligned SiGe heterojunction bipolar transistor (HBT). In conventional double-poly HBTs, the base link is formed by use of a sacrificial layer to grow the SiGe epitaxy between an external base polysilicon and the silicon substrate, resulting in a vertical base link. In this concept, the SiGe epitaxy is laterally connected to the extrinsic base poly forming a short and fully self-aligned base link. While strongly reducing process complexity, this concept maintains a minimal link resistance between the internal and the external base. We demonstrate the integration of this HBT with balanced dc and ac performance in a 0.25-μm bipolar complementary metal-oxide-semiconductor technology, featuring all passive devices necessary for RF design. The bipolar multitransistor yield shows similar values compared to our conventional double-poly integration concept.