Epitaxial-base double-poly self-aligned bipolar transistors

Abstract

The authors report the incorporation of Si and Si-Ge low temperature epitaxially (LTE) grown bases into an advanced submicron self-aligned double-poly device structure. The major advantages of using an LTE-base are the ability to incorporate coherently strained Si-Ge layers and to grow very thin in-situ doped layers with a boxlike dopant distribution. The epitaxial base layer was integrated using both epitaxy-after-sidewall (EAS) and epitaxy-before-sidewall approaches, and devices with an intrinsic base width of ≅60 nm and a pinch base resistance of 5.0 kΩ/□ in walled and non-walled emitter configurations were fabricated. The electrical characteristics of the walled-emitter devices obtained by the EAS approach were excellent. The application of the walled-emitter devices, due to their reduced parasitics and higher density, is very promising in high-performance low-power bipolar circuits.