Single crystal emitter gap for epitaxial Si- and SiGe-base transistors

An epitaxial base bipolar technology has been used for fabrication of graded SiGe-based HBTs (heterojunction bipolar transistors) or Si-base pseudo-HBTs with a self-aligned in-situ doped n-type low-temperature epitaxial (LTE) emitter. The thin LTE emitter provides an EB junction with low tunneling current and low capacitance in a n+ poly/n/p+/n thin base HBT design with very high base doping. The authors report on Si and SiGe devices utilizing a 40 nm P doped LTE emitter with an n+ poly contact and silicided p+ poly extrinsic base contact. Nearly ideal DC characteristics were obtained for a device with a peak base doping concentration of over 1*10/sup 19/ cm/sup -3/. 44 GHz f/sub T/ devices with an AC base resistance of only 150 Omega were used to fabricate 24 ps ECL (emitter coupled logic) and 19 ps NTL ring oscillators to demonstrate the performance potential of the structure.<>