High performance SiGe:C HBTs using atomic layer base doping

We applied atomic layer processing for base doping of high performance SiGe:C heterojunction bipolar transistors (HBTs) fabricated within a 0.25 mm BiCMOS technology. B atomic layer doping (ALD) was performed at 400 8C during an interruption of the epitaxial SiGe:C base layer deposition. Atomic level dopant location and dose control was achieved. Electrical properties of atomic layer and box-profile doped (standard) HBTs were compared, showing peak fT and fmax for the ALD HBTof 113 and 127 GHz, and of 108 and 123 GHz for the standard HBT, respectively. The internal base sheet resistances (RSBi) for the ALD and standard HBTs were comparable, indicating very similar active B dose for both doping variants. The HBTresults demonstrate the capability of atomic layer processing for doping of advanced devices, with critical requirements for dose and location control. # 2003 Elsevier B.V. All rights reserved