Optimization of external poly base sheet resistance in 0.13 μm quasi self-aligned SiGe:C HBTs

This paper investigates the optimization of the external polysilicon base sheet resistance of quasi self-aligned (QSA) SiGe:C HBTs from a 0.13 μm BiCMOS process. Taking advantage of optimized implant conditions to improve the doping of the external base poly, and using an optimized non-selective epitaxy process with improved growth rate ratio of 1.7 between the polycrystalline silicon and monocrystalline silicon of the base, the maximum oscillation frequency fmax reaches 300 GHz.