Impact on Low-Frequency Noise Properties from Lateral Design of Differentially Grown SiGe HBTs

SiGe heterojunction bipolar transistors (HBTs) are suitable for wireless applications due to their high speed, low high-frequency noise and low power dissipation. For some applications, such as voltage-controlled oscillators (VCO’s), the device must also exhibit low 1/ noise which will act to suppress undesired phase noise. In this work, SiGe HBTs based on chemical vapour deposition (CVD) epitaxy have been studied. The SiGe epitaxial film was grown differentially with a monocrystalline phase on top of the silicon collector, and a polycrystalline phase on top of the LOCOS. Figure 1 shows a cross-sectional TEM picture of the HBT investigated in this work. The interface between the polycrystalline and epitaxial Si/SiGe stack ...............