Polysilicon-Emitter, SiGe Base Heterojunction Bipolar Transistor using Solid-Source MBE

Using the Si/SiGe heteroepitaxy grown by a solid-source (SS) molecular beam epitaxy (MBE) on the LOCOS (LOCal Oxidation of Silicon)-patterned wafers, a Si/SiGe heterojunction bipolar transistor (HBT) which is isolated by polysilicon-filled trench has been fabricated. In order to reduce the extrinsic base resistance, titanium silicide (TiSi2) layer directly patterned on the epitaxially grown layer is used as a base electrode instead of the doped polysilicon. After growth of the Si/SiGe layer, one-step furnace annealing at 840°C has been applied for the drive-in and activation of arsenic in polysilicon-emitter. The Si/Si0.85Ge0.15/Si n-p-n HBT with the 1×4¿m² emitter typically shows unity current gain frequency fT of 20GHz, unity power gain frequency fmax of 15GHz, common-emitter current gain of 118, Early voltage in the range of 150-170, and breakdown voltage BVceo of 7.8V, which demonstrate a potential for high frequency analog IC applications.