ATMOSPHERIC-PRESSURE CVD-GROWN SIGE EPITAXIAL BASE HETEROJUNCTION BIPOLAR-TRANSISTOR USING A TISI2 BASE ELECTRODE

Using silicon/silicon germanium (Si/SiGe) heteroepitaxial layer, grown by commercialized atmospheric-pressure chemical vapor deposition (APC VD), on a wafer patterned by polysilicon-filled trench isolation and t he local oxidation of silicon (LOCOS), a Si/SiGe heterojunction bipola r transistor (HBT) has been fabricated. In order to reduce the base el ectrode resistance, titanium silicide (TiSi2) was used instead of dope d polysilicon. After growing the Si/SiGe epilayer, thermal annealing w as applied for emitter-base junction formation and dopant activation i n the polysilicon emitter. The Ge-composition-graded base Si/Si(0.85)G -e(0-0.15)/Si n-p-n HBTs with different emitter areas typically showed a cutoff frequency (f(T)) of 25 GHz, a collector-emitter breakdown vo ltage (BVCEO) of 7 V, a common-emitter current gain (beta) in the rang e of 150 similar to 220, and an Early voltage (V-A) in the range of 60 similar to 160 V for different device sizes. This Si/SiGe HBT grown u sing the APCVD technology demonstrates a potential for practical high- frequency analog and digital IC applications.