73-GHz self-aligned SiGe-base bipolar transistors with phosphorus-doped polysilicon emitters

The authors report a thermal-cycle emitter process using phosphorus for the fabrication of self-aligned SiGe-base heterojunction bipolar transistors. The low thermal cycle results in extremely, narrow basewidths and preservation of lightly doped spacers in both the emitter-base and base-collector junctions for improved breakdown. Transistors with 35-nm basewidths were obtained with low emitter-base reverse leakage and a peak cutoff frequency of 73 GHz for an intrinsic base sheet resistance of 16 k Omega / Square Operator . Minimum NTL (nonthreshold logic) and ECL (emitter-coupled logic) gate delays of 28 and 34 ps, respectively were obtained with these devices.<
>