73-GHz Self-Aligned SiGe-Base Bipolar Transistors with Phosphorus-Doped Polysilicon Emitters

We report a reduced 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 [formula omitted]. Minimum NTL and ECL gate delays of 28 and 34 ps, respectively, were obtained with these devices. © 1992 IEEE