Ultra-low base resistance self-aligned SEG SiGe HBTs for high-sensitivity wide-bandwidth amplifiers

To fabricate a SiGe HBT with low base resistance, a heavily boron-doped and high-Ge-content base and a high-peripheral-ratio emitter configuration were applied. To retain a high h_FE and f_T for low intrinsic/extrinsic base resistances, the Ge profile was carefully optimized. The emitter configuration with a high periphery-to-area ratio could be introduced through the advantage of the low parasitic capacitance in the self-aligned structure, and contributed to a further reduction of the base resistance without degradation of f_T and f_max. As a result, the base resistance was successfully reduced to about 1/3 of the previous HBT.