Self-aligned SiGe NPN transistors with 285 GHz fmax and 207 GHz fT in a manufacturable technology

This paper reports on SiGe NPN HBTs with unity gain cutoff frequency (f
_T
) of 207 GHz and an f
_max
extrapolated from Mason's unilateral gain of 285 GHz. f
_max
extrapolated from maximum available gain is 194 GHz. Transistors sized 0.12×2.5 μm
²
have these characteristics at a linear current of 1.0 mA/μm (8.3 mA/μm
²
). Smaller transistors (0.12×0.5 μm
²
) have an f
_T
of 180 GHz at 800 μA current. The devices have a pinched base sheet resistance of 2.5 k/spl Omega//sq. and an open-base breakdown voltage BV/sub CEO/ of 1.7 V. The improved performance is a result of a new self-aligned device structure that minimizes parasitic resistance and capacitance without affecting f
_T
at small lateral dimensions.