Self-aligned SiGe NPN transistors with 285 GHz f _MAX and 207 GHz f _T 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 kΩ/sq. and an open-base breakdown voltage BV 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.