Enhancing the Speed of SiGe HBTs Using fT-Doubler Techniques

A peak f
_T
of 325 GHz is achieved, for the first time, in a 130 nm, 200 GHz, 3
^rd
-generation SiGe HBT technology at 300 K, by utilizing f
_T
-doubler techniques. This speed enhancement is equivalent to gaining an additional generational node (from 3
^rd
to 4
^th
), with no underlying change to the transistor profile or lithography. The f
_T
-doubler can be treated as a single transistor unit cell during circuit design, which is verified by the investigation of its small-signal equivalent circuit. Reduced C
_pi
is demonstrated to be the root origin of the f
_T
-enhancement. The impact of emitter geometry on performance is investigated. A record f
_T
of 438 GHz is achieved at 93 K.