28-nm FDSOI nMOSFET RF Figures of Merits and Parasitic Elements Extraction at Cryogenic Temperature Down to 77 K

This paper presents detailed RF characterization of 28-nm FDSOI nMOSFETs at cryogenic temperatures down to 77 K. Two main RF figures of merit (FoM), i.e., current gain cutoff frequency (f
_T
) and maximum oscillation frequency (f
_max
), as well as elements of small-signal equivalent circuit are extracted from the measured S-parameters. Increases of f
_T
and f
_max
by about 85 GHz and about 30 GHz, respectively, are demonstrated at 77 K. The observed behavior of RF FoMs versus temperature is discussed in terms of small-signal equivalent circuit elements, both intrinsic and extrinsic (parasitics). This paper suggests 28-nm FDSOI as a good candidate for future cryogenic applications.