RF and hot carrier effects in metal gate/high-k dielectric nMOSFETs at cryogenic temperature

We investigate RF performances and hot carrier effects of nMOSFETs at cryogenic temperature. RF performances of HfO
₂
dielectric nMOSFET at 77 K are improved more than those of SiO
₂
dielectric nMOSFET although DC performances are improved similarly. The nMOSFET with HfO
₂
dielectric has 127.4 GHz f
_T
and 75.4 GHz f
_max
at 77 K. In hot carrier injection measurement, g
_m
of HfO
₂
nMOSFET at 77 K is degraded more than 300 K although V
_th
shift is less. The cause of g
_m
reduction is discussed related to the trapping.