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 HfO₂ dielectric nMOSFET at 77 K are improved more than those of SiO₂ dielectric nMOSFET although DC performances are improved similarly. The nMOSFET with HfO₂ dielectric has 127.4 GHz f_T and 75.4 GHz f_max at 77 K. In hot carrier injection measurement, g_m of HfO₂ 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.