Cryogenic operation of sub-30 nm nMOSFETs: impact of device architecture

Characteristics of carrier transport are analyzed on sub 30nm NMOSFETs at temperature ranging from 300K to 20K. In the on-state regime, degradation of the low field mobility on short channel transistors limits velocity overshoot and ballistic transport occurrence. Nevertheless, due to the drastic reduction of the subthreshold swing, large improvement of the Ion/Ioff trade-off is observed. Thus low temperature operation allows transistors to operate closer to their limit. In the linear regime (Vd<10mV), short channel transistors exhibits oscillations on the Id-Vg characteristics that remain up to 75K. These oscillations should be due to state assisted tunneling current.