Degradation of hard MOS devices at low temperature

A study of n-channel MOS transistors stressed under Fowler Nordheim injection was made both at room temperature and low temperature (77 K). Using alternatively positive and negative bias one can create interface states or bulk oxide charge at 300 K. This is comparable to ionising irradiation. At 77 K a slight reverse annealing occurs, due to the weak neutralization of interface states, under negative bias. Under positive bias no significant threshold voltage shift occurs at low temperature, almost all the interface charge being compensated by the oxide charge.