Reliability in submicron MOSFETs stressed at 77 K

Transconductance degradation in n channel MOSFETs stressed at 77 K was investigated, focused on low drain voltage stressing. Temperature dependence of degraded transconductance shows the existence of increased Coulomb centers in the channel, the origin of which is proposed from a viewpoint of Si-Si bond breaking at the Si/SiO2interface. Drain voltage dependence of substrate current was investigated in detail as a function of temperature. Results are discussed from viewpoints of both electron energy and temperature dependence of energy band gap in silicon. Gate oxide reliability at 77 K was also studied and it is shown that thinner gate oxides exhibit higher reliablity, even at 77 K as well as at room temperature. It is concluded that low temperature MOSFET operation is highly promising.