DOUBLE-CHANNEL HOT-CARRIER INJECTION EFFECTS IN NMOSFETS AT 77-K

Combined Delta V-TH, Delta V-FB, I-V and interface state measurements are employed to investigate double channel hot-carrier injection effects in NMOSFETs at 77 K. By comparing these measurements with those obtained at 295 K and analysing the roles that the effective negative charge and negative potential barrier play, qualitative results such as increased electron trapping and reduced interface state generation as well as enhanced degradation are obtained, which are in good agreement with reports on the effects of single-channel carrier injection. Furthermore, generated acceptor-like interface states seem to be most significant to the enhanced degradation at 77 K as compared with the fixed negative charge. In addition, carrier injection sequence-related phenomena are observed. In all cases, the stress caused by hole injection followed by electron injection can lead to a larger degradation than stress caused by the opposite injection sequence. Again these stresses are much more pronounced at 77 K than at 295 K. Possible mechanisms are put forward to interpret this.