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 effec ts in NMOSFETs at 77 K. By comparing these measurements with those obt ained at 295 K and analysing the roles that the effective negative cha rge and negative potential barrier play, qualitative results such as i ncreased electron trapping and reduced interface state generation as w ell as enhanced degradation are obtained, which are in good agreement with reports on the effects of single-channel carrier injection. Furth ermore, generated acceptor-like interface states seem to be most signi ficant to the enhanced degradation at 77 K as compared with the fixed negative charge. In addition, carrier injection sequence-related pheno mena are observed. In all cases, the stress caused by hole injection f ollowed by electron injection can lead to a larger degradation than st ress caused by the opposite injection sequence. Again these stresses a re much more pronounced at 77 K than at 295 K. Possible mechanisms are put forward to interpret this.