Breakdown modes and their evolution in ultrathin gate oxide

Post-breakdown current-voltage characteristics of metal-oxide-semiconductor (MOS) devices with an ultrathin gate oxide layer have been carefully studied. Several breakdown modes were identified. Specifically, it was found that the typical soft-breakdown mode induced in an oxide layer thinner than 3 nm is actually quite different from that in an oxide layer thicker than 3 nm. Based on these findings, we have also proposed a model to explain the evolution of different breakdown modes. The model takes into consideration the thermal runaway process at the breakdown moment, and is substantiated by a number of experimental findings. Impacts of each breakdown mode on device switching behavior are also discussed.