Channel Hot-Carrier degradation characteristics and trap activities of high-k/metal gate nMOSFETs

In this paper, the Hot-Carrier (HC) degradation characteristics and mechanisms of nMOSFETs with high-k/metal gate (HK/MG) structure are systematically investigated. The Idsat shift under different Vd states obeys power-law of Vg stress time, and the exponent of Vg stress time shifts from 0.5~0.7 at low stress to 0.2~0.3 at high stress, which is believed to be induced by different trap activities. There are two transitions in the curve of time to fail (TTF) and Vg stress, the 1^st valley point is resulted from impact ionization, and the 2^nd transition is attributed to the dominant roles exchange of the interface trap (Nit) and bulk trap (Not) in dielectric in degradation.