Modeling of Dispersive Transport in the Context of Negative Bias Temperature Instability

Negative bias temperature instability (NBTI) is one of the most serious reliability concerns for highly scaled pMOSFETs. It is most commonly interpreted by some form of reaction-diffusion (RD) model, which assumes that some hydrogen species is released from previously passivated interface defects, which then diffuses into the oxide. It has been argued, however, that hydrogen motion in the oxide is trap-controlled, resulting in dispersive transport behavior. This defect-controlled transport modifies the characteristic exponent in the power-law that describes the threshold-voltage shift. However, previously published models are contradictory and both an increase and a decrease in the power-law exponent have been reported. We clarify this discrepancy by identifying the boundary condition which couples the transport equations to the electro-chemical reaction at the interface as the crucial component of the physically-based description