Scalable model for predicting the effect of negative bias temperature instability for reliable design

The authors present a predictive model for the negative bias temperature instability (NBTI) of PMOS under both short term and long term operation. On the basis of the reaction-diffusion mechanism, this model accurately captures the dependence of NBTI on the oxide thickness (t_ox), the diffusing species (H or H₂) and other key transistor and design parameters. In addition, a closed form expression for the threshold voltage change (ΔV_th) under multiple cycle dynamic operation is derived. Model accuracy and efficiency were verified with 180, 130 and 90 nm silicon data. The impact of NBTI on the delay degradation of a ring oscillator and the various metrics of the SRAM such as its data retention voltage, read and hold margins, as well as read and write delay, is also investigated.