Evaluation of negative bias temperature instability in ultra-thin gate oxide pMOSFETs using a new on-line PDO method

A new on-line methodology is used to characterize the negative bias temperature instability (NBTI) without inherent recovery. Saturation drain voltage shift and mobility shift are extracted by I_D-V_D characterizations, which were measured before stress, and after every certain stress phase, using the proportional differential operator (PDO) method. The new on-line methodology avoids the mobility linearity assumption as compared with the previous on-the-fly method. It is found that both reaction--diffusion and charge-injection processes are important in NBTI effect under either DC or AC stress. A similar activation energy, 0.15 eV, occurred in both DC and AC NBTI processes. Also degradation rate factor is independent of temperature below 90℃ and sharply increases above it. The frequency dependence of NBTI degradation shows that NBTI degradation is independent of frequencies. The carrier tunnelling and reaction--diffusion mechanisms exist simultaneously in NBTI degradation of sub-micron pMOSFETs, and the carrier tunnelling dominates the earlier NBTI stage and the reaction--diffusion mechanism follows when the generation rate of traps caused by carrier tunnelling reaches its maximum.