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 temperatureinstability (NBTI) without inherent recovery. Saturation drain voltage shift andmobility shift are extracted by I_D-V_D characterizations, which weremeasured before stress, and after every certain stress phase, using theproportional differential operator (PDO) method. The new on-line methodology avoidsthe mobility linearity assumption as compared with the previous on-the-fly method.It is found that both reaction--diffusion and charge-injection processes areimportant 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 isindependent of temperature below 90du and sharply increases above it. Thefrequency dependence of NBTI degradation shows that NBTI degradation is independentof frequencies. The carrier tunnelling and reaction--diffusion mechanisms existsimultaneously in NBTI degradation of sub-micron pMOSFETs, and the carriertunnelling dominates the earlier NBTI stage and the reaction--diffusion mechanismfollows when the generation rate of traps caused by carrier tunnelling reaches itsmaximum.