Method to estimate profile of threshold voltage degradation in MOSFETs due to electrical stress

This paper presents a method to measure the threshold voltage degradation ΔVth along the channel direction due to electrical stress in MOSFETs. This method uses ΔVths measured after electrical stress at different drain bias Vds, and calculated the depletion length Ldep into the channel for each condition under which ΔVth is measured. By substituting ΔVth and Ldep into the proposed equation, the amount of degradation generated in each region of the MOSFET channel can be calculated. The ΔVth profiles of OFF-state stress and negative bias temperature instability in pMOSFET and hot carrier injection in nMOSFET were extracted using the proposed method. The degradation profiles correspond well with each stress characteristic.