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

Abstract

This paper presents a method to measure the threshold voltage degradation Delta V-th along the channel direction due to electrical stress in MOSFETs. This method uses Delta V(th)s measured after electrical stress at different drain bias V(d)s, and calculated the depletion length L-dep into the channel for each condition under which Delta V-th is measured. By substituting Delta V-th and L-dep into the proposed equation, the amount of degradation generated in each region of the MOSFET channel can be calculated. The Delta V-th 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.