Negative bias temperature instability and relaxation in HfSiON gate stack field effect devices

Negative bias temperature instability and relaxation measurements have been performed on HfSiON gate stack devices. The time exponent for threshold voltage shift evolution is observed to be temperature dependent. The dominant source of the positive charge induced threshold voltage variation is determined to be dielectric trapped charge and this is the source of variation during relaxation. Nonlinear threshold voltage shift versus inversion channel carrier mobility is observed. Its magnitude is inconsistent with expectations from existing models.