Energetic distribution of oxide traps created under negative bias temperature stress and their relation to hydrogen

By applying an incremental sweep technique to silicon devices subjected to negative bias temperature stress, we identify two significant peaks of recoverable oxide defects located energetically within the silicon band gap. The first peak is near midgap and is almost fully developed after ten seconds of stress while the second peak is found in the upper half of the silicon band gap and develops gradually as a function of stress time. We obtain very similar density-of-state profiles for two samples having vastly different hydrogen concentrations within the gate oxide indicating that the precursor for oxide trap creation is independent of hydrogen.