Physical mechanisms of negative-bias temperature instability

We report first-principles calculations that elucidate the mechanisms that underlie key features of negative-bias temperature instability (NBTI). We show that the depassivation of Si-H bonds by protons released in the Si substrate is consistent with the observed increase in interface-trap density. The calculated activation energy of 0.36 eV is in excellent agreement with observations for long stress times. Adequate amounts of hydrogen, needed to initiate depassivation, are likely to exist in the substrate, trapped in complexes with dopants. The role of holes in the H release mechanism is identified. Finally, we explain how the above mechanisms can account for various experimental NBTI observations. (C) 2005 American Institute of Physics.