Defect energy states in high‐K gate oxides

Abstract

AbstractThe electrical energy levels of the different charge states of the oxygen vacancy and the oxygen interstitial in HfO2 are calculated, using density functional methods which do not need a band gap correction. Lattice distortions around the defect sites produce substantial shifts in the energy levels. The energy levels are aligned to those of the Si channel. In HfO2, the oxygen vacancy gives an energy level in the Si gap or just above the gap, depending on its charge state. The O vacancy is identified as the main electrically active defect and trap. The oxygen interstitial gives levels just above the oxide valence band, and the neutral interstitial also gives a level near the Si conduction band. The defect wavefunctions are given. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)