It was recalled that high dielectric constant gate oxides such as HfO2 had suffered from charge trapping, threshold voltage shifts and a difficulty of metal or poly-Si gates to achieve band edge work function values. An investigation was made of how these were related to the O vacancies in a series of ab initio calculations. The O vacancy was found to correlate with optical, luminescence and charge pumping spectra. The O vacancy contributed to the Fermi level pinning effect, which limits the band edge work functions. Inhibiting motion of vacancies may allow less pinning of gate electrode work functions.

Oxygen Vacancies in High-k Oxides. K.Tse, D.Liu, K.Xiong, J.Robertson: Microelectronic Engineering, 2007, 84[9-10], 2028-31