Defect passivation in HfO2 gate oxide by fluorine

Abstract

The authors have calculated that fluorine substituting for oxygen gives no gap states in HfO2. This accounts for the good passivation of oxygen vacancies by F seen experimentally. Bonding arguments are used to account for why F may be the most effective passivant in ionic oxides such as HfO2, whereas hydrogen is effective in covalent solids. General principles of defect passivation in ionic oxides are discussed. Vacancies are more detrimental in ionic oxides than in SiO2 because they are more likely to be charged in the presence of a gate electrode.