Single and Multiple Oxygen Vacancies in Ultrathin $ \hbox{SiO}_{2}$ Gate Dielectric and Their Influence on the Leakage Current: An Ab Initio Investigation

A first-principles method has been applied to the investigation of oxygen vacancies in ultrathin SiO
₂
gate dielectric and their influence on the gate leakage current. From the energy point of view, the most favorable site for a single vacancy has been determined to be at the Si/SiO
₂
interface. The formation energies of two neutral vacancies show, in general, an attractive interaction between two defects. Our results also indicate a correlation between the leakage current and the position of vacancies. As the number of vacancies increases in the oxide layer, the leakage current rises almost exponentially. A chain of five vacancies results in an increase of the leakage current by more than three orders of magnitude, which could be considered as gate-dielectric breakdown.