Electron Tunneling through Ultrathin Gate Oxide Formed on Hydrogen-Terminated Si(100) Surfaces

Abstract

Current transport through ultrathin gate oxides grown on chemically cleaned Si(100) surfaces has been systematically investigated. It is shown that current through oxides thinner than 4.2 nm is controlled by direct tunneling (DT), while Fowler-Nordheim tunneling (FNT) predominates in transport through SiO 2 thicker than 5.1 nm. In the oxide thickness range between 4.2 and 5.1 nm, DT limits the current at low electric fields and FNT at high fields. The observed tunneling current is quantitatively explained by a theory based on the Wentzel-Kramers- Brillouin method (WKB approximation). Also, the influence of the Si surface microroughness on the tunneling current is discussed.