POST OXIDATION ANNEAL AND RE-OXIDATION EFFECTS IN 5 nm SiO//2 FILMS.

Abstract

Ultrathin silicon dioxide films, 5 nm thick, were grown in a double-walled furnace at 850 degree C in dry O//2. A consistent improvement in the electrical properties is observed following the oxidation either with a Post-Oxidation Anneal (POA) at 1000 degree C in N//2 or with the same POA followed by a short re-oxidation (Re-Ox) step in which 1 nm of additional oxide was grown. We attribute these results to the redistribution of hydrogen and water related groups as well as to a change in the concentration of sub-oxide charge states at the Si-SiO//2 interface. A further improvement observed after the short re-oxidation step had been attributed to the filling of the oxygen vacancies produced during the POA. High resolution Transmission Electron Microscopy cross-sectional observations of the Si-SiO//2 interface have evidenced an increase in the interface roughness after the thermal treatment at high temperature. These results are in agreement with recent XPS data.