Highly insulating ultrathin SiO2 film grown by photooxidation

Highly insulating ultrathin SiO2 films (<5 nm) were grown by means of vacuum ultraviolet photooxidation, by use of 126, 172, and 222 nm wavelength photons generated by excimer lamps. The ultrathin silicon dioxide films were grown onto the Si(001) substrate, at low temperature (<500 degreesC). We found that the densities of photooxidized SiO2 films were 13%-35% higher than that of thermally oxidized SiO2 film. The density profile was obtained by x-ray reflectivity and showed a remarkable decrease in the SiOx (suboxide) layer thickness at the SiO2-Si interface, in comparison with thermally oxidized conventional oxides. The Si 2p photoelectron spectrum confirmed that the SiOx layer was negligibly thin. High insulating performance of the SiO2 film was demonstrated. (C) 2003 American Institute of Physics.