Atomically flat, ultra thin-SiO2/Si(001) interface formation by UHV healing

Conventional wet cleaning and ultrahigh vacuum (UHV) heated cleaning prior to thermal oxidation were compared with respect to their effects on extremely thin SiO2/Si(001) interface roughness. Atomically flat SiO2/Si(001) interfaces were realized by preparing the Si(001)-2 x 1 surface in UHV followed by thermal oxidation. This planarization is significant in the range of oxide thickness (T-ox < similar to 9 nm). As for the 'wet-cleaned' surfaces, a wide variety of the interface roughness was observed at T-ox < similar to 4 nm which corresponds to the 'initial oxide thickness (T-io)' which appeared in the oxide growth kinetics. The electron scattering caused by the interface roughness might degrade the inversion electron mobility for the 'wet-cleaned' sample at T-ox < T-io.