Initial oxidation process by ozone on Si(1 0 0) investigated by scanning tunneling microscopy

Ozone is a strong oxidant due to its release of atomic oxygen. The initial ozone oxidation process at room temperature and the roughness of the interface were investigated using scanning tunneling microscopy (STM). The most favorable adsorption site was the bridge site on the Si dimer at initial oxidation using ozone gas. Less than 10% of the oxygen atoms on the surface were located at the bridge site between the Si dimers. The rest of the oxygen atoms were inserted into the backbond below the Si dimer atom near the defects. This indicates that the oxygen atom is inserted into the backbond of the Si dimer through original and etched defects. The interface of SiO2/Si was characterized after the oxide film was removed by hydrofluoric acid. STM images were obtained from the etched surface. The roughness of the STM image was below 0.2 nm rms. This result indicates that the interface between the silicon and ozone oxides limits the roughness to two to three SiO2 layers at most after oxidation by ozone.