OBSERVATION OF ATOMIC STEP MORPHOLOGY ON SILICON-OXIDE SURFACES

Atomic step structures on oxidized Si(111) surfaces are investigated by scanning electron microscopy with grazing incidence of the primary electron beam and by scanning force microscopy. Atomic step structures similar to those on clean Si(111) are preserved on a thermally oxidized surface at 900-degrees-C in dry O2 as well as on a naturally oxidized surface in air. The atomic step structures are also discernible on the SiO2/Si interface when a 20-nm-thick oxide layer is removed by HF etching. These results indicate that once a clean surface with atomic steps and terraces is formed, the surface morphology is stable against oxidation, and that the initial surface morphology is preserved as oxidation proceeds.