AVS 46th International Symposium
    Surface Science Division Wednesday Sessions
       Session SS1+EM-WeA

Paper SS1+EM-WeA9
Characterization by STM of Interface between Silicon and Silicon Dioxide Layers Fabricated by Highly Concentrated Ozone

Wednesday, October 27, 1999, 4:40 pm, Room 606

Session: Semiconductor Surface Science
Presenter: H. Itoh, Electrotechnical Laboratory, Japan
Authors: H. Itoh, Electrotechnical Laboratory, Japan
A. Kurokawa, Electrotechnical Laboratory, Japan
K. Nakamura, Electrotechnical Laboratory, Japan
S. Ichimura, Electrotechnical Laboratory, Japan
Correspondent: Click to Email
We will show that the silicon dioxide film fabricated by ozone exposure@footnote 1,2@ has smooth and flat interface keeping the original step and terrace feature. Hydrogen-terminated Si(100) wafer was used as a substrate. Flat surface was prepared by additional growth of epitaxial Si layers (thickness; 120 nm) on Si substrate, and atomic hydrogen was adsorbed on the surface for passivation. STM images showed that the prepared surface was atomically flat with wide terraces which is larger than 100nm. A high-concentration ozone generator was used to form ultra thin silicon dioxide film on the surface. The output from ozone generator was the mixture gas of ozone(30 vol%) and oxygen. The substrate was exposed to the gas at room temperature for half an hour to form silicon dioxide film. The thickness of the oxide film formed by the exposure was estimated to be 1 nm, which was analyzed from intensity of XPS Si-2p peaks. After the oxidation, the silicon dioxide fil! ! m was carefully removed by rinsing in HF solution to observe the interface structure. Slow etching rate in dilute HF solution(0.1%) was chosen to avoid uneven etching and the thickness was monitored every several minutes by XPS peaks to avoid overetching. The sample was inserted into ultra high vacuum(UHV) chamber and surface and interface was observed by scanning tunneling microscopy. STM images were obtained on the etched surface with monoatomic height resolution. Large terraces and few steps were observed in the STM images and surface roughness is estimated to be below 0.15 nm (rms.). This indicates that the silicon dioxide film was grown keeping the original step and terrace feature. The result suggests that Si was oxidized homogeneously and supports that the film was grown layer-by-layer mode. @FootnoteText@ @footnote 1@ A.Kurokawa et.al., Mater. Res. Symp. Proc.Vol. 513, p38, 1998, @footnote 2@ A.Kurokawa et.al., Mater. Res. Soc. Symp. Proc., 1999, in press