AVS 45th International Symposium
    Nanometer-scale Science and Technology Division Thursday Sessions
       Session NS-ThA

Paper NS-ThA9
Selective Etching of the SiO@sub 2@/Si Surface with Low Energy Electron Stimulated Reaction by using STM

Thursday, November 5, 1998, 4:40 pm, Room 321/322/323

Session: Nanoscale Manipulation and Chemical Modification
Presenter: N. Li, Osaka University, Japan
Authors: N. Li, Osaka University, Japan
T. Yoshinobu, Osaka University, Japan
H. Iwasaki, Osaka University, Japan
Correspondent: Click to Email
Nano-fabrication on the SiO@sub 2@/Si surface is such an important subject that it may relate directly to the silicon industry. It has been shown that with focused high energy (tens to a few hundreds keV) electron beam, such as employed in TEM or SEM, nanometer scale windows can be cut through the SiO@sub 2@ overlayer and nano-structures can be formed on the exposed Si surface in a subsequent growth.@footnote 1,2@ However, large scale applications of this technique has been prevented by the relatively low efficiency of the high energy e-beam in etching the SiO@sub 2@ layer, particularly compared to the cost to build and maintain such a high energy accelerating system. Here we report an experimental study on selective etching of the SiO@sub 2@/Si surface with a low energy electron stimulated surface reaction by using STM. The investigation was carried out on Si(001) surface either with a thin native oxide overlayer or with a thermal oxide overlayer prepared in the UHV chamber. By applying a voltage of ~70 to 150 V across the tip-surface vacuum gap in the STM setup, while the tip-surface separation was adjusted to ~100 to 200 nm, a field emission current of ~5 to several hundred nA can be obtained, with which the SiO@sub 2@/Si surface was irradiated. Subsequent STM imaging shows that within the exposed area, the SiO@sub 2@ overlayer can be effectively evacuated by a thermal annealing of the surface at a temperature of ~650 to 700 °C. This can be shown evidently in the STM images by the obvious contrast change and clear atomic steps appeared within the exposed areas. By adjusting the beam energy, beam current and tip-surface separation, windows down to tens of nanometers in diameter can be etched through the SiO@sub 2@ overlayer. This result demonstrates the possibility of fabricating the SiO@sub 2@/Si surface with a low energy electron stimulated surface etching, and also presents another possibility of conducting such a nano-fabrication in a well controlled way with the STM. @FootnoteText@ @footnote 1@D.R. Allee, C.P. Umbach, and A.N. Broers, J. Vac. Sci. Technol. B9, 2838, (1991) @footnote 2@S. Fujita, S. Maruno, H. Watanabe, and M. Ichikawa, J. Vac. Sci. Technol. A15, 1493, (1997)