On determination of properties of ultrathin and very thin silicon oxide layers by FTIR and X - ray reflectivity
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1066-A07-03
On determination of properties of ultrathin and very thin silicon oxide layers by FTIR and X - ray reflectivity Martin Kopani1, Matej Jergel2, Hikaru Kobayashi3, Masao Takahashi3, Robert Brunner2, Milan Mikula4, Kentarou Imamura3, Stanislav Jurecka5, and Emil Pincik2 1 School of medicine, Comenius University, Sasinkova 4, Bratislava, 811 08, Slovakia 2 Institute of Physics, Slovak Academy of Science, Dubravska cesta 9, Bratislava, 845 11, Slovakia 3 Japan Science and Technology Organization, Institute of Scientific and Industrial Research, Osaka University and CREST, 8-1, Mihogaoka, Ibaraki, Osaka, 567-0047, Japan 4 Department of Grafic Art Technology and Applied Photochemistry, Slovak University of Technology, Faculty of Chemical and Food Technology, Radlinskeho 9, Bratislava, 812 37, Slovakia 5 Department of Engineering Fundamentals, University of Zilina, Faculty of Electrical Engineering, kpt. J. Nalepku 1390, Liptovsky Mikulas, 031 01, Slovakia ABSTRACT We analyze properties of ultra-thin SiO2 + very thin SiOx double layer structure formed on high-doped n-type Si (100) wafers using FTIR, and X-ray reflectivity. The observed absorption band around 1230 cm-1 is attributed to the longitudinal optical mode of SiOx precipitates incorporated in silicon matrix. In particular, the corresponding peak positions indicate that there are precipitates of SiOx with x >1.8. The absorption band around 1070 cm-1 is attributed to the Si–O–Si stretching bond. This position is characteristic for stoichiometric SiO2. From the results it can be concluded that differently shaped particles co-exist in the samples. This assumption is supported by the oxide density measurements performed by FTIR and X-ray reflectivity. We determined density of oxide layers, roughness of corresponding interfaces, and surface roughness by the X-ray reflectivity. Additionally, we present the results of multifractal analysis on a complete set of six samples. INTRODUCTION Silicon very thin dioxide layers (thickness below 10 nm) belong among the most studied materials because their dielectric and interface properties are suitable for LSI technology and for production of advanced types of LCDs. The IR absorption spectra contain more absorption bands, e.g. at 800 and 1080 cm-1 [1]. Infrared spectroscopy can give structural information, information on different types of bonding, quantitative information and information about kinetics of sample. For the determination of parameters such as surface and interface roughness and density of investigated layers, X-ray reflectivity measurements can be used. Statistical characteristics of the surface roughness and fractal properties of the sample surfaces are reported and discussed in connection with the determination of the optical parameters of the studied structure. We discuss the results obtained by FTIR, X-ray reflectivity on double oxide layer structure prepared on Si (100) crystalline substrate. Total oxide thickness does not exceed 12 nm.
The first high-dense SiO2 layer of approx. 1.6 nm thickness is
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