Analytical Sciences

FTIR-ATR Evaluation of Organic Contaminant Cleaning Methods for SiO₂ Surfaces

Akihito SHINOZAKI,* Kenta ARIMA,* Mizuho MORITA,* Isao KOJIMA,** and Yasushi AZUMA**

*Department of Precision Science and Technology, Graduate School of Engineering, Osaka University, 2-1, Yamada-oka, Suita, Osaka 565-0871, Japan
**Materials Characterization Division, National Metrology Institute of Japan (NMIJ), National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba Central 5, Higashi 1-1, Tsukuba, Ibaraki 305-8565, Japan

The effectiveness of cleaning organic contaminants from silicon dioxide (SiO₂) surfaces was studied by conducting highly sensitive measurements using Fourier Transform Infrared Attenuated Total reflectance (FTIR-ATR) with a Si prism as the waveguide. To serve as an example, the surface of the prism was oxidized to an order of a few nanometers. The oxidized Si surface film was allowed to stand in the atmosphere and then wet-cleaned in a repeated manner; subsequently its thickness was measured by ellipsometry. Although, various wet-cleaning methods were tested, they only showed values of 0.1 - 0.2 nm larger than, but not equal to, the original thickness immediately after oxidation. FTIR-ATR measurements of the spectral change after exposure to air revealed that organic species, such as C-CH₃ and -(CH₂)_n-, increased with time. Wet-cleaning the sample failed to remove the C-CH₃ species, which indicates that they corresponded to the film thickness increment from the original.

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