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X-Ray Reflectivity and FTIR Measurements of N2 Plasma Effects on the Density Profile of Hydrogen Silsesquioxane Thin Films



V. J. Lee, C G. Chao, Eric K. Lin, Wen-Li Wu, B M. Fanconi, J K. Lan, Y L. Cheng, H C. Liou, Y L. Wang, M S. Feng


Non-destructive, specular X-ray reflectivity (SXR) measurements were used to investigate N2 plasma effects on the density depth profile of hydrogen silsesquioxane (HSQ) thin films. The SXR data indicate that the density profile of an HSQ film without plasma treatment is not uniform with at least four layers with different electron densities. When the HSQ film is treated with increasing plasma power or time exposed to the plasma, oscillations present in the SXR profile of the as-cured HSQ film decrease in amplitude and the absolute value of the reflectivity rapidly decreases. These changes in the reflectivity data are due to increases in the film roughness. Additionally, a layer denser than the rest of the film was observed at the film/air interface of each HSQ film. The thickness of the densified layer increased with plasma power and plasma exposure time. An HSQ film treated with N2 plasma at 200 W for 60 s had an HSQ layer almost fully densified to SiO2 and was approximately 14 nm thick. When the plasma power was 600 W and the exposure time was 60 s, the entire HSQ film (around 400 nm thick) was affected by the plasma. The densification of the films was confirmed by comparing intensities of the Si-H stretching peaks of HSQ films from the Fourier transform infrared (FTIR) absorption specta from each film. The Si-H peak intensities decreased with increasing plasma power and exposure time, consistent with film densification into a more SiO2 like structure.
Journal of the Electrochemical Society
No. 10


density profile, exposure time, FTIR, hydrogen silsesquioxane, low-k dielectric, plasma effect, plasma power, specular X-ray reflectivity


Lee, V. , Chao, C. , Lin, E. , Wu, W. , Fanconi, B. , Lan, J. , Cheng, Y. , Liou, H. , Wang, Y. and Feng, M. (2001), X-Ray Reflectivity and FTIR Measurements of N2 Plasma Effects on the Density Profile of Hydrogen Silsesquioxane Thin Films, Journal of the Electrochemical Society, [online], (Accessed June 25, 2024)


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Created September 30, 2001, Updated October 12, 2021