Thin Film Thickness Measurement by Surface Plasmon Resonance Using a Modified Otto’s Configuration Combined with Ellipsometry
Yasuhiro Mizutani and Tetsuo Iwata
Institute of Science and Technology, The University of Tokushima, Minamijo-sajima-cho 2-1, Tokushima 770-8506, Japan
We have developed a method of measuring thin film thickness by using two optical properties that are highsensitivity for a film thickness, such as surface plasmon resonance (SPR) and elliptical properties with SPR response. The SPR signal is high sensitivity, suitable for measuring the thickness of a sample with a thin layer. This phenomenon can be detected by measuring the absorbance on the sample surface. We focused on the Otto configuration, a famous method for the generation of a SPR signal, which consists of 4 layers such as a SiO2 substrate, air, dielectric material and a metal layer. It is useful for the measurement of thin film thickness because there is an air layer in the configuration. However, the configuration has the disadvantage: it is necessary to adjust the distance from sample surface to the SiO2 substrate on a nanometer order. To overcome the problem, we focused on the modified Otto’s configuration proposed by Bliokh et. al [Appl. Phys. Lett. 89, 021908 (2006)]. In the configuration, there is a plano-convex lens of SiO2 as the substrate. By using its curvature, there is no adjustment process and the SPR signal can be detected easily. The SPR signal has a polarization property that depends on the thin film thickness. By analyzing of polarization properties of the SPR signal by means of ellipsometry, thin film thickness can be measured with sub-nanometer accuracy which is higher than the SPR signals. In this paper, further results involving the measurement are presented and discussed.
-  A. Otto, “Excitation of nonradiative surface waves in silver by the method of frustrated total reflection,” Z. Phys. Vol.216, pp. 398-410, 1968.
-  E. Z. Kretschmann, “Die Bestimmung Optischer Konstanten von Mettlen duch Anregung von Oberfl?chenplasmaschwingungen,” Z. Phys., Vol.241, pp. 313-324, 1971.
-  Y. P. Bliokh, R. Vander, S. G. Lipson, and J. Felsteiner, “Visualization of the complex refractive index of a conductor by frustrated total internal reflection,” Appl. Phys. Lett., Vol.89, 021908, 2006.
-  T. Iwata and G. Komoda,“Measurements of complex refractive indices of metals at several wavelengths by frustrated total internal reflection due to surface plasmon resonance,” Appl. Opt., Vol.47, pp. 2386-2391, 2008.
-  H. Raether, “Surface Plasmons on Smooth and Rough Surfaces and on Gratings,” Springer-Verlag, 1988.
-  T. Iwata and S.Maeda, “Simulation of an absorption-based surfaceplasmon resonance sensor by means of ellipsometry,” Appl. Phys., Vol.46, pp. 1575-1582, 2007.
-  M. Osterfeld and H. Franke, “Optical gas detection using metal film enhanced leaky mode spectroscopy,” Appl. Phys. Lett., Vol.62, pp. 2310-2312, 1993.
-  L. Levesque, B. E. Paton, and S. H. Payne, “Precise thickness and refractive index determination of polymide films using attenuated total reflection,” Appl. Opt., Vol.33, pp. 8036-8040, 1994.
-  L. Levesque, and B. E. Paton, “Detection of defects in multiplelayer structures by using surface plasmon resonance,” Appl. Opt., Vol.36, pp. 7199-75203, 1997.
-  F. Yang, J. R. Sambeles, and G. W. Bradberry, “Long-range surface modes supported by thin films,” Phys. Rev Lett., Vol.44, pp. 5855-5872, 1991.
-  M. Fukui and K. Matsugi, “Attenuated total reflection mode of surface polaritons in semi-infinite and finite superlattices,” J. Phys. Soc. Jpn., Vol.56, pp. 2964-2976, 1987.