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25 February 2004 Characterization of multilayer dielectric coatings by ellipsometry and x-ray grazing incidence reflectometry
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Thin film multilayer dielectric coatings are widely used for the fabrication of various optical components. The precise knowledg of the optical constants and the thickness of the individual layers is one of the most important factors for the successful design and production of optical interference coatings with optimal performance. As thin film materials within a multilayer stack often have different optical constants compared to single layers deposited at the same conditions a disagreement between measured and predicted optical response of a multilayer system is observed. A better agreement can be achieved if the optical constants of the layer materials are determined from measurements of multilayer stacks. In the present work such an approach is applied for the optical characterization of popular optical coating materials. The optical constants of TiO2, Ta2O5, Al2O3 and HfO2 are determined in the spectral region 200 nm up to 800 nm using the following measurement techniques: spectroscopic ellipsometry, intensity transmission and X-ray grazing incidence reflectometry. The measured samples are periodic stacks consisting of 12 layers made of one of these materials in combination with SiO2. The ellipsometric and intensity transmission data are fitted simultaneously using the Tauc-Lorentz parameterization for the optical constants of the layers. The results are compared with the thickness of the layers obtained from X-ray grazing incidence reflectometry. The comparison of the predicted and measured optical response of a 3 material multilayer stack demonstrates the accuracy of the extracted optical constants.
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Diana A. Tonova and Bernhard von Blanckenhagen "Characterization of multilayer dielectric coatings by ellipsometry and x-ray grazing incidence reflectometry", Proc. SPIE 5250, Advances in Optical Thin Films, (25 February 2004);


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