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12 May 2007 Scatterometry based profile metrology of two-dimensional patterns of EUV masks
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Proceedings Volume 6607, Photomask and Next-Generation Lithography Mask Technology XIV; 66070S (2007)
Event: Photomask and Next-Generation Lithography Mask Technology XIV, 2007, Yokohama, Japan
EUV lithography is one of the most developing and promising lithography techniques. Recently many papers are focused on defect control of EUV mask multilayer blank, but development of profile metrology is also very important. 2D scatterometry becomes insufficient in conditions of further shrinking of feature size and complication of mask patterns. To overcome these limitations 3D scatterometry should be used. In this paper we study the precision of 3D scatterometry measurements of two-dimensional EUV mask features with variety of geometrical shapes. As in reflectometry of EUV mask we can use only one or a few wavelengths, we have to take into account intensities of many reflected orders to extract profile precisely. We calculate the library of diffraction efficiencies for periodic circular, elliptical, and rectangular shaped with rounded corners features using 3D RCWA method. Then we find the amplitudes of reflected diffraction orders from feature with random arbitrary shape, compare them with each set of data in the library, and extract the most appropriate shape. After that we analyze whether the extracted shape is really close to initial arbitrary shape or not. In some cases extracted shape is not the closest one to the real. It is demonstrated that non-zero value of azimuth angle of incident light influence on precision of feature shape determination and lead to deterioration of results. Using of polarized light helps to improve precision of results, but unlike 2D scatterometry the optimal polarization can not be determined unambiguously. According to received data we provide recommendations for optimal 3D EUV scatterometry measurements and determine the necessary steps of varying of geometrical parameters for library features.
© (2007) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Irina Pundaleva, Roman Chalykh, Heebom Kim, Byunggook Kim, and Hanku Cho "Scatterometry based profile metrology of two-dimensional patterns of EUV masks", Proc. SPIE 6607, Photomask and Next-Generation Lithography Mask Technology XIV, 66070S (12 May 2007);

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