30 September 2014 Determination of line profiles on nano-structured surfaces using EUV and x-ray scattering
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Abstract
Non-imaging techniques like X-ray scattering are supposed to play an important role in the further development of CD metrology for the semiconductor industry. Grazing Incidence Small Angle X-ray Scattering (GISAXS) provides directly assessable information on structure roughness and long-range periodic perturbations. The disadvantage of the method is the large footprint of the X-ray beam on the sample due to the extremely shallow angle of incidence. This can be overcome by using wavelengths in the extreme ultraviolet (EUV) spectral range, EUV small angle scattering (EUVSAS), which allows for much steeper angles of incidence but preserves the range of momentum transfer that can be observed. Generally, the potentially higher momentum transfer at shorter wavelengths is counterbalanced by decreasing diffraction efficiency. This results in a practical limit of about 10 nm pitch for which it is possible to observe at least the ± 1st diffraction orders with reasonable efficiency. At the Physikalisch-Technische Bundesanstalt (PTB), the available photon energy range extends from 50 eV up to 10 keV at two adjacent beamlines. PTB commissioned a new versatile Ellipso-Scatterometer which is capable of measuring 6" square substrates in a clean, hydrocarbon-free environment with full flexibility regarding the direction of the incident light polarization. The reconstruction of line profiles using a geometrical model with six free parameters, based on a finite element method (FEM) Maxwell solver and a particle swarm based least-squares optimization yielded consistent results for EUV-SAS and GISAXS. In this contribution we present scatterometry data for line gratings and consistent reconstruction results of the line geometry for EUV-SAS and GISAXS.
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Victor Soltwisch, Jan Wernecke, Anton Haase, Jürgen Probst, Max Schoengen, Michael Krumrey, Frank Scholze, Jan Pomplun, Sven Burger, "Determination of line profiles on nano-structured surfaces using EUV and x-ray scattering", Proc. SPIE 9235, Photomask Technology 2014, 92351D (30 September 2014); doi: 10.1117/12.2066165; https://doi.org/10.1117/12.2066165
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