Determination of optical constants of thin films in the EUV

Richard Ciesielski*, Qais Saadeh, Vicky Philipsen, Karl Opsomer, Jean Philippe Soulié, Meiyi Wu, Philipp Naujok, Robbert W.E. van de Kruijs, Christophe Detavernier, Michael Kolbe, Frank Scholze, Victor Soltwisch

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

18 Citations (Scopus)
52 Downloads (Pure)


The determination of fundamental optical parameters is essential for the development of new optical elements such as mirrors, gratings, or photomasks. Especially in the extreme ultraviolet (EUV) and soft x-ray spectral range, the existing databases for the refractive indices of many materials and compositions are insufficient or are a mixture of experimentally measured and calculated values from atomic scattering factors. Since the physical properties of bulk materials and thin films with thicknesses in the nanometer range are not identical, measurements need to be performed on thin layers. In this study we demonstrate how optical constants of various thin film samples on a bulk substrate can be determined from reflection measurements in the EUV photon energy range from 62 eV to 124 eV. Thin films with thickness of 20 nm to 50 nm of pure Mo, Ni, Pt, Ru, Ta, and Te and different compositions of NixAlx, PtTe, PtxMo, RuxTax, Ru3Re, Ru2W, and TaTeN were prepared by DC magnetron sputtering and measured using EUV reflectometry. The determination optical constants of the different materials are discussed and compared to existing tabulated values.

Original languageEnglish
Pages (from-to)2060-2078
Number of pages19
JournalApplied Optics
Issue number8
Publication statusPublished - 8 Mar 2022


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