Refined extreme ultraviolet mask stack model

Igor A. Makhotkin*, M. Wu, V. Soltwisch, Frank Scholze, Vicky Philipsen

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

10 Citations (Scopus)
141 Downloads (Pure)


A refined model of an extreme ultraviolet (EUV) mask stack consisting of the Mo/Si multilayer coated by a Ru protective layer and a TaBN/TaBO absorber layer was developed to facilitate accurate simulations of EUV mask performance for high-NA EUV photo-lithography (EUVL) imaging. The model is derived by combined analysis of the measured EUV and x ray reflectivity of an industry-representative mask blank. These two sets of measurements were analyzed using a combined free-form analysis procedure that delivers high-resolution x ray and EUV optical constant depth profiles based on self-adapted sets of sublayers as thin as 0.25 nm providing a more accurate description of the reflectivity than obtained from only EUV reflectivity. “Free-form analysis” means that the shape of the layer interfaces in the model is determined experimentally and is not given a priori by the structure model. To reduce the numerical effort for EUV imaging simulations, a low-resolution model of the multilayer and absorber stack with sublayer thicknesses larger than 2 nm, that fits to only the EUV reflectance, was derived from the high-resolution model. Rigorous high-NA EUVL simulations were done to compare the performance of the new model to our previous work.
Original languageEnglish
Article number38
Pages (from-to)498-503
Number of pages6
JournalJournal of the Optical Society of America. A: Optics, Image Science, and Vision
Issue number4
Publication statusPublished - 1 Apr 2021


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