Spectral characterization of an industrial EUV light source for nanolithography

F. Torretti, F. Liu, M. Bayraktar, J. Scheers, Z. Bouza, W. Ubachs, R. Hoekstra, O. Versolato

Research output: Contribution to JournalArticleAcademicpeer-review


The emission spectra from an industrial, droplet-based, laser-produced plasma, extreme ultraviolet light source for nanolithography are here presented and analyzed. The dependence of spectral features on the CO2-drive-laser intensity is studied by changing the beam spot size at constant pulse energy and duration. We characterize the spectrum by fitting the results of atomic structure calculations to the short-wavelength region (7-11 nm), where the contributions from various charge states can be resolved, and obtain the relative contributions of charge states Sn9+ -Sn15+ . These relative contributions are compared to charge state populations as calculated with the non-equilibrium plasma kinetics code flychk. The calculations are shown to be in good qualitative agreement with the results, showing that the effective plasma temperature, and with it, the shape of the unresolved, main emission feature at 13.5 nm, is a remarkably weak function of laser intensity under this source normal operating conditions.

Original languageEnglish
Article number055204
Pages (from-to)1-7
Number of pages7
JournalJournal of Physics D. Applied Physics
Issue number5
Early online date28 Nov 2019
Publication statusPublished - 1 Jan 2020


This project has received funding from European Research Council (ERC) Starting Grant No. 802648 and is part of the VIDI research programme with project number 15697, which is financed by NWO.

FundersFunder number
Horizon 2020 Framework Programme802648
European Research Council15697
Nederlandse Organisatie voor Wetenschappelijk Onderzoek


    • EUV source
    • laser-produced plasma
    • spectroscopy


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