Plasma and Fusion Research

Volume 21, 2401001 (2026)

Regular Articles

Atomic Processes in Laser-Produced Tin Plasmas for the Efficient Emission of Extreme-Ultraviolet (EUV) Radiation

Akira SASAKI^1,2), Atsushi SUNAHARA³⁾, Katsunobu NISHIHARA²⁾, Yu YAMAMOTO²⁾, Nozomi TANAKA²⁾, Shinsuke FUJIOKA²⁾, Tomoyuki JOHZAKI⁴⁾, Kentaro TOMITA⁵⁾, Masashi YOSHIMURA²⁾

1): QST, Kyoto 619-0215, Japan
2): University of Osaka, Osaka 565-0871, Japan
3): Purdue University, IN 47907, U.S.A.
4): Hiroshima University, Hiroshima 739-8511, Japan
5): Hokkaido University, Hokkaido 060-0808, Japan

(Received 30 August 2025 / Accepted 30 September 2025 / Published 31 March 2026)

Abstract

The atomic processes in laser-produced tin plasmas for the extreme ultraviolet light sources are investigated. The level population of complex tin ions is calculated using the collisional-radiative (CR) model, and then spectral emissivity and opacity are calculated, taking the spectral structure of unresolved transition array into account. A rule-based method for developing a large-scale CR model is discussed, which enables the simulation of the emission spectrum using a relatively compact model. The effect of configuration interaction on the wavelength of the emission and broadening of the main peak at λ = 13.5 nm by the emission from multiply excited states is discussed.

Keywords

EUV source, multiple charged ion, collisional-radiative model, laser-pumped plasmas, plasma spectroscopy

DOI: 10.1585/pfr.21.2401001

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References

[1] EUV Lithography, V. Bakshi (SPIE press, 2018).
[2] H. Mizoguchi et al., Proc. of SPIE 10143, 10143J-1 (2017).
[3] Q. Zhu et al., Proc. of SPIE 13424, 13240Y-1 (2025).
[4] R. Schupp et al., J. Phys. D 54, 365103 (2021).
[5] K. Nishihara et al., Phys. Plasmas 15, 056708 (2008).
[6] W. Svendsen et al., Phys. Rev. A 50, 3710 (1994).
[7] Modern Methods in Collisional-Radiative Modeling of Plasmas, Yu. Ralchenko (Springer, 2016).
[8] A. Bar-Shalom et al., J. Quant. Spectrosc. Radiat. Transfer 71, 169 (2001).
[9] F. Torretti et al., Nature. Commun. 11, 2334 (2020).
[10] W. Lotz, Z. Phys. 216, 241 (1968).
[11] R. Mewe, Astron. Astrophys. 216, 215 (1972).
[12] A. Sasaki et al., HEDP 32, 1 (2019).
[13] H. Ohashi et al., J. Phys. B: At. Mol. Opt. Phys. 43, 065204 (2010).
[14] A. Sasaki, Appl. Phys. Lett. 124, 064104 (2024).
[15] R. Piron et al., HEDP 23, 38 (2017).
[16] Proceedings of the 2023 EUVL source workshop, V. Bakshi et al., https://www.euvlitho.com/2023/2023 (2023).
[17] Y. Pan et al., Appl. Phys. Lett. 123, 204103 (2023).