Plasma and Fusion Research
Volume 20, 2401007 (2025)
Regular Articles
- Kansai Institute of Photon Science, National Institutes for Quantum Science and Technology, Kyoto 619-0215, Japan
Abstract
We investigate extreme-ultra-violet (EUV) emission from laser-produced tin plasmas for its application to microlithography. Strong emission occurs through 4d-4f and 4p-4d transitions, which appear as an unresolved transition array (UTA) due to the effect of configuration interaction (CI). Emissions from 8 to 13 times ionized tin overlap in the same λ=13.5 nm band, and both singly and multiply excited states of each ion contribute to the emission. We develop the collisional radiative model of tin ions, taking into account an appropriate set of atomic states that have a large population to contribute to the emission. The model is being validated through comparisons between the calculated and observed spectrums.
Keywords
atomic processes in plasmas, plasma spectroscopy, EUV, lithography, multiply charged ion, tin
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