EUV spectroscopy of highly chargedSn13+−Sn15+ions in an electron-beam ion trap

Abstract

Extreme-ultraviolet (EUV) spectra of Sn 13+ −Sn 15+ ions have been measured in an electron-beam ion trap (EBIT). A matrix inversion method is employed to unravel convoluted spectra from a mixture of charge states typically present in an EBIT. The method is benchmarked against the spectral features of resonance transitions in Sn 13+ and Sn 14+ ions. Three new EUV lines in Sn 14+ confirm its previously established level structure. This ion is relevant for EUV nanolithography plasma but no detailed experimental data currently exist. We used the Cowan code for first line identifications and assignments in Sn 15+. The collisional-radiative modeling capabilities of the Flexible Atomic Code were used to include line intensities in the identification process. Using the 20 lines identified, we have established 17 level energies of the 4p 4 4d configuration as well as the fine-structure splitting of the 4p 5 ground-state configuration. Moreover, we provide state-of-the-art ab initio level structure calculations of Sn 15+ using the configuration-interaction many-body perturbation code AMBiT. We find that the here-dominant emission features from the Sn 15+ ion lie in the narrow 2% bandwidth around 13.5 nm that is relevant for plasma light sources for state-of-the-art nanolithography.

Multiply-excited states and their contribution to opacity in CO2 laser-driven tin-plasma conditions

“…The ground opacity in this wavelength region is dominated by the transition 4p 6 1 S 0 − 4p 5 4d 1 P 1 , which has a calculated wavelength of 13.332 nm. This is in excellent agreement with experimental identifications of this transition at λ = 13.344 nm [29] and λ = 13.343 [18,74]. This transition is clearly much weaker than the 4p 6 4d 2 D 5/2 − 4p 5 4d 2 2 F 7/2 transition in Sn 13+ .…”

Relativistic Configuration-Interaction and Perturbation Theory Calculations of the Sn XV Emission Spectrum

“…Some estimate of accuracy of the CI-MBPT gA and related g f values can be obtained from the comparison of CI-MBPT and experimental emission intensities (the next section). It is also interesting to note that our CI-MBPT gA values of 1.64 × 10 12 s −1 for 1 S 0 − 1 P 1 transition agrees quite well with the gA value of [16] 1.8 × 10 12 s −1 , much better the comparison of our g f value with that of [6], 4.3 vs. 5.8. It is interesting to note that, in [17], it was pointed out that the wavelength of the resonant transition 1 S 0 − 1 P 1 was incorrectly reported to be 13.2643 nm [18], while the value reported in [17] was 13.3431 nm, in good agreement with [19], where the isoelectronic sequence of Kr was systematically studied.…”

Characterization of 1- and 2−μm -wavelength laser-produced microdroplet-tin plasma for generating extreme-ultraviolet light

“…Ever more powerful sources of EUV light are required for future lithography applications. This EUV light is generated from electronic transitions in multiplycharged tin ions that strongly emit radiation in a narrow band around 13.5 nm [8][9][10][11][12][13][14][15][16][17][18]. EUV-emitting plasma in an industrial nanolithography machine is driven by CO 2 -gas lasers with a 10-µm wavelength.…”