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Proceedings Paper

Parametric tradeoffs in laser plasma sources for EUV lithography: debris versus radiators
Author(s): Davide Bleiner; Bob Rollinger; Reza S. Abhari
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Paper Abstract

A mass spectrometry and time-resolved shadowgraphy study is presented, focusing on the radiators/debris transport process for an LPP-EUVL source, under worst-case scenarios such as solid target, wide angular dispersion, etc. The solid angle of ion debris ejection increases as a function of plume lifetime, and up to 0.5 μs (approx. 15 mm above target) does not exceed 0.3 πsr. around the target normal. The plume expansion is hypersonic (15-20 km/s) with the formation of a bow shock with an initial length scale of 5-8 mm that gradually reduces its aspect ratio. Primary (low energy) ion debris is induced directly during laser-surface interaction, whereas almost 90% of these primary ions are converted to Z=6 -12 secondary fast ions by means of laser-plasma interaction. At very high laser power, the fraction of primary ions converted to high charge ions is diminished to 70%, possibly due to increased LPP shielding. Hence, the external atomic degrees of freedom (kinetic energy) and the internal degrees of freedom (electronic configuration) are pumped concomitantly, which presents a tradeoff to combine fast ion debris minimization and efficient radiators' maximization. Nevertheless, the radiating body is observed fairly static with time, with a length-scale of a few mm's. Hence, the decoupling of the mass flux and radiation flux may be achieved either in the short (10< t < 100 ns) or in the very long (t > 500 ns) time scales. Considering the EUV emission time scale constraints, the former is the only viable solution for enabling LPP-based EUVL.

Paper Details

Date Published: 21 March 2008
PDF: 11 pages
Proc. SPIE 6921, Emerging Lithographic Technologies XII, 69210X (21 March 2008); doi: 10.1117/12.772613
Show Author Affiliations
Davide Bleiner, ETH Zurich (Switzerland)
Bob Rollinger, ETH Zurich (Switzerland)
Reza S. Abhari, ETH Zurich (Switzerland)

Published in SPIE Proceedings Vol. 6921:
Emerging Lithographic Technologies XII
Frank M. Schellenberg, Editor(s)

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