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Proceedings Paper

EUV microscopy using a lab-scale x-ray laser source
Author(s): Davide Bleiner; Felix Staub; Juerg E. Balmer
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Paper Abstract

High brightness extreme ultraviolet (EUV) light sources for laboratory operation are needed in nano-fabrication and actinic ("at-wavelength") mask inspection. Mask inspection in next generation lithography is crucial for high volume manufacturing. Plasma-based EUV sources have the required compactness. However, their incoherent emission lacks the brightness for fast and high contrast imaging. The X-ray laser is instead characterized by a remarkable brightness in a compact footprint facility. We evaluated a simple two-mirror optical setup for EUV microscopy illuminated with the BeAGLE X-ray laser system at the University of Berne. Single-shot acquisitions were sufficient to obtain high-contrast images of a Siemens star sample at diffraction-limit. Single-shot operation makes the overall acquisition speed limited by the laser repetition rate only. A reference calculation shows how-fast could be actinic inspection. The contrast was enhanced one order of magnitude by means of image processing. For a modest magnification (12x) no significant third-order aberrations were observed, even when tilting the spherical mirror-pair. For high magnification a Schwarzschild design is considered. The latter compensates astigmatism and coma with a mirror-pair per each element (condenser/magnifier), but introduces twice as many reflections as in the evaluated two-concave setup. Hence a compromise between aberration correction and enhancement of illumination must be found case by case.

Paper Details

Date Published: 5 October 2011
PDF: 12 pages
Proc. SPIE 8140, X-ray Lasers and Coherent X-ray Sources: Development and Applications IX, 814014 (5 October 2011); doi: 10.1117/12.893319
Show Author Affiliations
Davide Bleiner, Univ. Bern (Switzerland)
Felix Staub, Univ. Bern (Switzerland)
Juerg E. Balmer, Univ. Bern (Switzerland)

Published in SPIE Proceedings Vol. 8140:
X-ray Lasers and Coherent X-ray Sources: Development and Applications IX
James Dunn; Annie Klisnick, Editor(s)

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