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Proceedings Paper

Optical element for full spectral purity from IR-generated EUV light sources
Author(s): A. J. R. van den Boogaard; E. Louis; F. A. van Goor; F. Bijkerk
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Paper Abstract

Laser produced plasma (LLP) sources are generally considered attractive for high power EUV production in next generation lithography equipment. Such plasmas are most efficiently excited by the relatively long, infrared wavelengths of CO2-lasers, but a significant part of the rotational-vibrational excitation lines of the CO2 radiation will be backscattered by the plasma's critical density surface and consequently will be present as parasitic radiation in the spectrum of such sources. Since most optical elements in the EUV collecting and imaging train have a high reflection coefficient for IR radiation, undesirable heating phenomena at the resist level are likely to occur. In this study a completely new principle is employed to obtain full separation of EUV and IR radiation from the source by a single optical component. While the application of a transmission filter would come at the expense of EUV throughput, this technique potentially enables wavelength separation without loosing reflectance compared to a conventional Mo/Si multilayer coated element. As a result this method provides full spectral purity from the source without loss in EUV throughput. Detailed calculations on the principal of functioning are presented.

Paper Details

Date Published: 18 March 2009
PDF: 6 pages
Proc. SPIE 7271, Alternative Lithographic Technologies, 72713B (18 March 2009); doi: 10.1117/12.829011
Show Author Affiliations
A. J. R. van den Boogaard, FOM Institute for Plasma Physics Rijnhuizen (Netherlands)
E. Louis, FOM Institute for Plasma Physics Rijnhuizen (Netherlands)
F. A. van Goor, Univ. Twente (Netherlands)
F. Bijkerk, FOM Institute for Plasma Physics Rijnhuizen (Netherlands)
Univ. of Twente (Netherlands)

Published in SPIE Proceedings Vol. 7271:
Alternative Lithographic Technologies
Frank M. Schellenberg; Bruno M. La Fontaine, Editor(s)

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