Optical element for full spectral purity from IR-generated EUV light sources


Boogaard, A.J.R. van den and Louis, E. and Goor, F.A. van and Bijkerk, Fred (2009) Optical element for full spectral purity from IR-generated EUV light sources. In: Frank M. Schellenberg & Bruno M. La Fontaine (Eds.), Alternative Lithographic Technologies. Proceedings of SPIE, 7271 . SPIE, 72713B. ISBN 9780819475244

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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
Item Type:Book Section
Copyright:© 2009 COPYRIGHT SPIE--The International Society for Optical Engineering
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Link to this item:http://purl.utwente.nl/publications/77751
Official URL:https://doi.org/10.1117/12.829011
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