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Proceedings Paper

High-index materials for 193 nm immersion lithography
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Paper Abstract

193 nm immersion lithography optical projection systems using conventional UV optical materials and water as the immersion fluid, with planar lens/fluid interfaces, have a practical numerical aperture (NA) limit near 1.3. The bottleneck for pushing the NA further is the refractive index of the final lens element. Higher-index immersion fluids cannot alone give much improvement, because the NA is limited by the lowest material index. In this paper we consider the possibility of using novel high-index materials in the last lens element to get around this bottleneck and to push the NA limit to at least 1.5, while containing the lens system size and complexity. We discuss three classes of high-index (n>1.8), wide-band-gap, oxide-based materials that have the potential for being fabricated with optical properties appropriate for lithography optics: group-II oxides, magnesium-aluminum-spinel-related materials, and ceramic forms of spinel. We present theoretical calculations and experimental measurements of the optical properties of these materials, including intrinsic birefringence, and we assess their prospects.

Paper Details

Date Published: 12 May 2005
PDF: 11 pages
Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); doi: 10.1117/12.600109
Show Author Affiliations
John H. Burnett, National Institute of Standards and Technology (United States)
Simon G. Kaplan, National Institute of Standards and Technology (United States)
Eric L. Shirley, National Institute of Standards and Technology (United States)
Paul J. Tompkins, Corning Tropel Corp. (United States)
James E. Webb, Corning Tropel Corp. (United States)

Published in SPIE Proceedings Vol. 5754:
Optical Microlithography XVIII
Bruce W. Smith, Editor(s)

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