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Proceedings Paper

Optimal zone plates for x-ray lithography
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Paper Abstract

It is well known that zone plates can print extremely small features in microlithography. However, the size and complexity of zone plates has limited their application. In this paper simulated and experimental results are presented for simple zone plates with very high performance. It has previously been shown that submicron diameter zone plates, with only 2 or 3 zones, can focus 1 nm wavelength X-rays to less than 40 nm FWHM. A zone plate with two zones is a ring, whose ratio of outer radius to inner radius is about 0.7. This implies dimensions that may be too small for easy control. However, simulations have demonstrated excellent focusing for both clear and opaque rings over a ratio of radii of at least 0.6 to 0.8. For high contrast, 1 nm wavelength zone plates are typically fabricated in 200-300 nm thick gold. This leads to high aspect ratios, which are difficult to pattern. However simulations have shown excellent focusing in much thinner gold. In addition, conditions were found in 30nm to 90 nm thick gold which generate narrow dark "foci." The focusing of linear zone plates was also simulated. Linear zone plates with 3 and 5 zones produced excellent line foci, although linear zone plates with 2 and 4 zones were much poorer. Scaled up experiments in visible light supported both the circular and linear simulation results.

Paper Details

Date Published: 6 May 2005
PDF: 10 pages
Proc. SPIE 5751, Emerging Lithographic Technologies IX, (6 May 2005); doi: 10.1117/12.600591
Show Author Affiliations
R. Zheng, Louisiana State Univ. (United States)
L. Jiang, Louisiana State Univ. (United States)
M. Feldman, Louisiana State Univ. (United States)

Published in SPIE Proceedings Vol. 5751:
Emerging Lithographic Technologies IX
R. Scott Mackay, Editor(s)

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