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Proceedings Paper

Longer wavelength EUV lithography (LW-EUVL)
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Paper Abstract

Extreme UV Lithography (EUVL) is generally accepted as the leading candidate for next generation lithography. Several challenges remain for EUVL, especially as its insertion point is pushed to finer resolution. Although diffractive scaling may suggest a transition to shorter EUVL wavelengths, several issues arise that would make that difficult. Challenges involve issues such as flare, multilayer (ML) bandwidth, and reflector throughput which tend to worsen with decreasing wavelength. In this study, we have evaluated the tradeoff between flare scaling effects and diffractive scaling effects for EUVL, where flare induced image degradation is likely to dominate as sub-13.5 nm wavelengths are considered. With surface scatter effects scaling as 1/λ2, the idea of longer wavelength (LW-EUVL) becomes interesting. Since a working wavelength is driven by the selection of ML materials (which are molybdenum and silicon for 13.5 nm), the identification of suitable alternatives is an initial challenge. We have optimized aluminum and various refractory metals at 17.2 nm and present results. The optimized combination of aluminum with yttrium, zirconium, and other metals result in theoretical reflectivity values above 75%. We also describe possibilities for alternative LW-EUVL sources for 17.2 nm operation as well as the impact on resist absorption, especially through halogens of higher molar absorption (such as fluorine). The impact on mask absorber materials is also presented, which may also exhibit increased absorbance, leading to a lowering of film thickness requirements.

Paper Details

Date Published: 23 March 2012
PDF: 8 pages
Proc. SPIE 8322, Extreme Ultraviolet (EUV) Lithography III, 83222Z (23 March 2012); doi: 10.1117/12.917912
Show Author Affiliations
Christopher W. Maloney, Rochester Institute of Technology (United States)
Bruce W. Smith, Rochester Institute of Technology (United States)

Published in SPIE Proceedings Vol. 8322:
Extreme Ultraviolet (EUV) Lithography III
Patrick P. Naulleau; Obert R. Wood II, Editor(s)

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