Special Section on EUV Sources for Lithography

Out-of-band radiation mitigation at 10.6 μm by molecular absorbers in laser-produced plasma extreme ultraviolet sources

[+] Author Affiliations
Chimaobi Mbanaso, Alin Antohe, Horace Bull, Gregory Denbeaux

University at Albany, College of Nanoscale Science and Engineering, 255 Fuller Road, Albany, New York 12203

Frank Goodwin

SEMATECH, 257 Fuller Road, Suite 2200, Albany, New York 12203

Ady Hershcovitch

Brookhaven National Laboratory, Upton, New York 11973

J. Micro/Nanolith. MEMS MOEMS. 11(2), 021116 (May 10, 2012). doi:10.1117/1.JMM.11.2.021116
History: Received July 30, 2011; Revised November 5, 2011; Accepted January 17, 2012
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Abstract.  Out-of-band radiation in extreme ultraviolet (EUV) exposure tools remains one of the critical issues that must be addressed before the implementation of this lithography technique for high-volume manufacturing. The out-of-band spectrum at the intermediate focus of EUV sources that use a CO2 laser-produced plasma is dominated by scattered radiation from the drive laser, which operates near 10.6-μm wavelength. To reduce the unwanted heating of optical components in the exposure tool caused by the infrared wavelength, a 10.6-μm wavelength-absorbing gas can be used to reduce the number of photons at this wavelength reaching the intermediate focus. Gaseous sulfur hexafluoride (SF6), whose υ3 infrared active mode is vibrationally excited by radiation around 10.6-μm wavelength, can be used to function as a molecular absorber and thus, mitigate part of the infrared radiation. In this work, the optical absorption of gaseous SF6 is experimentally investigated at the CO2 laser wavelengths close to 10.6 μm as well as the EUV wavelength. Various considerations affecting the use of a gas-based spectral filter are also discussed in this paper.

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© 2012 Society of Photo-Optical Instrumentation Engineers

Citation

Chimaobi Mbanaso ; Alin Antohe ; Horace Bull ; Frank Goodwin ; Ady Hershcovitch, et al.
"Out-of-band radiation mitigation at 10.6 μm by molecular absorbers in laser-produced plasma extreme ultraviolet sources", J. Micro/Nanolith. MEMS MOEMS. 11(2), 021116 (May 10, 2012). ; http://dx.doi.org/10.1117/1.JMM.11.2.021116


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