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Journal of Micro/Nanolithography, MEMS, and MOEMS

Impact of photoacid generator leaching on optics photocontamination in 193-nm immersion lithography
Author(s): Vladimir Liberman; Mordechai Rothschild; Stephen T. Palmacci; Andrew Grenville
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Paper Abstract

Leaching of resist components into water has been reported in several studies. Even low dissolution levels of photoacid generator (PAG) may lead to photocontamination of the last optical surface of the projection lens. To determine the impact of this phenomenon on optics lifetime, we initiate a set of controlled studies, where predetermined amounts of PAG are introduced into pure water and the results monitored quantitatively. The study identifies the complex, nonlinear paths leading to photocontamination of the optics. We also discover that spatial contamination patterns of the optics are strongly dependent on the flow geometry. Both bare SiO2 surfaces as well as coated CaF2 optics are studied. We find that for all surfaces, at concentrations typical of leached PAG, below 500 ppb, the in situ self-cleaning processes prevent contamination of the optics.

Paper Details

Date Published: 1 January 2007
PDF: 7 pages
J. Micro/Nanolith. MEMS MOEMS 6(1) 013001 doi: 10.1117/1.2712841
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 6, Issue 1
Show Author Affiliations
Vladimir Liberman, MIT Lincoln Lab. (United States)
Mordechai Rothschild, MIT Lincoln Lab. (United States)
Stephen T. Palmacci, MIT Lincoln Lab. (United States)
Andrew Grenville

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