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Impact of photoacid generator leaching on optics photocontamination in 193-nm immersion lithography

Published in:
J. Micro/Nanolith. MEMS MOEMS, Vol. 6, No. 1, January-March 2007, pp. 013001-1 - 013001-7.

Summary

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.
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Summary

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...

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Marathon evaluation of optical materials for 157-nm lithography

Published in:
J. Microlithogr., Microfab., Microsyst., Vol. 2, No. 1, January 2003, pp. 19-26.

Summary

We present the methodology and recent results on the longterm evaluation of optical materials for 157-nm lithographic applications. We review the unique metrology capabilities that have been developed for accurately assessing optical properties of samples both online and offline, utilizing VUV spectrophotometry with in situlamp-based cleaning. We describe ultraclean marathon testing chambers that have been designed to decouple effects of intrinsic material degradation from extrinsic ambient effects. We review our experience with lithography-grade 157-nm lasers and detector durability. We review the current status of bulk materials for lenses, such as CaF(2) and BaF(2), and durability results of antireflectance coatings. Finally, we discuss the current state of laser durability of organic pellicles.
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Summary

We present the methodology and recent results on the longterm evaluation of optical materials for 157-nm lithographic applications. We review the unique metrology capabilities that have been developed for accurately assessing optical properties of samples both online and offline, utilizing VUV spectrophotometry with in situlamp-based cleaning. We describe ultraclean marathon...

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