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28 May 2004 Degradation mechanism and materials for 157-nm pellicles
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A great deal of resources has been invested by the semiconductor industry as a whole to make ready 157 nm as the next lithography technology node. Despite of all this effort serious infrastructure issues remain to be solved. Perhaps the first one is the availability of CaF2, but a close second is a suitable soft-pellicle material. It has been previously reported that standard 193nm materials, like Teflon AF and Cytop, fail catastrophically upon exposure at 157nm radiation; and that their transmission is very poor to non-existent. In this paper we report data showing that these materials have higher transmission and lifetimes than previously thought. The physical lifetime of Cytop of nearly 500 J/cm2 is remarkably high, although the transmission varies as a function dose suggesting physical and chemical changes from the onset. For Teflon AF the transmission is a more complex function of exposure dose, suggesting competing mechanisms. From experiments run with PVDF (polyvinyl difluoride), we conclude that the widely reported photodarkening effect is due to the presence of hydrogen in close proximity to a fluorine atom. From IR spectra we conclude that the dioxole moeity in Teflon AF undergoes a series of photochemical reactions that lead to the physical destruction of the polymer.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Cesar M Garza and Tom Bierschenk "Degradation mechanism and materials for 157-nm pellicles", Proc. SPIE 5377, Optical Microlithography XVII, (28 May 2004);


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