23 October 2015 Optical simulations for fractional fluorine terminated coatings on nanoimprint lithography masks
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Simulations of the optical intensity within Nano Imprint Lithography (NIL) mask features have been made for patterned quartz masks having ultrathin film coatings with different indices of refraction. Fractionally fluorine terminated surfaces, previously proposed for improving the yield of NIL processes, are briefly reviewed. Optical intensity solutions within the feature were obtained using Panoramictech Maxwell solver software for variances in the optical constants of the coating films, aspect ratio, feature size, and wavelength.. The coated masks have conformal surface, higher index of refraction under-layer coating and a fractional terminated fluorine hydrocarbon (FHC) monomolecular layer. The values of optical constants for the FHC layers are unknown, so a range of ad-hoc values were simulated. Optical constants for quartz mask and Al2O3, TiO2 and Si under-layer films are taken from the literature. Wavelengths were varied from 193nm to 365nm. The question of photo-dissociation of the FHC layer for higher energy photons is addressed from first principles, with the result that the F-terminated layers are stable at higher wavelengths. Preliminary simulations for features filled with resist over various substrates are dependent on the antireflection character of the underlying film system. The optical intensity is generally increased within the simulated mask feature when coated with a higher index/FHC films relative to the uncoated reference quartz mask for ~5nm physical feature sizes.
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Thomas E. Seidel, Thomas E. Seidel, Alexander Goldberg, Alexander Goldberg, Mathew D. Halls, Mathew D. Halls, } "Optical simulations for fractional fluorine terminated coatings on nanoimprint lithography masks", Proc. SPIE 9635, Photomask Technology 2015, 96350S (23 October 2015); doi: 10.1117/12.2197371; https://doi.org/10.1117/12.2197371


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