1 July 2009 Fluid-photoresist interactions and imaging in high-index immersion lithography
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Abstract
Optical immersion lithography using fluids with refractive indices greater than that of water (1.436) can enable numerical apertures of 1.55 or above for printing sub-45-nm lines. Two second-generation immersion fluid candidates, IF132 and IF169, both have indices above 1.64 and have been optimized to absorb less than 0.1 cm−1 at 193.4 nm. These fluids, although meeting the requirements of index and absorption, must also be compatible with current resists and processes to image the required fine line patterns. Results of fluid-resist interactions, with water and high-index fluids on four commercial resists, are shown. Photoacid generator (PAG) leaching measurements reveal much less leaching into both high-index fluids than into water, and in two water-immersion dedicated resists, no leaching is detected with the high-index immersion fluids. Little resist thickness change and swelling is detected by a quartz crystal microbalance (QCM) on contact with the fluids. Resist profile and line height changes due to pre- and postexposure fluid contact varies from one resist to the next, but overall the changes are minimal. Misting defects from high-index fluid-resist contact show lower counts than for water, and imaging on an immersion interference printer produces 36-nm half-pitch lines. We find no serious impediments to the use of high-index liquids based on these results.
© (2009) Society of Photo-Optical Instrumentation Engineers (SPIE)
Hoang V. Tran, Eric Hendrickx, Frieda Van Roey, Geert Vandenberghe, Roger H. French, "Fluid-photoresist interactions and imaging in high-index immersion lithography," Journal of Micro/Nanolithography, MEMS, and MOEMS 8(3), 033006 (1 July 2009). https://doi.org/10.1117/1.3224950 . Submission:
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