Fluid-photoresist interactions and imaging in high-index immersion lithography

Tran, HV, Hendrickx E, Van Roey F, Vandenberghe G, French RH.  2009.  

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.

Journal:

Journal of {Micro/Nanolithography}, {MEMS} and {MOEMS}

Volume:

8

Pagination:

033006

ISSN:

19325150

URL:

http://link.aip.org/link/JMMMGF/v8/i3/p033006/s1&Agg=doi

DOI:

10.1117/1.3224950
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