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Proceedings Paper

Immersion liquids for lithography in the deep ultraviolet
Author(s): Michael Switkes; Roderick R. Kunz; Roger F. Sinta; Mordechai Rothschild; Paula M. Gallagher-Wetmore; Val J. Krukonis; Kara Williams
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Paper Abstract

The requirements of liquids for use in immersion lithography are discussed. We present simple calculations of the transmission and index homogeneity requirements of the immersion liquid (T > 0.95 and δn < 5×10-7 respectively for sin θ = NA/n = 0.9 and a working distance of 1 mm) along with the temperature and pressure control requirements which follow from them. Water is the leading candidate immersion liquid for use at 193 nm, and we present data on its chemical compatibility with existing 193 nm resists through dissolution/swelling and surface energy studies. We find that it has a minimal impact on at least some current 193 nm resists. At 157 nm, suitably transparent immersion fluids remain to be identified. Perfluorinated polyethers (PFPE) are among the most transparent organics measured. The lowest PFPE absorbance at 157 nm can be further reduced by roughly a factor of two, from 6 to 3 cm-1 through removal of dis-solved oxygen. We also discuss our efforts to understand the origin of the remaining absorbance through supercritical CO2 fractionation.

Paper Details

Date Published: 26 June 2003
PDF: 10 pages
Proc. SPIE 5040, Optical Microlithography XVI, (26 June 2003); doi: 10.1117/12.485329
Show Author Affiliations
Michael Switkes, MIT Lincoln Lab. (United States)
Roderick R. Kunz, MIT Lincoln Lab. (United States)
Roger F. Sinta, MIT Lincoln Lab. (United States)
Mordechai Rothschild, MIT Lincoln Lab. (United States)
Paula M. Gallagher-Wetmore, Phasex Corp. (United States)
Val J. Krukonis, Phasex Corp. (United States)
Kara Williams, Phasex Corp. (United States)

Published in SPIE Proceedings Vol. 5040:
Optical Microlithography XVI
Anthony Yen, Editor(s)

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