Immersion liquids for lithography in the deep ultraviolet

Michael Switkes; Roderick R. Kunz; Roger F. Sinta; Mordechai Rothschild; Paula M. Gallagher-Wetmore; Val J. Krukonis; Kara Williams

doi:10.1117/12.485329

26 June 2003 Immersion liquids for lithography in the deep ultraviolet

Michael Switkes, Roderick R. Kunz, Roger F. Sinta, Mordechai Rothschild, Paula M. Gallagher-Wetmore, Val J. Krukonis, Kara Williams

Author Affiliations +

Proceedings Volume 5040, Optical Microlithography XVI; (2003) https://doi.org/10.1117/12.485329
Event: Microlithography 2003, 2003, Santa Clara, California, United States

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^-7respectively 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^-1through removal of dis-solved oxygen. We also discuss our efforts to understand the origin of the remaining absorbance through supercritical CO₂ fractionation.

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Michael Switkes, Roderick R. Kunz, Roger F. Sinta, Mordechai Rothschild, Paula M. Gallagher-Wetmore, Val J. Krukonis, and Kara Williams "Immersion liquids for lithography in the deep ultraviolet", Proc. SPIE 5040, Optical Microlithography XVI, (26 June 2003); https://doi.org/10.1117/12.485329

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