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Proceedings Paper

Immersion lithography fluids for high NA 193 nm lithography
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Paper Abstract

Immersion lithography has become attractive since it can reduce critical dimensions by increasing numerical aperture (NA) beyond unity. Among all the candidates for immersion fluids, those with higher refractive indices are desired. However, for many of the fluids, the strong absorption at 193nm becomes a serious problem. Therefore, it is essential to find a fluid that is transparent enough (with absorbance less than 0.5mm-1) and has high refractive index (above water, 1.44) at 193nm. Characterization of various fluid candidates has been performed and the absorbance of these fluids has been measured. To measure the absolute refractive index, a prism deviation angle method was developed. This method offers the possibility of measuring fluid refractive indices accurately. This paper also presents the obtained refractive indices of these fluids. Several candidates have been identified for 193nm application with refractive indices near 1.55, which is about 0.1 higher than that of water at this wavelength. Cauchy parameters of these fluids were generated and approaches were investigated to tailor the fluid absorption edges to be close to 193nm. The effects of these fluids on photoresist performance were also examined with 193nm immersion lithography exposure at various NA's. 1.5 NA was obtained to image 32nm lines with phosphoric acid as the immersion medium. These fluids are potential candidates for immersion lithography technology.

Paper Details

Date Published: 12 May 2005
PDF: 8 pages
Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); doi: 10.1117/12.602533
Show Author Affiliations
Jianming Zhou, Rochester Institute of Technology (United States)
Yongfa Fan, Rochester Institute of Technology (United States)
Anatoly Bourov, Rochester Institute of Technology (United States)
Neal Lafferty, Rochester Institute of Technology (United States)
Frank Cropanese, Rochester Institute of Technology (United States)
Lena Zavyalova, Rochester Institute of Technology (United States)
Andrew Estroff, Rochester Institute of Technology (United States)
Bruce W. Smith, Rochester Institute of Technology (United States)

Published in SPIE Proceedings Vol. 5754:
Optical Microlithography XVIII
Bruce W. Smith, Editor(s)

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