Articles

Index of refraction of high-index lithographic immersion fluids and its variability

[+] Author Affiliations
Min K. Yang

DuPont Company Central Research, Experimental Station, Wilmington, Delaware 19880-0400

Simon G. Kaplan

National Institute of Standards and Technology, Physics Laboratory, Gaithersburg, Maryland 20899

Roger H. French

DuPont Company Central Research, Experimental Station, Wilmington, Delaware 19880-0400

John H. Burnett

National Institute of Standards and Technology, Physics Laboratory, Gaithersburg, Maryland 20899

J. Micro/Nanolith. MEMS MOEMS. 8(2), 023005 (May 01, 2009). doi:10.1117/1.3124189
History: Received June 27, 2008; Revised November 14, 2008; Accepted March 16, 2009; Published May 01, 2009
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We have developed a number of second-generation high-index candidate immersion fluids that exceed the 1.6 refractive index requirement for immersion lithography at 193nm to replace the water used in first-generation immersion systems. To understand the behavior and performance of different fluid classes, we use spectral index measurements, based on the prism minimum deviation method, to characterize the index dispersion. In addition to fluid absorbance and index requirements, the temperature coefficient of the refractive index is a key parameter. We have used a laser-based Hilger–Chance refractometer system to determine the thermo-optic coefficient (dndT) by measuring the index change versus temperature at two different laser wavelengths, 632.8 and 193.4nm. Also, we determined the batch-to-batch (within a 6-month period), before and after irradiation (at 193.4nm), before and after air exposure, and before and after resist exposure (image printing test) variations of index and ΔnΔλ. The optical properties of these second-generation immersion fluids mostly compare favorably to water; the ratio of index of refraction at 193.4nm is 1.6441.437, the dispersion from d-line (Δn193-d) is 0.160 versus 0.103 and dndT at 193.4 is 550×106K vs. 93×106K, respectively.

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© 2009 Society of Photo-Optical Instrumentation Engineers

Citation

Min K. Yang ; Simon G. Kaplan ; Roger H. French and John H. Burnett
"Index of refraction of high-index lithographic immersion fluids and its variability", J. Micro/Nanolith. MEMS MOEMS. 8(2), 023005 (May 01, 2009). ; http://dx.doi.org/10.1117/1.3124189


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