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Proceedings Paper

Synthetic defocus in interferometric lithography
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Paper Abstract

Interference lithography has been widely utilized as a tool for the evaluation of photoresist materials, as well as emerging resolution enhancement techniques such as immersion lithography. The interferometric approach is both simple and inexpensive to implement, however it is limited in its ability to examine the impact of defocus due to the inherently large DOF (Depth-of-Focus) in two-beam interference. Alternatively, the demodulation of the aerial image that occurs as a result of defocus in a projection system may be synthesized using a two pass exposure with the interferometric method. The simulated aerial image modulation for defocused projection systems has been used to calculate the single beam exposure required to reproduce the same level of modulation in an interferometric system through the use of a “Modulation Transfer Curve”. The two methods have been theoretically correlated, by way of modulation for projection illumination configurations, including quadrupole and annular. An interferometric exposure system was used to experimentally synthesize defocus for modulations of 0.3, 0.5, 0.7 and 1.0. Feature sizes of 90nm were evaluated across dose and synthetic focus.

Paper Details

Date Published: 12 May 2005
PDF: 11 pages
Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005); doi: 10.1117/12.602948
Show Author Affiliations
Frank C. Cropanese, Rochester Institute of Technology (United States)
Anatoly Bourov, Rochester Institute of Technology (United States)
Yongfa Fan, Rochester Institute of Technology (United States)
Jianming Zhou, Rochester Institute of Technology (United States)
Lena Zavyalova, 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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