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Journal of Micro/Nanolithography, MEMS, and MOEMS

Optimal frequency coverages and parsings for imaging interferometric lithography
Author(s): Thanis M. Tridhavee; Balu Santhanam; Steven Roy Julien Brueck
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Paper Abstract

Imaging interferometric lithography (IIL) is an optical resolution enhancement technique, based on wavelength-division multiplexing, that combines off-axis illumination with multiple exposures and pupil filtering. In prior experiments, IIL was shown to be capable of improving the resolution of optics to subwavelength regimes but only in isolated parameter settings. The frequency parsing scheme plays a critical role in the resolution of aerial images from IIL and a platform for optimizing these frequency coverage parameters is currently lacking. We present three approaches to the optimization of IIL frequency coverage parameters. First, the exhaustive search approach and, then, the dynamic programming and greedy versions are presented. For unobstructed lenses and large numerical apertures, these approaches converge to frequency coverages with illumination points along the vertical and horizontal axes, while a lens with an obscured center results in a tilted frequency coverage. Two particular frequency parsing strategies are analyzed from the perspective of the quadratic term in the aerial intensity. Simulation results comparing the off-axis exposures with and without the on-axis exposure are presented. The effect of the quadratic terms on the exposure latitude is shown to have a positive effect in the dense edge areas and a negative effect on isolated edges.

Paper Details

Date Published: 1 July 2005
PDF: 14 pages
J. Micro/Nanolith. MEMS MOEMS 4(3) 033005 doi: 10.1117/1.2008969
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 4, Issue 3
Show Author Affiliations
Thanis M. Tridhavee, Univ. of Michigan (United States)
Balu Santhanam, The Univ. of New Mexico (United States)
Steven Roy Julien Brueck, The Univ. of New Mexico (United States)

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