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Journal of Micro/Nanolithography, MEMS, and MOEMS

Mask-roughness-induced line-edge roughness: rule of thumb
Author(s): Brittany M. McClinton; Patrick P. Naulleau
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Paper Abstract

Much work has already been done on how both the resist and line-edge roughness (LER) on a mask affect the final printed LER. What is poorly understood, however, is the extent to which system-level effects such as mask surface roughness, illumination conditions, and defocus couple to speckle at the image plane and factor into current LER limits. We propose a "rule-of-thumb" simplified solution that provides a fast and powerful method to determine mask-roughness-induced LER. Using a one-time aerial image modeling of the mask surface roughness to obtain clear-field speckle statistics, the LER for any feature can quickly be calculated from a simple analytic extension using feature-specific image log slope. We investigate how the clear-field speckle is scaled by the intensity at the line edge, and mathematically couples to LER in the simplified case of a knife edge. We apply this relation to nested lines and spaces and compare this analytic LER to fully simulated values. We present modeling data on an older generation mask with a roughness of 230 pm as well as the ultimate target roughness of 50 pm. Moreover, we consider feature sizes of 50 and 22 nm and show that as a function of correlation length, the LER peaks at the condition that the correlation length is approximately equal to the resolution of the imaging optic.

Paper Details

Date Published: 1 October 2010
PDF: 7 pages
J. Micro/Nanolith. 9(4) 041208 doi: 10.1117/1.3497607
Published in: Journal of Micro/Nanolithography, MEMS, and MOEMS Volume 9, Issue 4
Show Author Affiliations
Brittany M. McClinton, Univ. of California, Berkeley (United States)
Patrick P. Naulleau, Lawrence Berkeley National Lab. (United States)

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