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Proceedings Paper

Mask roughness induced LER: geometric model at long correlation lengths
Author(s): Brittany M. McClinton; Patrick P. Naulleau
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Paper Abstract

Collective understanding of how both the resist and line-edge roughness (LER) on the mask affect the final printed LER has made significant advances. What is poorly understood, however, is the extent to which mask surface roughness couples to image plane LER as a function of illumination conditions, NA, and defocus. Recently, progress has been made in formulating a simplified solution for mask roughness induced LER. Here, we investigate the LER behavior at long correlation lengths of surface roughness on the mask. We find that for correlation lengths greater than 3λ/NA in wafer dimensions and CDs greater than approximately 0.75λ/NA, the previously described simplified model, which remains based on physical optics, converges to a "geometric regime" which is based on ray optics and is independent of partial coherence. In this "geometric regime", the LER is proportional to the mask slope error as it propagates through focus, and provides a faster alternative to calculating LER in contrast to either full 2D aerial image simulation modeling or the newly proposed physical optics model. Data is presented for both an NA = 0.32 and an NA = 0.5 imaging system for CDs of 22-nm and 50-nm horizontal-line-dense structures.

Paper Details

Date Published: 8 April 2011
PDF: 8 pages
Proc. SPIE 7969, Extreme Ultraviolet (EUV) Lithography II, 79691Y (8 April 2011); doi: 10.1117/12.881677
Show Author Affiliations
Brittany M. McClinton, Univ. of California, Berkeley (United States)
Patrick P. Naulleau, Lawrence Berkeley National Lab. (United States)


Published in SPIE Proceedings Vol. 7969:
Extreme Ultraviolet (EUV) Lithography II
Bruno M. La Fontaine; Patrick P. Naulleau, Editor(s)

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