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Proceedings Paper

Source optimization incorporating margin image average with conjugate gradient method
Author(s): Jue-Chin Yu; Peichen Yu; Hsueh-Yung Chao
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Paper Abstract

Source optimization (SO) becomes increasingly important to resolution enhancement in sub-32 nm lithography nodes because the dense pattern configurations significantly limit the capability of mask correction. A key step in SO is the image formation by Abbe's method, which is a linear operation of integrating all source points' images incoherently to form aerial images. However, the aerial images are usually converted to resist images through the nonlinear sigmoid function. Such operation loses the merit of linearity in optimization and leads to slow convergence and time-consuming calculation. In this paper we propose a threshold-based linear resist model to replace the sigmoid model in SO. The effectiveness of our proposed model can be clearly seen from mathematical analysis. We also compare results based on linear and sigmoid models. Highly similar optimal sources are obtained, but the linear model has a significant advantage over the sigmoid in terms of convergence rate and simulation time. Furthermore, the process variations characterized by exposure-defocus (E-D) windows are still in similar trends for optimal sources based on two different resist models.

Paper Details

Date Published: 13 March 2012
PDF: 18 pages
Proc. SPIE 8326, Optical Microlithography XXV, 83261W (13 March 2012); doi: 10.1117/12.916597
Show Author Affiliations
Jue-Chin Yu, National Chiao Tung Univ. (Taiwan)
Peichen Yu, National Chiao Tung Univ. (Taiwan)
Hsueh-Yung Chao, ANSYS, Inc. (United States)

Published in SPIE Proceedings Vol. 8326:
Optical Microlithography XXV
Will Conley, Editor(s)

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