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Proceedings Paper

Simultaneous OPC and decomposition for double exposure lithography
Author(s): Shayak Banerjee; Kanak B. Agarwal; Michael Orshansky
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Paper Abstract

Double exposure techniques are an economically viable method for extending the life of the current 193nm wavelength immersion lithography techniques into future generations of semiconductor scaling. One popular example of double exposure is the use of double dipole illumination, where the X and Y dipoles are separately optimized for vertical and horizontal features respectively. The primary challenge in such double exposure techniques lies in the process of target layout decomposition into patterns that can be optimally printed using their respective source. Current approaches for decomposition are rule-based. They suffer from the drawbacks of scalability, rule count explosion and inability to guarantee sufficient yield in the presence of process variation. Further, rules are characterized specific to sources and are relatively easy to develop for dipoles, but far more difficult to develop for more complex sources such as used in source mask optimization (SMO). Decomposed target layouts have to further undergo optical proximity correction (OPC) in order to be converted to a mask for use in manufacturing. In this paper, we propose a novel approach which integrates the processes of decomposition and optical proximity correction. We preclude the intermediate target decomposition stage. Instead, we directly optimize the masks for both exposures simultaneously in order to obtain a wafer image that both closely matches the target layout and is also robust to process variation. For this purpose, we define a lithographic cost function that is a weighted sum of intensity error and intensity slope. We develop methods to analytically predict the change in this cost function due to movement of fragments on each mask. We then utilize a gradient-descent algorithm for fragment movement to minimize the cost function. Since our methodology is based on the knowledge of the SOCS decomposition kernels, it is not restricted to dipoles alone, but can be utilized for any complex sources for which such kernels are known. Our experiments on 1x metal (M1) show significant improvement in layout process window compared to traditional rule-based decomposition methods.

Paper Details

Date Published: 23 March 2011
PDF: 10 pages
Proc. SPIE 7973, Optical Microlithography XXIV, 79730E (23 March 2011); doi: 10.1117/12.879540
Show Author Affiliations
Shayak Banerjee, IBM Research (United States)
Kanak B. Agarwal, IBM Research (United States)
Michael Orshansky, The Univ. of Texas at Austin (United States)


Published in SPIE Proceedings Vol. 7973:
Optical Microlithography XXIV
Mircea V. Dusa, Editor(s)

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