Illumination system with freeform fly’s eye to generate pixelated pupil prescribed by source-mask optimization in extreme ultraviolet lithography

Jiahua Jiang; Qiuli Mei; Yanqiu Li; Yan Liu

doi:10.1117/1.OE.56.6.065101

16 June 2017 Illumination system with freeform fly’s eye to generate pixelated pupil prescribed by source-mask optimization in extreme ultraviolet lithography

Jiahua Jiang, Qiuli Mei, Yanqiu Li, Yan Liu

Author Affiliations +

Funded by: National Natural Science Foundation of China (NSFC), Natural Science Foundation of China, Major Scientific Instrument Development Project of the National Natural Science Foundation of China, National Science and Technology Major Project

Optical Engineering, Vol. 56, Issue 6, 065101 (June 2017). https://doi.org/10.1117/1.OE.56.6.065101

Abstract

Source-mask optimization (SMO) has emerged as a key technique for 7-nm node and beyond in extreme ultraviolet (EUV) lithography. The pupil required by SMO is usually pixelated, with a free choice of intensity per pixel. However, due to the discrete nature of the EUV illumination system, pupil intensity in current EUV SMO must also be discretized. An illumination system with a freeform fly’s eye that is able to generate the pixelated pupil is proposed. Clear apertures of the field facets in the fly’s eye are different from each other so that the intensity of each pixel on the pupil can meet the requirements of SMO. Each of the field facets is constructed with a freeform surface to get the required arc-shaped illuminated area on the reticle. A method integrated with a numerical method and an optimization process is used to design the freeform surface of the field facets. The simulation result of the design for a prescribed freeform pixelated pupil shows that the uniformity on the reticle is 96.4%, and the pupil intensity error is approximated to be 0.035. The results indicate that the system is effective in generating the required freeform pixelated pupil and reducing the restrictions imposed on the SMO process in EUV lithography.

CC BY: © The Authors. Published by SPIE under a Creative Commons Attribution 4.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its DOI.

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Jiahua Jiang, Qiuli Mei, Yanqiu Li, and Yan Liu "Illumination system with freeform fly’s eye to generate pixelated pupil prescribed by source-mask optimization in extreme ultraviolet lithography," Optical Engineering 56(6), 065101 (16 June 2017). https://doi.org/10.1117/1.OE.56.6.065101

Received: 21 January 2017; Accepted: 30 May 2017; Published: 16 June 2017

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