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23 March 2012 Aerial image monitor for wavefront metrology of high-resolution EUV lithography tools
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In this paper, we present an aerial image monitor suitable for use in high-NA EUV lithography tools, and discuss an application in an in-situ image-based reconstruction of the optical system aberrations. The working principle of the aerial image monitor relies on a scanning aperture that employs a binary, 2-dimensional uniformly redundant array (URA), which simultaneously provides high flux throughput and high spatial frequency bandwidth. Aerial images are captured through focus, and are fed into a computer algorithm that matches the measured images to a computer model with a trial set of pupil aberrations. The aberrations are then modified until the modeled images match the ones from the experiment. The Reduced Optical Coherent Sum (ROCS) decomposition for partially coherent aerial image calculation greatly reduces the computation time of each iteration which makes this method more computationally tractable.
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Ryan Miyakawa and Patrick Naulleau "Aerial image monitor for wavefront metrology of high-resolution EUV lithography tools", Proc. SPIE 8322, Extreme Ultraviolet (EUV) Lithography III, 832218 (23 March 2012);

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