5 July 2000 Double exposure technique to reduce line shortening and improve pattern fidelity
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A double exposure technique, so called nano-stepping, was investigated to evaluate its benefit for very dense features to reduce line shortening, improve pattern fidelity and resolution capability. The technique involves relaxing the pitch of dense patterns in one dimension and filling in the missing patterns by exposing the same reticle again, offset by an appropriate amount. This method suffers only small throughput loss compared to conventional dual reticle exposure techniques. For 1D patterns, 100 nm lines and spaces can be printed with a 248 nm exposure tool and a half tone mask. Dense 2D contacts with various length to width ratios can be achieved with minimum distance to adjacent neighbors.
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Gerhard Kunkel, Scott J. Bukofsky, Shahid A. Butt, Zhijian G. Lu, "Double exposure technique to reduce line shortening and improve pattern fidelity", Proc. SPIE 4000, Optical Microlithography XIII, (5 July 2000); doi: 10.1117/12.388943; https://doi.org/10.1117/12.388943

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