26 May 1995 Automatic laser-scanning focus detection method using printed focus pattern
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An innovative method of determining best focus with an optical exposure tool has been developed. The method uses wedge shaped marks in photoresist that can be measured automatically. The results show that best focus can be measured with a repeatability of 20 nm. The automatic focus measurement system can be used to characterize lens astigmatism, field curvature and tilt. Data shows good correlation with conventional methods using SEM linewidth measurement.
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Kyoichi Suwa, Kyoichi Suwa, Hiroki Tateno, Hiroki Tateno, Nobuyuki Irie, Nobuyuki Irie, Shigeru Hirukawa, Shigeru Hirukawa, } "Automatic laser-scanning focus detection method using printed focus pattern", Proc. SPIE 2440, Optical/Laser Microlithography VIII, (26 May 1995); doi: 10.1117/12.209298; https://doi.org/10.1117/12.209298

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