30 June 1987 A New Mask-To-Wafer Alignment Technique For Synchrotron Radiation X-Ray Lithography
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Abstract
A new interferometric optical-heterodyne method has been developed for detection of displacement between a mask and a wafer. This method uses three symmetrically-arranged gratings and detects the displacement from the phases of beat signals. Using a 0.76-μm-period-grating system and a He-Ne transverse-mode Zeeman laser( wave length = 0.6328 μm ), sensitivity better than 1° /0.01 μm was obtained and displacement smaller than 5nm was detected independently of the mask-wafer gap variations. With this method, a prototype alignment system having vertical mask and wafer stages was constructed for synchrotron x-ray lithography. The alignment accuracy better than 0.01 μm was achieved. Effects of several factors ( dimension of grating, resist coating, etc. ) influencing the alignment accuracy are discussed.
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Junji Itoh, Junji Itoh, Toshihiko Kanayama, Toshihiko Kanayama, Nobufumi Atoda, Nobufumi Atoda, Koichiro Hoh, Koichiro Hoh, } "A New Mask-To-Wafer Alignment Technique For Synchrotron Radiation X-Ray Lithography", Proc. SPIE 0773, Electron-Beam, X-Ray, and Ion-Beam Lithographies VI, (30 June 1987); doi: 10.1117/12.940347; https://doi.org/10.1117/12.940347
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