色収差2重焦点法によるSRステッパ用アライメント装置の開発

概要

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This paper describes an alignment system developed for synchrotron radiation (SR) X-ray stepper. A bifocal lens, which has two object planes and a single image plane on a common optical axis utilizing a longitudinal chromatic aberration, is applied to the alignment system. The chromatic bifocal lens observes high contrast images of alignment marks printed on a mask and wafer. To be unaffected by resist film coated on the wafer and a gap variation between mask and wafer, the wafer marks are observed with broadband light illumination. The mark images are focused on a CCD line sensor, and the video signal is digitized and used for the alignment algorithm. The algorithm calculates the displacement between the mask and wafer with a new correlation function. The alignment system detects the displacement between the mask mark and wafer marks with precision of better than 13 nm.
公益社団法人精密工学会の論文
1993-05-05