17 May 1994 Techniques for improving overlay on multilayer phase-shift masks
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Abstract
Techniques used to optimize the alignment performance of the CORE-2564PSM reticle writer are presented. In particular, unique procedures for accurately locating alignment marks with nonuniform background intensities are discussed. Site-by-site automatic illumination control is implemented to ensure optimal image intensity and contrast for the CCD-based image capture system. Process and metrology considerations that affect error measurement are discussed. The mean + range/2 aligned overlay of the CORE-2564PSM is shown to be 35 - 55 nm.
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Henry Chris Hamaker, Michael J. Bohan, Peter D. Buck, Claudia H. Geller, Takashi Makiyama, Francis P. Mathew, William S. Neeland, "Techniques for improving overlay on multilayer phase-shift masks", Proc. SPIE 2197, Optical/Laser Microlithography VII, (17 May 1994); doi: 10.1117/12.175411; https://doi.org/10.1117/12.175411
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