7 July 1997 Characterization of an EUV Schwarzschild objective using phase-shifting point diffraction interferometry
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Abstract
We report wavefront measurement of a multilayer-coated, reflective optical system at 13.4-nm wavelength performed using a novel phase-shifting point-diffraction interferometer. Successful interferometric measurements of a 10x Schwarzschild objective designed for extreme ultraviolet projection lithography with 0.1-micrometer resolution demonstrate high- precision with sub-nanometer resolution. The goal of the interferometry is to achieve wavefront measurement accuracy beyond lambda/50 rms at EUV wavelengths. Preliminary measurements are discussed and the paths toward achieving the target accuracy are identified.
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Kenneth A. Goldberg, Edita Tejnil, Sang Hun Lee, Hector Medecki, David T. Attwood, Keith H. Jackson, Jeffrey Bokor, "Characterization of an EUV Schwarzschild objective using phase-shifting point diffraction interferometry", Proc. SPIE 3048, Emerging Lithographic Technologies, (7 July 1997); doi: 10.1117/12.275787; https://doi.org/10.1117/12.275787
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