7 July 1997 Characterization of an EUV Schwarzschild objective using phase-shifting point diffraction interferometry
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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.
© (1997) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Kenneth A. Goldberg, Kenneth A. Goldberg, Edita Tejnil, Edita Tejnil, Sang Hun Lee, Sang Hun Lee, Hector Medecki, Hector Medecki, David T. Attwood, David T. Attwood, Keith H. Jackson, Keith H. Jackson, Jeffrey Bokor, 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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