Extreme ultraviolet interferometric measurements of diffraction-limited optics
- 1 November 1999
- journal article
- Published by American Vacuum Society in Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures
- Vol. 17 (6) , 2982-2986
- https://doi.org/10.1116/1.590939
Abstract
At-wavelength interferometric measurements of recently fabricated extreme ultraviolet (EUV) microstepper projection optics have revealed the highest performance for prototype EUV lithographic systems observed to date. The phase-shifting point diffraction interferometer is used to measure and align these two-mirror, multilayer-coated Schwarzschild optical systems designed with a numerical aperture of 0.088 and operating at 13.4 nm wavelength. Root-mean-square wave front error magnitudes as small as 0.60 nm have been achieved, actually exceeding the design tolerance set for these objectives.Keywords
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