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Interferometric at-wavelength flare characterization of EUV optical systems

United States Patent

May 15, 2001
View the Complete Patent at the US Patent & Trademark Office
Lawrence Berkeley National Laboratory - Visit the Technology Transfer and Intellectual Property Management Department Website
The extreme ultraviolet (EUV) phase-shifting point diffraction interferometer (PS/PDI) provides the high-accuracy wavefront characterization critical to the development of EUV lithography systems. Enhancing the implementation of the PS/PDI can significantly extend its spatial-frequency measurement bandwidth. The enhanced PS/PDI is capable of simultaneously characterizing both wavefront and flare. The enhanced technique employs a hybrid spatial/temporal-domain point diffraction interferometer (referred to as the dual-domain PS/PDI) that is capable of suppressing the scattered-reference-light noise that hinders the conventional PS/PDI. Using the dual-domain technique in combination with a flare-measurement-optimized mask and an iterative calculation process for removing flare contribution caused by higher order grating diffraction terms, the enhanced PS/PDI can be used to simultaneously measure both figure and flare in optical systems.
Naulleau; Patrick P. (Oakland, CA), Goldberg; Kenneth Alan (Berkeley, CA)
The Regents of the University of California (Oakland, CA)
09/ 627,533
July 28, 2000
The U.S. Government has certain rights in this invention pursuant to Contract No. DE-AC03-76SF00098 between the United States Department of Energy and the University of California for the operation of the Lawrence Berkeley National Laboratory.