Techniques are described for at-wavelength interferometry of multilayer coated optics designed for use in extreme-ultraviolet lithography. Broadly tunable undulator radiation, which covers the spectral region from 45 to 400 Å, is described. The coherent power available at these wavelengths is described, and several types of interferometer that might be suitable at these short wavelengths are also described.
© 1993 Optical Society of America
David Attwood, Gary Sommargren, Raul Beguiristain, Khanh Nguyen, Jeffrey Bokor, Natale Ceglio, Keith Jackson, Masato Koike, and James Underwood, "Undulator radiation for at-wavelength interferometry of optics for extreme-ultraviolet lithography," Appl. Opt. 32, 7022-7031 (1993)