Je. Bjorkholm et al., PHASE-MEASURING INTERFEROMETRY USING EXTREME-ULTRAVIOLET RADIATION, Journal of vacuum science & technology. B, Microelectronics and nanometer structures processing, measurement and phenomena, 13(6), 1995, pp. 2919-2922
We describe initial experiments carried out with a phase-measuring, la
teral-shearing interferometer that we have developed for use with radi
ation having a wavelength of about 13 nm. The system was developed for
testing the imaging quality of extreme ultraviolet (EUV) lithographic
cameras at the ,wavelength of their intended use. We describe here ou
r initial work in which we measured essentially spherical wave fronts
obtained by focusing undulator radiation onto a small pinhole. The int
erferometer is shown to have a sensitivity of 0.021 waves rms, or bett
er, at an operating wavelength of 13 nm, which is more than sufficient
to determine whether or not an EUV imaging system exhibits diffractio
n-limited performance. (C) 1995 American Vacuum Society.