Laser-generated water plasma source for extreme-ultraviolet lithography and at-wavelength interferometry

A laser-generated water plasma source has been built, operating around-the-clock. We characterized this source looking at several aspects that are important for a possible EUV source to be used in a next-generation lithographic tool. We characterized the source spectrally, measured the size of the source, the angular dependence of the EUV emission and the temporal dependence of the EUV pulses. We also investigated the level of debris produced by the source and the contamination of EUV optics by the water plasma. Finally, this laser-generated water plasma has been successfully used in a shearing interferometer, in which the imaging equality of EUV optics can be assessed accurately at-wavelength.