Characterization of a liquid-xenon-jet laser-plasma extreme-ultraviolet source

A liquid-xenon-jet laser-plasma source for extreme-ultraviolet ~EUV! and soft-x-ray generation has been characterized. Being a source candidate for EUV lithography ~EUVL!, we especially focus on parameters important for the integration of the source in EUVL systems. The deep-ultraviolet ~DUV! out-of-band radiation ~l5120–400 nm! was quantified, to within a factor of two, using a flying-circus tool together with a transmission-grating spectrograph resulting in a total DUV conversion efficiency ~CE! of ;0.33%/2psr. The size and the shape of the xenon plasma was investigated using an in-band-only EUV microscope, based on a spherical Mo/Si multilayer mirror and a charge-coupled device detector. Scalability of the source size from 20–270 mm full width at half maximum was shown. The maximum repetition-rate sustainable by the liquid-xenon-jet target was simulated by a double-pulse experiment indicating feasibility of .17 kHz operation. The xenon-ion energy distribution from the plasma was determined in a time-of-flight experiment with a Faraday-cup detector showing the presence of multi-kilo-electron-volt ions. Sputtering of silicon witness plates exposed to the plasma was observed, while a xenon background of .1 mbar was shown to eliminate the sputtering. It is concluded that the source has potential to meet the requirements of future EUVL systems. © 2004 American Institute of Physics. @DOI: 10.1063/1.1755441#