Debris from tape-target irradiated with pulsed YAG laser

For high brightness and debris-free laser-produced plasma EUV source, EUV spectra and debris were measured. The experimental debris scattering angle distribution and the amount of piled debris were estimated in the thickness of debris on silicon wafers from tape-target irradiated with pulsed YAG laser (SHG, E=0.8 J, t=7 ns) in more than 200,000 laser shots. The shape and size of debris were observed using scanning electron microscope. EUV spectra were obtained by using the grazing-incidence XUV spectrometer with the Au-coated toroidal mirror, diffraction grating and X-ray CCD camera. In 200,000 laser shots, for copper tape-target, 50 nm thick debris at 50° from target normal and 30 nm thick debris at more than 70° from target normal were obtained. More than 20 μm in diameter debris of aluminum and less than 1 μm in diameter debris of copper were observed. Laser-produced plasma EUV source system with low debris tape-target of thin metal and polymer films, debris-shield and debris-free EUV filter has been developed. We demonstrated successive 8 h generation of EUV with the developed laser-produced plasma EUV source system for EUV lithography.