Laser produced plasma light source for next generation lithography

Summary form only given, as follows. Our group is part of the Japanese Extreme Ultraviolet Lithography System Development Association and working on laser produced plasma light sources. The system we developed since the project start last year is based on Xenon as a plasma source. Being continuously recycled the Xenon is injected into the vacuum chamber via a small diameter nozzle A Master Oscillator Power Amplifier (MOPA) Nd:YAG laser system oscillating at 1064 nm and a maximum repetition rate of 10 kHz is used for plasma generation. For various Xenon target and laser parameters, including two laser pulse durations of several ns and 30 ns (fwhm), we evaluated plasma characteristics relevant for lithography systems including emission spectra, in-band energy, energy stability and EUV conversion efficiency, out-of-band energy and EUV emission symmetry. Beside plasma characteristics, the lifetime of the collector mirror placed inside the vacuum chamber near the plasma will be a critical issue being strongly correlated to plasma debris and ion impact. Xenon debris can be due to Xe solid phase formation on the mirror surface but might, be reduced by the heat load of the mirror. In a first step we concentrated therefore on time-of-flight measurements in order to measure energy distributions of ions emitted from the generated plasmas.