EUV characteristics of a high power and high repetition rate CO2 laser driven Xe plasma

A CO2 laser driven Xe jet plasma is presented as light source system for EUV lithography. A short-pulse TEA C02 master oscillator power amplifier system and a pre-pulse Nd:YAG laser were used for plasma generation. The dependence of EUV plasma parameters, e.g. conversion efficiency, plasma image and in-band and out-of-band spectra, on the delay time between the pre-pulse and the main pulse laser was investigated. A maximum conversion efficiency of 0.6 % was obtained at a delay time of about 200 ns. In addition, characteristics of fast ions were measured by the time-of-flight method. The peak energy of the fast ion energy distribution decreased significantly at delay times larger than 200 ns. This result is very promising with respect to collector mirror lifetime extension by magnetic field mitigation.