High-average-power EUV light source for the next-generation lithography by laser-produced Xe plasma

The main technological challenge of a future extreme ultraviolet (EUV) light source is the required average power of 115W at the intermediate focus. High repetition rate laser produced plasma (LPP) sources are very promising to face this challenge. We report the current status of the laser produced light source system we started to develop in 2002. The system consists of the following main components: The plasma target is a liquid xenon jet with a maximum diameter of 50 μm and a velocity of more than 30 m/s. A Nd:YAG laser oscillating at 1064 nm produces the plasma. The laser is a master oscillator power amplifier (MOPA) configuration with a maximum repetition rate of 10 kHz and an average power of 1.3kW. The EUV system currently delivers an average EUV in-band power of 7.2 W (2% bandwidth, 2π sr). In order to decrease debris and to reduce the supply of target material we started the development of a xenon droplet target. Currently droplets are generated in vacuum at a frequency of 140 kHz, i.e. 140000 droplets/s, having a diameter of 100 μm and a velocity of 28m/s.