Lifetime Calculations on Collector Optics from Laser Plasma Extreme Ultraviolet Sources with Minimum Mass

An ion flux and its kinetic energy spectrum are obtained using a self similar spherically symmetric fluid model of expansion of a collisionless plasma into vacuum. According to the ion flux and energy distribution, the collector optical lifetime is estimated by knowledge of the sputtering yield of conventional Mo/Si multilayer coatings for the CO₂ and Nd:YAG pulsed−laser produced plasmas based on the minimum mass tin droplet target without debris mitigation. The results show that the longer wavelength of the CO₂ laser produced plasma light source is more suitable for extreme ultraviolet lithography than Nd:YAG laser in respect of fast ion debris induced sputtering damage to the collector mirror.