抄録
Extreme ultraviolet (EUV) radiation from laser produced plasmas (LPP) has been theoretically studied as a light source for lithography in mass-production of the next generation semiconductor devices. One of the critical issues for realization of a LPP-EUV light source is the conversion efficiency (CE) from incident laser power to EUV radiation of 13.5nm wavelength (within 2% bandwidth). From an atomic physical point of view, we explain the reason why tin has been chosen as the most suitable radiation material compared with xenon and lithium. We also present a power balance model, which can be used for the optimization of laser and target conditions to obtain high CE. We propose a double-pulse irradiation scheme for high CE using a carbon dioxides laser and a droplet target. Using our benchmarked numerical simulation code, we show a possibility to obtain CE up to 5-7%, much higher presently achieved.
