Investigation of EUV sources for 13.5-nm operation

The internationally agreed semiconductor roadmap calls for the development of bright, narrow bandwidth sources of extreme UV radiation for lithography at 13.5 nm. Both pulsed discharge sources and laser produced plasmas have been proposed as possible candidates and xenon is currently the most favored constituent element since it possesses strong emission lines at the correct wavelength. In this paper we show from theoretical considerations that tin containing plasmas provide superior intesitiy, albeit at the expense of increased debris emission. We also show that for laser produced plasma sources, the brightness can be considerably enhanced by varying both the target constituents and the laser pulse profile. Various methods by which the debris problem might be reduced are discussed.