A compact ultrafast capillary discharge for EUV projection lithography

Extreme ultra-violet lithography (EUVL) is expected to play an important role in the next generation of lithography system for the production of sub-100 nm feature microelectronic devices. An efficient source of EUV radiation in the 10-15 nm region has to be developed to comply with the demands for practical application. In this paper, the authors report on the development of a novel ultrafast hollow cathode triggered capillary discharge fitting with the desirable EUV region by operating in Xenon at low pressure. After being triggered by means of the hollow cathode effect ,the discharge starts on-axis. The resulting plasma channel is then heated up using a stored energy of less than 0.2 J before attaining the maximum temperature of 30 eV within a nanosecond timescale. During a pulse length of 5 ns concerning the EUV emission, the transient plasma inside the capillary whose aspect ratio is much more than 10 emits mainly between 10 and 20 nm, with a source size of less than 200 μm in diameter. The spectrum consists of Xe VII to Xe X line radiation. This very high energy efficiency allows practical scaling of the device to operate in the multi-kHz regime. (5 pages)