A fast capillary discharge plasma dedicated to EUV radiation production-possible source for EUV lithography

A xenon filled capillary discharge has been developed for efficient EUV radiation production with emphasis on the wavelength range around 13.5 nm in view of application to EUV lithography. This source will be operated in a multi-watt, kHz and low debris mode for its use in a test bench for lithography (BEL). Fast rise time, few kA current applied across an alumina capillary produces radiation mostly in the EUV region (10-16 nm). A comprehensive study on plasma composition and plasma dynamics inside this fast capillary discharge (FCD) has been made in relation with the EUV photon yield at 13.5 nm. Time integrated as well as time resolved spectroscopy together with pinhole imaging measurements have been performed and have given information about the radiation processes from the xenon plasma and its dynamical behavior. Stable operation of the source at repetition rates up to 3 kHz has been demonstrated in burst mode over periods of a few seconds. In addition, the debris deposition rate on silicon targets has been determined after millions of shots. The results show the critical role of the discharge regime for this crucial issue.