Some parameter considerations for radiation sources at 11.5 and 13.5 nm

Abstract

The possible emission from dense plasmas produced in discharges is analyzed with respect to optimize the achievable radiance at 11.5 and 13.5 nm for applications in EUV lithography, although the considerations may readily be applied to other spectral regions and to laser-produced plasmas. Density and temperature requirements of the plasma are discussed. Once an emission line has been selected, the optimum temperature of the plasma for quasi-steady state conditions is around the temperature for maximum fractional abundance of the respective ion, and the maximum possible radiance is given by the Planck function. Suitable lines are identified and discussed.