Comparison of laser produced and gas discharge based EUV sources for different applications

Abstract

Pulsed plasmas, e.g., laser produced plasma (LPP) and gas discharge based pinch plasmas are known as intense sources of soft x-ray and extreme ultraviolet (EUV) radiation in the wavelength interval of about 1 nm to beyond 50nm. They can be generated in compact, laboratory scale devices. Both schemes exhibit similar source characteristics concerning, e.g., wavelength region, bandwidth, source size, emitted radiation per pulse or average emitted power when operated at similar parameters. By exploiting their technological degrees of freedom their source characteristics can be matched to the special demands of a given application like EUV-lithography or metrology, x-ray microscopy, XPS or other x-ray analytics. In this work laser produced and gas discharge based plasmas are compared with respect to their source characteristics. The comparison concerns to a laser produced plasma using a commercial 1 J Nd:YAG laser with different target concepts (liquid, cryogenic or solid target) and a gas discharge based EUV sources with electrical pulse energies of about 1 J. The same absolute calibrated diagnostics used for both plasmas allows for a direct comparison.