Compact laser plasma EUV source based on a gas puff target for metrology applications

A newly developed compact laser plasma EUV source for metrology applications is presented in the paper. The source is based on the double-stream gas puff target formed by pulsed injection of xenon into a hollow stream of helium. The outer stream of helium confines the inner stream of xenon improving the gas puff target characteristics. The main advantages of this target are higher density xenon at longer distance from the nozzle output and steep density gradients which cause efficient absorption of laser energy in a plasma and strong EUV production. Spectral, spatial, and temporal characteristics of EUV emission from the source are presented. Conversion efficiency of the laser energy into EUV energy at 13.5 nm of about 1.6% was measured. The source has been developed in the frame of the EUV sources development project under the MEDEA+ programme.