ISSUES OF LASER-PLASMA SOURCES FOR SOFT-X-RAY PROJECTION LITHOGRAPHY

Results of optimization of an excimer laser-induced plasma x-ray sourc e for projection lithography in the range lambda=13-15 nm are reported . A conversion efficiency of >0.7% in 2% BW has been achieved with hig h-Z target materials. Two methods of reducing contamination of optical elements by target debris have been tested: usage of a thin target la yer (for Ta 1 mu m was found to be optimal) and of a heavy buffer gas. The effect of the use of Ta-tape target and Kr buffer gas has been me asured by determining the reflectivity of a Mo-Si multilayer sample af ter 10(5) shots.