EUV Generation from Lithium Laser Plasma for Lithography

摘要

Hydrogen-like line emission from lithium has long been considered a candidate for EUV light source for lithography. We have completed the evaluation of the potential of lithium as a laser-plasma source, both theoretically and experimentally. Theoretical calculations show optimum intensity region for lithium for attaining high conversion is close to 5.0 x 10~(11) W/cm~2, with plasma temperature near 50 eV. Experimental studies compare directly, the conversion efficiency and optimum irradiation conditions for both planar tin and lithium solid targets. Best conversion efficiency found in this study is 2% for lithium, while CE measured is better than 4% for tin target at identical experimental conditions.