Enhancement of Sn plasma EUV emission by double-sided laser illumination

Abstract

Advancements in state-of-the-art nanolithography technology over the past decade have been raising an ongoing demand for improvement of the power and efficiency of extreme-ultraviolet (EUV) light sources that stand at its heart. This study introduces a double-sided laser illumination scheme aimed at enhancing EUV emission from such a laser-produced Sn plasma source. Using a solid-state laser, experiments were conducted with suspended solid Sn targets of varying thicknesses, evaluating the resulting effect on EUV output intensity. A significant increase in EUV emission to the collection side was observed due to the addition of illumination of the other side, particularly for thinner targets. For targets with thicknesses of 60 and 20 nm, an increase between 50% and 150% in EUV emission was detected in comparison with single-sided illumination. Extrapolating to a long laser pulse that burns through the target, the enhancement is projected to be 17% for a 300 nm thick target. These results highlight a promising way for further improvement of output power and energy efficiency in next-generation EUV light sources.