Extreme ultraviolet lithography requires a high-efficiency light source at 13 nm that is free from debris. Our mass-limited Sn-based laser plasma source shows 1.2% conversion efficiency. Emission spectra from the source were obtained to observe the effects of Sri concentration and effects of laser intensity. Debris measurements were analyzed, and an enhanced repeller field configuration shows marked improvement in mitigating debris. (C) 2004 American Vacuum Society.