A laser produced extreme ultraviolet (EUV) source based on a water droplet target has been implemented an auxiliary electrode system between the source and the first collector mirror. The auxiliary electrode system creates a repeller electric field, possibly a dc voltage imposed on the mirror that slows down and reverses the trajectories of ions from the source before they impact the collection mirror. The source modified according to the invention was evaluated with respect to the demands of EUV lithography and found to have much extended operational lifetimes. The spectral distribution of the generated radiation as well as the conversion efficiency into line radiation at 13 nm was determined. Long time measurements of the reflectivity of silicon/molybdenum multilayer mirrors for up to from 10.sup.7 to 10.sup.9 shots show the useful influence of the treatment of ions emitted from the source. Several methods of debris reduction were tested and discussed. Surface analysis of the treated
Application Serial Number
Assignee at Issuance
College of Optics and Photonics
Assignee at Filing
Nonprovisional Application Record
Richardson, Martin and Schriever, Guido, "Laser plasma source for extreme ultraviolet lithography using a water droplet target" (2002). UCF Patents. 288.