Interaction of Intense Laser Pulses with Droplet and Cluster Sources: Application to Extreme Ultraviolet Lithography and Plasma Waveguide Generation

Title of Document: INTERACTION OF INTENSE LASER PULSES WITH DROPLET AND CLUSTER SOURCES: APPLICATION TO EXTREME ULTRAVIOLET LITHOGRAPHY AND PLASMA WAVEGUIDE GENERATION Hua Sheng, Doctor of Philosophy, 2006 Directed By: Professor Howard M. Milchberg Department of Electrical and Computer Engineering & Institute for Physical Science and Technology Several topics were studied in the interaction of intense laser pulses with droplet and cluster sources. Laser pulse-formatting that can enhance laser-to-EUV conversion efficiency in the 13.5nm band for next generation lithography was first explored, using droplet sources as the laser target. Xenon droplets size distribution was measured, and the droplet plasma spectrum irradiated by various laser energies was scanned. A 2-pulse heater setup and a 4-pulse stacker scheme were built and studied. Results suggest that, unlike droplets of argon (Ar) and krypton (Kr), the ionizationstate distribution in xenon may be much more transient. The decay timescales for 13.5nm emissions are approximately 0.5-1.5ns, a timescale intermediate to the results from excitation and recombination emission in Ar and Kr droplet targets. Comparing xenon’s results with argon’s, the argon droplets generated a more robust ionizationstage distribution, while the xenon droplets generated a more transient ionization-