193 NM EXCIMER LASER DEVELOPMENT FOR LITHOGRAPHY

THE LASER PARAMETERS MOST IMPORTANT TO LITHOGRAPHY APPLICATIONS ARE BEAM QUALITY AND LASER WAVELENGTH. A SIGNIFICANT UP-GRADE OF ARF LASER PERFORMANCE IN THESE KEY AREAS CAN BE ACHIEVED IN AN ALTERNATIVE SYSTEM. AN UNSTABLE RESONATOR CAVITY IN WHICH THE EXCITATION LIFETIME IS ON THE ORDER OF 35 NSEC WILL BE USED AS AN OSCILLATOR. THIS IS MUCH LONGER EXCITATION TIME THAN IN DISCHARGE PUMPED ARF, THEREBY PROVIDING AMPLE TIME FOR THE BUILD-UP OF A HIGH BEAM QUALITY UNSTABLE RESONATOR CAVITY MODE. TEMPORALLY SELECTIVE AMPLIFICATION OF THE LATER PORTION OF THE OSCILLATOR OUTPUT WILL THEN TAKE PLACE IN A SEPARATE AMPLIFIER. THE NET CONVERSION EFFICIENCY OF ARF LASER PHOTONS TO VUV LASER PHOTONS IS PREDICTED TO BE 25%. TUNABLE EXCITATION WILL PERMIT LASING AT WAVELENGTHS OF 151.7, 162, 166, 172, OR 185 NM. USING COMMERCIALLY AVAILABLE LASERS, THE PREDICTED NO LASER OUTPUT AT 162 - 185 NM IS > 55 MJ/PULSE OR > 10 WATTS. SUCCESSFUL DEMONSTRATION OF LASING AT THESE WAVELENGTHS IN PHASE I WILL ULTIMATELY PERMIT THE EXTENSION OF THIS TECHNIQUE TO CO LASING AT 115 NM IN A FOLLOW-ON EFFORT. THIS CORRESPONDS TO A LASER PHOTON ENERGY IN EXCESS OF 10 EV, WHICH IS COMPARABLE TO THE CUT-OFF FREQUENCY OF SYNCHROTRON RADIATION. THE PROPOSED ARF PUMPED SYSTEM WILL PROVIDE AN EFFICIENT, TUNABLE VUV UP-GRADE OF EXISTING ARF LITHOGRAPHY SYSTEMS. THE UP-GRADE WILL SIGNIFICANTLY ENHANCE THE PERFORMANCE OF THESE CURRENT SYSTEMS, PROVIDING A LOW COST, SIMPLE TO OPERATE ALTERNATIVE TO SYNCHROTRON RADIATION SOURCES.