An ultra-line-narrowed high-power F/sub 2/ laser for dioptric design microlithography exposure tools

An ultra-line-narrowed high-power and high-repetition rate F/sub 2/ laser system has been developed for 157-nm microlithography exposure tools with dioptric projection design. The injection locked system (ILS) consists of a low-power seed laser with ultra-narrow spectral linewidth and a high-gain amplifier. More than 25-W output power, a spectral linewidth below 0.2 pm full-width at half-maximum (FWHM) and an energy stability (3-sigma) below 10% have been obtained at a 5-kHz repetition rate and for a delay time range between the two laser stages of about 15 ns. Directly compared with a master oscillator power amplifier system, the ILS had a better performance related to output energy, energy stability, and laser pulse duration.