Takuhiro Ono

Narrow-Band KrF Excimer Laser -- Tunable And Wavelength Stabilized

A tunable and wavelength stabilized KrF excimer laser has been developed. Two Fabry-Perot etalons of 2.4 THz and 170 GHz FSR are placed inside of the laser cavity to reduce the lasing bandwidth to 0.003 nm (3 pm). The wavelength was found to be tunable over a range from 248.1 nm to 248.6 nm. Within this tuning range, a stable wavelength setting to ±0.5 pm was achieved with a feedback system composed of a wavelength detector and a controlling mechanism. This wavelength-stabilized tunable KrF excimer laser will find its applications in optical microlithography, plasma diagnostics and photochemical reactions.

High-power and narrow-band excimer laser with a polarization-coupled resonator

As a light source for deep submicron lithography the authors have developed a long life and high power KrF narrow band excimer laser by installing a polarization coupled resonator into the conventional narrow band excimer laser with intra-cavity etalons. A maximum output power of 1O. 5Yi with a low etalon-load of L5W arid a narrow spectral band-width of 24pm at 200Hz is obtained. The central wavelength is stabilized to within only 5pm and drift is not observed when increasing the repetition rate from 4Hz to 200Hz without a wavelength feedback loop system. Furthermore the etalon-life is expected to be drastically prolonged to over a billion pulses resulting from the reduction of the etalonload to only about 10 of that in a conventional laser. 2.