NEW KRF AND ARF EXCIMER LASERS FOR ADVANCED DEEP-ULTRAVIOLET OPTICAL LITHOGRAPHY

Advanced deep ultraviolet (DUV) optical lithography requires reliable high repetition rate excimer lasers at low cost of ownership. We optimized all components of the laser cavity. The result is a new metal/high-density ceramic laser tube with long life discharge components. It meets the specifications of the next generation of DUV laser sources. The new laser cavity was tested in several test runs at 193 nm (ArF) and 248 nm (KrF) and demonstrated excellent gas lifetime data when compared to conventionally designed lasers. For the first time a KrF laser was successfully operated in a quasi sealed-off mode for more than 1 billion pulses. The lifetime data of narrow bandwidth lasers necessary for DUV optical lithography tools also increase significantly. A 500 Hz 6 W laser with a bandwidth of 0.9 mu m passed in a marathon test 1.1 billion pulses and the gas lifetime exceeded 200 million pulses routinely. Additionally, we operated this laser at 8 W average power and 600 Hz.