Performance characteristics of ultra-narrow ArF laser for DUV lithography

Today, commercial line-narrowed ArF lasers for Deep-UV lithography are typically producing spectral bandwidth of 0.6 pm FWHM. This value forces the stepper/scanner manufacturers to use large amount of CaF2 in the lens design as well as fused silica in order to compensate for chromatic aberrations. We describe in this paper the parameters -such as pulse duration, fluorine concentration and divergence- which influence the line-narrowing efficiency of ArF lasers. We are also presenting results obtained using a new optical cavity design using an etalon as output coupler that provides bandwidth of 0.3 pm at FWHM and 0.8 pm for 95% of the energy, performance that could allow to greatly reduce the need for CaF2.