Current status of radiation resistance of dielectric mirrors in the DUV

Dielectric mirrors are key optical components in ArF excimer laser based devices for applications in DUV photolithography as well as in material processing. In all these applications different requirements of laser radiation resistance have to be met in relation to fluence, repetition rate and pulse number lifetime. Investigations have been performed into the radiation resistance of dielectric mirrors consisting of fluorides and oxides with emphasis to the properties of bending point mirrors used in beam delivery systems of wafer steppers. Problems and limitations for the improvements of the laser-induced-damage-thresholds of the coatings are discussed.