Laser induced damage thresholds of dielectric coatings at 193 nm and correlations to optical constants and process parameters

Laser-induced damage thresholds of dielectric single layers and reflectors were measured at 193 nm. Layers of A1203 and SiO2 were prepared by electron beam evaporation and by ion beam sputtering; layers of NaF, AlF3, MgF2, GdF3, LaF3, NdF3 and YF3 were prepared by thermal evaporation. Spectrophotometric methods were used to evaluate optical constants and inhomogeneity coefficients in the spectral range between 150 nm and 250 nm. The dependence of refractive indices and absorption coefficients on process para- meters and deposition methods was analyzed in order to prepare low loss reflectors for 193 nm and 157 nm.