Optical Materials for Vacuum Ultraviolet Lithography: Interaction of Materials with Excimer Laser Pulses

Recent advances in optical materials for vacuum ultraviolet (VUV) lithography are reviewed from a view of interaction of excimer laser light with materials. Synthetic silica glasses applicable for F2 excimer laser totally differs from those for KrF and ArF lasers. A novel phenomenon was found in H2-impregnated SiO2 glasses byirradiation with F2 laser light pulses, i. e., bleaching of VUV absorption edge. Degradation of optical transmissionat 193 nm of calcium fluoride single crystals is primarily determined by the concentration of specific impuritycations such as Y3+ and Tb2+. Time resolved fluorescence was an effective technique to make screening of the fluoride crystals with high tightness to ArF laser pulses.