Damage behavior of SiO2 glass induced by 193-nm radiation under a simulated operating mode of lithography laser

Changes in optical absorption of lithographic-grade SiO2 glass containing hydrogen were examined when irradiated intermittently by ArF excimer laser (6.4 eV) under a simulated operating mode of lithography laser. Absorption intensity at 6.4 eV was increased during the irradiation and was decreased gradually after the termination of the irradiation. However, when re-irradiated, the absorption intensity was recovered instantly to the extent just before the termination of the irradiation. These observed phenomena could be explained by the formation and restoration of E' centers. E' centers were generated through two kinds of processes, dissociation of strained Si-O-Si bonds and dissociation of photo-induced ODCs, while E' centers were converted into SiHs by chemical reaction with hydrogen in SiO2 glass. The phenomenon of fast re-darkening was due to photolysis of SiHs into E' centers.