Kinetics of laser induced changes of characteristic optical properties in Lithosil® with 193nm excimer laser exposure

Fused silica is used as lens material in DUV microlithography systems. The kinetics of slow radiation induced defect generation in Lithosil (R) including absorption, hydrogen consumption and changes of the refractive index is described in detail and in very good agreement with measured data in previous papers. In addition to these effects after long time irradiation fused silica is characterized by rapid damage processes (RDP) after short time irradiation. A model describing the absorption of RDP in dependence on energy density, repetition rate and time is described in this paper, the sensitivity of RDP on pre-irradiation and illumination conditions is discussed. Furthermore a method to reduce energy dependent absorption of RDP is mentioned.