Enhanced Damage Resistance of Mo/Si Multilayer Mirror with Carbon Barrier Layers under Intense Nanosecond EUV Irradiation

The enhancement of damage-resistance capabilities has long been pursued for the development of multilayer mirrors in the field of extreme ultraviolet lithography. Here, single-shot damage experiments were conducted on periodic Mo/Si and Mo/C/Si/C multilayers using nanosecond 13.5 nm EUV radiation. It is revealed that the incorporation of carbon barrier layers significantly enhances the single-shot damage threshold of Mo/Si by about 46%. The crater-like and bump-like damages caused by compaction and expansion are, respectively, observed for Mo/Si and Mo/C/Si/C multilayers. According to characterization results, different damage mechanisms for these two samples have been identified, which are the diffusion reaction for the Mo/Si multilayer and the nonuniform graphitization for the Mo/C/Si/C multilayer. The nonuniform graphitization mechanism is further illustrated by molecular dynamics simulations. Based on the measured multilayer structure, the optical properties of the damaged Mo/C/Si/C multilayer were evaluated at a fluence of 2.68 J/cm² and found to be maintained at a high level.