Actinic inspection of the extreme ultraviolet optical parameters of lithographic materials enabled by a table-top, coherent extreme ultraviolet source

The interaction of extreme ultraviolet (EUV) light with matter is a critical step in EUV lithographic processes, and optimization of the optical material properties of all elements in the lithographic chain (from optical coatings and pellicles to photoresists) is crucial to harnessing the full power of EUV lithography. To optimize these materials, accurate measurements of EUV absorption and reflection are needed to extract the corresponding actinic optical properties and structural parameters. Here, we report on actinic EUV metrology-based absorption and reflection measurements enabled by coherent table-top EUV sources based on high-harmonic generation. We demonstrate the capabilities and flexibility of our setup with measurements on crystalline films, photoresist systems, and carbon nanotube membranes and provide extracted optical parameters, absorption kinetics, and 2D transmission maps, respectively. These results showcase the power of lab-based actinic inspection methods based on compact, coherent EUV sources for providing crucial data for material optimization and lithographic simulation.