Inspecting EUV mask blanks with a 193-nm system

Data and simulation results characterizing the capability of a DUV system to inspect EUV mask blanks and substrates are reported. Phase defects and particles on multilayer (ML) surfaces, ARC-coated absorber, and substrate material are considered. In addition to the previously reported results of inspecting phase defects on multilayer surfaces, phase defects on a quartz substrate surface are shown. The principle of phase detection is described. Simulations show that the 22-nm node requirement for phase defect detection should be met, assuming a reduction in the multilayer roughness. Initial inspections of deposited SiO2 spheres show sensitivities of at least 40 nm on ML and quartz; however, the availability of calibrated spheres of smaller diameters has limited testing below this value. Simulation results show relative sensitivities for detecting SiO2 spheres of different diameters on various EUV materials.