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Extreme ultraviolet mask substrate surface roughness effects on lithographic patterning J. Vac. Sci. Technol. B 28, C6E23 (2010); 10.1116/1.3502436 Protection and reduction of surface oxidation of Mo ∕ Si multilayers for extreme ultraviolet lithography projection optics by control of hydrocarbon gas atmosphere

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Mask blank inspection is a critical issue in EUV lithography. Visible-light inspection has the advantages of a high throughput and a low tool cost, while actinic inspection potentially has a high inspection capability. The Hamamatsu Photonics Super Fine Particle Detection System, which employs dark-field scattering optics, has a high detection sensitivity and throughput. It is able to detect PSL spheres with diameters below 50 nm on a Si substrate. So, we tried using it to detect fine PSL spheres on Mo/Si multilayer mask blanks. 60-nm PSL spheres were detected, but noise arising from the surface roughness of the Mo/Si multilayer prevented the accurate detection of PSL spheres with diameters of less than 50 nm. Thus, it is important to reduce the surface roughness of the multilayer in order to improve the inspection capability of visible-light inspection systems.

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