Scaling and readiness of underlayers for high-NA EUV lithography

With the introduction of high-numerical aperture extreme ultraviolet lithography, the thickness of layers in the lithographic stack will scale owing to reduced depth of focus and etch budget. While several studies have explored the impact of thickness scaling on photoresists, the consequence of thinning down underlayers for extreme ultraviolet (EUV) lithography has been scarcely investigated. In this work we assessed the readiness of nine state-of-the-art underlayers, spin-on and dry deposited, scaled in thickness series down to 4 nm nominal (~3 nm actual). Dose-to-size and exposure latitude changed by less than 5 % when thickness of underlayer was decreased. In summary, most of EUV underlayers investigated in this work showed minimal impact on the physical and chemical properties as well as the patterning performance when scaling in view of high numerical aperture extreme ultraviolet lithography.