CD metrology for EUV resist using high-voltage CD-SEM: shrinkage, image sharpness, repeatability, and line edge roughness

摘要

Background: Extreme ultraviolet (EUV) lithography was introduced for the high-volume manufacturing of state-of-the-art semiconductor devices in 2019. One of the issues for the CD metrology of an EUV resist pattern is the resist shrinkage since the ratio of the shrinkage to the CD increases in EUV lithography compared with that in immersion argon fluoride lithography. Aim: A CD-SEM metrology for an EUV resist that was compatible with low shrinkage and high spatial resolution was investigated by using primary electrons (PEs) with high energy. Approach: The shrinkage, image sharpness, repeatability, and line edge roughness (LER) were evaluated for the EUV resist using PEs with energies of 200, 800, and 4000 eV. Results: The smallest shrinkage was obtained under the conditions of the repeatability from 0.15 to 0.22 nm by using PEs with an energy of 4000 eV. Moreover, the LERs obtained for 200, 800, and 4000 eV were almost the same. Conclusions: While the electron irradiation damage for an under layer and the amount of shrinkage depending on pattern size could cause issues, the high voltage CD-SEM provides a solution to CD monitoring in high-volume manufacturing using EUV lithography.