Enhancing aspect profile of half-pitch 32 nm and 22 nm lithography with plasmonic cavity lens

Poor aspect profiles of plasmonic lithography patterns are suffering from evanescent waves' scattering loss in metal films and decaying exposure in photoresist. To address this issue, we experimentally report plasmonic cavity lens to enhance aspect profile and resolution of plasmonic lithography. The profile depth of half-pitch (hp) 32 nm resist patterns is experimentally improved up to 23 nm, exceeding in the reported sub-10 nm photoresist depth. The resist patterns are then transferred to bottom resist patterns with 80 nm depth using hard-mask technology and etching steps. The resolution of plasmonic cavity lens up to hp 22 nm is experimentally demonstrated. The enhancement of the aspect profile and resolution is mainly attributed to evanescent waves amplifying from the bottom silver layer and scattering loss reduction with smooth silver films in plasmonic cavity lens. Further, theoretical near-field exposure model is utilized to evaluate aspect profile with plasmonic cavity lens and well illustrates the experimental results.