Capillary-force-induced collapse lithography for controlled plasmonic nanogap structures

Abstract

The capillary force effect is one of the most important fabrication parameters that must be considered at the micro/nanoscale because it is strong enough to deform micro/nanostructures. However, the deformation of micro/nanostructures due to such capillary forces (e.g., stiction and collapse) has been regarded as an undesirable and uncontrollable obstacle to be avoided during fabrication. Here, we present a capillary-force-induced collapse lithography (CCL) technique, which exploits the capillary force to precisely control the collapse of micro/nanostructures. CCL uses electron-beam lithography, so nanopillars with various shapes can be fabricated by precisely controlling the capillary-force-dominant cohesion process and the nanopillar-geometry-dominant collapse process by adjusting the fabrication parameters such as the development time, electron dose, and shape of the nanopillars. CCL aims to achieve sub-10-nm plasmonic nanogap structures that promote extremely strong focusing of light. CCL is a simple and straightforward method to realize such nanogap structures that are needed for further research such as on plasmonic nanosensors. Microlithography: Pioneering lithography technique for fabricating plasmonic nano-gap structuresAn innovative technique-capillary-force-induced collapse lithography (CCL)-has been developed to easily fabricate plasmonic nano-gap structures, which with a nano-gap of <10nm are able to compress light and dramatically increase the intensity of electric fields. Deformation of nanostructures due to capillary forces (e.g., collapse) has been a considerable obstacle in fabricating plasmonic nano-gap structures. However, a team headed by Junsuk Rho at Pohang University of Science and Technology (POSTECH), Republic of Korea developed CCL, which exploits capillary forces to precisely control the collapse of the nanostructures. CCL allows the easy fabrication of sub-10-nm plasmonic nano-gap structures, which are difficult to achieve with conventional lithography. The authors believe that their simple, straightforward CCL technique will pave the way toward nano-manufacturing technology that enables the effective production of sub-10-nm plasmonic nano-gap structures on demand.