Development of a low cost roll-to-roll nanoimprint lithography system for patterning 8-inch wide flexible substrates

Abstract

Recent developments in flexible electronics, solar cells, displays, bio-chips and wearable technology have featured various micro/nanostructures in system designs. However, fabricating these micro/nanostructures on flexible substrates using existing technology such as photolithography, electron beam lithography (EBL) and other lithography techniques is troublesome, time consuming and costly. An in-house roll-to-roll ultraviolet nanoimprint lithography (R2R-UVNIL) system was designed and fabricated as an alternative low cost and large area patterning tool. It consists of a coating unit, soft-bake unit and imprinting unit which are connected together using a series of rollers. The aim of the integrated soft-bake stage was to minimise the mould sticking issues during the continuous R2R imprinting using solvent-based resist. The assembled R2R-UVNIL system was tested with imprinting process on an untreated commercial polyethylene terephthalate (PET) film as the flexible substrate, solvent-based SU8-2002 photopolymer as the resist and PDMS soft mould as the imprinting mould. The PDMS soft mould was replicated from an EBL patterned silicon master mould. Imprinting speeds of 50 to 150 mm/min have been achieved in this work, with relatively sound replication quality and formability for patterning sub-2 µm microstructures.