A Three‐Dimensional Ultraviolet Curable Nanoimprint Lithography (3D UV‐NIL)

Abstract

This study investigates the use of ultraviolet nanoimprint lithography (UV‐NIL) for patterning three dimensional (3D) structures. Generating the 3D structures is a challenging task especially on an insulating substrate such as quartz. The quartz transparent mold is essential for the UV‐NIL process. The 3D profiles were created on the negative tone photoresist, Microresist ma‐N2403 using a Raith‐ 150 electron beam lithography (EBL) tool in a single step variable dose controlled exposure. The developed 3D resist profiles were subsequently utilised as the 3D masking layer. The 3D patterns were transferred into the quartz mold substrates by a single‐step reactive ion etching (RIE). Surface roughness below 2 nm has been achieved when the RIE process pressure is lower than 6 mTorr. The replication of the 3D mold structure by using the UV‐NIL technique requires a two‐step imprint process. The master mold profile was replicated onto a Microresist Ormocomp US‐S4 resist on the first imprint to become the soft mold. The cured Ormocomp soft mold, was subsequently used as a mold for replicating the 3D pattern structures on the Microresist mr‐UVCur06 resist in the second imprint step to create a positive replica of the original mold. A test pattern of a 3D pyramid‐shaped array with multilevel features was successfully replicated using this technique. This paper reviews our recent work on 3D UVNIL mold making and imprinting processes.