The replication of three dimensional structures using UV curable nanoimprint lithography

Abstract

The 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. These transparent molds are essential for the UV-NIL process. The 3D profiles were created on the negative tone photoresist, Microresist ma-N2403 using a Raith150 electron beam lithography (EBL) tool in a single step variable dose controlled exposure. The developed 3D resist profiles subsequently were utilized as the 3D masking layer. The 3D patterns were transferred into the quartz mold substrates by a single-step reactive ion etching (RIE). 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, subsequently was 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 been replicated using this technique. The replicated 3D pattern on the resist could be utilised as the final 3D masking layer for the pattern transfer onto final substrate using RIE.