Fabrication of three dimensional structures for an UV curable nanoimprint lithography mold using variable dose control with critical-energy electron beam exposure

Abstract

In three dimensional (3D) printing the most challenging aspect is in the mold making process. The authors have developed a process for making 3D structures in a simple two-step process. The 3D profiles are created on a negative tone photoresist using electron beam lithography with variable dose and critical-energy electron beam exposure. Resist contrast profiles have been obtained with a negative tone photoresist from Microresist (ma-N2403) and subsequently have been utilized as the 3D masking layer. The 3D patterns have been transferred into a quartz mold by single-step reactive ion etching (RIE) with suitable resist-to-substrate selectivity. The precision of the fabricated structures is important, especially for micro-optic devices. Surface roughness below 2nm has been achieved when the RIE process pressure is lower than 6mTorr. The differences between intended and final dimensions are also analyzed. By employing this technique, complex structures for 3D quartz molds can be fabricated with simplified steps.