High resolution ion beam lithography at large gaps using stencil masks

Abstract

High resolution masked ion beam lithography (MIBL) is demonstrated at large mask-to-sample gaps using two new types of membrane stencil masks. Single layer Si-rich silicon nitride (SiN) membranes and Si3N4-SiO2-Si3N4 (N-O-N) sandwich structure membranes are deposited by processes which allow the stress in the films to be adjusted. Transmission holes are reactive-ion etched entirely through the membranes. This type of stencil mask virtually eliminates mask-induced scattering. Lines and spaces of 160 nm have been exposed in 0.5-μm polymethylmethacrylate (PMMA) at gaps as large as 275 μm, using 100-keV protons. Some of the stencil mask limitations are overcome by multiple exposures. The results suggest that MIBL can be an extremely high resolution proximity printing technique.