Scattering mask concept for ion-beam nanolithography

Abstract

In this article, we demonstrate the concept of scattering masks for ion-beam proximity lithography. In this process, stencil mask openings are fabricated with larger-than-nominal sizes and are coated with a conformal scatter layer that reduces the size of the features at the mask surface. The process reduces the complexity of etching high aspect-ratio mask openings. Printed images of masks with 100 and 40 nm circular openings, fabricated from masks with 225 nm openings, are shown. The printing process has excellent exposure latitude: less than a 20% change in critical dimension is observed for a 33% change in dose for 40 nm structures. We show that the diffuse background exposure that results from ions traversing through the scatter layer is around 0.1% of the primary exposure for a 2 μm pitch pattern.