Electron Beam Lithography on Irregular Surface Using Grafted PMMA Monolayer as Resist

Abstract

An electron beam resist is usually coated by conventional coating methods such as spin‐coating, which cannot be reliably applied on irregular surfaces. Here, it is demonstrated that a monolayer resist can be grafted on nonflat surface to enable nanofabrication on it. As a proof‐of‐concept of patterning on irregular surfaces, poly(methyl methacrylate) (contains 1.6% methacrylic acid that has the carboxyl group needed for grafting) is chosen and is grafted on irregular surfaces by thermal treatment which induces a chemical reaction of the carboxyl group with the hydroxyl group on substrate. Subsequently, nanostructures are patterned by electron beam lithography on this monolayer resist grafted on nonflat surface such as atomic force mocroscopy (AFM) cantilevers, and then the patterns are transferred to the layer underneath. A high resolution of 30 nm line width is achieved using this monolayer resist. Nanofabrication on irregular surfaces may have applications in the fields of tip‐enhanced Raman spectroscopy for chemical analysis and lab‐on‐fiber technology for sensor applications.