Negative electron-beam nanofabrication resist using acid-catalyzed protection of polyphenol provided by phenylcarbinol

A high-resolution negative electron-beam (EB) lithography resist based on an acid-catalyzed protection reaction of a polyphenol enabled by a phenylcarbinol has been developed for nanofabrication. Polyphenol-3, which is synthesized by condensation of $α,α,α′$-tris(4-hydroxyphenyl)1-ethyl-4-isopropylbenzene with m-cresol, was selected as the most suitable matrix resin for the resist. 1,3,5-tris[1-(1-hydroxyethyl)]benzene (Triol-2) was found to be the best protection reagent among the six phenylcarbinols evaluated. Line-and-space patterns of 80 nm with edge roughness of less than 10 nm were delineated by using a resist composed of Triol-2, diphenyliodonium triflate, and polyphenol-3 in conjunction with an EB writer (20 μC/cm² at 50 kV). Spectroscopic studies clearly showed that the acid-catalyzed protection reaction of the polyphenol brought about by Triol-2 is responsible for the resist insolubilization.