Ion etching of ultranarrow structures

We describe the use of Polymethylmethacrylate as both electron beam sensitive resist and ion etch mask for high-resolution pattern transfer. By using high-resolution electron beam lithography, chemically assisted ion beam etching, and in-situ metallization, we have fabricated ultra-narrow gates with lateral dimensions below 20 nm, spaced with < 50 nm pitch on high mobility 2D electron gas material. This technique, which is thought to provide extremely small lateral electron depletion lengths and well defined confienement potentials, allows us to produce new and more complicated structures for the study of quantum transport.