Nanofabrication on InP using focused ion beam lithography and Cl 2 etching: process and control

Abstract

A finely focused ion beam (FIB) of Ga + was used to write patterns with nanometer lateral dimensions on InP substrate that are covered with ultrathin oxide layers. Patterns were transferred into the substrates, several hundred nanometers deep, by Cl 2 etching to form nanostructures. Metal-organic molecular beam epitaxy (MOMBE) was employed to regrow on the patterned substrates and create fully buried quantum wire structures. Several process parameters of the FIB vacuum lithography that are essential to the control of the ultimate achievable feature size, were examined and optimized systematically. These parameters include quality of the oxide layers; energy, diameter and dose of the ion beam; rate and depth of the etching; orientation of the desired structure with respect to the substrate; and line pitch of the patterns. Under optimal process conditions, gratings with line width and spacings as small as 50 nm were fabricated.