Electron beam dot lithography for nanometer-scale tunnel junctions using a double-layered inorganic resist

Abstract

We have developed a metal–insulator–metal (MIM) junction fabrication process using top two layers of a separated by implanted oxygen substrate as a double-layered electron beam resist and a dot-exposure method in order to simplify the process sequence and fabricate smaller MIM junctions than those made by the conventional multiple-angle deposition–oxidation–deposition method. The diameter of the dot openings of a suspended mask tends to saturate with an increase in the exposed dose and is independent of the dot interval. We were able to successfully fabricate a series of Ti dots with minimum diameters of about 20 nm and much smaller junctions than the minimum dot size of 20 nm by an inorganic resist lift-off process. A one-dimensional array of six MIM junctions fabricated by this method showed typical current–voltage characteristics of tunnel junctions at room temperature.