ELECTRON-BEAM DOT LITHOGRAPHY FOR NANOMETER-SCALE TUNNEL-JUNCTIONS USING A DOUBLE-LAYERED INORGANIC RESIST

We have developed a metal-insulator-metal (MIM) junction fabrication p rocess using top two layers of a separated by implanted oxygen substra te as a double-layered electron beam resist and a dot-exposure method in order to simplify the process sequence and fabricate smaller MIM ju nctions than those made by the conventional multiple-angle deposition- oxidation-deposition method. The diameter of the dot openings of a sus pended mask tends to saturate with an increase in the exposed dose and is independent of the dot interval. We were able to successfully fabr icate a series of Ti dots with minimum diameters of about 20 nm and mu ch smaller junctions than the minimum dot size of 20 nm by an inorgani c resist lift-off process. A one-dimensional array of six MIM junction s fabricated by this method showed typical current-voltage characteris tics of tunnel junctions at room temperature. (C) 1997 American Vacuum Society.