Focused Ion Beam Fabrication of Fine Metal Structures by Oxide Resists

Abstract

It is demonstrated that 100-nm-width line patterns of refractory metals can be formed on Si substrates by a maskless process based on the combination of a focused ion beam (FIB) and high-contrast oxide resists. Thin amorphous films of MoO₃ were deposited by electron beam or resistance-heated evaporation onto Si wafers, and were exposed to 30∼50 keV Ga⁺ FIB. Fine line patterns of MoO₃, developed by chemical etching after line exposure, were reduced to Mo by heat treatment in H₂ atmosphere. The linewidth before and after reduction was measured as a function of the ion dose. A study of the beam profile of the FIB indicates that the limiting resolution of this resist work is determined by the FIB diameter.