50-nm Metal Line Fabrication by Focused Ion Beam and Oxide Resists

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Abstract
Ultrafine patterning of refractory metals has been studied by the use of focused ion beam (FIB) and oxide resists. Thin amorphous films of MoO3 and WO3 were deposited by electron beam evaporation onto Si wafers, and were exposed to a 50 keV Ga+ FIB. Developed resist patterns were directly reduced to Mo and W by heat treatment in H2 gas atmosphere. The linewidth before and after reduction was measured as a function of the line dose. It is demonstrated that from a bilayer resist MoO3/WO3, a 50 nm refractory metal line can be controllably fabricated without any other complicated processes. Some information about the electrical properties of the reduced patterns is also presented.