INTERFACE STUDIES OF TUNGSTEN NITRIDE AND TITANIUM NITRIDE COMPOSITE METAL GATE ELECTRODES WITH THIN DIELECTRIC LAYERS

Interface formation between reactively sputtered tungsten nitride (WNx ) or titanium nitride (TiNx) metallic films and thermally grown silico n dioxide (SiO2) layers is studied by interrupted growth with on-line Auger electron spectroscopy. For both composite metals, growth proceed s directly without a metal precursor layer. The chemical stability of these WNx/SiO2 and TiNx/SiO2 interfaces is investigated by rapid therm al annealing up to 850 degrees C. The WNx/SiO2 interface is stable up to 650 degrees C while TiNx/SiO2 is stable below 850 degrees C. Metal- oxide-semiconductor capacitors have been fabricated with WNx and TiNx gates and 7.5 nm thick thermal oxide gate dielectrics with interface t rap densities, D-it<2X10(11) cm(-2)eV(-1). Capacitance-voltage and cur rent-voltage measurements indicate the Fermi level for TiNx lies near midgap in Si, while for WNx it lies closer to the valence band. (C) 19 98 American Vacuum Society.