Enhancement of Oxidation Resistance and Electrical Properties of Indium-Doped Copper Thin Films

Abstract

Copper thin films with high conductivity and good resistance to electromigration can be used in advanced electronic devices. However, the poor corrosion resistance of copper must be overcome. This work elucidates the possibility of using a self-forming passivation layer to prevent copper oxidation in lightly indium-doped copper thin films deposited directly on glass substrates and annealed under various oxygen atmospheres. The resistivity of the studied film declined gradually as the film was annealed at an elevated temperature because of the grain growth of the Cu film and the precipitation of indium from the In-doped Cu thin film, as revealed by X-ray diffraction, four-point probe measurements, and transmission electron microscopy. A copper film with high indium content exhibited superior passivation when the film was annealed in an oxygen-rich ambient, but it exhibited high resistivity because of its high indium content. The electrical and passivation properties demonstrated that indium is a promising alloying element for use in copper films for future metallization structures and thin-film transistors.