This work investigates the effects of Ar+ ion implantation through a multilayer structure of SiO2(100 nm)/Mg(20 nm)/Cu/SiO2/Si on the oxidation resistance of Cu films. Experimental results indicate that implantation at 130 keV to a dose of 5 X 10(15) cm(-2) significantly enhances the oxidation resistance at temperatures up to 375 degrees C. At this energy, a small number of Mg atoms are knocked out, leading to formation of an impervious MgO barrier layer on the Cu surface, which effectively suppresses the oxidizing diffusion paths.