Annealed thin films of Cu/Mg/SiO2 are studied as possible conductors for microelectronics. Rutherford backscattering and sheet resistance measurements show that vacuum annealing at 350-400 degrees C results in transport of Mg from the buried layer to the surface of the copper where it reacts with impurities to form a thin surface layer of MgO. Such films are then exceedingly resistant to further oxidation. These films have a resistivity of 2.0 mu Omega-cm and are adherent to the SiO2 substrate. However, at temperatures 450-500 degrees C there is a reaction between Mg and the SiO2 substrate releasing free Si into the copper.