Factors affecting passivation and resistivity of Cu(Mg) alloy film

We have investigated the variables affecting passivation and resistivities of Cu alloy, which was sputter prepared from a Cu(6 at.%Mg) target. The results show that oxidation of Cu(Mg) alloy includes the surface segregation of Mg and its preferential oxidation. Sufficient surface segregation of Mg is necessary to form the high quality, protective MgO layer on the surface. The interfacial oxide layer produced from the reaction of Mg and SiO2 does not serve as a barrier against Mg diffusion, thereby the generation of free Si seems to continue until Mg is exhausted in copper. Therefore, lowering the contents of Mg in copper is required to reduce the resistivity of Cu(Mg) alloy. In-situ heating of substrate is very effective to reduce the Mg contents in copper alloy and to enhance the surface segregation of Mg, thereby facilitating the passivation of Cu(Mg) alloy with the low resistivity, especially during the low temperature oxidation.