OXIDATION CHARACTERISTICS OF AL-TA THIN ALLOY-FILMS AS A PASSIVATION LAYER ON CU

The oxidation characteristics of Al and Al-Ta alloy films (500 Angstro m) deposited as a passivation layer on Cu have been examined by depth profiling using Anger electron spectroscopy and X-ray photoelectron sp ectroscopy. Although alloying between Al and On takes place, the Al fi lms prevent the oxidation of Cu up to the oxidation temperature of sim ilar to 300 degrees C for 1 h in air, at which the surface-oxidized Al 2O3 layer maintains the self-passivating ability. At more elevated oxi dation temperatures, the further oxidation of Al and the formation of CuO in the Al-On alloy layer just beneath the oxide layer are confirme d to occur. On the contrary, the Al-Ta alloy films completely protect the Cu layer from oxidation even after oxidation at 500 degrees C for 1 h in air. This is achieved due to the formation of the Ta buffer lay er which separates the Cu layer from the surface-oxidized one, which i s formed by the preferential oxidation of Al and the rejection of Cu f rom the Al2O3 during the oxidation.