EFFECTS OF THE ADDITION OF SMALL AMOUNTS OF AL TO COPPER - CORROSION, RESISTIVITY, ADHESION, MORPHOLOGY, AND DIFFUSION

The properties of thin films of Cu with 1 at. % Al are explored. As-deposited films of Cu(1 at. % A1) oxidize orders of magnitude more slowly than do those of pure Cu. After Cu(1 at. % A1) films are annealed in Ar at 400-degrees-C for 30 min, very thin protective layers of aluminum oxide form on the surface. These thin oxide layers stop further oxidation of the copper. Cu(1 at. % A1) films also adhere better to SiO2 than do films of pure copper. Unlike pure Cu, films of Cu(1 at. % Al) remain microscopically smooth after anneals at temperatures up to 700-degrees-C. In addition, Cu(1 at. % Al) films show no diffusion of Cu (as measured by Rutherford backscattering spectroscopy) into SiO2 at temperatures up to 700-degrees-C. The addition of Al to Cu does increase its resistivity by about 2 muOMEGA cm per 1 at. % Al, but a possible procedure to avoid this problem is proposed.