Direct copper electrodeposition on novel CoMo diffusion barrier

In this work, an alkaline electrolyte containing copper sulfate and ethanediamine (En) as ligand was used for direct Cu electrodeposition on novel alloy barrier Co_xMo_y films and comparison was made between alkaline bath and H₂SO₄-CuSO4 acidic bath. In alkaline bath, the nucleation density of Cu on Co₁Mo₃ is much higher than that in acidic bath. It is found that the Cu island density increases and the surface roughness decreases with the higher content of Co in Co_xMo_y films. Results show that adhesion between Cu and Co is better than that between Cu and Mo, which affects initial nucleation behavior and surface roughness of the deposited Cu films. Uniform and conformal copper was successfully electroplated on 5 nm Co1Mo3 layers covered patterned wafers in alkaline bath without additives.