Effects of Chemical Additives of CMP Slurry on Surface Mechanical Characteristics and Material Removal of Copper

Investigations were performed to study the effects of H₂O₂ as oxidant, glycine as complexing agent, and benzotriazole (BTA) as inhibitor on surface mechanical characteristics and material removal of copper. Etch rates and surface roughness of Cu samples were measured in the presence of these chemicals at pH 4 or pH 10 under static conditions. Scanning electron microscopy images revealed that the surface of etched copper samples became layered and porous. Scratching experiments were carried out on the etched surface to investigate effects of these chemicals on mechanical removal of copper using atomic force microscopy. It was observed that the scratched depth of these etched Cu samples was higher than that of Cu metal. The addition of glycine enhanced chemical dissolution and mechanical removal greatly. However, the further addition of BTA made both of them decreased, suggesting BTA not only inhibitor of chemical dissolution, but also inhibitor of mechanical removal. In most cases, the measured hardness values of etched copper surface were slightly higher than that of Cu metal. These results indicated that changes of surface structure were the primary reason for increase of mechanical removal of copper, but not changes of copper surface nanohardness.