Cation Effect on Copper Chemical Mechanical Polishing

We examine the effect of cations in solutions containing benzotriazole (BTA) and H₂O₂ on copper chemical mechanical polishing (CMP). On the base of atomic force microscopy (AFM) and material removal rate (MRR) results, it is found that ammonia shows the highest MRR as well as good surface after CMP, while KOH demonstrates the worst performance. These results reveal a mechanism that small molecules with lone-pairs rather than molecules with steric effect and common inorganic cations are better for copper CMP process, which is indirectly confirmed by open circuit potential (OCP).