Chemical-Mechanical Polishing of Wafers with Copper Film by Nano-Scale Abrasives

In this paper, experiments are designed and conducted to investigate the effects of abrasive size for Chemical-Mechanical Polishing (CMP) of copper film under different additives in HNO3-based polishing slurries. Alumina modified colloidal silica 100S (phi 26nm), 200S (phi 40nm) and Al-2-O-3 (phi 90nm), are used as polishing abrasives in this study. Experiments showed the following results. (1) With citric acid as an additive to slurry, the removal rate (RR) of the CMP process increases with abrasive size. Surface quality, however, becomes worse at the same time. (2) With benzotriazole (BTA) as an additive, RR of the slurry with Al2O3 powder is slightly higher but it does not increase with the abrasive size in general. Surface quality tends to be worse at the same time though it is not as strong as that in the slurry with citric acid as the additive. (3) The size effect of abrasive on RR with citric acid as additive is stronger than that with BTA.