Effect of mechanical factor in uniformity for electrochemical mechanical planarization

Since copper (Cu) electrochemical mechanical planarization (ECMP) process is both a mechanical and electrochemical process, a polymeric pad must have mechanical integrity and chemical resistance to survive the rigors of polishing. Mechanically, a polishing pad should have acceptable levels of hardness and modulus, and good abrasion resistance to endure the Cu ECMP process. Chemically, a polishing pad should be able to survive the aggressive electrolyte chemistries, which include either highly alkaline, or high acidic electrolyte. Therefore, the characteristics of the polishing pad have been measured and evaluated. Although the material removal rate (MRR) is proportional to the current density of the Cu ECMP process, the planarization and uniformity in the wafer level are poor. To improve planarization of the wafer level, the effect of the abrasive is evaluated, with respect to the planarization and uniformity of the wafer and the abrasive properties of the electrolyte. In this study, the concentration of the abrasive (silica; SiO2) in the electrolyte with H3PO4 6 wt%, H2O2 0.5 wt%, and BTA 0.5 wt%, glycine 0.5 wt% and citric ammonium 5 wt% should be above 10 vol%.