Effect of mechanical polishing on copper in electrochemical-mechanical polishing

Electrochemical-mechanical polishing (ECMP) integrates electrochemistry with chemical-mechanical polishing (CMP) which is assisted by chemical reaction to remove surface material of wafer. The application of an additional electrical potential in ECMP intensifies chemical reaction to produce better material removal rate (MMR) and planarization of wafer compared with CMP. For copper wafer, the potentiodynamic polarization method is usually used to understand copper corrosion mechanism and susceptibility with the polishing slurry and it is very important index of voltage potential for copper-film polishing with ECMP system (Fig. 1). In this study, we use abrasive-free slurry for copper-ECMP system and aim at investigating the effect of mechanical polishing caused by pad on copper-film MRR (Fig. 2 and 3) and surface image (Fig. 4) accompanying with different voltage potential. The experimental results confirm the mechanical and electrochemical driving-force for copper-film polishing in ECMP system.