Electrochemical and mechanical characterization of surface reaction layers for copper and various CMP chemicals

Applying electrochemical and mechanical (physical) methods, we investigated the characteristics of the surface reaction layers formed on copper in various CMP chemicals. We monitored the growth of surface reaction layers via open circuit potential (OCP) changes and polarization curves obtained through in situ electrochemical observations, finding that OCP increased when polishing was stopped in quinaldic acid and BTA, indicating the formation of a passivation layer functioning as a potential barrier. We also assessed the mechanical properties of the surface layer by AFM. Based on the force curve data obtained via AFM, we estimated the thickness and modulus of the layers, using both approaching and retracting curves. We found that the copper reaction layer was stable and hard in quinaldic acid but unstable, soft and fragile in glycine, BTA and H2O2.