Effects of electrochemistry on surface roughness during chemical-mechanical polishing of copper

In this research, we investigated the electrochemical behavior of copper (Cu) surfaces during chemical-mechanical polishing (CMP) with alumina containing slurries. The variation of pH and the percent of oxidizer were tested against impressed anodic and cathodic potentials. The polarization curves as well as potential and current values were measured in order to investigate the effects of electrochemical interactions during polishing. The polishing performance was evaluated through friction, wear, and surface quality. Surface characterization was conducted using an atomic force microscope. The areas scanned contained surfaces having different post-CMP surface chemistry. In such, the electrochemical, chemical, and mechanical action could be revealed and compared in situ and simultaneously. Research results showed that in acidic environment, the low pH dominated the surface roughness over oxidizer and anodic current. At high pH, however, oxidizer and anodic current played important roles. As a result, an optimized polishing condition was proposed.