Characterization of Cu chemical mechanical polishing by electrochemical investigations

In order to investigate the chemical etching and passivating effects of Cu in the polishing slurry and to give some insights of the polishing process itself, the influence of the oxidizing agent (H2O2) was studied. The interaction between the Cu surface and the slurry was investigated by potentiodynamic measurements applied during the polishing process as well as under static conditions. It was shown that with increasing H2O2 concentration the wet etch rate and also the polish rate of Cu decreases. That can be explained by changes in the structure of the passivating layer and the dominating role of the dynamic repassivation during polishing. In addition, W-TI used as a barrier/adhesion layer in Cu chemical mechanical polishing (CMP) was also investigated in terms of electrochemical interaction with the polishing slurry and Cu. The observed acceleration of the W-Ti polish rate in the presence of Cu ions is caused by the galvanic interaction between Cu and W-Ti.