Study of Non-Preston Phenomena Induced from the Passivated Additives in Copper CMP

The requirement for the superplanarization of interconnect nanotechnology beyond poses an urgent need to study the complicated behavior of copper CMP. It is common practice in advanced copper chemical mechanical planarization (CMP) polishing to add the inhibitor into the slurry to keep the copper surface perfect and smooth and to protect the copper surface from corrosion. It is beneficial to have the polishing pressure cushion between abrasives and wafer under the different pattern features and is most important to overcome the planarization limitation. This study describes the behavior of non-Preston's phenomena under the passivated additives (inhibitors) and develops a model to explain the mechanism of the passivated-and-oxidated kinetics with non-Preston's polishing, which explains the mechanism of copper surface reactions during polishing. Furthermore, our model shows that the three regions are due to different relationships between removal rate and polishing pressure. Three regions are characterized as the threshold, linear, and saturated zones, which are governed by the chemical etching, the depth of abrasive particles indent into the copper oxide, and the oxidation rate, respectively. Most of all, the removal rate change can be simulated and predicted by the ratio between the inhibitor and oxidizer concentrations. Therefore, this study does not only contribute the understanding of the non-Preston's behavior but also provides the model under the assumption of the sequential stacked films of passivation and oxide films on the copper surface. The potentiodynamic methods are employed to test the assumption used in the mechanism and model.