Effect of slurry components on chemical mechanical polishing of copper at low down pressure and a chemical kinetics model

The practical use of low dielectric constant materials as inter-layer dielectrics is driving the demand for copper chemical mechanical polishing (CMP) at low down pressure, which is a challenge for the traditional CMP technology. To solve this issue, it is necessary to develop a chemically dominant CMP process at low down pressure. The chemical oxidation and dissolution of the oxidized copper are more important than mechanical. In this paper, the ingredient and prescription of slurry is found, which is used to achieve high surface removal rates and certain Within-Wafer Non-Uniformity at a down pressure of 4.3 kPa. The CMP slurry contains silica sols, H2O2 and chelating agent. A model of copper CMP at low down pressure based on the methods of chemical kinetics and oxidation reaction is presented. The model prediction trends are consistent with the experimental data.