Chemical roles on Cu-slurry interface during copper chemical mechanical planarization

In order to optimize the existing slurry for low down-pressure chemical mechanical polishing/planarization (CMP), copper CMP was conducted in H2O2 based slurries with benzotriazole (BTA) and glycine at different pH values. The film composition was investigated by the Nano Hardness Tester and XPS tests. Furthermore, the film structure forming on the copper surface at different pH values was investigated by adopting electrochemical impedance spectroscopy (EIS) technology. In the acidic slurry, discontinuous and porous BTA film covering the Cu/Cu2O surface enhanced the mechanical effect during Cu CMP process, resulted in highest CMP removal rate. In neutral slurry, the lowest CMP removal rate and static corrosion rate were resulted from compacted passivation film on the copper surface. In the alkaline slurry, the mechanical effect was limited by the rapid chemical dissolution. The results will benefit optimization of the slurry and operate conditions during low down-pressure CMP process.