Effect of Nano-MnO2 Abrasive in Chemical Mechanical Polishing of Tungsten for Integrated Circuits

At present, it is difficult for the common abrasives used in the chemical mechanical polishing (CMP) of tungsten (W) in integrated circuits to simultaneously achieve a higher W removal rate and excellent surface quality. The effect of nano-manganese dioxide (MnO2) in W CMP was proposed as an abrasive, an oxidizing agent, and a catalyst for Fenton-like reaction simultaneously through the chemical-mechanical synergism of MnO2. The possibility of the redox between MnO2 and W was verified by X-ray photoelectron spectroscopy, electrochemical and thermodynamic calculations. The density functional theory calculations indicated that the theoretical oxidation ability of MnO2 as an oxidant for W exceeded that of hydrogen peroxide (H2O2) and hydroxyl radical (·OH). The generation of the Fenton-like reaction was deduced, which further enhanced the oxidation ability of the W slurry. CMP experiments demonstrated that the W removal rate (4753 Å min−1) of the slurry with 0.8 wt% MnO2 abrasive was 2.75 times than that with common silica abrasive under the same concentration. The surface roughness (0.866 nm) was decreased by 37.7% compared with silica abrasive. The theoretical insights served as a foundation for the deliberate selection of abrasives within W slurry applications.