The influence of pH and H₂O₂ on surface quality and material removal rate during W-CMP

In the chemical mechanical polishing (CMP) process, chemical action is generally determined by pH regulator and oxidant in the polishing slurry. In this paper, tungsten (W) polished by CMP was examined, and the material removal mechanism was discussed. The influence of pH values and hydrogen peroxide (H2O2) concentrations on surface quality and material removal rate (MRR) were closely investigated. The MRR obtained from the CMP test indicates that the removal rate of W by the H2O2 oxidant reaches 34.10 & mu;m/h under acidic pH conditions and the H2O2 oxidant improves the polishing rate of W. The obtained potentiodynamic polarization results show that the passivation layer formed under the H2O2 action cannot prevent the further corrosion of the slurry to the sample, but W can stably generate a tungsten trioxide (WO3) passivation layer under acidic conditions. XPS data confirm that the formation and dissolution of tungsten oxide passivation layers with different compositions are the main causes of these results. By analyzing the different morphologies (corrosion pits, grain boundaries, etc.) formed after tungsten chemical mechanical polishing (W-CMP), the deformation and removal mechanisms involved in the process are more deliberately exposed. This study enriches the understanding of the corrosion damage and material removal mechanisms of pure tungsten during CMP and contributes to the efficient and high-precision manufacturing of W components.