Efficient chemical mechanical polishing of W promoted by Fenton-like reaction between Cu2+ and H2O2

Abstract

The Fenton-like reaction between Cu²⁺ and H₂O₂ was employed in chemical mechanical polishing to achieve efficient and high-quality processing of tungsten. The microstructure evolution and material removal rate of tungsten during polishing process were investigated via scanning electron microscopy, X-ray photoelectron spectroscopy, ultraviolet−visible spectrophotometry, and electrochemical experiments. The passivation behavior and material removal mechanism were discussed. Results show that the use of mixed H₂O₂+Cu(NO₃)₂ oxidant can achieve higher polishing efficiency and surface quality compared with the single oxidant Cu(NO₃)₂ or H₂O₂. The increase in material removal rate is attributed to the rapid oxidation of W into WO₃ via the chemical reaction between the substrate and hydroxyl radicals produced by the Fenton-like reaction. In addition, material removal rate and static etch rate exhibit significantly different dependencies on the concentration of Cu(NO₃)₂, while the superior oxidant for achieving the balance between polishing efficiency and surface quality is 0.5 wt.% H₂O₂ +1.0 wt.% Cu(NO₃)₂.