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

Abstract

Abstract In chemical mechanical polishing (CMP) process, chemical action is generally determined by pH regulator and oxidant in the polishing slurry. In this paper, tungsten was polished by CMP, and the material removal mechanism was discussed. The influence of pH values and H2O2 concentrations on surface quality and material removal rate (MRR) were studied deeply. The oxidation and dissolution kinetics of tungsten/tungsten oxide (W/WOx) during CMP process were investigated by electrochemical analysis and XPS. In addition, the microstructure of tungsten surface and its elemental composition and electronic state were also analyzed by SEM, white light interference and other characterization methods. Results reveal that tungsten has the best passivation effect at acidic pH, and the surface roughness increases with the increase of pH value, while the addition of H2O2 will deteriorate the surface quality of tungsten and improve the MRR. Besides, the different morphologies (corrosion pits, grain boundaries, etc.) formed after W-CMP indicate that the material removal mechanism is related to the composition of slurry.