Effects of oxidants on the removal of tungsten in CMP process

The effects of oxidants on tungsten chemical mechanical planarization (CMP) process were investigated using two different oxidants, hydrogen peroxide and ferric nitrate. The electrochemical redox properties of surface layer were characterized with potentiodynamic polarization test and resulting microstructural and chemical states of the surface layer were characterized with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) during CMP under different slurry chemicals. According to the analysis, the oxidation state and microstructure of surface layer were strongly influenced by the chemical composition of slurry. Moreover, the oxidation kinetics and resulting chemical state of oxide layer played critical roles in determining the overall CMP performance.