Study of novel chelator and 1, 2, 4-triazole on cobalt corrosion and Co/Cu surface finishing in barrier CMP

Abstract

Galvanic corrosion between cobalt (Co) and copper (Cu) and surface finishing in barrier chemical mechanic polishing (CMP) are two research hotspots in 14 nm and sub integrated circuit technology node. This paper discusses the effect of potassium hydrogen phthalate (KHP) chelator and 1, 2, 4-triazole (TAZ) inhibitor on cobalt corrosion and Co/Cu surface finishing in colloidal silica based slurry at pH 10. FTIR results show that KHP can chelate with cobalt and copper ions in the form of chelating bidentate bridge. The potentiodynamic polarization and SEM results reveal that cobalt corrosion is reduced with the synergistic effect of H2O2 and KHP; the addition of TAZ is beneficial for inhibiting the corrosion of cobalt and improving the surface roughness of Co/Cu. Meanwhile, the mechanism of cobalt corrosion is explored by X-ray photoelectron spectroscopy (XPS). An optimized colloidal silica based slurry containing KHP and TAZ obtained an acceptable corrosion potential gap (10 mV) and desirable removal rate selectivity to Co/Cu (0.76); low surface roughness (Co:Ra 1.70 nm, Cu:Ra 2.74 nm) with Co and Cu roughness reduction about 71% and 75%, respectively.