An investigation of slurry chemistry used in chemical mechanical planarization of aluminum

Slurry chemistries for chemical mechanical planarization of aluminum were investigated by electrochemical measurements with a rotating disk electrode setup. The electrochemical measurements were accompanied by polishing of both blanket and patterned aluminum wafers. Results of these two investigations led to the development of a potassium dichromate slurry which resulted in good surface finish and acceptable removal rates. The electrochemical measurements demonstrated the formation of a passivating layer at the surface. It was observed that in addition to oxidizing agents in the slurry, it was essential to have etchants to obtain a smooth and clean surface. Also, the abrasives used were found to have a major impact on the surface finish. The slurry was successfully used in producing aluminum patterns by the Damascene process. The resulting polishing behavior of aluminum is explained by a balance between the formation of a passivating layer on the surface and dissolution of the abraded surface in the slurry volume near the surface.