Study on the Mechanisms of Chemical Mechanical Polishing on Copper and Aluminum Surfaces Employing In Situ Infrared Spectroscopy

Abstract

The mechanisms of chemical mechanical polishing (CMP) on copper (Cu) and aluminum (Al) surfaces have been studied by in situ infrared reflection absorption spectroscopy (IR-RAS). The effect of the oxidant addition to the slurry was first investigated on the Cu surface. Based on the IR-RAS results of the polishing rates and the oxidation reduction potentials (ORP) of the Cu surfaces in the slurries, it was presumed that the cupric oxide (CuO) was very fragile, thereby being removed just after its growth on the Cu surface during CMP. Indeed, a 200-nm-thick CuO film grown on the Cu surface was completely removed after 0.5 min polishing. Hence, the CuO growth on the Cu surface is essential for a high rate Cu polishing. In the case of Al CMP, there was no significant difference between the polishing rates for the slurries with and without the oxidant addition compared with the case of Cu CMP. This was considered to be due to the passivation by a chemically stable and mechanically firm Al oxide on the surface during CMP. Thus, the polishing parameters which contribute to the removal of Al oxide are important for a high polishing rate.