Chemical-Mechanical Polishing of Copper in Glycerol Based Slurries

The development of a reliable/reproducible chemical-mechanical polishing (CMP) process to planarize and define copper using a dual damascene approach is essential for introducing copper as the interconnection metal. In this paper we present results of a new polishing slurry containing glycerol and Al2O3 abrasive. The slurry is a near-neutral medium and does not have the effect of acidic or basic slurries on copper. The effect of glycerol concentration and the abrasive size on the CMP behavior is investigated. The changes in the slurry temperature, pH, viscosity, dielectric constant and surface tension were examined as a function of the glycerol concentration. The results, indicating a strong dependence on both the glycerol concentration and the abrasive size, are explained on the basis of viscosity and dielectric constant of the solution and the van der waal forces and the electrostatic repulsion between the particles.