Effect of slurry viscosity modification on oxide and tungsten CMP

Abstract

Chemical mechanical polishing (CMP) of semiconductor substrates is a complex phenomenon that involved chemical and mechanical interactions between substrate material, slurry and pad. The effect of the physical properties of the slurry on the polishing rates is not very well understood. The rheological properties of polishing slurries affect material removal rate and surface quality of the semiconductor wafers. In this work, we have studied the effect of changing viscosity of a commercial colloidal silica-based slurry on removal rate. The pad material selected was a commercial pad. The results show that the effect of viscosity modifiers is very different for oxide and tungsten CMP. This can be related to the fundamental difference in the mechanism of material removal in the two cases. We have discussed these viscosity effects in relation to the mechanisms of materials removal pertaining to both oxide and metal CMP.