Titanium is being investigated as the adhesion promoter and diffusion barrier between silicon dioxide and copper in a copper metallization scheme. Chemical-mechanical polishing (CMP) is being used to define the inlaid copper interconnections. An investigation into the CMP of titanium has revealed an interaction between the presence of copper ions in the polish slurry and the polish rate of titanium. The polish rate of titanium increases dramatically when copper ions are present in the slurry from the previous copper polish step. In this paper, we present and discuss the results of these investigations.