The TiN/Ti chemical mechanical planarization (CMP) step is executed immediately following the main tungsten (W) CMP process in the contact module A2.In the preceding steps, a Ti/TiN stack was deposited to line the contact trenches, where Ti serves to getter residual oxygen and lower the metal-semiconductor contact barrier, while TiN acts as a diffusion barrier preventing WF6 from reacting with the underlying structures during W chemical vapor deposition P1.The fundamental physics of the metal-se