Chemical mechanical polishing of copper for multilevel metallization

A systematic study of Cu CMP in terms of process parameters has been performed. Correlations were found between the processing conditions and the across-wafer nonuniformity which is a critical aspect of the planarization process. Higher polish pressure and lower velocity during CMP tend to increase the center-to-edge variation of the removal rate. Polishing blanket Cu films, an across-wafer nonuniformity less than 5% has been achieved. We successfully demonstrate a process to polish CuW-Ti on patterned SiO2 films and stop at the dielectric in order to form Cu lines. We have examined the effects of Cu dishing and SiO2 thinning which lead to deviation of the Cu line thickness. Both were found to be sensitive to the pattern geometry and the overpolishing time. Cu dishing is affected by the line width and line space, SiO2 thinning depends only on the line space.