Chemical-mechanical planarization of Cu and Ta

As device dimensions continue to shrink, multilevel(>8) interconnects are r equired to efficiently implement complex logic device designs in a single s ilicon chip. When the number of metal interconnect levels increases, the av ailable depth-of-focus budget of lithographic tools imposes stringent plana rity requirements that can only be met currently by chemical-mechanical pla narization (CMP). Improved speed and performance are extracted from such de vices by switching to copper from Al/Cu as the interconnect metal and to lo wer dielectric constant inner layers. Use of copper also requires the simul taneous introduction of diffusion-barrier/ adhesion-promotion layers of tan talum or TaN. This paper reviews some of the recent advances in the fundame ntal understanding of the interplay between the mechanical and chemical com ponents of the material-removal process during CMP of copper and tantalum f ilms. The emphasis will be on the role of different process variables in sl urries containing silica or alumina abrasives in hydrogen peroxide/glycine solutions.