Copper chemical mechanical polishing using a slurry-free technique

A study of the chemical mechanical polishing (CMP) of thin copper films usi ng fixed-abrasive pads is presented. The composition of the polishing solut ion is optimized by investigating the impact of both the oxidizer concentra tion and the pH of the solution on the polishing characteristics of copper. The resulting optimum polishing solution gives a high removal rate ( > 300 nm/min), good uniformity (standard deviation 3%) and a very high selectivi ty for the oxide removal rate (> 100:1). The dependence of the removal rate of copper on the geometry is studied for different feature sizes and vario us pattern densities. The geometry dependency is considerably less in the s lurry-free process than in the conventional slurry CMP. This is crucial for copper CMP because it helps to minimize the overpolishing time and consequ ently the amount of dishing. Damascene copper structures have been successf ully made by polishing patterned test wafers. The amount of dishing of the copper lines is smaller than that for the conventional polishing technique. The polished wafers were easily cleaned; a standard rinsing step seemed to be sufficient. (C) 2001 Elsevier Science BN. All rights reserved.