Development of abrasive-free copper cmp process ? reduction of copper residue using randomly formed polyurethane pad

Abrasive free polishing (AFP) for copper interconnects was improved. A chemical mechanical polishing (CMP) process using in two-step Cu AFP conditions eliminates copper residue. The process has a higher short-yield margin than the conventional AFP process. It uses both a high selective barrier metal slurry and a randomly foamed polyurethane pad to achieve the same Cu wiring sheet resistance as a conventional polishing process. However, this method allows for increased depressions of less than 20% on a 20-μm Cu line of 98% density after Cu-AFP. We demonstrate that the process can meet the planarity target without any extra intermediate oxide polishes. Moreover, it is the compatible with low-k films and the Cu AFP process, and this prevents delamination and fractures in lowk materials during CMP. Therefore, this process should meet the requirements for Cu interconnects.