Study on the Effect of Nonionic Surfactant in Copper CMP Slurry

The effect of surfactant in alkaline slurry for copper chemical mechanical polishing (CMP) was studied through polishing experiments with slurries containing different weight percentage of four nonionic surfactants respectively. The results indicate that properly chosen nonionic surfactants with proper weight percentage could result in little negative influence on the material removal rate, but can help to improve copper wafer surface quality significantly. Alkylphenol ethoxylates was found to be an excellent surfactant for alkaline slurry and a surface roughness of Ra 0.89nm and a material removal rate of 526 nm/min were obtained when polishing with the slurry containing 0.25 wt% alkylphenol ethoxylates, while the surface roughness and the material removal rate were Ra 1.34nm and 525 nm/min respectively when polishing with the origin slurry. The density of polishing defects such as scratches and etch pits decreased significantly. The action mechanism of surfactant was further analyzed based on the experiment results.