Investigation on silica particle cleaning mechanism of surfactants for amorphous carbon post-CMP cleaning

Amorphous carbon is widely utilized as a hard mask to prevent pattern collapse in high-aspect-ratio etching processes. While chemical mechanical polishing (CMP) ensures surface quality for precise mask alignment, it introduces significant particle contamination. Surfactants can modulate the interfacial properties of solid-liquid systems. In this study, the cleaning mechanisms of nonionic, cationic, and anionic surfactants were systematically investigated. Experimental results demonstrate that nonionic and anionic surfactants exhibit superior cleaning performance by enhancing wettability, which accelerates the cleavage of Si–O–C bonds via hydroxyl ion (OH-) nucleophilic attack at pH 12. Both achieved particle removal efficiencies (PRE) exceeding 97%. In contrast, cationic surfactants are ineffective because their head groups are attracted to the oppositely charged surfaces, exposing hydrophobic tails and reducing wettability. These findings provide valuable insights for optimizing amorphous carbon post-CMP cleaning using surfactants.