Monodispersion of SiO₂/CeO₂ Binary Nano-Abrasives with Adjustable Size in Chemical Mechanical Polishing Performance of Copper

Abstract

Chemical mechanical polishing (CMP) is an efficient methodology to achieve atomic-level roughness and global planarization. The selection and structural design of the abrasive particles in the polishing slurries play an essential role in the CMP process. In this work, silica (SiO2) microspheres with adjustable size and structure were prepared by a modified Stöber template approach, and ceria (CeO2) nano-shell layers were coated via in-situ chemical precipitation on the core surfaces forming core/shell composite particles. The SiO2/CeO2 composites were characterized by XRD, SEM, TEM, XPS, and BET. The polishing performance of SiO2/CeO2 abrasives in copper (Cu) CMP was investigated by AFM. The small-sized (ca. 98 nm), large-sized (ca. 296 nm), and mesoporous (ca. 277 nm) composite abrasives were named as SiO2/CeO2-1, SiO2/CeO2-2, and mSiO2/CeO2, respectively. The best average surface roughness (Ra) and root-mean-square roughness (Rq) were obtained using SiO2/CeO2-1 abrasives, which decreased from 1.485 and 1.832 to 0.363 and 0.511 nm, respectively. The material removal rate (MRR) of the composite abrasives was improved to 279 nm/min by SiO2/CeO2-2 abrasives. The mSiO2/CeO2 composites were not manifested with evident superiority in terms of polishing characterization, which was attributed to the coating of CeO2 nanolayers. Finally, the material removal of Cu-CMP mechanisms was discussed.