Preparation of three-dimensional dendritic-like mesoporous silica particles and their pore size-dependent polishing behavior and mechanism

The type and structure of abrasive particles play a key role in the involved friction and wear processes during chemical mechanical polishing (CMP). This work aims to develop silica-based abrasives that improve both surface finish and removal rate. The uniform, three-dimensional, and dendritic-like mesoporous silica (D-mSiO) spheres with sub-100 nm size were synthesized in a heterogeneous oil–water biphase reaction system. The pore size of 3D-dendritic channels could be adjusted by regulating hydrophobic solvents in the upper oil phase. The improvements of root-mean-square roughness (0.18–0.26 nm) and removal rate (192–260 nm/min) were achieved for the D-mSiO particles compared to colloidal silica abrasives (0.37 nm, 112 nm/min). A reduction from 2.90 to 0.48 and 2.60 to 0.42 nm for the maximum asperity height and the maximum valley depth respectively was also observed after CMP with D-mSiO abrasives. Furthermore, the D-mSiO particles with an enlarged pore size achieved a reduced surface roughness and an enhanced removal rate. The improved polishing performance may be attributed to the enlarged real contact area, the promoted tribo-chemical wear, and the enhanced adhesion effect between particles and surfaces. The contact area mechanism and the contact-penetration-adhesion model may be predominant and significant for D-mSiO abrasives, rather than the traditional the indentation-based mechanism and the indentation-sliding model. The unique three-dimensional mesopores of D-mSiO abrasives are expected to play key role in material removal processes, and it will have more hopeful prospects in CMP performance improvements.