Core-shell PMMA@CeO2 abrasives for superior CMP: Tunable synthesis and DFT-elucidated mechanistic understanding

Achieving a simultaneous enhancement of material removal efficiency and surface quality remains a central challenge in chemical mechanical polishing (CMP) of silicon dioxide. Conventional CeO 2 abrasives, despite their high chemical activity, are prone to agglomeration and cause detrimental scratches. To address this, a core-shell structured poly(methyl methacrylate)@CeO 2 (PMMA@CeO 2 ) composite abrasive was rationally designed and synthesized, in which flexible PMMA microspheres serve as the core and epitaxially grown CeO 2 nanocrystals form the active shell. By precisely controlling the Ce precursor concentration from 2 to 20 mmol, the CeO 2 loading can be systematically tuned from approximately 15 wt% to a saturation level of ∼31.5 wt%, demonstrating a well-bounded and highly controllable synthesis. Comprehensive characterizations confirm the uniform core-shell morphology, high crystallinity, and a consistent high relative Ce 3+ whose absolute number increases with the tunable CeO 2 loading. The optimized abrasive achieves a material removal rate of 102 nm/min and an ultra-low surface roughness of 0.112 nm on SiO 2 film, approaching atomic-level smoothness. Density functional theory calculations suggest that the work function difference between CeO 2 (111) and SiO 2 (001) drives directional electron transfer from CeO 2 to SiO 2 . This electron redistribution strengthens the topmost Si-O bond via chemisorption while imposing tensile stress that elongates and weakens the sub-surface Si-O bonds, potentially promoting preferential cleavage under mechanical shear. This atomic-scale insight, combined with the mechanical buffering effect of the PMMA core, establishes a unique synergy in which the CeO 2 shell provides high chemical activity for efficient material removal and the PMMA core suppresses scratching to ensure atomically smooth, low-damage finishing. This work provides a rational design paradigm for core-shell abrasives and a fundamental theoretical basis for next-generation high-performance CMP materials.