Classification, performance and recycling of ceria-based materials used for chemical mechanical polishing

Abstract

Ceria (CeO2)-based materials, endowed with balanced chemical reactivity and moderate mechanical hardness, are extensively applied in ultra-precision surface processing fields such as integrated circuits (ICs), semiconductor substrates, optical glass, hard discs, computer magnetic heads, and quartz crucibles, serving as core abrasives in chemical mechanical polishing (CMP). This review comprehensively summarizes their research progress in CMP: material systems have evolved into four categories (pure CeO2, doped CeO2, CeO2-based core-shell materials, and composite modified CeO2), with synthesis methods advancing from traditional solid-phase processes to liquid-phase, solvothermal, and vapor-phase techniques for precise regulation of particle size (10–300 nm) and morphology (spherical, octahedral, etc.). For typical polished materials, the optimal surface roughness (Ra) reaches as low as 0.0117 nm (for silicon wafers polished with Co-doped CeO2) and the maximum material removal rate (MRR) attains 932.42 nm/min (for quartz glass polished with Y/Pr co-doped CeO2). The CMP mechanism relies on the synergistic effect of mechanical abrasion and chemical etching: Ce³⁺ promotes the formation of Ce-O-Si chemical bonds with polished materials (e.g., SiO2) via condensation reactions (Ce-OH + Si-OH→Si-O-Ce + H2O), while Ce4+ maintains reaction system stability, and factors such as particle size, crystal plane, Ce3+/Ce4+ ratio, slurry pH (optimal at 5 for SiO2 polishing), surfactants, and oxidants jointly regulate polishing performance. However, current research faces prominent challenges: imprecise nanoscale regulation of abrasive performance (e.g., agglomeration of sub-20 nm particles, uneven dopant distribution), insufficient environmental friendliness of polishing slurries (toxic reagents, poor degradability of additives), inadequate understanding of complex system mechanisms (unclear synergy of multi-component abrasives, difficulty in capturing instantaneous interface reactions), and cost constraints from rare earth resource dependence. Future research directions will focus on developing "doping-core-shell-composite" integrated modification technologies to prepare high-efficiency low-damage abrasives, constructing green recycling systems (e.g., gravity sedimentation-acid leaching, mechanochemical methods) for slurries and waste abrasives, integrating in-situ characterization (AFM, XPS) and DFT-ML coupled calculations to deepen multi-scale mechanism research, achieving intelligent process optimization based on machine learning, and developing specialized abrasives for third-generation semiconductors and optical crystals, thereby promoting large-scale and environmentally friendly applications in high-end manufacturing.