Ionic liquid-mediated morphology and structure of CeO2 nanoparticles for silicon wafers ultra-precision chemical mechanical polishing applications

Cerium dioxide is a crucial material in chemical mechanical polishing for integrated circuits and semiconductors. To address the challenges associated with conventional precipitation methods (such as small particle size and poor dispersion) and hydrothermal synthesis approaches (including large particle size, inhomogeneity and environmental pollution), this study proposed a green synthesis approach for the preparation of a series of high quality CeO 2 nanoparticles, which were synthesized by ionic thermal synthesis in 1-butyl-3-methylimidazole iodide salt ([Bmim]I) using cerium nitrate hexahydrate (Ce(NO 3 ) 3 ∙6H 2 O) as raw material without a template. The samples were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, Fourier infrared spectroscopy and Atomic Force Microscope. The experimental results demonstrated that when the precursor was prepared at a reaction temperature of 180 °C for 16 h, followed by washing, drying, and roasting at 700 °C for 2 h, the CeO 2 nanoparticles exhibited a regular morphology (blocks, polygons), uniform distribution, and a size ranging from 20 to 50 nm. Polishing tests were carried out on 2-inch silicon wafers. Atomic force microscopy characterization results demonstrated that the surface roughness of the polished silicon wafer can be reduced to as low as 0.205 nm. The calculated removal rates of MRR were 261.44 nm/min. When compared to the two commercially available polishing powders, the novel material demonstrated a 11.16 % higher material removal rate and achieved a 69.22 % reduction in surface roughness.