Preparation of lanthanide-doped polystyrene/CeO2 abrasives and investigation of slurry stability and photochemical mechanical polishing performance

With the pursuit of high efficiency and quality chemical mechanical polishing (CMP), exploring additional efficiency enhancement means based on the CMP has become a trend. Polystyrene/CeO 2 core-shell abrasives (core: 85 nm, shell: 10 nm) doped with Lanthanide (La, Nd, and Eu) were synthesized by a modified in situ chemical precipitation method, promising application for photocatalytic-assisted CMP of silica wafer. The doping of La, Nd, and Eu can reduce the band gap of CeO 2 from 3.24 eV to 3.23 eV, 3.20 eV, and 3.22 eV, respectively, indicating enhanced photocatalytic activity. Especially for Nd-doped abrasives, the content of Ce 3+ increases from 0.49 to 0.56, accompanied by the generation of oxygen vacancies , as proved by X-ray photoelectron spectroscopy (XPS) and Raman spectra . In addition, the prepared polishing slurry could remain stable for up to 7 days by the steric hindrance effect and electrostatic repulsion of the dispersants . The materials removal rate of Nd-doped abrasive in photocatalytic-assisted CMP of SiO 2 films reaches 174.3 ± 7.6 nm/min, which is 163% higher than those in CMP, while the surface roughness (Ra) in localized areas (2×2 µm 2 ) can be reduced from the initial 0.82 ± 0.01 nm to 0.36 ± 0.05 nm. Detailed reaction and removal mechanism involved in photocatalytic-assisted CMP processes is discussed.