Preparation of CeO2 abrasives by reducing atmosphere-assisted molten salt method for enhancing their chemical mechanical polishing performance on SiO2 substrates

Abstract

Ce3+ as the active site on the CeO2 abrasive surface is the key to enhancing the material removal rate (MRR). The CeO2 abrasives with high chemical activity were prepared by the molten salt method under a reducing atmosphere. The crystal structure and morphology of CeO2 abrasives were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), ultraviolet–visible diffuse reflectance spectroscopy (UV–Vis DRS), and X-ray photoelectron spectroscopy (XPS). The CeO2 abrasives were obtained under different atmospheres (Air, Ar, and Ar/H2). With the enhancement of the reducing atmosphere, the morphology of the abrasives transforms from spherical to octahedral, while more oxygen vacancies and Ce3+ are generated on the surface of CeO2 abrasives. The CMP experiments show that the MRRs of the CeO2-Air, CeO2-Ar, and CeO2-Ar/H2 abrasives on SiO2 substrates are 337.60, 578.74, and 691.28 nm/min, respectively. Moreover, as confirmed by atomic force microscopy (AFM), the substrate surfaces exhibit low roughness (∼0.5 nm) after being polished using all of the prepared samples. Especially, the MRR of CeO2-Ar/H2 abrasives is increased by 104.76% compared with CeO2-air abrasives. The improved CMP performance is attributed to the increased Ce3+ concentration and the octahedral morphology of the abrasives enhancing the chemical reaction and mechanical removal at the abrasive–substrate interface.