Preparation of Ceria-Coated Silica Nanoparticles and Their Chemical Mechanical Planarization Performance on Si-Face 6H-SiC Substrates
Zifeng Ni, Guomei Chen, Laijun Xu, Ping Zhang, Mengjiao Dai, Shanhua Qian, Da Bian, Haitao Zhang
Abstract
Ceria-coated silica (SiO 2 /CeO 2 ) composite abrasives were prepared through a novel homogeneous precipitation method using commercial silica (SiO 2 ) sol as the silicon resource and cerium nitrate (Ce(NO 3 ) 3 ) and hexamethylenetetramine (HMT) aqueous mixtures as coating precursors. The phase composition, nano-topography, size distribution, and chemical structure of as-prepared particles were characterized by X-ray diffraction, transmission electron microscopy, Zetasizer Nano ZS90 and Fourier infrared spectra. In addition, the possible coating mechanism was discussed. Then, chemical mechanical planarization behaviors of SiO 2 sol, ceria (CeO 2 ) sol, and the novel abrasives and on Si-face (0001) 6H-SiC were investigated by atomic force microscopy. The results indicated that the composite particles were mono-dispersed nano-spheres composed of amorphous SiO 2 core and cubic fluorite CeO 2 shell, possessing complete core–shell structure and particle size of about 110 nm. CeO 2 shell (10 nm) grew on the surface of SiO 2 core by formation of Ce–O–Si chemical bonds, forming stable core–shell structure. SiO 2 /CeO 2 composite abrasives provided an exponentially high material remove rate (MRR) of 1207 nm h −1 and an impressive surface finish with roughness average (Ra) 0.216 nm due to its active chemical property and unique structure.