Development of carbon sphere/ceria (CS/CeO2) heterostructured particles and their applications to functional abrasives toward photochemical mechanical polishing

Ceria (CeO2) possesses tribochemical ability and photochemical oxidation activity simultaneously. Herein, novel carbon-coupled CeO2 heterostructures were developed as functional abrasives toward photochemical mechanical polishing (PCMP) system. Polydispersed carbon spheres (CS) were uniformly grafted with pure and Y-doped CeO2 nanocrystals via an in-situ chemical precipitation approach. The resulting CS/CeO2 and CS/CeYO2 core/ shell hybrids were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, photoluminescence spectroscopy, and Raman spectroscopy. As confirmed by atomic force microscope, the developed hybrid abrasives allowed the nearly non-damage surfaces with angstrom-level roughness (0.10-0.13 nm Ra, 0.14-0.16 nm RMS, within 5.0 x 5.0 mu m(2)) in both CMP and PCMP experiments over oxide films. As expected, introduction of ultraviolet radiation and/or Y-doping modification were effective in enhancing removal rates (RR). The CS/CeYO2 abrasives offered a ca. 196% increment of RR-PCMP compared to the RR-CMP of undoped ones (139 nm/min vs 47 nm/min). The improved PCMP performance might be attributed to the cooperative effects of the CS/CeO(2 )heterostructures (overall modulus reduction, CS-CeO2 heterojunction construction, surface defect manipulation, etc.). The possible PCMP mechanism over CS/CeO2 was also discussed on the basis of the interfacial contact, the photochemical modification, and the tribochemical removal.