Nd3+-doped colloidal SiO2 composite abrasives: Synthesis and the effects on chemical mechanical polishing (CMP) performances of sapphire wafers

Abrasive is one of the most important factors in chemical mechanical polishing (CMP). In order to improve the polishing qualities of sapphire substrates, the novel Nd 3+ -doped colloidal SiO 2 composite abrasives were prepared by seed-induced growth method. In this work, there were a series of condensation reactions during the synthesis process of Nd 3+ -doped colloidal SiO 2 composite abrasives and the silica cores were coated by shells (which contains SiO 2 , Nd 2 Si 2 O 7 and Nd(OH) 3 ) via chemical bonds and hydrogen bonds in the Nd 3+ -doped colloidal SiO 2 composite abrasives, which made the composite abrasives’ core-shell structure more sTable Scanning electron microscopy (SEM) showed that Nd 3+ -doped colloidal SiO 2 composite abrasives were spherical and uniform in size. And the acting mechanisms of Nd 3+ -doped colloidal SiO 2 composite abrasives on sapphire in CMP were investigated. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) analysis and X-ray photoelectron spectroscopy (XPS) analysis demonstrated that the solid-state chemical reactions between the shells (which contained SiO 2 , Nd 2 Si 2 O 7 and Nd(OH) 3 ) of Nd 3+ -doped colloidal SiO 2 composite abrasives and the sapphire occurred during the CMP process. Furthermore, Nd 3+ -doped colloidal SiO 2 composite abrasives exhibited lower surface roughness and higher material removal rate (MRR) than the pure colloidal SiO 2 abrasives in the same polishing conditions, which was attributed to the solid-state chemical reactions between shells of Nd 3+ -doped colloidal SiO 2 composite abrasives and sapphire.