Preparation of La-doped colloidal SiO2 composite abrasives and their chemical mechanical polishing behavior on sapphire substrates

• Novel La-doped colloidal SiO2 composite abrasives were prepared which have inerratic spherical shape and excellent dispersibility.
• The chemical mechanical polishing (CMP) performances of the composite abrasives on sapphire substrate were investigated.
• Novel composite abrasives show excellent polishing characteristics comparison with pure colloidal SiO2 abrasive.
• We explore and report the acting mechanism of composite abrasives to sapphire CMP.

Chemical mechanical polishing (CMP) has become a widely accepted global planarization technology. Abrasive is one of the key elements in CMP process. In order to enhance removal rate and improve surface quality of sapphire substrate, a series of novel La-doped colloidal SiO2 composite abrasives were prepared by seed-induced growth method. The CMP performance of the La-doped colloidal SiO2 composite abrasives on sapphire substrate were investigated using UNIPOL-1502 polishing equipment. The analyses on the surface of polished sapphire substrate indicate that slurries containing the La-doped colloidal SiO2 composite abrasives achieve lower surface roughness, higher material removal rate than that of pure colloidal SiO2 abrasive under the same testing conditions. Furthermore, the acting mechanism of the La-doped colloidal silica in sapphire CMP was investigated. X-ray photoelectron spectroscopy analysis shows that solid-state chemical reactions between La-doped colloidal SiO2 abrasive and sapphire surface occur during CMP process, which can promote the chemical effect in CMP and lead to the improvement of material removal rate.