Boron nanoparticles (NPs) were synthesized using a home-built chemical vapor deposition system. These NPs were crystallized at 900°C that is lower than previous report. The size of boron NPs ranged from ∼5 nm to ∼1 μm. This was achieved by varying the volatilizing temperature of boron tribromide. Subsequently, boron NPs were oxidized by heat-treatment in air. Small-size oxidized boron NPs were investigated as an additive to SiO2 slurry. It was found that the slurry has an enhanced chemical-mechanical planarization (CMP) performance with the addition of those boron NPs. Results showed that the copper removal rate was increased while friction coefficient was reduced, a desirable condition for optimizing CMP processes. The outcome of this research is beneficial to process improvement in semiconductor industry.