Effects of chemical mechanical planarization slurry additives on the agglomeration of alumina nanoparticles II: Aggregation rate analysis

• The aggregation rate behavior and mechanism of alumina nanoparticles was measured.
• Mean aggregate sizes were measured over time with a variety of chemical additives.
• Reaction limited aggregation was observed, typically followed by a shift to diffusion limited aggregation.

The aggregation rate and mechanism of 150 nm alumina particles in 1 mM KNO3 with various additives used in chemical mechanical planarization of copper were investigated. The pH of each suspension was ∼8 such that the aggregation rate was slow enough to be measured and analyzed over ∼120 min. In general, an initial exponential growth was observed for most suspensions indicating reaction-limited aggregation. After aggregate sizes increase to >500 nm, the rate followed a power law suggesting diffusion-limited aggregation. Stability ratios and fractal dimension numbers were also calculated to further elucidate the aggregation mechanism.

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