Frictional, thermal and kinetic characterization of a novel ceria based abrasive slurry for silicon dioxide CMP

In this study, a novel slurry containing ceria as the abrasive particles was analyzed in terms of its frictional, thermal and kinetic attributes for interlayer dielectric (ILD) CMP application. The novel slurry was used to polish 200-mm blanket ILD wafers on an ICI000 K-groove pad with in-situ conditioning. Polishing pressures ranged from 1 to 5 PSI and the sliding velocity ranged from 0.5 to 1.5 m/s. Shear force and pad temperature were measured in real time during the polishing process. The frictional analysis indicated that boundary lubrication was the dominant tribological mechanism. The measured average pad leading edge temperatures increased from 26.4 to 38.4 °C with the increase in polishing power. The ILD removal rates also increased with the polishing power, ranging from 400 to 4000 A/min. The ILD removal rates deviated from Prestonian behavior at the highest ptimes; V polishing condition and exhibited a strong correlation with the measured average pad leading edge temperature. A modified two-step Langmuir-Hinshelwood kinetic model was used to simulate the ILD removal rates. In this model, transient flash heating temperature was assumed to dominate the chemical reaction temperature. The model successfully captured the variable removal rate behavior at the highest p× V polishing condition and indicated that the polishing process was mechanical limited in the low p× V polishing region and became chemically and mechanically balanced with increasing polishing power.