Flow-Induced Dynamic Dispersion in Dispersant-Free Mixed-Oxide Slurry Systems

Area of Science:

• Materials Science
• Chemical Engineering
• Nanotechnology

Background:

• Chemical-mechanical planarization (CMP) relies on stable slurry formulations.
• Traditional dispersants improve static particle dispersion but not dynamic flow behavior.
• SiO2-based slurries are crucial for semiconductor manufacturing planarization.

Purpose of the Study:

• To investigate a particle-mixing strategy for enhancing SiO2 slurry dispersion and CMP performance.
• To compare the effectiveness of particle mixing against chemical dispersants.
• To understand the underlying mechanisms of improved dispersion and flow behavior.

Main Methods:

• Preparation of bimodal SiO2 particle suspensions (25 and 55 nm) at various solid loadings.
• Rheological measurements to assess suspension flow behavior.
• Small-angle X-ray scattering (SAXS) and effective volume packing analysis.
• Chemical-mechanical planarization (CMP) testing.
• Numerical simulations coupling discrete element method (DEM) and computational fluid dynamics (CFD).

Main Results:

• Particle mixing suppressed agglomeration and shifted rheology from shear-thinning to Newtonian, indicating improved dynamic dispersion.
• Bimodal suspensions achieved higher material removal rates and lower surface roughness in CMP tests compared to monodisperse or dispersant-stabilized ones.
• Numerical simulations revealed denser particle contacts and higher localized stresses in bimodal systems, explaining enhanced CMP performance.

Conclusions:

• A particle-mixing strategy is superior to chemical dispersants for dynamic dispersion and performance of SiO2 slurries in CMP applications.
• Cooperative size effects in bimodal suspensions lead to improved structural organization and flow behavior.
• The enhanced CMP performance is attributed to optimized particle interactions and stress distribution within the bimodal slurry.