Magnetic particle dispersion in magnetorheological slurries for planarization enhancement

Abstract

This study investigates the application of an innovative magnetorheological (MR) slurry in chemical mechanical planarization (CMP), addressing challenges in precision, environmental sustainability, and adaptability to complex interconnect architectures faced by conventional CMP slurries. The MR slurry, composed of carbonyl iron particles (CI) and abrasive particles dispersed in an aqueous medium, achieves real-time control via magnetic field manipulation. Experimental results demonstrate that ammonium polyacrylic acid (PAA-NH₄) significantly improves the dispersion of both large and small CI particles, enhancing their alignment under an applied magnetic field. Rheological measurements, supported by finite element simulations, reveal that smaller, well-dispersed CI particles align more efficiently, forming closely packed and robust chain structures. This results in uniform magnetic brushes with improved coverage of the polishing surface, enabling a gentler, more efficient polishing process. Dispersed MR slurries achieve higher material removal rates (MRR) and better surface flatness, with smaller CI particles proving particularly effective due to their superior magnetization and stress application capabilities. These findings demonstrate the potential of MR slurries to deliver precise and efficient planarization in advanced applications.