Modeling the Effects of Abrasive Size Distribution, Adhesion, and Surface Plastic Deformation on Chemical-Mechanical Polishing

Abstract

A mechanical wear model for interactions between pad, wafer, and abrasives for surface removal during chemical mechanical polishing was developed. Effects of abrasive size distribution, surface softening, particle adhesion, and surface plastic deformation were included in the model. Interactions of particles that were trapped on the pad asperities with wafer surface were analyzed. Variations of surface hardness with the polishing time, down pressure, and relative velocity were also evaluated. Pads with wavy and random surface roughness were considered and model prediction results for dilute slurry concentrations were evaluated. Variations of the removal rate with down pressure, relative velocity, and surface hardness were analyzed. The results show that the surface removal rate decreases as abrasive size increases. Also for a constant relative velocity, the removal rate and the wafer surface hardness increase with increasing the slurry concentration and pressure. The results of the numerical simulations were compared with the available experimental data and good agreement was found.