A plasticity-based model of material removal in chemical-mechanical polishing (CMP)

It is well known that the chemical reaction between an oxide layer and a water-based slurry produces a softer hydroxylated interface layer. During chemical-mechanical polishing (CMP), it is assumed that material removal occurs by the plastic deformation of this interface layer. In this paper, the behavior of the hydroxylated layer is modeled as a perfectly plastic, material, and a mechanistic model for material removal rate (MRR) in CMP is developed. The deformation profile of the soft pad is approximated as the bending of a thin elastic beam. In addition to the dependence of MRR on pressure and relative velocity, the proposed plasticity-based model is also capable of delineating the effects of pad and slurry properties. The plasticity-based model is utilized to explore the effects of various design parameters (e.g., abrasive shape, size and concentration, and pad stiffness) on the MRR. Model predictions are compared with existing experimental observations from glass polishing, lapping, and CMP.