Multiscale material removal modeling of chemical mechanical polishing

This paper describes a multiscale model for material removal during conventional chemical mechanical polishing (CMP). Three spatial scales are considered in the integrated model: (i) abrasive particle scale; (ii) asperity scale; (iii) wafer scale. The model is based on the deformation of hyper-elastic asperities attached to a linear-elastic pad. ANSYS is used to perform finite element analyses of a single asperity to obtain the relations between the deformation of the asperity, and the contact stress and area. Those relations are used in an extended Greenwood–Williamson model to compute the local average contact pressures on the pad. The material removal model includes the abrasive wear caused by local contact stress between the abrasive particles and the wafer, the distribution of asperity heights, and the plastic deformation of the wafer. The material removal rate results for unpatterned wafers are used to predict the material removal rates on a feature. The results of a computer simulation of material removal and the time evolution of a feature are shown. Two FEM based codes, ANSYS and EVOLVE are used; the former for the contact stress analysis and the latter to generate a new surface.