Modeling of chemical mechanical polishing processes using a discretized geometry approach

A transport-based, three-dimensional numerical modeling approach has been d eveloped to simulate chemical mechanical polishing processes occurring in m icroelectronic materials processing. A unique aspect of this model is that the detailed morphology of the slurry flow domain between thr wafer and pol ishing pad is approximated with a regularly updated sequence of geometries evenly positioned along the polishing orbit. Additionally, the modeling app roach allows the use of any constitutive relationship for the rheological b ehavior of the polishing slurry. The local polishing rate is taken to be pr oportional to the local hydrodyanmic shear stress generated on the to-be-po lished wafer surface. To illustrate the modeling approach, the development of planarity Juring polishing of a prototypical 3 x 3 array of square rough ness elements was simulated. The rheology of the polishing medium was descr ibed as a power-law fluid with a Newtonian plateau, which is appropriate fo r an aqueous slurry of colloidal silica. Two modes of pad-to-wafer tracking during polishing are discussed. Modeling results show good agreement with typical experimental data. (C) 2000 The Electrochemical Society. S0013-4651 (99)06-045-0. All rights reserved.