A new contact model of pad surface asperities utilizing measured geometrical features

The primary model of the asperity contact in CMP process based on measured pad surface structures is proposed in the present study. The surface geometry of the used pad was analyzed, and it was clarified that the asperity geometries are in a variety of forms. Hence, GW model is considered to be appropriate as the CMP contact model. Considering the measured and identified geometrical features, a new contact model based on Hertzian elastic contact of an oval hemisphere was formulated. Probability functions of the asperity height and radii are also defined based on the measured results. Analytical investigation about the asperity contact indicated that the nominal contact pressure estimated by the proposed model showed a significant disagreement with that in the conventional model.