Modeling of chemical-mechanical polishing considering thermal coupling effects

Abstract

The removal of surface material in the conventional chemical-mechanical polishing (CMP) process is the result of synergetic effects of two dominant mechanisms: a mechanical process due to the abrasion of particles in the slurry, and a chemical process due to the reactions between the wafer and the chemicals in the slurry. In the overall material removal mechanism, in particular for metal layers, the mechanical and chemical effects are not independent, but are strongly coupled. Many models do not account for these coupling effects and cannot explain the non-Prestoman behavior that occurs when the material removal rate is a nonlinear function of the input areal power density. To address this deficiency and coupling effects, we propose a new integrated thermo-chemical-mechanical model that considers the synergistic effects of both the mechanical and chemical removal processes using the heat transfer mechanism as a bridge between them. In the modeling process, the material removal model is developed based on elastic and plastic contact mechanics and the dominant chemical reactions at the wafer surface. The temperature variation of the CMP system is treated as the Coupling factor. The mechanical abrasion by the abrasive particles causes friction, which generates frictional heat on the contacting interfacial area. This heat plays a key role in accelerating the overall chemical reaction for the material removal. We performed a computer simulation with the proposed model using known parameters, and compared the results with other data to ensure its validity. (C) 2008 Elsevier B.V. All rights reserved.