An integrated material removal model for silicon dioxide layers in chemical mechanical polishing processes

Abstract

The material removal rate in CMP processes obeys Preston's equation, which can be expressed as a linear function of the applied areal power density under usual operating conditions. However, some experimental results have shown a nonlinear relationship between the CMP material removal rate and the applied areal power density, suggesting non-Prestonian behavior under certain operating regimes. Although the material removal rate is caused by the coupled effect of both mechanical and chemical actions in actual CMP processes, the treatment of the chemical action as a mere supplementary means of softening the surface makes it difficult to explain this non-Prestonian behavior. In this work, we propose an integrated material removal model for silicon dioxide during CMP based on a multiscale mechanical abrasion model coupled with the slurry chemical diffusion effects. The synergetic effects on the material removal mechanism due to both mechanical and chemical actions are incorporated in the model, and the total material removal rate is predicted by accounting for both effects. Consequently, the non-Prestonian behavior often shown in silicon dioxide CMP may be explained using the proposed model. The validity of the model is supported by comparing the predicted material removal rates with experimental values available in the literature. (C) 2008 Elsevier B.V. All rights reserved.