A Model for Mechanical Wear and Abrasive Particle Adhesion during the Chemical Mechanical Polishing Process

Abstract

Abrasive particle-surface interactions are analyzed and processes of surface removal by adhesive and abrasive wear mechanisms during chemical mechanical polishing (CMP) are studied. The mechanical contact theory is used, and a model for interactions of pad asperities with abrasive particles and wafer is developed. The cases of hard and soft pads and dilute and dense slurries are analyzed. A model for the particle-scale surface removal process in the chemical-mechanical polishing is developed. The influence of abrasive particle adhesion to the surface is included in the analysis. Variations of polishing rate with pressure, abrasive particle size, and concentration, as well as pad characteristics (including asperity distribution and asperity elastic and plastic deformation) are studied. The functional dependence of the polishing rate on pressure and velocity was found to be related to the distribution of pad asperities. The linear variation predicted by Preston’s equation follows when the pad asperities have a random distribution. The sublinear dependence, however, is obtained when the pad asperities have a wavy distribution. The results also show that the abrasive particle adhesion affects the CMP process. The model predictions are presented in graphical form and are compared with the available semiempirical correlations and discussed. © 2001 The Electrochemical Society. All rights reserved.