Evolution of Copper-Oxide Damascene Structures in Chemical Mechanical Polishing : I. Contact Mechanics Modeling

Abstract

Nonplanarity arising from the chemical mechanical polishing of Cu-oxide damascene structures results in the exposure field (die-size) being partially out of focus in the subsequent lithography process. Thus the corresponding mechanisms of within-die polishing must be determined and the within-die nonplanarity due to polishing needs to be minimized to increase the process yield. In this paper, contact mechanics models were developed to explain the role of pattern geometry on the variation of material removal rate. The effects of Cu linewidth, area fraction, and the elastic properties of the polishing pad on pad displacement into low features were examined to focus on the mechanical aspects of the process. The pressure distribution on the high features was determined and the rate of pattern planarization was quantified. Experiments on patterned Cu wafers were conducted to verify the model. Based on these results, the planarization and polishing behavior and the within-die nonplanarity due to the variation of pattern geometry were discussed. © 2001 The Electrochemical Society. All rights reserved.