Evolution of Copper Oxide Damascene Structures in Cmp: I. Contact Mechanics Modeling

Non-planarity arising from the chemical mechanical polishing of Cu-oxide damascene results in the exposure field (die-size) being partially out of focus in the subsequent lithography process. The corresponding mechanisms for non-uniformity must be determined and minimized to increase the process yield. In this chapter, contact mechanics models are 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 are examined. The pressure distribution on the high features is determined and the rate of pattern planarization is quantified. Experiments on patterned Cu wafers are conducted to verify the model. Based on these results, the planarization and polishing behavior, and the within-die nonplanarity due to the pattern geometry variation are discussed.