Modeling and characterization of tungsten chemical and mechanical polishing processes

Due to the complexity of chemical mechanical polishing (CMP) in general and metal CMP in particular, modeling of CMP processes has been pursued only m inimally in the literature. A fundamental understanding of these metal CMP processes is needed to minimize manufacturing and development costs that wi ll continue to escalate as more devices migrate to subhalf-micrometer techn ologies where metallization schemes are more complicated. In this work, we have used two different models to characterize the tungsten CMP process. Wh ile the chemical Preston model is used to explain the effect of process par ameters on the mean polish rate, the slurry transport model is useful in ex plaining the within wafer uniformity for the polishing process. We successf ully validated the chemical Preston model using design of experiment (DOE) data and demonstrated the importance of slurry transport and the pad to waf er gap, to the within wafer uniformity for the embossed and regular politer polishing pads. We showed that better uniformity is obtained throughout th e wafer with the embossed politer than the regular politer pad due to the p resence of grooves in the embossed pad, which allow for better slurry trans port across the pad. We effectively characterized the process and studied t he effects of changing the various tool and process parameters on process p erformance. (C) 2001 The Electrochemical Society. All rights reserved.