A CMP MODEL COMBINING DENSITY AND TIME DEPENDENCIES

This work reviews and compares density and time-dependent dielectric CMP models. Model fits to experimental CMP data demonstrate that a density model alone cannot explain the polishing of medium-low and low density features. It is shown that time-dependent models, which take into account contact with down areas, can explain this effect. These models are combined into a single model, whose parameters can be chosen to provide a 50% decrease in fitting error over that of the density model. It also shown that even the combined time-density model cannot explain the polishing of certain low density features. Finally, variations of this model are given which significantly reduce the number of parameters to be found, and show potential for use in predicting post-polish thicknesses for arbitrary layouts.