A Mechanical Model for Erosion in Copper Chemical-mechanical Polishing

The Chemical-mechanical polishing (CMP) process is now widely employed in the ultra-large-scale integrated semiconductor fabrication. Due to the continuous decrease in the sub-micron feature size, characterization of erosion has become an important issue in Cu CMP. In this paper, the erosion in Cu CMP is considered at two levels: wafer and die levels. Erosion models are developed based on the material removal rates, Cu interconnect area fraction, linewidth and Cu deposit thickness. Experiments have been conducted to obtain the selectivity values among Cu, barrier layer and dielectric, and wafer-level material removal rate ratio for validating the new erosion model. The present model is compared with the existing models and is found to better agree with the experimental data.