Modeling Material Removal Rates for Copper CMP Using Copper Nanohardness and Etch Rates

Abstract

Measurements of copper nanohardness and etch rate were used with alumina agglomerate size distributions in a model to predict material removal rates MRRs, which were then compared to experimental copper chemical mechanical planarization (CMP) data. Generally, model predictions improved using measured nanohardness compared to predictions using a constant nanohardness of Cu metal. When the slurry pH was acidic (<4) the model overpredicted the MRR. An increase in the slurry pH (>7) increased the nanohardness, and MRR predictions agreed with experimental results. For slurries with small etch rates (<8nm/min), the nanohardness had little effect on the MRR predictions, and the model agreed with experiment. The model was very sensitive to the nanohardness for slurries with large etch rates (>8nm/min), and was unable to predict the MRR.