Slurry Flow in CMP Considering the Pad Roughness and Porosity

Chemical mechanical polishing (CMP) is a widely adopted technique to achieve high level of global and local planarity required in modern integrate circuit (IC) industries and hard disk manufacturing process, etc., wherein the slurry flow weighs heavily on the performance. The pad surface will alter the flow features considerably. A preliminary wafer-scale flow model for CMP is presented considering the roughness as well as the porosity of the pad. Numerical simulations were conducted to show the slurry flow features. The results show that the porosity of the pad is conducive to slurry delivering, and small porous parameter will lead to prominent increase of load capability, accounting for larger material removal rate. The rough surface carries additional fluid in the valleys of the polishing pad thereby provide some chemical reactions. The model predictions will be conducive to the removal rate and mass transport computation. This will shed lights on the mechanism of CMP process, which is for a long time considered as a difficult circle to square.