Threshold pressure and its influence in chemical mechanical polishing for IC fabrication

A microscopic analysis of the interaction between abrasive particles, the polished wafer surface, and polishing pad has shown that there can exist a threshold pressure in chemical mechanical polishing (CMP) for IC fabrication. When the applied pressure to the polished wafer is less than the threshold pressure, the CMP removal is negligible. It is found that the threshold pressure plays a significant role in CMP; e.g., it greatly influences the selectivity and the pattern density dependence of polishing. This new fundamental discovery is fully supported by a variety of experimental results on dielectric and metal CMP and it has important implications to CMP consumable development and process optimization.