Chemical Mechanical Polishing: Threshold Pressure and Mechanism

The material polishing or removal mechanism has been studied for chemical mechanical polishing (CMP) as used for integrated circuit fabrication.There can exist a threshold pressure in the CMP process due to the tribological interaction among abrasive particles, the polished wafer surface, and the polishing pad. The CMP material removed is negligible if the applied pressure to the wafer is less than the threshold value. A new polishing rate or removal rate equation is derived and it explains the anomalous pressure dependence of polishing rate, which was observed in a variety of dielectric and metal CMP processes. The existence of a threshold pressure in CMP processes has significant implications to CMP consumable development and CMP process optimization.