Kinetics of Polishing Friction for Copper Pits Formation during Copper Chemical Mechanical Polishing.

Copper pits formed after copper chemical mechanical polishing (CMP) are the critical defects in the copper dual damascene process because the imperfect copper surface can cause the interconnection to be missed or broken. There are many parameters contributing a flat copper surface, such as the polishing down-force, slurry pH value, and galvanic effects between barrier and copper materials. One of the important factors influencing the pit formation is the friction force. The kinetics of the polishing friction can be studied to understand the mechanism of the pit-defect formation. A mechanism is proposed and can be explained by two characteristics of pit-defect formation during the polishing, i.e., the location of the edges between the metal line and wafer and the magnitude of the friction torque inducing the defect. Furthermore, three different polishing platforms are used to demon- strate this kinetic approach toward understanding the role of the threshold of the friction force in the pit-defect immunization. With this understanding, the pit formation can be reduced significantly. [ABSTRACT FROM AUTHOR]