Impact of PAD Micro Contact Size and Distribution on the Planarization in CMP

Optimal planarization of the overburdened copper layers is a critical objective in the integrated circuit (IC) field and is mainly realized via chemical mechanical planarization (CMP) technique. As this kind of mechanical related performance is strongly related to the action of pad asperities, understanding the effect of the micro-contact conditions of pad asperities on the planarization process will be meaningful. In this study, a millimeter-sized polishing pad sample with a known contact condition is used and conducted on a copper patterned surface. Based on the real contact area image, the relationships between planarization efficiency and real contact condition are established. The results indicate that high material removal in up areas is necessary but is not a sufficient condition for material removal in down areas. Both contact spot size and distribution have an obvious effect on the planarization process. This study is expected to provide some insights into the planarization process from the microscale.