A study on the correlation between pad property and material removal rate in CMP

Chemical mechanical polishing (CMP) is a process with relative motion between pad and wafer while supplying slurry which abrasive particles are dispersed. This process consists of mechanical action by contact between pad and wafer and chemical action by the slurry chemicals. There are various factors affecting on material removal rate (MRR) in CMP. Especially, the pad plays a role of mechanical action by direct contact with wafer. Real contact area (RCA) between pad and wafer is an important factor when considering real contact pressure, friction and wear of pad asperities, which affects on the MRR and within wafer non-uniformity (WIWNU). This paper proposes a correlation between pad property and MRR in CMP process. The pad after conditioning had sharp asperities and changed to blunt ones as the polishing time became longer. This phenomenon was clarified by the roughness parameter of Rku. The high Rku pad just after conditioning made a high real pressure to the wafer, resulting in high MRR during CMP.