2017 年 83 巻 2 号 p. 173-179
Chemical mechanical polishing (CMP) is used in a wide range of processes in semiconductor production; however, the polishing mechanism of CMP is not yet completely understood. One reason that aggravates satisfactory understanding is that the polishing action in the fine gap between the semiconductor wafer and polishing pad cannot be directly observed. The behavior of the abrasive particles and chemical species in the slurry is believed to play a critical role in the polishing mechanism. Although the macroscale slurry flow has been studied by many researchers, the microscale slurry flow in the fine gap, especially in polishing pad asperities, has been largely unstudied. In this study, therefore, we attempted to visualize the slurry flow taking place in the asperities experimentally. Because the in-situ observation of the slurry flow is extremely difficult, a larger model of the pad asperities was built, based on the scaling laws of fluid dynamics. A refractive index matching technique and particle suspension method were applied in order to visualize the scaled-up slurry flow. As a result, the flows toward and away from the wafer surface have also been observed as suggested by previous studies.