Tangential flow filtration of ceria slurry: Application of a single-pass method to improve buff cleaning

Ceria slurries are used in the oxide chemical mechanical polishing (CMP) process due to their high polishing performance and selectivity characteristics. However, it takes great effort to remove small ceria particles that remain on the wafer surface during the post-CMP cleaning process. Therefore, we applied tangential flow filtration (TFF) systems, which can be used to separate small ceria particles before CMP process. In a previous study, we improved the post-CMP cleaning efficiency of the ceria slurry with a circulation-type TFF system. Herein, the correlations between the separation rate of ceria particles and parameters affecting the TFF system, such as membrane pore size, flow rate, and transmembrane pressure (TMP), were evaluated to improve buff cleaning efficiency. Finally, we also fabricated a single-pass TFF system to reduce the process time and loss of active ceria particles. With the single-pass TFF system, the basic properties and polishing performance of the ceria slurry did not change. In addition, the buff cleaning efficiency improved by up to 18.1%.