Roles of Surfactant Molecules in Post-CMP Cleaning

One major concern in post-CMP cleaning is particles contamination on the substrate surface after the CMP process. These particles can be abrasive particles from the slurry, debris from pad material, and particles of film being polished. The cleaning method used in this study is direct contact of the substrate surface and brush sweeping. To enhance the cleaning process, an anionic surfactant is added in the cleaning solution. In order to understand effects of surfactant molecules on post-CMP cleaning, for the first time, we use a tribological approach over a range of surfactant concentration and temperature. In this regard, we observe how the surfactant behavior before and after it reaches the critical micelles concentration (cmc). Experimental results show that increase in surfactant concentration can promote bilayer interaction of micelles on the hydrophilic particles. Based on our study, we propose an interactive explanation of surface molecules with the wafer surface and nanoparticles through friction. This understanding will serve as a guide on how much surfactant should be added in order to achieve effective particle removal.