Investigation of ceria-silica interactions during STI polishing

Historically, CMP solutions were based on cause-and-effect relationships, which hindered fundamental understanding of the slurry-wafer interactions that control the CMP process. One of the intriguing challenges is the understanding of the mechanism of enhanced oxide polishing using ceria particles. In this study we have conducted fundamental atomic force microscopy (AFM) and scanning electron microscopy (SEM) studies to investigate ceria-silica interactions. The results indicate that silica-silica interactions occurring at alkaline pH are more chemical in nature than ceria-silica interactions in the same pH regime. Based on these studies, a model for ceria-silica polishing has been proposed.