Effect of Complexing Agents on Surface Composition for Co Post-CMP Cleaning Process

Abstract

The effect of surface composition change based on complexing agents on cobalt (Co) post-chemical mechanical polishing cleaning (cleaning) is investigated. The change in chemical composition of the Co surface significantly affects Co cleaning performance, as well as dissolution capacity of the complexing agent and pH of cleaning solution. Oxide composition of the Co surface was manipulated using different types of complexing agents. Addition of citric acid and glycine in cleaning solution resulted in predominant formation of Co3O4 and CoOOH on the Co surface, respectively. The citric acid-derived Co3O4 surface embraces abundant –O– terminates, which attracts the complexing agent and silica abrasive relatively weakly, resulting in suppression of recess formation and reduction of surface particle residue after cleaning. On the contrary, the –OH terminated CoOOH surface formed by glycine bound strongly with silica. Therefore, preferential development of Co3O4 on the surface considerably enhances Co cleaning performance, which is achieved by introducing citric acid in the cleaning solution. To sum up, we suggested an unconventional insight to understand the effect of Co surface chemical state on cleaning performance.