Investigation of the behaviors of various electroplated copper films during CMP

Abstract

The behaviors of various electroplated copper films during CMP are important for removal mechanism and defect generation. This article was to study the characteristics of various copper films during CMP, including impurity effect and current density effect. Potentiodynamic polarization method was used to understand the removal behaviors. XRD and SIMS were applied to investigate the film texture and impurity content. Defect performance was decided in optical scan method and SEM reviewing. The research showed that (111)/(200) texture ratio determined removal rate and voids located in grain boundaries. Removal rate and void defects decreased with increasing (111)/(200) ratio. High (111)/(200) ratio has strong chemical resistance during polishing because (111) is the closed packed plane in the fee structure. For impurity study, carbon and sulfur are impure atoms to weaken Cu grain boundaries to generate more void defects, but are insufficient to determine the removal rate. Furthermore, a novel phenomenon was observed that interconnect surface generate copper extrusion with time after polishing. AES proved that the sulfur content of grain boundaries induce this reaction. Based on above studies, we attempt to describe the relation between copper film properties and polishing performance.