Behavior of copper removal by CMP and its correlation to deposit structure and impurity content

Knowledge of the removal behaviors of various electroplated copper films during chemical mechanical polishing (CMP) is important for thickness control and defect generation. In this paper, we investigate the effect of current density and impurities incorporated in blanket and pattern wafer by potentiodynamic polarization method, X-ray diffraction, and secondary ion mass spectroscopy. Defect count was decided by the optical scan method and scanning electron microscopy reviewing. Removal rate and corroded pits were found to decrease with increasing (111)/(200) ratio because (111), the close-packed plane of the face-centered cubic structure, has strong chemical resistance during polishing. Furthermore, incorporated impure atoms, such as carbon, chloride, and sulfur, tend to weaken grain boundaries to generate more corroded pits but do not affect removal rate. Besides, geometric constraint induces concentrated impurities to restrict copper grain growth and induce fast oxide growth rate, resulting in high dishing performance. (c) 2007 The Electrochemical Society.