Individual and interactive action mechanisms of mechanical, chemical, and electrical factors in Co polishing

With the continuous miniaturization of integrated circuit (IC) devices, Co is recognized as the most promising alternative to Cu as an interconnecting metal. During IC processing, Co surfaces need to be flattened. This work describes dynamic polishing experiments and static corrosion experiments on the electrical, chemical, and mechanical factors involved in cobalt electrochemical mechanical polishing (ECMP). Then, the impact and proportion of individual and combined factors on the Co-ECMP are quantitatively analyzed. The experimental results show that mechanical action, rather than individual chemical or electrical action, plays a primary role in Co-ECMP. The ratios of individual mechanical, chemical, and electrical action proportions are 50.46%, 11.17%, and 6.20%, respectively. However, chemical and electrical assistance with mechanical action can achieve twofold efficiency and high-quality polishing of Co. For example, the ratios of mechanical–chemical or electrical–chemical–mechanical cooperation are 72.05% or 100%, respectively. In addition, polarization curves, energy dispersive spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS) were used to analyze the Co-ECMP process and products. Atomic-level mechanism analysis is performed for each factor. The results indicate that in Co-ECMP, the oxides formed on the Co surface are mainly CoO, Co(OH)2, and Co3O4. The oxides react with the complexing agents to form loose and porous Co-benzotriazole (Co-BTA) complexes. Mechanical, chemical, and electrical factors collaborate to form and remove Co-BTA constantly, achieving rapid material removal and obtaining smooth atomic-level surfaces.