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 prospective alternative to Cu as an interconnecting metal. In the IC processing, Co surfaces need to be flattened. This paper conducts dynamic polishing experiments and static corrosion experiments on the electrical, chemical, and mechanical factors involved in the cobalt electrochemical mechanical polishing (ECMP). Then, the impact and proportion of individual and combining factors on Co ECMP are quantitatively analyzed. The experimental results show that mechanical action plays a primary role in Co ECMP, compared with individual chemical or electrical action. The ratio of individual mechanical, chemical, and electrical action proportion is 50.46%, 11.17%, and 6.20%, respectively. However, chemical and electrical assistance with mechanical action can achieve twice efficiency and high-quality polishing of Co. For instance, the ratio of mechanical-chemical or electrical-chemical-mechanical cooperation is 72.05% or 100% respectively. In addition, polarization curves, EDS, and XPS are used to analyze the Co ECMP process and products. And 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-BTA complexes. Mechanical, chemical, and electrical factors collaborate to constantly form and remove Co-BTA, achieving rapid material removal and obtaining atomic-level smooth surfaces.