Electrochemical Behavior and Analysis of Organic Additives in Cobalt Damascene Baths

The copper dual damascene process has been used in semiconductor manufacturing since it was introduced by IBM in mid-1990. Since then, copper interconnects shrunk dramatically following the principles of Moore’s law. Currently, there are questions regarding the extendibility of the copper dual damascene flow as the IC industry moves beyond the 10 nm node. Copper interconnects are becoming more compact at each node, causing an increase in the resistance-capacitance delay. Furthermore, voids that occur in heavily scaled vias severely impact yield. Leading semiconductor manufacturers are exploring novel metallization methods to solve these issues. One way to solve the problem is to identify metallization alternatives that provide resistance benefits over conventional technology without compromising reliability and yield. Cobalt is considered as a potential replacement candidate for copper.Cobalt plating baths typically contain cobalt salt, boric acid, and organic additives . We have recently developed new analytical techniques for complete analysis of cobalt damascene plating baths. Electrochemical methods are used to study behavior and analyze multiple organic additives present in cobalt plating baths , while other bath components can be effectively analyzed with traditional titration and/or spectroscopic methods. Fig. 1 shows the effects of commercial Suppressor and Accelerator additives used for cobalt plating. The voltammograms indicate decreased plating rate when Suppressor additive is injected into the VMS electrolyte. VMS stands for Virgin make-up solution, which contains only inorganic components. The injection of Accelerator into the electrolyte with Suppressor causes increased plating rate. Fig. 2 shows response curves of Suppressor and Accelerator. All responses are reproducible and allow accurate determination of organic additives in plating baths. This article will also reveal the effects of other bath components on the plating properties of cobalt. We will also present statistical results of electrochemical analysis of both organic additives. Figure 1