Superfilling of Cu-Ag using electrodeposition in cyanide-based electrolyte

Superfilling of Cu-Ag formetal interconnection was investigated in cyanide-based electrolyte. Superfilling was successfully achieved using the combination of KSeCN and thiourea. The trenches having widths in a range between 120 nm and 1.7 μm (depth: 400 nm) were filled without any voids. The continuous acceleration effect of KSeCN on Cu-Ag electrodeposition in the concentration range between 3.75 and 20 μM was confirmed, and thus the accumulation of KSeCN at the bottom of trench was surmised to be the main reason of Cu-Ag superfilling. Dissimilar to the previous superfilling of Ag or Au, which could be characterized as the fast surface diffusion of KSeCN, remarkable bumps and convex profiles at the corners of low-aspect-ratio trenches were developed. The proposed formula has led to defect-free superfilling of Cu-Ag with the Ag concentration in the range of 4.6 to 7.9 atom%.