Facile Formation of Cu-Ag Film by Electrodeposition for the Oxidation-Resistive Metal Interconnect

Abstract

Cu-Ag film could be a candidate to solve the reliability problem in semiconductor interconnection without severe increase in the resistivity. In this research, Cu-Ag film was successfully deposited in cyanide-based electrolyte using electrodeposition, and the effects of the electrolyte composition, applied potential, and the concentration of KAg(CN)2 were researched. Prior to Cu-Ag electrodeposition, the conditions of Cu electrodeposition in cyanide-based electrolyte were precedently optimized in terms of the film resistivity. Ag was co-deposited in the film with an addition of KAg(CN)2 in CuCN-based electrolyte, and the atomic concentration of Ag was successfully controlled by varying the concentration of KAg(CN)2. The film consisted of three phases; Cu (111), Ag (111), and the alloy. The resistivity of as-deposited Cu-Ag film was significantly higher than that of Cu; however, after annealing at 350°C in an N2 atmosphere for 1 hr, we obtained a resistivity comparable to that of Cu. The segregation of Ag atoms at the surface after the annealing was also confirmed, and it resulted in the increase in Ag atomic concentration at the surface and the reduction of surface roughness. Finally, it was confirmed that Cu-Ag film had superior oxidation resistance to Cu.