Acceleration Effect of CuCN in Ag Electroplating for Ultralarge-Scale Interconnects

Abstract

The addition of CuCN accelerated the deposition rate in cyanide-based Ag electroplating. The catalytic effect came from the high-order complexation of Cu with the free CN− ions in electrolyte. It changed the equilibrium state of the electrolyte, presented as an increase in the amount of Ag CN 2 − compared to Ag CN 3 2−. Because Ag CN 2 − could be reduced more easily, Ag electroplating was accelerated. Fourier transform infrared analysis showed the equilibrium change with the increase in Ag CN 2 − peak according to the CuCN addition. For superfilling, it is necessary to localize the complexation on the Cu surface.