Effects of complexing reagents on electroless nicke l-iron alloy plating for diffusion barrier of UBM

In this research, bath stability and deposition characteristics of electroless Ni-Fe were investigated with variations of sodium citrate concentrations. Complexing agents such as sodium citrate are one of the main components of the electroless plating bath. Since they could play various roles such as maintaining pH stability, preventing precipitation of metal salts, and reducing the concentrations of free metal ions, the concentrations of the complexing agent in the plating bath is an important parameter for electroless deposition processes. In this research, unstable baths were obtained without sufficient sodium citrate concentrations and these phenomena were analyzed. Moreover, deposition characteristics of electroless Ni-Fe for under bump metallurgy (UBM) diffusion barrier were also investigated using energy dispersive spectroscopy (EDS) and field emission scanning electron microscopy (FESEM).