Characterisation of the electroless nickel deposit as a barrier layer/under bump metallurgy on IC metallisation

Selective electroless nickel–phosphorus deposits on integrated circuit (IC) metallisation such as copper and aluminium were characterised using differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) for elemental analysis. Annealing the Ni–P deposits in nitrogen atmospheres at temperatures compatible with organic dielectrics for IC components, such as polyimide, was performed to characterise the deposits. The crystallisation behaviour of the electroless nickel deposits with different concentrations of co-deposited phosphorus was examined.