Interface reliability and diffusion barrier property of Co-W barrier layer with modulated structure

Abstract

Co-W alloy is a promising alternative of barrier layer in Sn/Cu joints in microelectronic packaging due to its appealing resistance to electro-migration and thermal fatigue. The amorphous Co-W alloy with high W content has well-performed barrier property. However, the modest interfacial strength between the amorphous Co-W and Sn limits its application. In this work, the Co-5 at. % W/Co-20 at. % W modulated-structure multilayer barriers were prepared by pulse electrodeposition with periodic change of deposition current density. The modulated Co-W barrier exhibited better diffusion barrier property with low rates of IMC growth and barrier consumption and ∼17 % higher shear strength than those of single-layer barrier. Early participation of amorphous structure slowed down the IMCs reaction during the isothermal aging in modulated Co-W barrier with 8–32 layers, while the finer grain in modulated Co-W barrier with 64–128 layers lead to quick diffusion of Co atoms, which was detrimental to barrier performance.