Effects of Amorphous Co W and Ni W Barrier Layers on the Evolution of Sn/Cu Interface

In advanced microelectronic packaging, a high-performance diffusion barrier layer is urgently required for Sn/Cu joint, to hinder the formation of Cu-Sn intermetallic compounds (IMCs). In this work, the barrier performance of electrodeposited Ni, Co, amorphous Ni-W and amorphous Co-W were studied. During 150 degrees C aging test, amorphous Co-W exhibited the best barrier performance among the four barrier layers with the slowest IMC growth rate. Compared with the reaction-controlled IMCs in Sn/Co/Cu sample, the IMCs' growth rates in the other three samples were limited by different diffusion species. Due to the larger diffusion flux of Ni diffusing from Ni-W layer than that of Co from Co-W layer, IMCs in Sn/Ni-W/Cu sample grew faster than Sn/Co-W/Cu sample. The nanoindentation test indicated that the IMCs formed in Sn/Co-W/Cu sample were less sensitive to brittle fracture than Sn/Ni-W/Cu sample. This research provides a scientific basis for the selection of barrier layers with excellent barrier performance and mechanical properties in electronic packaging.