Electroless Ni alloy plating as a diffusion barrier for through silicon vias in three-dimensional packaging

Abstract

Ni- and Co-based amorphous films are alternative diffusion barrier materials for Cu interconnection in three-dimensional (3D) packaging applications. In this paper, electroless Ni–P and Ni–W–P films deposited in through-silicon vias (TSVs) were prepared as a diffusion barrier and seed layer of Cu filling by using Sn–Pd activation pretreatment. The thermal stability of the electroless Ni alloy films subjected to rapid thermal annealing (RTA) in H2 atmosphere was investigated. The barrier properties of the electroless Ni alloy films were evaluated over a range of temperatures using auger electron spectroscopy (AES) and energy dispersive X-ray spectroscopy (EDS) line-scan. The microstructures, crystal structures and electrical resistivity were also examined. It was found that Ni alloy films are amorphous as deposited, that the films retain amorphous or amorphous-like structures after undergoing annealing at 400 °C for 1 h, and that they are feasible for the diffusion barrier layer for 3D Cu interconnect technology.