Barrier properties of ultrathin amorphous Al–Ni alloy film in Cu/Si or Cu/SiO2contact system

The diffusion barrier performance of an ultrathin amorphous Al–Ni (a‐Al–Ni) film as barrier layer in a sandwiched scheme Cu/barrier/Si and Cu/barrier/SiO2/Si is investigated. Microstructures, electrical properties, surface morphologies, and interfaces for the samples annealed at various temperatures are measured using X‐ray diffraction (XRD), sheet resistance measurements, atomic force microscopy (AFM), and transmission electron microscopy (TEM). The results present 4.5‐nm‐thick a‐Al–Ni can achieve good thermal stability up to 750 °C. Cu silicide cannot be observed in XRD data up to 800 °C. However, the abrupt increase in sheet resistance value and the appearing island‐like grains in AFM images for the sample annealed at 800 °C indicate the failure of the barrier structure. The failure mechanism of barrier layer is discussed and can be attributed to the dewetting of Cu film along grain boundary grooving. The amorphization of the barrier layer and clear interfaces with its adjacent layers are further authenticated by high resolution TEM. It is also found that the growth orientation and surface morphology of Cu film are related to the substrates (monocrystalline Si and amorphous SiO2) under the barrier layer.