Tungsten-based thin film metallic glass as diffusion barrier between copper and silicon

A qualified diffusion barrier layer in integrated circuits is essential to prevent the degradation of devices due to the inter-diffusion between Cu and Si for Cu metallization. In this work, the performance of amorphous W-Ni-B thin film metallic glass (TFMG) as the diffusion barrier layer is reported. The Cu (150 nm)/W-Ni-B (10 nm)/Si multilayered structures were fabricated by sputtering and annealing at 700-950 degrees C for 30 min. The mechanical properties and thermal characteristics of W-Ni-B TFMG were evaluated by nanoindentation and differential scanning calorimeter, respectively. The transmission electron microscope-EDS elemental mapping and line scan were used to study the element distribution and inter-diffusion behavior of the multilayered structure. It was found that W-Ni-B TFMG possessed high hardness of 20 GPa and high glass transition/crystallization temperatures of 863 degrees C/903 degrees C. The W-Ni-B TFMG could effectively block Cu-Si inter-diffusion for the annealing temperature up to 800 degrees C. Inter-diffusion and formation of Cu3Si compounds with high electric resistivity at 950 degrees C annealing resulted in failure of the barrier layer. Based on its unique combination of excellent barrier performance and high hardness, W-Ni-B TFMG could be regarded as a robust diffusion barrier layer for Cu interconnect technology.