Tantalum carbide and nitride diffusion barriers for Cu metallisation

摘要

The reactions in the Si/TaC/Cu and Si/Ta_2N/Cu metallisation systems were investigated by X-ray diffraction, Rutherford backscattering, scanning electron microscope and the transmission electron microscopy. The results were then combined with the assessed ternary Si-Ta-C, Ta-C-Cu, Si-Ta-N and Ta-N-Cu phase diagrams. It was found that both barriers ultimately failed due to diffusion of Cu through the barrier and accompanied formation of Cu_3Si at temperatures higher than 725℃. However, in the TaC barriers the formation of amorphous TaO_x. layer with significant amounts of C took place at the TaC/Cu interface already at 600℃. Similar behaviour at 'low' temperatures was also noted in the Ta_2N barriers.