The reactions in the Si/TaC/Cu and Si/Ta2N/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 Cu3Si at temperatures higher than 725°C. However, in the TaC barriers the formation of amorphous TaOx layer with significant amounts of C took place at the TaC/Cu interface already at 600°C. Similar behaviour at 'low' temperatures was also noted in the Ta2N barriers.
- Copper metallisation, tantalum carbide
- Diffusion barriers
- Phase diagrams
- Tantalum nitride