Tantalum carbide and nitride diffusion barriers for Cu metallisation
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 SiTaC, TaCCu, SiTaN and TaNCu 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 725C. 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 600C. Similar behaviour at low temperatures was also noted in the Ta2N barriers.
tantalum carbide diffusion barriers phase diagrams copper metallisation tantalum nitride