Interfacial reactions in the Si/TaC/Cu system

Interfacial reactions in the Si/TaC/Cu metallization system were investigated by utilizing transmission electron microscopy and a combined kinetic and thermodynamic analysis. The formation of an amorphous Ta[C,O] layer was observed at the TaC/Cu interface at 600 °C. After annealing at the same temperature a thin amorphous layer was detected also at the Si/TaC interface. After annealing at 750 °C the thickness of the amorphous layer at the Si/TaC interface had increased and a mixture of crystalline and amorphous phases could be detected inside the TaC layer. This was anticipated to be the preliminary stage of the formation of SiC and TaSi2 that occurred at 800 °C. Overlapping with thickening of the amorphous layer formation of large Cu3Si precipitates took place and the layered metallization structure was partially destroyed. In order to obtain more information on the reactions at the Si/TaC interface and the effect of oxygen on the stability of TaC the ternary Si-Ta-C and Ta-C-O phase diagrams were evaluated from the assessed binary data. Activity diagram was also calculated to evaluate the possible reaction sequence at the Si/TaC interface. The observed reaction structure was found to be consistent with the thermodynamics of the ternary system.