Effect on thermal stability of a Cu/Ta/Si heterostructure of the incorporation of cerium oxide into the Ta barrier

Abstract

The effects of CeO2 addition on the microstructural change of a Ta diffusion barrier film and thermal stability of the Cu/Ta/Si system were investigated. When a Ta layer was prepared with CeO2 addition, the silicide formation was retarded up to 800 °C. The Cu/Ta+CeO2/Si system retained its structure up to 800 °C without an increase in stack resistivity, while the Cu/Ta/Si structure degraded after annealing at 550 °C. The Ta+CeO2 diffusion barrier showed an amorphous microstructure and chemically strong bonds with Ta–Ce–O. It appeared that the thermal stability of the Cu/Ta+CeO2 interface as well as the Ta+CeO2/Si interface was higher than that of both Cu/Ta and Ta/Si interfaces. Therefore, the Ta film prepared by CeO2 addition effectively prevented the interdiffusion of Cu and Si through the diffusion barrier up to 800 °C.