Characterization of Sputtered Tantalum Carbide Barrier Layer for Copper Metallization

In this study, tantalum carbide ( TaC x ) films deposited by a sputtering process with a TaC target as diffusion barriers for Cu metallization were investigated for the first time. The thermal stability of Cu / TaC x / n ‐ Si and Cu / TaC x / p + n systems as a function of annealing temperature are reported and analyzed. The deposited TaC X , having an amorphous structure and a low resistance of around 385 μΩ cm, were characterized by sheet resistance measurement, X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy, scanning electron microscopy (SEM), secondary ion mass spectroscopy, and diode leakage current measurement. From XRD and SEM analysis, it was found that 600 Å TaC X in Cu / TaC x / Si structure can effectively prevent Cu penetration up to 600°C for 30 min, while more sensitive diode leakage measurement of Cu / TaC X / p + n indicates that the failure temperature is around 500°C. The failure of the TaC X layer was found to be mainly due to the diffusion of Cu along the localized defects of the TaC X barrier layer into underlying silicon. This has caused the formation of copper silicides and high junction leakage currents.