Characteristics of Plasma-Treated Amorphous Ta-Si-C Film as a Diffusion Barrier for Copper Metallization

Ta-Si-C film was prepared by magnetron sputtering, and the thermal stability of the plasma-treated film as a copper diffusion barrier was evaluated. The barrier properties and failure behaviors of the studied films were elucidated using a four-point probe, x-ray diffraction, scanning electron microscopy, and transmission electron microscopy. The as-deposited Ta-Si-C film had an amorphous structure, and the structure remained stable at an elevated temperature, allowing the film to be adopted as a barrier to inhibit Cu diffusion. The Cu/Ta 26 Si 41 C 32 /Si stacked structure had a failure temperature of 750°C/1 min when the 5-nm-thick Ta 26 Si 41 C 32 film was treated by exposure to Ar/H 2 plasma mixture, while the stacked film failed at 800°C/1 min when treated by exposure to Ar/N 2 plasma mixture. Using the Ar/N 2 plasma treatment favorably enhanced the thermal stability of the Ta 26 Si 41 C 32 thin film as a barrier for Cu interconnections. When the Ta-Si-C film thickness was further reduced to 2 nm, the film retained the barrier effect at 650°C, 700°C, and 750°C for Ta 34 Si 47 C 18 , Ta 30 Si 44 C 25 , and Ta 26 Si 41 C 32 compositions, respectively.