Ta-rich tantalum silicide nano-cluster diffusion barrier in ULSI metallization

Sputtered Ta-Si_x nanostructure film was investigated as a barrier material for Cu metallization. The TaSi_x film was deposited by co-sputtering of Ta and Si targets in Ar gas. The resistivity of the films varies from 238 μΩ-cm to 900 μΩ-cm with Si/Ta ratio from 0.256 to 2.172. XRD, HRTEM, XPS, and AES were employed to understand the crystalline structure, chemical structure, and atomic composition. Furthermore, we use C-V measurement to study the thermal stability of the TaSi film. The MOS capacitors of sputtered Cu or electroplating Cu/Ta-Si (30 nm)/methylsilsesquioxane (MSQ), porous SiO₂ or SiO₂/p-Si structure were annealed at the temperature from 350°C to 500°C for 30 min in nitrogen ambient. The MSQ and porous SiO₂ films with thickness 200 nm were spin-coated on the Si wafer. The dielectric constant of these films was about 2.6. From the flat band shift and the variation of inversion capacitance, the diffusion performance can be evaluated