Diffusion barrier properties of amorphous TiB_(2) for application in Cu metallization

摘要

Amorphous TiB_(2) films were obtained by magnetron cosputtering and conditions for obtaining good diffusion barrier properties against penetration by Cu were evaluated by Auger electron spectroscopy. Controlling the B/Ti ratio is of major importance. It was found that the best diffusion barrier properties were obtained in stoichiometric or overly stoichiometric titanium boride. Almost no penetration of Cu occurred at 953 K for 30 min. Films of TiB_(x) where x<2.0 are of inferior barrier quality. At B/Ti≈1.63 complete deterioration of the barrier property occurs. The effect of composition is explained in terms of the packing density of the amorphous film. Preliminary diffusion studies by secondary ion mass spectroscopy in the amorphous titanium boride of near-stoichiometric composition (B/Ti≈2.07) indicate that two mechanisms seem to operate in the TiB_(2) film. The low temperature mechanism occurs in the amorphous disordered structure, whereas at higher temperature diffusion occurs in an amorphous film in which short-range order exists. An activation energy of ≈2.0 eV was derived from the steep slope of the Arrhenius curve that represents diffusion in the short-range ordered region.