Amorphous TiB2 films were obtained by magnetron co-sputtering, and the conditions for obtaining good diffusion barrier properties against penetration by Cu were evaluated by using Auger electron spectroscopy. It was found that control of the B/Ti ratio was of great importance. The best diffusion barrier properties were exhibited by stoichiometric or over-stoichiometric material. Almost no penetration of Cu occurred during 0.5h at 953K (table 72). Films of TiBx, where x was less than 2.0, were of inferior barrier quality. When B/Ti was equal to about 1.63, complete deterioration of the barrier properties occurred. The effect of composition was explained in terms of the packing density of the amorphous film. Preliminary diffusion studies by secondary ion mass spectroscopy of amorphous material of near-stoichiometric composition (B/Ti equal to about 2.07) indicated that 2 mechanisms seemed to operate in the film. The low-temperature mechanism occurred in the amorphous disordered structure whereas, at higher temperatures, diffusion occurred in an amorphous film where short-range order existed. An activation energy of about 2.0eV was derived from the steep slope of the Arrhenius curve that represented diffusion in the short-range ordered region.

Diffusion Barrier Properties of Amorphous TiB2 for Application in Cu Metallization. J.Pelleg, G.Sade: Journal of Applied Physics, 2002, 91[9], 6099-104

Table 72

Diffusion of Cu in TiB2