Co-sputtered TiB2 as a diffusion barrier for advanced microelectronics with Cu metallization

Titanium boride thin films were deposited from separate Ti and B targets by magnetron co-sputtering and the conditions for obtaining good diffusion barrier properties were evaluated. The best diffusion barrier properties against Cu penetration were obtained when the film was amorphous and deposited with RF bias. Auger electron spectroscopy (AES) and plan-view scanning electron microscopy (SEM) revealed that Cu penetration into amorphous titanium boride is appreciably greater in the unbiased specimen. The as-deposited amorphous film has a resistivity of 450–500 μΩ · cm, but after following annealing at ∼ 723°C for 1 h a substantial decrease in resistivity was obtained while the structure of the boride remained amorphous. The amorphous boride is stable up to 890°C. The crystallization temperature can be decreased by RF bias application, and under these conditions microcrystalline TiB2 can be formed already at ∼ 400°C. Crystalline TiB2 has a strong (001) preferred orientation. TiSi2 (C-54) is also formed during annealing at temperatures exceeding 765°C as a result of the reaction of titanium boride containing free Ti with the silicon substrate.