Reduction of current leakage in chemical-vapor deposited Ta2O5 thin-films by oxygen-radical annealing [DRAM dielectric]

The electrical properties of CVD-Ta/sub 2/O/sub 5/ thin-films are improved by post-deposition oxygen-radical annealing. Since this annealing is carried out at very low pressure (10/sup -6/ torr), the growth of SiO/sub 2/ in Ta/sub 2/O/sub 5//Si interface is small, and the residual carbon in the film is reduced. The damage to the Ta/sub 2/O/sub 5/ film caused by oxygen ion bombardment is negligible, because few charged particles reach the film. A critical voltage V/sub crit/ of 1.45 V for the leakage current less than 10/sup -8/ A/cm/sup 2/ was realized by these Ta/sub 2/O/sub 5/ films with the effective thickness t/sub eff/ of 2.59 nm. The V/sub crit/ value for oxygen-radical annealing is higher than that for oxygen-plasma annealing.