Oxidation resistance of tantalum-ruthenium dioxide diffusion barrier for memory capacitor bottom electrodes

The effect of the RuO₂ addition into a Ta film on the oxidation resistance of a diffusion barrier for the Ta+RuO₂/Si system was investigated. The Ta+RuO₂/Si system was sustained up to 800°C without an increase in resistivity, while the Ta/Si structure completely degraded after annealing at 450°C. The Ta+RuO₂ diffusion barrier showed an amorphous microstructure for an as-deposited state and formed a conductive RuO₂ phase after annealing. Ta was sufficiently bound to oxygen of RuO₂ for an as-deposited state, but RuO₂ was divided into Ru and Ru-O binding states. Ta-O bonds showed a little change compared to the as-deposited state with increasing annealing temperature, whereas Ru-O bonds significantly increased. Therefore, the Ta layer deposited by the RuO₂ addition effectively prevented the indiffusion of oxygen up to 800°C and its oxidation resistance was superior to those of polycrystalline nitride (TiN, TaN) and ternary amorphous (TaSiN) barriers reported by others.