Amorphous Ta-Nanocrystalline RuO_(x) Diffusion Barrier for Lower Electrode of High Density Memory Devices

摘要

The effects of the amount of RuO_(2) added in the Ta film on the electrical properties of a Ta-RuO_(2) diffusion barrier were investigated using n~(++)-poly-Si substrate at a temperature range of 650-800℃. For the Ta layer prepared without RuO_(2) addition, Ta_(2)O_(5) phase formed after annealing at 650℃ by reaction between Ta and external oxygen, leading to a higher total resistance and a non-linear I-V curve. Meanwhile, in the case of the Ta film being deposited with RuO_(2) incorporation, not only a lower total resistance and ohmic characteristics exhibited, but also the bottom electrode structure was retained up to 800℃, attributing to the formation of a conductive RuO_(2) crystalline phase in the barrier film by reaction with the indiffused oxygen because of a Ta amorphous structure formed by chemically strong Ta-O or Ta-Ru-O bonds and a large amount of conductive RuO_(2) added. Since a kinetic barrier for nucleation in formation of the crystalline Ta_(2)O_(5) phase from an amorphous Ta(O) phase is much higher than that of crystalline RuO_(2) phase from nanocrystalline RuO_(x) phase, the formation of the RuO_(2) phase by reaction between the indiffused oxygen and the RuO_(x) nanocrystallites is kinetically more favorable than that of Ta_(2)O_(5) phase.