Electrical properties of the Ta-RuO2 diffusion barrier for high-density memory devices

초록

The electrical properties of a Ta layer prepared with and without RuO<inf>2</inf> addition were investigated. The Ta+RuO<inf>2</inf>/TiSi<inf>2</inf>/poly-Si/SiO<inf>2</inf>/Si contact system exhibited lower total resistance and ohmic characteristics up to 800 °C. Meanwhile, the Ta/TiSi<inf>2</inf>/poly-Si/SiO<inf>2</inf>/Si contact system showed higher total resistance and nonohmic behavior after annealing at 650 °C, attributed to the oxidation of both Ta and TiSi<inf>2</inf> layers. In the former case, a Ta+RuO<inf>2</inf> diffusion barrier showed an amorphous Ta microstructure and embedded RuO<inf>x</inf> nanocrystals in the as-deposited state. The conductive RuO<inf>2</inf> crystalline phase in the Ta+RuO<inf>2</inf> film was formed by reaction between the nanocrystalline RuO<inf>x</inf> and oxygen indiffused from air during annealing. When the Ta layer was deposited with RuO<inf>2</inf> addition, therefore, both the electrical properties and the oxidation resistance of the Ta+RuO<inf>2</inf> diffusion barrier were better than those of TiN, TaN, and Ta-Si-N barriers.