Tantalum-ruthenium dioxide as a diffusion barrier between Pt bottom electrode and TiSi2 ohmic contact layer for high density capacitors

초록

The effects of RuO<inf>2</inf> addition on the barrier properties of the Ta layer were investigated at the temperature range of 650-800°C in air. For the Pt/Ta/TiSi<inf>2</inf>/poly-Si/SiO<inf>2</inf>/Si structure, its layer structure was completely collapsed after annealing at 650°C, resulting in higher total resistance and Schottky characteristics. For the Pt/Ta+RuO<inf>2</inf>/TiSi<inf>2</inf>/poly-Si/SiO<inf>2</inf>/Si structure, however, it exhibited the lower total resistance and ohmic characteristics, and its layer structure was retained up to 800°C. A Ta amorphous structure by the chemically strong Ta-O or Ta-Ru-O bonds and nonstoichiometric, nanocrystalline RuO<inf>x</inf> resulted in the formation of a conductive RuO<inf>2</inf> phase in the Ta+RuO<inf>2</inf> barrier film after an annealing, leading to the prevention of the interdiffusion of Pt, Si, and external oxygen through the diffusion barrier as well as surface oxidation up to 800°C. Therefore, the thermal stability for the Pt/Ta+RuO<inf>2</inf>/TiSi<inf>2</inf>/poly-Si/SiO<inf>2</inf>/Si structure was higher than that for Pt/Ta/TiSi<inf>2</inf>/poly-Si/SiO<inf>2</inf>/Si structure. © 1999 American Institute of Physics.