Microcrystalline oxide-incorporated new diffusion barrier for dynamic random access memory and ferroelectric random access memory capacitor electrode

Microcrystalline oxide-incorporated new diffusion barrier for dynamic random access memory (DRAM) and ferroelectric random access memory (FRAM) capacitor electrodes is proposed. The thermal stability of the Pt/Ta+CeO₂/TiSi₂/poly-Si/SiO₂/Si contact system is investigated and is compared to that of the Pt/Ta/TiSi₂/poly-Si/SiO₂/Si contact system. The Pt/Ta+CeO₂/TiSi₂/poly-Si/SiO₂/Si contact system retained its structures up to 800°C without increase in electrical resistivity but the Pt/Ta/TiSi₂/poly-Si/SiO₂/Si contact system was completely degraded after annealing at 650°C. In the former case, since the addition of cerium dioxide (CeO₂) led to the stuffing of microcrystalline oxide along the grain boundaries in Ta matrix and CeO₂ was much heavier atomic weight than any stuffed elements, it prevented the interdiffusion of O, Pt, and Si through grain boundaries which can act as fast diffusion paths to high temperatures. It appears that the barrier properties of the microcrystalline oxide-incorporated new diffusion barrier are superior to polycrystalline transition metal barriers, polycrystalline nitride barriers, ternary amorphous compound barriers, and N₂- and O₂-stuffed barriers.