Investigation of Pt/Ta diffusion barrier using hybrid conductive oxide (RuO2) for high dielectric applications

Abstract

The Pt/Ta diffusion barrier using hybrid conductive oxide (RuO2) for dynamic random access memory and ferroelectric random access memory capacitor bottom electrodes is proposed. The thermal stability of Pt+RuO2 (50 nm)/Ta+RuO2 (50 nm)/TiSi2/poly-Si/SiO2/Si contact system is investigated and compared to that of the Pt(50 nm)/Ta(50 nm)/TiSi2/poly-Si/SiO2/Si contact system. The Pt+RuO2/Ta+RuO2/TiSi2/poly-Si/SiO2/Si contact system sustained its structure up to 650 °C, whereas Pt/Ta/TiSi2/poly-Si/SiO2/Si contact system was completely degraded after annealing at 650 °C. In the former case, the addition of ruthenium dioxide (RuO2) into the Pt bottom electrode layer led to retardation of the oxygen indiffusion, preventing the indiffusion of oxygen up to 650 °C. In addition, the Ta+RuO2 diffusion barrier showed an amorphous structure and RuO2 is bound to the Ta matrix, inhibiting the interdiffusion of O, Pt, and Si through grain boundaries which can act as fast diffusion paths up to high temperatures. Therefore, it appeared that the barrier properties of Pt/Ta diffusion barrier are improved by using hybrid conductive oxide (RuO2).