Barrier properties of Ta–RuO2 diffusion barrier for dynamic random access memory capacitor bottom electrodes

Abstract

We proposed the Ta–RuO2 diffusion barrier for oxygen in the dynamic random access memory capacitor bottom electrode, and investigated the barrier and electrical properties of the developed diffusion barrier. The Ta–RuO2/TiSi2/poly-Si/SiO2/Si contact system deposited with and without the SiO2 capping layer showed the lower total resistance and ohmic characteristics up to 800 °C. For the Ta–RuO2/TiSi2/poly-Si/SiO2/Si contact system, no other phases observed except for the formation of conductive RuO2 phase in the barrier film by reaction with the indiffused oxygen after annealing in air, but the thin oxidized layer at the Ta–RuO2/TiSi2 interface was formed by external oxygen. However, a large number of the crystallites in the annealed samples compared to that of as-deposited film were observed even after depth profile. The crystallites consisted of Ru and O containing a small amount of Ta. In addition, the embedded RuO2 crystalline phase was observed in the thin oxidized TiSi2 surface layer. Correspondingly, we suggest that the ohmic mechanism of the Ta–RuO2/TiSi2/poly-Si/SiO2/Si contact system is an embedded RuO2 crystalline phase involving a small amount of Ta in a Ta amorphous structure.