A novel diffusion barrier using oxygen stopping layer for high density FRAM

Abstract

A novel diffusion barrier was successfully developed by using an oxygen stopping layer between Ir barrier films. The oxygen stopping layer was generated by inserting a Ti layer between Ir films, which results in the sandwiched form of Ir/Ti/Ir multi-layer. The diffusion barrier properties were enhanced by refraining oxygen from penetrating into polysilicon plug, which might be attributed to the reaction of oxygen with the Ir-Ti layer. It was confirmed in Auger depth profile that the oxygen was well localized in the stopping layer after annealing at 700°C for 10 min in O2 ambient. The multi-stack barrier exhibited low contact resistance of 320 and 650 ohm for contact size of 0.6×0.6 and 0.4×0.4 μm2, respectively. The PZT films prepared on Pt/IrO2/Ir-Ti-Ir/poly substrate shows remnant polarization of 20 μC/cm2 and coercive voltage of 1.2V at 5V. It was demonstrated that this novel barrier can solve barrier contact problem occurred in high density 16Mb FRAM.