Ferroelectric capacitor with an asymmetric double-layer PLZT structure for FRAM

Abstract

We developed a lanthanum-doped Pb(Zr0.4,Ti0.6)O3 (PLZT)-based ferroelectric capacitor for low-voltage operation of ferroelectric memory for use in edge devices in the internet of things. The structure, consisting of PLZT stacked layers 30 and 90 nm thick, showed drastically improved performance in three main measures: low leakage current, high saturation polarization, and low saturation voltage. Secondary ion mass spectroscopy indicated that atomic interdiffusion between PLZT and IrOx in the top electrode (TE) was suppressed by the 30 nm thick PLZT, which plays the role of a diffusion barrier, producing a low leakage current and high saturation polarization. The higher oxygen atomic density of the PLZT near the TE interface lowers the oxygen vacancy, which should also suppress the leakage current and the P–V hysteresis shift (imprint). The large grain size and high crystalline quality of PLZT near the TE interface in the PLZT structure provide a high saturation polarization with low leakage current.