An improvement of low temperature characteristics of an La-doped Pb(Zr,Ti)O3 capacitor

Abstract

Abstract We developed a lanthanum-doped Pb(Zr0.4,Ti0.6)O3 (PLZT)-based ferroelectric capacitor (FE) aiming at low-voltage operation of ferroelectric random access memory at low temperatures down to −45 °C. High-temperature sputter-deposited IrO x (1 < x < 2) or HT-IrO x was employed as a top electrode (TE) instead of room-temperature (RT) deposited IrO x or RT-IrO x over two PLZT stacked layers. We observed that polarization characteristics drastically improved even at −45 °C by employing HT-IrO x and thinning PLZT, even though leakage current was increased by about one order of magnitude. Transmission electron microscopy observations showed that HT-IrO x has a columnar-like crystalline structure while RT-IrO x has a granular-like crystalline structure. Secondary ion mass spectroscopy indicated that Pb diffusion from PLZT into TE was suppressed by HT-IrO x , which is considered to cause the improvement of polarization characteristics.