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

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℃. High-temperature sputter-deposited IrOx (1<x<2) or HT-IrOx was employed as a top electrode (TE) instead of room-temperature (RT) deposited IrOx or RT-IrOx in addition with two PLZT stacked layers. We observed that polarization characteristics were drastically improved even at -45℃ by employing HT-IrOx and thinning PLZT, even though increasing leakage current by about one order of magnitude. Transmission electron microscopy (TEM) observed that HT-IrOx shaped columnar-like crystalline while RT-IrOx shaping granular-like crystalline. Secondary ion mass spectroscopy indicated that Pb diffusion from PLZT into TE was suppressed by HT-IrOx, which is considered to cause the improvement of polarization characteristics.