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

• Published in: Japanese Journal of Applied Physics Vol. 61; no. SN; p. SN1013
• Main Authors: Wang, Wensheng, Eshita, Takashi, Takai, Kazuaki, Nomura, Kenji, Yamaguchi, Hideshi, Nakamura, Ko, Ozawa, Soichiro, Nagai, Kouichi, Watanabe, Junichi, Mihara, Satoru, Hikosaka, Yukinobu, Saito, Hitoshi, Kojima, Manabu
• Format: Journal Article
• Language: English
• Published: Tokyo IOP Publishing 01-11-2022; Japanese Journal of Applied Physics
• Subjects: Capacitors; Columnar structure; Crystal structure; Crystallinity; endurance; FeRAM; ferroelectric capacitor; Ferroelectric materials; Ferroelectricity; High temperature; imprint; IrO; Lanthanum; Lead lanthanum zirconate titanate; Lead zirconate titanates; Leakage current; Low temperature; PLZT; polarization; Polarization characteristics; Random access memory; Room temperature; Secondary ion mass spectroscopy; Zirconium
• ISSN: 0021-4922; 1347-4065
• DOI: 10.35848/1347-4065/ac7f7b

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 IrOx (1 < x < 2) or HT-IrOx was employed as a top electrode (TE) instead of room-temperature (RT) deposited IrOx or RT-IrOx over two PLZT stacked layers. We observed that polarization characteristics drastically improved even at −45 °C by employing HT-IrOx and thinning PLZT, even though leakage current was increased by about one order of magnitude. Transmission electron microscopy observations showed that HT-IrOx has a columnar-like crystalline structure while RT-IrOx has a granular-like crystalline structure. 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.