SrBi_2Ta_2O_9 Thin Films Fabricated by Sol-Gel Method with IrO_2 Electrodes(Special Issue on Advanced Memory Devices Using High-ε and Ferroelectric Films)

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概要

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• We prepared alkoxide solutions to fabricate SrBi_2Ta_2O_9 (SBT) ferroelectric capacitors with IrO_2 electrodes. In this process, to minimize excess bismuth, the Sr:Bi:Ta mole ratio was kept at 0.9:2.1:2.0, i.e., neary stoichiometric. Three types of solution-mixed-only (MIX), complexed (COMP), and hydrolyzed (HYD)-were used. The HYD capacitor had low absolute leakage current, 10^<-7> A/cm^2 order, and good saturation properties to 6 V. When voltage was applied to each capacitor at 2 to 6 V, MIX and COMP capacitors showed only partial hysteresis loops due to a high leakage current, reflecting the I-V characteristics. These results are probably due to film density caused by metaloxane network bonding. A fatigue endurance test was conducted using cycling of polarization switching at 6 V using the HYD capacitor with IrO_2 elctrodes. Slight changes were, however, observed in hysteresis loop configuration, but good hysteresis properties were kept up ro 1.04×10^<12> cycles. We compared SBT ferroelectric thin films fabricated with Pt electrodes and with IrO_2 electrodes. Scarcely any difference due to SBT in the XRD pattern was seen, depending on the substrate material. We found that the use of IrO_2 electrodes had the effect of decreasing the crystallization temperature. On Pt and IrO_2 electrodes, the two films have surface morphology quite different from that of the rod-like structure wellknown for SBT films prepared using a metal 2-ethylhexanate solution. Their surfaces show a similar morphology with relatively large, closely packed grains. A comparison of the I-V characteristics after reannealing showed that the capacitor with IrO_2 electrodes had a higher leakage current than that with Pt electrodes. The leakage current was probably due to the density of the film and interface between the SBT film and electrodes.

• 社団法人電子情報通信学会の論文
• 1998-04-25

著者

• Koiwa Ichiro

  The Authors Are With Research And Development Group Oki Electric Industry Co. Ltd.

• Ashikaga Kinya

  The Authors Are With Research And Development Group Oki Electric Industry Co. Ltd.

• Kaifu Katsuaki

  The Authors Are With Research And Development Group Oki Electric Industry Co. Ltd.

• OKADA Yukihisa

  The authors are with Research and Development Group, Oki Electric Industry Co., Ltd.

• Okada Y

  Sumitomo Electric Ind. Osaka Jpn

関連論文

• SrBi_2Ta_2O_9 Thin Films Fabricated by Sol-Gel Method with IrO_2 Electrodes(Special Issue on Advanced Memory Devices Using High-ε and Ferroelectric Films)
• Crystallization Process of Sr_Bi_Ta_2O_9 Thin Films with Different Crystal Orientation Prepared by Chemical Liquid Deposition Using Alkoxide Precursor(Special Issue on Advanced Memory Devices Using High-ε and Ferroelectric Films)
• Structural Defects in Sr_Bi_Ta_2O_9 Thin Film for Ferroelectric Memory(Special Issue on Advanced Memory Devices Using High-ε and Ferroelectric Films)
• Submicron Ferroelectric Capacitors Fabricated by Chemical Mechanical Polishing Process for High-Density Ferroelectric Memories
• Submicron Ferroelectric Capacitors Fabricated by CMP Process for High-Density FeRAMs
• Preparation of Ferroelectric Sr_Bi_Ta_2O_9 Thin Films by Misted Deposition Method Using Alkoxide Solution(Special Issue on Advanced Memory Devices Using High-ε and Ferroelectric Films)

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