Control of Crystal Orientations and Its Electrical Properties of PZT/Ru and PZT/RuO 2 Thin Films by MOCVD
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Control of Crystal Orientations and Its Electrical Properties of PZT/Ru and PZT/RuO2 Thin Films by MOCVD Kazuo Shinozaki, Akinori Iwasaki, Naoki Wakiya and Nobuyasu Mizutani Department of Metallurgy and Ceramic Science, Tokyo Institute of Technology 2-12-1 Ookayama, Meguro-ku, Tokyo 152-8550, JAPAN ABSTRACT Ru and RuO2 thin films were deposited on (100)LaAlO3 (LAO), (100)MgO and (111)Pt/Ir/ SiO2/Si substrates by MOCVD. Pb(Zr,Ti)O3 (PZT) was fabricated on Ru/LAO and RuO2/LAO. Ru thin films deposited at 400oC or higher on LaAlO3 and MgO showed epitaxial (001) crystal orientation. (001) uniaxial Ru was deposited on Pt/Ir/SiO2/Si. RuO2 thin films with (100) orientation were deposited both on LaAlO3 and Pt/Ir/SiO2/Si. (110)-oriented RuO2 thin film was deposited on MgO. Epitaxial RuO2 thin films were deposited on LaAlO3 and MgO at 400oC or higher. The smoothest surfaces and the lowest room-temperature electrical resistivities were obtained at 400oC and 450oC, respectively. The crystal orientations and electrical properties of the PZT thin films deposited on the Ru and RuO2 thin films at 550oC were strongly affected by the crystal orientations and microstructure of the Ru and the RuO2 films. Rhombohedral Pb(Zr0.6Ti0.4)03 thin films deposited on RuO2/LAO and Ru/LAO at 550oC with lower growth rate (1.2nm/min) showed (110) and (001) orientation, respectively. The remanent polarization value (Pr) for (001) PZT on Ru/LAO was ~70 µC/cm2. (110) PZT on RuO2/LAO showed lower Pr (~30 µC/cm2), but showed low leakage current (10-9 A/cm2 at 500kV/cm). The dense microstructures and smooth surface structures brought the good leakage characteristics. INTRODUCTION Pb(Zr,Ti)O3 (PZT) is one of important materials to realize the non-volatile ferroelectric random-access-memory (FeRAM). To enhance the reliability of FeRAM, it is most important to control the crystal orientations and the texture of the PZT thin films to realize the well-oriented domains and homogeneous microstructures. Metal electrode, such as Pt, produces the detrimental effects to PZT thin film that is produced by the oxygen deficiency in PZT lattice near the interface with metal electrode. The oxide electrode, such as RuO2, IrO2, or the metal electrode with less detrimental like Ru has been applied to PZT based FeRAM. We have studied to grow epitaxial thin film on Si by introducing various buffer layers. For example, SrTiO3 thin film was epitaxially grown on Si substrate with [SrO or TiO2 atomic layer]/CeO2/(Y-doped ZrO2) buffer layer. [1] As a preliminary study to realize the PZT/(bottom electrode)/ (buffer layer)/(CeO2)/(Y-doped ZrO2)/Si epitaxial structure, we have tried to fabricate the RuO2 or Ru with different crystal orientation on various single crystal substrates, and deposited the PZT thin film on them. In this paper, formation condition, crystal orientation and electrical properties of Ru and RuO2 thin film deposited on LaAlO3, MgO and Pt/IrO2/SiO2/Si substrates were explained and the effect of the bottom electrode conditions of Ru/LaAlO3 and RuO2/LaAlO3 on
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