Browsing by Author "Si, Jie"

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    Ferroelectric bismuth titanate films by hot wall metalorganic chemical vapor deposition
    Si, Jie; Desu, Seshu B. (American Institute of Physics, 1993-06-01)
    Ferroelectric bismuth titanate thin films were successfully deposited on Si, sapphire disks, and Pt/Ti/SiO2/Si substrates by hot wall metalorganic chemical vapor deposition. Triphenyl bismuth [Bi(C6H5)3] and titanium ethoxide [Ti(C2H5O)4] were used as the precursors. The deposition rates were in the range of 3.9-12.5 nm/min. The Bi/Ti ratio was easily controlled by precursor temperature, carrier gas flow rate, and deposition temperature. As-deposited films were pure Bi4Ti3O12 phase. The films were specular and showed uniform and fine grain size. Optical constants as a function of wavelength, were calculated from the film transmission characteristics in the ultraviolet-visible-near infrared (UV-VIS-NIR) region. The 550-degrees-C annealed film showed a spontaneous polarization of 26.5 muC/cm2 and a coercive field of 244.3 kV/cm.
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    Metalorganic chemical vapor deposition of (Ba.sub.1-x Sr.sub.x)RuO.sub.3 /(Ba.sub.1-x Sr.sub.x)TIO.sub.3 /(Ba.sub.1-x Sr.sub.x)TiO.sub.3 /(Ba.sub.1- Sr.sub.x)RuO.sub.3 capacitors for high dielectric materials
    (United States Patent and Trademark Office, 1997-05-13)
    A dynamic random access memory device having a ferroelectric thin film perovskite (Ba.sub.1-x Sr.sub.x)TiO.sub.3 layer sandwiched by top and bottom (Ba.sub.1-x Sr.sub.x)RuO.sub.3 electrodes. The memory device is made by a MOCVD process including the steps of providing a semiconductor substrate, heating the substrate, exposing the substrate to precursors including at least Ru(C.sub.5 H.sub.5).sub.2, thereafter exposing the substrate to precursors including at least TiO(C.sub.2 H.sub.5).sub.4 and thereafter exposing the substrate to precursors including at least Ru(C.sub.5 H.sub.5).sub.2.
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    Metalorganic chemical vapor deposition of (ba.sub.1-x Sr.sub.x)RuO.sub.3 /Ba.sub.1-x Sr.sub.x)TiO.sub.3 /(Ba.sub.1-x SR.sub.x)RuO.sub.3 capacitors for high dielectric materials
    (United States Patent and Trademark Office, 1998-02-10)
    A dynamic random access memory device having a ferroelectric thin film perovskite (Ba.sub.1-x Sr.sub.x)TiO.sub.3 layer sandwiched by top and bottom (Ba.sub.1-x Sr.sub.x)RuO.sub.3 electrodes. The memory device is made by a MOCVD process including the steps of providing a semiconductor substrate, heating the substrate, exposing the substrate to precursors including at least Ru(C.sub.5 H.sub.5).sub.2, thereafter exposing the substrate to precursors including at least TiO(C.sub.2 H.sub.5).sub.4 and thereafter exposing the substrate to precursors including at least Ru (C.sub.5 H.sub.5).sub.2.
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    Metalorganic chemical vapor deposition of metal oxides
    Si, Jie (Virginia Tech, 1993)
    Ruthenium dioxide, zirconium dioxide and bismuth titanate thin films were deposited on Si, sapphire disks, and Pt/Ti/SiO₂/Si substrates by hot wall metalorganic chemical vapor deposition (MOCVD). Bis(cyclopentadienyl)ruthenium [Ru(C₅H₅)₂], zirconium tetramethylheptanedione [Zr(thd)₄], triphenylbismuth [Bi(C₆H₅)₃], and titanium ethoxide [Ti(C₂H₅O)₄] were used as precursors. MOCVD RuO₂ film structure was dependent on MOCVD process parameters such as bubbler temperature, dilute gas flow rates, deposition temperature, and total pressure. Either pure RuO₂, pure Ru, or a RuO₂ + Ru mixture was obtained under different deposition conditions. As-deposited pure RuO₂ films were specular, crack-free, and adhered well on the substrates. The Auger electron spectroscopy depth profile showed a good composition uniformity across the bulk of the films. The MOCVD RuO₂ thin films exhibited resistivities as low as 60 μΩ-cm. In addition, the reflectance of RuO₂ in the NIR region showed a metallic character. Zr(thd)₄ was synthesized and the process was optimized. Purity of Zr(thd)₄ was confirmed by melting point determination, carbon and hydrogen elemental analysis and proton nuclear magnetic resonance spectrometer (NMR). The MOCVD ZrO₂ film deposition rates were very small (≤ 1 nm/min) for substrate temperatures below 530°C. The film deposition rates were significantly affected by: (1) source temperature, (2) substrate temperature, and (3) total pressure. As-deposited films are carbon free. Furthermore, only the tetragonal ZrO₂ phase was identified in as-deposited films. The tetragonal phase transformed progressively into the monoclinic phase as the films were subjected to high temperature post-deposition annealing. The optical properties of the ZrO₂ thin films as a function of wavelength, in the range of 200 nm to 2000 nm, were also reported. In addition, a simplified theoretical model which considers only a surface reaction was used to analyze the deposition of ZrO₂ film. The deposition rates can be predicted well for various deposition conditions in the hot wall reactor. The deposition rates of MOCVD Bi₄Ti₃O₁₂ were in the range of 3.9-12.5 nm/min. The Bi/Ti ratio was controlled by precursor temperature, carrier gas flow rate, and deposition temperature. As-deposited films were pure Bi₄Ti₃O₁₂ phase. The films were specular and showed uniform and fine-grain morphology. Optical constants as a function of wavelength were calculated from the film transmission characteristics in the UV-VIS-NIR region. The 550°C annealed film had a spontaneous polarization of 26.5 μC/cm² and a coercive field of 244.3 kV/cm.
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    Rare earth manganate films made by metalorganic decomposition or metalorganic chemical vapor deposition for nonvolatile memory devices
    (United States Patent and Trademark Office, 1997-04-29)
    A ferroelectric memory device having a perovskite thin film of a rare earth manganate and processes for manufacturing the same. The perovskite thin film layer has properties consistent with high quality nonvolatile memory devices. The perovskite thin film layer can be applied by a MOCVD process, by a MOD process, or a liquid source delivery process, all of which are described.