Plasma-enhanced Metalorganic Chemical Vapor Deposition Research Articles

Oxide interfacial phases and the electrical properties of SrBi2Ta2O9 thin films prepared by plasma-enhanced metalorganic chemical vapor deposition

Bi-layered ferroelectric SrBi2Ta2O9 (SBT) films were successfully prepared on Pt/SiO2/Si and Pt/Ti/SiO2/Si substrates at 550 °C by plasma-enhanced metalorganic chemical vapor deposition. A BTO (Bi4Ti3O12 or Bi2Ti4O11) phase formed at the interface between SBT films and Pt/Ti/SiO2/Si during the SBT deposition at 550 °C. The BTO phase decreased the leakage current density of the SBT films. The leakage current densities of SBT films deposited on Pt/Ti/SiO2/Si and Pt/SiO2/Si substrates were about 5.0×10−8 and 5.0×10−7 A/cm2 at an applied field of 300 kV/cm, respectively. The SBT films were controlled by Schottky emission. The Schottky barrier heights of SBT films deposited on Pt/Ti/SiO2/Si and Pt/SiO2/Si were about 1.2 and 0.8 eV, respectively.

Synthesis and Characterization of Calcium Phosphate Coatings by Metalorganic Chemical Vapor Deposition

AbstractThin coatings of various calcium phosphates including tricalcium phosphate (TCP), calcium pyrophosphate, and hydroxyapatite were synthesized by plasma-enhanced metalorganic chemical vapor deposition (MOCVD). Structure, composition, and surface morphology of the coatings were characterized by x-ray diffraction, x-ray photoelectron spectroscopy, scanning electron microscopy, and atomic force microscopy. All coatings were very dense and free of cracks. X- ray diffraction showed that the as-grown coatings with the Ca/P ratio of 1.5±0.5 and 1.0±0.5 were crystalline μ- TCP and pyrophosphate, respectively. However, hydroxyapatite coatings with the Ca/P ratio of ∼1.67 were amorphous. The crystalline μ-TCP and pyrophosphate coatings exhibited strong growth texture. The textured orientations varied with different growth temperatures. In addition, the microstructure of the μ-TCP coatings strongly depended on the growth temperatures.

モード変換型マイクロ波プラズマＭＯＣＶＤ法による（１１１）配向ＺｒＯ２膜の低温堆積

ZrO2 films were deposited on 12×17×0.5mm Si(100) single-crystal substrates or 9×18×0.5mm glass substrates using plasma-enhanced metal organic chemical vapor deposition (PE-MOCVD) with Zr (DPM) and oxygen as reactants. A mode converter was used to generate the plasma. The mode converter changes the microwave mode from TE10 (rectangular) to TM01 (circular), rising plasma density. We anticipated that ZrO2 film would be deposited at a lower temperature. The film obtained at 500°C was polycrystalline, but a predominantly (111)-orientated film was obtained at 300°C. Similar results were obtained on Si and glass substrates. No impurity such as hydrocarbon or carbon was detected in films. ZrO2 films had a tetragonal phase with lattice parameters of a=b=0.507nm and c=0.518nm. ZrO2 films deposited at 300°C at different microwave powers exhibited the same X-ray diffraction patterns. Film orientation was independent of microwave power. Film deposited for one hour at 300°C was 90nm thick with 30nm roughness and a refractive index of 2.10. Film growth activation energy was 14.5kJ/mol. We concluded that plasma generated by converting microwave to TM01 mode deposited preferred (111)-oriented ZrO2 film at a low temperature of 300°C.

Metal / Silicon Multilayers Produced by Low-Temperature MOCVD

AbstractW/Si and Mo/Si multilayers with 20 periods (doublelayer spacing d = 24nm) were deposited on silicon substrates using (remote-) plasma-enhanced MOCVD. The substrate temperature was below 200°C, which is necessary to avoid interdiffusion of the layers. The layer thickness and growth was controlled by an in situ soft x-ray reflectivity measurement. The characterisation of the multilayers showed an excellent growth of the silicon layers, while the metal layers are rough with embedded crystallites.

Characterization of SrBi2Ta2O9 ferroelectric thin films deposited at low temperatures by plasma-enhanced metalorganic chemical vapor deposition

Ferroelectric bismuth-layer SrBi2Ta2O9(SBT) thin films were prepared on Pt/Ti/SiO2/Si substrate by plasma-enhanced metalorganic chemical vapor deposition. The films were crystallized at temperatures between 500 and 600 °C. The dielectric constant and dissipation factor of SBT films were 320 and 0.04 at an applied frequency of 1 MHz, respectively. The remanent polarization (Pr) and the coercive field (Ec) obtained for a 200 nm thick Sr0.9Bi2.3Ta2.0O9 films deposited at 550 °C were 15 μC/cm2 and 50 kV/cm at an applied voltage of 3 V, respectively. The leakage current density was about 5.0×10−8 A/cm2 at 300 kV/cm. The films showed fatigue-free characteristics up to 1.0×1011 switching cycles under 6 V bipolar pulse.

Structure and properties of Fe-containing polymer composite films prepared by PEMOCVD

Composite Fe-containing polymer films have been prepared by the plasma-enhanced metal-organic chemical vapor deposition (PEMOCVD), using ferrocene (Cp 2Fe) and H 2/Ar as precursor and working gas respectively. The structure and properties of films was characterized by X-ray photoelectron spectroscopy, Auger electron spectroscopy, transmission electron microscopy, transmission electron diffraction, and X-ray diffraction. The electrical and optical properties of the films were also investigated. The results show the films consist of microcrystalline Fe 2O 3 and Fe-C clusters embedded in an amorphous polymer matrix. The filling factor ( f) of Fe affects the structure and properties of films greatly.

Dependence of the properties of (Sr xTi 1− x)O 3 thin films deposited by plasma-enhanced metal–organic chemical vapor deposition on electron cyclotron resonance plasma

(Sr x Ti 1− x )O 3 (0.26≤ x≤0.55) thin films were prepared on p-type Si (100) and Pt/SiO 2/Si substrates. A stoichiometric perovskite SrTiO 3 film with good thickness and composition uniformity was obtained on 4 inch wafer (±7% temperature uniformity) using electron cyclotron resonance (ECR) plasma which compensated for the substrate temperature difference. It was found that the activity of the precursors can be controlled by changing the ECR plasma power and O 2-to-(Ar+O 2) flow rate ratio. The deposition rate and the Sr-to-Ti composition ratio of the films were increased with the ECR plasma power and the O 2-to-(Ar+O 2) flow rate ratio of the ECR plasma, because the activation and decomposition of the source of strontium vapor are more easily affected by the ECR oxygen plasma power than those of the source of titanium vapor. The crystallinity and the orientation of the film were controlled by its Sr-to-Ti composition ratio and oxygen activity or oxygen partial pressure. The films showed a uniform and fine grain structure, and a Sr-to-Ti composition dependence.

Effects of SrF2 phase on electrical properties of SrTiO3 thin films deposited by plasma-enhanced metalorganic chemical vapor deposition

The microstructure and electrical properties were investigated for SrTiO3(STO) thin films deposited on Pt/Ti/SiO2/Si(PTSS) and Pt/MgO(PM) substrates by plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD). SrF2 phase existing in the STO films deposited on PM at 500°C influences the dielectric constant, dissipation factor, and leakage current density of STO films. The dielectric constant and dissipation factor of STO films on PTSS and PM at 500°C were 210, 0.02 and 140, 0.07 at 100 kHz, respectively. Leakage current densities of STO films deposited on PTSS and PM at 500°C were about 1.5 × 10−8 A/cm2 and 1.0 × 10−6 A/cm2 at 2 V, respectively. The leakage current behavior regardless of SrF2 phase in STO films was controlled by Schottky emission with applied electric field.

The deposition of aluminum nitride on silicon by plasma-enhanced metal-organic chemical vapour deposition

Aluminium nitride (AlN) films were deposited by electron cyclotron resonance plasma-enhanced chemical vapour deposition using trimethylaluminum (TMA) as precurser at temperatures from 25 to 600 °C and at different concentrations of TMA. Adhesive layers with a thickness ranging from 100 to 200 nm and a refractive index of 1.65–2.0 are obtained. By Auger electron spectroscopy, reflectum high energy electron diffraction and ellipsometric measurements at 632 nm we found in all layers a high oxygen concentrations only slightly dependent on the deposition conditions. A quadrupole mass spectrometer was used to investigate the composition of the gas phase. The gas spectra did not indicate partial pressures of oxygen and water. Sputtering effects and plasma chemical etching of the microwave window made of quartz glass seem to be the source for the incorporated oxygen.

マイクロ波プラズマＭＯＣＶＤによる酸化シリコン薄膜の低温堆積

Silicon oxide film was deposited on a Si substrate by microwave (2.45GHz) plasma enhanced metal-organic chemical vapor deposition (PE-MOCVD) using hexamethyldisiloxane (HMDSO) as the silicon source, oxygen, and argon.The influence of the deposition temperature on the quality of the deposited film and on its deposition rate was investigated by means of FT-IR, XPS, and ellipsometry.In FT-IR measurement of the film, absorption bands from SiMex and/or Si-OH were observed as impurities in the low deposition temperature range (60-170°C), but these absorption bands disappeared at higher substrate temperatures (<170°C). Post plasma treatment of the deposited film using argon-oxygen plasma was also performed in an attempt to decrease impurities in the film, and as a result the SiMex band disappeared completely.In conclusion, MOCVD enhansed by microwave argon-oxygen plasma treatment proved to be in low temperature deposition of silicon oxide film from HMDSO.

Preparation of cobalt oxide films by plasma-enhanced metalorganic chemical vapour deposition

Co oxide films were prepared on glass substrates at 150–400°C by plasma-enhanced metalorganic chemical vapour deposition using cobalt (II) acetylacetonate as a source material. NaCl-type CoO films were formed at low O2 flow rate of 7cm3 min−1 and at a substrate temperature of 150–400°C. The CoO films possessed (100) orientation, independent of substrate temperature. Deposition rates of the CoO films were 40–47 nm min−1. The CoO film deposited at 400 °C was composed of closely packed columnar grains and average diameter size at film surface was 60 nm. At high O2 flow rate of 20–50 cm3 min−1, high crystalline spinel-type Co3O4 films were formed at a substrate temperature of 150–400°C. The Co3O4 film deposited at 400°C possessed (100) preferred orientation and the film deposited at 150°C possessed (111) preferred orientation. Deposition rates of the Co3O4 films were 20–41 nm min−1. Both Co3O4 films with (100) and (111) orientation had columnar structure. The shape and average size of the columnar grains at the film surface were different; a square shape and 35 nm for (100)-oriented Co3O4 film and a hexagonal shape and 60 nm for (111)-oriented film, respectively.

Electron Cyclotron Resonance Plasma‐Enhanced Metalorganic Chemical Vapor Deposition of Tantalum Oxide Thin Films on Silicon near Room Temperature

Films of tantalum oxide, ranging in thickness from 25 to 2000 nm, were successfully deposited on silicon by the electron cyclotron resonance plasma‐enhanced metalorganic chemical vapor deposition (ECR‐MOCVD) process at deposition rates of up to 33 nm/min. The films were produced by decomposition of tantalum pentaethoxide into tantalum oxide in an oxygen ECR microwave plasma. The films were amorphous (but fully dense) since the temperature of the substrate, which was unheated, was estimated to be 76–120°C. The growth of the tantalum oxide films was accompanied by the formation of an interlayer of silicon dioxide at the silicon interface. The tantalum oxide films were oxygen rich (relative to Ta2O5). The effective relative dielectric constant of these dual‐layer dielectrics ranged from ɛef= 8.5 to 24; this range was explained in terms of a bilayer consisting of a 13‐nm‐thick silicon dioxide layer of ɛsx= 4, and a tantalum oxide overgrowth of varying thickness having ɛtx∼ 25. A maximum breakdown strength of the films was 6.9 MV/cm and the leakage current at a field of 1 MV/cm was 3.0 × 10‐8. The breakdown properties were related to the presence of stray particles on the substrate; these properties are expected to improve considerably if the processing is carried out in a clean‐room environment. The silicon dioxide layer is believed to have grown by the diffusion of oxygen through the tantalum oxide overlayer despite the low substrate temperature.

Iron oxide films with spinel, corundum and bixbite structure prepared by plasma-enhanced metalorganic chemical vapor deposition

Iron oxide films of spinel, corundum and bixbite structure were prepared on glass substrates at 150–450°C by plasma-enhanced metalorganic chemical vapor deposition and the formation diagram was determined by X-ray diffraction and conversion electron Mössbauer spectroscopy measurements. Spinel-type Fe 3O 4+ δ films were formed in the low O 2 flow rate range of 10–25 cm 3 min −1 and the films deposited at 300°C or above possessed the (100) preferred orientation. For high O 2 flow rate in the range of 30–45 cm 3 min −1, corundum-type α-Fe 2O 3 films were formed at high substrate temperatures of 350–450°C and bixbite-type β-Fe 2O 3 films were formed at low substrate temperatures of 200–400°C. (100) oriented NaCl-type FeO coexisting with the Fe 3O 4+ δ films were infrequently formed under deposition conditions for (100) oriented Fe 3O 4+ δ films. The following two step growth model of preferentially (100) oriented Fe 3O 4+ δ films is proposed: (1) formation of a (100) oriented FeO film, (2) transformation of the FeO film into (100) oriented Fe 3O 4+ δ films by means of plasma oxidation during deposition. The deposition rate of the films increased with increasing RF power.

(100) Preferred Orientation of Spinel-Type Iron Oxide Films Prepared by Plasma-Enhanced Metalorganic Chemical Vapor Deposition

Spinel-type iron oxide films were prepared on glass substrates at 400° C by plasma-enhanced metalorganic chemical vapor deposition using iron (III) acetylacetonate and oxygen as source gas and oxidizing gas, respectively. The effects of angle (θ) of the source and oxygen gas nozzle to the substrate surface, applied negative dc bias voltage and addition of reducing gas, H2, on the orientation of the films have been investigated. Highly crystalline and (100)-oriented spinel-type iron oxide films were obtained under conventional conditions only when θ was lower than 20°. However, even for θ higher than 20°, highly crystalline and (100)-oriented films could be obtained by applying negative dc bias voltage or adding H2 during the deposition. Magnetic properties and microstructures of the films were also examined.

Preparation of Co Ferrite Films by Plasma-Enhanced Metalorganic Chemical Vapor Deposition

Thin films of Co ferrite and Co-Zn ferrite ( Co1-x Znx Fe2O4, 0≤x≤0.5) with partial preferential orientation of the (100) plane parallel to the film surface were prepared on soda-lime glass substrates at 400° C by plasmaenhanced metalorganic chemical vapor deposition. Faraday rotation of the CoFe2O4 film took the negative maximum value of -2.8×104 deg/cm near 700 nm in the wavelength range from 550 nm to 1100 nm. The Faraday hysteresis loop indicated that the CoFe2O4 film had perpendicular magnetic anisotropy, which was caused mainly by the intrinsic stress-induced uniaxial anisotropy. Faraday rotation at 800 nm and Curie temperature decreased with increasing Zn content x.

Observations on the Growth of YBa2Cu3O7 Thin Films at Very High Laser Fluences

AbstractThe pulsed-laser deposition (PLD) technique utilizes one of the most energetic beams available to form thin films of the superconducting oxide YBa2Cu3O7 (YBCO). IN this study we examine the growth of YBCO at very high laser fluences (25 to 40 J/cm2); a more typical fluence for PLD would be nearer to 3 J/cm2. the use of high fluences leads to unique film microstructures which, in some cases, appear to be related to the correspondingly higher moveabilities of the adatoms. Films grown on vicinal substrates, using high laser fluences, exhibited well-defined elongated granular morphologies (with excellent transition temperature, Tc, and critical current density, Jc). Films grown on vicinal substrates using off-axis magnetron sputtering, plasma-enhanced metal organic chemical vapor deposition (PE-MOCVD), or PLD at more typical laser fluences showed some similar morphologies, but less well-defined. Under certain growth conditions, using high laser fluences with (001) oriented substrates, the YBCO films can exhibit a mixture of a- and c-axis growth where both crystallographic orientations nucleate on the substrate surface at the same time, and grow in concert. the ratio of a-axis oriented to c-axis oriented grains is strongly affected by the pulse repetition rate of the laser.

Crystallographic Orientations of MgO Films Prepared by Plasma-Enhanced Metalorganic Chemical Vapor Deposition

Thin films of magnesium oxide (MgO) were prepared on glass substrates by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) and the relationship between deposition conditions and crystallographic orientations were studied. Highly crystalline and highly (100)-oriented MgO film was obtained at the vaporizing temperature of 210° C, O2 flow rate of 200 cm3· min-1, rf power of 400 W and substrate temperature of 400° C. The orientation of MgO films is changed from (100) to (110) upon increasing the vaporizing temperature from 210 to 240° C or upon decreasing the O2 flow rate from 200 to 50 cm3· min-1. These results indicated that the films deposited at the high arrival ratios of oxygen to magnesium precursor (O/Mg) onto the substrate had a (100) orientation, while those deposited at the low arrival ratios of O/Mg had a (110) orientation. The intrinsic stress of the (100) oriented film was tensile and the magnitude was 0.25 GPa.

Preparation of La-modified PbTiO3 thin films on the oxide buffer layers with NaCl-type structure

La-modified PbTiO3(PLT: Pb0.9La0.1Ti0.975O3) thin films by rf magnetron sputtering were prepared on the preferred (100)-oriented oxide buffer layers with NaCl-type structure, which were prepared by plasma-enhanced metalorganic chemical vapor deposition. Fused silica, (111)Si, soda-lime glass, and stainless steel were used as the substrates to prepare the oxide buffer layers. The c-axis and a-axis preferred oriented PLT thin films were obtained on the buffer layer, independent of the kind of substrate. Further, highly c-axis oriented PLT thin films were obtained when the substrate had a large thermal expansion coefficient. Significant pyroelectric currents were detected without a poling treatment. The NiCr/PLT/(100)Pt/(100)MgO/stainless steel structure had a dielectric constant of 250, a dielectric loss factor tan δ of 0.8%, and a pyroelectric coefficient of 3.8×10−4 C/m2 K.

Epitaxial growth of SrTiO3/YBa2Cu3O7−x heterostructures by plasma-enhanced metalorganic chemical vapor deposition

We report heteroepitaxial growth of SrTiO3 on YBa2Cu3O7−x/LaAlO3 substrates by plasma-enhanced metalorganic chemical vapor deposition. X-ray diffraction results indicated that SrTiO3 films were epitaxially grown on a (001) YBa2Cu3O7−x surface with [100] orientation perpendicular to the surface. The film composition, with Sr/Ti molar ratio in the range of 0.9 to 1.1, was determined by Rutherford backscattering spectrometry and energy dispersive spectroscopy. The thickness of the SrTiO3 films is 0.1–0.2 μm. The epitaxial growth was further evidenced by high-resolution transmission electron microscopy and selected area diffraction. Atomically abrupt SrTiO3/YBa2Cu3O7−x interface and epitaxial growth with [100]SrTiO3∥[001]YBa2Cu3O7−x were observed in this study. The superconducting transition temperature of the bottom YBa2Cu3O7−x layer, as measured by ac susceptometer, did not significantly degrade after the growth of overlayer SrTiO3. The capacitance-voltage measurements showed that the dielectric constant of the SrTiO3 films was as high as 315 at a signal frequency of 100 KHz. The leakage current density through the SrTiO3 films is about 1×10−6 A/cm2 at 2-V operation. Data analysis on the current-voltage characteristic indicated that the conduction process is related to bulk-limited Poole-Frenkel emission.

Heteroepitaxial growth of Ba1−xSrxTiO3/YBa2Cu3O7−x by plasma-enhanced metalorganic chemical vapor deposition

Epitaxial Ba1−xSrxTiO3(BST)/YBa2Cu3O7−x heterostructures with superior electrical and dielectric properties have been fabricated by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD). Data of x-ray diffraction and high resolution transmission electron microscopy showed that 〈100〉 oriented Ba1−xSrxTiO3 layers were epitaxially deposited on epitaxial (001) YBa2Cu3O7−x layers. The leakage current density through the Ba1−xSrxTiO3 films was about 10−7 A/cm2 at 2 V (about 2×105 V/cm) operation. Moreover, the results of capacitance-temperature measurements showed that the PE-MOCVD Ba1−xSrxTiO3 films had Curie temperatures of about 30 °C and a peak dielectric constant of 600 at zero bias voltage. The Rutherford backscattering spectrometry and x-ray diffraction results showed that the BST film composition was controlled between Ba0.75Sr0.25TiO3 and Ba0.8Sr0.2TiO3. The structural and electrical properties of the Ba1−xSrxTiO3/YBa2Cu3O7−x heterostructure indicated that conductive oxide materials with close lattice to Ba1−xSrxTiO3 can be good candidates for the bottom electrode.