Plasma-enhanced Metalorganic Chemical Vapor Deposition Research Articles

Direct Crystallization and Characterization of Bi3TiTaO9 Thin Films Prepared by Metalorganic Chemical Vapor Deposition

Bi3TiTaO9 (BTT) thin films were prepared on (111)Pt/Ti/SiO2/Si substrate by electron cyclotron resonance plasma-enhanced metalorganic chemical vapor deposition (ECR-MOCVD). BTT thin films deposited at 550°C were found to consist of a single phase of bismuth layer structure by X-ray diffraction (XRD). This temperature was lower than that reported in the data for obtaining single phase SrBi2Ta2O9 (SBT) thin films prepared by MOCVD. Furthermore, the reciprocal space mapping of BTT thin films showed the (103)-preferred orientation of this film, as well as the orientation of SBT thin films. The dielectric constant, εr, and loss tangent, tan δ, of the BTT thin film were 180 and 3% at 1 MHz, respectively. An abrupt increase of the leakage current of this film was observed at about 280 kV/cm.

Influences of Annealing on the Opto-electronic Properties ofZnO Films Grown by Plasma-Enhanced MOCVD

ZnO thin films have been grown on C-plane sapphiresubstrates by plasma-enhanced metal-organic chemical vapour deposition.The samples are then annealed at a higher temperature. Theresistivity, concentration of electron, mobility and optically pumpedthreshold of both as-grown and annealed films are investigated. Furthermore,their structural and optical properties are also examined with x-raydiffraction, emission spectra and optical transmission spectra. The resultsindicate that the quality of ZnO thin films can be improved by annealing.

Anode-supported planar solid oxide fuel cells by plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) and electrostatic spray deposition (ESD): Fabrication of dense thin layers of yttria-stabilized zirconia by PE-MOCVD

This paper reports a study of plasma-enhanced metalorganic chemical vapor deposition (PE-MOCVD) as a suitable technique for depositing dense, crack-free thin layers of yttria-stabilized zirconia onto porous substrates, as a step in the fabrication of anode-supported planar solid oxide fuel cells (SOFC). Our objective is to present an alternative method by which an SOFC assembly may be fabricated at lower temperature than by conventional methods. PE-MOCVD using zirconium tertbutoxide (ZrTB) -and yttrium hexafluoroacetylacetonate dihydrate (Y6FA) is capable of producing the electrolyte in thin dense layers on smooth surfaces, as demonstrated for Si(110) wafers. If a porous substrate is used, the average surface pore size should not exceed 1–2 μm to obtain a dense film. The crystalline phase of the film was related to the Y6FA concentration in the gas phase using x-ray diffraction. Depth profiling, using x-ray photoelectron spectroscopy, showed that Y is present (fairly uniform) at all depths of the film. Growth rates are dependent on the applied power but independent of substrate temperature. Film density, however, shows a significant dependence on substrate temperature.

High-Conductivity p-Type Transparent Copper Aluminum Oxide Film Prepared by Plasma-Enhanced MOCVD

Conductivity almost two orders of magnitude higher than any reported previously of transparent p-type Cu–Al–O films has been achieved by plasma-enhanced (PE) CVD using Cu(dpm)2 and Al(dpm)3 precursors, followed by an annealing process. The production of such highly conductive transparent semiconductor films could overcome difficulties associated with producing transparent devices such as transparent functional windows. Using PECVD to produce the films could give the possibility of scaling up the production to industrial levels.

High-Conductivity p-Type Transparent Copper Aluminum Oxide Film Prepared by Plasma-Enhanced MOCVD

Conductivity almost two orders of magnitude higher than any reported previously of transparent p-type Cu–Al–O films has been achieved by plasma-enhanced (PE) CVD using Cu(dpm)2 and Al(dpm)3 precursors, followed by an annealing process. The production of such highly conductive transparent semiconductor films could overcome difficulties associated with producing transparent devices such as transparent functional windows. Using PECVD to produce the films could give the possibility of scaling up the production to industrial levels.

Low-Temperature Preparation of SrBi2Ta2O9 Thin Films by Electron Cyclotron Resonance Plasma-Enhanced Metalorganic Chemical Vapor Deposition and Their Electrical Properties

A SrBi2Ta2O9 (SBT) thin film was prepared by electron cyclotron resonance plasma-enhanced metalorganic chemical vapor deposition (ECR-MOCVD). The deposition temperature dependence of the composition of the film was lesser than that of films prepared by conventional thermal MOCVD. An almost single phase of SBT was obtained at 610°C. The crystallinity of this film was higher than that of the film prepared by thermal MOCVD at 500°C and subsequent heat treatment at 800°C. The leakage current density of this film was small, on the order of 10-8 A/cm2 up to 240 kV/cm. Moreover, two fold the remanent polarization and the coercive field at an applied electric field of 400 kV/cm were 14.5 µC/cm2 and 77 kV/cm, respectively. These values were larger than those of the film prepared by thermal MOCVD at 500°C with heat treatment at 800°C.

Growth of SiC thin films on graphite for oxidation-protective coating

We have deposited thick SiC thin films on graphite substrates in the temperature range of 700–850 °C using single-molecular precursors by both thermal metal–organic chemical-vapor deposition (MOCVD) and plasma-enhanced MOCVD (PEMOCVD) methods for oxidation-protection wear and tribological coating. Hexamethyldisilane (HMDS), (CH3)3Si–Si(CH3)3, was used as a single-source precursor, and hydrogen and Ar were used as a bubbler and carrier gas. A highly oriented polyerystalline cubic SiC layer in the [111] direction was successfully deposited on graphite at temperatures as low as 800 °C with HMDS by PEMOCVD. For thermal MOCVD, on the other hand, only amorphous SiC layers were obtained at 850 °C. From this study, we confirmed that PEMOCVD was a highly effective process in improving the characteristics of the SiC layers compared to those grown by thermal MOCVD. The mechanical and oxidation-resistant properties have been assessed. The optimum SiC film was obtained at 850 °C and rf power of 200 W. The maximum deposition rate and microhardness are 2 μm/h and 4336 kg/mm2 Hv, respectively. The hardness was strongly influenced by the composition ratio of the SiC protective layers.

Low-temperature growth of Ti(C,N) thin films on D2 steel and Si(100) substrates by plasma-enhanced metalorganic chemical vapor deposition

We have deposited Ti(C,N) thin films on Si(100) and D2 steel substrates in the temperature range of 200–300 °C using tetrakis diethylamidotitanium (TDEAT) and titanium isopropoxide (TIP) by pulsed dc plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD). Radical formation and ionization behaviors in plasma are analyzed in situ by optical emission spectroscopy at various pulsed bias voltages and gas conditions. H2 and He+H2 gases are used as carrier gases to compare plasma parameters, and the effect of N2 and NH3 as reactive gas is also evaluated by the reduction of the C content of the films. Polycrystalline Ti(C,N) thin films were successfully grown on either D2 steel or Si(100) surfaces with TDEAT at temperatures as low as 200 °C. For TIP, however, only TiOCN thin films were obtained on Si(100) substrates. The best deposition process is evident for H2 and N2 gas atmospheres and bias voltage of 600 V. The higher film hardness is about 1760 Hk 0.01, but depends on gas species and bias voltage. Compared to TiN films, the Ti(C,N) film grown by PEMOCVD has very good conformability; the step coverage exceeds 85%, with an aspect ratio of more than 3.

Epitaxial growth of AlN films on Si substrates by ECR plasma assisted MOCVD under controlled plasma conditions in afterglow region

Wurtzite-type aluminum nitride (h-AlN) films were epitaxially grown on off-axis Si (111) substrates by electron–cyclotron–resonance plasma-enhanced metalorganic chemical vapor deposition (ECRMOCVD) using trimethylalminum (TMA) and ammonia (NH 3) as source gases. Plasma space potential in the growth chamber was lowered by setting the magnetic field distribution as a mirror field. For the growth of h-AlN with excellent crystallinity on Si substrates, nitridation of the substrate surface, growth of a low-temperature (LT) buffer layer, and epitaxial growth of AlN films were performed under a mirror field condition in a growth chamber. Thermal nitridation at 1050°C prior to the epitaxial growth appreciably improved the crystallinity of AlN films. The growth of buffer layer at temperatures below 650°C was not so effective for the improvement of the crystallinity and crystal orientation of AlN epitaxial layer. The proportion of domain including stacking faults and that whose c-axis was parallel to the substrate surface was very small ( I (0002)/( I (10–10)+ I (10–11))>700), irrespective of the gas feed ratio of N source to Al source (NH 3/TMA) during the epitaxial growth process. Under a small gas feed ratio (NH 3/TMA<200), however, the diffraction peak intensities from the non-epitaxial domains became large.

Growth of CdZnTe and CdSeTe crystals for p–i–n radiation detectors

High-energy radiation detectors being operated at room temperature have been extensively studied on the bulk CdZnTe. Metal organic chemical vapor deposition (MOCVD) technique has been intensively investigated in the low substrate temperature of epitaxial film growth. Hydrogen radicals generated by inductively coupled RF remote plasma are introduced into the reaction region with source materials. These epitaxial growth processes are carried out at a low substrate temperature below 200°C. The results obtained suggest that the remote plasma-enhanced MOCVD method can be one of the promising methods for CdZnTe–CdSeTe epitaxial growth. These growths are proposed for fabrication of the high-energy radiation detector. Using this technique, p-type CdZnTe layer and n-type CdSeTe epitaxial layer are formed on intrinsic CdZnTe substrate to form p–i–n diode.

Metal oxide/silicon oxide multilayer with smooth interfaces produced by in situ controlled plasma-enhanced MOCVD

Molybdenum oxide/silicon oxide and tungsten oxide/silicon oxide multilayer with 24 periods and a period thickness of 9.2 nm were fabricated with plasma-enhanced MOCVD. The layer thickness was controlled by an in situ soft X-ray reflectivity measurement. For the deposition of the SiO 2 layers, a new silicon organic precursor, pentamethylcyclopentadienyldisilane (Me 5C 5Si 2H 5) was used in an O 2 remote plasma process. The high quality of multilayer interfaces was observed by cross-section transmission electron microscopy (TEM), the interface Toughness wasmeasured by hard X-ray reflectivity and diffuse scattering at grazing incidence experiments to be about 0.1 nm. Auger electron spectroscopy (AES) gives the information, that the silicon oxide is practically carbon free, and the carbon content of the metal oxides is low (<5%).

Effect of Hydrogen on GaN Growth by Remote Plasma-Enhanced Metal-Organic Chemical Vapor Deposition

The effects of hydrogen on GaN growth by remote plasma-enhanced metal-organic chemical vapor deposition (RPE-MOCVD) were investigated. Hydrogen addition changed the gas-phase reaction in the plasma and resulted in a Ga excess growth condition by scavenging activated nitrogen species, resulting in decreased carbon incorporation in Ga-sites. Furthermore, the GaN layer had a smooth surface with Ga polarity, whereas the layer grown without hydrogen addition showed a facetted surface with N polarity.

Effect of rf power on the growth and electrical properties of SrBi2Ta2O9 thin films by plasma-enhanced metalorganic chemical vapor deposition

The SBT films were deposited on Pt/Ti/SiO2/Si substrates at 550°C by plasma-enhanced metalorganic chemical vapor deposition (PEMOCVD). The films were evaluated with different rf plasma power and showed a complete single phase with highly oriented (115) texture without fluorite phase at rf power of 100 W. The SBT films deposited at 100 W have a dielectric constant of 270 and dissipation factor of 0.04 at 100 kHz. The leakage current density of films prepared at 100 W was about 3.0 × 10−8 A/cm2 at 170 kV/cm. The SBT films deposited at 100 W by PEMOCVD showed enough dielectric and leakage properties to apply for nonvolatile memory devices.

Preferred orientations and microstructure of MgO films prepared by plasma-enhanced metalorganic chemical vapor deposition

NaCl-type magnesium oxide (MgO) films with (110) or (100) preferred orientation were prepared on glass substrate at 400°C by plasma-enhanced metalorganic chemical vapor deposition using Mg(C 5H 7O 2) 2 as a source material. The effect of deposition conditions, such as O 2 flow rate, carrier gas N 2 flow rate and total pressure during the deposition, on the preferred orientation of the MgO films were investigated. The total pressure during the deposition as well as the flow rate ratio of O 2 to Mg source material were found to play a significant role in the preferred orientation of the films. (110)-oriented MgO films were obtained at low pressure under 0.15 Torr, while (100)-oriented MgO films were obtained at high pressure of 1.0 Torr, under the condition of a constant ratio of O 2 to Mg source material. Rutherford backscattering and Auger electron spectra indicated that the O/Mg ratios of the films with (110) and (100) orientation were 0.97 and 1.61, respectively, and no impurities were contained in both the oriented films. Scanning electron micrographs showed that both films with (110) and (100) orientation were composed of closely packed columnar grains of diameter about 60 nm.

Plasma-enhanced metal organic chemical vapor deposition of high purity copper thin films using plasma reactor with the H atom source

In situ Fourier-transform infrared measurements have been carried out to study the effects of H atoms on removing impurities in Cu thin films during plasma enhanced metal organic chemical vapor deposition (PEMOCVD) using bis(hexafluoroacetylacetonato) copper (II), Cu(hfac)2 as a source material. The results show that H atoms are very effective in removing impurities in the film, as well as on its surface. Based on such knowledge regarding the effects of H atoms, a PEMOCVD reactor equipped with an H atom source is developed to control both densities of H atoms and Cu-contained radicals independently. High purity (≈100%) Cu films of a low resistivity of 2 μΩ cm can be deposited for a H2 gas volume fraction of 50%–67% by using the H atom source, while the high purity films were obtained only for a very high H2 gas volume fraction above about 90% in the case of no H atom source as reported previously. This feature opens up a possibility of deposition of high quality Cu films at a high rate using the reactor equipped with the H atom source, since a gas volume fraction of Cu metal organic material can be increased by more than five times.

Ferroelectric SrBi2Ta2O9 thin film deposition at 550 °C by plasma-enhanced metalorganic chemical vapor deposition onto a metalorganic chemical vapor deposition platinum bottom electrode

Ferroelectric bismuth-layer SrBi2Ta2O9 (SBT) thin films were prepared on Pt/SiO2/Si substrates by plasma-enhanced metalorganic chemical vapor deposition. The platinum bottom electrode deposited by metalorganic chemical vapor deposition shows a dense smooth state after deposition of SBT films and prevents bismuth diffusion into the platinum layer. The c-axis oriented SBT films were crystallized at a deposition temperature of 550 °C. The dielectric constant and dissipation factor of SBT films are 310 and 0.08, respectively, at 100 kHz. The remanent polarization and the coercive field obtained for 180 nm thick Sr0.9Bi2Ta2O9 films deposited at 550 °C were 15 μ/cm2 and 50 kV/cm, respectively, at an applied voltage of 5 V. The leakage current density was about 5.0×10−7 A/cm2 at 250 kV/cm. The films showed fatigue-free characteristics up to 7.0×109 switching bipolar pulses under 5 V.

Electrical properties of ferroelectric SrBi2Ta2O9 thin films deposited on MOCVD-Pt/SiO2/Si substrates by plasma-enhanced metalorganic chemical vapor deposition

The SrBi 2 Ta 2 O 9 thin films were prepared on MOCVD-Pt/SiO 2 /Si substrates at 550°C by plasma-enhanced metalorganic chemical vapor deposition. Platinum bottom films deposited by metalorganic chemical vapor deposition(MOCVD) showed a dense and stable state after deposition of SBT films and grains of SBT films show a rectangular shape. The SBT ferroelectric capacitor shows practically no polarization fatigue after the sample was switched up to 7.0x10 9 cycles. The retention characteristics of the SBT films looked very promising up to 10 5 see and the charge loss for 10 years was estimated to be 10% at room temperature. The leakage current density of the SBT films was about 4x10 -7 A/cm 2 at an applied electric field of 250 kV/cm. The leakage current behavior of SBT films was controlled by a Schottky emission and the schottky barrier height of SBT films was about 0.8 eV.

Low temperature deposition of Ba1-xSrxTiO3 thin films by ECR plasma-enhanced metalorganic chemical vapor deposition

The deposition temperature dependence of Ba0.7Sr0.3TiO3 (BST) thin film physical and electrical properties was investigated. Films were deposited between 250 and 500°C by electron cyclotron resonance (ECR) plasmaenhanced liquid source metalorganic chemical vapor deposition (MOCVD). Depositions were carried out in an oxygen plasma using the precursors Ba(thd)2•(polyamine), Sr(thd)2•(polyamine), and Ti(O-i-Pr)2(thd)2. With a constant ECR plasma power, composition and growth rate were independent of temperature within the full range investigated, in contrast to most thermally-driven CVD BST processes. Films grown above 350°C were crystalline as-deposited on Pt, and were (100)-textured. The dielectric properties depended strongly upon BST crystallinity, with a sharp increase in dielectric constant and its field dependence observed above 350°C. For slightly Ti-rich, 800Å thick films, dielectric constants of 281 were obtained at 500°C, following a 550°C top electrode anneal in O2. Over the full deposition temperature range investigated, the leakage current density was less than 10-7 A/cm2 at 2.0 V and dielectric loss tangents varied between 0.003 and 0.013.

Effect of second phase on the electrical properties of SrBi2Ta2O9 (SBT) thin films deposited at 550°C by PEMOCVD

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 Bi2Ti4O11 (BTO) phase was formed at the interface between SBT films and the Pt/Ti/SiO2/Si during the deposition of SBT films at 550°C. The leakage current density of the SBT films was decreased by the formation of BTO phase. The leakage current densities of SBT films deposited on Pt/SiO2/Si and Pt/Ti/SiO2/Si substrates were about 5.0 × 10-7 and 5.0 × 10-8 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/SiO2/Si and Pt/Ti/SiO2/Si were about 0.8 and 1.2 eV, respectively.

Effects of hydrogen on carbon incorporation in GaN grown by remote plasma-enhanced metal-organic chemical vapor deposition

The effects of hydrogen on carbon incorporation in GaN layers grown by remote plasma-enhanced metal-organic chemical vapor deposition were investigated. Gas-phase decomposition of TEGa was enhanced at high RF power and reactor pressure conditions. With increase in hydrogen fractions in the downstream plasma, optical emission intensity of CN abruptly decreased. It is suggested that active hydrogen species may scavenge the carbon-containing species in the gas phase, resulting in reduced carbon incorporation in GaN layers measured by 10K photoluminescence and secondary-ion mass spectroscopy.