Kunihide Tachibana

Preparation of Rutile TiO2 Films by RF Magnetron Sputtering.

TiO2 films were prepared by rf (13.56 MHz) magnetron sputtering using a mixture of Ar and O2 gases. At a total pressure of 2 mTorr, 100% rutile TiO2 films were successfully obtained on non heated substrates with rf power of 200 W, while 100% anatase TiO2 films were deposited at a pressure of 20 mTorr. Spatial profiles of both emission of excited species and plasma parameters were measured by optical emission spectroscopy (OES) and the Langmuir probe method. At a pressure of 2 mTorr, it was found that high-energy electrons are generated at a certain radial position near the cathode surface where the transverse magnetic field is maximum, and the strong localization of plasma was observed. It was proven that the energetic species impinging on the growing film are responsible for the formation of the rutile phase even if the substrate is at room temperature.

A Study on Radical Fluxes in Silane Plasma CVD from Trench Coverage Analysis

The precursors of the a-Si:H film in SiH4 plasma-enhanced CVD are investigated by use of trench coverage analysis. The cross sectional profile of deposited film in a trench is simulated by a direct Monte-Carlo method using the radical sticking probability β as an adjustable parameter. A comparison with the experimental results has shown that the trench coverage profiles are reproduced well by the model if two kinds of radicals, i.e., SiH3 and SiH2, are deposited independently on the substrate with the respective sticking probabilities of 0.1 and 1.0. The experimentally observed dependence of the trench profile on the plasma condition can be explained by the change in the radical deposition ratio, which becomes SiH3/SiH2=1/1 in pure SiH4 at low rf power and decreases to 1/2-1/3 in SiH4 diluted in Ar at high rf power. The above change in the contribution of two kinds of radicals to the deposition is also supported by the chemical kinetic calculation of the gas phase reactions and the radical transport to the substrate.

Spatio‐temporal measurement of excited Xe(1s4) atoms in a discharge cell of a plasma display panel by laser spectroscopic microscopy

Dynamic behavior of excited Xe atoms in the 1s4 state was measured in a micro‐discharge cell of a color plasma display panel by a laser absorption technique combined with an optical microscope. The maximum absorption in a pulsed discharge with a peak current of 160 μA amounted 6% in one pass of the laser beam through the panel of 200‐μm gap. This gives the path averaged density of 6.7×1012 cm−3. Measured spatio‐temporal characteristics of the excited atoms are discussed in a comparison with a one‐dimensional simulation by a fluid model.

Investigation of discharge phenomena in a cell of color plasma display panel. I: One-dimensional model and numerical method

A numerical simulation method using a one-dimensional fluid model under the local field approximation is presented in order to understand pulsed-dc discharge in He?Xe gas mixture in a cell of a full-color plasma display panel. Spatiotemporal behaviors of the electric field and number densities of twelve independent particles, including electrons and four kinds of ions, were calculated self-consistently at a gas pressure of 200?Torr (27?kPa) and an electrode distance of 0.02?cm. The imprisonment of 147-nm-resonance radiation, the excitation source of phosphors, was also taken into account. Calculated results of the discharge current and voltage are consistent with those of experiment. The waveform of 147-nm-resonance radiation agreed well with experiment, although that of the discharge current showed some difference, probably due to the local field approximation.

A Numerical Study on Gaseous Reactions in Silane Pyrolysis

A simple gaseous reaction model involving 11 elementary reactions for 10 chemical species is proposed for silane and disilane pyrolyses at 550–750 K; its appropriateness is examined by a calculation based on an one-dimensional nonsteady condition which includes gaseous reactions, diffusional transport and radical adsorptions. The calculated results show that the model can successfully explain the experimental behavior of a gas composition concerning the time lag of hydrogen molecule production as well as the temperature and pressure dependences of the saturated higher silane concentrations. The reaction model is applied to a SiH4–H2–N2 system; it predicts that dilution with hydrogen or the premixing of c.a. 4% of disilane is useful for obtaining a spatially uniform deposition rate in a flow-type CVD reactor.

On the Reaction Kinetics in a Mercury Photosensitized CVD of a-Si:H Films

The reaction kinetic processes for mercury photosensitized CVD (Hg*–CVD) in silane were analyzed using a time-dependent, one-dimensional calculation based on mass-, momentum- and energy-conservation equations, including simplified surface reactions such as radical adsorption and hydrogen elimination from the substrate. A good agreement between the measured and the calculated time-varying concentrations of species provides sufficient validity regarding the present model. It is also shown that the saturation of the SiH4 decomposition observed by many authors in closed systems can be explained by the abstraction of SiH4 from the surfaces by radicals peculiar to the Hg*–CVD (e.g., HgH); gas-phase reactions are significantly influenced by surface reactions when the volume-to-surface ratio becomes small.

Preparation and Characterization of Superconducting Y–Ba–Cu–O Films by the MOCVD Technique

Superconducting Y–Ba–Cu–O thin films were obtained by the MOCVD technique on MgO(100) substrates at 715°C without postannealing. β-diketonate chelates were used as source metal organic complexes. This paper describes the film characterizations of electrical resistivity, composition, surface morphology and microstructure. Superconducting films were composed of a dense matrix and dispersed particles. The Y–Ba–Cu composition of the matrix was close to the 1:2:3 superconducting phase, while the particles were mainly composed of CuO. The highest zero-resistant temperature obtained in this experiment was 85 K. The film was highly oriented with the c-axis normal to the substrate. The lattice constant of the film was 11.68 A.

In-situ measurement of gas-phase reactions during the metal-organic chemical vapor deposition of copper using Fourier-transform infrared spectroscopy

Abstract During the metal-organic chemical vapor deposition using bis-hexafluoroacetylacetonato-copper (Cu(HFA) 2 ) diluted with hydrogen gas, a gas-phase measurement was carried out using in-situ Fourier-transform infrared spectroscopy. The desorbates were investigated on titanium nitride (TiN), tungsten (W) and thermally oxidized silicon (SiO 2 ) substrates. At the initial stage of the deposition, the enol-form H-HFA was detected as desorbates on all substrates. As the deposition proceeded, different desorbates were observed on different substrates. In the case of W, the keto-form H-HFA was produced. When TiN was used, the substituted keto-form H-HFA desorbed due to reduction of the substituted Cu(HFA) on the surface by hydrogen, where the substituted structure means the replacement of the CF 3 group by the CF 2 H group. When SiO 2 was used, CF 3 COOH was observed due to the thermally decomposed keto-form HFA, which was one of the dissociatively adsorbed species of Cu(HFA) 2 . These differences in the gas-phase byproducts are explained based on the surface conditions.

Preparation of Nearly Stoichiometric Superconducting Y-Ba-Cu-O Films by an MOCVD Technique Using Ozone

Superconducting Y-Ba-Cu-O films of nearly stoichiometric composition (Y:Ba:Cu=1:2:3.6) were prepared by an MOCVD technique on MgO(100) substrates at 650°C without postannealing. By introducing ozone into the reactor, we obtained a film with higher zero resistive temperature (75 K) and better surface morphology and c-axis orientation, compared to a film of the same composition prepared without ozone.

Preparing YBCO superconducting films by MOCVD with UV-light irradiation

A technique for a low-temperature deposition of YBa 2 Cu 3 O 7− x superconducting films by MOCVD (metal-organic chemical vapor deposition) is described. By supplying oxygen (O 2 ) including 1.5% of ozone with a Hg-lamp irradiation during deposition, a superconducting film with a zero-resistive temperature of 45 K was obtained at 580°C of substrate temperature. Photo-excitation of both ozone and MO source materials seems to have a cooperative effect on the deposition.