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We have successfully reduced threshold voltage shifts of amorphous In–Ga–Zn–O thin-film transistors (a-IGZO TFTs) on transparent polyimide films against bias-temperature stress below 100 mV, which is equivalent to those on glass substrates. This high reliability was achieved by dense IGZO thin films and annealing temperature below 300 °C. We have reduced bulk defects of IGZO thin films and interface defects between gate insulator and IGZO thin film by optimizing deposition conditions of IGZO thin films and annealing conditions. Furthermore, a 3.0-in. flexible active-matrix organic light-emitting diode was demonstrated with the highly reliable a-IGZO TFT backplane on polyimide film. The polyimide film coating process is compatible with mass-production lines. We believe that flexible organic light-emitting diode displays can be mass produced using a-IGZO TFT backplane on polyimide films.

Threshold voltage shifts of a-IGZO TFTs on plastics against bias-temperature stress were successfully reduced below 0.03 V, equivalent to those on glass substrates. We have developed an 11.7-inch qHD (960xRGBx540) flexible bottom-emission active-matrix organic light-emitting diode (AMOLED) driven by a-IGZO TFT backplane fabricated on a transparent polyimide film.

We have investigated the effects of impurities in starting silicon films on excimer-laser-induced lateral growth characteristics. The films should have a low concentration of impurities to achieve long lateral growth, since impurities, such as carbon, nitrogen, oxygen, and fluorine, in the films were found to affect the lateral growth characteristics severely. A stacked structure with a capping layer is also considered essential for maintaining pure molten Si during lateral growth.

Characteristics have been investigated for both KrF excimer-laser light and KrF excimer-laser crystallization of Si thin films. The results were applied to design an optical system for growing densely packed and large grains. A high-resolution beam profiler confirmed that the laser light intensity distribution on the sample surface had a nearly ideal triangular form with a maximum-to-minimum intensity ratio of approximately 2, as designed. This distribution could grow 5-µm-long grains with a packing efficiency close to 100% by a single laser light pulse.

Microtexture was analyzed for Si films crystallized by a phase-modulated excimer laser annealing method, using Scanning Electron Microscopy (SEM), Transmission Electron Microscopy (TEM) and Electron Back-Scattering Pattern (EBSP). Threshold fluences were identified for crystallization, lateral growth and film braking, by comparing the surface morphology and the microscopic excimer laser light intensity profile. It was found that {001} and {110} orientations are preferable for lateral growth direction but the surface orientation is random. A possible origin of preferable orientations for laterally grown film was discussed.

One approach to achieving 99% combustion efficiency (C.E.) and 10 ppmV or lower NOx (at 15%O2 ) in a micro gas turbine (MGT) combustor fueled by biomass gas at a variety of operating conditions is with the use of flameless combustion (FLC). This paper compares experimentally obtained results and CHEMKIN analysis conducted for the developed combustor. As a result, increase the number of stage of FLC combustion enlarges the MGT operation range with low-NOx emissions and high-C.E. The composition of fuel has a small effect on the characteristics of ignition in FLC. In addition, NOx in the engine exhaust is reduced by higher levels of CO2 in the fuel.Copyright © 2007 by ASME

The deposition of SiO2 by remote PECVD using microwave activated oxygen species and SiH4 were examined. The deposition rate has been found to be greatly enhanced by reducing the distance between the substrate surface and the end of the supplying nozzle for the plasma excited oxygen species.The deposition rate decreased with increasing substrate temperature under the condition that the activated oxygen species and SiH4 molecules collide with each other many times. Its activation energy was -0.27 eV.It has been found that the gas phase reaction caused by the collision is important to obtain high quality films. A SiO2 film with a resistivity larger than 1×1016 Ω·cm was able be obtained with high deposition rates beyond 200 nm/min, at low temperatures below 400°C. The minimum interface state density was 4.3×1010 cm−2eV−1 for a film deposited at 230 nm/min, and 2.0×1010 cm−2eV−1 for a film deposited at 30 nm/min.

A conventional phase modulator having only “holes” (or “bumps”) on a quartz plate has been found to have insufficient depth-of-focus (DOF) characteristics. This poor DOF can be attributed to the phase advancement (or retardation) of the zeroth-order diffracted light wave. This phase effect has been applied to developing two types of modulator: one with a sufficiently large DOF, and the other, a single-plate phase modulator capable of producing a two-dimensional light intensity profile suitable for growing arrays of large grains. It was confirmed experimentally that this single-plate modulator could grow arrays of large grains 5 µm in pitch.

We have developed an advanced sample structure for large-grain growth by excimer-laser crystallization of Si. More than 10 μm long grains were grown laterally in a 50 nm thick Si layer by phase-modulated excimer-laser annealing. A photosensitive SiO x capping layer prepared using a conventional plasma-enhanced chemical vapor deposition apparatus enables this longer lateral growth with lower irradiated intensity of laser light than those with the conventional SiO 2 capping layer.

A high-purity hydrogenated amorphous silicon film has been successfully deposited using an advanced plasma-enhanced chemical vapor deposition system that is available for mass-production use. Oxygen and carbon concentrations in the film were as low as 1.3×1017 and 2.6×1016 atoms/cm3, respectively, i.e., about hundredth part of the typical values achieved using a recent large-area deposition system and as low as those in CZ-Si wafers. The film was characterized as a function of SiH4 gas flow rate and outgas rate from the reaction chamber, and the results suggest that oxygen and carbon in the film comes predominantly from H2O and CO2 out-gassing from the chamber wall, respectively.

Arrays of large Si grains have been grown by phase-modulated excimer-laser annealing at room temperature. Home-plate- and square-shaped grains could be grown over the whole irradiated substrate area. These results indicate that the fabrication of x-Si TFTs on glass is a realistic development target.

Phosphorus-doped microcrystalline silicon (µc-Si) films were prepared on intrinsic hydrogenated amorphous silicon (a-Si:H) by mercury photosensitized decomposition of silane-phosphine-hydrogen gas mixture. We have obtained a high deposition rate of 15 nm/min and a high dark conductivity of 1.2 (Ω·cm)-1 at the substrate temperature of 240° C. The photothermal deflection spectroscopy (PDS) measurement of n-type µc-Si film on a-Si:H showed that the µc-Si/a-Si:H interface state density made by photo-CVD was small compared with that of the same structure made by the conventional plasma enhanced CVD (PECVD) method.

The authors have developed a low-temperature process for the first time for the selective deposition of a silicon film on hydrogenated amorphous silicon (a-Si:H) and on silicon nitride (SiN x ) surfaces by mercury sensitized photochemical vapor deposition (Photo-CVD). The selective deposition of Si films was able to be achieved by hydrogen radical cleaning for 1 minute prior to the deposition. There were two different incubation periods for the a-Si:H and SiN x surfaces. Selective deposition was obtained by using this difference in the incubation periods between the deposition on an a-Si:H surface and on a SiN x surface. The field effect mobility and the off leakage current for thin film transistor (TFT) of the fabrication by using this selective deposition technique were of the 0.6 cm2 V-1 s-1 and 10-11 A order, respectively. It has been confirmed that photo-CVD is a promising method for the selective deposition process at a low temperature using a large-area glass substrate.

The authors have developed a low-temperature process for selective deposition of silicon by mercury sensitized photochemical vapor deposition (Photo-CVD) without using ultraclean technology. It was found that hydrogen radical pretreatment was required to obtain selective deposition. There was an incubation period for not only SiO2 surface but also Si surface. It was confirmed that mercury sensitized Photo-CVD is a promising method for selective deposition process at low temperature using large-area glass substrate.

The influence of nitrogen incorporation in a-Si:H films by mercury-photosensitized decomposition of a silaneammonia gas mixture was investigated. It was found that there are two different film structures of a-Si:H films. In a high nitrogen concentration, nitrogen is one of the elements of the a-SiN x alloy. On the other hand, in a low nitrogen concentration, nitrogen plays the role of a dopant in a-Si:H, and nitrogen-induced localized states are created at around 0.5 eV above the valence band edge.