In this paper, high-performance bottom-gate thin-film transistors (TFTs) with transparent zinc oxide (ZnO) channels have been developed. The ZnO film for active channels was deposited by RF magnetron sputtering. The crystallinity of the ZnO film drastically improved when it was deposited on a doublelayer SiO _x /SiN _x gate insulator. In order to achieve a ZnO TFT back-plane for liquid-crystal display (LCD) with the required pattern accuracy, dry etching of the ZnO film in an Ar and CH ₄ chemistry has been developed. The etching rate and tapered profile of the ZnO film could be controlled by the Ar content in the etching gases of Ar and CH ₄ . The saturation mobility (mu _sat ) of the ZnO TFT strongly depended on a gate voltage. A mu _sat of 5.2 & cm ² .(V .s) ^-1 at V _GS = 40 V and V _DS = 10 V, and an on/off-current ratio of 2.7 x 10 ⁷ were obtained. A drain-current uniformity of plusmn7% was achieved within a radius of 20 mm from the substrate center. A 1.46 -in diagonal LCD with 61 600 pixels has been driven by the ZnO-TFT back-plane. A moving picture image was available on fabricated LCD driven by the ZnO TFTs.

10.1109/ted.2008.2003330

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Citations (221)

Novel top‐gate zinc oxide thin‐film transistors (ZnO TFTs) for AMLCDs

Journal of the Society for Information Display (2007)

Takashi Hirao Mamoru Furuta Hiroshi Furuta Tokiyoshi Matsuda Takahiro Hiramatsu

Abstract— High‐performance top‐gate thin‐film transistors (TFTs) with a transparent zinc oxide (ZnO) channel have been developed. ZnO thin films used as active channels were deposited by rf magnetron sputtering. The electrical properties and thermal stability of the ZnO films are controlled by the deposition conditions. A gate insulator made of silicon nitride (SiN x ) was deposited on the ZnO films by conventional P‐CVD. A novel ZnO‐TFT process based on photolithography is proposed for AMLCDs. AMLCDs having an aperture ratio and pixel density comparable to those of a‐Si:H TFT‐LCDs are driven by ZnO TFTs using the same driving scheme of conventional AMLCDs.

Oxide thin-film transistor

10.1889/1.2451545

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Citations (98)

D-11-22 Hierarchical Motion Estimation using Extended Matching Templates

Proceedings of the IEICE General Conference (2005)

Toshio Kondo Jin Kobayashi Takahiro Hiramatsu Takahiro Sasaki Kazuhiko Ohno

Template

Template matching

Source

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Effect of Energetic Particle Bombardment on Microstructure of Zinc Oxide Films Deposited by RF Magnetron Sputtering

Japanese Journal of Applied Physics (2007)

Mamoru Furuta Takahiro Hiramatsu Tokiyoshi Matsuda Hiroshi Furuta Takashi Hirao

Zinc oxide (ZnO) films have been deposited on glass substrates by rf magnetron sputtering with Ar/O2 working gases. The crystallite size of the films was characterized by X-ray diffraction (XRD) analysis. At a deposition pressure of 1.0 Pa, the average crystallite size decreased with increasing O2 flow rate. Optical emission spectroscopy (OES) results showed that the average crystallite size can be controlled by the emission intensity ratio of O*/Ar. The XRD results of the ZnO deposited in both Ar/O2 and O2 working gases revealed that the bombardment of the energetic oxygen particles to the growing surface suppresses the surface migration of the sputtered adatoms and that of energetic argon particles enhances the surface migration of the adatoms. The crystallite size and total volume of the crystallite fraction in the film are affected by the flux of both energetic oxygen and argon particles present in the plasma, and are determined by the competition processes of the bombardment of energetic oxygen and argon under a constant deposition pressure.

Cavity magnetron

Deposition

10.1143/jjap.46.4038

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Citations (22)

Study on fabrication of conductive antimony doped tin oxide thin films (SnO_x:Sb) by 3rd generation mist chemical vapor deposition

Japanese Journal of Applied Physics (2019)

Li Liu Toshiyuki Kawaharamura Giang Dang E.K.C. Pradeep Shota Sato

Transparent conducing antimony doped tin oxide (SnOx:Sb) thin films were fabricated by solution-processed atmospheric-pressure 3rd generation mist chemical vapor deposition (3rd G mist CVD) system with two solution chambers and one mixing chamber to control the atmosphere in reaction area. To study how to reduce the resistivity, the effects of each additive component in dopant solution were investigated; this was followed by identification of components contributing to the fabrication of SnOx:Sb films. Experimentally, the HNO3 clearly affected the resistivity and the formation of SnO2 thin films through a change in the valence state of N derived from HNO3 promoting the transformation of Sn (II) and Sb (III) to Sn (IV) and Sb (V). Moreover, the values of electron and hole effective mass were defined using the specified referred parameters to confirm the band diagram of SnOx:Sb thin films fabricated by 3rd G mist CVD system.

Tin oxide

Mist

Transparent conducting film

10.7567/1347-4065/aaf4b6

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Citations (17)

Comparison of different annealing gases effects on the optical emission properties of zinc oxide thin films deposited by radio frequency sputtering

Chao Li Tokiyoshi Matsuda Yoichiro Nakanishi Keiji Ichinomiya Mamoru Furuta

Recent several years, ZnO thin film has attracted much more attention due to its promising electrical, optical and piezoelectric properties, which can be extensive apply in electronic and optoelectronic fields such as optical waveguides, solar cell, gas sensors, etc. Especially, ZnO is a wide-band gap of 3.37 eV and high efficiency as a low-voltage cathodoluminescent phosphor material in backlight for field emission display. Among the many fabrication techniques of ZnO film, magnetron radio frequency sputtering is considered as a convenient method to deposition homogeneous ZnO thin film on large area. In this research, we will compare the phosphor properties of ZnO film by post-thermal treatment in different gas ambient.

Field emission display

10.1109/ivnc.2009.5271839

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Enhanced Nucleation of Microcrystalline Silicon Thin Films Deposited by Inductively Coupled Plasma Chemical Vapor Deposition with Low-Frequency Pulse Substrate Bias

Japanese Journal of Applied Physics (2010)

Mamoru Furuta Takahiro Hiramatsu Takashi Hirao

Microcrystalline silicon (µc-Si) films were deposited by inductively coupled plasma chemical vapor deposition with a low-frequency and low-duty pulse substrate bias (PSB). The crystallinity of the films was significantly improved by the PSB. In the case of the low-frequency and low-duty PSB, the duty ratio affected the crystallinity more than the negative peak voltage. Cross-sectional transmission electron microscopy measurements revealed that the nucleation density at the µc-Si/glass interface was increased by the PSB. This technique will be useful in fabricating high-performance bottom-gate µc-Si thin-film transistors for large-area electronics.

Microcrystalline

10.1143/jjap.49.050202

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A 128×96 Pixel Stack-Type Color Image Sensor: Stack of Individual Blue-, Green-, and Red-Sensitive Organic Photoconductive Films Integrated with a ZnO Thin Film Transistor Readout Circuit

Japanese Journal of Applied Physics (2011)

Hokuto Seo Satoshi Aihara Toshihisa Watabe Hiroshi Ohtake Toshikatsu Sakai

A color image was produced by a vertically stacked image sensor with blue (B)-, green (G)-, and red (R)-sensitive organic photoconductive films, each having a thin-film transistor (TFT) array that uses a zinc oxide (ZnO) channel to read out the signal generated in each organic film. The number of the pixels of the fabricated image sensor is 128×96 for each color, and the pixel size is 100×100 µm 2 . The current on/off ratio of the ZnO TFT is over 10 6 , and the B-, G-, and R-sensitive organic photoconductive films show excellent wavelength selectivity. The stacked image sensor can produce a color image at 10 frames per second with a resolution corresponding to the pixel number. This result clearly shows that color separation is achieved without using any conventional color separation optical system such as a color filter array or a prism.

Color filter array

SIGNAL (programming language)

Photoconductivity

10.1143/jjap.50.024103

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Citations (38)

Effect of Pulsed Substrate Bias on Film Properties of SiO₂ Deposited by Inductively Coupled Plasma Chemical Vapor Deposition

Japanese Journal of Applied Physics (2010)

Takahiro Hiramatsu Tokiyoshi Matsuda Hiroshi Furuta Hiroshi Nitta Toshiyuki Kawaharamura

A high-quality SiO 2 film was successfully achieved at a temperature of 150 °C by inductively coupled plasma chemical vapor deposition (ICP-CVD) with a bipolar pulsed bias applied to a substrate. When the SiO 2 film was deposited without the pulsed substrate bias, its density rapidly decreased and its insulating property deteriorated. However, its densification was enhanced and its insulating property was improved by the pulsed substrate bias even though the deposition rate increased. A leakage current of less than 10.0 nA/cm 2 and a breakdown voltage of 5.2 MV/cm at 1.0 µA/cm 2 were obtained at a temperature of 150 °C with a deposition rate of 18.0 nm/min.

Biasing

Deposition

10.1143/jjap.49.03ca03

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Citations (5)