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Lcd and organic el display

Foreign code F190009814
File No. E06015US5
Posted date May 9, 2019
Country United States of America
Application number 201816027733
Gazette No. 20180323313
Date of filing Jul 5, 2018
Gazette Date Nov 8, 2018
International application number JP2005003273
International publication number WO2005088726
Date of international filing Feb 28, 2005
Date of international publication Sep 22, 2005
Priority data
  • P2004-071477 (Mar 12, 2004) JP
  • P2004-325938 (Nov 10, 2004) JP
  • 200510592431 (Feb 28, 2005) US
  • 2005JP03273 (Feb 28, 2005) WO
  • 200912504116 (Jul 16, 2009) US
  • 201113243244 (Sep 23, 2011) US
Title Lcd and organic el display
Abstract A switching element of LCDs or organic EL displays which uses a thin film transistor device, includes: a drain electrode, a source electrode, a channel layer contacting the drain electrode and the source electrode, wherein the channel layer comprises indium-gallium-zinc oxide having a transparent, amorphous state of a composition equivalent to InGaO3(ZnO)m (wherein m is a natural number less than 6) in a crystallized state, and the channel layer has a semi-insulating property represented by an electron mobility of more than 1 cm2/(V·sec) and an electron carrier concentration is less than 1018/cm3, a gate electrode, and a gate insulating film positioned between the gate electrode and the channel layer.
Outline of related art and contending technology BACKGROUND
Technical Field
The present invention relates to amorphous oxides and thin film transistors.
Background Art
A thin film transistor (TFT) is a three-terminal element having a gate terminal, a source terminal, and a drain terminal. It is an active element in which a semiconductor thin film deposited on a substrate is used as a channel layer for transportation of electrons or holes and a voltage is applied to the gate terminal to control the current flowing in the channel layer and switch the current between the source terminal and the drain terminal. Currently, the most widely used TFTs are metal-insulator-semiconductor field effect transistors (MIS-FETs) in which the channel layer is composed of a polysilicon or amorphous silicon film.
Recently, development of TFTs in which ZnO-based transparent conductive oxide polycrystalline thin films are used as the channel layers has been actively pursued (Patent Document 1). These thin films can be formed at low temperatures and is transparent in visible light; thus, flexible, transparent TFTs can be formed on substrates such as plastic boards and films.
However, known ZnO rarely forms a stable amorphous phase at room temperature and mostly exhibits polycrystalline phase; therefore, the electron mobility cannot be increased because of the diffusion at the interfaces of polycrystalline grains. Moreover, ZnO tends to contain oxygen defects and a large number of carrier electrons, and it is thus difficult to decrease the electrical conductivity. Therefore, it has been difficult to increase the on/off ratio of the transistors.
Patent Document 2 discloses an amorphous oxide represented by ZnxMyInzO(x+3y/2+3z/2) (wherein M is at least one element selected from Al and Ga, the ratio x/y is in the range of 0.2 to 12, and the ratio z/y is in the range of 0.4 to 1.4). However, the electron carrier concentration of the amorphous oxide film obtained herein is 1018/cm3 or more. Although this is sufficient for regular transparent electrodes, the film cannot be easily applied to a channel layer of a TFT. This is because it has been found that a TFT having a channel layer composed of this amorphous oxide film does not exhibit a sufficient on/off ratio and is thus unsuitable for TFT of a normally off type.
- Patent Document 1: Japanese Unexamined Patent Application Publication No. 2003-298062
- Patent Document 2: Japanese Unexamined Patent Application Publication No. 2000-044236
Scope of claims [claim1]
1. A Liquid Crystal Display (LCD) including:
a substrate; and
switching elements formed on the substrate;
wherein the substrate is one of a glass substrate, a plastic substrate or a plastic film, and
wherein each of the switching elements comprises a thin film transistor comprising:
a gate terminal formed over the substrate;
a gate insulating film formed on the gate terminal;
an amorphous oxide channel layer formed on the gate insulating film, the amorphous oxide channel layer including In, Ga, Zn and O;
a drain terminal formed on the amorphous oxide channel layer, the drain terminal partially overlapping with the gate terminal; and
a source terminal formed on the amorphous oxide channel layer and apart from the drain terminal, the source terminal partially overlapping with the gate terminal.
[claim2]
2. The LCD according to claim 1, wherein the switching element is operable in a normally off type.
[claim3]
3. The LCD according to claim 1, wherein the amorphous oxide channel layer is formed such that an electron mobility of the amorphous oxide channel layer increases with an electron carrier concentration of the amorphous oxide channel layer.
[claim4]
4. The LCD according to claim 1, wherein each thin film transistor further comprises a top-gate structure.
[claim5]
5. The LCD according to claim 1, wherein each thin film transistor further comprises a bottom-gate structure.
[claim6]
6. The LCD according to claim 1, wherein each of the drain terminal and the source terminal comprises a first layer contacting the amorphous oxide channel layer and a second layer formed on the first layer, the second layer comprising metal.
[claim7]
7. An organic Electroluminescence (EL) display including:
a substrate; and
switching elements formed on the substrate;
wherein the substrate is one of a glass substrate, a plastic substrate or a plastic film, and
wherein each of the switching elements comprises a thin film transistor comprising:
a gate terminal formed over the substrate;
a gate insulating film formed on the gate terminal;
an amorphous oxide channel layer formed on the gate insulating film, the amorphous oxide channel layer including In, Ga, Zn and O;
a drain terminal formed on the amorphous oxide channel layer, the drain terminal partially overlapping with the gate terminal; and
a source terminal formed on the amorphous oxide channel layer and apart from the drain terminal, the source terminal partially overlapping with the gate terminal.
[claim8]
8. The organic EL display according to claim 7, wherein the switching element is operable in a normally off type.
[claim9]
9. The organic EL display according to claim 7, wherein the amorphous oxide channel layer is formed such that an electron mobility of the amorphous oxide channel layer increases with an electron carrier concentration of the amorphous oxide channel layer.
[claim10]
10. The organic EL display according to claim 7, wherein each thin film transistor further comprises a top-gate structure.
[claim11]
11. The organic EL display according to claim 7, wherein the thin film transistor further comprises a bottom-gate structure.
[claim12]
12. The organic EL display according to claim 7, wherein each of the drain terminal and the source terminal comprises a first layer contacting the amorphous oxide channel layer and a second layer formed on the first layer, the second layer comprises metal.
  • Inventor, and Inventor/Applicant
  • HOSONO Hideo
  • HIRANO Masahiro
  • OTA Hiromichi
  • KAMIYA Toshio
  • NOMURA Kenji
  • CANON
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
  • TOKYO INSTITUTE OF TECHNOLOGY
IPC(International Patent Classification)
Reference ( R and D project ) ERATO HOSONO Transparent ElectroActive Materials AREA
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