Field-effect transistor and method for producing field-effect transistor

• US 10,672,914 B2
• Filed: 07/25/2014
• Issued: 06/02/2020
• Est. Priority Date: 07/31/2013
• Status: Active Grant

• Current Assignee: Ricoh Company Limited
• Original Assignee: Ricoh Company Limited
• Inventors: Matsumoto, Shinji, Ueda, Naoyuki, Nakamura, Yuki, Takada, Mikiko, Sone, Yuji, Saotome, Ryoichi, Arae, Sadanori, Abe, Yukiko
• Primary Examiner(s): Mengistu, Amare
• Assistant Examiner(s): Zubajlo, Jennifer L
• Application Number:
  US14/908,599
• Publication Number:
  US 20160190329A1
• Time in Patent Office: 2,139 Days
• CPC Class Codes: G09G 3/2092 Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165
• CPC Class Codes: H01L 27/1225 with semiconductor materials not belonging to the group IV of the periodic table, e.g. InGaZnO
• CPC Class Codes: H01L 29/41733 for thin film transistors with insulated gate
• CPC Class Codes: H01L 29/42384 for thin film field effect transistors, e.g. characterised by the thickness or the shape of the insulator or the dimensions, the shape or the lay-out of the conductor
• CPC Class Codes: H01L 29/45 Ohmic electrodes
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• CPC Class Codes: H01L 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H01L 29/78696 characterised by the structure of the channel, e.g. multichannel, transverse or longitudinal shape, length or width, doping structure, or the overlap or alignment between the channel and the gate, the source or the drain, or the contacting structure of the channel H01L29/78612 takes precedence; transistors having a drain offset region or a lightly doped drain [LDD] H01L29/78621

Abstract

To provide a field-effect transistor, containing: a gate electrode configured to apply gate voltage; a source electrode and a drain electrode, both of which are configured to take out electric current; an active layer formed of a n-type oxide semiconductor, provided in contact with the source electrode and the drain electrode; and a gate insulating layer provided between the gate electrode and the active layer, wherein work function of the source electrode and drain electrode is 4.90 eV or greater, and wherein an electron carrier density of the n-type oxide semiconductor is 4.0×10¹⁷ cm⁻³ or greater.

Claims

1. A field-effect transistor, comprising:

a gate electrode;

a source electrode and a drain electrode, each formed by a conductive material;

a n-type oxide semiconductor, provided in contact with the source electrode and the drain electrode; and

a gate insulating layer provided between the gate electrode and the n-type oxide semiconductor, wherein

a work function of the source electrode and the drain electrode formed by the conductive material is 4.90 eV or greater, and,

in a case that an electron carrier density of the n-type oxide semiconductor is 4.0×

10¹⁸ cm<sup>−

3</sup> or greater, a carrier mobility of the field-effect transistor is at least 3.8 cm²/Vs and an ON/OFF ratio of a drain-source current is 1.0×

10⁸ or greater between an OFF state in which a gate voltage is −

20 V and an ON state in which the gate voltage is 20 V.

2. The field-effect transistor according to claim 1, wherein the conductive material of the source electrode and the drain electrode is a metal, an alloy, or both.

3. The field-effect transistor according to claim 2, wherein the metal, the alloy, or both contain gold, silver, palladium, platinum, nickel, iridium, rhodium, or any combination thereof.

4. The field-effect transistor according to claim 1, wherein the source electrode and the drain electrode are formed by baking metal particles, alloy particles, an organometallic compound, or any combination thereof.

5. The field-effect transistor according to claim 1, wherein the n-type oxide semiconductor contains indium, zinc, tin, gallium, titanium, or any combination thereof.

6. The field-effect transistor according to claim 5, wherein the n-type oxide semiconductor further contains an alkaline earth metal.

7. A display element, comprising:

a light control element configured to control light output according to a driving signal; and

a driving circuit, which contains the field-effect transistor according to claim 1 and is configured to drive the light control element.

8. The display element according to claim 7, wherein the light control element contains an electroluminescent element or an electrochromic element.

9. The display element according to claim 7, wherein the light control element contains a liquid crystal element or an electrophoretic element.

10. An image display device, which displays an image corresponding to image data, the image display device comprising:

a plurality of display elements according to claim 7 arranged in a matrix;

a plurality of lines configured to separately apply a respective gate voltage to field-effect transistors in each of the plurality of display elements; and

a display control device configured to individually control the respective gate voltage of each of the field-effect transistors through the lines corresponding to the image data.

11. A system, comprising:

the image display device according to claim 10; and

an image data generating device configured to generate image data based on image information to be displayed, and output the generated image data to the image display device.

12. The field-effect transistor according to claim 1, wherein each of the source electrode and the drain electrode is a thin film electrode formed by the conductive material, and the work function of the thin film electrode formed by the conductive material is 4.90 eV or greater.

13. The field-effect transistor according to claim 1, wherein each of the source electrode and the drain electrode is a thin film electrode formed by the conductive material, and the work function of the thin film electrode formed by the conductive material is 4.90 eV or greater and is 6.00 eV or less.

14. The field-effect transistor according to claim 1, wherein each of the source electrode and the drain electrode is a thin film electrode formed by the conductive material, and the work function of the thin film electrode formed by the conductive material is 4.90 eV or greater, to prevent the thin film electrode from being oxidized by a heat treatment or oxidizing atmosphere treatment performed after the field-effect transistor has been formed.