LIQUID CRYSTAL DISPLAY DEVICE AND ELECTRONIC DEVICE INCLUDING THE SAME

• US 20110090416A1
• Filed: 10/18/2010
• Published: 04/21/2011
• Est. Priority Date: 10/21/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: YAMAZAKI, Shunpei, SHISHIDO, Hideaki, ARASAWA, Ryo
• Granted Patent: US 9,559,208 B2
• Time in Patent Office: Days
• US Class Current: 349/38
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/134336 Matrix
• CPC Class Codes: G02F 1/134345 Subdivided pixels, e.g. for grey scale or redundancy
• CPC Class Codes: G02F 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/136213 Storage capacitors associated with the pixel electrode
• CPC Class Codes: G02F 1/13624 having more than one switching element per pixel
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 2201/123 pixel
• CPC Class Codes: G02F 2201/40 Arrangements for improving the aperture ratio
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2300/0439 Pixel structures
• CPC Class Codes: G09G 2300/0465 Improved aperture ratio, e.g. by size reduction of the pixel circuit, e.g. for improving the pixel density or the maximum displayable luminance or brightness
• CPC Class Codes: G09G 3/3614 Control of polarity reversal in general
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3677 suitable for active matrices only
• 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 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 27/1255 integrated with passive devices, e.g. auxiliary capacitors
• CPC Class Codes: H01L 27/127 with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement
• CPC Class Codes: H01L 29/24 : including, apart from doping materials or other impurities, only semiconductor materials not provided for in groups H01L29/16, H01L29/18, H01L29/20, H01L29/22 including organic materials H10K99/00
• CPC Class Codes: H01L 29/4908 : for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/78609 : for preventing leakage current H01L29/78618 takes precedence
• 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

A liquid crystal display device is provided in which the aperture ratio can be increased in a pixel including a thin film transistor in which an oxide semiconductor is used. In the liquid crystal display device, the thin film transistor including a gate electrode, a gate insulating layer and an oxide semiconductor layer which are provided so as to overlap with the gate electrode, and a source electrode and a drain electrode which overlap part of the oxide semiconductor layer is provided between a signal line and a pixel electrode which are provided in a pixel portion. The off-current of the thin film transistor is 1×10⁻¹³ A or less. A potential can be held only by a liquid crystal capacitor, without a capacitor which is parallel to a liquid crystal element, and a capacitor connected to the pixel electrode is not formed in the pixel portion.

Claims

1. A liquid crystal display device comprising:

a thin film transistor; and

a liquid crystal element connected to the thin film transistor,

wherein the thin film transistor comprises an oxide semiconductor layer,

wherein the liquid crystal element is provided in a pixel, and

wherein an auxiliary capacitor is not formed in the pixel.

2. A liquid crystal display device according to claim 1, wherein off-current of the thin film transistor is 1×

10<sup>−

13</sup>A or less.

3. A liquid crystal display device according to claim 1, wherein the oxide semiconductor layer has a hydrogen concentration of 5×

10¹⁹/cm³ or less and a carrier concentration of 5×

10¹⁴/cm³ or less.

4. A liquid crystal display device according to claim 1, wherein the liquid crystal element is provided in a subpixel included in the pixel.

5. A liquid crystal display device according to claim 1,

wherein the thin film transistor further comprises:

a gate electrode;

a gate insulating layer which is provided so as to overlap the gate electrode; and

a source electrode and a drain electrode which are provided so as to overlap part of the oxide semiconductor layer,

wherein the oxide semiconductor layer is provided so as to overlap the gate electrode with the gate insulating layer interposed therebetween.

6. An electronic device comprising the liquid crystal display device according to claim 1.

7. A liquid crystal display device comprising:

a thin film transistor; and

a liquid crystal element connected to the thin film transistor,

wherein the thin film transistor comprises an oxide semiconductor layer,

wherein the liquid crystal element is provided in a pixel, and

wherein the thin film transistor and the liquid crystal element are isolated from an auxiliary capacitor in the pixel.

8. A liquid crystal display device according to claim 7, wherein off-current of the thin film transistor is 1×

10<sup>−

13</sup>A or less.

9. A liquid crystal display device according to claim 7, wherein the oxide semiconductor layer has a hydrogen concentration of 5×

10¹⁹/cm³ or less and a carrier concentration of 5×

10¹⁴/cm³ or less.

10. A liquid crystal display device according to claim 7, wherein the liquid crystal element is provided in a subpixel included in the pixel.

11. A liquid crystal display device according to claim 7,

wherein the thin film transistor further comprises:

a gate electrode;

a gate insulating layer which is provided so as to overlap the gate electrode; and

a source electrode and a drain electrode which are provided so as to overlap part of the oxide semiconductor layer,

wherein the oxide semiconductor layer is provided so as to overlap the gate electrode with the gate insulating layer interposed therebetween.

12. An electronic device comprising the liquid crystal display device according to claim 7.

13. A liquid crystal display device comprising:

a thin film transistor; and

a liquid crystal element connected to the thin film transistor through one wiring without branching,

wherein the liquid crystal element is provided in a pixel, and

wherein the thin film transistor comprises an oxide semiconductor layer.

14. A liquid crystal display device according to claim 13, wherein off-current of the thin film transistor is 1×

10<sup>−

13</sup> A or less.

15. A liquid crystal display device according to claim 13, wherein the oxide semiconductor layer has a hydrogen concentration of 5×

10¹⁹/cm³ or less and a carrier concentration of 5×

10¹⁴/cm³ or less.

16. A liquid crystal display device according to claim 13, wherein the liquid crystal element is provided in a subpixel included in the pixel.

17. A liquid crystal display device according to claim 13,

wherein the thin film transistor further comprises:

a gate electrode;

a gate insulating layer which is provided so as to overlap the gate electrode; and

a source electrode and a drain electrode which are provided so as to overlap part of the oxide semiconductor layer,

wherein the oxide semiconductor layer is provided so as to overlap the gate electrode with the gate insulating layer interposed therebetween.

18. An electronic device comprising the liquid crystal display device according to claim 13.

19. A liquid crystal display device comprising:

a thin film transistor;

a liquid crystal element connected to the thin film transistor; and

an auxiliary capacitor connected to the thin film transistor and the liquid crystal element,

wherein the thin film transistor comprises an oxide semiconductor layer,

wherein the liquid crystal element is provided in a pixel, and

wherein a capacitance of the auxiliary capacitor is smaller than a capacitance of the liquid crystal element.

20. A liquid crystal display device according to claim 19, wherein off-current of the thin film transistor is 1×

10<sup>−

13</sup> A or less.

21. A liquid crystal display device according to claim 19, wherein the oxide semiconductor layer has a hydrogen concentration of 5×

10¹⁹/cm³ or less and a carrier concentration of 5×

10¹⁴/cm³ or less.

22. A liquid crystal display device according to claim 19, wherein the liquid crystal element is provided in a subpixel included in the pixel.

23. A liquid crystal display device according to claim 19,

wherein the thin film transistor further comprises:

a gate electrode;

a gate insulating layer which is provided so as to overlap the gate electrode; and

a source electrode and a drain electrode which are provided so as to overlap part of the oxide semiconductor layer,

wherein the oxide semiconductor layer is provided so as to overlap the gate electrode with the gate insulating layer interposed therebetween.

24. An electronic device comprising the liquid crystal display device according to claims 19.