DISPLAY DEVICE

• US 20100072471A1
• Filed: 09/10/2009
• Published: 03/25/2010
• Est. Priority Date: 09/19/2008
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: AKIMOTO, Kengo, YAMAZAKI, Shunpei, UOCHI, Hideki, KOMORI, Shigeki, FUTAMURA, Tomoya, KASAHARA, Takahiro
• Granted Patent: US 9,196,633 B2
• Time in Patent Office: Days
• US Class Current: 257/43
• CPC Class Codes: G02F 1/136204 Arrangements to prevent high voltage or static electricity failures
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: H01L 27/0266 using field effect transistors as protective elements
• 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 29/7869 having a semiconductor body comprising an oxide semiconductor material, e.g. zinc oxide, copper aluminium oxide, cadmium stannate
• CPC Class Codes: H10K 59/1213 the pixel elements being TFTs
• CPC Class Codes: H10K 59/131 Interconnections, e.g. wiring lines or terminals

Abstract

A protective circuit includes a non-linear element which includes a gate electrode, a gate insulating layer covering the gate electrode, a first oxide semiconductor layer overlapping with the gate electrode over the gate insulating layer, and a first wiring layer and a second wiring layer whose end portions overlap with the gate electrode over the first oxide semiconductor layer and in which a conductive layer and a second oxide semiconductor layer are stacked. Over the gate insulating layer, oxide semiconductor layers with different properties are bonded to each other, whereby stable operation can be performed as compared with Schottky junction. Thus, the junction leakage can be reduced and the characteristics of the non-linear element can be improved.

Claims

1. A display device comprising:

a plurality of scan lines and a plurality of signal lines which intersect with each other over a substrate;

a pixel portion over the substrate, the pixel portion including a plurality of pixel electrodes arranged in matrix;

a signal input terminal in a periphery of the substrate; and

a non-linear element provided between the pixel portion and the signal input terminal,

wherein the pixel portion includes a thin film transistor,

wherein the thin film transistor includes;

a first oxide semiconductor layer including a channel formation region;

a gate electrode connected to one of the plurality of scan lines;

a first wiring layer connecting one of the plurality of signal lines and the first oxide semiconductor layer; and

a second wiring layer connecting one of the plurality of pixel electrodes and the first oxide semiconductor layer, and

wherein the non-linear element includes;

a gate electrode connected to one of the plurality of scan lines or one of the plurality of signal lines;

a gate insulating layer covering the gate electrode;

a second oxide semiconductor layer over the gate insulating layer, the second oxide semiconductor layer overlapping with the gate electrode;

a third wiring layer over the second oxide semiconductor layer, wherein an end portion of the third wiring layer overlaps with the gate electrode, and wherein the third wiring layer includes a stack of a first conductive layer and a third oxide semiconductor layer;

a fourth wiring layer over the second oxide semiconductor layer, wherein an end portion of the fourth wiring layer overlaps with the gate electrode, and wherein the fourth wiring layer includes a stack of a second conductive layer and a fourth oxide semiconductor layer; and

a fifth wiring layer connecting the gate electrode and one of the third wiring layer and the fourth wiring layer.

2. The display device according to claim 1,

wherein the second oxide semiconductor layer has higher oxygen concentration than the third oxide semiconductor layer and the fourth oxide semiconductor layer.

3. The display device according to claim 1,

wherein the second oxide semiconductor layer has lower electrical conductivity than the third oxide semiconductor layer and the fourth oxide semiconductor layer.

4. The display device according to claim 1,

wherein the second oxide semiconductor layer is oxygen-excess type while the third oxide semiconductor layer and the fourth oxide semiconductor layer are oxygen-deficiency type.

5. The display device according to claim 1,

wherein the first oxide semiconductor layer, the second oxide semiconductor layer, the third oxide semiconductor layer and the fourth oxide semiconductor layer include indium, gallium, and zinc.

6. The display device according to claim 1,

wherein the fifth wiring layer is formed from the same material as the pixel electrode.

7. The display device according to claim 1,

wherein the thickness of the channel formation region is smaller than other region in the first oxide semiconductor layer.

8. A display device comprising:

a plurality of scan lines and a plurality of signal lines which intersect with each other over a substrate;

a pixel portion over the substrate, the pixel portion including a plurality of pixel electrodes arranged in matrix;

a first protective circuit for connecting one of the plurality of scan lines and a first common wiring; and

a second protective circuit for connecting one of the plurality of signal lines and a second common wiring,

wherein the pixel portion includes a thin film transistor,

wherein the thin film transistor includes;

a first oxide semiconductor layer including a channel formation region;

a gate electrode connected to one of the plurality of scan lines;

a first wiring layer connecting one of the plurality of signal lines and the first oxide semiconductor layer; and

a second wiring layer connecting one of the plurality of pixel electrodes and the first oxide semiconductor layer,

wherein the first protective circuit and the second protective circuit each include a non-linear element, and

wherein each of the non-linear element includes;

a gate electrode connected to one of the plurality of scan lines or one of the plurality of signal lines;

a gate insulating layer covering the gate electrode,

a second oxide semiconductor layer over the gate insulating layer, the second oxide semiconductor layer overlapping with the gate electrode;

a third wiring layer over the second oxide semiconductor layer, wherein an end portion of the third wiring layer overlaps with the gate electrode, and wherein the third wiring layer includes a stack of a first conductive layer and a third oxide semiconductor layer;

a fourth wiring layer over the second oxide semiconductor layer, wherein an end portion of the fourth wiring layer overlaps with the gate electrode, and wherein the fourth wiring layer includes a stack of a second conductive layer and a fourth oxide semiconductor layer; and

a fifth wiring layer connecting the gate electrode and one of the third wiring layer and the fourth wiring layer.

9. The display device according to claim 8,

wherein the second oxide semiconductor layer has higher oxygen concentration than the third oxide semiconductor layer and the fourth oxide semiconductor layer.

10. The display device according to claim 8,

wherein the second oxide semiconductor layer has lower electrical conductivity than the third oxide semiconductor layer and the fourth oxide semiconductor layer.

11. The display device according to claim 8,

wherein the second oxide semiconductor layer is oxygen-excess type while the third oxide semiconductor layer and the fourth oxide semiconductor layer are oxygen-deficiency type.

12. The display device according to claim 8,

wherein the first oxide semiconductor layer, the second oxide semiconductor layer, the third oxide semiconductor layer and the fourth oxide semiconductor layer include indium, gallium, and zinc.

13. The display device according to claim 8,

wherein the fifth wiring layer is formed from the same material as the pixel electrode.

14. The display device according to claim 8,

wherein the thickness of the channel formation region is smaller than other region in the first oxide semiconductor layer.

15. A display device comprising:

a first wiring layer over a substrate;

a pixel over the substrate; and

a protective circuit over the substrate,

wherein the pixel includes;

a thin film transistor, wherein a gate electrode of the thin film transistor is connected to the first wiring layer; and

a pixel electrode connected to a source electrode or a drain electrode of the thin film transistor,

wherein the protective circuit includes;

a gate insulating film over the first wiring layer;

a first oxide semiconductor layer over the gate insulating film;

a second oxide semiconductor layer over the first oxide semiconductor layer;

a third oxide semiconductor layer over the first oxide semiconductor layer;

a second wiring layer over the second oxide semiconductor layer;

a third wiring layer over the third oxide semiconductor layer; and

a fourth wiring layer connecting the first wiring layer and the second wiring layer.

16. The display device according to claim 15,

wherein the first oxide semiconductor layer has higher oxygen concentration than the second oxide semiconductor layer and the third oxide semiconductor layer.

17. The display device according to claim 15,

wherein the first oxide semiconductor layer has lower electrical conductivity than the second oxide semiconductor layer and the third oxide semiconductor layer.

18. The display device according to claim 15,

wherein the first oxide semiconductor layer is oxygen-excess type while the second oxide semiconductor layer and the third oxide semiconductor layer are oxygen-deficiency type.

19. The display device according to claim 15,

wherein the first oxide semiconductor layer, the second oxide semiconductor layer and the third oxide semiconductor layer include indium, gallium, and zinc.

20. The display device according to claim 15,

wherein the fourth wiring layer is formed from the same material as the pixel electrode.

21. The display device according to claim 15,

wherein the thin film transistor comprises a fourth oxide semiconductor layer including a channel formation region, and

wherein the thickness of the channel formation region is smaller than other region in the fourth oxide semiconductor layer.