Display device including oxide semiconductor layer

• US 9,048,320 B2
• Filed: 09/10/2009
• Issued: 06/02/2015
• Est. Priority Date: 09/19/2008
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Yamazaki, Shunpei, Akimoto, Kengo, Komori, Shigeki, Uochi, Hideki, Futamura, Tomoya, Kasahara, Takahiro
• Primary Examiner(s): Nguyen, Lauren
• Application Number:
  US12/556,695
• Publication Number:
  US 20100072470A1
• Time in Patent Office: 2,091 Days
• Field of Search: 349/40, 349 42- 43
• US Class Current: 1/1
• CPC Class Codes: G02F 1/133 Constructional arrangements; Operation of liquid crystal cells; Circuit arrangements arrangements or circuits for control of liquid crystal elements in a matrix, not structurally associated with these elements G09G3/36
• CPC Class Codes: G02F 1/13306 Circuit arrangements or driving methods for the control of single liquid crystal cells G02F1/132, G02F1/133382 take precedence
• CPC Class Codes: G02F 1/1345 Conductors connecting electrodes to cell terminals
• CPC Class Codes: G02F 1/13452 Conductors connecting driver circuitry and terminals of panels
• CPC Class Codes: H01L 27/0251 for MOS devices
• 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

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, a channel protective layer overlapping with a channel formation region of the first oxide semiconductor layer, and a pair of a first wiring layer and a second wiring layer whose end portions overlap with the gate electrode over the channel protective 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 transparent pixel electrodes arranged in matrix;

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

a non-linear element 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 first gate electrode connected to one of the plurality of scan lines;

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

a second wiring layer connecting one of the plurality of transparent pixel electrodes and the first oxide semiconductor layer, the one of the plurality of transparent pixel electrodes being provided over the first oxide semiconductor layer, and wherein the non-linear element includes;

a second 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 second gate electrode;

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

a channel protective layer over the second oxide semiconductor layer, the channel protective layer overlapping with a channel formation region of the second oxide semiconductor layer, wherein the channel protective layer is an insulating layer comprising an oxide;

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

a transparent conductive film over the second gate electrode, the transparent conductive film connecting the second gate electrode and one of the third wiring layer and the fourth wiring layer.

4. A 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.

7. A 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.

10. A display device according to claim 1,

wherein the second oxide semiconductor layer is oxygen-excess type, and

wherein the third oxide semiconductor layer and the fourth oxide semiconductor layer are oxygen-deficiency type.

13. A 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.

16. A display device according to claim 1,

wherein the transparent conductive film is formed from the same material as the one of the plurality of transparent pixel electrodes.

19. A display device according to claim 1, wherein the channel protective layer comprises an oxide.

22. A display device according to claim 1, wherein the third oxide semiconductor layer comprises a crystalline region.

2. 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 transparent pixel electrodes arranged in matrix;

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

a second protective circuit 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 first gate electrode connected to one of the plurality of scan lines;

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

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

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

wherein the non-linear element includes;

a second 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 second gate electrode;

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

a channel protective layer over the second oxide semiconductor layer, the channel protective layer overlapping with a channel formation region of the second oxide semiconductor layer, wherein the channel protective layer is an insulating layer comprising an oxide;

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

a transparent conductive film over the second gate electrode, the transparent conductive film connecting the second gate electrode and one of the third wiring layer and the fourth wiring layer.

5. A display device according to claim 2,

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

8. A display device according to claim 2,

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

11. A display device according to claim 2,

wherein the second oxide semiconductor layer is oxygen-excess type, and

wherein the third oxide semiconductor layer and the fourth oxide semiconductor layer are oxygen-deficiency type.

14. A display device according to claim 2,

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.

17. A display device according to claim 2,

wherein the transparent conductive film is formed from the same material as the one of the plurality of transparent pixel electrodes.

20. A display device according to claim 2, wherein the channel protective layer comprises an oxide.

23. A display device according to claim 2, wherein the third oxide semiconductor layer comprises a crystalline region.

3. 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 transparent pixel electrode over a channel formation region of the thin film transistor and 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 channel protective layer over the first oxide semiconductor layer, wherein the channel protective layer is an insulating layer comprising an oxide;

a second oxide semiconductor layer over the first oxide semiconductor layer and the channel protective layer;

a third oxide semiconductor layer over the first oxide semiconductor layer and the channel protective layer;

a first conductive layer over the second oxide semiconductor layer;

a second conductive layer over the third oxide semiconductor layer; and

a transparent conductive film over the first wiring layer, the transparent conductive film connecting the first wiring layer and the first conductive layer.

6. A display device according to claim 3,

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

9. A display device according to claim 3,

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

12. A display device according to claim 3,

wherein the first oxide semiconductor layer is oxygen-excess type, and

wherein the second oxide semiconductor layer and the third oxide semiconductor layer are oxygen-deficiency type.

15. A display device according to claim 3,

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

18. A display device according to claim 3,

wherein the transparent conductive film is formed from the same material as the transparent pixel electrode.

21. A display device according to claim 3, wherein the channel protective layer comprises an oxide.

24. A display device according to claim 3, wherein the second oxide semiconductor layer comprises a crystalline region.