TRANSISTOR AND DISPLAY DEVICE

• US 20110062436A1
• Filed: 09/13/2010
• Published: 03/17/2011
• Est. Priority Date: 09/16/2009
• Status: Abandoned Application

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: MIYANAGA, Akiharu, HIROHASHI, Takuya, AKIMOTO, Kengo, YAMAZAKI, Shunpei, WATANABE, Ryosuke, SAKAKURA, Masayuki, SAKATA, Junichiro, KISHIDA, Hideyuki
• Application Number:
  US12/880,343
• Publication Number:
  US 20110062436A1
• Time in Patent Office: Days
• US Class Current: 257/43
• 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 29/04 characterised by their crystalline structure, e.g. polycrystalline, cubic or particular orientation of crystalline planes characterised by physical imperfections H01L29/30
• CPC Class Codes: H01L 29/045 by their particular orientation of crystalline planes
• CPC Class Codes: H01L 29/78618 characterised by the drain or the source properties, e.g. the doping structure, the composition, the sectional shape or the contact structure silicide contacts, electrodes in general H01L29/458
• 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 29/78693 the semiconducting oxide being amorphous
• 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 transistor having a favorable electric characteristics and high reliability and a display device including the transistor. The transistor is a bottom-gate transistor formed using an oxide semiconductor for a channel region. An oxide semiconductor layer subjected to dehydration or dehydrogenation through heat treatment is used as an active layer. The active layer includes a first region of a superficial portion microcrystallized and a second region of the rest portion. By using the oxide semiconductor layer having such a structure, a change to an n-type, which is attributed to entry of moisture to the superficial portion or elimination of oxygen from the superficial portion, and generation of a parasitic channel can be suppressed. In addition, contact resistance between the oxide semiconductor layer and source and drain electrodes can be reduced.

Claims

1. A transistor comprising:

a gate electrode layer;

a gate insulating layer over the gate electrode layer;

an oxide semiconductor layer over the gate insulating layer;

a source electrode layer and a drain electrode layer over the gate insulating layer, which overlap with part of the oxide semiconductor layer; and

an oxide insulating layer over the source electrode layer and the drain electrode layer, and on and in contact with the oxide semiconductor layer,

wherein the oxide semiconductor layer includes a first region of a superficial portion and a second region of the rest portion, and

wherein the second region of the oxide semiconductor layer is amorphous or is formed of a mixture of amorphousness and microcrystals, or is formed of microcrystals.

2. The transistor according to claim 1, wherein the first region of the oxide semiconductor layer is formed of microcrystals c-axis-oriented in a direction perpendicular to a surface of the oxide semiconductor layer.

3. The transistor according to claim 1, wherein a particle size of each of the microcrystals is from 1 nm to 20 nm.

4. The transistor according to claim 1, further comprising an oxide conductive layer provided between the oxide semiconductor layer, and the source electrode layer and the drain electrode layer.

5. The transistor according to claim 1, wherein each of the source electrode layer and the drain electrode layer has a three-layer structure formed of a first conductive layer, a second conductive layer, and a third conductive layer.

6. The transistor according to claim 1, wherein the transistor has a light-transmitting property.

7. The transistor according to claim 1, wherein an amorphous region in the second region is dotted with the microcrystals.

8. A transistor comprising:

a gate electrode layer;

a gate insulating layer over the gate electrode layer;

a source electrode layer and a drain electrode layer over the gate insulating layer;

an oxide semiconductor layer over the gate insulating layer, which overlaps with part of the source electrode layer and the drain electrode layer; and

an oxide insulating layer on and in contact with the oxide semiconductor layer,

wherein the oxide semiconductor layer includes a first region of a superficial portion and a second region of the rest portion, and

wherein the second region of the oxide semiconductor layer is amorphous or is formed of a mixture of amorphousness and microcrystals, or is formed of microcrystals.

9. The transistor according to claim 8, wherein the first region of the oxide semiconductor layer is formed of microcrystals c-axis-oriented in a direction perpendicular to a surface of the oxide semiconductor layer.

10. The transistor according to claim 8, wherein a particle size of each of the microcrystals is from 1 nm to 20 nm.

11. The transistor according to claim 8, further comprising an oxide conductive layer provided between the oxide semiconductor layer, and the source electrode layer and the drain electrode layer.

12. The transistor according to claim 8, wherein each of the source electrode layer and the drain electrode layer has a three-layer structure formed of a first conductive layer, a second conductive layer, and a third conductive layer.

13. The transistor according to claim 8, wherein the transistor has a light-transmitting property.

14. The transistor according to claim 8, wherein an amorphous region in the second region is dotted with the microcrystals.

15. A display device comprising:

a pixel portion formed over a substrate, the pixel portion including a first transistor; and

a driver circuit portion formed over the substrate, the driver circuit portion including a second transistor,

wherein each of the first transistor and the second transistor includes;

a gate electrode layer,

a gate insulating layer over the gate electrode layer,

an oxide semiconductor layer over the gate insulating layer,

a source electrode layer and a drain electrode layer over the gate insulating layer, which overlap with part of the oxide semiconductor layer, and

an oxide insulating layer in contact with the oxide semiconductor layer,

wherein the oxide semiconductor layer includes a first region of a superficial portion and a second region of the rest portion, and

wherein the second region of the oxide semiconductor layer is amorphous or is formed of a mixture of amorphousness and microcrystals, or is formed of microcrystals.

16. The display device according to claim 15, wherein the first region of the oxide semiconductor layer is formed of microcrystals c-axis-oriented in a direction perpendicular to a surface of the oxide semiconductor layer.

17. The display device according to claim 15, wherein a particle size of each of the microcrystals is from 1 nm to 20 nm.

18. The display device according to claim 15, further comprising an oxide conductive layer provided between the oxide semiconductor layer, and the source electrode layer and the drain electrode layer.

19. The display device according to claim 15, wherein each of the source electrode layer and the drain electrode layer has a three-layer structure formed of a first conductive layer, a second conductive layer, and a third conductive layer.

20. The display device according to claim 15, wherein the pixel portion has a light-transmitting property.

21. The display device according to claim 15, wherein an amorphous region in the second region is dotted with the microcrystals.

22. A display device comprising:

a pixel portion formed over a substrate, the pixel portion including a first transistor; and

a driver circuit portion formed over the substrate, the driver circuit portion including a second transistor,

wherein each of the first transistor and the second transistor includes;

a gate electrode layer,

a gate insulating layer over the gate electrode layer,

a source electrode layer and a drain electrode layer over the gate insulating layer,

an oxide semiconductor layer over the gate insulating layer, which overlaps with part of the source electrode layer and the drain electrode layer, and

an oxide insulating layer in contact with the oxide semiconductor layer,

wherein the oxide semiconductor layer includes a first region of a superficial portion and a second region of the rest portion, and

wherein the second region of the oxide semiconductor layer is amorphous or is formed of a mixture of amorphousness and microcrystals, or is formed of microcrystals.

23. The display device according to claim 22, wherein the first region of the oxide semiconductor layer is formed of microcrystals c-axis-oriented in a direction perpendicular to a surface of the oxide semiconductor layer.

24. The display device according to claim 22, wherein a particle size of each of the microcrystals is from 1 nm to 20 nm.

25. The display device according to claim 22, further comprising an oxide conductive layer provided between the oxide semiconductor layer, and the source electrode layer and the drain electrode layer.

26. The display device according to claim 22, wherein each of the source electrode layer and the drain electrode layer has a three-layer structure formed of a first conductive layer, a second conductive layer, and a third conductive layer.

27. The display device according to claim 22, wherein the pixel portion has a light-transmitting property.

28. The display device according to claim 22, wherein an amorphous region in the second region is dotted with the microcrystals.