Liquid crystal display device

• US 7,738,050 B2
• Filed: 06/24/2008
• Issued: 06/15/2010
• Est. Priority Date: 07/06/2007
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Kuwabara, Hideaki, Kimura, Hajime, Suzuki, Yukie, Yamazaki, Shunpei
• Primary Examiner(s): HEALY, BRIAN
• Application Number:
  US12/213,729
• Publication Number:
  US 20090009677A1
• Time in Patent Office: 721 Days
• Field of Search: 349/43, 349/56, 349/42, 349/138, 349/142, 349/143, 349/147, 257/66, 257/72, 257/59, 257/29, 257/E21.001, 257/E33.001
• US Class Current: 349/43
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/1339 Gaskets; Spacers; Sealing of cells
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• 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: H01L 27/1214 comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
• CPC Class Codes: H01L 27/1222 with a particular composition, shape or crystalline structure of the active layer
• CPC Class Codes: H01L 27/1288 employing particular masking sequences or specially adapted masks, e.g. half-tone mask
• 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 29/458 for thin film silicon, e.g. source or drain electrode
• CPC Class Codes: H01L 29/4908 for thin film semiconductor, e.g. gate of TFT
• CPC Class Codes: H01L 29/66765 Lateral single gate single channel transistors with inverted structure, i.e. the channel layer is formed after the gate
• CPC Class Codes: H01L 29/78678 with inverted-type structure, e.g. with bottom gate
• 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 method of manufacturing, with high mass productivity, liquid crystal display devices having highly reliable thin film transistors with excellent electric characteristics is provided. In a liquid crystal display device having an inverted staggered thin film transistor, the inverted staggered thin film transistor is formed as follows: a gate insulating film is formed over a gate electrode; a microcrystalline semiconductor film which functions as a channel formation region is formed over the gate insulating film; a buffer layer is formed over the microcrystalline semiconductor film; a pair of source and drain regions are formed over the buffer layer; and a pair of source and drain electrodes are formed in contact with the source and drain regions so as to expose a part of the source and drain regions.

Claims

1. A liquid crystal display device comprising:

a gate electrode;

a gate insulating film formed over the gate electrode;

a microcrystalline semiconductor film formed over the gate insulating film;

a buffer layer which is formed over the microcrystalline semiconductor film and has a concave portion;

source and drain regions formed over the buffer layer; and

source and drain electrodes in contact with the source and drain regions,

wherein;

the source and drain electrodes are not overlapped with end portions of the microcrystalline semiconductor film and the source and drain regions; and

end portions of the source and drain regions which are overlapped with the gate electrode are aligned with side faces of the concave portion of the buffer layer.

2. The liquid crystal display device according to claim 1, wherein the buffer layer is formed of an amorphous semiconductor film.

3. The liquid crystal display device according to claim 1, wherein the buffer layer is formed of an amorphous semiconductor film containing nitrogen.

4. The liquid crystal display device according to claim 1, wherein the buffer layer is formed of an amorphous semiconductor film containing hydrogen.

5. The liquid crystal display device according to claim 1, wherein the buffer layer is formed of an amorphous semiconductor film containing fluorine, chlorine, bromine, or iodine.

6. A liquid crystal display device comprising:

a gate electrode;

a gate insulating film formed over the gate electrode;

a microcrystalline semiconductor film formed over the gate insulating film;

a buffer layer which is formed over the microcrystalline semiconductor film and has a concave portion;

source and drain regions formed over the buffer layer; and

source and drain electrodes in contact with the source and drain regions,

wherein;

a part of the source and drain regions is in contact with the source and drain electrodes;

the other part of the source and drain regions is not in contact with the source and drain electrodes;

the buffer layer is exposed outside the source and drain electrodes;

the source and drain electrodes are not overlapped with end portions of the microcrystalline semiconductor film and the source and drain regions; and

end portions of the source and drain regions which are overlapped with the gate electrode are aligned with side faces of the concave portion of the buffer layer.

7. The liquid crystal display device according to claim 6, wherein the buffer layer is formed of an amorphous semiconductor film.

8. The liquid crystal display device according to claim 6, wherein the buffer layer is formed of an amorphous semiconductor film containing nitrogen.

9. The liquid crystal display device according to claim 6, wherein the buffer layer is formed of an amorphous semiconductor film containing hydrogen.

10. The liquid crystal display device according to claim 6, wherein the buffer layer is formed of an amorphous semiconductor film containing fluorine, chlorine, bromine, or iodine.

11. A liquid crystal display device comprising:

a gate electrode;

a gate insulating film formed over the gate electrode;

a microcrystalline semiconductor film formed over the gate insulating film;

a buffer layer which is formed over the microcrystalline semiconductor film and has a concave portion;

source and drain regions formed over the buffer layer;

source and drain electrodes in contact with the source and drain regions;

an insulating film in contact with the source and drain electrodes, a part of the source and drain regions, and a part of the buffer layer;

a pixel electrode formed over the insulating film and connected to one of the source and drain electrodes through a contact hole formed in the insulating film; and

a liquid crystal adjacent to the pixel electrode;

wherein;

the source and drain electrodes are not overlapped with end portions of the microcrystalline semiconductor film and the source and drain regions; and

end portions of the source and drain regions which are overlapped with the gate electrode are aligned with side faces of the concave portion of the buffer layer.

12. The liquid crystal display device according to claim 11, wherein the buffer layer is formed of an amorphous semiconductor film.

13. The liquid crystal display device according to claim 11, wherein the buffer layer is formed of an amorphous semiconductor film containing nitrogen.

14. The liquid crystal display device according to claim 11, wherein the buffer layer is formed of an amorphous semiconductor film containing hydrogen.

15. The liquid crystal display device according to claim 11, wherein the buffer layer is formed of an amorphous semiconductor film containing fluorine, chlorine, bromine, or iodine.

16. A liquid crystal display device comprising:

a gate electrode;

a gate insulating film formed over the gate electrode;

a microcrystalline semiconductor film formed over the gate insulating film;

a buffer layer which is formed over the microcrystalline semiconductor film and has a concave portion;

source and drain regions formed over the buffer layer;

source and drain electrodes in contact with the source and drain regions;

an insulating film in contact with the source and drain electrodes, a part of the source and drain regions, and a part of the buffer layer;

a pixel electrode formed over the insulating film and connected to one of the source and drain electrodes through a contact hole formed in the insulating film; and

a liquid crystal adjacent to the pixel electrode;

wherein;

a part of the source and drain regions is in contact with the source and drain electrodes;

the other part of the source and drain regions is not in contact with the source and drain electrodes;

the buffer layer is exposed outside of the source and drain electrodes; and

end portions of the source and drain regions which are formed over the gate electrode are aligned with side faces of the concave portion of the buffer layer.

17. The liquid crystal display device according to claim 16, wherein the buffer layer is formed of an amorphous semiconductor film.

18. The liquid crystal display device according to claim 16, wherein the buffer layer is formed of an amorphous semiconductor film containing nitrogen.

19. The liquid crystal display device according to claim 16, wherein the buffer layer is formed of an amorphous semiconductor film containing hydrogen.

20. The liquid crystal display device according to claim 16, wherein the buffer layer is formed of an amorphous semiconductor film containing fluorine, chlorine, bromine, or iodine.

21. A liquid crystal display device comprising:

a gate electrode;

a gate insulating film formed over the gate electrode;

a microcrystalline semiconductor film formed over the gate insulating film;

a buffer layer formed over the microcrystalline semiconductor film;

source and drain regions formed over the buffer layer; and

source and drain electrodes formed on the source and drain regions,

wherein;

the source and drain regions extend beyond outer side edges of the source and drain electrodes,

a portion of the buffer layer between the source and drain regions is thinned, and

the buffer layer extends beyond outer side edges of the source and drain regions.

22. The liquid crystal display device according to claim 21, wherein the buffer layer is formed of an amorphous semiconductor film.

23. The liquid crystal display device according to claim 21, wherein the buffer layer is formed of an amorphous semiconductor film containing nitrogen.

24. The liquid crystal display device according to claim 21, wherein the buffer layer is formed of an amorphous semiconductor film containing hydrogen.

25. The liquid crystal display device according to claim 21, wherein the buffer layer is formed of an amorphous semiconductor film containing fluorine, chlorine, bromine, or iodine.

26. The liquid crystal display device according to claim 21, wherein the portion of the buffer layer has side edges aligned with inner side edges of the source and drain regions.