DISPLAY DEVICE AND MANUFACTURING METHOD THEREOF

• US 20170271377A1
• Filed: 06/02/2017
• Published: 09/21/2017
• Est. Priority Date: 01/24/2010
• Status: Abandoned Application

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: YAMAZAKI, Shunpei
• Application Number:
  US15/611,980
• Publication Number:
  US 20170271377A1
• Time in Patent Office: Days
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/1336 Illuminating devices
• CPC Class Codes: G02F 1/134309 characterised by their geometrical arrangement
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G09G 2300/08 Active matrix structure, i.e. with use of active elements, inclusive of non-linear two terminal elements, in the pixels together with light emitting or modulating elements
• CPC Class Codes: G09G 2320/0214 with crosstalk due to leakage current of pixel switch in active matrix panels
• CPC Class Codes: G09G 2320/0626 for control of overall brightness
• CPC Class Codes: G09G 2360/144 the light being ambient light
• CPC Class Codes: G09G 3/3406 Control of illumination source illumination devices structurally associated with liquid crystal cells G02F1/1336
• CPC Class Codes: G09G 3/3648 using an active matrix G09G3/367 - G09G3/3696 take precedence
• CPC Class Codes: G09G 3/3659 the addressing of the pixel involving the control of two or more scan electrodes or two or more data electrodes, e.g. pixel voltage dependant on signal of two data electrodes
• 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 27/153 in a repetitive configuration, e.g. LED bars
• CPC Class Codes: H01L 29/045 by their particular orientation of crystalline planes
• CPC Class Codes: H01L 29/12 characterised by the materials of which they are formed
• 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 29/66742 Thin film unipolar transistors
• CPC Class Codes: H01L 29/66969 of devices having semiconductor bodies not comprising group 14 or group 13/15 materials comprising selenium or tellurium in uncombined form other than as impurities in semiconductor bodies of other materials, comprising cuprous oxide or cuprous iodide H01L21/02365
• 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: H10K 59/1213 : the pixel elements being TFTs

Abstract

Disclosed is a display device including a transistor showing extremely low off current. In order to reduce the off current, a semiconductor material whose band gap is greater than that of a silicon semiconductor is used for forming a transistor, and the concentration of an impurity which serves as a carrier donor of the semiconductor material is reduced. Specifically, an oxide semiconductor whose band gap is greater than or equal to 2 eV, preferably greater than or equal to 2.5 eV, more preferably greater than or equal to 3 eV is used for a semiconductor layer of a transistor, and the concentration of an impurity which serves as a carrier donor included is reduced. Consequently, the off current of the transistor per micrometer in channel width can be reduced to lower than 10 zA/μm at room temperature and lower than 100 zA/μm at 85° C.

Claims

1. (canceled)

2. A method for manufacturing a display device comprising a transistor and a pixel electrode, the method comprising:

forming an oxide semiconductor film over a substrate;

forming an oxide semiconductor layer by selectively etching the oxide semiconductor film;

performing a first heat treatment at a temperature from 400°

C. to 750°

C. inclusive,

forming a first insulating film over the transistor;

performing a second heat treatment at a temperature from 200°

C. to 400°

C. inclusive; and

after the second heat treatment, forming a second insulating film over the first insulating film,

wherein the pixel electrode is over the second insulating film and is electrically connected to the transistor through a contact hole provided in the first insulating film and the second insulating film,

wherein the transistor further comprises;

a source electrode electrically connected to the oxide semiconductor film; and

a drain electrode electrically connected to the oxide semiconductor film;

a gate electrode; and

a gate insulating film between the gate electrode and the oxide semiconductor film,

wherein the oxide semiconductor layer comprises a channel formation region of the transistor,

wherein the oxide semiconductor film comprises indium, zinc, and oxygen,

wherein the first insulating film is directly in contact with the oxide semiconductor layer,

wherein the first insulating film is one selected from the group consisting of silicon oxide and silicon oxynitride,

wherein the second insulating film has a function of blocking entry of moisture, and

wherein the second insulating film is one selected from the group consisting of silicon nitride, aluminum nitride, silicon nitride oxide and aluminum nitride oxide.

3. The method for manufacturing the display device according to claim 2, wherein the oxide semiconductor film comprises at least one metal element selected from the group consisting of gallium, aluminum, manganese, and cobalt.

4. The method for manufacturing the display device according to claim 2, the oxide semiconductor layer is formed before the first heat treatment.

5. The method for manufacturing the display device according to claim 4, wherein the source electrode and the drain electrode are in contact with the gate insulating film.

6. The method for manufacturing the display device according to claim 2, wherein the display device further comprises a liquid crystal layer over the pixel electrode.

7. The method for manufacturing the display device according to claim 6, wherein the display device further comprises a counter electrode over the liquid crystal layer.

8. The method for manufacturing the display device according to claim 2, wherein the oxide semiconductor film is an i-type semiconductor or a substantially i-type semiconductor.

9. The method for manufacturing the display device according to claim 2, wherein the oxide semiconductor film comprises a crystalline region.

10. The method for manufacturing the display device according to claim 9, wherein the crystalline region has a c-axis orientation with respect to a surface of the oxide semiconductor film.

11. The method for manufacturing the display device according to claim 9,

wherein the transistor has a characteristic that a current flowing between the source electrode and the drain electrode is lower than 10 zA/m at room temperature when a voltage of 3.1 V is applied between the source electrode and the drain electrode, and

wherein the current is normalized by a channel width of the transistor.

12. A method for manufacturing a display device comprising a transistor and a pixel electrode, the method comprising:

forming an oxide semiconductor film over a substrate;

forming an oxide semiconductor layer by selectively etching the oxide semiconductor film;

performing a first heat treatment at a temperature from 400°

C. to 750°

C. inclusive,

forming a first insulating film over the transistor;

performing a second heat treatment at a temperature from 200°

C. to 400°

C. inclusive; and

after the second heat treatment, forming a second insulating film over the first insulating film,

wherein the pixel electrode is over the second insulating film and is electrically connected to the transistor through a contact hole provided in the first insulating film and the second insulating film,

wherein the transistor further comprises;

a source electrode electrically connected to the oxide semiconductor film; and

a drain electrode electrically connected to the oxide semiconductor film;

a gate electrode; and

a gate insulating film between the gate electrode and the oxide semiconductor film,

wherein the oxide semiconductor layer comprises a channel formation region of the transistor,

wherein the oxide semiconductor film comprises indium, zinc, and oxygen,

wherein the first insulating film is directly in contact with the oxide semiconductor layer, and

wherein the second insulating film has a function of blocking entry of moisture.

13. The method for manufacturing the display device according to claim 12, wherein the oxide semiconductor film comprises at least one metal element selected from the group consisting of gallium, aluminum, manganese, and cobalt.

14. The method for manufacturing the display device according to claim 12, the oxide semiconductor layer is formed before the first heat treatment.

15. The method for manufacturing the display device according to claim 14, wherein the source electrode and the drain electrode are in contact with the gate insulating film.

16. The method for manufacturing the display device according to claim 12, wherein the display device further comprises a liquid crystal layer over the pixel electrode.

17. The method for manufacturing the display device according to claim 16, wherein the display device further comprises a counter electrode over the liquid crystal layer.

18. The method for manufacturing the display device according to claim 12, wherein the oxide semiconductor film is an i-type semiconductor or a substantially i-type semiconductor.

19. The method for manufacturing the display device according to claim 12, wherein the oxide semiconductor film comprises a crystalline region.

20. The method for manufacturing the display device according to claim 19, wherein the crystalline region has a c-axis orientation with respect to a surface of the oxide semiconductor film.

21. The method for manufacturing the display device according to claim 19,

wherein the transistor has a characteristic that a current flowing between the source electrode and the drain electrode is lower than 10 zA/m at room temperature when a voltage of 3.1 V is applied between the source electrode and the drain electrode, and

wherein the current is normalized by a channel width of the transistor.