Method for manufacturing display device

• US 8,372,664 B2
• Filed: 12/21/2010
• Issued: 02/12/2013
• Est. Priority Date: 12/25/2009
• Status: Active Grant

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Moriya, Koji, Tsuji, Takahiro
• Primary Examiner(s): Chaudhuri, Olik
• Assistant Examiner(s): JEFFERSON, QUOVAUNDA
• Application Number:
  US12/974,263
• Publication Number:
  US 20110159619A1
• Time in Patent Office: 784 Days
• Field of Search: 438/22, 438/26, 438/29, 438/30, 438/38, 438/455, 438/458, 438/689, 438/690, 438/798, 438/800, 438/126, 438/127, 438/149, 438/151, 438/795, 438/FOR.407, 438/FOR.410, 438/FOR.415, 438/FOR.416, 438/FOR.417, 257/E21.328, 257/E21.333, 257/E21.411, 349/187, 349/189, 349/190, 349/192
• US Class Current: 438/4
• CPC Class Codes: G09G 2300/043 Compensation electrodes or other additional electrodes in matrix displays related to distortions or compensation signals, e.g. for modifying TFT threshold voltage in column driver
• CPC Class Codes: G09G 2320/0252 Improving the response speed
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 2330/08 Fault-tolerant or redundant circuits, or circuits in which repair of defects is prepared
• CPC Class Codes: G09G 3/006 Electronic inspection or testing of displays and display drivers, e.g. of LED or LCD displays testing individual LED's G01R31/2635; testing lamps G01R31/44; testing of optical features of LCD displays G02F1/1309
• CPC Class Codes: G09G 3/20 for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
• CPC Class Codes: G09G 3/344 based on particles moving in a fluid or in a gas, e.g. electrophoretic devices electrophoretic devices per se G02F1/167
• 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 2924/00 Indexing scheme for arrangements or methods for connecting or disconnecting semiconductor or solid-state bodies as covered by H01L24/00
• CPC Class Codes: H01L 2924/0002 Not covered by any one of groups H01L24/00, H01L24/00 and H01L2224/00
• CPC Class Codes: H01L 33/0095 Post-treatment of devices, e.g. annealing, recrystallisation or short-circuit elimination

Abstract

One object is to provide a method for manufacturing a display device in which shift of the threshold voltage of a thin film transistor including an oxide semiconductor layer can be suppressed even when ultraviolet light irradiation is performed in the process for manufacturing the display device. In the method for manufacturing a display device, ultraviolet light irradiation is performed at least once, a thin film transistor including an oxide semiconductor layer is used for a switching element, and heat treatment for repairing damage to the oxide semiconductor layer caused by the ultraviolet light irradiation is performed after all the steps of ultraviolet light irradiation are completed.

Claims

1. A method for manufacturing a display device, comprising the steps of:

forming a pixel portion comprising a thin film transistor comprising an oxide semiconductor layer comprising a channel formation region over a first substrate;

forming a sealant comprising an ultraviolet curable resin over the first substrate to surround at least the pixel portion;

forming a liquid crystal layer comprising an ultraviolet curable resin to overlap the pixel portion by dropping a liquid crystal in a region surrounded by the sealant over the first substrate;

attaching a second substrate to the first substrate with the sealant between the second substrate and the first substrate;

irradiating the liquid crystal layer with ultraviolet light;

curing the sealant with ultraviolet light irradiation after irradiating the liquid crystal layer with ultraviolet light; and

performing heat treatment for repairing damage on the oxide semiconductor layer caused by the ultraviolet light irradiation from irradiating the liquid crystal layer with ultraviolet light and curing the sealant.

2. The method for manufacturing a display device according to claim 1, wherein the liquid crystal exhibits a blue phase.

3. The method for manufacturing a display device according to claim 1, further comprising irradiating the sealant with ultraviolet light to be temporarily cured before forming the liquid crystal layer.

4. The method for manufacturing a display device according to claim 1, wherein a pixel electrode electrically connected to the thin film transistor is subjected to surface treatment by ultraviolet light irradiation.

5. The method for manufacturing a display device according to claim 1, wherein the first substrate is divided along with the second substrate after curing the sealant.

6. The method for manufacturing a display device according to claim 1,

wherein a second thin film transistor comprising an oxide semiconductor layer is formed in a driver circuit portion of the display device, and

wherein the sealant overlaps with the driver circuit portion.

7. The method for manufacturing a display device according to of claim 1,

wherein the heat treatment is performed for greater than or equal to 1 hour and less than or equal to 15 hours.

8. The method for manufacturing a display device according to claim 1,

wherein the heat treatment is performed at greater than or equal to 125°

C. and less than or equal to 250°

C.

9. A method for manufacturing a display device, comprising the steps of:

forming a pixel portion comprising a thin film transistor comprising an oxide semiconductor layer comprising a channel formation region over a first substrate;

forming a sealant comprising an ultraviolet curable resin over a second substrate to surround at least the pixel portion;

forming a liquid crystal layer comprising an ultraviolet curable resin by dropping a liquid crystal in a region surrounded by the sealant over the second substrate;

attaching the first substrate to the second substrate with the sealant between the first substrate and the second substrate so that the pixel portion overlaps with the liquid crystal layer;

irradiating the liquid crystal layer with ultraviolet light;

curing the sealant with ultraviolet light irradiation after irradiating the liquid crystal layer with ultraviolet light; and

performing heat treatment for repairing damage on the oxide semiconductor layer caused by the ultraviolet light irradiation from irradiating the liquid crystal layer with ultraviolet light and curing the sealant.

10. The method for manufacturing a display device according to claim 9, wherein the liquid crystal exhibits a blue phase.

11. The method for manufacturing a display device according to claim 9, further comprising irradiating the sealant with ultraviolet light to be temporarily cured before forming the liquid crystal layer.

12. The method for manufacturing a display device according to claim 9, wherein a pixel electrode electrically connected to the thin film transistor is subjected to surface treatment by ultraviolet light irradiation.

13. The method for manufacturing a display device according to claim 9, wherein the first substrate is divided along with the second substrate after curing the sealant.

14. The method for manufacturing a display device according to claim 9,

wherein a second thin film transistor comprising an oxide semiconductor layer is formed in a driver circuit portion of the display device, and

wherein the sealant overlaps with the driver circuit portion.

15. The method for manufacturing a display device according to of claim 9,

wherein the heat treatment is performed for greater than or equal to 1 hour and less than or equal to 15 hours.

16. The method for manufacturing a display device according to claim 9,

wherein the heat treatment is performed at greater than or equal to 125°

C. and less than or equal to 250°

C.

17. A method for manufacturing a display device, comprising the steps of:

forming a pixel portion comprising a thin film transistor comprising an oxide semiconductor layer comprising a channel formation region over a first substrate;

forming a sealant comprising an ultraviolet curable resin over the first substrate to surround at least the pixel portion;

forming a liquid crystal layer comprising an ultraviolet curable resin to overlap the pixel portion by dropping a liquid crystal in a region surrounded by the sealant over the first substrate;

attaching a second substrate to the first substrate with the sealant between the second substrate and the first substrate;

irradiating the liquid crystal layer with ultraviolet light;

curing the sealant with ultraviolet light irradiation after irradiating the liquid crystal layer with ultraviolet light; and

performing heat treatment on the oxide semiconductor layer at greater than or equal to 125°

C. and less than or equal to 250°

C. after curing the sealant with ultraviolet light irradiation.

18. The method for manufacturing a display device according to claim 17, wherein the liquid crystal exhibits a blue phase.

19. The method for manufacturing a display device according to claim 17, further comprising irradiating the sealant with ultraviolet light to be temporarily cured before forming the liquid crystal layer.

20. The method for manufacturing a display device according to claim 17, wherein a pixel electrode electrically connected to the thin film transistor is subjected to surface treatment by ultraviolet light irradiation.

21. The method for manufacturing a display device according to claim 17, wherein the first substrate is divided along with the second substrate after curing the sealant.

22. The method for manufacturing a display device according to claim 17,

wherein a second thin film transistor comprising an oxide semiconductor layer is formed in a driver circuit portion of the display device, and

wherein the sealant overlaps with the driver circuit portion.

23. The method for manufacturing a display device according to claim 17,

wherein the heat treatment is performed for greater than or equal to 1 hour and less than or equal to 15 hours.

24. A method for manufacturing a display device, comprising the steps of:

forming a pixel portion comprising a thin film transistor comprising an oxide semiconductor layer comprising a channel formation region over a first substrate;

forming a sealant comprising an ultraviolet curable resin over a second substrate to surround at least the pixel portion;

forming a liquid crystal layer comprising an ultraviolet curable resin by dropping a liquid crystal in a region surrounded by the sealant over the second substrate;

attaching the first substrate to the second substrate with the sealant between the first substrate and the second substrate so that the pixel portion overlaps with the liquid crystal layer;

irradiating the liquid crystal layer with ultraviolet light;

curing the sealant with ultraviolet light irradiation after irradiating the liquid crystal layer with ultraviolet light; and

performing heat treatment on the oxide semiconductor layer at greater than or equal to 125°

C. and less than or equal to 250°

C. after curing the sealant with ultraviolet light irradiation.

25. The method for manufacturing a display device according to claim 24, wherein the liquid crystal exhibits a blue phase.

26. The method for manufacturing a display device according to claim 24, further comprising irradiating the sealant with ultraviolet light to be temporarily cured before forming the liquid crystal layer.

27. The method for manufacturing a display device according to claim 24, wherein a pixel electrode electrically connected to the thin film transistor is subjected to surface treatment by ultraviolet light irradiation.

28. The method for manufacturing a display device according to claim 24, wherein the first substrate is divided along with the second substrate after curing the sealant.

29. The method for manufacturing a display device according to claim 24,

wherein a second thin film transistor comprising an oxide semiconductor layer is formed in a driver circuit portion of the display device, and

wherein the sealant overlaps with the driver circuit portion.

30. The method for manufacturing a display device according to claim 24,

wherein the heat treatment is performed for greater than or equal to 1 hour and less than or equal to 15 hours.