Methods of forming active matrix display devices with reduced susceptibility to image-sticking and devices formed thereby

• US 5,917,564 A
• Filed: 10/14/1997
• Issued: 06/29/1999
• Est. Priority Date: 11/13/1996
• Status: Expired due to Term

• Current Assignee: Samsung Display Company Limited (Samsung Electronics Co. Ltd.)
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Lee, Won-Hee, Kim, Dong-Gyu
• Primary Examiner(s): NGUYEN, TIEP HUU
• Application Number:
  US08/950,334
• Time in Patent Office: 623 Days
• Field of Search: 349/141, 349/43, 349/46, 349/138, 257/59, 257/72
• US Class Current: 349/46
• CPC Class Codes: G02F 1/133397 for suppressing after-image or image-sticking
• CPC Class Codes: G02F 1/134363 for applying an electric field parallel to the substrate, i.e. in-plane switching [IPS]
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence

Abstract

Methods of forming active matrix display devices with reduced susceptibility to image sticking include the steps of forming a gate electrode on a face of a substrate and then forming a first insulating layer on the gate electrode and on the face to electrically isolate the gate electrode from adjacent regions. A first amorphous semiconductor layer is then formed on the first insulating layer. In particular, the first amorphous semiconductor layer, which acts as the active region of the TFT, is patterned to extend opposite the gate electrode. A channel protection layer is also formed on the first amorphous semiconductor layer. The channel protection layer is designed to protect the channel portion of the active region in the first amorphous semiconductor layer from potential damage which may occur during subsequent process steps. Then, the first insulating layer and the channel protection layer are etched simultaneously until the face of the substrate is exposed. Here, the step of forming a gate electrode includes the steps of forming a first conductive layer having a thickness of about 2000 Å on the face of the substrate and then patterning the first conductive layer to define a gate electrode of a thin-film transistor and a common electrode. The first insulating layer is then formed on the gate electrode and the common electrode, but is subsequently removed from the common electrode to reduce image-sticking effects which may impair display performance in in-plane switching (IPS) TFT-LCD display devices.

Claims

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

forming a gate electrode on a face of a substrate;

forming a first insulating layer on the gate electrode and on the face;

forming a first amorphous semiconductor layer on the first insulating layer, opposite the gate electrode;

forming a channel protection layer on the first amorphous semiconductor layer, opposite the gate electrode; and

etching the first insulating layer to expose the face of the substrate while simultaneously etching a portion of the channel protection layer extending opposite the gate electrode.

2. The method of claim 1, wherein said step of forming a gate electrode comprises the steps of:

forming a first conductive layer on the face of the substrate;

patterning the first conductive layer to define a gate electrode and a common electrode;

wherein said step of forming a first insulating layer comprises forming a first insulating layer on the gate electrode and on the common electrode; and

wherein said step of simultaneously etching the first insulating layer and a portion of the channel protection layer comprises etching the first insulating layer to expose the common electrode.

3. The method of claim 2, wherein said step of forming a channel protection layer is followed by the steps of:

forming a second amorphous semiconductor layer on the first amorphous semiconductor layer; and

forming a second conductive layer on the second amorphous semiconductor layer.

4. The method of claim 3, further comprising the steps of patterning the second conductive layer to define a pixel electrode and a data line.

5. The method of claim 4, wherein said step of simultaneously etching the first insulating layer and a portion of the channel protection layer comprises etching the second amorphous semiconductor layer, the first amorphous semiconductor layer and the first insulating layer to expose the face of the substrate.

6. The method of claim 5,

wherein said step of forming a second amorphous semiconductor layer comprises forming a second amorphous semiconductor layer on the channel protection layer;

and

wherein, said step of simultaneously etching the first insulating layer and a portion of the channel protection layer comprises etching the second amorphous semiconductor layer to define source and drain contact regions, using the pixel electrode and the data line as an etching mask.

7. The method of claim 6, wherein said step of simultaneously etching the first insulating layer and a portion of the channel protection layer comprises etching the channel protection layer using the pixel electrode and data line as an etching mask.

8. The method of claim 7,

wherein said step of forming a first insulating layer comprises forming a first insulating layer of a first material having a thickness in a range between about 2,000 and 4,000 Å

; and

wherein said step of forming a channel protection layer comprises forming a channel protection layer of the first material having a thickness greater than about 4,000 Å

.

9. The method of claim 8,

wherein said step of forming a first insulating layer comprises depositing a first layer of silicon nitride at a temperature greater than about 300°

C.; and

wherein said step of forming a channel protection layer comprises depositing a second layer of silicon nitride at a temperature less than about 250°

C.

10. The method of claim 9, wherein said step of patterning the second conductive layer comprises patterning the second conductive layer to define a pixel electrode which overlaps the common electrode.

11. The method of claim 10, wherein said step of forming a channel protection layer comprises forming a dielectric region of a storage capacitor on the common electrode.

12. The method of claim 8, wherein said step of forming a first amorphous semiconductor layer comprises forming a first amorphous semiconductor layer having a thickness less than about 1,000 Å

; and

wherein the channel protection layer has a thickness greater than the sum of the thicknesses of the first insulating layer and the first amorphous semiconductor layer.

13. The method of claim 4, wherein said step of patterning the second conductive layer comprises wet etching the second conductive layer;

and wherein said step of simultaneously etching the first insulating layer and a portion of the channel protection layer comprises wet etching the second amorphous semiconductor layer, the first amorphous semiconductor layer and the first insulating layer to expose the face of the substrate, using the pixel electrode as an etching mask.

14. The method of claim 2, wherein said step of patterning the first conductive layer comprises patterning the first conductive layer to define a gate electrode having a first width;

and wherein said step of forming a channel protection layer comprises forming a channel protection layer having a first region therein with a second width less than the first width and a second region therein with a third width greater than the first width.

15. A thin-film transistor display device, comprising:

a gate electrode on a face of a substrate;

a first electrically insulating layer having a first thickness, on the gate electrode;

a first amorphous silicon layer having a second thickness, on the first electrically insulating layer, opposite the gate electrode;

a channel protection layer having a third thickness greater than the sum of the first thickness and second thickness, on the first amorphous silicon layer;

a pixel electrode electrically coupled to a first end of the first amorphous silicon layer; and

a data line electrically coupled to a second end of the first amorphous silicon layer.

16. The display device of claim 15, wherein said gate electrode has a first width;

and wherein first and second opposing ends of said channel protection layer have a second width greater than the first width.

17. The display device of claim 16, wherein a portion of said channel protection layer extending intermediate the first and second opposing ends thereof, has a third width less than the first width.

18. The display device of claim 15, further comprising a common electrode line on the face of the substrate;

and wherein a portion of said common electrode line extends between said pixel electrode and the face.

19. The display device of claim 17,

wherein said first electrically insulating layer comprises silicon nitride and has a thickness in a range between about 2,000 and 4,000 Å

;

wherein said first amorphous silicon layer has a thickness of less than about 1,000 Å

; and

wherein said channel protection layer comprises silicon nitride and has a thickness greater than about 5,000 Å

.

20. The display device of claim 18,

wherein said first electrically insulating layer comprises silicon nitride and has a thickness in a range between about 2,000 and 4,000 Å

;

wherein said first amorphous silicon layer has a thickness of less than about 1,000 Å

; and

wherein said channel protection layer comprises silicon nitride and has a thickness greater than about 5,000 Å

.

21. A method of forming display device, comprising the steps of:

forming a first conductive layer on a face of a substrate;

etching the first conductive layer to define a gate electrode and a common electrode;

forming a first insulating layer on the gate electrode, on the common electrode and on the face;

forming a first amorphous semiconductor layer on the first insulating layer, opposite the gate electrode;

forming a channel protection layer on the first amorphous semiconductor layer, opposite the gate electrode;

forming a second amorphous semiconductor layer on the channel protection layer;

forming a second conductive layer on the second amorphous semiconductor layer; and

etching the second conductive layer, the second amorphous semiconductor layer, the first amorphous semiconductor layer and the first insulating layer to define a source electrode, a drain electrode and a pixel electrode;

wherein a thickness of the channel protection layer is greater than a sum of the thicknesses of the first insulating layer and the first amorphous semiconductor layer.

22. The method of claim 21, wherein the thickness of the first insulating layer is in a range between about 2000 Å

and 4000 Å

; and

wherein a thickness of the first amorphous semiconductor layer is less than about 1000 Å

.

23. The method of claim 22, wherein the second amorphous semiconductor layer comprises a doped amorphous silicon layer.