Liquid crystal display device with particular TFT structure and method of manufacturing the same

• US 7,102,718 B1
• Filed: 05/09/2000
• Issued: 09/05/2006
• Est. Priority Date: 03/16/2000
• Status: Expired due to Fees

• Current Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Original Assignee: Semiconductor Energy Laboratory Co., Ltd.
• Inventors: Hirakata, Yoshiharu, Yamazaki, Shunpei
• Primary Examiner(s): Font, Frank G.
• Assistant Examiner(s): RUDE, TIMOTHY L
• Application Number:
  US09/566,729
• Time in Patent Office: 2,310 Days
• Field of Search: 349/141
• US Class Current: 349/141
• CPC Class Codes: G02F 1/133345 Insulating layers G02F1/1335, G02F1/1337, G02F1/135, G02F1/136 take precedence
• CPC Class Codes: G02F 1/1337 Surface-induced orientation of the liquid crystal molecules, e.g. by alignment layers
• CPC Class Codes: G02F 1/133707 Structures for producing distorted electric fields, e.g. bumps, protrusions, recesses, slits in pixel electrodes
• 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 1/13439 characterised by their electrical, optical, physical properties; materials therefor; method of making
• CPC Class Codes: G02F 1/13452 Conductors connecting driver circuitry and terminals of panels
• CPC Class Codes: G02F 1/13458 Terminal pads
• CPC Class Codes: G02F 1/136204 Arrangements to prevent high voltage or static electricity failures
• CPC Class Codes: G02F 1/136231 for reducing the number of lithographic steps
• CPC Class Codes: G02F 1/136277 formed on a semiconductor substrate, e.g. of silicon
• CPC Class Codes: G02F 1/136286 Wiring, e.g. gate line, drain line
• CPC Class Codes: G02F 1/13629 Multilayer wirings
• CPC Class Codes: G02F 1/1368 in which the switching element is a three-electrode device G02F1/136277 takes precedence
• CPC Class Codes: G02F 1/1396 the liquid crystal being selectively controlled between a twisted state and a non-twisted state, e.g. TN-LC cell G02F1/141 takes precedence
• CPC Class Codes: H01L 27/12 the substrate being other than a semiconductor body, e.g. an insulating body
• 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 27/124 with a particular composition, shape or layout of the wiring layers specially adapted to the circuit arrangement, e.g. scanning lines in LCD pixel circuits wiring structures per se H01L23/52
• CPC Class Codes: H01L 29/78669 with inverted-type structure, e.g. with bottom gate

Abstract

In a liquid crystal display device of an IPS system, to realize reduction of manufacturing cost and improvement of yield by decreasing the number of steps for manufacturing a TFT.

The present invention adopts a channel etch type bottom gate TFT structure, and is characterized in that patterning of a source region 119 and a drain region 120 and patterning of a source wiring 121 and a pixel electrode 122 are carried out by the same photomask.

Claims

1. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a pixel electrode formed on the drain region; and

a source wiring formed on the source region;

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

an outside end face of the drain region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of the pixel electrode and the outside end face of said drain region is not covered with the pixel electrode; and

the source wiring is disposed above the common electrode with the insulating film interposed therebetween.

4. The liquid crystal display device in any one of claims 1 to 3, characterized in that said source region and said drain region are made from an amorphous semiconductor film containing an impurity element which imparts n-type conductivity.

5. The liquid crystal display device in any one of claims 1 to 3, characterized in that said insulating film, said amorphous semiconductor film, said source region, and said drain region are formed in succession without exposure to an atmosphere.

6. The liquid crystal display device in any one of claims 1 to 3, characterized in that said insulating film, said amorphous semiconductor film, said source region, or said drain region is formed by sputtering.

7. The liquid crystal display device in any one of claims 1 to 3, characterized in that said insulating film, said amorphous semiconductor film, said source region, or said drain region is formed by plasma CVD.

8. The liquid crystal display device in any one of claims 1 to 3, characterized in that said gate wiring is formed from a film of an element selected from the group consisting of Al, Cu, Ti, Mo, W, Ta, Nd, and Cr, from an alloy film of said elements, or from a lamination film of said elements.

9. The liquid crystal display device in any one of claims 1 to 3, characterized in that said source region and said drain region are formed by the same mask as said pixel electrode.

10. The liquid crystal display device in any one of claims 1 to 3, characterized in that said source region and said drain region are formed by the same mask as said source wiring.

11. The liquid crystal display device in any one of claims 1 to 3, characterized in that said source region and said drain region are formed by the same mask as said source wiring and said pixel electrode.

12. The liquid crystal display device in any one of claims 1 to 3, characterized in that in said amorphous semiconductor film, the film thickness in a region contacting said source region and said drain region is formed thicker than the film thickness in a region between the region contacting said source region and the region contacting said drain region.

13. The liquid crystal display device in any one of claims 1 to 3, characterized in that the pixel electrode is covered with a transparent conductive film.

14. The liquid crystal display device in any one of claims 1 to 3, characterized in that the source wiring and a terminal on an extension of the source wiring are covered with a transparent conductive film.

15. The liquid crystal display device in any one of claims 1 to 3, characterized in that said liquid crystal display device is a personal computer, a video camera, a portable information terminal, a digital camera, a digital video disk player, or an electronic amusement device.

16. The liquid crystal display device according to claim 1, further comprising an alignment film formed over at least said pixel electrode wherein said alignment film is in direct contact with a part of an upper surface of the insulating film.

2. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a pixel electrode formed on the drain region;

a source wiring formed on the source region;

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

an outside end face of the drain region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of the pixel electrode, and an outside end face of the other one of the source region is substantially coincident with an end face of the source wiring and the outside end face of said drain region is not covered with the pixel electrode; and

the source wiring is disposed above the common electrode with the insulating film interposed therebetween.

17. The liquid crystal display device according to claim 2, further comprising an alignment film formed over at least said pixel electrode wherein said alignment film is in direct contact with a part of an upper surface of the insulating film.

3. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a pixel electrode formed on one of the source region or the drain region; and

a source wiring formed on the other one of the source region or the drain region,

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

the amorphous semiconductor film and an amorphous semiconductor film containing an impurity element which imparts an n type conductivity are laminated under the source wiring;

the source wiring is disposed above the common electrode with the insulating film interposed therebetween;

the pixel electrode is covered with a transparent conductive film; and

an outside end face of the source region or the drain region and an end face of the pixel electrode contact a surface of the transparent conductive film.

18. The liquid crystal display device according to claim 3, further comprising an alignment film formed over at least said pixel electrode wherein said alignment film is in direct contact with a part of an upper surface of the insulating film.

19. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

at least one of a source wiring and a pixel electrode formed over the source region or the drain region,

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

at least one outside end face of said drain region and the source region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of at least one of the source wiring and the pixel electrode and the outside end face of said drain region is not covered with the pixel electrode; and

the source wiring is disposed above the common electrode with the insulating film interposed therebetween.

22. The liquid crystal display device in any one of claims 19 to 21, characterized in that said source region and said drain region are made from an amorphous semiconductor film containing an impurity element which imparts n-type conductivity.

23. The liquid crystal display device in any one of claims 19 to 21, characterized in that said insulating film, said amorphous semiconductor film, said source region, and said drain region are formed in succession without exposure to an atmosphere.

24. The liquid crystal display device in any one of claims 19 to 21, characterized in that at least one of said insulating film, said amorphous semiconductor film, said source region, and said drain region is formed by sputtering.

25. The liquid crystal display device in any one of claims 19 to 21, characterized in that at least one of said insulating film, said amorphous semiconductor film, said source region, and said drain region is formed by plasma CVD.

26. The liquid crystal display device in any one of claims 19 to 21, characterized in that said gate wiring is formed from a film of an element selected from the group consisting of Al, Cu, Ti, Mo, W, Ta, Nd, and Cr, from an alloy film of said elements, or from a lamination film of said elements.

27. The liquid crystal display device in any one of claims 19 to 21, characterized in that said source region and said drain region are formed by the same mask as said pixel electrode.

28. The liquid crystal display device in any one of claims 19 to 21, characterized in that said source region and said drain region are formed by the same mask as said source wiring.

29. The liquid crystal display device in any one of claims 19 to 21, characterized in that said source region and said drain region are formed by the same mask as said source wiring and said pixel electrode.

30. The liquid crystal display device in any one of claims 19 to 21, characterized in that in said amorphous semiconductor film, the film thickness in a region contacting said source region and said drain region is formed thicker than the film thickness in a region between the region contacting said source region and the region contacting said drain region.

31. The liquid crystal display device in any one of claims 19 to 21, characterized in that the pixel electrode is covered with a transparent conductive film.

32. The liquid crystal display device in any one of claims 19 and 20, characterized in that the source wiring and a terminal on an extension of the source wiring are covered with a transparent conductive film.

33. The liquid crystal display device in any one of claims 19 to 21, characterized in that said liquid crystal display device is at least one selected from the group consisting of a personal computer, a video camera, a portable information terminal, a digital camera, a digital video disk player, and an electronic amusement device.

34. The liquid crystal display device according to claim 19, further comprising an alignment film formed over at least said pixel electrode wherein said alignment film is in direct contact with a part of an upper surface of the insulating film.

20. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

at least one of a source wiring and a pixel electrode formed over the source region or the drain region,

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

the amorphous semiconductor film and an amorphous semiconductor film containing an impurity element which imparts an n type conductivity are laminated under the source wiring;

the source wiring is disposed above the common electrode with the insulating film interposed therebetween,

the pixel electrode is covered with a transparent conductive film; and

an outside end face of the source region or the drain region and an end face of the pixel electrode contact a surface of the transparent conductive film.

35. The liquid crystal display device according to claim 20, further comprising an alignment film formed over at least said pixel electrode wherein said alignment film is in direct contact with a part of an upper surface of the insulating film.

21. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

at least one of a source wiring and a pixel electrode formed over the source region or the drain region;

wherein at least one outside end face of the drain region and the source region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of at least one of the source wiring and the pixel electrode and the outside end face of said drain region is not covered with the pixel electrode;

the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

the source wiring and a terminal on an extension of the source wiring are covered with a transparent conductive film; and

the source wiring is disposed above the common electrode with the insulating film interposed therebetween.

36. The liquid crystal display device according to claim 21, further comprising an alignment film formed over at least said pixel electrode wherein said alignment film is in direct contact with a part of an upper surface of the insulating film.

37. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring, a common electrode and a common wiring formed on a surface over one of the pair of substrates;

an insulating film formed over the gate wiring, the common electrode and the common wiring;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a pixel electrode formed on the drain region; and

a source wiring formed on the source region;

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

an outside end face of the drain region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of the pixel electrode and the outside end face of said drain region is not covered with the pixel electrode; and

the source wiring extends across the common wiring with the insulating film interposed therebetween.

38. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring, a common electrode and a common wiring formed on a surface formed over one of the pair of substrates;

an insulating film formed over the gate wiring, the common electrode and the common wiring;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a pixel electrode formed on the drain region;

a source wiring formed on the source region;

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

an outside end face of the drain region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of the pixel electrode, and an outside end face of the source region is substantially coincident with an end face of the source wiring and the outside end face of said drain region is not covered with the pixel electrode; and

the source wiring extends across the common wiring with the insulating film interposed therebetween.

39. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring, a common electrode and a common wiring formed on a surface formed over one of the pair of substrates;

an insulating film formed over the gate wiring, the common electrode and the common wiring;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a pixel electrode formed on one of the source region or the drain region; and

a source wiring formed on the other one of the source region or the drain region,

wherein the pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the pixel electrode;

the amorphous semiconductor film and an amorphous semiconductor film containing an impurity element which imparts an n type conductivity are laminated under the source wiring;

the source wiring extends across the common wiring with the insulating film interposed therebetween;

the pixel electrode is covered with a transparent conductive film; and

an outside end face of the source region or the drain region and an end face of the pixel electrode contact a surface of the transparent conductive film.

40. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a metal pixel electrode formed on the drain region; and

a source wiring formed on the source region;

wherein the metal pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the metal pixel electrode;

an outside end face of or the drain region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of the metal pixel electrode and the outside end face of said drain region is not covered with the metal pixel electrode;

the source wiring is disposed above the common electrode with the insulating film interposed therebetween; and

said metal pixel electrode is covered with a transparent conductive film.

41. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a metal pixel electrode formed on the drain region;

a source wiring formed on the source region or the drain region;

wherein the metal pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the metal pixel electrode;

an outside end face of the drain region is substantially coincident with an outside end face of the amorphous semiconductor film and an end face of the metal pixel electrode, and an outside end face of the source region is substantially coincident with an end face of the source wiring and the outside end face of said drain region is not covered with the metal pixel electrode;

the source wiring is disposed above the common electrode with the insulating film interposed therebetween; and

said metal pixel electrode is covered with a transparent conductive film.

42. A liquid crystal display device comprising:

a pair of substrates;

liquid crystal molecules held between the pair of substrates;

a gate wiring and a common electrode formed over one of the pair of substrates;

an insulating film formed over the gate wiring and the common electrode;

an amorphous semiconductor film formed over the insulating film;

a source region and a drain region formed on the amorphous semiconductor film;

a metal pixel electrode formed on one of the source region or the drain region; and

a source wiring formed on the other one of the source region or the drain region,

wherein the metal pixel electrode and the common electrode are disposed so that the liquid crystal molecules are controlled by an electric field produced between the pixel electrode and the common electrode;

the insulating film covers at least a portion of said one of the pair of substrates wherein said portion is between the common electrode and the metal pixel electrode;

the amorphous semiconductor film and an amorphous semiconductor film containing an impurity element which imparts an n type conductivity are laminated under the source wiring;

the source wiring is disposed above the common electrode with the insulating film interposed therebetween;

said metal pixel electrode is covered with a transparent conductive film and an outside end face of the source region or the drain region and an end face of the metal pixel electrode contact a surface of the transparent conductive film.