Liquid crystal display device and method of manufacturing the same

• US 8,228,477 B2
• Filed: 07/27/2011
• Issued: 07/24/2012
• 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: Yamazaki, Shunpei, Hirakata, Yoshiharu
• Primary Examiner(s): Rude, Timothy L
• Application Number:
  US13/191,962
• Publication Number:
  US 20110281385A1
• Time in Patent Office: 363 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. A channel etch type bottom gate TFT structure, where patterning of a source region and a drain region and patterning of a source wiring and a pixel electrode are carried out by the same photomask.

Claims

1. A method of manufacturing a liquid crystal display device comprising:

forming a gate wiring over an insulating surface by using a first mask;

forming a common electrode over the insulating surface;

forming an insulating film over the gate wiring;

forming a first amorphous semiconductor film over the insulating film;

forming a second amorphous semiconductor film containing an impurity element which imparts n-type conductivity, over the first amorphous semiconductor film;

forming a conductive film over the second amorphous semiconductor film;

patterning the first amorphous semiconductor film, the second amorphous semiconductor film and the conductive film together by using a second mask; and

removing a portion of the first amorphous semiconductor film, a portion of the second amorphous semiconductor film and a portion of the conductive film to form a source region, a drain region, a source wiring after patterning the first amorphous semiconductor film, the second amorphous semiconductor film and the conductive film;

forming a transparent electrode electrically connected to the conductive film;

forming an alignment film over the transparent electrode and the common electrode; and

forming a protecting circuit comprising a same material as the common electrode when the common electrode is formed,

wherein the portion of the second amorphous semiconductor film is between the source region and the drain region,

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

wherein the gate wiring is separated from the common electrode, and

wherein the transparent electrode and the common electrode are overlapped with each other.

2. The method of manufacturing the liquid crystal display device according to claim 1, wherein the insulating film, the first amorphous semiconductor film, and the second amorphous semiconductor film are formed in succession without exposure to an atmosphere.

3. The method of manufacturing the liquid crystal display device according to claim 1, wherein the insulating film, the first amorphous semiconductor film, or the second amorphous semiconductor film is formed by sputtering.

4. The method of manufacturing the liquid crystal display device according to claim 1, wherein the insulating film, the first amorphous semiconductor film, or the second amorphous semiconductor film is formed by plasma CVD.

5. The method of manufacturing the liquid crystal display device according to claim 1, wherein the gate wiring is formed from an element selected from the group consisting of Al, Cu, Ti, Mo, W, Ta, Nd, and Cr, and an alloy of the elements.

6. The method of manufacturing the liquid crystal display device according to claim 1, wherein inside end faces of the first amorphous semiconductor film, the second amorphous semiconductor film and the conductive film are substantially coincided by removing the portion of the first amorphous semiconductor film, the portion of the second amorphous semiconductor film and the portion of the conductive film.

7. The method of manufacturing the liquid crystal display device according to claim 1, wherein the common electrode is formed by using the first mask.

8. A method of manufacturing a liquid crystal display device comprising:

forming a gate wiring over an insulating surface by using a first mask;

forming a common electrode over the insulating surface;

forming an insulating film over the gate wiring;

forming a first amorphous semiconductor film over the insulating film;

forming a second amorphous semiconductor film containing an impurity element which imparts n-type conductivity, over the first amorphous semiconductor film;

forming a conductive film over the second amorphous semiconductor film;

patterning the first amorphous semiconductor film, the second amorphous semiconductor film and the conductive film together by using a second mask; and

removing a portion of the first amorphous semiconductor film, a portion of the second amorphous semiconductor film and a portion of the conductive film to form a source region, a drain region, a source wiring after patterning the first amorphous semiconductor film, the second amorphous semiconductor film and the conductive film;

forming a transparent electrode electrically connected to the conductive film;

forming an alignment film over the transparent electrode and the common electrode; and

forming a protecting circuit comprising a same material as the common electrode when the common electrode is formed,

wherein the portion of the second amorphous semiconductor film is between the source region and the drain region,

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

wherein the gate wiring is separated from the common electrode,

wherein the transparent electrode and the common electrode are overlapped with each other, and

wherein the first amorphous semiconductor film and the second amorphous semiconductor film extends beneath the source wiring.

9. The method of manufacturing the liquid crystal display device according to claim 8, wherein the insulating film, the first amorphous semiconductor film, and the second amorphous semiconductor film are formed in succession without exposure to an atmosphere.

10. The method of manufacturing the liquid crystal display device according to claim 8, wherein the insulating film, the first amorphous semiconductor film, or the second amorphous semiconductor film is formed by sputtering.

11. The method of manufacturing the liquid crystal display device according to claim 8, wherein the insulating film, the first amorphous semiconductor film, or the second amorphous semiconductor film is formed by plasma CVD.

12. The method of manufacturing the liquid crystal display device according to claim 8, wherein the gate wiring is formed from an element selected from the group consisting of Al, Cu, Ti, Mo, W, Ta, Nd, and Cr, and an alloy of the elements.

13. The method of manufacturing the liquid crystal display device according to claim 8, wherein inside end faces of the first amorphous semiconductor film, the second amorphous semiconductor film and the conductive film are substantially coincided by removing the portion of the first amorphous semiconductor film, the portion of the second amorphous semiconductor film and the portion of the conductive film.

14. The method of manufacturing the liquid crystal display device according to claim 8, wherein the common electrode is formed by using the first mask.