# US 8,785,223 B2 · Method of fabricating fringe field switching liquid crystal display device

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- Number: US 8,785,223 B2
- Document ID: US8785223B2
- Status: Granted
- Kind: B2
- Application number: 14/138,929
- Filed: 2013-12-23
- Published: 2014-05-01
- Granted: 2014-07-22
- Earliest claimed: 2011-06-09
- Assignees: LG Display Co., Ltd.
- Applicants: LG Display Co., Ltd
- Inventors: Yong-Soo Cho; Young-Seok Choi; Dong-Hee Kim; Kyo-Ho Moon; Chul-Tae Kim; Kyu-Sun Choi
- Web page: https://patentgrep.com/patent/US8785223B2

## CPC

- G02F 1/1333: Constructional arrangements; {Manufacturing methods}(G02F1/135, G02F1/136 take precedence)
- G02F 1/1368: in which the switching element is a three-electrode device {(G02F1/136277 takes precedence)}
- H10D 86/0231: {using masks, e.g. half-tone masks}
- H10D 86/441: {Interconnections, e.g. scanning lines}
- H10D 86/60: wherein the TFTs are in active matrices
- G02F 1/134372: {for fringe field switching [FFS] where the common electrode is not patterned}
- G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS
- H10D: INORGANIC ELECTRIC SEMICONDUCTOR DEVICES

## Abstract

A method of fabricating a fringe field switching (FFS)-liquid crystal display (LCD) device may have the following advantage. An inferior connection between the drain electrode and the pixel electrode may be prevented by preventing formation of a copper compound on the drain electrode, by performing a back channel etching after patterning a pixel electrode, and by performing a wet strip rather than a dry strip. This may result in a direct contact between copper and ITO, thereby reducing the number of mask processes.

## Claims

### Claim 1

A method of fabricating a fringe field switching (FFS)-liquid crystal display (LCD) device, comprising:
forming a gate electrode and a gate line on a first substrate;
forming a gate insulation film on the first substrate where the gate electrode and the gate line have been formed;
forming, on the gate insulation film, an amorphous silicon thin film, an n+ amorphous silicon thin film, and a second conductive film;
forming, on the second conductive film, first to third photosensitive film patterns;
selectively removing the second conductive film by using the first to third photosensitive film patterns as a mask, thereby disposing a conductive film pattern formed of the second conductive film;
selectively removing the amorphous silicon thin film and the n+ amorphous silicon thin film by using the first to third photosensitive film patterns as a mask, thereby disposing an active layer and an n+ amorphous silicon thin film pattern formed of the amorphous silicon thin film and the n+ amorphous silicon thin film, below the conductive film pattern;
removing the third photosensitive film pattern through an ashing process, and forming fourth and fifth photosensitive film patterns having a thickness removed by a thickness of the third photosensitive film pattern;
selectively removing the conductive film pattern by using the fourth and fifth photosensitive film patterns as a mask, thereby disposing source and drain electrodes formed of the second conductive film on the n+ amorphous silicon thin film pattern;
selectively removing the n+ amorphous silicon thin film pattern through a dry etching using a plasma gas, by using the fourth and fifth photosensitive film patterns as a mask, thereby disposing an ohmic-contact layer formed of the n+ amorphous silicon thin film;
removing the fourth and fifth photosensitive film patterns;
forming a third conductive film on an entire surface of the first substrate;
forming a photosensitive film pattern on the third conductive film;
selectively removing the third conductive film by using the photosensitive film pattern as a mask, thereby disposing a pixel electrode directly electrically connected to the drain electrode and formed of the third conductive film;
forming a passivation film on the first substrate where the pixel electrode has been formed;
forming a common electrode formed in a single pattern over a pixel portion, and configured to generate a fringe field with a plurality of slits in each pixel region together with the pixel electrode; and
bonding the first substrate to a second substrate.

### Claim 2 (depends on 1)

The method of claim 1, wherein the second conductive film has a multi-layer structure of at least two layers having thereon a low resistance opaque conductive material including copper, or a copper alloy, or aluminum.

### Claim 3 (depends on 1)

The method of claim 1, wherein the third conductive film is formed of a transparent conductive material of a high transmittance including indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).

### Claim 4 (depends on 1)

The method of claim 1, wherein the fourth and fifth photosensitive film patterns are removed through a wet strip process.

### Claim 5 (depends on 1)

The method of claim 1, further comprising removing the photosensitive film pattern through a wet strip process.

### Claim 6 (depends on 1)

The method of claim 1, wherein the ohmic-contact layer formed of the n+ amorphous silicon thin film is disposed by selectively removing the n+ amorphous silicon thin film pattern through a dry etching using a plasma gas having Cl2 removed therefrom, using the fourth and fifth photosensitive film patterns as a mask.

### Claim 7

A method of fabricating a fringe field switching (FFS)-liquid crystal display (LCD) device, comprising:
forming a gate electrode and a gate line on a first substrate;
forming a gate insulation film, an amorphous silicon thin film, an n+ amorphous silicon thin film and a second conductive film on the first substrate where the gate electrode and the gate line have been formed;
forming first to third photosensitive film patterns on the second conductive film;
selectively removing the second conductive film, through a wet etching, by using the first to third photosensitive film patterns as a mask, thereby disposing a conductive film pattern formed of the second conductive film;
selectively removing the amorphous silicon thin film and the n+ amorphous silicon thin film, through a dry etching, by using the first to third photosensitive film patterns as a mask, thereby disposing an active layer and an n+ amorphous silicon thin film pattern formed of the amorphous silicon thin film and the n+ amorphous silicon thin film, below the conductive film pattern;
removing the third photosensitive film pattern through an ashing process, and forming fourth and fifth photosensitive film patterns having a thickness removed by a thickness of the third photosensitive film pattern;
selectively removing the conductive film pattern, through a wet etching, by using the fourth and fifth photosensitive film patterns as a mask, thereby disposing source and drain electrodes formed of the second conductive film on the n+ amorphous silicon thin film pattern;
removing the fourth and fifth photosensitive film patterns;
forming a third conductive film on an entire surface of the first substrate;
forming a photosensitive film pattern on the third conductive film;
selectively removing the third conductive film, through a wet etching, by using the photosensitive film pattern as a mask, thereby disposing a pixel electrode directly electrically connected to the drain electrode and formed of the third conductive film;
selectively removing the n+ amorphous silicon thin film pattern, through a dray etching, thereby disposing an ohmic-contact layer formed of the n+ amorphous silicon thin film;
removing the photosensitive film pattern;
forming a passivation film on the first substrate where the pixel electrode has been formed;
forming a common electrode formed in a single pattern over a pixel portion, and configured to generate a fringe field with a plurality of slits in each pixel region together with the pixel electrode; and
bonding the first substrate to a second substrate.

### Claim 8 (depends on 7)

The method of claim 7, wherein the second conductive film has a multi-layer structure of at least two layers having thereon a low resistance opaque conductive material including copper, or a copper alloy, or aluminum.

### Claim 9 (depends on 8)

The method of claim 8, wherein the third conductive film is formed of a transparent conductive material of a high transmittance including indium-tin-oxide (ITO) or indium-zinc-oxide (IZO).

### Claim 10 (depends on 8)

The method of claim 8, wherein the fourth and fifth photosensitive film patterns are removed through a wet strip process.