KR100654776B1 - liquid crystal display device - Google Patents

Abstract

The present invention provides a substrate comprising: a substrate in which a switching region and a pixel region are defined; A gate wiring extending in a lateral direction; A gate electrode protruding from the gate wiring and formed in the switching region, wherein the protruding portion is substantially rectangular in shape; A data line extending in the longitudinal direction; A source electrode extending from the data line in the vicinity of the gate electrode, the source electrode overlapping a first surface of the gate electrode with a predetermined area; A first drain electrode formed to overlap with a second surface not adjacent to the first surface of the gate electrode, and a predetermined area overlapping with a third surface adjacent to the first and second surfaces of the gate electrode, the second drain electrode and the first An array substrate of a liquid crystal display device including a pixel electrode in contact with the first and second drain electrodes and formed in the pixel region is disclosed.

Description

Liquid crystal display device             

1 is a cross-sectional view showing a cross section corresponding to one pixel portion of a general liquid crystal display device.

2 is a plan view illustrating a plane corresponding to a part of a general liquid crystal display;

3A to 3D are process diagrams showing a cross section process along cut line III-III of FIG. 2;

4 is a plan view of a liquid crystal display device employing a conventional double thin film transistor.

5 is a plan view illustrating a plane of a liquid crystal display according to an exemplary embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

 100: gate wiring 110: gate electrode

 200: data wiring 210: source electrode

 220: first drain electrode 230: second drain electrode

 300: pixel electrode

The present invention relates to an image display device, and more particularly, to a liquid crystal display (LCD) including a thin film transistor (TFT).

The driving principle of the liquid crystal display device uses the optical anisotropy and polarization property of the liquid crystal. Since the liquid crystal is thin and long in structure, the liquid crystal has directivity in the arrangement of molecules, and the direction of the molecular arrangement can be controlled by artificially applying an electric field to the liquid crystal.

Accordingly, when the molecular arrangement direction of the liquid crystal is arbitrarily adjusted, the molecular arrangement of the liquid crystal is changed, and light is refracted in the molecular arrangement direction of the liquid crystal due to optical anisotropy to express image information.

Currently, the active matrix liquid crystal display (AM-LCD) in which the above-described thin film transistor and pixel electrodes connected to the thin film transistor are arranged in a matrix manner has attracted the most attention due to its excellent resolution and ability to implement video.

In general, the structure of a liquid crystal panel, which is a basic component of a liquid crystal display, will be described.

1 is a cross-sectional view showing a cross section of a general liquid crystal panel.

In the liquid crystal panel 20, two substrates 2 and 4 having various kinds of elements are formed to correspond to each other, and the liquid crystal layer 10 is interposed between the two substrates 2 and 4. .

The liquid crystal panel 20 includes an upper substrate 4 having a color filter representing a color and a lower substrate 2 having a switching circuit capable of converting a molecular arrangement direction of the liquid crystal layer 10.

The upper substrate 4 includes a color filter layer 8 for implementing color and a common electrode 12 covering the color filter layer 8. The common electrode 12 serves as one electrode for applying a voltage to the liquid crystal 10. The lower substrate 2 has a thin film transistor S serving as a switching function and a pixel electrode 14 serving as an electrode for receiving a signal from the thin film transistor S and applying a voltage to the liquid crystal 10. It is composed of

The portion where the pixel electrode 14 is formed is called the pixel portion P. FIG.

In order to prevent leakage of the liquid crystal 10 injected between the upper substrate 4 and the lower substrate 2, sealants (sealant) is formed at the edges of the upper substrate 4 and the lower substrate 2. It is sealed with).

Referring to the operation and configuration of the lower substrate 2 in Figure 2 showing a plan view of the lower substrate 2 shown in FIG. 1 as follows.

The pixel electrode 14 is formed on the lower substrate 2, and the data line 24 and the gate line 22 are formed in the vertical and horizontal alignment directions of the pixel electrode 14, respectively.

In the active matrix liquid crystal display device, a thin film transistor S, which is a switching element for applying a voltage to the pixel electrode 14, is formed at one portion of the pixel electrode 14. The thin film transistor S includes a gate electrode 26, source and drain electrodes 28 and 30, and a gate electrode 26 is formed to protrude and extend in a portion of the gate wire 22. The source electrode 28 is connected to the data line 24.

The drain electrode 30 is electrically connected to the pixel electrode 14 through the drain contact hole 30 ′.

In addition, a storage capacitor C _st is formed in a portion of the gate line 22 to store charge together with the pixel electrode 14.

The storage capacitor C _{st is} formed using the gate wiring 22 as one electrode and the capacitor electrode 58 formed on the gate wiring as another electrode.

Referring to the operation of the active matrix liquid crystal display, when a signal is applied to the gate electrode 26 of the switching thin film transistor S, the data signal is applied to the pixel electrode 14 and the signal is applied to the gate electrode 26. If not applied, the data signal is not applied to the pixel electrode 14.

The manufacturing process of the liquid crystal panel constituting the liquid crystal display device is a complex process of several complex steps. In particular, the lower substrate on which the thin film transistor S is formed must go through several mask processes.

The performance of the final product is determined by this complex manufacturing process. Preferably, the simpler the process, the less likely it is that defects will occur. That is, since a number of major elements that determine the performance of the liquid crystal display are formed on the lower substrate, the manufacturing process should be simplified.

In general, the manufacturing process of the lower substrate is often determined by what material is used for each device to be made or designed according to the specification.

For example, in the past, a small liquid crystal display was not a problem, but in the case of a large area liquid crystal display of 12 inches or more, the resistivity value of the material used for the gate wiring is an important factor in determining the superiority of the image quality. Therefore, in the case of a large area liquid crystal display element, it is preferable to use a metal with low resistance, such as aluminum or an aluminum alloy.

Hereinafter, a manufacturing process of a conventional active matrix liquid crystal display device will be described with reference to FIGS. 3A to 3E. 3A to 3E are process diagrams showing a process of a cross section taken along cut line III-III of FIG. 2 for ease of explanation.

In general, the structure of a thin film transistor used in a liquid crystal display is an inverted staggered structure. This is because the structure is simple and the performance is excellent.

In addition, the reverse staggered thin film transistor is divided into a back channel etch type (EB) and an etch stopper type (ES) according to a channel forming method, and a simple back channel etch type structure is applied. The liquid crystal display device manufacturing process will be described.

First, a foreign material or an organic material is removed from the substrate 1, and the metal film is deposited by sputtering after cleaning to improve the adhesion between the metal film of the gate material to be deposited and the glass substrate. .

3A is a step of forming a gate electrode 26 and a gate wiring 22 by patterning the metal film after deposition. The gate electrode 26 material, which is important for the operation of the active matrix liquid crystal display, is mainly composed of aluminum having low resistance to reduce the RC delay, but pure aluminum has low chemical resistance to corrosion and is healed in subsequent high temperature processes. In the case of aluminum wiring, it is used in the form of an alloy or a laminated structure is applied because it causes a wiring defect problem due to the formation of the hi-lock.

Next, referring to FIG. 3B, after the gate electrode 26 and the gate wiring 22 are formed, a gate insulating film 50 is deposited over the upper portion and the entire surface of the exposed substrate 1.

In addition, amorphous silicon (a-Si: H: 52), which is a semiconductor material, and amorphous silicon (n ⁺ a-Si: H: 54) containing impurities are deposited on the gate insulating film 50 in succession.

The amorphous silicon 54 containing the impurity is to reduce the contact resistance between the metal layer to be formed later and the active layer 55.

Thereafter, as shown in FIG. 3C, the metal layer is deposited and patterned to form the source electrode 28 and the drain electrode 30.

In addition, a capacitor electrode 58 is formed on the insulating film 50 on the gate wiring 22 so as to overlap a part of the gate wiring 22. That is, in the third mask process, the source electrode 28, the drain electrode 30, and the capacitor electrode 58 are formed.

The ohmic contact layer existing between the source electrode 28 and the drain electrode 30 is removed using the source and drain electrodes 28 and 30 as a mask. If the ohmic contact layer between the source electrode 28 and the drain electrode 30 is not removed, a serious problem may occur in the electrical characteristics of the thin film transistor S, and a great problem may occur in performance.

Careful attention is required to removing the ohmic contact layer. In actual etching of the ohmic contact layer, since there is no etch selectivity with the active layer formed underneath, the active layer is overetched by about 50 nm. The etching uniformity directly affects the characteristics of the thin film transistor S. .

Thereafter, as shown in FIG. 3D, an insulating film is deposited and patterned to form a protective film 56 to protect the active layer 55. The passivation layer 56 may adversely affect the characteristics of the thin film transistor due to the unstable energy state of the active layer 55 and the residual material generated during etching, so that the inorganic silicon nitride layer (SiN _x ) or the silicon oxide layer (SiO ₂ ) or the like may be adversely affected. It is formed of inorganic BCB (Benzocyclobutene).

The passivation layer 56 requires high light transmittance, properties of a moisture resistant and durable material.

A process of forming a contact hole during patterning of the passivation layer 56 is added, and a drain contact hole 30 'and a storage contact hole 58' are formed, respectively.

The drain contact hole 30 'and the storage contact hole 58' are for contact with the pixel electrode.

Thereafter, a transparent conductive material (TCO) is deposited and patterned on the passivation layer 56 to form the pixel electrode 14. ITO (Indium Tin Oxide) is mainly used as the transparent conductive material. The pixel electrode 14 is in contact with the capacitor electrode 58 and is in electrical contact with the drain electrode 30 through the drain contact hole 30 ′.

As described above, the liquid crystal display includes a plurality of mask processes and etching processes, and thus requires careful processing.

However, the structure of the conventional liquid crystal display device described above has a structure for driving one pixel electrode 14 per one thin film transistor S, so that when a defect occurs in the thin film transistor S, one pixel is lost. A non-driven point defect can occur, which has a fatal effect on image quality.

In order to solve the above problems, as shown in FIG. 4, a liquid crystal display including two thin film transistors (double thin film transistors) using one gate electrode 62 has been researched and developed.

The double thin film transistor includes one gate electrode 62, two source electrodes 72a and 72b, and two drain electrodes 74a and 74b.

The liquid crystal display device employing a double thin film transistor includes a gate wiring 60 having a gate electrode 62 formed therein, and two source electrodes 72a and 72b and a drain electrode 74a and 74b which overlap and overlap the gate electrode. It is composed.

Here, each of the source electrodes 72a and 72b is formed to protrude / extend on the data line 70, respectively.

Meanwhile, the two drain electrodes 74a and 74b are in contact with one pixel electrode 76 simultaneously to drive the pixel.

In the case of the liquid crystal display device employing the above-described double thin film transistor, if a defect occurs in any one of the source and drain electrodes due to impurities or other defects that may occur in the manufacturing process, the defective electrode is produced. Can be repaired by laser cutting. That is, the production yield of the product is increased.

However, since the liquid crystal display employing the above-described double thin film transistor uses two thin film transistors in one pixel, overlap between the source and drain electrodes and the gate electrode increases, causing flicker of the screen due to parasitic capacitance. This has the disadvantage that flicker may occur.

In addition, the area of the pixel area is reduced by the two thin film transistors, and thus, the aperture ratio is fatal.

In order to solve the above-mentioned problems, an object of the present invention is to provide a thin film transistor which is easy to repair defects and does not affect image quality.

In order to achieve the above object, the present invention includes a substrate in which a switching region and a pixel region are defined; A gate wiring extending in the transverse direction on the substrate; A gate electrode protruding from the gate wiring and formed in the switching region, wherein the protruding portion is substantially rectangular in shape; A longitudinally extending data line on the substrate; A source electrode extending from the data line in the vicinity of the gate electrode and overlapping the protruding first surface of the gate electrode; If a defect occurs, the first drain electrode and the first surface of the gate electrode overlapping with the second surface which is not adjacent to the first surface of the gate electrode, which can be cut and repaired, and are simultaneously adjacent to the first surface and the second surface of the gate electrode. A second drain electrode overlapping the third surface; And a pixel electrode in contact with the first drain electrode and the second drain electrode and formed in the pixel area.

In addition, the present invention and the first substrate and the second substrate spaced apart from each other; A liquid crystal layer interposed between the first substrate and the second substrate; Data and gate wiring crossing each other on the first substrate; A gate electrode extending from the gate wiring, and a source electrode extending from the data wiring while overlapping with the gate electrode; A thin film transistor having a first drain electrode and a second drain electrode spaced apart from the source electrode and overlapping with the gate electrode, and repairing the defect by cutting the first drain electrode or the second drain electrode where the defect occurs; And a pixel electrode in contact with the first drain electrode and the second drain electrode.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, in the structure of a conventional double thin film transistor, by integrating two source electrodes into one, the generation area of the parasitic capacitance formed between the gate electrode and the source electrode is minimized, so that there is no deterioration in image quality and the repair is easy. To a liquid crystal display device.

5 is a plan view illustrating a plane of a liquid crystal display according to an exemplary embodiment of the present invention, wherein a gate wiring 100 is formed in a horizontal direction, and a predetermined position of the gate wiring 100 is a rectangular gate electrode having three surfaces exposed. 110 is protrudingly extended.

In addition, the data line 200 crosses the gate line 100 in the vertical direction, and the source electrode 210 protrudes and extends in the data line 200 near the gate electrode 110. It overlaps with the first surface of the gate electrode 110.

In addition, a first drain electrode 220 is formed in a direction corresponding to the source electrode 210 so as to overlap a second surface which is not adjacent to the first surface of the gate electrode 110, and the gate electrode 110 is formed. A second drain electrode 230 is formed while overlapping a predetermined area with a third surface adjacent to the first and second surfaces of the substrate.

On the other hand, the first and second drain electrodes 220 and 230 are in contact with the pixel electrode 300 at the same time, and if any one of the first and second drain electrodes 220 and 230 is defective in the manufacturing process of the thin film transistor. If this occurs, the laser can be cut and repaired.

The pixel electrode 300 may be a transmissive liquid crystal display using a substantially transparent transparent conductive metal, and may be a reflective liquid crystal display using a substantially opaque metal having excellent light reflectance.

As the transparent conductive metal used as the pixel electrode, indium tin oxide (ITO), indium zinc oxide (IZO), or the like is used.

In the liquid crystal display device employing the thin film transistor having the double drain electrode according to the present invention described above, since the pixel is driven by two drain electrodes using one source electrode in common, parasitic capacitance is generated less. There is an advantage that can prevent the degradation of the image quality.

In addition, even if a failure occurs in one drain electrode by the use of two drain electrodes can be driven by the other drain electrode has the advantage that the production yield of the product increases.

As described above, the liquid crystal display according to the present invention employs a thin film transistor including one source electrode and two drain electrodes using the source electrode in common, and thus the drain electrode is not deteriorated due to parasitic capacitance. There is a characteristic that can be repaired.

Claims (5)

A substrate in which a switching region and a pixel region are defined; A gate wiring extending in the transverse direction on the substrate; A gate electrode protruding from the gate wiring and formed in the switching region, wherein the protruding portion is substantially rectangular in shape; A longitudinally extending data line on the substrate; A source electrode extending from the data line in the vicinity of the gate electrode and overlapping the protruding first surface of the gate electrode; If a defect occurs, the first drain electrode and the first surface of the gate electrode overlapping with the second surface which is not adjacent to the first surface of the gate electrode, which can be cut and repaired, and are simultaneously adjacent to the first surface and the second surface of the gate electrode. A second drain electrode overlapping the third surface; A pixel electrode in contact with the first drain electrode and the second drain electrode and formed in the pixel region; Array substrate of a liquid crystal display comprising a. The method according to claim 1, And the pixel electrode is substantially transparent ITO and IZO. The method according to claim 1, And the pixel electrode is a substantially opaque metal. A first substrate and a second substrate spaced apart from each other; A liquid crystal layer interposed between the first substrate and the second substrate; Data and gate wiring crossing each other on the first substrate; A gate electrode extending from the gate wiring, and a source electrode extending from the data wiring while overlapping with the gate electrode; A thin film transistor having a first drain electrode and a second drain electrode spaced apart from the source electrode and overlapping with the gate electrode, and repairing the defect by cutting the first drain electrode or the second drain electrode where the defect occurs; A pixel electrode in contact with the first drain electrode and the second drain electrode; Liquid crystal display comprising a. The method according to claim 4, And the gate electrode and the first drain electrode extend in the data wiring direction, and the source electrode and the second drain electrode extend in the gate wiring direction.

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