KR100492728B1 - A liquid crystal display device having partially removed activation layer in drain region and method of fabricating thereof - Google Patents

Abstract

In the liquid crystal display of the present invention, the characteristics of the thin film transistor due to the light leakage current are prevented, and the gate line and the gate electrode formed on the substrate, the gate insulating layer stacked over the entire substrate, and the gate insulating layer A semiconductor layer having holes formed by removing a portion of the drain region, a data line, a source electrode and a drain electrode formed on the semiconductor layer, and a semiconductor layer on which the semiconductor layer is formed; And a pixel electrode formed on the protective layer and connected to the drain electrode through the contact hole.

Description

A liquid crystal display device in which a portion of an active layer of a drain region is removed and a method of manufacturing the same {A LIQUID CRYSTAL DISPLAY DEVICE HAVING PARTIALLY REMOVED ACTIVATION LAYER IN DRAIN REGION AND METHOD OF FABRICATING THEREOF}

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a liquid crystal display device, and more particularly, to prevent photo leakage current difference between thin film transistors caused by the area difference of the active layer of the drain region exposed during etching of the protective layer by etching the active layer of the drain region. The present invention relates to a liquid crystal display device capable of forming a thin film transistor having the same characteristics and a method of manufacturing the same.

Liquid crystal display devices are transmissive flat panel displays, and are widely applied to various electronic devices such as mobile phones, PDAs, and notebook computers. Such LCDs are currently being practically used in comparison with other flat panel displays in that they can be made light and small and have high image quality. Moreover, as the demand for digital TVs, high-definition TVs, and wall-mounted TVs increases, studies on large-area LCDs applicable to TVs are being actively conducted.

In general, LCDs can be divided into several methods depending on how the liquid crystal molecules are operated. However, active matrix thin film transistor LCDs are mainly used in terms of fast reaction speed and low afterimage. It is used.

The structure of the panel 1 of the TFT LCD is shown in FIG. As shown in the drawing, the liquid crystal panel 1 is formed with a plurality of gate lines 3 and data lines 5 arranged vertically and horizontally to define a plurality of pixels. A thin film transistor, which is a switching element, is disposed in each pixel, and when a scan signal is input through the gate line 3, the signal is switched and a signal input through the data line 5 is input to the liquid crystal layer 9. Is authorized. In the figure, reference numeral 11 denotes an accumulation capacitor, which serves to hold an input data signal until the next scanning signal is applied.

FIG. 2 is a diagram showing in detail the structure of the pixels constituting the TFT LCD panel 1, in which FIG. 2 (a) is a sectional view and FIG. 2 (b) is a plan view.

First, as shown in FIG. 2A, a gate electrode 22 is formed on a transparent substrate 20 such as glass, and a gate insulating layer 24 is stacked thereon. A semiconductor layer 26 is formed in the gate region on the gate insulating layer 24, and a source electrode 28a and a drain electrode 28b are formed on the semiconductor layer 26. Although not shown, an impurity semiconductor is stacked or doped with impurities between the semiconductor layer 26 and the source electrode 28a and between the semiconductor layer 26 and the drain electrode 28b to form an ohmic contact layer. ) Is formed.

The passivation layer 32 is formed over the entirety of the substrate 20 on the source electrode 28a and the drain electrode 28b. As shown in the drawing, a contact hole 31 is formed in the passivation layer 31 to form a pixel such as indium tin oxide (ITO) or indium zinc oxide (IZO) formed on the passivation layer 31. The electrode 30 is connected to the drain electrode 28b through the contact hole 31.

The contact hole 31 of the protective layer 32 is formed in the drain region. The contact hole 31 may be formed in various forms, but is mainly formed in a 'b' shape as shown in FIG. The contact hole 31 of the protective layer 32 is typically formed by a photo process. In other words, the photoresist is stacked on the protective layer 32 to form a pattern in which the contact hole 31 region is exposed, and then etching the region by dry etching using an etchant gas.

Meanwhile, Cr is mainly used as the source electrode 28a and the drain electrode 28b. In recent years, Mo, which has high electrical conductivity and is environmentally friendly, is mainly used. However, Mo has the property of being etched by etchant gas in view of its characteristics. Therefore, during dry etching of the protective layer 32, the drain electrode 28b of the contact hole 31 region is etched to expose the active layer of the drain region to the outside. However, in view of the advantages of Mo, this effect can be tolerated. In recent years, Mo is used as the source electrode 28a and the drain electrode 28b. As a result, the active layer in the drain region is inevitably generated. A liquid crystal display device having a structure exposed to the outside has been proposed.

Of course, when the active layer of the drain region is exposed to the outside as described above, the light leakage current is generated in the thin film transistor by light incident from the outside, so that the characteristics of the thin film transistor are changed, but the thin film transistor is designed in consideration of the light leakage current. By doing so, it becomes possible to have desired characteristics.

However, the following problem occurs in the liquid crystal display device in which a part of the active layer of the drain region is exposed as described above. Stepper exposure equipment must be used to form the contact hole 31 in the protective layer 32 over a large liquid crystal display device including a large number of pixels. If a difference occurs, the position of the contact hole 31 is changed, and as a result, the active layer area of the drain region exposed to the outside is changed.

3 shows the area change of the active layer in the drain region caused by the minute difference in the irradiation step. As shown in Fig. 3A, in the first passivation of the protective layer 32, the protective layer 32 and the drain electrode 28b are etched to expose the active layer in the lengths of a and b. As shown in FIG. 5, when the position of the contact hole 31 is shifted upward and to the right (ie, toward the pixel region) in a subsequent exposure process, the active layer exposed to the outside has a length of c (<a) and d (<b) becomes shorter than the initial length and eventually the exposed area becomes smaller. The change in the external exposure area of the active layer means that the amount of light incident on the active layer changes. Therefore, the light leakage current due to light incidence is changed, so that the characteristics of the thin film transistor are changed.

Such an exposed area of the drain region active layer is generated over the entire liquid crystal panel. Therefore, thin film transistors having different characteristics are formed in all the pixels of the liquid crystal panel, which is a major cause of defective liquid crystal display elements.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and a thin film formed over the entire liquid crystal panel by removing a portion of the active layer (semiconductor layer) in the drain region so that light incident through the contact hole of the protective layer does not affect the active layer. An object of the present invention is to provide a liquid crystal display device having a transistor having the same characteristics and a method of manufacturing the same.

In order to achieve the above object, the liquid crystal display device according to the present invention is a gate line and a gate electrode formed on a substrate, a gate insulating layer stacked over the entire substrate, and formed on the gate insulating layer, a part of the drain region And a protective layer having a contact hole formed in the drain region, the semiconductor layer having the holes removed, the data line, the source electrode and the drain electrode formed on the semiconductor layer, and the semiconductor layer formed thereon, and having a contact hole formed in the drain region. And a pixel electrode formed thereon and connected to the drain electrode through the contact hole.

In addition, the method of manufacturing a liquid crystal display device according to the present invention includes the steps of forming a gate line and a gate electrode on a substrate, laminating a gate insulating layer on the substrate, and forming a semiconductor layer on the gate insulating layer. Forming a hole by etching the drain region of the semiconductor layer, forming a data line, a source electrode and a drain electrode on the semiconductor layer, and laminating a protective layer on the source electrode and the drain electrode Forming a contact hole in the drain region, and forming a pixel electrode connected to the drain electrode through the contact hole on the protective layer.

The present invention provides a thin film transistor having the same characteristics throughout the liquid crystal panel. Particularly, in the present invention, the active layer of the drain region is formed in advance so that the active layer of the drain region exposed to the outside by the etching of the source / drain electrode does not exist in the thin film transistor including the source / drain electrode made of Mo which is etched when the protective layer is opened. This eliminates the change in characteristics of the thin film transistor due to the difference in the light leakage current.

In other words, when forming a contact hole in the protective layer by using a stepper exposure equipment, even if the position or area of the contact hole is changed due to the slight difference in each irradiation step, the characteristic layer is prevented by removing the active layer under the contact hole. do. By manufacturing such a thin film transistor, it is possible to form a thin film transistor having the same characteristics over all pixels of the liquid crystal panel, and as a result, it is possible to prevent defects of the liquid crystal display device in advance.

Hereinafter, a liquid crystal display device according to the present invention will be described in detail with reference to the accompanying drawings.

4 is a partial plan view showing the structure of one pixel of the liquid crystal display according to the present invention. As shown in the figure, the gate line 103 and the data line 105 are vertically and horizontally arranged in the liquid crystal panel 101. In fact, the entire liquid crystal panel 101 includes a plurality of gate lines 103 and data lines 105 to define a plurality of pixel regions.

A thin film transistor is formed at the intersection of the gate line 103 and the data line 105. The gate electrode 122 of the thin film transistor is connected to the gate line 103, and a semiconductor layer 126 is formed thereon. As shown in the figure, the semiconductor layer 126 is not only formed in the thin film transistor region but also formed under the data line 105. As described above, the reason why the semiconductor layer 126a is formed under the data line 105 is to ensure sufficient insulation distance between the gate line 103 and the data line 105. Although a gate insulating layer (not shown) is formed below the gate insulating layer, a gap between the gate line 103 and the data line 105 is secured by the semiconductor layer 126a to secure the data with the gate line 103. Line 105 is prevented from shorting.

On the other hand, a hole 133 is formed in the semiconductor layer of the drain region. The hole 133 is formed by etching a portion of the semiconductor layer of the drain region. Although the hole 133 is formed in the drawing, the hole 133 is not limited to a specific shape. For example, circular, elliptical, triangular, rectangular holes 133 may be formed, but may also be formed in other unique geometric shapes.

The source electrode 128a and the drain electrode 128b connected to the data line 105 are formed on the semiconductor layer 126. As the source / drain electrodes 128a and 128b, Mo, which is electrically conductive and environmentally friendly, is mainly used.

A protective layer 132 is stacked on the source / drain electrodes 128a and 128b. The protective layer 132 is stacked over the entire panel 101, and contact holes 131 are formed in the drain region of the thin film transistor. In addition, a pixel electrode made of ITO or IZO (not shown) is formed on the passivation layer 32 and electrically connected to the drain electrode 128b through the contact hole 131.

The contact hole 131 is formed to match the hole 133 formed in the drain region of the semiconductor layer. In reality, since the contact hole 131 is not matched to the hole 133 but most of the semiconductor layer (active layer) of the drain region is removed, the contact hole 131 is formed at a certain position of the drain region. Even if it is matched with the hole 133. In addition, the contact hole 131 is formed in the drain electrode 128b as well as the protective layer 132. This is because the drain electrode 128b made of Mo is easily removed by the dry etching process, which is the process of forming the contact hole 131, and thus, the drain electrode 128b is etched up to the drain electrode 128b during the process of forming the contact hole 131. That is, the contact hole 131 is formed from the protective layer 132 to the gate insulating layer (not shown) (since the hole 133 is formed in the active layer of the drain region in which the contact hole is formed).

As described above, since the hole 133 is formed in the active layer of the drain region, the contact hole 131 formed in the protective layer 132 is actually formed up to the gate insulating layer under the semiconductor layer. This means that there is no active layer under the contact hole 131, and the active layer is not affected by external light incident through the contact hole 131, so that no light leakage current is generated in the thin film transistor. it means. On the other hand, since the hole 133 is formed in most of the drain region of the active layer, the contact hole 131 is moved even when the position where the contact hole 131 is formed or its area is increased due to the irradiation error of the stepper exposure equipment. The lower portion of the active layer is not present. Therefore, the light leakage current of the thin film transistor does not occur due to the change of the area of the contact hole 131. As a result, the thin film transistor formed on all pixels of the liquid crystal panel always has uniform characteristics.

A method of manufacturing the liquid crystal display device configured as described above will be briefly described with reference to FIG. 5.

First, as shown in FIG. 5A, a metal layer is laminated and etched on a substrate (panel) to form a gate line 103 and a gate electrode 122, and a gate insulating layer not illustrated is stacked. Amorphous silicon (a-Si) is stacked thereon and etched to form semiconductor layers 126 and 126a having holes 133 in the drain region.

Subsequently, as shown in FIG. 5 (b), Mo and the source / drain electrodes 128a disposed on the semiconductor layer 126 and the data line 105 disposed along the semiconductor layer 126a are stacked and etched. 128b). Thereafter, as shown in FIG. 5C, a protective layer 132 is formed by stacking an inorganic material such as SiNx over the entire substrate, and then forms a contact hole 131 in the drain region using a stepper exposure apparatus. . In this case, the contact hole 131 may be formed in a 'b' shape as shown in the drawing, but may be formed in another shape.

Thereafter, the liquid crystal display device is completed by forming a pixel electrode (not shown) made of ITO or IZO connected to the drain electrode 128b through the contact hole 131 on the protective layer 132.

As described above, the biggest feature of the present invention is to form a hole by removing a part of the active layer in the drain region in advance in the process of forming the semiconductor layer. In the above description, the shape of the hole or contact hole formed in the active layer of the drain region and the structure of the entire thin film transistor are described. However, the present invention is not limited to the specific structure and shape described above. A liquid crystal display device having another shape or structure having a feature in which holes are formed in the semiconductor layer to remove the light leakage current of the thin film transistor can be easily invented by anyone in the technical field to which the present invention belongs. The present invention will include all such other examples and modifications.

As described above, in the present invention, the active layer in the drain region is removed in advance during the semiconductor layer forming process to form holes, so that light leakage due to light incident through the contact hole even if the contact hole formation position of the protective layer changes due to an exposure error. By eliminating the current, it is possible to form a thin film transistor which always has constant characteristics in all pixels of the liquid crystal display device.

1 is a plan view showing the structure of a general liquid crystal display device.

Fig. 2A is a sectional view showing the structure of one pixel of a conventional liquid crystal display element.

2B is an enlarged plan view showing the structure of one pixel of a conventional liquid crystal display device.

3 is a view showing a shape in which the position of the contact hole is moved by the irradiation error of the stepper exposure equipment.

4 is an enlarged plan view showing the structure of one pixel of the liquid crystal display device according to the present invention;

5 is a view showing a method of manufacturing a liquid crystal display device according to the present invention.

** Explanation of symbols for main parts of drawings **

101: liquid crystal panel 103: gate line

105: data line 122: gate electrode

126 semiconductor layer 128a, 128b source / drain electrodes

131: contact hole 132: protective layer

133: drain region active layer hole

Claims (13)

A gate line and a gate electrode formed on the substrate; A gate insulating layer stacked over the substrate; A semiconductor layer formed on the gate insulating layer, wherein a portion of the drain region is removed; A data line, a source electrode and a drain electrode formed on the semiconductor layer; A protective layer stacked over the entire substrate on which the semiconductor layer is formed and having contact holes formed in the drain region; And A pixel electrode formed on the protective layer and connected to the drain electrode through a contact hole, And a contact hole of the protective layer is formed in the drain region from which the semiconductor layer is removed, and the contact hole extends to the drain electrode to expose the gate insulating layer to the outside through the contact hole. The liquid crystal display device according to claim 1, wherein the source electrode and the drain electrode are made of Mo. delete The liquid crystal display of claim 1, wherein a region where the semiconductor layer is removed is wider than a contact hole. The liquid crystal display device of claim 1, wherein the semiconductor layer of the drain region is not exposed to the outside through the contact hole. The liquid crystal display of claim 1, wherein the removed region of the semiconductor layer is formed in a quadrangular shape, a circular shape, an elliptical shape, or a triangular shape. The liquid crystal display device of claim 1, wherein the contact hole has a 'b' shape. The liquid crystal display device of claim 1, wherein the semiconductor layer is formed along a data line. Forming a gate line and a gate electrode on the substrate; Depositing a gate insulating layer on the substrate; Forming a semiconductor layer on the gate insulating layer; Etching a portion of the semiconductor layer in the drain region; Forming a data line, a source electrode, and a drain electrode on the semiconductor layer; Stacking a passivation layer on the source electrode and the drain electrode, and etching the passivation layer and the drain electrode to form a contact hole exposing a gate insulating layer in the semiconductor layer removal region of the drain region; And And forming a pixel electrode connected to the drain electrode through the contact hole on the passivation layer. The method of claim 9, wherein the forming of the source electrode and the drain electrode comprises: Stacking a metal layer made of Mo; And And etching the metal layer. delete delete The method of claim 9, wherein the semiconductor layer of the drain region is not exposed to the outside through the contact hole.