KR20000065508A - Liquid Crystal Display and Method Thereof - Google Patents

Abstract

PURPOSE: A liquid crystal display and a method for manufacturing the same are provided to maximize an auxiliary capacity without manufacturing an additional mask. CONSTITUTION: A liquid crystal display and a method for manufacturing the same comprise a transparent substrate, a plurality of gate line(21) and a plurality of data line(25); a pixel electrode(24), a switching element, an auxiliary capacity electrode(23), and a common signal line(27). The gate lines and the data lines are arranged in a matrix shape on a surface of the substrate and restricts matrixes of each pixel area. The pixel electrode is arranged within each pixel area. The switching element transmits each signal to the each pixel electrode. The auxiliary capacity electrode is formed with the same mask pattern as the pixel electrode. The common signal line is connected with the auxiliary capacity electrode.

Description

Liquid Crystal Display and Manufacturing Method {Liquid Crystal Display and Method Thereof}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device (hereinafter referred to as LCD) and a method for manufacturing the same, and more particularly, to an active matrix liquid crystal display device and a method for manufacturing the same, in which the display capacity is improved by maximizing the auxiliary capacitance without reducing the aperture ratio.

In response to the demand for personalization and space saving of display devices in charge of the interface between humans and computers, liquid crystal displays (LCDs) and PDPs have been used instead of conventional display devices, particularly large and uncomfortable cathode ray tubes (CRTs). Various flat screens and flat panel display devices such as plasma display pannel and electroluminescence have been developed.

Among these flat panel displays, advances in liquid crystal display (LCD) technology have attracted the most attention, and in some forms, have come to realize the color quality of CRT or more. The driving method of the liquid crystal display device is a simple matrix type and an active matrix type, and uses the electro-optical properties of the liquid crystal in which the arrangement of liquid crystal molecules is changed by an electric field. In particular, an active matrix LCD that combines the above-mentioned liquid crystal technology and semiconductor technology is recognized as a display device that competes with CRTs and outperforms CRTs.

The active matrix LCD controls the operation of each pixel by using the switching characteristics of the device by adding an active element having a nonlinear characteristic to each pixel arranged in a matrix form, and provides a memory function through the electro-optical effect of the liquid crystal. will be. In an active matrix LCD using such an active element, tens to millions of elements are integrated on a glass substrate together with pixel address wiring to form a matrix driving circuit together with a TFT serving as a switching element.

However, in such an active matrix LCD, the number of pixels increases according to the trend of large screens and high resolution of the display device, and accordingly, the aperture ratio of each pixel decreases, resulting in a decrease in brightness of the corresponding LCD panel. Occurs.

On the other hand, in the active matrix LCD, a capacitance is generated between the gate and the drain electrode of the TFT. When the gate pulse falls from high to low, the potential of the pixel electrode drops under the influence of the capacitance. This voltage is commonly referred to as an offset voltage. This offset voltage causes the liquid crystal cell to apply a direct current voltage component, causing abnormalities such as image sticking and flicker. To reduce the offset voltage.

In addition, in order to ensure the uniformity of the image displayed on the active matrix LCD, it is necessary to maintain the applied voltage written through the data line for a predetermined time until the next writing. Auxiliary capacitance is formed in parallel with the cell.

FIG. 1 illustrates a pixel layout diagram of a conventional liquid crystal display in which a storage capacitor is formed, and shows only a part of the pixel region defined by the plurality of gate signal lines 11 and the plurality of data signal lines 15. .

As shown in FIG. 1, the storage capacitor C _st is formed in an independent wiring manner separately from the gate line 11, and the storage capacitor electrode 13 is separated from the gate line 11 and has a different factor. As an independent wiring scheme that is drawn out, the storage capacitor electrode 13 in the adjacent pixel region is connected to each other through the wiring connecting portion 13a.

However, in the conventional method, when the storage capacitor electrode 13 is used as an opaque metal (for example, Al) which is the same material as the gate line 11, the process can be simplified, but the The area occupied by the storage capacitor is excluded from the aperture ratio, so that the aperture ratio decreases by that amount. On the other hand, when the transparent metal is used as the storage capacitor electrode 13, the aperture ratio can be improved, but a separate layer for forming the storage capacitor electrode 13 is formed. It has a double side which requires mask pattern fabrication and additional process.

That is, in terms of simplifying the process, an increase in the auxiliary capacitance C _st means a decrease in the aperture ratio, and in view of increasing the aperture ratio, the complexity of the process and the increase in the limited auxiliary capacitance C _st are increased. This means an increase in production cost.

Accordingly, an object of the present invention is to provide a liquid crystal display device having improved display characteristics in view of the above and other disadvantages in forming the additional capacitance.

In particular, it is an object of the present invention to provide a liquid crystal display device capable of maximizing the auxiliary capacitance without lowering the aperture ratio and without further processing requiring additional mask fabrication.

It is also an object of the present invention to provide a simplified and suitable manufacturing method for manufacturing the above liquid crystal display device.

1 is a pixel layout diagram of a conventional storage capacitor method;

2 is a pixel layout diagram of a liquid crystal display according to an exemplary embodiment of the present invention;

3 is a cross-sectional view illustrating a lower substrate of the liquid crystal display of FIG. 2 taken along line AA ′ of FIG. 2;

4 is a pixel layout diagram of a liquid crystal display according to another exemplary embodiment of the present invention;

5A through 5E are cross-sectional views sequentially illustrating a method of forming a lower substrate of the liquid crystal display of the present invention.

* Description of the symbols for the main parts of the drawings *

20; Transparent insulating substrate 22; Gate insulation film

21; Gate signal line 25; Data signal line

23; Auxiliary capacitor electrode 24; Pixel electrode

27; Common signal line 26; Semiconductor layer

29; Shield

The liquid crystal display device according to the present invention for achieving the above object,

A plurality of gate lines and data lines arranged in a matrix on a surface of the substrate, the plurality of gate lines and data lines defining a matrix of each pixel region bordered by two adjacent gate lines and two data lines; A pixel electrode disposed in an area, a switching element disposed in each pixel area for transmitting a signal of each signal line to the pixel electrodes, and a pixel pattern formed in the same mask pattern as that of the pixel electrode, and the total area of each pixel electrode; And an auxiliary capacitance electrode formed to overlap each other via the insulating layer, and a common signal line which is independently wired from the gate line and driven independently of each gate line, and is directly connected to the auxiliary capacitance electrode.

On the other hand, in the method of manufacturing a liquid crystal display according to the present invention, a process of forming a storage capacitor electrode by depositing a first transparent conductive film on a transparent substrate and then patterning the same using a mask for forming a pixel electrode, and the resultant image Depositing a first metal on the substrate, patterning the same, and simultaneously forming a common signal line directly connected to the gate line and the storage capacitor electrode; and sequentially forming a gate insulating layer, a semiconductor layer, and an ohmic contact layer on the resultant. Patterning the ohmic contact layer and the semiconductor layer to remain only near the intersections of the signal lines, stacking and patterning a second metal layer on the resultant to form a source / drain of a plurality of data lines and the switching element, and the resultant Forming a contact hole exposing a part of the source or drain after laminating a protective film on the second layer; And depositing a transparent conductive film and patterning the same using the same mask used to form the storage capacitor electrode to form a pixel electrode.

According to the present invention which forms the storage capacitor in the unit pixel as described above, the storage capacitance can be maximized by performing trade-off on two aspects of improving the aperture ratio and simplifying the process. have.

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

2 is a diagram illustrating a pixel layout of the liquid crystal display according to the exemplary embodiment, and FIG. 3 is a cross-sectional view taken along the line AA ′ of FIG. 2. Although only a single pixel area (including a portion of the adjacent pixel area) of the active matrix LCD is shown in Fig. 2, the complete form is a plurality of gate signal lines 21 vertically and a plurality of horizontally in a right angle thereof. In the LCD field, a matrix-type pixel region is formed in an area in which the data signal lines 25 are arranged in a matrix and are respectively bordered by two adjacent gate signal lines 21 and two data signal lines 25. Anyone with ordinary knowledge can easily predict.

As shown in the figure, a plurality of gate lines 21 (scanning lines) and a plurality of data lines 25 (display signal lines) are arranged in a matrix on a transparent substrate and are demarcated by each gate line 21 and data lines 25. Defines each pixel region, and a pixel electrode 24 is formed in each pixel region.

A feature of the present invention is that the storage capacitor electrode 23 is formed of a transparent conductive film of the same material in the same mask pattern as the pixel electrode 24, so that the total area of each pixel electrode 24 and each storage capacitor electrode 23 are formed. The entire structure constitutes a storage capacitance in an overlapped form through the insulating layer. In addition, the common signal line 27 is independently wired from the gate line 21 and directly connected to the storage capacitor electrode 23 in the form of a single line crossing the middle of the pixel region. The gate lines 21 are simultaneously formed of the same opaque metal.

That is, in the present embodiment, the storage capacitor electrode 23 and the pixel electrode 24 maintain the same area. Therefore, the storage capacitor C _st is the total overlap area between the pixel electrode 24 and the storage capacitor electrode 23.

4 illustrates a pixel layout diagram of a liquid crystal display according to another exemplary embodiment of the present invention. The feature of this embodiment with reference to FIG. 4 is that the common signal line 27 is connected to the storage capacitor electrode 23 in order to minimize the unavoidable reduction of the aperture ratio by the overlapping area with the pixel electrode 24 in the embodiment. Except for the minimum area required, it is formed so as not to overlap with the pixel electrode 24. In this case, a portion where the common signal line 27 of FIG. 4 overlaps the pixel electrode 24 represents a portion that is directly contacted with the storage capacitor electrode 23.

Hereinafter, a manufacturing process of the liquid crystal display according to the exemplary embodiment will be described with reference to FIG. 5.

First, referring to FIG. 5A, the lower glass substrate 20 of the liquid crystal display panel is prepared, and transparent ITO is deposited thereon to be patterned to form the storage capacitor electrode 23. At this time, by using the same photo mask for subsequent pixel electrode formation, it is not necessary to separately make a photo mast for forming the storage capacitor electrode 23 and at the same time, the storage capacitance can be maximized.

Referring to FIG. 5B, an opaque metal, for example, aluminum (Al), is stacked on the entire surface of the resultant material, and then patterned to form a common signal line directly connected to the gate line 21 and the storage capacitor electrode 23. 27). In this case, the gate line 21 protrudes into the pixel region, and includes a gate 21a and a part of the gate line 21 of the switching element, and the common signal line 27 is the same material as the gate line 21. Are formed simultaneously. In addition, the gate 21a and the common signal line 27 may be formed in a double layer to improve electrical characteristics thereof.

Referring to FIG. 5C, a gate insulating film 22 such as silicon nitride (SiN _x ) and a semiconductor layer 26 such as amorphous silicon hydride (a-Si: H) are deposited on the entire surface of the resultant by chemical vapor deposition. . In this case, as the ohmic contact layer 28, a high concentration of amorphous silicon hydride (n ⁺ a-Si: H) doped with N-type may be formed on the semiconductor layer 26 as a thin film. In addition, when the switching element, which is the thin film transistor, is formed in an etch stopper shape, an etch stopper layer such as a nitride film may be formed on the semiconductor layer 26. Subsequently, the semiconductor layer 26 or the ohmic layer 28 is patterned to define a portion where the switching element is to be positioned near the intersection of the gate line 21 and the data line 25.

Referring to FIG. 5D, a predetermined metal is deposited on the resultant by a sputtering method, and then patterned to form source and drain electrodes 25a and 25b of the data line 25 and the TFT. Subsequently, a passivation layer 29 such as silicon nitride is formed on the entire surface of the resultant, and then contact holes exposing portions of the source or drain electrodes 25a and 25b are formed.

Subsequently, a transparent conductive film such as indium tin oxide (ITO) or the like is deposited, and then patterned using the same mask used to form the storage capacitor electrode 23 and connected to the source or drain electrode 25b of the TFT through the contact hole. By forming the pixel electrodes, the fabrication of the array substrate of the LCD as shown in Fig. 5D is completed. The transparent conductive film is not limited to ITO and may include a transparent conductive film such as ZnO or TiO.

In this case, the pixel electrode 24 is formed to overlap with the storage capacitor electrode 23 and the insulating layers 22 and 29 as described above. Therefore, a storage capacitor may be formed in the pixel area using the insulating layers as a dielectric material, and the signal voltage written through the data line 25 may be maintained for a predetermined time until the next input.

On the other hand, although not shown, the upper substrate of the liquid crystal display panel has a light shielding film formed on the inner surface of the front glass substrate along the periphery of each pixel region to define the opening surface of the liquid crystal display device in a matrix form. A color filter layer is formed on the light shielding film and the exposed opening surface, a normal protective layer is formed thereon, and a transparent upper common electrode is formed thereon to form a multilayer structure of the upper plate.

The upper plate structure and the lower plate structure described above are supported by a predetermined support, and liquid crystal is injected and sealed therebetween to complete the liquid crystal display panel.

This invention can be implemented in other various forms, without deviating from the mind or main characteristic. Therefore, the above-described embodiments are merely examples in all respects and should not be interpreted limitedly. The scope of the present invention is shown by the Claims, and is not restrict | limited by the specification body. Moreover, all the deformation | transformation and a change which belong to the equal range of a claim are within the scope of this invention.

As described above, according to the present invention, the subcapacity can be maximized without lowering the aperture ratio and without additional processing requiring additional mask fabrication.

Claims (7)

Transparent substrate; A plurality of gate lines and data lines arranged in a matrix shape on one surface of the substrate and defining a matrix of each pixel region bordered by two adjacent gate lines and two data lines; A pixel electrode disposed in each pixel region; A switching element disposed in each pixel region to transfer a signal of each signal line to each pixel electrode; A storage capacitor electrode formed in the same mask pattern as the pixel electrode and overlapping the entire area of the pixel electrode with an insulating layer; And And a common signal line which is independently wired from the gate line and driven independently of each gate line, and is connected directly to the auxiliary capacitor electrode. The liquid crystal display of claim 1, wherein the storage capacitor electrode is made of the same transparent conductive film as the pixel electrode. The liquid crystal display of claim 1, wherein the common signal line is formed of the same material as the gate line. The method of claim 1 or 3, wherein the common signal line, The liquid crystal display of claim 1, wherein the liquid crystal display is formed so as not to overlap with the pixel electrode except for a minimum area required for connection with the storage capacitor electrode in order to improve an aperture ratio of the device. Depositing a first transparent conductive film on the transparent substrate and patterning the substrate using a mask for forming a pixel electrode to form a storage capacitor electrode; Depositing and patterning a first metal on the resultant to simultaneously form a common signal line directly connected to a gate line and the storage capacitor electrode; Forming a gate insulating layer, a semiconductor layer, and an ohmic contact layer in turn on the resultant, and then patterning the ohmic contact layer and the semiconductor layer to remain only near the intersection of each signal line; Stacking and patterning a second metal layer on the resultant to form a source / drain of a plurality of data lines and a switching device; Forming a contact hole exposing a portion of the source or drain after laminating a protective film on the resultant; And And depositing a second transparent conductive film on the resultant and patterning the same using the same mask used to form the storage capacitor electrode to form a pixel electrode. The method of claim 5, wherein the first transparent conductive film of the storage capacitor electrode and the second transparent conductive film of the pixel electrode are formed of one of ITO, ZnO, and TiO. The method of claim 5, wherein the common signal line, A method of manufacturing a liquid crystal display device, characterized in that it is formed so as not to overlap with the pixel electrode except for the minimum area required for connection with the storage capacitor electrode in order to improve the aperture ratio of the device.