KR100372304B1 - Thin film transistor liquid crystal display and method for fabricating the same - Google Patents

Abstract

A field effect transistor having a gate terminal connected to the gate line and a source terminal connected to the data line,

A first storage capacitor connected between the drain terminal of the field effect transistor and the common electrode line;

And a second storage capacitor connected between the drain terminal of the field effect transistor and the front gate line.

A thin film transistor liquid crystal display device having an effect of preventing the reduction of the aperture ratio by forming a storage capacitor under the front gate electrode and suppressing an increase in parasitic capacitance generated when the storage capacitor is formed using only the front gate electrode. And a method for producing the same.

Description

Thin film transistor liquid crystal display device and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor liquid crystal display and a method of manufacturing the same. More specifically, in the case of forming a storage capacitor using only the front gate electrode while preventing the reduction of the aperture ratio by forming the storage capacitor under the front gate electrode. The present invention relates to a thin film transistor liquid crystal display device and a manufacturing method thereof capable of suppressing an increase in parasitic capacitance.

Currently, an active matrix liquid crystal display (AMLCD) using a thin film transistor as a switching element has been widely spotlighted for its portability and excellent image quality.

Thin Film Transistor (TFT) A liquid crystal display panel is a liquid crystal in which a transistor is incorporated in each pixel of a liquid crystal display. The transistor is formed of a thin film of amorphous silicon or the like on a glass substrate, and TN (Twisted Nematic) liquid crystal is used as the liquid crystal material.

The thin film transistor liquid crystal display panel has an advantage that crosstalk does not occur because only a pixel for inputting a signal can be turned on by operating a transistor of each pixel. In addition, since each pixel has a storage capacitor made of a thin film, the charge is accumulated therein, and thus there is an advantage that the display can be preserved even during the non-selection period.

Such a thin film transistor liquid crystal display device should have excellent optical characteristics, have high contrast, low flicker, and no image sticking. The characteristics required for the pixel in order to satisfy this are as follows.

1) charge / discharge time of pixels

The signal must be able to be written to the pixel within the given write time. This is related to the capacitance of the pixel, the applied signal voltage, the ON characteristic of the switching element, and the like.

2) signal delay

Insufficient charge and discharge of the pixel due to distortion of the signal due to the delay in propagation of the gate voltage or the data signal voltage causes problems such as resistance and parasitic capacitance of each signal line.

3) Signal voltage holding characteristic

The pixel must maintain the signal voltage well during the off time. This relates to the off resistance of the switching element, the resistance of the liquid crystal, the total capacitance of the pixel, and the like.

4) reduction of parasitic capacity

The parasitic capacitance of the switching element is the main cause of the level shift in the signal voltage entering the pixel. Therefore, it is necessary to sufficiently reduce such parasitic capacitance or to sufficiently increase the total electric total amount of the pixel mainly on the capacitance of the storage capacitor.

In the above description, the total capacitance of the pixel is represented by the sum of the capacitance of the liquid crystal formed between the pixel electrode and the opposite electrode, the capacitance of the storage capacitor, and the parasitic capacitance of the thin film transistor.

As mentioned above, in order to improve the image quality by maintaining the signal voltage well during off time or by reducing the level shift or flicker, it is necessary to increase the total capacitance of the pixel, which is mainly controlled by the size of the storage capacitor. Will be

Hereinafter, a liquid crystal display device according to the related art will be described with reference to the accompanying drawings.

1 is a pixel configuration diagram of a conventional liquid crystal display device of a common electrode line type thin film transistor,

2 is a diagram illustrating a pixel configuration of a conventional thin film transistor liquid crystal display device using a front-end gate line method.

There are two methods for forming the storage capacitor of the pixel. The first method is to separately prepare a common electrode line to form the storage capacitor Cst, as shown in FIG. 1, and the second is shown in FIG. As described above, the front gate line is used as one electrode of the storage capacitor Cst.

However, the method using the common electrode line as shown in FIG. 1 has the advantage that the parasitic capacitance of the gate line is reduced, while the number of wiring lines is increased. In addition, in this method, since the common electrode line is added, the opening ratio is reduced by the common electrode line.

As shown in FIG. 2, when the front gate line is used, an additional common electrode line is not required in addition to the gate line, and thus the aperture ratio may be increased. The pixel structure without the separate common electrode line is shown in US Patent No. 4,114,070 (Patent Date: September 12, 1978 AD).

As the diagonal length of the liquid crystal display device becomes smaller and becomes more precise, the area of the pixel is reduced, and it becomes difficult to secure necessary storage capacitance. Therefore, the technique for securing the aperture ratio is preferable as in the conventional structure using the shear gate line, but in such a conventional structure there is a problem that the parasitic capacitance of the gate line increases.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned disadvantages, which is generated when the storage capacitor is formed using only the front gate electrode while preventing the reduction of the aperture ratio by forming the storage capacitor under the front gate electrode. The present invention provides a thin film transistor liquid crystal display device and a method for manufacturing the same, which can suppress an increase in parasitic capacitance.

As a means for achieving the above object, the configuration of the pixel circuit of the present invention,

A field effect transistor having a gate terminal connected to the gate line and a source terminal connected to the data line,

A first storage capacitor connected between the drain terminal of the field effect transistor and the common electrode line;

And a second storage capacitor connected between the drain terminal of the field effect transistor and the front gate line.

As a means for achieving the above object, the configuration of the method of the present invention,

Forming a common electrode line on the substrate together with the gate pattern;

Depositing an insulating film and a silicon n + layer in order, and then depositing indium tin oxide (ITO) to form a transparent electrode;

After forming the transparent electrode pattern, depositing a metal for source / drain electrodes, and then forming a pattern;

Removing the n + layer between the source / drain electrodes and depositing a protective film,

A storage capacitor is formed between the common electrode line and the ITO, and at the same time, the storage capacitor is formed between the front gate line and the ITO.

As a means for achieving the above object, the configuration of another method of the present invention,

After depositing amorphous silicon on the substrate, forming polysilicon by forming polysilicon through various well-known methods such as low temperature crystallization process;

Forming a gate oxide film by a thermal oxidation process in a high temperature process and a deposition method in a low temperature process, and then depositing polysilicon for a gate pattern;

Forming a gate pattern and a common electrode line after the doping process to lower the resistance of the deposited polysilicon;

Forming a contact hole after coating an oxide film for the interlayer insulating film,

Forming an electrode by depositing ITO, depositing a metal for data wiring and an electrode, forming a pattern, and then forming a protective film,

A storage capacitor having an electrode separated by a gate insulating film is formed between the common electrode line, the gate electrode of the front end, and the polysilicon electrode.

Hereinafter, the most preferred embodiments of the present invention will be described with reference to the accompanying drawings so that those skilled in the art can easily implement the present invention.

3 is a block diagram illustrating a pixel circuit of a thin film transistor liquid crystal display according to an exemplary embodiment of the present invention.

As shown in FIG. 3, the pixel circuit of the thin film transistor liquid crystal display according to the embodiment of the present invention includes a field effect transistor having a gate terminal connected to a gate line and a source terminal connected to a data line; A first storage capacitor Cst connected between the drain terminal of the field effect transistor and the common electrode line, and a second storage capacitor Cst connected between the drain terminal of the field effect transistor and the front gate line. )

4 is a pixel structure diagram of an amorphous silicon thin film transistor liquid crystal display device according to an exemplary embodiment of the present invention.

5 is a cross-sectional view taken along line AA ′ of FIG. 4.

4 and 5, the amorphous silicon thin film transistor liquid crystal display device according to the embodiment of the present invention,

Forming a common electrode line 3 together with the gate pattern 2 on the substrate 1,

After depositing the insulating film 4 and the silicon n + layer in sequence, depositing ITO 5 to form a transparent electrode,

After forming the transparent electrode pattern 5, depositing a metal for source / train electrodes, and then forming a pattern;

By removing the n + layer between the source and train electrodes and depositing the protective film 6,

The storage capacitor is formed between the common electrode line 3 and the ITO 5, and at the same time, the storage capacitor Cst is formed between the gate line 2 and the ITO 5 at the front end.

6 is a pixel structure diagram of a polysilicon thin film transistor liquid crystal display device according to an exemplary embodiment of the present invention.

7 is a cross-sectional view taken along the line B-B 'of FIG.

FIG. 8 is a cross-sectional view taken along line CC ′ of FIG. 6.

6 to 8, the polysilicon thin film transistor liquid crystal display according to the embodiment of the present invention,

After depositing amorphous silicon on the substrate 11, forming silicon pattern 12 by making polysilicon through various well-known methods such as low temperature crystallization process,

Forming a gate oxide film 13 by about 1000 으로 by a thermal oxidation process in a high temperature process and a deposition method in a low temperature process, and then depositing polysilicon for a gate pattern and a common electrode line;

After the doping process to lower the resistance of the deposited polysilicon, forming a gate pattern 14 and a common electrode line 14 -A,

Coating an oxide film for the interlayer insulating film 15 to a thickness of about 8000 Å and forming a contact hole;

By depositing the ITO 16 to form the electrode, depositing the data wiring and the metal for the electrode, forming the pattern, and then forming the protective film 17,

A storage capacitor Cst having an electrode separated by the gate insulating film 13 is formed between the common electrode line 14 -A and the gate line 14 at the front end and the active layer polysilicon electrode 12. At this time, a capacitor by an interlayer insulating film is automatically generated between the common electrode line 14 -A and the gate line 14 and ITO 16 at the front end.

The thin film transistor liquid crystal display device and its manufacturing process according to the embodiment of the present invention having the above-described configuration are as follows.

First, the amorphous silicon thin film transistor liquid crystal display shown in FIGS. 4 and 5 will be described. In an amorphous silicon thin film transistor liquid crystal display device, it has a bottom gate type structure in which the gate of a thin film transistor is located below.

First, the gate pattern 2 is formed in the substrate 1. At this time, the common electrode line 3 is also formed at the same time.

Next, after the insulating film 4 and the silicon n + layer are sequentially deposited, ITO 5 is deposited to form a transparent electrode.

After forming the transparent electrode pattern 5, the metal for source / drain electrodes is deposited, and then a pattern is formed.

Next, the n + layer between the source / drain electrodes is removed, and the protective film 6 is finished after the deposition process.

In this case, the storage capacitor is formed between the common electrode line 3 and the ITO 5, and at the same time, it is formed between the gate line 2 and the ITO 5 at the front end.

Next, the polysilicon thin film transistor liquid crystal display device shown in FIGS. 6 to 8 will be described. In the polysilicon thin film transistor liquid crystal display device, it has a top gate type structure in which the gate of the thin film transistor is located above.

In most cases, polysilicon is deposited on the substrate 11 by low pressure chemical vapor deposition (LPCVD) or the like at a temperature of 540 ° C. To form a silicon pattern 12.

At this time, the silicon pattern 12 is formed in the portion where the channel of the thin film transistor and the storage capacitor are to be formed, as shown in FIG.

In the case of the high temperature process, the gate oxide film 13 is formed by about 1000 mV by the thermal oxidation process, and in the case of the low temperature process, polysilicon deposition is performed for the gate pattern.

Next, the gate pattern 14 is formed after the coating process to lower the resistance of the deposited polysilicon. The gate pattern 14 may use a metal in a low temperature process.

At this time, the gate electrode 14 and the counter electrode common electrode line 14 -A for forming the wiring and the storage capacitor Cst are simultaneously formed.

Subsequently, an oxide film for the interlayer insulating film 15 is coated to a thickness of about 800 GPa, and then contact holes are formed as shown in FIG.

After the formation of the contact hole, the ITO 16 is deposited to form an electrode. After depositing the data wiring and the metal for the electrode and forming the pattern, the process is completed by forming the protective film 17.

At this time, a storage capacitor Cst having an electrode separated by the gate insulating layer 13 is formed between the common electrode line 14 -A, the gate line 14 at the front end, and the silicon electrode 12. At this time, a storage capacity having electrodes separated by the interlayer insulating film 15 is also formed in parallel between the common electrode line 14 -A and the gate line 14 and the ITO electrode 16 at the front end.

As described above, in the embodiment of the present invention, the storage capacitor is prevented from being formed by forming the storage capacitor under the front gate line, and at the same time, the increase in parasitic capacitance generated when the storage capacitor is formed using only the front gate electrode is suppressed. A thin film transistor liquid crystal display device having an effect which can be achieved and a method of manufacturing the same can be provided. This effect of the present invention can be used in the fields of design, manufacture, sale, etc. of thin film transistor liquid crystal display devices.

1 is a configuration diagram of a pixel circuit of a conventional thin film transistor liquid crystal display device having a common electrode line method.

2 is a block diagram of a pixel circuit of a conventional thin film transistor liquid crystal display device using a front-end gate line method.

3 is a configuration diagram of a pixel circuit of a thin film transistor liquid crystal display device according to an exemplary embodiment of the present invention.

4 is a pixel structure diagram of an amorphous silicon thin film transistor liquid crystal display device according to an exemplary embodiment of the present invention.

5 is a cross-sectional view taken along the line A-A 'of FIG.

6 is a pixel structure diagram of a polysilicon thin film transistor liquid crystal display device according to an exemplary embodiment of the present invention.

7 is a cross-sectional view taken along the line B-B 'of FIG.

FIG. 8 is a cross-sectional view taken along line CC ′ of FIG. 6.

Claims (5)

Insulating substrate; A gate line formed on the insulating substrate; A common electrode line formed on the insulating substrate; A data line insulated from and intersecting the gate line and the common electrode line; A field effect transistor having a gate terminal connected to the gate line and a source terminal connected to the data line; A first storage capacitor connected to the common electrode line of the drain terminal of the field effect transistor; And A second storage capacitor connected to the drain terminal of the field effect transistor and the front gate line of the gate line Thin film transistor liquid crystal display comprising a. Forming an insulating substrate; Forming a gate pattern including a gate electrode and a gate line on the insulating substrate; Forming a common electrode line on the insulating substrate; Forming a gate insulating layer on the gate pattern and the common electrode line; Forming a semiconductor layer on the gate insulating film; Forming a data pattern on the gate insulating layer, the data pattern including a data line and a source electrode and a drain electrode in contact with the semiconductor layer; And Forming a passivation layer formed on the data pattern; forming a first storage capacitor between the common electrode line and the drain electrode; and a second storage between the front gate line of the gate line and the drain electrode. A method of manufacturing a thin film transistor liquid crystal display device further comprising the step of forming a capacitor. Insulating substrate; A gate line formed on the insulating substrate; A common electrode line formed on the insulating substrate; A data line insulated from and intersecting the gate line and the common electrode line; A pixel electrode insulated from the common electrode line and the gate line and overlapping at least a portion of the common electrode line and the gate line; And A thin film transistor electrically connected to the gate line, the data line, and the pixel electrode Liquid crystal display comprising a. Insulating substrate; A gate pattern formed on the insulating substrate and including a gate electrode and a gate line; A common electrode line formed on the insulating substrate; A gate insulating film formed on the gate pattern and the common electrode line; A semiconductor layer formed on the gate insulating film; A data pattern including a data line formed on the gate insulating layer, a source electrode and a drain electrode in contact with the semiconductor layer; A passivation layer formed on the data pattern; And A pixel electrode formed on the passivation layer and at least partially overlapping the common electrode line and the gate line; Liquid crystal display comprising a. Insulating substrate; A polycrystalline silicon layer formed on the insulating substrate; A gate insulating film formed on the polycrystalline silicon layer; A gate pattern formed on the gate insulating film; A common electrode line formed on the gate insulating film; An interlayer insulating layer formed on the gate pattern and the common electrode line; A data pattern formed on the interlayer insulating film; And A pixel electrode formed on the interlayer insulating layer and at least partially overlapping the common electrode line and the gate pattern; Liquid crystal display comprising a.