KR20030094752A - Liquid crystal display and fabrication method for thereof - Google Patents

Abstract

PURPOSE: A liquid crystal display and a method for manufacturing the same are provided to reduce image distortion caused due to cross-talk by lowering capacitance of data line to pixel. CONSTITUTION: A first substrate includes pixel electrodes(340) and TFT(Thin Film Transistor)s(330) formed at cross areas of gate lines(310b) and data lines(320a), and auxiliary electrode lines(350) additionally formed between the data lines and the pixel electrodes. A second substrate is opposite to the first substrate, and includes a color filter layer and an opposite electrode. A liquid crystal layer is formed between the first substrate and the second substrate.

Description

Liquid crystal display and manufacturing method thereof

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device and a manufacturing method thereof, and more particularly, to an active liquid crystal display device using a thin film transistor (TFT) as a switching element of each pixel, and a method of manufacturing the same.

Today, as the assumption of building a multimedia environment for use with the development of information and communication technology such as high speed internet network is increasing, the importance of the display field for processing and displaying a large amount of information is increasing. In particular, a display device suitable for a multimedia use environment must satisfy the requirements of miniaturization, light weight, low power consumption, and the like, and one of them has recently attracted attention.

A liquid crystal display device includes a lower plate on which TFTs and pixel electrodes are arranged, a lower plate facing the lower plate, a top plate on which a color filter and a counter electrode are formed, and a liquid crystal layer injected between both substrates. It is a display device using the electro-optic properties of the injected liquid crystal molecules.

FIG. 1 is a view showing a pixel portion formed on a lower plate of a conventional liquid crystal display, and FIG. 2 is a view showing an equivalent circuit for the pixel portion of FIG.

1 and 2, a plurality of gate lines 110 are formed in a horizontal direction, a plurality of data lines 120 are formed in a vertical direction, and the scan lines 110 are formed on the substrate. ) And the TFT 130 and the pixel electrode 140 are formed at the intersection of the signal line 120 and the signal line 120. (In practice, 130 represents the 'active area' of the TFT, but will be defined herein as referring to the TFT including the active layer.)

The TFT 130 may include a gate G, a source S, and a drain;

D) A semiconductor device having a terminal, the gate terminal of which is connected to the scan line 110, the source terminal of which is connected to the signal line 120, and the drain terminal of which is connected to the pixel electrode 140. The TFT 130 switches on and off the source and the gate according to the voltage applied to the gate terminal to charge or discharge the charge to the pixel electrode 140 connected to the drain terminal. Function as an element

In addition, the pixel electrode 140 generates an electric field together with the counter electrode (not shown) formed on the upper plate, thereby changing the arrangement of the liquid crystal molecules positioned therebetween, thereby controlling the amount of light passing through the liquid crystal molecules. To be implemented. In this case, a liquid crystal capacitor, that is, C _lc is formed in the liquid crystal molecule layer between the pixel electrode 140 and the counter electrode (not shown).

Meanwhile, a parasitic capacitance, that is, a capacitance of data line to pixel (C _dp ), is generated between the signal line 120a and the pixel electrode 140.

In general, when a gray voltage is applied to the signal line 120a, the voltage of the pixel electrode 140 (hereinafter, referred to as a 'pixel voltage') is changed by the C _dp . At this time, the change amount of the pixel voltage increases as the C _dp increases and the change amount of the gradation voltage applied to the signal line 120a increases. Due to this phenomenon, when C _dp increases, cross talk occurs. More details about this are as follows.

For example, when the gradation voltage is increased to charge a specific pixel with a high gradation voltage, other pixels on the same scan line are affected by the C _dp to have a higher pixel voltage than the original. Except for the pixel intended by this crosstalk, the same display data should be the same luminance as the original display data, but are actually displayed with different luminance. That is, the original image is distorted and output.

As described above, C _dp causes crosstalk to cause image distortion. However, the conventional technique has a limitation in reducing this, which is a fundamental problem that makes it difficult to manufacture a liquid crystal display device that provides a high quality image. there was.

SUMMARY OF THE INVENTION An object of the present invention is to provide a liquid crystal display device having less distortion of an image screen due to crosstalk by further forming an auxiliary electrode line between a signal line and a pixel electrode to reduce C _dp .

In addition, another object of the present invention is to provide a method of manufacturing a liquid crystal display device having a low distortion of the image screen due to crosstalk by further forming an auxiliary electrode line between the signal line and the pixel electrode to reduce C _dp .

1 is a view showing a pixel portion formed on a lower plate of a conventional liquid crystal display device.

FIG. 2 is a diagram illustrating an equivalent circuit for the pixel portion of FIG. 1. FIG.

3 is a view illustrating a lower plate configuration of a liquid crystal display according to an exemplary embodiment of the present invention.

4 is an enlarged view of A of FIG. 3;

FIG. 5 is a cross-sectional view of a substrate taken along the line a-a of FIG. 4. FIG.

6A to 6D illustrate a manufacturing process of a liquid crystal display according to an exemplary embodiment of the present invention.

7 is a view showing a lower plate configuration of a liquid crystal display according to another embodiment of the present invention.

FIG. 8 is an enlarged view of B of FIG. 7; FIG.

FIG. 9 is a cross-sectional view of a substrate taken along the line b-b of FIG. 8. FIG.

FIG. 10 is a cross-sectional view of the substrate of FIG. 8 taken along line c-c. FIG.

11 is a view for explaining a reduction effect of C _dp by additionally forming an auxiliary electrode line in the present invention.

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

110, 310, 710 ... scan lines 120, 320, 720 ... signal lines

130, 330, 730 ... TFT140, 340, 740 ... pixels

350, 750 ... Secondary electrode line 510, 910 ... Substrate

520, 920 ... gate 530, 930 ... insulating layer

540, 550 ... active layer 560, 960 ... source / drain

570, 970 ... shield 575, 975 ... contact hole

940, 950 ... first active layer 980, 990 ... second active layer

According to an aspect of the present invention, there is provided a display device including: a first substrate having a pixel electrode and a TFT formed at an intersection region of a scan line and a signal line, and further comprising an auxiliary electrode line between the signal line and the pixel electrode; A second substrate facing the first substrate and having a color filter layer and an opposite electrode formed thereon; And a liquid crystal layer formed between the first substrate and the second substrate. It is configured to include.

Here, the auxiliary electrode line is formed of a conductive material for forming the source / drain of the TFT, is formed on the active layer of the TFT, and is formed to have an overlapping area of a predetermined size or more with the gate of the TFT.

Therefore, when the TFT is on, a pixel voltage is applied to the auxiliary electrode line through the active layer, and when the TFT is off, the pixel voltage is formed by a capacitor formed by overlapping the auxiliary electrode line with the gate. Is maintained.

According to the present invention for achieving the above object, a pixel electrode and a first TFT are formed in an intersection region of a scan line and a signal line, and an auxiliary electrode line is further formed between the signal line and the pixel electrode, and the auxiliary electrode line and the pixel electrode are formed. A first substrate having a second TFT further formed therebetween; A second substrate facing the first substrate and having a color filter layer and an opposite electrode formed thereon; And a liquid crystal layer formed between the first substrate and the second substrate. It is configured to include.

Here, the second TFT is formed such that the auxiliary electrode line and the pixel electrode function as sources and drains, and the gate of the first TFT functions as a common gate.

According to another aspect of the present invention, there is provided a method of manufacturing a first and second substrates for a liquid crystal display device; Forming a scan line and a signal line crossing each other on the first substrate, forming a TFT and a pixel electrode in the cross region, and forming an auxiliary electrode line between the signal line and the pixel electrode; Forming a counter electrode and a color filter layer facing the pixel electrode on the second substrate; And bonding the first substrate and the second substrate to form a cell gap between the two substrates. It is made, including.

In the present invention, the total parasitic capacitance C _dp between the signal line and the pixel electrode is formed by the series coupling of the first parasitic capacitance between the signal line and the auxiliary electrode line and the second parasitic capacitance between the auxiliary electrode line and the pixel electrode. Is determined.

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

FIG. 3 is a view illustrating a lower plate configuration of a liquid crystal display according to an exemplary embodiment of the present invention, and FIG. 4 is an enlarged view of A of FIG. 3.

3 and 4, a scan line 310 is formed in a horizontal direction on the substrate, a signal line 320 is formed in a vertical direction crossing the scan line 310, and the scan line 310 and the signal line ( The TFT 330 and the pixel electrode 340 are formed in the intersection area of the 320 to form a pixel.

The TFT 330 is a semiconductor device having a source S, a drain D, and a gate G. The TFT 330 is turned on in response to a driving signal provided through a scan line 310b connected to a gate. A switching operation of turning on / off is performed, and a gray level signal provided to the signal line 320a is applied to the pixel electrode 340 to charge the pixel electrode 340 to a constant voltage or to adjust the charged voltage. It plays a role of confining for a certain time.

In particular, an auxiliary electrode line 350 is formed between the signal line 320a and the pixel electrode 340 on the substrate.

5 is a cross-sectional view illustrating a state in which the substrate of FIG. 4 is cut along aa line, and the gate electrode 520, the insulating layer 530, and the active layers 540 and 550 are sequentially stacked on the substrate 510. A source 560a, a drain 560b, and an auxiliary electrode line on the active layer 550;

350 is formed.

Here, the source 560a and the drain 560b may exchange their functions. That is, since the source 560a may function as a drain and the drain 560b may function as a source, the positions 560a may be interchanged with each other. Hereinafter, the source and the drain to be described are all used in this sense.

The auxiliary electrode line 350 is formed on the active layer 550 between the source 560a and the drain 560b and formed together with the source 560a and the drain 560b using a source / drain metal. It is preferable.

Meanwhile, the auxiliary electrode line 350 and the pixel electrode 340 maintain the same voltage. As such, the reason why the voltages are equal to each other is that the voltage change of the auxiliary electrode line 350 may affect the voltage of the pixel electrode 340 due to the parasitic capacitance between the two, thereby changing the original pixel voltage. The principle in which the auxiliary electrode line 350 and the pixel electrode 340 maintain the same voltage will be described below.

When the TFT 330 is turned on by the driving signal applied to the gate electrode 520, that is, when the source 560a and the drain 560b are turned on, the gray level provided to the signal line 320a of FIG. 4. The voltage is applied to the pixel electrode 340 via the source 560a, the active layers 550 and 540, and the drain 560b.

) And the auxiliary electrode line 350 via the source 560a and the active layers 550 and 540.

Subsequently, when the TFT 330 is off, the auxiliary electrode line 350 until the next on.

) And the voltage applied by the parasitic capacitance formed between the gate electrode 520 and the lower portion thereof, thereby maintaining the pixel voltage. At this time, in order to maintain the applied voltage more effectively, it is necessary to increase the area where the auxiliary electrode line 350 and the gate electrode 520 overlap with each other by a predetermined size or more.

Next, a manufacturing process of the liquid crystal display shown in FIG. 3 will be described with reference to FIGS. 6A to 6D.

First, as shown in FIG. 6A, a metal film 520a serving as a gate electrode is formed on the glass substrate 510 by sputtering, and a resist pattern 525 having a pattern shape corresponding to the gate electrode is formed thereon. When the etching is performed on the metal film 520a using this as an etching mask, the gate electrode 520 as shown in Fig. 6B is obtained.

Subsequently, the resist pattern 525 is removed, and a gate insulating layer 530, an i-layer (eg, a semiconductor layer made of undoped amorphous silicon) 540 on the gate electrode 520, and The active layers made of n layers (for example, semiconductor layers made of amorphous silicon doped with n-type impurities) 550 are sequentially stacked.

Thereafter, a metal film to be a source / drain is formed on the active layer 550 by sputtering, and a resist pattern 565 having a pattern shape corresponding to the source / drain and the auxiliary electrode line is formed thereon, which is then used as an etching mask. By performing selective etching on the metal film and the active layers 540 and 550, the source 560a, the drain 560a and the auxiliary electrode line 350 are formed as shown in FIG. 6C.

Thereafter, when the resist pattern 565 is removed, a passivation layer 570 is formed thereon, and a portion of the passivation layer 570 is etched, a contact hole 575 as shown in FIG. 6D is formed. Is formed. Subsequently, ITO (340 of FIG. 5) that is connected to the drain 560b through the contact hole 575 is deposited. The ITO 340 is a transparent conductor and functions as a pixel electrode 340 which generates an electric field in the liquid crystal layer between the two substrates together with the opposite electrode of the opposite substrate.

Through this manufacturing process, a lower plate of the liquid crystal display device as shown in FIG. 5 can be obtained. Then, a counter substrate having a color filter and a counter electrode is formed, and then a liquid crystal layer is formed between the two substrates to form a liquid crystal panel. do. A driving circuit portion for operating the liquid crystal panel is attached, and a known subsequent process such as a module process for attaching a backlight is sequentially performed to complete a practical liquid crystal display device.

FIG. 7 is a diagram illustrating a bottom plate configuration of a liquid crystal display according to another exemplary embodiment of the present invention, and FIG. 8 is an enlarged view of B of FIG. 7.

7 and 8, a scan line 710 is formed in a horizontal direction on the substrate, a signal line 720 is formed in a vertical direction crossing the scan line 710, and the scan line 710 and the signal line ( The first TFT 730 and the pixel electrode 740 are formed at the intersection of 720 to form a pixel.

In particular, an auxiliary electrode line 750 formed of ITO is formed between the signal line 720a and the pixel electrode 740 on the substrate, and the auxiliary electrode line 750 and the pixel electrode 740 are sourced and drained. A second TFT 760 is formed between the auxiliary electrode line and the pixel electrode. This will be described in more detail as follows.

First, FIG. 9 is a cross-sectional view illustrating a state in which the substrate of FIG. 8 is cut along a line bb. The gate terminal 920, the insulating layer 930, and the first active layers 940 and 950 are formed on the substrate 910. Formed sequentially, a source 960a and a drain 960b are formed thereon to form a first TFT, and a protective film 970 and a pixel electrode 740 are formed thereon. In this case, the pixel electrode 740 is electrically connected to the drain 960b through a contact hole formed by etching a portion of the passivation layer 970.

Next, FIG. 10 is a cross-sectional view illustrating a state in which the substrate of FIG. 8 is cut along the cc line, and the gate terminal 920, the insulating layer 930, and the protective film 970 are sequentially stacked on the substrate 910. The second active layers 980 and 990 are formed thereon.

Here, the second active layers 980 and 990 are, for example, undoped amorphous silicon (amorp)

a semiconductor layer having an i layer 980 composed of hous silicon and an n layer 990 composed of amorphous silicon doped with n-type impurities.

Meanwhile, the above-described second TFT 760 is formed by forming the auxiliary electrode line 750 and the pixel electrode 740 on both sides of the second active layer 990.

In this case, the auxiliary electrode line 750 and the pixel electrode 740 function as a source or a drain of the second TFT 760, and the gate terminal of the first TFT 730 is a gate terminal of the second TFT 760. It is common with. Accordingly, when the first TFT 730 is on, the second TFT 760 is also on. On the contrary, when the first TFT 730 is off, the second TFT 760 is also off. It becomes a state. That is, the second TFT 760 is driven together according to the driving signal of the first TFT 730.

On the other hand, the auxiliary electrode line 750 and the pixel electrode 740 maintain the same voltage, the principle is as follows.

First, when a driving signal is applied to the gate terminal 920 and the first TFT 730 and the second TFT 760 are turned on, the gray level voltage provided from the signal line is the source 960a and the first active layer 940 of FIG. 9.

950 is applied to the pixel electrode 740 via the drain 960b, which in turn serves as a source via the pixel electrode 740 and the second active layers 980 and 990 of FIG. 750 is applied.

Subsequently, when the driving signal applied to the gate terminal 920 is removed and the first TFT 730 and the second TFT 760 are turned off, the auxiliary electrode line 750 and the gate below the auxiliary electrode line are turned on until the next on. The pixel voltage is maintained by maintaining the voltage applied by the parasitic capacitance formed between the electrodes 920. In this case, as described above, in order to maintain the applied voltage more effectively, an area where the auxiliary electrode line 750 overlaps with the gate electrode 920 needs to be increased to a predetermined size or more.

Next, a manufacturing process of the liquid crystal display shown in FIG. 7 will be described with reference to FIGS. 9 to 10.

First, the first TFT 730, which functions as a switching element of each pixel, is formed on the substrate 910 by the number of pixels. In this case, a metal film serving as a gate is formed on the substrate 910 by the same method as described above, and the gate electrode 920 is formed by patterning the metal film. Subsequently, an insulating layer 930, a first active layer 940 and 950, and a metal film serving as a source / drain are sequentially formed on the substrate 910, and then selectively patterned to form a source 960a and a drain 960b. ), And a protective film 970 is formed thereon (see Fig. 9).

Subsequently, the auxiliary electrode line 750 and the pixel electrode 740 are formed on the substrate 910, and a second TFT 760 is formed to equalize each other. In this case, second active layers 980 and 990 having an i layer and an n layer are formed on the gate electrode 920 drawn in the first TFT (see FIG. 10). Subsequently, a portion of the passivation layer is etched to expose the drain 960b of the first TFT to form a contact hole 975 (see FIG. 9), and the contact hole 975 and the second active layer 980 and 990. ) And then selectively pattern the ITO film forming the auxiliary electrode line 750 and the pixel electrode 740 (see FIGS. 9 and 10). Here, the auxiliary electrode line 750 and the pixel electrode 740 function as a source / drain of the second TFT, and the auxiliary electrode line 750 and the gate electrode 920 function as a capacitor.

Through such a manufacturing process, a lower plate of the liquid crystal display device as shown in FIG. 9 can be obtained, and the substrate is completed in the liquid crystal display device through the subsequent steps of the aforementioned various steps.

As described above, in the above-described liquid crystal display device according to the present invention, C _dp generated between the pixel electrode and the signal line is smaller than before due to the auxiliary electrode line added therebetween. This will be described with reference to FIG. 11.

FIG. 11 is a view for explaining a reduction effect of C _dp by additionally forming an auxiliary electrode line according to the present invention. FIG. 11A is a bottom view of a conventional liquid crystal display without an auxiliary electrode line. The lower plate of the liquid crystal display according to the present invention further formed with an auxiliary electrode line.

Referring to FIG. 11A, C _dp = ε ₀ (A / d) in a conventional liquid crystal display substrate. Here, epsilon ₀ is the dielectric constant of the liquid crystal, d is a distance between the signal line 320a and the pixel electrode 340, and A is an area where the signal line 320a and the pixel electrode 340a face each other.

Referring to FIG. 11B, in the liquid crystal display substrate of the present invention, C _dp is a capacitance due to the series coupling of C ₁ and C ₂ . Here, C ₁ is the capacitance between the signal line and the auxiliary electrode line, C ₂ is the capacitance between the auxiliary electrode line and the pixel electrode, assuming that the auxiliary electrode line is located in the middle thereof, d = 1/2, so that C ₁ And C ₂ are ε ₀ (2 A / d), respectively. In general, the total capacitance according to the series coupling of the capacitor is C _total = (C ₁ × C ₂ ) / (C ₁ + C ₂ ), so C _dp = (ε ₀ (2A / d) × ε ₀ ( 2A / d)} / {ε ₀ (2A / d) + ε ₀ (2A / d)}. _Summarizing this, C _dp = 1/2 {ε ₀ (A / d)}, which is half the level of the conventional art described above.

Thus, the liquid crystal display device according to the present invention, because the C _dp less than the prior art, the generation of crosstalk due to C _dp significantly reduced.

As described above, the above embodiments are disclosed for the purpose of illustration, and those skilled in the art will appreciate that various modifications, improvements, substitutions, and additions may be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention should be defined by the appended claims.

The liquid crystal display device and its manufacturing method according to the invention as in the above description, by forming an additional auxiliary electrode line between the signal line and the pixel electrode allows reducing the parasitic capacitance i.e., C _dp generated therebetween. Therefore, the distortion of the video screen due to crosstalk is substantially improved.

Claims (15)

A first substrate having a pixel electrode and a TFT formed at an intersection area between the scan line and the signal line, and an auxiliary electrode line further formed between the signal line and the pixel electrode; A second substrate facing the first substrate and having a color filter layer and an opposite electrode formed thereon; And A liquid crystal layer formed between the first substrate and the second substrate; Liquid crystal display comprising a. The method of claim 1, And at least one auxiliary electrode line is formed between the signal line and the pixel electrode. The method of claim 1, And the auxiliary electrode line is formed of a conductive material for forming a source / drain of the TFT. The method of claim 1, And the auxiliary electrode line is formed on the active layer of the TFT and has an area overlapping with the gate of the TFT by a predetermined size or more. The method of claim 4, wherein When the TFT is on, a pixel voltage is applied to the auxiliary electrode line through the active layer. When the TFT is off, the pixel voltage is maintained by a capacitor formed by overlapping the auxiliary electrode line with the gate. Liquid crystal display device characterized in that. A first substrate having a pixel electrode and a first TFT formed at an intersection area between the scan line and the signal line, an auxiliary electrode line formed between the signal line and the pixel electrode, and a second TFT formed between the auxiliary electrode line and the pixel electrode; and; A second substrate facing the first substrate and having a color filter layer and an opposite electrode formed thereon; And A liquid crystal layer formed between the first substrate and the second substrate; Liquid crystal display comprising a. The method of claim 6, The auxiliary electrode line is formed of a conductive material for forming the pixel electrode. The method of claim 6, And the auxiliary electrode line is formed to have an area overlapping with the gate of the second TFT by a predetermined size or more. The method of claim 6, And wherein the second TFT is formed such that the auxiliary electrode line and the pixel electrode function as a source and a drain, and the gate of the first TFT functions as a common gate. The method according to claim 1 or 6, The total parasitic capacitance C _dp between the signal line and the pixel electrode is determined by a series coupling of the first parasitic capacitance between the signal line and the auxiliary electrode line and the second parasitic capacitance between the auxiliary electrode line and the pixel electrode. LCD display device. Providing first and second substrates for the liquid crystal display; Forming a scan line and a signal line crossing each other on the first substrate, forming a TFT and a pixel electrode in the cross region, and further forming an auxiliary electrode line between the signal line and the pixel electrode; Forming a counter electrode and a color filter layer facing the pixel electrode on the second substrate; And Bonding the first substrate and the second substrate to form a cell gap between the two substrates; Method of manufacturing a liquid crystal display device comprising a. The method of claim 11, And the auxiliary electrode line is formed of a conductive material for forming a source / drain of the TFT. The method of claim 11, Forming a second TFT in which the auxiliary electrode line and the pixel electrode function as a source and a drain, and the gate of the first TFT functions as a common gate; Method of manufacturing a liquid crystal display device further comprising. The method according to claim 11 or 13, And the auxiliary electrode line is formed of a conductive material for forming a pixel electrode. The method of claim 13, The auxiliary electrode line and the gate of the second TFT is formed to have an overlapping area of a predetermined size or more.