JPH0588200A - Liquid crystal display device and its manufacture - Google Patents

Abstract

PURPOSE:To provide the liquid crystal display device which has superior display characteristics such as a numeric aperture. CONSTITUTION:This liquid crystal display device is equipped with picture element electrodes 4 arrayed in matrix on a substrate 1, a picture element electrode protection film 6 provided on the picture element electrodes 4, a black matrix 7 which is formed in an area other than the picture element electrode protection film 6, thin film transistors as switching elements provided to the respective picture element electrodes 4, gate lines 2 connected to the gates of the thin film transistors of the same row, and signal lines 5 connected to the source and drain of one thin film transistor of the same column.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device and a manufacturing method thereof.

[0002]

2. Description of the Related Art An active matrix type liquid crystal display device is not only thin and lightweight like other liquid crystal display devices, but also has no deterioration in contrast and response even if it has a large number of pixels. Since it has features such as display capability, it is expected as a display device for personal computers and large-screen color televisions.

FIG. 7 is a sectional view of one pixel of a conventional active matrix type liquid crystal display device using a thin film transistor (TFT) as a switching element, and FIG. 8 is a plan view of one pixel of the liquid crystal display device. ..

This liquid crystal display device has a basic structure composed of an array substrate 67 and a counter substrate 68 made of two flat glasses, and a liquid crystal layer 55 sandwiched between these substrates 67 and 68. The array substrate 67 is the translucent insulating substrate 51.
A transparent pixel electrode 54 arranged in a matrix on the substrate 51, and a T connected to the pixel electrode 54.
It consists of FT69 etc. The gate electrode 52 of this TFT 69
Is connected to a gate line 65, the drain electrode 63 is connected to a signal line 66 provided in a direction perpendicular to the gate line 65,
The source electrode 64 is connected to the pixel electrode 54. On the other hand, the counter substrate 68 is a translucent insulating substrate 59 and a color filter corresponding to each pixel formed on the substrate 59.
57, a translucent counter electrode 56, and a black matrix 58. The TFT 69 is normally produced as follows.

First, a gate is formed on the translucent insulating substrate 51.
A low resistance metal film such as Mo or Mo-Ta that will become the cathode electrode 52 is deposited by sputtering. Next, a gate electrode-shaped photoresist pattern is formed on the low resistance metal film, and the low resistance metal film is etched using this as a mask to form a gate electrode 52.

Next, as the gate insulating film 53, a silicon oxide film, a silicon nitride film, or a laminated film of these insulating films is deposited on the entire surface by plasma CVD or the like. Next, an amorphous silicon film to be the active layer 60 and a silicon nitride film to be the channel protection film 61 are sequentially deposited on the gate insulating film 53. Next, the amorphous silicon film and the silicon nitride film are patterned using photolithography to form an active layer 60 and a channel protection film 61.

Next, after forming a contact layer 62 on the active layer 60 and the channel protective film 61, the TFT portion is patterned in an island shape. Next, a transparent conductive film to be the pixel electrode 54,
For example, ITO (Indium Tin Oxide)
A film is deposited, and the film is patterned into a predetermined shape by photolithography to form a pixel electrode 54, and then a through hole for capturing a contact of the gate electrode 65.
Open the door. Finally, an electrode material such as Al is deposited on the substrate 51 and patterned into a predetermined shape to form a drain electrode 63 and a source electrode 64.

In the above-mentioned TFT manufacturing method, various films and layers constituting the TFT are formed by using the photolithography technique. Therefore, the quality of the alignment between the mask patterns in the photolithography technique depends on the TFT.
Have a great influence on.

That is, in the method of manufacturing a TFT as described above,
Although about 6 to 7 photomasks are required, it is difficult to keep all the shifts between the photomasks within a predetermined accuracy, so that the TFT characteristics and display characteristics are deteriorated and the manufacturing yield is low. was there.

Further, in the conventional counter substrate 68, the black matrix 58 extends onto the pixel electrode 54. The liquid crystal layer 5 is formed by the array substrate 67 and the counter substrate 68.
This is because the margin is applied to the black matrix 58 so that the TFT 69 is covered with the black matrix 58 even if the array substrate 67 and the counter substrate 68 are deviated when holding 5.

The quality of the alignment between the black matrix 58 and the TFT 69 has a great influence on the characteristics and performance of the display device and the manufacturing cost. Therefore, it is necessary to introduce the alignment margin described above. Since the display area is smaller than that of the pixel electrode 54, the aperture ratio is reduced.

Therefore, in order to eliminate this kind of inconvenience, a manufacturing method using an electrolytic polymerization method has been proposed. In this method, the electrolytic polymerized film can be formed in a self-aligning manner with a desired electrode, so that it is possible to form an active layer and a black matrix having a desired shape without using photolithography.

However, in order to form a film without using photolithography, it is necessary to form an electrode having a complicated pattern, which causes a problem in the manufacturing process and the design process. Further, if the electrode pattern is simplified, such a problem does not occur, but it is necessary to remove an unnecessary electrolytically polymerized film, so that the photolithography process is indispensable. This causes a problem of misalignment between the photomasks, and the electrolytically polymerized film is made of a polymer material, which makes it difficult to perform patterning. As a result, it becomes impossible to perform fine processing with a required accuracy, resulting in reliability. There is also a problem that

[0014]

As described above, the conventional liquid crystal display device has a problem that the TFT characteristics and the display characteristics are deteriorated due to the displacement between the photomasks when the array substrate is formed, and the manufacturing yield is low. .. Further, a margin is provided in accordance with the black matrix so that the TFT is surely covered with the black matrix, but this causes a problem that the aperture ratio is lowered. Further, a method for forming a black matrix which does not require a composite margin using an electrolytic polymerization method has been proposed, but there is a problem in that manufacturing and designing becomes difficult because the electrode pattern becomes complicated.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a liquid crystal display device having excellent display characteristics which does not cause difficulties in manufacturing and designing, and a manufacturing method thereof. Especially.

[0016]

In order to achieve the above object, the liquid crystal display device of the present invention controls pixel electrodes arranged in a matrix, thin film transistors provided in each pixel electrode, and controlling the thin film transistors. In a liquid crystal display device having a gate line and a signal line for applying a desired voltage to a pixel electrode, a pixel electrode protective film formed on the pixel electrode and a region other than the pixel electrode protective film And a formed black matrix.

Further, according to the method of manufacturing a liquid crystal display device of the present invention, the pixel electrodes arranged in a matrix, the thin film transistors provided in each pixel electrode, and the thin film transistors are controlled to apply a desired voltage to the pixel electrodes. In a liquid crystal display device having a gate line and a signal line, a pixel electrode protective film is formed on the pixel electrode, and then a black matrix is formed on a region other than the pixel electrode protective film on the substrate by an electrolytic polymerization method. It is characterized by

[0018]

In the liquid crystal display device of the present invention, the black matrix is formed in a region other than the pixel electrode protective film. That is, since the thin film transistor is formed on the substrate, the black matrix and the thin film transistor array do not shift due to misalignment between the substrate and the counter substrate. Therefore, since it is not necessary to have a margin for the black matrix, it is possible to prevent the aperture ratio from lowering, thereby improving the display characteristics.

Further, in the method for manufacturing a liquid crystal display device of the present invention, since the pixel electrode protective film is provided on the pixel electrode, the black matrix can be formed in self-alignment with the pixel electrode protective film. Therefore, it is not necessary to design or manufacture a complicated electrode wiring, so that the display characteristics can be easily improved.

[0020]

EXAMPLE The structure of the liquid crystal display device of this example is basically the same as that of the conventional one, and a TFT as a switching element is used.
It has a basic configuration including an array substrate and a counter substrate including pixel electrodes and the like, and a liquid crystal layer sandwiched between the array substrate and the counter substrate. A feature of the liquid crystal display device of the present embodiment is that a pixel electrode protective film is provided on each pixel electrode arranged in a matrix, and a black matrix is formed in addition to the pixel electrode protective film.

FIG. 1 is a plan view of a manufacturing process of an array substrate of a liquid crystal display device according to this embodiment, FIG. 2 is a sectional view taken along the line AA ′ of the array substrate of FIG. 1, and FIG. ) BB
′ It is a cross-sectional view.

To make a liquid crystal display device as described above,
First, as shown in FIGS. 1 (a) and 2 (a), Mo or M to be the gate line 2 (gate electrode) is formed on the translucent insulating substrate 1.
A low resistance metal such as o-Ta is sputter-deposited and patterned to form a gate line 2. Next, the gate line 2 is covered with a gate insulating film 3 made of a silicon oxide film, a silicon nitride film, or a laminated film of these insulating films.

Next, a transparent conductive film which becomes the pixel electrode 4 and the source electrode, for example, ITO (Indium Tin O) is used.
xide) film is deposited on the substrate 1 and patterned by photolithography to form the pixel electrode 4. At this time, the transparent conductive film is patterned so that all the pixel electrodes 4 are electrically short-circuited with each other. Further, the width of the transparent electrode wiring 4a between the pixel electrodes 4 is set to the minimum width that can be processed, and the overlapping area between the gate line 2 and the pixel electrode 4 is made as small as possible. After that, a through hole for making contact with the gate line 2 is opened in the gate insulating film 3.

Then, as shown in FIGS. 1B and 2B, a metal film to be the signal line 5, such as a Mo / Al film or C, is formed.
A laminated metal film such as an r / Al film is deposited on the gate insulating film 3 and patterned by photolithography to form the signal line 5 having a predetermined pattern. Next, a pixel electrode protective film 6 made of an insulating film such as a silicon nitride film is formed on the pixel electrode 4.
To form. Next, the black matrix 7 is formed by using the electrolytic polymerization method. When this electrolytic polymerization method is performed by a three-electrode system, the signal line 5 and the pixel electrode 4 (transparent electrode wiring 4a) are used as working electrodes. At this time, by supplying a sufficiently large current to the working electrode, the black matrix 7 can be formed in all regions except the pixel electrode protective film 6. That is, the black matrix 7 can be formed in self-alignment with the pixel electrode protection film 6.

Here, since the black matrix 7 does not affect other films, it is necessary to ensure its insulating property. In order to ensure the insulating property of the black matrix 7, it may be reduced or oxidized depending on the material of the black matrix 7. For example, when the black matrix 7 is made of polypyrrole, the polypyrrole may be reduced. This is due to the property of polypyrrole that it exhibits good conductivity in the oxidized state but loses its conductivity in the reduced state. The pixel electrode protection film 6 also plays a role of preventing the influence of the reduction treatment or the oxidation treatment from reaching other films.

Then, as shown in FIGS. 1C, 2C, and 3, after depositing the protective film 8 on the entire surface, an opening is formed in the protective film 8 in the region to be the active layer 9. Then, the black matrix 7 in this opening is removed using a solvent. The black matrix 7 cannot be processed with high precision by ordinary photolithography, but by performing the removal processing of the opening portion with a solvent using a mask in this manner, high-precision processing can be performed. Next, the active layer 9 is formed by an electrolytic polymerization method using the signal line 5 and the pixel electrode 4 as working electrodes. At this time, since the protective film 8 is formed except the opening, the active layer 9
Are formed in self-alignment with the openings. Kotonoki Active Layer 9
Since the others are covered with the protective film 8, even if a voltage is applied to the working electrode to dope or de-dope the active layer 9 in order to secure the electrical characteristics of the active layer 9, Since only the active layer 9 is immersed in the electrolytic solution, the other films are not adversely affected.

Finally, after forming the channel protective film 10, in order to separate each pixel electrode 4, a through hole 11 is formed in a portion where the gate line 2 and the transparent electrode wiring 4a overlap each other.
To open. Since the width of the transparent electrode wiring 4a is made as small as possible as described above, the remaining transparent electrode wiring 4a
The parasitic capacitance formed by the gate line 2 and the gate line 2 becomes sufficiently small, and its influence can be ignored.

Thus, according to this embodiment, since the black matrix 7 can be formed on the array substrate in a self-aligning manner, the alignment margin of the black matrix 7 is not required, so that the reduction of the aperture ratio can be prevented. In addition, the active layer 9
Since it can be formed without using photolithography, the number of times of photomask alignment is reduced, so that TFT characteristics and display characteristics can be improved and reliability can be improved.

FIG. 4 is a plan view of an array substrate of a liquid crystal display device according to a second embodiment of the present invention, and FIGS. 5 and 6 are AA ′ and BB ′ of the array substrate of FIG. 4, respectively. FIG. 1 to 3 are denoted by the same reference numerals, and detailed description thereof will be omitted.

This will be described according to the manufacturing process.
When the gate line 2 is formed on the translucent insulating substrate 1, the auxiliary capacitance electrode 12 is also formed at the same time. At this time, as the shape of the auxiliary capacitance electrode 12, a shape that surrounds the pixel electrode 4 formed in a later step as shown in FIG. 4 is adopted.

Then, similarly to the previous embodiment, the gate insulating film 3, the pixel electrode 4, the signal line 5 and the pixel electrode protective film 6 are sequentially formed, and then a negative photoresist is applied to the back surface of the substrate 1. The photoresist is exposed by irradiating light from the gate line, and then the photoresist is developed.
The photoresist on the auxiliary capacitance electrode 12 can be selectively removed.

Next, the pixel electrode protective film 6 is etched using the remaining photoresist as a mask, and then the black matrix 7 is formed by electrolytic polymerization. Next, a protective film 8 is formed on the black matrix 7, and a negative photoresist is applied on the protective film 8. Then, a resist pattern is formed by backside exposure, the protective film 8 is removed by using this as a mask, and then the black matrix 7 under the removed protective film 8 is also removed. As a result, the gate line 2
Also, an opening having the same wiring width as the auxiliary capacitance electrode 12 can be formed in a self-aligning manner. Next, using an electrolytic polymerization method, activity 9
After forming the semiconductor layer to be the active layer 9, the semiconductor layer is patterned in the channel width direction to form the active layer 9.
At this time, the semiconductor layer 13 that does not function as an element is formed, but this does not affect the device at all and is left as it is. Finally, the channel protection film 10 is formed to complete the TFT.

Also in the case of this embodiment, the same effect as that of the above-mentioned embodiment can be obtained. Further, in this embodiment, the pixel electrode 4
Since the auxiliary capacitance electrode 12 that surrounds the pixel electrode protective film 6 is formed, the position of the pixel electrode protective film 6 can be accurately determined, and the black matrix 7 can be reliably formed in a predetermined region. In addition, since the protective film 8 is formed in self-alignment with the gate line 2,
As a result, the active layer 9 having an accurate dimension in the channel direction can be obtained. As a result, the TFT characteristics and display characteristics are further improved.

The present invention is not limited to the above embodiment. For example, in the above embodiment, the pixel electrode protective film is formed after forming the signal line, but the same effect can be obtained by forming the signal line after forming the pixel electrode protective film. Also, when a switching element other than the TFT is used, the black matrix can be similarly formed on the array substrate in a self-aligning manner. Besides, various modifications can be made without departing from the scope of the present invention.

[0035]

As described above in detail, according to the present invention, since the black matrix can be formed on the array substrate in a self-aligning manner, the alignment matrix of the black matrix and the complicated electrode are not necessary. The display characteristics such as the aperture ratio can be improved without causing any difficulty in the manufacturing process and the design process.

[Brief description of drawings]

FIG. 1 is a plan view of a manufacturing process of an array substrate of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view taken along the line AA ′ of the array substrate of FIG.

3 is a cross-sectional view of the array substrate of FIG. 1 taken along the line BB ′.

FIG. 4 is a plan view of an array substrate of a liquid crystal display device according to a second embodiment of the present invention.

5 is a cross-sectional view taken along the line AA ′ of the array substrate of FIG.

6 is a cross-sectional view taken along the line BB ′ of the array substrate of FIG.

FIG. 7 is a cross-sectional view of a conventional liquid crystal display device.

FIG. 8 is a plan view of a conventional array substrate.

[Explanation of Codes] 1 ... Transparent insulating substrate, 2 ... Gate line, 3 ... Gate insulating film, 4 ... Pixel electrode, 5 ... Signal line, 6 ... Pixel electrode protective film,
7 ... Black matrix, 8 ... Protective film, 9 ... Active layer, 1
0 ... Channel protective film, 11 ... Through hole, 12 ... Auxiliary capacitance electrode, 51 ... Translucent insulating substrate, 52 ... Gate electrode,
53 ... Gate insulating film, 54 ... Pixel electrode, 55 ... Liquid crystal layer,
56 ... Counter electrode, 57 ... Color filter, 58 ... Black matrix, 59 ... Translucent insulating substrate, 60 ... Active layer, 61 ... Protective film, 62 ... Contact layer, 63 ... Drain electrode, 64 ... Source Electrodes, 65 ... Gate lines, 66 ... Signal lines, 67 ... Array substrate, 68 ... Counter substrate, 69 ... TF
T.

Claims (2)

[Claims] 1. A pixel electrode arranged in a matrix on a substrate, a thin film transistor as a switching element provided on each pixel electrode, a pixel electrode protective film provided on the pixel electrode, and other than on the pixel electrode protective film. A black matrix formed in the region of, a gate line connected to the gates of the thin film transistors in the same row, and a signal line connected to one source / drain of the thin film transistors in the same column. A liquid crystal display device comprising: 2. A step of forming a gate line on a substrate, a step of forming a signal line and a pixel electrode, a step of forming a pixel electrode protective film on the pixel electrode, and the pixel by an electrolytic polymerization method. And a step of forming a black matrix in a region on the substrate other than the electrode protection film.