JPH04369623A - Active matrix type liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide an active matrix type liquid crystal display device excellent in display quality while easily improving the yield without altering the manufacture process. CONSTITUTION:In the active matrix type liquid crystal display device consists of a 1st substrate 11 where thin film transistors(TFT) 24 which have drain electrodes 20 serving also as data lines and gate electrodes 14 serving also as gate line are arranged at the respective intersections of data lines 19 and gate lines formed on an insulating substrate 12 while crossing each other, a 2nd substrate 31 where a counter electrode 33 is formed, and liquid crystal 41 sandwiched between the 1st substrate 11 and 2nd substrate 31, the gate lines and data lines 19 are formed in the same layers with electrodes which are closer to the insulating substrate 12 between the gate electrodes 14 or drain electrodes 20 except at the intersection part of them by using the same material.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix liquid crystal display device using thin film transistors (hereinafter abbreviated as TFTs) as switching elements.

0002

[Prior Art] Generally, liquid crystal display devices are used for television displays, graphic displays, etc., and the development of large-capacity, high-definition active matrix type liquid crystal display devices.
Practical applications are increasing. In this type of liquid crystal display device, semiconductor switches are used as means for driving and controlling each pixel so that high contrast display without crosstalk can be achieved.

TFTs are often used as semiconductor switches because they are capable of transmissive display and can easily be made to have a large area. FIG. 3 is a cross-sectional view of a conventional active matrix liquid crystal display device using an array of TFTs. , III-II in Fig. 4
4 shows a cross section corresponding to part I, and FIG. 4 is a plan view of a part of the first substrate in FIG. 3.

Reference numeral 11 in the figure is a first substrate, and this first substrate 11 has a gate line 13 on an insulating substrate 12 made of, for example, transparent glass, and a gate integrated with the gate line 13. −
A gate electrode 14 is formed, and an insulating film 16 is formed to cover the gate line 13 and gate electrode 14. Furthermore, a semiconductor layer 17 made of, for example, amorphous silicon is formed at a predetermined position on this insulating film 16, and a transparent pixel electrode 18 is formed at another predetermined position.

Further, a data line 19 made of aluminum, for example, which intersects with the gate line 13 on the insulating film 16, is formed.
a drain electrode 20 that is integrated with the tangent wire 19 and located on the semiconductor layer 17;
A source electrode 21 made of aluminum, for example, is formed to connect the transparent pixel electrode 18 and the transparent pixel electrode 18 .

[0006] An insulating protective film 22 is formed at a predetermined position on the insulating substrate 12 on which each element is arranged as described above, and a liquid crystal alignment film 23 is further formed over the entire upper surface of this film. In this way, the first substrate 11 is formed, and the gate electrode 14,
A TFT 24 consisting of a semiconductor layer 17, a drain electrode 20, and a source electrode 21 is formed.

On the other hand, the second substrate 31 has a transparent counter electrode 33 and a liquid crystal alignment film 34 formed in this order on an insulating substrate 32 made of glass, for example. The peripheral portions of the first substrate 11 and the second substrate 31 are sealed with a gap of about 6 μm maintained, and a liquid crystal 41 is sealed and held in this gap.

FIG. 5 shows an equivalent circuit of the above liquid crystal display device. That is, a plurality of gate lines 13 parallel to each other,
A TFT 24 is arranged at each intersection with a plurality of data lines 19 that are orthogonal to this and parallel to each other, and each gate electrode 14 of this TFT 24 is connected to the gate line 13 for each row. , each drain electrode 20 is connected to the data line 19 for each column, and each source electrode 21 is connected to each transparent pixel electrode 18, and a liquid crystal is connected between the transparent pixel electrode 18 and the transparent counter electrode 33. He is holding 41.

During operation, the gate lines 13 are sequentially scanned and driven by address signals, and the TFTs 24 are sequentially rendered conductive row by row. On the other hand, in synchronization with the scanning of the gate line 13, pixel signals are supplied to the data line 19 in parallel to the selected number columns. As a result, the signal voltage is sequentially guided to the transparent pixel electrode 18 row by row, and the liquid crystal 41 held between the transparent counter electrode 33 is excited and becomes an image signal to display an image.

0010

In the conventional active matrix type liquid crystal display device as described above, the protective film 22 cannot be formed at a sufficiently high temperature in order to avoid deterioration of the electrical characteristics of the TFT 24. Therefore, the protective film 22 is not necessarily a strong film. Therefore, foreign matter mixed in during the manufacturing process or a spacer for creating a gap may break through the protective film 22 and reach the data line 19. In this case, if the mixed foreign matter is conductive, the data line 19 and the transparent counter electrode 33 will be short-circuited, resulting in a line defect in the display. Furthermore, the liquid crystal 41 may deteriorate due to chemical or electrochemical reactions between it and the data line 19, resulting in local display defects.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an active matrix liquid crystal display device which can easily improve yield without changing the manufacturing process and at the same time has good display quality. .

0012

[Means for Solving the Problems] This invention provides a structure in which a plurality of data lines and a plurality of gate lines are formed on an insulating substrate so as to intersect with each other, and the data lines are connected to each intersection point. A first substrate on which a thin film transistor having a drain electrode that also serves as the drain electrode and a gate electrode that also serves as the gate line is disposed, and a second substrate that is disposed with a predetermined gap from the first substrate and has a counter electrode formed thereon. an active matrix liquid crystal display device comprising: a second substrate; and a liquid crystal sandwiched between the first substrate and the second substrate;

[0013] The gate line and the data line are in the same layer as either the gate electrode or the drain electrode near the insulating substrate at a portion other than the intersection thereof. These are active matrix liquid crystal display devices made of the same material.

[0014]

[Function] According to the present invention, the gate line and the data line are placed in the same layer as either the gate electrode or the drain electrode near the insulating substrate at the portion other than the intersection of the two. Since they are made of the same material inside, the wiring is confined under a sufficiently strong gate insulating film, and the protective film is prevented from being penetrated by foreign matter or spacers mixed in during the manufacturing process. As a result, an active matrix liquid crystal display device that can easily improve yield and have good display quality can be obtained without changing the manufacturing process.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail below with reference to the drawings.

FIG. 1 is a cross-sectional view of an active matrix liquid crystal display device of the present invention, showing a cross section corresponding to the section I-I in FIG. 2, and FIG. 2 is a plan view of a part of the first substrate in FIG. It is.

[0017] This liquid crystal display device is basically as shown in Figs.
It has the same configuration as the conventional liquid crystal display device shown in FIG. 5, and corresponding parts are given the same reference numerals and will be explained according to the manufacturing process.

First, the first substrate 11 is formed by depositing molybdenum to a thickness of 150 nm on an insulating substrate 12 made of, for example, transparent glass by sputtering.
Then, a gate electrode 14 integrated with this gate line 13 is patterned. At this time, a portion 19 of the data line, which will become a data line in a later process, is formed at the same time.

Next, gate wires 13 and
An insulating film 16 made of silicon dioxide, for example, is formed to a thickness of 300 mm by plasma CVD so as to cover the gate electrode 14.
Deposit to nm. Furthermore, amorphous silicon, for example, is deposited at a predetermined position on this insulating film 16 to a thickness of 300 nm by plasma CVD to form a pattern of a semiconductor layer 17. Next, a transparent pixel electrode 18 is formed at another predetermined position on the insulating film 16 by depositing, for example, ITO to a thickness of 150 nm by sputtering. Next, the insulating film 16
An opening 25 is opened at a predetermined position on the top to expose the material surface of the data line 19.

Furthermore, a data line 19 made of, for example, aluminum is connected to the insulating film 16 at a position intersecting with the gate line 13 through an opening 25, and a data line 19 is connected at a position on one side of the semiconductor layer 17. drain electrode 20, this drain electrode 2
0 and the other side of the semiconductor layer 17 and the transparent pixel electrode 18
A source electrode 2 made of, for example, aluminum and connected to
Form 1.

Next, after depositing an insulating protective film 22 made of silicon dioxide to a thickness of 200 nm on the entire surface of the insulating substrate 12 on which each element is arranged as described above, the upper surface of the transparent pixel electrode 18 at a predetermined position is The silicon dioxide is removed, and a liquid crystal alignment film 23 made of polymide is further coated on the entire upper surface.

In this manner, the first substrate 11 is formed, and the TFT 24 consisting of the gate electrode 14, the semiconductor layer 17, the drain electrode 20, and the source electrode 21 is formed on the first substrate 11. .

On the other hand, for the second substrate 31, a transparent counter electrode 33 made of ITO having a thickness of 100 nm and a liquid crystal alignment film 34 are sequentially formed on an insulating substrate 32 made of glass, for example. Then, the first substrate 11 and the second substrate 31 are
The peripheral portion is sealed with a gap of approximately μm maintained, and the liquid crystal 41 is further enclosed and held within this gap.

As shown in FIG. 5, a TFT 24 is placed at each intersection between a plurality of gate lines 13 parallel to each other and a plurality of data lines 19 perpendicular to the gate lines 13 and parallel to each other. Each gate electrode 14 of the TFT 24 is connected to the gate line 13 for each row, and each drain electrode 20 is connected to the data line 1 for each column.
9 and connect each source electrode 21 to each transparent pixel electrode 1.
Connect to 8.

As described above, since the data line 19 is formed of the same material in the same layer as the gate line 13, the data line 19
An insulating film 16 can be disposed on 9. As a result, foreign matter or spacers mixed in during the manufacturing process will not break through the protective film and reach the data line 19, and the causes of line defects and poor display quality can be eliminated.

[0026]

[Effects of the Invention] According to the present invention, the gate line and the data
Since the terminal wire is formed of the same material in the same layer as the gate electrode or the drain electrode, whichever electrode is closer to the insulating substrate, at a portion other than the intersection of the two, the gate electrode is sufficiently strong. The wiring is confined under the protective insulating film, and the protective film is prevented from being penetrated by foreign matter or spacers that get mixed in during the manufacturing process. As a result, without changing the manufacturing process,
An active matrix liquid crystal display device with easy improvement in yield and good display quality can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view taken along line I-I in FIG. 2 showing an active matrix liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a plan view showing a part of FIG. 1;

FIG. 3 is a sectional view taken along line III-III in FIG. 4 showing a conventional active matrix liquid crystal display device.

FIG. 4 is a plan view showing a part of FIG. 3;

FIG. 5 is an equivalent circuit diagram of the liquid crystal display device of FIGS. 3 and 4. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11... First substrate, 13... Gate line, 14... Gate electrode, 17... Semiconductor layer, 18... Transparent pixel electrode, 19... Data line, 20... Drain electrode, 21... Source electrode , 24...T
FT, 25...Aperture, 31...Second substrate, 33...Transparent counter electrode, 41...Liquid crystal.

Claims (1)

[Claims] 1. A plurality of data lines and a plurality of gate lines are formed on an insulating substrate to intersect with each other, and a drain electrode that also serves as the data line and a drain electrode that also serves as the data line and the gate line are formed at each intersection point. A first transistor in which a thin film transistor having a gate electrode that also serves as a gate line is arranged.
a second substrate disposed at a predetermined gap from the first substrate and on which a counter electrode is formed; and a liquid crystal sandwiched between the first substrate and the second substrate. In the active matrix type liquid crystal display device comprising the above-mentioned game
The data line and the data line are formed of the same material in the same layer as either the gate electrode or the drain electrode near the insulating substrate at a portion other than the intersection thereof. An active matrix liquid crystal display device characterized by: