JPH0850303A - Array substrate for liquid crystal display device - Google Patents

Abstract

PURPOSE:To provide an array substrate for a liquid crystal display device in which the opening ratio can be improved and the consumption of power can be reduced. CONSTITUTION:The array substrate 21 is produced by the following method. Address wiring 27 and auxiliary capacitance wiring 28 are formed on a glass substrate 22. Then a thin film transistor 41 including the address wiring 27 as a part is formed in such a manner that the source electrode 39 of this the film transistor 41 faces the auxiliary capacitance wiring 28. Thus, an auxiliary capacitor 43 is formed between the source electrode 39 and the auxiliary capacitance wiring 28. The thin film transistor 41 and a transparent pixel electrode 42 are formed in layers different from each other. It is not necessary to form a space between the transparent pixel electrode 42 and data wiring 38 in this array substrate compared to a structure having a thin film transistor 41 and a transparent pixel electrode 42 in a same layer, and thereby, the opening ratio can be increased.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an array substrate for an active matrix liquid crystal display device.

[0002]

2. Description of the Related Art Conventionally, as shown in FIGS. 4 and 5, an active matrix array substrate for a liquid crystal display device has an aluminum (Al) film or SID 90 on a glass substrate 2 where the array substrate 1 is an insulating substrate. DIGEST
The material of the address wiring 3 including the address electrode to be the gate electrode composed of the multilayer wiring containing aluminum (Al) described in p408 is deposited by a film forming method such as a sputtering method to form a film, and the dry etching method is used. And the like. After that, a gate insulating film 4 is deposited, an ohmic contact layer 6 on the drain side and an ohmic contact layer 7 on the source side are formed on the gate insulating film 4, and an ITO (Indi
um Tin Oxide) transparent pixel electrode 8 is formed.

A drain electrode 9 is formed on the ohmic contact layer 6 on the drain side, and a data line 10 intersecting with the address line 3 is formed on the drain electrode 9 as shown in FIG. Furthermore, a source electrode 11 connected to the transparent pixel electrode 8 is formed on the ohmic contact layer 7 on the source side, and a thin film transistor 12 serving as a switching element is formed by these. Further, a protective film is formed on the drain electrode 9 and the source electrode 11, etc.
14 are formed. Further, as shown in FIG. 5, an auxiliary capacitance electrode 15 is formed corresponding to the position of the transparent pixel electrode 8.

A counter substrate (not shown) is disposed so as to face the array substrate 1, and liquid crystal is sandwiched between the array substrate 1 and the counter substrate to form a liquid crystal display device.

Further, by using the array substrate having the above-mentioned structure, the screen diagonal is 12 inches and the number of pixels is 1024 (width) ×
768 (vertical), a liquid crystal display device having an aperture ratio of 40% is obtained,
It shows good display characteristics. That is, this is because the resistance value of the address wiring is reduced by using the aluminum film as the material of the address wiring.

On the other hand, as the display area of the liquid crystal display device becomes larger and finer, the length of the address wiring becomes longer and the resistance value of the address wiring becomes higher. Since the waveform of the signal is distorted and the propagation delay of the address signal occurs, the image becomes non-uniform and the image quality is deteriorated.

Since it becomes necessary to reduce the resistance value of the address wiring, the line width of the address wiring becomes thicker,
The pixel aperture ratio becomes small, the contrast ratio of the image display of the transparent pixel electrode is lowered, and the display quality is lowered.

Further, in order to maintain the contrast ratio of the pixel display of the transparent pixel electrode, it is necessary to increase the brightness of the backlight provided on the back surface of the liquid crystal display device, which increases power consumption. Then, in order to reduce the power consumption, it is necessary to maintain the aperture ratio large or about 40%.

[0009]

As described above, the conventional array substrate for a liquid crystal display device has a problem that the aperture ratio may decrease and power consumption may increase.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an array substrate for a liquid crystal display device capable of improving the aperture ratio and reducing the power consumption.

[0011]

According to another aspect of the present invention, there is provided an array substrate for a liquid crystal display device, wherein address wirings, data wirings intersecting with the address wirings, and the data wirings are connected via drain electrodes. Thin film transistor,
In an array substrate for a liquid crystal display device, in which a transparent pixel electrode driven through a source electrode of the thin film transistor and an auxiliary capacitance line that forms an auxiliary capacitance for holding the potential of the transparent pixel electrode are formed on an insulating substrate. The auxiliary capacitance is formed between the source electrode and the auxiliary capacitance line.

An array substrate for a liquid crystal display device according to a second aspect is the array substrate for a liquid crystal display device according to the first aspect, wherein the transparent pixel electrode and the address wiring include at least a gate insulating film material and a protective insulating film of a thin film transistor. They are separated by more than one type of insulating film.

An array substrate for a liquid crystal display device according to a third aspect of the present invention is the array substrate for a liquid crystal display device according to the first or second aspect, wherein the transparent pixel electrodes and the data lines are formed of different materials.

The array substrate for a liquid crystal display device according to a fourth aspect is the same as the array substrate for a liquid crystal display device according to the second aspect, wherein the protective insulating film is a compound containing carbon and fluorine.

An array substrate for a liquid crystal display device according to a fifth aspect is the array substrate for a liquid crystal display device according to the second or fourth aspect, in which the protective insulating film is formed by either coating or printing from a liquid material. It is a thing.

[0016]

The array substrate for a liquid crystal display device according to claim 1 is
Since the auxiliary capacitance is formed between the source electrode of the thin film transistor and the auxiliary capacitance line formed so as to face the source electrode, the area narrowed by the auxiliary capacitance line can be reduced, so that the aperture ratio is improved.

An array substrate for a liquid crystal display device according to a second aspect is the array substrate for a liquid crystal display device according to the first aspect, wherein the transparent pixel electrode and the address wiring include at least a gate insulating film material of a thin film transistor and a protective insulating film. Since it is separated by more than one kind of insulating film, it can be surely insulated, and the distance is not unnecessarily increased.

An array substrate for a liquid crystal display device according to a third aspect is the same as the array substrate for a liquid crystal display device according to the first or second aspect, in which the transparent pixel electrodes and the data wirings are formed of different materials, and thus are formed of the same layer. Since it is not necessary to increase the distance between the transparent pixel electrode and the data wiring as compared with the case where it is formed, the aperture ratio is improved.

An array substrate for a liquid crystal display device according to a fourth aspect is the same as the array substrate for a liquid crystal display device according to the second aspect, in which the protective insulating film is a compound containing carbon and fluorine, and therefore has excellent flatness and a film thickness. Can be made thinner and smaller.

The array substrate for a liquid crystal display device according to claim 5 is the array substrate for a liquid crystal display device according to claim 2 or 4, wherein the protective insulating film is formed by either coating or printing from a liquid material. , Easy to form.

[0021]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of an array substrate for a liquid crystal display device of the present invention will be described below with reference to the drawings.

As shown in FIGS. 1 and 2, the array substrate
Reference numeral 21 denotes a lower address wiring 23 and a lower auxiliary capacitance wiring 24 including an address electrode serving as a gate electrode of aluminum (Al) on a glass substrate 22 which is a transparent insulating substrate provided with a silicon oxide (SiO _x ) film on the surface. Is formed, an upper address wiring 25 of molybdenum (Mo) / tantalum (Ta) is formed above the lower address wiring 23, and an upper auxiliary capacitance wiring 26 is similarly formed above the lower auxiliary capacitance wiring 24. Lower address wiring 23 and upper address wiring 25
And the lower auxiliary capacitance wiring 24 and the upper auxiliary capacitance wiring 26 form an auxiliary capacitance wiring 28. And above these, silicon oxide (Si
An insulating film 29 of O _x ) is formed.

A first semiconductor layer 31 of silicon nitride (SiN _x ) and a second semiconductor layer of amorphous silicon (a-Si) are formed on the insulating film 29 above the address wiring 27.
32 is stacked and formed, and an etching stopper layer 33 of silicon nitride (SiN _x ) is further formed on the center of the second semiconductor layer 32.

Further, n-doped amorphous silicon (n + a-Si) is formed on one end side of the etching stopper layer 33.
An ohmic contact layer 34 on the drain side of
Similarly, on the other end side, the ohmic contact layer 35 on the source side is formed.
Are formed.

Further, a drain electrode 37 in which three layers of chromium (Cr), aluminum (Al) and chromium (Cr) are laminated is formed on the drain side ohmic contact layer 34. As shown in FIG. 2, the data wiring 38 intersecting the address wiring 27 is formed.
Further, a source electrode 39 is similarly formed on the source-side ohmic contact layer 35 so as to face the auxiliary capacitance line 28, and an inverted stagger type thin film transistor (TFT) 41 serving as a switching element is formed by these. . Further, an insulating film 40 made of a fluorine resin containing carbon and fluorine is formed on the insulating film 29, and the source electrode is formed on the insulating film 40.
An ITO (Indium Tin Oxide) transparent pixel electrode 42 connected to 39 is formed.

Then, the auxiliary capacitance line 28 and the source electrode
An auxiliary capacitance 43 is formed between 39, and a fluororesin insulating film 40 is formed on the thin film transistor 41 and the auxiliary capacitance 43.

A counter substrate (not shown) is arranged so as to face the array substrate 21, and liquid crystal is sandwiched between the array substrate 21 and the counter substrate to form a liquid crystal display device.

In the circuit configuration, as shown in FIG. 3, the address wirings 27 and the data wirings 38 are arranged in a grid pattern, and the thin film transistors 41 are formed in a matrix at the intersections of the address wirings 27 and the data wirings 38. Has been done.

The gate of the thin film transistor 41 is connected to the address wiring 27 and the drain thereof is connected to the data wiring 38,
The transparent pixel electrode 42 is connected to the source. further,
It has a liquid crystal capacitance 45 and an auxiliary capacitance 43.

Next, the manufacturing process of the above embodiment will be described.

First, a silicon oxide (SiO _x ) film is formed on the glass substrate 22 by the plasma CVD method, and an aluminum film 10 is formed on the glass substrate 22 by the sputtering method.
0 nm, then 20 molybdenum / tantalum films continuously.
Deposit 0 nm. The aluminum can be an aluminum alloy, for example, aluminum containing 1 atomic percent of copper and 0.5 percent of silicon. Then, the address wiring 27 is formed on the laminated film by photolithography.
Pattern is formed by dry etching using carbon tetrafluoride (CF ₄ ) + oxygen (O ₂ ), sulfur hexafluoride (SF ₆ ) + oxygen (O ₂ ), or a mixed gas thereof.
The upper address wiring 25 and the upper auxiliary capacitance wiring 26 of the molybdenum / tantalum film are etched so that a taper of 30 ° or less is formed. Next, aluminum is etched using a mixed acid of phosphoric acid + nitric acid + acetic acid to form the lower address wiring.
23 and lower auxiliary capacitance wiring 24 are formed, and address wiring 27
And the pattern of the auxiliary capacitance wiring 28 is completed.

Subsequently, four layers of a silicon oxide (SiO _x ) film by a thermal CVD method, a silicon nitride (SiN _x ) film, an amorphous silicon (a-Si) film and a silicon nitride (SiN _x ) film are formed by a plasma CVD method. Deposit one after another. Then, the upper SiN _x film is patterned to form the etching stopper layer 33, and after the pretreatment, the n-doped amorphous silicon (n + a-Si) film is subjected to plasma CV.
Deposit by the D method.

Further, three layers of chromium, aluminum and chromium are deposited by the sputtering method and then patterned to form a data wiring 38, a drain electrode 37 and a source electrode 39. After that, the n-doped amorphous silicon (n + a-Si) film on the back channel which becomes the etching stopper layer 33 is removed by RIE (Reactive Ion Eching), and the ohmic contact layer 34 on the drain side and the ohmic contact on the source side are removed. Form layer 35.

Furthermore, a liquid of fluororesin is added to a film thickness of 50.
Insulating film with 0 nm coating and heat treatment at 180 ℃ for 1 hour
Form 40 and 44. The insulating film 44 is a thin film transistor.
It also serves as a passivation for 41. Further, the insulating film 44 has almost no hygroscopic property, and the reliability of the thin film transistor 41 is similar to that of the conventional silicon nitride film.

Subsequently, a transparent pixel electrode 42 of an ITO (Indium Tin Oxide) film is formed as a transparent pixel electrode by a sputtering method, and the array substrate 21 is completed.

According to the structure of the above embodiment, the liquid crystal display device having a diagonal of 12 inches and a number of 1024.times.768 pixels can increase the aperture ratio by 20 to 25% of the conventional one.

Further, since the fluororesin-based insulating film 40 is provided on the lower surface of the transparent pixel electrode 42, the lower portion of the transparent pixel electrode 42 can be flattened, and the step coating property and the flattening property are excellent.

Further, since the thin film transistor 41 and the transparent pixel electrode 42 are arranged in different layers, the transparent pixel electrode 42 and the data wiring 38 are different from the structure in which the thin film transistor 41 and the transparent pixel electrode 42 are formed in the same layer. The aperture ratio can be increased without the need to provide a space.

Furthermore, the step difference in the portion in contact with the liquid crystal is small, the edge reverse due to the lateral electric field does not occur, and the aperture ratio can be further increased.

Further, the conventional TEOS (Tetra-ethyl-orth
In the case of an oxide film formed by a CVD method using o-silicate), the insulating film 40
The film thickness of 1 is required to be as thick as 1 μm or more for the flattening, but if the insulating film 40 of the fluororesin is superior in flatness, the film thickness can be reduced. Therefore, the source electrode 39 and the transparent pixel electrode 42 are not electrically connected to each other through a large step, and the open defect of the connection portion is unlikely to occur.

Further, as in the prior art, when the auxiliary capacitor has the same layer as the address wiring as one electrode and the other as the transparent pixel electrode of ITO, it is formed of a laminated film of a gate insulating film and a passivation film. Therefore, the electric capacity becomes small in the same area, and if the capacity becomes the same, the aperture ratio will decrease. However, as described above, if the auxiliary capacitance 43 is formed using the same source electrode 39 as the signal line wiring, instead of the transparent pixel electrode, the aperture ratio is improved.

The insulating films 40 and 44 are not limited to those coated with a liquid, and may be formed by printing.

[0043]

According to the array substrate for a liquid crystal display device of the first aspect, the auxiliary capacitance is formed between the source electrode of the thin film transistor and the auxiliary capacitance line formed facing the source electrode. Since the area narrowed by the capacity wiring can be reduced, the aperture ratio can be improved.

According to the array substrate for a liquid crystal display device described in claim 2, in addition to the array substrate for a liquid crystal display device according to claim 1, the transparent pixel electrodes and the address wirings are made of a gate insulating film material and a protective insulating film of a thin film transistor. Since they are separated by at least two types of insulating films including them, they can be surely insulated and the distance is not unnecessarily increased, so that the size can be reduced.

According to the liquid crystal display device array substrate of the third aspect, in addition to the liquid crystal display device array substrate of the first or second aspect, the transparent pixel electrodes and the data lines are made of different materials. Since it is not necessary to increase the distance between the transparent pixel electrode and the data line as compared with the case where they are formed in the same layer, the aperture ratio can be improved.

According to the array substrate for a liquid crystal display device of the fourth aspect, in addition to the array substrate for the liquid crystal display device of the second aspect, the protective insulating film is a compound containing carbon and fluorine, and therefore has excellent flatness. The film thickness can be made thinner and the size can be reduced.

According to the liquid crystal display array substrate of the fifth aspect, in addition to the liquid crystal display array substrate of the second or fourth aspect, the protective insulating film is formed by applying or printing from a liquid material. Since it is formed, it can be easily formed.

[Brief description of drawings]

FIG. 1 is a sectional view showing an embodiment of an array substrate for a liquid crystal display device of the present invention.

FIG. 2 is a plan view of the same.

FIG. 3 is an equivalent circuit diagram of the above.

FIG. 4 is a cross-sectional view showing a conventional array substrate for a liquid crystal display device.

FIG. 5 is a plan view of the same.

[Explanation of symbols]

 22 Glass substrate as insulating substrate 27 Address wiring 28 Auxiliary capacitance wiring 29, 40 Insulating film 38 Data wiring 39 Source electrode 41 Thin film transistor 42 Transparent pixel electrode 43 Auxiliary capacitance

Claims (5)

[Claims] 1. An address wire, a data wire arranged to intersect with the address wire, a thin film transistor connected from the data wire via a drain electrode, a transparent pixel electrode driven via a source electrode of the thin film transistor, In an array substrate for a liquid crystal display device, in which an auxiliary capacitance line that forms an auxiliary capacitance for holding the potential of the transparent pixel electrode is formed on an insulating substrate, the auxiliary capacitance is the source electrode and the auxiliary capacitance line. An array substrate for a liquid crystal display device, which is formed between the two. 2. The liquid crystal display array according to claim 1, wherein the transparent pixel electrode and the address wiring are separated by at least two kinds of insulating films including a gate insulating film material and a protective insulating film of a thin film transistor. substrate. 3. The array substrate for a liquid crystal display device according to claim 1, wherein the transparent pixel electrode and the data line are made of different materials. 4. The array substrate for a liquid crystal display device according to claim 2, wherein the protective insulating film is a compound containing carbon and fluorine. 5. The array substrate for a liquid crystal display device according to claim 2, wherein the protective insulating film is formed by applying or printing from a liquid material.