JPH0961835A - Liquid crystal display substrate and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a liquid crystal display substrate with which the easy execution of the remedy to hillocks is possible even if aluminum or its alloy is used as conductive layers by coating the surface of at least the parts of the first conductive layer to be superposed on another conductive layer with an ITO film. SOLUTION: At least the parts of the upper layer to be superposed on the other conductive layer are previously coated with the ITO film in the case where the aluminum or its alloy is formed as the ITO film of the lower layer. Scanning signal lines 2 formed first on the main surface of the transparent substrate 1 are composed of an alloy of, for example, Al-Ti-Ta and both flanks parallel with its extension direction are formed gently to a tapered shape. Hillock preventive films 5 are formed atop the scanning signal lines 2 in the state of completely covering both flanks of the scanning signal lines 2. The hillock preventive films 5 are composed of the ITO films. Pixel electrodes 4 are formed of the ITO films and are formed by the same stage as for the hillock preventive films 5. As a result, there is no need for adding a special stage to the formation of the hillock preventive films 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display substrate and a method for manufacturing the same.

[0002]

2. Description of the Related Art A liquid crystal display substrate is provided with transparent substrates arranged to face each other with a liquid crystal interposed therebetween, and a conductive layer having a multi-layer structure with an insulating film formed on at least one of the transparent substrates facing the liquid crystal. There is. This is because it is necessary to supply a video signal and the like to each pixel that constitutes the display surface by this conductive layer.

It is known that aluminum or its alloy is the most preferable material for the conductive layer because of its low resistance and ease of processing.

However, when the conductive layer made of aluminum or the like is positioned as a lower layer and another conductive layer (which may be aluminum or the like) is formed as an upper layer through an insulating film, the lower layer is formed when the insulating film is formed. It is also known that whisker-shaped protrusions called so-called hillocks grow from the conductive layer, and the lower conductive layer is short-circuited with the upper conductive layer via this hillock.

For this reason, when aluminum or the like is used as the lower conductive layer, the surface of the conductive layer is anodized to form an aluminum oxide film. This is because the aluminum oxide film serves as a barrier and has an effect that hillocks are not generated at all.

[0006]

However, the anodization of the conductive layer made of aluminum or the like is as follows.
I could not avoid making the work extremely complicated.

This is because the transparent substrates on which the conductive layers are formed must be arranged vertically in parallel with the electrolytic solution to be submerged and the aluminum oxide film must be formed over an extremely long time.

The present invention has been made under such circumstances, and an object thereof is to provide a liquid crystal display substrate which can easily take measures against hillock even when aluminum or its alloy is used as a conductive layer, and its manufacture. There is a way to provide.

[0009]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

Means 1. A first conductive layer is formed of aluminum or an alloy thereof on at least one liquid crystal side surface of the transparent substrates arranged to face each other with the liquid crystal interposed therebetween, and another conductive layer is formed with the first conductive layer and the insulating film interposed therebetween. In the liquid crystal display substrate formed to overlap, the first
The conductive layer is characterized in that an ITO film is coated on at least the surface of the portion thereof that overlaps with the other conductive layer. Here, the other conductive layers include not only the wiring but also the semiconductor layer formed in the channel region of the thin film transistor TFT.

Means 2. In the structure of means 1, the liquid crystal display substrate having a pixel electrode formed of an ITO film,
The ITO film formed on the surface of the conductive layer is formed simultaneously with the pixel electrode.

[0012]

The liquid crystal display substrate configured as in the means 1 is used as a countermeasure against hillocks of aluminum or its alloy.
It is constructed based on the result that a TO (Indium-Tin-Oxide) film is extremely effective.

That is, when aluminum or its alloy is formed as the lower conductive film, the ITO film is covered at least in a portion overlapping with the other upper conductive film, so that the insulating film is formed thereafter. At least, no hillock is generated in the portion.

Therefore, even if an upper conductive film is formed on this portion, the conductive layer can be prevented from being electrically short-circuited with the lower conductive film by the hillocks.

Here, the coating with the ITO film can be formed by selective etching by the well-known photolithography technique, and can be performed extremely easily as compared with the work by anodization.

Further, since the method of manufacturing the liquid crystal display substrate configured as in the means 2 is intended for forming the pixel electrode by the ITO film, it is formed on the surface of the conductive film made of aluminum or its alloy. By forming the ITO film at the same time when the pixel electrode is formed, the effect that the manufacturing process is not increased at all is brought about.

[0017]

[Embodiment 1 ] FIG. 2 is a plan view showing an embodiment of the liquid crystal display substrate according to the present invention. The figure shows a plan view showing a configuration of a unit pixel on the liquid crystal side of one of the transparent substrates arranged to face each other with the liquid crystal interposed therebetween. Further, FIG. 1 shows a sectional view taken along line II in the figure.

The liquid crystal display substrate shown in this embodiment is
The so-called vertical electric field method is provided with electrodes on each of the transparent substrates that are arranged to face each other with the liquid crystal in between.
The light transmittance of the liquid crystal is changed by generating an electric field in the direction perpendicular to the transparent substrate by these electrodes.

In FIG. 2, first, scanning signal lines 2 extending in the x direction and arranged in parallel in the y direction in the figure are formed on the main surface of the transparent substrate 1. Further, a video signal line 3 extending in the y direction and arranged in parallel in the x direction is formed. The scanning signal lines 2 and the video signal lines 3 are insulated from each other at their intersections via an interlayer insulating film.

In this way, the scanning signal line 2 and the video signal line 3
A rectangular region surrounded by and becomes a unit pixel region, and the pixel electrode 4 is formed in this region.

A thin film transistor TFT having a so-called MIS structure having the scanning signal line 2 as a gate electrode is formed in a partial area on one scanning signal line 2, and the thin film transistor TFT scans from the scanning signal line 2. It is turned on by the supply of a signal (voltage).

On the other hand, the video signal supplied via the video signal line 3 is applied to the pixel electrode 4 via the drain electrode and the source electrode of the turned-on thin film transistor TFT.

As a result, an electric field is generated between the pixel electrode 4 and a common electrode formed on another transparent substrate (not shown) which is arranged so as to be opposed to the pixel electrode 4 via the liquid crystal, so that the light transmittance of the liquid crystal is changed. It has become.

The pixel electrode 4 and the pixel electrode 4
A capacitive element Cadd formed on the scanning signal line 2 is formed between the adjacent scanning signal line 2 that does not contribute to supplying the video signal to the
By d, the image information after the thin film transistor TFT is turned off can be stored for a long time.

Next, a detailed description of each component in such a schematic structure will be given below in the order of manufacturing steps.

First, the scanning signal line 2 formed first on the main surface of the transparent substrate 1 is made of, for example, an alloy of Al-Ti-Ta (or Al-Ta), and is parallel to the extending direction thereof. As shown in FIG. 1, both side surfaces have a so-called tapered shape and are gently formed.

A hillock prevention film 5 is formed on the upper surface of the scanning signal line 2 in a state where the scanning signal line 2 covers all the both side surfaces. This hillock prevention film 5
Is composed of an ITO (Indium-Tin-Oxide) film.

The pixel electrode 4 is ITO (Indium-Tin-Oxide)
It is formed of a film and is formed in the same process as the hillock prevention film 5 made of the same material as described above. As a result, it is possible to obtain the effect that it is not necessary to add a special step to the formation of the hillock prevention film 5.

In this embodiment, the hillock prevention film 5 and the pixel electrode 4 are both amorphous ITO.
It is formed by a film. By using this amorphous ITO film, aqua regia can be used as the wet etching liquid, and so-called battery reaction with the scanning signal line 2 made of an aluminum alloy can be suppressed. In addition, since the amorphous ITO film can be formed at room temperature without heating, it is possible to prevent hillocks from being generated.

This amorphous ITO film can be formed by, for example, a sputtering method, and the conditions are as follows: the amount of water added in Ar gas is 1.7%, the degree of vacuum is 9 × 10 to ⁴ Pa or less, Gas pressure: 0.67%, Ar gas flow rate: 150 sec, H ₂ O flow rate: 2.6 sc
cm (Standard cubic cm per minute) and DCpo
wer: 1.3 kW. In this case, the substrate was not heated and the film formation temperature was kept at 100 ° C. or lower. Also, IT
O target composition: In ₂ O ₃ 95% (85% to 95
%) And Sn ₂ O ₃ 5% (5% to 15%).

The insulating film 6 made of a silicon nitride film
This insulating film 6 is formed over the entire area except for a portion where a hole is formed in the central portion except the periphery of the pixel electrode 4 and a terminal portion.

This insulating film 6 is a thin film transistor TFT.
As a gate insulating film in the formation region, as an interlayer insulating film at the intersection of the scanning signal line 2 and the video signal line 3, and as a dielectric film in the formation region of the capacitive element Cadd. It is supposed to function as.

A semiconductor layer 7 is formed on the upper surface of the insulating film 6 (gate insulating film) in the formation region of the thin film transistor TFT.

When forming the insulating film 6 and the semiconductor layer 7, the ITO film already formed is subjected to crystallization baking at 240 ° C. and then formed by the CVD method to reduce the ITO film. It has the effect of resistance.

The video signal line 3 is formed.
The video signal line 3 is made of Al, for example.

In this case, the video signal line 3 has a drain electrode 3a of the thin film transistor TFT extending from a part thereof.
And the thin film transistor TF connected to the pixel electrode 4 at the same time as the video signal line 3.
The source electrode 3b of T and the other electrode 8 (see FIG. 2) of the capacitive element Cadd connected to the pixel electrode 4 are formed.

Further, the surface processed in this way has
For example, a protective film 9 made of a silicon nitride film is formed,
The protective film 9 is perforated so that the central portion of the pixel electrode 4 excluding the peripheral portion is exposed.

FIG. 3 shows a sectional view of a terminal portion formed by extending the scanning signal line 2 to the periphery of the transparent substrate 1.

In the figure, a terminal 4T made of an ITO film is partially overlapped and formed at the end of the scanning signal line 2 made of an alloy of Al-Ti-Ta (or Al-Ta). A conductor layer 3T made of Al is formed across the 4T and the scanning signal line 2. Here, the terminal 4T is formed in the same process as the pixel electrode 4, and the conductor layer 3T is formed in the same process as the video signal line 3.

The hard ITO film is a suitable material for the terminal 4T, and is intended to supplement the insufficient contact property with the scanning signal line 2 by the conductor layer 3T.

FIG. 4 is a view showing a cross section taken along line IV-IV in FIG.

As is clear from the figure, Al-Ti-Ta (or Al-) is formed in the lower layer in the peripheral portion of the pixel electrode 4.
A light-shielding film 10 made of an alloy of Ta) is formed. The light-shielding film 10 is formed at the same time when the scanning signal line 2 is formed, and is covered with the pixel electrode 4 to prevent hillocks.

A light-shielding film 12, which is a so-called black matrix, is also formed on another transparent substrate 11 (a color filter is also formed, but not shown in the figure) which is opposed to the liquid crystal via the liquid crystal. However, the provision of the above-described light-shielding film 10 also has the effect of facilitating the alignment of the upper transparent substrate 11 with the lower transparent substrate 1.

The liquid crystal display substrate according to the embodiment described above is constructed based on the result that an ITO (Indium-Tin-Oxide) film is extremely effective as a countermeasure against hillocks of aluminum or its alloy.

That is, when the scanning signal line 2 is formed by using aluminum or its alloy as the lower conductive film,
By covering the surface with the ITO film, hillocks will not occur even if the insulating film 6 is formed thereafter.

Therefore, even if another conductive film is formed on the upper surface of the insulating film 6 so as to overlap with the scanning signal line 2, this conductive layer is electrically short-circuited with the scanning signal line 2 by the hillocks. Will be able to prevent.

Here, the coating with the ITO film can be formed by selective etching by a well-known photolithography technique, and can be performed extremely easily as compared with the work by anodization.

FIG. 5 is an explanatory view comparing the case where the ITO film is used as the hillock prevention layer 5 and the case where it is not used. The figure (a) is a top view and the figure (b) is sectional drawing in the bb line of the figure (a). In the area where the hillock prevention layer 5 is not formed, the spot A is seen on the surface, and this spot indicates the hillock B, whereas in the area where the hillock prevention layer 5 is formed, It turns out that no spots or hillocks have occurred.

Further, by simultaneously forming the hillock prevention layer 5 made of the ITO film formed on the surface of the scanning signal line 2 made of aluminum or its alloy when the pixel electrode 4 is formed, the manufacturing process is not increased at all. Bring about the effect.

Embodiment 2 FIG . FIG. 6 is a plan view showing another embodiment of the liquid crystal display substrate according to the present invention. The figure shows a plan view showing a configuration of a unit pixel on the liquid crystal side of one of the transparent substrates arranged to face each other with the liquid crystal interposed therebetween. 7 is a sectional view taken along line VII-VII in the figure. Note that the upper transparent substrate is also shown in FIG. 7.

The liquid crystal display substrate shown in this embodiment is of a so-called lateral electric field type, and one of the transparent substrates arranged to face each other with the liquid crystal in between is provided with a pair of electrodes. The light transmittance of the liquid crystal is changed by generating an electric field in a direction parallel to the transparent substrate by each electrode.

In the figure, first, scanning signal lines 22 are formed on the main surface of the transparent substrate 21 and extend in the x direction and are arranged in parallel in the y direction in the figure. Further, video signal lines 23 extending in the y direction and arranged in parallel in the x direction are formed.
The scanning signal lines 22 and the video signal lines 23 are insulated from each other at their intersections via an interlayer insulating film.

As described above, the rectangular region surrounded by the scanning signal lines 22 and the video signal lines 23 becomes a unit pixel region, which extends in the y direction and is arranged in parallel in the x direction. The display electrodes 24 and the reference electrodes 25 are spaced apart from each other and arranged alternately. The reference electrode 25
Is applied with a constant voltage via a reference signal line 25A that is arranged close to and parallel to the scanning signal line 22, respectively.

A thin film transistor TFT having a so-called MIS structure using the scanning signal line as a gate electrode is formed in a part of the scanning signal line 22. The thin film transistor TFT has a scanning signal (voltage) from the scanning signal line 22. It is designed to be turned on by the supply of.

On the other hand, the video signal supplied through the video signal line 23 is applied to the display electrode 24 through the drain electrode and the source electrode of the turned-on thin film transistor TFT.

As a result, an electric field parallel to the transparent substrate 21 is generated between the display electrode 24 and the reference electrode 25 arranged to face the display electrode 24, so that the light transmittance of the liquid crystal is changed. It has become.

Next, a detailed description of each constituent member in such a schematic structure will be given below in the order of manufacturing steps.

First, the scanning signal lines 22 formed first on the surface of the transparent substrate 21 are made of, for example, an alloy of Al-Ti-Ta (or Al-Ta), and both side surfaces parallel to the extending direction thereof. As shown in FIG. 7, is formed into a so-called tapered shape and is formed gently.

Then, on the upper surface of the scanning signal line 22,
A hillock prevention film 26 is formed in a state where the scanning signal line 22 covers all the both side surfaces. The hillock prevention film 26 is composed of an ITO (Indium-Tin-Oxide) film. The formation of the hillock prevention film 26 and the like are performed through substantially the same steps as those shown in the first embodiment.

The reference electrode 25 and the reference signal line 25A are
The scanning signal line 22 is made of the same material as that of the scanning signal line 22, and is formed in the same process as the scanning signal line 22. Therefore, the upper surfaces of the reference electrode 25 and the reference signal line 25A are also covered with the hillock prevention film 26.

Then, the insulating film 2 made of a silicon nitride film
7 is formed, and the insulating film 27 is formed over almost the entire area.

This insulating film 27 is a thin film transistor TF.
It functions as a gate insulating film in the region where T is formed and as an interlayer insulating film at the intersection of the scanning signal line 22 (and the reference signal line 25A) and the video signal line 23.

A semiconductor layer 28 is formed on the upper surface of the insulating film 27 (gate insulating film) in the formation region of the thin film transistor TFT.

The video signal line 23 is formed. The video signal line 23 is made of Al, for example.

In this case, the video signal line 23 has the drain electrode 2 of the thin film transistor TFT extending from a part thereof.
3A, the display electrode 24 is formed simultaneously with the video signal line 23 by being connected to the source electrode 23B of the thin film transistor.

Also in the embodiment described above, even if the scanning signal line 22, the reference electrode 25, and the reference signal line 25A are made of an aluminum alloy, the occurrence of hillocks can be prevented.

Compared to the vertical electric field method shown in the first embodiment, the present method increases the capacitance of the common wiring, so that the wiring delay of the scanning signal line is likely to occur. This problem can be solved by reducing the time constant by reducing the wiring resistance by using Al wiring. Al is used for the gate without using anodization
The present invention, in which the above can be used, is particularly effective in the second embodiment.

In any of the above-mentioned embodiments, the hillock prevention layer is formed over the entire area of the signal line formed of an aluminum alloy, but the invention is not necessarily limited to this, and the conductivity with the upper layer is not limited to this. It goes without saying that it may be only a portion that overlaps with the layer through the insulating film.

[0069]

As is apparent from the above description,
According to the liquid crystal display substrate and the manufacturing method thereof according to the present invention, even if aluminum or its alloy is used as the conductive layer, it is possible to easily take measures against the hillock.

[Brief description of drawings]

FIG. 1 is a sectional view of an essential part showing an embodiment of a liquid crystal display substrate according to the present invention.

FIG. 2 is a plan view showing an embodiment of a liquid crystal display substrate according to the present invention.

FIG. 3 is a cross-sectional view showing an embodiment of a liquid crystal display substrate according to the present invention, showing a terminal portion.

FIG. 4 is a sectional view taken along line IV-IV in FIG.

FIG. 5 is an explanatory diagram showing an effect of the present invention.

FIG. 6 is a cross-sectional view of essential parts showing another embodiment of the liquid crystal display substrate according to the present invention.

FIG. 7 is a plan view showing an embodiment of a liquid crystal display substrate according to the present invention.

[Explanation of symbols]

2, 22 ... Scanning signal line, 4 ... Pixel electrode, 5, 26 ...
... hillock prevention layer, 25 ... reference electrode.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Hideaki Yamamoto 3300 Hayano, Mobara-shi, Chiba Pref. Electronic Device Division, Hitachi, Ltd.

Claims (3)

[Claims] 1. A first conductive layer made of aluminum or an alloy thereof is formed on at least one liquid crystal side surface of transparent substrates arranged to face each other with a liquid crystal interposed therebetween, and the first conductive layer and an insulating film are interposed therebetween. In a liquid crystal display substrate formed by superimposing another conductive layer, the first conductive layer is coated with an ITO film at least on a surface of a portion thereof overlapping with the other conductive layer. Liquid crystal display substrate. 2. A liquid crystal display substrate having a pixel electrode formed of an ITO film, the ITO being formed on a surface of the first conductive layer.
The method for manufacturing a liquid crystal display substrate according to claim 1, wherein the film is formed simultaneously with the pixel electrode. 3. The method according to claim 2, wherein when forming the first conductive layer, a light-shielding film made of aluminum or its alloy is formed on the entire area or a part of the periphery of the area where the pixel electrode is formed. Liquid crystal display substrate manufacturing method.