JPH07128676A - Liquid crystal display substrate - Google Patents

Abstract

PURPOSE:To prevent electric short of a wiring layer essentially comprising aluminum with upper layers due to hilloak or whiskers of the wiring layer by forming a metal layer having higher melting point than aluminum on the wiring layer where a conductive layer or a semiconductor layer is to be laminated. CONSTITUTION:In this liquid crystal display substrate, at least a wiring layer 2A essentially comprising aluminum is formed on one surface of a transparent substrate 1 where a liquid crystal is to be present, and a conductive layer or a semiconductor layer 5 with an insulating film 7A is laminated on the aluminum layer 2A. At least on the upper surface of the wiring layer 2A where the conductive layer or semiconductor layer 5 are to be laminated, a metal layer 2B having higher melting point than aluminum is formed. Namely, a tantalum layer 2B having higher melting point than aluminum is formed on the upper surface of gate signal lines 2 comprising aluminum. Thereby, even when a semiconductor layer 5 is laminated with an interlayer insulating film 7, electric short between the gate signal wire 2 and the semiconductor layer 5 can be prevented.

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,
In particular, it relates to improvement of a wiring layer containing aluminum as a main component formed on the liquid crystal side surface thereof.

[0002]

2. Description of the Related Art An active matrix type liquid crystal display device is provided with a non-linear element (switching element) corresponding to each of a plurality of pixel electrodes arranged in a matrix. Since the liquid crystal in each pixel is theoretically always driven (duty ratio 1.0), the active system has better contrast than the so-called simple matrix system, which employs the time-division driving system, and especially the color liquid crystal display device. Then it is becoming an indispensable technology. A typical example of the switching element is a thin film transistor (TFT).

The wiring layer for supplying a signal to the pixel electrode or the non-linear element is usually made of aluminum (Al) or its alloy which can be processed with high precision.

An active matrix type liquid crystal display device using thin film transistors is disclosed in, for example, Japanese Patent Application Laid-Open No. 63-309921, "1.
2.5-inch active matrix color LCD ", Nikkei Electronics, pages 193-210, 1986 12
Known on the 15th of March, published by Nikkei McGraw-Hill, Inc.

[0005]

However, when aluminum (Al) or its alloy is used for the wiring layer, fine projections called hillocks or whiskers are formed on the surface due to the characteristics of the material. It has come to the point that there are problems due to this.

That is, the fine projections of the wiring layer are formed so as to project to the conductive layer or the semiconductor layer formed thereabove even if the insulating layer is interposed therebetween. This is because it causes an electrical short circuit with the semiconductor layer.

Therefore, the present invention has been made under such circumstances, and the object thereof is that a wiring layer containing aluminum as a main component is laminated on the upper layer by its hillocks or whiskers. It is to provide a liquid crystal display substrate which can prevent an electrical short circuit with the existing layers.

[0008]

In order to achieve such an object, the present invention is basically based on at least one of the transparent substrates arranged to face each other with a liquid crystal interposed therebetween, on at least the liquid crystal side. In a liquid crystal display substrate in which a wiring layer containing aluminum as a main component is formed and a conductive layer or a semiconductor layer is stacked on the surface of the aluminum layer with an insulating film interposed therebetween, a wiring in which at least the conductive layer or the semiconductor layer is stacked. A metal layer having a melting point higher than that of aluminum is formed on the upper surface of the layer.

[0009]

In the liquid crystal display substrate thus constructed, a metal layer having a higher melting point than aluminum is formed on the upper surface of the wiring layer containing aluminum as a main component.

Therefore, even if fine projections called hillocks or whiskers are formed on the surface of the wiring layer at the stage of forming the wiring layer, the metal layer formed on the upper surface of the fine projections on the surface of the metal layer It does not project, and the fine protrusions as described above do not occur in the metal layer itself.

Therefore, even if a conductive layer or a semiconductor layer is laminated via an insulating layer, an electrical short circuit will not occur between the wiring layer and the laminated body.

Therefore, the wiring layer containing aluminum as a main component does not cause an electrical short circuit between the wiring layer and the upper layer due to hillocks or whiskers.

[0013]

EXAMPLES Example 1. FIG. 2 is a configuration diagram of a liquid crystal display substrate according to the present invention, and is a plan view showing a liquid crystal side surface of one of the transparent glass substrates arranged to face each other with a liquid crystal interposed therebetween. The figure is a plan view showing the configuration of one of the pixel electrodes arranged in a matrix and the vicinity thereof.

In the figure, on the main surface of the transparent glass substrate 1, there are gate signal lines 2 extending in the x direction in the figure. A plurality of gate signal lines 2 are arranged in parallel in the y direction in the figure. It is set up.

On the other hand, there is a drain signal line 3 extending in the y direction in the figure, and a plurality of the drain signal lines 3 are arranged in parallel in the x direction in the figure. These drain signal lines 3 are insulated from each other by an interlayer insulating film (not shown) formed at least with the gate signal lines 2 and intersect each other.

A pixel electrode 4 is formed in a rectangular area surrounded by the gate signal line 2 and the drain signal line 3.
The pixel electrode 4 is composed of a transparent conductive layer (for example, ITO), and a part of the pixel electrode 4 is formed on the gate signal line 2 through another conductive layer (T).
The source electrode 4A is formed by extending to the portion of (FT).

The thin film transistor (TFT) is formed by sequentially forming on the surface of the gate signal line 2 a gate insulating film formed in the same step as the interlayer insulating film and a semiconductor layer 5 made of, for example, a (amorphous) -Si. The drain electrode 4B formed on the semiconductor layer 5 so as to face the source electrode 4A is formed integrally with the drain signal line 3.

The other part of the pixel electrode 4 extends to a part of the other adjacent gate signal line 2 and is overlapped with a dielectric film formed in the same step as the interlayer insulating film. The capacitor Cadd is formed in this overlapping region.

The glass substrate 1 having the above structure
A protective film (not shown) having a hole formed in the central portion of the surface of the pixel electrode 4 except for the peripheral portion is formed of, for example, a silicon nitride film.

FIG. 3 shows the thin film transistor (T
It is the figure which expanded and showed the part of (FT), and the sectional drawing in the II line is shown in FIG.

In FIG. 1, there is a transparent glass substrate 1,
A gate signal line 2 is formed on its main surface, and the gate signal line 2 is made of an aluminum (Al) layer 2A,
A tantalum (Ta) 2B layer is laminated on the surface thereof.

Tantalum layer (Ta) 2B in this case
Has a width narrower than that of the aluminum (Al) layer 2A. As a result, when viewed two-dimensionally, each tantalum (Ta) layer 2B has a lower aluminum (Al) layer on each side in the longitudinal direction. The layer 2A is in an exposed state.

The reason for forming in this way is that the side surface of the gate signal line 2 having a laminated structure is provided with the above-mentioned step so that the gate signal line 2 has a shape close to an inclined surface, and then the gate signal line 2 is formed so as to straddle it. This is to prevent a step break at the step of the other layer.

If there is no need for such consideration, as shown in FIG. 4, aluminum (A
It goes without saying that the l) layer 2A and the tantalum (Ta) layer 2B may have the same width. In this case, there is an effect that each layer can be sequentially formed over the entire area of the transparent glass substrate 1 and then formed with the same mask.

An interlayer insulating film 7 made of, for example, a silicon nitride film is formed on the surface of the transparent glass substrate 1 so as to cover the gate signal line 2 thus formed. The interlayer insulating film 7 is intended to perform interlayer insulation with the drain signal line 3 shown in FIG. 2 which will be formed later, but particularly in a thin film transistor (TFT) forming region, it functions as a gate insulating film 7A. ing.

Further, a semiconductor layer 5 made of, for example, amorphous (α) -Si is formed on the upper surface of the gate insulating film 7A.

In this case, even if fine projections called hillocks or whiskers are formed on the surface of the aluminum layer (Al) 2A at the stage of forming the aluminum layer (Al) 2A, the tantalum layer ( The Ta) 2B does not project to the surface of the tantalum layer (Ta) 2B, and the tantalum layer (Ta) 2B itself does not have the above-described fine protrusions.

Therefore, even if the semiconductor layers 5 are stacked with the gate insulating film 7A interposed therebetween, the gate signal lines 2 and the semiconductor layers 5 are formed.
There is no possibility of causing an electrical short circuit between the and.

On the surface of the semiconductor layer 5, the source electrode 4A and the drain electrode 4 which are arranged to face each other.
B is formed.

In the thin film transistor (TFT) having such a structure, when a voltage is applied to the gate signal line 2, a channel layer is formed in the semiconductor layer 5 via the gate insulating film 7A, and this channel layer is interposed. Drain signal line 3
The signal from the (drain electrode 4B) is applied to the source electrode 4A connected to the pixel electrode 4.

Example 2. As shown in FIGS. 5 and 6, the aluminum layer (Al) 2A and the tantalum layer (T) are formed.
Needless to say, a) After forming the gate signal line 2 made of 2B, the surface thereof may be anodized to form an oxide film over the entire surface including the side surface.

That is, in FIG. 5, by forming the gate signal line 2 as shown in FIG. 4 and then performing anodization,
The aluminum oxide layer 10A is formed on the side surface of the aluminum layer (Al) 2A, and the tantalum oxide layer 10B is formed on the side surface and the main surface of the tantalum layer (Ta) 2B. In this case, as shown in FIG. 5, since the insulating film is formed on the entire exposed surface of the gate signal line 2, it is possible to improve the withstand voltage together with the interlayer insulating film 7 not shown. become able to.

Further, as shown in FIG. 7, when the foreign material 20 is attached to the surface of the aluminum (Al) layer 2A, the tantalum (Ta) layer 2B formed on the upper surface of the aluminum (Al) layer 2A is pinned at the location of the foreign material 20. Although holes are formed, the pinholes are blocked by anodizing.

Further, in FIG. 6, after the gate signal line 2 is formed as in FIG. 1, anodization is performed to form an aluminum oxide layer 10A on the side surface of the aluminum layer (Al) 2A and a tantalum layer ( The tantalum oxide layer 10B is formed on the side surface and the main surface of Ta) 2B. In this case, the same effect as that of FIG. 5 is obtained, but since the taper is formed in the step portion, it is possible to prevent the further formation of the upper interlayer insulating film 7 or the conductor layer from being discontinuous. You will be able to.

Example 3. FIG. 8 shows the aluminum layer (A
1) The gate signal line 2 composed of 2A and the tantalum layer (Ta) 2B has a tapered taper on its side surface, and has a structure having no stepped portion as in the above-described embodiment.

The gate signal line 2 having such a taper on its side surface is composed of an aluminum layer (Al) 2 which constitutes the gate signal line 2.
It can be formed by using a so-called anisotropic etching solution when etching A and the tantalum layer (Ta) 2B.

The sectional view shown in FIG. 8 corresponds to that in FIG.
VIII-VIII line, as shown in the figure,
After that, when the interlayer insulating film 7 and the drain signal line 3 are formed, there is an effect that they can be formed with a uniform layer thickness without causing step breakage.

According to the liquid crystal display substrate according to each of the above-described embodiments, the tantalum (T) having a melting point higher than that of aluminum is particularly formed on the upper surface of the gate signal line 2 made of aluminum.
a) The layer 2B is formed.

Therefore, even if fine projections called hillocks or whiskers are formed on the surface of the aluminum layer 2A when it is formed, the tantalum (Ta) layer 2B is formed on the upper surface thereof. The tantalum (T
The a) layer 2B does not project to the surface, and the tantalum (Ta) layer itself does not have the above-mentioned fine protrusions.

Therefore, the semiconductor layer 5 is formed through the interlayer insulating film 7.
Even if they are stacked, an electrical short circuit will not occur between the gate signal line 2 and the semiconductor layer 5.

Therefore, the gate signal line 2 made of aluminum will not cause an electrical short circuit between the gate signal line 2 and the semiconductor layer 5 stacked thereabove due to its hillocks or whiskers.

In the above-mentioned embodiments, the gate signal line 2 has been described as being made of aluminum.
It is needless to say that the alloy is not limited to this and may be an alloy containing aluminum as a main component.

In the above-mentioned embodiments, the electrical short circuit with the semiconductor layer 5 is described, but it goes without saying that the electrical short circuit with the drain signal line can be prevented.

In the above-mentioned embodiment, tantalum (Ta) is used as the refractory metal, but the refractory metal is not limited to this. The point is that a metal having a higher melting point than aluminum (Al) is applied. be able to.

In the above-described embodiment, the case where the gate signal line 2 is located below the drain signal line 3 is explained. However, it goes without saying that the present invention can be applied to the drain signal line 3 when the drain signal line 3 is formed as a lower layer with respect to the gate signal line 2 and is made of a material containing aluminum as a main component.

[0046]

As is apparent from the above description,
According to the liquid crystal display substrate of the present invention, it is possible to prevent the wiring layer containing aluminum as a main component from causing an electrical short circuit between the wiring layer and the layer stacked thereabove due to hillocks or whiskers.

[Brief description of drawings]

FIG. 1 is a sectional view 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 algae substrate according to the present invention.

FIG. 3 is an enlarged plan view of a main part of FIG.

FIG. 4 is a sectional view showing another embodiment of the liquid crystal display substrate according to the present invention.

FIG. 5 is a sectional view showing another embodiment of the liquid crystal display substrate according to the present invention.

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

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

FIG. 8 is a sectional view showing another embodiment of the liquid crystal display substrate according to the present invention.

[Explanation of symbols]

 1 transparent glass substrate 2 gate signal line 2A aluminum layer 2B tantalum layer 3 drain signal line

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ryoji Orisuke 3300 Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Devices Division (72) Inventor Koya Kosai 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Electronic Device Division (72) Inventor Juichi Horii 3300 Hayano, Mobara-shi, Chiba Hitachi Ltd. Electronic Device Division (72) Inventor Masaaki Matsuda 3300 Hayano, Mobara-shi, Chiba Hitachi Electronic Device Division (72) ) Inventor Keiichiro Ashizawa 3300 Hayano, Mobara-shi, Chiba Hitachi, Ltd. Electronic Device Division

Claims (1)

[Claims] 1. A wiring layer containing aluminum as a main component is formed on at least the liquid crystal side of one of the transparent substrates arranged to face each other with a liquid crystal interposed therebetween, and an insulating film is formed on the surface of the aluminum layer via an insulating film. In a liquid crystal display substrate in which a conductive layer or a semiconductor layer is laminated, at least a wiring layer on which the conductive layer or the semiconductor layer is laminated is formed with a metal layer having a melting point higher than that of aluminum. Display board.