JP3192813B2 - Liquid crystal display - Google Patents

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 more particularly to a structure of wiring electrodes on an array substrate.

[0002]

2. Description of the Related Art As a liquid crystal display device for displaying characters such as characters and figures, a matrix type is used in which an address wiring electrode and a data wiring electrode intersect and each of the intersecting sections is a pixel. An active matrix type liquid crystal display device having a driving switching element corresponding to each pixel is also frequently used. Such switching elements include thin film transistors (hereinafter referred to as TFTs).
) And a non-linear resistance element (MIM) are typical,
Among them, TFT is excellent in high-speed response and suitable for full-color display.

The configuration of an array substrate of such an active matrix type liquid crystal display device is described in, for example, IEICE Tech.
Vol. 110, no. That is, the address wiring electrode is made of aluminum (Al) and molybdenum-tantalum alloy
An address wiring electrode and an auxiliary capacitance wiring electrode are formed as a laminated structure of (Mo.Ta). In the formation method, Al is first deposited on an insulating substrate such as glass by a sputtering method, and is patterned into a predetermined wiring electrode shape. Then
An alloy of Mo and TA is deposited and processed to completely cover the Al pattern to form an address wiring electrode and an auxiliary capacitance wiring electrode. A transistor active part, a pixel electrode part, a data wiring electrode and a source / drain electrode are sequentially formed,
An array substrate for an active matrix type liquid crystal display device is formed.

FIG. 3 shows a schematic sectional configuration of such a TFT portion, and FIG. 4 shows a schematic sectional configuration of an address wiring electrode portion. 3 and 4, a gate electrode 2a, an address (gate) wiring 2b, gate insulating films 3a and 3b, a semiconductor layer 4, an etching stopper layer 5, a contact layer 6, and a pixel electrode are provided on an insulating substrate 1 made of glass. 7,
A source electrode 8, a drain electrode 9, and a protective film 10 are sequentially formed. With a substrate having such a configuration, a liquid crystal display device having a display surface with a diagonal size of 13.8 inches and 900 address lines can obtain good display characteristics with a pixel aperture ratio of about 30%.

[0005]

As the display surface of such a liquid crystal display device becomes larger in screen and higher in definition, the length of the address wiring electrode becomes longer and the aperture ratio of the pixel becomes almost constant. The width of the address wiring electrode tends to be narrow. These trends lead to higher resistance of the address wiring electrodes,
The waveform of the address signal is distorted, causing a signal propagation delay. This appears as non-uniformity of the image, which leads to a decrease in image quality.

As a countermeasure, it has been considered that the address wiring electrode and the auxiliary capacitance wiring electrode have a laminated structure of aluminum and a high melting point metal to reduce wiring resistance and to reduce signal propagation delay. However, such a laminated structure requires at least two patterning steps in order to completely cover aluminum with the high melting point metal. This is because when aluminum is used alone as an address wiring electrode, heat resistance and chemical resistance are poor, and process consistency for forming an array substrate is lacking.

For example, when aluminum is used alone, the gate insulating film is formed at a substrate temperature of 300 ° C. or more.
Aluminum hillocks are generated by thermal stress considered to be caused by a difference in thermal expansion coefficient with the substrate, and the interlayer insulating property is significantly impaired. In order to use aluminum as an address wiring electrode in this manner, a laminated structure that is completely covered with a high melting point metal is required, which complicates the process and lowers the throughput.

[0008]

According to the present invention, there is provided an address wiring electrode formed on a substrate, a data wiring electrode disposed so as to intersect with the address wiring electrode, and an auxiliary electrode provided in parallel with the address wiring electrode. A capacitor wiring electrode, a transparent pixel electrode defined by the address wiring electrode and the data wiring electrode, and at least a switching element corresponding to the transparent pixel electrode and connected to the address wiring electrode and the data wiring electrode. In a liquid crystal display device having an array substrate, the address wiring electrode and the auxiliary capacitance wiring electrode are a first metal made of Al or an Al alloy formed on the substrate and a high melting point metal laminated on the first metal. And a second metal thereof, for example, Ta or a Ta alloy, in a direction parallel to the data wiring electrode of the first metal. Width is a liquid crystal display device is larger than a width of the second metal, also, the angle between the substrate in the thickness direction side surface of the first metal is a liquid crystal display device is an acute angle.

[0009]

In the configuration of the address wiring electrode and the auxiliary capacitance wiring electrode as described above, for example, Al is used as the first metal.
With a film thickness of 100 nm, and an alloy layer of Mo and Ta as a second metal as a refractory metal laminated on the first metal.
In the case of a structure with a thickness of 200 nm, after patterning an alloy layer of Mo and Ta by dry etching, patterning is performed on Al using normal wet etching. In this case, Al side etching occurs, and after the gate insulating film is formed, the side etching portion becomes hollow, resulting in Al corrosion and poor step coverage.

[0010] However, by dry etching, Mo
By continuously etching the alloy layer of Al and Ta and the Al layer, a taper shape in which the angle formed between the side surface in the thickness direction of the wiring electrode and the substrate is obtained is obtained. In this tapered shape, the difference between the width of the Al pattern and the pattern width of the alloy layer of Mo and Ta can be within 1 μm. That is,
The Al layer has an exposed portion within 1 μm on the side surface. Such a shape does not provide a structure in which the Al layer is completely covered with the alloy layer of Mo and Ta, and therefore, the presence or absence of Al hillocks in the subsequent heating process becomes a problem. But,
If the exposed portion of the Al layer is within 1 μm, Al hillocks do not occur even in a heating process at 450 ° C. or less, and processing can be performed without any problem in the array substrate process.

Therefore, compared with the structure in which the alloy layer of Mo and Ta completely covers the Al layer, it is not necessary to consider much the exposure misalignment between the Al layer pattern and the alloy layer pattern of Mo and Ta. Therefore, the wiring width of Al can be increased. For example, the wiring resistance in the case of the conventional structure in which the Al layer is completely covered with the alloy layer of Mo and Ta is 9 KΩ, whereas the wiring resistance is about half, 4.5 KΩ.
It can be. In other words, in other words, if the wiring resistance is kept constant, the wiring width can be reduced, so that the aperture ratio of the pixel can be improved.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows a schematic cross section of a protective film type inverted stagger type TFT portion, and FIG. 2 shows an equivalent circuit of an array substrate having the inverted stagger type TFT portion.

In FIG. 2, first, address wiring electrodes 12 and data wiring electrodes 13 are arranged in a matrix on a transparent glass substrate 11, and auxiliary capacitance wiring electrodes 14 are connected to address wiring electrodes.
It is formed so as to be substantially parallel to 12. In the vicinity of each intersection of these wiring electrodes, amorphous silicon (a-S
i) A TFT 15 made of a film is formed. The drain electrode 17 of the TFT 15 is connected to the data wiring electrode 13, and the gate electrode is formed simultaneously with the address wiring electrode 12.
The source electrode of the TFT 15 is connected to a display electrode 16 and a liquid crystal capacitor 17 of each pixel, and an auxiliary capacitor 18 formed by an auxiliary capacitor wiring electrode and a pixel electrode.

Next, a process of manufacturing the array substrate shown in FIG. 1 will be described. First, SiOx is formed on the glass substrate 21 by a plasma CVD method. An Al film 22 and an alloy film 23 of Mo and Ta are successively deposited thereon by sputtering to have a thickness of 100 nm and 200 nm, respectively.
At this time, the Al film is made of an Al alloy, for example, Cu 1 atomic%, Si 0.5
An Al alloy film containing atomic% is also possible.

A part of the address wiring electrode pattern including the gate electrode and a part of the auxiliary capacitance wiring electrode are formed on the laminated film by photolithography, and a chemical dry etching (CDE) of CF4 + O2 mixed gas is performed. Using Mo
Etching is performed so that the angle formed between the alloy film 23 and the substrate is 30 degrees or less. The etching conditions at this time were: O2 flow rate 30 SCCM, CF4 flow rate 160 SCCM, etching pressure
30 Pa.

Subsequently, for example, reactive ion etching (RIE) of a Cl 2 -based mixed gas of Cl 2 + BCl 3 + He is performed to form Al.
The film 22 is etched. The etching condition at this time is Cl
2 Flow rate 30 SCCM, BCl3 flow rate 100 SCCM, He flow rate 70 SCCM, pressure
15Pa. The width of the Al film is 1 μm larger than the width of the alloy film 23 of Mo and Ta by controlling the over-etching time.
The size was controlled to be within. By the above process, the address wiring electrode and the auxiliary capacitance wiring electrode pattern are completed.

Subsequently, four layers of SiOx24, SiNx25, amorphous silicon (a-Si) 26, and SiNx27 are successively deposited by a plasma chemical vapor deposition (CVD) method.
Then, after patterning the upper layer of SiNx27 and performing a pretreatment, N ^{+ is used} as a source / drain electrode contact.
A type a-Si film 28 is deposited by a plasma CVD method. Note that an SiO2 film may be used instead of the SiOx film by a thermal CVD method.

Next, the a-Si film is patterned, and an indium-tin-oxide (ITO) film 29 is formed as a transparent pixel electrode serving as a display electrode and patterned. This electrode is also used as a part of one electrode of the storage capacitor.
Subsequently, an opening of the address wiring pad portion is formed with an HF-based etchant. Next, Cr, Al, Al 3
A layer is deposited and formed as a data line, a source electrode 30 and a drain electrode 31. Thereafter, the N ⁺ -type a-Si film 28 on the back channel is removed by RIE. Next, as a passivation, a plasma CVD method is used.
By forming the SiNx film 32, a liquid crystal display array substrate is completed.

Although the average wiring width of the address wiring electrodes of this array substrate was 10 μm and the wiring length was 20 cm, the resistance value of the address wiring electrodes was about 4.5 KΩ, and the conventional Al layer was replaced with Mo.
The wiring resistance in the case of the structure completely covered with the alloy layer with Ta was 9 KΩ, but about half.

By performing taper etching on the alloy layer of Mo and Ta on the address wiring electrode and the auxiliary capacitance wiring electrode, hillocks do not occur in the Al film even if the lower Al film does not have a large taper. Therefore, the step coverage of the gate insulating film was improved, and the same interlayer insulating property as that of the related art was obtained.

[0021]

As described above, according to the present invention, the address wiring electrode and the auxiliary capacitance wiring electrode have a laminated structure composed of the first metal layer and the second metal layer, and the data of the first metal is formed. The width in the direction parallel to the wiring electrode is the second width.
The width of the first metal is larger than the width of the first metal, and the angle between the side surface in the thickness direction of the first metal and the substrate is made an acute angle.
The resistance of the address wiring electrode and the auxiliary capacitance wiring electrode can be reduced. Accordingly, the aperture ratio of the pixel can be substantially increased, and the screen size and the definition of the liquid crystal display device can be increased. In addition, since only one photo process is required in the manufacturing process, the process can be simplified and the throughput can be increased.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a configuration of a TFT unit according to an embodiment of the present invention.

FIG. 2 is a schematic diagram showing an equivalent circuit of an array substrate having the TFT unit of FIG.

FIG. 3 is a schematic sectional view showing a configuration of a conventional TFT unit.

FIG. 4 is a schematic sectional view showing a configuration of a conventional address wiring electrode.

[Description of Signs] 11 ... Glass substrate 12 ... Address wiring electrode 13 ... Data wiring electrode 14 ... Auxiliary capacitance wiring electrode 15 ... TFT 16 ... Pixel electrode 22 ... First metal film 23 ... Second metal film.

Claims (2)

(57) [Claims] An address wiring electrode formed on a substrate; a data wiring electrode arranged to cross the address wiring electrode; an auxiliary capacitance wiring electrode provided in parallel with the address wiring electrode; A liquid crystal display device having an array substrate including at least an electrode, a transparent pixel electrode partitioned by the data wiring electrode, and a switching element corresponding to the transparent pixel electrode and connected to the address wiring electrode and the data wiring electrode. The address wiring electrode and the auxiliary capacitance wiring electrode are formed of a first metal made of Al or an Al alloy formed on a substrate and a second metal laminated on the first metal. the said data line electrodes parallel to the width of the metal much larger than the width of the second metal, the difference is within 1μm
The liquid crystal display device which is characterized in that a. 2. The liquid crystal display device according to claim 1, wherein
The liquid crystal display device according to claim 1, wherein an angle formed between a side surface of the first metal in a thickness direction and the substrate is an acute angle.