JP2514166B2 - Method for manufacturing active matrix liquid crystal display device - Google Patents

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 device having polycrystalline silicon or amorphous silicon and a conductive transparent electrode as constituent members, and more particularly to a method for making ohmic contact between the both members.

[0002]

2. Description of the Related Art As a large-capacity display device using liquid crystal, an active matrix system using a transistor as a switching device for each pixel is ideal, and theoretically the display capacity is infinite. This method constitutes a transistor array in a conventional silicon substrate or SOS board,
A liquid crystal was enclosed between the substrate and the glass plate to form a liquid crystal panel.

However, the method of forming the transistor array on the silicon substrate or the SOS substrate can be easily manufactured by the conventional semiconductor manufacturing technique, but the cost of the silicon wafer or the SOS substrate is high and the semiconductor manufacturing cost is high. The active matrix type liquid crystal panel has a drawback that it is very expensive. As a method for manufacturing an active matrix type liquid crystal panel at a lower cost, an array of thin film transistors (TFT) made of polycrystalline silicon or amorphous silicon is formed on a glass plate to form an active matrix. A method has been proposed.

[0004] The configuration of pixels used in a conventional liquid crystal display device using an active matrix scheme as an example in FIG. In FIG. 1, the switching transistor 1
The gate electrode is connected to the gate line 4, the source electrode is connected to the source line 5, and the drain electrode is connected to the drive electrode of the liquid crystal 3 and one electrode of the capacitor 2.

FIG. 2 shows an example of a plan view of the structure of one pixel when an active matrix is formed on a glass plate using TFTs. 6 is the drain of the TFT,
It is polycrystalline silicon that forms the channel and source,
The gate electrode is connected to the gate line 4, and the source electrode is connected to the source line 5. On the other hand, if the liquid crystal drive electrode 11 is provided by extending the polycrystalline silicon that constitutes the drain of the TFT as can be seen from the figure, the liquid crystal drive electrode 1
Therefore, it is not necessary to provide the manufacturing process 1 for that purpose. However, in the case of a light transmission type liquid crystal display device, the liquid crystal display electrode 11
Must be a transparent electrode with conductivity. TF
Polycrystalline silicon used as a material for T6 does not allow light to pass therethrough even if the thickness thereof is reduced to about 1000 angstroms. Furthermore, when it is used as a driving electrode due to coloring due to interference color, the display quality of a liquid crystal display body is improved. Markedly reduced.

[0006]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
A conductive transparent material should be used as the liquid crystal driving electrode. It is a general method of a display device using liquid crystal to use tin oxide or isodium oxide as a conductive transparent substance, and stability, conductivity, and light transmittance are very good,
Ideal as a transparent electrode.

However, as shown in FIG. 2, the transparent electrode 1
1 and polycrystalline silicon 6 must be taken electrical contacts, even if directly connected so the contact hole 9 was apertures polycrystalline silicon 6 and the transparent electrode 11 on the insulating layer on the drain electrode electrically contacts However, even if there is no contact or there is contact, it will not be completely ohmic.

[0008]

The present invention has been made in view of the above points.
Liquid crystal was sandwiched between a pair of substrates.
And the transparent substrates arranged in a matrix on the one substrate.
A bright electrode is formed, and a thin film transistor is formed on the transparent electrode.
Active matrix liquid crystal display device
In the method of manufacturing a device, the thin film transistor on the substrate.
Non-single-doped with source / drain regions doped with impurities
Forming a non-single crystalline silicon thin film
After forming a conductive metal on the thin film,
Patterning using photolithography technology
And the non-single crystal silicon thin film and the conductive metal are arranged.
The transparent electrode on the substrate, and the transparent electrode on the conductive metal.
Formed to extend over the substrate without conductive metal,
And then performing heat treatment , the non-single-crystal silicon
The thin film and the transparent electrode are electrically connected via the conductive metal.
It is characterized by being connected.

[0009]

The present invention will be described in detail below with reference to the drawings.

FIG. 3 illustrates a manufacturing process of an active matrix liquid crystal display device using a TFT according to the present invention. Particularly, the manufacturing process of the contact region between the drain of the TFT and the transparent electrode for driving the liquid crystal is shown. It is sectional drawing which showed an example in the order of the process. FIG. 3A shows a cross section when a polycrystalline silicon thin film 13 is formed on the surface of the glass plate 12 and the portions other than the drain, channel and source regions of the TFT are removed by etching. High-concentration impurities are diffused in the drain and source regions of the TFT.

Next, as shown in FIG. 3B, a silicon oxide film 14 is formed extending on the surface of the polycrystalline silicon thin film 13. This silicon oxide film may be obtained by thermally oxidizing the surface of polycrystalline silicon 13 or may be obtained by a vapor phase reaction growth method. Further, instead of the silicon oxide film, another insulating film such as a silicon nitride film or an alumina film may be used.

Next, the silicon oxide film 14 on the drain region is formed.
A contact hole is opened in the hole and a drain electrode extraction window is created. Next, as shown in FIG. 3, the aluminum thin film 15 is formed by extending at least all the contact hole portions opened in FIG. 3B. For this purpose, after forming an aluminum thin film on the entire surface of the glass plate, the photolithography technique is used to leave the aluminum in a desired region, and the others are removed by etching, whereby the structure shown in FIG. 3C can be obtained.

Next, a conductive transparent material such as tin oxide or indium oxide is formed on the entire surface as a liquid crystal driving electrode, and a liquid crystal driving electrode having a desired pattern is obtained by a photolithography technique. Cross-sectional structure of the substrate at this time is a is as shown in FIG. 3 (d), the polycrystalline silicon of the drain region 13
Are in contact with the transparent electrode 16 via the aluminum 15. With this configuration, this is 300 ~ 400 ℃
Polycrystalline silicon 13 and transparent electrode 1 by heating to
6 a and complete O Mi click-conductive state with a low contact resistance through the aluminum and. 1 aluminum thin film
It is opaque even if it is thinned to about 000 angstroms, but since the aluminum used in the present invention is formed only on the upper portion of polycrystalline silicon, the opacity of aluminum does not cause any drawback. Finally, liquid crystal orientation treatment is performed on the entire surface of the glass plate to complete one panel plate of the liquid crystal display device.

[0014]

As described above, the use of the production method of the present invention
The polycrystalline silicon and tin oxide thin film transistor, there is the transparent electrode such as indium oxide is possible with simple low resistance O Mi click contact therebetween through the aluminum, yet due to the intervention of aluminum There is no effect on the characteristics of the display device. The material of the TFT in the present invention is not limited to polycrystalline silicon,
It may be any non-single-crystal silicon such as amorphous silicon, metal via between the drain and the transparent electrode effects of the present invention other metal not be limited to the aluminum does not change.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration example of one pixel of an active matrix liquid crystal display device.

FIG. 2 is a plan view showing an example of a configuration of one pixel on a panel of a conventional active matrix liquid crystal display device using TFTs.

3A to 3D are cross-sectional views showing an example of a method of manufacturing an active matrix according to the present invention in the order of steps.

[Explanation of symbols]

 1,6 ・ ・ TFT 2 ・ ・ Capacitor 3 ・ ・ Liquid crystal 4,7 ・ ・ Gate line 5,8 ・ ・ Source line 9,10 ・ ・ Contact hole, 11 ・ ・ Transparent electrode for liquid crystal drive 12 ・ ・ Glass plate 13 ..Polycrystalline silicon 14..Silicon oxide 15..Aluminum 16..Conductive transparent electrode

Claims (1)

(57) [Claims] 1. An active matrix liquid crystal display in which a liquid crystal is sandwiched between a pair of substrates, transparent electrodes arranged in a matrix are formed on the one substrate, and thin film transistors are connected to the transparent electrodes. In the method of manufacturing a device, a step of forming a source / drain region of the thin film transistor on the substrate with a non-single-crystal silicon thin film doped with impurities; and a step of forming a conductive metal on the non-single-crystal silicon thin film,
Patterning the conductive metal using a photolithography technique; forming the transparent electrode on the substrate on which the non-single-crystal silicon thin film and the conductive metal are arranged; Formed so as to extend on the substrate, and then
And a step of performing heat treatment , wherein the non-single crystal silicon thin film and the transparent electrode are electrically connected to each other through the conductive metal.