JPH06236893A - Manufacture of tft liquid crystal display - Google Patents

Abstract

(57) [Abstract] [Purpose] When A1 is used as the main material of the source / drain electrodes of a TFT liquid crystal display device, the uppermost layer film on A1 is electrolytically corroded with ITO during development of a positive photosensitive resin. Suppress the reaction,
A source / drain electrode whose etching shape is a forward taper is obtained. [Structure] An intermediate layer film 8 serving as a source / drain electrode of a TFT liquid crystal display device is formed as a three-layer laminated film together with an uppermost layer film 9 and a lowermost layer film 7 of the same kind, and is formed on this three-layer laminated film. A positive photosensitive resin 10 is applied to form a predetermined pattern, only the uppermost layer film 9 is selectively etched, and then only the intermediate layer film 8 is selectively etched. After removing 10, the lowermost layer film 7 is etched to form source / drain electrodes.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a TFT liquid crystal display device, and more particularly to a method of forming source / drain electrodes.

[0002]

2. Description of the Related Art In recent years, there has been a strong demand for a TFT liquid crystal display device having a large size, and it has been required to reduce the wiring resistance of the source / drain electrodes. The source / drain electrodes of a conventional TFT liquid crystal display device are made of Cr, Ti, etc. in a single layer, but Cr or Ti has a resistivity of several 1
It is necessary to use a metal having a large resistivity of 0 to several 100 μΩ · cm and a lower resistivity. Au, A as the low-resistivity metal
Although g, Al, and Cu are mentioned, Al is most suitable because of cost and ease of handling. Further, in the case of Al, since ohmic contact with the underlying a-Si layer and the gate electrode is poor, it is usually necessary to use Cr or Ti as a barrier metal and use it in a laminated film of Al / Cr or Al / Ti.

On the other hand, in photolithography, which is an important technique for producing a TFT liquid crystal display device,
A positive photosensitive resin is mainly used from the viewpoint of pattern accuracy and work safety.

[0004]

However, when a positive type photosensitive resin is used for forming an Al pattern, Al dissolves in a developing solution at the time of development, so that ITO (tin-containing indium oxide) which is a pixel electrode material is used. Causes an electrolytic corrosion reaction,
The problem that ITO dissolves occurs. This problem can be solved by using a negative-type photosensitive resin, but as described above, in photolithography, the negative type has been changed to a positive type, and the use of a negative-type photosensitive resin is a fundamental solution. It doesn't.

The present invention is intended to solve such a conventional problem, in which a positive type photosensitive resin is used as a source material without causing electrolytic corrosion reaction with ITO which is a pixel electrode material.
It is an object of the present invention to provide a method for manufacturing a TFT liquid crystal display device capable of forming a drain electrode.

[0006]

In order to achieve the above-mentioned object, the present invention forms a three-layer laminated film of conductive thin films having an intermediate layer and an uppermost layer and a lowermost layer made of the same material, A positive type photosensitive resin is applied on this three-layer laminated film to form a predetermined pattern, and only the uppermost layer is selectively etched, and then only the intermediate layer is selectively etched. After removing the resin, the uppermost layer and the lowermost layer on the intermediate layer are simultaneously etched to form the source / drain electrodes.

[0007]

According to the present invention, when Al is used as the main material of the source / drain electrodes of the TFT liquid crystal display device by the above method,
The uppermost layer film on Al is IT when developing a positive photosensitive resin.
The etching shape is controlled by suppressing the electrolytic corrosion reaction with O, removing the positive photosensitive resin after etching the intermediate layer Al, and simultaneously etching the lowermost layer and the uppermost layer remaining on the intermediate layer. It is possible to obtain a source / drain electrode having a forward taper.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In the figure, 1 is a translucent insulating substrate, 2 is a gate electrode, 3 is an interlayer insulating film, 4
Is a semiconductor layer, 5 is an ohmic contact layer, 6 is a pixel electrode, 7 is a lowermost layer film, 8 is an intermediate layer film serving as source / drain electrodes, 9 is an uppermost layer film, 10 is a positive photosensitive resin, 1
Reference numeral 1 is a source / drain electrode.

Next, a method of manufacturing the TFT liquid crystal display device having the above structure will be described. As the translucent insulating substrate 1, a 7059 glass substrate manufactured by Corning Incorporated was used. 1 Al thin film on glass substrate by DC sputtering method
A film having a film thickness of 50 nm was formed and a predetermined pattern was formed by a wet etching method to obtain a gate electrode 2. And
As the interlayer insulating film 3, a silicon nitride film having a thickness of 400 nm is formed at a substrate temperature of 350 ° C. by a plasma CVD method, and a semiconductor layer 4
As the a-Si film and the ohmic contact layer 5 as the n ⁺ -type a-Si film with a thickness of 50 nm. Then, the a-Si film 4 and the n ⁺ type a-Si film 5
Were patterned into islands. After that, the ITO thin film is DC
A film having a thickness of 100 nm was formed by a sputtering method, and a predetermined pattern was formed by a wet etching method to form a pixel electrode 6 (FIG. A).

Subsequently, a Ti thin film 5 is formed as the lowermost layer film 7.
0 nm, 300 nm Al thin film as the intermediate layer film 8 and 500 nm thick Ti thin film as the uppermost layer film 9 in DC.
A continuous film was formed by the sputtering method (Fig. B). Then, a positive photosensitive resin 10 is applied to form a predetermined pattern (FIG. C), and the Ti thin film of the uppermost layer film 9 is used as an etching gas by a dry etching method by using a mixed gas of Cl ₂ , BCl ₃ and SF ₆ . It was selectively etched at (Fig. D).

Then, the Al thin film of the intermediate layer film 8 was selectively etched by a wet etching method with a mixed solution of phosphoric acid and nitric acid as an etching solution (FIG. 6E). After that, the positive photosensitive resin 10 is removed (FIG. F), and the uppermost layer film 9 on the intermediate layer film 8 and the Ti thin film of the lowermost layer film 7 are dry etched by using Cl ₂ and BCl _{3 as} etching gas. And S
The source / drain electrodes 11 were formed by selectively etching with a mixed gas of F ₆ (FIG. G).

When the source / drain electrodes 11 are formed as described above, it is possible to control the electrolytic corrosion reaction with ITO during the phenomenon of the positive type photosensitive resin, and it is desirable that the sectional shape after etching is also a forward taper. The shape could be obtained.

The etching of the uppermost layer film 9 may be wet etching, but an etching solution that does not etch the intermediate layer film 8 (for example, EDTA in the case of a Ti thin film,
It is necessary to use a mixed solution of hydrogen peroxide water and ammonia).

[0014]

According to the present invention, as is apparent from the above-described embodiments, the source / drain electrodes of the TFT liquid crystal skin device have three layers of conductive thin films having the intermediate layer and the uppermost layer and the lowermost layer made of the same material. A three-layer laminated film is formed, a positive type photosensitive resin is applied on this three-layer laminated film to form a predetermined pattern, only the uppermost layer is selectively etched, and then only the intermediate layer is selectively etched. After etching and removing the positive photosensitive resin,
Since the uppermost layer and the lowermost layer on the intermediate layer are simultaneously etched to form the source / drain electrodes, the following two effects can be obtained.

First, when Al is used for the source / drain electrodes, it is possible to control the electrolytic corrosion reaction with ITO, which is a pixel electrode, when forming a pattern using a positive photosensitive resin. Second, since the uppermost layer can be etched at the same time when the lowermost layer is etched, the sectional shape of the etching can be a forward taper.

[Brief description of drawings]

1 (a) to (d) TF in one embodiment of the present invention
Sectional structural drawing showing manufacturing process of T liquid crystal display device

2 (e) to (g) TF in one embodiment of the present invention
Sectional structural drawing showing the continuation of the manufacturing process of the T liquid crystal display device.

[Explanation of symbols]

 1 Translucent Insulating Substrate 2 Gate Electrode 3 Interlayer Insulating Film 4 Semiconductor Layer 5 Ohmic Contact Layer 6 Pixel Electrode 7 Bottom Layer Film 8 Intermediate Layer Film 9 Top Layer Film 10 Positive Photosensitive Resin 11 Source / Drain Electrodes

Claims (3)

[Claims] 1. A translucent insulating substrate on which a gate electrode, an interlayer insulating film, a semiconductor layer, an ohmic contact layer, and a pixel electrode are formed, and an intermediate layer having an uppermost layer and a lowermost layer made of the same material. Forming a three-layer laminated film of a conductive thin film which is formed, applying a positive photosensitive resin on the three-layer laminated film to form a predetermined pattern, selectively etching only the uppermost layer, Then, only the intermediate layer is selectively etched to remove the positive photosensitive resin, and then the uppermost layer on the intermediate layer and the exposed lowermost layer are simultaneously etched to form source / drain electrodes. A method for manufacturing a TFT liquid crystal display device, comprising: 2. The TFT according to claim 1, wherein the intermediate layer of the three-layer laminated film is a thin film containing Al as a main component.
Liquid crystal display device manufacturing method. 3. The method of manufacturing a TFT liquid crystal display device according to claim 1, wherein the uppermost layer and the lowermost layer of the three-layer laminated film are thin films containing Ti or Mo as a main component.