JP3116665B2 - Manufacturing method of laminated electrode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a laminated electrode comprising a combination of a transparent conductive oxide material and aluminum.

In a thin film transistor which is a driving element of a liquid crystal display device, a photo sensor used as a light receiving element such as a solar cell or a facsimile, and the like, an oxide transparent conductive material having excellent translucency and aluminum having a small specific resistance are used. The device is made by laminating. Hereinafter, the present invention will be described using a thin film transistor used in a liquid crystal display device as an example.

There are two types of liquid crystal display devices, a simple matrix type and an active matrix type, which are used depending on the application. The active matrix type is provided with a thin film transistor (hereinafter, referred to as a TFT) for each pixel. Is selected, the TFT can be turned on and the other TFTs can be turned off.
Even if the number of scanning lines is large, cross-talk can be suppressed and a high contrast can be obtained. Therefore, it is used for large-area displays such as large televisions.

[0004]

2. Description of the Related Art TFTs constituting an active matrix type liquid crystal display device are classified into a staggered type and an inverted staggered type according to the arrangement of a source / drain electrode and a gate electrode. Here, the bus line,
Aluminum (Al), tantalum (Ta), chromium (Cr), etc. have attracted attention as constituent materials for gate electrodes, source / drain electrodes, etc. Ta and Cr have excellent chemical resistance. There is a problem with its high resistivity. Also, Al
Has a low resistivity, but has a problem with corrosiveness. Therefore, corrosiveness is covered by other technologies. on the other hand,
As a transparent electrode forming a pixel, an oxide transparent conductive material made of a solid solution (abbreviated as ITO) of tin oxide (SnO ₂ ) and indium oxide (In ₂ O ₃ ) is used.

FIG. 2 shows a cross-sectional structure of a staggered TFT. The manufacturing method is such that after a film of aluminum (Al) is formed on an insulating substrate 1 to a thickness of about 600 mm by a sputtering method, a photolithography technique is used. A pattern is formed using (photolithography) to form a drain bus line 2.
Next, I is placed on the insulating substrate 1 including the drain bus line 2.
TO is formed to a thickness of about 300 mm by sputtering and IT
An O film 3 is formed, and then n ⁺ a-Si (amorphous silicon) is formed thereon by a plasma vapor deposition method (P-CVD method).
A contact layer 4 is formed by forming a film to a thickness of about 200 °, and a resist 5 is coated thereon by a spin coating method, and then selectively exposed and developed to form a contact layer 4 on the pixel electrode forming portion and the drain electrode forming portion. The resist 5 is left. Next, after the exposed contact layer 4 made of n ⁺ a-Si is dry-etched with carbon tetrafluoride (CF ₄ ) gas, the ITO film 3 is selectively etched using a chlorine-based etchant. Do. Next, after the resist 5 is dissolved and removed, P-CVD is performed on the substrate 1 having the contact layer 4 made of n ⁺ a-Si on the surface.
The semiconductor layer 6 made of a-Si is formed to a thickness of about 400
Further, a gate insulating layer 7 made of Si ₃ N ₄ is further formed on this to about 3000Å.
The gate electrode film 8 made of Al is formed thereon to a thickness of about 800. Next, a resist is coated on the substrate 1 and subjected to selective exposure and development to form a resist pattern 9 for gate electrode patterning and element isolation.
Next, the exposed portion of the gate electrode film 8 is covered with phosphoric acid (H ₃ PO _3).
4) in liquid systems and also, the gate insulating layer 7 and the semiconductor 6 and the contact layer 4 is dry-etched with CF ₄ based gas, across the drain electrode 12 and source electrode 11 on the insulating substrate 1, a- A TFT composed of a laminate of the Si semiconductor layer 6, the Si ₃ N ₄ gate insulating layer 7, and the gate electrode 13 is completed. (D in the same figure) A staggered TFT is manufactured as described above. On the insulating substrate 1, a large number of drain bus lines 2 made of Al serve as pixel electrodes as apparent from the figure. The pattern is formed with the electrode 11 interposed therebetween.

However, as described above, since the thickness of the ITO film 3 covering the drain bus line 2 is as thin as about several hundreds of mm, the occurrence of pinholes and cracks cannot be avoided. Selective etching 3 is performed using a chemical such as acid or alkali (wet etching)
For this reason, Al is partially etched, so that disconnection of the drain bus line 2 is likely to occur, which lowers the reliability of the liquid crystal display device. Therefore, it is necessary to improve the corrosion resistance of the drain bus line 2.

[0007]

Al is a metal having a low resistivity and is suitable as a constituent material of a bus line having a large amount of electricity. However, chrome (Cr), molybdenum (Mo), and the like have been used as constituent materials of bus lines and electrodes due to poor corrosion resistance. However, if Al can be used, there is nothing better than this. The problem here is not Al itself, but when forming a pattern by applying chemical etching after forming an ITO film or insulating film on Al which has already been patterned such as a bus line, Pinholes and cracks exist because the film and the insulating film are thin, and the etchant penetrates through these defects to attack Al.

Further, an alkaline solution (eg, tetramethylammonium) is used in a developing solution (eg, MF-319) used for developing a positive resist (eg, MP-1400, Shipley) used in the photolithography process. (Hydroxide)
Therefore, when ITO and Al are in contact with each other, an electrochemical phenomenon occurs and abnormal corrosion occurs.

Therefore, a method is employed in which anodic oxidation or heating in an oxidizing atmosphere, for example, O ₂ gas is performed before performing chemical etching. However, anodic oxidation is effective when an insulating film is coated on Al, but cannot be used when a conductive film such as an ITO film is coated because the conductive film is dissolved by voltage application. . In addition, heating in O ₂ air has not been recognized to be so effective in improving corrosion resistance. So, Al
The problem is to put into practical use an effective method for preventing the corrosion of Al when a conductive film such as an ITO film is formed in contact with the top.

[0010]

Means for Solving the Problems The above-mentioned problems are encountered in a process of manufacturing an electrode in which Al and ITO are laminated on a transparent insulating substrate.
After coating the upper part of the Al thin film pattern formed on the substrate with ITO, heat treatment is performed in a reduced pressure steam atmosphere to oxidize the surface of the Al thin film exposed through pinholes or cracks. The problem can be solved by configuring a manufacturing method.

[0011]

According to the present invention, the exposed Al is subjected to steam treatment heated to a high temperature such as 200 to 600 ° C. to convert the exposed Al into alumina (γ ′
Al ₂ O ₃ ). In other words, Al rapidly oxidizes when placed in the atmosphere, forming a very dense passive film (amorphous Al oxide film) with a thickness of several tens of millimeters, and this thickness depends on the heating temperature. Does not increase so much and therefore does not contribute much to the improvement of corrosion resistance. On the other hand, Al easily oxidizes (corrodes) to water and varies depending on the processing temperature. Bayer light (Al ₂ O ₃ -3H ₂ O) or boehmite (Al ₂ O ₃ -H ₂ O)
O).

Therefore, the present invention provides a relatively thick and dense .gamma. ' To obtain Al ₂ O ₃ ,
In our experiments, a dielectric strength of ² MV / cm ² was obtained.

An advantage of adopting this method is that washing and drying steps are not required, which greatly contributes to mass production.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Sputtering method on an insulating substrate 1 made of glass
After forming an Al film 15 to a thickness of about 600 mm by
Is coated with a resist by spin coating,
The resist is applied only to the drain bus line
I made strike pattern 16. (End of Fig. 1A)_ThreePO_FourSelective etching of Al film 15
After making drain bus line 2
The ITO film 19 was formed to a thickness of 800 mm by the
At this time, the pinhole 17 and the
Cracks 18 are inevitably occurring. Next, the insulating substrate 1 is put into an electric furnace equipped with an exhaust device.
Then, the insulating substrate 1 is heated to 400 ° C., and the inside of the apparatus is evacuated to 1.
While maintaining the pressure at 0 torr, supply heated steam 20 at a flow rate of 200 sccm.
And hold it for one hour, under pinhole 17 and crack 18
Al exposed part is γ´Al _TwoO_ThreeChanged to 21. Next, a resist is coated on this, selective exposure and development processing are performed.
Contact each drain bus line 2 by
Resist pattern only on the drain and source electrode formation areas
Horn 22 was formed. (D in the same figure) Subsequently, the ITO film 19 is selectively etched with an HCl-based etchant.
And then removing the resist pattern 22
A pattern as shown in FIG.
In the drain bus line 2
No bugs occurred.

[0015]

According to the present invention, in a device in which Al and ITO are laminated to form an electrode and Al is used as a conductor line, Al can be used without fear, thereby minimizing the pattern and improving the performance. Can be improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating a manufacturing process of a staggered TFT.

[Explanation of symbols]

 2 Drain bus line 3,19 ITO film 11 Source electrode 12 Drain electrode 13 Gate electrode 15 Al film 17 Pinhole 18 Crack 20 Heated steam

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor: Tamotsu Wada, Fujitsu Limited, 1015 Uedanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture 56) References JP-A-4-217378 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1343

Claims (1)

(57) [Claims] In a manufacturing process of an electrode in which aluminum and an oxide transparent conductive material are laminated on a transparent insulating substrate, an oxide transparent conductive material is coated on an aluminum thin film pattern formed on the substrate, and then the reduced pressure steam is applied. A method for manufacturing a laminated electrode, comprising performing heat treatment in an atmosphere to oxidize the surface of an aluminum thin film exposed through pinholes or cracks.