JPH07325321A - Production of liquid crystal display device - Google Patents

Abstract

PURPOSE:To prevent the erosion of Al by the formation of a masking resist with an active matrix liquid crystal display device formed by using anodically oxidized Al gate TFTs. CONSTITUTION:Contact protective films 12CTG, 12CTS consisting of Al are previously formed on contact terminals 11CTG, 11CTS of gate lines 12GL and auxiliary capacitance lines 12SL. Etching of Al is executed via contact holes CTG, CTS after anodic oxidation, by which the contact protective films 12CTG, 12CTS are removed together with the Al2O3 films an Ta of the contact terminals 11CTG, 11CTS is exposed. The good ohmic contact of contact metals 19CT of upper layers and connecting lines 19SC is obtd.

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 liquid crystal display device, and more particularly to a method for manufacturing a liquid crystal display device in which Al is used for a gate wiring and the surface thereof is anodized.

[0002]

2. Description of the Related Art Liquid crystal display devices have advantages such as small size, thin shape, and low power consumption, and are being put to practical use in fields such as OA equipment and AV equipment. In particular, an active matrix type using a thin film transistor (hereinafter abbreviated as TFT) as a switching element enables driving with a duty ratio of substantially 100%, and a fine moving image display is realized.

The active matrix type liquid crystal display device is
A substrate in which TFTs and display electrodes are arranged in a matrix (TFT substrate) and a substrate having a common electrode (counter substrate)
Are bonded together, and liquid crystal is sealed in the gap. The TFT is a switching element that selects the data signal input to the display electrode, and the same row is connected to one gate line and the same column is connected to one drain line. The gate line group is line-sequentially scanned to turn on all TFTs for each row, and a data signal synchronized with this is input to each display electrode. The potential of the common electrode is set in synchronization with the scanning signal, and the liquid crystal in the gap is driven by the voltage between the opposing display electrodes, and the light transmittance is adjusted for each pixel to obtain the desired display screen. To be Further, the driving state of the liquid crystal during the OFF period is maintained by the voltage held in the liquid crystal capacitor in which both electrodes are opposed to each other, but the holding characteristic can be improved by adding the auxiliary capacitor in parallel with the liquid crystal capacitor. it can. The auxiliary capacitance is set by placing a dedicated auxiliary capacitance electrode on the display electrode and setting the same potential as the common electrode, or
It is obtained by extending a part of the gate line and overlapping it with the display electrode.

As a TFT, an inverted stagger type in which a gate electrode is provided below a channel is generally used. However, in this structure, since the gate wiring is the lowermost layer, a defect that occurs in a subsequent manufacturing process becomes a problem. That is, in order to reduce the signal delay due to the wiring resistance, it is desirable to use Al having a low specific resistance as the gate wiring material.
Is likely to have a projection-like defect (hillock) on its surface, which may grow in a subsequent high-heat process to penetrate the insulating film, resulting in a short circuit. Further, when Cr is used, it is suitable in terms of strength, but it causes signal delay due to its high specific resistance. In order to solve these problems, for example, Al described in JP-A-2-85826 is disclosed.
There is anodic oxidation. This is because Al is used as a gate wiring material and an Al ₂ O ₃ film formed on the surface as a protective film by an anodic oxidation method.
By forming the insulating film, signal delay and hillock generation are prevented.

A conventional example using the anodized gate Al will be described below. FIG. 12 is a plan view of the TFT substrate,
FIG. 7A is an enlarged plan view of a substrate end portion, and FIG. In the pixel portion, a gate line (12GL) having a gate electrode (12G) portion and a drain line (19DL) having a drain electrode (19D) portion are arranged to intersect. A display electrode (18PX) is formed in a region surrounded by both lines (12GL, 19DL) and is connected to a source electrode (19S) of a TFT formed at an intersection of both lines (12GL, 19DL). . In addition, an auxiliary capacitance electrode (12SE) is insulatingly arranged below the display electrode (18PX) to form an auxiliary capacitance. On the other hand, a gate line (12GL) is extended to the end portion of the substrate and connected to the gate input terminal (18GP). In addition, the auxiliary capacitance line (12S) integrated with the auxiliary capacitance electrode (12SE).
L) is extended, is commonly connected by a connection line (19SC), and is connected to the auxiliary capacitance input terminal (18SP). The gate line (12GL) and the auxiliary capacitance line (12SL) are the voltage supply line (12A) for anodic oxidation.
L) and are commonly connected, and are integrated with the voltage supply terminal (12AP) for anodic oxidation.

Gate electrode (12G), gate line (1
2GL), the auxiliary capacitance electrode (12SE), the auxiliary capacitance line (12SL), the voltage supply line (12AL) and the voltage supply terminal (12AP) are formed of Al in the same layer, and in the pixel region on the left side of the X-ray, The gate and the auxiliary capacitance wiring (12G, 12GL, 12SE, 12SL) are anodized. Below the gate line (12GL) and the auxiliary capacitance wiring (12SE, 12SL), the same wiring (11GL, 11SE,
11SL) are connected to form a gate electrode (12G)
Is a single layer film of Al to reduce the step difference of the TFT.
In addition, the drain line (19DL) and the connection line (19
SC) is made of Al or the like in the upper layer with the insulating film sandwiched therebetween, and is composed of a display electrode (18PX) and a gate input terminal (1).
8GP) and the auxiliary capacitance input terminal (18SP) are also formed of ITO in this layer. Connection line (19SC)
And the auxiliary capacitance line (12SL) are connected through a contact hole (CTS) opened in the insulating film, and the gate input terminal (18GP) and the gate line (12GL) are contact holes (CTG) opened in the insulating film. Via a contact metal (19CT) made of Al. The connecting portions of the auxiliary capacitance line (12SL) and the gate line (12GL) are contact terminals (11CTS, 11CTG) where Ta of the lower film is exposed, and the connecting line (19SC) and contact metal (19CT), respectively. It is connected to the. This is because Ta has higher reliability than Al and is suitable for contact formation when exposed to the atmosphere.

The TFT substrate is manufactured as follows. First, by forming and etching Ta, gate and auxiliary capacitance wiring (11GL, 11SL, 11SE, 11CTS, 1
After forming 1 CTG), the gate / auxiliary capacitance and voltage supply wiring (12G, 12) are formed by Al film formation and etching.
GL, 12SL, 12SE, 12AL, 12AP). Next, after masking the area on the right side of the X-ray in the figure with a resist, the substrate is dipped in an anodizing solution, and a predetermined DC voltage is applied from the voltage supply terminal (12AP) to obtain gate / auxiliary capacitance. Wiring (12G, 12G
L, 12SL, 12SE) on the surface of the anodic oxide film, that is,
An Al ₂ O ₃ insulating film is formed. After removing the resist, Al ₂ O ₃
In order to improve the film quality of the above, heat treatment at 200 to 400 ° C. is performed. Since a contact will be formed later in the area on the right side of the X-ray, the masking resist prevents contact of the anodizing liquid, and at least the contact terminals (11CTG, 11CT).
S) is exposed. Incidentally, Ta can be anodized and does not dissolve even if it comes into contact with an anodizing liquid like Cr, so it is suitable for two-layer wiring with the anodizing gate Al. Then, an insulating film such as SiN _x , an island layer of a-Si, and a display electrode (18PX) made of ITO, a gate input terminal (18GP), and an auxiliary capacitance input terminal (18S).
After forming P), the insulating film is etched to form predetermined contact holes (CTS, CTG). And
By laminating and etching Al, the source / drain electrodes (19S, 19D) and the drain line (19S
DL), the connection line (19SC) and the contact metal (19CT) are formed, and the auxiliary capacitance line (12SL), the connection line (19SC) and the gate line (12GL) are respectively provided via the contact holes (CTS, CTG). ) And the gate input terminal (18GP) are connected. Finally, the voltage supply wiring (12AL, 12AP) is removed by cutting the substrate along the line Y in the figure.

[0008]

As described above, the conventional method
Since selective etching of Al ₂ O ₃ with respect to 1 is difficult, a masking resist is formed in advance in a region where an anodic oxide film is unnecessary, such as a contact forming portion, to prevent anodic oxidation. In consideration of safety and accuracy, a masking resist used is, for example, a pattern of a novolac-based positive photoresist. However, since the organic alkaline aqueous solution containing tetramethylammonium hydroxide used as the developer reacts with Al, the exposed Al is eroded in the area where the masking resist is not formed.

In particular, when there are crystal defects or impurities in the film due to the cleaning step of the substrate before the film formation of Al or the foreign substances during film formation, erosion is promoted by the developing solution. For this reason, there are regions where the film thickness is extremely thin and regions where the line width is narrow, which leads to an increase in wiring resistance. Further, when the transparent film becomes transparent due to anodic oxidation and becomes a transparent pinhole, the light shielding failure occurs in the Al single layer portion in the non-display area, which leads to a decrease in contrast. In particular, since the gate electrode (12G) plays a role of preventing light from entering the a-Si, there is a problem that the OFF current increases when light is leaked.

[0010]

SUMMARY OF THE INVENTION The present invention is a method of manufacturing a liquid crystal display device, which has been made to solve the above problems. First, on a substrate, etching selectivity with respect to Al can be obtained. A step of forming a contact terminal of the first wiring by forming a film of a first conductive material that is present and capable of being anodized and etching the same; and covering the first conductive material with Al.
And forming an island-shaped contact protective film on the contact terminal while forming a first wiring connected to the contact terminal and a voltage supply wiring for anodic oxidation by etching the film. A step of forming an anodic oxide film of Al or an anodic oxide film of the first conductive material on the surface by anodizing the entire region of the first wiring, and forming an insulating layer and a non-single-crystal semiconductor film on the entire surface. The step of sequentially forming the non-single-crystal semiconductor film to form an island shape and the step of forming a transparent conductive film on the entire surface and etching the display electrode arranged in a matrix and the edge portion of the substrate. A step of forming an array of external connection terminals, and a step of exposing the contact protective film by opening a contact hole on the contact terminal by etching the insulating layer. And a step of removing the Al anodic oxide film on the contact protection film and the contact protection film by etching Al using the insulating layer having the contact hole as a mask, and a second conductive material on the entire surface. And forming a second wiring, and forming a contact metal for connecting the contact terminal to the external connection terminal through the contact hole.

Secondly, in the first structure, the contact protection film is formed inside the opening region of the contact hole, and the opening region of the contact hole extends to the Al portion of the first wiring. There is no configuration. Thirdly, in the first configuration, the first conductive material is Ta.

[0012]

In the first structure, the island-shaped contact protection film made of Al is provided on the contact terminal, so that A
By the etching of 1, the contact protective film is removed together with the Al ₂ O ₃ film to expose the contact terminal.
As a result, the contact can be formed after the entire surface of the gate wiring is anodized, so that the masking resist need not be formed. Therefore, Al is not eroded by the alkaline developer,
It is possible to prevent an increase in wiring resistance due to a reduction in film thickness and line width and a reduction in contrast due to light leakage.

In the second structure, when Al is etched using the contact hole as a mask, since the Al does not reach the edge of the contact hole, only the contact protection film and the anodic oxide film on the surface of the contact protection film are removed and side etching is performed. It is prevented. In the third structure, Ta can be anodized, so that in the two-layer structure with Al and the wiring structure, A
l has a defect and is not eroded even when immersed in an anodizing solution,
An anodic oxide film is formed to prevent disconnection.

[0014]

EXAMPLES Next, examples of the present invention will be described with reference to FIGS. The same reference numerals are used for the same reference numerals as in the conventional example. The planar structure of the TFT substrate is the same as that of the conventional example shown in FIG. 12, and in the method of manufacturing a liquid crystal display device according to the present invention, a connection portion between a gate line (12GL) and a contact metal (19CT) and an auxiliary capacitance line ( It is characterized by the connecting portion between 12SL) and the connecting line (19SC).

In FIG. 1, (a) is a gate line (1
2B) is an enlarged view of a connection portion between a contact metal (19CT) and (2CT), and (b) is an auxiliary capacitance line (12SL).
It is an enlarged view of the connection part of the connection line (19SC). Gate line (1 with a double-layered structure of Ta and Al)
1GL, 12GL and auxiliary capacitance line (11SL, 1SL)
2SL is a contact terminal (11CTG,
11CTS) part is a single layer film of Ta. That is,
There is no upper film of Al and the lower film of Ta is exposed. Further, in the area of the contact terminals (11CTG, 11CTS), a contact protective film (1) in which Al is formed in an island shape.
2CTG, 12CTS). Contact protective film (1) for contact terminals (11CTG, 11CTS)
2CTG, 12CTS) is not adhered to the anodic oxide film in the region, and the contact protection film (12CTG, 12CTS) is removed later by etching Al to form Ta.
Is exposed. Therefore, good ohmic contact between the gate line (12GL) and the contact metal (19CT) and between the auxiliary capacitance line (12SL) and the connection line (19SC) can be obtained.

Hereinafter, referring to FIGS. 1 and 12,
The manufacturing method will be described with reference to FIGS. 2 to 11 are cross-sectional views showing the manufacturing process. The left side of each figure is the sectional structure of the pixel portion, and the right side is the contact terminal (11C).
It is a sectional structure of a TG) portion. First, Ta is sputtered on a transparent substrate (10) such as glass to about 100.
The gate line (11GL), the auxiliary capacitance electrode (11SE), and the gate line (11GL) are formed by stacking them to a thickness of 0Å and patterning them by photoetching.
Contact terminals (11CTG) are formed. At this point, the auxiliary capacitance line (11SL) and its contact terminal (11CTS) are simultaneously formed.

Subsequently, Al is sputtered to about 150.
By stacking to a thickness of 0Å and patterning this by photo-etching, the gate electrode (12G) of the TFT, T
a and an auxiliary capacitance electrode (12SE) forming a two-layer film structure,
A gate line (12GL) that forms a two-layer film structure with Ta integrally with the gate electrode (12G), and a contact protection film (12CTG) of the contact terminal (11CTG) are formed. (See above, FIG. 3) At this time, at the same time, the auxiliary capacitance line (12SL) that forms a double-layered film structure with Ta, the contact protection film (12CTS) of the contact terminal (11CTS), and the voltage supply for anodization. The wiring (12AL, 12AP) is formed.

Subsequently, as described below, Al wiring (12G,
12GL, 12SE, 12SL) is anodized. Immediately
Then, the substrate that has undergone the steps up to FIG. 3 is treated with 3% tartaric acid.
Diluted with ren glycol or propylene glycol
Immerse in the anodizing solution and remove all from the voltage supply terminal (12AP)
For Al wiring (12G, 12GL, 12SE, 12SL)
Apply DC voltage. As a result, the surface of Al and Ta
Is anodized and Al ₂O₃(13A) and Ta₂O_Five(1
3T) is deposited. (See above, FIG. 4) Next, as the gate insulating film (14) on the entire surface, for example,
SiN_XBy plasma CVD to 2000-4000Å
And then a-
Etching stopper for Si (15) about 1000Å
(16) SiN_XTo a thickness of 2500 Å
Stack. (Refer to FIG. 5 for the above) SiN of the uppermost layer_XIs a part corresponding to the gate electrode (12S)
Etching is performed by removing the
It becomes a topper (16). Furthermore, to improve contact
Phosphorus-doped a-Si (hereinafter, N⁺Abbreviated as a-Si
(17) by plasma CVD to a thickness of about 500Å
Stack it up. (See above, see Figure 6.) This N⁺a-Si (17) and a-Si (16) are the same
By etching with the mask of
An FT channel contact layer is formed. (Below
(See FIG. 7, above) Next, ITO is used as a transparent electrode material by sputtering or the like.
To a thickness of about 500 to 1000Å,
By etching, the display electrode (18PX) and the
A gate input terminal (18GP) is formed. (End of Figure 8
At this time, the auxiliary capacitance input terminal (18SP) is formed at the same time.
Be done.

Then, a predetermined portion of the gate insulating film (14) is removed by etching to remove the contact hole (C
The TG) is opened to expose the contact protection film (12CTG) of the gate line. (Refer to FIG. 9 above.) At this time, at the same time, the contact protective film (1
A contact hole (CTS) is also opened on the 2CTS).

Subsequently, this substrate is immersed in an etchant such as phosphoric acid to form a contact hole (CT).
Wet etching of Al is performed using G, CTS) as a mask. As a result, the contact terminals (11CTG, 1
1CTS) contact protection film (1
2CTG, 12CTS) attached to the surface of Al ₂
The contact terminal (11) is removed together with O ₃ (13A).
Ta in this part of CTG, 11 CTS) is exposed.
That is, since Ta has etching selectivity with Al, T
a (11CTG, 11CTS) and Ta ₂ O ₅ (13T) remain, Al (12CTG, 12CTS) and Al ₂ O ₃
Only (13A) is removed. When the contact protection film (12CTG, 12CTS) and the gate / auxiliary capacitance line (12GL, 12SL) are integrally formed, the gate insulating film (14) is used as a mask.
Side etching occurs in the etching of 1 and the gate insulating film (14) and the underlying gate / auxiliary capacitance line (11GL,
11SL), a space is created, leading to a decrease in reliability. Therefore, contact protection film (12CTG, 12C
TS) is formed inside the opening area of the contact hole (CTG, CTS), and the gate / auxiliary capacitance line (12GL, 12SL) is formed in the contact hole (CT).
(G, CTS) is prevented from reaching the opening area. As a result, the Al etching can be limited to the removal of the contact protection film (12CTG, 12CTS). Next, as the source / drain wiring material, for example, a lower film of Mo is 1000Å and an upper film is 70 by sputtering.
A two-layer film made of 00Å Al is formed and this is etched. As a result, the source / drain electrodes (19S, 1
9D) and the contact terminal (11C
A contact metal (19CT) connecting the TG) and the gate input terminal (18GP) is formed. (End of Fig. 1
1) At this time, at the same time, the drain line (19DL) integrated with the drain electrode (19D) is formed, and the connection line (19SC) is formed and connected to the contact terminal (11CTS) of the auxiliary capacitance line. It is connected to the capacitance input terminal (19SP).

Contact terminal (11CTG, 11CT
S) is a contact protective film (12CTG, 12CTS)
Since the adhesion of the anodic oxide film was prevented by coating with, the Ta was exposed at the portion where the contact protection film (12CTG, 12CTS) was removed. Therefore, good ohmic contact with the contact metal (19CT) and the connection line (19SC) can be obtained.

[0022]

As is apparent from the above description, the island-shaped contact protection film is provided in advance on the contact terminals of the lower gate and the auxiliary capacitance wiring.
Prevents oxidation of the contact terminals during anodization,
The contact terminal is exposed by removing the contact protective film and the anodic oxide film attached to the surface later. Therefore, good ohmic characteristics can be obtained in forming a contact with an upper terminal or wiring with the insulating film interposed therebetween.

Further, since the contact protection film is formed at the same time when the Al wiring for the gate / auxiliary capacitor is formed, the number of steps for removing the contact protection film is increased, the cost is not increased significantly, and the masking resist is formed. Since the peeling process is eliminated, the cost is reduced.

[Brief description of drawings]

FIG. 1 is a partial plan view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 3 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the present invention.

FIG. 4 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 5 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 6 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the present invention.

FIG. 7 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 8 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 9 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 10 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 11 is a cross-sectional view illustrating the method of manufacturing the liquid crystal display device according to the embodiment of the invention.

FIG. 12 is a plan view of a liquid crystal display device.

[Explanation of symbols]

10 Transparent Substrate 11 Ta 12 Al 13 Al ₂ O ₃ 14 Gate Insulating Film 15 a-Si 16 N ⁺ a-Si 17 Etching Stopper 18 ITO 19 Al / Mo

Claims (3)

[Claims] 1. A step of forming a contact terminal of a first wiring by forming a film of a first conductive material having etching selectivity with respect to Al and capable of anodizing on a substrate and etching the film. And forming an Al film by coating the first conductive material and etching the Al to form a first wiring connected to the contact terminal and a voltage supply wiring for anodization, and the contact terminal. A step of forming an island-shaped contact protection film thereon, and a step of forming an anodized film of Al or an anodized film of the first conductive material on the surface by anodizing the entire region of the first wiring. And a step of sequentially forming an insulating layer and a non-single-crystal semiconductor film on the entire surface, and etching the non-single-crystal semiconductor film to form islands, and forming a transparent conductive film on the entire surface and etching, Mato Forming a display electrode arranged in a matrix and external connection terminals arranged at the end of the substrate, and etching the insulating layer to open a contact hole on the contact terminal to form the contact protective film. And exposing the insulating layer having the contact hole as a mask.
a step of removing the Al anodic oxide film on the contact protection film and the contact protection film by performing etching of 1 and forming a second conductive material on the entire surface and etching the second wiring. And forming a contact metal for connecting the contact terminal to the external connection terminal through the contact hole. 2. The contact protection film is formed inside the opening region of the contact hole, and the opening region of the contact hole does not reach the Al portion of the first wiring. A method for manufacturing the liquid crystal display device described. 3. The method of manufacturing a liquid crystal display device according to claim 1, wherein the first conductive material is Ta.