JPH06148683A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To improve response speed and to prevent the open defect, etc., in junctures by constituting all metallic wiring layers of multilayered structures formed by holding the upper layer and lower layer metals of an intermediate layer consisting of Al or Al alloy with the same metals. CONSTITUTION:The lower layer Cr 21, the Al 22 and the upper layer Cr 23 are deposited by continuous sputtering on a glass substrate 10. The metals of these three layers are continuously etched by using a photoresist 30 as a mask and using gaseous chlorine via a photolithography stage and are then subjected to a post treatment with O2 plasma. The photoresist 30 is removed from three layers of the metallic wirings 20 formed in such a manner and a silicon nitride film 40 is deposited thereon. The silicon nitride film in through- hole parts 50 is selectively removed. The wiring resistance and signal delay time of about 1/3 the wiring resistance and signal delay time in the case of formation with the single layer of the Cr are attained if the wirings are constituted in such a manner. The Al does not come into direct contact with the other thin film layers even in the structure during the production process and after the production and eventually, the open defect and joint leakage in the junctures are prevented and the adhesive strength to the glass substrate, etc., is improved.

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,
Particularly, it relates to a wiring structure of a liquid crystal display device having a high response speed.

[0002]

2. Description of the Related Art The metal wiring of a conventional liquid crystal display device has T
a, Ti, Cr or Mo was used. or,
Single layer of Al, Al alloy or Al, A for high speed
A two-layer metal of an l alloy film and a Ta, Ti, Cr or Mo film was used. Furthermore, Ta, Ti, C
In some cases, r or Mo, and Al or Al alloy for the wiring part, are used properly depending on the case.

[0003]

[Problems to be Solved by the Invention] Ta, Ti, C for wiring
When r, Mo, or the like is used, the resistivity of these metals is high (2 to 5 times as high as the Al ratio), which causes a problem when high-speed response is required or in a large-screen display device. Further, when Al or an Al alloy is used, although the resistivity is low, (a) the surface is easily oxidized to form aluminum oxide, and as a result, an open defect is likely to occur at the connection portion, (b)
(C) Glass substrate, transparent conductive film (ITO: Indium Tin Oxide) that causes a junction leak by generating a spike at a contact portion with the impurity-added semiconductor Si
The adhesion strength with the film etc. is small, and (d) the work function differs depending on the metal.
Compared with the case of using a, Ti, Cr or Mo, Al
, The threshold voltage is different. Therefore, it may be necessary to change the design of the drive circuit, (e) weak against mechanical shock from the outside, (f) relatively small atomic weight (26.9).
8), problems such as easy disconnection failure due to electromigration, hillock, etc., (g) chemical reaction under the influence of chlorine, moisture, electric field, etc., causing Al corrosion and causing disconnection. There is a point.

As a measure against the above (b), Al--Si,
As a measure against (f), an Al alloy such as Al-Cu or Al-Ti may be used, but not all the problems (a) to (g) can be solved. Al or Al alloy and Ta,
For a two-layer metal wiring such as Ti, Cr or Mo, Al
The problems caused on the layer side always remain and cannot solve all the problems (a) to (g). Also, the Al layer or A
The method of properly using the alloy layer and the Ta, Ti, Cr, or Mo metal causes an increase in the number of lithography processes,
As a matter of course, there is a problem that some of the problems (a) to (g) that cannot be solved remain.

[0005]

In the liquid crystal display device of the present invention, Ta / Al / Ta, Ti / Al / Ti, Cr / Al
Al as Ta / Cr or Mo / Al / Mo,
It has a three-layer metal wiring structure sandwiched by Ti, Cr, Mo and the like. Further, after patterning the metal wiring, the metal surface or side wall portion is covered with a surface protective film made of a silicon nitride film or a gate insulating film except for the through holes.

[0006]

Thus, by introducing Al, the wiring resistance can be made sufficiently low, and the contact with other thin film materials is Ta, Ti, C.
Problems with Al due to r or Mo (a)
All of (e) are eliminated. The problem (f) is also solved because Al is made into a sandwich structure with another metal and hillocks are generated. The problem (g) is also solved because the surrounding area is covered with a silicon nitride film having high moisture resistance.

[0007]

The present invention will be described below with reference to the drawings. 1A to 1C are schematic cross-sectional views of a wiring structure showing the concept of the skeleton of the present invention. As shown in FIG. 1A, a lower layer Cr2 is formed on the glass substrate 10 by continuous sputtering.
1, Al22, upper layer Cr23 500, 100 respectively
Deposit 0.5 Å. Next, FIG. 1 (b)
Through the photolithography process as described above, using the photoresist 30 as a mask, chlorine-based gas (Cl ₂ , CCl _4, etc.)
The upper layer Cr23, Al22, and the lower layer Cr21 are continuously etched by using the above, and an O ₂ plasma post-treatment is performed to remove residual chlorine at the end. Thus, the three-layer metal wiring 20 is formed. Next, as shown in FIG. 1C, the photoresist 3
0 is removed, a silicon nitride film 40 is deposited, and a silicon nitride film in the through hole portion 50 is selectively removed through a photolithography process.

With this structure, the resistivity of Al (about 2.5 μΩ · cm) is equal to that of Cr (about 13 μΩ · cm).
Approximately ⅕ of the same thickness of a single Cr layer 2000
The wiring resistance and the signal delay time are about 1/3 of the case of forming the angstrom. The surface and side walls are covered with a silicon nitride film having excellent moisture resistance except the through holes, and the upper layer Cr23 and the lower layer Cr21 are in contact with Al.
Alternatively, it is only the silicon nitride film on the side wall.

FIG. 2 is a sectional view of an inverted stagger TFT structure glass substrate of a liquid crystal display device according to an embodiment of the present invention.
(A) is a TFT portion, (b) is a scanning signal wiring portion, (c) is a video signal wiring portion, (d) is a through hole portion, (e) is a connection portion between the scanning signal wiring portion and external wiring, ( f) shows a connecting portion between the video signal wiring portion and the external wiring. ITO is selectively formed on the glass substrate 10 as the transparent conductive film 61 for storage capacitor electrodes. Next, the three-layer metal wiring described in FIG. 1 is selectively formed as the gate metal wiring 24. Next, a silicon nitride film, a Si film 71, and an n-type Si film 72 are continuously grown as the gate insulating film 41, and the n-type Si film 72 and the Si film 71 are selectively etched. Next, the gate insulating film 4 is formed to form the through holes.
1 is selectively etched. Further drain metal wiring 25
Then, a three-layer metal wiring is selectively formed, and then ITO is selectively formed as the transparent conductive film 62 for pixel electrodes. Next, the n-type Si film 72 on the TFT channel portion is selectively etched to form a TFT. Further, a silicon nitride film is deposited as the surface protection film 42, and the connection portion with the external wiring, the pixel portion and the like are selectively etched. Anisotropic conductive film 90 is provided on the external wiring and the connecting portion.
It is attached to the external connection terminal 100 via. In addition, the external connection terminal 100 has a resin coating film 11 for preventing water penetration.
0 is coated. Thus, the cross-sectional structure at each part shown in (a) to (f) can be obtained.

FIG. 3 is a plan view of the external connection terminal portion on the TFT glass substrate side at the connection portion shown in FIGS. 2 (e) and 2 (f).

As shown in FIGS. 1 to 3, Al22 of the metal wiring portion is covered with an upper layer Cr23 and a lower layer Cr21, and the side wall portion is further covered with a gate insulating film 41 or a surface protective film 42.
Will be covered with the silicon nitride film.

In the above embodiment, the Cr-Al-Cr 3
The layer metal film has been described. However, Al is Al-S
It may be an Al alloy such as i, Al-Cu, Al-Ti. Further, as the upper Cr, other metals such as Ta, Ti and Mo which are usually used for metal wiring of liquid crystal display devices may be used.

[0013]

As described above, the present invention is based on Cr-Al.
Since -Cr and the three-layer metal are continuously grown and the three-layer metal is subjected to the batch lithography, Al does not come into direct contact with other thin film layers in the manufacturing process and the structure after the manufacturing. Therefore, all the problems (a) to (e) described in the section of problem are solved. Further, since the upper layer and the lower layer are sandwiched by Cr, the occurrence of hillock and electromigration, which is the problem of (f), is suppressed. Further, the problem of (g) Al corrosion is solved by covering the entire wiring including the Al side wall with a silicon nitride film having high moisture resistance. In particular, water that permeates through the interface of a different substance at the connection with the external wiring becomes a problem.
As can be seen from the above, the problem is solved by making the through hole part an internal contact with the panel side three-layer metal wiring and covering the side wall part and the outer peripheral part of the through hole with a silicon nitride film.

[Brief description of drawings]

1A to 1C are schematic cross-sectional views of a wiring structure showing the concept of the present invention.

FIGS. 2A to 2F are cross-sectional views of respective portions of a TFT glass substrate of a liquid crystal display device showing an embodiment of the present invention.

3 is a plan view of an external connection terminal portion on the TFT glass substrate side in the connection portion in FIG.

[Explanation of symbols]

 10 glass substrate 20 three-layer metal wiring 21 lower layer Cr 22 Al 23 upper layer Cr 24 gate metal wiring 25 drain metal wiring 30 photoresist 40 silicon nitride film 41 gate insulating film 42 surface protective film 50 through hole portion 61 storage capacitor electrode transparent conductive film 62 transparent conductive film for pixel electrode 71 Si film 72 n-type Si film 90 anisotropic conductive film 100 external connection terminal 110 resin coat film

Claims (4)

[Claims] 1. A liquid crystal display, wherein all metal wiring layers are three-layer metal wirings in which Al or Al alloy is used as an intermediate layer and upper and lower metal layers of the intermediate layer are sandwiched by the same metal. apparatus. 2. The same metal in the upper and lower layers is Ta, T
The liquid crystal display device according to claim 1, wherein the liquid crystal display device is i, Cr or Mo. 3. The liquid crystal display device according to claim 1, wherein the outer peripheral surface portion and the side wall portion of the external connection terminal portion of the metal wiring layer are covered with a surface protective film or a gate insulating film. 4. The liquid crystal display device according to claim 3, wherein the surface protective film and the gate insulating film are a single layer of a silicon nitride film or a multilayer film including a layer of the silicon nitride film.