JPH04232922A - Production of liquid crystal display device - Google Patents

Abstract

PURPOSE:To enable formation of large-size low-resistance wiring material at low cost compared to a conventional method and to supply stable signals by using a conductive oxide film as a part of the wiring material since the conductive oxide film is stable without increase in resistance against an oxygen atmosphere, and especially to obtain a good effect when a Cu film is used as a part of wiring material by adding characteristics required to a connecting area with a driving IC. CONSTITUTION:A wiring pattern 2 is formed with using a conductive oxide film material, on which a Cu single layer film or a multilayer film 10 containing at least one Cu layer is selectively deposited by plating. Further, a metal film 4' in the area not included by a counter electrode substrate and a substrate connecting sealing material is selectively removed by etching.

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 an active matrix liquid crystal display device.

0002

[Prior Art] In recent years, active matrix liquid crystal display devices have been developed in which thin film transistors (hereinafter referred to as TFTs) operating as switching transistors are connected to each display electrode of a large number of pixels arranged in a matrix, and these TFTs are used as drive circuits. However, since this liquid crystal device is very light and thin, it is attracting attention as a thin display device that can be used as a replacement for CRT, whether it is portable or wall-mounted.

FIG. 5(a) shows a plan view of each pixel of a TFT in a conventional active matrix display device.
FIG. 5(b) shows a cross-sectional view of the TFT of FIG. 5(a) taken along line BB'.

As shown in FIG. 5(b), a TFT is formed on one transparent insulating substrate 1 of a liquid crystal display device, and has a gate electrode 2 provided locally on a gate wiring 20 and a gate electrode 2 provided on the entire surface of the substrate. A so-called inverse stack consisting of a gate insulating film 3 formed into an island, a semiconductor film 4 formed into an island, an impurity semiconductor film 5 forming ohmic contacts at the source and drain positions of the semiconductor film 4, a source electrode 7, and a drain electrode 6, respectively. A display electrode 8 is connected to the source electrode 7, and a drain wiring 60 for supplying a display signal is connected to the drain electrode 6.

Each electrode of the TFT array of the above-mentioned active matrix display device is formed using semiconductor process technology. That is, the electrode forming material is deposited by a method such as vapor deposition, sputtering, or CVD, and then microfabricated by photoetching.

[0006] Furthermore, it is desired that the performance of liquid crystal display devices be improved by providing higher definition and larger area. When achieving higher definition and larger area, it is necessary to reduce the wiring resistance of the gate wiring for supplying gate signals and the drain wiring for supplying display signals in the TFT array, and to suppress signal delay as much as possible. For example, the resistance of Cu is about 0.0% compared to the resistance of Al.
It is as low as 7 times, and in addition, EM (Electro Migr
However, due to the characteristics of Cu, its adhesion with insulating films such as glass (SiO2) and SiNx is not very good, and the oxidation of the Cu film progresses to the inside in an oxygen atmosphere, increasing the resistance. Therefore, when forming a Cu wiring pattern on a glass substrate, it is necessary to use another metal film under the Cu film to improve adhesion, and over the Cu film to prevent oxidation. need to be formed. Part 1
For example, "JAPAN DISPLAY CON
FERENSE, p502 (1989), T.
A low resistance gate wiring made of a/Cu/Ta has been proposed.

[0007] However, this film deposition requires the use of expensive equipment such as sputtering and has a low throughput, resulting in an increase in manufacturing costs.

[0008]

[Problems to be Solved by the Invention] As mentioned above, the equipment used in the TFT manufacturing process is expensive and has a low throughput, which is a major cause of increased manufacturing costs for active liquid crystal display devices, especially TFT arrays. It has become.

[0009] Furthermore, when increasing the definition and area,
It is necessary to reduce the wiring resistance of the gate wiring for supplying gate signals and the drain wiring for supplying display signals in the TFT array, and to suppress signal delay as much as possible. For the above-mentioned reasons, conventional manufacturing methods are expensive, and the larger the area pattern, the higher the manufacturing cost.

[0010] Furthermore, there is a problem that oxidation of the Cu film progresses to the inside in an oxygen atmosphere, resulting in an increase in resistance.

[0011]

[Means for Solving the Problems] A method for manufacturing a liquid crystal display device of the present invention includes disposing thin film transistors at each intersection of a plurality of gate wirings and a plurality of drain wirings on one transparent insulating substrate. , a display electrode substrate provided with a display electrode coupled to each drain wiring via the respective thin film transistors, and a counter electrode substrate provided with a counter electrode at a position opposite to the display electrode on the other transparent insulating substrate. In a liquid crystal display device comprising a liquid crystal material injected between both electrode substrates, after forming the gate wiring with a conductive oxide, metal is selectively deposited on the conductive oxide by a plating method. This forms a gate wiring made of a conductive oxide and a metal film.

Furthermore, thin film transistors are arranged on one light-transmitting insulating substrate at each intersection of a plurality of gate wirings and a plurality of drain wirings, and a display electrode is connected to each drain wiring through each of the thin film transistors. a counter electrode substrate having a counter electrode on the other transparent insulating substrate at a position opposite to the display electrode, and a liquid crystal material inserted between the two electrode substrates. In the device, after forming the drain wiring with a conductive oxide, metal is selectively deposited on the conductive oxide using a plating method, thereby forming a drain wiring composed of a conductive oxide and a metal film. It is something that forms.

Furthermore, the metal film formed by the plating method is Cu.
It consists of a single layer film or a multilayer film containing at least one layer of Cu.

Furthermore, by selectively etching and removing the metal film in the area exposed from the sealant for connecting the counter electrode substrate and the substrates, the display electrode substrate in the area covered with the sealant for connecting the counter electrode substrate and the substrates can be removed. Only the upper gate wiring is made of a conductive oxide and a metal film, and the gate wiring on the display electrode substrate in the area exposed from the counter electrode substrate and the substrate connection sealant is made of a conductive oxide.

In addition, by selectively etching and removing the metal film in the area exposed from the sealant for connecting the counter electrode substrate and the substrate, the area covered by the sealant for connecting the counter electrode substrate and the display electrode substrate can be removed. Only the upper drain wiring is made of a conductive oxide and a metal film, and the drain wiring on the display electrode substrate in the area exposed from the counter electrode substrate and the substrate connection sealant is made of a conductive oxide.

[0016]

[Function] According to the present invention, by using a plating method, it is possible to easily deposit a metal film such as a Cu film, which is a low resistance wiring material, at low cost and with high mass productivity, thereby increasing equipment costs. This makes it easy to form a film over a large area. Therefore, it is possible to form a large area of low-resistance wiring material at a lower cost than in the conventional method. In addition, the conductive oxide film is a stable material that does not increase resistance even in an oxygen atmosphere, so using it as part of the wiring material enables stable signal supply, especially in the connection area with the drive IC. Provides reliable adhesion.

[0017]

[Example] Fig. 1 shows a plan view of each pixel of a TFT array of an active matrix liquid crystal display device obtained by the manufacturing method of the present invention, and sectional views of each manufacturing process along line BB' in Fig. 1. are shown in FIGS. 2(i) to (vi). The manufacturing method of the present invention will be explained below with reference to FIG.

First step [FIG. 2(i)] ITO, In2O
3. A gate electrode 2 made of a conductive oxide film material such as SnO2, ZnO, Cd2SnO4, etc. and a gate wiring 20 locally provided with the gate electrode 2 are formed.

Here, since the gate electrode made of a conductive oxide film material is transparent in order to shield the channel portion from light, it is necessary to make the gate electrode opaque.

Second step [FIG. 2(ii)] Then, a metal film is formed by plating on the gate wiring 20 formed of the conductive oxide film material and the gate electrode 2 electrically connected to the gate wiring 20. Deposit 10. Through this step, the resistance of the gate wiring 20 can be reduced and the gate electrode 2 can be made opaque. The material of the metal film 10 to be plated includes Au,
Cu, Ni, Pd, Ag, Pt, In, Ru, Rh, C
r, Sn, Pb, Sn-Pb (solder), Zn, Co, F
Metals such as e can be deposited. Among such metal films, Cu is the most excellent in terms of low resistance and cost. However, Cu does not have very good adhesion to the conductive oxide film material, and the adhesion is further improved if another metal film is interposed between the Cu film and the conductive oxide film material. The intervening metal film includes Ni, In, Sn, Pb,
Metals such as Sn-Pb (solder), Zn, Co, and Cr are excellent. Further, since the Cu film is easily oxidized, other metal films for preventing oxidation, such as Au, Pt, Pd, Cr, Ni, etc., may be deposited on the Cu film. The metal film deposited by plating in this manner may be a single layer film or a multilayer film. Further, the metal film deposited on the conductive oxide film is not limited to Cu, but any material can be used as long as it can be deposited on the conductive oxide film by a plating method and lowers the wiring resistance. As the plating method, electrolytic plating method and electroless plating method can be applied.

Third step [FIG. 2(iii)] First insulating film 3
(gate insulating film), semiconductor film 4, and second insulating film 5 (passivation insulating film) are successively deposited by plasma CVD or the like, and the second insulating film 5 is formed into an island.

Fourth step [FIG. 2(iv)] Plasma CVD
After depositing the impurity semiconductor film 4', the semiconductor film 4 and the impurity semiconductor film 4' are formed into islands.

Fifth step [FIG. 2(v)] ITO, In2O
3. Deposit a conductive oxide film material such as SnO2, ZnO, Cd2SnO4, etc., and simultaneously form the drain electrode 6, source electrode 7, display electrode 8, and drain wiring 60 using the conductive oxide film material. . Thereafter, the impurity semiconductor film 4' in the channel portion is removed by etching.

Sixth step [FIG. 2(vi)] A metal film 11 is deposited by plating on the drain wiring 60 formed of a conductive oxide film and the drain electrode 6 electrically connected to the drain wiring 60. The material for the metal film 11 to be plated should be selected to reduce the wiring resistance of the gate wiring for supplying gate signals and the drain wiring for supplying display signals in the TFT array, and to reduce signal delay when achieving high definition and large area. Au, Cu, Ni, Pd must be suppressed as much as possible.
, Ag, Pt, In, Ru, Rh, Cr, Sn, Pb,
Metals such as Sn--Pb (solder), Zn, Co, and Fe can be deposited. Among these metals, Cu is the most superior in terms of low resistance and cost. The resistance of Cu is about 0.7 times lower than that of Al, and in addition, the resistance of Cu is about 0.7 times lower than that of Al.
(electro migration) resistance. However, since the Cu film does not have good adhesion to insulating films such as glass (SiO2) and SiNx, as shown in FIG. Adhesion is improved by interposing another metal film 12 between them. The intervening metal film 12 is made of Ni, In, Sn, Pb, Sn-Pb (
Solder), metals such as Zn, Co, and Cr are excellent. or,
Since there is a problem that the Cu film oxidation progresses to the inside in an oxygen atmosphere and the resistance increases, other metal films for preventing oxidation, such as Au, Pt, Pd, Cr, Ni, etc., are deposited on the Cu film. Good too. The metal film deposited in this manner may be a single layer film or a multilayer film. Further, the metal film deposited on the conductive oxide film is not limited to Cu, but any material can be used as long as it can be deposited on the conductive oxide film by the plating method as described above and lowers the wiring resistance.

[0025] As the plating method, electrolytic plating is suitable. Electroless plating can also be applied, but in that case it is necessary to coat the areas where the metal film is not deposited with a resist. That is, when electroless plating is applied, one mask process is added. Further, when electrolytic plating is applied, it is necessary to remove the impurity semiconductor film 4' in the channel portion by etching in advance. When the impurity semiconductor film 4' is present in the channel part, the source electrode 7
The metal film 10 is also deposited on the conductive oxide film of the display electrode 8, which is undesirable.

FIG. 3 shows a plan view of the active matrix substrate 30 produced by the above process. In FIG. 3, the scanning line 20 (gate wiring), the signal line 60 (drain wiring), the terminal electrodes of the gate terminal 21 and the drain terminal 61 on which the driving IC is mounted, and the T at the intersection of the scanning line 20 and the signal line 60
It is composed of an FT 13 and a display electrode 8 connected to the source electrode 7 of the TFT 13. A counter electrode substrate 40 is bonded to the active matrix substrate 30 of FIG. 3, and liquid crystal is injected to complete an active liquid crystal display panel. A plan view of the completed active liquid crystal display panel is shown in FIG. However, when a metal film is used as the constituent material of the scanning line 20 or the signal line 60, the problem arises that the metal film oxidizes in areas that come into contact with oxygen (air), resulting in a change in wiring resistance. This tendency is particularly noticeable in Cu films, and metals such as Al and Cr form a stable passive film (oxide film) on the surface, making it difficult for oxidation to progress inside, and the influence of oxidation is small. Cu
When a film is used as a wiring material and the Cu surface is not coated with another metal film for oxidation prevention, it is necessary to eliminate the effects of this oxidation. The area affected by oxidation is the drive I
These are the terminal electrodes 21 and 61 that mount C, and the area inside the area coated with the counter electrode substrate and the bonding resin (sealant) is blocked from oxygen, so the effect of oxidation is not considered. It's fine. That is, in FIG. 4, oxidation of the Cu film does not occur in the region inside the counter electrode substrate (TFT region), but oxidation of the Cu film occurs in the region outside the counter electrode substrate. As a countermeasure, ■Coating a resin on the Cu film to block the ingress of oxygen, ■Coating other metal films (Au, Pt, etc.) on the Cu film to prevent oxidation.
(2) Etching away the Cu film to expose the conductive oxide layer (conductive oxide is not affected by oxidation) is a possible method, but as a result of investigation, method (2) was found to be the simplest and most effective. In (2), after bonding the counter electrode substrate 40 to the active matrix substrate 30 and injecting liquid crystal to complete the liquid crystal display panel shown in FIG. It is sufficient to remove the film by etching, and the influence of oxidation on the Cu film can be eliminated by a simple method. In method (2), only the terminal electrodes 21, 61 connected to the driving IC are made of a conductive oxide film.

Naturally, the methods (1) to (2) are applicable when metals that are susceptible to oxidation are used as part of the wiring material, and are limited to cases where a metal film is formed by plating. isn't it. In particular, when a Cu film is used as part of the wiring material, a conductive oxide film is added to the counter electrode substrate 4.
Only the terminal electrode part connected to the drive IC exposed from 0C
The most effective method is to remove the U film by etching.

[0028]

Effects of the Invention As is clear from the above explanation, according to the manufacturing method of the present invention, a metal film (particularly Cu) is deposited by a plating method on a wiring pattern formed of a conductive oxide film. Compared to photo-etching, it is possible to form a metal film, which is a low-resistance wiring material, at a lower manufacturing cost. Furthermore, conductive oxide was applied to the gate wiring and drain wiring on the counter electrode substrate on which the drain wiring, drain electrode, source electrode, and display electrode were formed using a conductive oxide film, and on the display electrode substrate that had areas exposed from the substrate connection sealant. By configuring it with a material, it is possible to provide a stable signal in an oxidizing atmosphere.

[Brief explanation of the drawing]

FIG. 1 (a) shows T of a display device obtained by the present invention.
FIG. 3B is a plan view of the FT section, and FIG. 3B is a cross-sectional view of the TFT section of the display device obtained by the present invention.

FIG. 2 is a cross-sectional view of each manufacturing process taken along line BB' in FIG. 1(a).

FIG. 3 is a plan view of an active matrix substrate manufactured by the manufacturing process of the present invention.

FIG. 4 is a plan view of a liquid crystal display panel obtained by the present invention.

FIG. 5 is a cross-sectional view of a TFT section of a conventional display device.

[Explanation of symbols]

1 Insulating substrate 2 Gate electrode 3 Gate insulating film 4 Semiconductor film 4' Impurity semiconductor film 5 Passivation insulating film 6 Drain electrode 7 Source electrode 8 Display electrode 10 Metal film 11 forming part of gate wiring Part of gate wiring Metal film 13 TFT 20 Gate wiring 21 Gate terminal electrode 30 Active matrix substrate 40 Counter electrode substrate 60 Drain wiring 61 Drain terminal electrode

Claims (6)

[Claims] 1. Thin film transistors are arranged at each intersection of a plurality of gate wirings and a plurality of drain wirings on one light-transmitting insulating substrate, and a display electrode is connected to each drain wiring through each thin film transistor. A liquid crystal display comprising: a display electrode substrate provided with a display electrode; a counter electrode substrate provided with a counter electrode on the other transparent insulating substrate at a position opposite to the display electrode; and a liquid crystal substance injected between the two electrode substrates. In the device, after forming the gate wiring with a conductive oxide, metal is selectively deposited on the conductive oxide using a plating method, thereby forming a gate wiring composed of a conductive oxide and a metal film. 1. A method of manufacturing a liquid crystal display device, characterized by forming a liquid crystal display device. 2. Thin film transistors are disposed at each intersection of a plurality of gate wirings and a plurality of drain wirings on one light-transmitting insulating substrate, and a display electrode is connected to each drain wiring through each thin film transistor. a counter electrode substrate having a counter electrode on the other transparent insulating substrate at a position opposite to the display electrode, and a liquid crystal material inserted between the two electrode substrates. In the device, after forming the drain wiring with a conductive oxide, metal is selectively deposited on the conductive oxide by a plating method,
A method for manufacturing a liquid crystal display device, comprising forming a drain wiring made of a conductive oxide and a metal film. 3. The method of manufacturing a liquid crystal display device according to claim 1, wherein the metal film formed by the plating method is a Cu single layer film or a multilayer film containing at least one layer of Cu. 4. The method of manufacturing a liquid crystal display device according to claim 2, wherein the metal film formed by the plating method is a Cu single layer film or a multilayer film containing at least one layer of Cu. 5. By selectively etching and removing the metal film in the area exposed from the counter electrode substrate and the sealant for connecting the substrate, the area on the display electrode substrate covered by the sealant for connecting the counter electrode substrate and the substrate is removed. A claim characterized in that only the gate wiring is made of a conductive oxide and a metal film, and the gate wiring on the display electrode substrate in the area exposed from the counter electrode substrate and the sealant for connecting the substrate is made of a conductive oxide. Item 1. Method for manufacturing a liquid crystal display device. 6. By selectively etching and removing the metal film in the area exposed from the counter electrode substrate and the substrate connection sealant, the display electrode substrate in the area covered with the counter electrode substrate and the substrate connection sealant is removed. A claim characterized in that only the drain wiring is made of a conductive oxide and a metal film, and the drain wiring on the display electrode substrate in the area exposed from the counter electrode substrate and the sealant for connecting the substrate is made of a conductive oxide. Item 2. Method for manufacturing a liquid crystal display device.