JPH02272774A - Active matrix circuit board - Google Patents

Abstract

PURPOSE:To manufacture a transparent conductive film while protecting it against etchant, etc., by laminating a conductive film which can be selectively etched on the transparent conductive film, and forming in a multilayer structure of the conductive film including a layer formed of aluminum film. CONSTITUTION:A drain bus line 9 is formed in a multilayer structure in which wirings of a metal film 92 made of aluminum, etc., are laminated on wirings made of a transparent conductive film 97 and a metal film 91 such as a chromium film, etc., and the wiring width of the film 92 is formed to be larger than wirings made of the films 97, 91. At the drain and source electrodes 5, 6 of a thin film transistor 89, patterns 51, 61 formed of the same material as that of the film 92 of the drain bus line 9 are extended from the pattern made of the films 97, 7 and conductive films 521, 621, and a drain electrode 5, a source electrode 6 are electrically connected with a semiconductor film 4. With this structure, after the film 97 is photoetched, a defect due to a remaining foreign material can be alleviated, and the transparent conductive film can be protected against medicines such as etchant, developer, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an active matrix circuit board using amorphous silicon thin film transistors as switching elements, a method for manufacturing the same, and an image display device using the same.

[Conventional technology]

Liquid crystal display devices that use active matrix circuit boards with amorphous silicon thin film transistors as switching elements are used to increase capacity and improve image quality of liquid crystal display devices, which have features such as being lightweight, thin, low power consumption, and full-color display. was put into practical use.

FIG. 4 shows an example of the structure of an amorphous silicon transistor (part of an active matrix circuit board) and its manufacturing process. For this kind of thing, see, for example, Electronics Letter 19. Pages 506 to 507 (1983) (Electronics Lett,
19, 506-507 (1983)). FIG. 4 shows the manufacturing process from the middle. In the figure, 1 is an insulating substrate such as a glass plate, 2 is a gate electrode (first electrode) made of a metal film such as chromium, and 3 is a gate insulating film made of an insulating thin film such as a silicon nitride film. 4 is a semiconductor film made of an amorphous silicon film;
1 and 51.61 are n-type semiconductor films made of an amorphous silicon film doped with phosphorus, etc., and 52 and 62 are drain electrodes or source electrodes (second and third electrodes) made of metal films such as aluminum. , 7 represents a display pixel electrode, and 1o represents a photoresist. Hereinafter, a typical manufacturing process for an active matrix circuit board will be outlined with reference to FIG. 4, focusing on the thin film transistor section.

(a) A metal film such as chromium is formed on the tIA edge plate substrate 1 by a sputtering method or the like, and a gate electrode pattern 2 is formed using a well-known photoetching process. Next, a silicon nitride film is formed as the gate insulating film 3, an amorphous silicon film is formed as the semiconductor film 4, and an n
An amorphous silicon film doped with phosphorus is continuously formed as a mold semiconductor film 41 . Well-known photoresist process and CF,
An island pattern 4 of an amorphous silicon film is formed by dry etching using a gas containing h and SF.

(b) Goo 1-bus line connected to gate electrode 2 (
(not shown) to bring out connection terminals with external electrical circuits.
Photoetching of the gate insulating film 3 is performed.

(c) A transparent conductive film made of tin oxide and indium oxide is formed by sputtering or the like, and a display pixel electrode pattern 7 is formed by a well-known photoetching process.

(d) A metal film such as aluminum is formed by a sputtering method or the like. Next, patterns for the train electrode 5 and source electrode 6 are formed by a well-known photoetching process, and the n-type amorphous silicon present on the channel of the thin film transistor is etched by dry etching using a gas containing CF4 or SF. The membrane is removed to separate the ohmic contacts 51 and 61 of the electrode section. The figure shows the state before the photoresist is removed.

With the above steps, the thin film transistor (Actidama 1-RIX circuit board) shown in FIG. 4 is completed.

[Problem to be solved by the invention]

The above conventional technology has been developed to improve chemical resistance of transparent conductive films used for display pixel electrodes, drain electrodes and source electrodes that are formed after forming a transparent conductive film pattern, and conductive films that form bus lines (to reduce the resistance of bus lines). No consideration has been given to compatibility with aluminum-based thin films (in which aluminum-based thin films are often used), and in some cases, there has been a problem in that under the following circumstances, deterioration is likely to occur.

(1) The transparent conductive film pattern may be damaged by chemicals (for example, an etching solution for aluminum film, etc.).

(2) When the transparent conductive film pattern and the aluminum film coexist and a positive photoresist is used to pattern the aluminum film, the transparent conductive film pattern is corroded by battery action during resist I development.

(3) Cleaning after forming the transparent conductive film pattern is difficult, and pinholes may occur frequently in the conductive film used for drain electrodes, source electrodes, and bus lines.

The object of the present invention is to be able to manufacture a transparent conductive film while protecting it,
Another object of the present invention is to provide a structure of an active matrix substrate that improves compatibility between a transparent conductive film and a thin film formed thereon, a method for manufacturing the same, and an image display device using the same.

[Means to solve the problem]

In order to achieve the above object, the present invention provides (a) a chemically stable and transparent conductive film between an aluminum-based thin film, which is a low-resistance material constituting a drain bus line, and a transparent conductive film made of indium oxide or tin oxide; Inserting a conductive film that can be selectively etched with the conductive film; (b) sequentially forming the transparent conductive film and the conductive film to be inserted, handling this overlapping film as a single film, and performing the same photo-etching; The first layer of the display pixel electrode and the bus line is produced by the process, and (c) the gate bus line, drain electrode, and source electrode are formed by a multilayer film of at least IWJ or more including an aluminum-based thin film layer, and then the display pixel electrode is formed. The upper opaque conductive film is removed.

[Effect]

A conductive film (metal film) is formed to cover a transparent conductive film made of indium oxide and/or tin oxide before forming display pixel electrodes and bus lines by photoetching the transparent conductive film.

Since the generation of foreign matter during the photo-etching process of the transparent conductive film is prevented and the surface of the transparent conductive film is protected, the occurrence of pinholes in the thin film formed on the transparent conductive film is significantly reduced, and the etching solution for the aluminum film is This has the effect of preventing corrosion of the transparent conductive film caused by chemicals such as a positive resist developer and the like.

〔Example〕

Example 1 An example of the present invention will be described below with reference to FIGS. 1 and 2.

Figure 1 (,) shows the equivalent circuit of an active matrix circuit using amorphous silicon thin film transistors, and Figure 1 (b) shows the equivalent circuit of an active matrix circuit using amorphous silicon thin film transistors.
is a cross-sectional view of the thin film transistor in the active matrix circuit board, and figure (c) is a cross-sectional view of the drain bus line in the active matrix circuit board, taken along line A-A in figure (a).
A cross-sectional view of the direction is shown. In the figure, 1 is an insulating substrate such as a glass plate, 2 is a gate electrode made of a metal film such as chromium, 3 is a gate l/IA edge film made of a silicon-based insulating thin film such as a silicon nitride film, and 4 is a non-containing insulating substrate. A semiconductor film made of a crystalline silicon film, 51 and 61 a semiconductor film made of an n-type amorphous silicon film doped with phosphorus, 5 a drain electrode,
6 is a source electrode, 7 is a display pixel electrode made of tin oxide or indium oxide, 97 is a part of a drain bus line made of the same transparent conductive film as the display pixel electrode, 521 and 6
21 is a metal film such as a chromium film that can be selectively etched with the transparent conductive film, 522 and 622 are low resistance metal films such as aluminum, 8 is a gate bus line, 9 is a drain bus line, 91 is 521 92 is a layer for implanting a drain bus line made of the same material as 522 and 621.
The layer constituting the drain bus line is made of the same material as 22, -25 is a liquid crystal, and 89 is a thin film transistor. In this embodiment, the present invention is applied to the following points.

(1) The drain bus line has a multilayer structure in which a wiring made of a metal film 92 such as an aluminum film (second wiring) is laminated on a wiring made of a transparent conductive film 97 and a metal film 91 such as a chromium film (first wiring) It is said that

(2) In the drain bus line, the wiring (second wiring) made of a metal film 92 such as an aluminum film and the line width are changed to the wiring (second wiring) made of a transparent conductive film 97 and a metal film 91 such as a chromium film.
(first wiring).

(3) Drain electrode (second electrode) of thin film transistor
and a source electrode (third electrode), a transparent conductive film 97
, 7 and the first conductive films 521, 621, the patterns 51 and 61 formed of the same material as the conductive film 92 constituting the second wiring of the drain bus line 9 are made to protrude from the pattern consisting of the drain electrode and the source. This was used as an electrical contact between the electrode and the semiconductor film.

Hereinafter, with reference to FIG. 2, an outline of the manufacturing process of the active matrix circuit board shown in FIG. 1 will be explained, focusing on thin film transistors.

(A) Chromium (Cr) on an insulating substrate 1 such as a glass plate
A metal film such as a film is formed by a sputtering method or the like, and a pattern of a gate electrode (first electrode) 2 is formed by a well-known photoetching process.

(B) Plasma CV D (Chemical Va
A silicon nitride film serving as the gate insulating film 3, an amorphous silicon film serving as the semiconductor film 1, and an n-type amorphous silicon film 41 are formed by a porDeposition method or the like.

(C) A semiconductor film island pattern 4 made of an amorphous silicon film is formed by a well-known photoetching process and dry etching using a fluorine compound gas.

(D) Photoetching is performed on the gate insulating film 3 in order to expose a connection terminal of the gate bus line 8 (not shown) to an external electric circuit.

(E) A display pixel electrode consisting of a transparent conductive film made of tin oxide and indium oxide and a metal film such as a chromium film is formed by a sputtering method or the like, and a transparent conductive film and a metal film such as a chromium film are formed by a well-known photoetching process. and source electrode part (
7+621), and a drain electrode (97+521) consisting of a transparent conductive film and a metal film such as a chromium film is formed. Here, a transparent conductive film and a metal film such as a chromium film are etched using the same photoresist pattern.
21) may be placed inside the transparent conductive film etching pattern (97, 7) to prevent the chromium film pattern from retreating to the lower part of the transparent conductive film pattern.

(F) A metal film such as aluminum is formed by sputtering or the like, and electrode patterns 52 and 62 made of the metal film are formed by a well-known photoetching process. Next, the metal film 621 such as a chromium film existing on the display pixel electrode 7 is removed. Here, the pattern 622 made of a metal film such as aluminum may be placed inside the metal film pattern 621 such as a chromium film by immersing it in an etching solution for a metal film such as aluminum. Thereafter, by dry etching using a well-known fluorine compound gas, the n-type amorphous silicon film on the channel of the thin film 1-transistor was removed by 51 cm.
and 61 to form a drain electrode (second electrode) 5 and a source electrode (third electrode) 6. The figure also shows a photoresist pattern.

The road board is completed. The steps to which the present invention is applied are (E) and (
F) can be summarized as follows.

(1) The laminated film of a transparent conductive film and a chromium film is treated as a single film, and a display pixel electrode pattern and a drain bus line consisting of an M-layer film of a transparent conductive film and a chromium film are formed in the same photoetching process. 1 wiring is formed.

(2) After forming the drain electrode, source electrode, and drain bus line, the chromium film present on the display pixel electrode is removed.

As described above, by applying the present invention, the influence of foreign particles remaining after photoetching a transparent conductive film can be significantly reduced, and
Damage to the transparent conductive film caused by an etching solution for the aluminum film or a developer during photoetching can be prevented. For example, as shown in Figure 4, when an active matrix circuit board is manufactured using a positive type photoresist by the conventional method, one to two pinholes occur per 100 pixels, and the display Deterioration often occurred in the pixel electrodes. In contrast, by applying the present invention, 1
At around 00,000 pixels, it is hardly observed.

Such an effect is obtained in the present invention by covering the transparent conductive film with a metal film that can be selectively etched. This is particularly effective when, as in this embodiment, the display pixel electrode is a transparent conductive film made of indium oxide or tin oxide, and the drain bus line is a laminated film of a transparent conductive film and an aluminum-based thin film. In order to prevent the battery action caused by the positive resist developer, it is also important to prevent the transparent conductive film and the aluminum thin film from coming into contact with each other in the developer. To deal with this, the wiring width of the second wiring (including the aluminum thin film) constituting the drain bus line is made larger than the wiring width of the first wiring (including the transparent conductive film), and the second wiring is It is also effective to protect the first wiring from the developer using a multilayer film of a thin film and a photoresist. Based on the size of the pixels on the active matrix circuit board, the width of the second wiring constituting the drain bus line that is larger than the first wiring width is considered to be 0.1 to 50 μm, but it is 1 to 5 μm.
is practical.

In this example, a first conductive film is laminated on a transparent conductive film of a first wiring constituting a drain bus line (second bus line).
Although the conductive film is a chromium film, it is not necessarily limited to a chromium film as long as it can be selectively etched with the transparent conductive film and there is no problem with adhesion. Furthermore, although the second wiring constituting the drain bus line (second bus line) is made of an aluminum-based thin film, Si, Ti,
It may be an aluminum film containing elements such as Pt or Pd, or may have a multilayer structure including an aluminum film. In addition, in order to improve the covering state of the first wiring with the second wiring constituting the drain bus line (second bus line), the wiring width of the wiring formed by the first conductive film is changed to a transparent conductive layer. It is also effective to make the wiring smaller than that of film wiring in order to increase the effects of the present invention. Considering the wiring width of the drain bus line (second bus line), it is recommended to make the wiring width of the first conductive film 0 to 10 μm smaller than the wiring made of the transparent conductive film. is practical.

Example 2 This example relates to an image display device consisting of a liquid crystal display device using the thin film transistor and active matrix circuit board shown in Example 1, and FIG. 3(a) is a plan view of the main part thereof. (b) shows a cross-sectional view.

In the figure, 80 is the thin film transistor 8 shown in FIG.
Connect the drain bus line 9 to the drain electrode 5 of 9,
An active matrix circuit board in which a gate bus line 8 is connected to the gate electrode 2, and a display pixel electrode 7 is connected to the source electrode 6, 20 is a polarizing plate, 21 is a color filter,
23 is a counter electrode of the display pixel electrode 7 made of a transparent conductive film, which is also made of a transparent conductive film; 22.26;
24 represents a protective film, 24 represents an alignment film, and 25 represents a liquid crystal filling the void.

This example of the image display device has the above-described configuration and is for color display. Further, this display device can be easily manufactured using a manufacturing process similar to that of a well-known color liquid crystal display device.

Note that in an actual display device, in addition to the configuration shown in FIG. 5, various electric circuit control systems, illumination means from the back, etc. are provided as well-known image display driving means.

〔Effect of the invention〕

According to the present invention, since an active matrix circuit board is manufactured by handling a laminated film consisting of a transparent conductive film and a selectively etched conductive film formed thereon as if it were a single film, the transparent conductive film can be photo-etched. This has the effect of significantly reducing the influence of foreign matter remaining afterwards and protecting the transparent conductive film from chemicals such as etching solution and developer. Therefore,
In such active matrix circuit boards and image display devices, damage to the transparent conductive film and occurrence of defects due to foreign matter remaining after photo-etching the transparent conductive film can be significantly reduced, so the manufacturing yield of drain bus lines and display pixel electrodes can be greatly improved. There is an effect that can be done.

[Brief explanation of drawings]

FIG. 1(a) is an equivalent circuit of an active matrix circuit according to an embodiment of the present invention, FIG. 1(b) is a cross-sectional view of a thin film transistor used in the same active matrix circuit board, and FIG. 1(C) is a drain bus in the same active matrix circuit board. 2 is an explanatory diagram showing an embodiment of the active matrix circuit board manufacturing process shown in FIG. 1 in terms of a thin film transistor section; FIGS. 3(a) and 3(b) are image displays according to the present invention. FIG. 4 is a plan view and a cross-sectional view showing one embodiment of the device, respectively, and FIG. 4 is a cross-sectional view of the structure of a thin film transistor section in a conventional active matrix circuit board. DESCRIPTION OF SYMBOLS 1... Insulating substrate, 2... Gate electrode (first electrode), 3... Goo 1~insulating film, 4... Semiconductor film, 5...
... Drain electrode (second electrode), 6... Source electrode (third electrode), 7... Display pixel electrode, 8... Gate bus line, 9... Drain bus line, 41, 5
1°61...n-type semiconductor film, 52.62...metal film. 20... Polarizing plate, 21... Color filter, 22° 26... Protective film, 23... Counter electrode, 24... Alignment film. 25...Liquid crystal. 80...Active polymer 1~RISC circuit board, 89...Thin film transistor. 10...Photoresist, 521°621...Chromium film, 522°622...Aluminum film. F-JL4>/iy, Rai>, 2j-*,
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Claims (1)

[Claims] 1. A first electrode serving as a gate electrode on an insulating substrate;
a gate insulating film formed to cover the first electrode; a semiconductor film pattern made of a thin film mainly composed of silicon disposed on the gate insulating film so that at least a portion thereof is on the first electrode; , a plurality of thin film transistors each having second and third electrodes serving as a drain electrode or a source electrode having at least an overlapping portion with the first electrode are arranged at both ends of the semiconductor film pattern, and each thin film transistor is arranged in a matrix. The first electrodes are connected to form a first bus line, and the second electrodes are connected to form a second bus line.
In an active matrix circuit board comprising a bus line and a display pixel electrode made of a transparent conductive film connected to the third electrode, the second bus line is connected to the third electrode on the transparent conductive film constituting the display pixel electrode. An active matrix circuit characterized in that it has a multilayer structure consisting of a first wiring formed by laminating one conductive film and a second wiring formed of at least one conductive film including a layer made of an aluminum film. substrate.