JPH0481820A - Active matrix substrate and liquid crystal display element using the same - Google Patents

Abstract

PURPOSE:To obtain the liquid crystal display element which is free from the shorting defects between picture element electrodes and signal lines and has the excellent electrical connectability between the picture element electrodes and source electrodes by using transparent conductive films which consist of conductive particles and a resin and have 0.1 to 3mum film thickness as the picture element electrodes. CONSTITUTION:A material prepd. by dispersing and dissolving 40pts.wt. indium oxide particles contg. 5 atomic% tin and having 20nm average grain size and 30pts.wt. polymethacrylic polymer contg. 2.5wt.% benzophenone thickener in ethyl cellosolve and adjusting the viscosity of the soln. to 25cps is used as the material for forming the picture element electrodes. After this material is applied by a spinner method on a substrate, the coating is dried for 15 minutes at 100 deg.C. The coating is then exposed to picture element electrode pattern shapes by an ordinary method and after the coated films of unexposed parts are developed away by using a developer of sodium orthosilicate, the substrate is washed and is heat treated for 30 minutes at 180 deg.C, by which the picture element electrodes are formed. The film thickness after the treatment is specified to 0.1 to 3mum.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to an active matrix substrate comprising a plurality of switching elements arranged in a matrix, wirings and pixel electrodes connected to each electrode of these elements, and the active matrix substrate. This invention relates to a liquid crystal display element using.

[Conventional technology]

As an example of active matrix substrate for liquid crystal display device +
Japan Display' 89p510-5
13, a plan view of one pixel is shown in FIG. 2, a sectional view of its thin film transistor portion is shown in FIG. 3, and its manufacturing process is shown in FIG. 4.

In the figure, on an insulating substrate 1 such as a glass substrate, a gate electrode 2 made of a metal film such as chromium (Cr), a gate insulating film 3 made of a silicon nitride film, etc., and a semiconductor film made of an amorphous silicon film etc. 4, a drain electrode 5 and a source electrode 6 made of a metal film such as chromium (Cr) or aluminum (Al), a pixel electrode 7 made of a transparent conductive film, and a protective film 8 made of a silicon nitride film or the like are sequentially formed. ing. In the active matrix substrate, the gate electrode 2 is connected to a scanning line 9, the drain electrode 5 is connected to a signal line 10, and the source electrode 6 is connected to a pixel electrode 7, which is one electrode of a liquid crystal cell.

The transparent conductive film used for the pixel electrode of such a conventional active matrix substrate is an indium tin oxide (ITO) transparent conductive film formed by sputtering, as shown in Flat Panel Display' 90p.257-263. It is being

[Problem to be solved by the invention]

In the above-mentioned conventional technology, since the IT○ transparent conductive film for the pixel electrode is formed by sputtering, the crystallinity of the obtained IT○ transparent conductive film tends to change due to fluctuations in film forming conditions such as sputtering power and substrate temperature. .

This fluctuation in the crystallinity of the IT○ transparent conductive film causes the etching properties of the ■To transparent conductive film to fluctuate, and etching remains are likely to occur within the substrate. The etching residue causes a short circuit between the data wiring and the pixel electrode, and the signal from the data wiring is transmitted to the pixel electrode regardless of the state of the switching element, resulting in a point defect in the liquid crystal display element and a short circuit defect. was there. In addition, IT for pixel electrodes
○ When a transparent conductive film is formed by sputtering, the throwing power of the IT ○ transparent conductive film is poor at steep stepped portions.

There is a problem in that the ITO transparent conductive film is broken at the step portion of the source electrode, resulting in a defective electrical connection between the pixel electrode and the source electrode in the active matrix substrate.

An object of the present invention is to provide an active matrix substrate that is free from short-circuit defects between pixel electrodes and signal lines and has excellent electrical connectivity between pixel electrodes and source electrodes, and a defect-free liquid crystal display element using the active matrix substrate. Our goal is to provide the following.

[Means to solve the problem]

In order to achieve the above objective, in forming pixel electrodes of active matrix substrates, conductive particles are formed in a resin by pattern printing or coating, heat curing, and processing into a pattern. Thickness 0.1~
The thickness was set to 3 μm.

[Effect]

In the present invention, a liquid material made of conductive particles and resin is applied using a printing method, a spinner method, etc. to form a pixel electrode, so the coating film flows easily and becomes flat, and the step part of the source electrode is easily coated. It also has good coverage even with respect to the source electrode, and a good electrode connection with the source electrode can be obtained6.The film thickness after curing is 0.
If it becomes thinner than 1 μm, the connection resistance with the source electrode tends to increase, and if it becomes too thick than 3 μm, the printing accuracy of the liquid crystal alignment film for forming a liquid crystal display element decreases.
This results in a decrease in the image quality of the display element.

For this reason, the film thickness is preferably 0.1 μm to 3 μm.

In addition, in the present invention, the coating film made of conductive particles and resin can be formed into a pattern by a printing method, or the resin can be made photosensitive and patterned by exposure and development after coating. Etching residues that occur during processing are less likely to occur, and short circuits between pixel electrodes and signal lines are less likely to occur.

Further, as the conductive particles used in the present invention, there are indium oxide containing tin, tin oxide containing antimony, etc., but indium oxide containing tin is suitable because it provides a coating film with the lowest resistance value. There is. Note that it is preferable that the particle size is 50 nm or less because this reduces the connection resistance between the source electrode and the pixel electrode and the sheet resistance of the coating film.

[Example 1] An example of the present invention will be described with reference to FIG. FIG. 1 shows the cross-sectional structure of a thin film transistor portion of an active matrix substrate according to the present invention in the order of manufacturing steps, which were formed by the following processes (1) to (7).

(1) Chromium (
A metal film such as Cr) is formed by a sputtering method.

Next, the gate electrode 2 is formed by a normal photoetching process.
A pattern is formed (FIG. 1(a)).

(2) Silicon nitride film (SiliconNi) used as gate insulating film and interlayer insulating film is made by plasma CVD method
amorphous silicon film 4 used as a semiconductor film and a glabellar insulation film.
morphous 5ilicon (hereinafter referred to as a-5i film) and a phosphorus (P)-doped a-3i film (n-type a-5i film, hereinafter referred to as n+BSx film, not shown) used as an electrode contact. Films are formed one after another without breaking the vacuum in the reaction chamber (Fig. 1(b)).

(3) The a-5i film is separated into elements by normal photolithography and dry etching to form islands of the semiconductor film 4 (FIG. 1(C)).

(4) A Cr film 21 and an A1 film 22 to be used as a drain electrode, a source electrode, and a signal line are sequentially formed by sputtering (FIG. 1(d)).

(5) A1 film and Cr
The film is etched to form a drain electrode 5, a source electrode 6, and a signal line (not shown) of the thin film transistor.

Then, n+a-5i on the channel of the thin film transistor
The film is removed by dry etching or the like to obtain a thin film transistor (FIG. 1(e)).

(6) Next, pixel electrodes of the active matrix substrate related to the present invention are formed (FIGS. 1(f) and (g)).

(7) A protective film 8 for the thin film transistor is formed using epoxy resin or the like, and the active matrix substrate is completed (FIG. 1(h)).

The detailed manufacturing process for forming the pixel electrode in (6) above was performed in the following manner.

The forming material has an average particle size of 20 nm and 5 at.

40 parts by weight of indium oxide particles containing mic% tin;
30 parts by weight of a polymethacrylic acid polymer containing 2.5 wt % of a benzophenone type increaser was dispersed and dissolved in ethyl cellosolve to give a viscosity of 25 cps.

After coating this material on the substrate obtained in steps up to (5) using a spinner method (Fig. 1 (f-1)), it was heated at 100°C for 15
It was dried for a minute (FIG. 1 (f-2)). Next, the pixel electrode pattern is exposed to light using a normal method, and the coating film in the unexposed areas is developed and removed using a sodium orthosilicate developer, washed with water, and heat-treated at 180°C for 30 minutes. was formed (Fig. 1(g)).

As a result of examining the active matrix substrate manufactured by the above method, there was no occurrence of short circuit between the pixel electrode and the signal line. Further, as a result of examining the connection resistance value between the pixel electrode and the source electrode, it was found to be 8 to 10 Ω, which was a good result. Furthermore, a liquid crystal display element was manufactured using this active matrix substrate, and a lighting test was conducted to examine the image quality. As a result, the brightness of each pixel was uniform.

[Example 2] An active matrix substrate and a liquid crystal display element were produced in the same manner as in Example 1, except that the pixel electrodes were formed using the following method.

As a pixel electrode forming material, the average particle size is Ionm and 5 a
40 parts by weight of indium oxide particles containing tomic% tin and 30 parts by weight of a transparent epoxy resin were dispersed and dissolved in ethyl cellosolve acetate to give a viscosity of 25 cps. This material was applied onto the substrate obtained in the steps up to (5) of Example 1 using a spinner method, and then heated at 150"C for 30 minutes.
Heated for minutes. Next, using a commercially available positive resist on this coating film, a photoresist is formed in the shape of a pixel electrode pattern using the usual method, and after decomposing the exposed transparent epoxy resin with oxygen plasma, the remaining tin is removed by spray washing with water. The indium oxide particles contained therein were removed. Next, the positive photoresist was peeled off in a conventional manner, washed, and dried to obtain a pixel electrode.

As a result of examining an active matrix substrate on which pixel electrodes were formed using the above method, no short circuit occurred between one pixel electrode and a signal line. Further, the connection resistance value between the pixel electrode and the source electrode was 7 to IOKΩ, which was a good result. Furthermore, a liquid crystal display element was manufactured using this active matrix substrate, and a lighting test was conducted to examine the image quality. As a result, the brightness of each pixel was uniform.

〔Effect of the invention〕

According to the present invention, an active matrix substrate having no short-circuit defects between pixel electrodes and signal lines and excellent connectivity between pixel electrodes and source electrodes can be manufactured with high yield.
Using this active matrix substrate, a liquid crystal element with good image quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing the manufacturing process of an embodiment of an active matrix substrate according to the present invention, FIGS. 2 and 3 are plan and cross-sectional views showing a part of a conventional active matrix substrate, and FIG. This is a conventional active matrix substrate manufacturing process. 1... Insulating substrate, 2... Gate electrode, 3
...Gate insulating film, 4...Semiconductor film, 5...
・Drain electrode, 6... Source electrode, 7...
- Pixel electrode, 8... Protective film, 9... Scanning line, 10... Signal line, 21- Cr film, 21=Al film. 70...Transparent conductive film. 3rd area + j) Toumatsuki 411. March 1 te [shih] sound - 21 fortune q% ===

Claims (1)

[Claims] 1. In an active matrix substrate consisting of a plurality of switching elements arranged in a matrix, wiring connected to each electrode of these elements, and a pixel electrode, the pixel electrode is made of conductive particles and resin. An active matrix substrate characterized by using a transparent conductive film with a thickness of ~3 μm. 2. The active matrix substrate according to claim 1, wherein the conductive particles are indium oxide added with tin oxide. 3. A liquid crystal display element using the active matrix substrate according to claim 1 or 2.