JPH0961802A - Evaluating method of defect in glass substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To judge whether defects are present or not in a glass substrate before the glass substrate is subjected to a producing process. SOLUTION: This method includes a process to form an ITO film all of at least the area which is to be inspected whether defects are present or not on a glass substrate 1, a process to selectively etch the ITO film into a specified pattern, and a process to visually check the ITO film 8A remaining after the selective etching. The specified pattern is composed of an assembly of patterns each having a long peripheral length present in each region determined by finely dividing the inspection region.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a defect evaluation method for a glass substrate, and more particularly to a defect evaluation method for a glass substrate used for a liquid crystal display substrate.

[0002]

2. Description of the Related Art A liquid crystal display substrate has glass substrates arranged opposite to each other with a liquid crystal interposed therebetween as an envelope. The liquid crystal side surface of each glass substrate is formed by a so-called photolithography technique. Signal lines, electrodes, switching elements, etc. are formed.

In this case, it goes without saying that it is desirable that no defects such as so-called latent scratches (polishing scratches filled with abrasive particles or the like) are formed on the surface of each glass substrate on the liquid crystal side. This is because, when such a defect is formed, a signal line or the like having a disconnection is formed at the defect portion.

[0004]

However, it is difficult to recognize the above-mentioned defects such as latent scratches even by observing them with a microscope, and it becomes clear when the above-mentioned disconnection of the signal line can be recognized in the course of the manufacturing process. I did nothing.

Therefore, the present invention has been made under such circumstances, and an object of the present invention is to detect a defect in a glass substrate, which makes it possible to determine whether or not a defect exists in the glass substrate before being subjected to a manufacturing process. To provide an evaluation method.

[0006]

SUMMARY OF THE INVENTION Among the inventions disclosed in the present application, the outline of a representative one will be briefly described.
It is as follows.

Means 1. The method includes a step of forming an ITO film at least in the entire defect evaluation region of the glass substrate, a step of selectively etching the ITO film in a predetermined pattern, and a step of visually inspecting the ITO film remaining by the selective etching. It is characterized in that the predetermined pattern is composed of an aggregate of patterns having a large peripheral length, which are present in each area obtained by finely dividing the defect evaluation area.

Means 2. In the configuration of the means 1, the glass substrate constitutes an envelope of the liquid crystal display substrate, and is used as a photomask when selectively etching the ITO film formed on the glass substrate, and is used in manufacturing the liquid crystal display substrate. One of the photomasks is used.

[0009]

According to the construction described in the means 1, when there is a defect in the defect evaluation region on the surface of the glass substrate, the ITO (Imdium-Tin-Oxide) film formed by selective etching has the defect formed. A notch is formed in the existing portion, and this notch can be easily observed by visual observation with a microscope.

It has been found that this ITO film is a material that reacts sensitively to defects such as latent scratches formed on the glass substrate and is prone to the above-mentioned notches. I that has penetrated into latent scratches, etc.
It is considered that the etching solution for the TO film easily corrodes the ITO film.

In this case, the pattern of the ITO film is an aggregate of patterns having a large peripheral length which are present in each of the regions where the defect evaluation region is finely divided, so that the defect of the ITO film is present regardless of where the defect exists. The probability of being positioned in the peripheral portion of the pattern is increased, and the above notch is likely to occur.

From this, there is an effect that fine defects can be found with almost no oversight.

Further, according to the constitution shown in the means 2, there is no need to specially prepare the photomask for forming the ITO film having the above pattern, and the existing photomask can be used as it is.

[0014]

FIG. 2 is a diagram showing an embodiment of an equivalent circuit of a liquid crystal display substrate having a glass substrate which is a target of the defect evaluation method according to the present invention. Although the figure is an equivalent circuit, it is drawn corresponding to the actual geometrical arrangement.

In FIG. 1, gate signal lines extending in the x direction and arranged in parallel in the y direction on the liquid crystal side surface of one glass substrate 1 of the glass substrates arranged to face each other with the liquid crystal interposed therebetween. 2 and video signal lines 3 insulated from the gate signal lines 2 and extending in the y direction and arranged in parallel in the x direction.

A rectangular region surrounded by the gate signal line 2 and the video signal line 3 constitutes a unit pixel region, and a gate signal (voltage) is supplied from one gate signal line 2 to each of these regions. Thin film transistor TF to turn on
A video signal (voltage) from the video signal line 3 is provided through the thin film transistor TFT which is turned on.
It is supplied to.

The pixel electrode 3 is provided with a floating capacitance Cadd between the pixel electrode 3 and the other gate signal line 2 so that a video signal after the thin film transistor TFT is turned off can be stored for a long time.

A common electrode common to each unit pixel is formed on the surface of the other glass substrate facing the glass substrate 1 with the liquid crystal in between, and the pixel electrode to which the video signal is supplied is formed. An electric field is generated between the liquid crystal and the liquid crystal layer 3 to change the light transmittance of the liquid crystal.

3A and 3B are configuration diagrams showing an embodiment of the unit pixel. FIG. 3A is a plan view and FIG. 3B is a view.
3 is a cross-sectional view taken along line bb.

First, a scanning signal line (for example, an Al alloy layer) 2 is formed on the main surface of the glass substrate 1, and an insulating film (for example, an Al film) formed over the entire area of the glass substrate 1 so as to cover the scanning signal line 2 as well. A video signal line (eg, a sequentially laminated body layer of Cr and Al alloy layers) 3 is formed on a silicon nitride film 4.

This insulating film 4 serves as an interlayer insulating film at the intersection of the scanning signal line 2 and the video signal line, as a gate insulating film in the formation region of the thin film transistor TFT, and further in the formation region of the stray capacitance Cadd. It functions as a dielectric film.

A part of the scanning signal line 2 extends to the formation region of the thin film transistor TFT, and the gate electrode of the thin film transistor TFT is formed. Then, a semiconductor layer (for example, amorphous Si) 5 is formed on the surface of the insulating film 4 (gate insulating film) on the gate electrode 2A,
A drain electrode 3A and a source electrode 6 are formed on the upper surface of the semiconductor layer 5 so as to be separated from each other. Here, the drain electrode 3A is formed integrally with the video signal line 3.

A protective film 7 is formed over the entire surface of the glass substrate 1 thus constructed, and the contact hole formed in the protective film 7 is formed on the upper surface of the protective film 7. A pixel electrode (Imdium-Tin-Oxide) 8 connected to the source electrode 6 is formed.

The pixel electrode 8 extends on the protective film 7 so as to overlap with the other gate signal line 2, and a floating capacitance Cadd is formed between the pixel electrode 8 and the gate signal line 2 at this overlapping portion.

The liquid crystal display substrate thus constructed is manufactured by repeating the microfabrication of the deposited film formed on the entire main surface of the glass substrate 1 by the selective etching method using the so-called photolithography technique several times. To be done.

In this case, the fact that the glass substrate 1 has no defects on its main surface is one of the factors for performing subsequent fine processing by the selective etching method using the photolithography technique without damage.

FIG. 4 is a process diagram showing an embodiment of a glass substrate defect evaluation method performed as a pre-stage for sequentially performing such fine processing.

Step 1. One glass substrate is selected and extracted from the plurality of glass substrates divided for each lot. Multiple glass substrates divided into lot units are formed in the same process and cleaned in the same way, so if there is a defect in the extracted glass substrate, all glass substrates in each lot unit It is based on the empirical rule that similar flaws may have occurred in.

Step 2. The glass substrate taken out is immersed in an alkaline cleaning liquid. This cleaning solution has a pH of 12 to 1
3. The liquid temperature is preferably 50 to 60 ° C., and the dipping time is suitably 10 to 15 minutes.

Step 3. In this way, an ITO film having a film thickness of about 100 nm is formed on the entire main surface of the glass substrate treated with the alkaline cleaning liquid.

Step 4. I formed on the entire area of the glass substrate
So-called patterning is performed on the TO film by using a selective etching method based on a so-called photolithography technique.

As the photomask by the photolithography technique in this case, the photomask for forming the pixel electrode (indicated by reference numeral 8 in FIG. 3) used in the manufacture of the liquid crystal display substrate and already existing is used as it is.

Also, aqua regia is used as an etchant for the selective etching.

As shown in FIG. 1, the glass substrate thus obtained is formed by arranging the patterned ITO films 8A on the surface of the glass substrate 1 in a matrix.

Step 5. Each ITO film 8A is sequentially observed visually by a microscope. In this case, as shown in FIG. 5, the ITO film 8A may be recognized as a shape in which the notch 10 is formed in the periphery thereof.

In this case, it is proved that there is a defect 11 such as a latent scratch on the surface of the glass substrate at the notch 10. An aqua regia etchant invades the latent wound,
This is because the infiltrated etchant easily erodes the ITO film 10.

As described above, according to the evaluation methods shown in the examples, when there is a defect 11 on the surface of the glass substrate 1,
The ITO film 8A formed by the selective etching has a shape in which the notch 10 is formed in the portion where the defect is formed, and the notch 10 can be easily observed by visual observation with a microscope.

From this fact, there is an effect that fine defects can be found almost without overlooking.

Further, since the photomask used for manufacturing the liquid crystal display substrate and already existing for forming the pixel electrode 8 is used as it is, it is necessary to form the ITO film 8A for defect evaluation. This has the effect of eliminating the need to create a special photomask.

In the above-described embodiment, the ITO film 8A is formed with the area corresponding to the display portion of the liquid crystal display substrate as the defect evaluation area, but this defect evaluation area is not necessarily limited to the display area. Needless to say, the area may be narrower or wider than that.

Although the photomask used in the manufacture of the liquid crystal display substrate is used as it is in the above-mentioned embodiment, the present invention is not limited to this, and a photomask for defect evaluation is specially prepared. It goes without saying that the ITO film 8A having a pattern as shown in FIG. 6 may be formed.

In this case, the pattern of the ITO film 8A is not particularly limited as long as it is an aggregate of patterns having a large peripheral length which are present in each area obtained by finely dividing the defect evaluation area.

The larger the peripheral length of the pattern, the higher the probability that the defect will be located in the peripheral portion of the pattern of the ITO film, regardless of the location of the defect. Therefore, it is easier to find the defect. Play.

Further, in the above-mentioned embodiment, the method for evaluating defects of the glass substrate constituting the liquid crystal display substrate is shown, but it is not always limited to the glass substrate constituting the liquid crystal display substrate. There is no end.

[0045]

As is apparent from the above description,
According to the glass substrate defect evaluation method of the present invention, it becomes possible to determine whether or not a defect exists in the glass substrate before being subjected to the manufacturing process.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing an embodiment of a defect evaluation method according to the present invention, showing a pattern of an ITO film formed on a glass substrate.

FIG. 2 is a diagram showing an example of an equivalent circuit of a liquid crystal display substrate including a glass substrate which is a target of the defect evaluation method according to the present invention.

3A and 3B are configuration diagrams showing an embodiment of a unit pixel, FIG. 3A is a plan view, and FIG. 3B is a sectional view taken along line bb of FIG. 3A.

FIG. 4 is a process drawing showing an embodiment of a glass substrate defect evaluation method according to the present invention.

FIG. 5 is an explanatory diagram showing a defect evaluation method according to the present invention.

FIG. 6 is an explanatory view showing an embodiment of a defect evaluation method according to the present invention, showing a pattern of an ITO film formed on a glass substrate.

[Explanation of symbols]

1 ... Glass substrate, 8A ... ITO film, 10 ... Notches, 11 ... Latent scratches.

Claims (2)

[Claims] 1. A step of forming an ITO film on at least the entire area of a defect evaluation region of a glass substrate, a step of selectively etching the ITO film in a predetermined pattern, and a visual inspection of the ITO film remaining by the selective etching. A glass substrate, characterized in that the predetermined pattern is composed of an aggregate of patterns having a large peripheral length that exist in each of the regions obtained by finely dividing the defect evaluation region. Defect evaluation method. 2. The glass substrate constitutes an envelope of a liquid crystal display substrate, and is used as a photomask for selectively etching an ITO film formed on the glass substrate, and is used for manufacturing the liquid crystal display substrate. The defect evaluation method for a glass substrate according to claim 1, wherein any one of photomasks is used.