JP2000105385A - Production of liquid crystal display element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To efficiently form alignment marks to be used for the second time at the time of subjecting a transparent substrate with transparent electrodes to multiple exposure twice. SOLUTION: A photoresist 2 is applied on the transparent substrate 1 with the transparent electrodes and is subjected to the first time of the exposure via a photomask 3a having prescribed electrode forming patterns. In succession, the photoresist is subjected to the second time of the exposure by using a photomask 3b having the same electrode forming patterns. At this time, the alignment mark M when executing the exposure of the second time are formed in the prescribed positions of the photoresist 2 by a laser beam at the time of the exposure of the first time.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a liquid crystal display device, and more particularly, to a technique for aligning a transparent substrate in a transparent electrode patterning step.

[0002]

2. Description of the Related Art A transparent electrode of a liquid crystal display element is made of ITO (In).
Dim Tin Oxide), but its IT
O patterning has become increasingly finer, and the line spacing between electrodes has recently been reduced to 10 μm or less.

In general, the patterning of ITO is performed in the order of substrate cleaning → photoresist coating → prebaking → exposure → development → postbaking → etching → photoresist stripping. Usually, ITO of a TN or STN type liquid crystal display element is used.
For patterning, a non-imaging type exposure machine using parallel light is used.

[0004]

However, if foreign matter adheres to a photomask used at the time of exposure, a leak between electrodes may occur at the same place in the same lot due to the foreign matter. Such a defect is found in an inspection process using, for example, a short / open checker after the photoresist is removed.

Conventionally, in order to repair this kind of defective product, after patterning is completed, the ITO at the leak portion is volatilized by laser light, or a photoresist is again applied and re-patterning is performed by double exposure. But anyway, considerable time and effort is spent.
In particular, in the case of double exposure, the photomask must be aligned with reference to the previously formed ITO pattern, so that the operation is considerably difficult.

Therefore, as another method, an alignment mark is formed in advance on a predetermined portion of the transparent substrate by chrome or the like, and the transparent substrate is positioned by the mark to perform double exposure. That is, exposure is performed twice using a plurality of photomasks having the same pattern.

[0007] According to this method, the probability that foreign matter adheres to the same portion of the two photomasks stochastically is extremely low, so that the rate of occurrence of inter-electrode leakage can be reduced accordingly. However, an additional step of forming an alignment mark on the transparent substrate is required, which is not preferable in terms of production efficiency.

In the case of a substrate with a color filter, it is conceivable to use an alignment mark for forming a color filter. Since the mark gaps are different, the alignment accuracy is reduced, which is inconvenient.

[0009]

In order to solve such a problem, the present invention provides a method of applying a photoresist on a transparent substrate provided with a transparent electrode, and applying the photoresist through a photomask having a predetermined electrode forming pattern. And then a second exposure using a photomask having the same electrode formation pattern, followed by a predetermined step on a transparent substrate through various steps including a development step, an etching step and a photoresist stripping step. In the method for manufacturing a liquid crystal display element for forming a transparent electrode pattern according to (1), the second exposure is performed at a predetermined position of the photoresist by a laser beam during the first exposure.
It is characterized in that an alignment mark for performing the second exposure is formed. At this time, it is preferable to perform two exposures using an exposure machine of the same type and performance.

As described above, according to the present invention, since the alignment mark is formed at the time of the first exposure, the step of forming the alignment mark on the transparent substrate in advance is not required.

In the present invention, the distance between the electrode forming patterns of the photomask used for the second exposure is the first.
It is preferable that the width is substantially smaller than the distance between the electrode forming patterns of the photomask used for the second exposure. According to this, even if there is some misalignment in the alignment at the time of the second exposure, it is possible to suppress the enlargement between the lines and the reduction in the line width due to the enlargement.

[0012]

Next, embodiments of the present invention will be described in more detail with reference to the drawings.

First, in the present invention, the patterning of the ITO is performed by washing the substrate, applying a photoresist, prebaking, exposing for the first time, exposing for the second time, developing, and postbaking.
Etching is performed in the order of photoresist removal.
2 shows a schematic diagram at the time of the first exposure.

According to this, a photomask having a predetermined electrode forming pattern is applied to a photoresist 2 applied on a transparent substrate with transparent electrodes (entire transparent electrode substrate) 1 by, for example, a non-imaging type exposure machine 4. Exposure is performed through 3a. In the first exposure step, a laser irradiator 5 for forming an alignment mark M on the photoresist 2 is provided.

In this embodiment, one laser irradiator 5
, Alignment marks M are formed at two positions on the left and right sides of the photoresist 2. Therefore, the laser irradiator 5 is arranged so that the optical axis is parallel to the substrate surface on the side of the transparent substrate 1. is set up. A beam splitter (light splitter) 6a and a reflection mirror 6b are arranged on the optical axis.

In this case, as viewed from the laser irradiator 5, the beam splitter 6a is disposed on the positioning mark M on the near side, and the reflecting mirror 6b is disposed on the positioning mark M on the opposite side.

The alignment mark M is formed in a margin other than the liquid crystal display. Although not shown in detail, the photomask 3a is provided with a light transmitting portion having a shape corresponding to the alignment mark M. That is, the shape of the translucent portion is drawn as the alignment mark M on the photoresist 2 by the laser light from the laser irradiator 5.

The formation of the alignment mark M by the laser beam may be performed at the same time as the exposure or before or after the exposure. Further, since the laser beam only needs to volatilize the photoresist 2 alone, the power may be very small.

After the first exposure, the transparent substrate 1 with a transparent electrode is directly transferred to a second exposure step, and FIG. 2 is a schematic diagram at the time of the second exposure. This second
In the second exposure step, for example, the non-imaging type exposure machine 4 and the photomask 3b are used as in the first exposure step. However, when the second exposure is performed, the position formed beforehand is used. The entire alignment is performed based on the alignment mark M.

In this embodiment, two CCD cameras 7,
7, the alignment marks M on both the left and right sides are read, and the coordinate position of each alignment mark M is determined by image processing means (not shown).
, The photomask 3b is positioned.

After the positioning, exposure is performed again (second time) by the exposing machine 4. Thus, if there is a leak between the electrodes during the first exposure, the leak between the electrodes is repaired. Although the same electrode formation pattern as that of the photomask 3a at the time of the first exposure is provided on the photomask 3b, in this embodiment, the line pitch of the photomask 3b is larger than the line pitch of the photomask 3a. 1
２2 μm.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS XGA (Extended
Video Graphics Array: 1024 ×
For the purpose of patterning of 768 pixels), a positive type photoresist was applied to the cleaned entire transparent electrode substrate at 1.5 μm.
After thick coating and pre-baking, the first exposure was performed by the above-described apparatus, and a photomask alignment mark was drawn on the photoresist by laser light.

Next, the whole transparent electrode substrate is transferred to a second exposure step, and a photomask having a line gap of 2 μm narrower than the first exposure is positioned with reference to the alignment mark formed in the first exposure. Then, it was exposed again.

As a result, the leakage failure between the electrodes is about 5
%Met. By the way, according to the conventional method, the first
The rate of occurrence of inter-electrode leak failure when only the first exposure was performed was 15%. According to the present invention, the rate of occurrence of failure due to inter-electrode leakage could be reduced by about 10%. In addition, a repair was performed on 5% of the defective substrates with a laser beam to volatilize the leak portion, and the time required for the repair was reduced to 1/3 of the conventional time.

[0025]

As described above, according to the present invention,
Apply a photoresist on a transparent substrate with a transparent electrode,
When performing multiple exposures twice, the laser beam is used to form alignment marks at the predetermined positions of the photoresist at the time of the first exposure, so that the alignment marks are formed on the transparent substrate in advance. The step of forming alignment marks is not required, and the productivity is further improved.

[Brief description of the drawings]

FIG. 1 shows a first example of a liquid crystal display device during a manufacturing process according to the present invention.
FIG. 4 is a schematic view showing a second exposure step.

FIG. 2 shows a second example of the liquid crystal display device during the manufacturing process according to the present invention.
FIG. 4 is a schematic view showing a second exposure step.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Transparent substrate with a transparent electrode 2 Photoresist 3a, 3b Photomask 4 Exposure machine 5 Laser irradiation machine 6a Beam splitter 6b Reflection mirror 7 CCD camera

Claims (2)

[Claims] 1. A photoresist is applied on a transparent substrate with a transparent electrode, a first exposure is performed through a photomask having a predetermined electrode formation pattern, and subsequently, a photomask having the same electrode formation pattern A second exposure using, followed by forming a predetermined transparent electrode pattern on a transparent substrate through various steps including a developing step, an etching step, and a photoresist stripping step. A method for manufacturing a liquid crystal display element, comprising: forming a positioning mark for performing a second exposure at a predetermined position of a photoresist by a laser beam at the time of the second exposure. 2. The space between the electrode formation patterns of the photomask used for the second exposure is substantially smaller than the space between the electrode formation patterns of the photomask used for the first exposure. The method for manufacturing a liquid crystal display device according to claim 1, wherein: