JP2000206561A - Production of liquid crystal display device and liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to suppress the occurrence of dot defects by the defective contact between pixel electrodes and drain electrodes, to improve the yield of products, to prevent the breakage of the electrical connection in the connecting sections of the pixel electrodes and the drain electrodes by thermal impact, etc., and to improve the reliability of the products. SOLUTION: Apertures 9 for electrically connecting the pixel electrodes and the drain electrodes to an interlayer insulating film are formed. At this time, a method of forming the apertures 9 of such a shape with which the electrically good connection characteristic may be secured between the pixel electrodes and the drain electrodes is established. The electrically good connection characteristic is secured between the pixel electrodes and the drain electrodes by the method of forming the apertures 9 described above.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is used as a display device for displaying images on a display monitor or the like.
The present invention relates to a method of manufacturing a liquid crystal display device that displays an image by driving liquid crystal by an electric signal, and a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, as a display device for displaying an image on a display monitor such as a notebook personal computer or a portable terminal, a liquid crystal display device that drives a liquid crystal by an electric signal to display an image has been widely used. Active matrix type liquid crystal display devices capable of display have received great attention due to their excellent display performance. This active matrix type liquid crystal display device has a configuration in which a large number of pixel electrodes and a large number of non-linear elements such as thin film diodes and thin film transistors for driving each pixel electrode are arranged in a two-dimensional matrix on a transparent substrate. In the following description, a case where a thin film transistor is used as a nonlinear element will be described.

In the conventional active matrix type liquid crystal display device, a pixel electrode is formed first, and then a scanning line electrode, a thin film transistor, and a signal line electrode are formed. In such a configuration, in order to prevent a short circuit between the pixel electrode, the scanning line electrode, and the signal line electrode, as shown in FIG. It was necessary to form the gate electrode 2 apart from the (gate) electrode 2 and the signal line (source) electrode 5, and it was not possible to increase the aperture ratio of the image display portion.

For this reason, recently, an interlayer insulating film having a thickness of several μm is formed between the scanning line electrode 2, the thin film transistor Tr and the signal line electrode 5 and the pixel electrode 8, and the scanning line electrode 2 and the signal line electrode 5 are formed. Even if the distance X between the pixel electrode 8 and
It is considered that a short circuit between them is prevented by an interlayer insulating film to increase the aperture ratio of a display portion.

FIG. 4 is a sectional view showing a part of an active matrix type liquid crystal display device. In this liquid crystal display device, a scanning line electrode, a thin film transistor, and a signal line electrode are formed on a transparent substrate, an interlayer insulating film is formed thereon, and a pixel electrode is further formed thereon. A transparent substrate 1 and a scanning line (gate) electrode 2, a gate insulating film 3, a semiconductor layer 4, a signal line (source) electrode 5, a drain electrode 6, an interlayer insulating film 7, and a pixel electrode 8 are formed.

In this active matrix type liquid crystal display device, an interlayer insulating film 7 is formed after a thin film transistor Tr as a non-linear element is formed on a transparent substrate 1. The interlayer insulating film 7 is provided with an opening 9 having a V-shaped cross section. Here, the angle between the side surface of the opening 9 and the drain electrode 6 is defined as a taper angle θ. After this,
The pixel electrode 8 is formed, and the drain electrode 6 and the pixel electrode 8 are electrically connected through the opening 9.

The interlayer insulating film 7 is generally made of a photosensitive resin and is formed by the steps shown in FIG. First, in step S1, for example, a photosensitive acrylic resin is applied to a thickness of several μm. In step S2, a pre-bake step is performed in which a heat treatment is performed on the applied resin film to evaporate the solvent in the resin film. Next, in step S3, patterning is performed by an exposure / development process, and an opening 9 is formed in the resin film. Then, in step S5, a decoloring process is performed by irradiating ultraviolet rays in a post UV process. Finally, in step S6,
A post-baking step is performed, and heat treatment is again performed to cure the photosensitive acrylic resin, thereby forming the interlayer insulating film 7.

[0008]

However, when the interlayer insulating film 7 in the liquid crystal display device is formed in the above-described conventional manufacturing method, the taper angle θ of the opening 9 is large, The pixel electrode 8 in the opening 9
In some cases, cracks occur, and the pixel electrode 8 and the drain electrode 6 cannot be electrically connected or good contact cannot be obtained, which causes a point defect and lowers the product yield. Had a point.

Further, there is another problem that the electrical connection between the pixel electrode 8 and the drain electrode 6 is broken due to thermal shock or the like, and the reliability of the liquid crystal display device as a product is reduced. Was.

The present invention solves the above-mentioned conventional problems. It is possible to suppress the occurrence of point defects due to poor contact between the pixel electrode and the drain electrode, and to significantly improve the product yield. A method of manufacturing a liquid crystal display device and a liquid crystal display device capable of preventing disconnection of electrical connection due to thermal shock or the like at a connection portion between a pixel electrode and a drain electrode and improving product reliability. A display device is provided.

[0011]

According to the present invention, there is provided a method for manufacturing a liquid crystal display device and a liquid crystal display device, wherein a pixel electrode and a drain electrode are electrically connected to an interlayer insulating film. A method for forming an opening having such a shape that electrical good connection characteristics can be secured between the pixel electrode and the drain electrode when forming the opening for forming the opening Thereby, electrically favorable connection characteristics are secured between the pixel electrode and the drain electrode.

As described above, it is possible to suppress the occurrence of point defects due to poor contact between the pixel electrode and the drain electrode, to significantly improve the product yield, and to improve the connection between the pixel electrode and the drain electrode. Disconnection of the electrical connection due to thermal shock or the like can be prevented, and the reliability of the product can be improved.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS According to a method of manufacturing a liquid crystal display device according to the first aspect of the present invention, a scanning line electrode and a signal line electrode made of a light-shielding substance are arranged on a transparent substrate, and a non-linear element is arranged at the intersection of the matrix and the non-linear element. , A thin film of resin is formed thereon, an opening having a V-shaped cross section is formed in the resin film, an interlayer insulating film is formed, and one of the nonlinear elements is further formed thereon. A method for forming a pixel electrode so as to be electrically connected to one electrode and an opening provided in the interlayer insulating film, wherein the step of forming the interlayer insulating film includes at least the interlayer insulating film. A step of applying a resin for forming a film on the upper surface side of the transparent substrate, a heat treatment of the applied resin to evaporate a solvent thereof, and a pre-bake step of forming the resin film; Putter against And exposing and developing process for forming the opening by training, and post-UV irradiating ultraviolet rays for performing decoloring processing on the resin film,
A post-bake step of performing a heat treatment for curing the decolorized resin film to form the interlayer insulating film.Before the post-UV step, a heat treatment different from the pre-bake step and the post-bake step is performed. The method includes a baking step for performing the baking step.

According to a second aspect of the present invention, there is provided a method of manufacturing a liquid crystal display device, wherein the baking temperature t2 in the baking step performed before the post-UV step according to the first aspect is equal to or lower than the baking temperature t1 in the pre-baking step. I do.

According to a third aspect of the present invention, there is provided a liquid crystal display device manufactured by the method for manufacturing a liquid crystal display device according to the first or second aspect, wherein the opening provided in the interlayer insulating film is provided. If the angle between the side surface of the non-linear element and one electrode of the nonlinear element is a taper angle θ, θ ≦ 50 °, and the interlayer insulating film is defined by the intersection of the side surface of the opening and the upper surface of the interlayer insulating film. Is formed in a curved shape.

According to the above method and configuration, when forming an opening for electrically connecting the pixel electrode and the drain electrode to the interlayer insulating film, the electrical connection between the pixel electrode and the drain electrode is made. A method for forming an opening having such a shape that good connection characteristics can be ensured, and the method for forming the opening ensures electrically good connection characteristics between the pixel electrode and the drain electrode. .

Hereinafter, a method for manufacturing a liquid crystal display device and a liquid crystal display device according to an embodiment of the present invention will be specifically described with reference to the drawings.

FIG. 4 is a partial sectional view showing a schematic structure of a general liquid crystal display device. As shown in FIG. 4, for example, a scanning line (gate) electrode 2 is formed on a transparent substrate 1 made of glass, quartz, or the like by sputtering, photolithography, or etching of Al. Next, the gate insulating film 3
For example, SiNx is successively deposited by a plasma CVD method, and then a-Si is deposited as the semiconductor layer 4.
Next, for example, Ti is deposited by a sputtering method, and a signal line (source) electrode 5 and a drain electrode 6 are formed by photolithography and etching. An interlayer insulating film 7 is formed thereon with a thickness of several μm.

This interlayer insulating film 7 is formed according to the process flow shown in FIG. Specifically, in the coating process of step S1,
After forming the signal line (source) electrode 5 and the drain electrode 6, for example, a photosensitive acrylic resin is applied as a resin for forming the interlayer insulating film 7. Next, in the pre-bake step of step S2, a heat treatment at 90 ° C. is performed using, for example, a hot plate as a heating unit, and the solvent in the applied acrylic resin is evaporated. Next, step S
In the exposure / development step 3, patterning is performed on the resin film made of the acrylic resin from which the solvent has evaporated, and an opening 9 having a V-shaped gradient is formed in the cross section of the resin film.
At the opening 9 after the exposure / development step of step S3, the taper angle θ is very large, and a typical value is about θ = 70 °.

Thereafter, in the conventional method of manufacturing a liquid crystal display device, as shown in the process flow of FIG.
In the post-UV step, the resin film is decolorized by irradiating ultraviolet rays. Finally, in a post-bake step of step S6, a heat treatment is performed at, for example, 220 ° C. for 90 minutes.
The photosensitive acrylic resin is cured.

In such a conventional method for manufacturing a liquid crystal display device, the final taper angle of the opening 9 is determined in step S3.
It is almost equal to the taper angle after the end, and is about θ = 70 °, which is a very large angle. For this reason, if, for example, ITO is subsequently formed as the pixel electrode 8 by sputtering, cracks occur in the ITO in the opening 9, and when the pixel electrode 8 and the drain electrode 6 cannot be electrically connected or a good contact is obtained. In some cases, this may cause a point defect, which lowers the yield.

That is, in the conventional method of manufacturing a liquid crystal display device, the substrate surface temperature gradually rises during irradiation with ultraviolet rays in the post-UV step of step S5. 7 does not melt,
The taper angle θ of the opening 9 is maintained in the state after the end of step S3.

Therefore, in the manufacturing method of the present embodiment, as shown in FIG. 1, before the post UV step of step S5, a baking step is performed as a step S4.
More specifically, after the exposure / development step of step S3, in the baking step of step S4, a heat treatment at 135 ° C. is performed using, for example, a hot plate as a heating means.

FIG. 2 is a schematic view showing the tapered shape of the opening 9 in each of the manufacturing methods according to the prior art and the present embodiment. According to the method of forming the interlayer insulating film in the manufacturing method of the present embodiment, the taper angle θ of the opening 9 is reduced and the interlayer insulating film 7 is melted as compared with the conventional forming method. ○ The part surrounded by a circle is rounded and IT
O coverage was significantly improved, and the IT
O cracks can be suppressed.

As described above, the baking step is performed as a step S4 before the post-UV step in the step S5, so that the interlayer insulating film 7 has a good electrical contact between the pixel electrode 8 and the drain electrode 6. The opening 9 can be formed in a shape that can secure connection characteristics.

Therefore, the pixel electrode 8 and the drain electrode 6
There is no point defect due to poor contact, and the product yield can be significantly improved.

Assuming that the baking temperature in the pre-baking step in step S2 is t1 and the baking temperature in the baking step before the post-UV step in step S4 is t2, if t2> t1, then the post-UV step in step S5 is performed. The effect of bleaching is reduced and the transmittance is reduced.

For this reason, the baking temperature t2 in the baking step before the post-UV step is changed to the baking temperature t1 in the pre-baking step.
The following is preferable because the transmittance of the interlayer insulating film 7 is improved and a liquid crystal display device with high transmittance is obtained.

Next, a polyimide-based alignment film was applied to the array substrate manufactured by such a manufacturing method, and rubbing was performed using a nylon cloth or the like to perform an alignment process. A substrate with a color filter and a transparent electrode, which has been subjected to the same orientation treatment as this substrate, is bonded together, and between them, for example, a nematic liquid crystal ZLI-4792 manufactured by Merck with a small amount of chiral material CN manufactured by Chisso Petrochemical is filled, and a liquid crystal display device is formed. Produced.

In the liquid crystal display device thus obtained, good contact between the pixel electrode 8 and the drain electrode 6 is obtained, and the yield does not decrease due to poor contact between the pixel electrode 8 and the drain electrode 6. . Also,
For example, even when a thermal shock test at -30 ° C. and + 70 ° C. was performed, no disconnection occurred between the pixel electrode 8 and the drain electrode 6, and no change in the connection resistance was observed. As described above, according to the method of manufacturing a liquid crystal display device of the present embodiment, a highly reliable liquid crystal display device in which electrical connection is not broken due to thermal shock or the like can be realized.

Although a thin film transistor is used as the nonlinear element in the above embodiment, a thin film diode or MIM may be used.

[0032]

As described above, according to the present invention, when forming an opening for electrically connecting a pixel electrode and a drain electrode to an interlayer insulating film, the pixel electrode and the drain electrode are It is possible to establish a method of forming an opening having such a shape that electrical good connection characteristics can be secured between the pixel electrode and the drain electrode by the method of forming the opening. And excellent connection characteristics.

As a result, it is possible to suppress the occurrence of point defects due to a defective contact between the pixel electrode and the drain electrode, to significantly improve the yield of the product, and to improve the connection between the pixel electrode and the drain electrode. Disconnection of electrical connection due to thermal shock or the like can be prevented, and the reliability of the product can be improved.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a step of forming an interlayer insulating film in a method of manufacturing a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a comparison between a conventional example and a conventional example of an opening shape of an interlayer insulating film in a liquid crystal display device according to the manufacturing method of the embodiment.

FIG. 3 is a plan view showing a schematic configuration of a liquid crystal display device according to a general manufacturing method and a partially enlarged view thereof.

FIG. 4 is a partial cross-sectional view showing a schematic configuration of a liquid crystal display device according to a general manufacturing method.

FIG. 5 is a flowchart showing a step of forming an interlayer insulating film in a conventional method of manufacturing a liquid crystal display device.

[Explanation of symbols]

Reference Signs List 1 transparent substrate 2 scanning line (gate) electrode 3 gate insulating film 4 semiconductor layer 5 signal line (source) electrode 6 drain electrode 7 interlayer insulating film 8 pixel electrode 9 opening (of interlayer insulating film) X (pixel electrode and scanning line) Electrode or signal line electrode)
Distance Tr Thin film transistor θ Taper angle (of opening)

Claims (3)

[Claims] 1. A scanning line electrode and a signal line electrode made of a light-shielding substance and a non-linear element are formed in a matrix at intersections thereof on a transparent substrate, and a thin film is formed by a resin on the non-linear element. An opening having a slope having a V-shaped cross section is provided to form an interlayer insulating film, and further electrically connected to one electrode of the non-linear element through the opening provided in the interlayer insulating film. A method of manufacturing a liquid crystal display device in which a pixel electrode is formed as described above, wherein the step of forming the interlayer insulating film includes at least a step of applying a resin for forming the interlayer insulating film to an upper surface side of the transparent substrate. A pre-baking step for subjecting the applied resin to heat treatment to evaporate the solvent thereof to form the resin film, and an exposure and development step for forming the opening by patterning the resin film. And a post-UV step of irradiating the resin film with ultraviolet rays for performing a decolorizing treatment, and a post-baking step of performing a heat treatment for curing the decolorized resin film to form the interlayer insulating film. A method of manufacturing a liquid crystal display device, comprising a bake step for performing a heat treatment different from the pre-bake step and the post-bake step before the post-UV step. 2. A baking temperature t2 in a baking step performed before a post-UV step is equal to a baking temperature t1 in a pre-baking step.
2. The method for manufacturing a liquid crystal display device according to claim 1, wherein: 3. A liquid crystal display device manufactured by the method for manufacturing a liquid crystal display device according to claim 1, wherein a side surface of an opening provided in the interlayer insulating film and one of the non-linear elements are provided.
If the angle between the two electrodes is a taper angle θ, θ ≦ 50 °
A liquid crystal display device wherein the interlayer insulating film is formed such that an intersection between a side surface of the opening and an upper surface of the interlayer insulating film is curved.