JPH07230099A - Production of substrate for liquid crystal display device - Google Patents

Abstract

PURPOSE:To increase the thickness of wiring electrodes without losing the smoothness of a surface and to obtain a substrate lowered in resistance by filling the recessed parts formed by formation of substrate side electrodes of an insulating substrate in the state of patterning these electrodes with an insulating film mainly consisting of SiO2. CONSTITUTION:A conductive film 3a is formed at a prescribed thickness on the main surface of the insulating substrate 1 in a first stage. Hydrophobic resist films 8 are formed in prescribed patterns on this conductive film 3a in a second stage. The conductive film 3a is etched with these hydrophobic resist films 8 as an etching mask to form the wiring electrodes 3 of the prescribed patterns in a third stage. An aq. satd. hydrogen silicofluoride acid of SiO2 is brought into contact with the parts on the main surface of the insulating substrate 1 where the wiring electrodes 3 are not formed, by which the insulating films 9 mainly consisting of the SiO2 are formed at the thickness approximately equal to the thickness of the wiring electrodes 3 in a fourth stage. The resist film 8 is removed in a fifth stage.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a substrate for a liquid crystal display device in which wiring electrodes made of a conductive film are formed on an insulating substrate, and more specifically, it is particularly suitable for a large area and high definition liquid crystal display device. And a substrate for a liquid crystal display device.

[0002]

2. Description of the Related Art In recent years, thin film transistors (hereinafter referred to as "TF
"T" type structure or metal insulating film contact (MIM) type structure has been developed and put into practical use by developing a high quality image liquid crystal display device by active matrix type driving on each pixel for the purpose of high speed driving. . In the active matrix type liquid crystal display device represented by this TFT type, as shown in FIG. 7, a switching element 20 provided in each pixel is provided.
A substrate-side wiring electrode 30 made of an Al film or the like for supplying electric power and signals for driving pixels is installed on the wiring electrode 30, and a switching element 20 made of a SiO ₂ insulating film or Si / SiN is provided on the wiring electrode 30. And the counter electrode 40 is formed.

However, at present, there is a demand for a liquid crystal display device having a larger area and a higher definition, and further increasing the density of pixels,
Further, in order to suppress power consumption and heat generation in the wiring electrodes, it is necessary to reduce the resistance of each wiring electrode 30. In order to reduce the resistance, the wiring electrode 30 must be thickened. However, when the substrate wiring electrode 30 is thickened, the switching element 20 and the counter electrode 4 formed on the wiring electrode 30 are formed above the wiring electrode 30.
There is a problem that 0 is affected by the unevenness of the substrate and uneven brightness or display color is likely to occur due to poor conduction.

On the other hand, a super-twisted nematic (hereinafter referred to as "STN") type liquid crystal display device in which a liquid crystal element is directly driven by a wiring electrode is also widely used. However, even in this STN type, a voltage drop due to high definition is avoided. Therefore, it is necessary to reduce the resistance of the wiring electrode to the pixel. Therefore, STN
In the mold, it has been proposed to provide a thin metal auxiliary electrode below the wiring electrode, but in order to realize a sufficiently low resistance value, the film thickness of the auxiliary electrode must be increased, and as a result, The unevenness of the electrodes affects the upper element structure,
After all, there was a problem that unevenness in volatility due to poor continuity was likely to occur.

In order to solve the problems associated with the higher definition of such a TFT type or STN type liquid crystal display device, as shown in FIG. 6, the substrate 10 is etched to form a concave portion 60 on the surface thereof, There is disclosed a method of thickening the wiring electrode on the substrate side by forming a metal film such as Al by vacuum deposition from above and removing unnecessary portions by lift-off to form the electrode 30 in the recess 60 ( JP-A-4-90514).

[0006]

However, in the method disclosed above, there is a problem in smoothness such as generation of minute irregularities on the etching surface, and lift-off of unnecessary portions of the metal film to be the wiring electrode 30. When the fine patterning by the method is performed, the edge portion of the wiring electrode 30 is peeled off due to the influence of resist peeling and the like, resulting in a groove 70 having a width of several hundred nm or more and a depth of about the film thickness. Therefore, this groove 7
When 0, the continuity between the wiring electrode 30 and the surface of the substrate 10 becomes insufficient, resulting in an influence on the upper element structure.
Problems such as poor continuity could not be solved sufficiently.

In view of such circumstances, it is an object of the present invention to provide a method for manufacturing a substrate for a liquid crystal display device in which the wiring electrodes have a thick film and low resistance without losing the surface smoothness.

[0008]

The above object of the present invention is achieved by a method of manufacturing a substrate for a liquid crystal display device by sequentially performing the following steps. First step: Conductive film 3a is formed on the main surface of insulating substrate 1 to have a predetermined thickness. Second step: A hydrophobic resist film 8 is formed in a predetermined pattern on the conductive film 3a. Third step: Using the hydrophobic resist film 8 as an etching mask, the conductive film 3a is etched to form the wiring electrode 3 having a predetermined pattern. Step 4: the in portions not forming the wiring electrode A on the main surface of the insulating substrate 1, mainly SiO ₂ by contacting the saturated hydrosilicofluoric acid solution of SiO ₂
The insulating film 9 made of is formed to a thickness substantially equal to that of the wiring electrode. Fifth step: The hydrophobic resist film 8 is removed.

Here, as the insulating substrate 1, various low alkali glass, soda lime silicate glass or other glass which is alkali passivated with SiO ₂ or the like can be used, but not limited to these, PET ( It may be an organic substrate such as polyethylene terephthalate).

The material of the conductive film 3a is A
1, Cr, Cu, Ta, Mo, Ag, Au, Ta-Mo
Etc. These compounds, ITO (indium tin oxide), S
nO ₂ , a carbon material or the like can be used.

The resist means a corrosion resistant substance used for patterning a conductive film, and a photoresist used for photolithography or the like can be used. The formation of the resist film on the conductive film can be performed by a roll coater or the like in addition to the method by spin coating. The resist film may be patterned by a method other than photolithography such as partial film formation by a printing method.

Further, the thickness of the conductive film 3a formed in the first step is 100 nm to 3 μm.
It is formed to a thickness for obtaining a wiring electrode having a necessary resistance value up to a certain degree. For example, when a Cr metal film having a thin film resistance of 50 μΩcm is used as a wiring material for an STN type LCD substrate, a color STN type L is required if the film thickness is about 500 nm or more.
It functions as a lower buried auxiliary electrode for reducing the apparent specific resistance per unit length of an ordinary 70 μm wide ITO transparent wiring electrode to about half or less when manufacturing a CD. Also, for example, T
Α-T with thin film resistance of 25μΩcm for FT type LCD substrate
a When using a metal film as a wiring material, the film thickness is 500 nm
A color TFT that was previously possible only up to about 20 inches when a film of a certain size or more was embedded in the substrate as address wiring.
Type LCD panel can be manufactured up to 50 inch class or more.

Table 1 shows examples of the types of LCD substrates to which the present invention is applied and the required electrode film thickness for each type of metal.

[0014]

[Table 1]

Cu (thin film resistance 2.5 μΩcm),
If Au (the same 3 μΩcm) or Al (the same 4 μΩcm) can be used without problems such as hillock generation and adhesion, the film thickness becomes smaller according to the thin film resistance.

In the fourth step, mainly Si
As a method of forming the insulating film 9 made of O _2, a method of hydrolyzing a metal alkoxide, a method of plating, or the like can be used, but the method of the present invention selectively forms a film on a hydrophilic surface of glass or the like. And preferable from the viewpoint of film thickness controllability. In this method, the substrate is immersed in an aqueous solution of hydrosilicofluoric acid saturated with SiO ₂ , and a boric acid aqueous solution or the like is added as an initiator to cause a supersaturated state of SiO ₂ in the solution to cause SiO ₂ on the substrate. This is a method of forming a thin film.

Further, in the step of forming the SiO ₂ thin film, in order that the SiO ₂ thin film is not deposited on the surface of the resist film but only on the insulating substrate, the chemistry of the surface of the insulating substrate and the surface of the resist film is changed. It is preferable to have different physical properties. Specifically, since the surface of an insulating substrate that is normally used is hydrophilic, the SiO ₂ thin film can be selectively deposited only on the insulating substrate by making the surface of the resist film hydrophobic to some extent. .

In order to effectively carry out the selective deposition of this SiO ₂ thin film, it is better that the resist surface has higher hydrophobicity,
Specifically, the contact angle of water droplets of pure water is preferably 70 degrees or more. Further, if the contact angle is 80 degrees or more, it becomes easy to further increase the thickness of the SiO ₂ thin film. If the hydrophobicity is low, the cost will be high, but the resist surface will be sufficiently protected while avoiding as much as possible the adhesion of fine particles, which become nuclei for the precipitation and growth of SiO ₂ on the resist in a VLSI class clean room. By washing with pure water, SiO ₂ can be selectively deposited on the surface of the substrate.

Normally used resists are composed of photodegradable polymers in the case of positive type and photocrosslinking type polymers in the case of negative type, but the required reaction properties and adhesion to the inorganic surface such as the substrate are required. Therefore, the hydrophobicity of the surface thereof is about 30 to 60 degrees in terms of contact angle with pure water. Therefore, in order to more effectively carry out the present invention, it is preferable to improve the hydrophobicity of the resist film surface by any of the following methods. In addition, a plurality of the following methods may be used in combination to increase the hydrophobicity. Method using a hydrophobic resist: Hydrophobicity of the surface is improved by substituting the hydrogen of the hydrocarbon group contained in the resist with fluorine by heat treatment in fluorine gas to increase the hydrophobicity. Method of adding a hydrophobic substance to the resist; a surface hydrophobizing agent having a fluorocarbon group at the end is mixed with the resist before film formation. When this resist is formed into a film and dried, fluorocarbon groups exhibiting strong hydrophobicity appear on the surface of the resist film, so that the surface is remarkably hydrophobized. A method of applying a hydrophobic substance to the surface of the resist film; after forming a predetermined pattern on the conductive film using a normal resist, a hydrophobic treatment agent is applied to the surface of the film by spraying or printing to make it hydrophobic.

When manufacturing a liquid crystal display device from the substrate for a liquid crystal display device according to the present invention, the steps are not particularly limited. That is, the element substrate can be manufactured by forming the active phase such as Si, the pixel electrode such as ITO, the counter electrode wiring, and the like by a conventionally known method.

Further, the conductive film 3 in the third step
The removal of a can be carried out by etching removal, but when the surface of the resist film is hydrophobized, a method of not corroding and removing the hydrophobized region is preferable.
In that case, it is preferable to remove it by wet etching with an acidic aqueous solution.

Further, in order to further ensure the surface smoothness of the substrate for liquid crystal display device obtained by the present invention,
It is preferable to make the width of the pattern of the hydrophobic resist formed in the second step wider than the width of the pattern of the wiring electrode to be finally obtained by a predetermined amount. By doing so, the hydrophobic resist film 8 becomes overhung on the wiring electrode 3 after etching, and the hydrophobic resist film 8 causes excessive growth of the insulating film 9 on the boundary surface of the wiring electrode 3. Since this is suppressed, the surface smoothness of the film on this boundary surface is guaranteed.

That is, if a so-called just etching method is adopted in which the pattern width of the hydrophobic resist is made equal to the pattern width of the wiring electrode, the insulating film deposited from the liquid phase is not only from the substrate surface but also from the side surface of the wiring electrode 3. Also grows, and as a result, the surface rises near the electrodes and may adversely affect the smoothness of the film, so the above-mentioned method is effective for preventing this.

When this "overhang" method is used, etching is carried out a little more excessively than when "just etching" is carried out, and the conductive film under the hydrophobic resist film is cut from the side surface to form an "overhang" state. Try to make it. The length of the overhang is preferably 5 nm or more and half the width of the wiring electrode 3 or less. If it is less than 5 nm, the effect of surface smoothing cannot be sufficiently obtained, and if it is more than half the width of the wiring electrode 3, the overhanging part of the hydrophobic resist may hang down and hinder the surface smoothness. Is.

[0025]

The substrate for a liquid crystal display device manufactured according to the present invention realizes thickening of the conductive film that functions as a wiring electrode on the substrate side, while reducing the unevenness of the substrate by forming the insulating film. Since it has a structure that makes it possible, it has an effect of reducing the influence of unevenness on the upper element structure such as a switching element.

Further, in the present invention, the resist originally formed for patterning the conductive film can simultaneously act as a means for selectively forming the insulating film only on the substrate. By using such a method, the surface of the resist film is not covered with an insulating material mainly composed of SiO ₂ , and the resist film can be removed without any trouble.

Furthermore, by improving the hydrophobicity of the resist surface, the buried insulating film can be completely selectively formed, and the conductive film to be formed can be easily thickened.

[0028]

EXAMPLES The present invention will now be described in more detail with reference to examples. (Example 1) Length 400 mm, width 400 mm, thickness 2 m
m of a low alkali glass for TFT (manufactured by NH Techno Glass Co., Ltd .; NA45) was used as a substrate, and after cleaning this, a Mo-α-Ta film for an electrode was formed to a thickness of 1 μm by sputtering film formation. Next, a positive photoresist resin solution (novolak) was spin-coated on the Mo-α-Ta film for electrode to form a resist film having a thickness of 1 μm. Further, the film-coated substrate was heated in a fluorine gas stream at 100 ° C. for 10 minutes. At this stage, the contact angle of pure water on the coating surface was measured and found to be about 70 degrees.

Next, this was dried in an oven, exposed to ultraviolet light through a predetermined positive photomask for patterning electrodes, and the resist was developed with a KOH 1% developer. Furthermore, M is used as an etchant for Mo-α-Ta.
O-α-Ta film is etched and M of a predetermined pattern is formed.
An o-α-Ta electrode was obtained. This etching is so-called just etching in which the width of the resist pattern and the width of the electrode pattern are equal. Thereafter, the resist film in a state in which left, by a liquid phase deposition method using a deposition of SiO ₂ in the hydrosilicofluoric acid solution as the SiO ₂ saturated, resist coating was hydrophobic surface by the The film thickness of 1 μm, which is the same as that of the Mo-α-Ta electrode film, is selectively applied only to the exposed portion of the hydrophilic glass substrate surface that does not exist.
m of SiO ₂ insulating film was formed. After that, the remaining resist film is peeled off with a peeling solution, and Mo-on the glass substrate.
The surface of the α-Ta electrode and the S
A glass substrate with embedded wiring electrodes was obtained in which the surface of the iO ₂ insulating film was smooth and continuous.

Further, a Si semiconductor active layer, an ITO transparent pixel electrode, and a Ta counter electrode wiring are sequentially formed on the surface of the glass substrate by using a photolithography technique to form 128 vertical columns.
A high-density active matrix device of 0 × 3 and 1024 in width was manufactured on a substrate. On the other hand, a counter glass substrate on which a Cr black matrix, an RGB color filter resin layer, an overcoat resin layer, an ITO transparent electrode of a counter electrode, and a dielectric light shielding layer containing a liquid crystal polymer material are sequentially formed is provided.
While aligning this with the active matrix element substrate, a sealing treatment was performed with a combined adhesive. As described above, a large area high image quality active matrix type RGB color liquid crystal display panel was produced.

(Example 2) 400 mm long and 400 m wide
m, a 2 mm thick SiO ₂ passivation film (Nippon Sheet Glass Co., Ltd .; H coat) soda lime glass was used as a substrate, and after cleaning this, a Cr film for electrodes was formed with a film thickness of 0.5 μm by sputtering film formation. . Next, an acrylic monomer having a long-chain fluorocarbon group as a side chain was added to the negative photoresist resin solution so that the volume ratio with the resist was 0.5%, and mixed with a stirrer for 5 minutes. Then, this photoresist resin solution was spin-coated to a film thickness of 1 μm on the electrode Cr film to obtain a resist film. When the hydrophobicity of the resist film surface was measured at this stage, the contact angle of pure water was about 90 degrees.

Next, this was dried in an oven, exposed to ultraviolet light through a predetermined negative photomask for patterning electrodes, and the resist was developed with a developing solution. Further, the Cr film was etched with a Cr etchant to obtain a Cr electrode having a predetermined pattern. This etching is
The so-called just etching is used in which the width of the resist pattern and the width of the electrode pattern are equal. Then, with this resist left as it is, the presence of a resist film whose surface has been hydrophobized by the liquid phase film formation method using precipitation of SiO ₂ by pH control in a saturated hydrofluoric acid solution. In addition to the exposed portions, only the exposed portion of the hydrophilic glass substrate surface was selectively formed with an insulating film of SiO ₂ having the same film thickness of 0.5 μm as the Cr electrode film. After that, the remaining resist film is peeled off by a peeling solution, and the Cr electrode is patterned on the glass substrate, and the surface of the electrode and Si
A buried electrode glass substrate was obtained in which the surface of the O ₂ insulating film was smooth and continuous.

Further, a transparent electrode ITO having a thickness of 300 nm is formed thereon by a sputtering method, and predetermined patterning is performed by photolithography, and then an ITO counter electrode / overcoat / color filter / which is separately prepared.
An STN liquid crystal phase was provided between the soda lime silicate glass substrate and the counter substrate having the structure, and a sealing operation and the like were performed to fabricate an STN type RGB color liquid crystal display panel.

(Example 3) In Example 1, a pattern in which the width of each electrode is 500 nm wider on each side than the pattern of the electrode to be finally obtained when the resist is developed into a predetermined pattern. And After that, with Mo-α-Ta etchant, Mo-α-Ta
Also when the film was etched, the excess was etched by 500 nm on one side of the width of the resist pattern. Due to this so-called over-etching, the width of the electrode pattern formed is equal to that of the first embodiment, and the resist pattern is 50 on one side of the electrode pattern.
The width was wide by 0 nm, and when viewed from the cross-sectional direction, it was in an overhanging state by this length.

A buried electrode glass substrate was obtained in the same manner as in Example 1 except for the above. This substrate was further excellent in surface smoothness, and the surface of the electrode and the surface of the SiO ₂ insulating film were completely smooth and continuous. Was.

[0036]

According to the present invention, the insulating film mainly composed of SiO ₂ is filled as a whole by filling the recesses formed by the formation of the electrode on the surface of the insulating substrate in which the substrate side electrode is patterned. A continuous embedded electrode substrate having a smooth surface can be obtained. That is,
Since the resistance of the electrodes can be reduced without affecting the operation of the wiring and switching elements formed on the substrate, it is possible to manufacture a liquid crystal display device with a larger area, higher pixel density, and higher image quality than before. Becomes

In particular, by increasing the hydrophobicity of the resist surface, the selectivity at the time of forming the insulating film mainly composed of SiO ₂ is increased, and the thickening of the electrode is facilitated.

Furthermore, when the above-mentioned "overhang" method is adopted, the surface smoothness of the embedded electrode substrate becomes more complete and reliable.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a part of a substrate for a liquid crystal display device manufactured by a manufacturing method according to the present invention.

FIG. 2 is a diagram showing, step by step, the method of Examples 1 and 2 (so-called just etching method) of the method of manufacturing a substrate for a liquid crystal display device according to the present invention.

FIG. 3 is a diagram showing, step by step, the method of Example 3 (method utilizing resist overhang) of the method for manufacturing a substrate for a liquid crystal display device according to the present invention.

FIG. 4 is a diagram schematically showing a swelling of an insulating film which may occur by a just etching method.

FIG. 5: The insulating film grows from the side surface of the wiring electrode as well.
Of the process that causes the swelling of the insulating film (the arrow indicates the growth direction of the insulating film).

FIG. 6 is a schematic sectional view of a part of a substrate for a liquid crystal display device by a conventional method.

FIG. 7 is a schematic diagram of a switching portion of each pixel by an active matrix method.

[Explanation of symbols]

 1, 10; Insulating substrate 3, 30; Substrate side wiring electrode 3a; Conductive film 8; Resist film 8a; Overhang portion of resist film 9; Insulating film 9a; Insulating film 20 during growth 20; Switching element 40 Counter electrode 50; pixel electrode 60; recess 70 formed by etching the substrate 70; groove formed in the substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuro Yoshii 3-5-11 Doshumachi, Chuo-ku, Osaka, Japan Sheet glass Co., Ltd. (72) Inventor Hideaki Saito 3-5-11 Doshomachi, Chuo-ku, Osaka Japan Sheet Glass Co., Ltd. (72) Inventor Seiji Ohno 3-5-11 Doshumachi, Chuo-ku, Osaka City Japan Sheet Glass Co., Ltd. (72) Inventor Yukisa Kusuda 3-5-11 Doshomachi, Chuo-ku, Osaka Japan Sheet Glass Within the corporation

Claims (4)

[Claims] 1. A conductive film having a predetermined thickness is formed on a main surface of an insulating substrate, a hydrophobic resist film is formed on the conductive film in a predetermined pattern, and the hydrophobic resist film is etched. The conductive film is etched as a mask to form a wiring electrode having a predetermined pattern, and a portion of the main surface of the insulating substrate where the wiring electrode is not formed is saturated with SiO ₂ and fluorinated. A method for producing a substrate for a liquid crystal display device, comprising forming an insulating film mainly composed of SiO ₂ to a thickness substantially equal to that of the wiring electrode by bringing it into contact with a hydrogen acid aqueous solution, and removing the hydrophobic resist film. 2. The method according to claim 1, wherein the surface of the hydrophobic resist film has a contact angle of water droplets of pure water of 70 degrees or more. 3. The method according to claim 1, wherein the predetermined pattern of the hydrophobic resist film is a pattern in which the predetermined pattern of the wiring electrode is widened by a predetermined length. 4. The method according to claim 3, wherein the predetermined length is 5 nm or more and half the width of the predetermined pattern of the wiring electrode or less.