JP3726492B2 - Manufacturing method of liquid crystal display device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a manufacturing method for improving and uniformizing characteristics of active elements in a liquid crystal display device.
[0002]
[Prior art]
In the manufacturing process of an element substrate on which an active element of a conventional liquid crystal display device is formed, a base film is formed immediately after washing the surface of the glass substrate with sulfuric acid, and is then put into the active element manufacturing process.
[0003]
The main purpose of forming the base film is to improve the adhesion between a conductive film such as a tantalum film, which is formed in the next step and constitutes an active element, and a glass substrate.
[0004]
Since the base film does not directly constitute an active element, such a cleaning method has been considered sufficient.
[0005]
[Problems to be solved by the invention]
However, the conventional cleaning prior to the formation of the base film has the following problems.
[0006]
For example, in the cleaning method using sulfuric acid, organic impurities adhering to the glass substrate cannot be completely removed, and the impurities may remain in the lower layer of the active element. These have caused slight peeling of the underlying film due to stress applied to the substrate during the manufacturing process, and have been a factor that significantly deteriorates the characteristics of the active element. This was a major cause of defective pixel defects in the entire liquid crystal display device. That is, as a result, the yield is reduced and the manufacturing cost is increased.
[0007]
An object of the present invention is to remove organic impurities in the stage before the formation of a base film, which is the initial stage of the manufacturing process, to increase the manufacturing yield.
[0008]
[Means for Solving the Problems]
According to a method of manufacturing a liquid crystal display device of the present invention, a pair of substrates each including an element substrate on which a plurality of active elements are formed and a counter substrate disposed to face the element substrate are sandwiched between the pair of substrates. In the manufacturing method of the liquid crystal display device including the liquid crystal layer, the step of washing the element substrate with sulfuric acid and the element substrate with plasma cleaning using oxygen gas to remove organic impurities on the element substrate surface And a step of forming an insulating base film on the cleaned surface of the element substrate, and a step of forming the active element on the insulating base film. To do.
The method for manufacturing a liquid crystal display device according to the present invention includes a pair of substrates each including an element substrate on which a plurality of active elements are formed and a counter substrate disposed to face the element substrate, and is sandwiched between the pair of substrates. In the method of manufacturing a liquid crystal display device including a liquid crystal layer, an impurity on the surface of the element substrate is obtained by cleaning the element substrate with sulfuric acid and plasma cleaning the element substrate with helium gas or argon gas. A step of forming an insulating base film on the cleaned surface of the element substrate, and a step of forming the active element on the insulating base film. Features.
[0009]
According to the present invention, since the plasma cleaning process is introduced after the surface cleaning of the glass substrate with sulfuric acid, the organic impurities can be completely removed. After that, since the base film is formed and then put into the active element manufacturing process, there are no impurities on the lower layer side of the active element, the characteristics of the active element are uniformly good, and the entire liquid crystal display device has a large pixel defect defect. Can be reduced. As a result, the yield can be greatly improved.
[0010]
The active element is a two-terminal nonlinear element formed by laminating a first conductive layer, an insulator layer, and a second conductive layer.
[0011]
According to the present invention, the characteristics are particularly effective in a two-terminal nonlinear element having a laminated structure that is easily affected by impurities in the lower layer of the active element.
[0012]
In addition, after the step of plasma cleaning the element substrate, a step of forming an insulating base film on the element substrate is included.
[0013]
According to the present invention, since the base film is formed on the substrate from which the organic impurities have been removed, the characteristics of the active element are uniformly improved in the subsequent active element forming step, and the entire liquid crystal display device has a pixel. Defect defects can be greatly reduced.
[0014]
The step of plasma cleaning the element substrate is a plasma cleaning with oxygen.
[0015]
According to the structure of this invention, since the removal performance of the impurity in a washing | cleaning process is high and the hydrophilic property of a transparent substrate can be improved, it is suitable for the board | substrate process in a subsequent process.
[0016]
Further, the step of plasma cleaning the element substrate is plasma cleaning with helium.
[0017]
According to the present invention, since the substance has a relatively low molecular weight, there is little damage to the transparent substrate.
[0018]
The step of plasma cleaning the element substrate is plasma cleaning with argon.
[0019]
According to the present invention, since the substance has a large molecular weight, other than organic substances can be removed, and the cleaning efficiency can be improved.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[0021]
FIG. 1 is a plan view showing a manufacturing process of an element substrate when a two-terminal nonlinear element is formed as an active element.
[0022]
First, since the organic substance a may adhere on the element substrate 10 until the element substrate manufacturing process is input, the surface of the element substrate 10 made of glass is washed with sulfuric acid, and then oxygen (O ₂ ) Surface cleaning is performed by plasma cleaning process P. In this step, organic substances that cannot be removed only by washing with sulfuric acid are removed.
[0023]
Examples of the organic substances that may adhere to the element substrate include oils and fats by the operator's fingerprint, and foamed materials such as polypropylene and polystyrene that are used as cushioning members in the process of transporting the transparent substrate.
[0024]
In the plasma cleaning process, the element substrate 10 is set in a chamber, O ₂ gas is introduced, and then a high-frequency electric field is applied between the lower electrode on which the element substrate is placed and the upper electrode disposed opposite thereto. By applying this, the O ₂ gas is excited, and the organic substance a which is a foreign substance on the substrate is removed.
[0025]
Note that the plasma cleaning treatment can also be performed with helium (He), argon (Ar), or the like. Since Ar is a relatively inexpensive substance with a large molecular weight, other than organic substances can be removed, and cleaning efficiency can be improved. Although He is expensive, it is a relatively low molecular weight substance, so damage to the transparent substrate can be reduced. O ₂ has high organic substance removal performance and can improve the hydrophilicity of the transparent substrate.
[0026]
The gas introduced for the removal of the organic substance and the conditions for the plasma cleaning process can be selected depending on the desired removal efficiency, the material of the transparent substrate, and the relationship with the subsequent steps.
[0027]
Next, an active element is formed on the transparent substrate that has been subjected to organic substance removal by sulfuric acid cleaning and plasma cleaning processing.
[0028]
First, a tantalum (Ta) film is formed as a base film with a thickness of about 50 nm by sputtering. Thereafter, a tantalum oxide film 11 is formed by a thermal oxidation method. This film is formed in order to improve the adhesion between the Ta layer, which will be formed next, and the substrate and the substrate.
[0029]
This underlayer may be formed directly by tantalum oxide by RF sputtering, or Ta may be formed by reactive sputtering using Ar / O ₂ gas, or after Ta is formed on the substrate, the anode The surface may be oxidized by an oxidation method to form a base tantalum oxide film.
[0030]
Next, a Ta film constituting the first conductive layer of the two-terminal nonlinear element is formed on the tantalum oxide film 11 which is a base film by a sputtering method to a thickness of about 120 to 180 nm. For example, as shown in FIG. The wiring layer 12 is formed by patterning into a predetermined shape. In the wiring layer 12, a first electrode portion 12a serving as an element portion corresponding to each pixel region disposed along the extension is formed. The cross-sectional view shown in FIG. 2 is a cross-sectional view taken along line AA shown in step 3 of FIG.
[0031]
Next, anodization is performed on the wiring layer 12 including the electrode portion 12a in a chemical conversion solution (electrolytic solution) made of a citric acid aqueous solution or the like, and an anodic oxide film 12b is formed on the surface.
[0032]
Thereafter, the element substrate 10 is heat-treated in an inert gas at 300 to 450 ° C. for about 2 hours, and then rapidly cooled in air. By this heat treatment step, characteristics such as current-voltage characteristics of the two-terminal nonlinear element can be made desired.
[0033]
On the surface of the element substrate 10 thus treated, chromium (Cr) is formed to a thickness of about 100 nm by sputtering, and patterned so as to partially overlap the anodic oxide film 12b. A second electrode portion 13 to be a conductive layer is formed. A portion where the first conductive layer 12a, the anodic oxide film 12b, and the second conductive layer 13 are stacked is a two-terminal nonlinear element portion.
[0034]
Here, indium-tin oxide (ITO) may be used as the second conductive layer. When ITO is used as the second conductive layer, the pixel electrode described below can be formed at the same time, and part of the manufacturing process of the element substrate can be omitted.
[0035]
Finally, ITO is formed into a thickness of about 50 nm by a sputtering method and patterned to form the pixel electrode 15 so as to overlap the second electrode portion 13.
[0036]
FIG. 3 shows a partial structure of a liquid crystal display device using the element substrate 10 thus formed as one substrate.
[0037]
The element substrate 10 is bonded to the other substrate and the counter substrate 20 via a sealing material and a spacer (not shown). A mosaic type color filter layer 21 is formed on the inner surface (the lower surface side in the figure) of the counter substrate 20, and the red (R), green (G), and blue (B) of the color filter layer 21 are formed. A black matrix 22 is formed between the colors. On the protective film (not shown) formed on the color filter layer 21, the counter electrode 23 is formed in a stripe shape in the direction intersecting with the wiring layer 12 of the element substrate, for example, by ITO.
[0038]
An alignment film (not shown) is formed on the element substrate 10 and the counter substrate 20, and a liquid crystal layer, a spacer, and the like (not shown) are disposed between the alignment films. Further, polarizing plates 30 and 31 are attached to the surfaces of the element substrate 10 and the counter substrate 20 opposite to the surfaces facing each other.
[0039]
In this structure, a drive signal is applied to the wiring layer 12 connected to the counter electrode 23 and the two-terminal nonlinear element by a drive circuit (not shown). As a result, the two-terminal nonlinear element is driven, and the alignment state of the liquid crystal is controlled to perform display.
[0040]
In the present embodiment, a two-terminal nonlinear element has been described as an example of an active element. However, the present invention is not limited to this. For example, a liquid crystal display device in which a thin film transistor (TFT) is formed as an active element. The present invention can also be applied to a manufacturing method, and the same effects can be obtained.
[0041]
A 4-inch liquid crystal display device (442 × 238 pixels) was produced by the process according to the embodiment of the present invention described above and the conventional process, and the number of pixel defects was compared. However, it was 0.155 in the present invention.
[0042]
This is because by removing impurities including organic substances immediately after the process is put in, no impurities are present under the active element, and the element characteristics can be improved uniformly.
[0043]
Therefore, pixel defects are drastically reduced in the entire liquid crystal display device, and as a result, the yield can be greatly improved and the manufacturing cost can be reduced.
[Brief description of the drawings]
FIG. 1 is an enlarged plan view of a pixel including a two-terminal nonlinear element described in an embodiment of the present invention.
FIG. 2 is a diagram illustrating a manufacturing process of an element substrate of a two-terminal nonlinear element according to an embodiment of the present invention.
FIG. 3 is a partial cross-sectional view of a liquid crystal display device described in an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Element substrate 11 ... Tantalum oxide film 12 ... Wiring layer 12a ... 1st electrode part 12b ... Anodized film 13 ... 2nd electrode part 14 ... 2 terminal type nonlinear Element part 15 ... Pixel electrode 20 ... Counter substrate 23 ... Counter electrode

Claims (3)

Manufacture of a liquid crystal display device comprising a pair of substrates comprising an element substrate on which a plurality of active elements are formed and a counter substrate disposed opposite to the element substrate, and a liquid crystal layer sandwiched between the pair of substrates In the method
Washing the element substrate with sulfuric acid;
Removing the organic impurities on the surface of the element substrate by plasma-cleaning the element substrate using oxygen gas;
Forming an insulating base film on the cleaned surface of the element substrate;
Forming the active element on the insulating base film;
A method for producing a liquid crystal display device comprising: Manufacture of a liquid crystal display device comprising a pair of substrates comprising an element substrate on which a plurality of active elements are formed and a counter substrate disposed opposite to the element substrate, and a liquid crystal layer sandwiched between the pair of substrates In the method
Washing the element substrate with sulfuric acid;
Removing the impurities on the surface of the element substrate by plasma-cleaning the element substrate using helium gas or argon gas; and
Forming an insulating base film on the cleaned surface of the element substrate;
Forming the active element on the insulating base film;
A method for producing a liquid crystal display device comprising:   3. The method of manufacturing a liquid crystal display device according to claim 1, wherein the active element is a two-terminal nonlinear element formed by laminating a first conductive layer, an insulator layer, and a second conductive layer. .

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