JPH07140491A - Liquid crystal display device and its production - Google Patents

Abstract

PURPOSE:To provide a liquid crystal display device which does not deteriorate current-voltage characteristics by lessening the application of a photoetching method necessary for formation of nonlinear resistance elements. CONSTITUTION:This liquid crystal display device is constituted by disposing plural pixel display electrodes 7, the plural nonlinear resistance elements 13 consisting of MIM elements having a lower electrode-insulator-upper electrode structure electrically connected respectively to the plural pixel display electrodes 7 and wiring electrodes connecting these plural nonlinear resistance elements 13 on one of substrates facing each other via a liquid crystal compsn. These nonlinear resistance elements 13 are formed of the structure obtd. by diffusing the metal different from the metal of the upper electrodes 12 near the surface of the insulator 4 of the upper electrode 12 side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display device having a MIM element having a lower electrode-insulator-upper electrode structure or a non-linear resistance element having a series structure of the MIM elements as a switching element, and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have come to be used for displaying large-capacity information such as personal computers, word processors, OA equipment, and image displays for TVs. Display of image quality is required.

In this liquid crystal display device for displaying large-capacity information, generally, wiring electrodes in rows and columns formed at a predetermined pitch on a pair of substrates facing each other are made to face each other so as to be orthogonal to each other. A matrix-type liquid crystal display device is used in which a region defined by wiring electrodes in columns is one pixel, and a nematic liquid crystal composition is sandwiched between these substrates. In particular, as a liquid crystal display device for large-capacity, high-definition information display, which is intended for TV image display, graphic display, etc., switching is performed for each pixel as driving and control means for each pixel so that high contrast without crosstalk can be obtained. An active matrix type liquid crystal display device in which elements are arranged has been put to practical use.

As the switching element, there are a three-terminal type thin film transistor and a two-terminal type non-linear resistance element composed of a lower electrode-insulator-upper electrode structure MIM element. Among them, the two-terminal type non-linear resistance element made of the MIM element has a simpler structure than the three-terminal type thin film transistor, has fewer manufacturing steps, and can be expected to improve the manufacturing yield and reduce the manufacturing cost.

FIG. 10 shows an MIM of one substrate (array substrate) of such an active matrix type liquid crystal display device.
The structure of one pixel portion including a non-linear resistance element composed of an element (single MIM element) is shown. The structure of this one pixel portion will be described according to the manufacturing process shown in FIG. This FIG.
(B) to (g) of FIG. 10 show the main steps of the flowchart of FIG.

First, a Ta film is formed on one substrate 1 made of glass by a thin film forming method such as a sputtering method or a vacuum deposition method, and a Ta or a lower electrode 2 of a MIM element and a row or a column are formed by a photo-etching method (1st PEP). Wiring electrode (not shown)
Then, the wiring 3 for anodizing the lower electrode 2 and the wiring electrode is formed (FIG. 11B). Next, the Ta film of the lower electrode 2 and the wiring electrode is formed by, for example, the anodic oxidation method using an aqueous solution of citric acid to form the insulator 4 made of the Ta oxide film on the lower electrode 2 and the Ta film on the wiring electrode. An oxide film is formed (FIG. 11C). Next, the wiring 3 and Ta on the wiring 3 are formed by photolithography (2nd PEP).
The oxide film is removed (FIG. 11 (d)). Further, the upper electrode 5 of the MIM element made of the Cr film is formed on the insulator 4 by the usual thin film forming method and the photo-etching method (3rd PEP) to complete the nonlinear resistance element 6 made of the MIM element (FIG. 11 (e). )). After that, a transparent conductive film connected to the upper metal 5 of this MIM element is formed (FIG. 11F), and this transparent conductive film is processed by photoetching (4th PEP) to form the pixel display electrode 7. (FIG. 11 (g)).

The basic manufacturing technique of the non-linear resistance element composed of such an MIM element is disclosed in Japanese Patent Laid-Open No. 55-161273.
Japanese Unexamined Patent Application Publication No. 58-58
-178320.

According to the basic manufacturing technique of the non-linear resistance element composed of the above MIM element, the photo-etching method is used for the manufacture.
It is necessary to apply once (1st PEP to 3rd PEP). The photo-etching method requires many steps of forming a thin film and then applying a photoresist, exposing and baking a mask pattern, developing, etching, removing a photoresist, and cleaning. Therefore, in the active matrix liquid crystal display device, the manufacturing yield is improved and the manufacturing cost can be reduced as the number of manufacturing steps by the photoetching method is reduced.

From this point of view, instead of forming the upper electrode of the non-linear resistance element made of the MIM element with the Cr film, the transparent conductive film of the pixel display electrode is directly formed on the insulator to form the upper electrode. There is known a technique for reducing the number of photo-etching processes to two.

By the way, generally, the operation of the matrix type liquid crystal display device is performed by AC driving. Therefore, a non-linear resistance element composed of an MIM element used in an active matrix type liquid crystal display device has a bidirectional diode characteristic, and the symmetry between the positive voltage and the negative voltage of the current-voltage characteristic drives the liquid crystal display device. Greatly affects the quality of the displayed image.

In FIG. 12, Cr, Ti, Al, Ta and Mo are used as the upper electrodes of the non-linear resistance element composed of the MIM element.
-Current-voltage characteristics (VI) when using a Ta alloy or the like
Characteristics) are shown by curves 9a to 9e. These curves 9a-9e
As is clear from the above, when each of the above metals is used as the upper electrode, the current-voltage characteristics exhibit symmetry in any case, the liquid crystal display device is normally driven, and the displayed image is not affected. However, when a transparent conductive film made of ITO (Indium Tin Oxide) used for forming the pixel display electrode as the upper electrode is directly formed on the insulator, the current-voltage characteristics of the non-linear resistance element are as shown by the curve 9f in FIG. Since the positive voltage and the negative voltage are asymmetrical, the liquid crystal display device cannot be normally driven, and the quality of the displayed image is significantly deteriorated.

On the other hand, in order to compensate the symmetry of the current-voltage characteristics of the non-linear resistance element composed of MIM elements, a non-linear resistance element 6 having a structure in which a pair of MIM elements are connected in series is known as shown in FIG. Has been. The series-structured non-linear resistance element 6 is a single MI shown in FIGS.
Similar to the non-linear resistance element composed of the M element, a Ta film is formed on one substrate 1 made of glass by a thin film forming method such as a sputtering method or a vacuum deposition method, and the Ta film is formed by a photo-etching method (1stPE
P) forms the lower metal 2 of the MIM element, the wiring electrodes in rows or columns, and the wiring for anodizing these lower electrodes 2 and the wiring electrodes. Next, the insulator 4 made of a Ta oxide film is formed on the lower electrode 2 by an anodic oxidation method using an aqueous solution of citric acid, and Ta is formed on the wiring electrode.
After forming the oxide film, the wiring used for the anodic oxidation is removed by the photo-etching method (2nd PEP). Further, the upper electrode 5 of the MIM element made of the Cr film is formed on the insulator 4 by the usual thin film forming method and the photo-etching method (3rd PEP) to complete the nonlinear resistance element 6 made of the MIM element.
After that, a transparent conductive film connected to the upper electrode 5 is formed,
The pixel display electrode 7 is formed by processing by photolithography (4th PEP).

The nonlinear resistance element 6 having such a series structure of MIM elements is extremely effective for compensating the symmetry of the current-voltage characteristic, but the nonlinear resistance element made of a single MIM element shown in FIG. Similar to the device, three times of photo-etching are required to form the MIM device, and four times (1st PEP to 4th PEP) of photo-etching are required to form the required substrate, resulting in problems of manufacturing yield and manufacturing cost.

Also in this non-linear resistance element having a serial structure of MIM elements, the upper electrode of one MIM element is formed by directly forming a transparent conductive film made of ITO used for forming a pixel display electrode on an insulator. If so, the current-voltage characteristic of the non-linear resistance element loses its non-linearity as shown by the curve 9g in FIG. 15, the liquid crystal display device cannot be driven normally, and the quality of the displayed image is significantly deteriorated. Let

[0015]

As described above, the non-linear resistance element composed of a single MIM element requires the photolithography method to be applied three times to form it. The photo-etching method is
Since many steps are required, it is expected that as the number of manufacturing steps by this photo-etching method is reduced, the manufacturing yield is improved and the manufacturing cost is reduced. From this point of view, instead of forming the upper electrode of the non-linear resistance element composed of the MIM element with a metal such as Cr, the transparent conductive film of the pixel display electrode is directly formed on the insulator, and the manufacturing process by the photo-etching method is performed. A technique for reducing the number to two is known.

However, the liquid crystal display device using the non-linear resistance element composed of the MIM element utilizes the bidirectional diode characteristic of the non-linear resistance element and operates the liquid crystal by AC driving, so that the positive voltage of the current-voltage characteristic is obtained. The symmetry of the negative voltage has a great influence on the driving of the liquid crystal display device and further on the quality of the displayed image. When Cr, Ti, Al, Ta, or Mo-Ta alloy is used as the upper electrode of the non-linear resistance element, the symmetry of current-voltage characteristics is obtained in any case, and the liquid crystal display device is normally driven. However, it does not affect the quality of the displayed image. However, when a transparent conductive film made of ITO used for forming the pixel display electrode is formed as an upper electrode by directly forming a film on the insulator, the current of the non-linear resistance element-
There is a problem that the voltage characteristics become asymmetric between positive voltage and negative voltage, normal driving of the liquid crystal display device cannot be obtained, and the quality of the displayed image is significantly deteriorated.

On the other hand, it is known that if the non-linear resistance element has a series structure of MIM elements, the symmetry of the current-voltage characteristics of the non-linear resistance element composed of the MIM elements can be compensated. However, even if the MIM elements are connected in series like this,
Photolithography is required four times to form a required substrate, which makes it difficult to improve the manufacturing yield and reduce the manufacturing cost. Also, regarding the non-linear resistance element having the series structure of the MIM elements, it is assumed that the upper electrode of one of the MIM elements is formed by directly forming the transparent conductive film made of ITO used for forming the pixel display electrode on the insulator. However, there is a problem that the non-linearity of the current-voltage characteristic of the non-linear resistance element is lost, the liquid crystal display device cannot be normally driven, and the quality of the displayed image is significantly deteriorated.

The present invention has been made in order to solve the above problems, and determines the number of times of the photo-etching method necessary for forming a non-linear resistance element composed of an MIM element or a non-linear resistance element composed of a series structure of MIM elements. It is an object of the present invention to provide a liquid crystal display device which is reduced and does not deteriorate the symmetry and non-linearity of the current-voltage characteristics of a non-linear resistance element, and to obtain a manufacturing method thereof.

[0019]

A plurality of pixel display electrodes are provided on one of substrates facing each other through a liquid crystal composition, and a lower electrode electrically connected to each of the plurality of pixel display electrodes.
In a liquid crystal display device provided with a plurality of non-linear resistance elements composed of MIM elements having an insulator-upper electrode structure and wiring electrodes connecting the plurality of non-linear resistance elements, the non-linear resistance elements are provided above the insulator. A metal different from the upper metal was diffused in the vicinity of the surface on the electrode side.

Further, a plurality of pixel display electrodes are provided on one of the substrates facing each other with the liquid crystal composition interposed therebetween, and a lower electrode-insulator-upper electrode structure electrically connected to each of the plurality of pixel display electrodes. In a liquid crystal display device provided with a plurality of non-linear resistance elements having a series structure of MIM elements and wiring electrodes connecting the plurality of non-linear resistance elements, the non-linear resistance elements are provided on the upper electrode side of the insulator. The structure is such that a metal having a current-voltage characteristic that is non-linear and symmetrical is diffused near the surface.

Further, a plurality of nonlinear resistance elements made of the MIM element or a plurality of nonlinear resistance elements made of a serial structure of MIM elements are diffused in the vicinity of the surface of the nonlinear resistance element on the side of the upper electrode with Ta as the lower electrode. C metal
At least 1 of r, Ti, Al, Ta, Mo-Ta alloy
Seeded

A plurality of pixel display electrodes are provided on one of the substrates facing each other with the liquid crystal composition interposed therebetween, and a lower electrode-insulator-upper electrode structure electrically connected to each of the plurality of pixel display electrodes. In the method of manufacturing a liquid crystal display device, the lower electrode of the non-linear resistance element, comprising: a plurality of non-linear resistance elements having the MIM element or a series structure of the MIM elements; and wiring electrodes connecting the plurality of non-linear resistance elements. And a step of forming an insulator on the lower electrode, and forming a metal film different from that of the upper electrode on the insulator and forming a metal of the metal film near the surface of the insulator on the side of the upper electrode. A non-linear resistance element was formed by the steps of removing the metal film after being diffused into and the step of forming the upper electrode on the insulator after removing the metal film.

Further, a plurality of pixel display electrodes are provided on one of the substrates facing each other with the liquid crystal composition interposed therebetween, and a lower electrode electrically connected to each of the plurality of pixel display electrodes-insulator-.
In a liquid crystal display device provided with a plurality of nonlinear resistance elements having a series structure of MIM elements having an upper electrode structure and wiring electrodes connecting the plurality of nonlinear resistance elements, an upper electrode of an insulator of the nonlinear resistance element A metal whose current-voltage characteristics are non-linear and symmetrical is diffused in the vicinity of the side surface, and a film of this metal is the same as the pixel display electrode and the wiring electrode in the pixel display electrode formation portion and the wiring electrode formation portion, respectively. It was provided in the shape.

Further, the lower electrode of the non-linear resistance element is Ta, and the metal diffused in the vicinity of the upper electrode side surface of the non-linear resistance element and the metal formed in the pixel display electrode formation portion and the wiring electrode formation portion. The film of Cr, Ti, A
1, at least one of Ta and Mo-Ta alloy.

[0025]

When the upper electrode of the non-linear resistance element made of the MIM element is formed by directly forming the transparent conductive film made of ITO forming the pixel display electrode on the insulator, the non-linear resistance element has an asymmetric current-voltage characteristic. The reason for this is considered to be that there is a problem in the contact level due to the contact between the insulator and the transparent conductive film. However, the contact level between the insulator and the upper electrode has no problem in the symmetry of the current-voltage characteristics of the non-linear resistance element when the upper electrode is formed of Cr, Ti, Al, Ta, or Mo-Ta alloy. (See Figure 12). So MI
If a metal different from the upper electrode is diffused in the vicinity of the surface of the insulator of the non-linear resistance element including the M element on the upper electrode side, the contact level between the insulator and the upper electrode changes, and this insulator Even if the upper electrode is formed on the transparent conductive film made of, for example, ITO, the discontinuity of the contact level between the insulator and the upper electrode is eliminated, and the current-voltage characteristics of the nonlinear resistance element can be made symmetrical. it can.

Regarding the non-linear resistance element having a series structure of MIM elements of the lower electrode-insulator-upper electrode structure, even if the non-linear resistance element made of a single MIM element has asymmetric current-voltage characteristics, Although it becomes symmetric by adopting the series structure, the steepness appears on the side of lower positive and negative voltages. Therefore, when the MIM element having no non-linearity (see FIG. 13) is connected in series on one side of the positive / negative voltage of the current-voltage characteristic, the non-linearity is lost (see FIG. 15). However, even in the case of a non-linear resistance element having a series structure of MIM elements, if a metal whose current-voltage characteristics are non-linear and symmetrical is diffused in the vicinity of the surface of the insulator on the upper electrode side, for example, one MIM element is used.
Even if the upper electrode of the element is formed of a transparent conductive film made of, for example, ITO, sufficient non-linearity can be obtained.

The diffusion of a metal different from the upper electrode near the surface of the insulator of the non-linear resistance element made of such an MIM element and the upper electrode of the insulator of the non-linear resistance element having the series structure of the MIM elements Diffusion of the metal in which the current-voltage characteristics near the surface on the side are non-linear and symmetrical should be easily formed by forming a metal film different from the upper electrode on the insulator and then removing this metal film. You can

Furthermore, a current-appears near the surface of the insulator of the non-linear resistance element having the serial structure of the MIM elements on the upper electrode side.
When a metal whose voltage characteristics are non-linear and symmetrical is diffused, and a film of this metal is provided in the same shape as the pixel display electrode and the wiring electrode in the formation portion of the pixel display electrode and the wiring electrode, respectively, Even if the upper electrode of the MIM element is formed of a transparent conductive film made of, for example, ITO, not only sufficient non-linearity can be obtained, but also deterioration of the pixel display electrode can be prevented.

That is, in order to manufacture an array substrate having a non-linear resistance element having a serial structure of MIM elements, unnecessary Ta is formed by a chemical dry etching method after forming a lower electrode made of a Ta film and an insulator made of a Ta oxide film.
The film and the Ta oxide film on it are removed and then ITO
Forming a pixel display electrode of a transparent conductive film. In this case, when the unnecessary Ta film and the Ta oxide film thereon are removed by the chemical dry etching method, the base glass substrate is damaged and the transparent conductive film made of ITO is etched by the photoetching method to display pixels. Although penetration easily occurs when forming the electrode, if a metal film that diffuses near the surface of the insulator of the nonlinear resistance element on the upper electrode side is provided in the pixel display electrode formation portion and the wiring electrode formation portion, Since the metal film is formed after the lower electrode and the insulator are formed by chemical dry etching, the transparent conductive film made of ITO does not come into direct contact with the base glass substrate, so that the stain of the transparent conductive film made of ITO is not observed. It is possible to prevent jamming.

[0030]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be described based on embodiments with reference to the drawings.

Example 1. FIG. 1 shows the structure of one pixel portion including a non-linear resistance element composed of a single MIM element in the liquid crystal display device of the first embodiment. The structure of this liquid crystal display device
A description will be given according to the manufacturing method shown in FIG.

In this liquid crystal display device, a film having a thickness of 0.3 μm is formed on one substrate 1 made of glass by a sputtering method.
A Ta film of m 2 is formed, and a lower electrode 2 of the MIM element, a wiring electrode in a row or a column, and a wiring 3 for anodizing these lower electrode 2 and the wiring electrode are formed by a photo-etching method (1st PEP). (FIG.2 (b)). Photo-etching of this Ta film is performed by coating a photoresist, exposing and baking a mask pattern, developing, chemical dry etching (CDE) with plasma gas in which CF ₄ and O ₂ are mixed at a ratio of 1: 2, and removing the resist. Cleaning is done in order.

Next, the lower electrode 2 formed by the above-mentioned photo-etching method is used as one electrode, and a 0.01 wt% citric acid aqueous solution is used as a forming solution to form the Ta film of the lower electrode 2 and the wiring electrode by anodizing. , An insulator 4 made of a Ta oxide film is formed on the lower electrode 2, and T is formed on the wiring electrode.
a oxide film is formed (FIG. 2C). In this case, in order to keep the temperature of the chemical conversion solution constant and to make the growth of the Ta oxide film uniform, the chemical conversion solution may be stirred.

Next, the substrate 1 on which this Ta oxide film is formed
While heating, the Cr film 10 having a film thickness of 0.05 μm is formed on the Ta electrode film of the lower electrode 2 and the wiring electrode by the sputtering method (FIG. 2D). When the Cr film 10 is formed on the Ta oxide film in this way, Cr diffuses in the vicinity of the surface of the Ta oxide film, as described later. Then, using a solution prepared by dissolving 17 g of ceric ammonium nitrate, 5 cc of perchloric acid, and 10 cc of water, a Cr film 1 on the Ta oxide film was used.
0 is removed to expose the Ta oxide film (FIG. 2).
(E)).

Next, the transparent conductive film 11 made of ITO is formed by the sputtering method (FIG. 2 (f)). Then, the image display electrodes 7 and M are formed by photolithography (2nd PEP).
The upper electrode 12 made of the transparent conductive film 11 of the IM element is formed. This photo-etching is carried out in the order of photoresist coating formation → mask pattern exposure / baking → development → etching with an aqueous solution of an equal amount of hydrochloric acid and nitric acid → resist removal → cleaning. In this case, preferably, the Ta oxide film on the wiring electrode is removed by chemical dry etching using the resist pattern for forming the image display electrode 7 and the upper electrode 12, and the image display electrode 7 and the upper electrode are removed. An array substrate 12 having a non-linear resistance element 13 made of an MIM element 12 made of a transparent conductive film is obtained (FIG. 2 (g)).

After that, an alignment film forming liquid made of polyimide is applied to the electrode forming surface of this array substrate and dried.
Rubbing is performed in one direction with a cotton cloth or the like to form an alignment film that regulates the alignment of the liquid crystal. On the other hand, after forming a predetermined counter electrode on the other substrate made of glass, similarly, an alignment film forming liquid is applied and dried, and then rubbed to form a counter substrate.

Thereafter, the array substrate and the counter substrate are arranged so as to face each other so that the rubbing directions of the alignment films are orthogonal to each other, and a spacer material is interposed between the both substrates to hold them at a predetermined interval. The periphery of the substrate is adhesively fixed while leaving the liquid crystal composition injection port. Then, after injecting the liquid crystal composition from the liquid crystal composition injection port, the liquid crystal composition injection port is sealed. After that, a deflection plate is attached to the outer surfaces of both substrates so as to be along the rubbing direction of the alignment film. In this case, the ends of the wiring electrodes are drawn out to the outside of the substrate and connected to the drive circuit.

As in this liquid crystal display device, a single MIM
When the Cr film 10 is formed on the insulator 4 made of the Ta oxide film on the lower electrode 2 before the upper electrode 12 made of the transparent conductive film of the nonlinear resistance element made of the element is formed, as shown in FIG. , Cr diffuses near the surface of the insulator 4. FIG. 3 shows the composition distribution of a three-layer laminated film composed of a lower Ta film (lower electrode) centering on a Ta oxide film (insulator) and an upper Cr film by Auger analysis. The element concentrations of Cr, O, and Ta in the depth direction from the Cr film are shown. Curve 15 is Cr, curve 16 is O, curve 17
Indicates the concentration distribution of Ta. As shown by the curve 17, Ta of the lower electrode exists in high concentration on the substrate side. Further, as is clear from the curves 16 and 17, Ta and O are present in a considerable part of the insulator. And curve 1
As is clear from 5, the Cr deposited on the insulator is diffused near the surface of the insulator.

Cr diffused near the surface of the insulator 4
Changes the contact level of the upper electrode 12 with respect to the insulator made of a Ta oxide film made of a transparent conductive film.
Even if is formed of a transparent conductive film made of ITO, as shown by a curve 18 in FIG. 4, the non-linear resistance element made of the MIM element has a sufficient current-voltage characteristic that symmetry between positive voltage and negative voltage is obtained. . As a result, it is possible to obtain a liquid crystal display device in which the quality of the displayed image is not deteriorated even when the upper electrode 12 of the non-linear resistance element made of the MIM element is formed of the transparent conductive film.
As a result of actually manufacturing an active matrix type liquid crystal display device having a diagonal of 12 inches, a pixel pitch of 210 μm and a number of pixels of 1152 × 900 dots, the current-voltage characteristic symmetry shown in FIG. 4 was obtained, and a good quality image was obtained. The liquid crystal display device can display. Moreover, by forming the upper electrode 12 with a transparent conductive film, it is possible to reduce the photo-etching method at the time of forming the non-linear resistance element made of the MIM element to two times, improve the production yield, and reduce the production cost. Get out.

In the above-mentioned embodiment, C is provided near the surface of the resistor of the non-linear resistance element composed of the MIM element on the upper electrode side.
r was diffused, but curve 1 in FIG.
As shown in FIG. 9, even if Ti, Al, Ta, Mo—Ta alloy or the like is diffused near the surface of the resistor on the upper electrode side, M
Since the current-voltage characteristics of the non-linear resistance element including the IM element are symmetrical, the liquid crystal display device can display a high-quality image as in the case where Cr is diffused.

Example 2. FIG. 5 shows the structure of one pixel portion including a non-linear resistance element having a series structure of MIM elements in the liquid crystal display device of the second embodiment. The structure of this liquid crystal display device
Description will be given according to the manufacturing method shown in FIG.

In this liquid crystal display device, first, on one substrate 1 made of glass, a film thickness of 0.
A Ta film with a thickness of 3 μm is formed, and photo-etching method (1st PEP)
Thus, the lower electrode 2 of the MIM element having a series structure made of a Ta film, the row or column wiring electrode, and the wiring 3 for anodizing the lower electrode 2 and the wiring electrode are formed (FIG. 6B). Photo-etching of this Ta film is performed by coating a photoresist, exposing and baking a mask pattern, developing, CF.
Chemical dry etching (CDE) using a plasma gas in which ₄ and O ₂ are mixed in a ratio of 1: 2 → removal of resist → cleaning is performed in this order.

Next, the lower electrode 2 formed by this photoetching method is used as one electrode, and an insulator 4 made of a Ta oxide film is formed on the lower electrode 2 by anodization using 0.01 wt% citric acid aqueous solution as a chemical conversion solution. And forming a Ta oxide film on the wiring electrode (FIG. 6C). In this case, in order to keep the temperature of the chemical conversion solution constant and to make the growth of the Ta oxide film uniform, the chemical conversion solution may be stirred.

Next, unnecessary Ta such as wiring for forming the Ta oxide film is formed by the photo-etching method (2nd PEP).
The film and the Ta oxide film formed thereon are removed (FIG. 6).
(D)). This photo-etching is performed in the order of photoresist coating formation → mask pattern exposure / baking → development → chemical dry etching with plasma gas in which CF ₄ and O ₂ are mixed at a ratio of 1: 1 → photoresist removal → cleaning.

Next, the substrate 1 on which the Ta oxide film is formed
While heating the bottom electrode 2 by the sputtering method
And a Cr film with a thickness of 0.05 μm on the Ta oxide film of the wiring electrode
The film 10 is formed (FIG. 6E). Then, using a solution prepared by dissolving 17 g of ceric ammonium nitrate, 5 cc of perchloric acid, and 10 cc of water, a Cr film 1 on the Ta oxide film was used.
0 is removed to expose the Ta oxide film (FIG. 6).
(F)).

Next, the transparent conductive film 11 made of ITO is formed by the sputtering method (FIG. 6 (g)). Then, by photolithography (3rd PEP), an array substrate having a nonlinear resistance element 13 having a series structure of MIM elements in which the image display electrode 7 and the upper electrode 12 are made of a transparent conductive film is obtained. This photo-etching is a photoresist coating formation →
The mask pattern is exposed and baked, followed by development, etching with an aqueous solution of an equal amount of hydrochloric acid and nitric acid, removal of photoresist, and cleaning.

After that, an alignment film forming liquid made of polyimide is applied to the electrode forming surface of the array substrate and dried.
Rubbing is performed in one direction with a cotton cloth or the like to form an alignment film that regulates the alignment of the liquid crystal. On the other hand, a predetermined counter electrode is formed on the other substrate made of glass, and similarly, an alignment film forming liquid is applied and dried, and then rubbed to form a counter substrate.

After that, the array substrate and the counter substrate are arranged so as to face each other so that the rubbing directions of the alignment films are perpendicular to each other, and a spacer material is interposed between the both substrates to hold them at a predetermined interval. The periphery of the substrate is adhesively fixed while leaving the liquid crystal composition injection port. Then, after injecting the liquid crystal composition from the liquid crystal composition injection port, the liquid crystal composition injection port is sealed. After that, a deflection plate is attached to the outer surfaces of both substrates so as to be along the rubbing direction of the alignment film. In this case, the ends of the wiring electrodes are drawn out to the outside of the substrate and connected to the drive circuit. Reference numeral 21 shown in FIG. 6 is a wiring electrode.

As in this liquid crystal display device, before forming the upper electrode 12 made of the transparent conductive film of the nonlinear resistance element having the series structure of MIM elements, the insulator 4 on the lower electrode 2 is formed.
When the Cr film 10 is formed thereon, Cr diffuses near the surface of the insulator 4, as shown in FIG. The Cr diffused in the vicinity of the surface of the insulator 4 changes the contact level of the upper electrode 12 made of the transparent conductive film with respect to the insulator made of the Ta oxide film, and the current-voltage of the nonlinear resistance element made of the MIM element. As for the characteristic, as shown in FIG. 4, a sufficient symmetry between the positive voltage and the negative voltage is obtained. As a result, when the upper electrode of the non-linear resistance element having the conventional series structure of MIM elements is formed of the transparent conductive film, the non-linearity is lost as shown in FIG. 15, and the quality of the display image is significantly deteriorated. It is possible to obtain a liquid crystal display device in which the quality of the displayed image does not deteriorate without losing the nonlinearity. As a result of actually manufacturing an active matrix type liquid crystal display device having a diagonal of 4 inches, a pixel pitch of 180 μm and a number of pixels of 480 × 320 dots, the symmetry of current-voltage characteristics shown in FIG.
Moreover, a liquid crystal display device capable of displaying an image with a bright background and good quality could be obtained. Moreover, by forming the upper electrode 12 with the transparent conductive film, the photo-etching method at the time of forming the substrate can be reduced to three times, the manufacturing yield can be improved, and the manufacturing cost can be reduced.

In the second embodiment, Cr is diffused in the vicinity of the upper electrode side surface of the resistor of the nonlinear resistance element having the serial structure of the MIM element. However, regarding the nonlinear resistance element having the serial structure of the MIM element, Also Ti, Al, T
Even if a, Mo-Ta alloy or the like is diffused in the vicinity of the surface of the resistor on the upper electrode side, symmetry of the current-voltage characteristic is obtained, and C
As in the case where r is diffused, the liquid crystal display device can display an image of good quality.

Example 3. FIG. 8 shows the structure of one pixel portion including a non-linear resistance element having a series structure of MIM elements in the liquid crystal display device of the third embodiment. The structure of this liquid crystal display device
Description will be given according to the manufacturing method shown in FIG.

In this liquid crystal display device, first, on one substrate 1 made of glass, a film thickness of 0.
A Ta film with a thickness of 3 μm is formed, and photo-etching method (1st PEP)
Thus, the lower electrode 2 of the MIM element having a series structure made of a Ta film, the wiring electrode in the row or column, and the wiring for anodizing the lower electrode 2 and the wiring electrode are formed (FIG. 9).
(B)). Photo-etching of this Ta film is carried out by applying a photoresist, exposing and baking a mask pattern, developing, CF ₄
Chemical dry etching using a plasma gas in which 1: 1 and O ₂ are mixed in a ratio of 1: 2, photoresist removal, and cleaning are performed in this order.

Next, the lower electrode 2 formed by the above-mentioned photo-etching method is used as one electrode, and a 0.01 wt% citric acid aqueous solution is used as a chemical conversion solution by anodization to form an insulator 4 made of a Ta oxide film on the lower electrode 2. And a Ta oxide film is formed on the wiring electrode (FIG. 9C). In this case, in order to keep the temperature of the chemical conversion solution constant and to make the growth of the Ta oxide film uniform, the chemical conversion solution may be stirred.

Next, unnecessary Ta such as wiring for forming the Ta oxide film is formed by the photo-etching method (2nd PEP).
The film and the Ta oxide film formed thereon are removed (FIG. 9).
(D)). This photo-etching is performed in the order of photoresist coating formation → mask pattern exposure / baking → development → chemical dry etching with plasma gas in which CF ₄ and O ₂ are mixed at a ratio of 1: 1 → photoresist removal → cleaning. Next, while heating the substrate 1 having the Ta oxide film formed thereon, a film thickness of 0.05 μm is formed on the Ta oxide film of the lower electrode 2 and the wiring electrode by a sputtering method.
A Cr film 10 of m is formed (FIG. 9E). Further, a transparent conductive film 11 made of ITO is formed on the Cr film 10 by a sputtering method (FIG. 9 (f)). Then, the image display electrode 7 made of the transparent conductive film and the upper electrode 12 made of the transparent conductive film of the MIM element are formed by the photoetching method (3rd PEP) (FIG. 9G). This photo-etching consists of photoresist coating → exposure and mask pattern exposure →
Development → Etching with an equal amount of hydrochloric acid and nitric acid →
Cleaning is done in order.

Next, using the above photoresist, 17 g of ceric ammonium nitrate, 5 cc of perchloric acid,
The array substrate is obtained by removing the Cr film 10 except the image display electrode 7 and the upper electrode 12 with a solution dissolved at a rate of 10 cc of water (FIG. 9 (g)). Reference numeral 21 shown in FIG. 8 is a wiring electrode.

After that, an alignment film forming liquid made of polyimide is applied to the electrode forming surface of the array substrate and dried.
Rubbing is performed in one direction with a cotton cloth or the like to form an alignment film that regulates the alignment of the liquid crystal. On the other hand, a predetermined counter electrode is formed on the other substrate made of glass, and similarly, an alignment film forming liquid is applied and dried, and then rubbed to form a counter substrate.

After that, the array substrate and the counter substrate are arranged so as to face each other so that the rubbing directions of the alignment films are orthogonal to each other, and a spacer material is interposed between the both substrates to hold them at a predetermined interval. The periphery of the substrate is adhesively fixed while leaving the liquid crystal composition injection port. Then, after injecting the liquid crystal composition from the liquid crystal composition injection port, the liquid crystal composition injection port is sealed. After that, a deflection plate is attached to the outer surfaces of both substrates so as to be along the rubbing direction of the alignment film. In this case, the ends of the wiring electrodes are drawn out to the outside of the substrate and connected to the drive circuit.

As in this liquid crystal display device, the upper electrode 1 made of the transparent conductive film of the non-linear resistance element made of the MIM element.
When the Cr film 10 is formed on the insulator 4 on the lower electrode 2 before forming 2, the Cr diffuses in the vicinity of the surface of the insulator 4 (see FIG. 3) and oxidizes, as in the second embodiment. By changing the contact level of the upper electrode 12a made of a transparent conductive film with respect to the insulator 4 made of a film, the current-voltage characteristics of the non-linear resistance element made of the MIM element are sufficiently positive and negative as shown in FIG. Voltage symmetry is obtained. Moreover, in this liquid crystal display device, since the pixel display electrode 7 is composed of the Cr film and the transparent conductive film formed thereon, deterioration of the pixel display electrode 7 can be prevented. That is, a non-linear resistance element having a series structure of MIM elements is formed by forming a lower electrode made of a Ta film and an insulator made of a Ta oxide film, and then forming an unnecessary Ta film and an unnecessary Ta film on the Ta film by a chemical dry etching method. The Ta oxide film is removed, and then a pixel display electrode of a transparent conductive film made of ITO is formed. In this case, the base glass substrate is damaged by the chemical dry etching method, and when the transparent conductive film made of ITO is etched to form the pixel display electrode, penetration easily occurs. When the Cr film formed on the insulator is left in the pixel display electrode forming portion, the Cr film is formed after the unnecessary Ta film and the Ta oxide film formed thereon are removed by chemical dry etching. Since the transparent conductive film made of ITO does not come into direct contact with the underlying glass substrate, it is possible to prevent the transparent conductive film made of ITO from soaking in.

As a result, when the upper electrode of the non-linear resistance element having the conventional MIM element series structure is formed of the transparent conductive film, the non-linearity is lost as shown in FIG. 15, and the quality of the displayed image is significantly deteriorated. However, it is possible to provide a liquid crystal display device that displays a good-quality image without losing its non-linearity and with no penetration into the pixel display electrode 7. Even if the Cr film is formed on the pixel display electrode forming portion as described above, since the Cr film is thin, the quality of the display image is hardly affected. As a result of actually manufacturing an active matrix type liquid crystal display device having a diagonal of 4 inches, a pixel pitch of 180 μm and a pixel number of 480 × 320 dots, as shown in FIG.
It was possible to obtain a liquid crystal display device having the symmetry of the current-voltage characteristics shown in (3) and displaying an image of good quality without seeping into the pixel display electrode. Moreover, by forming the upper electrode 12 with the transparent conductive film, the photo-etching method at the time of manufacturing the substrate can be reduced to three times, the manufacturing yield can be improved, and the manufacturing cost can be reduced.

In Example 3, Cr was diffused in the vicinity of the upper electrode side surface of the resistor of the nonlinear resistance element having the serial structure of the MIM element. However, regarding the nonlinear resistance element having the serial structure of the MIM element, Also, in addition to Cr, T
Even if i, Al, Ta, Mo-Ta alloy or the like is diffused in the vicinity of the surface of the resistor on the upper electrode side, and these metals are provided in the portion where the pixel display electrode is formed, symmetry of current-voltage characteristics can be obtained. In addition, it is possible to prevent the transparent conductive film of the pixel display electrode from seeping into the liquid crystal display device and display a high quality image.

[0061]

According to the present invention, there is provided a liquid crystal display device having a plurality of non-linear resistance elements each having a lower electrode-insulator-upper electrode structure MIM element electrically connected to each pixel display electrode or a series structure of MIM elements. A non-linear resistance element,
If a structure in which a metal different from the upper electrode is diffused near the surface of the insulator on the side of the upper electrode, the contact level between the insulator and the upper electrode changes, and a transparent material such as ITO is formed on the insulator. Even if the upper electrode is formed of a conductive film, the discontinuity of the contact level between the insulator and the upper electrode is eliminated, and the positive voltage and the negative voltage of the current-voltage characteristic of the nonlinear resistance element can be made symmetrical. Thus, the liquid crystal display device can display an image of good quality. Moreover, the number of times the photo-etching method is applied can be reduced in the production, and the production yield can be improved.
The manufacturing cost can be reduced.

The diffusion of a metal different from the upper electrode near the surface of the insulator of the non-linear resistance element made of such MIM element or the upper electrode of the insulator of the non-linear resistance element having the series structure of MIM elements The diffusion of the metal in which the current-voltage characteristics in the vicinity of the side surface are non-linear and symmetrical is facilitated by forming a metal layer different from the upper electrode on the insulator as described above, and then removing this metal layer. Can be formed. Further, a metal whose current-voltage characteristics are non-linear and symmetrical is diffused in the vicinity of the upper electrode side surface of the insulator of the non-linear resistance element having a series structure of MIM elements, and the metal layer is used as a pixel display electrode and wiring. If the electrodes are provided in the same shape as the pixel display electrode and the wiring electrode, the upper electrode of one MIM element is, for example, I.
Even if it is formed of a transparent conductive film made of TO, not only sufficient non-linearity can be obtained, but also the penetration of the pixel display electrode can be eliminated, and a liquid crystal display device that displays a high quality image is provided. be able to. In addition, the number of times the photo-etching method is applied can be reduced in manufacturing, the manufacturing yield can be improved, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view for explaining a structure of a liquid crystal display device according to a first embodiment of the present invention.

FIG. 2 (a) is a flow chart for explaining the manufacturing method, and FIGS. 2 (b) to 2 (g) are views for explaining the main steps thereof.

FIG. 3 is a diagram showing diffusion of Cr into an insulator of a MIM element.

FIG. 4 is a diagram showing a structure in which Cr is diffused into the above insulator and ITO is used as an upper electrode.
It is a figure which shows the current-voltage characteristic of the MIM element formed by.

FIG. 5 is a diagram showing diffusion of Ti into an insulator of a MIM element.

FIG. 6A is a plan view for explaining the structure of the liquid crystal display device according to the second embodiment of the present invention, and FIG.
It is a -B line sectional view.

FIG. 7 (a) is a flowchart for explaining the manufacturing method, and FIGS. 7 (b) to 7 (h) are views for explaining the main steps thereof.

8A is a plan view for explaining the structure of the liquid crystal display device according to the third embodiment of the present invention, and FIG. 8B is its B view.
It is a -B line sectional view.

FIG. 9A is a flowchart for explaining the manufacturing method, and FIGS. 9B to 9H are diagrams for explaining the main steps thereof.

FIG. 10 is a cross-sectional view illustrating a structure of a conventional liquid crystal display device.

FIG. 11A is a flow chart for explaining the manufacturing method, and FIGS. 11B to 11G are views for explaining the main steps thereof.

FIG. 12: The upper electrode is Cr, Ti, Al, Ta, Mo-
It is a figure which shows the current-voltage characteristic of the MIM element which consists of Ta etc.

FIG. 13 is a diagram showing current-voltage characteristics of an MIM element whose upper electrode is made of ITO.

FIG. 14 (a) is a plan view for explaining the structure of a liquid crystal display device having a non-linear resistance element having a conventional MIM element series structure, and FIG. 14 (b) is a cross-sectional view taken along line BB thereof. Is.

FIG. 15 is a diagram showing a current-voltage characteristic of a non-linear resistance element having a series structure of MIM elements each having an upper electrode made of ITO.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Lower electrode 4 ... Insulator 7 ... Image display electrode 10 ... Cr film 12 ... Upper electrode 13 ... Non-linear resistance element 21 ... Wiring electrode

Claims (6)

[Claims] 1. A plurality of pixel display electrodes on one of substrates facing each other with a liquid crystal composition interposed therebetween, and a lower electrode-insulator-upper electrode structure electrically connected to each of the plurality of pixel display electrodes. A plurality of non-linear resistance elements including MIM elements of
In the liquid crystal display device including a wiring electrode connecting the plurality of nonlinear resistance elements, the nonlinear resistance element has a metal different from the upper electrode diffused in the vicinity of the surface of the insulator on the upper electrode side. A liquid crystal display device characterized by the following. 2. A plurality of pixel display electrodes on one of substrates facing each other through a liquid crystal composition, and a lower electrode-insulator-upper electrode structure electrically connected to each of the plurality of pixel display electrodes. A liquid crystal display device provided with a plurality of nonlinear resistance elements having a serial structure of MIM elements and wiring electrodes connecting the plurality of nonlinear resistance elements, wherein the nonlinear resistance element is the upper electrode of the insulator. A liquid crystal display device, characterized in that a metal whose current-voltage characteristics are non-linear and symmetrical is diffused in the vicinity of the surface on the side. 3. The lower electrode of the nonlinear resistance element is made of Ta, and the metal diffused in the vicinity of the surface of the nonlinear resistance element on the upper electrode side is at least one of Cr, Ti, Al, Ta, and Mo-Ta alloy. The liquid crystal display device according to claim 1 or 2, wherein 4. A plurality of pixel display electrodes on one of substrates facing each other with a liquid crystal composition interposed therebetween, and a lower electrode-insulator-upper electrode structure electrically connected to each of the plurality of pixel display electrodes. Of the MIM element or a plurality of non-linear resistance elements having a serial structure of the MIM elements, and a wiring electrode connecting the plurality of non-linear resistance elements. Forming an electrode, forming the insulator on the lower electrode, forming a metal film different from the upper electrode on the insulator, and applying a metal of the metal film to the upper portion of the insulator. Forming the non-linear resistance element by a step of removing the metal film after being diffused in the vicinity of the surface on the electrode side and a step of forming the upper electrode on the insulator after removing the metal film. Method of manufacturing a liquid crystal display device according to claim. 5. A plurality of pixel display electrodes on one of substrates facing each other with a liquid crystal composition interposed therebetween, and a lower electrode-insulator-upper electrode structure electrically connected to each of the plurality of pixel display electrodes. In a liquid crystal display device provided with a plurality of non-linear resistance elements having a serial structure of MIM elements and wiring electrodes connecting the plurality of non-linear resistance elements, the surface of the insulator of the non-linear resistance element on the upper electrode side. A metal whose current-voltage characteristics are non-linear and symmetrical is diffused in the vicinity, and a film of this metal has the same shape as the pixel display electrode and the wiring electrode in the pixel display electrode formation portion and the wiring electrode formation portion, respectively. A liquid crystal display device comprising: 6. The lower electrode of the non-linear resistance element is made of Ta, and is formed in the metal diffused near the surface of the non-linear resistance element on the upper electrode side, the pixel display electrode forming portion and the wiring electrode forming portion. Metal film is Cr, Ti, A
The liquid crystal display device according to claim 5, wherein the liquid crystal display device is made of at least one of 1, 1, Ta and Mo-Ta alloy.