JPH1168194A - Manufacturing two-terminal nonlinear elements and two-terminal nonlinear element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of manufacturing two-terminal nonlinear elements and two-terminal nonlinear element which forms an anodic oxidation film having a uniform distribution of the film quality in a substrate to produce two-terminal nonlinear elements having uniform characteristics. SOLUTION: The method of manufacturing two-terminal nonlinear elements each having a lower and upper electrodes 33, 36 and first insulation film 34 held between these electrodes 33, 36 comprises forming a metal film covering approximately the entire surface of a substrate 31, anodic-oxidizing it to form an anodic oxidation film on the surface layer of the metal film, etching the metal film and anodic oxidation film to form lower electrodes 33 of the nonlinear elements and first insulation film 34.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-terminal nonlinear element and a method of manufacturing the same, and more particularly to a two-terminal nonlinear element suitably used for a liquid crystal display device and a method of manufacturing the same.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have low power consumption.
Because of their thin and lightweight characteristics, they have been used for display applications such as personal computers, word processors, office automation terminal displays, and televisions, and higher capacity displays and higher image quality are required.

A conventional liquid crystal display device is a TN (Twisted Nematic).
matic) method or STN (SuperTwisted Nematic)
Although simple matrix driving is performed by the voltage averaging method of this method, this method is not suitable for large-capacity display because a sufficient contrast ratio cannot be obtained due to an increase in scanning lines.

Therefore, active driving has been developed in which switching elements are provided for individual pixels constituting a display screen. As the switching element, a thin film transistor or a two-terminal non-linear element is used. However, a liquid crystal display device using a two-terminal non-linear element which has a simple structure and is advantageous in terms of manufacturing cost is promising. Insulator
Those having a metal (Metal-Insulator-Metal, hereinafter referred to as MIM) structure have been put to practical use.

A conventional MIM element can be manufactured, for example, as follows. A conventional manufacturing method will be described with reference to FIGS.

First, a signal wiring 12 of FIGS. 1A and 2A and a lower part of FIGS. 1A and 1B are formed on a glass substrate 11 of FIG. A metal thin film serving as the electrode 13, for example, a tantalum thin film, is
Laminate to a thickness of 00 nm. The obtained tantalum thin film is patterned into a predetermined shape by photolithography,
These are signal wiring 12 and lower electrode 13. The material of the lower electrode may be Al or the like.

After that, the surface of the lower electrode 13 made of a tantalum thin film is anodized by anodizing method to a thickness of about 60
An insulating film 14 made of tantalum pentoxide having a thickness of nm is formed.
At this time, a portion (for example, a terminal electrode) of the tantalum thin film that is not desired to be anodized is covered with a protective film.

Next, a titanium thin film serving as the upper electrode 15 is laminated to a thickness of about 400 nm on almost the entire surface of the substrate in this state by a sputtering method or the like. The obtained titanium thin film is patterned into a predetermined shape by a photolithography method to form an upper electrode 15. Further, a transparent electrode film made of ITO (indium tin oxide) or the like is laminated, and this is patterned to form the pixel electrode 17 and the terminal electrode 18. The terminal electrode 18 is connected to the signal wiring 12 and the signal wiring 12.
Are electrically connected at the upper surface and the tapered portion (side surface).

[0009]

As described above, in the production of a conventional MIM element, anodization is performed after patterning an anodically oxidizable metal thin film such as a tantalum thin film. In this method, since the metal thin film portion to be anodized has a fine pattern (for example, a lower electrode), the formation current during the anodization does not flow evenly in the substrate. Therefore, the film quality of the anodic oxide film in the substrate becomes uneven, and the characteristics (threshold voltage: V
th, contrast ratio: CR, withstand voltage) may vary depending on the position in the substrate. This is because the metal thin film has a fine pattern, which complicates the path through which current flows during anodic oxidation, and that there is a large difference in the electrical resistance value between each part of the patterned metal thin film. is there.

[0010] In order to make the current density in the substrate uniform during anodization, the metal thin film formed on almost the entire surface of the substrate is anodized before patterning the metal thin film, and then the metal whose surface is anodized is formed. A method of patterning a thin film can be considered. Such a method is described in, for example, Japanese Patent Publication No. 4-69.
No. 27 is disclosed. However, in this example, a protective film is formed on a corresponding portion of the metal thin film by a printing method or the like before the anodic oxidation in order to leave a portion (for example, a terminal electrode) that is not anodized.

The distribution of current density in the substrate during anodization is as follows:
Since it is affected by the presence of the protective film, the uniformity of the current density in the substrate is lower than that of the entire surface by anodic oxidation. That is, the method is not substantially full-surface anodic oxidation. In addition, when printing the protective film, a small amount of the protective film material may adhere to a portion serving as the lower electrode of the switching element due to scattering or the like, which may affect the formation of the anodic oxide film. As a result, there is a problem that the film quality of the anodic oxide film becomes non-uniform in the substrate, and the above characteristics (Vth, CR, withstand voltage) vary within the substrate.

The present invention solves the above problems, and forms an anodic oxide film having a uniform film quality distribution in a substrate.
An object of the present invention is to provide a method for manufacturing a two-terminal nonlinear element having uniform characteristics and a two-terminal nonlinear element.

[0013]

A method for manufacturing a two-terminal nonlinear element according to the present invention includes a lower electrode, an upper electrode, and a first insulating film sandwiched between the lower electrode and the upper electrode. A method for manufacturing a plurality of two-terminal nonlinear elements, comprising:
Forming a metal thin film covering substantially the entire surface of the substrate, anodizing the metal thin film to form an anodic oxide film on the surface of the metal thin film, and etching the metal thin film and the anodic oxide film Forming the lower electrode and the first insulating film of the plurality of two-terminal nonlinear elements, thereby achieving the above object.

The step of etching the metal thin film and the anodic oxide film is a step of forming the lower electrode and the first insulating film and forming a signal wiring having the anodic oxide film on a top surface. After the etching step,
Forming a second insulating film covering the lower electrode and the etched end of the first insulating film; and forming an upper electrode covering at least a part of the first insulating film on the lower electrode. May be included.

In the step of forming the upper electrode, the upper electrode covers at least a part of the first insulating film on the lower electrode and a part of the anodic oxide film formed on a top surface of the signal wiring. May be formed.

After the step of forming the upper electrode, a step of forming a pixel electrode electrically connected to the upper electrode and a terminal electrode electrically connected to the signal wiring by using the same material. May be further included.

Forming a terminal electrode and a pixel electrode on the substrate using the same material before forming the metal thin film covering substantially the entire surface of the substrate; The lower electrode may be formed to be electrically connected to the pixel electrode on the bottom surface of the lower electrode.

[0018] The upper electrode may be formed of a material different from the material of the terminal electrode and the pixel electrode. Further, the upper electrode may be formed of the same material as that of the terminal electrode and the pixel electrode.

The step of forming the second insulating film includes a step of forming a second insulating film covering an etched end of the lower electrode and the first insulating film and an etched end of the signal wiring having the anodic oxide film on the top surface. May be formed.

The step of forming the second insulating film includes the step of depositing a second insulating film covering the lower electrode and the first insulating film, and the step of etching the second insulating film to form the second insulating film on the lower electrode. Forming an opening at the center of the first insulating film.

It is preferable that the material of the second insulating film is made of a material different from the material of the first insulating film, and that the second insulating film is selectively etched.

A two-terminal nonlinear element according to the present invention is a two-terminal nonlinear element having a lower electrode, an upper electrode, and a first insulating film sandwiched between the lower electrode and the upper electrode. The first insulating film is formed of a film obtained by anodizing a surface layer of the lower electrode, and is formed only on a top surface of the lower electrode.
The side surface of the lower electrode is covered with a second insulating film made of a material different from the first insulating film, thereby achieving the above object.

According to another aspect of the present invention, there is provided an active matrix substrate having a plurality of two-terminal nonlinear elements and a signal wiring on a substrate, wherein the two-terminal nonlinear elements include:
A lower electrode, an upper electrode, and a first insulating film sandwiched between the lower electrode and the upper electrode;
It is made of a film obtained by anodizing the surface layer of the lower electrode, is formed only on the top surface of the lower electrode, and the top surface of the signal wiring is
An active matrix in which a surface layer of the signal wiring is covered with a film obtained by anodizing, and a side surface of the lower electrode and a side surface of the signal wiring are covered with a second insulating film made of a material different from the first insulating film; A substrate is provided.

The operation will be described below.

According to the present invention, the metal thin film formed on almost the entire surface of the substrate is anodized on a relatively large surface without being covered with the protective film. Therefore, since the anodic oxidation is performed at a uniform formation current density, an anodic oxide film having a uniform film quality is formed. In addition, since there is no step of printing the protective film, the protective film does not adhere to the region of the metal thin film that will become the switching element portion, so that an anodic oxide film of uniform film quality can be obtained.

By covering the etched end of the lower electrode exposed by the patterning after anodic oxidation with the second insulating film, a short circuit between the lower electrode and the upper electrode at the etched end can be reduced.

A pair of two-terminal non-linear elements having opposite polarities of metal (lower electrode) -insulating film-metal (upper electrode) and metal (upper electrode) -insulating film-metal (lower electrode) are connected in series. By doing so, the symmetry of the current-voltage characteristics of the two-terminal nonlinear element is improved as compared with the case where the number of the two-terminal nonlinear element is one, and the afterimage phenomenon or the like during panel lighting is reduced.

Further, by covering the etched end of the signal wiring exposed by the patterning after the anodic oxidation with the second insulating film, a short circuit between the signal wiring and the pixel electrode at the etched end can be reduced.

Further, by covering the portion covering the etched end of the first insulating film and the lower electrode with the second insulating film, it is possible to reduce the dielectric breakdown in the first insulating film portion where the electric field tends to concentrate.

After anodizing the metal thin film, patterning of the signal wiring is performed, and a terminal electrode is formed so as to cover the signal wiring, so that the signal wiring and the terminal are formed at the etched end (tapered portion, side surface) of the signal wiring. Electrical continuity with the electrodes can be obtained. In addition, a configuration can be employed in which the signal wiring is electrically connected to a terminal electrode formed of the same metal as the lower electrode. In addition, a configuration can be employed in which the signal wiring is electrically connected to a terminal electrode formed of the same metal as the upper electrode.

Further, by changing the material of the first and second insulating films, the first insulating film can be etched without being eroded by an etchant when patterning the second insulating film, so that the characteristics of the anodic oxide film are not affected. .

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION

(Embodiment 1) Embodiment 1 of the present invention will be described with reference to FIGS. 3 to 6 are views for explaining a method of manufacturing the active matrix substrate according to the first embodiment of the present invention, and are a plan view and a sectional view of a two-terminal nonlinear element, a pixel electrode portion, and a terminal electrode portion.

First, a tantalum thin film serving as the signal wiring 32 and the lower electrode 33 shown in FIGS. 3 and 4 is deposited to a thickness of about 300 nm on almost the entire surface of the glass substrate 31 shown in FIGS. The entire surface of the obtained tantalum thin film is anodized to form a first insulating film 34 of tantalum pentoxide having a thickness of about 60 nm. Then,
The signal wiring 32 and the lower electrode 33 are formed by patterning the tantalum thin film on which the first insulating film 34 is formed into a predetermined shape by photolithography. Next, a silicon nitride film serving as the second insulating film 35 is stacked at a temperature of about 300 ° C. and a thickness of about 300 nm by P-CVD (plasma chemical vapor deposition) so as to cover the obtained substrate surface. The obtained silicon nitride film is patterned into a predetermined shape by photolithography to form a second insulating film 35. Since the first insulating film and the second insulating film are formed of different materials, when the pattern is formed by using the etching method, the second insulating film is selectively formed by utilizing the difference in the etching speed depending on the material. Can be etched. MI
Since the first insulating film forming a part of the M element can be prevented from being damaged by the etchant, deterioration of the characteristics of the MIM element can be suppressed. The pattern of the second insulating film is preferably formed to have an opening at the center of the first insulating film on the lower electrode and to cover the etched end of the first insulating film. It is preferable that the thickness of the second insulating film be larger than the thickness of the first insulating film. Second
By using a thin film deposition technique such as CVD for the insulating film, a thick film can be formed more easily than in the anodic oxidation method.

Next, a titanium thin film serving as the upper electrode 36 is laminated to a thickness of about 400 nm on the entire surface of the substrate in this state by sputtering or the like, and is patterned into a predetermined shape by photolithography to form the upper electrode 36. Further, a transparent electrode film made of ITO (indium tin oxide) or the like is laminated, and is patterned to form a pixel electrode 37 and a terminal electrode 38. A part of the pixel electrode 37 is formed so as to overlap with a part of the upper electrode 36, whereby the pixel electrode 37 is electrically connected to the upper electrode. The upper surface of the signal wiring 32 is covered with a first insulating film 34, and the terminal electrode 38 is electrically connected to the signal wiring 32 at a tapered portion (side surface) of the signal wiring 32.

Thus, an active matrix substrate provided with the MIM element as a switching element is obtained. Table 1 shows the results of measuring the IV characteristics of the MIM device of the active matrix substrate obtained in the present embodiment and the MIM device obtained by the conventional manufacturing method (anodic oxidation after lower electrode patterning). As the characteristic value of the MIM element, the voltage (V) -current (I) of the Poole-Frenkel effect
The relational expression of: I = α value (coefficient relating to conductivity) and β value (coefficient relating to nonlinearity) in αVexp (βV ^1/2 ) were used.

[0036]

[Table 1] Characteristic value Conventional example The present invention Inα-30.00 ± 1.00-30.00 ± 0.30β3.00 ± 0.503.00 ± 0.10 As is clear from Table 1, almost all of the substrate 11 According to the method of the present invention in which the tantalum thin film is anodized to form the first insulating film 34 before the lower electrode 33 is formed by patterning the tantalum thin film formed on the entire surface, lnα showing the characteristics of the nonlinear element is obtained. The variations in the values and the β values were both smaller than in the conventional example, and the uniformity of the device characteristics was improved. In this embodiment, the tantalum thin film is formed on almost the entire surface of the substrate. However, it is needless to say that the tantalum thin film does not need to be formed on the peripheral portion of the substrate where the MIM element and the like are not formed.

The liquid crystal layer of the liquid crystal display device manufactured using the active matrix substrate provided with the MIM element according to the present invention is not particularly limited. For example, a TN mode liquid crystal layer can be used. In addition, on the liquid crystal layer side of the opposing substrate which is disposed to oppose the active matrix substrate so as to sandwich the liquid crystal layer, the pixel electrode 37 connected to the signal wiring 32 is opposed, and the extension direction of the signal wiring 32 is set. Are provided with rectangular scanning wirings extending in a direction perpendicular to the direction. Note that the signal wiring (inputting a data signal) and the scanning wiring (inputting a scanning signal) are interchangeable, and the scanning signal may be input to the signal wiring and the data signal may be input to the scanning wiring. The MIM element according to the present invention and the method for manufacturing the same are known in the art.
It can be widely applied to an IM type active matrix substrate and a liquid crystal display device using the same.

(Embodiment 2) The embodiment of the present invention is shown in FIGS.
This will be described with reference to FIG. 7 to 10 are views for explaining a method for manufacturing an active matrix substrate according to Embodiment 2 of the present invention, and are a plan view and a sectional view of a two-terminal nonlinear element, a pixel electrode portion, and a terminal electrode portion.

First, a transparent electrode film made of ITO or the like shown in FIGS. 7 and 8 is laminated on the glass substrate 71 shown in FIGS. 8 and 10 by sputtering or the like, and is patterned to form a pixel electrode 77 and a terminal electrode 78. I do. Next, a tantalum thin film to be the signal wiring 72 and the lower electrode 73 is laminated on the entire surface to a thickness of about 300 nm by a sputtering method or the like, and the entire surface of the tantalum thin film is anodized by the anodization method to form a pentoxide film having a thickness of about 60 nm. The first made of tantalum
An insulating film 74 is formed. After that, the signal wiring 72 is patterned by photolithography into a predetermined shape.
And the lower electrode 73.

Next, silicon nitride to be the second insulating film 75 is laminated by P-CVD at about 300 ° C. at a thickness of about 300 nm, and patterned into a predetermined shape by photolithography to form the second insulating film 75. . Next, a titanium thin film serving as the upper electrode 76 is laminated to a thickness of about 400 nm on the entire surface of the substrate in this state by a sputtering method or the like, and is patterned into a predetermined shape by a photolithography method to form the upper electrode 76. The terminal electrode 78 is electrically connected to the signal wiring 72 at the bottom surface of the signal wiring 72. Pixel electrode 7
7 and the lower electrode 73 are electrically connected at the bottom surface of the lower electrode 73.

The characteristics of the MIM element of the active matrix substrate thus obtained were evaluated in the same manner as in the first embodiment. As a result, the same effects as in the first embodiment were obtained.

In this embodiment, as can be seen from FIG. 8, one two-terminal non-linear element having the opposite polarity is connected in series to the path from the signal wiring 72 to the pixel electrode 77. That is, the signal wiring 72 (metal: tantalum) -first
Insulating film (insulator: tantalum pentoxide)-upper electrode 76 (metal: titanium) and upper electrode 76 (metal: titanium)-first
Insulating film (insulator)-lower electrode 73 (metal: tantalum)
Are connected in series symmetrically with respect to the upper electrode 76. With this configuration, the symmetry of the voltage-current characteristics with respect to the polarity of the voltage is improved as compared with the case where one MIM element is used. Therefore, when a liquid crystal display device is configured using the active matrix substrate of the present embodiment, occurrence of defects such as an afterimage phenomenon is suppressed even when AC driving (driving for changing the polarity of voltage for each field or frame) is performed. Is done.

The signal wiring 72 and the upper electrode 76 are
The connection may be made directly without passing through the second insulating film 75.

(Embodiment 3) FIG. 11 shows an embodiment of the present invention.
This will be described with reference to FIGS. 11 to 15 are views for explaining a method of manufacturing an active matrix substrate according to Embodiment 3 of the present invention, and are a plan view and a cross-sectional view of a two-terminal nonlinear element, a pixel electrode portion, and a terminal electrode portion.

First, the glass substrate 1 shown in FIGS.
1 by sputtering or the like over almost the entire surface of
A tantalum thin film serving as the lower electrode 113 is laminated to a thickness of about 300 nm, and the entire surface of the tantalum thin film is anodized by anodic oxidation to form a first insulating film 114 of tantalum pentoxide having a thickness of about 60 nm. I do.

Thereafter, the lower electrode 113 is patterned by photolithography into a predetermined shape. Next, silicon nitride to be the second insulating film 115 is laminated by P-CVD at about 300 ° C. at a thickness of about 300 nm and patterned into a predetermined shape by photolithography to form the second insulating film 115.

Next, a titanium thin film serving as the signal wiring 112 and the upper electrode 116 is laminated to a thickness of about 400 nm on the entire surface of the substrate in this state by sputtering or the like, and is patterned into a predetermined shape by photolithography to form the signal wiring 112. And the upper electrode 116. Further IT
A transparent electrode film made of O or the like is laminated, and this is patterned to form a pixel electrode 117 and a terminal electrode 118.
Note that the signal wiring 112 and the lower electrode 113 are formed on the second insulating film 1.
15 may be directly connected without going through. Terminal electrode 1
Numeral 18 is electrically connected to the signal wiring 112 via the upper surface and the tapered portion (side surface) of the signal wiring 112.

The characteristics of the MIM element of the active matrix substrate thus obtained were evaluated in the same manner as in the first embodiment. As a result, the same effects as in the first embodiment were obtained.

(Embodiment 4) Embodiment 4 of the present invention is shown in FIG.
This will be described with reference to FIGS. 16 to 20 are views for explaining a method for manufacturing an active matrix substrate according to Embodiment 4 of the present invention, and are a plan view and a cross-sectional view of a two-terminal nonlinear element, a pixel electrode portion, and a terminal electrode portion.

First, the glass substrate 1 shown in FIGS.
FIG. 1 is formed on almost the entire surface of the substrate 61 by a sputtering method or the like.
A tantalum thin film to be the lower electrodes 163 of 7 and 18 is laminated to a thickness of about 300 nm, and the entire surface of the tantalum thin film is anodized by anodic oxidation to form a first insulating film 164 made of tantalum pentoxide having a thickness of about 60 nm. I do. Thereafter, a lower electrode 163 is formed by patterning into a predetermined shape by photolithography.

Next, silicon nitride to be the second insulating film 165 is laminated by P-CVD at about 300 ° C. at a thickness of about 300 nm and patterned into a predetermined shape by photolithography to form the second insulating film 165. . Next, a transparent electrode film made of ITO or the like is laminated on the entire surface of the substrate in this state by a sputtering method or the like, and is patterned to form a signal wiring 162, an upper electrode 166, a pixel electrode 167, and a terminal electrode 168. Note that the signal wiring 162 and the lower electrode 163 may be directly connected without interposing the second insulating film 165. Since the terminal electrode 168 is the same transparent electrode film as the signal wiring 162, there is no connection portion.

The characteristics of the MIM element of the active matrix substrate thus obtained were evaluated in the same manner as in the first embodiment. As a result, the same effects as in the first embodiment were obtained.

(Embodiment 5) FIG. 2 shows Embodiment 5 of the present invention.
This will be described with reference to FIGS. 21 to 24 are views for explaining a method for manufacturing an active matrix substrate according to Embodiment 5 of the present invention, and are a plan view and a cross-sectional view of a two-terminal nonlinear element, a pixel electrode portion, and a terminal electrode portion.

First, a tantalum thin film serving as the signal wiring 212 and the lower electrode 213 shown in FIGS. 21 and 22 is laminated to a thickness of about 300 nm on the glass substrate 211 shown in FIGS. 22 and 24 by sputtering or the like. A first insulating film 214 of tantalum pentoxide having a thickness of about 60 nm is formed by anodizing the entire surface of the thin film. Thereafter, patterning into a predetermined shape is performed by a photolithography method to form the signal wiring 212 and the lower electrode 213. Next, silicon nitride to be a second insulating film 215 is
A second insulating film 215 is formed by laminating about 300 nm in thickness at about 300 ° C. by a VD method and patterning it into a predetermined shape by a photolithography method.

Next, a titanium thin film serving as the upper electrode 216 is laminated to a thickness of about 400 nm on the entire surface of the substrate in this state by a sputtering method or the like, and is patterned into a predetermined shape by a photolithography method to form the upper electrode 216. Further, a transparent electrode film made of ITO or the like is laminated, and this is patterned and the pixel electrode 217 and the terminal electrode 21 are patterned.
8 is formed. Note that since the upper surface of the signal wiring 212 is covered with the first insulating film 214, the terminal electrode 218 is electrically connected to the signal wiring 212 via a tapered portion of the signal wiring 212.

The characteristics of the MIM element of the active matrix substrate thus obtained were evaluated in the same manner as in the first embodiment. As a result, the same effects as in the first embodiment were obtained.

In the first embodiment, since the etched end of the first insulating film 34 in FIG. 4 is not covered with the second insulating film 35,
The electric field tends to concentrate at that portion, and dielectric breakdown may occur. In the present embodiment, the first insulating film 214 of FIG.
Is covered with the second insulating film 215, the withstand voltage increases. As a result, the pixel defect occurrence rate due to dielectric breakdown in the fifth embodiment was reduced from about 0.01% or more of the panel pixel number in the first embodiment to about 0.005% or less.

(Embodiment 6) FIG. 2 shows Embodiment 6 of the present invention.
This will be described with reference to FIGS. FIGS. 25 to 29 are views for explaining a method of manufacturing an active matrix substrate according to Embodiment 6 of the present invention, and are a plan view and a cross-sectional view of a two-terminal nonlinear element, a pixel electrode portion, and a terminal electrode portion.

First, the glass substrate 2 shown in FIGS.
A tantalum thin film to be the signal wiring 252 and the lower electrode 253 is laminated to a thickness of about 300 nm on almost the entire surface of the thin film 51 by sputtering or the like, and the entire surface of the tantalum thin film is anodically oxidized by anodization to form a film of about 60 nm thick. A first insulating film 254 made of tantalum oxide is formed. Thereafter, patterning into a predetermined shape is performed by a photolithography method to form a signal wiring 252 and a lower electrode 253. Next, silicon nitride to be the second insulating film 255 is formed by P-CV
A layer having a thickness of about 300 nm is formed at a temperature of about 300 ° C. by a method D, and is patterned into a predetermined shape by a photolithography method to form a second insulating film 255. Next, a titanium thin film serving as the upper electrode 256 is laminated to a thickness of about 400 nm on the entire surface of the substrate in this state by a sputtering method or the like, and is patterned into a predetermined shape by a photolithography method.
56. Further, a transparent electrode film made of ITO or the like is laminated, and is patterned to form a pixel electrode 257 and a terminal electrode 258. Since the upper surface of the signal wiring 252 is covered with the first insulating film 254, the terminal electrode 258 is electrically connected to the signal wiring 252 by a tapered portion of the signal wiring 252.

The characteristics of the MIM element of the active matrix substrate thus obtained were evaluated in the same manner as in the first embodiment. As a result, the same effects as in the first embodiment were obtained.

In the first embodiment, the tapered portion of the signal wiring 32 shown in FIG. 6 is covered by the terminal electrode 38 at the terminal electrode 38, but the tapered portion of the signal wiring 32 is exposed at other portions. Therefore, the presence of foreign matter or the like between the exposed portion of the signal wiring 32 and the pixel electrode 37 causes the signal line 32 and the pixel electrode 37 to be electrically connected (short-circuited),
Pixel defects sometimes occurred. On the other hand, in the present embodiment, as shown in FIGS.
The tapered portion 52 is covered with the second insulating film 255.
As a result, the signal line 32 and the pixel electrode 37 in the sixth embodiment
The pixel defect occurrence rate due to the short circuit from 0% to 0.01% or more of the panel pixel number in the first embodiment.

(Embodiment 7) Embodiment 7 of the present invention is shown in FIG.
This will be described with reference to FIGS. 30 to 33 are views for explaining a method for manufacturing an active matrix substrate according to Embodiment 7 of the present invention, and are a plan view and a cross-sectional view of a two-terminal nonlinear element, a pixel electrode portion, and a terminal electrode portion.

First, almost the entire surface of the glass substrate 301 shown in FIGS.
The tantalum thin film to be the signal wiring 302 and the lower electrode 303 is stacked to a thickness of about 300 nm, and the entire surface of the tantalum thin film is anodized by anodization to obtain a thickness of about 60 nm.
A first insulating film 304 made of tantalum pentoxide having a thickness of nm is formed. Then, the signal wiring 302 and the lower electrode 3 are patterned by photolithography into a predetermined shape.
03. Next, silicon nitride to be the second insulating film 305 is laminated by P-CVD at about 300 ° C. at a thickness of about 300 nm and patterned into a predetermined shape by photolithography to form the second insulating film 305.

Next, a titanium thin film serving as the upper electrode 306 is laminated to a thickness of about 400 nm on the entire surface of the substrate in this state by sputtering or the like, and is patterned into a predetermined shape by photolithography to form the upper electrode 306. Furthermore, a transparent electrode film made of ITO or the like is laminated,
This is patterned to form a pixel electrode 307 and a terminal electrode 3
08 is formed. The upper surface of the signal wiring 302 is the first insulating film 3
04, the terminal electrode 308 is connected to the signal wiring 3
02 is electrically connected to the signal wiring 302 by a tapered portion. The first insulating film 304 and the upper electrode 306 are connected at an opening of the second insulating film 305 having a contact hole shape.

The characteristics of the MIM element of the active matrix substrate thus obtained were evaluated in the same manner as in the first embodiment. As a result, the same effects as in the first embodiment were obtained.

In the first embodiment, since the etched end of the first insulating film 34 shown in FIG. 4 is not covered with the second insulating film 35, the electric field tends to concentrate at that portion, and dielectric breakdown may occur. In the present embodiment, the etched end of the first insulating film 304 in FIG. 31 is covered with the second insulating film 305. As a result, the pixel defect occurrence rate due to dielectric breakdown in Embodiment 7 was reduced from 0.01% or more of the panel pixel number in Embodiment 1 to 0.005% or less.

[0067]

As described above, according to the present invention, the metal thin film formed on almost the entire surface of the substrate is anodized on a relatively large surface without being covered with the protective film. Therefore, since anodic oxidation is performed at a uniform formation current density,
An anodic oxide film having a uniform film quality is formed. In addition, since there is no step of printing the protective film, the protective film does not adhere to the region of the metal thin film that will become the switching element portion, so that an anodic oxide film of uniform film quality can be obtained. As a result, a two-terminal nonlinear element having uniform characteristics over the entire surface of the substrate can be obtained.

The method for manufacturing a two-terminal nonlinear element and the two-terminal nonlinear element according to the present invention are suitably applied to an active matrix type liquid crystal display device, and can provide a liquid crystal display device having a uniform in-plane distribution of display characteristics. .

A pair of two-terminal non-linear elements having opposite polarities of metal (lower electrode) -insulating film-metal (upper electrode) and metal (upper electrode) -insulating film-metal (lower electrode) are connected in series. With this configuration, the symmetry of the current-voltage characteristics of the MIM element is improved as compared with the case where the number of the two-terminal nonlinear element is one, and the afterimage or the like during panel lighting is reduced.

Further, by covering the etched end of the signal wiring and the etched end of the lower electrode exposed by the patterning after the anodic oxidation with the second insulating film, defects due to short circuit and dielectric breakdown can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional general two-terminal nonlinear element and a pixel electrode unit. (A) is a plan view, and (b) is a cross-sectional view taken along the line AA 'of (a).

FIG. 2 is a diagram showing a conventional general terminal electrode portion.
(A) is a plan view, and (b) is a cross-sectional view taken along the line XX 'of (a).

FIG. 3 is a plan view of a two-terminal nonlinear element and a pixel electrode unit according to the first embodiment of the present invention.

FIG. 4 is a cross-sectional view of a two-terminal nonlinear element (BB ′) according to the first embodiment of the present invention.

FIG. 5 is a plan view of a terminal electrode unit according to the first embodiment of the present invention.

FIG. 6 shows a terminal electrode portion (C-
It is sectional drawing of (C 'part).

FIG. 7 is a plan view of a two-terminal nonlinear element and a pixel electrode unit according to a second embodiment of the present invention.

FIG. 8 is a sectional view of a two-terminal nonlinear element part (DD ′ part) according to a second embodiment of the present invention.

FIG. 9 is a plan view of a terminal electrode unit according to a second embodiment of the present invention.

FIG. 10 shows a terminal electrode portion (E-
It is sectional drawing of E 'part).

FIG. 11 is a plan view of a two-terminal nonlinear element and a pixel electrode unit according to a third embodiment of the present invention.

FIG. 12 is a cross-sectional view of a two-terminal nonlinear element unit (FF ′) according to a third embodiment of the present invention.

FIG. 13 is a cross-sectional view of a two-terminal nonlinear element (GG ′) according to Embodiment 3 of the present invention.

FIG. 14 is a plan view of a terminal electrode unit according to Embodiment 3 of the present invention.

FIG. 15 shows a terminal electrode portion (H-
(H 'section).

FIG. 16 is a plan view of a two-terminal nonlinear element and a pixel electrode unit according to a fourth embodiment of the present invention.

FIG. 17 is a sectional view of a two-terminal nonlinear element part (II ′ part) according to a fourth embodiment of the present invention.

FIG. 18 is a cross-sectional view of a two-terminal nonlinear element part (JJ ′ part) according to a fourth embodiment of the present invention.

FIG. 19 is a plan view of a terminal electrode unit according to Embodiment 4 of the present invention.

FIG. 20 is a diagram showing a terminal electrode portion (K-
(K 'section).

FIG. 21 is a plan view of a two-terminal nonlinear element and a pixel electrode unit according to a fifth embodiment of the present invention.

FIG. 22 is a sectional view of a two-terminal nonlinear element part (LL ′ part) according to a fifth embodiment of the present invention.

FIG. 23 is a plan view of a terminal electrode unit according to Embodiment 5 of the present invention.

FIG. 24 is a diagram showing a terminal electrode portion (M-
(M 'section) is a sectional view.

FIG. 25 is a plan view of a two-terminal nonlinear element and a pixel electrode unit according to a sixth embodiment of the present invention.

FIG. 26 is a cross-sectional view of a two-terminal nonlinear element (NN ′) according to Embodiment 6 of the present invention.

FIG. 27 is a diagram illustrating a signal wiring unit (O-
FIG.

FIG. 28 is a plan view of a terminal electrode unit according to Embodiment 6 of the present invention.

FIG. 29 is a diagram showing a terminal electrode portion (P-
FIG.

FIG. 30 is a plan view of a two-terminal nonlinear element and a pixel electrode unit according to a fifth embodiment of the present invention.

FIG. 31 is a cross-sectional view of a two-terminal nonlinear element part (QQ ′ part) according to Embodiment 5 of the present invention.

FIG. 32 is a plan view of a terminal electrode unit according to Embodiment 5 of the present invention.

FIG. 33 shows a terminal electrode portion (R-
(R ′ section) is a sectional view.

[Explanation of symbols]

11, 31, 71, 111, 161, 211, 251,
301 glass substrate 12, 32, 72, 112, 162, 212, 252,
302 signal wiring 13, 33, 73, 113, 163, 213, 253,
303 Lower electrode 14 Insulating film 34, 74, 114, 164, 214, 254, 304
First insulating film 35, 75, 115, 165, 215, 255, 305
Second insulating films 15, 36, 76, 116, 166, 216, 256,
306 upper electrode 17, 37, 77, 117, 167, 217, 257,
307 pixel electrode 18, 38, 78, 118, 168, 218, 258,
308 terminal electrode 16 MIM element

Claims (12)

[Claims] 1. A method for manufacturing a plurality of two-terminal nonlinear elements having a lower electrode, an upper electrode, and a first insulating film sandwiched between the lower electrode and the upper electrode, the method comprising: Forming a metal thin film covering substantially the entire surface; anodizing the metal thin film to form an anodic oxide film on a surface layer of the metal thin film; etching the metal thin film and the anodic oxide film; Forming the lower electrode and the first insulating film of the plurality of two-terminal nonlinear elements. 2. The step of etching the metal thin film and the anodic oxide film includes forming the lower electrode and the first insulating film and forming a signal wiring having the anodic oxide film on a top surface. Forming a second insulating film covering the lower electrode and an etched end of the first insulating film after the etching step;
Forming an upper electrode covering at least a part of the first insulating film on the lower electrode.
3. The method for manufacturing a two-terminal nonlinear element according to item 1. 3. The step of forming the upper electrode covers at least a part of the first insulating film on the lower electrode and a part of the anodic oxide film formed on a top surface of the signal wiring. 3. The method according to claim 2, wherein the step of forming the upper electrode is performed.
Manufacturing method of terminal nonlinear element. 4. After the step of forming the upper electrode, a pixel electrode electrically connected to the upper electrode and a terminal electrode electrically connected to the signal wiring are formed using the same material. 4. The method according to claim 2, further comprising the step of: 5. A step of forming a terminal electrode and a pixel electrode using the same material on the substrate before the step of forming the metal thin film covering substantially the entire surface of the substrate, 4. The device according to claim 2, wherein a bottom surface of the signal wiring is electrically connected to the terminal electrode, and the lower electrode is formed to be electrically connected to the pixel electrode on a bottom surface of the lower electrode. 5. A method for manufacturing a two-terminal nonlinear element. 6. The method according to claim 4, wherein the upper electrode is formed of a material different from a material of the terminal electrode and the pixel electrode. 7. The method according to claim 4, wherein the upper electrode is formed of the same material as the material of the terminal electrode and the pixel electrode. 8. The step of forming the second insulating film includes a step of covering an etched end of the lower electrode and the first insulating film and an etched end of the signal wiring having the anodic oxide film on a top surface. 3. The method for manufacturing a two-terminal nonlinear element according to claim 2, which is a step of forming an insulating film. 9. The step of forming the second insulating film includes: depositing a second insulating film covering the lower electrode and the first insulating film; and etching the second insulating film, and 3. The method of manufacturing a two-terminal nonlinear element according to claim 2, further comprising: forming an opening at the center of the first insulating film. 10. The two-terminal nonlinear element according to claim 9, wherein a material of the second insulating film is made of a material different from a material of the first insulating film, and the second insulating film is selectively etched. Method. 11. A two-terminal nonlinear element having a lower electrode, an upper electrode, and a first insulating film sandwiched between the lower electrode and the upper electrode, wherein the first insulating film is The lower electrode is made of a film obtained by anodizing the surface layer, and is formed only on the top surface of the lower electrode. The side surface of the lower electrode is covered with a second insulating film made of a material different from the first insulating film. Two-terminal nonlinear element. 12. An active matrix substrate having a plurality of two-terminal nonlinear elements and signal wiring on a substrate, wherein the two-terminal nonlinear elements include a lower electrode, an upper electrode, the lower electrode, and the upper electrode. A first insulating film sandwiched between the first electrode and the second electrode, the first insulating film being made of a film obtained by anodizing a surface layer of the lower electrode, formed only on the top surface of the lower electrode, The top surface of the wiring is covered with a film obtained by anodizing the surface layer of the signal wiring, and the side surface of the lower electrode and the side surface of the signal wiring are formed of a second insulating film made of a material different from the first insulating film. Active matrix substrate covered.