JPH0743749A - Two-terminal nonlinear element and its production - Google Patents

Abstract

PURPOSE:To form a uniform liquid crystal panel having good display characteristics. CONSTITUTION:Anodically oxidized films 4 on the flanks of a lower electrode 2 are formed to a film thickness larger than the film thickness of the anodically oxidized film 5 on the front surface thereof by conducting a stage for etching the lower electrode 2, a stage for anodically oxidizing the lower electrode 2 while allowing a photosensitive resin 3 to remain and conducting the anodic oxidation again with a voltage lower than the previous time after this photosensitive resin 3 is peeled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a two-terminal non-linear element used as a switching element in a liquid crystal display device and a method for manufacturing the non-linear element.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices have been used as AV (Audio Visual).
sual), OA (Office Automation), and various other fields. Especially Low e
nd (Twisted Nematic), STN (S
High-quality products are equipped with passive type liquid crystal display devices such as upper twisted nematic (Twisted Nematic) type.
A liquid crystal display device of an active matrix drive system using a transistor as a switching element is mounted.

The liquid crystal display device of the active matrix drive system has the characteristics of color reproducibility superior to that of a CRT (Cathode Ray Tube), thinness and lightness, and low power consumption, and its application is rapidly expanding. is doing. However, when a TFT is used as a switching element,
For its manufacture, a thin film forming step and a photolithography step are required 6 to 8 times or more, and the reduction of cost is the most important issue.

On the other hand, two switching elements are used.
The liquid crystal display device using the terminal non-linear element has a cost advantage over the liquid crystal display device using the TFT and has a display quality advantage over the passive type liquid crystal display device. Have shown rapid development.

As the above-mentioned two-terminal non-linear element, the Schottky diode method, the varistor method, and the MIM have long been used.
(Metal-Insulator-Metal) type is known, and in recent years, D ² R (Double Diode Plus Rese)
The t) method and the organic ferroelectric thin film method are being researched and developed. However, MIM is currently in practical use.
System and D ² R system two-terminal non-linear element only. Among them, MIM type two-terminal non-linear element (MIM element)
Has a structure in which an upper electrode is formed on a lower electrode with an insulating layer interposed therebetween. A Ta thin film is used as a lower electrode, and this is anodized by an anodizing method to form an insulating layer. In addition, an upper electrode made of Ta, Ti, Al or the like may be further formed on this structure. MI above
The M element can be manufactured by one third or less of the manufacturing process as compared with the TFT. Therefore, the liquid crystal display device using the MIM element as the switching element occupies the mainstream of the two-terminal non-linear element liquid crystal display device.

The MIM element has a structure in which an insulating film is interposed between the lower electrode and the upper electrode.

FIG. 4 is a cross-sectional view of a conventional two-terminal non-linear element, and the process of making this liquid crystal cell is performed as follows.

The lower electrode 32 is formed of a tantalum thin film on the insulating substrate 31 by the sputtering method, and the surface thereof is anodized by the anodizing method to form an anodized film 33 of tantalum pentoxide. Next, a resist 34 is applied to the entire surface, the entire surface of the insulating substrate 31 is exposed from the back surface thereof, and then the insulating film 3 is patterned by the plasma CVD method.
5 is made of silicon nitride. After that, the resist 34 and the insulating film 35 on the upper surface thereof are separated by a lift-off method in which the resist 34 is removed to simultaneously remove the upper insulating film 35. Then, the upper electrode 36 is formed of indium tin oxide by the sputtering method to form the two-terminal nonlinear element. (JP-A-3-52277) In a liquid crystal display device using the above-mentioned two-terminal non-linear element, there is a problem of afterimage caused by positive / negative asymmetry of voltage-current characteristics of the element,
Various improvements have been made to address the problem of crosstalk caused by device capacitance and liquid crystal layer capacitance.
For example, the formation of the insulating layer, which is the basic technology of the present invention, is usually performed by anodizing the lower electrode.
The above-mentioned anodizing method is a technology that has been established for a long time as disclosed in Japanese Patent Publication No. 46-17267, but an insulator layer with high throughput and excellent productivity is provided. Is a way that can be obtained.

[0009]

When a two-terminal non-linear element is formed in a liquid crystal display device, the capacitance of the element has a great influence on the display characteristics of the panel. In other words, the element capacity (hereinafter referred to as C _MIM ) is the capacity of the liquid crystal portion (hereinafter referred to as C _LC
It is said that the display characteristics are better as it is sufficiently smaller than the above (1), and normally the display characteristics are best in the range of C _MIM / C _LC ≧ 1/10. However, as the definition of the panel becomes higher, the pixel area tends to become smaller, and the capacitance C _{LC of the} liquid crystal portion also decreases accordingly. for that reason,
In order to maintain good display characteristics, it becomes necessary to reduce the element capacitance C _MIM . However, when the pattern of the lower electrode is simply thinned to reduce C _MIM , the pattern accuracy is deteriorated, which causes a variation in display within the panel. The present invention has been made to solve the above problems, and an object of the present invention is to provide a two-terminal nonlinear element having a small element capacitance and a manufacturing method thereof, without changing the patterning accuracy.

[0010]

A two-terminal non-linear element of the present invention is formed by anodizing a substrate, a lower electrode formed of a metal thin film on the substrate, and a surface layer of the lower electrode. In a two-terminal non-linear element including an anodized film and an upper electrode made of a metal thin film formed so as to cover the anodized film, the anodized film has a top surface thinner than a side surface. It is characterized by being formed,
Thereby, the above object is achieved.

A method of manufacturing a two-terminal non-linear element according to the present invention comprises:
Substrate, lower electrode made of metal thin film disposed on the substrate, anodized film formed by anodizing the surface layer of the lower electrode, and metal formed so as to cover the anodized film In a two-terminal nonlinear element including an upper electrode made of a thin film, a step of applying a resin on the lower electrode, a step of etching the lower electrode, and anodization with the resin left on the lower electrode The method is characterized by including a step and a step of performing anodic oxidation again at a lower voltage than the previous step after peeling off the resin, thereby achieving the above object.

The method for manufacturing a two-terminal non-linear element according to the present invention includes a substrate, a lower electrode formed of a metal thin film on the substrate, and an anode formed by anodizing the surface layer of the lower electrode. In a two-terminal non-linear element including an oxide film and an upper electrode made of a metal thin film formed so as to cover the anodized film, two kinds of anodizable metals are continuously formed in two layers. A step, a step of applying a resin on the two-layer metal, and a step of patterning the two-layer metal,
After removing the resin, a step of anodizing the two layers of metal, and etching the upper metal and the anodic oxide film of the upper metal of the two layers of metal, and then lowering the lower metal to a lower level than in the previous step The method is characterized by including a step of performing anodic oxidation again with a voltage, whereby the above object is achieved.

Further, according to the method of manufacturing a two-terminal nonlinear element of the present invention, a substrate, a lower electrode formed of a metal thin film on the substrate, and an anode formed by anodizing the surface layer of the lower electrode. In a two-terminal nonlinear element including an oxide film and an upper electrode formed of a metal thin film so as to cover the anodic oxide film, after forming a metal capable of anodic oxidation,
A step of continuously forming an insulating film on the metal; a step of patterning the metal and the insulating film; a step of anodizing the metal and the insulating film with the insulating film left; After peeling, the step of re-anodizing the metal at a voltage lower than that in the previous step is included, whereby the above object is achieved.

[0014]

According to the present invention, the anodic oxide film formed by anodizing the surface layer of the lower electrode has a thickness of the upper surface smaller than that of the side surface by the means for solving the above problems. As a result, the element area can be reduced, and a two-terminal nonlinear element having a small element capacitance can be formed.
The reason will be described below.

Tantalum, which is often used as the lower electrode, is reduced at a rate of 7 Å / V by anodic oxidation for 1 hour, and tantalum oxide is deposited at a rate of 17 Å / V. For example, when the first anodic oxidation is performed at 250 V, a total of 0.35 μm of tantalum is anodized on both sides of the device. Here, the tantalum electrode has a width of 5 μm and a film thickness of 300.
If it is 0 Å, this anodic oxidation will reduce the electrode width to 4.65 μm. Also,
Assuming that the film thickness of the anodic oxide film on the top surface of the device is 650 angstroms, the film thickness of tantalum oxide on the side surface part of the device is 3250 angstroms. When the element capacitance is calculated from these, it can be seen that the capacitance of the two-terminal nonlinear element of the present invention is reduced by about 15% as compared with the capacitance of the conventional two-terminal nonlinear element.

As described above, the two-terminal nonlinear element according to the present invention can reduce the element capacitance without deteriorating the pattern accuracy, so that it is possible to form a uniform liquid crystal panel having good display characteristics. You can do it.

[0017]

EXAMPLES The present invention will be described in detail below with reference to specific examples.

(Embodiment 1) FIG. 1 is a sectional view showing a two-terminal non-linear element used in one embodiment of the present invention and a manufacturing method thereof. First, a tantalum thin film having a thickness of about 1000 to 3000 angstroms is formed as the lower electrode 2 on the transparent insulating substrate 1, a photosensitive resin 3 is applied on the lower electrode 2, and a predetermined pattern is exposed. Next, development is performed and etching is performed. At this time, instead of the photosensitive resin 3, a resin may be patterned by using a printing method. Next, the tantalum thin film that is the lower electrode 2 is anodized while leaving the photosensitive resin 3 on the above-described pattern to form a tantalum oxide film that will be the anodized film 4. The anodizing chemical solution was 1 wt% ammonium borate and the anodizing voltage was 100 to 250V. At this time, only the side surface of the tantalum thin film which is the lower electrode 2 is anodized, and the upper surface of the photosensitive resin 2 on the lower electrode 2 is not anodized. Next, after peeling off the photosensitive resin 3, a voltage 2 lower than the anodizing voltage is applied.
Anodization is performed again at 0 to 50 V to form a tantalum oxide film to be the anodized film 5 on the upper surface of the lower electrode 2 made of tantalum. Through the above steps, the thickness of the anodic oxide film 5 on the upper surface of the lower electrode 2 can be made smaller than that of the anodic oxide film 4 on the side surface of the lower electrode 2.
Used as the terminal non-linear element part.

Finally, aluminum is formed on the anodic oxide film 5 thus formed, and the upper electrode 6 is formed by performing a predetermined patterning. Here, the lower electrode 2 is not limited to a tantalum thin film, and may be anodized and can be easily formed by sputtering or the like.
Niobium can also be used. Further, the upper electrode 6 is not limited to aluminum as long as it can be easily formed by a sputtering method, a vacuum deposition method or the like, and for example, titanium, chromium, niobium or the like can be used. The two-terminal non-linear element thus formed can reduce the element capacitance without changing the line width of the lower electrode 2, so that it is possible to form a liquid crystal panel having good display characteristics and uniform.

It is needless to say that the two-terminal nonlinear element of the present invention is not limited to the above embodiment, and the manufacturing method thereof is not limited to that of the above embodiment.

(Embodiment 2) FIG. 2 is a sectional view showing a two-terminal non-linear element used in one embodiment of the present invention and a manufacturing method thereof. First, on the transparent insulating substrate 11, the first
Tantalum thin film as the metal layer 12 of 1000 to 3000
After being formed to a thickness of about angstrom, aluminum is continuously used as the second metal layer 13 in an amount of 1000 to 200.
It is formed with a thickness of about 0 angstrom. A photosensitive resin is applied on the second metal layer 13, a predetermined pattern is exposed, and then development is performed to form the first and second metal layers 12,
Two layers of 13 are simultaneously etched, and peeling is performed. next,
Anodization of the tantalum thin film, which is the first metal layer 12, is performed while leaving the aluminum, which is the second metal layer 13, on the pattern described above. The chemical solution for this anodic oxidation is 1 wt% ammonium borate and the anodic oxidation voltage is 100.
~ 250V. At this time, aluminum oxide serving as an anodized film is formed on the surface of the aluminum, and tantalum oxide serving as an anodized film 14 is formed on the side surface of the tantalum thin film which is the first metal layer 12. There is. Next, the second metal layer 13 made of aluminum and the anodic oxide film 15 made of aluminum oxide are formed at 50 ° C.
Peel off with phosphoric acid. After that, the remaining tantalum thin film of the first metal layer 12 is anodized again at a voltage of 20 to 50 V, which is lower than the anodization voltage, to form the anodized film 17.
A tantalum oxide film to be formed is formed on the upper surface of the first metal layer 12 made of tantalum. Through the above steps, the thickness of the anodic oxide film 17 on the upper surface of the first metal layer 12 can be made smaller than that of the anodic oxide film 14 on the side surface of the first metal layer 12. 17 is used as a two-terminal nonlinear element portion. Finally, aluminum is formed on the anodic oxide film 17 formed as described above, and the upper electrode 16 is formed by performing predetermined patterning.

Here, the first metal layer 12 is not limited to a tantalum thin film, and it is sufficient that it can be anodized and can be easily formed by sputtering or the like. For example, aluminum, titanium, niobium, etc. are also used. Is possible. The second metal layer 13 is not limited to aluminum, can be anodized, can be easily formed by sputtering, and the first metal layer 12 can also be formed.
It is preferable that the etching be easier than that, and titanium, niobium, or the like can be used, for example. Further, the upper electrode 16 is not limited to aluminum as long as it can be easily formed by sputtering, vacuum deposition, or the like, and titanium, chromium, or the like can also be used.

The two-terminal nonlinear element thus formed can reduce the element capacitance without changing the line width of the lower electrode (the first metal layer in the second embodiment) 13.
It is possible to form a liquid crystal panel having good display characteristics and uniform.

Needless to say, the two-terminal non-linear element of the present invention is not limited to the above embodiment, and the manufacturing method thereof is not limited to that of the above embodiment.

(Embodiment 3) FIG. 3 is a sectional view showing a two-terminal nonlinear element used in an embodiment of the present invention and a method of manufacturing the same. First, a tantalum thin film having a thickness of about 1000 to 3000 angstroms is formed as the lower electrode 22 on the transparent insulating substrate 21, and then silicon nitride having a thickness of about 1000 to 3000 angstroms is continuously formed as the insulating film 23. A photosensitive resin is applied on the insulating film 23, a predetermined pattern is exposed, and then development is performed to simultaneously etch two layers of the lower electrode 22 and the insulating film 23 to separate them. Next, the tantalum thin film that is the lower electrode 22 is anodized while leaving the insulating film 23 on the pattern described above. The anodizing chemical solution is 1 wt% ammonium borate and the anodizing voltage is 1
It was set to 00-250V. At this time, tantalum oxide serving as the anodic oxide film 24 is formed on the side surface of the tantalum thin film serving as the lower electrode 22. Next, the insulating film 23 made of silicon nitride is peeled off with a buffered hydrofluoric acid. Then, the remaining tantalum thin film of the lower electrode 22 is anodized again at a voltage of 20 to 50 V lower than the anodizing voltage,
A tantalum oxide film to be the anodic oxide film 25 is formed on the upper surface of the lower electrode 22 made of tantalum. By the above process,
The anodic oxide film 25 on the upper surface of the lower electrode 22 can be made thinner than the anodic oxide film 24 on the side surface of the lower electrode 22, and this anodic oxide film 25 is used as a two-terminal nonlinear element portion. Finally, aluminum is formed on the anodic oxide film 25 formed as described above, and predetermined patterning is performed to form the upper electrode 26.

Here, the lower electrode 22 is not limited to a tantalum thin film and can be anodized and can be easily formed by sputtering or the like. For example, aluminum, titanium, niobium or the like can be used. is there. The insulating film 23 is not limited to silicon nitride as long as it can be easily formed by sputtering, vacuum deposition, CVD, or the like. For example, silicon oxide or tantalum oxide can be used. is there. Further, the upper electrode 26 is not limited to aluminum as long as it can be easily formed by a sputtering method or a vacuum deposition method, and titanium, chromium, niobium or the like can be used.

Since the two-terminal non-linear element thus formed can reduce the element capacitance without changing the line width of the lower electrode 22, it is possible to form a uniform liquid crystal panel having good display characteristics.

It is needless to say that the two-terminal nonlinear element of the present invention is not limited to the above embodiment and the manufacturing method thereof is not limited to that of the above embodiment.

[0029]

As described above, in the two-terminal nonlinear element according to the present invention, it is possible to easily make the anodic oxide film on the upper surface thinner than the anodic oxide film on the side surface of the lower electrode arranged on the substrate. Therefore, it is possible to realize a two-terminal non-linear element having a small element capacitance without changing the patterning accuracy, and thus it is possible to form a uniform liquid crystal panel having good display characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a two-terminal nonlinear element and a method for manufacturing the same according to the present invention.

FIG. 2 is a cross-sectional view showing an embodiment of a two-terminal nonlinear element and a method for manufacturing the same according to the present invention.

FIG. 3 is a cross-sectional view showing one embodiment of a two-terminal nonlinear element and a method for manufacturing the same according to the present invention.

FIG. 4 is a cross-sectional view showing a conventional two-terminal non-linear element and a method for manufacturing the same.

[Explanation of symbols]

 1, 11, 21, 31 Transparent insulating substrate 2, 22, 32 Lower electrode 12 First metal layer 3 Photosensitive resin 13 Second metal layer 23, 35 Insulating film 15, 33 Anodized film 34 Resist 4, 14 , 24 Anodized film (side surface of electrode) 5, 17, 25 Anodized film (upper surface of electrode) 6, 16, 26, 36 Upper electrode

Claims (4)

[Claims] 1. A substrate, a lower electrode formed of a metal thin film on the substrate, an anodized film formed by anodizing a surface layer of the lower electrode, and an anodized film covering the anodized film. A two-terminal non-linear element including an upper electrode formed of a metal thin film, wherein the anodic oxide film is formed so that the film thickness on the upper surface is thinner than the film thickness on the side surface. . 2. A substrate, a lower electrode formed of a metal thin film on the substrate, an anodized film formed by anodizing a surface layer of the lower electrode, and an anodized film covering the anodized film. In a two-terminal non-linear element including an upper electrode formed of a metal thin film formed as described above, a step of applying a resin on the lower electrode, a step of etching the lower electrode, and a step of leaving the resin on the lower electrode. A method of manufacturing a two-terminal non-linear element, comprising: a step of performing anodic oxidation as it is, and a step of performing anodic oxidation again at a lower voltage than the previous step after peeling off the resin. 3. A substrate, a lower electrode formed of a metal thin film disposed on the substrate, an anodized film formed by anodizing a surface layer of the lower electrode, and an anodized film covering the anodized film. In a two-terminal non-linear element consisting of an upper electrode composed of a metal thin film formed by forming a metal thin film, a step of continuously forming two kinds of anodizable metals in two layers, and a resin on the two layers of metal. A step of applying, a step of patterning the metal of the two layers, a step of anodizing the metal of the two layers after peeling the resin, After the etching of the anodic oxide film, a step of performing anodic oxidation on the lower metal again at a voltage lower than that in the previous step is included. 4. A substrate, a lower electrode formed of a metal thin film disposed on the substrate, an anodized film formed by anodizing a surface layer of the lower electrode, and an anodized film covering the anodized film. A two-terminal non-linear element including an upper electrode made of a metal thin film formed by forming an anodizable metal, and then forming an insulating film continuously on the metal; and the metal and the insulating film. A step of patterning, a step of anodizing the metal and the insulating film with the insulating film left, and a step of peeling the insulating film and then anodizing the metal again at a lower voltage than the previous step. A method for manufacturing a two-terminal non-linear element, comprising: