JPH0572570A - Liquid crystal display device and production thereof - Google Patents

Abstract

PURPOSE:To form MIM elements having satisfactory nonlinearity and hardly causing dielectric breakdown in a high yield and to obtain a liquid crystal display device having excellent characteristics at a low cost. CONSTITUTION:A lower electrode pattern 2 of Al, etc., is formed on a substrate 1. A nonlinear resistance film 3 of a metal nitride, metal oxide or metal oxynitride having a higher metal content than stoichiometric ratio is formed on the entire surface of the substrate 1 except the external electrode leading part. The part of the resistance film 3 near the edge 7 of the electrode pattern 2 is converted into an insulating film 4 of a metal oxide or metal oxynitride having stoichiometric ratio. An upper electrode 5 is formed on the electrode pattern 2 with the resistance film 3 in-between so that it is connected to an image element electrode 6 disposed on the resistance film 3.

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 nonlinear resistance element in series with a liquid crystal for each pixel between a liquid crystal and a liquid crystal drive electrode.

[0002]

2. Description of the Related Art Generally, in a MIM element, when a non-linear resistance film is formed on a lower electrode pattern, step coverage of a non-linear resistance film against a step of the lower electrode pattern becomes a problem. However, this will cause dielectric breakdown of the device. Also, when patterning the lower electrode by an etching process,
The etching taper surface adversely affects the operation of the device, causing the device to fail or deteriorate. Therefore, as a means for solving the above problems, as shown in FIG.
-270027), a lower electrode 2 is formed on a substrate 1, the lower electrode 2 is anodized 3 and is covered with an intermediate layer 4 made of an insulating film, and the lower electrode 2 of the intermediate layer 4 is covered. There is one in which a hole is made in a portion corresponding to the flat portion and the upper electrode 5 is arranged in that portion so as to be connected to the pixel electrode 6.
This prevents the etching taper surface of the element lower electrode from being used as an element.

[0003]

However, in order to form the above structure, a photoresist process using a mask is generally used. Therefore, the mask alignment must be performed accurately while avoiding the tapered surface of the lower electrode. However, since the number of processes is increased, there is a problem that the yield is deteriorated and the cost is increased. Further, the above-mentioned conventional one uses SiN _x as the non-linear resistance film, but since it is usually formed by plasma CVD, it is necessary to raise the temperature to about 300 ° C., and the heat resistance of the substrate is required. It

It is an object of the present invention to provide a liquid crystal display device having excellent characteristics by forming MIM elements having good non-linearity which are less likely to cause dielectric breakdown defects with good yield and at low cost.

[0005]

SUMMARY OF THE INVENTION The present invention is an active matrix liquid crystal display device comprising two opposed transparent substrates, a liquid crystal layer held between the substrates, a non-linear resistance film provided between liquid crystal driving electrodes, and the like. In the case where the non-linear resistance film is a metal nitride film, a metal oxide film or a metal oxynitride film having a metal content higher than the stoichiometric ratio, at least on the lower electrode edge portion other than the lower electrode flat portion. The nonlinear resistance film is characterized in that it is self-selectively oxidized or nitrided to be a metal nitride, a metal oxide, or a metal oxynitride having a stoichiometric ratio.

Further, in the method of manufacturing a liquid crystal display device according to the above invention, in order to provide selectivity between the lower electrode flat portion and other portions, a photoresist using backside exposure using the lower electrode pattern as a mask is used. A resist pattern having the same shape as the lower electrode pattern is formed on the nonlinear resistance film by a method. The selective treatment of oxidation and nitridation is performed by anodic oxidation, plasma treatment or ion implantation. On the board
Using polymer films (PC, PES, NAP) such as glass and polyethylene terephthalate (PET),
The nonlinear resistance film is formed by a sputtering method, an ion plating method, or an ECR plasma reactive vapor deposition method.

Further, the present invention provides a lower electrode in an active matrix liquid crystal display device comprising two opposed transparent substrates, a liquid crystal layer held between the substrates, a non-linear resistance film provided between liquid crystal driving electrodes, and the like. It is characterized in that the non-linear resistance film and the insulating intermediate layer are formed by a photoresist method using back surface exposure using a pattern as a mask.

In the method of manufacturing the liquid crystal display device described above, the non-linear resistance film and the insulating intermediate layer are formed by a photoresist method using backside exposure using the lower electrode pattern as a mask. First, lift-off using a positive resist is used to form an insulating intermediate layer on a portion other than the lower electrode pattern, and lift-off using a negative resist is used to form a nonlinear resistance film on the lower electrode pattern. To form. Substrates include glass and polyethylene terephthalate (P
Polymer films such as ET) (PC, PES, NAP)
Is used to form the non-linear resistance film by a sputtering method, an ion plating method, or an ECR plasma reactive vapor deposition method.

[0009]

EXAMPLES Next, the present invention will be described based on examples.

FIG. 1 shows an embodiment of the liquid crystal display device according to the present invention. A lower electrode pattern 2 made of Al or the like is formed on a substrate 1, and a metal nitride, a metal oxide, or a metal oxide having a metal content higher than a stoichiometric ratio is formed on the entire surface of the substrate 1 excluding the external electrode lead-out portion. A non-linear resistance film 3 made of nitride is formed. In addition, the non-linear resistance film 3 near the edge portion 7 of the lower electrode pattern 2 is oxidized to form an insulating film 4 made of a metal oxide or a metal oxynitride that matches the stoichiometric ratio. An upper electrode 5 is provided above 2 via a non-linear resistance film 3, and the top electrode 5 is connected to a pixel electrode 6 arranged on the non-linear resistance film 3. FIG. 3 is a plan view of this.

In the method of manufacturing the liquid crystal display device, as shown in FIG. 4, first, the lower electrode pattern 2 is formed on the substrate 1, and the entire surface of the substrate 1 excluding the external electrode lead-out portion is higher than the stoichiometric ratio. A non-linear resistance film 3 made of metal nitride, metal oxide or metal oxynitride having a high metal content is formed. Further, a positive resist 8 is applied on the entire surface of the substrate 1 from above. Next, back surface exposure is performed using the lower electrode pattern 2 as a mask to form a resist pattern 8a on the flat portion of the lower electrode 2 of the nonlinear resistance film 3 as shown in FIG. The resist pattern 8a is formed with a width narrower than that of the lower electrode pattern 2 so as not to be applied onto the lower electrode edge 7 due to light wraparound during exposure and irregular reflection in the resist.

Next, the non-linear resistance film 3 is anodized using the lower electrode pattern 2 as an anode. In anodization,
Since self-selective oxidation is carried out from the portion where the resistance is low and the current easily flows, the reaction occurs from the vicinity of the edge portion 7 of the lower electrode 2 where the thickness of the nonlinear resistance film is thin. As a result, as shown in FIG. 1, the non-linear resistance film 3 near the lower electrode edge portion 7 becomes an insulating film 4 made of a metal oxide film or a metal oxynitride film having a stoichiometric ratio, and other non-linear films are formed. The insulating property is higher than that of the resistance film portion 3, and the element portion is specified in the flat portion of the lower electrode 2 excluding the lower electrode edge portion 7.

Further, not only the thin film portion but also the defective portion which is apt to cause the dielectric breakdown can be made into the insulating film in a self-selective manner by this step.
Dielectric breakdown of the device can be dramatically reduced. The anodic oxidation needs to be performed until the edge portion of the lower electrode is completely oxidized. In addition, the anodic oxidation is a strong acid type,
It is possible to use either a weak acid type liquid, but it is preferable to use a weak acid type liquid such as tartaric acid which can obtain a non-porous one. After the above process is completed, the resist pattern 8a is removed to form the upper electrode 5 and the pixel electrode 6 to form one pixel of the liquid crystal display device. In the MIM element thus formed, the functional portion as an element is limited by the metal compound layer having a stoichiometric ratio, so that the characteristics are stable and the yield is improved.

A second embodiment of the present invention will be described. The same parts as those in the previous embodiment are designated by the same reference numerals and the description thereof will be omitted.

In the liquid crystal display device according to the second embodiment, as shown in FIG. 2, the lower electrode pattern 2 is formed on the substrate 1, and the flat portion of the lower electrode 2 and the external electrode lead-out portion are excluded. A non-linear resistance film 3 made of metal nitride or the like having a metal content higher than the stoichiometric ratio is formed on the entire surface of the.
An insulating film 4 made of a metal oxide or a metal oxynitride having a stoichiometric ratio is formed on the non-linear resistance film 3 except the edge portion 7 of the lower electrode pattern 2 and the flat portion of the lower electrode 2. Are arranged.

The method of manufacturing this liquid crystal display device will be described with reference to FIGS.
Up to the formation of the structure is the same as in the previous embodiment. afterwards,
A portion other than the resist pattern 8a is nitrided or oxidized by plasma treatment or ion implantation to obtain a metal nitride, a metal oxide or a metal oxynitride having a stoichiometric ratio. The metal compound layer that is in the stoichiometric ratio needs to have a thickness that covers at least the edge portion 7 of the lower electrode 2 as shown in FIG. However, even if all of the non-linear resistance film 3 other than on the lower electrode pattern 2 is replaced with a metal compound layer having a stoichiometric ratio, there is no problem as long as the lower electrode has sufficient conductivity for signal transmission. After the above process is completed, the upper electrode and the pixel electrode are formed to form one pixel of the liquid crystal display device.

The MIM element thus formed is
Since the functional portion as an element is limited by the metal compound layer having a stoichiometric ratio, the characteristics are stable and the yield is improved.

Next, a third embodiment of the present invention will be described. The same parts as those in the first and second embodiments are designated by the same reference numerals and the description thereof will be omitted.

The liquid crystal display device according to the third embodiment is shown in FIG.
As shown in (g), the lower electrode 2 is formed on the substrate 1, and an AlN film conforming to the stoichiometric ratio is provided on the entire surface of the substrate 1 excluding the flat upper surface of the lower electrode 2. ing.
Further, a non-linear resistance film 3a is arranged on a flat upper surface of the lower electrode 2, and an upper electrode 5 is provided on the nonlinear resistance film 3a and connected to the pixel electrode 6.

In this method of manufacturing a liquid crystal display device, first, as shown in FIG. 6A, an electrode pattern 2 is formed on a substrate 1.
Is formed by using lift-off using a resist, a positive resist 9 is applied to the entire surface of the substrate 1, and back surface exposure is performed using the electrode pattern 2 as a mask.
A resist pattern 9a is formed on top. In this step, by performing the back surface exposure using the electrode pattern as a mask, it is not necessary to separately prepare a mask, and complicated work such as mask alignment can be omitted. Next, as shown in FIG. 6B, an AlN film 4 having a stoichiometric ratio, for example, is formed on the entire surface of the substrate 1 as an insulating intermediate layer.
The electrode pattern 2 is formed thicker than the electrode pattern 2 by a sputtering method, an ion plating method, an ECR plasma reactive vapor deposition method, or the like, which can form a film without heating, and lift-off is performed as shown in FIG. The insulating film 4 is left on.

Next, as shown in FIG. 6D, a negative resist 10 is applied to the entire surface of the substrate 1 and backside exposure is performed using the electrode pattern as a mask to form an opening on the electrode 2.
In this step, by performing the back surface exposure using the electrode pattern 2 as a mask, it is not necessary to separately prepare a mask, and complicated work such as mask alignment can be omitted. Through the above steps, the contact portion between the lower electrode of the MIM element and the non-linear resistance film can be specified to the portion excluding the edge portion of the lower electrode 2, and the problem of element failure due to the influence of the edge portion can be solved. ..

Next, as shown in FIGS. 6 (e) and 6 (f),
By a sputtering method, an ion plating method, an ECR plasma reaction deposition method, or the like, which can form a film on the entire surface of the substrate 1 without heating,
For example, AlN _x (x <1) or the like in which the resistance value shows nonlinearity 3
And the resist is lifted off to form the non-linear resistance film 3 only on the electrode pattern 2. AlN _x is
It is a material that can control the nonlinearity of the resistance by changing the value of x. Next, the upper electrode 5 and the pixel electrode 6 are sequentially formed by a photoresist process.

In the above embodiments, the photoresist is subjected to backside exposure using the g-line (436 nm) of a mercury lamp. The substrate 1 is 400 nm as well as glass.
, P having high transmittance of 80% or more at the wavelength of
There is no problem even if it is a polymer film such as C, PES or NAP. In addition, the AlN film formed on the substrate and having a stoichiometric ratio also has a thickness of 80 nm at a wavelength of 300 nm or more.
Since it has a high transmittance of not less than%, it does not hinder the practice of the present invention.

Regarding the substrate temperature at the time of forming the MIM element, since the low temperature film forming process such as the sputtering method, the ion plating method and the ECR plasma reactive vapor deposition method is used, the above-mentioned polymer film can be sufficiently dealt with. Further, when such a polymer film is used as a substrate, a phenomenon that the substrate shrinks during the film forming process is observed. For this reason, the conventional method causes misalignment of the mask pattern, resulting in a MIM element. Although there is a problem that it is not possible to accurately form the portion, according to the present invention, it is possible to accurately finish the configuration of the lower electrode and the non-linear resistance film without using a separate mask, and also to the polymer film substrate. I can handle it enough. Further, in the conventional method, since the pixel electrode is formed directly on the substrate, deterioration of the pixel electrode due to the influence of the substrate becomes a problem when a polymer film substrate is used. The AlN layer having a stoichiometric ratio provided as a layer serves as a passivation film, and the problem of deterioration of the pixel electrode can be solved.

[0025]

Since the present invention is constructed as described above, it has the following effects. According to claim 1, only the flat portion of the lower electrode is specified, and the MIM
It can be used as an element portion, which can prevent the dielectric breakdown at the lower electrode edge portion that frequently occurs, and can dramatically improve the yield. Claims 2 and 4
As a result, only the vicinity of the lower electrode edge portion of the non-linear resistance film can be oxidized. According to the third and fourth aspects, a portion of the nonlinear resistance film other than the flat portion of the lower electrode can be oxidized or nitrided. According to claim 4, the mask can be omitted to simplify the process, and the cost can be reduced. Further, it is possible to realize accurate patterning. According to the fifth and sixth aspects, in the formation of the non-linear resistance film and the insulating intermediate layer, the photoresist method can be performed without the need for a separate mask, and complicated work such as mask alignment can be omitted. You can According to claim 7, the insulating intermediate layer can be used as a passivation film, and deterioration of the pixel electrode can be prevented. According to the seventh and eighth aspects, the MIM element portion can be specified in the portion excluding the edge portion of the lower electrode, defect and deterioration of the element can be eliminated, and a liquid crystal display device having good nonlinear characteristics can be formed. .. According to claim 9, it is possible to deal with a flexible liquid crystal display device. According to claim 10, low temperature film formation is possible, and MIM can be formed on the polymer film.

[Brief description of drawings]

FIG. 1 is a sectional view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a sectional view of a liquid crystal display device according to a second embodiment of the present invention.

FIG. 3 is a plan view of a liquid crystal display device according to an embodiment of the present invention.

FIG. 4 is a diagram showing part of the process of manufacturing a liquid crystal display device according to an embodiment of the present invention.

FIG. 5 is a diagram showing a part of the manufacturing process of the liquid crystal display device according to the embodiment of the present invention.

6A to 6F are diagrams showing a manufacturing process of a liquid crystal display device according to a third embodiment of the present invention, and FIG. 6G is a liquid crystal display device according to the third embodiment of the present invention. FIG.

FIG. 7 is a cross-sectional view of a conventional MIM type liquid crystal display device.

[Explanation of symbols]

 1 substrate 2 lower electrode 3 non-linear resistance film 4 insulating film 5 upper electrode 6 pixel electrode

Claims (10)

[Claims] 1. An active matrix liquid crystal display device comprising two opposed transparent substrates, a liquid crystal layer held between the substrates, a non-linear resistance film provided between liquid crystal driving electrodes, and the like. In a metal nitride film, a metal oxide film, or a metal oxynitride film having a metal content higher than the stoichiometric ratio, at least the non-linear resistance film on the lower electrode edge portion other than the lower electrode flat portion is oxidized or nitrided. And a liquid crystal display device characterized by using a metal nitride, a metal oxide, or a metal oxynitride that has a stoichiometric ratio. 2. The non-linear resistance film in the vicinity of the edge portion of the lower electrode and the low resistance portion in the film are self-selectively oxidized or nitrided by anodic oxidation using the lower electrode pattern as an anode to obtain a stoichiometric ratio. The method for producing a liquid crystal display device according to claim 1, wherein the metal oxide or the metal oxynitride is used. 3. A metal nitride or a metal oxide having a stoichiometric ratio by self-selectively oxidizing or nitriding a portion of the nonlinear resistance film other than a flat portion of the lower electrode by plasma treatment or ion implantation. Alternatively, the method of manufacturing a liquid crystal display device according to claim 1, wherein the metal oxynitride is used. 4. The non-selected portion of oxidation or nitridation is formed on the non-linear resistance film by a photoresist method using back surface exposure using the lower electrode pattern as a mask. Liquid crystal display device manufacturing method. 5. An active matrix liquid crystal display device comprising two transparent substrates facing each other, a liquid crystal layer held between the substrates, a non-linear resistance film provided between liquid crystal driving electrodes, and the like. A non-linear resistance film and an insulating intermediate layer are formed by a photoresist method using the backside exposure described above. 6. A nonlinear resistance film and an insulating intermediate layer,
6. The method for manufacturing a liquid crystal display device according to claim 5, wherein the method is performed by a photoresist method using backside exposure using the lower electrode pattern as a mask. 7. The method of manufacturing a liquid crystal display device according to claim 5, wherein the insulating intermediate layer is formed on a portion other than the flat portion of the lower electrode pattern by utilizing lift-off using a positive resist. .. 8. The method of manufacturing a liquid crystal display device according to claim 5, wherein the non-linear resistance film is formed on the flat portion of the lower electrode pattern by utilizing lift-off using a negative resist. 9. A substrate and a polymer film (PC, PE) such as glass and polyethylene terephthalate (PET).
S, NAP) is used, The manufacturing method of the liquid crystal display device of Claim 1, 5 characterized by the above-mentioned. 10. The method of manufacturing a liquid crystal display device according to claim 1, wherein the nonlinear resistance film is formed by a sputtering method, an ion plating method, or an ECR plasma reactive vapor deposition method.