JP3285383B2 - Liquid crystal display device and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a liquid crystal display device which drives a liquid crystal by controlling MIM (metal layer-insulator layer-metal layer) elements which are non-linear elements arranged in a matrix, and this structure. And a manufacturing method for forming the same.

[0002]

2. Description of the Related Art M formed by using two photomasks
When the IM device is used as a switching device,
991, SID DIGEST, p219. The MIM element described in this document will be described with reference to the cross-sectional view of FIG. 5 and the circuit diagram of FIG.

As shown in FIGS. 5 and 6, a row electrode 13 is formed on one substrate 12, a pixel electrode 15 is formed on an anodic oxide layer 14, and a plurality of MIM elements 32 are arranged.
A scanning electrode 31 is formed on the other substrate, a liquid crystal 33 is injected between the two substrates, and a MIM element 3 serving as a switching element is formed.
2 to display an image.

A method of manufacturing the MIM element having the conventional structure is described as follows.
This will be described with reference to FIG.

[0005] A tantalum layer is formed to a thickness of 200 nm on a substrate 12 made of glass by a sputtering method, and is dried by a dry etching method using a first photoresist.
The row electrode 13 is formed by etching the tantalum layer.

Thereafter, an anodic oxide layer 14 is formed on the surface of the row electrode 13 to a thickness of 80 nm by an anodic oxidation method.

Further, a transparent electrode film made of, for example, indium tin oxide is formed to a thickness of 50 nm by sputtering.
The pixel electrode 15 is formed by etching the transparent conductive film using the second photoresist.

[0008] In this way, the MIM element is formed using two photomasks. Thereafter, heat treatment is performed in a nitrogen atmosphere to stabilize the device characteristics.
An IM element is formed.

[0009]

However, the device characteristics of the above-described conventional MIM structure largely depend on the conditions for forming the transparent electrode film to be the pixel electrode 15 and the heat treatment conditions thereafter. Variation increases. This variation in threshold voltage causes problems such as display unevenness, deterioration of display quality, and shortening of the operating life of the MIM element.

The voltage value when the current value in the ON state of the MIM element flows by ^10-8 A when the conditions for forming the transparent electrode film, for example, the amount of oxygen introduced into the sputtering apparatus is changed by 3% to 15%. FIG. 7 shows the variation of a certain threshold voltage.
Shown in

In the graph of FIG. 7, the horizontal axis shows the amount of oxygen introduced into the sputtering apparatus when forming the transparent electrode layer, and the vertical axis shows the variation in the threshold voltage of the MIM element. The solid line 51 in FIG. 7 indicates the maximum value of the threshold voltage,
A broken line 52 indicates the minimum value of the threshold voltage. At this time, an indium oxide target containing 8% tin oxide was used for sputtering.

As shown by a solid line 51 and a dashed line 52 in FIG. 7, it can be seen that when the oxygen introduction amount exceeds 5%, the variation in the threshold voltage sharply increases.

Further, in the above-described heat treatment in a nitrogen atmosphere, if the heat treatment is performed in an atmosphere in which the residual oxygen concentration exceeds 500 ppm in the heat treatment apparatus, the threshold voltage may vary as in the data shown in FIG. Was revealed by experiment.

[0014] These causes are caused by the anodic oxide layer 1 shown in FIG.
This is because oxygen diffuses from the outside to the interface between the pixel electrode 15 and the row electrode 13 or the interface between the row electrode 13 and the anodic oxide layer 14 to form an electrical barrier layer at these interfaces.

[0015] An object of the present invention is to solve the above-mentioned problems and to achieve M
An object of the present invention is to provide a configuration of a liquid crystal display device capable of suppressing variation in threshold voltage of an IM element and a method of manufacturing the same.

[0016]

In order to achieve the above object, the present invention employs the following MIM element structure and a method of manufacturing the same.

The MIM element structure according to the present invention comprises an MIM element formed by forming a lower electrode layer, an insulator layer and a transparent electrode layer on a substrate.
In a liquid crystal display device using an element, an intermediate metal layer is provided between an insulator layer and a transparent electrode layer.

According to the method of manufacturing an MIM element of the present invention, a lower electrode layer is formed on the entire surface of a substrate, a first photoresist is formed on the lower electrode layer, and the lower electrode is formed using the first photoresist as a mask. Are patterned to form row electrodes,
Removing the photoresist, forming an anodized layer by anodizing the surface of the row electrode, sequentially forming an intermediate metal layer and a transparent electrode layer on the entire surface, and forming a second photoresist. Etching the transparent electrode and the intermediate metal layer using the second photoresist as a mask to form a pixel electrode, and removing the second photoresist.

[0019]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing the configuration of the liquid crystal display device of the present invention and the manufacturing process thereof, and FIG. 2 is a plan view showing the liquid crystal display device of the present invention. First, the MIM of the liquid crystal display device of the present invention
The element structure will be described with reference to FIG.

The MIM element structure according to the present invention is shown in FIG.
As shown in (d), a row electrode 13, an anodized layer 14, and a pixel electrode 15 are sequentially provided on a substrate 12, and an intermediate metal having a role of an oxygen diffusion barrier layer is provided below the pixel electrode 15 made of a transparent electrode layer. A layer 17 is provided.

The intermediate metal layer 17 having the role of the oxygen diffusion barrier layer of the present invention is made of a metal having a high chemical activity, such as indium, tantalum, chromium, or titanium. By providing the intermediate metal layer 17, oxygen from the outside is trapped by the intermediate metal layer 17, and variation in threshold voltage due to the influence of oxygen can be reduced.

Next, a method for manufacturing a liquid crystal display device of the present invention will be described.
This will be described with reference to FIGS. 1A to 1D and FIG.

First, as shown in FIG. 1A, a tantalum film having a thickness of 200 nm is formed as a lower electrode layer on a substrate 12 made of glass by a sputtering method.

Thereafter, a photoresist is formed on the entire surface by a coating method, exposed and developed using a first photomask, and the photoresist is patterned to form a first photoresist 21.

Thereafter, the tantalum film is etched by dry etching using the first photoresist 21 as an etching mask, and the row electrodes 13 are patterned. The plane pattern shape of the row electrode 13 is shown by a solid line 23 in FIG.

After that, the first
Of the photoresist 21 is removed.

Next, as shown in FIG. 1B, the surface of the row electrode 13 is anodized in a 0.1% citric acid solution,
A tantalum oxide, which is the anodic oxide layer 14 having a thickness of m, is formed.

Next, as shown in FIG. 1C, 100% argon gas was introduced into the sputtering chamber at a rate of 100 cc / min.
A film is formed on the entire surface to a thickness of 5 to 10 nm.
A transparent electrode layer made of indium tin oxide as a material 5 is continuously formed with a thickness of 50 nm.

Thereafter, a photoresist is formed on the entire surface by a coating method, exposure and development are performed using a second photomask, and the photoresist is patterned to form a second photoresist 22.

As the intermediate electrode layer 17, in addition to indium, tantalum, chromium, titanium, or an alloy mainly composed of these materials can be used.

Thereafter, using the second photoresist 22 as an etching mask, the transparent electrode layer and the intermediate metal layer 17 are etched using a dry etching method or a wet etching method to form the pixel electrode 15.

The dashed-dotted line 25 in FIG. 2 shows the planar pattern shape of the pixel electrode 15 and the intermediate metal layer 17.

After that, the second photoresist 22 is removed. Thereafter, heat treatment is performed in a nitrogen atmosphere at a temperature of 350 ° C. for 1 hour to stabilize MIM element characteristics. Thus, the MIM element is formed using two photomasks.

FIG. 4 is a sectional view showing a liquid crystal display device according to another embodiment of the present invention.

The difference between the structure shown in FIG. 4 and the structure shown in FIG. 1D lies in the pattern shape of the intermediate metal layer 17. That is, in the first embodiment shown in FIG. 1D, the intermediate metal layer 17 has the same pattern shape as the pixel electrode 15, but in the second embodiment shown in FIG. They have the same pattern shape.

FIG. 3 shows the relationship between the amount of oxygen introduced when the pixel electrode 15 which is a transparent electrode layer of the MIM element formed by the manufacturing method of the present invention and the variation in the threshold voltage of the MIM element.
Is shown in the graph.

The horizontal axis of the graph in FIG. 3 indicates the amount of oxygen introduced into the sputtering apparatus when forming the transparent electrode layer, and the vertical axis indicates the variation of the threshold voltage of the MIM element. Further, the solid line 53 in the graph of FIG.
4 indicates the minimum value of the threshold voltage.

As is clear from the graph of FIG. 3, the variation of the threshold voltage of the MIM element of the present invention is smaller than that of the conventional MIM element.

This is because, in the MIM element of the present invention, the provision of the intermediate metal layer 17 allows the intermediate metal layer 17 to trap oxygen from the external atmosphere and prevent diffusion of oxygen into the anodic oxide layer 14. In addition, the variation of the threshold voltage is reduced.

The MIM element structure of the present invention is not easily affected by the partial pressure of oxygen when the pixel electrode 15 made of a transparent electrode layer is formed, and the variation in the threshold voltage of the MIM element is reduced even when the amount of introduced oxygen is increased. , The margin of the MIM element manufacturing conditions,
That is, the process window can be expanded. Further, there is an effect that the current value variation at the time of writing is reduced.

[0041]

As is apparent from the above description, in the liquid crystal display device of the present invention, the threshold voltage of the MIM element is formed by forming the intermediate metal layer between the anodic oxide layer and the transparent electrode layer. And the variation in the current value at the time of writing is reduced. Further, it is possible to greatly widen the process window of the transparent electrode layer forming condition and the heat treatment condition, so that the display quality of the liquid crystal display device is improved and the reliability is improved.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view illustrating a structure of a liquid crystal display device according to an embodiment of the present invention and a manufacturing method thereof.

FIG. 2 is a plan view illustrating a liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a graph showing a relationship between an oxygen introduction amount and a variation in threshold voltage at the time of manufacturing an MIM element in an example of the present invention.

FIG. 4 is a sectional view showing a liquid crystal display device according to another embodiment of the present invention.

FIG. 5 is a sectional view showing an MIM element in a conventional liquid crystal display device.

FIG. 6 is a circuit diagram showing an equivalent circuit of a liquid crystal display device using an MIM element.

FIG. 7 is a graph showing a relationship between an oxygen introduction amount and a threshold voltage variation at the time of manufacturing a conventional MIM element.

[Explanation of symbols]

 12 Substrate 14 Anodized layer 15 Pixel electrode 17 Intermediate metal layer

Claims (2)

(57) [Claims] 1. A metal layer obtained by forming a lower electrode layer insulation layer and the transparent electrode layer on a substrate - insulator layer - a liquid crystal display device using an MIM element having a metal layer structure, before serial transparent electrode layer, a liquid crystal, characterized in that an intermediate metal layer made of an alloy mainly of indium or the indium between the consists of indium tin oxide, before Symbol insulator layer and the transparent electrode layer Display device. Wherein the lower electrode layer is formed on the whole surface of the substrate, forming a first photoresist on the <br/> lower electrode layer, said first
Forming a row electrode by patterning the previous SL lower electrode layer using a photoresist mask, a step of forming an anodic oxide film of the row electrode anodized, and the entire surface to the intermediate metal layer oxide A transparent electrode layer made of indium tin is sequentially formed, a second photoresist is formed,
To form the intermediate metal layer and the etching pixel electrode and the transparent electrode layer by using the second photoresist mask
A method of manufacturing a that step and the liquid crystal display device Ru wherein the intermediate electrode layer is indium, or the indium main
A method for manufacturing a liquid crystal display device , comprising forming an alloy as a component .