JPH05210122A - Structure of nonlinear active element of liquid crystal display device and production thereof - Google Patents

Abstract

PURPOSE:To drastically decrease the initial defects of the nonlinear active element of MIM or MSI type of a liquid crystal display device and to improve the yield thereof by preventing the shorting destruction of the element in the level difference part of a lower electrode. CONSTITUTION:A positive resist 14 is applied over the entire surface on the lower electrode 13 of the nonlinear active element and is subjected to exposing on the rear surface with the lower electrode 13 as a mask, then to a stage for developing the resist. This resist is anodized in the state of partly exposing the electrode part 13a inclusive of the level difference part of the lower electrode 13 and the exposed part is formed as a passivated layer 16.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a nonlinear active liquid crystal display device using a metal-insulating layer-metal type or a metal-semiconductive insulating layer-metal type non-linear active element as an active matrix type display device. The present invention relates to a device structure and a manufacturing method thereof.

[0002]

2. Description of the Related Art In recent years, as a liquid crystal display device, in a laptop or portable information processing device typified by a personal computer, a color display unit
High definition is desired. An active matrix system is adopted as a display device that satisfies such requirements.

In the active matrix system, by arranging a non-linear active element in each pixel, it is possible to eliminate unnecessary signal interference and achieve high image quality. Further, in this active matrix system, a TFT (Thin) in which a thin film transistor including a three-terminal element is formed.
Film Transistor) type or MIM (Met) using a non-linear active element composed of two-terminal element metal-insulating layer-metal or metal-semiconductive insulating layer-metal
al Insulator Metal) type is known.

The MIM non-linear element is an application of the non-linear current-voltage characteristic of the insulator itself to the ON / OFF switching characteristic. In addition, the MIM method that uses a semiconductive insulating layer as an insulating layer that is an active layer is particularly suitable for MSI (Metal Semi Insulator).
It is called the Metal type. This MSI type has the advantage that the resistivity can be changed by changing the element ratio of the main elements forming the semiconductive insulating layer or by doping various elements.

FIG. 3 shows a cross section of a known MIM element. The MIM element uses a photolithography technique to form a lower electrode 6, an insulating layer 7, and an upper electrode 8 on the substrate 1.
Are sequentially patterned. However, in this structure, since the step portion 7a of the insulating layer 7 is thinner than the lower electrode 6, there is a drawback that the lower electrode 6 and the upper electrode 8 are short-circuited at the step portion 7a due to electric field concentration. .. Reference numeral 9 is a pixel electrode.

Therefore, in JP-A-1-270027 and JP-A-1-283524, as shown in FIG. 4, the side surface of the lower electrode 6 is tapered and the intermediate insulating layer 10 is formed. By providing the contact hole 10a, the upper electrode 8 is formed in the contact hole 10a portion via the insulating or semiconductive insulating layer 7.
There has been proposed an MIM element structure that does not utilize the tapered portion as an element.

The disadvantage of this method is that the number of steps is increased, the layer structure is complicated, and the device yield is reduced. Further, when the contact hole 10a is formed, an altered layer is formed on the surface of the lower electrode 6, which causes variations in the characteristics of the device.

[0008]

SUMMARY OF THE INVENTION The present invention solves the conventional problems in a liquid crystal display device using a MIM or MSI type non-linear active element, reduces the number of manufacturing steps, and reduces the element in the step portion of the lower electrode. It is an object of the present invention to provide a means capable of preventing short-circuit breakdown, significantly reducing the initial failure of the element, and improving the yield.

[0009]

In order to achieve the above object, the present invention provides an active matrix liquid crystal display having a non-linear active element of the type metal-insulating layer-metal or metal-semi-conducting insulating layer-metal. In the device, an insulating or passivating layer is formed on a step portion of the lower electrode of the nonlinear active element.

The present invention also provides a method of manufacturing a non-linear active element in an active matrix liquid crystal display device having a non-linear active element of a metal-insulating layer-metal or metal-semiconductive insulating layer-metal type. After forming the lower electrode of, the whole surface is coated with a positive resist, the back surface is exposed by using the lower electrode as a mask, and a part of the electrode portion including the stepped portion of the lower electrode is exposed through a step of resist development. It is characterized by forming a structure and insulating or passivating this exposed portion.

The present invention is a method of manufacturing a non-linear active element in an active matrix liquid crystal display device having a non-linear active element of a metal-insulating layer-metal or metal-semiconductive insulating layer-metal type. After forming the electrodes, a positive resist is applied over the entire surface, and when the back surface exposure is performed using the lower electrode as a mask, the mask for patterning the insulating layer or the semiconductive insulating layer is overlaid and the simultaneous exposure is performed. The structure is characterized in that the electrode portion including the stepped portion of the electrode is partially exposed, and the insulating portion of the lower electrode is provided only in the portion where the insulating layer or the semiconductive insulating layer is formed.

[0012]

With the structure of the present invention, the step portion of the lower electrode of the nonlinear active element serves as an insulator, and even if the insulating layer or the semiconductive insulating layer in this portion becomes thin, the electric field does not concentrate. Therefore, the short-circuit breakdown of the element at this step portion is eliminated. In the method for manufacturing a nonlinear active element of the present invention, since the lower electrode is used as a mask, it is not necessary to manufacture a new mask as in a normal exposure process, and the work required for mask alignment is simplified. Bring about the action of.

[0013]

EXAMPLES The present invention will be described below based on examples.
FIG. 1 shows a cross-sectional view of one dot of a liquid crystal display device. In this figure, the pixel electrodes and liquid crystal which face each other are omitted for simplicity. A first embodiment of the present invention will be described with reference to FIG.

First, the etch stopper layer 12 is formed on the substrate 11. The etch stopper layer 12 is preferably translucent so as not to impair the brightness of the liquid crystal panel. In addition, the material of the substrate 11 is PET or N.
When using a plastic film such as AP, it is necessary to have a function as a gas barrier layer against oxygen and moisture. In the first embodiment, PET is used for the substrate 11 and the DC magnetron sputtering method is used for the etch stopper layer 12.
An AlN film having a thickness of 2000Å was formed. In addition to the AlN film, a Ta ₂ O ₅ film or SiO is used as the etch stopper layer 12.
It is possible to apply _two films.

Next, the lower electrode 13 is formed by a photolithography process. As the electrode material of the lower electrode 13, Al that can be continuously formed without breaking the vacuum after the etching stopper layer 12 was formed was used. A positive resist 14 is applied over the entire surface, and ultraviolet rays are irradiated from the back surface using the lower electrode 13 as a mask as shown in FIG.

After that, the resist pattern 15 formed by the development process becomes slightly smaller than the width of the lower electrode 13. This is because the irradiation light is diffracted at the end of the lower electrode 13 or reflected on the surface of the positive resist 14. As a result, as shown in FIG. 1B, the shoulder portion 13a of the electrode including the stepped portion of the lower electrode 13 is partially exposed.

When anodic oxidation is performed with the lower electrode 13 as an anode in a neutral solution such as a mixed solution of 3% tartaric acid and ethylene glycol, the exposed portion of the lower electrode 13 made of Al is oxidized and has a barrier property. High passivation layer 16
(Al ₂ O ₃ ) is formed. After that, as shown in FIG. 1C, the resist pattern 15 is removed, and the semiconductive insulating layer 1 is removed.
7, the upper electrode 18 and the pixel electrode 19 are successively patterned to form a nonlinear active element. In this embodiment, AlNx (x <1) is used for the semiconductive insulating layer 17, Ni is used for the upper electrode 18, and ITO (In ₂ is used for the pixel electrode 19).
SnO ₂ ) was formed by the DC magnetron sputtering method.

Since the step portion 13a of the lower electrode 13 is an insulator by the passivation layer 16 having a high barrier property in the non-linear active element manufactured according to this embodiment, the step portion 16a is semiconductively insulated. Even if the layer 17 becomes thin,
The electric field is not concentrated unlike the conventional example. As a result, the short circuit breakdown of the non-linear active element at the step portion 13a of the lower electrode 13 was eliminated, and the initial failure of the non-linear active element was significantly reduced, and the yield could be improved.

Further, by adopting the backside exposure method using the lower electrode 13 as a mask, compared with the case where the resist pattern 15 is formed by a normal exposure process, a new mask is manufactured and the mask alignment accuracy is of the order of 1 micron. Is not required, and has a great advantage in terms of cost and workability.

Although Al is used for the lower electrode 13 in this embodiment, Ta or Ti, which has a relatively low resistance and can be easily anodized, can be used. By this anodic oxidation method, the step portion 13a of the lower electrode 13 is made into an insulating layer,
It is possible to manufacture the nonlinear active element by a manufacturing method having high mass productivity. Electrolytes used for these anodic oxidations are already known.

Further, for metals such as Cr and Ni which are generally difficult to be anodized, passivation can be carried out by an ion implantation method. That is, oxygen ions are implanted into the exposed portion of the lower electrode 13 with an oxygen ion beam focused on several thousand Å. At this time, the accelerating voltage is changed so that oxygen is almost uniformly distributed in the thickness direction of the lower electrode 13, and the implantation is performed several times.
Further, the insulating layer 16 is formed by making the region into which oxygen is injected by the annealing treatment an oxide. After that, the resist pattern 15 is removed in the same manner, and the semiconductive insulating layer 17,
The upper electrode 18 and the pixel electrode 19 may be successively patterned to form a nonlinear active element.

Next, a second embodiment of the present invention will be described. In this embodiment, as in the first embodiment, the etch stopper layer 12 and the lower electrode 13 are formed on the substrate 11,
A positive resist 14 is applied on the entire surface. And
When performing back surface exposure using the lower electrode 13 as a mask, a negative mask for patterning the semiconductive insulating layer 17 is used as the substrate 1.
Simultaneous exposure is performed by stacking on the back surface of 1. As a result of this simultaneous exposure, as shown in the plan view of FIG. 4, the lower electrode 13 is formed only in a minute area where a nonlinear active element is formed in the subsequent steps.
The shoulder portion 13a of the electrode including the stepped portion is exposed. After that, the nonlinear active element is completed through the same steps as those in the first embodiment.

According to the second embodiment, similarly to the first embodiment, the initial failure of the nonlinear active element can be reduced to improve the yield, and the anode of the exposed portion of the lower electrode 13 can be improved. At the time of oxidation, the portion to be anodized is small, so that the energization time can be shortened and the throughput can be increased.
Further, since the amount of gas generated is small, manufacturing equipment such as a method of rocking a work and a method of stirring a liquid can be simplified.

Furthermore, it is desirable that the lower electrode 13 has a sufficiently low wiring resistance as a data line. According to this embodiment, it is possible to minimize the reduction of the effective line width due to the partial anodic oxidation of the lower electrode 13, that is, the increase of the wiring resistance. As a result, it is not necessary to increase the line width of the lower electrode 13 by several percent in advance, and a sufficient aperture ratio can be obtained for the liquid crystal panel.

Further, there is an advantage that a mask for patterning the semiconductive insulating layer 17 is used as a negative mask as a mask to be overlapped at the time of back surface exposure, and that this mask does not cause a new increase in cost.

[0026]

According to the structure of the present invention, since the step portion of the lower electrode of the produced nonlinear active element serves as an insulator, even if the semiconductive insulating layer is thinned at this portion, it is as in the conventional structure. The electric field is not concentrated, the short-circuit breakdown of the element at the stepped portion of the lower electrode is eliminated, and there is an effect that the initial failure of the element is significantly reduced and the yield is improved. Further, in the present invention, since the back surface exposure using the lower electrode as a mask is adopted, new mask fabrication and mask alignment accuracy on the order of 1 micron are required as compared with the case where a resist pattern is formed by a normal exposure process. Therefore, there are great advantages in terms of cost and workability.

[Brief description of drawings]

FIG. 1 is an explanatory diagram for explaining an example of a manufacturing process of the present invention, in which (a) is a stage in which a lower electrode and a positive resist are formed on a substrate provided with an etch stopper layer, and back surface exposure is performed, (B) shows a stage in which a resist pattern is formed on the lower electrode, and (c) shows a stage in which a nonlinear active element is completed by using the exposed portion of the lower electrode as a passivation layer.

FIG. 2 is a plan view showing another example of the manufacturing process of the present invention.

FIG. 3 is a sectional view showing an example of a conventional nonlinear active element.

FIG. 4 is a sectional view showing another example of a conventional nonlinear active element.

[Explanation of symbols]

 11 substrate 12 etch stopper layer 13 lower electrode 13a step portion of lower electrode 14 positive resist 15 resist pattern 16 passivation layer or insulating layer 17 semiconductive insulating layer 18 upper electrode 19 pixel electrode

Claims (5)

[Claims] 1. An active matrix liquid crystal display device having a non-linear active element of metal-insulating layer-metal or metal-semi-conducting insulating layer-metal type, wherein a step portion of a lower electrode of the non-linear active element is A structure of a non-linear active element in a liquid crystal display device, characterized in that an insulating or passivating layer is formed. 2. A method of manufacturing a non-linear active element in an active matrix liquid crystal display device having a non-linear active element of metal-insulating layer-metal or metal-semi-conducting insulating layer-metal type, wherein a lower electrode having a predetermined shape is used. After formation, a positive resist is applied over the entire surface, backside exposure is performed using the lower electrode as a mask, and a resist development process is performed to form a structure in which the electrode portion including the stepped portion of the lower electrode is partially exposed. , A method for manufacturing a non-linear active element in a liquid crystal display device, characterized in that the exposed portion is insulated or passivated. 3. The lower electrode is made of Al, Ta or T
3. The method for manufacturing a non-linear active element in a liquid crystal display device according to claim 2, wherein i is used and an anodic oxidation method is used as a means for passivating the stepped portion of the lower electrode. 4. The method for manufacturing a non-linear active element in a liquid crystal display device according to claim 2, wherein an ion implantation method and an annealing treatment are used as means for insulating the stepped portion of the lower electrode. 5. A method of manufacturing a non-linear active element in an active matrix liquid crystal display device having a non-linear active element of metal-insulating layer-metal or metal-semi-conducting insulating layer-metal type, wherein a lower electrode having a predetermined shape is used. After formation, a positive resist is applied over the entire surface, and when backside exposure is performed using the lower electrode as a mask, a mask for patterning an insulating layer or a semiconductive insulating layer is overlaid and simultaneously exposed to form a lower electrode. Non-linear active in a liquid crystal display device, characterized in that a structure in which an electrode portion including a step portion is partially exposed is formed, and an insulating portion of a lower electrode is provided only in a portion where an insulating layer or a semiconductive insulating layer is formed. Manufacturing method of device.