JPH02210331A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To contrive the reduction of a disconnection of wiring and the conversion to a low resistance of a wiring resistance by forming a common electrode by a multi-layer structure of two layers and forming the uppermost layer by the same material as that of a picture element electrode, and covering its lower layer with the uppermost layer or an insulation layer for constituting an MIM element. CONSTITUTION:On a substrate 1, a common and lower electrode 2 is accumulated and formed by using a high conductive material and it is converted to a prescribed pattern, and also, on its common and lower electrode 2 or the substrate 1, an insulation film 4 is accumulated and formed and converted to a prescribed pattern. Subsequently, an upper and auxiliary electrode 5 is formed on them by using the same material as that of the common and lower electrode 2, and thereafter, a transparent picture element electrode 6, and a transparent electrode 3 for forming the uppermost layer of the common electrode are accumulated and formed simultaneously by the same transparent electrode material. Next, a pattern of a display picture element part and a pattern of a transparent electrode part are provided, so that the pattern of the latter covers an exposed part of the common and lower electrode 2, and also, does not come into contact with the upper and auxiliary electrode 5. In such a way, the wiring resistance becomes low, and also, the disconnection is corrected naturally by the transparent electrode, and the yield is improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a liquid crystal display device used for a display of a computer terminal, etc., a pocket TV, a wall-mounted TV, etc., and particularly relates to an active matrix type liquid crystal display using an MIM element. It is related to the device.

[Prior art and problems to be solved by the invention] One of the typical driving methods for liquid crystal display devices is the active matrix driving method. It is attracting attention because it is capable of large-capacity display comparable to CRT displays. A liquid crystal display device using an active matrix driving method has a configuration in which a switching element is added to each pixel.

MIM elements composed of metal-insulator-metal have been published in various papers, patent publications, etc. as switching elements used in such active matrix drive type liquid crystal display devices.

6 to 9 show active matrix substrate configurations in conventional liquid crystal display devices.
The figures show different configuration examples, and Fig. 6(a), Fig. 7(a), and Fig. 8(a) are cross-sectional views, Fig. 6(b), Fig. 7(b), and Fig. 8(a) are cross-sectional views. FIG. 9(b) is a plan view, and FIG. 9 is a perspective view of the configuration example shown in FIG. 6. In these figures, 51 is a common and upper electrode, 52 is an insulating layer, 53 is a lower and auxiliary electrode, 54 is a pixel electrode, 51' is a common and lower electrode, 53
' is an upper and auxiliary electrode, and 54' is an upper and pixel electrode. Figures 6 and 9 are examples in which an auxiliary electrode is provided and an element is configured in MI, and Figure 7 is an example in which an auxiliary electrode is also provided and an element is configured in the MI, but the top and bottom of the common electrode and pixel electrode are FIG. 8 is an example in which the relative positional relationship is opposite to that in FIG. 6, and an example in which the pixel electrode and the common electrode each serve as the common electrode of the MIM element without using an auxiliary electrode. In this way, each display pixel electrode is provided with at least one MIM element for driving the liquid crystal or improving the performance of the liquid crystal display.

However, in the above configuration, although the electrodes are multilayered in some parts, the common electrode is not multilayered throughout, and there is a risk of disconnection during the process of forming each layer.

Furthermore, if a material with relatively high resistance is used, the overall wiring resistance increases, causing problems in driving the liquid crystal. Furthermore, when etching the pixel electrode and the common electrode, if the two materials used for these do not have a good etching selectivity, they will be etched together, and the common electrode or pixel electrode will also be etched, resulting in display defects. There is a drawback.

On the other hand, Japanese Unexamined Patent Publication No. 62-251725 discloses a technique for reducing wiring defects and wiring resistance by forming a common electrode in two layers. However, in this case, if the etching selectivity between the second layer and the second layer of the common electrode cannot be maintained, there is a problem in that the second layer is etched and defects such as wire breakage occur.

The present invention aims to provide a liquid crystal display device that reduces the occurrence of disconnections in wiring, lowers the wiring resistance, and has fewer defects even when using materials with difficult etching selectivity. purpose.

[Means and operations for solving the problems] In order to achieve the above object, according to the present invention, a liquid crystal layer is sandwiched between a pair of substrates, and a common electrode is provided on the inner surface of at least one of the substrates.
In a liquid crystal display device in which a plurality of image electrodes are formed, each of which is connected to the common electrode via an MIM (metal-insulator-metal) element, the common electrode has a multilayer structure of at least two layers, and the most A liquid crystal display device is provided, wherein the upper layer is made of the same material as the pixel electrode, and the lower layer is covered with an insulating layer constituting the uppermost layer or the Akoga element.

As the insulator of the HIM element in the liquid crystal display device, it is preferable to use a hard carbon film containing at least one of an amorphous material and a microcrystalline material whose main constituent elements are carbon atoms and hydrogen atoms.

Next, an example of the structure of an active matrix substrate in a liquid crystal display device according to the present invention will be explained in detail with reference to the drawings.

FIG. 1 shows a first configuration example, and FIG. 1(a) is a cross-sectional view,
FIG. 1(b) is a plan view. Also.

FIG. 2 shows a second configuration example, and FIG. 2(a) is a cross-sectional view,
FIG. 2(b) is a plan view. In these figures, 1
2 is a substrate, 2 is a common and lower electrode, 3 is a transparent electrode, 4 is an insulating layer, 5 is an upper and auxiliary electrode, 6 is a pixel electrode, and 6' is an upper and pixel electrode.

First, the configuration and manufacturing method of the first configuration example will be explained. A transparent substrate such as glass, plastic, or flexible plastic is used as the substrate l. A common and lower electrode 2 is formed on the substrate l. The common and lower electrodes 2 are Afl, Ni-Cr.

No, Cr, Ni, Ti, Zr, Nb, Au, Ag, P
Using a highly conductive material such as T, Cu, or Ta, the film is deposited to a thickness of several hundred to several thousand layers by sputtering, vapor deposition, CVD, or the like. This is patterned into a predetermined pattern using a photolithography and etching process.

Furthermore, an insulating film 4 made of SiNx, i-C (hard carbon), SiC, etc. is deposited on the common and lower electrodes 2 or the substrate 1 by CVD, sputtering, vapor deposition, etc., and then photolithography is performed. - After patterning into a predetermined pattern by an etching process or a lift-off method, the upper and auxiliary electrodes 5 are formed thereon using the same material as used for the common and lower electrodes 2. Thereafter, the transparent pixel electrode 6 and the transparent electrode 3 forming the uppermost layer of the common electrode are deposited simultaneously using the same transparent electrode material. Materials include ITO, ZnO:l, Zn
O:Si, SnO, and:Sb are used, and are deposited to a film thickness of about 100 to 14 cm by CVD, sputtering, vapor deposition, or the like. and.

It is patterned into a pattern as described below using a photolithography and etching process. That is, the patterning shape of the transparent electrode material has a pattern of a display pixel portion and a pattern of a transparent electrode (common electrode top layer) portion, and the latter pattern covers the exposed portions of the common and lower electrodes 2, and , so that it does not come into contact with the upper and auxiliary electrodes 5.

In this way, when patterning the transparent electrode material of the pixel electrode 6, the patterning is performed in a pattern that leaves the transparent electrode 3 on the common and lower electrodes 2 as well.

The effective resistance of the common electrode is reduced, and the wiring resistance is also reduced, which is advantageous for driving the liquid crystal. Furthermore, even if the common electrode is disconnected in the previous process, it is corrected in this process, reducing the total number of defects. Furthermore, even if the common and lower electrodes 2 are etched with the etchant of the transparent electrode material of the pixel electrode 6, if the pattern is as described above, the exposed portions will be covered with the transparent electrode 3 and the resist. Therefore, the MIM element part is not etched, and the upper part, the auxiliary electrode 5, and the insulating layer 4 are not etched.
Therefore, it is not etched, and there is no need to consider the etching selectivity between the electrode material of the common and lower electrode 2 and the electrode material of the transparent electrode 3, and any conductive material can be used.

In the case of the above pattern, there is a concern about the part where the common and lower electrodes 2 are covered only with the absolute S' layer 4 (the first
In the part marked (■) in the figure, the etchant seeps in through the pinhole of absolute mM4 and etches the electrode material. However, if there is such a pinhole, M
I-A elements also have many defects such as short circuits and do not function as MIM elements.

Furthermore, even if the MIM element functions but there is a pinhole, the probability that there will be a pinhole is very small because the area of this 0 part is very small, and it is highly unlikely that the common electrode will be etched by the etchant and disconnected.

In the above structure, when a hard carbon film (i-C) is used for the insulating layer 4, the hard carbon film has very few pinholes.
In addition, since it is chemically stable, the above-mentioned zero etching does not occur, and it has been found that it is an especially advantageous insulating material for MIM elements of liquid crystal display devices.

Next, the configuration and manufacturing method of the second configuration example will be described. The formation of the common and lower electrodes 2 and the formation of the insulating layer 4 are performed in the same manner as in the first configuration example.

Next, the upper and pixel electrodes 6' and the transparent electrode 3 forming the uppermost layer of the common electrode are simultaneously deposited using the same transparent electrode material. The patterning shape of the transparent electrode material in this case has a pattern for the display pixel portion and the upper electrode portion, and a pattern for the transparent electrode (common electrode uppermost M) portion, and the latter pattern is the exposed portion of the common electrode and the lower electrode 2. The pixel electrode 6' is shaped so as to cover the area where the pixel electrode 6' is located, and not to contact the upper part and the pixel electrode 6'. Even with the above configuration and steps, the same advantages as the first configuration example can be obtained.

Next, the hard carbon film preferably used for the insulating layer 4 in the above configuration example will be described in detail.

Although this hard carbon film can also be formed by an ion beam method, an example using a plasma CVD method will be explained here. As the apparatus, for example, a parallel plate type plasma CVD apparatus is used. First, the substrate on which the film is to be formed is attached to the RF power supply side where positive ion bombardment is promoted due to self-bias. and hydrocarbons (e.g. Cl-14, C
2H,,C3H,,C4H□. Paraffinic hydrocarbons such as C2)1. When a raw material gas containing a mixture of acetylene hydrocarbons (e.g., acetylene hydrocarbons, etc.) and hydrogen is introduced into the device, and a high frequency electric field of 13.56 MHz is applied between parallel plate electrodes, a glow discharge is generated. As the raw material gas, hydrogen can be mixed with all hydrocarbons such as olefin hydrocarbons, acetylene hydrocarbons, diolefin hydrocarbons, and even aromatic hydrocarbons. By this glow discharge, the raw material gas is decomposed into radicals and ions and reacts.
A hard carbon film partially containing an amorphous or microcrystalline substance made of carbon atoms C and hydrogen atoms H is deposited on the substrate. This hard carbon film is generally called a diamond-like carbon film, an i-C film, an amorphous diamond film, or a diamond thin film. The deposition conditions for such a hard carbon film are as follows: RF output: 0.1-50 W/aJ Pressure: 10-''-10 Torr Deposition temperature: room temperature-950°C.

The physical properties of the film created under these deposition conditions and the MIM
What are the nonlinear characteristics of the element?

Specific resistance (1): 10"-10L30cm Vickers hardness (H): ~9500kg-mm-"Refractive index (
n): 1.9-2.4 defect density = l
O11-10130-3 Nonlinear characteristic β: 2-9 It has physical properties and characteristics. However, the specific resistance was measured by IV characteristics using a coplanar cell.

The Vickers hardness was measured by a micro Vickers meter, the refractive index by an ellipsometer, and the defect density by ESR. Further, according to X-ray and electron diffraction analysis, it has been found that it is in an amorphous state (a-C:H) or an amorphous state containing microcrystalline grains of about 50 to several particles. Results of analysis by Raman spectroscopy and IR absorption method,
As shown in FIGS. 3 and 4, it has been revealed that there are interatomic bonds in which carbon atoms form a hybrid orbital of SF3 and a hybrid orbital of SPl. In addition, such a hard carbon film is mainly composed of SF3 and contains SF3,
There are some that are mainly SF3 and some that include SF3. In addition, during film formation, the smaller the RF output and the lower the pressure, the higher the specific resistance and hardness of the film, and the larger the hydrogen mixing ratio, the higher the refractive index and the lower the defect density. can be obtained.

In this way, by forming the insulating film of the MIM element from a hard carbon film, variations in element characteristics are reduced and the MIM element can withstand mechanical damage. This is I
When the N element is used as an active element for a liquid crystal display, there is less damage caused by the rubbing process when filling the liquid crystal material, and the yield is improved.

Also, the capacitance of LCD and MIM element is Cbeo:CM
+M=IO: Approximately 1 is required, and a smaller dielectric constant of the insulating film is advantageous for processing. The dielectric constant ε of the hard carbon film is i
``Since it is as small as F4r r , it can be formed with high precision without requiring much fine processing, and from this point as well, the yield is improved.

In the MI element, in terms of IV characteristics, QnI oe sr
'r4 shi< has a relationship of nnl/Vocv'V-.

The IV characteristics in this case are shown in FIG.

The substrate obtained according to the manufacturing method of the above configuration example can be used, for example, to configure a liquid crystal display device by using a substrate provided with a common transparent electrode on the entire surface as the other substrate, and sealing liquid crystal between these two substrates. used. Although the liquid crystal display device in this case has a black and white display, it is also possible to provide a color display by providing a color filter inside or outside the liquid crystal layer. As described above, the liquid crystal display device of the present invention is not limited to either monochrome display or color display, but can be applied to an active matrix active liquid crystal display device of any desired display method.

〔Example〕

Examples of the present invention are listed below, but the present invention is not limited only to these Examples.

Example 1 A Pyrex substrate was used as a transparent substrate, and Al1 was deposited to a thickness of 1000 nm on the transparent substrate by a vapor deposition method.
A lower electrode and a common electrode were formed by patterning into a predetermined pattern. Next, a hard carbon film was deposited to a thickness of 600 mm using a plasma CVD method.

The film forming conditions at this time are as follows. Pressure 0.035
Torr, RF output 0.2V/cd, substrate temperature 30℃,
C) lJCH4+H, = 100Vo part, total flow rate 1
Then, the hard carbon film was patterned into a predetermined pattern by dry etching to form an insulating layer. At this time, a mixed gas of Ar and CO was used as the etching gas. Next, the resist was patterned so that the resist remained in areas other than where the upper and auxiliary electrodes were to be deposited, and PT was deposited thereon to a thickness of 500 nm by EB evaporation.

Thereafter, the resist was removed with acetone, and the PT was lifted off and patterned into a predetermined pattern to form upper and auxiliary electrodes. Next, ITO was deposited by EB evaporation.
This ITO film is then patterned with a resist to form a pattern portion that covers the common electrode (lower layer) but does not touch the upper electrode, and a pattern portion that connects to the upper electrode and becomes the pixel electrode. This is then etched to form a pixel electrode and a transparent electrode (the top layer of the common electrode).
It was used as a substrate for a liquid crystal display device. H for etching ITO
An etchant of Cl2:H20=1:1 was used. When this etchant is used, if AQ of the common electrode is exposed as in the conventional case, A[ is etched and becomes a defect as a disconnection, but in the configuration of this embodiment, no etching disconnection of AQ was observed. When a liquid crystal display device was manufactured using the substrate obtained as described above, a device with few defects and good display quality was obtained.

Example 2 A plastic substrate was used as a transparent substrate, and Cr was deposited on the substrate as an electrode material to a thickness of 1200 nm by vapor deposition, and then patterned into a predetermined pattern by a photolithography/etching process. , formed the common and bottom electrodes.

Next, a hard carbon film was deposited to a thickness of 800 mm by plasma CVD, and then patterned into a predetermined pattern by dry etching to form a green layer.

Formed. Furthermore, after using ITO as an electrode material and depositing it to a thickness of 1000 nm by vapor deposition, the pixel electrode covers the pattern part that also serves as the upper electrode and the Cr common electrode (lower layer of the common electrode), but does not come into contact with the pixel electrode. The ITO film was patterned with a pattern consisting of a pattern portion, a pixel electrode and a transparent electrode (common electrode uppermost M) were formed, and a substrate for a liquid crystal display device was obtained. When a liquid crystal display device was manufactured using this substrate, as in Example 1, there were few defects and the display quality was good.

Example 3 Using a Pyrex substrate as a transparent substrate, using Ni-Cr as an electrode material on the substrate, 60% was deposited by EB evaporation.
After being deposited to a thickness of 0.05 mm, the common and lower electrodes were formed by patterning into a predetermined pattern using a photolithography and etching process. Next, plasma C
5i) SiNx film from I4 and NH3 using VD method
After depositing to a thickness of 0.000, photolithography
An insulating layer was formed by patterning into a predetermined pattern using an etching process. Furthermore, Z as an electrode material
8 by RF magnetron sputtering using nO:tQ
The pixel electrode and the transparent electrode (
A common electrode uppermost layer) was formed to obtain a substrate for a liquid crystal display device. When a liquid crystal display was manufactured using this substrate, good characteristics similar to those of Examples 1 and 2 were obtained.

〔Effect of the invention〕

As described above in detail, according to the present invention, since the common electrode has a multilayer structure, the wiring resistance is low, which is advantageous for driving liquid crystal. Furthermore, even if the lower layer of the common electrode is broken due to dust or handling during each process, the disconnection is naturally corrected by the transparent electrode on the top layer, improving yield.

Furthermore, since the transparent electrode (the uppermost layer of the common electrode) and the insulating film cover the lower layer of the common electrode, even if the electrode material of the lower layer of the common electrode is a material that can be etched with the etchant for the transparent electrode material, there is no process of etching the transparent electrode. It is not etched and can be used with any electrode material.

In addition to the above advantages, when a hard carbon film is used as the insulating layer that forms part of the MIM element of the liquid crystal display element of the present invention, this film has fewer bepinholes than other insulators and is chemically stable. , the probability of wire breakage is reduced and the yield is improved. Furthermore, since the hard carbon film has a low dielectric constant, the device area can be increased, and variations in device precision can be reduced.

Furthermore, the hard carbon film has strong mechanical strength, which is advantageous for manufacturing liquid crystal panels, and improves the manufacturing yield.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing a first configuration example of an active matrix substrate in a liquid crystal display device according to the present invention, FIG. 2 is a diagram showing a second configuration example of an active matrix substrate in a liquid crystal display device according to the present invention, and FIG. The figure shows the analysis results of the hard carbon film by Raman spectroscopy, Figure 4 shows the analysis results of the hard carbon film by IR absorption method, and Figure 5 shows the results of the analysis of the hard carbon film by Raman spectroscopy.
Graphs showing IV characteristics of IM elements, Figures 6 to 8
The figures each show a configuration example of an active matrix substrate in a conventional liquid crystal display device, and FIG. 9 is a perspective view of an active matrix substrate of the type shown in FIG. 6. 1... Substrate 3... Transparent electrode 5... Upper and auxiliary electrode 6'... Upper and pixel, element electrode 2... Common and lower electrode 4... Insulating layer 6... Pixel electrode

Claims (1)

[Claims] (1) A liquid crystal layer is sandwiched between a pair of substrates, a common electrode is provided on the inner surface of at least one of the substrates, and a plurality of images each connected to the common electrode via an MIM (metal-insulator-metal) element. In a liquid crystal display device in which an electrode is formed, the common electrode has a multilayer structure of at least two layers, the uppermost layer of which is made of the same material as the pixel electrode, and the lower layer of which is made of the same material as the uppermost layer or the MIM element. A liquid crystal display device characterized by being coated with an insulating layer.