JP2589331B2 - Liquid crystal display - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an active matrix type liquid crystal display device using a metal-insulating film-metal element (MIM element).

2. Description of the Related Art Liquid crystal display devices have been put to practical use as lightweight and thin flat panel displays, and are currently used as displays for portable computers and pocket televisions. It is also expected to be used as a high-resolution display for personal computers and word processors, and as a large display for home or high-definition television.

Here, a simple matrix system is generally used as a driving system of the liquid crystal display. However,
Considering the display performance such as the contrast ratio, the number of pixels, the response, etc. in order to increase the resolution, the display performance of the simple matrix drive system is limited, and it is not suitable for a high-resolution display. Therefore, a thin film transistor (TFT)
An active matrix method using a two-terminal element such as a three-terminal element such as a MIM element is promising as a driving method. Examples of these are disclosed in, for example, JP-A-57-1965.
No. 89, JP-A-62-62333, JP-A-60-241021
There are those as shown in Japanese Patent Publication No.

Here, in the case of using a metal-insulating film-metal element (MIM element) in which an insulating film is interposed between a lower electrode and an upper electrode, the insulating film is formed, for example, as described in Japanese Patent Laid-Open No.
As shown in 196589 and JP-A-62-62333, most of them are formed by anodizing a lower metal electrode such as Ta or Al. However, since the insulating film formed by this method is limited to the oxide of the lower electrode, there is a problem that the degree of freedom in material design is lacking, or that the heat treatment at a high temperature is required and the substrate is limited to those having heat resistance. .

On the other hand, there is also a method of forming an insulating film by coating by a wet method such as a spin coating method, a constant speed pulling method after immersion, or a dry method such as a vapor deposition method, a sputtering method and a CVD method. This is disclosed, for example, in Japanese Patent Application Laid-Open No. 60-241021, and its structure is shown in FIG. That is, Al, Ni, Ta, or the like is formed as a lower electrode 2 on a glass substrate 1 by vapor deposition, sputtering, etc., and further formed on the lower electrode 2 and the substrate 1.
An insulating film 3 made of PVDF, polyimide, or the like is formed by vapor deposition, dip coating, or the like, and a transparent electrode 4 is formed on the insulating film 3 as an upper electrode. This is so formed that the insulating film 3 and the upper transparent electrode 4 overlap over almost the entire surface, as is apparent from the state shown in the figure. In this case, when an organic thin film colored like polyimide is used for the insulating film, the transmittance of the transparent electrode 4 part also serving as a pixel electrode becomes low.

Objective The present invention has been made in view of the above-mentioned points, and solves the drawbacks caused by the anodic oxidation method, and can minimize a decrease in transmittance of a pixel portion even if an insulating film is colored. It is an object of the present invention to obtain a liquid crystal display device that does not require heat resistance.

Configuration In order to achieve the above object, the present invention provides a liquid crystal display device using a metal-insulating film-metal element in which an insulating film is interposed between a lower electrode and an upper electrode. The insulating film is formed by patterning a film made of a hard carbon film containing at least one of amorphous and microcrystalline using carbon atoms and hydrogen atoms as main structure forming elements by a dry coating method.

Further, it can be formed as an insulating film of the MIM element by vapor phase synthesis with good controllability and uniformity at a low temperature of about room temperature.
It is formed of a hard carbon film as small as r ≒ 4.

Hereinafter, a first embodiment of the present invention will be described with reference to FIG. 1 and FIG. First, a lower electrode 12 is formed on the substrate 11 by a vapor deposition method, and is patterned into a predetermined pattern by etching. The lower electrode 12 has a thickness of 3000 mm and a material of, for example, Al, but is not limited to Al. Next, a hard carbon film 13 is formed as an insulating film on the substrate 11 and the lower electrode 12 by a plasma CVD method (dry coating method), and is patterned into a predetermined pattern by dry etching. The method of forming the hard carbon film 13 and its characteristics will be described later, and the thickness is, for example, 800 Å.
Next, the upper transparent electrode 14 also serving as a pixel electrode is formed by a sputtering method, and is patterned into a predetermined pattern. The transparent electrode 14 is made of, for example, ITO, and has a thickness of 1000 °.

Thus, the lower electrode 12 (metal) -hard carbon film 13
(Insulating film)-MIM with transparent electrode 4 (metal) connected in series
An element is configured. The overall configuration of the liquid crystal display device including such a MIM element conforms to that described in the above-mentioned publication.

In such a configuration, in this embodiment, the size of the pattern of the hard carbon film (insulating film) 13 of the MIM element is, as shown in FIG.
Since it is set to have an area larger than the area that overlaps with the part that overlaps via 13, the insulation function is reliably ensured, and the hard carbon film 13 is patterned to prevent defects such as short circuits. Will not occur. Therefore, the yield is also improved. Further, the hard carbon film 13 is colored, for example, brown, but the patterning of the hard carbon film 13 causes the overlapping portion between the hard carbon film 13 and the transparent electrode 14 to be a very small part of the transparent electrode 14. Limited, the transparent electrode 14 is mostly present alone, and the transmittance of the pixel does not decrease.

Further, in this embodiment, since the insulating film is formed based on the wet or dry coating method, it is possible to select a material which cannot be handled by the anodic oxidation method or the like, for example, hard carbon iC or the like. And the characteristics of the MIM element can be further improved.

Therefore, an example of a method of synthesizing (forming) the hard carbon film 13 in the present embodiment will be described by a plasma CVD method. 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 self-bias promotes positive ion bombardment. For example, a raw material gas obtained by mixing a hydrocarbon such as CH ₄ , C ₂ H ₆ , C ₃ H ₈ or C ₄ H ₁₀ with hydrogen is introduced into the apparatus, and a high-frequency electric field of about 13.56 MHz is applied between the parallel plate electrodes. When applied, a glow discharge occurs. The raw material gas is decomposed into radicals and ions by the glow discharge and reacts with each other. A carbon film is deposited. This hard carbon film is generally called a diamond-like carbon film, an iC film, an amorphous diamond film or a diamond thin film. Conditions required for such reactions, RF output: 0.1~5.0W / cm ² pressure: 10 ^-3 to 10 Torr Deposition temperature: room temperature to 600 ° C.

The hard carbon film formed by such a film forming method has a specific resistance (ρ) of 10 ⁶ to 10 ¹³ Ωcm, a Vickers hardness (H) of up to 9500 kg · mm ^{-2 and a} refractive index (n) of 1.9 to 2.4. Density: has physical properties of 6 × 10 ¹⁶ to 10 ¹⁸ cm ⁻³ . However, the specific resistance was measured by an IV characteristic using a coplanar cell, the Vickers hardness was measured by a micro Vickers meter, the refractive index was measured by an ellipsometer, and the defect density was measured by ESR. According to X-ray and electron diffraction analysis, the amorphous state (a-C:
H) or in an amorphous state containing fine crystal grains of about 50 to 100 °. Analysis by IR absorption and Raman spectroscopy, carbon atoms as shown in FIGS. 3 and 4 is SP ³
Between hybridized and atoms to form a hybrid orbital of the SP ² bond that is clearly summer that are mixed in. Such a hard carbon film as the containing SP ² mainly of SP ^3, SP
It is as including SP ^{3 2} a mainly.

In film formation, the smaller the RF output and the lower the pressure,
As the resistivity and hardness of the film increase and the hydrogen mixture ratio increases, the refractive index increases and the defect density decreases, that is, a high-quality film can be obtained.

Furthermore, since the hard carbon film has the characteristic that the film quality does not deteriorate even when manufactured at a relatively low temperature such as from normal temperature to about 150 ° C., it is most suitable for lowering the element manufacturing process, and The material is not limited to glass or the like, and the degree of freedom in selection is increased.

In addition, a film of substantially the same quality can be formed not only by the plasma CVD method as illustrated but also by an ion beam method using the same source gas.

As described above, by forming the insulating film of the MIM element with the hard carbon film 13, variation in element characteristics is reduced, and the MIM element can withstand mechanical damage. That is, the damage due to the rubbing process when the liquid crystal material is sealed is small, and the yield is improved. Also, such a hard carbon film
Since the substrate 13 can be formed at a low temperature of about room temperature, the substrate is not limited to a substrate having heat resistance, the degree of freedom of the selection is increased, and the dielectric constant εr of the hard carbon film 13 is about εr ≒ 4. Since it is small, it can be formed with high precision without the need for fine processing as far to the left, and the yield is improved from this point as well.

Next, a second embodiment of the present invention will be described with reference to FIGS. In this embodiment, schematically, the upper electrode 15
Are formed independently of the transparent electrode 14 as a pixel electrode, and are electrically connected to the transparent electrode 14 via the upper electrode 15.

First, the lower electrode 12 is formed on the substrate 11 and patterned. Next, a resist is applied thereon and patterned, and then a hard carbon film 13 is formed thereon by a coating method. Then, the hard carbon film 13 is patterned by a so-called lift-off method of removing the resist. Thereafter, the upper electrode 15 is formed on the hard carbon film 13 and the like by a sputtering method, and is patterned into a predetermined pattern. Here, the upper electrode 15 has a thickness of, for example, Pt material.
Although formed to have a thickness of 1000 °, another material such as the same material as that of the lower electrode 12 may be used. Thereafter, a transparent electrode 14 serving as a pixel electrode is formed, and patterning is performed so that a part of the transparent electrode 14 covers the upper electrode 15. As a result, according to the present embodiment,
The transparent electrode 14 and the hard carbon film 13 do not directly contact each other,
At the time of formation, deterioration of the bonding state due to deterioration of the surface of the hard carbon film does not occur, and the device characteristics become more stable.

Effect As described above, the present invention provides a liquid crystal display device using a metal-insulating film-metal element in which an insulating film is interposed between a lower electrode and an upper electrode, and a wet or dry coating on the lower electrode. The insulating film is formed by patterning a film made of a hard carbon film containing at least one of amorphous and microcrystalline with carbon atoms and hydrogen atoms as main tissue forming elements by the method, so that the insulating film is colored. Even if it is, the decrease in the transmittance of the pixel part can be suppressed as much as possible,
Even if the insulating film is formed at a relatively low temperature when formed, the film quality is not degraded, so that the heat resistance is not required as a base material, and the degree of freedom in selecting the material can be increased. Having.

[Brief description of the drawings]

1 is a plan view showing a first embodiment of the present invention, FIG. 2 is a schematic perspective view, FIG. 3 is a wave number-absorption coefficient characteristic diagram, FIG. 4 is a wave number-intensity characteristic diagram, and FIG. FIG. 6 is a schematic perspective view showing a second embodiment of the present invention, FIG. 6 is a schematic perspective view showing a conventional example, and FIG. 11 ... substrate, 12 ... lower electrode, 13 ... insulating film made of hard carbon film, 14 ... upper electrode, 15 ... upper electrode

Continuation of the front page (72) Inventor Katsuhiko Tani 1-3-6 Nakamagome, Ota-ku, Tokyo Inside Ricoh Co., Ltd. (56) References JP-A-64-40929 (JP, A) JP-A-61-241726 (JP, A) JP-A-60-241021 (JP, A)

Claims (1)

(57) [Claims] In a liquid crystal display device using a metal-insulating film-metal element in which an insulating film is interposed between a lower electrode and an upper electrode, a carbon atom is formed on the lower electrode by a wet or dry coating method. A liquid crystal display device characterized in that the insulating film is formed by patterning a film made of a hard carbon film containing at least one of an amorphous material and a microcrystalline material using hydrogen and hydrogen atoms as main structure forming elements.