JPH0566423A - Liquid crystal display device - Google Patents

Abstract

PURPOSE:To obtain a liquid crystal display device in which the short circuit of an element is prevented while preventing the lowering of yield and the dispersion of the characteristic of the element is reduced. CONSTITUTION:In an active matrix type liquid crystal display device where a non-linear active element 32 having the structure of metal-semiconducting insulating layer-metal is formed on a substrate 31, and one metallic part of the element 32 on the substrate side is set as a lower electrode 34 and the metallic part of the other side is set as an upper electrode; a 1st insulating layer 36 having an upper surface positioned on nearly the same plane as the upper surface of the lower electrode 34 of the element 32 is formed around the lower electrode 34 on the substrate 31 separately from the semiconducting insulating layer 33 of the element 32.

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,
In particular, the present invention relates to a liquid crystal display device using a non-linear active element having a metal-insulating layer-metal structure or a metal-semiconductive insulating layer-metal structure.

[0002]

2. Description of the Related Art In recent years, in a laptop or portable information processing apparatus represented by a personal computer, it has been desired to colorize a display portion and increase the definition thereof.
An active matrix type liquid crystal display device is known as a display device satisfying such requirements. In the active matrix method, by arranging a non-linear active element in each pixel, it is possible to eliminate interference of extra signals and achieve high image quality.

In the active matrix system, in addition to a TFT (Thin Film Transistor) system using a 3-terminal element, a MIM (Metal Insurator Meta) using a 2-terminal element is used.
l) method, and the MIM method uses a non-linear active element having a metal-insulating layer-metal structure. This MIM non-linear active element applies the non-linear current-voltage characteristic of the insulator itself to ON / OFF switching characteristics. In particular, the MIM (Metal Insulation) method that uses a semiconductive insulating layer as the insulating layer which is the active layer is used in the MIM method.
or Metal) method.

FIG. 7 is a view showing a cross section of a conventional MIM element. In FIG. 7, the MIM element is one in which the lower electrode 6, the insulating layer 7, and the upper electrode 8 are sequentially formed on the substrate 1 by using a photolithography method and patterned, and the pixel electrode 9 is formed on the upper electrode 8. It is connected. In such a structure, since the thickness of the insulating layer 7 near the corners of the lower electrode 6 becomes thin, the electric field is concentrated so that the lower electrode 6 is prevented.
There is a problem that the corners of the and the upper electrode 8 are short-circuited. For the purpose of solving such a problem, for example, those disclosed in JP-A-1-270027 and JP-A-1-283524 have been proposed, and are shown in FIG.

In FIG. 8, the corner portions of the lower electrode 26 are tapered to form the intermediate insulating layer 22, and then the contact holes are formed so that the tapered portion is not used as an element. Reference numeral 21 is a substrate, 26 is a lower electrode, 27 is an insulating layer or a semiconductive insulating layer, 28 is an upper electrode, and 29 is a pixel electrode. On the other hand, in a liquid crystal display device, a light-transmissive plastic substrate such as polyethylene terephthalate (hereinafter referred to as PET) is considered promising instead of a glass substrate due to demands for further reduction in weight and thickness. Since such a plastic substrate contains a large amount of water in the gap between the molecular chains, when the active element is arranged on such a substrate as described above, H ₂ O is not contained as an impurity in the activation layer of the active element. When mixed in a specific amount, it adversely affects the electrical characteristics of the device. As a countermeasure against this, a plastic substrate is previously subjected to a heat degassing treatment in a vacuum, but in reality, it is not possible to obtain a sufficient degassing effect because the temperature cannot be raised so much due to the heat resistance of the substrate. .. Also,
Since the plastic substrate has higher moisture permeability than the inorganic material substrate such as glass and has a low barrier property against elements such as alkali, the reliability of the active element is uncertain under severe usage conditions such as portable use. Therefore, an oxide such as SiO ₂ or a nitride such as Si ₃ N ₄ is formed as a protective film between the plastic substrate and the nonlinear active element. These protective films are formed by a plasma CVD (Chemical Vapor Deposition) method or a reactive sputtering method.

[0006]

However, in the conventional liquid crystal display device as shown in FIG. 8, the corner portions of the lower electrode 26 are tapered and the intermediate insulating layer 22 is further formed. Therefore, there is a problem that the number of manufacturing steps increases, the layer structure becomes complicated, and the yield of the device decreases, and an etching-altered layer is formed on the surface of the insulating layer that is the active layer or the semiconductive insulating layer 27. It has been a cause of variations in the characteristics of the device.

Further, in the conventional liquid crystal display device using the plastic substrate, there are problems that the brightness of the display is lowered and the cost is increased due to the following reasons. .. That is, since a protective layer such as an oxide or a nitride is formed on a plastic substrate by a plasma CVD method or a reactive sputtering method, the substrate temperature rises to 150 to 300 ° C. and the heat resistance is high in these methods. It was necessary to select the substrate. Alternatively, it is necessary to reduce the input energy to suppress the temperature rise of the substrate to form a film, which slows down the film formation rate and makes it easier to take in atmospheric gas as impurities, impairing the film transmittance and barrier properties. Become. In addition, generally, a film formed at a low temperature by these methods has many pinholes, and it is necessary to increase the film thickness of the protective film. Therefore, the transmittance of the film also decreases from this point. Further, when the transmittance of the protective film is low as described above, the brightness of the entire liquid crystal display unit becomes dark, so that the protective film cannot be formed on the entire plastic substrate and only on the portion where the nonlinear active element is arranged. It is necessary to perform patterning so as to form a protective film, which increases costs.

Therefore, the invention according to claims 1 and 2 provides a liquid crystal display device capable of preventing a short circuit of an element while preventing a decrease in yield and reducing variations in element characteristics. The task is to do. Another object of the present invention is to provide a liquid crystal display device in which the brightness of the display is improved and the cost is reduced when a plastic substrate is used.

[0009]

The invention according to claim 1 is
A non-linear active element having a metal-insulating layer-metal structure or a metal-semi-conducting insulating layer-metal structure is formed on a substrate, and one metal portion on the substrate side of the non-linear active element is a lower electrode and the other metal portion. In the active matrix type liquid crystal display device in which the upper electrode is the upper electrode, the first insulating layer having an upper surface located substantially on the same plane as the upper surface of the lower electrode of the nonlinear active element is used as an insulating layer of the nonlinear active element and a semi-conductive layer. It is characterized in that it is formed around the lower electrode on the substrate separately from the insulating layer.

According to a second aspect of the present invention, in addition to the structure of the first aspect, the first insulating layer is made of a translucent oxide, nitride or oxynitride. .. According to a third aspect of the present invention, in a liquid crystal display device in which a nonlinear active element is formed on a transparent substrate made of plastic, a light-transmitting film made of an aluminum nitride film or an aluminum oxynitride film is provided between the transparent substrate and the nonlinear active element. Forming a transparent insulating protective film, and the transparent insulating protective film,
The film is formed by an electron cyclotron resonance plasma activated reactive vapor deposition method or an electron cyclotron resonance plasma assisted ion beam sputtering method.

[0011]

According to the first aspect of the invention, the formation of the first insulating layer prevents the gap between the corner of the lower electrode and the upper electrode from being narrowed, and prevents the electric field from concentrating on the corner of the lower electrode. To be done. Therefore, the short circuit of the element is prevented. In addition, the interface between the insulating layer of the nonlinear active element or the semiconductive insulating layer and the upper electrode is prevented from being exposed to the etching gas during the manufacturing process.

According to the invention of claim 2, in addition to the function of claim 1, since the first insulating layer has a light-transmitting property, the brightness of the panel is impaired even if the first insulating layer is formed on the entire surface of the transparent substrate. I don't care. In the invention according to claim 3, since the translucent insulating protective film is composed of an aluminum nitride film or an aluminum oxynitride film, the liquid crystal panel is prevented from being lowered in transmittance and has a barrier resistance against moisture or alkali. Further, it becomes possible to form a transparent insulating protective film over the entire surface of the transparent substrate. In addition, the translucent insulating protective film is formed by electron cyclotron resonance plasma activated reactive evaporation method or electron cyclotron resonance plasma assisted ion beam sputtering method, which prevents the occurrence of pinholes and raises the substrate temperature. Can be suppressed to about 100 ° C.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a liquid crystal display device according to the invention of claims 1 and 2. Note that FIG. 1 shows one dot of the liquid crystal display device, and for simplification, the illustration of the configuration on the opposite side including the liquid crystal layer is omitted.

First, the structure will be described. In FIG. 1C, 31 is a substrate, and a non-linear active element 32 having a metal-semiconductive insulating layer-metal structure is formed on the substrate 31. The liquid crystal display device of the present embodiment is an active matrix type element (MSI element), 33 is a semiconductive insulating layer,
One metal portion of the nonlinear active element 32 on the substrate 31 side is a lower electrode 34, and the other metal portion is an upper electrode 35. Reference numeral 36 denotes a first insulating layer having an upper surface located substantially on the same plane as the upper surface of the lower electrode 34 of the nonlinear active element 32.
Is formed around the lower electrode 34 on the substrate 31 separately from the semiconductive insulating layer 33 of the nonlinear active element 32. An insulating layer may be used instead of the semiconductive insulating layer 33, and in this case, the nonlinear active element 32 is a MIM element.

Next, a method of manufacturing the liquid crystal display device having the above structure will be described. First, as shown in FIG. 1A, an etch stopper layer 37 and a first insulating layer 36 are successively formed on a substrate 31. Next, a resist 38 is applied on the first insulating layer 36,
A concave pattern is formed in the shape of the lower electrode. Here, the combination of the etch stopper layer 37 and the first insulating layer 36 must be a combination of materials having sufficient selectivity with respect to the etching gas such as CF ₄ . Further, it is desirable that these materials have a light-transmitting property that does not impair the brightness of the liquid crystal panel. In this embodiment, SiO ₂ is used for the etch stopper layer 37 and AlN is used for the first insulating layer 36, and these layers are formed by the sputtering method. For the first insulating layer 36, another transparent nitride such as Si ₃ N ₄ or a transparent oxide such as Ta ₂ O ₅ or a transparent oxynitride is used. Good.

Next, as shown in FIG. 1B, after removing the first insulating layer 36 exposed in the concave pattern by etching, a metal layer 39 is formed on the entire surface. At this time, the metal layer 39
The thickness of the first insulating layer 36 is substantially the same as that of the first insulating layer 36.
The portion removed by etching of 36 is replaced with the metal layer 39. Next, the metal layer 39 on the resist 38 is removed by a lift-off method, and the remaining metal layer portion is used as the lower electrode 34, and as shown in FIG. 1C, the semiconductive insulating layer 33, the upper electrode 35 and the pixel. The electrode 40 is successively formed. In this embodiment, the metal layer 39, that is, the lower electrode 34 is made of Al, the semiconductive insulating layer 33 is made of AlNx (X <1), the upper electrode 35 is made of Ni, and the pixel electrode is made of ITO (Indium Tin Oxide). It was formed by a sputtering method or a reactive sputtering method.

According to the above-described structure, since the first insulating layer 36 having the upper surface located on the same plane as the upper surface of the lower electrode 34 is formed around the lower electrode 34, the corners of the lower electrode 34 are formed. It is possible to prevent the gap between the upper portion and the upper electrode 35 from being narrowed, and to prevent the electric field from concentrating on the corner portion of the lower electrode 34. Therefore, it is possible to prevent short-circuit breakdown of the element, and it is possible to significantly reduce the initial failure of the element.

Further, unlike the conventional case, the interface between the semiconductive insulating layer and the upper electrode is not exposed to the etching gas during the process, so that variations in device characteristics can be reduced. Further, as compared with the conventional one in which the corners of the lower electrode are tapered, the element structure and the manufacturing process can be simplified, and the reduction in yield can be prevented.

Furthermore, since the first insulating layer 36 is composed of a translucent oxide, nitride or oxynitride, even if the first insulating layer 36 is formed on the entire surface of the PET substrate 31, the panel is not formed. The first insulating layer does not lose its brightness.
It is possible to eliminate 36 patterning. Therefore, the cost can be reduced. Furthermore, since the etch stopper layer 37 formed on the entire surface of the substrate also functions as a barrier layer against the intrusion of moisture and alkali elements into the substrate when a plastic film is used as the substrate as in this embodiment, It is possible to suppress the change with time of the element.

FIG. 2 is a diagram showing a second embodiment of the liquid crystal display device according to the invention described in claims 1 and 2. Figure 2
In (c), 51 is a substrate, and a metal-
A non-linear active element 52 having a semiconductive insulating layer-metal structure is formed. The liquid crystal display device of this embodiment is an active matrix type element (MSI element), 53 is a semiconductive insulating layer, one metal portion of the nonlinear active element 52 on the substrate 51 side is the lower electrode 54, and the other is The metal part is the upper electrode 55
Has become. Reference numeral 56 is a first insulating layer having an upper surface located substantially on the same plane as the upper surface of the lower electrode 54 of the nonlinear active element 52, and the first insulating layer 56 is different from the semiconductive insulating layer 53 of the nonlinear active element 52. It is separately formed around the lower electrode 54 on the substrate 51. An insulating layer may be used instead of the semiconductive insulating layer 53. In this case, the nonlinear active element 52 is the MIM.
It becomes an element.

Next, a method of manufacturing the liquid crystal display device having the above structure will be described. First, as shown in FIG. 2A, a lower electrode 54 made of Al is patterned on a substrate 51 using a positive resist 57. Then, mask the resist 57,
As shown in FIG. 2B, a first insulating layer 56 having substantially the same thickness as the lower electrode 54 is formed. The first insulating layer 56 may be formed on the entire surface of the substrate 51 if it is made of a material having a light-transmitting property, but if not, it must be patterned to an appropriate size. In this embodiment, AlN is deposited on the entire surface of the substrate 51 by the reactive sputtering method.

Next, the resist is lifted off by the lift-off method.
57 and the first insulating layer 56 on the lower electrode 54 are removed, and the semiconductive insulating layer 53, the upper electrode 55 and the pixel electrode 58 are successively formed. The material of each layer and the film forming method are the same as those in the first embodiment. According to the configuration as described above, similarly to the first embodiment described above, it is possible to prevent short-circuit breakdown of the element due to electric field concentration due to the corner portion of the lower electrode 54, and it is possible to reduce the variation of the element. it can.

3 to 6 are views showing an embodiment of the liquid crystal display device according to the invention described in claim 3. In FIGS. 3 and 4, reference numeral 61 is a transparent substrate made of polyethylene terephthalate (hereinafter referred to as a PET substrate), and a nonlinear active element 62 is formed on the PET substrate 61. Reference numeral 63 denotes a translucent insulating protective film formed between the PET substrate 61 and the non-linear active element 62, and the translucent insulating protective film 63 is an AlN film, that is, an aluminum nitride film. The AlN film has an electric resistance of 10
Not only is it a good insulator of ¹¹ to 10 ¹³ Ωcm, but it is also a chemically very stable film. Moreover, since the band gap is as large as 6.2 eV and light is transmitted to the ultraviolet region, it can be formed on the entire surface of the PET substrate 61 without impairing the brightness of the display. The transparent insulating protective film 63 is formed by an electron cyclotron resonance plasma activated reactive vapor deposition method or an electron cyclotron resonance plasma assisted ion beam sputtering method, as described later. Note that P
The ET substrate 63 may be made of another plastic material.

Next, a method for forming the transparent insulating protective film 63 and a method for forming the non-linear active element 62 will be described. When the translucent insulating protective film 63 is formed by the electron cyclotron resonance plasma activated reactive evaporation method, the film forming apparatus shown in FIG. 5 is used. First, the PET substrate 61 is attached to the water-cooled substrate holder 65 connected to the rotating mechanism 64. The Al atoms evaporated from the electron gun evaporation source 66 react with the active species in the N ₂ plasma extracted by the divergent magnetic field from the plasma generation chamber 67, and PE
A 1500Å thick AlN film, that is, a transparent insulating protective film 63 is formed on the entire surface of the PET substrate 61 on the T substrate 61. The DC coil 68 is an electromagnet for generating a cyclotron resonance magnetic field of electrons with respect to the microwave introduced into the plasma generation chamber 67. The film forming pressure at this time is 8 × 10 ⁻⁵
The degree of vacuum is 1 to 2 orders of magnitude higher than that of ordinary plasma CVD method or reactive sputtering method. Further, when the translucent insulating protective film 63 is formed by the electron cyclotron resonance plasma assisted ion beam sputtering method, the film forming apparatus shown in FIG. 6 is used. This apparatus uses an ion beam sputtering source composed of an ion source 69 and a sputtering target 70 in place of the electron gun evaporation source 66 described above.

On the other hand, in forming the non-linear active element 62, a transparent pixel electrode 71, a lower electrode 72, an insulating layer 73 and an upper electrode 74 are sequentially patterned as shown in FIG. Forming 62.
According to the above configuration, the nonlinear active element 62 and the PET
Since the translucent insulating protective film 63 made of AlN is formed between the substrates 61, the moisture contained in the PET substrate 61 and the alkali or the like that permeates the substrate can be prevented without lowering the transmittance of the liquid crystal panel. The barrier resistance against elements can be improved. Moreover, since the transparent insulating protective film 63 can be formed on the entire surface of the PET substrate 61, there is no need to pattern the transparent insulating protective film 63, and the increase in cost can be minimized.

Further, since the transparent insulating protective film 63 is formed by the reactive vapor deposition method or the reactive sputtering method using the electron cyclotron resonance plasma source, the temperature rise of the PET substrate 61 is suppressed to 100 ° C. A dense film with few holes can be formed, the thickness of the light-transmitting insulating protective film can be reduced, and the brightness of display can be improved.

Further, although the plastic substrate generally has low heat resistance, the use of the above-mentioned method enables the film formation at an extremely low temperature, thereby increasing the degree of freedom in selecting the substrate material.

[0028]

According to the first aspect of the present invention, the first insulating layer having an upper surface located substantially on the same plane as the upper surface of the lower electrode of the nonlinear active element is used as the insulating layer of the nonlinear active element and the semiconductive layer. Since it is formed around the lower electrode on the substrate separately from the insulating layer, it is possible to prevent a decrease in yield while preventing a short circuit of the element and further reduce variations in element characteristics.

According to the invention of claim 2, in addition to the effect of claim 1, even if the first insulating layer is formed on the entire surface of the transparent substrate, the brightness of the display is not impaired. The patterning of one insulating layer can be made unnecessary, and the cost can be reduced. According to the invention of claim 3, a translucent insulating protective film made of an aluminum nitride film or an aluminum oxynitride film is provided between the transparent substrate and the non-linear active element by electron cyclotron resonance plasma activated reactive deposition method. Alternatively, since the film is formed by the electron cyclotron resonance plasma assisted ion beam sputtering method,
It is possible to reduce the cost while improving the brightness of the display.

[Brief description of drawings]

FIG. 1 is a view showing a manufacturing process of a first embodiment of a liquid crystal display device according to the invention of claims 1 and 2,
(A) shows the patterning process of the first insulating layer, (b) shows the forming process of the lower electrode, and (c) shows the forming process of the semiconductive insulating layer and the upper electrode.

FIG. 2 is a diagram showing a manufacturing process of a second embodiment of the liquid crystal display device according to the invention of claims 1 and 2,
(A) shows the patterning process of the lower electrode, (b) shows the forming process of the first insulating layer, and (c) shows the forming process of the semiconductive insulating layer and the upper electrode.

FIG. 3 is a main part top view showing an embodiment of the liquid crystal display device according to the invention of claim 3;

4 is a cross-sectional view taken along the line AA in FIG.

FIG. 5 is a schematic cross-sectional view of a manufacturing apparatus used when the translucent insulating protective film of FIG. 3 is formed by using an electron cyclotron resonance plasma activated reactive vapor deposition method.

FIG. 6 is a schematic cross-sectional view of a manufacturing apparatus used when the translucent insulating protective film of FIG. 3 is formed by an electron cyclotron resonance plasma assisted ion beam sputtering method.

FIG. 7 is a cross-sectional view of a main part of a conventional liquid crystal display device.

FIG. 8 is a cross-sectional view of a main part of another conventional liquid crystal display device.

[Explanation of symbols]

 31, 51 Substrate 32, 52 Non-linear active element 33 53 Semi-conductive insulating layer 34, 54 Lower electrode 35, 55 Upper electrode 36, 56 First insulating layer 61 Transparent substrate made of plastic 62 Non-linear active element 63 Translucent insulation protection film

Claims (3)

[Claims] 1. A non-linear active element having a metal-insulating layer-metal structure or a metal-semiconductive insulating layer-metal structure is formed on a substrate, and one metal portion on the substrate side of the non-linear active element is a lower electrode. In the active matrix type liquid crystal display device in which the other metal portion serves as an upper electrode, the first insulating layer having an upper surface located substantially on the same plane as the upper surface of the lower electrode of the non-linear active element is isolated from the non-linear active element. A liquid crystal display device characterized in that it is formed around the lower electrode on the substrate separately from the layer and the semiconductive insulating layer. 2. The liquid crystal display device according to claim 1, wherein the first insulating layer is made of a translucent oxide, nitride or oxynitride. 3. A liquid crystal display device in which a non-linear active element is formed on a transparent substrate made of plastic, and a transparent insulating protection film made of an aluminum nitride film or an aluminum oxynitride film is provided between the transparent substrate and the non-linear active element. A liquid crystal display device, wherein a film is formed, and the translucent insulating protective film is formed by an electron cyclotron resonance plasma activated reactive vapor deposition method or an electron cyclotron resonance plasma assisted ion beam sputtering method.