JP3381278B2 - Liquid crystal device manufacturing method, liquid crystal device, laptop personal computer and liquid crystal television equipped with the liquid crystal device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of forming an insulating film, a method of manufacturing a non-linear element using the method of forming the insulating film, a liquid crystal device having the non-linear element, and a wrap having the liquid crystal device. It relates to top PCs and LCD TVs.

[0002]

2. Description of the Related Art In recent years, liquid crystal display devices such as liquid crystal panels as panels for liquid crystal televisions and laptop personal computers have been developed. As a switching element of the liquid crystal display device, a three-terminal element thin film transistor (Thi) is used.
n Film Transistor (TFT) and 2
Terminal element metal-insulating film-metal diode (Metal)
-Insulator-Metal (MIM) and the like have been researched and developed, and among them, MIM elements (non-linear active elements) have been attracting attention because of their simple manufacturing process and high yield. FIG. 6 is a cross-sectional view of a non-linear active element formed by a conventional technique for each manufacturing process. The conventional technique will be briefly described by using this. First, as shown in FIG. 6A, a metal thin film is formed on a transparent insulating substrate 601 by a sputtering method or the like, and patterned into a desired shape to form a lower electrode 602. Ta, Al, or the like is often used for the lower electrode 602. Then, an insulating film 603 is formed by an anodic oxidation method using the lower electrode 602 as an anode and the counter substrate as a cathode. This state is shown in FIG. After that, a metal thin film is again formed by a sputtering method or the like, and patterning is performed to form the upper electrode 604, and the nonlinear active element is completed as shown in FIG. 6C. The upper electrode 604
In addition to the metal thin film used for the lower electrode, a Cr or ITO thin film may be used.

FIG. 7 is a diagram for explaining the anodizing method used for forming the insulating film 603. 701 is a chemical conversion liquid,
Reference numeral 702 is an anode made of the lower electrode 602, 703 is a cathode which is a counter electrode, and 704 is a DC power source. The anodic oxide film 603 is formed by such a method, but in the conventional technique, an aqueous solution of citric acid, an aqueous solution of phosphoric acid, an aqueous solution of sulfuric acid, or the like is often used as the chemical conversion liquid 701. Further, for the anodization, a method of using a DC power source 704, applying a bias to a constant voltage by a constant current method, and then setting a time to obtain a desired film thickness by a constant voltage method is used.

[0004]

However, with the recent development of liquid crystal display devices, the demand for non-linear elements as switching elements has increased. Under such circumstances, the following problems have been pointed out in the nonlinear active element shown in the above-mentioned conventional technique. That is, the current-voltage characteristic changes as the non-linear active element is operated. FIG. 8 shows current-voltage characteristics of a non-linear active element formed by the manufacturing method shown in the prior art. Citric acid was used as the chemical conversion liquid in the anodizing method. White circles are initial characteristics, and black circles are current-voltage characteristics after operating for a certain period of time. As shown in this figure, the initial current −
The voltage characteristics and the current-voltage characteristics after operation are very different. For example, comparing the voltage values at which the current becomes 1 μA, a characteristic change of about 1 V is observed. It is known that this amount of change in characteristics depends on the operating voltage. Therefore, when this non-linear active element is used as a switching element of a liquid crystal display device, the degree of writing varies depending on the operating voltage applied up to the previous period, In addition, the voltage applied to the liquid crystal decreases with the operation time, which causes a phenomenon that writing to the liquid crystal becomes insufficient. This is one of the main causes of afterimages and image sticking. The causes of such characteristic changes include contamination of the lower electrode surface and the interface with the insulating film due to residual resist and impurities in the air, and defects in the insulating film due to impurities mixed during anodization. With the conventional techniques as described above, it is difficult to form a clean interface and an insulating film with few defects. Therefore, the characteristic change between the initial characteristic and the characteristic after operation is small, and thus a highly reliable nonlinear active It was difficult to form an element.

The present invention solves the problems of the prior art as described above, and an object of the present invention is to form a nonlinear active element having a small amount of change in characteristics and excellent reliability.

[0006]

A method of manufacturing a liquid crystal device according to the present invention comprises a non-linear element including a lower electrode, an insulating film and an upper electrode, the step of forming the lower electrode, and the insulating film by an anodic oxidation method. And a step of forming the upper electrode, in a method of manufacturing a liquid crystal device, before forming the insulating film, the lower electrode as a cathode and the counter electrode as an anode, a constant in the chemical conversion liquid. A first step of applying a time bias to generate hydrogen on the lower electrode side;
After the first step, a second step of inverting the polarities of the voltages applied to the lower electrode and the counter electrode to form an insulating film on the lower electrode is included. In the first step, hydrogen is generated on the lower electrode side,
The surface of the lower electrode or the insulating film is cleaned by this hydrogen, and then a clean lower electrode-insulating film interface or an insulating film containing less impurities can be formed in the second step. Furthermore, the manufacturing method of the liquid crystal device of the present invention is characterized in that the first step and the second step are repeated a plurality of times. The liquid crystal device of the present invention is equipped with the non-linear element manufactured by the above-described method for manufacturing the non-linear element, and can be installed in a laptop personal computer, a liquid crystal television or the like.

[0007]

EXAMPLES Example 1 An example of a method for manufacturing a nonlinear active element of the present invention will be described.
This will be described in detail with reference to element cross-sectional views in each manufacturing process. First, as shown in FIG. 1A, the transparent insulating substrate 101
A metal thin film having a thickness of about 2000 Å to 5000 Å is formed on the lower electrode and patterned into a desired shape to form the lower electrode 102.
And eggplant For the lower electrode 102, the same metal as shown in the prior art is used. In this embodiment, a tantalum metal thin film is used, and its thickness is 3500Å
Formed by. After that, the lower electrode 102 is used as a cathode, the counter substrate is used as an anode, and a bias is applied for a certain period of time. Then, the insulating film 103 is used as an anode and the counter substrate is used as a cathode.
It is formed so as to have a certain thickness. This state is shown in Figure 1.
It is (b). In this example, an aqueous citric acid solution was used as the chemical conversion liquid. A constant voltage method, a constant current method, or the like is used as the anodizing method for forming the insulating film. In the present embodiment, the lower electrode 102 is used as an anode, and
After raising the voltage by a constant current method of mA / cm 2, anodization was performed by a constant voltage method of 30 V to form an insulating film of about 600 Å. After that, a metal thin film is formed again and patterned into a desired shape to form the upper electrode 104, and the nonlinear active element is completed as shown in FIG.

FIG. 2 is a diagram for explaining the anodizing method used in this embodiment. 201 is a chemical conversion liquid, 202 is a lower electrode, 203 is a counter electrode, and 204 is a DC power supply.
In this embodiment, first, as shown in FIG. 2A, the lower electrode 202 is used as a cathode and the counter electrode 203 is used as an anode, and a bias is applied for a certain period of time. Anodization is performed by using the electrode 202 as an anode and the counter electrode as a cathode.

FIG. 3 shows the initial voltage-current characteristics and the current-voltage characteristics after the operation of the nonlinear active element formed according to this embodiment. White circles are initial current-voltage characteristics, and black circles are those after operation. As compared with the characteristics formed by the conventional technique shown in FIG. 8, it can be seen that the amount of change in characteristics is small. For example, comparing the voltage difference at 1 μA, it can be seen that the voltage is reduced to about 0.3V. This is because by applying a bias with the lower electrode as the cathode and the counter electrode as the anode before forming the insulating film,
In order to clean the surface of the lower electrode with hydrogen generated at the cathode, the interface with the insulating film formed thereafter is
This is because it can be cleaned.

(Embodiment 2) An embodiment of the method for manufacturing a nonlinear active element of the present invention will be described.
This will be described in detail with reference to FIGS. 1 and 4. First, the lower electrode 102 is formed on the transparent insulating substrate 101 in the same manner as described in the previous embodiment. After that, in the chemical conversion liquid, the polarities of the lower electrode 102 and the counter electrode are reversed at regular intervals to form the insulating film 103. Then, the upper electrode 104 is formed to complete the nonlinear active element.

FIG. 4A is a graph showing the voltage applied to the lower electrode 102 and the counter electrode when the insulating film 103 is formed in this embodiment, with time as the horizontal axis. In FIG. 4A, the upper diagram shows the lower electrode 1
02 applied to the counter electrode, and the lower diagram shows the bias applied to the counter electrode.
When a positive bias is applied to the lower electrode, an insulating film is formed on the lower electrode, and when a positive bias is applied to the counter electrode, hydrogen is generated on the lower electrode side. The surface of the lower electrode or the insulating film is cleaned by this hydrogen, so that a clean lower electrode-insulating film interface or an insulating film with less impurities can be formed. In this embodiment, a bias as shown in FIG. 4A was applied to the lower electrode and the counter electrode to form the insulating film. However, as another example, the counter electrode is a common electrode and the lower electrode is It is obvious that a bias such as the pulse signal shown in FIG. 4 (b) may be applied. Further, the period for applying the bias can be set arbitrarily. Also,
By using the counter electrode as a common electrode and applying a bias as shown in FIG. 4C to the lower electrode, another lower electrode can be used in place of the counter substrate, and the number of processed substrates is doubled. The counter electrode is also unnecessary.

FIG. 5A shows the initial voltage-current characteristics and the current-voltage characteristics after the operation of the nonlinear active element formed according to this embodiment. White circles are initial current-voltage characteristics, and black circles are those after operation. As compared with the characteristic of the non-linear active element formed by the conventional technique shown in FIG. 8, it can be seen that the amount of change in the characteristic is extremely small. For example, comparing the difference in voltage value at 1 μA, it can be seen that the voltage is reduced to about 0.1 V or less. this is,
By reversing the polarities of the lower electrode and the counter electrode at regular intervals, the insulating film is formed while cleaning the lower electrode surface and the insulating film surface, so a clean metal-insulating film interface and insulation with few traps This is because a film can be formed.

[0013]

As described above, according to the method for manufacturing a non-linear active element of the present invention, a bias is applied to the cathode by using the lower electrode as the cathode and the counter electrode as the anode before forming the insulating film. The generated hydrogen enables the surface of the lower electrode to be cleaned. After that, by forming an insulating film by using the lower electrode as an anode and the counter electrode as a cathode, a clean insulating film-lower electrode interface can be formed. Furthermore, by forming the insulating film while reversing the polarities of the lower electrode and the counter electrode at regular intervals, it is possible to perform anodic oxidation while cleaning the surfaces of the lower electrode and the insulating film. -The insulating film interface and the insulating film with few defects can be formed. Further, in this case, the counter substrate is unnecessary and the number of processed substrates is doubled, so that cost reduction can be realized.

The non-linear active element thus obtained is
It is possible to have stable characteristics with a small change in characteristics.
Therefore, by using the nonlinear active element of the present invention, it is possible to improve the image quality of the liquid crystal display device.

[Brief description of drawings]

FIG. 1 illustrates a nonlinear active device according to an embodiment of the present invention,
The element sectional view for every manufacturing process.

FIG. 2 is a diagram illustrating an anodizing method in a reference example of the present invention.

FIG. 3 is a diagram showing current-voltage characteristics of a non-linear active element formed in a reference example of the present invention.

FIG. 4 is a diagram showing a voltage applied to a lower electrode and a counter electrode in the anodic oxidation method according to the example of the present invention.

FIG. 5 is a diagram showing current-voltage characteristics of a non-linear active element formed in an example of the present invention.

FIG. 6 is an element cross-sectional view of a non-linear active element according to a conventional technique for each manufacturing process.

FIG. 7 is a diagram illustrating an anodizing method in a conventional technique.

FIG. 8 is a diagram showing voltage-current characteristics of a non-linear active element formed by a conventional technique.

[Explanation of symbols]

101, 601 ... Transparent insulating substrate 102, 602 ... Lower electrode 103, 603 ... Insulating film 104, 604 ... Upper electrode 201, 701 ... Chemical liquid 202, 702 ... Lower electrode 203, 703 ... Counter electrode 204, 704 ... DC power supply

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-53-131932 (JP, A) JP-A-53-138938 (JP, A) JP-A-55-11184 (JP, A) JP-A-57- 118601 (JP, A) JP-A-3-148638 (JP, A) JP-A-3-259226 (JP, A) JP-A-3-48824 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G02F 1/1365 H01L 49/02 C25D 11/00

Claims (5)

(57) [Claims] 1. A non-linear element including a lower electrode, an insulating film, and an upper electrode is provided, the step of forming the lower electrode, the step of forming the insulating film by an anodic oxidation method, and the step of forming the upper electrode. In the method for manufacturing a liquid crystal device, including the step of generating hydrogen on the side of the lower electrode by applying a bias for a certain period of time in a chemical conversion liquid with the lower electrode as a cathode and the counter electrode as an anode before forming the insulating film. And a second step of forming an insulating film on the lower electrode by reversing the polarities of the voltages applied to the lower electrode and the counter electrode after the first step. And a method for manufacturing a liquid crystal device. 2. The method for manufacturing a liquid crystal device according to claim 1, wherein the first step and the second step are repeated a plurality of times. 3. A liquid crystal device manufactured by using the method for manufacturing a liquid crystal device according to claim 1. 4. A laptop personal computer equipped with the liquid crystal device according to claim 3. 5. A liquid crystal television equipped with the liquid crystal device according to claim 3.