JPH07104318A - Mim type nonlinear element and its manufacture - Google Patents

Abstract

PURPOSE:To manufacture the MIM type nonlinear element having uniform electrical characteristics by controlling the atomic ratio of oxygen to tantalum in the metal oxide film to a value in a specified range. CONSTITUTION:As for the elements in the metal oxide film 13, the ratio of oxygen (O) to tantalum (Ta) is <2.5 O/Ta at the time of anodically oxidizing the first metallic film 12 with a chemical conversion solution obtained by dissolving a solute into alcohol used as the solvent, differently from that of >2.5 O/Ta at the time of performing the above anodic oxidation wherein water is used as the solvent. At the time of adjusting the ratio of oxygen to tantalum to <2.5, O/Ta, the steepness of the voltage-current characteristics is increased. Accordingly, the metal oxide film 13 is preferably formed by anodically oxidizing the first matallic film 12 with a solution obtained by dissolving a suitable solute into an alcohol solvent. At this time, the MIM type nonlinear element which is capable of driving the liquid crystal may be provided even by adopting the double-layered wiring with Al as the first metallic film 12, that is concurrently used as the scanning line, and lowering its electric resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a MIM type non-linear element, and more particularly to obtaining a voltage-current characteristic suitable for driving a liquid crystal and obtaining an element having uniform electric characteristics in a substrate.

[0002]

2. Description of the Related Art Generally, in an active matrix type liquid crystal display device, between a substrate on one side where a matrix array is formed by providing a non-linear element for each pixel region and a substrate on the other side where a color filter is formed. Is filled with liquid crystal and the alignment state of the liquid crystal in each pixel area is controlled to display predetermined information. Here, as the non-linear element, a three-terminal element such as a thin film transistor (TFT) or a two-terminal element such as a metal-insulator-metal (MIM) type non-linear element is used, but the screen size and cost of the liquid crystal display element are reduced. In order to meet the above requirement, the method using the MIM type non-linear element is advantageous because the manufacturing process is short. Moreover, when the MIM type non-linear element is used, the scanning line can be provided on the substrate on one side where the matrix array is formed and the signal line can be provided on the substrate on the other side. There is also an advantage that a crossover short circuit between the scanning line and the signal line, which is the cause, does not occur.

In an active matrix type liquid crystal display panel using such a MIM type non-linear element,
As shown in FIG. 3, which is an equivalent circuit of the liquid crystal display panel, MI is provided between each scanning line 31 and each signal line 32 in each pixel region 3.
An M-type non-linear element 1 (indicated by a varistor symbol in the figure) and a liquid crystal display element 2 (indicated by a capacitor symbol in the figure) are shown as connected in series, and are connected to the scanning line 31 and the signal line 32. Based on the applied signal, the liquid crystal display element 2
The display operation is controlled by switching the display state to the non-display state or the intermediate state.

As indicated by reference numeral 41 in FIG. 4A, in the MIM type non-linear element 1, the applied voltage V _NL and the current I _NL have a non-linear relationship. The threshold voltage of the MIM type non-linear element 1 is V _th , and the threshold voltage of the liquid crystal display element 2 is V _th .
_b , and the potential to be in the display state is (V _b + ΔV), FIG.
As shown in (b), in the selection period, the potential difference V (applied voltage to the unit pixel) between the scanning line 31 and the signal line 32 in the predetermined pixel region 3 is set to (V _b + V _th ). The liquid crystal display element 2 can be brought into a non-display state, and the potential difference V between the scanning line 31 and the signal line 32 is (V _b + V _th +
By setting ΔV), the liquid crystal display element 2 can be brought into a display state. On the other hand, in the non-selection period, the electric potential V applied to the unit pixel is set to be close to the electric potential remaining in the liquid crystal display element 2, and if the difference is V _th or less,
During the non-selection period, the MIM type non-linear element 1 is always in the cutoff state, and the state defined in the selection period is maintained as it is.

As described above, it is possible to obtain an ideal MIM type non-linear element 1 in which the capacitance of the MIM type non-linear element is sufficiently small and the non-linearity of the voltage-current characteristic is sufficiently high, and the wiring for giving a signal to the MIM type non-linear element is obtained. This is the most basic operation example when the resistance can be made sufficiently low. As an element having a sufficiently small capacity and a high voltage-current characteristic, as shown in JP-A-2-93433, 10 atomic% or less of silicon is added to a Ta film forming a first metal film, and the film is used as an anode. MIM produced by including silicon in a tantalum oxide film formed by oxidation
Type nonlinear element 1. In addition, since the Ta film has a tetragonal structure in a thin film state and has a very high specific resistance of 180 μΩ · cm, it has a two-layer structure of an alloy film with another anodizable metal or an anodizable low resistance metal. It is considered to use a membrane.

A general structure of such a MIM type non-linear element will be described with reference to FIG. 1 (b) which is a cross-sectional view of AA 'in FIG. 1 (a) which is a plan view of the MIM type non-linear element. MI
The M-type non-linear element 1 is formed on the front surface side of the transparent substrate 11 and is Ta conductively connected to the scanning circuit side via the scanning line 31.
The first metal film 12 mainly containing atoms, the metal oxide film 13 on the surface side thereof, and the pixel electrode 1 formed on the surface side
5 and a second metal film 14 made of Cr that is electrically connected. The metal oxide film 13 is formed by anodizing the first metal film 12 so that the Ta film has a uniform film thickness and is formed without pinholes.

A general process example for realizing this structure is as follows.

1. By depositing a Ta film on a glass substrate by sputtering and performing thermal oxidation, a T film of about 1000Å can be obtained.
1. a step of forming an a ₂ O ₅ film; Next, as shown in FIG. 2A, a first metal film containing Ta atoms as a main component and containing impurity atoms other than Ta atoms was formed by co-sputtering or electron beam evaporation to a thickness of about 5000 Å.
2. Deposit and pattern. Next, as shown in FIG. 2B, a step of forming an oxide film on the surface side of the first metal film by anodizing at 30 V using a dilute aqueous solution of citric acid as a chemical conversion solution, and 4. Next, the substrate in the state of FIG.
4. Heat treatment at a temperature of 600 ° C. for 1 to 2 hours, Next, as shown in FIG. 2C, a step of depositing and patterning a Cr film to be a second metal film by a sputtering method of about 1500 Å, 6. Next, as shown in FIG. 2D, a conventional process has been started from the step of depositing an ITO film, which is one of the transparent conductive films to be the pixel electrodes, by a sputtering method to about 2000 liters and patterning it.

[0009]

[Problems to be Solved by the Invention] However, MIM
In the liquid crystal display panel using the non-linear element 1, there are problems that the gradation of color is not clean, crosstalk is conspicuous, and an afterimage is likely to occur after displaying a still image. As the cause, in the present invention, as a result of investigating the relationship between each component of the matrix array and the display performance,
It has been confirmed that the cause is related to the element forming the metal oxide film 13 forming the MIM type nonlinear element 1 and its composition ratio. Each issue will be described in detail below.

The first problem is that there is no color gradation. The cause is the voltage of the MIM type non-linear element-
The steepness of the current characteristics is small, the leakage current during the non-selection period is large, and the element capacitance is large. As a countermeasure, it is preferable to mix silicon atoms or the like into the metal oxide film 13, but if the film is formed by anodic oxidation of the first metal film, it is difficult to oxidize silicon in an aqueous solution, and thus it is difficult to form a uniform film. Therefore, JP-A-2-93433 describes that the amount of silicon added should be 10 atomic% or less.

As a cause of the second problem of crosstalk, the wiring resistance of the first metal film 12 forming the scanning line 31 whose main component is tantalum, which has a high resistance in a thin film, is high, and the MIM type non-linear element is used. The leakage current in the off state is large. As a method of reducing wiring resistance,
There is a method in which the first metal film has a two-layer structure with a low resistance metal such as aluminum or copper, or an alloy with the metal is used to reduce the resistance value. It was not deposited.

The occurrence of the afterimage which is the third problem is caused by the change with time of the voltage-current characteristics. When the voltage-current characteristic of the MIM type non-linear element changes due to the voltage application, FIG.
As shown in (b), in the initial stage of the operation, the potential difference V between the scanning line 31 and the signal line 32 is set to (V _b + V _th ), so that the liquid crystal display element 3 is brought into the non-display state and the potential difference V is reduced. Although the liquid crystal display element 3 could be controlled to the display state by setting (V _b + V _th + ΔV), the applied voltage V _NL and the current I _{NL of} the MIM type non-linear element 1 shift depending on the use history. The alignment state of the liquid crystal display panel does not change as in the initial operation. Therefore, afterimages are generated on the liquid crystal display panel, which causes a problem that the display quality is deteriorated. The afterimage phenomenon not only makes the liquid crystal display element difficult to see, but also causes a decrease in contrast and a decrease in color purity in the case of color display.

[0013]

Means for Solving the Problems M formed on the surface of a substrate
In the IM type non-linear element, the atomic ratio of oxygen atoms to tantalum atoms in the metal oxide film forming the insulating film is O / Ta <2.5.
If so, the steepness of the voltage-current characteristic is increased. The insulating film can be obtained by anodizing a first metal film, which is a metal film containing tantalum atoms, using a chemical conversion solution in which a solute is dissolved in an alcohol solution, and is not easily oxidized by the first metal film. Even if the element is included, an oxide film having a uniform film quality and a uniform film thickness within the substrate surface is formed. In particular, an ethylene glycol solution among alcohol solutions can form an oxide film without unevenness, and the dielectric constant of the insulating film can be 22 or less to improve the voltage-current characteristics of the MIM type non-linear element.

In order to obtain a MIM type non-linear element more suitable for driving a liquid crystal than the above description, the insulating film is solute with an ethylene glycol solution of the first metal film which is a metal film containing tantalum and silicon atoms. By using an anodic oxide film that uses a chemical solution in which is dissolved, even if a large amount of silicon atoms are contained, a uniform metal oxide film can be deposited within the substrate, and the steepness of the voltage-current characteristics is large and the device capacitance is large. A small MIM type non-linear element of Furthermore, in the first metal film, tungsten, rhenium, iridium, etc.
When the group 7 and 8 atoms are contained, the element is incorporated into the metal oxide film, and the change of the current value with time when a voltage is applied can be suppressed.

[0015]

EXAMPLES The present invention will be described in detail below based on examples.

The manufacturing process common to the present invention is shown below. FIG. 1 shows a diagram showing a top view of an active matrix using the liquid crystal display device of the present invention and a diagram showing a cross section taken along the line AA ′. The MIM type non-linear element 1 is formed at the intersection of the scanning line 12 made of the first metal film and the second metal film 14, and the pixel electrode is indicated by 15.
11 is a transparent substrate such as glass or quartz, 11a is a tantalum deposited by sputtering (Ta), tantalum oxide film all film deposited by thermally oxidation or sputtering (TaO _X), 12 is a tantalum It is a metal film as a main component. This is because the tantalum oxide film 11a prevents film peeling of the first metal film 12 and diffusion of impurities from the substrate due to heat treatment after the metal oxide film 13 is deposited.
It is not necessary to deposit if none of the above matters. Next, the first metal film 12 is anodized with a chemical conversion solution in which alcohol is used as a solvent and a solute is added thereto to form a metal oxide film 13 containing the elements contained in the first metal film 12. It 14 is a second metal film, the type of which is determined by what kind of process is adopted. A pixel electrode 15 is made of a transparent conductive film such as an ITO film. Further, as shown in FIG. 11, in order to shorten the manufacturing process, the second metal film may also be used as the transparent conductive film 111 such as the ITO film which is the pixel electrode.

The above-mentioned manufacturing method of the tapering is the same as that of the prior art. The present invention refers to the structure of the first metal film, the material of the metal oxide film, and the manufacturing method.

A method of increasing the steepness of the first MIM type non-linear element will be described. Among the elements contained in the metal oxide film 13, the atomic ratio of tantalum (Ta) to oxygen (O) is 0 / when the first metal film 12 is anodized with a chemical conversion solution containing alcohol as a solvent and a solute added thereto. Ta <2.5, which is different from O / Ta> 2.5 when water is used as a solvent. When the atomic ratio of oxygen to tantalum is set to 0 / Ta <2.5 in this way, the steepness of the voltage-current characteristic becomes large. Generally, the metal oxide film also contains elements other than Ta and O. However, the atomic ratio of tantalum and oxygen described here corresponds to that of the elements contained in the metal oxide film 13. It is the atomic ratio of tantalum to oxygen. O /
It has been stated that when Ta <2.5, the steepness of the voltage-current characteristic increases, but specifically, the voltage-current characteristic of the MIM type nonlinear element is expressed linearly on the horizontal axis and the current value on the vertical axis. In FIG. 5, which is represented by the logarithm of the value divided by, the characteristic 51 of the alcohol solution formation is 52 as compared with the characteristic 51 of the aqueous solution formation. That is, it is shown that 52 is larger than the inclination of 51. Further, the value of the slope will be hereinafter referred to as a β value.

There are various kinds of alcohol solutions, but since the present invention is intended for a MIM type non-linear element for driving a liquid crystal display element, the electric characteristic of the element is about 1 m square. The condition is that it is uniform no matter where it is prepared on the substrate having the size of 1. In this respect, the ethylene glycol solution was the best.

When ethylene glycol is used as the anodizing chemical solution, the solubility of the solute is often smaller than that of the aqueous solution, and it is necessary to immerse the solution in a sulfuric acid solution to remove the solution adhering to the substrate after the anodization is completed. In some cases, the handling becomes complicated, so that the solution may be mixed with ethylene glycol and water to cause a slight decrease in β value, but the above problem may be solved. FIG. 6 shows the relationship between the β value and the concentration of ethylene glycol in the mixed solution of ethylene glycol and water. This is the measurement data of the MIM type non-linear element produced by forming the first metal film as an alloy film in which tantalum is added with several atomic% of tungsten and using citric acid as a solute for anodic oxidation at 30V. The β value greatly changes at the ethylene glycol concentration of 50%, and O / Ta = 2.5 at this concentration. That is, even if water is contained in the ethylene glycol solvent of the anodizing chemical solution, a relatively large β value can be obtained if the water content is such that O / Ta <2.5. In the MIM type non-linear element for which the data of FIG. 6 was obtained, the ethylene glycol concentration at which the β value suddenly decreased was 50%, but depending on the solute used for the anodizing chemical solution and the element forming the first metal film, The ethylene glycol concentration is different to obtain a large β value. Therefore, the concentration of water added to ethylene glycol varies depending on the process conditions and needs to be optimized for each.

Second, it is necessary to increase the β value and reduce the capacitance of the MIM type non-linear element. Since the liquid crystal display element using the MIM type non-linear element is connected in series with the liquid crystal as shown in FIG. 3, in order to prevent the outflow of the charges during the liquid crystal holding period, the MIM type non-linear element should be used with respect to the liquid crystal display element 2. It is desirable to make the capacitance of the element 1 as small as possible. As a method of reducing the capacitance, a method of adding a material having a relative dielectric constant smaller than that of the metal oxide film 13 whose main component is TaO _x having a relative dielectric constant of 28 when manufactured by a conventional method is used. However, it is difficult to manufacture an element having the same voltage-current characteristics on a 1 m square substrate. Two methods for uniformly forming the metal oxide film 13 having a relative dielectric constant of 22 or less will be described below.

First, as shown in FIG. 2A, the first metal film 1
2 is a tantalum film containing 10 atomic% or less of elements of groups 6, 7 and 8 in the periodic table, the film is anodized using a solution of ethylene glycol as a solvent and a suitable solute, and after heat treatment Then, the second metal film 14 may be deposited as shown in FIG. The MIM type non-linear element thus manufactured has a relative permittivity of 22 or less and an atomic ratio of O / Ta <2.5. The MIM type non-linear element does not have different voltage-current characteristics before and after the voltage application for a certain period of time, which has been conventionally seen, and does not change the current value flowing when the direction of current flow is changed. Further, the β value becomes large, and the device is suitable for driving a liquid crystal. The electrical characteristics differ depending on the type of solute. For example, if phosphoric acid is used, the relative permittivity is 18 and the β value is 3
After anodizing at a voltage of 0 V, it becomes about 5, and with citric acid the values are 21 and 4.5, respectively, and the characteristics are poor, but the uniformity of the device characteristics within the substrate is better with the citric acid solute. ing. When the solute is difficult to dissolve in ethylene glycol, water may be added in the range where the relative permittivity of the metal oxide film 13 is 22 or less and the atomic ratio is O / Ta <2.5.

As a second method, as shown in FIG. 2A, the first metal film 12 is an alloy film containing tantalum and 15 atomic% or more of silicon atoms, and the film is made of ethylene glycol as a solvent. Anodization is performed using a solution in which a solute is dissolved, and after heat treatment, the second metal film 1 is formed as shown in FIG.
4 may be deposited. It was difficult to form an element having uniform electric characteristics with a chemical conversion solution using water as a solvent, but when ethylene glycol was used as a solvent, the electric characteristics of the element became almost constant. Further, although it was difficult to anodize the first metal film in which the atomic ratio of silicon atoms was more than half, it was difficult to anodize it.
It has become possible to deposit a metal oxide film which can be a MIM type non-linear element even with the tantalum alloy film of. Further, the β value was about 20% larger than that in the case of anodizing in an aqueous solution when the conditions of solute and anodizing were the same.

If a MIM type non-linear element having a relative permittivity of 22 or more is produced, the β value is small, so that a very complicated driving method is used or a panel design is not made to reduce the aperture ratio. Couldn't move. However, the present invention simplifies the drive circuit, increases the aperture ratio, and provides contrast even in a large panel.
An IM type non-linear element was obtained.

Thirdly, a method of reducing the wiring resistance of the scanning lines to reduce crosstalk will be described. As shown in FIG. 1a, the first metal film 12 is formed on the scan line 3 shown in FIG.
Since it also doubles as 1, the wiring delay becomes a problem when the size of the liquid crystal display element increases. By the way, when the main component of the first metal film is Ta, the specific resistance is 200 μΩ.
cm, which is more than 10 times that of a normal metal, the first metal film 12 is made of aluminum (Al) 12b as shown in FIG. 7 instead of FIG.
There is a method of forming a two-layer film with 2a, or a method of forming the first metal film as an alloy film containing Al as a main component and Ta. However,
As shown in FIG. 7, when an anodic oxide film is deposited on the side surface of the Al film 12b, if the solvent of the anodizing chemical solution is water, the Al oxide film is deposited and easily dissolved in water by an electric reaction with the Ta film. Eventually, the oxide film is not deposited on the side of the Al film, and the first metal film and the second metal film of the MIM type nonlinear element are short-circuited. Here, when the solvent is ethylene glycol, the oxide film is deposited without any problem.

A method of using ethylene glycol for anodic oxidation of Al is disclosed in Japanese Patent Application Laid-Open No. 2-85826, but in the present invention, the Ta film and the Al film are simultaneously oxidized and the Ta and Al oxide film to be deposited is deposited. This is because the electric conductivity of the Al oxide film is smaller than that of the Ta oxide film. That is, since the Al oxide film has a sufficiently lower electric conductivity than the Ta oxide film, the above requirement can be achieved if an oxide film having a similar thickness is deposited. Is prevented by using ethylene glycol solution. Even if the anodizing chemical solution contains water, an Al oxide film having a sufficient film thickness is deposited in the concentration region where the β value becomes large as shown in FIG.

Even when the first metal film 12 is an alloy film of Al and Ta, when the anodizing chemical solution is ethylene glycol as a solvent, the metal oxide film 13 containing Al and Ta is uniformly deposited on the surface of the substrate. To be done. When the alloy film of Al and Ta is anodized in an aqueous solution, the Al oxide is not stably deposited, so that the variation in the film thickness within the substrate surface is large. Al and T
In the MIM type non-linear element produced by anodizing the alloy film of a, the current value decreases in proportion to the Al content because the Al oxide in the metal oxide film does not participate in electrical conduction.
There is no change in the steepness of the voltage-current characteristics. Therefore, in order to form an excellent liquid crystal display panel, the metal oxide film 1
Al in the film is higher than that in an element in which Al is not included in 3
By increasing the size of the MIM type non-linear element according to the content, it is possible to provide a liquid crystal display panel in which the wiring resistance of the scanning line 31 does not change and the wiring resistance is small.

Fourthly, a method of suppressing the change with time of the voltage-current characteristic which causes the afterimage will be described. As described in the second method, the first metal film is an alloy film of tantalum atoms and elements of groups 6, 7, and 8 of the periodic table, and the film is anodized with an ethylene glycol solvent to form a metal oxide film. When a MIM type non-linear element is manufactured by depositing, the β value becomes large, the change in the voltage-current characteristics before and after the voltage is applied to the element for a certain time is eliminated, and the current is the first metal. It is possible to eliminate the difference in current value between the case of flowing from the film to the second metal film and the opposite case. Further, the first metal film is a tantalum film containing 15 atomic% or more of silicon atoms and a film containing several atomic% of tungsten,
When the MIM type non-linear element is manufactured by anodizing the film using a chemical conversion solution using ethylene glycol as a solvent, the element capacity is small, the β value is larger, and the voltage-current characteristics change even when a voltage is applied to the element. It is possible to manufacture a two-terminal element that is optimal for driving a liquid crystal that does not.

The above are the problems solved by the present invention,
The same result can be obtained by using a conductive film such as a metal film or a transparent conductive film as the second metal film. The effects on the liquid crystal display element when the steepness (β value) of the voltage-current characteristic becomes large, when the capacitance of the MIM type nonlinear element becomes small, and when the wiring resistance of the scanning line decreases will be described below. To do.

The effect of improving the steepness of the voltage-current characteristics, for example, for driving a liquid crystal display element will be described. In the multiplex drive, the display state is modulated by the difference in the voltage that charges the unit pixel during the selection period, but the data potential to be written in synchronization with other scanning lines on the signal line constantly fluctuates (in one horizontal period cycle). Accordingly, the unit pixel that has already been selected is also applied as a disturbance amount which is a change in the applied voltage of the selected pixel. That is,
There is at least a positive correlation between the dynamic range in which modulation is possible and the voltage applied to the unit pixel at the time of non-selection, and the voltage applied to the unit pixel during the non-selection period is reduced to obtain a display with sufficient contrast. You will not be able to do things.

When the steepness is small, the current value in the non-selection period also becomes large if the current value in the sufficient selection period is maintained, and the charge of the liquid crystal layer to be held by the voltage applied in the non-selection period is MIM type nonlinear. It flows out through the element. On the contrary, if the modulation voltage width is not sufficient to hold this charge, the contrast cannot be increased in the display pixel. Further, crosstalk occurs because the amount of charge outflow varies depending on the display image of other portions. In addition to these, the small steepness causes a large change in the voltage applied to the liquid crystal layer particularly when the applied voltage waveform changes due to wiring delay or the like during the selection period. As described above, if the steepness is increased, the above-mentioned adverse effect does not appear, so that a clean liquid crystal display device can be provided.

Further, as the steepness increases, the range of selection of usable liquid crystals expands. That is, from the above, it is possible to widen the range of the effective value voltage that can be applied to the liquid crystal. Thus, if the effective voltage range that can be applied to the liquid crystal can be increased and widened, for example, with respect to a liquid crystal having a voltage-transmittance curve in which the transmittance gradually increases even when a high voltage is applied, which is seen in polymer dispersed liquid crystals Also, it is possible to utilize the performance of it.

Next, the effect when the capacitance (C _MIM ) of the MIM type non-linear element is lowered will be described. The voltage (V _ap ) applied to the unit pixel is divided by C _MIM and the capacitance of the liquid crystal layer (C _lc ), but as the value of C _MIM increases, of the change amount of V _ap The proportion added to the MIM type non-linear element becomes smaller. That is, the amount by which the liquid crystal layer voltage is raised and the amount by which it is pushed down at the beginning and end of the selection period (so-called field through voltage).
Will increase. In particular, the field-through voltage amount at the end of the selection period lowers the liquid crystal voltage itself and also reduces the dynamic range of the display image because the field-through voltage amount varies depending on the modulation degree of the signal. Specifically, even if the signal voltage or its modulated voltage width is the same, when C _MIM is large, a sufficient contrast cannot be obtained as a display image.

Further, C _MIM has a great influence on the liquid crystal layer voltage even in the non-selection period. On the signal line, the data potential to be written in synchronism with other scanning lines constantly rises and falls (in one horizontal period cycle), and is applied to the already selected unit pixel as a disturbance amount which is a change in V _ap. It As described above, the larger C _MIM is, the larger the voltage applied to the liquid crystal layer for the change in V _ap is, and the liquid crystal layer that should be held is disturbed. The amount of this disturbance depends on the displayed image. The difference is that it causes a fatal defect in the display device called crosstalk. In the actual image, the display pattern appears as a phenomenon of thin tail.

With respect to crosstalk, attempts have been made to make the amount of disturbance uniform (not depending on the display image) by performing pulse width modulation or the like of the display state depending on the charging time, but at present a sufficient effect. I have not come to get. As described above, this is caused by the timing shift due to the wiring delay, the increase in the spatial frequency of the image, the even-odd pattern, and the like. In other words, the only solution is to reduce the amount of disturbance itself.

Next, the scanning line 3 formed of the first metal film 12
The effect when the wiring resistance of No. 1 is reduced will be described. As shown in FIG. 3, a signal voltage as shown in FIG. 8A is applied to the MIM type nonlinear element 1 and the liquid crystal display element 3 connected in series from the scanning circuit and the signal supply circuit. At this time MIM
Since the voltage applied to the non-linear element 1 is as shown in FIG. 8B, a voltage is applied to the liquid crystal display element 3 as shown in FIG. 8C, and the light switching operation is controlled. Here, the region indicated by "T" is a selection period of a certain pixel, and the other region is a non-selection period. FIG. 8 shows that the MIM type non-linear element 1 is turned on during the selection period.

Now, the signal voltage as shown in FIG. 8A is applied to the pixel (area A in FIG. 3) near the scanning circuit and the signal supply circuit, which waveform is almost the same as the applied waveform. However,
When the resistance value of the scanning line 31 is high, a signal delay occurs and the applied waveform is considerably blunted in the pixel region 2 distant from the scanning circuit.

For example, in the panel in which the scanning circuit and the signal supply circuit are arranged as shown in FIG. 3, the leftmost pixel (area A in FIG. 3) and the rightmost pixel (B in FIG. 3) in the first row. Compare the voltage waveforms applied to the area). The reason why the pixel in the first row is selected is that the voltage applied to one pixel is determined by the difference between the voltage supplied from the signal supply circuit and the voltage supplied from the scanning circuit, so that the signal delay of the signal line 32 is ignored. This is because Therefore, in the nth row far from the signal supply circuit, the delay of the signal line becomes a problem. Here, the signal delay of the scanning line 31 becomes a problem in the selection period of the pixel in which the voltage value varies greatly, and therefore only this case will be described.

9A, 9B, and 9C are voltages applied to the A region of FIG. 3, and FIGS. 9D, 9E, and 9F are before and after the selection period of the voltage applied to the B region. It is a waveform and is for the case where the same signal is input. (A) and (d), (b) and (e), (c) and (f) show the voltage waveform applied to the pixel region 2, the voltage waveform applied to the MIM type nonlinear element 1, and the liquid crystal display, respectively. 3 shows a voltage waveform applied to the element 3.

The voltage shown in FIG. 9A is applied to the area A in FIG. 3, but the signal delay of the scanning line 31 is applied to the area B.
The waveform is blunted as shown in FIG. as a result,
A voltage as shown in FIG. 9B is applied to the MIM type non-linear element 1 in the A region, but as shown in FIG. 9E in the B region, the voltage applied to the MIM type non-linear element 1 is △ V
Since drops by _M, a voltage difference △ V _L to the write voltage of the liquid crystal display device 3 occurs. When this voltage difference ΔV _L does not reach one gradation, even if ΔV _L displays a picture as a display, human eyes cannot perceive the difference. However, when the screen becomes large or multi-gradation display is performed, when a picture is displayed, the unevenness of the screen due to ΔV _L comes to be recognized. At this time, since the resistance value of the first metal film is high, even if the magnitude of ΔV _L becomes a problem, for example, if the resistance value becomes 1/10, ΔV _L also becomes 1/10 and the unevenness of the screen occurs. Becomes difficult to detect with human eyes.

Further, from the above discussion, the reduction of the wiring resistance of the scanning line 31 has the effect of reducing the crosstalk.
Since the reduction of crosstalk is also effective by reducing the capacitance of the MIM type non-linear element as described above, the effect is further enhanced when the wiring resistance of the scanning line is reduced. In a liquid crystal display panel in which scanning lines are formed in the horizontal direction, as shown in FIG.
It is assumed that the black area 102 is displayed while displaying.
At this time, the white level of the area 103 is darker than the white level of the area 104. In other words, crosstalk is determined by the product of wiring resistance and capacitance applied to a certain scan line,
Since the capacity of the liquid crystal is parallel to the substrate (when the liquid crystal is blocking light) and when it is perpendicular (when the liquid crystal is transmitting light), the capacity is about twice as large, so it passes through the black area. The scanning line 105 for scanning has a larger product of wiring resistance and capacitance than the scanning line 106 passing only in the white region. Therefore, in order to prevent the product of the wiring resistance and the capacitance from having a great influence on ΔV _L between the scanning lines 105 and 106, the wiring resistance may be reduced.

From the above, the scanning line 31 is provided in the direction in which the wiring length is shortened in order to reduce the liquid crystal capacitance applied to the wiring.
The wiring can be formed in a direction in which the wiring length becomes long while suppressing the crosstalk that appears remarkably in the terminal element. Then, the pixel area can be increased and the aperture ratio is improved, so that the liquid crystal display panel can be brightened.

[0043]

As described above, the atomic ratio of tantalum and oxygen in the metal oxide film of the MIM type nonlinear element is O / Ta <
By setting it to 2.5, the β value can be increased, and an element having uniform electric characteristics in the substrate can be manufactured. In order to obtain the above MIM type non-linear element, the metal oxide film may be formed by anodizing the first metal film into a solution of a suitable solute in an alcohol solvent. At this time, it is possible to provide the MIM type non-linear element that can drive the liquid crystal even if the first metal film that also serves as the scanning line is made into a two-layer wiring with Al to reduce the resistance. Further, the same effect can be obtained by manufacturing an element having a relative dielectric constant of 22 or less. The MIM type non-linear element may use ethylene glycol as a solvent for anodic oxidation. At this time, if tungsten atoms are added to the metal oxide film, the characteristic shift and the polarity difference caused by the voltage application for a certain period of time are eliminated, so that a liquid crystal display element without an afterimage can be provided.

[Brief description of drawings]

FIG. 1A is a top view of a MIM type non-linear element of the present invention. (B) Sectional drawing of the MIM type | mold nonlinear element of this generation side.

FIG. 2 is a cross-sectional view showing a manufacturing process of a MIM type nonlinear element.

FIG. 3 is an equivalent circuit diagram of an active matrix liquid crystal display device.

FIG. 4A is a diagram showing a relationship between an applied voltage and a current value of a conventional MIM type nonlinear element. (B) A diagram showing the relationship between the applied voltage to the unit pixel of the liquid crystal display element and the brightness.

FIG. 5 is a diagram showing a relationship between an applied voltage and a current value of a MIM type nonlinear element.

FIG. 6 is a graph showing the relationship between the concentration of ethylene glycol as a solvent and water during anodic oxidation and the β value of the voltage-current characteristic of the MIM type non-linear element.

FIG. 7 is a sectional view of a MIM type non-linear element.

FIG. 8 is a diagram showing a drive voltage waveform of a liquid crystal display panel.

FIG. 9 is a diagram showing drive voltage waveforms at both ends of the liquid crystal display panel.

FIG. 10 is a diagram showing a liquid crystal display panel having crosstalk.

FIG. 11A is a top view of the MIM type non-linear element of the present invention. (B) Sectional drawing of the MIM type | mold nonlinear element of this generation side.

[Explanation of symbols]

1 MIM nonlinear device 2 liquid crystal display device 3 pixel region 11 transparent substrate 11a TaO _X film 12 first metal film 12a tantalum metal of lower resistance than the metal film 12b tantalum as a main component film 13 metal oxide film 14 second Metal film of 15 Pixel electrode 31 Scan line 32 Signal line 41 Initial voltage-current characteristics 42, 43 Voltage-current characteristics after voltage application 51 Voltage-current characteristics anodized with aqueous solution solvent 52 Voltage anodized with ethylene glycol solvent- Current characteristics 101 White area 102 Black area 103 White area affected by black area 104 White area not affected by black area 105 Scan line with crosstalk 106 Scan line without crosstalk 111 Second metal film and pixel Transparent conductive film forming the electrode

Claims (9)

[Claims] 1. A MIM type non-linear element comprising a first metal film-insulating film-second metal film or conductive film formed on a surface of a substrate, wherein the insulating film is an oxide film of a metal containing tantalum atoms. An MIM type non-linear element characterized in that the atomic ratio of tantalum (Ta) atoms to oxygen (O) atoms is O / Ta <2.5. 2. A MIM type non-linear element comprising a first metal film-insulating film-second metal film or conductive film formed on the surface of a substrate, wherein the insulating film is a metal film containing tantalum atoms. A method of manufacturing a MIM type non-linear element, characterized in that the first metal film is a film anodized using a chemical conversion solution in which a solute is dissolved in an alcohol solution. 3. The insulating film according to claim 2, wherein the first metal film, which is a metal film containing tantalum atoms, is anodized using a chemical conversion solution obtained by dissolving a solute in a mixed solution of alcohol and water. A method of manufacturing a MIM type non-linear element, which is characterized in that 4. The MIM, wherein the alcohol according to claim 2 or 3 is ethylene glycol.
Method of manufacturing type nonlinear element. 5. A MIM type non-linear element comprising a first metal film-insulating film-second metal film or conductive film formed on the surface of a substrate, wherein the insulating film is an oxide film of a metal containing tantalum atoms. A MIM type non-linear element having a relative dielectric constant of 22 or less. 6. A MIM type non-linear element comprising a first metal film-insulating film-second metal film or conductive film formed on the surface of a substrate, wherein the insulating film comprises tantalum atoms and a periodic table of 6, An MI characterized in that the first metal film, which is a metal film containing at least one element of Group 7 or 8 is anodized using a chemical conversion solution in which a solute is dissolved in an ethylene glycol solution.
Method for manufacturing M-type non-linear element. 7. The insulating film according to claim 6, wherein the first metal film, which is a metal film containing tantalum and silicon atoms, is anodized using a chemical conversion solution obtained by dissolving a solute in an ethylene glycol solution. A method of manufacturing a MIM type non-linear element, comprising: 8. The insulating film according to claim 6, wherein the first metal film, which is a metal film containing tantalum, silicon and tungsten atoms, is anodized using a chemical conversion solution obtained by dissolving a solute in an ethylene glycol solution. M as a film
IM-type non-linear element manufacturing method. 9. The MIM type nonlinear element according to claim 1, wherein the second metal film or conductive film is a transparent conductive film.