JP3169319B2 - Manufacturing method of nonlinear element - 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 for manufacturing a non-linear element used in a display device having a display medium such as a liquid crystal.

[0002]

2. Description of the Related Art Recently, OA of personal computers and the like has been developed.
With the downsizing of devices, demands for high-performance flat panel displays are increasing. Research and development of a liquid crystal panel, an EL panel, or a plasma panel has been promoted as a flat panel. In particular, liquid crystal panels have been commercialized as a wide range of display devices from watches and calculators to personal computers and televisions. In the future,
As multimedia becomes more advanced, higher functions such as higher resolution, higher contrast, full color, and power saving drive are required.

As a display device satisfying these requirements, there is an active matrix type liquid crystal display device in which an active element is added to each of a plurality of pixels arranged in a matrix. As the active element,
The two types of active elements having three terminals and nonlinear elements having two terminals have been vigorously developed. In particular, a two-terminal nonlinear element requires a smaller number of masks at the time of manufacture than a three-terminal active element represented by a TFT, so that lower cost can be expected.

At present, as a two-terminal non-linear element, a non-linear element using tantalum oxide for a non-linear resistance layer (Japanese Patent Publication No. Sho.
No. 1-32674), a non-linear element using a silicon nitride film or a silicon oxide film (Japanese Patent Publication No. 6-17957) or a non-linear element using zinc sulfide (Japanese Unexamined Patent Publication No. 6-313899).
No.) has been developed. In particular, a nonlinear element using zinc sulfide not only has a large nonlinearity of the IV characteristic,
By doping impurities into zinc sulfide, I-
Since the V characteristic can be controlled, an IV characteristic element can be designed according to the electro-optical characteristics of the display medium, and as a result, a large contrast display device can be provided.

[0005]

By the way, as a method for producing a zinc sulfide film, EB (Electron Beam) vapor deposition,
Sputtering method, CVD (Chemical Vapor Depositi
On) method and MBE (Molecu1ar Beam Epitaxy) method are known. In particular, the sputtering method is effective in productivity because the film is denser than the EB evaporation method and can be formed more easily than the CVD method or the MBE method.

In general, a sputtering method uses a substance to be formed as a target and uses an inert gas typified by helium, argon, xenon, or the like as a sputtering gas. Then, the sputtering gas is ionized by discharge, the ions collide with the target, atoms or molecules on the target surface are sputter-evaporated, and the sputter-evaporated target material adheres to the substrate to form a thin film. .

When zinc sulfide is formed by the sputtering method, a zinc sulfide target is used, and when impurities are mixed in the zinc sulfide film, a zinc sulfide target mixed with impurities is used. Further, as a sputtering gas, for example, argon is introduced into the evacuated chamber to a gas pressure capable of discharging, and discharge is performed by a high-frequency power supply. Parameters for performing sputtering control include input power of a high-frequency power supply, sputtering gas pressure, sputtering gas flow rate, substrate temperature, and the like. A zinc sulfide film is formed by optimizing each parameter.

Here, a conventional method for manufacturing a nonlinear element having a nonlinear resistance layer containing zinc sulfide as a main component and characteristics of the nonlinear element will be described. Regarding the manufacturing method, first, a conductive film to be a first electrode is formed over an insulating substrate. Here, Ta was used as the first electrode. Next, while using a firing target of zinc sulfide mixed with nickel and using argon gas as a sputtering gas, a zinc sulfide film mixed with nickel to be a nonlinear resistance layer is formed on the first electrode. At this time, the thickness of the nonlinear resistance layer was 80 nm. Further, a second electrode is formed on the non-linear resistance layer to complete the non-linear element. Here, Al was used as the second electrode.

In general, the following five characteristics are required for a nonlinear element. High steepness of IV characteristics High symmetry of IV characteristics in forward and reverse directions High element withstand voltage No change over time Small change in IV characteristics due to environmental temperature Figure 1 ( 12 in a) shows the IV characteristics of the nonlinear element manufactured by the above-described conventional manufacturing method. Here, a case where a positive voltage is applied to the second electrode is defined as a forward direction, and a case where a negative voltage is applied is defined as a reverse direction. In the fabricated conventional nonlinear element having a nonlinear resistance layer containing zinc sulfide as a main component, the steepness of the IV characteristic is 10% by taking the ratio of the current value flowing when a voltage of 20 V and 5 V is applied. ^The value was as high as ⁵ or more, indicating that the nonlinear characteristics were good. However, the asymmetry is slightly recognized in the forward and reverse IV characteristics, and when a general signal whose waveform is shown in FIG. 5 as an example is continuously applied, the IV characteristics are shifted. . The state of the shift of the IV characteristic varies depending on the method of manufacturing the nonlinear element, but in the nonlinear element manufactured as described above, the shift to the higher voltage side was performed. Further, when the temperature characteristics of the nonlinear element were examined, it was found that the current flowed as the temperature increased, in other words, the IV characteristics shifted to a lower voltage side.

As described above, a nonlinear element having a nonlinear resistance layer containing zinc sulfide as a main component and manufactured by a conventional manufacturing method does not satisfy all the characteristics required for the nonlinear element.

The present invention has been made to solve such problems of the prior art, and has a high steepness of the IV characteristic, a symmetry of the IV characteristic in the forward direction and the reverse direction, and the like. It is an object of the present invention to provide a non-linear element which can improve the element withstand voltage, does not change with time in the IV characteristics, and has excellent temperature characteristics.

[0012]

According to a method of manufacturing a nonlinear element of the present invention, a partial pressure of a hydrogen gas when an inert gas is set to 1 in a nonlinear resistance layer provided between a pair of electrodes.
Because the ratio is formed by a sputtering method using a Supattaga scan which ranged from 0.01 to 0.5, the object is achieved.

[0013]

Another method of manufacturing a non-linear element according to the present invention is as follows.
The nonlinear resistance layer provided between the pair of electrodes
Firing target, or zinc sulfide and impurities
Using a firing target made of
To the sputtering method using inert gas and hydrogen gas
To achieve the above purpose.
You.

In the method for manufacturing a nonlinear element according to the present invention,
A first electrode, which is one of the pair of electrodes, is formed over a substrate, and is stacked on or partially in contact with the first electrode to form a non-linear resistance layer. An electrode may be laminated on the non-linear resistance layer or formed in partial contact therewith.

[0016]

According to the present invention, a non-linear resistance layer mainly composed of zinc sulfide sandwiched between a pair of electrodes is produced by sputtering using an inert gas and a hydrogen gas as a sputtering gas.

Further, when a sputtering gas having a partial pressure ratio of hydrogen in the range of 0.01 to 0.5 when the inert gas is set to 1 is used, the symmetry of the IV characteristic of the non-linear element is obtained. It has an effect on sex.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below.

In the present invention, a non-linear resistance layer mainly composed of zinc sulfide is formed on the first electrode on the insulating substrate by a sputtering method. Its formation, for example,
Sputtering is performed using a zinc sulfide target mixed with nickel and using an argon gas and a hydrogen gas as a sputtering gas to form a nonlinear resistance layer. The thickness of the nonlinear resistance layer was 80 nm. Further, Al is formed as a second electrode on the non-linear resistance layer to complete the non-linear element. The thickness of the non-linear resistance layer is not limited to 80 nm as described above.
What is necessary is just to select suitably according to a use.

Here, the only difference from the conventional example is that the film formation is carried out using argon gas and hydrogen gas as the sputtering gas as the conditions for forming the nonlinear resistance layer. Is the same.

FIG. 1A shows the symmetry of the IV characteristic of the nonlinear element of the present invention. As can be understood from this figure, the IV characteristic 11 of the nonlinear element of the present invention has improved symmetry of the IV characteristic and the element withstand voltage as compared with the characteristic 12 of the conventional nonlinear element. Is allowed.

FIG. 1B shows a temperature characteristic showing a change in current with respect to temperature when a constant voltage is applied to the nonlinear element. Here, the temperature characteristic is represented by the reciprocal of the temperature on the horizontal axis and l on the vertical axis.
og (current value) is shown in a so-called Arrhenius plot. The graph of the temperature characteristics indicates that the larger the slope, the larger the change in current with temperature. Therefore, as can be understood from this figure, the current-temperature characteristic 101 of the nonlinear element of the present invention has a gentler gradient than the current-temperature characteristic 102 of the conventional nonlinear element, and the IV characteristic changes with temperature. It was observed that it was small.

Further, when the voltage shown in FIG. 5 was continuously applied and the change over time of the nonlinear element of the present invention was examined, no change in the IV characteristics was observed.

FIG. 1C shows the relationship between the partial pressure ratio of hydrogen gas to argon gas and the symmetry of the IV characteristics. The horizontal axis shows the hydrogen partial pressure ratio when the argon gas is set to 1, and the vertical axis shows the symmetry of the forward and reverse current values at a voltage of 15 V. The value indicating this symmetry is defined by equation (1).

1- (| I (+)-I (-) |) / I (+) Equation (1) where I (+) = forward current at voltage 15V I (-) = current at voltage 15V The current in the opposite direction, that is, the value 1 indicates complete symmetry,
The value decreases as the symmetry worsens. The partial pressure ratio of hydrogen was set to 0.1 when argon gas was set to 1.
There is an effect in the range of 01 to 0.5.

The non-linear element manufactured according to the present invention has I
The steepness of the -V characteristic is high, the symmetry in the forward and reverse directions and the element breakdown voltage can be improved, and the IV characteristic does not change with time, and the temperature characteristic is excellent. Therefore, for example, when a liquid crystal display device is manufactured using the nonlinear element of the present invention, since the symmetry in the forward and reverse directions is good, the polarity of the voltage applied to the liquid crystal by the positive / negative selection potential of the scanning signal. This eliminates the difference due to the polarity of the applied voltage of the liquid crystal, and reduces the image sticking and the afterimage phenomenon due to the application of the direct current to the liquid crystal layer, resulting in a low cost, high quality, high image quality, and highly reliable display device. Provided.

In the configuration of the non-linear element of the present invention, a first electrode, which is one of a pair of electrodes, is formed on a substrate, and is laminated on the first electrode or in a state where the first electrode is partially in contact with the first electrode. A non-linear resistance layer is formed. Further, a second electrode which is the other of the pair of electrodes may be stacked on the non-linear resistance layer, or may be formed so as to be in partial contact therewith.

Next, a specific embodiment of the present invention will be described.

(First Embodiment) As a first embodiment, a white tailor type guest-host liquid crystal display device using the nonlinear element of the present invention will be described.

FIG. 2A is a plan view showing one pixel of the element-side substrate of the nonlinear element having the nonlinear element according to the present embodiment, and FIG. 2B is a plan view of FIG. FIG. 4 shows a cross-sectional view taken along line A ′. FIG. 3 is a perspective view showing two pixels of a reflective white tailor type guest-host liquid crystal display device. This liquid crystal display device has a configuration in which a white tailor-type guest-host liquid crystal 34 is sandwiched between an element-side substrate 27 and an opposite-side substrate 29.

The element-side substrate 27 has a scanning electrode 22 on the glass substrate 21 with the first electrode 22a as a part.
An insulating film 23 is formed on the scanning electrode 22 having the first electrode 22a as a part, and a contact hole 23a is formed on the first electrode 22a in the insulating film 23. On the insulating film 23 and the contact hole 2
A non-linear resistance layer 24 is formed inside 3a. This nonlinear resistance layer 24 is made of a zinc sulfide film containing nickel as an impurity.

The pixel electrode 2 is formed on the nonlinear resistance layer 24.
5 are formed. A portion of the pixel electrode 25 near the contact hole 23a forms a second electrode 25a, and the second electrode 25a and the first electrode 22a opposed to each other with the non-linear resistance layer 24 interposed therebetween constitute the non-linear element 26 of this embodiment. You.

One of the opposing substrates 29 is a glass substrate 28.
On the counter electrode 30 made of ITO (indium-tin-oxide)
Are formed. The counter electrode 30 is provided to face the pixel electrode 25.

Next, a method of manufacturing the nonlinear element according to the present embodiment will be described as a part of the manufacturing process of the liquid crystal display device having such a configuration. First, the element-side substrate 27 will be described.

After a Ta film is formed to a thickness of 200 nm on the glass substrate 21 by sputtering, predetermined patterning is performed to form a scanning electrode 22 and a first electrode 22a.

Next, an insulating film 23 is formed. In this example, an organic photosensitive resin was used as the insulating film. Use of a photosensitive resin has an advantage that the patterning process can be simplified. The insulating film 23 is formed, for example, by applying a photosensitive resin to a thickness of about 1.4 μm by a spin coating method, and then, through an exposure and development step, a contact hole for connecting the non-linear resistance layer 24 and the pixel electrode 25. 23a was formed. After that, the surface of the insulating film 23 is made uneven by a photo process.

Next, the non-linear resistance layer 24 is formed by a sputtering method. As a sputtering method, a firing target of zinc sulfide mixed with nickel was used, and argon gas and hydrogen gas were used as sputtering gases. In addition, argon gas was set to 50 sccm, and hydrogen gas was set to 5 sccm at a flow rate of 5 sccm, and the non-linear resistance layer 24 made of a zinc sulfide film containing nickel was formed on the insulating film 23 by sputtering.
The film was formed to a thickness of nm. When the nonlinear resistance layer 24 is formed of a zinc sulfide film mixed with nickel, it is possible to control the current flowing through the element while maintaining the steepness of the IV characteristics in accordance with the mixed amount of nickel. Element design according to characteristics is possible. When the amount of nickel in the non-linear resistance layer 24 is determined by analysis by the flameless atomic absorption method, the amount of nickel in the zinc sulfide film is 0.4%.
wt%.

Although the argon gas and the hydrogen gas are separately introduced into the chamber here, a gas in which an argon gas and a hydrogen gas are mixed in advance may be prepared and introduced into the chamber. Although argon gas is used as the inert gas, the same effect can be obtained by using other types of inert gas such as helium, neon, and xenon.

Next, a pixel electrode 25 also serving as a second electrode is formed. The formation of the pixel electrode 25 also serving as the second electrode
For example, this was performed by forming a film of aluminum to a thickness of about 200 nm by sputtering and patterning it into a predetermined shape.

Next, the procedure for manufacturing the opposing substrate will be described. An ITO film was formed on the glass substrate 28 by about 200 nm sputtering. After that, a photo process was performed, and after etching with hydrobromic acid, the resist was stripped and patterned to form a stripe-shaped counter electrode 30.

Next, the element-side substrate 2 manufactured in the above steps
After applying an alignment film 33 to the surface on the side on which elements and electrodes are formed, the two substrates 2 and 7
7 and 29 were bonded so that the alignment film 33 was on the inside.

Next, a liquid crystal display device is completed by injecting a white tailor type guest host liquid crystal 34 between the substrates 27 and 29 and sealing the injection port.

The liquid crystal display device manufactured as described above exhibits good reflection characteristics (VR characteristics) with respect to the liquid crystal driving voltage, has no change in VR characteristics even after long-term aging, and has a temperature characteristic. , It was confirmed that good display quality was obtained.

(Second Embodiment) As a second embodiment, a transmission type liquid crystal display device will be described.

FIG. 4A is a plan view of one pixel portion of the element-side substrate, and FIG. 4B is a cross-sectional view taken along the line BB 'of FIG. 4A. This liquid crystal display device is manufactured as follows.

First, after a Ta film is formed to a thickness of about 300 nm on the glass substrate 41 by, for example, sputtering, predetermined patterning is performed to form a first electrode 42a.

Next, a non-linear resistance layer 44 is formed under the same sputtering conditions as in the first embodiment.

Next, an insulating film 43 provided with a contact hole 43a is formed to a thickness of, for example, 500 nm. The method for forming the insulating film 43 is performed in the same manner as in the first embodiment.

Next, a second electrode 46 is formed. This second
The electrode 46 is formed by, for example, forming a Cr film to a thickness of 200 nm by sputtering and then patterning the Cr film into a predetermined shape.

Next, a pixel electrode 45 is formed. The pixel electrode 45 is formed by, for example, forming an ITO film by sputtering and patterning the ITO film into a predetermined shape so that a part of the ITO film is in contact with the second electrode 46. Thus, the element-side substrate is completed.

Next, an opposing substrate was formed in accordance with the first embodiment, and an alignment film (not shown) was applied to the element-side substrate and the opposing substrate on the surface on which the elements and electrodes were formed. After that, the alignment film is subjected to an alignment treatment, and both substrates are bonded to each other. Then, after injecting liquid crystal between both substrates, the injection port is sealed, and the fabrication of the liquid crystal display device of this embodiment is completed. The liquid crystal display device manufactured in this example shows good transmission characteristics ( VT characteristics) with respect to the liquid crystal driving voltage,
No change in the V-T characteristics against grayed, also it was confirmed that excellent display quality can be obtained with respect to temperature characteristics.

[0052]

As described above in detail, in the case of the present invention, the nonlinear resistance layer containing zinc sulfide as a main component is formed by a sputtering method using an inert gas and a hydrogen gas as a sputtering gas. , The steepness of the IV characteristics is high, the symmetry of the IV characteristics in the forward and reverse directions and the element withstand voltage can be improved, and there is no change with time in the IV characteristics, and the nonlinear characteristics are excellent in temperature characteristics. Devices can be manufactured.
Further, the liquid crystal display device using the non-linear element manufactured according to the present invention is low in cost and excellent in reliability.

[Brief description of the drawings]

1A is a diagram showing an IV characteristic of a non-linear element of the present invention and an IV characteristic of a conventional non-linear element, and FIG. 1B is a diagram showing a temperature characteristic of a current of the non-linear element of the present invention and a conventional non-linear element. FIG. 3C is a diagram showing the temperature characteristics of the current of the nonlinear element, and FIG.
It is a figure which shows the relationship between the range of the partial pressure ratio of hydrogen which has an effect on the symmetry of a -V characteristic, and the symmetry of an IV characteristic.

FIG. 2A is a plan view illustrating a part of one pixel of an element-side substrate of the liquid crystal display device according to the first embodiment, and FIG. 2B is a cross-sectional view taken along line AA ′ of FIG. is there.

FIG. 3 is a perspective view illustrating several pixels of the liquid crystal display device according to the first embodiment.

FIG. 4A is a plan view illustrating a part of one pixel of an element-side substrate of a liquid crystal display device according to a second embodiment, and FIG. 4B is a cross-sectional view taken along line BB ′ of FIG. is there.

FIG. 5 is a diagram illustrating an example of an applied waveform used for explaining a case where an IV characteristic shifts in a conventional nonlinear element.

[Explanation of symbols]

 21, 41, substrate 22a, 42a, first electrode 24, 44 non-linear resistance layer 23, 43 interlayer insulating film 25a, 46 second electrode 22, 42 scanning electrode 25, 45 pixel electrode 27 element side substrate 29 opposing side substrate 33 orientation Film 34 White tailor type guest-host liquid crystal 101 Current temperature characteristic of nonlinear element of the present invention 102 Current temperature characteristic of conventional nonlinear element

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H01L 21/363 G02F 1/1365

Claims (4)

(57) [Claims] 1. A non-linear resistance layer provided between a pair of electrodes is divided by an amount of hydrogen gas when an inert gas is set to 1.
Method of manufacturing a nonlinear element is formed by a sputtering method using <br/> the Supattaga scan which ranged from 0.01 to 0.5 ratio. 2. A non-linear resistance provided between a pair of electrodes.
The layer is heated using a firing target consisting of zinc sulfide.
Sputter gas using an inert gas and hydrogen gas
A method for manufacturing a non-linear element formed by a tarling method. 3. A nonlinear resistance provided between a pair of electrodes.
Layer with a firing target consisting of zinc sulfide and impurities.
Using an inert gas and a hydrogen gas as a sputtering gas.
Of nonlinear elements formed by the used sputtering method
Construction method. 4. A method according to claim 1 , wherein a first electrode, which is one of said pair of electrodes, is formed on a substrate, laminated on said first electrode, or partially contacted to form a non-linear resistance layer. method of manufacturing a nonlinear element according to any one of claims 1 to 3 and the second electrode are laminated in the nonlinear resistor layer, or formed in contact part which is the other.