JPH09197437A - Liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress an irregular etching state during etching and to obtain a liquid crystal display device having uniform characteristics all over the substrate even for a large screen by depositing a conductive film on an array substrate to be formed. SOLUTION: The array substrate 101 is produced by forming a transparent conductive film 105 comprising an ITO thin film having 200nm thickness on a glass substrate 104, forming a transparent insulating film 106 comprising a silicon oxide film having 500nm thickness on the ITO film 105, and further forming a thin film transistor 107, an auxiliary capacitor 108, a pixel electrode 109 and a driving circuit for a liquid crystal thereon. In this method, since the conductive film 105 is formed on the substrate and is used to control the voltage for etching, the ohmic joint part in the contact area 111 of the semiconductor film with a source electrode 116 and a drain electrode 117 can be uniformly formed all over the substrate, and thereby, a liquid crystal display device having high display quality can be obtd. Moreover, decrease in the production yield due to irregular etching can be decreased and the productivity can be increased.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a liquid crystal display device and a method for manufacturing the same.

[0002]

2. Description of the Related Art In an active matrix type liquid crystal display device, a semiconductor element such as a thin film transistor, a pixel electrode, an auxiliary capacitor, a conductor wiring, etc. are provided on at least one of two electrode plates holding a liquid crystal. Are formed. In order to form these, it is necessary to sequentially deposit a semiconductor layer, an insulating film layer, an electrode film layer and the like, and pattern them into a predetermined shape.

In patterning, a mask pattern is transferred by photolithography to a resist or the like deposited on a film to be patterned, and then an unnecessary portion of the film to be patterned is dry-etched or wet-etched. Is removed by etching to pattern into a predetermined shape.

There are several types of dry etching methods such as a plasma etching method, a sputter etching method, and a reactive ion etching method (RIE method). For example, in the reactive ion etching method, an etching gas is turned into a plasma state by discharge excitation. Then, the substrate on which the film to be patterned is deposited is exposed to the atmosphere and a predetermined potential is applied to remove a predetermined portion of the film to be patterned.

In this etching, since the substrate is insulative, electric charges are nonuniformly accumulated on the substrate during the etching, so that there is a problem that the etching does not proceed uniformly in each portion of the substrate.

In addition, the etching does not proceed uniformly due to the influence of the thin film that has been patterned in advance under the film to be etched, or the shape of the etching apparatus is not uniform, especially the back surface of the insulating substrate (opposite to the film to be etched). There is a problem that the etching does not proceed uniformly due to the non-uniformity of the shape of the portion in contact with the surface.

Due to such non-uniform etching, it is impossible to form an array substrate having uniform characteristics, especially a thin film transistor having uniform characteristics, and there is a problem that display quality is deteriorated or display defects occur. .

Further, in manufacturing the liquid crystal display device, there are problems that the yield is reduced and the cost is increased.

[0009] For example, there is a similar problem when spraying spacers. That is, particularly when electrostatically spraying spacers, spacer spraying that requires a high degree of uniformity due to electrostatic effects on the pattern formed on the substrate, the stage on which the substrate is placed, or the chamber of the spraying device, etc.
There was a problem that it could not be performed uniformly.

On the other hand, liquid crystal display devices have been used for a wide range of applications in recent years, and are used under severe temperature and humidity conditions. For example, under a bad condition such as a vehicle-mounted display device, dew condensation occurs on the liquid crystal display device, resulting in a malfunction.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem. That is, an object of the present invention is to provide a liquid crystal display device having uniform characteristics and high display quality.

Another object of the present invention is to provide a liquid crystal display device having a high yield and high productivity.

Another object of the present invention is to provide a method of manufacturing a liquid crystal display device having excellent characteristics by making etching uniform.

It is another object of the present invention to provide a method for manufacturing a liquid crystal display device having a high yield and high productivity.

It is another object of the present invention to provide a liquid crystal display device in which spacers are more evenly distributed and which has a high display quality.

Still another object of the present invention is to provide a liquid crystal display device which is provided with a heater for preventing dew condensation in a consistent manner and which can be used under severe temperature and humidity conditions.

[0017]

A liquid crystal display device according to the present invention includes an insulating substrate, a conductive film formed on the insulating substrate, an insulating film formed on the conductive film, and an insulating film formed on the insulating film. An array substrate having a pixel electrode formed on the film and a thin film transistor array for selectively driving the pixel electrode, a counter substrate having a transparent electrode, and a liquid crystal layer sandwiched between the array substrate and the counter substrate are provided. It is characterized by having done.

The liquid crystal display device of the present invention comprises an insulating substrate,
Array substrate having a conductive film formed on the insulating substrate, an insulating film formed on the conductive film, a pixel electrode formed on the insulating film, and a thin film transistor array for selectively driving the pixel electrode And a liquid crystal layer sandwiched between the array substrate and the counter substrate, and a heater means for applying a voltage to the conductive film to heat the conductive film.

As the insulating substrate, a transparent insulating substrate such as a glass substrate may be used.

The conductive film is, for example, ITO (Indium).
A transparent conductive film such as a Tin Oxide) thin film may be formed.

The insulating film formed on the conductive film may be a silicon oxide film, for example.

A method of manufacturing a liquid crystal display device according to the present invention comprises a step of sequentially forming a conductive film and an insulating film on an insulating substrate,
And a step of patterning by removing a predetermined portion of the thin film deposited on the insulating film by etching while controlling the potential of the conductive film.

That is, the liquid crystal display device of the present invention comprises a conductive film formed on a transparent insulating substrate, an insulating film is formed on the conductive film, and a thin film transistor is formed on the insulating film. A pixel electrode and its peripheral circuit are formed.

As the conductive film, for example, a MoW alloy thin film may be deposited, or ITO (Indium Ti) may be deposited.
n Oxide) thin films may be deposited.

The conductive film may be a MoW alloy thin film, an ITO thin film, or a thin film having a resistivity of about 5 Ω · cm to about 10000 Ω · cm.

The conductive film may be formed so as to cover the entire surface of an insulating substrate such as glass, or the deposited conductive thin film may be patterned into a predetermined shape. Even in this case, it is preferable to perform patterning so as to cover at least about 10% of the substrate area.

For example, the conductive film may be patterned into a predetermined shape and used as a black matrix. That is, the conductive film may be formed so as to fill the gap between the pixel electrodes and shield the thin film transistor region.

Such a conductive film is formed on an insulating substrate, a thin film semiconductor layer is deposited after a buffer layer of a transparent insulating film or the like is interposed, and then the thin film semiconductor layer and the subsequently deposited film are deposited. Of these, an etching process is performed on a film that requires patterning, such as a gate insulating film, an interlayer insulating film, various electrode films, and the like.

In the present invention, during this etching step, etching is performed while controlling the potential of the substrate to be patterned by a conductive film having a predetermined shape formed on the substrate in advance. For example, a conductive film on the patterned substrate,
The electrodes on which the substrate to be patterned of the etching apparatus is placed may be electrically connected.

The etching process may be a plasma etching method, a sputter etching method, or a reactive ion etching method (RIE method).

During this etching, since the conductive film electrically connected to the electrodes of the etching apparatus is present on the substrate, the charge is not unevenly accumulated on the substrate during the etching, and the substrate Etching proceeds uniformly in each part.

Further, due to the presence of the conductive film, even if a pre-patterned thin film existing under the film to be etched is formed, its influence can be greatly reduced, and the shape of the etching apparatus is not uniform, especially. It is possible to reduce the influence of the nonuniformity of the shape of the portion in contact with the back surface (the surface opposite to the film to be etched) of the insulating substrate and perform the etching uniformly.

Further, in the liquid crystal display device of the present invention, the array substrate or the liquid crystal display device is heated by applying a voltage to the above-mentioned conductive film forming the array substrate to prevent or remove dew condensation. For example, by forming a MoW alloy thin film having a thickness of about 200 nm as a conductive film and applying a voltage of about 30 V, the liquid crystal display device is heated to about 60 ° C.
Can be heated to a degree.

As described above, in the liquid crystal display device of the present invention, the etching rate is made uniform over the entire substrate,
The ohmic junction between the contact region of the semiconductor film and the source / drain electrode is uniform over the entire substrate,
High display quality and high productivity. Further, the conductive film reduces disturbance caused by an external electromagnetic field.

In the liquid crystal display device of the present invention, by depositing a conductive film on the array substrate to be formed, it is possible to suppress the occurrence of etching unevenness during etching in the subsequent etching step, and to prevent the entire substrate from appearing even on a large screen. A liquid crystal display device having uniform characteristics is manufactured.

[0036]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a liquid crystal display device 1 according to the present invention.
It is sectional drawing which shows a pixel part schematically.

The liquid crystal display device 100 includes an array substrate 1
The liquid crystal layer 103 is sandwiched between 01 and the counter substrate 102.

In the array substrate 101, an ITO thin film having a thickness of 200 nm is formed as a transparent conductive film 105 on a glass substrate 104, and the transparent insulating film 1 is formed on the ITO thin film 105.
A silicon oxide film having a thickness of 500 nm is formed as 06, and the thin film transistor 10 is formed on such a substrate portion.
7, an auxiliary capacitance 108, a pixel electrode 109, and a liquid crystal drive circuit (not shown) are formed.

On the other hand, on the opposite substrate 102, a transparent electrode is formed of, for example, ITO on the surface on the liquid crystal sandwiching side.

As the glass substrate 104, high melting point glass containing an alkali metal may be used. Since the conductive film can prevent the diffusion of the alkali metal in the glass substrate, an inexpensive glass substrate can be used.

The ITO thin film is, for example, magnetron DC.
In ₂ O ₃ and SnO ₂ may be formed in a ratio of 90:10 (molar fraction) by a sputtering method.

The silicon oxide film is, for example, atmospheric pressure CVD.
It may be formed by a method.

Although FIG. 1 illustrates a coplanar type thin film transistor, other types of thin film transistors such as a positive stagger type thin film transistor and an inverted stagger type thin film transistor may be used.

The channel region 1 is formed on the transparent insulating film 106.
A semiconductor film including 10 and the contact region 111 is formed. As this semiconductor film, an amorphous silicon film was formed by a plasma CVD method and annealed by an excimer laser to form a non-single crystal silicon film. In this step, for example, an excimer laser beam having a wavelength of 308 nm is shaped in a beam having a length of 300 mm and a width of 0.4 mm by passing through an optical system for improving a light intensity distribution in a vacuum, and then an optical filter is used. After setting the desired laser intensity, a predetermined region of the amorphous silicon film formed on the substrate is scanned and irradiated with a beam, and this region is crystallized to form a non-single-crystal crystalline silicon film. Good. Further, in order to prevent damage to the semiconductor film, the light intensity may be increased stepwise and irradiation may be performed three times.

The semiconductor film is not limited to a non-single crystal silicon film, but an amorphous silicon film, or Te, CdSe.
Alternatively, a semiconductor film other than silicon may be used.

The contact region of the semiconductor film was formed by implanting impurity ions by ion doping and activating with laser. Also at this time, laser irradiation was performed three times as in the case of crystallization described above.

On the upper side of the semiconductor film, a gate insulating film 112, a gate electrode 113, Cs patterned into a predetermined shape are formed.
Electrode 114, first interlayer insulating film 115, source electrode 11
6, the drain electrode 117, the second interlayer insulating film 118, and the pixel electrode 109 are formed.

The liquid crystal display device 100 illustrated in FIG. 1 is provided with a conductive film 105 on the substrate portion, and etching is performed while controlling the potential by this conductivity. Therefore, the contact region 111 of the semiconductor film and the source are formed. This is a liquid crystal display device with high display quality in which an ohmic junction between the electrode 116 and the drain electrode 117 is formed uniformly over the entire substrate.

Further, the liquid crystal display device is highly productive, which can reduce the reduction in yield due to nonuniform etching.

FIG. 2 shows an example of a patterning process in manufacturing the liquid crystal display device illustrated in FIG.

In FIG. 2, the contact region 11 of the semiconductor film is shown.
1 and the source electrode / drain electrode in ohmic contact, the source electrode of the gate insulating film 112 and the first interlayer insulating film 115 are formed by reactive ion etching.
The region 204 corresponding to the drain electrode is removed by etching.

The substrate 20 is placed on the electrode 201 of the etching apparatus.
2 is placed and etching is performed, but the exposed portion of the conductive film 105 is formed on the end surface of the substrate 202, and the electrode 201 of the etching apparatus is held by the substrate holding terminal 203 and at the same time electrically connected. Has been done.

Therefore, the conductive film 105 formed in advance is formed.
As a result, the potential distribution on the surface of the substrate 202 is kept substantially constant during etching, so that the etching amount of each portion of the substrate and each pixel is also kept substantially uniform. Also, charge-up is prevented.

Therefore, the etching rate is made uniform over the entire substrate, the bonding state between the contact region of the semiconductor film and the source / drain electrodes becomes constant, and a liquid crystal display device having uniform characteristics can be formed.

Although an example of the patterning step has been described here, the same applies to other patterning steps.

Although the reactive ion etching method has been described as an example here, another etching method such as a plasma etching method or a sputter etching method may be applied.

As described above, by performing etching while controlling the potential of the substrate uniformly by the conductive film formed on the substrate, it is possible to manufacture an array substrate having uniform properties throughout. Further, it is possible to reduce the defective product rate due to uneven etching and improve the productivity.

That is, by adopting the above-described etching process in which the substrate potential is controlled, the defective pixels that cannot obtain the designed display performance are 0.12% to 0.001% in the total number of pixels. And was able to be greatly reduced.

Further, in the liquid crystal display device illustrated in FIG. 1, since the transparent conductive film is deposited on the entire surface of the substrate, sodium, potassium, calcium, boron or the like is not deposited on the glass substrate or the thin film semiconductor layer or the gate insulating film. It also has the effect of preventing diffusion.

In this embodiment, not only the pixel portion but also the pixel drive circuit is formed on the same substrate, but the transparent conductive film is deposited on the base of this circuit portion. FIG. 3 is a sectional view schematically showing another example of the liquid crystal display device of the present invention. The figure shows one pixel portion.

The liquid crystal display device 300 includes the array substrate 3
01 and a counter substrate 302 having a transparent electrode formed of, for example, ITO, a liquid crystal layer 303 is sandwiched. The array substrate 301 includes a glass substrate 304 and a conductive film 305 on which Mo (molybdenum) W having a thickness of 200 nm is formed.
A (tungsten) alloy thin film is formed. The conductive film may be deposited on the entire surface of the substrate by, for example, magnetron DC sputtering method. In addition to the MoW alloy film, the conductive film may be formed using a Si film doped with another metal or impurity ions.

The conductive film 305 may be formed into a predetermined shape by a photo etching process or the like. .

A 500 nm-thickness silicon oxide film is formed as a transparent insulating film 306 on the MoW alloy thin film 305, and the thin film transistor 30 is formed on such a substrate portion.
7, a pixel electrode 309, an auxiliary capacitance (not shown), and a drive circuit are formed.

The silicon oxide film 306 is formed by atmospheric pressure CVD, for example.
A method may be used for the deposition.

For forming a semiconductor film of a thin film transistor, an amorphous silicon film having a thickness of about 70 nm is deposited by a plasma CVD method, and this is left in a furnace heated to about 500 ° C. for about 3 hours to make it amorphous. The hydrogen concentration in the high-quality silicon film may be reduced.

The annealing is performed in a vacuum of 5 × 10 ⁻³ Pa or less by passing an excimer laser beam having a wavelength of 308 nm through an optical system for improving the light intensity distribution.
After beam shaping into a beam shape of 00 mm and a width of 0.4 mm, the laser intensity is set to a desired value with an optical filter, and then a predetermined region of the amorphous silicon film formed on the substrate is scanned and irradiated with the beam. The region may be crystallized to form a non-single crystal silicon film.

Semiconductor film, gate insulating film, gate electrode, C
For the deposition and patterning of the s electrode, the first interlayer insulating film, the source electrode, the drain electrode, the second interlayer insulating film, the pixel electrode, etc., as described in FIG. 2, the conductive film deposited on the substrate portion. Therefore, the substrate potential may be controlled to make the etching rate uniform.

When patterning the semiconductor film to form a channel region and a contact region of the semiconductor film,
It was designed such that these portions were arranged directly above the conductive film formed in a predetermined shape. As a result, there is no reduction in the aperture ratio due to the conductive film having a predetermined shape (see FIG. 4).

Further, the formed MoW alloy thin film having a predetermined shape may be used as a black matrix. By doing so, the contrast of the screen is improved and the leak current of the thin film transistor is also reduced.

In the liquid crystal display device illustrated in FIG. 3,
Since the MoW alloy thin film formed on the array substrate and formed into a predetermined shape is also used as a heater for preventing dew condensation, a voltage applying unit (not shown) for externally applying a voltage to the conductive film 305 is provided. .

For example, by applying a voltage of about 30 V to the conductive film 305, the liquid crystal display device can be heated to about 60 ° C. Thus, the conductive film 305
By providing a heater means for applying a voltage to and heating it, it can be used even under severe temperature and humidity conditions.

FIG. 4 is a plan view schematically showing an array substrate of the liquid crystal display device illustrated in FIG. Conductive film 305
Is shaped so that it also functions as a heater. That is, the conductive film 305 may be patterned so as to cover the gate line and the thin film transistor 307 and not overlap the display portion as much as possible, and to be thin and long so as to be efficient as a heater. 3 in the figure
Reference numeral 08 is an auxiliary capacitance section.

The pattern of the conductive film 305 illustrated in FIG. 4 has a connection portion outside the display portion of the substrate so that the potential of the entire substrate can be uniformly controlled during etching.
The connection portion 305b is adapted to be connected to the electrode of the etching apparatus during etching, and is, for example, a portion corresponding to the substrate holding terminal 203 of FIG. This connection 3
05b not only functions as a black matrix if it is cut along the AB direction in FIG. 4 in a later step,
A zigzag pattern that is efficient as a dew condensation preventing heater is also formed.

Further, even when the spacers are sprayed, the potential of the entire substrate can be kept uniform and the spacers can be sprayed more uniformly. In particular, when electrostatically spraying the spacers, it is possible to prevent the effects of the spraying stage and the chamber on which the substrate is placed. Therefore, the connection portion 305b may be cut after the spacers are sprayed.

The pattern of the conductive film 305 is shown in FIG.
The pattern is not limited to the pattern illustrated in FIG. 2, and the pattern can make the potential of the entire array substrate uniform during the array substrate manufacturing process and the spacer spraying process, and functions as a heater after being assembled as a liquid crystal display device. If

The present invention can be applied to not only a transmission type liquid crystal display device but also a reflection type liquid crystal display device.

[0077]

As described above, the liquid crystal display device of the present invention is a liquid crystal display device having uniform characteristics over the entire substrate, high display quality, and high productivity. It is also possible to reduce the disturbance due to the external electromagnetic field.

Further, in the liquid crystal display device of the present invention,
By applying a voltage to the conductive film formed on the substrate to form a heater means, dew condensation can be prevented, and the heater can be used even under severe temperature and humidity conditions.

In the liquid crystal display device of the present invention, by depositing a conductive film on the array substrate, it is possible to suppress the occurrence of etching unevenness during etching in a subsequent etching process and to make the characteristics uniform over the entire substrate. A liquid crystal display device can be manufactured.

Further, even in a large-screen liquid crystal display device having a large substrate size, a liquid crystal display device having uniform characteristics over the entire substrate can be manufactured.

Further, even when the spacers are sprayed, the potential of the substrate, which is the material to be sprayed by the spacers, can be kept uniform throughout, and the spacers can be sprayed more uniformly. Therefore, the thickness of the liquid crystal layer can be formed more uniformly, and the liquid crystal display device has high display quality.

Further, the occurrence of defects due to the non-uniform etching process can be significantly reduced, the productivity of liquid crystal display device manufacturing can be improved, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing a liquid crystal display device of the present invention.

FIG. 2 is a diagram schematically showing one step of a method for manufacturing a liquid crystal display device of the present invention.

FIG. 3 is a sectional view schematically showing a liquid crystal display device of the present invention.

FIG. 4 is one of the conductive film patterns of the liquid crystal display device of the present invention.
The figure which shows an example.

[Explanation of symbols]

100 ... Liquid crystal display device, 101 ... Array substrate, 10
2 ... Counter substrate 103 ... Liquid crystal layer, 104 ... Glass substrate, 105 ...
ITO thin film 106: transparent insulating film 107: thin film transistor,
108 ... Auxiliary capacitance 109 ... Pixel electrode, 110 ... Channel region, 111
...... Contact area 112 ...... Gate insulating film, 113 ...... Gate electrode, 11
4 ... Cs electrode 115 ... first interlayer insulating film, 116 ... source electrode,
117 ... Drain electrode 118 ... Second interlayer insulating film 201 ... Electrode, 202 ... Substrate, 203 ... Substrate holding terminal 300 ... Liquid crystal display device, 301 ... Array substrate, 30
2 ... Counter substrate 303 ... Liquid crystal layer, 304 ... Glass substrate, 305 ...
Conductive film 305b ... Connection pattern, 306 ... Transparent insulating film 307 ... Thin film transistor, 308 ... Auxiliary capacitor, 3
09 ... Pixel electrode

Claims (4)

[Claims] 1. An insulating substrate, a conductive film formed on the insulating substrate, an insulating film formed on the conductive film, a pixel electrode formed on the insulating film, and a pixel electrode formed on the insulating film. A liquid crystal display device comprising: an array substrate having a thin film transistor array that is selectively driven; a counter substrate on which a transparent electrode is formed; and a liquid crystal layer sandwiched between the array substrate and the counter substrate. 2. An insulating substrate, a conductive film formed on the insulating substrate, an insulating film formed on the conductive film, a pixel electrode formed on the insulating film, and a pixel electrode formed on the insulating film. An array substrate having a thin film transistor array that is selectively driven, a counter substrate on which a transparent electrode is formed, a liquid crystal layer sandwiched between the array substrate and the counter substrate, and the conductive film are heated by applying a voltage. A liquid crystal display device comprising a heater means. 3. The liquid crystal display device according to claim 1, wherein the conductive film is a transparent conductive film. 4. A step of sequentially forming a conductive film and an insulating film on an insulating substrate, and a predetermined portion of the thin film deposited on the insulating film is removed by etching while controlling the potential of the conductive film. And a step of patterning the liquid crystal display device.