JPH09281476A - Liquid crystal display device and its production - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique of manufacturing a liquid crystal display device capable of making image display with high image quality. SOLUTION: The applications of the black matrix to be disposed at a liquid crystal display device are divided and two kinds for pixel regions and driving circuit regions are used. The structure to arrange the black matrix is specified. Namely, the pixel electrode regions 107 are provided with the black matrix 102 on an active matrix substrate 101 side and the driving circuit regions 105 are provided with the black matrix 104 on the counter substrate 103 side.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD [0001] The invention disclosed in the present specification is:
The present invention relates to a structure of a liquid crystal display device including a semiconductor device including a crystalline thin film semiconductor. In particular, it relates to the configuration of an active matrix type liquid crystal display device in which pixel TFTs and circuit TFTs are integrated on the same substrate.

[0002]

2. Description of the Related Art Recently, a technique for producing a thin film transistor (TFT) on an inexpensive glass substrate has been rapidly developed. The reason is that the demand for active matrix liquid crystal display devices has increased.

An active matrix type liquid crystal display device is
Pixel TFTs and pixel electrodes are arranged in each of the millions of pixels arranged in a matrix, and the electric charge flowing in and out of each pixel electrode is controlled by the switching function of the pixel TFT.

Then, each pixel TFT is controlled by a circuit TFT arranged in a driving circuit area formed around the pixel area. The circuit TFT constitutes an analog buffer circuit, an inverter circuit, etc. by the combination.

As described above, the active matrix type liquid crystal display device includes the pixels T arranged in a matrix in the pixel region.
This is an integrated circuit in which the FT and the circuit TFT arranged in the drive circuit area are all integrated on the same substrate.

By the way, when a liquid crystal display device is driven to display an image, it is common to dispose a black matrix (BM) having a light-shielding property above a wiring or above a transistor which does not need to transmit visible light. is there.

This has the effect of preventing the electrical characteristics of the thin film transistor from deteriorating due to the photoexcitation phenomenon of the active layer (semiconductor layer), and prevents the display image from being disturbed when the electric field is disturbed at the edge of the pixel electrode. Has the effect of
In particular, the liquid crystal display device for a projector that is irradiated with light of about 1 million lux is a major problem of deterioration due to photoexcitation, and therefore the arrangement of the black matrix is indispensable.

As the black matrix, a metal thin film having a light shielding property such as a titanium film or a chromium film, or a resin material in which a black pigment is dispersed can be used. In addition, a black matrix has often been provided on the counter substrate side for the sake of simplicity of manufacturing.

However, conventionally, in the cell assembling process, the bonding precision between the element side substrate (referred to as an active matrix substrate in this specification) and the counter substrate is poor, and a black matrix must be formed with a large alignment margin. It was a situation where the desired position could not be shielded.

Forming a black matrix with a large alignment margin leads to a reduction in the aperture ratio of the pixel region and is not preferable.

Further, it has been suggested that the current bonding technology may not be compatible with further miniaturization of device elements in the future if the black matrix is provided on the counter substrate side with the current bonding technology as it is.

Therefore, in recent years, "BM on TF" has been formed in which a black matrix is formed on the active matrix substrate side.
The "T" structure is becoming mainstream. In this case, a black matrix can be formed above or below the pixel electrode via an interlayer insulating film to shield a desired position from light.

The above-mentioned "BM on TFT" structure can minimize the alignment margin when forming the black matrix, and is a very effective means for improving the aperture ratio.

It is also possible to superimpose the black matrix and the pixel electrode via the interlayer insulating film and form the auxiliary capacitance there, as already filed by the present inventors.
In that case, the black matrix is set to the same potential as the counter electrode.

As described above, the "BM on TFT" structure is a technique having various merits, but the effect is exerted only in the pixel region, and there is a demerit in the drive circuit region.

The circuit TFT arranged in the drive circuit area is
Due to its application, high speed operation is required as compared with the pixel TFT. However, when the black matrix is formed above the driving circuit, a parasitic capacitance is formed between the black matrix and the circuit TFT, which causes a problem that the operating speed is reduced.

When the operating speed of the circuit TFT is reduced, the image display speed becomes slow, and various problems such as flicker and flicker of the displayed image occur. That is, there is a problem that the quality of the liquid crystal display device is significantly impaired.

[0018]

SUMMARY OF THE INVENTION It is an object of the invention disclosed in the present specification to provide a technique for realizing a liquid crystal display device capable of solving the above problems and displaying a high quality image. .

[0019]

The structure of the invention disclosed in the present specification comprises an active matrix substrate provided with a pixel region and a drive circuit region on the same substrate, and an opposite substrate facing the active matrix substrate. In the active matrix type liquid crystal display device having a structure in which a liquid crystal layer is sandwiched between the active matrix substrate and the counter substrate, a black matrix is arranged on the active matrix substrate side in the pixel region, A black matrix is arranged on the counter substrate side in the drive circuit region.

FIG. 1 is a schematic view of a liquid crystal display device according to the present invention.
Shown in In FIG. 1, 101 is an active matrix substrate, and circuit TFTs are arranged in the drive circuit area.
Pixel TFTs are arranged in a matrix in the pixel region. A glass substrate or the like is used as the active matrix substrate 101.

A black matrix 102 is formed in the pixel area of the active matrix substrate 101, leaving only the image display area. Although it seems to be divided in the drawing, it actually has a matrix shape.

A counter substrate 103 is arranged so as to face the active matrix substrate 101. Then, in the area of the counter substrate 103 that overlaps with the drive circuit area,
Black matrix 104 for shielding circuit TFT from light
Are formed.

Then, the active matrix substrate 101 and the counter substrate 103 are bonded to each other with a sealant (not shown) with a spacer (not shown) sandwiched therebetween. Therefore,
The diameter of the spacer is the distance between the substrates (cell gap).

The sealing material also has a function as a sealing material for enclosing the liquid crystal layer sandwiched between the active matrix substrate 101 and the counter substrate 103. Therefore, the injection port is formed in advance in the sealing material before the liquid crystal is injected, and the injection port is sealed after the liquid crystal is injected.

In the liquid crystal display device shown in FIG. 1 having the above-mentioned structure, since the pixel area has the "BM on TFT" structure, it is possible to efficiently shield visible light without lowering the aperture ratio. It is possible. The liquid crystal display device actually manufactured by the present inventors had an aperture ratio of more than 60%.

Since the black matrix 104 is provided on the counter substrate 103 side in the drive circuit area, the circuit TFT
There is no case in which a parasitic capacitance is formed between and to reduce the operation speed of the circuit TFT.

Since the circuit TFT only needs to be shielded from light, it is sufficient that the black matrix 104 can cover the entire driving circuit region. That is, it is not necessary to perform the alignment with a high precision like the black matrix 102 formed in the pixel region, and therefore the alignment can be provided on the counter substrate 103 side.

Two sets of black matrices 102,
The portions 104 are formed so as to partially overlap each other. In FIG. 1A, an end portion of the black matrix 102 provided in the pixel region is patterned to be slightly thicker than other portions, and overlaps with the black matrix 104 provided on the counter substrate 103 side by a distance X. It is composed.

At this time, the counter substrate 103 shown in FIG.
The black matrix 104 on the side has a shape as shown in FIG. 1B and faces the active matrix substrate 101. That is, the area corresponding to the drive circuit area 105 is completely shielded from light, and the window 107 is formed in the area corresponding to the pixel area 106 (area surrounded by a dotted line).

One side of the window 107 is formed smaller than the pixel area 106 by the distance X described above, and it is possible to shield the area inside the pixel area 106 from each side by the distance X. ing.

With such a structure, even if the structure of the present invention uses two sets of black matrices,
It is possible to fabricate a liquid crystal display device in which unnecessary portions of the entire surface of the substrate are shielded from light and unnecessary light does not leak from the gap.

According to another aspect of the invention, there is provided an active matrix substrate having a pixel region and a drive circuit region provided on the same substrate, and a counter substrate which faces the active matrix substrate and faces the active matrix substrate. In a process of manufacturing an active matrix liquid crystal display device having a structure in which a liquid crystal layer is sandwiched between a substrate and the counter substrate, a first black matrix is selectively formed in the pixel region on the active matrix substrate side. And a step of selectively forming a second black matrix in the drive circuit region on the counter substrate side.

The configuration of the present invention described above will be described in detail in the examples described below.

[0034]

【Example】

[Embodiment 1] In this embodiment, a manufacturing process of a circuit TFT and a pixel TFT arranged on an active matrix substrate will be described with reference to FIG. 2, and a manufacturing process of a counter substrate will be described with reference to FIG.

First, an insulating substrate, for example, a glass substrate 201 represented by Corning 7059 or 1737 is prepared. The base film 20 is formed on the glass substrate 201.
As No. 2, a silicon oxide film is formed to a thickness of 2000Å.

Next, an amorphous silicon film (not shown) is formed to a thickness of 500 Å. The film may be formed by a plasma CVD method or a low pressure thermal CVD method.

After forming an amorphous silicon film (not shown), crystallization is performed by an appropriate crystallization method to form a crystalline silicon film (not shown). For example, means such as heat treatment at about 600 ° C. and annealing with excimer laser are generally used.

Further, it is possible to use a means for holding the metal element that promotes crystallization in the amorphous silicon film during the crystallization process. Details of this means are described in JP-A-6-232059 and JP-A-7-321339. By this means, it is possible to obtain a silicon film having good crystallinity by heat treatment at a relatively low temperature for a short time.

When the crystalline silicon film is obtained by the heat treatment by the above means, it is effective to anneal the crystalline silicon film with a laser or strong light having an energy equivalent to that of the laser. As a result, the crystallinity of the crystalline silicon film can be significantly improved.

Next, the obtained crystalline silicon film (not shown) is patterned to form an island-shaped semiconductor layer 203 forming the active layer of the circuit TFT and an island-shaped semiconductor layer 204 forming the active layer of the pixel TFT. To do.

Once the active layers are constructed, cover them 1200
A silicon oxide film 205 having a thickness of Å is formed by a plasma CVD method. This silicon oxide film 205 later functions as a gate insulating film. Note that a silicon oxynitride film (for example, SiO _X
N _Y ) or a silicon nitride film may be used.

Next, an aluminum film 206 to which 0.2% by weight of scandium has been added is formed to a thickness of 2500 Å by the sputtering method. Addition of scandium has an effect of suppressing generation of hillocks and whiskers on the surface of the aluminum film. The aluminum film 206 later functions as a gate electrode.

Further, instead of the aluminum film, other metal materials such as Mo, Ti, Ta and Cr may be used, or a conductive film such as polysilicon or a silicide material is used. I don't mind.

Next, the aluminum film 206 is formed in the electrolytic solution.
Is used as an anode for anodic oxidation. 3% as electrolyte
The neutralized ethylene glycol solution of tartaric acid with ammonia water is used to adjust the pH to 6.92. In addition, the formation current is 5 mA and the ultimate voltage is 10 V using platinum as a cathode.
Process as

The dense anodic oxide film (not shown) thus formed has the effect of enhancing the adhesion to the photoresist later. Further, the film thickness can be controlled by controlling the voltage application time. (Fig. 2 (A))

When the state of FIG. 2A is obtained in this way, the aluminum film 206 is patterned to form a prototype of a later gate electrode and a gate line (not shown).
Then, the second anodic oxidation is performed to form the porous anodic oxide films 207 and 208. The electrolytic solution is a 3% oxalic acid aqueous solution, and the treatment is carried out at a formation current of 2 to 3 mA and a reaching voltage of 8 V using platinum as a cathode. (FIG. 2 (B))

At this time, anodization proceeds in a direction parallel to the substrate. Moreover, the length of the porous anodic oxide films 207 and 208 can be controlled by controlling the voltage application time.

Further, after removing the photoresist with a dedicated stripping solution, a third anodic oxidation is performed. At this time, a 3% tartaric acid ethylene glycol solution neutralized with aqueous ammonia to adjust the pH to 6.92 is used. And a formation current of 5 to 6 mA using platinum as a cathode,
The processing is performed with the reaching voltage of 100V.

Anodized films 209 and 21 formed at this time
0 is very dense and strong. Therefore,
It has an effect of protecting the gate electrodes 211 and 212 from damage caused in a subsequent process such as a ping process.

Further, since the strong anodic oxide films 209 and 210 are hard to be etched, there is a problem that the etching time becomes long when the contact hole is formed. Therefore, it is desirable that the thickness be 1000 mm or less.

Next, in the state shown in FIG. 2B, impurities are implanted into the active layers 203 and 204 by the ion doping method. For example, if an N-channel TFT is manufactured, P (phosphorus) may be used as an impurity, and if a P-channel TFT is manufactured, B (boron) may be used as an impurity.

In this embodiment, only an example of manufacturing an N channel type TFT will be described, but if a known technique is used, N
It is also possible to form a channel TFT and a P-channel TFT on the same substrate.

By this ion implantation, the source / drain regions 213 and 214 of the circuit TFT and the source / drain regions 215 and 216 of the pixel TFT are formed in a self-aligned manner.

Next, the porous anodic oxide films 207 and 208 are formed.
Is removed and ion implantation is performed again. The dose at this time is lower than that of the previous ion implantation.

By this ion implantation, the low concentration impurity regions 217 and 218 of the circuit TFT and the channel forming region 221 are formed.
And low concentration impurity regions 219 and 220 of the pixel TFT,
The channel formation region 222 is formed in a self-aligned manner.

After the state shown in FIG. 2C is obtained, next, laser light irradiation and thermal annealing are performed. In this embodiment, the energy density of the laser light is 160 to 170 mJ / cm ² and the thermal annealing is performed at 300 to 450 ° C. for 1 hour.

By this step, the crystallinity of the active layers 203 and 204 damaged by the ion doping step is improved, and
Activation of the implanted impurity ions is performed.

Next, a silicon nitride film (or a silicon oxide film) may be formed as the first interlayer insulating film 223 to a thickness of 3000 Å by the plasma CVD method. The interlayer insulating film 223 may have a multi-layer structure.

After forming the first interlayer insulating film 223, a contact hole is formed in a region where an electrode / wiring is formed. A source wiring (also called a data line) 224, a gate wiring 225, and a drain wiring 226 of the circuit TFT are formed of a laminated film of a material containing aluminum as a main component and titanium.
And the source wiring 227 and the drain electrode 2 of the pixel TFT
28 is formed.

At this time, since the gate electrode 212 of the pixel TFT is integrated with a gate line (not shown) drawn out of the pixel region, it is not necessary to make a contact. Further, the drain electrode 228 plays a role of a conductive line that connects the pixel electrode and the active layer later.

Next, a second interlayer insulating film 229 is formed by plasma CVD to a thickness of 0.5 to 5 μm. As the interlayer insulating film 229, a silicon oxide film, a silicon nitride film, a single layer or a laminated film using an organic resin material or the like can be used.

When an organic resin material such as polyimide is used as the second interlayer insulating film 229, the film thickness can be easily increased, and a function as a flattening film can be added. That is, it is possible to minimize the steps on the active matrix substrate.

After forming the second interlayer insulating film 229, the black matrix 230 is formed to a thickness of 1000 to 2000Å. As the black matrix 230, a metal thin film such as a chromium film or a titanium film or a resin material in which a black pigment is dispersed can be used. In addition, it is preferable to form a thick pattern with a margin at the end portion of the pixel region so as to overlap the black matrix on the counter substrate side.

With such a structure, a margin of the distance X can be secured as shown in FIG. 1A, and when the substrates are bonded to each other, a position shift occurs to form a gap through which light leaks. There is nothing.

When the black matrix 230 is formed on the active matrix substrate side in this way, the light-shielding region can be covered with the minimum required occupying area, which is effective without impairing the aperture ratio.

Next, the second interlayer insulating film on the drain electrode 228 of the pixel TFT is etched to form a contact hole, and the pixel electrode 231 made of a transparent conductive film electrically connected to the drain electrode 228 is formed. To do.

At this time, when the pixel electrode 232 is formed so that the black matrix 230 and the pixel electrode 232 are overlapped with each other as shown in FIG. 2E, the overlapped region can be utilized as an auxiliary capacitance.

In this way, an active matrix substrate having circuit TFTs and pixel TFTs as shown in FIG. 2E is formed. In practice, hundreds of thousands of circuits T
The FT constitutes a CMOS circuit or the like and is arranged in the drive circuit area, and tens to millions of pixel TFTs are arranged in the pixel area.

Next, details of the manufacturing process of the counter substrate will be described with reference to FIGS. First, as shown in FIG. 3A, a black matrix 302 is formed on the counter substrate 301.
Form to a thickness of 00 to 2000Å.

The black matrix 302 is arranged only in a region facing the drive circuit region when cells are assembled later. As the black matrix 302, a metal thin film or a resin material containing a black pigment is used as described above.

Next, when it is necessary to display an image in color, a color filter 303 is formed. The color filter is required to have a uniform thickness and flatness, excellent heat resistance and chemical resistance. (Fig. 3 (A))

The color filter 303 has a known structure. That is, in the area on the counter substrate 301 corresponding to each pixel electrode of the active matrix substrate, R (red),
G (green) and B (blue) are regularly arranged. The thickness of the color filter is 1.5 to 2.0 μm.

Therefore, although the color filter 303 shown in FIG. 3 (A) is described as a single coating, it is actually a color filter corresponding to R (red), G (green) and B (blue). It is a collection of patterns.

Next, a flattening film 304 made of a translucent resin material is formed to a thickness of 2.0 to 3.0 μm so as to cover the black matrix 302 and the color filter 303. The flattening film 304 also has a function as a protective film that protects the color filter. (FIG. 3 (B))

Then, a counter electrode 305 made of a transparent conductive film is formed on the flattening film 304 to a thickness of 1000 Å. Further, an alignment film 306 having a thickness of 800 Å is formed on the counter electrode 305 to complete a counter substrate as shown in FIG.

Next, the outline of the cell assembling process for completing the liquid crystal display device will be described with reference to FIG.

After the active matrix substrate and the counter substrate are completed through the above steps, a rubbing process is performed on both substrates to give the alignment film a desired orientation. This step determines the orientation of the liquid crystal material near the substrate. (Fig. 4 (A))

After the rubbing process is completed, a sealing material 406 is formed by screen printing so as to surround the drive circuit area and the pixel area of the counter substrate. As the sealing material 406, an epoxy resin and a phenol curing agent dissolved in a solvent of ethyl cellosolve can be used. Also,
An opening (liquid crystal injection port) for injecting a liquid crystal material later is formed in a part of the sealing material 40.

The sealing material 406 has not only the effect of adhering the substrates to each other, but also the effect of sealing the liquid crystal material only around the image display area so that the injected liquid crystal material does not leak.

Next, spacers 407 are sprinkled on the counter substrate. Polymer-based, glass-based, or silica-based spherical fine particles are used as the spacers 407, and the fine particles are sprayed from a nozzle and dispersed on the entire surface of the active matrix substrate. (FIG. 4
(B))

The advantage of performing the above sealing material / spacer spraying process on the counter substrate side is prevention of contamination of the TFT circuit and electrostatic breakdown. In particular, it is desirable to perform the spacer spraying process on the counter substrate side because static electricity is generated.

Next, the active matrix substrate and the counter substrate are bonded together. The distance X (margin for alignment) to be ensured as shown in FIG. 1A may be determined according to the accuracy of this bonding. Further, at the time of bonding, the spacer 407 is sandwiched between both substrates, and the diameter of the spacer 407 determines the cell gap. (FIG. 4 (C))

After the bonding of the active matrix substrate and the counter substrate is completed, the liquid crystal material is injected through the opening formed in the sealant 406 in advance so that the liquid crystal is held in the pixel region. A known vacuum injection method may be used to inject the liquid crystal material.

Finally, the opening is sealed to fill the liquid material, and the liquid crystal display device as shown in FIG. 4D is completed.
The black matrix arranged in this liquid crystal display device is
As described above, the pixel region is arranged on the active matrix substrate side, and the driving region is arranged on the counter substrate side.

[0085]

The liquid crystal display device using the present invention has the following advantages. (1) Since the black matrix can be formed in the pixel region with the minimum necessary alignment margin, the aperture ratio is not sacrificed. (2) In the pixel area, the auxiliary capacitance can be formed by the black matrix and the pixel electrode. (3) In the drive circuit area, the black matrix and the circuit T
No parasitic capacitance is formed between the TFT and FT, and the operating speed of the circuit TFT does not decrease.

[Brief description of drawings]

FIG. 1 illustrates a structure of a liquid crystal display device.

FIG. 2 illustrates a manufacturing process of a thin film transistor.

FIG. 3 is a view showing a manufacturing process of a counter substrate.

FIG. 4 is a diagram showing an outline of a cell assembling process.

[Explanation of symbols]

101 glass substrate 102 active matrix substrate side black matrix 103 glass substrate 104 counter substrate side black matrix 105 drive circuit region 106 pixel region 107 black matrix window

Claims (4)

[Claims] 1. An active matrix substrate having a pixel region and a drive circuit region provided on the same substrate, and a counter substrate facing and facing the active matrix substrate, wherein the active matrix substrate and the counter substrate are provided. In an active matrix liquid crystal display device having a liquid crystal layer sandwiched therebetween, a black matrix is arranged on the active matrix substrate side in the pixel region, and a black matrix is arranged on the counter substrate side in the drive circuit region. And a liquid crystal display device. 2. The liquid crystal display device according to claim 1, wherein the black matrix on the side of the active matrix substrate and the black matrix on the side of the counter substrate overlap each other at least partially through the liquid crystal layer. 3. An active matrix substrate having a pixel region and a drive circuit region provided on the same substrate; and a counter substrate facing and facing the active matrix substrate, wherein the active matrix substrate and the counter substrate are provided. A step of selectively forming a first black matrix in the pixel region on the active matrix substrate side in the process of manufacturing an active matrix type liquid crystal display device having a structure in which a liquid crystal layer is sandwiched between And a step of selectively forming a second black matrix in the drive circuit region, wherein the method for manufacturing a liquid crystal display device. 4. The liquid crystal display device according to claim 3, wherein the first black matrix and the second black matrix are formed so as to overlap each other at least partially through the liquid crystal layer. Manufacturing method.