JP2001133766A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a liquid crystal display device which can display an image of high picture quality. SOLUTION: The liquid crystal display device has a first substrate having a driving circuit region and a pixel region where a first black matrix is formed, and a second substrate on which a second black matrix formed and facing the first substrate. The second black matrix is formed to face the region of the first substrate except for the pixel region.

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 using a thin film semiconductor having crystallinity. In particular, the present invention relates to a 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 manufacturing a thin film transistor (TFT) on an inexpensive glass substrate has been rapidly developed. The reason is that the demand for the active matrix type liquid crystal display device has increased.

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

[0006] Each pixel TFT is controlled by a circuit TFT arranged in a drive circuit area formed around the pixel area. The circuit TFT constitutes an analog buffer circuit, an inverter circuit, and the like according to the combination.

[0005] As described above, an active matrix type liquid crystal display device includes pixels T arranged in a matrix in a 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 an image is displayed by driving a liquid crystal display device, a black matrix (BM) having a light-shielding property is generally arranged above a wiring or 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 the effect of preventing the display image from being disturbed when the electric field is disturbed at the pixel electrode end. And has the effect.
In particular, in a liquid crystal display device for a projector which is irradiated with light of about 1 million lux, deterioration of the liquid crystal display due to light excitation is a serious problem.

As the black matrix, a light-shielding metal thin film such as a titanium film or a chromium film, or a resin material in which a black pigment is dispersed can be used. Until now, a black matrix has often been provided on the counter substrate side for ease of manufacture.

However, conventionally, in the cell assembling process, the bonding accuracy between the element-side substrate (referred to as an active matrix substrate in this specification) and the counter substrate is poor, and a large alignment margin must be taken to form a black matrix. The desired position could not be shielded from light.

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

Further, it has been suggested that the alignment margin is too large when a black matrix is provided on the counter substrate side without using the current bonding technique, and there is a possibility that it will not be possible to cope with miniaturization of device elements which will be advanced in the future.

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

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

Further, as already filed by the present inventors, it is possible to overlap the black matrix and the pixel electrode via an interlayer insulating film and form an auxiliary capacitance there.
In that case, the black matrix is kept at the same potential as the counter electrode.

As described above, the "BM on TFT" structure is a technology having various merits, but the effect is exhibited only in the pixel region, and disadvantageous in the drive circuit region.

The circuit TFT arranged in the drive circuit area is
For that purpose, high-speed operation is required compared to pixel TFTs. However, when a black matrix is formed above the driving circuit, a problem arises in that a parasitic capacitance is formed between the black matrix and the circuit TFT, thereby lowering the operation speed.

When the operation speed of the circuit TFT decreases, the image display speed decreases, and various problems such as flickering and flicker of the displayed image occur. That is, the quality of the liquid crystal display device is significantly impaired.

[0018]

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

[0019]

The structure of the invention disclosed in this specification is based on an active matrix substrate having a pixel area and a drive circuit area provided on the same substrate, and a counter substrate facing the active matrix substrate. In an active matrix liquid crystal display device having a configuration 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, In the driving circuit region, a black matrix is arranged on the counter substrate side.

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

In the pixel area of the active matrix substrate 101, a black matrix 102 is formed except for an image display area. Although it looks like it is divided in the drawing, it actually has a matrix shape.

A counter substrate 103 is arranged to face the active matrix substrate 101. Then, in a region overlapping the drive circuit region on the opposing substrate 103,
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 sealing material (not shown) with a spacer (not shown) interposed 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 sealing the liquid crystal layer sandwiched between the active matrix substrate 101 and the counter substrate 103. Therefore, before the liquid crystal is injected, an injection port is formed in the sealing material in advance, 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-described structure, the pixel region employs the "BM on TFT" structure, so that visible light can be efficiently blocked without lowering the aperture ratio. It is possible. The aperture ratio of the liquid crystal display device actually manufactured by the present inventors exceeded 60%.

In the drive circuit area, since the black matrix 104 is provided on the counter substrate 103 side, the circuit TFT
Does not reduce the operating speed of the circuit TFT by forming a parasitic capacitance between the circuit TFT and the TFT.

Since the circuit TFT only needs to be shielded from light, the black matrix 104 only needs to cover the entire driving circuit area. In other words, there is no need to perform positioning with a high degree of precision as in the case of the black matrix 102 formed in the pixel region, and therefore, it can be provided on the counter substrate 103 side.

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

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

One side of the window 107 is formed to be smaller than the pixel area 106 by the above-described distance X, so that an area that is inward from each side of the pixel area 106 by the distance X can be shielded. ing.

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

According to another aspect of the present invention, there is provided an active matrix substrate provided with a pixel region and a drive circuit region on the same substrate, and a counter substrate facing the active matrix substrate and facing the active matrix substrate. In the process of manufacturing an active matrix liquid crystal display device having a configuration 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 embodiments described below.

[0034]

[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, a substrate having an insulating property, 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 200 nm.

Next, an amorphous silicon film (not shown) is formed to a thickness of 50 nm. 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.

In the crystallization step, a means for holding a metal element which promotes crystallization in the amorphous silicon film may be used. Details of this means are described in JP-A-6-232059 and JP-A-7-321339. According to this means, a silicon film having good crystallinity can be obtained by a heat treatment at a relatively low temperature for a short time.

When a crystalline silicon film is obtained by the heat treatment by the above-described means, it is effective to anneal the crystalline silicon film with a laser or strong light having energy equivalent to that of the laser. Thereby, 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-like semiconductor layer 203 constituting an active layer of a circuit TFT and an island-like semiconductor layer 204 constituting an active layer of a pixel TFT. I do.

Once the active layers have been constructed, they are
A silicon oxide film 205 having a thickness of nm is formed by a plasma CVD method. This silicon oxide film 205 functions as a gate insulating film later. Note that a silicon oxynitride film (for example, SiO 2
_X N _Y ) or a silicon nitride film may be used.

Next, an aluminum film 206 to which 0.2% by weight of scandium is added is formed to a thickness of 250 nm by sputtering. Addition of scandium has an effect of suppressing generation of hillocks and whiskers on the surface of the aluminum film. This aluminum film 206 functions as a gate electrode later.

In place of the aluminum film, another metal-based material, for example, Mo, Ti, Ta, Cr or the like may be used, or a conductive film such as polysilicon or silicide-based material may be used. No problem.

Next, the aluminum film 206 is placed in an electrolytic solution.
Is used as an anode for anodic oxidation. 3% as electrolyte
The ethylene glycol solution of tartaric acid is neutralized with aqueous ammonia and adjusted to pH = 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 improving the adhesion to the photoresist later. Further, the film thickness can be controlled by controlling the voltage application time. (Fig. 2 (A))

In this manner, when the state shown in FIG. 2A is obtained, 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 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, the anodic oxidation proceeds in a direction parallel to the substrate. Further, the length of the porous anodic oxide films 207 and 208 can be controlled by controlling the voltage application time.

Further, after the photoresist is removed with a dedicated stripper, 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.

At this time, the formed anodic oxide films 209 and 21
0 is very dense and strong. Therefore,
This has an effect of protecting the gate electrodes 211 and 212 from damage caused in a later step such as a ping step.

Further, since the strong anodic oxide films 209 and 210 are hardly etched, there is a problem that the etching time is long when forming a contact hole. Therefore, the thickness is desirably 100 nm or less.

Next, in the state shown in FIG. 2B, impurities are implanted into the active layers 203 and 204 by ion doping. 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 fabricating an N-channel TFT will be described.
It is also possible to form a channel TFT and a P-channel TFT on the same substrate.

By this ion implantation, source / drain regions 213 and 214 of the circuit TFT and 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
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 formation region 221 are formed.
And low-concentration impurity regions 219 and 220 of the pixel TFT,
A channel forming region 222 is formed in a self-aligned manner.

After the state shown in FIG. 2C is obtained, 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 in the ion doping step is improved, and
Activation of the implanted impurity ions is performed.

Next, a silicon nitride film (may be a silicon oxide film) is formed as a first interlayer insulating film 223 to a thickness of 300 nm by a plasma CVD method. This interlayer insulating film 223 may have a multilayer structure.

After forming the first interlayer insulating film 223, a contact hole is formed in a region where an electrode and a wiring are to be formed. Then, a source wiring (also referred to as 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 mainly composed of aluminum and titanium.
And the source wiring 227 and the drain electrode 2 of the pixel TFT
28 are 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. In addition, 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 to a thickness of 0.5 to 5 μm by a plasma CVD method. As the interlayer insulating film 229, a single layer or a stacked film using a silicon oxide film, a silicon nitride film, an organic resin material, or the like can be used.

When an organic resin material such as polyimide is used for the second interlayer insulating film 229, the thickness can be easily increased, so that 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 100 to 200 nm. 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. Further, it is preferable to form a thick pattern with a margin at an end portion of the pixel region so as to overlap the black matrix on the counter substrate side.

With such a configuration, a margin of the distance X can be secured as shown in FIG. 1A, and a gap in which light leaks due to displacement when bonding the substrates to each other can be formed. There is nothing.

When the black matrix 230 is formed on the active matrix substrate side as described above, the light-shielding region can be covered with a minimum occupied area, which is effective without impairing the aperture ratio.

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

At this time, as shown in FIG. 2E, when the pixel electrode 232 is formed so that the black matrix 230 and the pixel electrode 232 overlap, the overlapping area can be used as an auxiliary capacitance.

Thus, 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 process of manufacturing the counter substrate will be described with reference to FIG. First, as shown in FIG. 3A, a black matrix 302 is
It is formed to a thickness of 0 to 200 nm.

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

Next, when an image needs to be displayed in color, a color filter 303 is formed. The color filter is required to be uniform in thickness and flat, and to be excellent in heat resistance and chemical resistance. (FIG. 3 (A))

The color filter 303 has a known structure. That is, R (red), R (red),
G (green) and B (blue) are arranged regularly. The thickness of the color filter is 1.5 to 2.0 μm.

Therefore, although the color filter 303 shown in FIG. 3A is described as a single film, it is actually a color filter corresponding to R (red), G (green), and B (blue). 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 for protecting the color filters. (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 100 nm. Further, an alignment film 306 is formed to a thickness of 80 nm on the counter electrode 305 to complete a counter substrate as shown in FIG.

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

After the active matrix substrate and the opposing substrate are completed through the above steps, a rubbing process is performed on both substrates to give the alignment film a desired orientation. By this step, the orientation of the liquid crystal material in the vicinity of the substrate is determined. (FIG. 4 (A))

After the rubbing process is completed, a sealing material 406 is formed by screen printing so as to surround the driving circuit area and the pixel area of the counter substrate. As the sealing material 406, a material obtained by dissolving an epoxy resin and a phenol curing agent 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 bonding 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 sprayed on the opposing substrate. As the spacer 407, polymer-based, glass-based, or silica-based spherical fine particles are used, and are sprayed from a nozzle and dispersed over the entire surface of the active matrix substrate. (FIG. 4
(B))

An advantage of performing the above-described sealing material / spacer spraying step on the counter substrate side is prevention of contamination of the TFT circuit and electrostatic breakdown. In particular, since the spacer dispersing step involves generation of static electricity, it is desirable to perform the step on the counter substrate side.

Next, the active matrix substrate and the counter substrate are bonded to each other. The distance X to be secured (positioning margin) as shown in FIG. 1A may be determined based on the accuracy of the bonding. Further, at the time of bonding, a spacer 407 is sandwiched between the two substrates, and the cell gap is determined by the diameter of the spacer 407. (FIG. 4 (C))

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

Finally, the opening is sealed and a liquid material is sealed therein to complete a liquid crystal display device as shown in FIG.
The black matrix arranged in this liquid crystal display device is
As described above, the pixel region is disposed on the active matrix substrate side, and the drive region is disposed on the counter substrate side.

[0085]

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

[Brief description of the 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 view schematically showing a cell assembling step.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 101 Glass substrate 102 Active matrix substrate side black matrix 103 Glass substrate 104 Opposite substrate side black matrix 105 Drive circuit area 106 Pixel area 107 Black matrix window

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H01L 29/78 619B

Claims (8)

[Claims] A first substrate having a pixel region on which a first black matrix is formed and a driving circuit region; and a first substrate facing the first substrate and having a second black matrix formed thereon. A liquid crystal display device comprising: a second substrate; and the second black matrix facing a region of the first substrate other than the pixel region. 2. A first substrate having a pixel region on which a first black matrix is formed and a driving circuit region, and a first substrate facing the first substrate and having a second black matrix formed thereon. 2. The liquid crystal display device according to claim 1, wherein the second black matrix has a portion facing the region of the first substrate excluding the pixel region and overlapping the pixel region. 3. A first substrate having a pixel region in which a first black matrix is formed and a driving circuit region, and a first substrate facing the first substrate and having a second black matrix formed thereon. A plurality of pixel electrodes are provided in the pixel region, a first thin film transistor is connected to each of the plurality of pixel electrodes, and the first circuit is connected to the drive circuit region. A plurality of second thin film transistors for controlling the thin film transistors are provided, and the second black matrix has a portion opposed to a region excluding the first pixel region and overlapping the pixel region. apparatus. 4. The liquid crystal display device according to claim 1, wherein the first black matrix includes a metal thin film or a resin. 5. The liquid crystal display device according to claim 1, wherein the second black matrix includes a metal thin film or a resin. 6. A liquid crystal display according to claim 4, wherein said metal thin film is a chromium thin film or a titanium thin film. 7. The liquid crystal display device according to claim 1, wherein the first and second black matrices have overlapping portions. 8. A projector comprising the liquid crystal display device according to claim 1.