JPH08220560A - Active matrix display device - Google Patents

Abstract

PURPOSE: To improve the reliability of an active matrix type liquid crystal display device in which a picture element area and a peripheral driving circuit area are integrated. CONSTITUTION: By providing a thin film transistor 208 to compose a peripheral driving circuit at the inner side (at the liquid crystal side) than a sealing member 210, the peripheral driving circuit is protected from the external side. As a result, the reliability of the peripheral driving circuit for a long period can be increased. And the wiring to a thin film transistor 207 provided from the thin film transistor 208 composing the peripheral driving circuit to a picture element area is made shorter, and the improvement of the display property by reducing the wiring resistance can be accomplished.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technique for miniaturizing an active matrix display device and obtaining high reliability.

[0002]

2. Description of the Related Art FIG. 4 is a sectional view showing a state of a panel constituting a conventional active matrix display device. FIG.
As is apparent from the above, since the pixel region (404) is surrounded by the sealing material (402) (also referred to as a sealing material), only the pixel region (404) of the active matrix display device is in contact with the liquid crystal and peripheral driving is performed. Circuit area (403) T
The FT is in contact with the atmosphere. This is a remnant when only the pixel TFT existed on the substrate of the active matrix display device and the drive circuit was an external IC before. As described above, in the conventional technique, the mounting position of the drive circuit is not optimized when the pixel region (404) and the peripheral drive circuit region (403) are formed on the same glass substrate (401). It was

[0003]

In the conventional active matrix display device, since the drive circuit TFT is exposed to the outside, it is necessary to pay close attention to the handling of the substrate of the active matrix display device during the panel assembly process. It was Under such circumstances, a form of an active matrix display device that is easy to handle in the manufacturing process has been desired. Also, from the viewpoint of reliability, the pixel is protected by a liquid crystal material, a sealing material, etc., whereas the drive circuit is only covered with a thin oxide film, which is resistant to temperature and contamination. It's getting weaker.

[0004]

In order to minimize the damage during the panel assembly process of the drive circuit of the active matrix display device and solve the reliability problem, the drive circuit of the active matrix display device is directly touched. Any form is acceptable. Therefore, as shown in FIG. 1, the peripheral drive circuit region (10
3) is mounted in a liquid crystal material or a sealing material.

The invention disclosed in this specification will be shown below. One of the inventions disclosed in this specification is, in an active matrix display device, a pixel thin film transistor of the active matrix display device and a driving circuit thin film transistor of the pixel are present on the same substrate, and the pixel thin film transistor and the driving circuit thin film transistor are It is characterized in that the liquid crystal is sealed so that both of them come into contact with the liquid crystal material directly or through a thin film.

Generally, since the thin film transistor is covered with an interlayer insulating film made of a silicon oxide film or the like, it comes into contact with the liquid crystal through this insulating film. By adopting the above configuration, the thin film transistor of the peripheral drive circuit can be substantially enclosed in the liquid crystal. That is, the thin film transistor of the peripheral driver circuit can be sealed with liquid crystal.

According to another aspect of the invention, a liquid crystal is held between a pair of translucent substrates, and thin film transistor circuits arranged in a matrix on one surface of the pair of substrates, and And a peripheral drive circuit formed of thin film transistors connected to the matrix circuit,
Liquid crystal or a sealing material is present on the upper surface of the peripheral drive circuit, and a space for arranging an integrated circuit connected to the peripheral drive circuit is formed between the pair of substrates. Characteristic active matrix display device.

A specific example of the above configuration is shown in FIG. Figure 2
Shown in FIG. 4 is a cross-sectional view showing a schematic configuration of an active matrix type liquid crystal display device in which a liquid crystal 209 is sandwiched between a pair of glass substrates 202. In the structure shown in FIG. 2, a thin film transistor 207 of the active matrix circuit, a thin film transistor 208 of a peripheral drive circuit for driving the thin film transistor 207, and a thin film transistor 208 of the peripheral drive circuit are supplied with a video signal and various control signals. It has an integrated circuit (IC) 211 for sending.

In the structure shown in FIG. 2, liquid crystal is present on the upper surface of the thin film transistor 208 of the peripheral drive circuit. In addition, the integrated circuit 211 sealed with the sealing material 210
Are arranged in a space formed between the pair of glass substrates 202.

According to another aspect of the invention, in the active matrix display device, the pixel thin film transistor of the active matrix display device and the driving circuit thin film transistor of the pixel are present on the same substrate, and the driving circuit thin film transistor is sealed by a sealing material. It is characterized by having done.

A specific example of the above configuration is shown in FIG. FIG.
In the configuration shown in (1), the thin film transistor 308 forming the peripheral drive circuit is sealed with the sealing material 310.

[0012]

[Function] The peripheral drive circuit area is an area where liquid crystal is present,
Alternatively, the peripheral drive circuit region can be substantially sealed in the liquid crystal material or the sealing material by being present in the sealing material. Then, it is possible to prevent moisture from entering from the outside into the peripheral drive circuit region having a high packaging density. In addition, the influence of stress can be mitigated.

[0013]

【Example】

[Embodiment 1] FIG. 2 is a sectional view of an active matrix display device according to the present invention. In the active matrix display device, the pixel substrate (20) is provided on the glass substrate (202).
A transparent electrode (204) and an alignment film (205) are attached on 7). This glass substrate is called a TFT substrate. T
The FT substrate is a polarizing plate (20) from the side farther from the liquid crystal material (209).
1) and the glass substrate (202) are arranged in this order. Also,
The other glass substrate is called a color filter substrate. The alignment film (205), the transparent electrode (204), the color filter (203), the glass substrate (202), and the polarizing plate (201) are arranged from the side closer to the liquid crystal material (209). And
A large number of glass or resin spacers (206) for maintaining a constant gap between the two glass substrates are scattered in the liquid crystal material (209).

The polarizing plate (201) is a filter having a thickness of about 80 to 210 μm which limits the vibrating direction of light passing therethrough. As shown in FIG. 6, the structure of the polarizing plate has a polarizing film 604 made of PVA (polyvinyl alcohol) in the center and a cellulose-based protective layer 603 attached thereto. Further, an adhesive layer 602 and a release film 601 are attached on the outer side of the layer near the liquid crystal material, and a protective film 605 for protecting the surface is attached on the opposite side. When using it,
The release film 601 is peeled off, and the adhesive layer 602 is formed on the glass substrate.
Use by sticking. The role of the alignment film (205) is to allow the liquid crystal molecules to enter the grooves formed in the alignment film (205) when the voltage is turned off and to arrange the liquid crystal molecules in a certain direction. For the alignment film material, polyimide or polyamic acid is used in a solvent of 5 to 10
What was dissolved by weight% is used. In addition, the alignment film (2
The thickness of 05) is about 0.05 to 0.1 μm, and the film thickness is required to be uniform. The liquid crystal material (209) is in the center of the active matrix display device, and stands up when the voltage is ON and twists when the voltage is OFF, thereby playing a role of a switch for controlling passage / blocking of light. The raw material of the liquid crystal material (209) is benzene, toluene or the like. The color filter (203) is a color synthesizing filter for colorizing a monochrome liquid crystal display. The color filter (203) is composed of three colors of RGB (Red, Green, Blue), one pixel TFT and one of the color filters (203).
The colors of the individual are overlapping. Sealing material (210)
Serves as an adhesive for attaching the two glass substrates. Raw materials for the encapsulant (210) include silicon, acrylic, epoxy and the like.

The fact that the pixel TFT is in the liquid crystal region is the same as in the conventional active matrix display device, but in the present invention, the drive circuit TFT (20) which is conventionally outside the encapsulation is used.
8) is arranged in the liquid crystal enclosure area. The inclusion of the drive circuit in the liquid crystal encapsulation region has the following advantages. 1. Improved stain resistance. 2. Image quality is improved by shortening the signal lines connected to the pixels. 3. The liquid crystal material serves as a cushioning material and can prevent unnecessary stress from being applied to the thin film transistor. In addition, in the present embodiment, not only the drive circuit is placed in the liquid crystal enclosed area, but also the microprocessor (2
By placing the control integrated circuit such as 11) in the encapsulating material, it is possible to suppress the distance between the drive circuit and the control integrated circuit, and to reduce unnecessary noise of the signal. Here, when the control integrated circuit is encapsulated, the substrate on the opposite side is partially thinned to facilitate mounting. By placing the control integrated circuit in the sealing region, the reliability is improved as compared with the conventional structure. The control circuit referred to here is an integrated circuit formed using a silicon edge crystal wafer, and specific examples thereof include a memory, an I / O port, various other control circuits, a circuit that handles video signals, and Mention may be made of integrated circuits having any combination thereof. Of course, these integrated circuits are arranged in the required number.

The method of arranging the integrated circuits is based on the COG (Chip
It is desirable to be mounted on the board with On Glass). However, even if the wiring is formed by the wire bonding method, the wiring is substantially sealed by the sealing material, so that the reliability can be high.

Although not shown in the figure, it is necessary to form a shielding film such as a chromium film or an aluminum film for shielding light on the upper surface of the peripheral drive circuit area.

In the structure shown in FIG. 2, a part of the glass substrate 202 is thinned and the integrated circuit 211 is arranged in that part. This is because the gap where the liquid crystal is injected is a few μ.
This is because the thickness of the integrated circuit is about several hundred μm while the thickness is about m. In FIG. 2, a part of the upper glass substrate 202 side is thin, but a part of the glass substrate 202 side on which the TFT is arranged may be thin. Further, both glass substrates may be thinned and an integrated circuit may be arranged in that portion.

A manufacturing process for obtaining the active matrix circuit of this embodiment will be described with reference to FIGS. The left side of the figure shows the manufacturing process of the TFT of the peripheral driving circuit, and the right side shows the manufacturing process of the TFT of the active matrix circuit. First, a silicon oxide film having a thickness of 1000 to 3000 Å is formed as a base oxide film (502) on a quartz substrate or a glass substrate (501). As a method of forming this silicon oxide film, a sputtering method in an oxygen atmosphere or a plasma CVD method may be used.

Next, an amorphous or polycrystalline silicon film is formed by plasma CVD method or LPCVD method 30.
0 to 1500Å, preferably 500 to 1000Å is formed. And 500 degreeC or more, Preferably it is 800-95.
Thermal annealing is performed at a temperature of 0 ° C. to crystallize the silicon film. After crystallizing by thermal annealing, optical annealing may be performed to further enhance the crystallinity. In addition, when crystallizing by thermal annealing, Japanese Patent Laid-Open No. 6-244
103, 6-244104,
An element (catalyst element) that promotes crystallization of silicon such as nickel may be added.

Next, the silicon film is etched to form the active layers (503) (for P-channel type TFT) and (504) (for N-channel type TFT) of the TFT of the island-shaped peripheral drive circuit and the TFT of the matrix circuit ( Pixel TFT active layer (50
5) is formed. Further, a gate insulating film (506) of silicon oxide having a thickness of 500 to 2000 Å is formed by a sputtering method in an oxygen atmosphere. A plasma CVD method may be used as a method for forming the gate insulating film. When the silicon oxide film is formed by the plasma CVD method, dinitrogen monoxide (N ₂ O) or oxygen (O ₂ ) is used as a source gas.
₂ ) and monsilane (SiH ₄ ) are preferably used.

Thereafter, a polycrystalline silicon film having a thickness of 2000 Å to 5 μm, preferably 2000 to 6000 Å (containing a trace amount of phosphorus for enhancing conductivity) is formed on the entire surface of the substrate by the LPCVD method. Then, this is etched to form gate electrodes (507, 508, 509). (FIG. 5A) After that, phosphorus is injected into all the island-shaped active layers by ion doping in a self-aligned manner using phosphine (PH ₃ ) as a doping gas using the gate electrode as a mask.
The dose amount is 1 × 10 ^{12 to} 5 × 10 ¹³ atoms / cm ² .
As a result, weak N-type regions (510, 511, 512) are formed. (Fig. 5 (B))

Next, the active layer of the P-channel TFT (50
3) and a photoresist mask (513) covering the pixel TFT active layer (505) parallel to the gate electrode and up to 3 μm away from the end of the gate electrode (509). 514) is formed. Then, again, phosphorus is injected by the ion doping method using phosphine as a doping gas. The dose amount is 1 × 10 ^{14 to} 5 × 10 ¹⁵ atoms / cm ² . As a result, a strong N-type region (source / drain) (515,
516) is formed. Active layer of pixel TFT (505)
In the weak N-type region (512), the region (517) covered with the mask (514) remains weak N-type because phosphorus is not implanted in this doping. (Fig. 5
(C))

Next, the active layer of the N-channel TFT (50
4, 505) is covered with a photoresist mask (518), and boron is implanted into the island region (503) by an ion doping method using diborane (B ₂ H ₆ ) as a doping gas. The dose amount is 5 × 10 ¹⁴ to 8 × 10 ¹⁵ atoms / c
m ² In this doping, since the dose amount of boron exceeds the dose amount of phosphorus in FIG. 5C, the weak N-type region (510) previously formed is a strong P-type region (5).
Invert to 19). By the above doping, strong N type regions (source / drain) (515, 516), strong P
A type region (source / drain) (519) and a weak N type region (low concentration impurity region) (517) are formed. In this embodiment, the width x of the low concentration impurity region (517) is
The thickness is about 3 μm. (FIG. 5 (D))

Thereafter, thermal annealing is performed at 450 to 850 ° C. for 0.5 to 3 hours to recover the damage due to the doping, activate the doping impurities, and recover the crystallinity of silicon. Then, a silicon oxide film having a thickness of 3000 to 6000Å is formed as an interlayer insulator (520) on the entire surface by plasma CVD. This may be a silicon nitride film or a multilayer film of a silicon oxide film and a silicon nitride film. Then, the interlayer insulator (520) is etched by a wet etching method to form contact holes in the source / drain.

Then, a thickness of 200 is obtained by the sputtering method.
A titanium film of 0 to 6000 Å is formed, and this is etched to form electrodes and wirings (521, 522, 52) of peripheral circuits.
3) and electrode / wiring of pixel TFT (524, 525)
To form. Further, a silicon nitride film (526) having a thickness of 1000 to 3000 Å is formed as a passivation film by the plasma CVD method, and this is etched to form a contact hole reaching the electrode (525) of the pixel TFT. Finally, the thickness of 500-
A 1500 Å ITO (indium tin oxide) film is etched to form a pixel electrode (527). In this way, the peripheral logic circuit and the active matrix circuit are integrally formed. (Fig. 5 (E))

The process of assembling the active matrix display device of this embodiment will be described below. The TFT substrate and the color filter substrate are thoroughly washed with various chemicals such as the etching liquid resist stripping liquid used for the surface treatment. Next, the alignment film is attached to the color filter substrate and the TFT substrate.
The alignment film has certain grooves formed therein, and liquid crystal molecules are uniformly arranged along the grooves. For the alignment film material, use a solvent such as butyl cellulose or n-methylpyrrolidone, and use about 10% of the solvent.
What melt | dissolved the polyimide of weight% is used. This is called a polyimide varnish. The polyimide varnish is printed by a flexographic printing device as shown in Fig. *. And T
The alignment films attached to both the FT substrate and the color filter substrate are heated and cured. This is called baking. Baking is to heat and blow the polyimide varnish by sending hot air with a maximum operating temperature of about 300 ° C. Then, the glass substrate surface to which the alignment film is attached is set to a length of 2 to 3 mm.
Rubbing with a buff cloth (fibers such as rayon and nylon) in a certain direction to make fine grooves is performed. And T
On each of the FT substrate or the color filter substrate, spherical spacers of polymer type, glass type, silica type or the like are scattered. Spacer spraying methods include a wet method in which spacers are mixed with a solvent such as pure water or alcohol and sprayed on a glass substrate, and a dry method in which spacers are sprayed without using any solvent. Then, a sealing material is applied to the outer frame of the TFT substrate. The application of the sealing material has the role of adhering the TFT substrate and the color filter substrate and the purpose of preventing the injected liquid crystal material from flowing out. As a material for the encapsulating material, an epoxy resin and a phenol curing agent dissolved in a solvent of ethyl cellosolve are used. After the sealing material is applied, the two glass substrates are bonded together. The method employs a heat curing method in which the encapsulant is cured in about 3 hours by a high temperature press at about 160 ° C. Finally, a liquid crystal material is put in from a liquid crystal injection port of an active matrix display device in which a TFT substrate and a color filter substrate are bonded together, and after the liquid crystal material is injected, the liquid crystal injection port is sealed with an epoxy resin. The active matrix display device is assembled as described above.

[Embodiment 2] FIG. 3 is a sectional view of an active matrix display device according to the present invention. As is apparent from the figure, the microprocessor (311) for controlling the active matrix display device and the drive circuit TFT (30
By encapsulating 8) with a sealing material (310), the drive circuit T
The FT (308) is protected so that it is not exposed to the outside. In this embodiment, except that the amount of circuit (driving circuit TFT (308)) enclosed by the sealing material (310) is different,
The configuration and the manufacturing process are the same as those of the example (1).

[Embodiment 3] This embodiment relates to a configuration in which a spare peripheral circuit (redundant circuit) is provided. FIG. 7 shows a schematic top view of the liquid crystal display panel shown in this embodiment. Since FIG. 7 is a view seen from above, only one glass substrate 701 is shown. However, in reality, another glass substrate that is paired with the glass substrate 701 is attached to the glass substrate 701. In the structure shown in FIG. 7, the peripheral drive circuit region 703 and the pixel regions 704 arranged in a matrix are arranged inside the sealing material 702. Since the inside of the sealing material 702 is filled with liquid crystal, the peripheral drive circuit region 703 and the pixel region 704 are formed.
The thin film transistor arranged in the above state has a liquid crystal present on the upper surface thereof.

Further, integrated circuits (ICs) constituting various control circuits connected to the peripheral drive circuit are arranged in the sealing material 702 and are just molded by the sealing material 702.

Reference numeral 705 denotes a spare peripheral drive circuit area, which is used when a defect occurs in the peripheral drive circuit arranged in the area 703. 706
Reference numeral denotes a connection terminal to the outside, through which a video signal and a necessary signal are input from the rotating section. The liquid crystal display panel shown in FIG. 7 contains all necessary circuits between a pair of glass substrates. Moreover, since all of these circuits are sealed with the sealing material or the liquid crystal, the reliability can be made extremely high.

Although the dimension ratio is not accurate in the drawing, the width of the peripheral drive circuit is about several millimeters. Although the width of the sealing material is determined by the integrated circuit connected to the peripheral driving circuit, the width is about several mm or less (if the integrated circuit can be made small, it can be about 1 mm).
Can be Therefore, it has an extremely simple appearance that it is composed of a pair of glass substrates in appearance, except that there is an edge of several mm to 1 cm around the area where the liquid crystal display is actually performed and the external output terminals are excluded. can do.

[0033]

As described above, by disposing the drive circuit TFT of the active matrix display device inside the encapsulating material region, it is possible to improve the temperature resistance and contamination resistance of the drive circuit TFT. Further, it is possible to reduce the size of the active matrix display device. Further, the voltage drop due to the shortening of the image signal line can be reduced, and the characteristics can be improved.

By arranging the peripheral drive circuit area in the liquid crystal area or the area where the sealing material is provided, the peripheral drive circuit area is sealed by the liquid crystal or the sealing material, so that the reliability due to the influence of moisture is increased. Sexual deterioration can be prevented. Further, since the liquid crystal or the sealing material serves as a buffer material, it is possible to prevent unnecessary stress from being applied to the peripheral drive circuit region.

Further, by disposing the control integrated circuit connected to the peripheral drive circuit in the encapsulating material, it is possible to prevent the deterioration of reliability due to the influence of moisture. In addition, since a required circuit can be arranged between the pair of glass substrates, reliability can be improved, and a miniaturized liquid crystal display device having a simple appearance without unnecessary unevenness can be provided. Obtainable.

[Brief description of drawings]

FIG. 1 is a schematic diagram of an active matrix display device according to the present invention.

FIG. 2 is a sectional view of an active matrix display device according to an embodiment (No. 1).

FIG. 3 is a cross-sectional view of an active matrix display device according to an example (No. 2).

FIG. 4 is a schematic diagram of a conventional active matrix display device.

FIG. 5: Manufacturing process of Example (No. 1)

FIG. 6 Configuration of polarizing plate

FIG. 7 is a schematic diagram of an active matrix display device of an example.

[Explanation of symbols]

101, 202, 302, 401 Glass substrate 102, 210, 310, 402 Sealing material 103, 208, 308, 403 Driving circuit TFT 104, 207, 307, 404 Pixel TFT 201, 301 Polarizing plate 203, 303 Color filter 204, 304 transparent electrode 205, 305 alignment film 206, 306 spacer 209, 309 liquid crystal material 211, 311 microprocessor 501 substrate 502 base film (silicon oxide) 503 to 505 active layer (silicon) 506 gate insulating film (silicon oxide) 507 to 509 Gate electrode / gate line 510 to 512 Weak N-type region 513, 514 Photoresist mask 515, 516 Strong N-type region (source / drain) 517 Low-concentration impurity region 518 Photoresist mask 519 Strong P-type region (source) / Drain) 520 Interlayer insulator (silicon oxide) 521 to 525 Metal wiring / electrode 526 Passivation film (silicon nitride) 527 Pixel electrode (IT
O)

Front page continuation (72) Inventor Toshimitsu Onuma 398 Hase, Atsugi City, Kanagawa Semiconductor Energy Research Institute Co., Ltd. (72) Inventor Satoshi Teramoto 398 Hase, Atsugi City, Kanagawa Semiconductor Energy Research Institute Co., Ltd.

Claims (10)

[Claims] 1. In an active matrix display device, a pixel thin film transistor of the active matrix display device and a driving circuit thin film transistor of the pixel are present on the same substrate, and both the pixel thin film transistor and the driving circuit thin film transistor are directly or through a thin film. An active matrix display device characterized in that liquid crystal is sealed so as to come into contact with a liquid crystal material. 2. The active matrix display device according to claim 1, wherein the peripheral circuit is provided in a liquid crystal region inside the sealing material. 3. The control circuit for controlling the active matrix display device according to claim 1, wherein a COG (Chip On Glas) is provided.
s) is mounted on a substrate, and the control circuit is enclosed in a liquid crystal sealing material of the active matrix display device. 4. The control circuit for controlling the active matrix display device according to claim 3, wherein a COG (Chip On Glas) is provided.
An active matrix display device characterized in that the thickness of the substrate at the mounting position is made thin on the substrate on which the control circuit is mounted in order to mount on the substrate in step s). 5. The control circuit for controlling the active matrix display device according to claim 3, wherein a COG (Chip On Glas) is provided.
The active matrix display device is characterized in that the thickness of the substrate at the mounting position is reduced on the opposite side substrate on which the control circuit is mounted in order to mount it on the substrate in step s). 6. The active matrix display device according to claim 3, wherein the control circuit is an integrated circuit manufactured using a single crystal silicon substrate. 7. A liquid crystal is held between a pair of translucent substrates, and a thin film transistor circuit arranged in a matrix on one surface of the pair of substrates and connected to the matrix circuit. And a liquid crystal or sealing material is present on the upper surface of the peripheral drive circuit, and the peripheral drive circuit is connected between the pair of substrates. An active matrix display device is characterized in that a void for arranging the integrated circuit is formed. 8. The active matrix display device, wherein the pixel thin film transistor of the active matrix display device and a driving circuit thin film transistor of the pixel are present on the same substrate, and the driving circuit thin film transistor is encapsulated by a sealing material. Active matrix display device. 9. The control circuit for controlling an active matrix display device according to claim 8, wherein a COG (Chip On Glas) is provided.
An active matrix display device characterized in that the thickness of the substrate at the mounting position is made thin on the substrate on which the control circuit is mounted in order to mount on the substrate in step s). 10. A COG (Chip On Glas) control circuit for controlling an active matrix display device according to claim 8.
In order to mount the control circuit on the substrate in step s), the thickness of the substrate at the mounting position is reduced in the opposite substrate on which the control circuit is mounted.