JP3594863B2 - Method for manufacturing active matrix display device - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an active matrix type liquid crystal display device, and more particularly to an active matrix type liquid crystal display device with an improved aperture ratio and reduced steps.
[0002]
[Prior art]
An active matrix type liquid crystal display device has pixels arranged at each intersection of a matrix, and all pixels are provided with switching elements, and pixel information is controlled by turning on / off switching elements. Say. Liquid crystal is used as a display medium of such a display device. In the present invention, a three-terminal element, that is, a thin film transistor having a gate, a source, and a drain is used as the switching element.
[0003]
In the description of the present invention, a row in a matrix refers to a row in which scanning lines (gate lines) arranged in parallel with the row are connected to gate electrodes of thin film transistors in the row, and a column refers to the column. A signal line (source line) arranged in parallel with a row is connected to a source (or drain) electrode of a thin film transistor in the column. Further, a circuit for driving a scanning line is referred to as a scanning line driving circuit, and a circuit for driving a signal line is referred to as a signal line driving circuit. The thin film transistor is called a TFT.
In recent years, in the market of viewfinders and projectors for video cameras, liquid crystal display devices in which a driving circuit is formed simultaneously with pixel TFTs on a glass substrate using polysilicon TFTs are becoming mainstream.
Further, in order to improve the reliability of the liquid crystal display device and reduce the size of the substrate, a driving circuit is provided in the liquid crystal region as in the case of the pixel TFT.
[0004]
FIG. 2 shows a first conventional example of an active matrix type liquid crystal display device. As shown in this example, in the active matrix type liquid crystal display device, a signal line driving circuit is disposed at an upper part of FIG. 2 and a scanning line driving circuit is disposed at a left side, and the signal lines and the scanning lines are driven.
FIG. 3 is an enlarged view of a part of the pixel matrix of FIG. FIG. 3 shows a region where light does not pass between the ITO pixel electrodes due to the overlap of the black matrix on the counter substrate and the ITO pixel electrodes. The black matrix is a layer that blocks light in the gaps between pixel electrodes and in the TFT area, determines the aperture ratio of the panel, and has a significant effect on display brightness. The aperture ratio is obtained by dividing the opening area of the black matrix by the area of the pixel cell, and the larger the value, the more advantageous the display.
FIG. 4 shows a cross-sectional view of this example. In color display, improvement of luminance is a major issue, and it is necessary to increase the aperture ratio. Further, by improving the aperture ratio, the brightness of a light source such as a backlight can be reduced, and the power consumption of the liquid crystal display device can be reduced.
[0005]
[Problems to be solved by the invention]
When a black matrix is formed on the counter substrate, the area of the opening cannot be increased because the black matrix enters the ITO pixel electrode by about 5 to 7 μm as shown in FIG. 3 due to the bonding accuracy between the TFT substrate and the counter substrate. There was a problem.
[0006]
FIG. 5 shows a second conventional example in which a solution to the problem is implemented. In this example, the black matrix was transferred from the opposite substrate to the TFT substrate. At this time, since the black matrix and the ITO pixel electrode are formed on the same substrate, the bonding accuracy is improved, and the overlap region can be about 2 μm.
Thus, by transferring the black matrix to the TFT substrate, in the example of FIG. 3, the aperture ratio is changed from about 15% (overlapping area 7 μm) shown in FIG. 3A to about 40% shown in FIG. (Overlap area 2 μm).
In particular, as described above, in the case where the opposing substrate has a size facing the driving circuit and the driving circuit is provided in the liquid crystal region, the driving circuit region and the pixel region are close to each other. Also, the need for light shielding occurs.
[0007]
When the black matrix for light shielding of the pixel is transferred to the TFT substrate and the light shielding of the driving circuit is performed by the light shielding film, there is no problem with the light shielding. The capacity cannot be ignored.
When the thickness of the interlayer film is 300 nm and a nitride film is used, the capacitance of the insulating film per unit area is 2.50 × 10 ⁻¹⁶ [F / μm ² ]. If there is a wiring having a length of 50000 μm, the capacitance between the wiring of the drive circuit and the black matrix is 1.25 × 10 ⁻⁹ [F]. At this time, the delay time of the wiring of the drive circuit is 1.25 × 10 ⁻⁷ [s] when the sheet resistance of the wiring is 0.2 [Ω / μm ² ], which is a problem when the wiring is driven at several MHz. Become.
The drive circuit has more important circuit characteristics than the pixel TFT and needs to be improved.
[0008]
FIG. 6 shows a third conventional example in which a solution to the problem of deteriorating drive circuit characteristics by transferring a black matrix from a counter substrate to a TFT substrate is provided. In this example, only the black matrix of the pixel portion is transferred to the TFT substrate, and the black matrix of the driving portion is formed on the opposite substrate.
However, in this case, although the aperture ratio is improved, the number of steps increases because the black matrix is formed on both the TFT substrate and the counter substrate.
[0009]
An object of the present invention is to provide a liquid crystal display device having an improved aperture ratio without increasing the number of steps.
SUMMARY OF THE INVENTION It is an object of the present invention to provide a liquid crystal display device in which a driving circuit can be shielded from light without increasing the number of steps.
[0010]
[Means for Solving the Problems]
In order to solve the above problems, the present invention provides
A pixel to which the thin film transistor is connected, a pixel portion arranged in a plurality of matrices, and a driving circuit portion configured to be driven by the thin film transistor and driving the pixel portion, a first insulating substrate having on the same surface,
Opposite to the substrate, a second insulating substrate having a color filter,
A liquid crystal material filled between the first insulating substrate and the second insulating substrate,
In an active matrix type liquid crystal display device having at least
A light-shielding structure formed by providing three types of color filters of R (red), G (green), and B (blue) on the second insulating substrate at a position facing the drive circuit unit. An active matrix type liquid crystal display device provided with a film.
[0011]
Further, another configuration of the present invention includes:
A pixel to which the thin film transistor is connected, a pixel portion arranged in a plurality of matrices, and a driving circuit portion configured to be driven by the thin film transistor and driving the pixel portion, a first insulating substrate having on the same surface,
Having a color filter provided at a position facing the pixel portion, a second insulating substrate facing the first insulating substrate,
A liquid crystal material filled between the first insulating substrate and the second insulating substrate,
In an active matrix type liquid crystal display device having at least
A black matrix is provided in the pixel portion;
A light-shielding film formed by providing three types of color filters of R (red), G (green), and B (blue) on the second insulating substrate at a position facing the drive circuit unit. Is provided, which is an active matrix liquid crystal display device.
[0012]
Further, another configuration of the present invention includes:
A pixel to which the thin film transistor is connected, a pixel portion arranged in a plurality of matrices, and a driving circuit portion configured to be driven by the thin film transistor and driving the pixel portion, a first insulating substrate having on the same surface,
Having a color filter provided at a position facing the pixel portion, a second insulating substrate facing the first insulating substrate,
A liquid crystal material filled between the first insulating substrate and the second insulating substrate,
In an active matrix type liquid crystal display device having at least
The pixel portion is provided with a black matrix,
The drive circuit unit has a wiring member made of the same material as the black matrix,
A light-shielding film formed by providing three types of color filters of R (red), G (green), and B (blue) on the second insulating substrate at a position facing the drive circuit unit. Is provided, which is an active matrix liquid crystal display device.
[0013]
Further, another configuration of the present invention includes:
In each of the above configurations, each of the three types of color filters of R (red), G (green), and B (blue) constituting the light shielding film is the same as the same type of color filter provided at a position facing the pixel portion. And an active matrix type liquid crystal display device having the same composition.
[0014]
Further, another configuration of the present invention includes:
A pixel to which the thin film transistor is connected, a pixel portion arranged in a plurality of matrices, and a driving circuit portion configured to be driven by the thin film transistor and driving the pixel portion, a first insulating substrate having on the same surface,
Having a color filter provided at a position facing the pixel portion, a second insulating substrate facing the first insulating substrate,
A liquid crystal material filled between the first insulating substrate and the second insulating substrate,
In an active matrix type liquid crystal display device having at least
The pixel portion is provided with a black matrix,
The drive circuit unit has a wiring member made of the same material as the black matrix,
An active matrix liquid crystal display device, wherein a light-shielding film is provided on the second insulating substrate at a position facing the drive circuit portion.
[0015]
Further, another configuration of the present invention includes:
In each of the above structures, the drive circuit is in contact with a liquid crystal material directly or through a thin film, which is an active matrix liquid crystal display device.
[0016]
Further, another configuration of the present invention includes:
In each of the above structures, the active matrix liquid crystal display device is characterized in that the opposing substrate has a size facing the driving circuit.
[0017]
The present invention overcomes the above problems and improves the aperture ratio without increasing the number of steps, and the configuration is shown in FIG.
In this example, a black matrix of a pixel portion is provided on a TFT substrate in order to improve an aperture ratio, and three color filters R 1, G 2, and B 3 are provided as light shielding films of a drive circuit portion at the same position on an opposite substrate. .
FIG. 10 shows the spectral characteristics of the color filters R 1, G 2, and B 3.
When three color filters R 1, G 2, and B 3 are stacked, visible light does not pass through as shown in FIG. 10 and can be used as a light shielding film.
In addition, since it is not necessary to form a light-shielding film in the same layer as the black matrix of the pixel portion on the driving circuit, the material used as the black matrix in the pixel portion is used as a material constituting the wiring material of the driving circuit portion. It can be used.
[0018]
【Example】
[Example 1]
Hereinafter, a method for manufacturing a substrate of a liquid crystal display device using an active matrix circuit in this embodiment will be described.
Hereinafter, a manufacturing process for obtaining the monolithic active matrix circuit of this embodiment will be described with reference to FIG. This step is for a low temperature polysilicon process.
The left side of FIG. 7 shows the manufacturing process of the TFT of the 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 100 to 300 nm was formed as a base oxide film (702) on a glass substrate (701) as a first insulating substrate. As a method for forming the silicon oxide film, a sputtering method in an oxygen atmosphere or a plasma CVD method may be used.
[0019]
Thereafter, an amorphous silicon film was formed to a thickness of 30 to 150 nm, preferably 50 to 100 nm by a plasma CVD method or an LPCVD method. Then, thermal annealing was performed at a temperature of 500 ° C. or more, preferably 500 to 600 ° C., to crystallize the silicon film or to improve the crystallinity. After crystallization by thermal annealing, light (eg, laser) annealing may be performed to further enhance crystallization. Further, at the time of crystallization by thermal annealing, as described in JP-A-6-244103 and JP-A-6-244104, an element (catalytic element) such as nickel for promoting crystallization of silicon may be added.
[0020]
Next, the silicon film is etched, and the active layers (703) (for p-channel TFTs) and (704) (for N-channel TFTs) of the TFTs of the island-shaped drive circuit and the TFTs (pixel TFTs) of the matrix circuit are formed. An active layer (705) was formed. Further, a gate insulating film (706) of silicon oxide having a thickness of 50 to 200 nm was formed by a sputtering method in an oxygen atmosphere. As a method for forming the gate insulating film, a plasma CVD method may be used. When a silicon oxide film is formed by a plasma CVD method, it is preferable to use dinitrogen monoxide (N ₂ O) or oxygen (O ₂ ) and monosilane (SiH ₄ ) as source gases.
[0021]
Thereafter, aluminum having a thickness of 200 to 600 nm was formed over the entire surface of the substrate by a sputtering method. Here, aluminum containing silicon, scandium, palladium, or the like may be used to prevent hillocks from being generated by a subsequent thermal process. This is etched to form gate electrodes (707, 708, 709). (Fig. 7 (A))
Next, this aluminum is anodized. The surface of aluminum becomes aluminum oxide (710, 711, 712) by anodic oxidation, and has an effect as an insulator. (Fig. 7 (B))
[0022]
Next, a photoresist mask (713) covering the active layer of the P-channel TFT is formed. Then, phosphorus is implanted by ion doping using phosphine as a doping gas. The dose is 1 × 10 ^{12 to} 5 × 10 ¹³ atoms / cm ² . As a result, strong N-type regions (source, drain) (714, 715) are formed. (Fig. 7 (C))
Next, a photoresist mask (716) covering the active layer of the N-channel type TFT and the active layer of the pixel TFT is formed. Then, boron is implanted again by ion doping using diborane (B ₂ H ₆ ) as a doping gas.
The dose is 5 × 10 ¹⁴ to 8 × 10 ¹⁵ atoms / cm ² . As a result, a P-type region (717) is formed. By the above doping, a strong N type region (source, drain) (714, 715) and a strong P type region (source, drain) (717) are formed. (Fig. 7 (D))
[0023]
Thereafter, thermal annealing was performed at 450 to 850 ° C. for 0.5 to 3 hours to recover damage due to doping, activate doping impurities, and recover silicon crystallinity. Thereafter, a silicon oxide film having a thickness of 300 to 600 nm was formed as an interlayer insulator (718) on the entire surface by a plasma CVD method. This may be a silicon nitride film or a multilayer film of a silicon oxide film and a silicon nitride film. Then, the interlayer insulating film (718) was etched by a wet etching method or a dry etching method to form contact holes in the source / drain.
[0024]
Then, an aluminum film having a thickness of 200 to 600 nm or a multilayer film of titanium and aluminum is formed by a sputtering method. This was etched to form electrodes / wirings for peripheral circuits (719, 720, 721) and electrodes / wirings for pixel TFTs (722, 723). (FIG. 7E) Further, a silicon nitride film (724) having a thickness of 100 to 300 nm is formed as a passivation film by a plasma CVD method, and this is etched to form a contact hole reaching the electrode (723) of the pixel TFT. Was formed. Next, an ITO (indium tin oxide) film having a thickness of 50 to 150 nm formed by a sputtering method was etched to form a pixel electrode (725). Then, a silicon nitride film (726) having a thickness of 200 nm was formed by a plasma CVD method, and this was etched to form an interlayer film.
[0025]
Finally, a 200 nm-thick titanium or chromium film is formed by a sputtering method. This was etched to form a pixel portion black matrix (727). Here, the black matrix is the uppermost layer, but the ITO and the black matrix may be reversed.
[0026]
Next, a method of manufacturing the counter substrate will be described with reference to FIG.
FIG. 8 is a process sectional view of the counter substrate in the first embodiment.
A 1.6 μm thick red color resist as a color filter (802) is applied on a glass substrate (801) as a second insulating substrate using a spinner. Next, it is dried at a temperature of 90 ° C., exposed, developed, washed with water, and dried at a temperature of 210 ° C.
As a result, a red (R) color filter is formed on the entire surface of the drive circuit portion formed on the first insulating substrate and at a position on the counter substrate facing the R (red) region of the pixel portion. You.
Next, in the same manner, in the position on the opposing substrate opposite to the region coated with red (R) facing the entire surface of the drive circuit in the previous step and the G (green) region of the pixel portion, a thickness of 1. A 4 μm G (green) color filter (803) is formed.
Next, in the same manner, in the area on the opposing substrate opposite to the area where G (green) has been applied facing the entire surface of the drive circuit in the previous step and the G (green) area of the pixel portion, a thickness of 1. A 5 μm B (blue) color filter (804) is formed.
Thereafter, O ₂ ashing is performed to remove the residual, and then an overcoat film having a thickness of 1.1 μm for protecting the color filters is formed.
Finally, an ITO (indium tin oxide) film having a thickness of 50 to 150 nm is formed on the entire surface by a sputtering method to form a counter electrode (805).
[0027]
In this manner, at the position on the opposing substrate facing the pixel portion, three color filters of R, G, and B corresponding to individual pixels are provided, and the opposing substrate faces the entire driving circuit portion. In the upper region, three types (three colors) of R, G, and B color filters are provided in an overlapping manner.
When three types of color filters of R, G, and B (three colors) are superimposed, almost no visible light passes therethrough, so that a black display is obtained visually, and a substantial light-shielding film can be formed.
[0028]
Next, an assembly process of the active matrix type liquid crystal display device will be described below. Wash the TFT substrate and the counter substrate, and thoroughly remove the chemicals.
Next, an alignment film is attached to the TFT substrate and the counter substrate. A certain groove is formed in the alignment film, and the liquid crystal molecules are uniformly arranged along the groove. As the material for the alignment film, a material obtained by dissolving about 10% by weight of a polyimide in a solvent such as butyl cellulose or n-methylpyrrolidone is used. This is called a polyimide varnish. The polyimide varnish is printed by a flexographic printing device.
[0029]
Then, the alignment film attached to both the TFT substrate and the opposite substrate is heated and cured. This is called baking, in which hot air having a maximum temperature of about 300 ° C. is sent and heated to bake and cure the polyimide varnish. Next, the glass substrate to which the alignment film is attached is rubbed in a predetermined direction with a buff cloth (fiber such as rayon or nylon) having a length of 2 to 3 mm to perform a rubbing step of forming fine grooves.
Then, spherical spacers of polymer type, glass type, silica type or the like are sprayed on either the TFT substrate or the counter substrate. As a method of dispersing the spacers, there are a wet method in which the spacers are mixed with a solvent such as pure water or alcohol and the spacers are dispersed on a glass substrate, and a dry method in which the spacers are dispersed without using any solvent.
[0030]
Next, a sealing material is applied to the outer frame of the pixel portion of the TFT substrate. The purpose of applying the sealing material is to bond the TFT substrate to the counter substrate and to prevent the injected liquid crystal material from flowing out. As a material of the sealing material, a material obtained by dissolving an epoxy resin and a phenol curing material in a solvent of ethyl cellosolve is used. Two glass substrates are bonded to each other to apply a sealing material. The method employs a heat-curing method in which the sealing material is cured by a high-temperature press at about 160 ° C. in about 3 hours.
Next, the TFT substrate and the opposing substrate are bonded to each other, a liquid crystal material is inserted from a liquid crystal injection port, and the liquid crystal material injection port is sealed.
As described above, the liquid crystal display device of the present embodiment is configured.
[0031]
[Example 2]
FIG. 9 shows a second embodiment of the present invention, in which a wiring material of a drive circuit is formed using the same material as the material forming the black matrix of the pixel portion.
That is, a thin film of titanium, chromium, or the like formed to form a black matrix of the pixel portion is used not only for the black matrix but also as a wiring material of a driving circuit.
[0032]
When the black matrix exists on the TFT substrate in this way, as described above, in order to prevent the occurrence of capacitive coupling on the drive circuit, a thin film of titanium or chromium of the same material as the black matrix in the pixel portion is processed, A light-shielding film cannot be formed.
However, there is no problem in providing a thin film of titanium or chromium so as not to cover the entire drive circuit but to cover a part of the drive circuit so that capacitive coupling does not become a problem.
Since a thin film of titanium or chromium has high conductivity, by using this film to form a wiring material, it is possible to reduce the area by increasing the wiring density of the drive circuit and improving the element density. .
[0033]
FIG. 12 shows a configuration of the inverter chain.
FIG. 12B illustrates an example in which a thin film of titanium, chromium, or the like formed to form a black matrix is used not only for the black matrix but also for a wiring material of a driving circuit to form an inverter chain. Show.
As shown in FIG. 12A, when another wiring crosses the inverter chain, and when no wiring material is used, the wiring must be passed between the inverters.
However, as shown in FIG. 12B, a wiring material is formed at the same time when a black matrix is formed, and the wiring material is used to form a wiring crossing the inverter chain, so that the wiring can be overlapped with the inverter.
As a result, the area of the drive circuit can be reduced by increasing the density of the drive circuit by increasing the number of wiring layers.
[0034]
[Example 3]
FIG. 11 shows a third embodiment of the present invention, which is an example of a TFT substrate without using a color filter.
Generally, a color filter is not used in a three-panel type liquid crystal projector or the like. In this case, a normal light-shielding film is formed on the opposing substrate, and the wiring material of the driving circuit is formed of the same film as the black matrix of the pixel. Becomes possible.
This example shows a case where ITO is formed on the uppermost layer.
[0035]
【The invention's effect】
As described above, in the present invention, a black matrix is used as a light-shielding film for a pixel portion on a TFT substrate, and color filters R 1, G 2, and B 3 are provided at the same position on a counter substrate as a light-shielding film for a drive circuit portion. By providing the stacked sheets, the aperture ratio can be improved without increasing the number of steps.
In addition, by using the same film as the black matrix as a wiring material, the density of the driving circuit can be increased.
[Brief description of the drawings]
FIG. 1 is an example of a cross-sectional view of an active matrix liquid crystal display device. FIG. 2 is a diagram showing a first conventional example of an active matrix liquid crystal display device. FIG. 3 is an enlarged view of a first conventional example of an active matrix liquid crystal display device. FIG. 4 is a sectional view of a first conventional example of an active matrix liquid crystal display device. FIG. 5 is a sectional view of a second conventional example of an active matrix liquid crystal display device. FIG. 6 is a third view of an active matrix liquid crystal display device. FIG. 7 is an example of a process cross-sectional view (TFT substrate) of a low-temperature polysilicon process of the present invention. FIG. 8 is an example of a process cross-sectional view of a counter substrate of the present invention. FIG. 10 is a view showing spectral characteristics of color filters (R, G, B). FIG. 11 is a view showing a third embodiment of the present invention. FIG. 12 is a drive using the present invention. Diagram showing a circuit pattern example Description of the code]
701, 801 Glass substrate 702 Underlying silicon oxide 703 to 705 Silicon active layer 706 Gate insulating film 707 to 709 Al gate terminal 710 to 712 Anodized film 713 to 716 Photoresist 714 to 715 Strong N-type region (source, drain)
717 Strong P-type region (source, drain)
718, 726 Interlayer insulating film 719-724 Al electrode 725 Pixel transparent electrode 727 Black matrix 802-804 Color filter

Claims (4)

A first insulating substrate having a pixel portion and a drive circuit portion;
In a method for manufacturing an active matrix display device including a second insulating substrate opposed to the first insulating substrate,
Forming a thin film transistor on each of the pixel portion and the drive circuit portion of the first insulating substrate;
At the same time as forming a black matrix on the thin film transistor of the pixel portion, forming a wiring connected to the thin film transistor of the drive circuit portion with the same material as the black matrix,
When the first insulating substrate and the second insulating substrate are bonded to each other , a portion of the second insulating substrate facing the drive circuit on the first insulating substrate has an R (red) color. Forming a light-shielding film by superposing a G (green) color filter and a B (blue) color filter ;
The first insulating substrate and the second insulating substrate are bonded together such that the light-shielding film on the second insulating substrate faces the drive circuit section of the first insulating substrate. A method for manufacturing an active matrix display device. A first insulating substrate having a pixel portion and a drive circuit portion having an inverter chain;
In a method for manufacturing an active matrix display device including a second insulating substrate opposed to the first insulating substrate,
Forming a thin film transistor on each of the pixel portion and the drive circuit portion of the first insulating substrate;
At the same time as forming a black matrix on the thin film transistor of the pixel portion, forming a wiring connected to the thin film transistor of the drive circuit portion with the same material as the black matrix,
When the first insulating substrate and the second insulating substrate are bonded to each other , a portion of the second insulating substrate facing the drive circuit on the first insulating substrate has an R (red) color. Forming a light-shielding film by superposing a G (green) color filter and a B (blue) color filter ;
The first insulating substrate and the second insulating substrate are bonded together such that the light-shielding film on the second insulating substrate faces the drive circuit section of the first insulating substrate. A method for manufacturing an active matrix display device. 3. The method for manufacturing an active matrix display device according to claim 1, wherein the black matrix of the pixel portion and the wiring of the drive circuit portion are made of titanium or chromium. 4. The method according to claim 1, wherein an active layer of the thin film transistor is made of polysilicon.

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