JP2001100247A - Active matrix type liquid crystal display device and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the alignment defect of liquid crystals. SOLUTION: The upper part of a thin-film transistor 2, gate wiring 4 and source wiring 7 is provided with a first planarization layer 10 and the surface of the first lanarization layer 10 is provided with a first pixel electrode 12. A second planarization layer 11 is disposed on a contact connecting a drain region and the first pixel electrode 12 and a second pixel electrode 13 is disposed on the first pixel electrode 12 and the second planarization layer 11.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix type liquid crystal display device and a method of manufacturing the same, and more particularly to a pixel electrode and a switching thin film transistor (TFT).
And a flattening technique for an active matrix substrate formed integrally.

[0002]

2. Description of the Related Art FIG. 7 is a schematic sectional view showing a general structure of an active matrix type liquid crystal display device according to the prior art. As shown in FIG. 7, a plurality of thin film transistors (TFTs) 32 are formed in a matrix on the surface of an insulating substrate 31. The thin film transistor 32 uses a semiconductor thin film 44 patterned in an island shape as an element region. On the semiconductor thin film 44, a gate wiring 43 is formed by patterning via a single gate insulating film. A source wiring 34 is electrically connected to a source region of the thin film transistor 32 via a first interlayer insulating film 33. Further, a pixel electrode 36 is electrically connected to a drain region of the thin film transistor 32 via a first interlayer insulating film 33 and a second interlayer insulating film 35. The lower insulating substrate 31 on which the thin film transistors 32 and the pixel electrodes 36 are integrally formed is hereinafter referred to as an “active matrix substrate 45”. The surfaces of the second interlayer insulating film 35 and the pixel electrode 36 are covered with an alignment film 37. Opposite substrates 38 are arranged at predetermined positions at positions opposing the active matrix substrate 45. A black matrix (light shielding layer) 3 is provided on the inner surface of the counter substrate 38.
9, the counter electrode 40 and the alignment film 41 are formed. Between the active matrix substrate 45 and the counter substrate 38, a liquid crystal 42 whose orientation is controlled by the orientation films 37 and 41 is provided.
Has been injected.

In the above-mentioned active matrix type liquid crystal display device, when an image signal is supplied via the source wiring 34 in a state where a selection signal is applied to the gate wiring 43 of the thin film transistor 32, a predetermined signal voltage is applied to the pixel electrode 36. The molecular arrangement of the liquid crystal 42 changes according to the voltage written between the pixel electrode 36 and the counter electrode 40. Thus, an image is displayed.

[0004]

In the conventional active matrix type liquid crystal display device shown in FIG. 7, a thin film transistor 32, a gate wiring 43, a source wiring 34 and the like are integrally formed on an active matrix substrate 45. Its surface is very undulating and contains countless irregularities and steps. This makes it difficult to control the alignment of the liquid crystal 42,
There is a problem that uniform image display cannot be obtained. In particular, in the step portion at the end of the pixel electrode 36, the alignment of the liquid crystal is disturbed, and a reverse tilt domain in which the pretilt angle is reversed occurs, and the display quality is significantly impaired. In addition, in the conventional structure, the active matrix substrate 45
There is a problem that the direction of the electric field applied to the liquid crystal 42 becomes non-uniform due to the influence of the unevenness of the surface, and it becomes difficult to uniformly control the transmittance. The orientation of the liquid crystal 42 is changed by an electric field applied between the pixel electrode 36 and the counter electrode 40, and on / off control is performed.
Of the source wiring 34 and the gate wiring 43 in the peripheral direction, this acts synergistically with the disturbance of the pretilt angle, and the normal operation is disturbed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems in the prior art, and can suppress defective alignment of liquid crystal, improve the aperture ratio of liquid crystal display, and simplify the manufacturing process. It is an object of the present invention to provide an active matrix type liquid crystal display device, which has good adhesion between the planarizing layer and the pixel electrode, and has good electrical connection between the source region and the pixel electrode, and a method for manufacturing the same. I do.

[0006]

In order to achieve the above object, an active matrix type liquid crystal display device according to the present invention comprises a plurality of thin film transistors arranged in a matrix, wherein the thin film transistors are connected to a gate wiring. An active matrix liquid crystal display device having a gate electrode, a source region connected to a source line, and a drain region connected to a pixel electrode, wherein the thin film transistor, the gate line, and the source line A first planarization layer is provided, a first pixel electrode is provided on the first planarization layer, and a second planarization is provided on a contact connecting the drain region and the first pixel electrode. A layer provided between the first pixel electrode and the second pixel electrode.
Wherein a second pixel electrode is provided on the flattening layer. According to the configuration of the active matrix type liquid crystal display device, the pixel electrode can be completely flattened. As a result, the alignment of the liquid crystal on the pixel electrode is not disturbed by the steps, so that the liquid crystal can be controlled stably and an image can be accurately reproduced.

Further, in the configuration of the active matrix type liquid crystal display device according to the present invention, a connection electrode for connecting the first pixel electrode and the drain region is further provided, and the connection electrode and the first pixel electrode are connected. And the first
Are preferably connected via a contact hole penetrating the flattening layer. According to this preferred example, the first
Pixel electrode and the drain region can be easily connected by the connection electrode, and the electric resistance can be stabilized. As a result, the liquid crystal on the pixel electrode can be controlled electrically stably, so that an image can be accurately reproduced. In this case, it is preferable that all or a part of the connection electrode is provided in the same layer as the source wiring. According to this preferred example, by using the same material as the source wiring for the connection electrode, the connection electrode can be formed in the same process as the source wiring, so that the step of forming the connection electrode can be omitted. In this case, it is preferable that the semiconductor device further includes a silicide compound layer or a metal nitride layer that connects the first pixel electrode and the connection electrode. According to this preferred example, the contact characteristics of the pixel electrode are improved. as a result,
Since the liquid crystal on the pixel electrode can be controlled electrically stably, an image can be accurately reproduced. In this case, a black matrix is further formed integrally with the boundary between the first or second pixel electrodes arranged in a matrix, and a part of the black matrix is formed by the silicide compound layer or the metal nitride. It is preferably formed of a material layer. According to this preferred example, the black matrix on the counter substrate side can be omitted. Further, the formation accuracy of the black matrix can be improved from the mechanical alignment accuracy of the active matrix substrate to the counter substrate to the lithography accuracy of the semiconductor process. Further, it is preferable that the black matrix also serves as the source wiring. According to this preferred example, by using a conductive material having a light-shielding property as a material of the source wiring, the disorder of the orientation can be shielded from light. As a result, it is possible to improve the display quality and the aperture ratio without newly providing a light shielding film.

Further, in the configuration of the active matrix type liquid crystal display device of the present invention, the first and second pixel electrodes provided on the first and second planarization layers, and the gate wiring Preferably, at least one of the source wirings is provided so as to overlap in the wiring width direction. According to this preferred example, the aperture ratio can be improved, and the lateral electric field can be prevented. As a result, the liquid crystal on the pixel electrode can be stably controlled by the electric field in the vertical direction, so that it is possible to suppress poor alignment of the liquid crystal and to reproduce an image accurately.

In the configuration of the active matrix type liquid crystal display device according to the present invention, it is preferable that the first and second flattening layers are made of an organic film. In this case, it is preferable that the organic film is made of a positive photosensitive acrylic resin. According to this preferred example, a positive photosensitive acrylic resin is applied by a spin coating method, patterned by exposure and alkali development,
A flattening layer having a thickness of several μm can be easily obtained. As a result, the productivity is better than when an inorganic film is used, and the pixel electrode can be completely flattened at low cost.

In the configuration of the active matrix type liquid crystal display device according to the present invention, it is preferable that the first and second flattening layers are made of resin which has been subjected to optical or chemical decolorization. According to this preferred example, an active matrix liquid crystal display device having a high transmittance can be realized.

In a method of manufacturing an active matrix type liquid crystal display device according to the present invention, a plurality of thin film transistors are formed in a matrix on a substrate, and a gate wiring connected to a gate electrode of the thin film transistor and a thin film transistor of the thin film transistor are formed. Forming a source line connected to the source region so as to intersect with each other, and forming a contact connected to the drain region of the thin film transistor;
Forming an organic film on the source wiring and the contact by spin coating, and then patterning the organic film to form a first planarization layer;
Forming a contact hole reaching the contact by penetrating the first planarization layer; forming a first pixel electrode layer on the first planarization layer and in the contact hole; After an organic film is formed on the first pixel electrode layer by a spin coating method, the organic film is patterned and a second film is formed in the contact hole.
Forming a flattening layer, forming a second pixel electrode layer on the first pixel electrode layer and the second flattening layer, and forming the first and second pixel electrode layers. And forming a pixel electrode by patterning the pixel electrode into a predetermined shape. According to the method of manufacturing an active matrix type liquid crystal display device, a relatively thick flattening can be performed by the organic film, and the pixel electrode can be completely flattened. As a result, disconnection on the drain side of the pixel electrode, which has occurred at the stepped portion due to the underlying wiring or the like, can be prevented, and alignment failure due to the step can be prevented. In addition, the source wiring and the pixel electrode are insulated from each other, and the number of defective picture elements due to electric leakage between the source wiring and the pixel electrode is extremely reduced, so that the manufacturing yield can be improved and the manufacturing cost can be reduced. Becomes possible.

In the method of manufacturing an active matrix type liquid crystal display device according to the present invention, the first and second pixel electrode layers may be connected to at least one of the gate line and the source line at an end thereof. It is preferable to form them so as to overlap in the width direction.

In the method of manufacturing an active matrix liquid crystal display device according to the present invention, the organic film is made of a positive photosensitive acrylic resin, and the first and second planarizing layers and the contact hole are It is preferably formed by exposing and developing the positive photosensitive acrylic resin. According to this preferred example, it is not necessary to form a film by CVD or the like necessary for forming a flattening layer using an inorganic film, a pattern forming step by a photoresist, an etching, a resist peeling, a washing step, and a photosensitive acrylic resin. The flattening layer can be formed only by applying, exposing, and developing the resin. Therefore, the manufacturing process can be shortened and simplified, and the manufacturing cost can be reduced. In this case, it is preferable that the method further includes a step of exposing and developing the positive photosensitive acrylic resin and thereafter exposing the entire surface of the substrate or at least the entire surface of the pixel electrode. According to this preferred example, an unnecessary photosensitive agent contained in the photosensitive acrylic resin can be reacted to make the acrylic resin transparent. Therefore, it is possible to realize a flattening layer having high transparency. In this case, further, after exposing and developing the positive photosensitive acrylic resin, the temperature of the positive photosensitive acrylic resin is kept at 100 until the step of exposing the entire surface of the substrate or at least the entire surface of the pixel electrode is completed. It is preferred to keep the temperature below ° C. According to this preferred example, an unnecessary photosensitive agent contained in the photosensitive acrylic resin can be reacted stably. Therefore, it is possible to realize a flattening layer having high transparency and stable transmittance. In this case, the positive photosensitive acrylic resin is used in a concentration of 0.1 to 0.5 mol%.
Preferably, the first and second planarization layers are formed by performing paddle development with a tetramethylammonium hydroxide developer. According to this preferred example, the photosensitive acrylic resin is exposed according to a desired pattern, and is developed by an alkaline solution, tetramethylammonium hydroxide (hereinafter abbreviated as “TMAH”). The etched portion is etched with an alkaline solution to form a contact hole and the like. However, when the concentration of the TMAH developer is 0.5 mol% or more, the amount of decrease in the thickness of the photosensitive acrylic resin in the unexposed portion is large, and it is difficult to control the thickness. When the concentration of the TMAH developer is as high as 2.4 mol%, a modified product of the photosensitive acrylic resin remains as a residue in a developing portion, resulting in a contact failure. Further, when the concentration of the TMAH developer is 0.1 mol% or less, it is difficult to control the concentration in a developing device of a type in which the developer is circulated and used repeatedly because the concentration varies greatly. On the other hand, if the concentration of the TMAH developer is set to 0.1 to 0.5 mol%, the above-mentioned problem is solved, and the flattening layer can be stably formed.

In the method for manufacturing an active matrix type liquid crystal display device according to the present invention, it is preferable that the thickness of the first flattening layer is 1.0 μm or more. According to this preferred example, the pixel electrode and each wiring (gate wiring,
Source wiring) overlaps 1 μm or more,
The capacitance between each wiring and the pixel electrode is sufficiently small, and the time constant is also small. Therefore, the influence of the capacitance component on the display, such as crosstalk, is reduced, and a better display is obtained.

Further, the method of manufacturing an active matrix type liquid crystal display device according to the present invention further comprises a step of applying hexamethyldisilazane to a portion where the organic film is to be formed before forming the organic film. Is preferred. According to this preferred example, the adhesion between the organic film and the portion where the organic film is formed is improved. Therefore, the occurrence of peeling of the organic film in the subsequent diffusion step and assembly step can be prevented.

In the method for manufacturing an active matrix type liquid crystal display device according to the present invention, before forming the first pixel electrode layer, the surface of the first planarizing layer made of the organic film may be removed. It is preferable that the method further includes a step of performing an Ar reverse sputtering process by RF (high frequency). According to this preferred example, the adhesion between the first planarization layer and the first pixel electrode layer formed thereon is improved. Therefore, a device that is more stable to processing during the liquid crystal panel assembly process is realized, and the yield is improved. In this case, it is preferable that the Ar reverse sputtering process is performed after forming the contact hole in the first planarization layer made of the organic film. According to this preferred example,
The residue in the contact hole portion connecting the first pixel electrode and the drain region or the connection electrode can be removed. Therefore, occurrence of a connection failure in the contact hole can be suppressed. In this case, the organic film is heated to 110 ° C. before the Ar reverse sputtering process is performed.
Preferably, the method further comprises a step of heating to a temperature of up to 240 ° C. According to this preferred example, the organic film can be cured by a crosslinking reaction. Therefore, the occurrence of peeling of the organic film in the subsequent diffusion step and assembly step can be prevented. Further, deterioration of the organic film due to a process such as formation of a pixel electrode can be suppressed.

In the method of manufacturing an active matrix liquid crystal display device according to the present invention, it is preferable that the first flattening layer between the pixel electrodes is removed by a thickness of 5 to 100 nm. According to this preferred example, complete insulation between the pixel electrodes can be achieved. Therefore,
It is possible to suppress defects such as leaks between pixels, and to stabilize yield and performance. In this case, the first
It is preferable to remove the flattening layer by plasma etching using oxygen plasma. According to this preferred example, for example, even when the surface is deteriorated and carbonized, the first flattening layer between the pixel electrodes can be removed. Therefore, regardless of the process conditions of the previous process,
It is possible to suppress defects such as leaks between pixels, and to stabilize yield and performance.

Further, the method of manufacturing an active matrix type liquid crystal display device according to the present invention preferably further comprises a step of exposing the contact to the outside before forming the organic film. According to this preferred example, before forming the organic film, the inorganic material such as the SiO ₂ film and the SiN film on the contact terminal for connection to the outside is removed, and the contact terminal is exposed, so that the SiO ₂ film is exposed.
It is possible to eliminate the damage to the organic film in the etching of the _two films and the SiN film and the like and the resist removing process therefor.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described more specifically with reference to embodiments. It should be noted that the drawings used in the following description are only schematically shown to the extent that the present invention can be understood, and the present invention is not limited to the examples shown in the drawings.

FIG. 1 is a schematic sectional view showing a basic configuration of an active matrix substrate according to an embodiment of the present invention, and FIG. 2 is a basic configuration of an active matrix liquid crystal display device according to an embodiment of the present invention. FIG.

In FIG. 1, an active matrix substrate 17 is formed using an insulating substrate 1 made of quartz glass or the like, and a plurality of thin film transistors (hereinafter abbreviated as “TFT”) 2 are arranged in a matrix on the surface thereof. Each of them is formed in an integrated manner in an arranged state. The TFT 2 uses a semiconductor thin film 3 patterned in an island shape as an element region. That is, the source region 3a and the drain region 3b are provided in the semiconductor thin film 3. The semiconductor thin film 3 is made of, for example, polysilicon. Incidentally, the material of the semiconductor thin film 3 is not limited to polysilicon, and single crystal silicon or amorphous silicon can also be used.
On the semiconductor thin film 3, a gate wiring 4 is formed by patterning via a single layer of a gate insulating film 4a. The gate wiring 4 is made of, for example, polysilicon. Here, a part of the gate wiring 4 and a part overlapping with the semiconductor thin film 3 becomes a “gate electrode”. On the insulating substrate 1, a first interlayer insulating film 5 is formed so as to cover the TFT2. The first interlayer insulating film 5 is made of, for example, a laminate of glass doped with nitrogen and glass doped with boron and phosphorus. A source line 7 is electrically connected to a source region 3 a of the TFT 2 via a first contact hole 6 provided in the first interlayer insulating film 5. The source wiring 7 is made of, for example, aluminum and forms an image signal line and the like. On the other hand, TF
The connection electrode 16 is electrically connected to the drain region 3b of T2 via the first contact hole 6. As described above, a part of the connection electrode 16 is provided in the same layer as the source wiring 7. Therefore, if the same material as the source wiring 7 is used for the connection electrode 16, the connection electrode 16 can be formed in the same process as that of the source wiring 7, so that the step of forming the connection electrode 16 can be omitted.
Note that the entire connection electrode 16 may be provided on the same layer as the source wiring 7.

On the first interlayer insulating film 5, a second interlayer insulating film 8 is formed so as to cover the source wiring 7. The second interlayer insulating film 8 is made of, for example, a silicon oxide film grown by a plasma CVD method. A second contact hole 9 is provided in the second interlayer insulating film 8 on the connection electrode 16, and WSi as a silicide compound is formed as a barrier metal 14.
WSi is also formed on the second interlayer insulating film 8 as a light shielding layer 15 of the TFT 2. In addition, barrier metal 1
4. The material of the light-shielding layer 15 is not necessarily limited to a silicide compound such as WSi. For example, a metal nitride or the like can be used.

Further, a first planarization layer 10 made of an organic film material is formed on the second interlayer insulating film 8, and a second contact hole 9 is provided in the first planarization layer 10. Have been. A first pixel electrode 12 and a second pixel electrode 13 are formed on the first flattening layer 10 by patterning, and the first pixel electrode 12 is formed by a barrier metal 14 and a connection electrode 16. Is electrically connected to the drain region 3b of the TFT 2 via Further, a second planarization layer 11 made of an organic film material is interposed in the second contact hole 9 between the first pixel electrode 12 and the second pixel electrode 13. As an organic film material of the first and second planarization layers 10 and 11, for example, an acrylic resin or a polyimide resin can be used. In the present embodiment,
An acrylic resin having a predetermined viscosity and suitable for filling unevenness is used. The individual first pixel electrodes 12 arranged in a matrix form correspond to the drain region of the corresponding TFT 2 via the second interlayer insulating film 8 and the second contact hole 9 provided in the first planarization layer 10. 3b.

As shown in FIG. 2, a counter substrate 21 made of quartz glass or the like is arranged at a predetermined position at a position opposing the active matrix substrate 17. Counter substrate 2
A counter electrode 23 and an alignment film 24 are sequentially formed on the inner surface of 1. Also, an alignment film 25 is formed on the surface of the active matrix substrate 17. The liquid crystal 4 is provided between the active matrix substrate 17 and the counter substrate 21.
2 are injected, thereby forming an active matrix type liquid crystal display device. The alignment of the liquid crystal 22 is controlled by a pair of alignment films 24 and 25, for example, a twist nematic mode is obtained.

In the present active matrix type liquid crystal display device, unlike the conventional structure, there is no contact hole in the pixel electrode, the alignment film 25 has an extremely flat surface and no step, so that uniform rubbing is performed. Processing can be performed. Therefore, uniform orientation control over the entire screen is possible. Further, since there is no uneven portion in the pixel electrode, the liquid crystal 22 is driven and controlled by a vertical electric field acting between the counter electrode 23 and the second pixel electrode 13, and the influence of the horizontal electric field is reduced. small. As a result, degradation of display quality due to the reverse tilt domain, which has conventionally been a problem, can be effectively improved. Further, at the boundary between pixel electrodes adjacent to each other, the source line 7
Can be at least partially shielded by using as a black matrix. However, TFT
This light-shielding structure cannot be adopted for two parts. Therefore, in order to selectively shield the TFT2 portion,
Light shielding layer 15 made of silicide compound or metal nitride, etc.
Is used.

Next, a method of manufacturing the active matrix substrate shown in FIG. 1 will be described with reference to FIGS.

First, in step A in FIG. 3, a low pressure CVD (LPCV
An amorphous silicon film is formed by the method D). Next, amorphous silicon is grown in a solid phase to have a large grain size, and is converted to polysilicon. Next, the polysilicon is patterned into an island shape to form an element region. Thereby, a semiconductor thin film 3 made of polysilicon is obtained. Next, the surface of the semiconductor thin film 3 made of polysilicon is thermally oxidized (heating temperature: 1100 ° C., heating time: 23 minutes).
Thus, a gate oxide film (gate insulating film) 4a made of SiO ₂ is obtained. At the same time, the semiconductor thin film 3 made of polysilicon is patterned so that a storage capacitor can be formed.

Next, in step B of FIG.
Polysilicon is formed on the film 4a by LPCVD.
Film. And this polysilicon by phosphorus doping
After reducing the resistance of the
You. As a result, the gate wiring 4 and the storage capacitor wiring 4b are obtained.
Can be Next, the N-channel type TFT 2 is
(Lightly doped drain) structure.
The gate line 4 as a mask
A dose of 1 × 10 is applied to the semiconductor thin film 3 made of silicon. ¹³/ C
m^TwoImplant phosphorus ions and further mask the LDD region
The semiconductor thin film 3 with a dose of 4 × 10^Fifteen/ Cm^Twoof
Phosphorus ions are implanted, and a source region 3a is formed in the semiconductor thin film 3.
A drain region 3b is provided.

Through the above steps, a plurality of N-channel TFTs 2 are formed on the insulating substrate 1 in a matrix.
When a P-channel TFT is formed, boron ions are implanted.

Next, in step C of FIG.
A first interlayer insulating film 5 made of a laminate of glass doped with nitrogen and glass doped with boron and phosphorus is deposited on the surface of the substrate by a normal pressure CVD (APCVD) method. Next, after patterning a first contact hole 6 in the first interlayer insulating film 5, aluminum (Al) is entirely formed by sputtering. Then, this is patterned into a predetermined shape,
Is processed into a source wiring 7 electrically connected to the source region 3a. At this time, the connection electrode 16 is also formed at the same time. Here, the source wiring 7 is formed so as to intersect with the gate wiring 4.

Next, in step D of FIG. 3, a silicon oxide film is deposited on the first interlayer insulating film 5 by a plasma CVD method to form a second interlayer insulating film 8, and aluminum (Al) Is completely covered.
Further, a second contact hole 9 is formed in the second interlayer insulating film 8 on the connection electrode 16.

Next, in step E of FIG. 3, WSi is entirely formed by sputtering. Then, this is patterned into a predetermined shape to form a barrier metal 14 for the connection electrode 16 and a light shielding layer 15 for the TFT 2.

Next, in step F of FIG. 4, a liquid positive photosensitive acrylic resin (organic film) having a predetermined viscosity (viscosity: 30 cp) is spin-coated on the second interlayer insulating film 8 by a spin coating method. To form a second interlayer insulating film 8
The surface of is flattened. Next, the positive photosensitive acrylic resin is exposed using an i-line stepper, and the concentration is 0.1 to
Developed by a paddle developing method using a 0.5 mol% tetramethylammonium hydroxide developing solution,
A second contact hole 9 is formed. The drain region 3 of the TFT 2 is formed at the bottom of the second contact hole 9.
b or the connection electrode 16 is exposed. Next, the entire surface of the substrate or at least the entire surface of the effective pixel electrode region is exposed to ultraviolet light to make the positive photosensitive acrylic resin transparent. Next, heat treatment is performed to cure the positive photosensitive acrylic resin. The heating method may be either a hot plate method or a clean oven method. In the case of the hot plate method, the heating temperature is 220 ° C., and the heating time is 10 minutes. In the case of the clean oven method, the heating temperature is 220 ° C.
℃, the heating time is 60 minutes. Thereby, the first planarization layer 10 is obtained. The thickness of the first planarization layer 10 is 1.
It is desirable that the thickness be 0 μm or more. If the thickness of the first planarization layer 10 is set to 1.0 μm or more, even if the pixel electrode and each wiring (gate wiring and source wiring) overlap by 1 μm or more, the distance between each wiring and the pixel electrode can be reduced. Has a sufficiently small capacity and a small time constant. Accordingly, the influence of the capacitance component on the display, such as crosstalk, is reduced, and a better display is obtained. However, when the thickness of the first flattening layer 10 is 5.0 μm or more, the uniformity of the film thickness is poor and unevenness is likely to occur, which is not desirable.

After exposing and developing the positive photosensitive acrylic resin, the temperature of the positive photosensitive acrylic resin is kept at 100 until the step of exposing the entire surface of the substrate or at least the entire effective pixel electrode region with ultraviolet light is completed. By keeping the temperature at not more than ° C., it is possible to stably make the positive photosensitive acrylic resin transparent.

Before applying a positive photosensitive acrylic resin (organic film) on the second interlayer insulating film 8, hexamethyldisilazane is applied to the surface of the second interlayer insulating film 8. In addition, the adhesion between the second interlayer insulating film 8 and the positive photosensitive acrylic resin (organic film) can be improved.

If the flattening layer is made of a positive photosensitive acrylic resin as in the present embodiment, a thin film can be formed by the spin coating method. A thin film can be easily formed. In addition, patterning can be performed by exposure and alkali development, which is advantageous in terms of productivity. The positive photosensitive acrylic resin used here is colored before coating, and can be decolorized and made transparent by performing an overall exposure process after patterning. Such a decolorization treatment can be performed not only optically but also chemically.

Next, in step G of FIG. 4, a transparent conductive film is formed on the first flattening layer 10 by sputtering to form a first pixel electrode 12. In this embodiment, ITO is used as the material of the transparent conductive film. The ITO as a material of the transparent conductive film is also filled in the second contact hole 9 and the first pixel electrode 1
2 is a TFT via a barrier metal 14 and a connection electrode 16
2 is electrically connected to the drain region 3b.

Before the transparent conductive film is formed by sputtering and the first pixel electrode 12 is formed, the surface treatment of the first flattening layer 10 is performed by Ar reverse sputtering using RF (high frequency). A first pixel electrode 12 made of a first planarization layer 10 and a transparent conductive film formed thereon
And the device is more stable to the processing during the assembly process.
Yield also improves.

Before the Ar reverse sputtering process, the positive photosensitive acrylic resin (organic film) is heated to 110 ° C. to 240 ° C.
When heated to ° C., the positive photosensitive acrylic resin (organic film) can be cured by a crosslinking reaction. Therefore,
The peeling of the positive photosensitive acrylic resin (organic film) in the subsequent diffusion step and assembly step can be prevented. Further, deterioration of the positive photosensitive acrylic resin (organic film) due to a process such as formation of a pixel electrode can be suppressed.

Next, in step H of FIG. 4, a liquid positive photosensitive acrylic resin having a predetermined viscosity is applied on the first pixel electrode 12 by spin coating. Next, the positive photosensitive acrylic resin is exposed using an i-line stepper, and developed using a paddle developing method.
Remove unnecessary parts. As a result, the inside of the second contact hole 9 is filled with the positive photosensitive acrylic resin. Next, the entire surface of the substrate or at least the entire surface of the effective pixel electrode region is exposed to ultraviolet light to make the positive photosensitive acrylic resin transparent. Next, heat treatment is performed to cure the positive photosensitive acrylic resin. Thereby, the second planarization layer 11 is obtained.

In this case as well, after exposing and developing the positive-type photosensitive acrylic resin, the positive-type photosensitive acrylic resin is exposed until the step of exposing the entire substrate or at least the entire effective pixel electrode region with ultraviolet light is completed. 100 ℃ of resin temperature
It is desirable to keep the following.

Also in this case, the first pixel electrode 12
It is desirable to apply hexamethyldisilazane to the surface of the first pixel electrode 12 before applying a positive photosensitive acrylic resin (organic film) on the surface.

Next, in step I of FIG. 5, a transparent conductive film is formed on the second planarization layer 11 and the first pixel electrode 12 by sputtering to form a second pixel electrode 13. . In this embodiment, ITO is used as the material of the transparent conductive film.

Next, in step J of FIG. 5, ITO as a material of the first and second pixel electrodes 12 and 13 is patterned into a predetermined shape to form a pixel electrode.

By the way, when the surface treatment of the first flattening layer 10 is performed by Ar reverse sputtering by RF,
In the case where the first and second pixel electrodes 12 and 13 are formed by forming a transparent conductive film by sputtering, the planarization layer may be damaged and the insulating property may be reduced.

Therefore, finally, in step K of FIG. 5, the first flattening layer 10 between the pixel electrodes patterned into a predetermined shape in step J of FIG. 5 is subjected to plasma etching using oxygen plasma. It is removed by a thickness of 5 to 100 nm. The conditions of the oxygen plasma etching in this case are: 300 W, 800 mTorr, 400 sc
cm, 50 ° C.

Through the steps described above, an active matrix substrate having the pixel electrodes completely flattened can be obtained.

Hereinafter, the means for improving the aperture ratio in the present invention will be described with reference to FIG. FIG. 6 is a schematic sectional view showing a black matrix structure according to one embodiment of the present invention.

First, in order to facilitate understanding, a conventional black matrix structure will be described with reference to FIG. As shown in FIG. 8, on the inner surface of the active matrix substrate 51, a plurality of pixel electrodes 52 are formed in a matrix at a predetermined arrangement pitch. A source wiring 53 is formed between adjacent pixel electrodes 52, and a predetermined gap is provided between the pixel electrode 52 and the source wiring 53. Therefore, the size of the pixel electrode 52 is smaller than the arrangement pitch. A counter substrate 55 is disposed at a position facing the active matrix substrate 51 with the liquid crystal 54 interposed therebetween. A counter electrode 56 is formed on the inner surface of the counter substrate 55. Further, a black matrix 57 is formed in a pattern on the inner surface of the counter substrate 55 so as to match between the pixel electrodes 52 adjacent to each other. In order to secure an alignment margin between the active matrix substrate 51 and the counter substrate 55, the black matrix 57 overlaps the edge of the pixel electrode 52 in plan view, and the size of the opening surrounded by the black matrix 57 is The size is smaller than the size of the pixel electrode 52. With the above configuration, light leakage is prevented by the black matrix 57, and the contrast is improved. However, FIG.
As can be understood from FIG.
2, the size of the opening defining the effective pixel area is further reduced. Therefore, the aperture ratio remains at a relatively small value.

On the other hand, in the black matrix structure of the present invention shown in FIG. 6, a flattening layer 68 is formed so as to fill the unevenness of the surface of the active matrix substrate 61, and a predetermined layer is formed on the flattening layer 68. The pixel electrodes 62 are formed at an arrangement pitch of. The active matrix substrate 61 has pixel electrodes 6 adjacent to each other.
The source wiring 63 is formed in a pattern so as to be aligned with the boundary between the two. Therefore, the source wiring 63 functions as a black matrix. Source wiring 6
Numeral 3 overlaps the end of the pixel electrode 62 by about 1 μm in the wiring width direction when viewed in plan. Therefore, the size of the pixel electrode 62 is slightly shorter than the arrangement pitch. On the other hand, since it is not necessary to form a black matrix on the opposing substrate 65 which is disposed at a position opposing the active matrix substrate 61 with the liquid crystal 64 interposed therebetween, the size of the opening viewed from the opposing substrate 65 depends on the pixel size and the source size. The overlapped portion of the wiring 63 is subtracted, which is only slightly smaller than the arrangement pitch. Therefore, the aperture ratio can be considerably improved as compared with the conventional black matrix structure.

Although the source wiring 63 and the black matrix are used here as well, the present invention is not necessarily limited to this configuration. For example, the second wiring may be formed along the boundary between the pixel electrodes 62 adjacent to each other. A metal film for light shielding may be provided over the insulating film. However, the light-shielding structure using only the source wiring 63 cannot be adopted for the TFT portion. Therefore, in the structure shown in FIG. 1, a light-shielding layer 15 made of a silicide compound layer or a metal nitride layer is provided on the second interlayer insulating film 8 in order to selectively shield the TFT 2.

Although the case where the source wiring 63 overlaps the end of the pixel electrode 62 in the wiring width direction when viewed in plan is described here as an example, the gate wiring and the source wiring are not shown. If at least one of them is provided so as to overlap with the pixel electrode 62 in the wiring width direction, the same effect can be obtained.

[0053]

As described above, according to the present invention,
The pixel electrode can be completely flattened. As a result, the alignment of the liquid crystal on the pixel electrode is not disturbed by the steps, so that the liquid crystal can be controlled stably and an image can be accurately reproduced. In addition, since the alignment layer provided so as to cover the pixel electrodes in the matrix shape is not affected by the step, the reverse tilt domain can be reduced. Further, since there is no raised portion around the pixel electrode, the liquid crystal can be stably controlled to be turned on / off without being affected by a lateral electric field. Further, since the black matrix pattern can be integrally formed on the active matrix substrate by using the flattening layer, there is no need to consider an alignment error in bonding, and the alignment accuracy of the pair of upper and lower substrates is reduced. In addition to this, the effective display portion of the pixel electrode can be enlarged and the aperture ratio can be improved as compared with the related art.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view illustrating a basic configuration of an active matrix substrate according to an embodiment of the present invention.

FIG. 2 is a schematic cross-sectional view illustrating a basic configuration of an active matrix liquid crystal display device according to an embodiment of the present invention.

FIG. 3 is a process chart showing a method for manufacturing an active matrix substrate in one embodiment of the present invention.

FIG. 4 is a process chart showing a method for manufacturing an active matrix substrate in one embodiment of the present invention.

FIG. 5 is a process chart showing a method for manufacturing an active matrix substrate in one embodiment of the present invention.

FIG. 6 is a schematic sectional view showing a black matrix structure according to one embodiment of the present invention.

FIG. 7 is a schematic cross-sectional view showing a general structure of an active matrix type liquid crystal display device according to the related art.

FIG. 8 is a schematic cross-sectional view illustrating a black matrix structure according to the related art.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Insulating substrate 2 Thin film transistor (TFT) 3 Semiconductor thin film 4 Gate wiring 5 First interlayer insulating film 6 First contact hole 7 Source wiring 8 Second interlayer insulating film 9 Second contact hole 10 First planarization layer DESCRIPTION OF SYMBOLS 11 2nd planarization layer 12 1st pixel electrode 13 2nd pixel electrode 14 Barrier metal 15 Shield layer 16 Connection electrode 17 Active matrix substrate

Continued on the front page F term (reference) 2H092 GA29 HA27 JA24 JA37 JA41 JA46 JB58 MA05 MA07 MA08 MA09 MA10 MA12 MA17 MA29 NA04 NA07 NA18 NA19 NA25 NA27 NA29 5C094 AA03 AA05 AA10 AA36 AA43 AA55 BA03 BA43 CA19 DA13 DB04 EA04 ED04 FA02 FB01 FB02 FB12 FB15 GB10 JA01 JA08 JA20

Claims (24)

[Claims] 1. A thin film transistor comprising: a plurality of thin film transistors arranged in a matrix; wherein the thin film transistors include a gate electrode connected to a gate wiring, a source region connected to a source wiring, and a drain region connected to a pixel electrode. An active matrix type liquid crystal display device having
A first planarization layer is provided above the thin film transistor, the gate wiring, and the source wiring, a first pixel electrode is provided on the first planarization layer, and the drain region and the first pixel are provided. An active element, wherein a second planarizing layer is provided on a contact connecting to an electrode, and a second pixel electrode is provided on the first pixel electrode and the second planarizing layer. Matrix type liquid crystal display device. 2. A contact hole for connecting the first pixel electrode to the drain region, wherein the connection electrode and the first pixel electrode penetrate the first planarization layer. The active matrix liquid crystal display device according to claim 1, wherein the active matrix type liquid crystal display device is connected via a liquid crystal display. 3. The active matrix liquid crystal display device according to claim 2, wherein all or a part of the connection electrode is provided in the same layer as the source wiring. 4. The active matrix type liquid crystal display device according to claim 2, further comprising a silicide compound layer or a metal nitride layer connecting the first pixel electrode and the connection electrode. 5. A black matrix is formed integrally with a boundary of the first or second pixel electrode arranged in a matrix, and a part of the black matrix is formed of the silicide compound layer or the metal nitride. The active matrix liquid crystal display device according to claim 4, wherein the active matrix liquid crystal display device is formed by a layer. 6. The active matrix liquid crystal display device according to claim 5, wherein said black matrix also serves as said source wiring. 7. The first and second pixel electrodes provided on the first and second planarization layers, and at least one of the gate wiring and the source wiring are arranged in a wiring width direction. 2. The active matrix liquid crystal display device according to claim 1, wherein the active matrix liquid crystal display device is provided in an overlapping manner. 8. The active matrix type liquid crystal display device according to claim 1, wherein said first and second planarization layers are made of an organic film. 9. The active matrix type liquid crystal display device according to claim 8, wherein said organic film is made of a positive photosensitive acrylic resin. 10. The first and second flattening layers are made of optically or chemically decolorized resin.
4. The active matrix type liquid crystal display device according to item 1. 11. A plurality of thin film transistors are formed in a matrix on a substrate, and a gate wiring connected to a gate electrode of the thin film transistor and a source wiring connected to a source region of the thin film transistor are formed so as to cross each other. And forming a contact connected to the drain region of the thin film transistor;
After forming an organic film on the thin film transistor, the gate wiring, the source wiring and the contact by a spin coating method, patterning the organic film to form a first planarization layer, Forming a contact hole reaching the contact through the planarization layer, forming a first pixel electrode layer on the first planarization layer and in the contact hole, and forming the first pixel Forming an organic film on the electrode layer by a spin coating method, and then patterning the organic film to form a second planarization layer in the contact hole; and forming the first pixel electrode layer and the Forming a second pixel electrode layer on the second planarization layer; and patterning the first and second pixel electrode layers into a predetermined shape to form a pixel electrode. Method for manufacturing an active matrix type liquid crystal display device including the step of forming. 12. The active matrix according to claim 11, wherein the first and second pixel electrode layers are formed such that an end thereof overlaps at least one of the gate wiring and the source wiring in a wiring width direction. Manufacturing method of a liquid crystal display device. 13. The organic film is made of a positive photosensitive acrylic resin, and the first and second planarizing layers and the contact holes are formed by exposing and developing the positive photosensitive acrylic resin. A method for manufacturing an active matrix liquid crystal display device according to claim 11. 14. The method of manufacturing an active matrix liquid crystal display device according to claim 13, further comprising a step of exposing the entire surface of the substrate or at least the entire surface of the pixel electrode after exposing and developing the positive photosensitive acrylic resin. Method. 15. After exposing and developing the positive photosensitive acrylic resin, the temperature of the positive photosensitive acrylic resin is kept at 100 ° C. until the step of exposing the entire surface of the substrate or at least the entire surface of the pixel electrode is completed. The method for manufacturing an active matrix liquid crystal display device according to claim 14, wherein the following is maintained. 16. The first and second planarization layers by subjecting the positive photosensitive acrylic resin to paddle development with a tetramethylammonium hydroxide developer having a concentration of 0.1 to 0.5 mol%. 14. The method for manufacturing an active matrix liquid crystal display device according to claim 13, wherein: 17. The method according to claim 17, wherein the thickness of the first planarization layer is 1.0 μm.
The method of manufacturing an active matrix type liquid crystal display device according to claim 11, wherein m is not less than m. 18. The method of manufacturing an active matrix liquid crystal display device according to claim 11, further comprising a step of applying hexamethyldisilazane to a portion where the organic film is to be formed before forming the organic film. . 19. The method according to claim 19, further comprising performing an Ar reverse sputtering process by RF (high frequency) on a surface of the first planarization layer made of the organic film before forming the first pixel electrode layer. A method for manufacturing an active matrix liquid crystal display device according to claim 11. 20. The method according to claim 19, wherein the Ar reverse sputtering is performed after forming the contact hole in the first planarization layer made of the organic film. 21. Before performing the Ar reverse sputtering process,
20. The method according to claim 19, further comprising a step of heating the organic film to 110C to 240C. 22. The method according to claim 11, wherein the first flattening layer between the pixel electrodes is removed by a thickness of 5 to 100 nm. 23. The method according to claim 22, wherein the removal of the first planarization layer is performed by plasma etching using oxygen plasma. 24. The method according to claim 1, further comprising: exposing the contact to the outside before forming the organic film.
2. The method for manufacturing an active matrix liquid crystal display device according to item 1.