JPH09133927A - Active matrix substrate, manufacturing method thereof, and liquid crystal display device - Google Patents

Abstract

(57) Abstract: An active matrix substrate having a high aperture ratio is provided in order to achieve high brightness and low power consumption of a liquid crystal display device. A gate electrode is formed of a transparent conductive film, and a gate insulating layer and another insulating layer are stacked between a pixel electrode and a gate electrode in the preceding stage to form an additional capacitance. [Effect] Since the additional capacitance portion can be used as the opening, the brightness of the liquid crystal display device can be improved. In addition, the power consumption of the liquid crystal display device can be reduced. Since the gate electrode width is large, it can contribute to simplification of the manufacturing process, leading to a reduction in manufacturing cost.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an active matrix substrate which constitutes a liquid crystal display device and the like, a manufacturing method thereof, and a liquid crystal display device.

[0002]

2. Description of the Related Art In a conventional active matrix liquid crystal display substrate, a gate electrode and a drain electrode made of metal are formed, and a thin film transistor is formed in the vicinity of the intersection thereof. The transparent electrode of the pixel is connected to the source electrode of the thin film transistor. To alleviate the effect of parasitic capacitance formed between the gate electrode and the source electrode, the transparent electrode of the pixel is overlapped with the gate electrode of the previous stage through the insulating film to form an additional capacitance. . Since the liquid crystal is not driven in the portion other than the transparent electrode of the pixel, light leaks from the gap between the transparent electrode and the gate and drain electrodes even during black display. In order to suppress light leakage in this portion, when manufacturing a liquid crystal display, a black matrix is formed of a metal or the like on a substrate facing the active matrix substrate. in this case,
It is necessary to have a black matrix with a width that includes the distance between the transparent electrodes and the alignment accuracy of the counter substrate.

There is a method of suppressing light leakage by forming a black matrix on the active matrix substrate side without imposing a burden on the black matrix alignment accuracy of the counter substrate. SID (Sympo
sium for information-dis
play) 95 DIGEST (1995) p. Fifteen
The gate electrode of the preceding stage is formed in a ring shape around the pixel electrode to form a black matrix and at the same time have a function of additional capacitance. An example in which the gate electrode and the drain electrode are formed of a transparent conductive film is disclosed in JP-A-61-48886. In this case, since the drain electrode becomes the transparent portion, the aperture ratio can be improved.

[0004]

However, in an active matrix substrate having a conventional structure in which the gate and drain wirings are formed of a metal film, since these wirings block light, light is transmitted through the transparent electrode of the pixel. It is difficult to increase the area, that is, the aperture ratio. Therefore, the display brightness of the display is reduced. Alternatively, when trying to obtain high brightness, the power consumption of the backlight becomes large, especially for portable battery-powered computer.
When used for a display device such as a computer, there is a problem that it cannot be used for a long time. Further, when the gate electrode is made of a transparent conductive film, the transparent conductive film has a high resistivity,
It is necessary to consider the wiring width. Further, since the area of intersection with the pixel electrode becomes large, there is a problem that it is difficult to form an additional capacitor having an appropriate value. An object of the present invention is to provide an active matrix substrate, a method of manufacturing the same, and a liquid crystal display device which solve these problems.

[0005]

Therefore, in the present invention, as shown in FIG. 1, a transparent conductive film is used for the gate wiring, and two or more layers of insulating films are provided on the gate wiring at the preceding stage. By laminating the transparent electrodes of the pixels to form an additional capacitance, the aperture ratio was improved. Since the transparent conductive film transmits light, the portion of the additional capacitance can also be used as the opening, and the aperture ratio can be improved. Further, by interposing the two-layer insulating film, the capacitance value can be suppressed to an appropriate value even if the area of the additional capacitance portion is large. As the transparent conductive film, indium oxide (ITO) added with tin oxide or the like is used. The transparent conductive film has a resistivity higher than that of a metal film by about one digit and has a value of about 150 μΩcm. Therefore, it is necessary to make the wiring width of the transparent conductive film larger by about one digit than the wiring width of the metal film.

A gate for a display having a display unit of 9 to 10 inches corresponding to A4 size which is useful for portable use.
It is necessary that the wire resistivity of the wire is 1.5 kΩ / cm or less. Considering the transmittance, the thickness of the ITO film is 30
It is necessary that the thickness be 0 nm or less. Therefore, the wiring width needs to be 30 μm or more. Also,
Since the width of the wiring is as large as 30 μm or more, it is possible to form this pattern using a printing method. The value of the additional capacitance with respect to the parasitic capacitance of a normal thin film transistor structure is 0.05 to 0.5 pF, more preferably 0.1 to 0.3 pF.
F. When the area of the additional capacitance is S (μm ² ), the thickness of the insulating film is d (μm), and the relative permittivity is ε, εS / d is 0.0056 to 0.056 μm, and more preferably 0.0.
It is desirable that the thickness is 11 to 0.034 μm. The relative permittivity of the SiO ₂ film and the SiN film used in the present invention is 5-7. When these films are used, S / d is 800 to 1
1000 μm, more preferably 1600 to 6600 μ
m. When the width of the additional capacitance is 80 μm and the gate line width (W) is 50 μm, the thickness of the insulating layer is 0.36 to 5 μm.
m, more preferably 0.6 to 2.5 μm.

In the present invention, this insulating film has a two-layer structure of a first insulating layer and a gate insulating layer or a gate insulating layer and a protective insulating layer, or a gate insulating layer, a protective insulating layer and a first insulating layer. The insulating layer 1 has a three-layer structure. When forming the first insulating layer having a particularly large film thickness, a SiO ₂ film was formed by a sputtering method. The method for forming the SiO ₂ film, In addition, SOG
(Spin on Glass) method and the like. The thickness of the gate insulating film in the thin film transistor section is 0.2 to 0.5.
It is desirable that it is μm. Therefore, when a particularly thick first insulating layer is used, the first insulating layer near the thin film transistor is removed.

[0008]

According to the present invention, since the gate wiring is transparent, the additional capacitance portion formed through the transparent electrode and the insulating film of the pixel in the next stage can also be used as the opening. It is possible to improve the aperture ratio of the active matrix substrate. Therefore, when used in a liquid crystal display element, it is possible to increase the brightness and reduce the power consumption. Further, a battery-powered computer equipped with a liquid crystal display device including the active matrix substrate of the present invention.
Can be used for a long time. Further, since the line width of the gate wiring is as large as several tens of μm, the printing process can be performed, and the manufacturing process can be simplified.

The present invention will be described below with reference to embodiments. FIG. 1 shows a schematic plan view of the produced active matrix substrate, and FIG. 2 shows a schematic sectional view. Moreover, FIG. 3 to FIG.
Up to now, a schematic plan view in the middle of manufacturing is shown. An embodiment will be described with reference to these drawings.

An ITO film was formed on the well cleaned insulating substrate 1 by magnetron sputtering at a substrate temperature of 300.degree. The film thickness was 300 nm. A photosensitive resin pattern was formed on the ITO film by a photo-etching process, and processed into a gate electrode 2 having a width of 50 μm by wet etching (FIG. 3). At this time, HBr is used as an etching solution for 50 to 6
Etched at 0 ° C. The taper angle at the end of the ITO film was about 10 °. With such an angle, the coverage of the film laminated thereon can be improved.

Then, the thus-prepared substrate is placed in an RF plasma CVD apparatus, and SiH ₄ , NH ₃ , and N ₂ are placed.
Substrate gas temperature of 300 ℃
Then, the SiN film of the gate insulating layer 3 was formed to a film thickness of 300 nm. Then, the substrate temperature was set to 250 ° C., and monosilane SiH ₄ was used as a source gas, and an a-Si: H film having a film thickness of 200 nm was formed thereon as a semiconductor layer 4. Further, the substrate temperature was set to 230 ° C., and the n-type a-Si film 5 was formed using a mixed gas of SiH ₄ , PH ₃ and hydrogen as a raw material. The formed semiconductor layer and the n-type a-Si film were processed into islands by photolithography and etching (Fig. 4).

Then, Cr was formed by magnetron sputtering at a substrate temperature of 150 ° C. to a film thickness of 200 nm. After the photosensitive resin pattern was formed in the mask process, the source electrode 6 and the drain electrode 7 were processed by etching. In addition, n of the channel portion of the thin film transistor
The mold a-Si film was removed by dry etching (FIG. 5).
A protective insulating layer 8 (SiN) is formed on top of this by RF plasma CV.
After being formed to a thickness of 500 nm by the D method, a through hole was formed on the source electrode 6 by a photo-etching process. Further, the protective insulating films on the gate electrode terminal portion and the drain electrode terminal portion were removed. An ITO film is formed thereon by a magnetron sputtering method, and ITO of the pixel electrode 9 and the gate electrode terminal portion is formed by a photolithography method and etching.
A coating film 10 and an ITO coating film 11 on the drain electrode terminal portion were formed (FIG. 1). The right half of FIG. 2, that is, the portion 1 where the upper (previous) gate electrode 14 and the pixel electrode 9 in FIG.
2 acts as an additional capacity portion.

In the active matrix substrate of the present invention, since the gate electrode of the additional capacitance portion 12 is formed of the transparent conductive film, the additional capacitance portion 12 can also be used as the opening portion and the aperture ratio of the pixel can be increased. . As a result of producing a liquid crystal display device using the active matrix substrate of the present invention, a display with high brightness was obtained. The liquid crystal display device created here has a counter electrode facing the active matrix substrate, a liquid crystal part provided between the counter electrode and the active matrix substrate, and a light source provided on the opposite side of the active matrix substrate. Is.

FIG. 6 is a schematic plan view of the produced active matrix substrate, and FIG. 7 is a schematic sectional view taken along the line BB 'of FIG. The second embodiment will be described with reference to these drawings.
An ITO film having a film thickness of 300 nm was formed on the well-washed insulating substrate 1 by magnetron sputtering at a substrate temperature of 300 ° C. An organic resin pattern was formed on the ITO film by a printing method and processed into a gate wiring 2 having a width of 50 μm by wet etching. At this time, HBr was used as an etching solution, and etching was performed at 50 to 60 ° C. I
The taper angle at the end of the TO film was about 10 °. With such an angle, the coverage of the film laminated thereon can be improved.

Next, the thus-prepared substrate is set in a magnetron sputtering apparatus, and the first insulating layer 13 is placed.
As a result, a SiO ₂ film was deposited to a thickness of 1 μm. Then, a through hole for the thin film transistor portion was formed by photolithography and etching. Then, in the same manner as in the first embodiment, the substrate temperature is set to 230 ° C. and the SiN film of the gate insulating layer 3 and the semiconductor layer 4 are formed by the plasma CVD method.
A-Si: H film and n-type a-Si film 5 were formed. The formed semiconductor layer and the n-type a-Si film were processed into islands by photolithography and etching.

Then, the source electrode 6 and the drain electrode 7 were formed by the same method as in the first embodiment, and the n-type a-Si film in the channel portion was removed. Further, the ITO film of the pixel electrode 9 and the ITO coating film 11 of the drain electrode terminal portion were formed by the same method as in the first embodiment. Then, after forming the protective insulating film 8 by the same method as in the first embodiment, the protective insulating film and the gate electrode on the pixel electrode and the source electrode terminal portion and the drain electrode terminal portion are formed by photolithography and etching. -The insulating film was removed.

In the active matrix substrate of the present invention, since the gate electrode of the additional capacitance portion 12 is formed of the transparent conductive film, the additional capacitance portion 12 can also be used as the opening portion and the aperture ratio of the pixel can be increased. . As a result of producing a liquid crystal display device using the active matrix substrate of the present invention, a display with high brightness was obtained. Further, since the photosensitive resin transfer by the printing method is used for the processing of the gate electrode, the process can be simplified and the manufacturing cost can be reduced.

FIG. 8 is a schematic plan view of the produced active matrix substrate, and FIG. 9 is a schematic sectional view taken along the line CC ′ of FIG. The third embodiment will be described with reference to these drawings.
In the same manner as in the second embodiment, the gate electrode 2, the first insulating layer 13, the gate insulating layer 3, the semiconductor layer 4, the n-type a-Si are provided on the well-washed insulating substrate 1. A film 5, a source electrode 6 and a drain electrode 7 were formed. Then, in the same manner as in the first embodiment, the protective insulating layer 8 is formed and processed, and the ITO film is further formed, and then the pixel electrode 9, the ITO coating film 10 on the gate wiring terminal portion, and the drain electrode. Terminal part I
The TO coating film 11 was processed. At this time, the pixel electrode 9 has a structure of riding on the drain electrode 7.

In the active matrix substrate of the present invention, since the gate electrode of the additional capacitance portion 12 is formed of the transparent conductive film, the additional capacitance portion 12 can also be used as the opening portion and the aperture ratio of the pixel can be increased. . In addition, since the pixel electrode has a structure that rides on the drain electrode,
The vertical black matrix of the opposite substrate becomes unnecessary, and the aperture ratio can be further increased. As a result of producing a liquid crystal display device using the active matrix substrate of the present invention, a display with high brightness was obtained. As a result of producing a liquid crystal display device using the active matrix substrate of the present invention, a display with high brightness was obtained.

[0020]

As described above, according to the present invention, an active matrix substrate having a large aperture ratio can be manufactured. Therefore, a liquid crystal display device with high brightness can be manufactured using this active matrix substrate. In addition, when used in a portable computer or the like, it can contribute to reduction in power consumption and can be used for a long time. Further, since the printing method can be applied to the processing of the gate electrode of the active matrix substrate, the manufacturing process can be simplified and the cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic plan view of an active matrix substrate according to the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line A-A ′ of FIG.

FIG. 3 is a schematic plan view of the active matrix substrate of the present invention during manufacturing.

FIG. 4 is a schematic plan view of the active matrix substrate of the present invention during manufacturing.

FIG. 5 is a schematic plan view of the active matrix substrate of the present invention during manufacturing.

FIG. 6 is a schematic plan view of an active matrix substrate according to the present invention.

FIG. 7 is a schematic sectional view taken along the line B-B ′ of FIG. 6.

FIG. 8 is a schematic plan view of an active matrix substrate according to the present invention.

9 is a schematic cross-sectional view taken along the line C-C ′ of FIG.

[Explanation of symbols]

 1 insulating substrate, 2 gate electrode, 3 gate insulating layer, 4 semiconductor layer, 5 n-type a-Si film, 6 source electrode, 7 drain electrode, 8 protective insulating film, 9 pixel electrode, 10 ITO coating film for gate electrode terminal portion, 11 ITO coating film for drain electrode terminal portion, 12 additional capacitance portion, 13 first insulating layer, 14 gate electrode in previous stage.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiko Ando 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Tetsuro Minemura 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Ltd. Hitachi Research Laboratory

Claims (8)

[Claims] 1. An active matrix substrate having a plurality of gate electrodes made of a transparent conductive film, a gate insulating layer, a semiconductor layer, a source electrode, a drain electrode, and a pixel transparent electrode on an insulating substrate. An active matrix substrate characterized in that an additional capacitance is formed by laminating a gate insulating layer and an insulating layer different from the gate insulating layer between the gate electrode and the pixel transparent electrode of the next line. 2. The active matrix substrate according to claim 1, wherein an insulating layer different from the gate insulating layer is a protective insulating layer. 3. The active matrix substrate according to claim 1, wherein an insulating layer different from the gate insulating layer is a first insulating layer formed under the gate insulating layer. 4. The insulating layer different from the gate insulating layer is a first insulating layer and a protective insulating layer which are formed under the gate insulating layer. Active matrix substrate. 5. An insulating layer different from the gate insulating layer is S.
The active matrix substrate according to claim 1, which is iO ₂ . 6. The active matrix substrate used for display selection, wherein the width of the gate electrode is 30 μm or more when the diagonal dimension of the screen display portion is 9 inches or more. 1. The active matrix substrate according to 1. 7. A transparent conductive film is formed on an insulating substrate, a photosensitive resin pattern is transferred by a printing method and processed into a gate electrode, and then a first insulating layer is formed and processed. A method of manufacturing an active matrix substrate, which comprises forming and processing an insulating layer, a semiconductor layer, a source electrode, and a drain electrode. 8. A liquid crystal display device, comprising: the active matrix substrate according to claim 1; a counter electrode; and a liquid crystal portion formed between the substrate and the counter electrode.