JPH0792491A - Thin-film transistor substrate for active matrix display device - Google Patents

Abstract

PURPOSE:To increase an opening rate and capacitance for charge accumulation and to improve a pixel display characteristic without increasing the number of stages by constituting capacitance parts for charge accumulation of transparent electrodes consisting of polycrystalline silicon and transparent electrodes used as pixel electrodes. CONSTITUTION:The film of the polycrystalline silicon is formed as an active semiconductor layer 2 on a light transparent glass substrate 1 and is worked to an island shape. The film of silicon dioxide is formed as a gate insulating layer 5 thereon and further, the film of, for example, chromium is formed as gate electrodes 6 and is worked to the island shape. Source regions 3, drain regions 4 and the capacitance electrodes 11 for charge accumulation are formed by using the gate electrodes 6 as a mask and introducing phosphorus as an impurity. Further, the silicon dioxide is formed as an interlayer insulating layer 7 thereon and thereafter, contact holes are formed. Films of source electrodes 8 and drain electrodes 9 are formed of, for example, titanium and aluminum in this order and are worked. The film of ITO is thereafter formed and worked as the pixel electrodes 10, by which the active matrix substrate is completed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thin film transistor substrate for an active matrix display device such as a liquid crystal display device.

[0002]

2. Description of the Related Art FIG. 7, FIG. 8 and FIG. 9 show structural examples of a unit pixel of a conventional active matrix liquid crystal display device. Figure 7
Is a plan view of a unit pixel configuration example, and FIGS. 8 and 9 are schematic cross-sectional views taken along lines EE ′ and FF ′ of FIG. 7, respectively. The manufacturing method will be described below.

First, regions 3, 4 are formed on the transparent glass substrate 1.
And the active semiconductor layer 2 is formed. A gate insulating layer 5 and gate electrodes 6 and 6'are formed thereon. Next, a source region 3 and a drain region 4 are formed by forming a mask with a photoresist and adding an impurity by an ion implantation method. Then, after removing the photoresist, the interlayer insulating layer 7 is formed, and after further opening,
The source electrode 8 and the drain electrode 9 are formed. Finally, the pixel electrode 10 and the passivation layer are formed to complete the thin film transistor substrate. The passivation layer is omitted because it is not directly related to the present invention. The charge storage capacitor for holding image signals and the like is composed of the gate electrode 6 ′ at the previous stage, the interlayer insulating layer 7, and the pixel electrode 10.

[0004]

However, in such a pixel structure of the conventional thin film transistor substrate, since the charge storage capacitance is formed by the gate electrode and the pixel electrode of another row which shields light, it is effective as a display. There is a drawback that the pixel area, that is, the aperture ratio is reduced.

The present invention is intended to solve such a conventional problem, and has a large aperture ratio, a large charge storage capacity, and an active image display having a good image display characteristic without increasing the number of steps. An object is to provide a thin film transistor substrate for a matrix display device.

[0006]

In order to achieve the above object, the present invention provides a first transparent electrode made of polycrystalline silicon formed at the same time as a semiconductor layer of a transistor portion and a second transparent electrode which becomes a pixel electrode. The transparent electrode constitutes the charge storage capacitor portion.

[0007]

According to the present invention, with the above structure, since the charge storage capacitor section transmits light, a large aperture ratio can be obtained.
Further, the charge storage capacity can be increased, and good image display characteristics can be provided without increasing the number of steps.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1, FIG. 2 and FIG. 3 show structural examples of a unit pixel of an active matrix liquid crystal display device according to a first embodiment of the present invention. FIG. 1 is a plan view of a unit pixel configuration example, and FIGS. 2 and 3 are schematic sectional views taken along the lines AA ′ and BB ′ of FIG. 1, respectively. The manufacturing method will be described below.

First, as the active semiconductor layer 2 on the transparent glass substrate 1, for example, LP-CVD (Low Pressure Chemic) is used.
Al Vapor Deposition) method is used to form a polycrystalline silicon film, which is then processed into islands using photolithography and etching. As the gate insulating layer 5, silicon dioxide is formed thereon by, for example, the atmospheric pressure CVD method. Further, for example, a chromium film is formed as the gate electrode 6, and is processed into an island shape by using photolithography and etching.
Then, using the gate electrode 6 as a mask, phosphorus is introduced as an impurity by, for example, an ion implantation method to form the source region 3, the drain region 4, and the charge storage capacitor part electrode 11. On top of that, as the interlayer insulating layer 7, for example, atmospheric pressure CVD
After forming silicon dioxide by the method, contact holes are formed by photolithography and etching, and the source electrode 8 and the drain electrode 9 are formed, for example, in the order of titanium and aluminum, and processed. afterwards,
ITO is deposited and processed as the pixel electrode 10 to complete the active matrix substrate. Further, a passivation layer may be formed in some cases.

As shown in FIG. 3, the charge storage capacitance portion of the active matrix substrate thus manufactured is composed of polycrystalline silicon formed at the same time as the semiconductor layer of the transistor portion, an insulating layer and a pixel electrode. When the unit pixel is configured as described above, the charge storage capacitance section transmits light, so that the charge storage capacitance can be increased without lowering the aperture ratio, and good image display characteristics can be obtained without increasing the number of steps. A substrate for an active matrix liquid crystal display device having the same can be provided. The polycrystalline silicon electrode of the charge storage capacitor part of the unit pixel, which is formed at the same time as the semiconductor layer of the transistor part, is connected to the gate electrode of another stage and is connected to the gate electrode of the other stage as a common wiring. Sometimes connected. In the latter case, the modulation drive can be performed without considering the influence of the potential change of the gate line, and the display characteristics such as the brightness adjustment and the contrast adjustment can be controlled.

(Second Embodiment) Next, examples of the constitution of a unit pixel of an active matrix liquid crystal display device according to a second embodiment of the present invention are shown in FIGS. 4, 5 and 6. FIG. 4 is a plan view of a unit pixel configuration example, and FIGS. 5 and 6 are C of FIG. 4, respectively.
The schematic sectional drawing along the -C 'line and the DD' line is shown. The manufacturing method thereof will be described below.

First, as an active semiconductor layer 2 on a transparent glass substrate 1, for example, LP-CVD (Low Pressure Chemic) is used.
Al Vapor Deposition) method is used to form a polycrystalline silicon film, which is then processed into islands using photolithography and etching. Silicon dioxide is formed thereon as the gate insulating layer 5 by atmospheric pressure CVD, for example. Further, for example, a chromium film is formed as the gate electrode 6, and is processed into an island shape by using photolithography and etching. Then, using the gate electrode 6 as a mask, phosphorus is introduced as an impurity by, for example, an ion implantation method to form the source region 3, the drain region 4, and the charge storage capacitor part electrode 11. Then, an ITO film is formed and processed as the pixel electrode 10. After that, for example, silicon dioxide is formed as the interlayer insulating layer 7 by the atmospheric pressure CVD method, and then a contact hole is formed by photolithography and etching, and the source electrode 8 and the drain electrode 9 are formed in the order of titanium and aluminum, Processing is completed to complete an active matrix substrate. Further, a passivation layer may be formed in some cases.

As shown in FIG. 6, the charge storage capacitance portion of the active matrix substrate thus manufactured is composed of polycrystalline silicon formed at the same time as the semiconductor layer of the transistor portion, an insulating layer and a pixel electrode. When the unit pixel is constructed according to the second embodiment, in addition to the effect similar to that of the first embodiment, the ITO as the pixel electrode is electrically insulated and separated through the insulating layer when the source and drain electrodes are formed. Therefore, corrosion of ITO due to electrochemical reaction between ITO and dissimilar metals can be avoided.

In the first and second embodiments, ITO is used for the second transparent electrode which becomes the pixel electrode, but it may be made of polycrystalline silicon, or may be light-transmitting such as an oxide semiconductor such as zinc oxide. Any material may be used as long as it is a conductive layer.

[0016]

As described above, according to the present invention,
Since the electrode of the light-transmitting charge storage capacitor can be formed at the same time as the semiconductor layer of the transistor portion, the aperture ratio and the charge storage capacitor can be increased without increasing the number of steps, and a favorable image can be obtained. A thin film transistor substrate for an active matrix display device having display characteristics can be realized.

[Brief description of drawings]

FIG. 1 is a plan view showing a unit pixel configuration according to a first embodiment of the present invention.

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

3 is a schematic cross-sectional view taken along the line B-B ′ of FIG.

FIG. 4 is a plan view showing a unit pixel configuration according to a second embodiment of the present invention.

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

6 is a schematic cross-sectional view taken along the line D-D ′ of FIG.

FIG. 7 is a plan view showing a conventional unit pixel configuration.

8 is a schematic cross-sectional view taken along the line E-E ′ of FIG.

9 is a schematic cross-sectional view taken along the line F-F ′ of FIG. 7.

[Explanation of symbols]

 1 Translucent Glass Substrate 2 Active Semiconductor Layer 3 Source Region 4 Drain Region 5 Gate Insulating Layer 6 Gate Electrode 6'Previous Stage Gate Electrode 7 Interlayer Insulating Layer 8 Source Electrode 9 Drain Electrode 10 Pixel Electrode 11 Charge Storage Capacitance Part Electrode

Claims (4)

[Claims] 1. At least a transistor portion and a charge storage capacitance portion, the charge storage capacitance portion being sandwiched between a first transparent electrode, a second transparent electrode serving as a pixel electrode, and the second transparent electrode. In a thin film transistor substrate for an active matrix display device having an insulating layer, the first transparent electrode is made of polycrystalline silicon, and is formed at the same time as the semiconductor layer of the transistor section. substrate. 2. The thin film transistor substrate for an active matrix display device according to claim 1, wherein the second transparent electrode is polycrystalline silicon. 3. The thin film transistor substrate for an active matrix display device according to claim 1, wherein the second transparent electrode is an oxide semiconductor layer. 4. The thin film transistor substrate for an active matrix display device according to claim 3, wherein the oxide semiconductor layer includes a layer mainly containing indium oxide, tin oxide, or both.