JP2002231961A - Liquid crystal display - Google Patents

Abstract

(57) Abstract: Provided is an active matrix type liquid crystal display device capable of reducing variation in capacitance between a source and a gate and capacitance between a drain and a gate of a thin film transistor in the liquid crystal display device. SOLUTION: A gate electrode, a gate insulating film, a semiconductor film, a source electrode and a drain electrode are provided over an insulating substrate, and a contact between the semiconductor film near the gate electrode and the source electrode and the drain electrode is formed by a source electrode. In an active matrix type liquid crystal display device including a thin film transistor serving as a region and a drain region, a step formed by a gate electrode of a thin film transistor and a semiconductor film is used to etch up to an upper surface of a convex portion formed by the gate electrode in the semiconductor film. Thus, the source electrode and the drain electrode of the thin film transistor are formed in a self-aligned manner.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an active matrix type liquid crystal display device.

[0002]

2. Description of the Related Art First, an example of the structure of a thin film transistor in a conventional active matrix type liquid crystal display device will be described with reference to FIG. FIG. 2 is a cross-sectional flowchart of a manufacturing process of a thin film transistor in a conventional active matrix type liquid crystal display device.

First, in FIG. 2A, a glass substrate 1
After forming a gate electrode conductive film 12 of aluminum or the like on the upper surface of 1, a photosensitive agent 13 is applied, and a predetermined pattern is formed by photolithography using a photomask.

Next, in FIG. 2B, a part of the gate electrode conductive film 12 is removed by etching using the photosensitive agent 13 as a mask, the gate electrode conductive film 12 is formed in a predetermined pattern, and an insulating film such as an oxide film is formed. A film 14 is formed on the upper surface, and a semiconductor film 15 such as amorphous silicon is formed on the upper surface.
The photosensitive agent 16 is applied, and a predetermined pattern is formed by photolithography using a photomask.

[0005] Then, in FIG.
A portion of the semiconductor film 15 is removed by etching using a mask as a mask, a predetermined pattern is formed, a source / drain wiring conductive film 17 of aluminum or the like is formed on the upper surface, a photosensitive agent 18 is applied, and a photomask is used. A predetermined pattern is formed by lithography.

[0006] Finally, in FIG.
Using a mask as a mask, a part of the source / drain wiring conductive film 17 is removed by etching to form a predetermined pattern. At this time, a part of the semiconductor film 15 is also removed by etching.

[0007]

In general, the structure of a thin film transistor in an active matrix type liquid crystal display device having a thin film transistor is different from a case where an element such as a transistor is formed on a silicon substrate like an LSI, and a gate electrode conductive film is formed. The upper surface (lower surface) of the substrate 12 and the lower surface (upper surface) of the source / drain wiring conductive film 17 overlap each other. At this time, the capacitance is formed by the overlap of the gate electrode conductive film 12 and the source / drain wiring conductive film 17.

The capacitance formed due to the overlapping structure of the source / drain wiring conductive film 17 and the gate electrode conductive film 12 of such a thin film transistor greatly varies due to misalignment at the time of photolithography. actually,
The development of LCD exposure equipment focuses on expanding the area that can be exposed at one time in order to respond to the increase in the screen size of LCDs. In some cases, the overlapping amount of the source / gate or drain / gate of the thin film transistor in the device may be shifted by 1 μm or more. For example, if the designed overlap amount is 3 μm, the change amount of the capacitance formed by the structure in which the source / drain wiring conductive film 17 and the gate electrode conductive film 12 overlap with each other is 30% or more. Variations in the liquid crystal display device having such a capacity appear as flickers or the like on the display screen, which is one of the causes of deteriorating the display quality.

According to the present invention, in order to solve the above-mentioned problems, a source-gate capacitance and a drain-gate of a thin film transistor are provided.
It is an object of the present invention to provide an active matrix type liquid crystal display device capable of reducing variation in capacitance between gates in the liquid crystal display device.

[0010]

In order to achieve the above object, an active matrix type liquid crystal display device according to the present invention comprises a gate electrode, a gate insulating film, a semiconductor film, a source electrode and a drain formed on an insulating substrate. An active matrix liquid crystal display device comprising a thin film transistor having electrodes, and a contact between the semiconductor film near the gate electrode and the source electrode and the drain electrode is a source region and a drain region, respectively. A source electrode and a drain electrode of a thin film transistor are formed in a self-aligned manner by utilizing a step formed by a film and etching the upper surface of a projection formed by a gate electrode in a semiconductor film.

[0011] With this configuration, the capacitance between the source and the gate and the capacitance between the drain and the gate of the thin film transistor do not depend on the misalignment of the photolithography, and the step formed by the gate electrode and the semiconductor layer is used. By etching up to the upper surface of the convex portion formed by the gate electrode, the source / drain electrodes of the thin film transistor can be formed in a self-aligned manner. An active matrix type liquid crystal display device with high display quality can be provided in which almost no variation occurs in the display device and flicker (flicker) of the display screen does not occur.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an active matrix type liquid crystal display according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional flowchart showing a manufacturing process of a thin film transistor in an active matrix liquid crystal display device according to the present invention.

First, in FIG. 1A, a glass substrate 1
After a gate electrode conductive film 2 is formed on the upper surface of the substrate, a photosensitive agent 3 is applied, and a predetermined pattern is formed by photolithography using a photomask.

Next, in FIG. 1B, a part of the gate electrode conductive film 2 such as aluminum is removed by etching using the photosensitive agent 3 as a mask, and the gate electrode conductive film 2 is formed in a predetermined pattern. After forming an insulating film 4 on the upper surface, a semiconductor film 5 of amorphous silicon or the like is formed on the upper surface, a photosensitive agent 6 is applied, and a predetermined pattern is formed by photolithography using a photomask.

In FIG. 1C, a part of the semiconductor film 5 is removed by etching using the photosensitive agent 6 as a mask to form a predetermined pattern, and a source / drain wiring conductive film 7 of aluminum or the like is formed on the upper surface. Later, photosensitive agent 8
Is applied. At this time, the photosensitive agent 8 is applied so as to be flat. Next, a predetermined pattern is formed by photolithography using a photomask.

Finally, in FIG. 1D, after a part of the source / drain wiring conductive film 7 is removed by etching using the photosensitive agent 8 as a mask, the etching rate of the photosensitive agent 8 and the source / drain wiring conductive film 7 is reduced. To about 1: 1 by etching to the upper surface of the semiconductor film 5 to form the source / drain wiring conductive film 7.

In this process, the capacitance formed by the source / drain wiring conductive film 7 and the gate electrode conductive film 2 is determined by the position of the edge of the semiconductor film 5 at the edge of the source / drain wiring conductive film 7. 5 is determined by the position of the gate electrode conductive film 2, the alignment is not affected at all by the alignment deviation formed by photolithography for forming the source / drain wiring conductive film 7, and the liquid crystal display device The variation in the capacitance between the source and the gate or between the drain and the gate of the thin film transistor within the transistor hardly occurs.

Further, since the overlapping portion between the upper surface (lower surface) of the gate electrode conductive film 2 and the lower surface (upper surface) of the source / drain wiring conductive film 7 is extremely small as compared with the prior art, 1
The capacitance between the source and the gate or the capacitance between the drain and the gate of the thin film transistor occupying the pixel is also reduced, and it can be expected that the variation in the capacitance has less influence on the display quality.

In the step of forming the source / drain electrodes, the photosensitive agent 8 is flattened, the source / drain wiring conductive film 7 is etched using the photosensitive agent 8 as a mask, Although the step of etching the photosensitive agent 8 at an etching rate of 1: 1 was performed, each step may be performed separately and divided into two steps.

The material to be etched at an etching rate of 1: 1 with the source / drain wiring conductive film 7 is not particularly limited to a photosensitive agent as long as it is an insulating material that can be planarized. Further, similar effects can be expected even if the source / drain electrodes are formed by polishing physically instead of etching at an etching rate of 1: 1.

As described above, according to this embodiment, the capacitance between the source and the gate and the capacitance between the drain and the gate of the thin film transistor are formed by the gate electrode and the semiconductor layer without depending on the misalignment of the photolithography. By utilizing the steps, the source / drain electrodes of the thin film transistor can be formed in a self-aligned manner, so that variations in the source-gate capacitance and the drain-gate capacitance of the thin film transistor in the liquid crystal display device are extremely reduced. Thus, it is possible to provide an active matrix type liquid crystal display device having high display quality without causing flickers or the like on the display screen.

[0022]

As described above, according to the active matrix type liquid crystal display device of the present invention, by forming the source and drain electrodes of the thin film transistor in a self-aligned manner, the capacity between the source and the gate and the drain and the gate of the thin film transistor are formed. The conventional active matrix liquid crystal display is designed to minimize the variation in the inter-capacitance in the liquid crystal display device and to suppress the deterioration of the display quality due to the variation in the source-gate capacitance and the drain-gate capacitance of the thin film transistor in the liquid crystal display device. It is possible to maintain a higher display quality than the device.

[Brief description of the drawings]

FIG. 1 is a cross-sectional flowchart of a manufacturing process in an active matrix type liquid crystal display device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional flowchart of a manufacturing process in a conventional active matrix type liquid crystal display device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 11 Glass substrate 2, 12 Gate electrode conductive film 3, 6, 8, 13, 16, 18 Photosensitizer 4, 14 Insulating film 5, 15 Semiconductor film 7, 17 Source / drain wiring conductive film

Claims (1)

[Claims] A gate electrode, a gate insulating film, a semiconductor film, a source electrode and a drain electrode on an insulating substrate, wherein the semiconductor film near the gate electrode and the source electrode and the drain electrode An active matrix type liquid crystal display device including a thin film transistor whose contacts are a source region and a drain region, respectively, wherein a step formed by the gate electrode and the semiconductor film of the thin film transistor is used to form the gate in the semiconductor film. An active matrix type liquid crystal display device, wherein the source electrode and the drain electrode of the thin film transistor are formed in a self-aligned manner by etching up to an upper surface of a projection formed by an electrode.