Active solid-state devices (e.g. – transistors – solid-state diode – Non-single crystal – or recrystallized – semiconductor... – Amorphous semiconductor material
Reexamination Certificate
1998-11-04
2001-07-17
Prenty, Mark V. (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Non-single crystal, or recrystallized, semiconductor...
Amorphous semiconductor material
C257S072000
Reexamination Certificate
active
06262436
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an LCD (liquid crystal device) operated by thin film transistors as active matrix switching elements, and particularly relates to a semiconductor device for a flat liquid crystal display and method of making the same.
This application is based on Patent Application No. Hei 9-302579 filed in Japan, the content of which is incorporated herein by reference.
2. Background Art
Recently, thin film transistors (TFT) are being widely used as active switching elements for driving liquid crystal flat display devices. Among those thin film transistors, a forward stagger type configuration, in which a gate electrode is mounted on the upper side of a channel layer, and source and drain electrodes are mounted in the lower side, is advantageously used because of its simple structure, and reduced number of lithographic steps in manufacturing, and such that the manufacturing cost is low.
An example of the representative forward stagger type TFT is shown in FIG.
5
. The TFT is provided with, on an insulating substrate such as a glass plate, a metallic light shielding film
3
, a transparent interlayer insulating film
4
, a pixel electrode
12
, a source electrode
5
, a drain electrode
6
, an n+ amorphous silicon layer
7
, an amorphous silicon layer
8
, a gate insulating film
9
, a gate electrode
10
; and the TFT is covered and protected by a protective insulation film
13
. The source electrode
5
and drain electrode
6
are formed on a pixel electrode
12
and a residual layer
14
made of the same material as that of the pixel electrode, and the drain electrode
6
is connected to the pixel electrode
12
through the residual layer
14
.
A practical example of an active matrix panel is disclosed in Japanese Patent Application, First Publication No. Hei 7-239481, in which, as shown in
FIG. 5
, an n+ amorphous silicon
7
is separated into the source electrode
5
side and the drain electrode
6
side.
In this forward stagger type TFT, it is necessary to provide a formation process of a light shielding film, in order to suppress the leak current caused by the light admittance to the amorphous silicon layer
8
.
In contrast, in a TFT disclosed in Japanese Patent Application, First Publication No. Hei 9-92618, a black matrix normally formed by a Cr film at the color filter side is mounted at the TFT substrate side, concurrently with the formation of the light shielding film.
Japanese Patent Application, First Publication No. Hei 5-210119 has proposed an active matrix liquid crystal display screen, in which the black matrix and the color filter are formed under the forward type stagger TFT, concurrently with the formation of the light shielding layer.
In the conventional forward stagger type TFT, a photolithographic process is needed for forming the light shielding film, so that, it is difficult to reduce the number of manufacturing processes, and it is not advantageous to adopt such TFT for flat type display devices for which cost reduction is required.
As disclosed in the above mentioned prior art references, when the black matrix is formed at the color filter side, it is necessary to precisely align the black matrix with the TFT substrate, that is, the black matrix must be overlapped accurately with the TFT substrate. For this reason, it is necessary but difficult to increase a so-called aperture which corresponds to expanding the area of the pixel electrode.
It is therefore an object of the present invention to provide a semiconductor device and a method of manufacturing the same, which is particularly suitable for a flat display LCD operated by an active matrix display principle using the a-SiTFT, and which has an increasing aperture, and a reduced manufacturing cost by reduction of the number of manufacturing processes.
SUMMARY OF THE INVENTION
A semiconductor device of the present invention is provided with a source electrode and a drain electrode on an insulating film formed on a surface of an insulating substrate, and an amorphous silicon (a-Si), a gate insulating layer, and a gate electrode are formed in this order on the insulating film so as to cover at least a part of the source and drain electrodes. Subsequently, the drain electrode of the semiconductor device is connected to a pixel electrode to construct a forward stagger type thin film transistor element (TFT). The insulating film has a light shielding property, and the light shielding film on the transparent substrate is removed excluding the area covered by the source electrode, the drain electrode and the drain signal line, and the gate electrode and the gate signal lines.
In this structure, the light shielding film may be formed by combining two film layers laminating a light shielding organic film with an insulating inorganic film.
The semiconductor device of the present invention is suitable for color liquid crystal display devices driven by a-SiTFTs and active matrix display systems driven by a-SiTFTs.
This color liquid display devices can be used as liquid crystal flat display devices by forming a transparent smoothening film so as to cover the substrate region where the light shielding film is removed.
Furthermore, in the present invention, the insulating film with a light shielding property can mask wiring of the source electrode, the drain electrodes and the drain signal line, and the gate electrode and the gate signal line, and removes all of the light shielding insulating layer except areas covered by those electrodes and signal lines.
In this case, the region where the light shielding insulating film is removed is covered by forming a transparent, smoothening film for smoothening such substrate region. When this device is used for an active matrix type display device in which respective a-SiTFTs are connected to each pixel electrode, said pixel electrode is formed so as to overlap at least either one of the drain signal line or the gate signal line, and is connected to the drain electrode through a contact hole formed through the transparent smoothening film.
Consequently, as shown above, since the light shielding film is selected from a material which can be etched by an etching gas simultaneously during the etching process of the TFT, the conventional process for forming the light shielding film can be eliminated. This is realized by using gases with a selective etching property which are not capable of etching wiring materials and the gate insulating film, but are capable of etching the amorphous silicon film and the light insulating film.
REFERENCES:
patent: 6057904 (2000-05-01), Kim et al.
NEC Corporation
Prenty Mark V.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Semiconductor device and method of making the same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor device and method of making the same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor device and method of making the same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2561110