Liquid crystal cells – elements and systems – Particular structure – Having significant detail of cell structure only
Reexamination Certificate
2000-12-22
2004-10-19
Ngo, Huyen (Department: 2871)
Liquid crystal cells, elements and systems
Particular structure
Having significant detail of cell structure only
C349S043000, C349S046000
Reexamination Certificate
active
06806933
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a method of manufacturing an array substrate for a LCD device.
2. Description of Related Art
Active matrix LCD devices, where thin film transistors (TFTs) and pixel electrodes are arranged in the form of a matrix, have been widely used due to a high resolution and an excellent performance of implementing moving images.
FIG. 1
is a cross-sectional view illustrating a liquid crystal panel of a typical active matrix LCD device. As shown in
FIG. 1
, the liquid crystal panel
20
includes lower and upper substrates
2
and
4
with a liquid crystal layer
10
interposed. The lower substrate
2
on a transparent substrate
1
has two regions: a region S; and a region P. TFTs are arranged on the region S as a switching element, and pixel electrodes
14
are arranged on the pixel region P. The upper substrate
4
includes a color filter
8
and a common electrode
12
on a transparent substrate
1
. Through the pixel electrode
14
and the common electrode
12
, voltages are applied to the liquid crystal layer
10
. In order to prevent a leakage of the liquid crystal, edge portions of the two substrate
2
and
4
are sealed by a sealant
6
.
FIG. 2
is a plan view illustrating the lower array substrate
2
of FIG.
1
. As shown in
FIG. 2
, gate lines
22
are arranged in a transverse direction, and data lines
24
are arranged in a longitudinal direction perpendicular to the gate lines
22
. A pixel region is defined by the gate and data lines
22
and
24
, and pixel electrodes
14
is formed on the pixel region. Thin film transistors (TFTs) “T” are formed at a crossing point of the gate and data lines
22
and
24
. Each of the TFTs “T” includes a gate electrode
26
, a source electrode
28
and a drain electrode
30
. The gate electrode
26
extends from the gate line
22
, and the source electrode
28
extends from the data line
24
. The drain electrode
30
is spaced apart from the source electrode
28
and contacts with the pixel electrode
14
through a contact hole
30
a.
Over a portion of the gate line
22
, a storage capacitor Cst is formed. In other words, in order to form the storage capacitor Cst, a portion of the pixel electrode
14
overlaps a portion of the gate electrode
22
while interposing an insulating layer therebetween.
The active matrix LCD device is operated as follows. When a voltage is applied to the gate electrode
26
of the TFT “S”, a data signal is applied to the pixel electrode
14
. On the contrary, when no voltage is applied to the gate electrode
26
, data signal is not applied to the pixel electrode
14
.
The liquid crystal panel
20
is manufactured through several complex processes. Especially, the lower substrate is manufactured through several mask processes. In general, the more complex the manufacturing process is, the higher a possibility of an inferiority rate becomes. Therefore, it is important to simplify a manufacturing process.
Whether a manufacturing process of the lower substrate is complex or not depends on a kind of a material used to form components and a device performance. For example, in case of a large LCD device of more than 12 inches, a specific resistance value of a material used for a gate line is a very important parameter to determine a display quality. Therefore, in case of a large-sized LCD device, a low resistive material such as aluminum and aluminum alloy is preferably used as a material of a gate electrode. However, an aluminum-based metal is low in resistance but has a low corrosion resistance. Since aluminum has a low corrosion resistance, it may be opened in a subsequent process due to an etchant. In order to prevent a possible line open, a metal having a high corrosion resistance such as Cr and Mo is used as the second metal layer. That is, when a low resistive aluminum-based metal is used as a first metal layer to reduce a RC delay, the other metal such Cr and Mo is used a second metal layer.
FIGS. 3A
to
3
C are cross-sectional views taken along line III—III of
FIG. 2
, and illustrate a manufacturing process of the gate line. First, as shown in
FIG. 3A
, an AlNd layer
40
and a molybdenum (Mo) layer
42
are formed sequentially on a substrate
1
. Then, a photoresist
44
is applied on the molybdenum layer
44
.
Subsequently, as shown in
FIG. 3B
, the AlNd layer
40
and the molybdenum (Mo) layer
42
are simultaneously etched through a mask process to form the gate line
22
of a dual-layered structure. At this time, the AlNd layer
40
and the molybdenum (Mo) layer
42
have different etching rate from each other due to Galvanic Corrosion. For the more detail, since the AlNd layer
40
has a high etching rate in an etching solution, it is difficult to control the etching rate. Further, since the AlNd layer
40
is higher in etching rate than the molybdenum layer
42
, its vertical side portion is more etched than that of the molybdenum layer
42
. Therefore, the gate line
22
has a taper shape and an overhang “O” that a side portion of the molybdenum layer
42
is protruded outwardly.
The gate pattern having such an overhang cannot have a good step coverage for an insulating layer formed thereon. Therefore, the gate pattern may cause defects such as a line open and a dielectric breakdown. Further, overhang can occur in the gate line of a single-layered structure, and defects such as a line open may occur. Such defects lower a manufacturing yield as well as electrical characteristics of the gate line. Such problems lower a manufacturing yield and electrical characteristics of the gate line. In order to remove the overhang portion “O”, as shown in
FIG. 3C
, only the second metal layer
42
is dry-etched using the patterned photoresist
45
as a mask. At this time, the photoresist
45
and the overhang portion “O” of the molybdenum
42
are simultaneously removed. In other words, the gate electrode and the gate line having no overhang are formed in such a way that an etching gas containing an oxygen (O
2
) and a fluorine-based gas used an dry-etching gas ashes a portion of the photoresist
45
and then a portion of the molybdenum layer
42
is oxidized and removed.
However, since the method of manufacturing an array substrate described above additionally employs the dry-etching in order to remove the overhang portion of the electrode line, the manufacturing process becomes complicated and the number of the manufacturing processes becomes increased. Further, since the dry-etching process uses the large-sized equipment compared with the wet-etching process, a production cost becomes increased.
SUMMARY OF THE INVENTION
To overcome the problems described above, preferred embodiments of the present invention provide a method of manufacturing an array substrate by a simple manufacturing process at a low production cost.
Another object of the present invention is to provide a method of manufacturing an array substrate for a liquid crystal display device having a high aperture ratio.
In order to achieve the above object, the preferred embodiments of the present invention provide a method of manufacturing an array substrate, comprising: forming an electrode line on a substrate using a wet etching technique; and forming an organic insulating layer on an exposed surface of the substrate while covering the electrode line, wherein the electrode line has a side portion having an overhang or a taper angle of more than 45° C.
The organic insulating layer is made of one of benzocyclobutene, an olefin-based insulating material, an acrylic-based insulating material, and a silicon-based insulating material.
The electrode line may have first and second metal layers of a dual-layered structure, and a side portion of the first metal layer is more etched than that of the second metal layer. The first metal layer is made of one of aluminum, an aluminum alloy, AlNd, copper and a copper alloy, and the second metal layer is made of one of Cr, Cr-alloy, Mo, Mo-alloy, Ta, Ta-al
Birch & Stewart Kolasch & Birch, LLP
LG. Philips LCD Co. Ltd.
Ngo Huyen
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