Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
1998-03-12
2001-10-30
Hjerpe, Richard (Department: 2674)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S043000, C445S024000, C345S092000
Reexamination Certificate
active
06310666
ABSTRACT:
This application claims the benefit of Korean patent application No. 97-54963, filed Oct. 24, 1997, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method for manufacturing a liquid crystal display (LCD) device including a thin film transistor (TFT), and more particularly, to a method for protecting the TFT from damage due to radio frequency discharge during dry etching.
2. Discussion of the Related Art
As shown in
FIG. 1
, a conventional liquid crystal display (LCD) device includes two panels and a liquid crystal layer between them. The first panel (an active panel) includes a plurality of gate lines
70
on a transparent substrate
10
, a gate pad
75
at an end of each gate line
70
, and a gate shorting bar
76
connecting to each gate pad
75
at an edge portion of the transparent substrate
10
. The conventional LCD further includes a plurality of a data lines
80
crossing the gate lines
70
and substantially perpendicular to the gate lines
70
, a data pad
85
at an end of each data line
80
, and a data shorting bar
86
connecting each data pad
85
at another edge portion of the transparent substrate
10
. The conventional LCD further includes a pixel electrode
40
located at an area surrounded by two neighboring gate lines
70
and two neighboring data lines
80
, and a thin film transistor TFT
31
connected to the pixel electrode
40
near an intersection of the gate line
70
and the data line
80
. The TFT
31
includes a gate electrode
70
a
extended from the gate line
70
, a source electrode
80
a
extended to form the data line
80
, a drain electrode
80
b
facing the source electrode
80
a,
and a semiconductor layer
90
between the gate electrode
70
a
and the source and drain electrodes
80
a
and
80
b.
The second panel (a color filter panel) (not shown), includes a color filter, a black matrix, and a common electrode on a second transparent substrate. Before the first and second panels are joined each other, the gate shorting bar
76
and the data shorting bar
86
are removed by cutting them or etching the transparent substrate
10
along line I—I of FIG.
1
.
The gate shorting bar
76
and the data shorting bar
86
are used for anodizing the gate line
70
and gate electrode
70
a,
or for testing the TFT
31
.
A method for manufacturing the active panel of the LCD will be described with reference to
FIGS. 2A
to
2
D showing cross-sectional views along line II—II of FIG.
1
.
As shown in
FIG. 2A
, a metal such as aluminum is deposited on a transparent substrate
10
and patterned to form the gate line
70
, the gate electrode
70
a
extending from the gate line
70
, and the gate shorting bar
76
. The gate shorting bar
76
generally covers the edge portion of the transparent substrate
10
. A gate insulation layer
50
, including silicon nitride (SiN
x
) or silicon oxide (SiO
x
), is formed on the gate electrode
70
a
and the gate shorting bar
76
. A semiconductor layer
90
, including amorphous silicon (a-Si), and doped semiconductor layers
92
a
and
92
b
, including impurity doped amorphous silicon (n
+
a-Si), are formed sequentially on the gate insulation layer
50
. The data line
80
, including chromium, is formed on the gate insulation layer
50
. The source electrode
80
a
is formed extending from the data line
80
and in ohmic contact with the doped semiconductor layer
92
a,
and the drain electrode
80
b
is formed facing the source electrode
80
a
and in ohmic contact with the doped semiconductor layer
92
b.
Not shown in the cross-sectional view is that the data pad
85
is formed at the end of the data line
80
. The data pad
85
is connected to the data shorting bar
86
located on the edge of the transparent substrate
10
, as shown in FIG.
1
. The data pad
85
and the gate shorting bar
86
can be formed simultaneously with the data bus line
80
. Alternatively, they can be formed simultaneously with the gate line
70
and can connect to the data line
80
through a contact hole (not shown) formed in the gate insulation layer
50
.
A protection layer
55
including silicon nitride, silicon oxide, or benzo-cyclo-butene (BCB), is deposited covering the transparent substrate
10
and the TFT
31
.
A photo-resist layer is coated on the protection layer
55
by a spin coating method. The photo-resist layer is patterned using a mask to form a photo-resist pattern
60
that exposes a portion of the protection layer
55
covering the drain electrode
80
b,
as shown in FIG.
2
B. The edge of the gate shorting bar
76
is exposed even if the gate insulation layer
50
, the protection layer
55
, and the photo-resist pattern
60
cover the entire surface of the transparent substrate
10
. The LCD panel, as shown in
FIG. 2B
, is placed in an etching chamber. The protection layer
55
is etched along with the photo-resist pattern
60
using a dry etching method in which a gas such as SF
6
or CF
4
is brought to a plasma state using a radio frequency (RF) generator. The Si radical of the exposed part of the protection layer
55
reacts with the plasma gas because the protection layer
55
includes SiN
x
, SiO
x
, or BCB. A volatile material, such as, SiF
4
, results when removing the exposed portion of the protection layer
55
from the surface of the transparent substrate
10
.
During the etching process using a radio frequency discharge, the TFTs
31
can be damaged by static electricity resulting from charges stored at an exposed edge of the gate shorting bar
76
. Furthermore, after the etching processing is finished, the etched shape can be different from what was intended. For example, as shown in
FIG. 2C
, the contact hole
37
over the drain electrode
80
b
does not have the desired shape. Additionally, the photo-resist pattern
60
is not removed entirely, and photo-resist remnants
60
′ will remain on some portions of the protection layer
55
.
An indium tin oxide (ITO) layer is deposited over the protection layer
55
and patterned to form a pixel electrode
40
in contact with the drain electrode
80
b
through the contact hole
37
. However, as shown in
FIG. 2D
, contact condition of the pixel electrode
40
with the drain electrode
80
b
is poor because the contact hole
37
does not have the desired shape. Additionally, the pixel electrode
40
does not settle on the protection layer
55
due to the photo-resist remnant
60
′, so a portion of the pixel electrode can wear off.
Finally, the active panel is cut along line I—I shown in
FIG. 1
to remove the portion having the gate shorting bar
76
and data shorting bar
86
. The removing method uses either mechanical cutting or etching.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a method for manufacturing a liquid crystal display device that substantially obviates one or more of the problems due to the limitations and disadvantages of the related art.
One object of the present invention is to protect the TFTs from radio frequency discharge during dry etch processing.
Another object of the present invention is to form an etched shape as intended by preventing static electricity on the etched surface.
Another object of the present invention is to produce a clean surface without any photo-resist remnants after the dry etch process is finished.
Additional features and advantages of the present invention will be set forth in the description which follows, and will be apparent from the description, or may be learned by practice of the invention.
The objectives and other advantages of the invention will be realized and attained by the structure and process particularly pointed out in the written description as well as in the appended claims.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, in accordance with one aspect of the present invention there is provided a method for manufacturing a liquid crystal display device, including the steps of f
Hjerpe Richard
LG. Philips LCD Co. Ltd.
Nguyen Francis
LandOfFree
Manufacturing method of liquid crystal display preventing RF... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manufacturing method of liquid crystal display preventing RF..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacturing method of liquid crystal display preventing RF... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2560726