Liquid crystal cells – elements and systems – Particular excitation of liquid crystal – Electrical excitation of liquid crystal
Reexamination Certificate
2001-02-06
2002-11-05
Parker, Kenneth (Department: 2871)
Liquid crystal cells, elements and systems
Particular excitation of liquid crystal
Electrical excitation of liquid crystal
C349S038000, C349S039000, C349S042000, C349S192000
Reexamination Certificate
active
06476881
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device and a defect repairing method therefor, and more specifically, to a liquid crystal display device which allows disconnection defects caused in the process of manufacturing the liquid crystal display device to be readily repaired with a higher success rate than conventional cases, so that the device can be modified into a non-defective device, and a defect repairing method therefor.
2. Description of the Related Art
Active matrix type liquid crystal display devices used as a display device in OA-related equipment including computers have attracted attention as a high picture quality flat panel display. The liquid crystal display device has a redundant structure which can repair disconnection defects caused in the manufacturing process, in order to increase the manufacturing yield. The general structure of a conventional liquid crystal display device will be now described in conjunction with
FIGS. 27
to
29
.
FIG. 27
is a view of the surface of an array substrate for a liquid crystal display panel in a conventional liquid crystal display device, viewed from the liquid crystal layer side. As shown in
FIG. 27
, a plurality of data bus lines (drain bus lines)
11
a
,
11
b
,
11
c
, etc. extending in the vertical direction in the figure are formed on the substrate. A plurality of gate bus lines
13
a
,
13
b
, etc. denoted by the broken line extending in the horizontal direction in the figure are also formed on the substrate. Pixels are formed in regions defined by these data bus lines
11
a
,
11
b
,
11
c
and the gate bus lines
13
a
,
13
b
. In the vicinity of crossing positions of the data bus lines
11
a
,
11
b
,
11
c
and the like and the gate bus lines
13
a
,
13
b
and the like, TFTs
15
a
,
15
b
, etc. are formed.
For example, in the case of the TFTs
15
a
and
15
b
as shown in the upper part of the figure, drain electrodes
17
a
,
17
b
are led out from the data bus lines
11
a
,
11
b
shown at the left of the TFTs
15
a
,
15
b
, and their ends are formed to be positioned on one end side on channel protection films
19
a
,
19
b
formed on the gate bus line
13
a.
Meanwhile, source electrodes
21
a
,
21
b
are formed to be positioned on the other end side on the channel protection films
19
a
,
19
b
. In this structure, the region of the gate bus line
13
a
immediately under the channel protection films
19
a
,
19
b
serves as a gate electrode for these TFTs
15
a
,
15
b
. Although not shown, a gate insulating film is formed on the gate bus lines
13
a
,
13
b
, on which an active semiconductor layer forming a channel is formed. In the TFT structure as shown in
FIG. 27
, gate electrodes are not formed in the manner in which they are led out from the gate bus lines
13
a
,
13
b
, but a part of the linearly provided gate bus lines
13
a
,
13
b
is each used as a gate electrode.
A storage capacitor bus line
23
is formed in the region denoted by the broken line extending in the horizontal direction virtually in the center of the pixel region. Storage capacitor electrodes
25
a
,
25
b
are formed for each pixel at an over layer of the storage capacitor bus line
23
through an insulating film. Pixel electrodes
27
a
,
27
b
of a transparent electrode material are formed at an over layer of the source electrodes
21
a
,
21
b
and the storage capacitor electrodes
25
a
,
25
b
through a protection film. The pixel electrodes
27
a
,
27
b
are electrically connected with the source electrodes
21
a
,
21
b
through contact holes
29
a
,
29
b
provided in a protection film formed at the under layer. The pixel electrodes
27
a
,
27
b
are also electrically connected with the storage capacitor electrodes
25
a
,
25
b
through contact holes
31
a
,
31
b.
The TFT described above has an inverted staggered structure, while there are thin film transistors having other structures such as a staggered type or planar type structure having a drain electrode at the lowermost layer for example and a gate electrode at an over layer of thereof. In any of these structures, each metal layer is placed through an insulating film.
Each of the gate bus lines
13
has lead-out portions
33
a
,
33
b
, etc. led out into the pixels perpendicularly to the extending direction of the bus line. The lead-out portion
33
b
for example has a region overlapping the pixel electrode
27
b
at the upper right part of the pixel when viewed in the normal direction to the panel surface.
FIG. 28
shows a section of the lead-out portion
33
a
taken along line E-E′ in FIG.
27
. As shown in
FIG. 28
, the gate bus line
13
a
is formed on a glass substrate
35
. The lead-out portion
33
b
is formed as it is led out to the side of the gate bus line
13
a
. A gate insulating film
37
is formed immediately on the gate bus line
13
a
, and the pixel electrode
27
b
is formed on the lead-out portion
33
b
through a protection film
39
.
For example, as shown in
FIG. 27
in the upper right part, when the gate bus line
13
a
is disconnected at a disconnection portion
41
, the defect is repaired as follows. More specifically, the disconnection portion
41
is located between the TFT
15
b
and the data bus line
11
c
, and therefore a laser beam is irradiated upon a laser irradiation position
43
shown at the upper right corner of the pixel electrode
27
b
. The irradiation energy of the laser beam causes the pixel electrode
27
b
and the metal forming the lead-out portion
33
b
immediately below to be melted, connected and short-circuited. Thus, the right end of the disconnection portion
41
of the gate bus line
13
a
is electrically connected with the pixel electrode
27
b
through the lead-out portion
33
b.
Similarly, a laser beam is irradiated upon laser irradiation positions
45
on the side of the source electrode
21
b
of the TFT
15
b
to short-circuit the source electrode
21
b
and the left end of the disconnection portion
41
of the gate bus line
13
a
. A laser beam is also irradiated upon a laser irradiation position
47
shown on the proximal side of the data bus line
11
b
to electrically isolate the drain electrode
17
b
from the data bus line
11
b
. Thus, the disconnection portion
41
of the gate bus line
13
a
is short-circuited by the pixel electrode
27
b
and the disconnection defect is repaired.
According to the above-described defect repairing method, the repair success ratio can hardly be increased.
FIG. 29
is a sectional view of the device when a laser beam is irradiated upon the laser beam irradiation position
43
shown in FIG.
27
. The distance d between the lower layer gate bus line
13
a
and the upper layer pixel electrode
27
b
is for example as thick as 800 nm. Therefore, as shown in
FIG. 29
, if the metal forming the lower layer gate bus line
13
a
as thick as 100 nm for example melts with the irradiation of a laser beam
49
, only a small area is short-circuited with the upper layer pixel electrode
27
b
, and sometimes almost no short circuit is formed.
In order to reduce the manufacturing cost, it is strongly desirable to improve the manufacturing yield. As one means therefor, there is a strong demand to increase the repair success rate for repairing defect portions.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a liquid crystal display device which allows disconnection defects caused in the manufacturing process to be readily repaired with a higher success rate than conventional cases so that the device can be modified into a non-defective device, and a defect repairing method therefor.
The above-described object is achieved by a liquid crystal display device including a lead-out portion led out from a bus line formed on a substrate and extending at an under layer of a pixel electrode through an insulating film, and an isolated intermediate conductive layer formed in the insulating film between said lead-out portion and said pixel electrode.
According to the present invention
Kawai Satoru
Ozaki Kiyoshi
Tsukao Kouji
Chung David
Fujitsu Limited
Parker Kenneth
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