Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing... – Defect correction or compensation
Reexamination Certificate
2002-02-11
2003-09-30
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
Defect correction or compensation
C349S038000, C349S039000, C349S043000, C349S187000
Reexamination Certificate
active
06628368
ABSTRACT:
This application incorporates by reference of Taiwan application Serial No. 90104273, filed on Feb. 23, 2001.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates in general to a liquid crystal display (LCD) capable of being repaired and method for repairing the same, and more particularly to a LCD capable of being repaired for detects in data lines and method for the same.
2. Description of the Related Art
Liquid crystal displays are widely used because of having low radiation and compactness. For high-end products, thin film transistor LCDs (TFT-LCDs) are employed due to high brightness and wide view angles. In order to make products more competitive, manufacturers make efforts in the increase in yields and the reduction in cost.
A conventional TFT-LCD has a front plate and a rear plate. The front plate includes a number of transparent pixel electrodes, color filters, and black matrices. The rear plate includes a number of scan lines, data lines, storage capacitors, switching elements (e.g., TFTs), and transparent pixel electrodes.
FIG. 1
illustrates a pixel layout of a conventional TFT-LCD. The TFT-LCD has a number of scan lines
102
and data lines
104
perpendicularly intersecting the scan lines
102
, thus forming a number of pixel regions. Each of the pixel regions is defined by a corresponding scan line and data line. Each pixel region includes a storage capacitor Cs, a TFT, and a transparent pixel electrode
106
. The TFT is formed with a drain electrode G, a drain electrode D, and a source electrode S, and a channel
110
. The scan lines
102
are connected to the gate electrodes of the TFTs while the data lines
104
are connected to the drain electrodes of the TFTs. The transparent pixel electrode
106
is coupled to the source electrode of the corresponding TFT.
FIG. 2
is a cross-sectional view taken along line AA′ of FIG.
1
. Referring to
FIGS. 1 and 2
, a conventional method for manufacturing a TFT is described below.
First, after a plate
202
is provided, a first metal layer is formed and then patterned to form a gate electrode G. Next, an isolation layer
204
is formed on the plate
202
and is used to cover the gate electrode G. An amorphous-Si (a-Si) layer is formed on the isolation layer
204
and then patterned to form the channel
110
. After that, a second metal layer is formed, covering the channel
110
and the isolation layer
204
. By performing a photolithography process on the second metal layer, the drain electrode D and the source electrode S are formed. Next, a protection layer
206
is formed on the drain electrode D and source electrode S so as to cover the isolation layer
204
. The contact
108
is then formed within the protection layer
206
, thus causing the protection layer
206
to expose the source electrode S through the contact
108
. Finally, the transparent pixel electrode
106
is formed over the protection layer
206
and fills the contact
108
so that the transparent pixel electrode
106
is electrically coupled to the source electrode S.
The scan lines
102
and data lines
104
are respectively formed during the patterning of the gate and the source/drain (S/D) electrodes. The isolation layer
204
is used to separate the scan lines
102
and data lines
104
.
FIG. 3
is a cross-sectional view taken along line BB′ of FIG.
1
. With reference to
FIGS. 1
,
2
, and
3
, a conventional method for manufacturing a storage capacitor is described below.
A storage capacitor Cs is formed with a common electrode
112
and a capacitor electrode
114
while the common electrode
112
and capacitor electrode
114
are separated by the isolation layer
204
. The storage capacitor Cs is formed together with the formation of the TFT. The common electrode
112
is formed after the formation and patterning of the first metal layer. Likewise, after the formation and patterning of the second metal layer, the capacitor electrode
114
is formed. The protection layer
206
covers the capacitor electrode
114
and the isolation layer
204
. A contact
116
is formed within the protection layer
206
. When the transparent pixel electrode
106
is formed over the protection layer
206
, the transparent pixel electrode
106
and the capacitor electrode
114
are electrically coupled through the contact
116
. In addition, storage capacitors of all pixels of the TFT-LCD have their common electrodes connected to a common voltage of the TFT-LCD.
Unfortunately, defects may occur during the manufacturing of the common electrodes of the storage capacitors Cs and thus degrade the quality of the TFT-LCD. For example, when cracks or undesired particles occur on the plate
202
, the common electrode
112
is formed with defects. In the worst case, the common electrode
112
may be disconnected due to serious defects. In additional, the common electrodes of all the storage capacitors Cs are coupled to the respective scan lines
102
. Therefore, when disconnection occurs in one of the common electrodes, such as the common electrode
112
, the other common electrodes that share the identical scan line with the common electrode
112
would have their signal path opened so that their associated storage capacitors cannot operate. In another case, defects that occur in the isolation layer
204
of the storage capacitor Cs due to undesired particles on the plate
202
during the manufacturing process may result in the capacitor electrode
114
and the common electrode
112
short-circuited. If the two electrodes are short-circuited, a signal on one scan line associated with the short circuit will interfere with the common electrodes on the scan line and the storage capacitors Cs on the same scan line cannot operate properly.
A conventional approach to solving the problems due to the defects is to break the connection of the TFT and the transparent pixel electrode of a pixel having a malfunctioned storage capacitor Cs so as to prevent the short-circuited common electrode
112
from affecting the other storage capacitors along the associated scan line. However, the pixel associated with the malfunctioned storage capacitor Cs cannot be lighted.
In addition, disconnection may also occur in the data lines
104
due to defects or notching occurred during the formation of the data lines
104
by patterning the second metal layer. When the disconnection of the data lines
104
occurs, the data lines
104
operate improperly. In the worst case, the entire rear plate of the LCD may be useless due to serious disconnection of the data lines
104
. Conventionally, repair cannot be made directly on the rear plate where the disconnection of the data lines
104
occurs. To compensate for the problem due to the disconnection of the data lines
104
, operations performed by a control circuit of the rear plate should be particularly designed. However, the control circuit can only be designed to perform compensating operations on a limited number of data lines disconnected. If an increased number of disconnected data lines are required, the cost of the control circuit for the requirement increases correspondingly.
SUMMARY OF THE INVENTION
It is therefore an object of the invention to provide a liquid crystal display (LCD) capable of being repaired for defects in data lines and storage capacitors of the LCD, and a method for repairing the same. According to the invention, at least two storage capacitors are employed in each pixel, a first and a second ring-type conductors are connected and formed between two adjacent scan lines and correspond to the data line associated with the pixel. The problems due to the defects in data lines and storage capacitors of the LCD can be resolved. In addition, the LCD has an increased yield and a reduced cost.
The invention achieves the above-identified object by providing a liquid crystal display capable of being repaired for defects in data lines. The liquid crystal display includes multiple scan lines, multiple data lines, multiple transparent pixel electrodes, multiple switching devices, multiple first storag
Chi Mei Optoelectronics Corp.
Chowdhury Tarifur R.
Groden Ruth
Rabin & Berdo P.C.
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