Liquid crystal cells – elements and systems – Nominal manufacturing methods or post manufacturing...
Reexamination Certificate
2001-08-22
2003-11-25
Chowdhury, Tarifur R. (Department: 2871)
Liquid crystal cells, elements and systems
Nominal manufacturing methods or post manufacturing...
C349S042000, C349S043000, C257S059000, C257S072000
Reexamination Certificate
active
06654094
ABSTRACT:
BACKGROUND OF INVENTION
1. Field of the Invention
The present invention provides a method of fabricating a thin-film-transistor liquid-crystal-display (TFT-LCD), more particularly, a method of making the TFT-LCD by a five-masks process with redundant interconnections.
2. Background of the Invention
Due to the continued development and advancement in electrical technology, the range of application of a flat panel display is also increased. The kinds of the present flat panel display include liquid crystal displays (LCD), plasma display panels (PDP), electro-luminescent displays (ELD), field-emission displays (FED) light emitting diode displays (LED), and vacuum fluorescent displays (VFD).
A TFT-LCD usually includes a plurality of thin film transistors with a matrix structure, capacitors, and connecting pads to drive a plurality of liquid crystal pixels so as to generate color-rich graphics. A conventional LCD includes a transparent substrate having a matrix of thin film transistors, pixel electrodes, scan lines, signal lines, a color filter substrate, and a layer of liquid crystal materials positioned between the transparent substrate and the color filter substrate. Since the TFT-LCD is the advantages of lightweight, low energy consumption, and radiation free, it is employed in various portable electronic devices such as a notebook and PDA. Further, the TFT-LCD is slowly replacing the CRT of desktop computers.
Please refer to FIG.
1
.
FIG. 1
is a layout diagram of the conventional thin film transistor liquid crystal display (TFT-LCD)
10
. The conventional TFT-LCD
10
is manufactured on a transparent glass substrate
11
. As shown, on the glass substrate
11
are at least a thin film transistor(TFT)
40
, a plurality of scan lines
12
, and a plurality of signal lines
14
which are perpendicular to the scan lines
12
. In the TFT-LCD
10
, each thin film transistor
40
includes a gate electrode
42
, a source
43
, and a drain
44
. Each TFT is used to drive a corresponding pixel electrode
16
, which is made of indium tin oxide (ITO) layer, on the substrate
11
. The gate electrode
42
, usually made of polysilicon, is formed with the scan lines
12
at the same time. The source
42
and the drain
44
respectively connect with the pixel electrode
16
and the signal lines
14
via contact holes
46
and
48
. For simplicity, other components of the TFT-LCD
10
, such as the capacitor and connecting pad are omitted in FIG.
1
.
According to the prior art, a redundant transparent conductive line
30
is formed to prevent short circuit of the signal lines
14
. The redundant transparent conductive line
30
is formed above the signal line
14
and simultaneously formed with the pixel electrode
16
. The transparent conductive line
30
is an ITO layer, and connects with the source electrode
43
, drain electrode
44
, and the signal line
14
through a source contact hole
46
, a drain contact hole
48
and a signal line contact hole
52
, respectively.
Usually, the signal lines
14
and the scan lines
12
are formed on different surfaces, this is to say, at least one layer is formed between the signal line
14
and the scan line
12
, such as a semiconductor layer or an insulating layer. Hence, a short circuit may occur at the crossing region
32
of the signal lines
14
and scan lines
12
because the uneven surface of the intersection
32
. To solve the problem, the ITO line
30
is formed over the signal line
14
to be a redundant line in the conventional method. The redundant line
30
can establish a connection with the signal line
14
via the signal line contact hole
52
, so as to transmit the signal even a short circuit of the signal line
14
is happened at the crossing region
32
.
However, the redundant ITO line
30
may be connected to the pixel electrode
16
because of the contaminants produced in the manufacturing process, resulting in a short circuit or a point defect, and the yield of the TFT-LCD
10
is reduced. In
FIG. 1
, the defect region marked by a dotted frame
50
represents the most likely region of the point defects. Thus, reducing the point defect is important in improving the yield of the TFT-LCD
10
.
SUMMARY OF INVENTION
It is therefore a primary object of the present invention to provide a method of fabricating a thin film transistor liquid crystal display (TFT-LCD) to minimize the defect region, so as to increase the yield of the TFT-LCD.
REFERENCES:
patent: 5714769 (1998-02-01), Kim
patent: 6480244 (2002-11-01), Murade et al.
patent: 2002/0044231 (2002-04-01), Yeo et al.
patent: 2002/0093016 (2002-07-01), Lim et al.
patent: 2002/0130324 (2002-09-01), Song et al.
patent: 2002/0171083 (2002-11-01), Lim et al.
patent: 2002/0171781 (2002-11-01), Kim
AU Optronics Corp.
Chowdhury Tarifur R.
Hsu Winston
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