Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
2001-10-31
2003-09-16
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C438S151000, C438S158000, C438S161000, C438S578000, C349S114000
Reexamination Certificate
active
06620655
ABSTRACT:
This application claims the benefit of Korean patent application Nos. 2000-64739 and 2000-64740, both filed on Nov. 1, 2000 in Korea, which is hereby incorporated by reference as if fully set forth herein.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly to a transflective liquid crystal display (LCD) device implementing selectable reflective and transmissive modes.
2. Discussion of the Related Art
Generally, a transflective LCD device has advantages of both a transmissive LCD device and a reflective LCD device. Because the transflective LCD device uses a back light as well as an ambient light source, it is not dependent upon exterior light source conditions, and consumes relatively low power.
FIG. 1
is an exploded perspective view illustrating a typical transflective LCD device. The transflective LCD device
11
includes an upper substrate
15
and a lower substrate
21
that are opposed to each other, and a liquid crystal layer
23
interposed therebetween. The upper substrate
15
and the lower substrate
21
are called a color filter substrate and an array substrate, respectively. On the upper substrate
15
, a black matrix
16
and a color filter layer
17
including a plurality of red (R), green (G), and blue (B) color filters are formed. The black matrix
16
surrounds each color filter such that an array matrix feature is formed. Further on the upper substrate
15
, a common electrode
13
is formed to cover the color filter layer
17
and the black matrix
16
.
On the lower substrate
21
opposing the upper substrate
15
, thin film transistors (TFTs) “T”, as switching elements, are formed in shape of an array matrix corresponding to the color filter layer
17
. In addition, a plurality of crossing gate and data lines
25
and
27
are positioned such that each TFT “T” is located near each crossing portion of the gate and data lines
25
and
27
. The crossing gate and data lines define a pixel region “P”. On the pixel region “P”, a pixel electrode
19
is formed. The pixel electrode
19
includes a transmissive portion “A” and a reflective portion “C”.
FIG. 2
is a schematic cross-sectional view illustrating operation modes of the typical transflective LCD device
11
. As shown, the transflective LCD device
11
includes the upper substrate
15
having the common electrode
13
, the lower substrate
21
having the pixel electrode
19
, the liquid crystal layer
23
interposed therebetween, and a back light
41
disposed below the lower substrate
21
. The pixel electrode
19
includes a reflective electrode
19
b
having a through-hole “A” and a transparent electrode
19
a
positioned below the reflective electrode
19
b
. The transparent electrode
19
a
is separated from the reflective electrode
19
b
by a passivation layer
20
interposed therebetween.
For a reflective mode, the transflective LCD device
11
uses a first ray “B” of ambient light, which may radiate from an exterior natural light source or from an exterior artificial light source. The first ray “B” passes through the upper substrate
15
and is reflected by the reflective electrode
19
b
back through the liquid crystal layer
23
, which is aligned by the application of an electric field between the reflective electrode
19
b
and the common electrode
13
. Accordingly, the aligned liquid crystal layer
23
controls the first ray “B” so as to display an image.
For a transmissive mode, the transflective LCD device
11
uses a second ray “F” of light, which radiates from the back light
41
. The second ray “F” sequentially passes through the transparent electrode
19
a
, the through-hole “A” of reflective electrodes
19
b
and the liquid crystal layer
23
which is aligned by the application of an electric field between the transparent electrode
19
a
and the common electrode
13
. Accordingly, the aligned liquid crystal layer
23
controls the second ray “F” so as to display an image.
FIG. 3
is an expanded plan view illustrating a portion of an array substrate for a conventional transflective LCD device. As shown in
FIG. 3
, gate lines
25
are arranged in a transverse direction, and data lines
27
are arranged perpendicular to the gate lines
25
. Both the gate lines
25
and the data lines
27
are formed upon an array substrate
21
(in FIG.
1
), and a pair of gate lines
25
and data lines
27
define a pixel region “P”. Each of thin film transistors (TFTs) “T” is arranged at a position where both the gate line
25
and the data line
27
cross one another. A pixel electrode
19
comprising both a transparent electrode
19
a
and a reflective electrode
19
b
is disposed on the pixel region “P” defined by the gate line
25
and data line
27
.
Each TFT “T” includes a gate electrode
32
to which a scanning signal is applied, a source electrode
33
to which a video signal is applied, and a drain electrode
35
which inputs the video signal to the pixel electrode
19
. Further, each TFT “T” includes an active layer
34
between the source electrode
33
and the drain electrode
35
. A portion of the gate line
25
defines a storage capacitor “S” with a portion of the pixel electrode
19
. Furthermore, gate pads
29
and data pads
31
are respectively disposed at end portions of gate lines
25
and data lines
27
. The gate pads
29
and the data pads
31
are to be electrically connected with a drive IC (not shown).
Still referring to
FIG. 3
, the pixel electrode
19
is a transflective electrode having both the transparent electrode
19
a
and the reflective electrode
19
b
. Specifically, the transparent electrode
19
a
is first formed on the pixel region “P”, and is electrically connected with the drain electrode
35
. Then, the reflective electrode
19
b
is formed over the transparent electrode
19
a
, and is also electrically connected with the drain electrode
35
via the transparent electrode
19
a
. Thus, the reflective electrode
19
b
has a through hole “A” corresponding to a transmissive portion of the LCD device
11
such that rays of back light
41
(in
FIG. 2
) can pass through the through hole “A” for function in the transmissive mode. Portion “C” of the reflective electrode
19
b
serves as a reflective portion of the LCD device
11
such that rays of the ambient light are thereby reflected.
In the above-mentioned structure, however, two patterning processes are respectively required when forming the transparent electrode
19
a
and the reflective electrode
19
b
. At this time of patterning, the transparent electrode
19
a
and the reflective electrode
19
b
are corroded by an etching solution due to Galvanic corrosion. Accordingly, to solve this problem, an insulator (e.g., the passivation layer
20
of
FIG. 2
) is interposed between the transparent electrode
19
a
and the reflective electrode
19
b.
With reference to
FIGS. 4A
to
4
D,
5
A to
5
D and
6
A to
6
D, a fabrication process for the conventional array substrate is explained.
FIGS. 4A
to
4
D are sequential cross-sectional views taken along line IV—IV of
FIG. 3
,
FIGS. 5A
to
5
D are sequential cross-sectional views taken along line V—V of
FIG. 3
, and
FIGS. 6A
to
6
D are sequential cross-sectional views taken along line VI—VI of FIG.
3
.
At first, as shown in
FIGS. 4A
,
5
A and
6
A, a first metal is deposited and patterned upon a transparent substrate
21
such that a gate pad
29
, a gate line
25
, and a gate electrode
32
are formed. For the first metal, aluminum (Al) or aluminum neodymium (AlNd) is conventionally employed. The gate line
25
extends from and is connected with the gate pad
29
, and the gate electrode
32
protrudes from the gate line
25
(in FIG.
3
). Thereafter, a gate-insulating layer
43
is formed on the transparent substrate
21
to cover the metal layer previously formed. The gate-insulating layer
43
may be an inorganic substance, such as silicon nitride (SiN
x
) or silicon oxide (SiO
2
). Subsequently, amorphous silicon (a-Si) and impurity-doped amorphous silico
Choi Jae-Beom
Ha Kyoung-Su
Kim Woong-Kwon
Kwon Oh-Nam
Lee Kyoung-Muk
Isaac Stanetta
LG.Phillips LCD Co., Ltd.
Mckenna Long & Aldridge
Niebling John F.
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