Semiconductor device manufacturing: process – Making field effect device having pair of active regions... – On insulating substrate or layer
Reexamination Certificate
1999-01-06
2001-11-27
Niebling, John F. (Department: 2812)
Semiconductor device manufacturing: process
Making field effect device having pair of active regions...
On insulating substrate or layer
C438S030000, C438S609000
Reexamination Certificate
active
06323068
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a liquid crystal display device, and more particularly, to a liquid crystal display device in which a pixel driving thin film transistor(TFT) and a driver circuit region are integrated on the same panel.
2. Discussion of the Related Art
An active matrix liquid crystal display used for a liquid crystal display (LCD) with large area and high resolution includes a pixel driving TFTs for driving display pixels and a driver circuit TFTs for applying signals to gate bus lines and data bus lines coupled to the pixel driving TFTs.
In general, there are two types of driver circuit unit. The first one is such that the driver circuit unit is a separate integrated circuit for driving signal lines, and the integrated circuit is attached to one end of the substrate of the liquid crystal panel. The second type is such that the driver circuit unit is formed on an LC panel as one piece. In the second type, typically, complementary metal oxide semiconductor TFTs (CMOS TFTs) using polycrystalline silicon (p-Si) with a high electric field effect mobility have been used for the driver circuit. Since these CMOS TFTs are made of p-Si, the switching speed is much higher than that for amorphous silicon TFTs. Further, because the driver circuit TFTs and the pixel driving TFTs may be fabricated at the same time, the fabrication cost can be reduced.
FIG. 1A
to
FIG. 1H
are drawings showing a method of fabricating a conventional liquid crystal display device integrated with a driver circuit. A substrate
1
is divided into a pixel region and a driver circuit region. The driver circuit region is further divided into a part B for N-channel metal oxide semiconductor TFTs(NMOS TFTs) and a part A for P-channel metal oxide semiconductor TFTs(PMOS TFTs).
As shown in
FIG. 1A
, a buffer layer
3
is provided on the substrate
1
, and then p-Si is deposited on the buffer layer
3
and patterned to form semiconductor layers
4
a,
4
b,
4
c
in the pixel region and the driver circuit region. As a result, one semiconductor layer
4
c
is provided on the pixel region and two semiconductor layers
4
a,
4
b
are formed on the driver circuit region. The semiconductor layer
4
c
formed on the pixel region is for a pixel driving TFT for driving the pixel. The semiconductor layers
4
b,
4
c
are for NMOS and PMOS TFTs, respectively.
As shown in
FIG. 1B
, an insulating layer
5
, such as SiO
2
or SiNx, a metal layer
6
, such as Al, Al alloy, or Cr, and photoresist
20
a
are successively formed over the substrate
1
. The insulating layer
5
and the metal layer
6
are patterned by photolithography to form a gate insulating layer
5
and gate electrodes
6
a,
6
b,
6
c,
as shown in FIG.
1
C. Subsequently, as shown in
FIG. 1D
, n
−
doping in low impurity-concentration is executed into the entire surface of the substrate
1
to form an n
−
layer
12
b
and a channel layer
12
a
in each of the semiconductor layers
4
a,
4
b,
4
c.
Here, the n
−
type ions are blocked by the gate electrodes
6
a,
6
b,
6
c,
and do not reach the channel layer
12
a.
Thereafter, as shown in
FIG. 1E
, in order to form a lightly doped drain (LDD) structure, n
+
doping in high impurity concentration is executed after a photoresist layer
20
b
is deposited over the substrate and patterned to cover part A of the driver circuit region, the gate electrode
6
c,
and some part of the semiconductor layer
4
c
of the pixel region.
Accordingly, n
+
layers
12
c
are formed by the n
+
doping in the semiconductor layers of the pixel region and part B of the driver circuit region. The LDD structure is made by forming n
+
layer
12
c
with high impurity-concentration and n
−
layer
12
b
with low impurity-concentration in the semiconductor layer
4
c
of the pixel region.
As shown in
FIG. 1F
, after photoresist layer
20
b
is removed, another photoresist layer
20
c
is deposited and patterned to cover the pixel region and part B of the driver circuit region. Then, p
+
doping with high impurity-concentration is executed to form p
+
layer
12
d
in part A of the driver circuit region.
Such a method of forming a p
+
layer is called a counter doping method. When the n
−
doping is executed, the concentration of ions doped in the semiconductor layers is about 10
16
-10
18
atoms/cm
3
, and when the p
+
doping is executed, the concentration of ions doped in the semiconductor layer is about 10
19
-10
21
atoms/cm
3
. Therefore, the n
−
layer becomes a p
+
layer by the p
+
doping. This way, TFTs having an LDD structure including the n
+
layers
12
c
and n
−
layers
12
b
are formed in the pixel region, and CMOS TFTs having NMOS TFTs including the n
+
layers
12
c
and PMOS TFTs including the p
−
layers
12
d
are formed in the driver circuit region.
As shown in
FIG. 1G
, after the photoresist layer
20
c
is removed, an insulating layer
7
, such as SiNx or SiO
2
, is deposited over the entire surface of the substrate
1
. Contact holes are then formed in the insulating layer
7
, and a metal such as Al is deposited and patterned to form source/drain electrodes
8
.
And, as shown in
FIG. 1H
, after indium tin oxide (ITO) is deposited and patterned to form a transparent electrode
9
[a passivation layer
10
is further deposited]. Finally, TFTs having an LDD structure are formed in the pixel region and CMOS TFTs are formed in the driver circuit region, thereby completing a liquid crystal display device integrated with a driver circuit.
However, the liquid crystal display device integrated with a driver circuit formed by the above-mentioned method have complex processes.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a liquid crystal display device integrated with a driving circuit and a method for fabricating the same that substantially obviates one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention is to provide a liquid crystal display device integrated with a driver circuit in which source/drain electrodes and bus lines have high reliability against disconnection and which has a simpler fabrication process.
Additional features and advantages of the invention will be set forth in the description which follows, and in part 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 particularly pointed out in the written description and claims hereof as well as the appended drawings.
To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described, the present invention provides a method for fabricating a liquid crystal display device integrated with a driver circuit on a substrate, a surface of the substrate being divided into a P-channel region, an N-channel region, and a pixel region, the method including the steps of forming a gate electrode on each of the P-channel, N-channel, and pixel regions of the substrate; forming a gate insulating layer on the entire surface of the substrate including the gate electrodes; forming a first transparent electrode layer over the gate insulating layer; forming a conductive layer over the first transparent electrode layer; forming a second transparent electrode layer over the conductive layer; removing portions of the first transparent electrode layer, the conductive layer, and the second transparent electrode layer to form source/drain electrodes adjacent the gate electrodes in each of the P-channel, N-channel, and pixel regions of the substrate; doping first impurities into the second transparent electrode layer in the P-channel region; doping second impurities into the second transparent electrode layer in the N-channel region and in the pixel region; forming a semiconductor layer over the entire
LG Electronics Inc.
Morgan & Lewis & Bockius, LLP
Niebling John F.
Stevenson André
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