U.S. patent application number 09/739823 was filed with the patent office on 2001-10-04 for thin film transistor substrate and fabricating method thereof.
Invention is credited to Lee, Hyun Kyu.
Application Number | 20010025988 09/739823 |
Document ID | / |
Family ID | 19635164 |
Filed Date | 2001-10-04 |
United States Patent
Application |
20010025988 |
Kind Code |
A1 |
Lee, Hyun Kyu |
October 4, 2001 |
Thin film transistor substrate and fabricating method thereof
Abstract
A thin film transistor substrate having a structure in which a
thin film transistor array is formed on color filters. In the
substrate, a thin film transistor is formed on the color filters. A
smoothing layer compensates for step coverage between the color
filters and is provided with a recess in which a gate electrode of
the thin film transistor is to be formed. Accordingly, step
coverage in the gate electrode is eliminated, so that it becomes
possible to manufacture a large-dimension panel without a
limitation to the thickness and profile of the gate electrode.
Inventors: |
Lee, Hyun Kyu; (Seoul,
KR) |
Correspondence
Address: |
BIRCH STEWART KOLASCH & BIRCH
PO BOX 747
FALLS CHURCH
VA
22040-0747
US
|
Family ID: |
19635164 |
Appl. No.: |
09/739823 |
Filed: |
December 20, 2000 |
Current U.S.
Class: |
257/347 ;
257/350; 257/E29.137; 257/E29.283; 427/402; 427/58; 438/149;
438/584 |
Current CPC
Class: |
G02F 1/136222 20210101;
G02F 1/133357 20210101; G02F 1/1368 20130101; H01L 29/78636
20130101; H01L 29/42384 20130101 |
Class at
Publication: |
257/347 ; 427/58;
427/402; 438/584; 257/350; 438/149 |
International
Class: |
B05D 001/36; B05D
005/12; H01L 021/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 31, 1999 |
KR |
P99-68077 |
Claims
What is claimed is:
1. A thin film transistor substrate including color filters,
comprising: a thin film transistor formed on the color filters; and
a smoothing layer compensating for a step coverage between the
color filters and being provided with a recess in which a gate
electrode of the thin film transistor is to be formed.
2. The thin film transistor substrate according to claim 1, wherein
the recess of the smoothing layer has the same bulk as the gate
electrode.
3. A method of fabricating a thin film transistor substrate having
a thin film transistor formed on color filters, comprising the
steps of: forming the color filters on a transparent substrate;
forming a smoothing layer on the color filters and then pattering
it to thereby define a recess in which a gate electrode of the thin
film transistor is to be formed; and forming the thin film
transistor on the smoothing layer.
4. The method according to claim 3, wherein the recess of the
smoothing layer has the same bulk as the gate electrode.
5. The method according to claim 3, wherein said step of forming
the thin film transistor includes: forming the gate electrode in
the recess of the smoothing layer; and sequentially forming a gate
insulating film, a semiconductor layer and source and drain
electrodes on the gate electrode and the smoothing layer.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] This invention relates to a thin film transistor substrate,
and more particularly to a thin film transistor substrate that has
a structure in which a thin film transistor array is formed on
color filters. Also, the present invention is directed to a method
of fabricating such a thin film transistor substrate.
[0003] 2. Description of the Related Art
[0004] Generally, in a liquid crystal display (LCD) having a thin
film transistor array provided on color filters, a thin film
transistor substrate includes color filters formed on a transparent
substrate; and switching devices of thin film transistors (TFT's)
consisting of gate electrodes, a gate insulating film, an active
layer, an ohmic contact layer and source and drain electrodes, and
pixel electrodes, each of which is provided on the color
filters.
[0005] FIG. 1 is a section view showing a structure of a
conventional thin film transistor substrate having a thin film
transistor array provided on color filters. Referring to FIG. 1,
the thin film transistor substrate includes a black matrix 4 formed
in a lattice shape on a transparent substrate 2 to divide the
substrate 2 into a plurality cell areas in which color filter is to
be formed and to prevent a color interference between the cell
areas. On the transparent substrate 2 divided into cell units by
means of the black matrix 4, red, green and blue color filters 6
for transmitting the respective red, green and blue color lights
are provided. The color filters 6 are made from an acrylic or
polyimide resin dispersed with pigments, and formed on the black
matrix 4 to be separated from each other for the purpose of
preventing a color mixture. On the surfaces of the color filters 6
is coated a smoothing layer 8 for preventing a contamination in the
color filters 6 and for compensating for a step coverage or
morphological difference between the red, green and blue color
filters 6 formed separately to smooth the substrate. A gate
electrode 10 is formed on the smoothing layer 8. The gate electrode
10 is formed by depositing a gate metal material, that is, any one
of metal materials such as Al, Mo, Cr, Ta and an Al alloy or
building a double layer of the metal materials on the smoothing
layer 8 and thereafter patterning it. On the smoothing layer formed
with the gate electrode 10, a gate insulating film 11 made from
SiN.sub.X or SiO.sub.X, etc. is provided. A semiconductor layer 12
and an ohmic contact layer 14 are formed by disposing amorphous
silicon (a-Si) and amorphous silicon (n.sup.+ a-Si) doped with an
impurity on the gate insulating film 11 and then patterning it.
Source and drain electrodes 16 and 18 are formed by depositing a
metal such as Al, Mo, Cr, Ta or an Al alloy, etc. and then
pattering it. A pixel electrode 22 is made by forming a protective
film from a material of SiN.sub.X or SiO.sub.X, etc. and a
transparent electrode material (e.g., indium tin oxide (ITO)) and
thereafter patterning them.
[0006] As described above, the conventional thin film transistor
substrate inevitably requires the smoothing layer 8 so as to
compensate for step coverage between the red, green and blue color
filters 6. However, the smoothing layer 8 does not make a little
effect to a step coverage removal in the thin film transistor
formed at the upper portion of the smoothing layer 8. In the thin
film transistor, a badness may occur at the layers (i.e., the
semiconductor layer and the source and drain electrodes) disposed
in the post process due to a step coverage in the gate electrode.
Upon manufacturing of a large-dimension panel, it is necessary to
form the gate electrode into a double metal layer for the sake of a
good signal transmission. However, since a step coverage in the
gate electrode is enlarged in the case of forming the gate
electrode into a double metal layer, it becomes difficult to form a
double layer of gate electrode and a material selection of the gate
electrode is limited.
SUMMARY OF THE INVENTION
[0007] Accordingly, it is an object of the present invention to
provide a thin film transistor substrate wherein a gate electrode
is provided within a smoothing layer so as to compensate for step
coverage in a thin film transistor.
[0008] A further object of the present invention is to provide a
method of fabricating a thin film transistor substrate wherein a
gate electrode is provided within a smoothing layer so as to
compensate for step coverage in a thin film transistor.
[0009] In order to achieve these and other objects of the
invention, a thin film transistor substrate according to one aspect
of the present invention includes a thin film transistor formed on
color filters; and a smoothing layer compensating for a step
coverage between the color filters and being provided with a recess
in which a gate electrode of the thin film transistor is to be
formed.
[0010] A method of fabricating a thin film transistor substrate
according to another aspect of the present invention includes the
steps of forming color filters on a transparent substrate; forming
a smoothing layer on the color filters and then pattering it to
thereby define a recess in which a gate electrode of the thin film
transistor is to be formed; and forming the thin film transistor on
the smoothing layer.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] These and other objects of the invention will be apparent
from the following detailed description of the embodiments of the
present invention with reference to the accompanying drawings, in
which:
[0012] FIG. 1 is a section view showing a conventional thin film
transistor substrate having a color filter on array structure;
[0013] FIG. 2 is a section view showing a thin film transistor
substrate having a color filter on array structure according to an
embodiment of the present invention; and
[0014] FIG. 3A to FIG. 3C are section views for explaining a method
of fabricating the thin film transistor substrate shown in FIG.
3.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0015] Referring to FIG. 2, there is shown a thin film transistor
substrate according to an embodiment of the present invention in
which a thin film transistor array is formed on color filters. The
thin film transistor substrate includes a black matrix 26 and color
filters 28 formed on a transparent substrate 24, a patterned
smoothing layer 30 formed on the color filters 28, a gate electrode
32, a gate electrode 32 provided at the patterned portion of the
smoothing layer 30, a thin film transistor consisting of a gate
insulating film 34, a semiconductor layer 36, an ohmic contact
layer 38 and source and drain electrodes 40 and 42, and a pixel
electrodes 46. The smoothing layer 30 formed on the color filters
30 has a recess with the same size as the gate electrode 32 defined
at a position where the gate electrode 32 is to be formed. The gate
electrode 32 is formed in the recess of the smoothing layer 30.
Thus, step coverage of the gate electrode 32 is eliminated. As a
result, a limit to the thickness and profile of the gate electrode
32 is removed, so that it becomes not only easy to provide the gate
electrode 32 having a double metal layer structure essential to a
large-dimension panel, but also a wide selection for a material of
the gate electrode 32 becomes possible.
[0016] FIG. 3A to FIG. 3C explains a method of fabricating the thin
film transistor substrate according to an embodiment of the present
invention. Referring to FIG. 3A, the black matrix 36 and the color
filter 28 are formed on the transparent substrate 24. the black
matrix 36 is formed in a lattice shape on a transparent substrate 2
to divide the substrate 2 into a plurality cell areas in which
color filter is to be formed and to prevent a color interference
between the cell areas. On the transparent substrate 24 divided
into cell units by means of the black matrix 26, red, green and
blue color filters 28 are separately provided so as to transmit the
respective red, green and blue color lights.
[0017] As shown in FIG. 3B, a smoothing layer 30 is coated on the
color filters 28 so as to prevent a contamination in the color
filters 28 and compensate for a step coverage or morphological
difference between the red, green and blue color filters 28 formed
separately. Then, a portion where the gate electrode is to be
formed in the smoothing layer 30 is patterned to define a recess
30A having the same position and size as the gate electrode.
[0018] Subsequently, as shown in FIG. 3C, the thin film transistor
consisting of the gate electrode 32, the gate insulating film 34,
the semiconductor layer 36, the ohmic contact layer 38 and the
source and drain electrodes 40 and 42, the protective film 44 and
the pixel electrode 46 are formed on the smoothing layer 30. The
gate electrode 32 is provided at the recess 30A of the smoothing
layer 30. The gate electrode 32 is formed from any one of metal
materials such as Al, Mo, Cr, Ta and an Al alloy, or a double layer
of the metal materials. Thereafter, the semiconductor layer 36 and
the ohmic contact layer 38 is formed by entirely coating the gate
insulating film 34 made from SiN.sub.X or SiO.sub.X, etc. thereon
and by disposing an amorphous silicon (a-Si) and an amorphous
silicon (n.sup.+ a-Si) doped with an impurity on the gate
insulating film 34 and then patterning it. The source and drain
electrodes 40 and 42 are formed by depositing a metal such as Al,
Mo, Cr, Ta or an Al alloy, etc. and then pattering it. The
protective film 44 is formed from a material of SiN.sub.X or
SiO.sub.X, etc. over the entire substrate and then patterned to
define a contact hole. A transparent electrode material (e.g.,
indium tin oxide (ITO)) is formed on the protective film 44 and
then patterned to provide the pixel electrode 46, thereby
completing the thin film transistor substrate. The pixel electrode
46 is electrically connected, via the contact hole, to the drain
electrode 42.
[0019] As described above, according to the present invention, the
gate electrode is formed in the recess defined by patterning the
smoothing layer of the color filters to thereby eliminate step
coverage in the gate electrode. Accordingly, a limit to the
thickness and profile of the gate electrode 32 is removed, so that
it becomes not only easy to provide the gate electrode 32 having a
double metal layer structure essential to a large-dimension panel,
but also a wide selection for a material of the gate electrode 32
becomes possible.
[0020] Although the present invention has been explained by the
embodiments shown in the drawings described above, it should be
understood to the ordinary skilled person in the art that the
invention is not limited to the embodiments, but rather that
various changes or modifications thereof are possible without
departing from the spirit of the invention. Accordingly, the scope
of the invention shall be determined only by the appended claims
and their equivalents.
* * * * *