Liquid crystal display and fabricating method thereof

Details Liquid crystal display and fabricating method thereof Liquid crystal display and fabricating method thereof

2001-08-08

2003-09-09

Niebling, John F. (Department: 2812)

Liquid crystal cells, elements and systems

Particular structure

Having significant detail of cell structure only

Reexamination Certificate

active

06618110

ABSTRACT:

The present invention claims the benefit of Korean Patent Application No. P2000-45944 filed on Aug. 8, 2000 in Korea, which is hereby incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a liquid crystal display, and more particularly to a liquid crystal display and a fabricating method thereof.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) controls light transmissivities of liquid crystal cells in response to video signals. An active matrix LCD provided with a switching device for each liquid crystal cell is suitable for displaying moving images. A thin film transistor (TFT) is used as a switching device in the active matrix LCD.
FIG. 1
is a plan view showing a structure of a conventional LCD, and
FIG. 2
is a cross-sectional view of the conventional LCD along A-A′ in FIG.
1
.
In
FIGS. 1 and 2
, the conventional LCD includes a TFT having a gate electrode
13
, agate insulating film
15
and an active layer
17
disposed on a substrate
11
. The LCD also includes a source electrode
21
and a drain electrode
23
on the active layer
17
, and a pixel electrode
29
that is electrically connected to the drain electrode
23
via a contact hole
27
. The TFT applies a data signal from a data line
24
to a pixel electrode
29
during a period in which a scanning pulse is applied to the gate electrode
13
. The gate electrode
13
is electrically connected to the gate line
14
while the source electrode
21
is electrically connected to the data line
24
. The drain electrode
23
is electrically connected to the pixel electrode
29
via a contact hole
27
formed in a protective layer
25
. The pixel electrode may be formed of a conductive material such as indium-tin-oxide (ITO), indium-zinc-oxide (IZO) or indium-tin-zinc-oxide (ITZO). The gate insulating film
15
may be formed of an inorganic insulating material and the source electrode
21
, the data line
24
, and the active layer
17
may be formed on the gate insulating film
15
. The protective layer
25
may be made from an inorganic insulating material or an organic material.
FIGS. 3A
to
3
E show a process of fabricating the conventional LCD shown in FIG.
1
and in particular shows the TFT portion of the LCD.
In
FIG. 3A
, aluminum (Al) or a copper (Cu) is deposited on a transparent substrate
11
by a sputtering process, for example, to form a metallic thin film. The metallic thin film is patterned by photolithographic and wet etching processes, thereby forming the gate electrode
13
.
In
FIG. 3B
, a gate insulating film
15
is formed on the transparent substrate
11
to cover the gate electrode
13
. The gate insulating film
15
is formed by deposition of an insulation material such as silicon oxide or silicon nitride. An active layer
17
and an ohmic contact layer
19
are sequentially formed on the gate insulating film
15
by a chemical vapor deposition (CVD) process, wherein the active layer
17
is formed from an amorphous silicon or a polycrystalline silicon that is not doped with an impurity. The ohmic contact layer
19
is made from an amorphous silicon or polycrystalline silicon doped with an n-type or p-type impurity at a high concentration The ohmic contact layer
19
and the active layer
17
are patterned by photolithographic and anisotropic etching processes, thereby exposing the gate insulating film
15
. Portions of the active layer
17
and the ohmic contact layer
19
remain only at a portion corresponding to the gate electrode
13
.
In
FIG. 3C
, molybdenum (Mo) or a molybdenum alloy such as molybdenum-tungsten (MoW), molybdenum tantalum (MoTa) or molybdenum-niobium (MoNb), is deposited on the gate insulating film
15
by a CVD or sputtering process to cover the ohmic contact layer
19
. The metal or the metal alloy deposited in this manner makes ohmic contact to the ohmic contact layer
19
. Then, the metal or the metal alloy is patterned, along with the ohmic contact layer
19
, by photolithographic and etching processes, thereby exposing a portion of the active layer directly above the gate electrode
13
and forming the source electrode
21
and the drain electrode
23
.
In
FIG. 3D
, an inorganic insulating material such as silicon nitride or silicon oxide, or an organic insulation material having a small dielectric constant such as an acrylic organic compound, Teflon, BCB (benzocyclobutane), Cytop or PFCB (perfluorocyclobutane), is deposited on the gate insulating layer
15
, thereby forming a protective layer
25
. Then, a contact hole
27
is formed in the protective layer
25
exposing the drain electrode
23
.
In
FIG. 3E
, a transparent conductive material such as ITO, IZO or ITZO is deposited onto the protective layer
25
and into the contact hole
27
, thereby forming the pixel electrode
29
. The pixel electrode
29
electrically contacts with the drain electrode
23
via the contact hole
27
.
However, in the conventional LCD, since the contact hole must be formed in the protective layer to electrically connect the drain electrode to the pixel electrode, an aperture ratio is reduced and a complicated process is required.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to a liquid crystal display and fabricating method thereof that substantially obviate one or more of the problems due to limitations and disadvantages of the related art.
An object of the present invention to provide a liquid crystal display and a fabricating method thereof wherein a drain electrode and a pixel electrode are connected to each other without any contact hole, thereby increasing an aperture ratio.
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 learned by practice of the invention. The objective and other advantages of the invention will be realized and attained by the structure and method 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 a liquid crystal display device includes a transparent substrate, a gate electrode disposed on the transparent substrate, a gate insulating film disposed on the transparent substrate and covering the gate electrode, an active layer disposed on the gate insulating film an ohmic contact layer disposed on the active layer, a source electrode disposed on the ohmic contact layer and at one side of the gate electrode, a drain electrode disposed on the ohmic contact layer and at another side of the gate electrode, the drain electrode including an L-shaped portion and a plurality of protrusions, a protective layer disposed on the active layer covering upper surfaces of the source electrode and the drain electrode, and a pixel electrode disposed on the protective layer and electrically contacting a side surface of the drain electrode.
In another aspect, a method of fabricating a liquid crystal display device includes the steps of forming a gate electrode on a transparent substrate, forming a gate insulating film, an active layer and an ohmic contact layer on the transparent substrate to cover the gate electrode, forming a source electrode and a drain electrode on the ohmic contact layer and patterning the drain electrode to form an L-shaped portion and a plurality of protrusions, forming a protective layer on the source and drain electrodes such that side surfaces of the protective layer, the drain electrode, the ohmic contact layer and the active layer are exposed, and forming a pixel electrode on the protective layer to electrically contact the side surface of the drain electrode.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.


REFERENCES:
patent: 6266117 (2001-07-01), Yanagawa
patent: 6278504 (2

Affiliated with

Also associated with

Rating

Liquid crystal display and fabricating method thereof does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Liquid crystal display and fabricating method thereof, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Liquid crystal display and fabricating method thereof will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3073919