Active solid-state devices (e.g. – transistors – solid-state diode – Thin active physical layer which is – Low workfunction layer for electron emission
Reexamination Certificate
2003-01-22
2004-11-02
Baumeister, Bradley (Department: 2815)
Active solid-state devices (e.g., transistors, solid-state diode
Thin active physical layer which is
Low workfunction layer for electron emission
C438S020000, C313S309000, C313S310000, C313S336000, C313S351000, C445S049000, C445S050000, C445S051000
Reexamination Certificate
active
06812480
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application claims the priority of Korean Patent Application No. 2002-3687, filed on Jan. 22, 2002, which is incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a field emission display device having carbon nanotubes and a method of fabricating the same, and more particularly, to a field emission display device in which an alignment error between a gate electrode and a cathode electrode due to high-temperature firing does not occur, and a method of fabricating the same.
2. Description of the Related Art
Display apparatuses used for personal computers (PCs) and television receivers include cathode-ray tubes, liquid crystal displays (LCDs), plasma display panels (PDPs), and field emission displays (FEDs), which use high-speed thermionic emission.
FEDs using carbon nanotubes is much more advantageous than cathode-ray tubes in a wide view angle, high resolution, low power, and temperature stability. Such FEDs can be applied to various fields such as car navigation apparatuses and view finders of electronic video equipment. Particularly, FEDs can be used as alterative display apparatuses for PCs, personal data assistants (PDAs), medical instruments, high definition television (HDTV), and so on.
FIG. 1
is a diagram showing the structure of a conventional field emission display device. Referring to
FIG. 1
, the conventional field emission display device includes a substrate
1
; an indium tin oxide (ITO) electrode layer
2
formed on the substrate
1
; a mask cathode layer
3
formed on the ITO electrode layer
2
such that the ITO electrode layer
2
is partially exposed; an insulation layer
5
formed on the mask cathode layer
3
such that a well
8
is formed; a gate electrode
6
formed in the shape of a strip on the insulation layer
5
; and an electron emitting source
31
including carbon nanotubes formed on the ITO electrode layer
2
exposed at the bottom of the well
8
.
FIGS. 2A through 2J
are diagrams showing the stages in a procedure of forming a triode structure before printing carbon nanotube paste in a conventional method of fabricating a field emission display device.
As shown in
FIG. 2A
, the ITO electrode layer
2
is formed on the substrate
1
, and the mask electrode layer
3
is deposited on the ITO electrode layer
2
. The substrate
1
is made of glass, and the mask cathode layer
3
is made of a material such as a metal or amorphous silicon which blocks ultraviolet rays.
As shown in
FIG. 2B
, photoresist
11
-
1
is deposited on the mask cathode layer
3
; a mask
71
-
1
is disposed above the mask cathode layer
3
; and ultraviolet rays are radiated for exposure. After exposure, etching and cleaning are performed, thereby forming a hole
4
in the mask electrode layer
3
, as shown in FIG.
2
C.
As shown in
FIG. 2D
, the insulation layer
5
is formed on the mask cathode layer
3
and is then fired at a temperature higher than 550° C. for an insulation characteristic. Thereafter, the gate electrode
6
is deposited on the insulation layer
5
, as shown in FIG.
2
E.
FIG. 2F
shows a photoprocess including exposure, development, etching, and cleaning for patterning the gate electrode
6
. Reference numeral
71
-
2
denotes a mask, and reference numeral
11
-
2
denotes photoresist. If the photoprocess is completed, the gate electrode
6
having a hole
7
, as shown in FIG.
2
G. Thereafter, wet or dry etching is performed to etch the insulation layer
5
and the mask cathode layer
3
, thereby forming the well
8
such that the ITO cathode layer
2
is partially exposed at the bottom of the well
8
, as shown in FIG.
2
H.
As shown in
FIG. 2I
, after photoresist
11
-
3
is deposited and a mask
71
-
3
is disposed, a photoprocess is performed, thereby patterning the gate electrode
6
in the shape of a strip, as shown in FIG.
2
J.
In the above-described conventional method of fabricating a field emission display device, the substrate
1
made of glass may be deformed by the heat during high-temperature firing, so an alignment mark may be displaced. Due to displacement of the alignment mark, the center of the hole
4
of the mask cathode layer
3
does not exactly meet the center of the well
8
after the gate electrode
6
is deposited and patterned, as shown in FIG.
2
I. As a result, the electron emitting source
31
is displaced from the center of the well
8
to the right or left. Due to an alignment error between the gate electrode
6
and the electron emitting source
31
, the gate electrode
6
may become in contact with or very close to the ITO cathode layer
2
, resulting in current leak or a decrease in the amount of electrons emitted.
FIGS. 2K through 2Q
are diagrams showing the stages in a procedure of making carbon nanotubes into an electron emitting source in the triode structure formed by the procedure including the stages shown in
FIGS. 2A through 2J
in the conventional method.
In injecting carbon nanotube paste into the well
8
, a lift-off method using a sacrificial layer, a method of performing direct alignment and injecting carbon nanotube paste, or a rear exposure method can be used. When the method of performing direct alignment and injecting carbon nanotube paste is used, it is difficult to achieve a high aspect ratio due to an alignment error in equipment and viscosity of a carbon nanotube material. In the rear exposure method, since a sacrificial layer is not used, a large amount of residues are produced.
Accordingly, a lift-off process using photoresist as a sacrificial layer is generally used, as shown in
FIGS. 2K through 2Q
, in fabricating an electron emitting source using carbon nanotube paste.
Referring to
FIG. 2K
, photoresist
11
-
4
is deposited on the substrate
1
having a triode structure shown in
FIG. 2J
such that the well
8
, the insulation layer
5
, and the gate electrode
6
are covered with the photoresist
11
-
4
. Thereafter, a photoprocess is performed, thereby etching the photoresist
11
-
4
only formed in the well
8
, except for the photoresist
11
-
4
formed on the insulation layer
5
and the gate electrode
6
, as shown in FIG.
2
I.
After the etching step, as shown in
FIG. 2M
, carbon nanotube paste
12
is injected into the well
8
by a screen printing method and is deposited on the entire surface of the photoresist
11
-
4
, and then rear exposure is performed. Here, the photoresist
11
-
4
is used as a sacrificial layer.
If the rear exposure is completed, as shown in
FIG. 2N
, the carbon nanotube paste
12
is divided into exposed carbon nanotube paste
13
and non-exposed carbon nanotube paste
13
′. This happens because the carbon nanotube paste
13
′ positioned in front the mask cathode layer
3
is not exposed to ultraviolet rays.
Thereafter, development using a developer such as acetone or Na
2
CO
3
(0.4% wt) is performed. As a result, the exposed carbon nanotube paste
13
remains, but the non-exposed carbon nanotube paste
13
′ is lifted off simultaneously with diffusion of the photoresist
11
-
4
as a sacrificial layer to the developer, so carbon nanotube paste
14
having a shape shown in
FIG. 2O
can be obtained. Here, residue
14
′ of the non-exposed carbon nanotube paste
13
′ may not dissolves in the developer, or some of the exposed carbon nanotube paste
13
may be exposed to the developer, so carbon nanotube paste may adhere to the gate electrode
6
or the insulation layer
5
.
Thereafter, the resultant structure shown in
FIG. 2O
is fired at a nitrogen atmosphere at a high temperature of about 460° C., thereby shrinking the carbon nanotube paste
14
to form a shrunken carbon nanotube paste
15
, as shown in FIG.
2
P. Then, the surface of the carbon nanotube paste
15
is mechanically processed to reveal carbon nanotubes sunken into the carbon nanotube paste
15
, thereby forming the electron emitting source
31
, as shown in FIG.
2
Q. The residue
14
′ still remains.
The residue
14
′
Lee Hang-woo
Lee Sang-jin
Park Shang-hyeun
Baumeister Bradley
Samsung SDI & Co., Ltd.
LandOfFree
Triode structure field emission display device using carbon... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Triode structure field emission display device using carbon..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Triode structure field emission display device using carbon... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3309772