Electric lamp and discharge devices – With luminescent solid or liquid material – Vacuum-type tube
Reexamination Certificate
1999-02-25
2002-08-13
Patel, Vip (Department: 2879)
Electric lamp and discharge devices
With luminescent solid or liquid material
Vacuum-type tube
C313S309000, C313S336000, C313S351000, C445S024000, C445S050000, C445S051000
Reexamination Certificate
active
06433473
ABSTRACT:
FIELD OF THE INVENTION
The present claimed invention relates to the field of flat panel displays. More particularly, the present claimed invention relates to the formation of a row electrode for a flat panel display screen structure.
BACKGROUND ART
Field emission display devices are typically comprised of numerous layers. The layers are formed or deposited using various fabrication process steps. Prior Art
FIG. 1A
is a schematic side sectional view of a portion of a pristine conventional field emission display structure. More specifically, Prior Art
FIG. 1A
illustrates an emitter electrode layer
100
having an overlying resistive layer
102
and an overlying inter-metal dielectric layer
104
. Field emitter structures, typically shown as
106
a
and
106
b
, are shown disposed within cavities formed into inter-metal dielectric layer
104
. A gate electrode
108
is shown disposed above inter-metal dielectric layer
104
. As mentioned above, Prior Art
FIG. 1
schematically illustrates a portion of a pristine conventional field emission display structure. However, conventional field emission display structures are typically not pristine. That is, manufacturing and fabrication process variations often result in the formation of a field emission display structure containing significant defects.
With reference next to Prior Art
FIG. 1B
, a side sectional view of a portion of a defect-containing field emission display structure is shown. During the fabrication of conventional field emission display structures, the aforementioned layers are often subjected to caustic or otherwise deleterious substances. Specifically, during the fabrication of various overlying layers, emitter electrode layer
100
is often subjected to processes which adversely affect the integrity of emitter electrode
100
. As shown in the embodiment of Prior Art
FIG. 1B
, certain fabrication process steps can deleteriously etch or corrode emitter electrode
100
. In fact, some conventional fabrication processes can result in the complete removal of at least portions of emitter electrode
100
. Such degradation of emitter electrode
100
can render the field emission display device defective and even inoperative.
With reference next to Prior Art
FIG. 1C
, a side sectional view of a portion of another defect containing field emission display structure is shown. In addition to unwanted corrosion or etching of the emitter electrode, other defects can occur which degrade or render the field emission display structure inoperable. In the embodiment of Prior Art
FIG. 1C
, feature
110
represents a “short” extending between emitter electrode
100
and gate electrode
108
. Such shorting can occur in a conventional field emission display device when the emitter electrode is not properly insulated from the gate electrode. That is, if a region on the conductive surface of the emitter electrode is exposed and, therefore, not properly insulated from the gate electrode, shorting to the gate electrode can occur. Portions of the emitter electrode may remain exposed when deposition of various layers over the emitter electrode is not consistent or complete, or when the layers are degraded (e.g. etched or corroded) by subsequent process steps. The inconsistent deposition or degradation of the layers between the emitter electrode and the gate electrode can result in the existence of non-insulative paths which extend from the emitter electrode to the gate electrode. Such a short can render the field emission display device defective and even inoperative. All of the above-described defects result in decreased field emission display device reliability and yield.
Referring now to Prior Art
FIG. 1D
, a simplified schematic top plan view of emitter electrode and gate electrode orientation is shown. As shown in Prior Art
FIG. 1D
, emitter electrodes
150
,
152
,
154
, and
156
are typically the display row electrodes and are conventionally disposed underlying gate electrodes
158
,
160
, and
162
which are typically display column electrodes. Only a few emitter and column electrodes are shown in Prior Art
FIG. 1D
for purposes of clarity. It will be understood, however, that in a conventional field emission display device numerous additional emitter and column electrodes will be present.
Referring still to Prior Art
FIG. 1D
, during typical operation, one of row electrodes
150
,
152
,
154
, and
156
will have a current driven therethrough. A desired one of column electrodes
158
,
160
, and
162
has an electrical potential applied with respect to the row electrodes such that the subpixel located at the intersection of the activated column and emitter electrode emits electrons. It will be understood that in conventional field emission display devices each subpixel has a corresponding intersection of an emitter and a column. For example, when emitter electrode
150
has current passed therethrough and column electrode
158
has a potential applied thereto, the subpixel corresponding to the intersection of emitter electrode
150
and column electrode
158
will emit electrons. Additionally, in conventional field emission display devices, subpixels are oriented in rows across the display. Therefore, when current is passed through a row electrode each and every subpixel in that row is activated (the subpixel emits electrons only when the corresponding column electrode has the said electrical potential applied thereto). Thus, the current in the row electrode must supply all the subpixels in that row. For purposes of the present discussion it will be assumed that the current is driven through row electrodes
150
,
152
,
154
, and
156
by drivers
164
,
166
,
168
, and
170
, respectively. That is, in the representation of Prior Art
FIG. 1D
, the current is passed through row electrodes
150
,
152
,
154
, and
156
from left to right. As a result of activating each and every subpixel in the row (i.e. sharing the row electrode current between all of the subpixels), a subpixel corresponding to, for example, the intersection of row electrode
150
and column
158
will be more brightly illuminated than the subpixel corresponding to, for example, the intersection of row electrode
150
and column
160
due to the voltage drop along the row caused by the emitter current drain from each activated subpixel. This decrease or “drop-off” in the brightness of subpixels adversely affects the characteristics of a field emission display device.
Furthermore, the emitter electrodes must also be protected from degradation during subsequent processing. The emitter electrodes must also be manufactured and utilized in a manner which reduces shorts occurring between the emitter electrode and the gate electrode.
Thus, a need exists for a field emission display device wherein display characteristics such as display brightness are not degraded by current drain across the length of the row electrode. Still another a need exists for a field emission display structure which is less susceptible to emitter electrode degradation. A further need exists for a gate electrode structure and gate electrode formation method for use in a field emission display device wherein the gate electrode reduces the occurrence of gate to emitter shorts.
SUMMARY OF INVENTION
The present invention provides a field emission display device wherein display characteristics such as display brightness are not degraded by current drain across the length of the row electrode. The present invention further provides a field emission display structure which is less susceptible to emitter electrode degradation. The present invention also provides a gate electrode structure and gate electrode formation method for use in a field emission display device wherein the gate electrode reduces the occurrence of gate to emitter shorts.
Specifically, in one embodiment, the present invention provides a structure and method for forming a column (sometimes referred to as “row”) electrode for a field emission display device wherein the column (or row) electrode is disposed beneath the field
Chakravorty Kishore K.
Hansen Ronald L.
Nadi Fariborz
Spindt Christopher J.
Stanners Colin D.
Candescent Intellectual Property Services Inc.
Haynes Mack
Patel Vip
Wagner , Murabito & Hao LLP
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