Electric lamp or space discharge component or device manufacturi – Process – With assembly or disassembly
Reexamination Certificate
2000-08-31
2002-07-30
Ramsey, Kenneth J. (Department: 2879)
Electric lamp or space discharge component or device manufacturi
Process
With assembly or disassembly
Reexamination Certificate
active
06425791
ABSTRACT:
BACKGROUND OF THE INVENTION
1. The Field of the Invention
The present invention relates to field emission devices. More particularly, the present invention relates to field emission devices having a buffer layer, and to methods of making and using the field emission devices.
2. The Relevant Technology
Integrated circuits are currently manufactured by an elaborate process in which semiconductor devices, insulating films, and patterned conducting films are sequentially constructed in a predetermined arrangement on a semiconductor substrate. In the context of this document, the term “semiconductor substrate” is defined to mean any construction comprising semiconductive material, including but not limited to bulk semiconductive material such as a semiconductive wafer, either alone or in assemblies comprising other materials thereon, and semiconductive material layers, either alone or in assemblies comprising other materials. The term “substrate” refers to any supporting structure. As used herein, “field emission device” is defined to mean any construction for emitting electrons in the presence of an electrical field, including but not limited to an electron emission tip or tip either alone or in assemblies comprising other materials or structures. “Electron emission apparatus” refers to one or more field emission devices or any structure or product including one or more field emission devices.
Recently, miniaturization of structures within integrated circuits has focused attention and effort to incorporating field emission devices within semiconductor substrates. A field emission device typically includes an electron emission tip, or tip, configured for emitting a flux of electrons upon application of an electric field to the field emission device. An array of miniaturized field emission devices can be arranged on a plate and used for forming a visual display on a display panel. Indeed, field emission devices have been shown to be a promising alternative to cathode ray tube display devices. For example, field emission devices may be used in making flat panel display devices for providing visual display for computers, telecommunication, and other graphics applications. Flat panel display devices typically have a greatly reduced thickness compared to the generally bulky cathode ray tubes.
Field emission devices ordinarily include various structures formed from successive layers during the manufacturing process.
FIG. 1
illustrates a portion of a conventional flat panel display, including a plurality of field emission devices. Flat panel display
10
comprises a baseplate
12
and a face plate
14
. Baseplate
12
includes substrate
16
, which is preferably formed from an insulative glass material. Column interconnects
18
are formed and patterned over substrate
16
. The purpose and function of column interconnects
18
is disclosed in greater detail below. Furthermore, a resistor layer
20
, which is also discussed in greater detail below, may be disposed over column interconnects
18
. Electron emission tips
22
are formed over substrate
16
at the sites from which electrons are to be emitted, and may be constructed in an etching process from a layer of amorphous silicon that has been deposited over substrate
16
. Electron emission tips
22
are protrusions that may have one of many shapes, such as pyramids, cones, or other geometries that terminate at a fine point for the emission of electrons.
An extraction grid
24
, or gate, which is a conductive structure that supports a positive charge relative to the electron emission tips
22
during use, is separated from substrate
16
with a dielectric layer
26
. Extraction grid
24
includes openings
28
through which electron emission tips
22
are exposed. Dielectric layer
26
electrically insulates extraction grid
24
from electron emission tips
22
and the associated column interconnects which electrically connect the emission tips with a voltage source
30
.
Face plate
14
includes a plurality of pixels
32
, which comprise cathodoluminescent material that generates visible light upon being excited by electrons emitted from electron emission tips
22
. For example, pixels
32
may be red/green/blue full-color triad pixels. Face plate
14
further includes a substantially transparent anode
34
and a glass or another transparent panel
36
. Spatial support structures
39
are disposed between baseplate
12
and face plate
14
and prevents the face plate from collapsing onto the baseplate due to air pressure differentials between the opposite sides of the face plate. In particular, the gap between face plate
14
and baseplate
12
is typically evacuated, while the opposite side of the face plate generally experiences ambient atmospheric pressure.
The flat panel display is operated by generating a voltage differential between electron emission tips
22
and grid structure
24
using voltage source
30
. In particular, a negative charge is applied to electron emission tips
22
, while a positive charge is applied to grid structure
24
. The voltage differential activates electron emission tips
22
, whereby a flux of electrons
40
is emitted therefrom. In addition, a relatively large positive charge is applied to anode
34
using voltage source
30
, with the result that flux of electrons
40
strikes the face plate. The cathodoluminescent material of pixels
32
is excited by the impinging electrons, thereby generating visible light. The coordinated activation of multiple electron emission tips over the flat panel display
10
may be used to produce a visual image on face plate
16
.
FIGS. 2 and 3
further illustrate field emission devices of the prior art. In particular, electron emission tips
22
are grouped into discrete emitter sets
42
, in which the bases of the electron emission tips in each set are commonly connected. As shown in
FIG. 3
, for example, emitter sets
42
are configured into columns (e.g., C
1
-C
3
) in which the individual emitter sets
42
in each column are commonly connected. Additionally the extraction grid
24
is divided into grid structures, with each emitter set
42
being associated with an adjacent grid structure. In particular, a grid structure is a portion of extraction grid
24
that lies over a corresponding emitter set
42
and has openings
28
formed therethrough. The grid structures are arranged in rows (e.g., R
1
-R
3
) in which the individual grid structures are commonly connected in each row. Such an arrangement allows an X-Y addressable array of grid-controlled emitter sets. The two terminals, comprising the electron emission tips
22
and the grid structures, of the three terminal cold cathode emitter structure (where the third terminal is anode
34
in face plate
14
of
FIG. 1
) are commonly connected along such columns and rows, respectively, by means of high-speed interconnects. In particular, column interconnects
18
are formed over substrate
16
, and row interconnects
44
are formed over the grid structures.
In operation, a specific emitter set is selectively activated by producing a voltage differential between the specific emission set and the associated grid structure. The voltage differential may be selectively established through corresponding drive circuitry that generates row and column signals that intersect at the location of the specific emitter set. Referring to
FIG. 3
, for example, a row signal along for R
2
of the extraction grid
24
and a column signal along column C
1
of emitter sets
42
activates the emitter set at the intersection of row R
2
and column C
1
. The voltage differential between the grid structure and the associated emitter set produces a localized electric field that causes emission of electrons from the selected emitter set.
Early field emission devices were assembled without resistor layer
20
and suffered from uneven emission between different electron emission tips
22
, with the result that noticeably bright and dim spots were produced on the screens of the flat panel displays. The problem of uneven emission was signif
Alwan James J.
Raina Kanwal K.
Micro)n Technology, Inc.
Ramsey Kenneth J.
Workman & Nydegger & Seeley
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