Electric lamp and discharge devices – Discharge devices having a thermionic or emissive cathode
Reexamination Certificate
1998-04-08
2003-02-18
Patel, Ashok (Department: 2879)
Electric lamp and discharge devices
Discharge devices having a thermionic or emissive cathode
Reexamination Certificate
active
06522053
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a field emission element for allowing electrons to be emitted from a surface of a metal or a semiconductor by utilizing a field emission phenomenon, a method of fabricating the element, and a field emission display using the field emission element.
A field emission element, which allows electrons to be emitted from a solid due to no thermal excitation, is typically used for an electron source for drive of a FED (Field Emission Display).
As such a field emission element, there has been known a Spindt type in which a cold cathode for emitting electrons is formed into a pyramid or cone shape.
A method of fabricating the related art Spindt type field emission element will be described with reference to
FIGS. 27A
to
27
C and
FIGS. 28A and 28B
.
As shown in
FIG. 27A
, a cathode electrode
101
made from chromium (Cr), niobium (Nb), tantalum (Ta), tungsten (W) or the like is formed into a specific pattern on a glass substrate
100
. A gate electrode
103
made from Cr, Nb, Ta, W or the like is formed into a pattern crossing the pattern of the cathode electrode
101
on the cathode electrode
101
through a silicon oxide (SiO
2
) film
102
. A resist film
104
is formed on the gate electrode
103
, and an opening
105
is formed in the resist film
104
at a specific position by photolithography. Then, the gate electrode
103
is etched using the resist film
104
as an etching mask, to form an opening
106
having a diameter of about 1 &mgr;m in the gate electrode
103
.
As shown in
FIG. 27B
, the SiO
2
film
102
is etched through the opening
106
of the gate electrode
103
, to form a through-hole
107
in the SiO
2
film
102
. At this time, the SiO
2
film
102
is side-etched, so that as shown in
FIG. 27B
, the through-hole
107
is slightly wider than the opening
106
of the gate electrode
103
.
As shown in
FIG. 27C
, the resist film
104
is removed and a peeling layer
108
made from aluminum (Al) or the like is formed on the gate electrode
103
by oblique vapor-deposition.
As shown in
FIG. 28A
, a metal material such as molybdenum (Mo) or W or a semiconductor material such as diamond is vapor-deposited in the direction substantially perpendicular to the substrate
100
, to form a vapor-deposition layer
109
on the gate electrode
103
, and also to form, through the opening
106
of the gate electrode
103
, a cathode cone (or emitter cone)
110
made from the above material on a portion of the cathode electrode
101
exposed in the through-hole
107
of the SiO
2
film
102
.
Then, as shown in
FIG. 28B
, the peeling layer
108
is removed by dissolution, to peel the vapor-deposition layer
109
on the gate electrode
103
.
With these steps, a Spindt type field emission element is formed in which the cathode cone
110
as a field emission source is provided in the fine opening
106
formed in the gate electrode
103
.
The field emission element thus formed is used as an electron source for drive of a display such as a FED.
For example, as shown in
FIG. 29
, when a specific voltage Vg is applied between the gate electrode
103
and the cathode electrode
101
of one selected from the field emission elements arranged in a matrix pattern corresponding to a matrix pattern of pixels, there occurs concentration of an electric field at a peak portion of the cathode cone
110
. This allows electrons to be emitted from the peak portion of the cathode cone
110
. The electrons thus emitted are accelerated by a voltage Va applied between the gate electrode
103
and a transparent electrode
111
as an anode, and then collide with a phosphor screen
112
, thereby allowing light emission of the phosphor screen
112
.
In the above-described related art Spindt type field emission element, field emission characteristics thereof are largely affected by a distance between the opening
106
of the gate electrode
103
and the peak portion of the cathode cone
110
. On the other hand, such a distance is dependent on in-plane uniformity of thickness of the vapor-deposition film
109
, and more specifically, the distance varies depending on the amplified non-uniformity of the film thickness. Accordingly, for example, in order to fabricate a display having uniform field emission characteristics, the above step of forming the vapor-deposition layer
109
is required to be carried out such that the vapor-deposition film
109
is uniformly formed at a high accuracy over the entire surface of the substrate.
However, it has been very difficult to form the vapor-deposition film
109
uniformly at a high accuracy over the entire surface of a large-area substrate, and therefore, it has failed to realize a large-area display with a high quality.
Another problem of the related art Spindt type field emission element is that the fabricating yield has been poor because of contamination of the element occurring upon peeling of the vapor-deposition layer
109
.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a field emission element having a structure capable of relatively easily, uniformly controlling a distance between a gate electrode and an electron emitting portion of a cathode electrode, a method of manufacturing the element, and a display using the element.
Another object of the present invention is to provide a field emission element having a structure without requiring a step of peeling a vapor-deposition layer, a method of fabricating the element, and a display using the element.
To achieve the above objects, according to a first aspect of the present invention, there is provided a field emission display having a field emission element, the field emission element including: a first electrode, and a second electrode laminated to the first electrode through an insulating layer, the first electrode having an opening, the second electrode having a hole of a planar shape corresponding to that of the opening at a position matched with the opening, the insulating layer having a through-hole continuous to the opening and the hole; wherein an upper edge portion of the hole is formed into a cross-sectional shape having an edge angle in a range of 80 to 100°; and at least part of the upper edge portion of the hole is exposed in the through-hole; whereby electrons are emitted from the second electrode through the upper edge portion of the hole exposed in the through-hole by applying a specific voltage between the first electrode and the second electrode.
According to a second aspect of the present invention, there is provided a method of fabricating a field emission display, including the steps of: forming a first electrode layer on an insulating substrate; forming an insulating layer on the first electrode layer; forming a second electrode layer on the insulating layer; forming an opening in the second electrode layer at a specific position; etching the insulating layer through the opening of the second electrode layer, to form in the insulating layer a through-hole continuous to the opening of the second electrode layer and wider than the opening; and anisotropic-etching the first electrode layer through the opening of the second electrode layer and the through-hole of the insulating layer, to form in the first electrode layer a hole continuous to the through-hole of the insulating layer and having a planer shape being substantially the same as that of the opening of the second electrode layer.
According to a third aspect of the present invention, there is provided a method of fabricating a field emission display, including the steps of: forming a first insulating layer on a conductive substrate or semiconductor substrate; forming a first electrode layer on the first insulating layer; forming a second insulating layer on the first electrode layer; forming a second electrode layer on the second insulating layer; forming an opening in the second electrode layer at a specific position; etching the second insulating layer through the opening of the second electrode layer, to form in the second insulating layer a
Iwase Yuichi
Okita Masami
Kananen, Esq. Ronald P.
Patel Ashok
Rader & Fishman & Grauer, PLLC
Sony Corporation
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