Semiconductor device manufacturing: process – Electron emitter manufacture
Reexamination Certificate
1999-10-05
2001-10-02
Bowers, Charles (Department: 2813)
Semiconductor device manufacturing: process
Electron emitter manufacture
Reexamination Certificate
active
06297067
ABSTRACT:
This application is based on Japanese patent application No. 10-285661 filed on Oct. 7, 1998, the entire contents of which are incorporated herein by reference as non-essential subject matter.
BACKGROUND OF THE INVENTION
a) Field of the Invention
The present invention relates to a field emission element, and more particularly to manufacturing technologies for a field emission element having a field emission cathode from the tip of which electrons are emitted.
b) Description of the Related Art
A field emission element emits electrons from a sharp tip of an emitter (electron emission cathode) by utilizing electric field concentration. For example, a flat panel display can be structured by using a field emitter array (FEA) having a number of emitters disposed on the array. Each emitter controls the luminance of a corresponding pixel of the display.
In order to apply an electric field to the emitter tip of a field emission element and emit electrons therefrom, the gate electrode biased to a positive potential relative to the emitter (cathode) is disposed near the emitter electrode.
An increase in an emission current from the emitter (i.e., a lowered threshold voltage between the gate and emitter), a high speed drive, and the like are requisites for a field emission element. In order to provide these requisites, it is necessary to devise the structure and shape of a field emission element. It is also necessary to devise a manufacture method in order to manufacture such a field emission element stably and reliably.
A low threshold voltage between the gate and emitter can be achieved by making the distance between the emitter and gate electrode surfaces as gate hole of a gate electrode
100
has a rectangular cross section. There is a danger of a short circuit between the gate and emitter electrodes if a distance between the surface of the emitter electrode
110
and the upper edge of the gate electrode
100
is made short. From this reason, the gate electrode
100
cannot be disposed too near the emitter electrode
110
.
If a thickness t of the gate electrode
100
is made large, an electric field at the tip of the emitter electrode
110
becomes high so that the threshold voltage between the gate and emitter can be lowered without reducing an emission current. In other words, a larger emission current can be obtained without raising a voltage between the gate and emitter. Further, if the thickness t of the gate electrode
100
is made large, the wiring resistance of the gate electrode
100
becomes low so that a high speed drive becomes possible. However, if the thickness t of the gate electrode
100
having a rectangular cross section of the gate hole such as shown in
FIG. 16
is made large, the danger of the short circuit at the upper edge of the gate electrode
100
increases. In order to avoid this, it is necessary to set a longer distance between the tip surface of the emitter electrode
110
and the surface of the gate electrode
100
by reducing the thickness t. It is therefore difficult to lower the threshold voltage.
Another requisite for a field emission element is a sharp tip of the emitter electrode
110
. Namely, if an apex angle of the tip of the emitter electrode
110
is made small, the electric field at the tip of the emitter electrode
110
becomes high. It is therefore possible to lower a threshold voltage between the gate and emitter without reducing an emission current, and hence obtain a large emission current without raising a voltage between the gate and emitter. From this reason, it is an important issue to adopt a manufacture method capable of easily sharpening the tip of an emitter electrode
110
having a desired shape.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a manufacture method for a field emission element having a structure capable of increasing an emission current from the emitter (i.e., lowering a threshold voltage between the gate and emitter) and executing a high speed drive.
It is another object of the invention to provide a manufacturing method for a field emission element having a structure capable of disposing the emitter and gate electrodes as near as possible.
It is another object of the invention to provide a manufacture method for a field emission element capably of sharpening the tip of the emitter electrodes to a large extent.
According to one aspect of the present invention, there is provided a method of manufacturing a field emission element, comprising the steps of: (a) forming a surface layer including a gate film made of a conductive material on a substrate; (b) forming a resist pattern on the surface layer by photolithography, the resist pattern having an opening with a predetermined shape; (c) reflowing the resist pattern to make the opening have an inner diameter gradually reducing toward the substrate; (d) anisotropically etching the gate film by using the reflowed resist pattern as a mask to form an opening through the gate film, the opening having an inner diameter reducing gradually toward the substrate; (e) forming a first sacrificial film covering the gate film having the opening; (f) forming an emitter film made of a conductive material on the first sacrificial film; and (g) removing a portion or a whole of the substrate and a portion of the first sacrificial film to expose the emitter film and the gate film.
According to another aspect of the present invention, there is provided a method of manufacturing a field emission element, comprising the steps of: (a) forming a surface layer including a gate film made of a conductive material on a substrate; (b) forming a low melting point film on the surface layer by photolithography, the low melting point film having a melting point lower than a melting point of the surface layer and an opening with a predetermined shape; (c) reflowing the low melting point film to make the opening have an inner diameter gradually reducing toward the substrate; (d) anisotropically etching the gate film by using the reflowed low melting point film as a mask to form an opening through the gate film, the opening having an inner diameter reducing gradually toward the substrate; (e) forming a first sacrificial film covering the gate film having the opening and/or the low melting point film; (f) forming an emitter film made of a conductive material on the first sacrificial film; and (g) removing a portion or a whole of the substrate and a portion of the first sacrificial film to expose the emitter film and the gate film.
The opening is formed through the gate film, the opening having an inner diameter gradually reducing toward the substrate. This opening allows the surfaces of the gate and emitter electrodes to become near each other in a broad area.
Since such a gently tapered opening is formed by reflowing the resist pattern or low melting point film, the very gentle curve of the opening can be formed with good reproductivity.
By shortening the distance between the surfaces of the emitter and gate electrodes as much as possible without any danger of a short circuit, a low threshold voltage can be obtained. Furthermore, if the thickness of the gate electrode is made large, an electric field at the tip of the emitter electrode can be made strong so that the threshold voltage between the gate and emitter electrodes can be lowered without reducing the emission current. In other words, a large emission current can be obtained without raising the voltage between the gate and emitter electrodes. If the gate electrode is made thick, the gate wiring resistance lowers so that a high speed drive becomes possible.
If the etching conditions are selected, the shape of the tip of the emitter electrode can be controlled and the tip can be made sharp. Namely, by making small the apex angle of the tip of the emitter electrode, the electric field at the tip can be made strong so that the threshold voltage between the gate and emitter electrodes can be lowered without reducing the emission current, and that a large emission current can be obtained without raising the voltage betwee
Bowers Charles
Ostrolenk Faber Gerb & Soffen, LLP
Pert Evan
Yamaha Corporation
LandOfFree
Manufacture of field emission elements does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Manufacture of field emission elements, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Manufacture of field emission elements will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2567613