JP2000067737A - Field emission type cold cathode element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make utilization in a wider field possible by covering the tip of an emitter exposed with a substance easily emitting electrons. SOLUTION: This field emission type cold cathode element with a gate is produced in a transfer mold process, and the tip of an emitter 4 is covered from the top with a low-field emission electron emission material film 6 (for example, carbon film). Electron emission from the tip of the emitter 4 is conducted in a low electric field. A field emission type cold electrode element with high characteristics can easily be obtained without using complicated process, In this process, although the film 6 deposits even on a gate electrode 7 in addition to the tip of the emitter 4, electron emission from this film 6 does not occur from the relation of potential distribution, and no trouble is generated. Usually, the film deposited on the tip of the emitter 4 and the film deposited on the gate electrode 7 are separated by breaking caused by an overhanging shape of the gate electrode 7. Therefore, short circuit between the emitter 4 and the gate electrode 7 can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission type cold cathode device used for a power device, an amplifier, a display, an electron radiator and the like.

[0002]

2. Description of the Related Art Until now, vacuum tubes and semiconductor elements have been used everywhere as electronic devices. Among them, the vacuum tube has disadvantages in that the loss of the heater is large due to the use of thermionic emission and the life of the filament is short. Also,
The size was quite large and the device could not be made compact.

On the other hand, the performance of semiconductor devices has been improved one after another with the development of microfabrication technology. However, Joule heat is generated due to the movement of carriers in solids, and the loss is large. It has been a long time since the limits of performance have been said. In addition, it has been pointed out that the internal electronic state is affected by heat, radiation, and the like, causing a failure or malfunction.

As described above, there has been a problem that conventional elements have been expected to be overcome while being widely used.

[0005]

As described above, the conventional electronic device has many problems to be overcome in order to expand the range of use.

Accordingly, an object of the present invention is to provide a field emission type cold cathode device which can overcome these disadvantages and can be used in a wider field than ever before.

[0007]

According to the present invention, a material (C, CN, BC) which emits electrons in a low electric field on an emitter is provided.
N, Cs, GaN, AlN, etc.) can be easily added, thereby providing a low-loss, high-efficiency field emission cold cathode device.

[0008]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a view showing a main part of a field emission cold cathode device according to an embodiment of the present invention. In this figure, after a field emission type cold cathode device with a gate is formed by a method called a transfer molding method, the tip of the emitter is covered with a material 6 (C is used in this example) which emits electrons from above the device with a low electric field. It is a thing. As a result, electrons can be emitted from the tip of the emitter in a lower electric field, and a field emission cold cathode device having high performance can be easily obtained.

If the device is covered with the low-field electron emission material 6 after the device is formed, not only a device having good characteristics can be easily obtained without going through a complicated process, but also the electron emission characteristics can be improved by some process. Unnecessary damage to the surface state of the low-field electron emission material, which has a great influence, is eliminated, so that an element having better characteristics can be obtained.

In this case, the film 6 is deposited not only on the tip of the emitter but also on the gate electrode 7, but there is no problem because the potential distribution does not cause electron emission from this film. Rather, when the element is operated, adverse effects on the gate electrode due to ions generated from the residual gas are prevented by coating the gate electrode, which is a preferable state.

[0012] Usually, the film deposited on the tip of the emitter and the film deposited on the gate electrode 7 are disconnected due to the overhanging shape of the gate electrode 7 and are separated.
Therefore, this method does not short-circuit the emitter and the gate. Even if short-circuited, especially carbon-based low-field electron emission materials generally have high resistance and almost no gate,
There is no problem because no current flows between the emitters.

Although a triode structure is used in this example, a similar effect can be obtained with a diode structure without a gate.

In actual use of the device, an anode electrode is provided at a position opposed to the emitter, and the whole is incorporated in a vacuum package.

FIG. 2 shows another embodiment according to the present invention.
This figure shows that a field emission type cold cathode device with a gate is manufactured by a method of manufacturing an emitter using a rotating oblique deposition called a Spindt method, and then a material 6 (C in this example) that emits electrons from above the device with a low electric field. ) Covers the tip of the emitter.

FIG. 3 shows another embodiment according to the present invention.
In this figure, a field emission type cold cathode device with a gate is formed by a method called the Gray method, and then the tip of the emitter is covered with a material (in this example, C) which emits electrons from above the device with a low electric field. .

FIG. 4 shows another embodiment according to the present invention.
In this figure, the material of the substrate 8 (highly doped Si, Al, Mo, etc.) is formed without forming a convex emitter.
Such as metals) are directly covered with a material that emits electrons in a low electric field.

Since each of the above-mentioned materials can emit electrons in a low electric field, sufficient electron emission characteristics can be obtained without sharpening the tip of the emitter to cause electric field concentration.

According to this method, devices can be mass-produced at a high yield and at low cost.

FIG. 5 shows that the underlayer is directly covered with the low-field electron emission material 6 in FIG.
3 is an example in which the substrate is covered with a low field electron emission material 6 from above. By doing so, for example, Si
In the case where is used, although it is highly doped, it has higher resistance than metal. Therefore, when the emitter is used together with the metal 13 as in this example, the conduction loss can be further reduced.

Further, since the metal 13 can be deposited at the same time as the formation of the gate electrode 7, there is no particular problem that the cost is increased.

FIG. 6 shows another embodiment according to the present invention.
This figure shows that when an element is manufactured by the method shown in FIGS. 4 and 5, a short circuit may occur between the emitter and the gate due to the emitter material or the low-field electron emission material. It is an example showing.

The emitter formation region is prepared by etching the gate electrode and the insulating film by RIE or the like in advance. After that, only the insulating film 3 is etched back. As a result, the gate electrode 7 is overhanged,
The emitter material 13 and the low-field electron emission material 6 to be formed thereafter are disconnected, so that a short circuit between the emitter and the gate can be reliably prevented.

FIG. 7 shows another embodiment according to the present invention.

In the embodiments described above, the shape in which the gate electrode is overhanged has been used in order to prevent a short circuit between the emitter and the gate.

However, when such an element shape is used, the gate electrode may be unnecessarily covered with the emitter, and electrons emitted from the emitter may flow toward the gate and may not reach the anode. May occur. This leads to a decrease in the current-carrying ability and a decrease in the gain, which greatly deteriorates the characteristics of the element.

In this embodiment, for example, undoped polysilicon 14 is sandwiched between the insulating film 3 and the gate electrode 7, and the insulating film is etched back using the polysilicon as a mask, and the gate electrode is also etched back. , So that the gate electrode does not carelessly cover the emitter. As a result, the effective opening area of the gate electrode with respect to the emitter is increased by the etch back, and an unnecessary increase in gate current can be prevented. Since the polysilicon 14 has a high resistance and no current flows through this portion, there is no problem existing in the above embodiments.

FIG. 8 shows another embodiment according to the present invention.

In this embodiment, by providing the gate electrode in two stages, the insulating film is etched back using the lower (closer to the emitter) gate electrode 16 as a mask to prevent short-circuiting between the gate and the emitter. After completion, by applying a negative bias to the lower gate 16, the trajectory of the electrons emitted by the electric field generated from the upper gate electrode 7 is collected at the center, and unnecessary electron current flowing into the gate is further reduced. Can be.

FIG. 9 shows another embodiment according to the present invention.

In this example, an emitter having a sharpened tip is used instead of using a planar emitter in FIG.

FIG. 10 shows an example of taking out a gate wiring according to the present invention.

A gate electrode pad portion 18 for performing gate wiring is provided on a part of the element surface, and a gate wiring is formed at this location by wire bonding or the like.

In the present invention, the entire surface is covered with a low-field electronic material after all the element shapes are formed. In this case, however, the pad portion for the gate wiring is also covered at the same time.

Normally, the thickness of the low-field electronic material is extremely small, and therefore, if the ultrasonic bonding or the like is performed without particularly removing the film at the pad portion, the film can easily penetrate the film and make contact with the gate electrode.

If it is desired to remove the film in the pad portion, there is no problem because the film can be easily removed by a method that does not affect the film in other portions by mechanical polishing or the like. Furthermore, if the pad portion is formed on one side of the element, only this portion can be easily removed by etching or the like.

In any case, the gate wiring can be performed without damaging the surface state of the film of the low-field electron emission material.

In this example, the gate wiring is formed from above the element, and the emitter (cathode) wiring is formed from the bottom of the element.
The cathode wiring can also be formed from above the element, similarly to the gate wiring.

[0039]

According to the present invention, it is possible to provide a field emission type cold-cathode device having excellent current-carrying ability without incurring extra processes and increase in cost.

As a result, it is possible to easily increase the current and the breakdown voltage of the field emission type cold cathode device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main part of a field emission cold cathode device according to an embodiment of the present invention.

FIG. 2 is a diagram showing a main part of a field emission cold cathode device according to another embodiment of the present invention.

FIG. 3 is a diagram showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 4 is a view showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 5 is a view showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 6 is a view showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 7 is a diagram showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 8 is a diagram showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 9 is a diagram showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 10 is a diagram showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

FIG. 11 is a view showing a main part of a field emission cold cathode device according to still another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... p-type Si substrate 2 ... n-type Si layer 3 ... insulating film 4 ... emitter 5 ... emitter back surface layer 6 ... low field electron emission material film 7 ... gate electrode 8 ... emitter substrate 9 ... lift-off buffer layer 10 ... emitter material DESCRIPTION OF SYMBOLS 11 ... Mask for anisotropic etching 12 ... Gate insulating film 13 ... Low resistance emitter film 14 ... Gate buffer layer 15 ... Second insulating film 16 ... Second gate electrode 17 ... Emitter array part 18 ... Gate pad (contact) Department

Claims (5)

[Claims] 1. An emitter having a sharp tip and a convex shape, an insulating film provided around the emitter so that the emitter tip is exposed, and an emitter provided on the insulating film so that the emitter tip is exposed. A field emission type cold cathode device comprising: a gate electrode; and the exposed tip of the emitter is covered with a substance which facilitates emission of electrons. 2. The field emission cold cathode device according to claim 1, wherein the gate electrode around the emitter is also covered with the same material as the tip of the emitter. 3. The field emission cold cathode device according to claim 2, wherein the emitter has a planar structure. 4. A second insulating film provided around the emitter so that the emitter tip is exposed, and a second insulating film provided on the second insulating film such that the emitter tip is exposed.
2. The field emission cold cathode device according to claim 1, further comprising a gate electrode. 5. The field emission cold cathode device according to claim 4, wherein the emitter has a planar structure.