JPH1167060A - Field emission cold cathode - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a field emission cold cathode in which a high density electron current can be obtained, and of which manufacture is easy. SOLUTION: Plural micro-field emission cathodes are disposed as concentric circles on a substrate, and rings of deflection electrodes 8, 9, 10... are provided to enclose the respective concentric circles. The rings of the delection electrodes 8-10 are connected to each other through resistances 11, the deflection electrode 8 as the innermost circle is connected to a gate electrode 5 of the micro-field emission cathode, and the ring of the deflection electrode 10 as the outermost circle is connected to a negative voltage source. For the rings of the deflection electrodes 8-10, therefore, a lower voltage is applied to one than that applied on one on the inner circumferential side of it, and a negative potential gradient is generated from a center part toward the outer circumferential part, thereby electrons field-emitted from a cone emitter 6 of the micro-field emission cathode are converged to a center part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a field emission cold cathode using field emission, and more particularly to a field emission cold cathode in which a plurality of minute field emission cathodes are arranged.

[0002]

2. Description of the Related Art An electric field applied to a metal or semiconductor surface is 10
^{When the} voltage is set to about ⁹ [V / m], electrons pass through the barrier due to the tunnel effect, and are emitted in a vacuum even at room temperature.
This is called field emission, and a cathode that emits electrons based on such a principle is called a field emission cathode (FEC). In recent years, it has been possible to manufacture a field emission cold cathode by integrating micron-sized field emission cathodes (micro field emission cathodes) in an array using semiconductor processing technology.

[0003] Various types of field emission cathodes are known. One example of such a field emission cathode is Spindt.
FIG. 6A shows a configuration of a field emission cold cathode using an FEC called a dt) type. Although the field emission cold cathode operates in a vacuum atmosphere, the configuration in the vacuum atmosphere is omitted in the following drawings and description. In FIG. 6A, a substrate 10 such as silicon or glass is used.
1, a cathode electrode 102 made of a metal such as molybdenum or niobium is formed, and a resistance layer 103 made of amorphous silicon doped with impurities is formed thereon. A plurality of cone-shaped emitters 106 made of metal such as molybdenum are arranged on the resistance layer 103.
Silicon dioxide (SiO 2)
₂ ) is formed, and the insulating layer 1 is formed.
The gate electrode 105 is formed on the gate electrode 04. That is, the cone-shaped emitter 106 is located in the opening 107 provided in the gate electrode 105 and the insulating layer 104, and the tip portion faces the opening 107.

The pitch between the cone-shaped emitters 106 can be set to 10 μm or less, and tens of thousands to hundreds of thousands of emitters 106 can be provided on one substrate. Further, since the distance between the gate electrode 105 and the tip of the cone of the emitter 106 can be set in submicron units, a gate-emitter voltage Vge of only several tens of volts is applied between the gate electrode 105 and the emitter 106. This allows electrons to be field-emitted from the emitter 106. If the anode electrode 108 to which the positive voltage Va is applied is provided opposite to the gate electrode 105, electrons emitted from the emitter 106 can be collected by the anode electrode 108.

As described above, the distance between the tip of the cone-shaped emitter 106 and the gate electrode 105 is extremely short, on the order of submicron, and a very large number of emitters 106 are formed on one substrate 101. Since the gate 105 and the emitter 106 may be short-circuited due to dust or the like during the manufacturing process, if any one of them is short-circuited, no voltage is applied between all the gates and the emitter, and the operation becomes impossible. In some cases, local degassing occurs during the initial operation, and this gas may cause a discharge between the emitter and the gate or the anode, causing a large current to flow to the cathode and destroying the cathode. is there. Therefore, the above-described resistance layer 103 is provided, and a voltage drop is generated in a direction in which electron emission of the emitter 106 is suppressed in accordance with an increase in the current flowing through the certain emitter 106, thereby preventing the current from being concentrated on a specific emitter 106. Therefore, the production yield of the field emission cold cathode is improved and stable operation is achieved.

Here, such a field emission cold cathode is usually manufactured by the following steps. First, the substrate 101
The cathode electrode 102, the resistive layer 103, the insulating layer 10
4. A gate electrode 105 is sequentially formed to form a laminated substrate. Next, the uppermost surface of the laminated substrate, that is, the gate electrode 1
After applying a photoresist layer on the photoresist layer 05, an opening pattern corresponding to the opening 107 is formed in the photoresist layer. Next, an opening corresponding to the opening pattern is formed in the gate electrode 105 and the insulating layer 104 by etching. Next, a release layer is formed on the surface of the gate electrode 105, and a high melting point metal material such as molybdenum is deposited to form a cone-shaped emitter 106, and the release layer is removed. In this way, a large number of minute field emission cathodes are simultaneously manufactured on the substrate 101.

[0007] It is generally known that electrons are emitted from the cone-shaped emitter 106 of the small field emission cathode at a predetermined spread angle. Therefore, a field emission cathode has been proposed in which the trajectories of electrons emitted from such a cone-shaped emitter are focused. The field emission cathode is provided with an electrode (hereinafter, referred to as a focusing electrode) for focusing electrons emitted from the emitter 106 above the gate electrode in addition to the gate electrode described above. 1
The spread of the electrons emitted from 06 is prevented.

FIG. 6B shows an example of the configuration of a minute field emission cathode in this field emission cold cathode. In this figure, the same components as those in FIG. 6A are denoted by the same reference numerals, and redundant description will be omitted. As shown in the figure, in this minute field emission cathode, an insulating layer 109 is also provided above a gate electrode 105, and a focusing electrode 110 is provided thereon. The focusing electrode 110 has a cathode electrode 102, an emitter 106 , A negative voltage is applied. Thus, the gate electrode 105
Of the electron emitted from the emitter 106 is focused by the focusing electrode 110 to reach the anode electrode 108 by applying a negative voltage Vgs to the focusing electrode 110. It will be. As described above, the focusing electrode 110 can focus the trajectory of the electrons emitted from the emitter 106 of the micro field emission cathode.

Such a field emission cold cathode has advantages that a higher current density can be obtained as compared with a hot cathode, the speed dispersion of emitted electrons is small, heat is not generated, and power consumption is low. The use as an electron source in flat panel displays, various sensors, and the like has been proposed.
Further, it has been proposed to use a field emission cold cathode as an electron gun such as a microwave tube by utilizing the above-described characteristics (Japanese Patent Application Laid-Open No. 8-255558).

FIG. 7 shows a configuration of an electron gun using the proposed field emission cold cathode. In this figure, 11
Reference numeral 1 denotes a substrate, which is formed in a spherical shape as indicated by reference numeral 112. Reference numeral 113 denotes an insulating layer formed on the spherical substrate 111, and reference numeral 114 denotes a gate electrode layer formed on the insulating layer 113. The substrate 111, the spherical surface 112, the insulating layer 113 and the gate electrode layer 114 constitute a field emission cold cathode 115. Also, 1
Reference numeral 16 denotes a conical emitter formed by processing the substrate 111, 117 denotes a cavity, and 118 denotes an opening. These form a minute field emission cathode 119. Reference numeral 121 denotes a Wehnelt electrode; 122, an anode; the same potential or a negative potential as that of the substrate 111 or the electrode layer 114 is applied to the Wehnelt electrode 121;
Is applied. In the electron gun configured as described above, each minute field emission cathode 119 is formed on a spherical surface 112, and electrons emitted from each emitter 116 are focused by a Wehnelt electrode 121, and a high-density electron beam 123 is formed. can get.

The field emission cold cathode is manufactured by a processing method using a focused ion beam (FIB). First, a spherical surface 112 is formed on the surface of a substrate 111 by a mechanical method, and an insulating layer 113 and an electrode layer 114 are stacked thereon. Next, using a ion beam generator, a focused ion beam is applied to the portion of the spherical surface 112 serving as an electron emission region, and the position and direction of the substrate 111 are controlled so that the ion beam is drawn so as to draw a circle having a diameter of 1 μm or less. By controlling, the electrode layer 114, the insulating layer 113, and a part of the substrate 111 are removed to form the opening 118, the cavity 117, and the emitter 116 at the same time.

[0012]

According to the electron gun using the field emission cold cathode shown in FIG. 7, the minute field emission cathodes are arranged on the substrate 111 having a spherical shape. The convergence ratio of the electrons emitted from each minute field emission cathode can be increased, and the current density is high and a stable electron beam 123 can be formed. However, since the field emission cold cathode is formed in a spherical shape using a processing method using a focused ion beam (FIB),
It is necessary to sequentially form the opening 117, the cone-shaped emitter 116, and the like, so that the manufacturing process is complicated and uniformity and reproducibility at each emitter level are difficult.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a field emission cold cathode which can be easily manufactured and can obtain a high-density electron flow by focusing the trajectories of emitted electrons.

[0014]

In order to achieve the above object, a field emission cold cathode according to the present invention comprises a plurality of concentrically arranged minute field emission cathodes, and each concentric circle in the arrangement of the minute field emission cathodes. And a plurality of ring-shaped deflection electrodes formed so as to surround. Further, in the plurality of ring-shaped deflection electrodes, a lower voltage is applied to the ring-shaped deflection electrode located on the outer periphery side than to the ring-shaped deflection electrode located on the inner periphery side. Further, the plurality of ring-shaped deflection electrodes are connected via a resistance region.

Since a negative potential gradient is formed from the center toward the outer periphery by the ring-shaped deflection electrode, electrons emitted from each minute field emission cathode are deflected toward the center. Therefore, an electron beam with a high current density can be generated even when the electron beam is formed on a flat substrate that is easy to manufacture.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a view showing a schematic structure of a field emission cold cathode of the present invention, wherein (a) is a plan view of the field emission cold cathode of the present invention, and (b) is a cross-sectional view thereof. . In FIG. 1, 1 is an insulating substrate made of glass or the like, 2 is a cathode electrode formed of a metal such as aluminum on the substrate in a stripe shape, and 3 is amorphous silicon provided on the substrate 1 and the cathode electrode 2. And the like. Reference numeral 6 denotes a cone-shaped emitter made of a metal such as molybdenum on the resistance layer 3, 4 denotes an insulating layer formed in a region of the resistance layer 3 where the emitter 6 is not formed, and 5 denotes an insulating layer. A gate electrode (pull-out gate electrode) 7 formed above is an opening. The emitter 6 and the gate electrode 5 form a minute field emission cathode as described above. As shown in FIG. 1A, the minute field emission cathodes are arranged concentrically. The concentric arrangement of the minute field emission cathodes is hereinafter referred to as an array ring. Although only three array rings are shown in this figure, the number can be any number depending on the current density and the like.

Reference numerals 8, 9 and 10 denote ring-shaped deflecting electrodes formed on the insulating layer 4 so as to surround the array ring. 9 and 10 toward. Although only three ring-shaped deflection electrodes are shown in this figure, the number of ring-shaped deflection electrodes can be any number corresponding to the number of array rings. further,
11 is a resistor, 12 is a terminal to which a negative voltage is applied,
As shown, the resistor 11 is connected to the gate electrode 5 and the terminal 12.
Is divided into the ring-shaped deflection electrodes 8,
A higher deflection electric field is obtained by applying a lower deflection voltage to the outer circumferences of 9, 9 and 10. As a result, a negative potential gradient is formed in the vicinity of the field emission cold cathode from the center toward the outer periphery, and electrons emitted from the emitter 6 are deflected toward the center. Becomes Note that the resistor 11 can be actually realized by connecting between the deflection electrodes or between the deflection electrode and the gate electrode with a thin resistance region. FIG. 1 shows a case where the substrate 1 is an insulating substrate made of glass or the like.
The cathode line 2 electrically insulated from the substrate may be formed by ion implantation or the like.

FIG. 2 shows an example of a simulation result of the electron orbit emitted from each emitter 5 in the field emission cold cathode of the present invention thus configured. 2A is a diagram showing the trajectory of electrons emitted from the emitter 6 of the small field emission cathode provided on the left side, and FIG.
(B) is a diagram showing the trajectory of electrons emitted from the emitter 6 provided at the center. Reference numerals 8 to 10 denote the ring-shaped deflection electrodes. In the simulation shown in this figure, Vg1 = 0 V is applied to the innermost ring-shaped deflection electrode 8, and Vg2 = Vg2 is applied to the ring-shaped deflection electrode 9. -1
It is assumed that a deflection voltage of Vg3 = −200 V is applied to the ring-shaped deflection electrode 10 at 00 V, respectively. The relative intensity of the current density is indicated by the size of a bar graph immediately above each graph.

As shown in FIG. 2A, the electrons emitted from the emitter 6 at a position away from the center are caused by the deflection voltage applied to the ring-shaped deflection electrodes 8 to 10. Due to the potential gradient, the trajectory of the electrons emitted from the outer ring array is more deflected toward the center. Further, as shown in (b), the electrons emitted from the emitter 6 provided at the center position are proceeding directly above. Therefore, the electrons emitted from each of the emitters 6 are concentrated at a position immediately above the center position, and a high-density electron beam can be obtained.

In this manner, an array ring of minute field emission cathodes is provided on a concentric circle, and a plurality of ring-shaped deflection electrodes are provided so as to surround each array ring. From the center of the field emission cold cathode to give a negative potential gradient from the center of the field emission cold cathode to the outside, so that electrons emitted from the minute field emission cathode are You can focus. The degree of concentration of the electrons can be controlled by the potential gradient.
It can be controlled by the voltage applied to the ring-shaped deflection electrodes, the width and position of each ring-shaped deflection electrode, or the position of the array ring. As described above, according to the field emission cold cathode of the present invention, the electrons emitted from the small field emission cathode array arranged concentrically can be effectively concentrated. Further, since the micro field emission cathode array is formed on a flat substrate, it can be easily manufactured by using the above-described simple process.

FIG. 3 is a diagram showing an example of a result of simulating a current density distribution, that is, a change in the electron trajectory when the voltage applied to the ring-shaped deflection electrodes 8 to 10 is changed. Here, Vg1, Vg2 and Vg3 are:
These are deflection voltages applied to the ring-shaped deflection electrodes 8, 9 and 10, respectively. The horizontal axis represents the distance, and the vertical axis represents the current value relative distribution of the anode electrode provided at a predetermined interval from the field emission cold cathode, that is, the amount of electrons reaching the position.

As shown in FIGS. 3A to 3D, by applying different deflection voltages to the ring-shaped deflection electrodes 8 to 10, the position where the electrons reach (the arrival spot) changes. I have. In this simulation, the voltages Vg1 = − are applied to the ring-shaped deflection electrodes 8 to 10, respectively.
In the case of (d) where 50 V, Vg2 = -100 V and Vg3 = -200 V were applied, the spot diameter reached was 60 μm,
It can be seen that the electrons are most focused.

Next, a second embodiment of the present invention will be described with reference to FIG. In this embodiment, the ring-shaped deflection electrode is formed above the gate electrode 5, and FIG. 4A is a plan view thereof.
(B) is a sectional view thereof. In FIG. 4, the same components as those in FIG. 1 are denoted by the same reference numerals to avoid duplication of description. As shown, in this embodiment, a second insulator layer 13 is formed above the gate electrode 5, and the above-described ring-shaped deflection electrodes 8 to 10 are formed above the insulator layer 13. I have. Further, reference numeral 14 shown in FIG. 4A indicates that the gate electrode 5 and the ring-shaped deflection electrode 8, the ring-shaped deflection electrodes 8 and 9, the ring-shaped deflection electrodes 9 and 10, the ring-shaped deflection electrode 10 and the outer periphery thereof are further provided. This is a resistance region for connecting between the provided ring-shaped deflection electrodes or terminals. The resistance region 14 divides a gate voltage of the gate electrode 5 and a negative voltage applied to a terminal (not shown) to apply a predetermined deflection voltage to each ring-shaped deflection electrode.

In the embodiment described above, the microfield emission cathode structure shown in FIG. 6A is used, but the focusing electrode shown in FIG. 6B is used. Still another embodiment of the present invention using a small field emission cathode having the following will be described. FIGS. 5A and 5B are views showing an example of the configuration of still another embodiment of the present invention, wherein FIG. 5A is a plan view thereof, and FIG. In this figure, the same components as those in FIGS. 1 and 2 are denoted by the same reference numerals to avoid duplication of description. FIG. 5 shows a case where the resistance region 14 is formed in the insulating layer 1.

As shown, in this embodiment, a focusing electrode 15 is provided near the opening 7 above the second insulator layer 13 in the same manner as shown in FIG. 4B. ing. In the present invention, since the minute field emission cathode is an array ring formed in a ring shape as described above, the focusing electrode 15 is also formed in a ring shape, which is referred to as a focusing electrode ring. And The ring-shaped deflection electrodes 8 to 10 are arranged between the focusing electrode rings toward the outer periphery. That is, in this embodiment, ring-shaped deflection electrodes and focusing electrode rings are alternately arranged concentrically on the second insulator layer 13. And 14
Are resistance regions connecting between the ring-shaped deflection electrodes and between the innermost ring-shaped deflection electrode 8 and the gate electrode 5. Since the gate electrode 5 is formed on the first insulator layer 4, this connection is required to connect the innermost ring-shaped deflection electrode 8 and the gate electrode 5 via the resistance region 14. In this embodiment, as shown in FIG. 2A, this connection is made using an opening 7 of one small field emission cathode. Further, in order to supply the same negative potential to the focusing electrodes 15, the focusing electrode rings are connected to each other by a connection region 16 as shown in FIG.

The field emission cold cathode of the present invention described above
It can be used not only as an electron beam source such as a microwave tube, but also as an electron source such as a beam processing machine. In addition, although the Spindt type field emission cathode has been described as an example, the invention is not limited thereto, and the present invention can be applied to other types.

[0027]

As described above, according to the field emission cold cathode of the present invention, the ring-shaped deflection electrode generates a negative potential gradient from the center to the outer periphery. Electrons emitted from the emission cathode can be focused. Therefore, an electron gun having a high current density can be formed using a flat substrate that can be easily processed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of a field emission cold cathode according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a simulation result of electron orbits emitted from the field emission cold cathode of the present invention.

FIG. 3 is a diagram showing a simulation result of a current density distribution when a voltage applied to a ring-shaped deflection electrode in the present invention is changed.

FIG. 4 is a diagram showing a schematic configuration of another embodiment of the field emission cold cathode of the present invention.

FIG. 5 is a diagram showing a schematic configuration of still another embodiment of the field emission cold cathode of the present invention.

FIG. 6 is a diagram showing a configuration of a conventional field emission cold cathode.

FIG. 7 is a diagram showing a configuration of a proposed field emission cold cathode.

[Explanation of symbols]

 1, 101, 111 Substrate 2, 102 Cathode electrode 3, 103 Resistive layer 4, 13, 104, 109, 113 Insulating layer 5, 105, 114 Gate electrode 6, 106, 116 Emitter 7, 107, 118 Opening 8, 9 , 10 ring-shaped deflection electrode 11 resistor 12 terminal 14 resistance region 15, 110 focusing electrode 16 connection portion 107 cavity 108 anode 112 spherical portion 115 field emission cold cathode 119 minute field emission cathode

Claims (3)

[Claims] A plurality of minute field emission cathodes arranged concentrically; and a plurality of ring-shaped deflection electrodes formed so as to surround each concentric circle in the arrangement of the minute field emission cathodes. Field emission cold cathode. 2. In the plurality of ring-shaped deflection electrodes, a lower voltage is applied to a ring-shaped deflection electrode located on an outer peripheral side than to a ring-shaped deflection electrode located on an inner peripheral side thereof. The said claim 1 characterized by the above-mentioned.
The field emission cold cathode as described. 3. The field emission cold cathode according to claim 1, wherein the plurality of ring-shaped deflection electrodes are connected via a resistance region.