JP3407289B2 - Electron emission device and driving method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron emission device capable of controlling electrons field-emitted from a cold cathode. More specifically, the present invention relates to an electron emission device having a linear relationship between an input signal voltage and an anode current. The present invention relates to an electron emission device that can be used in an amplifier, a linear amplifier, a switching circuit, and the like, and a driving method thereof.

[0002]

2. Description of the Related Art A conventional electron emitting device is disclosed in Junji Ito, Applied Physics, Vol. 59, No. 2, pp. 164-169 (1
990). FIG. 33 is a schematic plan view of a conventional multipole field electron emission device.

This is called a plane type triode element and has a structure in which a wedge-shaped emitter electrode (cathode electrode) 102, a gate electrode 103 having a pillar, and an anode electrode 104 are formed side by side in order on a surface of a quartz substrate 101. Is. These three electrodes are formed by processing a tungsten thin film having a thickness of 1 μm by a photoetching technique. 170 emitter electrodes 102 are arranged at a pitch of 10 μm. The distance between the emitter electrode 102 and the gate electrode 103 is 15 μm, and the gate electrode 103 and the anode electrode 104 are
The distance between and is 10 μm.

The electrical characteristics of this flat type triode element are 5 × 1.
When measured at a vacuum degree of 0 ⁻⁶ Pa, the emitter emission current is a Fowler-Nordheim (F · N) tunnel current, the gate voltage is 220 V, and the anode voltage is 31 V.
At 8 V, an anode current of about 1.2 μA is obtained.
This results in an anode current of about 7 nA per emitter electrode. The transconductance is about 0.1 μS.

[0005]

However, the conventional planar type triode element has some problems as described below. That is, the electrons emitted from the emitter electrode 102 travel toward the anode electrode 104,
Gate electrode 103 applied with a positive potential on the way
Exists, some of the emitted electrons flow into it. Since this gate current is as large as or more than the anode current, the gate input resistance becomes very small. That is,
The yield of electrons flowing into the anode electrode 104 (anode current / total emission current) is lowered, which causes deterioration of electrical characteristics such as low power efficiency and low transconductance. In the prior art, the yield was about 60%. When controlling the anode current with a triode element having a small gate input resistance, a pre-stage circuit for introducing an input signal to the gate electrode 103 needs to be capable of handling a large current or power. Due to such restrictions, it has been difficult to use the conventional triode element as a current amplifier or a power switching device.

The emitter emission current is an FN tunnel current, which increases and decreases exponentially with respect to the gate voltage. Therefore, the anode output current changes exponentially with respect to the gate input signal. There is a problem that such a triode element having a non-linear input / output relationship is not suitable for application to a linear amplifier or the like.

Furthermore, in order to increase the mutual conductance of the triode element and improve the performance, the gate electrode 103 is used.
The emission area of the emitter electrode 102 needs to be increased by devising the structure of (1). However, if the emission area is increased, the number of electrons that flow into the gate electrode 103 also increases, and thus it is difficult to obtain a high-performance power amplifier in the related art. There was a problem such as.

Further, the cathode electrode 102 and the gate electrode 10
3 is formed in the same photoetching process. The distance between these electrodes is determined by the resolution at the time of resist exposure, and the practical limit is 0.8 μm. Moreover, the smaller the size, the greater the variation. The threshold voltage of electron emission of the field electron emission device and its uniformity largely depend on the distance between the cathode electrode 102 and the gate electrode 103. Therefore, the conventional planar triode element has a problem that it is difficult to reduce the threshold voltage, and even if it is possible, the uniformity is poor.

Further, the threshold voltage of the field electron emission device largely depends on the radius of curvature of the tip of the cathode electrode 102.
That is, the smaller the tip radius of curvature, the lower the threshold voltage, and the tip radius of curvature is 1 to obtain a practical threshold voltage.
It is desirable that it is 000 angstroms or less. However, in the prior art, the limit of 2000 angstroms due to the sag of the photoresist made it difficult to manufacture a practical tip radius of curvature.

Therefore, the present invention is intended to overcome the above-mentioned problems of the prior art. The object of the present invention is to have a large gate input resistance, a linear input / output relationship, and a mutual conductance. A large and high-performance electron emission device and a driving method thereof are provided.

[0011]

An electron emission device according to the present invention comprises a cathode electrode for emitting electrons, a gate electrode for applying an electric field to the cathode electrode, an anode electrode for collecting emitted electrons, and the cathode electrode. The cathode electrode and the suppressor electrode are provided with at least a control electrode which is provided between the anode electrodes and controls the emitted electrons, and a screen electrode and a suppressor electrode which are provided between the control electrode and the anode electrode. And a means for applying a gate voltage to the gate electrode and the screen electrode, and a means for applying an anode voltage to the anode electrode so as to control the anode current by applying an input signal voltage to the control electrode. It is characterized in that it is configured in.

Further, the driving method of the electron emitting device according to the present invention includes a cathode electrode for emitting electrons, a gate electrode for applying an electric field to the cathode electrode, an anode electrode for collecting emitted electrons, the cathode electrode and the anode. At least a control electrode provided between the electrodes for controlling the emitted electrons, and a screen electrode and a suppressor electrode provided between the control electrode and the anode electrode are provided, and the cathode electrode and the suppressor electrode are grounded. Then, a gate voltage is applied to the gate electrode and the screen electrode, an anode voltage is applied to the anode electrode, and an input signal voltage is applied to the control electrode to control the anode current.

[0013]

[0014]

[0015]

EXAMPLES The present invention will be described based on examples. FIG. 1 is a partial perspective view of a novel quadrupole field electron emission device. This device has a gate electrode 5 and a control electrode 6 made of a molybdenum (Mo) thin film having a thickness of 1000 Å on a surface of a flat substrate 1 made of quartz. It has an island-shaped insulating layer 2 made of a 5000 angstrom silicon dioxide thin film. The surface of the island-shaped insulating layer 2 adjacent to the gate electrode 5 has an overhanging emission protrusion 4 and a thickness of 200.
The surface of the island-shaped insulating layer 2 adjacent to the control electrode 6 has a thickness of 20 Å and has a cathode electrode 3 of 0 Å.
It has an anode electrode 7 of 00 angstrom.

The cathode electrode 3 has a structure in which a first cathode electrode 3a made of a tungsten (W) thin film having a thickness of 1000 angstrom and a second cathode electrode 3b made of a molybdenum (Mo) thin film having a thickness of 1000 angstrom are laminated. is there. The anode electrode 7 has a structure in which a first anode electrode 7a and a second anode electrode 7b made of the same thin film as the cathode electrode 3 are laminated. The four electrodes, namely the cathode electrode 3, the gate electrode 5, the control electrode 6 and the anode electrode 7, are arranged on the surface of the flat substrate 1 in this order.

The cathode electrode 3 has emission projections 4 arranged in a line at a pitch of 5 μm. The ejection protrusion 4 is the flat substrate 1.
With a structure protruding in the direction of the gate electrode 5 parallel to the surface of
The island-shaped insulating layer 2 does not exist near the tip. The radius of curvature of the tip of the emission protrusion 4 in the plane direction is about 400 angstroms.

The gate electrode 5 is formed on the cathode electrode 3 in a self-aligned manner, and has a cutout portion having substantially the same shape as the emission projection 4 in the vertical lower portion of the emission projection 4. The distance (L _gk ) between the gate electrode 5 and the emission protrusion 4 is determined by the film thickness of the island-shaped insulating layer 2 and the gate electrode 5, which is a value obtained by subtracting the film thickness of the gate electrode 5 from the film thickness of the island-shaped insulating layer 2 ( L _gk = 4000 angstroms). According to the recent thin film manufacturing method, the controllability of the film thickness is very good, and therefore, the L _gk of this device has the characteristics of excellent controllability, reproducibility, and uniformity.

The width of the gate electrode 5 near the tip of the emission projection 4 is about 2 μm, and the gate electrode 5 and the control electrode 6 are
Is 4 μm, the width of the control electrode 6 is 8 μm, the distance (space) between the control electrode 6 and the anode electrode 7 is about 10 μm, and the width of the anode electrode 7 is 10 μm.
It is 0 μm. The smaller the width of the gate electrode 5, the smaller the gate current and the better the power efficiency. Further, the larger the width and the larger area of the anode electrode 7, the better the electron yield. The larger the width of the control electrode 6, the larger the mutual conductance and the better the controllability of the anode electrode. However, the amount of electrons (control current) flowing into the control electrode 6 also increases, and thus the balance is determined. The width of the control electrode 6 is preferably larger than the width of the gate electrode 5 and smaller than the width of the anode electrode 7. To increase the amplification factor (μ = C _CG / C _AG : C _CG is the capacitance between the gate electrode 5 and the control electrode 6 and C _AG is the capacitance between the gate electrode 5 and the anode electrode 7), the width of the control electrode 6 is narrowed. The space between the control electrode 6 and the anode electrode 7 may be increased.

FIG. 2 is for explaining a method of manufacturing the quadrupole field electron emission device shown in FIG. 1 of the present embodiment, and is a schematic longitudinal sectional view after the main manufacturing steps are completed. Figure 2 (A)
FIG. 3 is a cross-sectional view after an insulating layer 8, a cathode electrode layer 9, and an etching protection layer 10 are sequentially laminated on the surface of the flat substrate 1 and a photoresist 11 is further formed. The flat substrate 1 is an insulating quartz substrate. The insulating layer 8, the cathode electrode layer 9, and the etching protection layer 10 are successively deposited by the sputtering method, and are a 5000 angstrom silicon dioxide thin film, a 1000 angstrom W thin film, and a 2000 angstrom silicon dioxide thin film, respectively. The photoresist 11 is the cathode electrode 3
And the anode electrode 7 is patterned.

FIG. 2B is a sectional view after the etching protection layer 10 is processed by the over-etching method to form the etching mask 12. The over-etching method is to remove more of the etching protection layer 10 than the region defined by the shape of the photoresist 11 by means of selectively etching the etching protection layer 10 using an HF-based etching solution or the like. . The etching mask 12 having the shape of the emission protrusion 4 having a small radius of curvature is formed by over-etching the etching protection layer 10 inward from the outer periphery of the photoresist 11 to be larger than the radius of curvature of the portion of the photoresist 11 corresponding to the emission protrusion 4. Can be obtained. In this embodiment, since the radius of curvature of the photoresist 11 is 3000 angstrom,
Etching mask 1 with over-etching of 00 angstrom and having a radius of curvature of 300 angstrom
Got 2.

In FIG. 2C, the cathode electrode layer 9 is etched to form a first cathode electrode 3a and a first anode electrode 7.
It is sectional drawing after forming a. After removing the photoresist 11, the cathode electrode layer 9 was processed using the etching mask 12 having a sharp emission projection shape. A dry etching method is used for processing the cathode electrode layer 9, and a gas flow rate ratio CF ₄ / O ₂ = 60/200, RF
The power was 700 W for 5 minutes. At this time, the cathode electrode layer 9 is over-etched, and the radius of curvature of the tip is 300.
A first cathode electrode 3a having a sharp emission projection shape of angstrom was obtained.

FIG. 2D is a cross-sectional view after the insulating layer 8 is partially removed by etching to form the island-shaped insulating layer 2 and the emission projections 4 are exposed. Using the first cathode electrode 3a and the first anode electrode 7a as a mask for etching,
An unnecessary portion of the insulating layer 8 was removed with an HF-based etching solution to form the island-shaped insulating layer 2. At this time, the emission projections 4 were overhanged and exposed from the island-shaped insulating layer 2. The etching mask 12 was removed, and the flat substrate 1 was made of quartz and was hardly etched.

FIG. 2E is a cross-sectional view after forming the gate electrode layer 13 by the directional particle deposition method. A sputtering method was used as the directional particle deposition method to deposit a Mo thin film having a thickness of 1000 Å to form the gate electrode layer 13. The directional particle deposition method is a method in which particles are ejected from a particle source almost perpendicularly to the surface of the flat substrate 1 and deposited. When this method is used, the overhanging portion such as the emission protrusion 4 becomes a shadow, and the Mo thin film 131 deposited on the first cathode electrode 3a or the Mo thin film 132 deposited on the surface of the first anode electrode 7a and the flat substrate. The gate electrode layer 13 deposited on the surface of No. 1 is electrically divided, and the missing portion having the same shape as the emission projection 4 is self-aligned with the vertical lower portion of the emission projection 4 (even if the position of one electrode is shifted, the other The position of the electrode is formed at a position corrected accordingly.). As such a directional particle deposition method, a vapor deposition method, a sputtering method, an ECR (Electron Cycle)
Otron Resonance) plasma deposition method, cluster ion beam method and the like can be applied.

FIG. 2F is a sectional view after the gate electrode layer 13 and the Mo thin films 131 and 132 are etched to form the second cathode electrode 3b, the gate electrode 5, the control electrode 6 and the second anode electrode 7b. is there. A photo-etching technique is used to cover the missing portions of the emission protrusions 4 and the gate electrodes 5 with a resist, and then dry etching is performed to remove Mo.
The thin film was etched.

The radius of curvature of the tip of the emission protrusion 4 of the cathode electrode 3 of the completed multipolar field electron emission device was 400 angstrom. This is because the second cathode electrode 3b is laminated so that it is more rounded than the first cathode electrode 3a. However, due to this roundness, the area of the emission protrusion 4 that receives the electric field concentration is expanded, and it becomes possible to obtain stable electron emission with a large emission amount. In addition, when the materials of the first cathode electrode 3a and the second cathode electrode 3b are different from each other, the emission protrusion 4 is mainly removed by etching away either the first cathode electrode 3a or the second cathode electrode 3b in the emission protrusion 4. Was thinned and the radius of curvature of the tip in the film thickness direction was reduced, so that a lower threshold multi-pole field electron emission device was realized.

The threshold voltage can be reduced by shortening the distance between the cathode electrode and the gate electrode with good uniformity and reducing the radius of curvature of the tip of the emission protrusion. The manufacturing method will be described below by taking a triode field electron emission device as an example.

FIG. 3 is a schematic perspective view of a triode field electron emission device manufactured by the manufacturing method. This device includes a flat substrate 1, an island-shaped insulating layer 202 formed of a silicon oxide film on the surface thereof, and a cathode electrode 203 having an emission protrusion 4 formed overhanging on the surface thereof.
Gate electrode 205 formed in self-alignment with emission protrusion 4
And the anode electrode 7 provided on the surface of the flat substrate 1 are the main constituent elements. In addition, around the island-shaped insulating layer 202,
In particular, the sloped surface 21 is formed on the flat substrate 1 near the gate electrode 205.
3 is provided. The inclined surface 213 has an advantage that the ratio of electrons emitted from the emission protrusions 4 flowing into the gate electrode 5 is reduced and the power efficiency of the field electron emission device is improved.

This field electron emission device has 100 emission protrusions 4 arranged in parallel at a pitch of 5 μm.
The tip radius of curvature is 400 Å. The distance (L _GK ) between the cathode electrode 203 and the gate electrode 205 is 4000 Å, the width of the gate electrode 205 at the tip of the emission protrusion 4 is 2 μm, and the distance (L _AK ) between the cathode electrode 203 and the anode electrode 7 is about 10 μm. . The flat substrate 1 is a # 7059 glass substrate (manufactured by Corning Incorporated), the island-shaped insulating layer 202 is a silicon oxide film having a film thickness of 5000 angstrom, and the first cathode electrode 203a is 10 film in thickness.
The molybdenum (Mo) thin film having a thickness of 00 Å, the second cathode electrode 203b, the gate electrode 205, and the anode electrode 7 are made of a tantalum (Ta) thin film having a thickness of 2000 Å. The angle of the slope 213 is about 10
It is degree.

4A to 4F are schematic vertical sectional views of the flat substrate 1 at the end of the main manufacturing steps according to the method of manufacturing the field electron emission device shown in FIG. Also in FIG.
4A to 4C are schematic plan views of the planar substrate 1 corresponding to FIGS. 4B, 4D, and 4E, respectively. Hereinafter, a method for manufacturing the field electron emission device of this embodiment will be described.

First, an insulating layer 8 serving as an etching mask layer and a cathode electrode layer 9 are laminated and formed on the surface of the flat substrate 1, and then a resist layer 11 is formed (FIG. 4).
(A)). The flat substrate 1 is an insulating # 7059 glass substrate. The insulating layer 8 is a silicon dioxide thin film with a thickness of 5000 angstroms formed by atmospheric pressure CVD,
The cathode electrode layer 9 has a film thickness of 100 deposited by the sputtering method.
It is a 0 angstrom Mo thin film. Resist layer 11
Was formed into a shape of the cathode electrode 203 by a photo-etching method.

Next, the cathode electrode layer 9 is replaced with the resist layer 1
Then, the temporary cathode electrode 91 is formed.
(FIG. 4 (B) and FIG. 5 (A)). The Mo thin film of the cathode electrode layer 9 was etched by the dry etching method using CF ₄ gas. The resist tip 11a has a tip curvature radius of about 7,000 angstroms, and the temporary cathode electrode 91 has the same radius.

Next, the insulating layer 8 is processed by an over-etching method to form an etching mask 81 (FIG. 4).
(C)). The over-etching method is a method of etching and removing the insulating layer 8 deep inside the region defined by the shape of the temporary cathode electrode 91 by using an isotropic etching means. According to the isotropic etching means, the temporary cathode electrode 9
Since the etching progresses from the outer periphery of 1 to the inner direction at a constant speed, the shape of the convex portion becomes sharp. Therefore, the over-etching method is characterized in that the radius of curvature of the tip can be reduced in the convex portion.

Here, HF is used as an isotropic etching means.
The silicon dioxide thin film of the insulating layer 8 was excessively etched using a system etching solution. Excessive etching of about 1.5 μm from the outer periphery of the temporary cathode electrode 91
An inverse taper-shaped etching mask 81 was formed, and the tip radius of curvature of its protruding portion was about 300 Å. The radius of curvature of the tip of the temporary cathode electrode 91 is 7,000.
Sharpness of about 20 times was achieved compared with that of Angstrom. In this step, the surface of the flat substrate 1 was also etched, and the slope 213 was formed around the etching mask 81. The etching rate of the insulating layer 8 was about 5 times higher than that of the flat substrate 1, and therefore the slope of the slope 213 formed below the emission protrusion 4 was about 10 degrees.

Next, the temporary cathode electrode 91 is etched into the shape of the etching mask 81 to form the first cathode electrode 203a (FIGS. 4D and 5).
(B)). When the surface of the temporary cathode electrode 91 was covered with the protective resist layer 11 and was dry-etched from the back surface, the first cathode electrode 203a having a planar shape equivalent to that of the etching mask 81 was formed. The radius of curvature of the tip of the emission protrusion 4 of the first cathode electrode 203a was about 300 angstrom.

Next, the side surface of the etching mask 81 is removed by etching to form the island-shaped insulating layer 202, and the resist layer 11 is removed (FIGS. 4 (E) and 5 (C)). The side surface of the etching mask 81 is removed by about 0.7 μm to form the first cathode electrode 203a in an eave shape, and the emission projection 4 is formed.
Was exposed as an overhang.

Finally, after forming an electrode layer of Ta thin film by the directional particle deposition method, it is etched to form the second cathode electrode 203b, the gate electrode 205 and the anode electrode 7 (FIG. 4 (F)). )). A gate electrode 205 made of a Ta thin film having a thickness of 2000 angstrom was formed by using a sputtering method as the directional particle deposition method. When the directional particle deposition method is used, the overhanging portion such as the emission protrusion 4 becomes a shadow, and the first cathode electrode 2
The layer of the second cathode electrode 203b deposited on the surface of 03a and the layer of the gate electrode 205 deposited on the surface of the flat substrate 1 are electrically separated, and the missing portion having the same shape as the emission protrusion 4 is vertically below the emission protrusion 4. Is formed in a self-aligned manner. As such directional particle deposition method, sputtering method, vapor deposition method, E
CR (Electron Cyclotron Res
once) plasma deposition method, cluster ion beam method, etc. can be applied.

The electrode layer of the Ta thin film was processed by the dry etching method to form the gate electrode 205 and the anode electrode 7. At this time, it is important to cover with a photoresist so that the missing portion is not eroded. The cathode electrode 203 includes a first cathode electrode 203a and a second cathode electrode 203b.
And the tip radius of curvature was about 400 angstroms. The first cathode electrode 203
When the material of a and the second cathode electrode 203b are different, one of the electrodes may be removed at the emission protrusion 4 and the rest may be used as an electron emission electrode. If the emission projections 4 are made thin in this way, the radius of curvature of the tip in the film thickness direction becomes small, and a lower threshold value can be achieved.

The electrical characteristics of the field electron emission device manufactured as described above were measured in a high vacuum. When the anode cathode voltage _V ak = 200V constant grounding the cathode electrode 205, the cathode current _I k = 4 × ¹⁰ in the gate cathode voltage ^{_{V gk = 60V - 8 A,}} 6 × 10 at 100V
^-5 A was obtained. The parasitic capacitance between the cathode electrode 203 and the gate electrode 205 was about 10 fF.

In the present embodiment, the Mo thin film and the Ta thin film were used as the electrode material for the cathode electrode 203 and the like, but the present invention is not limited to this, and other metals such as tungsten, silicon, chromium, aluminum and the like are also available. An alloy containing as a component can be used. Further, as the flat substrate 1, an insulating substrate in which an insulating material is provided on the surface of a conductive substrate such as a silicon substrate, or a ceramic substrate having good thermal conductivity such as an alumina substrate may be used. Furthermore, the insulating layer 8 or the etching mask 81 is not limited to the silicon dioxide thin film, and a silicon nitride thin film, an alumina thin film, or the like can be used.

In order to reduce the threshold voltage of electron emission, the emission protrusions 4 may be coated with a material having a small work function such as barium, thorium or cesium, and the cathode electrode 203 may be formed of such a material. Good.

In order to reduce the noise of electron emission, it is possible to increase the S / N ratio by providing a sufficiently large number of emission protrusions 4 and simultaneously driving these to simultaneously emit electrons. It should be noted that the same effect can be obtained if the electron emission is generated not only at one point of the tip of the emission protrusion 4 but also from a plurality of auxiliary protrusions formed beside the tip. Further, by connecting a self-bias resistor or a non-linear resistor in series with the cathode electrode, it is possible to prevent overcurrent and reduce noise.

Further, by forming a phosphor on the surface of the anode electrode 7 to form a light emitting display, or by forming a material such as a copper thin film which generates X-rays and exciting it with an electron beam, a fine pattern can be obtained. An X-ray source can be constructed. As a matter of course, the above manufacturing method can be similarly used in the quadrupole field electron emission device shown in FIG.

As described above, the method of manufacturing the electric field electronic device of the present invention has the following remarkable effects. (1) Compared with the method of manufacturing a cathode electrode by over-etching the cathode electrode layer or the etching mask layer formed on the surface of the cathode electrode layer, it is possible to manufacture an emission protrusion having a smaller tip curvature radius. This is because the etching characteristic of the etching mask formed on the surface of the flat substrate 1 is very isotropic, and an etching means such as a wet etching method having a high etching rate can be used. Since it is difficult to wet-etch Mo and the like, it is difficult to form the emission projections 4 by the over-etching method. (2) L _gk is generally determined by the film thickness of the island-shaped insulating layer and the gate electrode. The controllability of the film thickness is excellent due to the development of LSI technology, and a field electron emission device having good uniformity and a low electron emission threshold voltage is realized. In the conventional technology, L
_{Although gk} had a limit of 0.8 μm, it was found that the _gk was 0.8 μm.
It is possible to manufacture a film having a thickness of 1 μm or less. (3) By the over-etching method, the radius of curvature of the tip of the emission projection 4 was made small, and the low threshold value could be achieved. In the prior art, the radius of curvature of the tip was limited to about 2000 angstroms, but the present invention enables it to be 400 angstroms or less. (4) The over-etching method has a feature that a convex portion such as the emission protrusion 4 becomes a sharp convex portion having a smaller radius of curvature, while a concave portion becomes a smooth concave portion. By utilizing such a property, the convex portion and the concave portion of the cathode electrode can be selectively used to prevent accidental electron emission and short circuit between the electrodes. (5) The gate electrode can be formed in a self-aligned manner with respect to the cathode electrode, the parasitic capacitance between the electrodes can be reduced, and high speed operation can be achieved. In particular, the first cathode electrode having a small specific resistance is provided to reduce the wiring resistance, which is suitable for manufacturing a high-speed device having a smaller wiring delay.

FIG. 6A is a schematic plan view of a flat quadrupole vacuum tube using the above-mentioned novel quadrupole field electron emission device, and FIG. 6B is a schematic sectional view taken along the line AA.

In the flat quadrupole vacuum tube, the flat substrate 1 having the above-mentioned quadrupole field electron emission device and the counter substrate 14 are arranged substantially in parallel, and the sandwiching body 17 is provided around the flat substrate 1,
This is a structure in which a quadrupole field electron emission device is enclosed in a vacuum layer 23 surrounded by the counter substrate 14 and the sandwiching body 17. The counter substrate 14 is made of a quartz substrate, has a conductive thin film 15 for preventing electrification on the surface facing the vacuum layer 23, and has a sealing port 16 for evacuating and sealing the vacuum layer 23. The sealing port 16 is made of Au / Au inside the opening formed with the Cr / Au thin film.
The Sn alloy is melted and filled with holes. The getter material 18 is Al.Ba previously formed on the surface of the counter substrate 14.
It is made of an alloy thin film, and after the vacuum layer 23 is completed, it is heated by a laser and vapor-deposited on the wall surface of the vacuum layer 23 to revive the getter effect. The holding body 17 is made of low melting glass powder and has a diameter of 100.
A glass fiber having a diameter of μm is mixed and fired. The glass fiber is adhered to each substrate with good airtightness, and the gap of the vacuum layer 23 is maintained at 100 μm.

External extraction terminals of each electrode of the quadrupole field electron emission device, that is, the cathode terminal 19 and the gate terminal 2
0, the control terminal 21 and the anode terminal 22 are led out of the vacuum layer 23 by a metal thin film from between the holding body 17 and the flat substrate 1. The size of the flat quadrupole vacuum tube is 7 mm in width, 4 mm in length, and 2.2 mm in thickness, which is 1/1 in volume as compared with the conventional thermionic emission type vacuum tube.
Very small, less than 000. The vacuum degree of the vacuum layer 23 is 1 ×
It is 10 ⁻⁷ Torr or less. Although the anode electrode 7 is formed on the surface of the flat substrate 1, the present invention is not limited to this, and may be formed on the surface of the counter substrate, for example. Further, at this time, the control electrode 6 is positioned so as to be located between the emission protrusion 4 and the anode electrode 7 so that the vacuum layer 2 is formed.
3 may be arranged inside.

The electric emission characteristics of the quadrupole field electron emission device are shown in FIGS. FIG. 7 is an electrical connection diagram of a cathode-electrode grounded voltage amplifier using a quadrupole field electron emission device. The quadrupole vacuum tube described above is represented by a symbol mark 30 shown in the center of FIG. 7. This means that the cathode electrode 3, the gate electrode 5, the control electrode 6 and the anode electrode 7 are enclosed in the vacuum layer 23.

The driving method of the voltage amplifier using the quadrupole field electron emission device is as follows. That is, the cathode electrode 3 is grounded, a positive potential gate voltage 26 ( _VGK ) is applied to the gate electrode 5, and the load resistance 2 is applied to the anode electrode 7.
Anode voltage 27 (V of positive potential through 8 ( _RL )
_AK ) and a control bias voltage 25 (V _CK ) and an input signal voltage 24 (V _in ) connected in series to the control bias voltage 25 (V _CK ) are applied to the control electrode 6.
An output signal voltage 29 (V _out ) proportional to the input signal voltage 24 is obtained from the connection portion of the load resistance 28 and the load resistance 28.

FIG. 8 is a graph showing electron emission characteristics of the above-mentioned quadrupole field electron emission device. In the electrical connection diagram of FIG. 7, the input signal voltage 24 and the control bias voltage 25 are 0 V, the anode electrode 27 is V _AK = 400 V, and the gate current 32 ( _IG ) and the anode current with respect to the gate voltage 26 of the quadrupole field electron emission device. 31 _(I A)
It is the result of measuring the dependency of. The gate current 32 and the anode current 31 exponentially increase with respect to the gate voltage 26, indicating that the emission current is an FN tunnel current. The anode current 31 is about two orders of magnitude smaller than the gate current 32. In the conventional driving method in which the anode voltage 31 is controlled by the gate voltage 26, the power conversion efficiency is poor because I _G > I _A , and the transfer characteristic is also an exponential function, which makes it difficult to use in a linear amplifier or the like. Therefore, the anode current 31 is controlled by the voltage applied to the control electrode 6.

FIG. 9 is a graph showing the input / output static characteristics of the quadrupole field electron emission device described above. This is because the gate voltage 26 is V _GK = 140 V, the input signal voltage 24 is 0 V, and the anode electrode 27 is V _AK = 400 V in the electrical connection diagram of FIG. 7.
As a result, the dependence of the control current 33 (I _C ) and the anode current 34 on the control bias voltage 25 of the quadrupole field electron emission device is measured. V _CK <
Anode current 34 is exponential (non-linear) in the range of 0V
However, the anode current 34 changes linearly (linearly) in the range of V _CK > 0V. That is, V _CK
Since the anode current 34 is proportional to the voltage applied to the control electrode 6 in the range of> 0 V, it can be used as a linear amplifier. At this time, the control current 33 is 1% or less of the anode current 34, and the field-effect voltage amplifier has a good input / output power conversion efficiency.

The control mechanism of the anode current 34 by the electric field effect of the control electrode 6 is similar to that of the grid electrode of the conventional thermionic emission type vacuum tube. That is, the anode current 34 is controlled by the electric field (potential gradient) formed between the control electrode 6 and the cathode electrode 3 by the potential of the control electrode 6.
When a negative voltage is applied to the control electrode 6 and a negative electric field is formed in the vicinity of the emission protrusion 4, repulsive force is applied to the emitted electrons toward the anode electrode 7 and the amount of electrons that can reach the anode electrode 7 is limited. .

The electrons jumping out from the cathode electrode have an initial velocity and thus fly toward the anode electrode.
When a negative potential control electrode is present on the way, the potential is slowed down by this negative potential gradient, and some electrons return to the cathode electrode direction. Thus, the electrons stay between the cathode electrode and the control electrode to form an electron cloud (space charge limited region). The electrons that can flow to the anode electrode are statistically limited to those having higher energy than the control potential. It is known that the conduction of electrons in such a space charge limited region has a very small noise current. The fluctuation of the space charge is smaller than the fluctuation of the emission current from the cathode electrode (noise current), especially the fluctuation of the electrons with small energy can be almost ignored, and only a part of the electrons with high energy causes the noise of the anode current. This is because The conventional triode field electron emission device does not have the space charge limiting region described above, and most of the electrons emitted from the cathode electrode reach the anode electrode (conduction of electrons in the emission limiting region), so the emission current noise is reduced. Appears as noise in the anode current.

On the other hand, when a positive voltage is applied to the control electrode 6, the repulsive force on the emitted electrons weakens and the anode current 34 increases. By the way, the positive potential gate electrode 5 plays the same role as the space charge grid electrode of the conventional pentode vacuum tube, and prevents the space charge from staying in the vicinity of the cathode electrode 3. In the present invention, in order to prevent the influence of secondary electrons of the anode electrode 7, a suppression electrode may be additionally formed between the anode electrode 7 and the control electrode 6 as described later.

By setting the control bias voltage 25, the linear region and the non-linear region can be used properly. The operation in the linear region is convenient for a linear amplification function such as a voltage amplifier, and the operation in the non-linear region is convenient for a switching function. Further, when the gate voltage 26 is reduced, the control bias voltage 25 that gives the boundary between the linear region and the non-linear region shifts to the low voltage side. Therefore, by arbitrarily setting the gate voltage 26, the set voltage of the control bias voltage 25 can be freely set. It has features such as selection. But,
In the above-mentioned quadrupole field electron emission device, as shown in FIG. 8, the gate current is significantly larger than the anode current, and the existence of the reactive current flowing through the gate electrode is inefficient.

FIG. 10 is a graph showing the static characteristics of the anode of the multipole field electron emission device of this example. In the electrical connection diagram of FIG. 7, the gate voltage 26 is V _GK = 140 V, the input signal 24 is 0 V, and the control bias voltage 2 is
5 is a result of measuring V _AK -I _AK static characteristics when V _CK was changed to V _CK = 20, 40, 60, 80 V. Figure 1
0 multipole field emission device of the present embodiment as seen from the _{referred I AK} in the range of V AK> 150 V becomes approximately constant and _{I AK} is increased in proportion to _{V GK,} conventional thermionic It has the static characteristics of the anode similar to the emission type pentode vacuum tube. This characteristic has a very large anode resistance,
Moreover, since the input and output are in a proportional relationship, they are most suitable for applications such as linear amplifiers.

The load resistance 28 in FIG. 7 is set to R _L = 5G.
If Ω, the load straight line 36 can be drawn on the graph of the anode electrode static characteristics of FIG. The basic function as an amplifier was confirmed by such a circuit. That is, when the control bias voltage 25 is set to V _AK = 40 V and a sine wave of 20 V (v _in = 20 sin (ωt) V) is applied as the input signal 24, a sine wave of 50 V (v _out = −50 sin) is output as the output signal 29. (Ωt) V) was obtained, and the voltage amplification factor was confirmed to be 2.5 times, confirming the amplification function. When the frequency ω was increased and the frequency characteristics of the amplifier were measured, the cutoff frequency ω _c was 100 MHz or higher.

FIG. 11 shows the control voltage 25 (V _CK ).
The relationship between the gate electrode I _G , the anode current I _A, and the control current I _C is shown. Gate current I _G
Is almost constant. Control current I _C is V _CK
When <V _GK , I _C <0. Ion current in vacuum and surface leak current of the substrate can be considered as the cause of the negative current, but it is probably surface leak current between the gate electrode and the gate electrode because the current is stable. The anode current I _A monotonically increases with respect to the control voltage V _CK . Especially when the control voltage is large, the anode current increases almost in proportion to this. That is, a linear region was recognized in the transfer characteristic. It was found that the emission current was almost constant with respect to V _CK , and the emission current was determined by the gate voltage and was not affected by other electrode potentials.

FIG. 12 shows the anode characteristics with the control voltage V _CK as a parameter. The anode current I _A increases depending on both the anode voltage V _AK and the control voltage V _CK , and follows the following equation.

I _A = K (V _CK + aV _AK ) ⁿ where K, a and n are constants. This characteristic is similar to the characteristic of the thermionic emission type triode vacuum tube in the space charge limited region. Amplification factor μ is (= 1 / a) and the mutual conductance _{g m (= dI A / dI} CK) and is estimated from the diagram _V AK _{= 300 V,} respectively 1 and 2.6E-10S when V CK = 150V. The n value is about 1.
It was 3. When V _CK > V _GK , a part of the anode current tends to flow into the control current.

In the characteristic of FIG. 12, g _m and μ are very small. Practically, 1 mS or more and 100 or more are required respectively. There are several ways to improve each of them, but it is effective to increase the emission current, especially for g _m .

In order to further improve the voltage amplification factor, the transconductance and the frequency characteristic, the number of emission projections 4 of the cathode electrode 3 is increased to increase the emission current, or the structure of the gate electrode 3 is devised to make an invalid gate. It is necessary to reduce the electrodes and increase the anode current. In this embodiment, the number of the ejection protrusions 4 is 6, but this is
If the emission current is increased 10,000 times, the voltage amplification factor and mutual conductance are increased 10,000 times, and the frequency characteristic is about 1 time.
I was able to improve it by 00 times. In order to reduce the ineffective gate current, the structure in which the width of the gate electrode 5 is made smaller, or the structure in which the gate electrode 5 is formed on the slope having an opening angle in the projecting direction of the emission projection 4 is used, It suffices to reduce the probability of collision with 5.

In this embodiment, the cathode electrode 3 is grounded as an electrical connection method, but the present invention is not limited to this.
For example, an electrical connection method in which the gate electrode 5 is grounded may be used. FIG. 13 is an electrical connection diagram in which the multi-pole field electron emission device of this embodiment is used in a gate electrode grounding type voltage amplifier. The gate electrode 5 is grounded and a negative cathode voltage 37 is applied to the cathode electrode 3. According to this electric connection method, unlike the one shown in FIG. 7, the boundary between the linear region and the non-linear region does not change depending on the value of the emission current, so that the amplifier is easy to use.

When the emission current is large, in order to obtain an emission current with less noise, a driving method in which a self-bias resistor R _SB is inserted between the cathode electrode and the anode electrode as shown in FIG. 14 can be considered. FIG. 15 shows this anode characteristic.
2MΩ self-bias resistor R to stabilize the emission current
_SB was inserted in series with the cathode electrode. V _KG = -27
The emission current was about 10 μA at 0V. From this graph, g _m = 10 nS and μ = 1.5 were obtained.

The characteristics are summarized in Table 1. Among the quadrupole devices, A corresponds to FIG. 12 and B corresponds to FIG.

[0066]

[Table 1]

FIG. 16 is a circuit diagram of a quintuple field electron emission device in which a screen electrode S is added to the quadrupole field electron emission device, and FIG. 17 is a diagram showing its anode characteristic. The number of protrusions of the cathode electrode is 10,000, V _KG = -140
V, cathode electrode current I _k = 20 mA, V _SG = 10
It is measured under the conditions of 0 V and R _L = 1 KΩ.
In FIG. 17, if a load of R _L = 80 KΩ is inserted (shown by a broken line), the amplification factor is 4 times. The operating point in this case is _V i = -40V. The device having the five poles has a characteristic that the electric field near the control electrode does not fluctuate due to the presence of the screen electrode even if the anode voltage fluctuates, so that the anode current remains unchanged. That is, the anode resistance γa γa = ΔV _A / ΔI _A increases.

In the next embodiment, the structure and manufacturing method of a flat type hexapole field electron emission device will be described. FIG. 18 (A),
(B) And (C) is a schematic plan view of a planar hexapole field electron emission device, a schematic vertical sectional view taken along the line BB and a schematic vertical sectional view taken along the line CC, respectively. This device has a screen electrode 50 and a suppressor electrode 53 between the control electrode 6 and the anode electrode 7 of the quadrupole field electron emission device.
It is a structure provided with. The control electrode 6 and the screen electrode 50 are the columnar control electrode 64 and the columnar screen electrode 65 formed on the respective electrodes.
Each is equipped with. These columnar electrodes are formed so as to pierce the plane defined by the surface of the cathode electrode 3, and the height thereof is at least larger than the film thickness of the island-shaped insulating layer 2.

The columnar control electrode 64 has a diameter of 3 μm,
The columnar shape has a height of 5 μm, and is provided at a pitch of 10 μm so as to be arranged between the two emission protrusions 4 at a position apart from the emission protrusions 4 by about 10 μm. The columnar screen electrode 65 has a flat plate shape with a width of 5 μm, a thickness of 3 μm, and a height of 5 μm.
They are provided one by one with a distance of 0 μm. The suppressor electrode 53 has a width of 5 μm and is provided between the anode electrode 7 and the screen electrode 50. The distance from the screen electrode 50 is about 20 μm and the distance from the anode electrode 7 is about 50 μm.
m.

The cathode electrode 3 has eight emission protrusions 4 formed at a pitch of 5 μm. The thickness of the island-shaped insulating layer 2 is 5
000 angstroms. The gate electrode 5 is formed on the cathode electrode 3 in a self-aligned manner, the distance between the gate electrode 5 and the emission projection 4 is 3000 angstrom, and the width in the vicinity of the tip is about 2 μm. The distance from the control electrode 6 is 4 μm.

The electrons emitted from the cathode electrode 3 by the electric field of the gate electrode 5 are controlled by the electric field of the control electrode 6, and the amount of electrons that can reach the anode electrode 7 is limited. The screen electrode 50 is held at a constant potential,
The fluctuation of the electric field of the control electrode 6 due to the electric field of the anode electrode 7 is prevented. The suppressor electrode 53 prevents secondary electrons generated from the anode electrode 7 from returning to the control electrode 6. FIG. 19 is for explaining the method of manufacturing the sextupole field electron emission device of the present embodiment, and is a schematic vertical cross-sectional view after the main manufacturing steps are completed. The manufacturing method will be described below.

First, the insulating layer 8 and the cathode electrode layer 9 are sequentially formed on the surface of the flat substrate 1, and a photoresist 11 is further formed (FIG. 19A). The flat substrate 1 is made of an alumina substrate. Since a ceramic substrate such as an alumina substrate is insulative and has a large thermal conductivity, it is excellent as a substrate for a field electron emission device that handles large power.
Besides, a crystalline substrate such as a semi-insulating GaAs substrate or a diamond substrate may be used. The insulating layer 8 has a film thickness of 50
The silicon dioxide thin film having a thickness of 00 angstrom and the cathode electrode layer 9 are made of a tantalum (Ta) thin film having a thickness of 1000 angstrom. The photoresist 11 is used for forming the cathode electrode 3.

Next, the cathode electrode layer 9 is processed by the over-etching method to form the first cathode electrode 3a (FIG. 1).
9 (B)). A dry etching method was used as the excess etching method. CF ₄ / O ₂ gas = 120/10
When the etching method was performed at 0 and RF power of 700 W for 25 minutes, the cathode electrode layer 9 was over-etched by about 1 μm, and the emission protrusion 4 having the tip curvature radius of 300 angstrom was formed.

Next, the insulating layer 8 is partially removed by etching to form the island-shaped insulating layer 2, and the photoresist 11 is used.
Are removed (FIG. 19C). The method of forming the island-shaped insulating layer 2 is the same as the method described in the above embodiment.

Next, the column forming layer 56 is formed (FIG. 17).
(D)). The pillar forming layer 56 is made of a photosensitive polyimide resin having a film thickness of 5 μm formed by a coating method. As the photosensitive polyimide resin, for example, negative type PI-410 (manufactured by Ube Industries, Ltd.) or the like can be used. In addition, the pillar formation layer 5
It is obvious that, in addition to such an organic material, an inorganic material can be used as the material of 6.

Next, the pillar forming layer 56 is photoetched, and the control electrode pillars 64 and the screen electrode pillars 6 are formed.
5 is formed (FIG. 19E). When the pillar forming layer 56 is a photosensitive material, it can be processed by a photoetching method, and when it is an organic material or an inorganic material other than this, RIE (Reactive)
An anisotropic etching method such as e Ion Etching) is suitable.

Next, the gate electrode layer 133 is formed by the directional particle deposition method (FIG. 19F). A sputtering method was used as the directional particle deposition method to form a gate electrode layer 133 made of a Ta thin film having a film thickness of 2000 angstrom. The gate electrode layer 133 was also deposited on the side surfaces of the control electrode pillar 64 and the screen electrode pillar 65 so as to cover them.

Finally, the gate electrode layer 133 is processed by etching, and the second cathode electrode 3b, the gate electrode 5, the control electrode 6, the columnar control electrode 64, the screen electrode 50, the columnar screen electrode 65, and the suppressor electrode 53.
Then, the anode electrode 7 is formed (FIG. 19G).

When the control electrode column 64 and the screen electrode column 65 are made of an organic material, a high vacuum state can be maintained by removing them. A method of removing these will be described. First, a resist is applied to the surface of the flat substrate 1. At this time, the film thickness of the resist becomes thinner than the other at the tip portions of the columnar control electrodes 64 and the columnar screen electrodes 65. Next, when the resist is ashed by the dry etching method, the gate electrode layer 1 at the tip of the columnar electrode is formed.
33 appears. When this gate electrode layer 133 is also removed by etching, the tips of the respective electrode columns are exposed through the openings. Finally, these electrode columns are removed with a solvent or the like. The columnar electrode manufactured in this manner has no organic material as a degassing source inside and is hollow, so that a high vacuum state can be generated and maintained by heating and exhausting.

FIG. 20 is a schematic perspective view of a sextupole vacuum tube using the sextupole field electron emission device of this embodiment. This is a hexapole field electron emission device vacuum-packaged in a metal can. That is, the flat substrate 111 on which the hexapole field electron emission device is formed is fixed to the hermetic seal 160,
Connect each electrode and hermetic terminal 161 to the wire 16
The vacuum layer 164 is formed by connecting the two and sealing the hermetic seal 160 and the cap 163 in vacuum. A getter material 165 is formed and revived on the inner wall surface of the cap 163 in order to maintain a high vacuum.

FIG. 21 is an electrical connection diagram of a cathode-electrode grounded voltage amplifier using the above-mentioned hexapole field electron emission device. The sextupole vacuum tube shown in FIG. 18 is represented by a symbol mark 66 shown in the center of FIG. This is the cathode electrode 3,
Gate electrode 5, control electrode 6, screen electrode 5
0, the suppressor electrode 53 and the anode electrode 7 are enclosed in the vacuum layer 164. The cathode electrode 3 and the suppressor electrode 53 are grounded, a positive potential gate voltage 26 is applied to the gate electrode 5, a control bias voltage 25 and an input signal voltage 24 serially connected thereto are applied to the control electrode 6, and the anode electrode Load resistance 2 to 7
An anode voltage 27 is applied via 8. Although an arbitrary positive potential can be applied to the screen electrode 50, it is set to the same potential ( _VGK ) as the gate electrode 5 in order to simplify the number of power supplies and the number of wirings. The connection between the cathode electrode 5 and the suppressor electrode 53, and between the gate electrode 5 and the screen electrode 50 can be performed on the surface of the flat substrate 1 or inside the vacuum layer 164. By the above electrical connection method, the number of terminals and the number of power sources are the same as those of the quadrupole vacuum tube already described, though it has six poles.

Next, a method of driving the hexapole field electron emission device will be described. First, a constant gate voltage 2 is applied to the gate electrode 5.
When 6 is applied, a certain amount of electrons are emitted from the cathode electrode 3. The amount of emitted electrons is always constant unless the gate voltage 26 is changed. In this state, when the anode voltage 27 is kept constant and the input signal voltage 24 which is DC biased is applied to the control electrode 6, the anode current is controlled in proportion to this and the output signal voltage 29 amplified by the load resistor 28 is obtained. To be The electric field effect on the electrons of the control electrode 6 is the same as that described in the disclosed embodiment. The screen electrode 50 has a role of preventing electric field fluctuation near the control electrode 6 due to voltage fluctuation of the anode electrode 7 and improving anode resistance and frequency characteristics. The suppressor electrode 53 prevents secondary electrons generated from the anode electrode 7 from flowing toward the control electrode 50.

V _AK = 300V, V _GK = 160V, V
_{When the} sextupole field electron emission device was driven with _GK = 60 V and R _L = 1 GΩ, a voltage amplification factor μ = 8 was obtained. At this time, the mutual conductance g _m = 2 × 10 ⁻⁹ S. Further, the frequency characteristics were improved by about twice as compared with the quadrupole field electron emission device described in the above embodiment. It is considered that this is due to the shielding effect of the anode electric field by the screen electrode 50.

FIG. 22 is another electrical connection diagram of the hexapole field electron emission device, and FIG. 23 is a diagram showing its anode characteristic. The number of projections on the cathode electrode is 10,000
V _{K G} = -140V, the cathode current _I K = 20 m
It is measured under the conditions of A, V _SG = 100 V, and R _L = 1 KΩ. As is apparent from comparison of FIG. 23 with FIG. 17, the anode resistance is further increased by the presence of the suppressor electrode, and saturation characteristics are exhibited even in a region where V _AG is small. γ _a
= 8 MΩ.

The present invention can be applied not only to the flat type device as described above, but also to the vertical type device. In this embodiment, as an example of this, a vertical quadrupole field electron emission device formed on the surface of a silicon single crystal substrate will be described.

FIG. 24 is a schematic partial vertical sectional view of a vertical quadrupole field electron emission device of this embodiment. This device is (1
A conductive flat substrate 40 made of an n-type silicon single crystal substrate having a (00) plane, and provided on the surface of the flat substrate 40.
A cathode electrode 41 having a weight shape protruding in a direction perpendicular to the surface, a first insulating layer 42 provided on the surface of the flat substrate 40 and opened around the cathode electrode 41, and a surface of the first insulating layer 42 A gate electrode 43 provided around the cathode electrode 41 and a second insulating layer 44 provided on the surface of the gate electrode 43 and opened around the cathode electrode 41, and provided on the surface of the second insulating layer 44. The counter substrate 46 having a control electrode 45 opened around the cathode electrode 41 and an anode electrode 47 arranged on the control electrode 45 via a vacuum layer 48 is a main component.

The cathode electrode 41 is manufactured by processing the surface of the flat substrate 40 by an anisotropic etching method, and has a substantially conical shape. The weight axis is perpendicular to the plane substrate 40, the height is about 1.2 μm, and the cross-section apex angle is about 9 μm.
It is 0 degrees. In the present invention, a cathode electrode formed by another manufacturing method may be used, for example, a Spindt type may be used. First insulating layer 42
And the second insulating layer 44 is made of a silicon dioxide thin film,
Film thickness is 6000 Å and 3 μm, respectively
Is. The opening diameters of the two insulating layers are almost the same and are about 3 μm. The gate electrode 43 and the control electrode 45 are made of Mo.
It is a thin film, and the film thickness is 2000 angstrom and 3000 angstrom, respectively. The aperture diameters of both electrodes are almost the same and are about 1.2 μm. The flat substrate 40 and the counter substrate 46 are bonded to each other with a sandwiching body formed around them, and a vacuum layer 48 is formed between them. The vacuum layer 48 has a thickness of about 50 μm. An aluminum thin film or a transparent conductive film is used for the anode electrode 47.

The operation mechanism of this quadrupole field electron emission device will be described. When a positive potential is applied to the gate electrode 43 with respect to the cathode electrode 41, electrons are field-emitted from the projection tip of the cathode electrode 41. The emitted electrons pass through the openings of the gate electrode 43 and the control electrode 45 and pass through the anode electrode 4
You can reach 7. However, the amount of electrons that can reach the anode electrode 47 (anode current) is controlled by the voltage of the control electrode 45. The control of the anode current by the electric field effect of the control electrode 45 is the same as the mechanism described in the first embodiment. Therefore, there is a linear region in which the voltage of the control electrode 45 and the anode current are in a proportional relationship. That is, when the voltage of the control electrode 45 is negatively large, a negative potential gradient is formed in the direction of the cathode electrode 41 from the control electrode 45, and the emitted electrons are repelled in the direction of the gate electrode 43. In such a case, the anode current is small. On the other hand, when the voltage of the control electrode 45 is large, a positive potential gradient is formed, many electrons can pass through this, and a large anode current is obtained.

The electrical characteristics of the quadrupole field electron emission device of this example in which 10,000 cathode electrodes 41 were formed were measured.
In the cathode grounded circuit, the gate voltage is 120
An emission current of 3 mA was obtained at V, and the change in the anode current with respect to the voltage of the control electrode 45, that is, the mutual conductance was g _m = 20 μS. The reactive current flowing through the gate electrode 43 was 1% or less, and good characteristics were obtained.

It is obvious that the electrical characteristics can be further improved by forming a screen electrode, a suppressor electrode, etc. in the quadrupole field electron emission device of this embodiment. Although the anode electrode 47 is formed on the counter substrate 46 in this embodiment, it may be formed on the surface of the flat substrate 40. At this time, the control electrode 45 is devised so as to be arranged between the anode electrode 47 and the gate electrode 43. For example, it may be installed in the air inside the vacuum layer 48. Further, in order to reduce the overlapping capacitance between the electrodes and improve the frequency characteristics and the breakdown voltage, it is appropriate to thin the wiring below the cathode electrode 41 and remove the excess area to eliminate the overlapping portion. is there. In this case, the insulating flat substrate 40 is used.

As in the quadrupole field electron emission device of this embodiment, the gate electrode 43 is formed perpendicularly to the electron emission direction from the cathode electrode 41, or the opening of the gate electrode 43 surrounds the flow path of emitted electrons. The multi-pole field electron emission device thus formed has a small reactive current flowing into the gate electrode 43 and has high power efficiency. This is because when the emitted electrons pass through the gate electrode 43, they only cross a distance of about the film thickness of the gate electrode 43, and because they pass near the center of the opening, the emitted electrons collide with the gate electrode 43. This is because the probability of doing is small. It is very effective to apply such a structure to a lateral multipole field electron emission device.

In order to increase the mutual conductance of the model multi-pole tube element and improve the performance, for example, the structure of the gate electrode 5 in the quadrupole field electron emission device shown in FIG. However, if the emission area is increased, the number of electrons flowing into the gate electrode 5 also increases, which makes it difficult to obtain a high-performance power amplifier.

FIG. 25 is a partially enlarged perspective view of a multipole field electron emission device in which the structure of the gate electrode 51 is ring-shaped. The cathode electrode 3 has the same structure as that shown in FIG. An opening 52 is provided in a part of the gate electrode 51 at a position corresponding to the emission protrusion 4 of the cathode electrode 3, and electrons emitted from the emission protrusion 4 are allowed to pass through the opening 52. It becomes smaller, the reactive current can be reduced, and the input resistance can be increased.

The opening 52 is not limited to the shape shown in FIG. 25. An opening-shaped electrode having the same potential is formed around the emission protrusion 4, and electrons emitted from the emission protrusion in the opening-shaped electrode. Any structure may be used as long as it can pass through. Therefore, the opening 52 may be circular or angular. Further, even if the openings 52 are not formed corresponding to all the emission projections 4, for example, every other opening 52 is formed corresponding to the emission projections 4, it can function as an electron emission device.

By providing an opening in the gate electrode 51,
I, as shown in FIG._G  ≧ I _A  Power conversion efficiency
Is significantly improved, and the presence of the control electrode
Field emission device having linear input / output static characteristics
Can be provided. 61 is a control electrode
7 is an anode electrode. In FIG. 25,
The structure of the trawl electrode 61 emits like the gate electrode 51.
A second opening 62 is provided for passing an electric current
However, the control electrode 61 does not necessarily have such a structure.
It is not necessary to make the structure, and it is the plate-like electrode shown in FIG.
But it doesn't matter.

The quadrupole field electron emission device having the structure of the gate electrode as shown in FIG. 25 has the linear input / output relationship of the structure shown in FIG. 1 and the gate current is remarkably reduced (the gate current is the anode current). 1/10 or less of),
The gate reactive current can be significantly reduced.

FIG. 26 shows the control electrode 61.
It is a perspective view in which a columnar control electrode 63 is provided. In the figure, the columnar control electrode 63 is shown by the adjacent opening 52.
It is provided in the middle. The shape may be a cylinder or a prism.

In the multipole field electron emission device of the present invention, the number of multipolarity is arbitrary, and of course, it may be, for example, a hexapole field electron emission device. 18 (A), (B),
Gate electrode 2 of the hexapole field electron emission device shown in (C)
A structure in which 0 is replaced with the gate electrode 51 shown in FIG. 25 is conceivable.

It is a device in which the gate electrode 5 in FIG. 18 is replaced with the structure of the gate electrode 51 shown in FIG. In this case, the electrons emitted from the emission projections 4 are controlled by the electric field of the control electrode 6, and the amount of electrons that can reach the anode electrode 7 is limited. The screen electrode 50 is held at a constant potential, and prevents the electric field of the control electrode 6 from fluctuating due to the electric field of the anode electrode 7. The suppressor electrode 53 prevents secondary electrons generated from the anode electrode 7 from returning to the control electrode 6.

However, the above-described three-dimensional structure of the gate electrode has manufacturing problems such as difficulty in gap control due to the thin film manufacturing technology, and the electric field distribution between the cathode electrode and the gate electrode is not uniform, and Ia / Ig There are limits to the characteristics. Further, the manufacturing process requires four photomask processes, which requires a complicated manufacturing technique. Therefore, a gate electrode having a uniform structure for the three-dimensional electric field distribution between the cathode electrode and the gate electrode is provided, and it is self-aligned in the manufacturing thereof (even if the position of one electrode is displaced, the other It is desirable to have a structure that allows for manufacturing in which the positions of the electrodes are correspondingly modified.

What is disclosed below is a multi-pole field electron emission device and a method for manufacturing the same which have solved the technical problems, in which an extremely stable electrode is formed and the Ia / Ig characteristics are remarkably improved. . It is formed on an insulating layer provided on the surface of an insulating flat substrate and has a cathode electrode having a plurality of emission protrusions overhanging from the insulating layer,
The insulating projection includes an anode electrode formed on the surface of the insulating flat substrate for collecting emitted electrons, a plurality of columnar gate electrodes provided between the cathode electrode and the anode electrode, and the emission protrusions are adjacent to each other. The multi-pole field electron emission device is characterized in that it is located in the middle of the gate electrode, and the shape of the gate electrode is a projection corresponding to the emission projection on the cathode electrode side. In this multi-pole field electron emission device, an insulating layer and an electrode layer are sequentially formed on the surface of an insulating flat substrate, a resist is applied while leaving a flat pattern of the gate electrode, and then the electrode layer and the insulating layer are formed into the flat pattern. It is manufactured by forming an emission protrusion by over-etching beyond the plane pattern with an etching solution that has entered from, and then forming a columnar gate electrode at the position of the plane pattern and removing the resist.

FIG. 27 (a) shows a novel multi-pole electric field electronic device.
It is a top view, the figure (b) is the aa line, the figure (c).
Is a vertical cross-sectional view of the bb line, and FIG.
FIG. This device is a table of a flat substrate 1 made of quartz.
The cathode electrode 303, the gate electrode 305, and the
The electrode 307. The cathode electrode 303 is SiO _Two
  Emission overhanging the surface of the island-shaped insulating layer 302
Formed with a thin film (for example, about 2000) with protrusions 4
Be done. The cathode electrode 303 is a stack of a plurality of thin films
(For example, a molybdenum thin film is laminated on a tungsten thin film.
Thing). The emission protrusion 4 is the surface of the flat substrate 1.
It has a structure protruding in the direction of the gate electrode 305 in parallel with the
The island-shaped insulating layer 302 does not exist near the tip of the. Emission collision
The radius of curvature of the tip of the origin 4 in the plane direction is 400 angstroms.
Or less.

The gate electrode 305 is formed in self alignment with the cathode electrode 303, and one angle θ in the direction of the cathode electrode 303 in the shape of a pentagonal prism is, for example, 60 ° to 90 °.
Have an angle of. The emission protrusions 4 are adjacent to the gate electrode 30.
They are formed equidistantly in the middle position of 5. Therefore, the electric field distribution in the vicinity of the emission protrusion 4 is bilaterally symmetrical. When the height G of the pentagonal prism of the gate electrode 305 is made higher than that of the cathode electrode 303, the electric field distribution in the vicinity of the emission protrusion 4 is bilaterally symmetric and is substantially uniform in the vertical direction. Therefore, the electrons emitted from the emission protrusions 4 due to the electric field between the cathode electrode 303 and the gate electrode 305 pass through between the adjacent gate electrodes 305, efficiently reach the anode electrode 307, and flow into the gate current. The current can be significantly reduced. That is, the Ia / Ig characteristic (power conversion efficiency) is significantly improved.

The structure of the gate electrode 305 is not limited to the pentagonal prism, but may be a columnar structure in which the electric field distribution in the vicinity of the emission protrusion 4 is formed symmetrically and the emitted electrons are efficiently emitted to the anode electrode 307. It suffices (for example, a triangular prism, a column having a curved rear portion, etc.).

Although the present embodiment discloses a planar type triode field electron emission device, the present invention can also be implemented in a quadrupole or pentapole multipole field electron emission device.

In FIG. 27, 71 is a gate electrode wiring. To give an example of the dimensions of each part, the distance A3 μm between the gate electrodes 305, the side B5 μm of the pentagonal prism of the gate electrode 305,
Side C 7 μm, gap D between gate electrode 305 and cathode electrode 305 1.5 μm, thickness E of island-shaped insulating layer 302
The thickness is 0.5 μm, and the thickness F of the gate electrode 303 is 0.1 μm.

Next, the outline of the method for manufacturing the above-mentioned invention device will be described. 28, 29, and 30 are explanatory views of the manufacturing process. First, as shown in the longitudinal sectional view of FIG.
An O ₂ film 311 is further formed, and a tungsten film 312 is formed thereon by a method such as sputtering. The material of the film is not limited to tungsten and may be tantalum, for example. After that, as shown in the plan view of FIG. 28B, the resist hole 3 having the columnar shape (plan view) of the gate electrode is formed.
A resist film 314 is formed with 13 left. FIG. 28
28C is a vertical cross-sectional view taken along line bb of FIG. 28B,
The reference numerals are the same as those in FIGS. 28 (a) and 28 (b). If this is etched with CF ₄ gas or the like, the resist holes 31
The tungsten film 315 exposed at 3 is etched, and the SiO ₂ film 316 is exposed as shown in the vertical cross-sectional view of FIG. 29A in FIG. 28C.

Then, when the HF-based etchant is used for etching, the SiO ₂ film 316 of FIG. 29A is etched, and when it is over-etched, the vertical cross section of the SiO ₂ film 311 is substantially reverse tapered as shown in FIG. 29B. Become a state.
Next, when the tungsten film 312 is etched with a CH ₄ -based etchant, the plan view of FIG. 29C and its cc view are shown.
As shown in FIG. 29D, which is a vertical cross-sectional view of the line, the etching of the tungsten film 312 proceeds to the broken lines 317 and 318, and the cathode emission protrusion 319 is formed. The emission projections 319 are formed on the inversely tapered SiO ₂ film. In the method of the present invention, since the etching agent that has entered from the resist hole 313 excessively etches the tungsten film from both adjacent resist holes 313 along the shape of the resist hole 313, the tip of the emission projection 319 of the cathode electrode formed is While being sharp, the position of the tip is equidistant from the adjacent resist hole 313. Therefore, in the manufacturing process, even if an error occurs in the set position of the resist hole 313, the formed emission protrusion 319 can always be positioned in the middle of the adjacent resist holes 313, and is formed by the emission protrusion 319 and the gate electrode. The electric field distribution is always symmetrical. That is, the cathode electrode and the gate electrode can be formed in a self-aligned manner.

After that, when a material for forming the gate electrode such as molybdenum is formed into a film by vapor deposition or sputtering, as shown in the sectional view of FIG.
21 and 322 are formed, and the molybdenum film 321 serves as a gate electrode having a resist hole 313 in plan view. The molybdenum film 321 can be formed to have a height higher than that of the tungsten film 312 depending on manufacturing conditions of evaporation or sputtering. Next, when the resist film 314 is lifted off, FIG. 30A becomes as shown in FIG.
A cathode electrode and a gate electrode as shown in 7 (c) are formed.

In the present invention, the anode electrode is formed by
The tungsten film 320 whose edge is a broken line 317 formed by over-etching in the step of FIG. 29C.
May be used as the anode electrode. The anode electrode may be formed separately, but in that case, the tungsten film 3
20 may be used as a control electrode of the multi-pole electric field electronic device, or may be removed if unnecessary.

Note that the gate electrode wiring 71 in FIG. 27 is patterned by a photomask in advance. Therefore, this manufacturing method can be manufactured by the two photomask steps of the photomask step of patterning the gate electrode wiring and the photomask step of forming the resist film of FIG.

The apparatus and manufacturing method of the present invention can be applied to a cathode electrode having a large thickness. The thickness of the cathode electrode of the conventional multi-pole field electron emission device is about 0.1 μm, but if it is thickened (for example, 1 μm) while maintaining the shape of the emission protrusion (wedge type), the emission current is large and large. Suitable for electric power. In the manufacturing method of the present invention, even when the tungsten film 312 is thick, the emission projections of the cathode electrode are sharply formed, and therefore the same manufacturing can be performed.

Since the position of the gate electrode wiring 71 can be arbitrarily formed, if it is formed close to the cathode electrode side, the electric field between the cathode electrode and the gate electrode is increased, and a device with good electric field efficiency can be provided. it can.

In the step of FIG. 30A of the above manufacturing method, when the molybdenum film 321 is formed by vapor deposition or sputtering, the molybdenum bridge 32 is formed between the molybdenum film 321 and the molybdenum film 322 as shown in FIG.
There are 3 things you can do. Since this is inconvenient for forming the gate electrode, it is advisable to adopt a manufacturing method in which such a bridge 323 is not formed.

The manufacturing method will be described below. Figure 32
28A is a partially enlarged process showing the same process as FIG. 28C, but when the gate electrode wiring is formed on the substrate 1 in advance, the wiring pattern 325 corresponding to the shape of the resist hole (the material is Although it does not matter, for example, aluminum is formed.

In this state, if the SiO ₂ film 311 is over-etched, the wiring pattern 325 is exposed as shown in FIG. 9B, so that the vapor deposition is performed on the wiring pattern 325 as shown in FIG. Alternatively, the aluminum film layer 326 is thinly formed by sputtering. 32
Reference numeral 7 is an aluminum film layer formed on the resist 314.

Next, after the tungsten film 312 is over-etched ((d) in the figure), the resist film 314 around the resist hole 328 is removed by O ₂ plasma or the like ((e) in the figure), and then the gate electrode is formed. The gate electrode metal 329 (which may be aluminum or molybdenum), which is the material of (3), is formed by vapor deposition or sputtering (FIG. 6F), and then the resist is turned off. ((G) of the same figure). By this manufacturing process, since the periphery of the resist 14 is removed when the gate electrode is formed, the bridge as described above is difficult to form.

[0118]

Since the present invention has the above-mentioned constitution, it has the following remarkable effects. (1) Since the voltage of the control electrode and the anode current have a linear relationship, the input / output transfer characteristic is linear. Moreover, the anode resistance is very high. Therefore, it can be applied to a linear amplifier, which is difficult in the prior art. (2) A multi-pole field electron emission device that has a significantly reduced reactive current flowing in the gate and has an efficient linear amplification action from the viewpoint of current consumption. (3) Since the input resistance of the control electrode is very large, it can be used for field effect type amplifiers and switching devices. (4) Compared with the conventional thermionic emission type vacuum tube, the current, voltage and electric power that can be handled are equal to or more than that, and it is very small. (5) Since the transconductance and the linearity of the transfer characteristic can be controlled by the gate voltage, circuits having different characteristic parameters can be easily configured by the same device. (6) There is a large degree of freedom in the configuration of the device according to the application, such as one with excellent frequency characteristics, one with excellent power efficiency, and the amount of power that can be handled.

[Brief description of drawings]

FIG. 1 is a partial perspective view of a novel quadrupole field electron emission device.

FIG. 2 is a process drawing of the manufacturing method of the method for manufacturing the quadrupole field electron emission device shown in FIG.

FIG. 3 is a partially enlarged perspective view of a novel quadrupole field electron emission device showing an embodiment of the present invention.

FIG. 4 is a process diagram (longitudinal sectional view) of a method for manufacturing the quadrupole field electron emission device shown in FIG.

5 is a plan view of the process drawing shown in FIG. 4. FIG.

6 is a schematic plan view of a planar quadrupole vacuum tube using the quadrupole field electron emission device shown in FIG. 1 and a schematic longitudinal sectional view taken along the line AA.

FIG. 7 is an electrical connection diagram of a grounded cathode electrode type using a quadrupole field electron emission device.

8 is a graph showing the electron emission characteristics of FIG.

9 is a graph showing the input / output static characteristic of FIG.

10 is a graph showing the static characteristics of the anode of FIG.

FIG. 11 is a diagram showing a relationship between a control current and a gate current, an anode current, and a control current of a quadrupole field electron emission device.

FIG. 12 is an anode characteristic diagram of a quadrupole field electron emission device.

FIG. 13 is another electrical connection diagram of the quadrupole field electron emission device.

FIG. 14 is another electrical connection diagram of the quadrupole field electron emission device.

FIG. 15 is an anode characteristic in the case of the electrical connection diagram of FIG.

FIG. 16 is an electrical connection diagram of a quintuple field electron emission device.

FIG. 17 is an anode characteristic in the case of the electrical connection diagram of FIG. 16.

FIG. 18A is a schematic plan view of a hexapole field electron emission device, and FIGS. 18B and 18C are schematic vertical sectional views thereof.

FIG. 19 is a manufacturing process diagram of the sextupole field electron emission device shown in FIG. 18;

FIG. 20 is a schematic perspective view of a sextupole vacuum tube using the sextupole field electron emission device.

FIG. 21 is an electrical connection diagram of a hexapole field electron emission device.

FIG. 22 is another electrical connection diagram of the hexapole field electron emission device.

FIG. 23 is an anode characteristic diagram of FIG. 22.

FIG. 24 is a schematic vertical sectional view of a vertical quadrupole field electron emission device.

FIG. 25 is a schematic perspective view of a quadrupole field electron emission device in which openings are provided in a gate electrode and a control electrode.

FIG. 26 is a schematic perspective view of an example in which the control electrode of FIG. 25 is a columnar electrode.

FIG. 27A is a plan view of a triode field electron emission device showing another embodiment of the present invention. (B) is a longitudinal cross-sectional view taken along the line aa of (a). (C) is a vertical cross-sectional view taken along line bb of (a). (D)
Is a partial perspective view.

FIG. 28 is a process drawing for explaining the manufacturing method of the triode field electron emission device of FIG. 27.

FIG. 29 is a process drawing for explaining the manufacturing method of the triode field electron emission device of FIG. 27.

FIG. 30 is a process drawing for explaining the manufacturing method of the triode field electron emission device of FIG. 27.

FIG. 31 is an explanatory view when a bridge is formed in the manufacturing method of FIGS.

FIG. 32 is an explanatory diagram of a case where no bridge is formed in the manufacturing method of FIGS.

FIG. 33 is a schematic plan view of a conventional triode electron field emission device.

[Explanation of symbols]

1 flat board 2 Island insulation layer 3 cathode electrode 3a First cathode electrode 3b Second cathode electrode 4 emission protrusion 5 Gate electrode 6 control electrodes 7 Anode electrode 7a First anode electrode 7b Second anode electrode

Continuation of front page (51) Int.Cl. ⁷ Identification code FI H01J 19/38 H01J 19/40 19/40 21/10 21/10 1/30 F (31) Priority claim number Japanese Patent Application No. 3-222088 ( 32) Priority date August 7, 1991 (1991.8.7) (33) Priority claiming country Japan (JP) (31) Priority claim number Japanese Patent Application No. 3-309757 (32) Priority date 1991 October 29 (1991.10.29) (33) Priority claiming country Japan (JP) (56) References JP-A-2-226635 (JP, A) JP-A-59-16255 (JP, A) Kai 63-143731 (JP, A) JP-A-1-154426 (JP, A) Toshio Sasao, Vacuum Tube Engineering, Japan, Sankyo Publishing Co., Ltd., February 15, 1965, pp. 106-10 (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01J 1/304 H01J 1/46 H01J 1/52 H01J 3/08 H01J 19/24 H01J 19/38 H01J 19/40 H01J 21/10-21/14

Claims (2)

(57) [Claims] 1. A cathode electrode which emits electrons, a gate electrode which applies an electric field to the cathode electrode, an anode electrode which collects emitted electrons, and an emission electrode which is provided between the cathode electrode and the anode electrode. And a screen electrode and a suppressor electrode provided between the control electrode and the anode electrode, the cathode electrode and the suppressor electrode are grounded, and the gate electrode and the screen electrode are gated. Means for applying a voltage,
An electron emission device comprising: means for applying an anode voltage to the anode electrode, wherein an input signal voltage is applied to the control electrode to control an anode current. 2. A cathode electrode that emits electrons, a gate electrode that applies an electric field to the cathode electrode, an anode electrode that collects emitted electrons, and a cathode electrode that is provided between the cathode electrode and the anode electrode. And a screen electrode and a suppressor electrode provided between the control electrode and the anode electrode, the cathode electrode and the suppressor electrode are grounded, and the gate electrode and the screen electrode are gated. A method for driving an electron-emitting device, characterized in that a voltage is applied, an anode voltage is applied to the anode electrode, and an input signal voltage is applied to the control electrode to control the anode current.