JP3010304B2 - Vacuum tube - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a vacuum tube having an amplifying and oscillating action by controlling a flow of electrons emitted from an electron source.

[Prior Art] Conventionally, as a vacuum tube formed in a planar shape on a flat substrate, an electron source (hereinafter, a cathode), an electrode for controlling the flow of electrons (hereinafter, a gate), and an electrode for collecting electrons (hereinafter, a collector) are respectively provided. There is known a triode vacuum tube having a single layer and independently formed on the same substrate (US Pat. No. 4,827,177). In a configuration having a large number of electron emission sources on the same substrate, the cathode, the gate, and the collector are arranged linearly so as to be parallel to each other with substantially the same thickness.

[Problems to be Solved by the Invention] However, in the above-mentioned conventional example, since the arrangement of the gate and the collector is not made in consideration of the divergence of the electrons emitted from the cathode, only a part of the electrons emitted from the cathode is gated. And the transconductance, which is one of the characteristics of the vacuum tube, is small, and it is difficult to obtain good amplification and oscillation.

In addition, since the cathode, gate, and collector are arranged linearly, one active element region becomes vertically long in a configuration using a large number of cathodes, so there are restrictions on layout and wiring when integrating on a substrate. There was a problem that would occur.

According to the vacuum tube of the present invention, in the arrangement of the collector, the cathode and the gate on the same substrate, a gate is provided around the collector and the cathode is formed around the gate. In addition, the collector, gate, and cathode are sequentially separated by an insulating layer so as to form a layer structure, so that electrons are emitted inward from the outer periphery and are collected by the collector in the center. is there.

Hereinafter, the operation of the vacuum tube of the present invention will be described as an example with reference to FIG. In FIG. 5, one field emission electron source using an acute electrode 4a (hereinafter referred to as a tip) processed so that electrons are emitted by an electric field as a cathode and an extraction electrode 3 for applying an electric field to the tip 4 is shown. Used. High voltage 8 between the extraction electrode 3 and the tip 4a
, Electrons are emitted from a sharp point at the tip of the tip 4. At this time, the relationship between the electric field and the emission current is emitted according to Fowler-Nordheim equation. The current density of electrons is higher as the radius of curvature of the tip of the tip 4a is smaller, and the emission current density of electrons is also increased by reducing the distance between the extraction electrode 3 and the tip 4a. The electrons emitted from the tip of the tip 4a diverge with a certain solid angle. For example, when the extraction electrode 3 is formed at a position lower than the tip 4a as shown in FIG. Can be directed almost vertically downward to the substrate. Further, by forming the cathode and the gate electrode 2 and the collector electrode 1 on different surfaces so as to have different heights, the electrons emitted from the cathode surely pass over the gate electrode 2 and are collected on the collector electrode 1. I did it. As a result, not only the number of electrons collected by the collector electrode 1 but also the number of electrons controlled by the gate electrode 2 increased, thereby increasing the transconductance and improving the amplifying and oscillating effects.

By arranging the gate electrode 2 and the cathode electrode (3 and 4) around the collector electrode 1 around the collector electrode, an active element having a size suitable for integration can be formed. It has a large degree of freedom in arrangement. As a result, the floating capacitance component can be reduced, so that higher-speed switching can be performed.

FIG. 1 is a drawing that best illustrates the features of the present invention.
In FIG. 1, 1 is a collector electrode, 2 is a gate electrode, 3 is an extraction electrode, 4 is an electron emission electrode, 5 is an insulating substrate, and a cross section taken along line AA of FIG. 1 is shown in FIG. The connection of the power supply when operating as a vacuum tube is the same as that shown in FIG.

In the vacuum tube of this embodiment, Ni (nickel) is vapor-deposited on the insulating substrate 5 made of quartz at a thickness of 2000 mm, and a pattern is formed by using a photolithography technique. Electrode 1 was formed. Next, an insulating layer 6-1 of SiO ₂ was deposited by sputtering to have a thickness of 5000 °. Next, SiN (silicon nitride)
After depositing the film 7-1 by thermal CVD at 1000 ° C., a pattern is formed on the SiN film using photolithography technology, and dry etching is performed using CF ₄ to form a donut-shaped hole for the gate electrode 2. Using the same resist,
The gate electrode 2 was formed in a self-aligned manner by depositing Ni. The process for forming the gate electrode 2 was repeated to form the extraction electrode 3 and the electron emission electrode 4. The electron emission electrode 4 is made of W (tungsten) and has a tip with a radius of curvature of 0.
So as to 1μm drawn using an electron beam resist was etched with CF _4, to form a fine electron emission electrode 4. Next, a pattern having substantially the same size as the inner diameter of the extraction electrode 3 is formed using photolithography technology, and etched sequentially using a hydrofluoric acid-based wet etching solution of SiO ₂ and SiN and an etching ratio of dry etching of CF _4. By doing so, the SiO ₂ and SiN layers on the collector electrode 1 were removed, and the vacuum tube shown in FIG. 1 was formed.

Note that Ni was used for the collector electrode 1, the gate electrode 2, and the extraction electrode 3, and W was used for the electron emission electrode 4. However, the structure of the present device is not limited to only these materials. The layers are not limited to the material of SiO ₂ or SiN.

Next, the operation of this element will be described. This element is 10 ^-6 Pa
A bias is applied between the electron emission electrode 4 and the extraction electrode 3 in the following vacuum, and electrons are emitted from the tip of the electron emission electrode 4 based on the principle of field emission in which the extraction electrode 3 has a positive potential. At this time, not all the emitted electrons are emitted in one direction, but are emitted with a certain extent.

In order to prevent the vacuum tube characteristics from deteriorating due to the spread, most of the emitted electrons are guided to the gate electrode 2 and the collector electrode 1 by disposing the extraction electrode 3 slightly below the horizontal direction of the electron emission electrode 4. When the potential applied to the gate when the electrons pass through the gate electrode 2 is made positive, the electrons are accelerated and reach the collector electrode 1, and when the potential is made negative, the electrons are decelerated and the number of electrons reaching the collector electrode 1 is reduced. Utilizing it, the amplification and the oscillating action can be performed reliably. In this embodiment, by using a plurality of field emission type electron sources as the electron sources, it is possible to form the vacuum tube by a process in which the electron emission current is stable and relatively easy.

FIG. 3 and FIG. 4 show a second embodiment of the present invention.

FIG. 3 shows a cross section of the vacuum tube in the middle of manufacturing.
FIG. 4 shows a cross section of the vacuum tube at the final stage of production.

A collector electrode 1 in FIG. 3 in the present embodiment, the gate electrode 2, the lead-out electrodes 3, and the electron emission electrode 4 is formed by using a photolithography technique and the etching technique described above, SiO ₂
Are sequentially obtained by using only the interlayer insulation of FIG.
Each material is the same as in the first embodiment. Next, after forming the electron emission electrode 4 in the same manner as in the first embodiment, a resist is formed using a mask having a diameter substantially equal to the outer diameter of the collector electrode 1 so that the upper part of the collector electrode 1 is opened.
The electrode layers 2 and 3 and the insulating layers 6-1, 6-1 and 6-3 were removed by wet etching, and finally a vacuum tube having a sectional view as shown in FIG. 4 was formed. According to the vacuum tube of the present embodiment, the manufacturing process can be greatly reduced, and the cost can be reduced.

[Effect of the Invention] As described above, when a vacuum tube is formed using an electron source that emits electrons in parallel to the substrate, the direction in which electrons are emitted is not completely parallel to the substrate. As described above, by changing the heights of the extraction electrode, the gate electrode, and the collector electrode, electrons emitted efficiently are used, and the effect as an electron tube is improved. Particularly in the configuration of a triode vacuum tube, there is an improvement in the mutual conductance.

In addition, by arranging the whole element in a circular shape, the degree of freedom in layout is increased in the integrated substrate, whereby the resistance of the wiring, the stray capacitance, and the like are reduced, and higher-speed operation becomes possible.

[Brief description of the drawings]

FIG. 1 is a top view of a vacuum tube according to a first embodiment of the present invention,
FIG. 2 is a sectional view taken along line AA in FIG. 1, and FIGS.
FIG. 5 is a cross-sectional view of a vacuum tube during the process of the embodiment, and FIG. 1 ... collector electrode, 2 ... gate electrode, 3 ... lead-out electrode, 4 ... electron emission electrode, 4a tip, 5 ... insulating substrate, 6-1,6-2,6-3,6-4, 7-1, 7-2, 7-3 ... insulating layer, 8, 9, 10 ... power supply.

Continuation of front page (56) References JP-A-63-10428 (JP, A) JP-A-63-187535 (JP, A) JP-A-1-300558 (JP, A) (58) Fields studied (Int .Cl. ⁷ , DB name) H01J 19/24 H01J 21/06 H01J 1/30

Claims (4)

(57) [Claims] An electrode for receiving electrons, at least one electrode for controlling the flow of electrons, and an electron source for emitting at least one electron are formed in layers in this order on an identical substrate, separated by an insulating layer. A vacuum tube, wherein an electrode for controlling the flow of electrons is arranged around an electrode for receiving electrons, and an electron source for emitting electrons is arranged around the electrode for controlling the flow of electrons. 2. The vacuum tube according to claim 1, wherein an electron source for emitting electrons, an electrode for controlling the flow of electrons, and an electrode for receiving electrons are arranged concentrically. 3. An electron source which emits electrons is constituted by an acute angle electrode and an extraction electrode, and the acute angle electrode and the extraction electrode are arranged on different planes. Item 3. The vacuum tube according to Item 2 or 2. 4. The vacuum tube according to claim 1, wherein an electron source for emitting electrons is formed at the outermost periphery.