JPH04277434A - Electron emitting electrode and its manufacture - Google Patents

Abstract

PURPOSE:To fabricate an electron emitting electrode having an acute tip on a base board easily in uniform shape. CONSTITUTION:A (100) Si substrate 11 is subjected to anisotropic etching to form pyramidal holes 14 of several mums square, and thereover W is built up in several thousands of Angstrom thick to construct foil-form pyramidal electrodes 18 and wirings 16. Further thereover a resin is deposited to form a supporting base board 17, and then the Si substrate solely is removed by etching. Because the etching holes 14 can be formed in a very uniform shape over the whole base board surface, the foil-form pyramidal electrodes deposited thereon can be embodied in a very uniform shape.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electron-emitting electrode and a method for manufacturing the same.

0002

2. Description of the Related Art In place of conventional vacuum tubes, micro vacuum tubes using silicon microfabrication technology have come to be manufactured. With this technology, the distance between the electrode tubes can be made much shorter than in conventional vacuum tubes, and it is possible to function as a high-speed device. In addition, it has the characteristics of not having a filament to emit electrons, which is required in conventional vacuum tubes, and there is no need to have a power source to heat the electrodes. Therefore, it is possible to achieve a high degree of integration that was not possible with conventional vacuum tubes. Research is also being conducted to use integrated electron-emitting devices as display devices using the same principle as Brownian tubes.

FIG. 2 shows a conventional manufacturing process for vacuum tubes using semiconductors. First, a low resistance semiconductor substrate 3 is prepared. (1) An oxide film 2 of about 7000A is grown thereon. A metal such as tungsten is deposited 1 thereon. A hole is made in the tungsten by etching, and the oxide film underneath is also removed by etching. (2) Next,
As the sacrificial layer 4, a metal layer having chemical properties different from those of the previous metal is deposited. Next, metal is deposited from an oblique direction while rotating the substrate to produce the eaves 5 for forming a cone. There is a small hole in the center of the eaves, and molybdenum is deposited perpendicular to the hole. (3) Finally, the sacrificial layer deposited earlier is removed by chemical etching to obtain the electrode 7 with a sharp tip (4).

0004

[Problem to be Solved by the Invention] Conventionally, attempts have been made to fabricate vacuum devices on silicon substrates, but
For its manufacture, special equipment was required, such as a vapor deposition machine with a rotating mechanism. Further, since the amount of vapor deposition varies within a single substrate or between substrates, it is extremely difficult to produce a protrusion structure having a uniform shape over the entire substrate using the above-described method. Therefore, there were problems in that characteristic distribution occurred and the yield decreased.

[0005]

[Means for Solving the Problems] The present invention is an electron-emitting electrode characterized by having a sharp-pointed protrusion made of a foil-like conductive material on a substrate made of an insulator. In addition, the manufacturing method of this electron-emitting electrode involves anisotropically etching a single crystal semiconductor to form fine holes with a V-shaped cross section, then depositing a conductive thin film thereon, and then layering a supporting layer made of an insulator on top of that. After providing the single crystal semiconductor, there is a step of etching away the single crystal semiconductor.

[0006]

[Operation] If a single crystal silicon substrate is used as a starting material, a microstructure with a sharp point can be easily produced by etching with a solution such as an anisotropic etching solution. For example, an oxide film is previously provided on the surface of a single crystal silicon substrate whose main surface is the (100) plane, and
0> By creating a square region of the oxide film along the crystal axis and etching that region with an anisotropic etching solution such as hydrazine, pyramid-shaped holes can be formed accurately and are highly reproducible. It can be easily manufactured. Therefore, a conductive material that is not attacked by silicon etching solution is deposited on the surface of this hole. Additionally, insulators are installed on top of the material to provide support and reinforcement. After such an operation, if the silicon substrate is placed in a solution that etches only silicon, the silicon substrate will be etched, and a microstructure made of a conductive material with a sharp point can be easily produced.

[0007]

[Example] Fig. 1 shows an example of the present invention. The electrode structure includes a foil pyramid electrode made of metal on an insulator such as polyimide resin. Only the surface of this pyramid-shaped protrusion is conductive, and the inside is filled with an insulating material that serves as a support for the electrode. This structure increases the strength of the thin foil pyramid.

[0008] The manufacturing method will be described below. First, a (100)-oriented silicon substrate 11 is prepared, and an oxide film 12 is provided on the surface by thermal oxidation or the like. In order to obtain the pyramid shape by anisotropic etching, the oxide film 12 is etched to form a required number of square openings 13 of several μm square in the <110> direction (see Fig. A). Using this oxide film 12 as a mask, anisotropic etching is performed using an alkaline solution such as hydrazine to form a precise pyramid-shaped etching hole 1.
4 can be formed extremely uniformly over the entire surface of the substrate. After that, the oxide film 12 is removed (Figure B). Next, a conductive thin film of tungsten or the like having a thickness of several thousand amps is deposited over the entire surface by sputtering. This thin film is etched to form etching holes 14.
The thin film in the inner part and the part where the wiring 16 is fixed is left. In this embodiment, separate wiring is provided for each etching hole (Figure C). After this, the support substrate 17
Deposit polyimide resin (Figure D). In this case, it is desirable to first apply a thin layer of resin to fill the holes, followed by a thick layer of resin for support. Finally, etching is performed using an etching solution that dissolves only the silicon substrate, such as an alkaline solution or a fluoronitric acid solution, to obtain a pyramid-shaped electrode 18 (Fig. E).

[0009] Various materials can be used for the electrode material, including conductive polymers.

Furthermore, in this embodiment, a foil-shaped pyramid electrode 1 is used.
8 and the wiring 16 are formed from the same tungsten thin film, but it is not necessary to do so. Instead, a conductive thin film is formed only in and around the etching hole 14, and an insulating film such as SiO2 is deposited on the entire surface, and then the necessary parts are formed. Different materials can be used for the wiring metal 16 and the electrode 18 by providing a contact hole in the contact hole, forming the wiring metal 16 thereon, and making necessary connections through the contact hole.

Furthermore, in this embodiment, a conductive thin film was formed directly on the silicon etching hole 14, but the etching hole 14
Either oxidize the surface of 4 thinly and then form a conductive thin film, or
If the pyramid electrode 18 is formed and then the electrode surface is thinly oxidized as shown in FIG. 1(E), the electron emission efficiency will be increased.

Furthermore, a silicon substrate is not necessarily required to form the etching holes; instead, a substrate in which a silicon single crystal film is formed on a glass substrate may be prepared, and the etching holes may be formed in this single crystal film. If this substrate can be made cheaply, the cost can be reduced, and it is also possible to obtain a large area, which is difficult to do with a silicon substrate.

Various materials can be used for the insulator serving as the support layer, and in addition to polyimide, aramid resin or the like may be used. Heating the electrode is effective in increasing electron emission efficiency, but in this case, if a material containing silicon oxide that can form an inorganic glass (for example, SOG (spin-on glass)) is used as a support layer, the electrode can be heated. Even at high temperatures, the substrate will not melt or soften.

[0014] In addition, conventional pyramid-shaped electrodes are made of solid metal, and it is difficult to cool the tip where the current is concentrated, and when the current density is high, the tip can melt due to heat generation (meltdown). . However, if the electrode is shaped like a foil, it can be made hollow, and by flowing a coolant into this cavity, the tip can be sufficiently cooled. It should be noted that the manufacturing method of the present invention can also form a cone made of solid metal as in the conventional method, and in that case, it is also effective because the shape of the tip can be made uniform.

Furthermore, in the present invention, since any material can be formed into a sharp tip, it is possible to use a superconductor as an electrode. In superconductors, the energy dispersion of electrons is degenerated to a very small state, so it is possible to emit electrons with a very small energy dispersion, that is, to obtain a nearly monochromatic electron flow. In the embodiment, a silicon substrate was used as the initial molding material, but any other material that exhibits etching characteristics similar to silicon may be used. Further, in the embodiment, pyramid-shaped fine holes were formed, but even if the holes are not pyramid-shaped, if the cross section is V-shaped, it can be used when forming the tip of the cone.

[0016]

[Effects of the Invention] A method of directly using anisotropic etching of silicon, which has been widely used in the past to obtain a sharp electrode structure, or a method of depositing metal through a narrow slit,
Compared to the method of obtaining a cone, in the present invention, a pyramid-shaped hole is created in advance in a reliable manner, and a conductive material is deposited thereon, so that the shape of the tip can be made uniform over the entire substrate. becomes easier. Further, the present invention does not require special manufacturing equipment or complicated processes.

[Brief explanation of the drawing]

FIG. 1 is a manufacturing process diagram of a vacuum tube showing an embodiment of the present invention.

FIG. 2 is a diagram showing the manufacturing process of a conventional semiconductor vacuum tube.

[Explanation of symbols]

1 Metal gate 2 Oxide film 3 Silicon substrate 4. Sacrificial layer 5 Eaves for cone formation 6 Metal gate 7 Electrode 11 Silicon substrate 12 Oxide film 13 Opening 14 Etching hole 15 Conductor 16 Wiring metal 17 Support board 18 Electrode

Claims (2)

[Claims] 1. An electron-emitting electrode characterized in that it has a sharp-pointed protrusion made of a foil-like conductive material on a substrate made of an insulator. 2. After a single crystal semiconductor is anisotropically etched to form fine holes with a V-shaped cross section, a conductive thin film is deposited over the holes, and a support made of an insulator is further deposited on top of the holes. A method for manufacturing an electron emitting electrode, which includes a step of etching away a single crystal semiconductor after forming a layer.