JPH04137434A - Manufacture of field emission type cathode and vacuum transistor - Google Patents

Abstract

PURPOSE:To obtain a field emission type cathode with a high emission efficiency, an even form, and thereby with an even property, by leading an organometal compound material gas on the surface of a specific substrate crystal, and attaching a semiconductor formed on a processing substrate, three- dimensionally according to the organometal compound gas. CONSTITUTION:An insulating membrane is formed on the surface of a substrate crystal with a specific exponent of surfaces, the insulating thin film is removed partially in the form corresponding to a field emission type cathode to be formed, and an organometal compound material gas is led on the substrate crystal surface. Then, a semiconductor corresponding to the compound gas is deposited on the substrate crystal surface by using an organometallic chemical vapor deposition method (MOCVD method) to form a field emission type cathode. Consequently, a field emission type cathode with a small radius of curvature at the top, and with a good form and well controlled, can be obtained.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing a field emission cathode used in ultra-high-speed micro vacuum tubes, ultra-small cathode ray tubes, flat displays, etc., and a method for producing a vacuum using the cathode. The present invention relates to a method for manufacturing a transistor.

[Prior Art 1] Attempts have been made to use micron-sized cathodes to create minute vacuum transistors and flat panel displays that can be integrated using semiconductor microfabrication techniques. Ito, Applied Physics, Vol. 59, No. 2 (1990)
Trends in this field are described in pages 164-169. In conventional attempts to fabricate vacuum transistors, a vacuum evaporation method using a pinhole mask or an anisotropic etching method of Si has been used to fabricate a field emission cold cathode.

[Problem to be Solved by the Invention 1 Electron emission efficiency largely depends on the radius of curvature of the cold cathode where the electric field is concentrated. However, the radius of curvature of a cold cathode that can be produced by the conventional method is about 0.05 μm, and the electron emission efficiency is not sufficient. Furthermore, in the conventional method, it is difficult to control the shape of the cathode tip, and as a result, there is a problem in that uniform characteristics cannot be obtained.

SUMMARY OF THE INVENTION An object of the present invention is to solve these conventional problems and provide a method for manufacturing a field emission cathode that has high electron emission efficiency, a uniform shape, and therefore uniform characteristics.

A further object of the present invention is to provide a method for manufacturing a vacuum transistor that uses the above-mentioned cathode, has a short electron transit time, and has a large mutual conductance.

[Means for Solving the Problems] In order to achieve the above object, a method for manufacturing a field emission cathode according to the present invention includes a step of forming an insulating thin film on a substrate crystal surface having a predetermined index plane, and a step of forming an insulating thin film on a substrate crystal surface having a predetermined index plane. a step of partially removing the insulating film into a shape corresponding to the desired field emission type cathode, and introducing raw material atoms or raw material compounds onto the surface of the substrate crystal to precipitate a semiconductor corresponding to the raw material on the substrate crystal. The method is characterized by comprising a step of forming a field emission type cathode.

The method for manufacturing a vacuum transistor according to the present invention includes a step of forming an insulating thin film on a substrate crystal surface having a predetermined index plane, and a step of partially removing the insulating film into a shape corresponding to a three-dimensional structure to be formed. , a step of introducing a raw material atom or a raw material compound onto the surface of the substrate crystal and depositing a semiconductor corresponding to the raw material on the substrate crystal to form a field emission type cathode having a three-dimensional structure; and further comprising a metal layer on an insulating layer. forming a gate and a collector.

[Function 1] The field emission cold cathode of the present invention is capable of conducting organometallic vapor phase epitaxy in which an organometallic compound raw material gas is introduced onto a predetermined substrate crystal surface, and a semiconductor corresponding to the organometallic compound gas is deposited on the substrate crystal surface. It is formed by attaching a semiconductor to be formed on a processed substrate in a three-dimensional shape using a method (MOCVD method) according to an organic metal compound gas. If this method is used, the radius of curvature of the tip of the cold cathode will be less than 10 0, and a uniform shape can be achieved with good reproducibility.

Since the method for manufacturing a vacuum transistor according to the present invention uses such a cold cathode, a vacuum transistor with high mutual conductance and stable characteristics can be manufactured.

[Example 1 Hereinafter, the present invention will be explained in detail with reference to Examples.

FIG. 1 is a schematic diagram showing an embodiment of the present invention. It has an emitter (cathode) 2 on a substrate 1, and further has a collector (anode) 4 and a gate (grid) 5 on an insulating film 3. This structure is a known structure except for the emitter (cathode) portion.

First, the procedure for manufacturing a GaAs cold cathode using GaAs(111)B as a substrate crystal by metal organic vapor phase epitaxy will be explained step by step.

(111) The plane orientation of the facet plane formed on the 8th plane is
As shown in the figure.

First, the substrate fabrication conditions will be shown. After depositing 10 to 1100 nm of an insulating film of silicon oxide, silicon nitride, etc. on the GaAs(111)B substrate surface by sputtering or vapor phase chemical precipitation, known photolithography or electron beam lithography and etching techniques are used. Then, the insulating thin film is removed in a triangular shape corresponding to the bottom of the tetrahedron shown in FIG. A crystal is grown only on the portion where the insulating film has been removed, using conditions that allow the crystal to grow while exposing the facet side as shown in FIG. 2.

Next, details of crystal growth conditions will be shown. Growth was performed under a reduced pressure of 0.1 atm using a horizontal high-frequency heating path. Trimethylgallium and arsine were used as raw materials. The partial pressures inside the reaction tube were 2.6 x 10-' atm and 4.
7 x 10-'atm, and the total gas flow rate, including the hydrogen carrier gas, was 4 liters/min. A GaAs layer is grown only on the triangular GaAs (111) 8 plane from which the insulating film has been removed. The growth temperature was 800°C. (111
) On GaAs, mirror-like layered growth is obtained at temperatures above 750° C., a (110) plane appears on the side surfaces, and no growth occurs on the insulating film. GaA grown in this way
The apex of the s tetrahedron is used as a cathode. The radius of curvature of the emitter tip according to the invention is less than 10 nII+.

Next, an example of manufacturing a vacuum transistor will be shown. In the example shown in Figure 1, the n-type emitter (cathode) 2 is
After forming, an insulating film 3 (SiO□) was deposited. The thickness of the insulating layer was set to be slightly thinner than the height of the emitter.

Then, the insulating film was removed only from the emitter portion. Next, a gate (grid) 5 and a collector electrode (anode) 4 made of gold or aluminum were sequentially formed around the emitter by vapor deposition or sputtering.

When a positive voltage is applied to the collector and a negative voltage is applied to the emitter, the electric field concentrates at the tip of the emitter, causing electron emission. The smaller the radius of curvature of the tip, the higher the electric field and the easier it is for electrons to come out. Electrons flow from the emitter to the collector, but when a negative voltage is applied to the gate, the electrons do not flow (and the current decreases).A transistor operates based on this principle.

The characteristics of the fabricated GaAs vacuum transistor are that the emitter height is 0.1 μm and the distance between the emitter tip and the gate is 1 μm.
m, the distance between the emitter tip and the collector was 2 μm, the mutual conductance was ioms, and the electron transit time was 0.1 ps. This is an improvement of more than three orders of magnitude over the characteristics of conventional vacuum transistors. The reason is that by using the manufacturing method according to the present invention, the emitter tip becomes sharp, and as a result, a large amount of electrons are emitted even at a low voltage.

When using GaAs(ill)A as the substrate, GaAs(ill)A is used as the substrate.
By performing facet growth of As at 650° C., a field emission type cathode with a sharp tip can be produced as in the above embodiment.

As an example of manufacturing materials other than GaAs, an insulating film is attached on a 5i (111) substrate, the insulating film is removed in a triangular shape by photolithography and etching, and then vapor phase chemical precipitation method (
A Si tetrahedral structure was fabricated using a CVD method (CVD method) to form a field emission type cathode. The radius of curvature of the tip of this cathode was also 10 nm or less. Using this cathode as an emitter, a vacuum transistor was fabricated in the same manner as in the example described above. The obtained characteristics were comparable to those of a GaAs vacuum transistor.

[Advantageous Effects of the Invention 1] As explained above, according to the present invention, a field emission type cathode having a small radius of curvature at the tip (and a well-controlled shape) can be manufactured, and a vacuum transistor using this cathode can be manufactured. The mutual inductance of is high and the electron transit time is short.

The field emission type cold cathode according to the present invention is a cathode of a cathode ray tube,
It can be applied to flat displays, etc.

[Brief explanation of the drawing]

FIG. 1 is a schematic cross-sectional view showing one embodiment of the present invention; FIG. 2 is a perspective view showing a model of a tetrahedral structure. 1... board, 2...emitter, 3... Insulating film, 4...Collector, 5...Gate.

Claims (1)

[Claims] 1) A step of forming an insulating thin film on a substrate crystal surface having a predetermined index plane, and a step of partially removing the insulating film into a shape corresponding to a field emission cathode to be formed. and introducing raw material atoms or raw material compounds onto the substrate crystal surface,
A method for manufacturing a field emission cathode, comprising the step of depositing a semiconductor corresponding to the raw material on the substrate crystal to form a field emission cathode. 2) A step of forming an insulating thin film on a substrate crystal surface having a predetermined index plane, a step of partially removing the insulating film in a shape corresponding to a three-dimensional structure to be formed, and a step of forming a raw material on the substrate crystal surface. guide atoms or raw material compounds,
A step of depositing a semiconductor according to the raw material on the substrate crystal to form a three-dimensional field emission type cathode, and a step of further forming a metal layer on the insulating layer to form a gate and a collector. A method for manufacturing a vacuum transistor characterized by the following.