JPS6147038A - Thermion cathode and method of producing same - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a thermionic cathode useful in electron beam devices. More specifically, the thermionic cathode of the present invention has an emission surface at the top of the cathode with an N. It is shaped and surrounded by layer B, so that its thin film layer covers the remainder of the cathode surface. The invention also relates to a method of manufacturing the cathode.

Various different methods have been developed in the existing technology to limit the emissive surface of the cathode, but for thermionic cathodes, one of the most important is to limit the emissive surface of the cathode by applying a potential that is more negative than the one adjacent to the pole. Limit the emission surface depending on the surface area. One of its drawbacks is that it is extremely difficult to irradiate the emitting surface with a strong accelerating electric field through the electrodes in order to minimize the space potential effect and the energy dispersion of the emitted electrons of the intense beam. be. Regarding electric field-emitting cathodes and thermionic-emitting cathodes, their emission surfaces depend on applying a strong accelerating electric field to the tip surface.
limited to its sharp tip.

One of the drawbacks is that for field emission, the tip surface is several hundred nanometers in diameter, and for thermal field emission, it emits a powerful electron beam from the tip surface, which is more than a few micrometers in diameter. The straw is that it is extremely difficult.

The present invention provides a unique method of defining the emission surface of the thermionic cathode top by using a thin film layer made of a high work function material to cover the remainder of the cathode surface. This method is based on the discharge '6L flow density J, Ka! J f'r
- G7y (Richardson) formula J
= Ar2e-8/'T. In this formula, A is a constant, 2 is a work function (unit: eV), and k
is the Boltzmann constant and T is the absolute temperature expressed in zero.

Small differences in work function result in large differences in emitted charge. To take an example, the ratio of the emission current intensity of lanthanum hexaboride (ρ = 2.S2) as a single heat emitting substance to rhenium (a = Hiro.za7) as a thin film layer material is / At an operating temperature of 77.3°. wo×10
It is. The cathode of the invention is used in an electron gun having several electrodes, applying an accelerating electric field to the emission surface above the cathode and simultaneously projecting the emission surface into its conjugate plane.

1% since the emission surface is surrounded by the upper surface of the thin film layer.
The emissive surface can be corroded by impurities, which are build-up of the thin film material due to surface migration, diffusion into the cathode body, evaporation, etc. at the operating temperature of the cathode.

The corrosion causes unstable emission of electrons and shortens the life of the cathode. Despite the above-mentioned advantages of the cathode, it is advantageous to have a non-circular emission surface. Additionally, this corrosion can be prevented by providing a buffer zone between the upper surface of the thin film layer and the emitting surface.

Accordingly, there is a need for an improved thermionic cathode having a non-circular emitting surface on top of the cathode and a means to prevent corrosion during operation of the cathode at high temperatures.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method and apparatus for generating an intense and stable electron beam over a long period of time from an emitting surface of a certain shape.

An object of the present invention is to provide a method and apparatus for generating an electron beam from a surface of a certain shape.

It is a further object of the invention to provide a method for manufacturing a thermionic cathode for generating an intense and stable electron beam over a long period of time with an emitting surface of a certain shape.

Another object of the present invention is to provide: l) a method for producing a thermionic electron Km emitting a meson beam from a surface of a defined shape of a triole;

The device of the present invention handles the remaining part of the @pole 'lr, the r8 film layer #I! It is a thermionic cathode with a fixed form of emission surface on the top of the cathode. Certain shapes of emission surfaces include round, square, rectangular; square, trapezoidal, and trapezoidal. This emission surface is a flat surface made of a single crystal.The emission surface of a certain form is made of a bare thermionic emission material with a low work function. The thin film layer is selected from a monolayer, a double film layer and a multilayer. The material of the single layer has a high work function and does not chemically react with the thermionic emitter at the operating temperature of the joint electrode. The material inside the bilayer and the innermost layer of the multilayer does not chemically react with the thermionic emitter at the operating temperature of the cathode. Also, the outside of the double membrane layer,
Also, the work function of the outermost material of the multilayer is important.

According to an important feature of the invention, it is ensured that the cathode generates an intense and stable electron beam by isolating the shaped emission surface of the upper part of the cathode from the upper narrow surface of the thin film layer. Equipment is provided.

According to the invention, one end of the rod-shaped body made of thermionic emitting material is formed by mechanical grinding or by etching. According to known coating techniques, the rod is coated with a thin layer. The upper end of the shaped rod is cut off by mechanical grinding or polishing.

According to an important feature of the invention, the membrane layer near the edge of the emission surface is removed, separating the emission surface from the top of the membrane layer.

According to the invention, one end of the rod made of thermionic emitter 'tvJJx is shaped by mechanical grinding or electrolytic etching. The molded upper end of this rod-shaped body is mechanically ground or polished.
1C1 & cut and polished. The rod is coated with a thin film layer. The precisely molded swing part is
Using existing conductor integrated circuit manufacturing techniques, the thin film layer on the cut optical surface is patterned and then delineated.

□ According to a particularly important feature of the invention, the shaped emissive surface is self-aligned with a mesa structure separating it from the membrane layer.

The above-mentioned and other objects, features and advantages of the invention will become apparent from the description of preferred embodiments shown in the drawings.

Detailed Description of the Preferred Embodiment In FIG. 1, one pole of the present invention includes a rod-shaped body l of a certain shape made of a thermionic-emitting material with a low work function, and an emission surface 3.
It consists of a rod-shaped body other than lt-cover-r8 exchange layer 2). The thin film layer 2 consists of an inner layer 4 which does not chemically react with the thermionic emitting substance under unipolar operation and an outer layer 5 made of a material with a high work function.

Release xmJ, Rlchard
son).

As mentioned above, the equation depends on the exponential term of the work function ρ, so if the work function is slightly different, the emission ′m 6
The rc tD capability is greatly different. For example, rhenium (Δ=
The ratio of lI, g 7 eV) to that is 17
3°K (about 'I-, 9X 1 at D'lJb operating temperature)
0'? be. However, the emission surface 3 occupies only a small portion of the total pole surface. It is therefore necessary to provide # with a means of defining the emission surface of the side surface 6 close to the circumferential edge of the upper surface of the pole. Said means is described in the application filed by the present inventor on March 5, 1912, entitled "Lumiton beam t-
U.S. Patent Application for Method and Apparatus for Generating Mutsi
This is the same as explained in detail in "Ass, Colo 7".

A material that can be used for the inner layer 4 is tantalum boride (zrB
2) Borides such as niobium boride (NbB2), carbides such as tantalum carbide (TaC) and zirconium carbide (ZrC), tantalum nitride (TaN), and zirconium carbide (ZrC)
nitrides such as rN) and carbon (C). Materials that can be used for the outer layer 5 include rhenium (Re), tantalum (Ta
), molybdenum (MO), and tungsten, which are listed in preferred order (from slowest to fastest) based on their chemical reaction rates at high temperatures to lanthanum (LaB5). .

When using a material that does not chemically react with the thermionic emitting material at high temperatures and has a high work function, such as Reniu for wooden lanthanum, as shown in Figure 7, it is possible to Only one membrane layer 7 may be used. Other materials that can be used as a single membrane layer are tantalum and carbon for trellised lanthanum. These substances also have a low vapor pressure, and the area of the emission surface ranges from several thousand square micrometers to several square micrometers.

For a cathode structure whose emission surface 3 is dependent on the upper surface 8 of a thin film /IF2 as shown in Figure IFJ3, the operating temperature should be carefully controlled. It is necessary to prevent corrosion of the discharge surface 3.

The corrosion is a result of the unnecessary accumulation of impurities, p5.
Mt- Atomic atoms formed and attached to the emission surface 3 10% 111%-
, l 2.13.14.15.

This makes the emission of electrons unstable and shortens the life of the cathode. Impure v! The unnecessary accumulation of J9 is thought to be due to the following mechanism.

l　Surface movement of inner layer atoms lO and outer layer atoms 11.

Y Inner layer atoms to cathode body 12 and outer layer 1 = d atoms 1
Diffusion of 3.

3. Evaporated atoms 14 in the inner layer and 1 evaporated atoms in the outer layer
Accumulation of 5.

Thin film M atoms 10.11.12.13 begin to accumulate on the emission surface from the edge inward. However, since the cathode is operating at high temperatures, the cathode structure shown in FIG. 3 becomes as shown in FIG. 9.

This is because the evaporation rates of the thermionic emission material, the inner layer material, and the outer layer material are different from each other (the evaporation rates gradually become smaller in this order). Toko; Rode, 7th
The cathode structure as shown in the figure has an emitting surface 3t which is recessed by the thin film layer 2. The evaporated atoms 14.15 of the thin film layer structure 2 thus accumulate over the emission surface.

Corrosion of the emission surface as a result of unwanted accumulation of impurities 9 due to surface migration, diffusion into the body and evaporation makes the emission of the beam electrons unstable and reduces the overall lifetime of the cathode. The rates of surface transport, diffusion into the body, and evaporation are, respectively, Rlchardso
can be dependent on an equation containing an exponential term for temperature similar to the exponential term in the equation for n. That is, the speed tri increases exponentially as the operating temperature increases.

Another embodiment of the thermionic cathode device of the present invention for preventing corrosion of the cathode at high temperatures will be described below. That is, the cathode structure shown in FIG. S has a buffer zone 16 between the thin film layer 2 and the emission surface 3. The radiation surface 3 is isolated from the thin m-layer 2. A key feature of this structure is that the emitting surface 3 is located on the upper surface 8 of the thin film layer 2.

Not only must the thin film layer atoms 1O111, 12, 13 pass through the buffer zone 16, but also the evaporated atoms 14.1
5 does not begin to adhere to the emissive surface 3 until the thermionic emissive material has evaporated below the upper surface 8 of the thin film layer 2. The surface area of the buffer zone 16 is much smaller than the surface area of the emission surface 3 (a plane made of a single crystal). Some inhomogeneous emission occurs from the buffer zone, but this emission line is negligible.

A cathode device consisting of a rod made of thermionic emissive material and a thin film layer may be fabricated by any known method.

For example, the following method may be used.

Example 1 Cathode formed from wooden lanthanum coated with a double film layer consisting of ovized tantalum and rhenium (Figs. 6 to 1) Step 1: Single crystal Lad6 rod-shaped body (Fig. 1) The
The cross section is square (approximately 2! r0 square μm) and the length is approximately 21
Make it so that it becomes II11. The rods are cut from arc melted materials or crystals produced in the 1iLa86y & NiAl bath method from arc melted materials.

Step 2: Shape the rod into the desired shape (Figs. 7a-7b, 7c) by mechanical grinding or galvanic etching. A cone-shaped rod (7a)
The drawing is used to create a circular emission surface. A rod in the form of a square pyramid (Figure 7b) is used to create a square emission surface. Also, a roof-like rod-shaped body (7th C
The drawing is used to create a rectangular emission surface.

Step 3. Coat the shaped rod with a thin layer of tantalum borosilicate using any existing coating technique.

Step 4: The tantalum boride coated rod is then coated with Silenicum by any known coating technique.

Step 5: Vertex 17 of the pole dependent on mechanical grinding or polishing
・Obtain the upper surface 3 of the required thickness by cutting (Fig. 1, Fig. GB, Fig. 1.RC).

Step 6: Add a thin film layer close to green around the top surface 3.
The edge 18 around the upper surface 8 of the thin film layer 2 is scraped away. The removed surface 16 becomes a buffer zone 16 separating the upper surface 3 from the thin film layer 2 (Figs. qa, 9b, dc).
figure〕.

Step 7: After washing, the rod can be used. If a buffer band at the cathode location as shown in FIG. 1 is unnecessary at one pole operating temperature, step 6 of the embodiment/s is omitted. Also, if the thin film layer with a high punishment function does not chemically react with the thermionic emitting material at the operating temperature of the cathode in the cathode device shown in FIG. .

The precise and precise shapes of the emitting surface and buffer zone may be manufactured by any known method of manufacturing semiconductor integrated circuits. For example, the following method may also be used.

Example 2 A patterned monopole made of trellised lanthanum coated with a double thin film layer of titanium boride and rhenium (
pattern unipolar).

Status f1: Same as Sudetsu 7″1 in Meisei.

Step 2: Shape the end of the rod into a truncated cone shape by slow erosion or mechanical grinding (Fig.

Mechanically polish the upper surface 19 of the truncated cone.

Snug 3: The rod is coated with a thick film layer 20 of positive photoresist by spraying with liquid photoresist or by dipping in liquid photoresist (first/first step).
figure).

Step 4: After pre-baking to strengthen the adhesion of the photoresist film layer 20, the opaque/yellow turn (23, 24, 2
5) Expose the upper surface of the truncated cone to intense light [21 (Fig. 1/Fig. 72) through a glass mask (Fig. 72).

Step 5: Remove the exposed surfaces of the photoresist 20t (by dipping or spraying with a suitable solution) to remove the photoresist 20t. The photoresist 26 below the opaque pattern forms the upper part 19 of the truncated cone.
(@IJa figure, No. 1, 71). 13th c.
figure).

Steps are performed to etch the wooden shelf lantern to the desired thickness (5OOOA). The upper surface 27 underlying the resist 26 remains similar to the grooves and turns of the resist (1st GA, 1st Figure, 1st Figure C).

The mej structure 27 on the upper surface of the truncated cone has a radiation surface 3
This is a buffer zone that separates the film from the thin film layer.

Step 7: Coat the rod with a thin film of boron by any known coating technique (Figure 15).

Step f8: The titosane boride coated rod is then coated with a thin layer of rhenium according to any known coating technique.
- Covering (Fig. 15).

Step 9: 7 Otoresist 2 in a suitable stripping solution
By removing 6, the double layer of titanium boride and rhenium on photoresist 26 (FIG. 1S) is stripped.

Step 10: Start getting it. If the operating temperature of the cathode does not require a buffer band, step 6 in embodiment 2 is omitted.

Furthermore, if the high work function thin film layer does not chemically react with the thermionic emissive material at the unipolar operating temperature, Stain f7 in Example A can also be omitted.

The present invention has been explained in accordance with the most practical and preferable system, but is it in accordance with the present invention? Similar effects can be achieved even if modifications are made within the scope disclosed in the IMU document. The semiconductor integrated circuit manufacturing technology used in the present invention includes photo etching, electron beam etching, ion beam etching, wet etching, and dry etching such as ion milling, plasma etching, and reactive ion etching. .

Instead of the resist stripping method (S7 to 7 method), it is also possible to remove thermionic emitting material by attaching a thin film I- to areas other than the emission surface using any existing semiconductor integrated circuit manufacturing technology. It is also possible to create a molded release surface of a molded surface of a frustoconical rod made from a truncated conical rod.

Other modifications or equivalents to the embodiments described herein will be apparent to those skilled in the art. That is, the scope of the present invention is determined only by the claims and their equivalents.
It should be passed around.

[Brief explanation of drawings]

FIG. 1 is a fragmentary enlarged cross-sectional view showing a thermionic cathode with two thin film layers υ according to the invention. FIG. 2 is a fragmentary enlarged cross-sectional view showing a thermionic cathode with a single thin film layer according to the invention. FIG. 3 is a fragmentary enlarged cross-sectional view showing the surface migration, diffusion and evaporation of thin film layer atoms into the bulk body. Figure 5 is an enlarged cross-sectional view showing the structural changes of the cathode after operating at high temperatures. FIG. 5 is an enlarged cross-sectional #r view showing the buffer zone between the thin film layer and the emission surface according to the present invention. FIG. 6 is a schematic diagram illustrating nine LaB4 rods cut from an arc-fused composite material according to the present invention. Figures 7A, 7S and 7C are schematic diagrams illustrating the state in which both ends of a bar are formed into a conical shape, a pyramid shape and a roof shape, respectively, by mechanical grinding according to the present invention. Figures A, G and G are schematic diagrams showing the next state in which the upper parts of both ends of a cone-shaped, pyramid-shaped and roof-shaped body are cut off by mechanical grinding according to the present invention. be. Figures 9A, 78 and 90 are circular,
9 of the thin film layer near the top surface in the shape of squares and rectangles
FIG. 3 is a schematic diagram showing the respective parts being removed by mechanical grinding. FIG. 70 is a schematic view showing one end of the rod-shaped body being shaped into a truncated cone by mechanical grinding or polishing according to the present invention. FIG. 1 is an enlarged fragmentary cross-sectional view showing the photolithography technique for transferring an opaque pattern image on a glass mask to a resist coated on a truncated cone of LaB6 according to the present invention; be. FIG. 12 is a schematic diagram showing circular, square, and rectangular opaque patterns/l on a glass mask according to the present invention. FIGS. 138, 73B and/or 70 are schematic diagrams showing circular and square resist pattern after resist development according to the present invention, respectively. Figure 144, Figure 1B, and Figure 1C are schematic diagrams showing mesa structures with circular, square, and rectangular top surfaces, respectively, after wet etching of La84 according to the present invention. be. FIG. 1S is a fragmentary enlarged cross-sectional view showing adhesion resistance of the thin film layer before lift-off treatment according to the present invention. FIG. 76 shows the p-emitting surface according to the present invention. FIG. 6 is an enlarged cross-sectional view showing self-alignment to the structure. Figure 13A Figure 138 l/i 100 Figure 15
Figure 16 Procedural amendment IF (method) 1. Display of the case Patent Application No. 137051 of 1982 2. Title of the invention Thermionic cathode and its manufacturing method 3. Person making the amendment Relationship with the case Applicant name Jason Jin Kim 4, agent

Claims (5)

[Claims] (1) A thermionic cathode consisting of a rod-shaped body made of a thermionic-emitting substance, which comprises an emission surface formed of a single crystal plane forming the upper surface of the rod-shaped body, and a single film layer. a covered conical side surface, and the membrane layer is made of a material that does not chemically react with the thermionic emissive material at the operating temperature of the cathode, has a high work function, and has a low vapor pressure. Characteristic thermionic cathode. (2) A thermionic cathode consisting of a rod-shaped body made of a thermionic-emitting substance, which comprises an emission surface formed of a single crystal plane forming the upper surface of the rod, and covered with a multilayer film. the innermost film layer of the multilayer film layer is made of a substance that does not chemically react with the thermionic emissive substance at the operating temperature of the cathode; A thermionic cathode characterized in that the layer is made of a material with a high work function and a low vapor pressure. (3) A thermionic cathode consisting of a rod-shaped body made of a thermionic-emitting substance, which includes an emission surface formed of a single crystal plane forming the upper surface of the rod-shaped body, and covered with a multilayer film. a conical side surface; and a buffer zone separating the emission surface and the conical side surface from each other; 1. A thermionic cathode comprising a substance that does not chemically react with the multilayer film, wherein the outermost film layer of the multilayer film layer is comprised of a material having a high work function and a low vapor pressure. (4) A method for manufacturing a thermionic cathode, which includes the step of cutting out a single crystal rod-shaped body from a thermionic-emitting substance with a low work function, and forming one end of the rod-shaped body into a conical, pyramidal or roof shape. a step of coating the shaped rod-shaped body with a thin film layer having an outermost surface made of a material with a high work function and an innermost surface made of a material that does not chemically react with the thermionic-emitting material; A method characterized in that it comprises the step of cutting off the top of said one end of the shaped body to form an emission surface consisting of a circular, square or rectangular single crystal plane. (5) A method for producing a thermionic cathode, which includes the step of cutting out a single crystal rod-shaped body from a thermionic-emitting substance with a low work function, and forming one end of the rod-shaped body into a conical, pyramidal or roof shape. a step of coating the shaped rod-shaped body with a thin film layer having an outermost surface made of a material with a high work function and an innermost surface made of a material that does not chemically react with the thermionic-emitting material; cutting off the top of the one end of the shaped body to form an emission surface consisting of a circular, square or rectangular single crystal plane; and removing a patterned portion of the thin film layer to form a buffer zone. A method characterized by comprising: