JP3295864B2 - Field emission cathode and method of manufacturing the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a field emission cathode and a method for manufacturing the same. A field emission cathode that emits electrons by a high electric field has long been proposed as a cathode replacing a hot cathode of a vacuum tube, but has not been put to practical use.

In recent years, attempts have been made to manufacture field emission cathodes using microfabrication techniques developed as semiconductor manufacturing techniques. By using this microfabrication technology, a minute field emission cathode on the order of microns in which a high electric field can be formed can be manufactured, and since it has a fine structure, high-density integration is possible.

On the other hand, considering the performance of a field emission cathode as an electron source, it has advantages such as higher efficiency and higher density of electron beam than a hot cathode which requires heating means. Have. In addition, since the emitted electrons can move freely in a vacuum, they can move at a higher speed than when they move while colliding with atoms or the like constituting a crystal, such as a conductor or a semiconductor. . Taking advantage of these features, it is expected that the field emission cathode is applied to high-speed arithmetic elements, thin high-brightness displays, and the like.

[0004]

2. Description of the Related Art A field emission cathode comprises an emitter tip having a sharp tip and an electron extraction gate electrode having an opening at the tip of the emitter tip. When an appropriate voltage is applied between the emitter tip and the gate electrode,
A high electric field is applied to the tip of the emitter tip, and electrons are field-emitted from the emitter tip. As a method for manufacturing a field emission cathode, a vapor deposition method and an etching method are known.

FIGS. 4A to 4D are views for explaining a process of manufacturing a field emission cathode by a conventional vapor deposition method, and FIGS. In this figure, 21 is a substrate, 22 is an insulating film, 22 ₁ is an opening, 23 is a gate electrode material layer, 23 ₁ is an opening, 24 is a sacrificial layer, 25 is an electron emitting material, and 25 ₁ is an emitter tip.

A method for manufacturing a field emission cathode by a conventional vapor deposition method will be described with reference to this manufacturing process diagram.

First step (see FIG. 4A) An insulating film 22 made of SiO ₂ is deposited on a substrate 21 made of Si, and a gate electrode material layer 23 made of Mo is formed thereon. A resist film having an opening thereon is formed, and a gate electrode material layer 2 is formed through the opening of the resist film.
3 is selectively etched to form an opening 23 _1, the insulating film 22 through the opening 23 ₁ is selectively etched by RIE to form an opening 22 _1.

[0008] the second step (see FIG. 4 (B)) oblique vapor deposition method to form a sacrificial layer 24 of Al ₂ O ₃ only on the gate electrode material layer 23 having an opening 22 _1.

A third step is deposited by vapor deposition (FIG. 4 (C) see) the electron-emitting material 25 made of Mo from the top of the sacrificial layer 24, the emitter having a sharp tip on the bottom surface of the opening 22 ₁ of the insulating film 22 to form a tip 25 _1. The electron emission material 25 is also deposited on the sacrificial layer 24 by this vapor deposition.

Fourth step (see FIG. 4D) The sacrifice layer 24 is removed by etching to lift off the electron emission material 25 deposited on the sacrifice layer 24 to complete the field emission cathode.

FIGS. 5A to 5G are views for explaining a process for manufacturing a field emission cathode by a conventional etching method, and FIGS. In this figure, 31 is a substrate, 31 ₁
Protrusions, 31 ₂ emitter tip, 32 oxide film, 3
2 ₁ etching mask, 33 oxide film, 34 _1, 34
₂ an insulating film, 35 _1, 35 ₂ a gate electrode material film, 35
₃ is a gate electrode.

A method for manufacturing a field emission cathode by a conventional etching method will be described with reference to this manufacturing process explanatory diagram.

First Step (See FIG. 5A) An upper surface of a substrate 31 made of Si is thermally oxidized to form an oxide film 32 made of SiO ₂ .

[0014] patterned to form an etching mask 32 _first round using a second step (see FIG. 5 (B) refer) photolithography an oxide film 32 formed in the first step.

A third step using (FIG. 5 (C) see) etching mask 32 ₁ formed in the second step R
By etching the substrate 31 by IE, forming the protrusions 31 ₁ under the etching mask 32 _1.

[0016] In the fourth step (FIG. 5 (D) refer) projections 31 ₁ of the surface formed in the third step is thermally oxidized Si
The oxide film 33 made of O ₂ to form, to form an emitter tip ₃₁₂ having a sharp tip to the substrate.

Fifth step (see FIG. 5E) The emitter tip 31 formed in the fourth step_TwoAcid around
On the oxide film 33 and the etching mask 32₁On the spa
Insulating film 34 made of SiN by ttarig ₁, 34
_Two, And a gate electrode material made of Cr thereon
Material film 35₁, 35_TwoTo form

[0018] Sixth Step (Fig. 5 (F) see) the oxide film 32 and oxide film 33 made of SiO ₂ is etched, the insulating film 34 ₂ and the gate electrode material film 35 made of SiN on the emitter tip 31 ₂ Lift off ₂

The seventh step (see FIG. 5 (G)) to form a gate electrode 35 ₃ by patterning the gate electrode material film 35 ₁ on the insulating film 34 ₁ to complete the field emission cathode.

[0020]

Since the electron extraction voltage of the field emission cathode is determined by the degree of electric field concentration at the tip of the emitter tip, reducing the opening of the gate electrode around the tip of the emitter tip requires the electron extraction voltage. It is an effective means for lowering However, according to the conventional method for manufacturing a field emission cathode, the opening of the gate electrode cannot be made smaller than the opening of the insulating film surrounding the emitter tip. SUMMARY OF THE INVENTION It is an object of the present invention to provide a field emission cathode in which an opening of a gate electrode is smaller than an opening of an insulating film surrounding an emitter tip and can reduce an electron extraction voltage.

[0021]

In the method of manufacturing a field emission cathode according to the present invention According to an aspect of the steps of forming the emitter tip for emitting electrons on a substrate, an insulating film have the opening surrounding the emitter tip , insulating and depositing a material which can be removed by etching on the surface and the insulating film of the emitter tip, forming a sacrificial layer having a smaller opening than the opening of the insulating film, the sacrificial layer
Step of patterning into a shape larger than the edge film opening
If, depositing a gate electrode material over the said sacrificial layer,
The step of forming the gate electrode by removing the sacrificial layer was employed.

In this case, a step of forming an insulating film having an opening on the substrate, and an emitter having a sharp tip on the substrate exposed at the bottom of the opening by depositing a conductive material through the opening. Tips can be formed.

In this case, an island-shaped etching mask is formed on the surface of the plate-like body, and the plate-like body is selectively etched using the island-like etching mask, thereby forming a sharp-pointed emitter tip. be able to.

In the field emission cathode according to the present invention, a conical emitter tip for emitting electrons is formed on the substrate,
An insulating film having an opening surrounding the conical emitter tip is formed, a first gate electrode having an opening having a first opening diameter is formed on an upper surface of the insulating film, and a first gate electrode is formed on the first gate electrode. and the insulation rather smaller than the opening diameter of the first
Second having a second opening having an opening diameter a small than the opening of the film
Is formed.

[0025]

In general, when a substance is deposited on a plane having an opening by a method such as vapor deposition, the deposit grows at the upper edge of the opening while projecting obliquely into the opening, and the inner diameter of the opening of the deposit gradually becomes smaller. It is becoming. This phenomenon has been conventionally used, and the emitter tip is formed by utilizing this phenomenon in the conventional method of manufacturing the field emission cathode by the vapor deposition method shown in FIG.

In the method of manufacturing a field emission cathode according to the present invention, the inner diameter of the opening is reduced by depositing a sacrificial layer to be removed later on the insulating film having the opening, and then the gate electrode is formed thereon. Accordingly, a gate electrode having an opening smaller than the opening of the insulating film supporting the gate electrode can be formed.

[0027]

Embodiments of the present invention will be described below. (First Embodiment) FIGS. 1 and 2 are explanatory views of a manufacturing process of a field emission cathode according to a first embodiment, and (A) to (E) show respective steps. In this figure, 1 is a substrate, 2 is an insulating film,
2 ₁ opening, 3 emitter tip, 4 _1, 4 ₂ sacrificial layer, 4 ₃ opening, 4 ₄ sacrificial layer which is patterned, 5
₁ , 5 ₂ are gate electrode material layers, 5 ₃ are gate electrodes, 5 ₄
Is an opening.

The first embodiment of the present invention will be described with reference to FIGS.
A method for manufacturing the field emission cathode of the embodiment will be described.

[0029] The substrate 1 comprising a first step (see FIG. 1 (A)) Si, an insulating film 2 made of SiO ₂ having an opening 2 ₁ formed thereon, in the opening 2 the _first insulating film 2 Next, a structure having an emitter tip 3 made of Mo formed so as to protrude from the surface of the insulating film 2 by the thickness of a sacrificial layer described later is prepared. This structure may be formed by the above-described vapor deposition method or may be formed by an etching method.

Second step (see FIG. 1B) Si to be removed later is formed on the entire surface of the structure prepared in the first step.
When a material for forming a sacrificial layer made of O is deposited,
A sacrificial layer 4 on the surface of the tip 3 and on the insulating film 2 ₁, 4_Two
Is deposited, but the sacrificial layer 4 deposited on the insulating film 2_Two
Is the opening 2 in the insulating film 2₁Sacrificial layer 4_Twoof
Opening 4_ThreeIs the opening 2 in the insulating film 2₁Smaller.

The patterning of the third step (FIG. 1 (C) see) sacrificial layer 4 ₂ formed on the insulating film 2, a slightly larger circular shape than the opening 2 the _first insulating film 2 by RIE.

The fourth step (FIG. 2 (D) refer) gate electrode material layer 5 ₁ made of Mo on the emitter tip sacrificial layer on top of 3 4 ₁ and patterned sacrificial layer 4 ₄ on the insulating film 2 , depositing a 5 _2.

The fifth step (FIG. 2 (E) refer) Finally the sacrifice layer 4 ₁ and the patterned sacrificial layer 4 ₄ were H
The opening 5 close to the tip of the emitter tip 3 is removed by wet etching using an F aqueous solution or the like.
₄ to form the gate electrode 5 ₃ having.

According to this embodiment, a field emission cathode having a low electron extraction voltage can be easily formed in a self-aligned manner.

(Second Embodiment) FIG. 3 is an explanatory view of the structure of a field emission cathode according to a second embodiment. In this figure, 11 is a substrate, 12 denotes an insulating film, 12 ₁ opening, 13 the emitter tip, 14 first gate electrode, 15 is a second gate electrode.

In the field emission cathode of the second embodiment, S
opening 12 on a substrate 11 made of ₁Insulating film 1 having
2 are formed, and this opening 12₁M on the substrate 11 in
The emitter tip 13 made of o is formed, and the insulating film 1 is formed.
2 and a first gate electrode 14 made of Mo and a second
A gate electrode 15 is formed.

The field emission cathode of this embodiment is the first type.
Before the second step of the embodiment, the insulating film 2 (see FIG. 1B)
The first gate electrode is easily formed by forming a material layer for forming the first gate electrode on the first gate electrode by a conventionally known appropriate method.

According to this embodiment, the gate electrode has the first
Since the gate electrode and the second gate electrode are present in double, the concentration of the electric field at the tip of the emitter tip 13 is increased, so that the electron extraction voltage can be reduced. In this embodiment, the first gate electrode and the second gate electrode are in contact with each other and have the same potential. However, an insulating film is interposed between the first gate electrode and the second gate electrode to insulate them. By applying different potentials, it is possible to adjust so that the electric field concentration at the tip of the emitter tip 13 is optimized.

[0039]

As described above, according to the present invention,
High-efficiency compared to hot cathodes, high-density electron beams can be formed, and a field-emission cathode that operates at a low voltage can be easily realized. In the field of technology.

[Brief description of the drawings]

FIG. 1 is an explanatory view (1) of a manufacturing process of a field emission cathode according to a first embodiment, in which (A) to (C) show each process.

FIG. 2 is an explanatory view (2) of the manufacturing process of the field emission cathode of the first embodiment, and (D) and (E) show each process.

FIG. 3 is a diagram illustrating the configuration of a field emission cathode according to a second embodiment.

FIG. 4 is an explanatory view of a manufacturing process of a field emission cathode by a conventional vapor deposition method, wherein (A) to (D) show each process.

FIGS. 5A to 5G are explanatory views of a manufacturing process of a field emission cathode by a conventional etching method, wherein FIGS.

[Explanation of symbols]

1 substrate 2 insulating film 2 ₁ opening 3 emitter tip 4 _1, 4 ₂ sacrificial layer 4 ₃ opening 4 ₄ patterned sacrificial layer 5 _1, 5 ₂ gate electrode material layer ₃ gate electrode ₄ opening 11 substrate 12 insulating film 12 ₁ opening 13 emitter tip 14 first gate electrode 15 second gate electrode 21 substrate 22 insulating film 22 ₁ opening 23 gate electrode material layer 23 ₁ opening 24 sacrifice layer 25 electron emitting material 25 ₁ emitter tip 31 substrate 31 ₁ protrusion 31 ₂ emitter tip 32 oxide film 32 ₁ etching mask 33 oxide film 34 ₁ , 34 ₂ insulating film 35 ₁ , 35 ₂ gate electrode material film 35 ₃ gate electrode

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Osamu Toyoda 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Inside Fujitsu Limited (56) References JP-A-4-274123 (JP, A) JP-A-5-242797 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01J 9/02 H01J 1/304

Claims (4)

(57) [Claims] A step of forming an emitter tip for emitting electrons on a substrate and an insulating film having an opening surrounding the emitter tip; and removing the emitter tip by etching on a surface of the emitter tip and the insulating film. Depositing a material capable of forming a sacrificial layer having an opening smaller than the opening of the insulating film; patterning the sacrificial layer into a shape larger than the opening of the insulating film; A method for manufacturing a field emission cathode, comprising: depositing a gate electrode material; and removing the sacrificial layer to form a gate electrode. Forming an insulating film having an opening on the substrate; and depositing a conductive material through the opening to form an emitter tip having a sharp tip on the substrate exposed at the bottom of the opening. 2. The method according to claim 1, wherein
3. The method for producing a field emission cathode described in 1. above. 3. An island-shaped etching mask is formed on the surface of a plate-like body, and the plate-like body is selectively etched using the island-like etching mask to form a sharp-tipped emitter tip. The method for manufacturing a field emission cathode according to claim 1. 4. A conical emitter tip for emitting electrons is formed on a substrate, an insulating film having an opening surrounding the conical emitter tip is formed, and a first opening diameter of the first opening diameter is formed on an upper surface of the insulating film. the first gate electrode is formed with an opening, on the first gate electrode, the opening of the small second opening diameter than the opening of the small rather and the insulating film than the opening diameter of the first A field emission cathode, wherein a second gate electrode is formed.