JP3011160B2 - Micro cold cathode and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a structure of a micro cold cathode, and more particularly to a micro cold cathode having a low emission threshold voltage and a method of manufacturing the same.

[0002]

2. Description of the Related Art A conventional cold cathode structure comprises a cone-shaped emitter, a gate electrode for applying an electric field, and an insulating layer filling the gap therebetween. In order to lower the emission threshold voltage of the cold cathode, it is necessary to increase the electric field intensity applied to the emitter tip by reducing the radius of curvature of the tip of the emitter or reducing the distance between the emitter and the gate.

In general, Spindt et al. (CA Spindt,
J. Appl. Phys., Vol. 47, p5248 (196)), a method of forming an emitter by a vapor deposition method, and a method of forming an emitter by HF Gray et al., IEDM Tech. Dig., P. 776,
(1986)), a method of etching a silicon substrate to form an emitter is known.

A conventional flow of manufacturing a cold cathode by etching a silicon substrate will be described with reference to FIG. First, a disk-shaped silicon oxide film mask 22 (with a minimum diameter of about 0.3 μm) is formed at a predetermined position on a silicon substrate 21 (FIG. 2).
(A)). Next, the silicon substrate 2 isotropically etched.
1 is etched by about 1000 ° as shown in FIG. A silicon oxide film 23 and a cone-shaped emitter 24 are formed on the surface of the silicon substrate by a method such as thermal oxidation (FIG. 2C). Insulating film 25 such as nitride film and gate film 2
6 (FIG. 2D), and finally, a silicon oxide film 22 is formed.
And 23 are etched to lift off the insulating film 25 and the gate film 26 on the mask 22 and to remove the emitter 24.
Is exposed, a cold cathode device as shown in FIG. 2E is formed. As described above, a technique for manufacturing a gate using a mask at the time of manufacturing an emitter is known.

Another manufacturing method will be described with reference to FIG. First, a cone-shaped emitter 34 is formed on a silicon substrate 31 in the same manner as in FIG. 2.
(C)) After removing the mask 32, an insulating film 33 and a gate film 36 are formed, and a mask 37 is formed with a photoresist so as to form a desired opening (FIG. 3).
(D)). Finally, the gate film 36 and the insulating film 33 are removed by etching using the mask 37, and the resist used as the mask 37 is removed to form a gate as shown in FIG.

[0006]

In the prior art shown in FIG. 2, since the gate is formed using the mask for forming the emitter, it is difficult to form a gate having a diameter smaller than the diameter of the emitter. There is a limit to reducing the distance between the emitter and the gate. Further, when the mask is lifted off, there are problems that the emitter is destroyed by the floating gate film and the tip is chipped, and the gate film adheres to the side surface of the insulating film to cause insulation failure.

In the prior art shown in FIG. 3, when the insulating film is etched, the tip of the emitter is easily damaged by over-etching or the like. Further, there is a limit to miniaturization of a gate opening pattern formed in a photoresist mask.

As a method for miniaturizing the gate opening, Japanese Patent Application Laid-Open No. Hei 8-17330 discloses a method of forming a nitride film etching mask 42 on the surface of a substrate 41 (step (a)) as shown in FIG. After forming the columnar structure 43 on the silicon substrate 41 through the mask 42 by anisotropic etching,
The side surface of the columnar structure and the substrate surface are etched by anisotropic etching to form a constriction 44, and an upper structure 45 and a lower structure 46 forming a pair of conical silicon (step (b)). Further, the pair structure is reduced by isotropic etching to form a micro pair structure including an upper microstructure 47 and a lower microstructure 48 (step (c)), and oxidation of silicon is performed on the surface of the micropair structure by thermal oxidation. A film 49 is formed and the upper microstructure 47 and the lower microstructure 48 are separated by an oxide film 49. Thereafter, the lower microstructure 48 is masked using the upper microstructure 47 as a mask.
Forming an insulating film 50 and a gate film 51 around the step (step (d)). Finally, the upper microstructure 47 on which the insulating film 50 and the gate film 51 are adhered is removed by etching 49 of the oxide film. The oxide film 49 at the apex of the cone or polygonal cone of the structure 48 is removed, and the emitter 52 having a sharp tip is removed.
Is formed (step (e)). It is described that such a method can provide a small gate opening smaller than the limit of lithography.

However, in this method, in order to form an upper / lower pair structure by anisotropic etching first, it is inevitable to use wet etching, which may contaminate the microstructure portion. The substrate to be formed must have a (100) surface, and the problem that the substrate is limited remains. In addition, the upper microstructure shown in FIG. 4C has a problem that the constricted portion is extremely thin and is lost during the manufacturing process, so that the mask cannot be used.

Accordingly, it is an object of the present invention to provide a method of manufacturing a cold cathode device in which a gate opening is miniaturized and damage to the tip of an emitter is prevented.

[0011]

Means for Solving the Problems The present inventors have made intensive studies in view of the above problems, and as a result, have reached the present invention. That is, the present invention relates to a method for manufacturing a micro-cold cathode having a sharp-pointed emitter and a gate formed so as to surround the emitter, wherein (a) after forming a nitride film and a silicon oxide film on a silicon substrate, Forming the nitride film and the silicon oxide film as a mask for forming an emitter by using a resist as a mask; (b) forming a silicon columnar structure by etching a silicon substrate using the mask for forming an emitter; (c) Oxidizing to form a constriction at the center of the columnar structure with a silicon oxide film; (d) anisotropically etching the silicon oxide film using the nitride film as a mask;
Performing silicon anisotropic etching to form a silicon columnar structure below the constricted portion while leaving the silicon oxide film below the nitride film; (e) removing the silicon oxide film by wet etching; (F) removing the nitride film by wet etching, and then performing anisotropic etching of the silicon oxide film using the silicon portion above the two-part constricted portion as a mask; (G) a step of forming an insulating film and a gate film and further forming a silicon oxide film; (h) a step of removing the silicon oxide film by dry etching to expose a gate film above the emitter; and (i) ) After etching the gate film to the tip of the emitter, remove the silicon film above the constriction used as a mask, and wet-etch the insulating film. It is a manufacturing method for a micro cold cathode which comprises a step of exposing the emitter tip grayed.

The present invention also relates to a micro cold cathode formed by the above method.

[0013]

According to the present invention, the diameter of the remaining silicon portion becomes smaller than the diameter of the oxidizing mask by oxidizing the silicon portion so that the silicon portion remains above the emitter, so that a minute gate opening can be formed. In addition, since the emitter tip is protected by the thick oxide film until the final step, the emitter tip does not chip. Further, since the emitter tip is formed by the oxidation method of the silicon substrate, the substrate to be used is not limited. Since a gate opening having a very small diameter can be formed in this manner, the distance between the emitter and the gate can be reduced, and the emission threshold can be reduced.

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described specifically with reference to the drawings, but the present invention is not limited to these embodiments.

FIG. 1 is a schematic sectional view showing a manufacturing process according to an embodiment of the present invention.

First, a nitride film 2 is formed on a silicon substrate 1 by 80
After the silicon oxide film 3 is formed at 5000.degree., The nitride film 2 and the silicon oxide film 3 are formed into a disk-shaped mask (5000.degree..phi.) For forming the emitter using the photoresist 4 as a mask (FIG. 1A).

Using this mask, the silicon substrate 1 is
Etching is performed to form a silicon columnar structure 5 (FIG. 1B).

Next, a silicon oxide film 6 is formed to a thickness of 2500 ° on the silicon substrate 1 including the silicon columnar structure 5 by thermal oxidation, and a constriction 7 of the oxide film is formed at the center of the silicon columnar structure 5 (FIG. c)).

The silicon oxide film is anisotropically etched by 260
0 °, the silicon oxide film 3 on the nitride film 2 and the silicon oxide film 6 on the silicon substrate 1 are removed. At this time, the silicon oxide film 6 around the constriction 7 of the columnar structure
Remains intact. Further, silicon anisotropic etching is performed at 4000 °, and the second columnar structure 8 shown in FIG.
Get.

After the silicon oxide film 6 remaining in the constricted portion 7 is removed using an etching solution containing hydrofluoric acid or the like, the silicon oxide film 6 is oxidized until the constricted portion of the silicon columnar structure 8 is divided into two (3).
000Å). At this time, an upper silicon portion 10 divided by the silicon oxide film 9 and a silicon portion 11 serving as an emitter are formed below the lower portion (FIG. 1E).

After the nitride film 2 is removed by wet etching, anisotropic (dry) etching of the silicon oxide film 9 is performed using the silicon portion 10 remaining on the emitter as a mask.
000 ° (FIG. 1 (f)).

The silicon oxide film 12 as an insulating film is
At 00 °, a gate film 13 is formed at 1000 °, and a silicon oxide film 14 is formed at 6000 °. At this time, reflow is performed to thin the silicon oxide film 14 above the emitter (FIG. 1 (g)).

The silicon oxide film 14 is dry-etched until the gate film 13 above the emitter is exposed (FIG. 1).
(H)).

After the gate film 13 is etched to the tip of the emitter 11 using the remaining silicon oxide film 14 as a mask, the silicon oxide film 13 used as a mask is removed, and the silicon portion 10 formed on the emitter is etched. Further, by exposing the tip of the emitter 11 by wet-etching the insulating film 12, FIG.
Is formed.

The gate diameter of the micro cold cathode device thus formed is about 3000 ° φ, which can be smaller than the disk-shaped mask (5000 ° φ) used first.
Further, since the tip of the emitter is protected by the silicon oxide film until the final step, the tip of the emitter is not chipped or the upper silicon portion 10 is not dropped in the manufacturing process. Further, since the constricted portion is formed by forming an oxide film, the surface orientation of the substrate is not limited, and contamination can be prevented.

[0026]

As described above, according to the manufacturing method of the present invention, a gate can be formed very close to an emitter, and as a result, an emission threshold can be lowered. Further, damage to the tip of the emitter and leakage between the emitter and the gate can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional process view illustrating a manufacturing method of the present invention.

FIG. 2 is a process sectional view illustrating a method for manufacturing a cold cathode according to a conventional technique.

FIG. 3 is a process cross-sectional view for explaining another conventional cold cathode manufacturing method.

FIG. 4 is a process sectional view for explaining a conventional technique described in JP-A-8-17330.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 silicon substrate 2 nitride film 3, 6, 9, 14 silicon oxide film 4 photoresist 5 first columnar structure 7 constriction 8 second columnar structure 10 upper silicon unit 11 emitter unit 12 insulating film 13 gate film

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H01J 9/02 H01J 1/30

Claims (2)

(57) [Claims] 1. A method of manufacturing a micro cold cathode having an emitter having a sharp tip and a gate formed so as to surround the emitter, wherein (a) after forming a nitride film and a silicon oxide film on a silicon substrate, Forming the nitride film and the silicon oxide film as a mask for forming an emitter using a resist as a mask, (b) using the mask for forming the emitter,
A step of etching a silicon substrate to form a silicon columnar structure, (c) a step of oxidizing and forming a constriction in the center of the columnar structure with a silicon oxide film, and (d) a silicon oxide film using the nitride film as a mask. Performing anisotropic etching and silicon anisotropic etching to form a silicon columnar structure below the constricted portion while leaving the silicon oxide film below the nitride film; (e) removing the silicon oxide film by wet etching; A step of oxidizing the constricted portion in the silicon columnar structure until it is divided into two parts, (f) removing the nitride film by wet etching, and then using the silicon part on the constricted part that has been divided into two parts as a mask, anisotropically forming the silicon oxide film (H) forming an insulating film and a gate film, and further forming a silicon oxide film;
Removing the silicon oxide film by dry etching to expose the gate film above the emitter; and (i) removing the silicon film above the constricted portion used as a mask after etching the gate film to the emitter tip position, A method for manufacturing a micro cold cathode, further comprising a step of exposing the tip of the emitter by wet etching the insulating film. 2. A micro cold cathode formed by the method according to claim 1.