JPH08255555A - Needle electrode and manufacturing method thereof - Google Patents

Abstract

(57) [Summary] [Object] The present invention relates to a needle-shaped electrode used for a quantum mechanical tunneling phenomenon in a vacuum or between solids and a solid, and a manufacturing method thereof, and is applicable to a stable and large-area device. Provide a needle-shaped electrode used for various field emission. A needle-shaped electrode having a structure in which at least a silicon needle-shaped structure is provided on a metal oxide conductor on a substrate, and the tip of the silicon needle-shaped structure is covered with a metal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a needle electrode used for a quantum mechanical tunneling phenomenon in vacuum or between solids and a method for manufacturing the same.

The technology utilizing the phenomenon of tunneling of electrons into a vacuum is currently used in high-resolution electron microscope electron guns and
It has been researched and developed, and partly put into practical use, as a display element in which field emission electrodes are arranged in a matrix, and as a scanning probe microscope capable of performing an atomic dimension evaluation method of a material surface.

[0003]

2. Description of the Related Art In the above-mentioned techniques, by making the region where electron tunneling occurs conventionally extremely narrow,
The characteristics of the device are improved. Therefore, the electrode that normally causes tunneling has the shape of a sharp needle, and this needle-shaped electrode is called a tip.

For example, to produce field emission,
It is known that for needle electrodes the electric field is inversely proportional to the average radius of curvature of the tip, although a very strong electric field is required. In particular, in the case of a display that uses field emission, it is necessary to obtain a large current at a low voltage, so the radius of curvature of the tip must be about 10 nm.

It is well known that, even in the scanning probe microscope, when the tunneling phenomenon is utilized, the shape of the tip has a great influence on the surface image obtained. Therefore, the technology to obtain a well-controlled needle electrode is
It is essential for these applied technologies.

In the prior art, this needle electrode was formed by using a chemical etching or sputtering technique using a photolithography technique.

[0007]

For this reason, the existing photolithography technology is not sufficient to form needle electrodes of about 10 nm with good reproducibility. Therefore, it is unavoidable to rely on empirical methods. This has been a factor of reducing reliability and increasing manufacturing cost.

Further, particularly in the case of a display element or the like using field emission, it is necessary to use silicon as the material of the needle electrode in order to apply the photolithography technique. In the case of a needle-shaped electrode that emits electrons, when the surface is oxidized by molecules adsorbed on the surface of the needle-shaped electrode from the atmosphere, especially when oxygen or water contained in the atmosphere oxidizes the surface, the work function of the surface changes The characteristics change significantly, and stable operation becomes difficult.
In particular, a semiconductor such as silicon is a problem because it is an active substance. Furthermore, since the oxide of silicon is more stable than that of silicon alone, it is difficult to clean the surface once contaminated. Therefore, the atmosphere for operating the needle-shaped electrode is problematic. There was a drawback that it was necessary to make the ultra high vacuum.

The present invention provides a needle-like electrode used for field emission or the like which is stable and can be applied to a device having a large area, without requiring such a difficult microfabrication or ultra-high vacuum technique. With the goal.

[0010]

FIG. 1 is a diagram illustrating the principle of the present invention. In the figure, 1 is a substrate such as silicon (Si) or glass, 2 is a metal oxide conductor containing at least one of indium (In), tin (Sn) and zinc (Zn), 3 is a needle structure of silicon, 4 is at least In, S
A metal 5 made of n, Zn, gold (Au), silver (Ag), platinum (Pt), or the like is the needle electrode of the present invention.

As shown in FIG. 1, an object of the present invention is to have at least a silicon needle-like structure 3 on a metal oxide conductor 2 on a substrate 1, and at least a tip portion of the silicon needle-like structure 3 at the tip. This is achieved by coating with a metal such as In or Pt.

[0012]

In the present invention, as shown in FIG. 1, the surface of the needle-shaped electrode 5 is protected by covering the tip of the silicon needle-shaped structure 3 which is the main part of the needle-shaped electrode 5 with the metal 4. .

Since the oxide of metal generally has a higher vapor pressure than that of a simple substance of metal, heating the needle electrode 5 makes it possible to remove the contamination of the metal surface by the oxide relatively easily. Even if the surface is contaminated by the atmosphere and the emission characteristics are deteriorated, it can be easily regenerated.

Further, metal 4 for surface protection is made of gold, platinum,
It is possible to prevent oxidation due to the atmosphere by using a noble metal such as silver that is hard to oxidize.

[0015]

2 to 4 are explanatory views of the first to third embodiments of the present invention. In the figure, 11 is a Si substrate, 12 is an In oxide conductor (ITO film), 13 is a Si needle structure, and 13 'is S.
i and 14 are In, 15 is a needle-like electrode, 16 is a SiO ₂ film, 17 is an opening, 18 is a reducing atmosphere containing hydrogen, 19 is an ITO alteration layer (In), 20 is an electrode, and 21 is an insulating layer ( SiO ₂ , SiN
Etc.), 22 is a spacer, 23 is a grid electrode, 24 is a phosphor,
Reference numeral 25 is a counter electrode.

In the first embodiment of the present invention, an oxide conductor such as ITO is formed on a glass or Si substrate 11.
An (Indium Tin Oxide) film 12 is deposited to a thickness of 50 nm by DC sputtering. A SiO ₂ film 16 having a thickness of 100 nm is deposited thereon by a plasma CVD method or the like, and is formed only on a portion where a needle electrode 15 is formed by a technique such as photolithography as shown in FIG. An opening 17 is provided.

Next, the Si substrate 11 is placed in a chamber of a general parallel plate type plasma CVD apparatus, and hydrogen 30
0 sccm is introduced to maintain the pressure at 0.6 Torr, the substrate temperature is set to 200 ° C., 300 W power is applied from a 13.56 MHz high frequency power supply, and plasma is generated in a reducing atmosphere 18 containing hydrogen. When the treatment is performed in plasma for 10 minutes, the surface of the ITO film 12 is reduced, and the ITO-modified layer made of metallic In is reduced as shown in FIG. 2B.
19 is formed.

Next, 40 sccm of silane gas and 160 sccm of hydrogen gas were introduced into the chamber, and the pressure was adjusted to 1.0.
Keep at Torr, 2 from 13.56MHz high frequency power supply
By applying a power of 00 W and decomposing silane (SiH ₂ ) in the plasma, the deposition rate of silicon is increased and Si needle-like structure 13 is formed, as shown in FIG. The tip of the Si needle-like structure 13 is covered with In14 to form a needle-like electrode 15.

Next, the SiO ₂ film 16 which is the mask layer is removed by diluted hydrofluoric acid or the like. At this time, as shown in FIG. 2D, the layer of silicon 13 'on the mask layer is also lifted off. In the first embodiment of the present invention, the mask layer SiO
_Although the position where the needle-shaped electrode 15 is formed is determined by the opening 17 of the _two films 16, the photolithography process for forming the needle-shaped electrode 15 is not included. No pollution of 15.

Next, a second embodiment of the present invention will be described with reference to FIG. In the above-described first embodiment, the needle electrode
The mask layer made of the SiO ₂ film 16 or the like was formed to determine the position of 15. However, in the case of a display or the like utilizing field emission, it is necessary to form many needle-shaped electrodes 15 on the ITO electrode. .

On the glass or Si substrate 11, as shown in FIG.
As shown in, the ITO film 12 is formed by DC sputtering to a thickness of 50 nm.
To the thickness of. Subsequently, similarly to the first embodiment of the present invention, as shown in FIG. 3B, a reducing atmosphere 18 is formed by hydrogen plasma to form an ITO altered layer 19.

Next, as in the first embodiment, as shown in FIG.
As shown in FIG. 3, Si needle-like structure 13 is formed by depositing silicon. In the second embodiment, the mask layer causes I
Since the region of the TO-altered layer 19 is not limited, the needle electrodes 15 are randomly formed on the ITO film 12. The needle electrode 15 can be used as it is, but the surface may be cleaned. Then, the tip of the Si needle-like structure 13 is coated with In14.

As shown in FIG. 3D, the reducing atmosphere 18 containing hydrogen is set to an ultrahigh vacuum, and the DC power source 21 is connected so that the needle electrode 15 is positive with respect to the electrode 20. Needle electrode 15
When the electric field strength on the surface of the electrode is set to several MV / cm or more, the oxide on the surface of the needle electrode 15 is ionized and desorbed.

Also, a reducing atmosphere 18 containing hydrogen is filled with an inert gas such as hydrogen or argon, and the pressure is adjusted to 2-3 mmT.
You may keep it at orr. In the case of hydrogen, it is possible to carry out chemical cleaning in which the oxide on the surface is desorbed while being hydrided. In the case of an inert gas, no chemical action occurs, but due to the ions of the inert gas ionized on the surface of the needle electrode 15, the ions of the inert gas are accelerated and collide with the surface of the needle electrode 15 by the electric field, Surface oxide can be removed by sputtering.

The release characteristics obtained according to the invention depend on the metal. The electron emission characteristics of semiconductors and metals are very different. In many cases, the properties of electron emission from metals do not cause any disadvantages. However, when the electron emission characteristics of the semiconductor are desired, as shown in FIG. 3E, at this stage, the coated metal such as In14 is removed and the Si needle-like structure 13 is exposed. Good.

Further, a third embodiment of the present invention will be described with reference to FIG. FIG. 4 is a constitutional view of the present invention and shows a cross-sectional view of a field emission type flat display embodying the present invention.

Unlike thermionic emission, the field emission is small in size because it is not necessary to heat the cathode, and the emission area is small, so that it becomes a high-brightness electron source. Further, since the voltage for electron emission can be lower than that of a CRT or the like, research and development are being promoted as one method of a flat display.
However, since the characteristics of the field emission cathode are difficult to stabilize, it is necessary to prepare a large number of finely shaped cathodes for one pixel, which makes its fabrication difficult.

In this embodiment, as shown in the second embodiment, the photolithography process is not required, and as shown in FIG. 4, the tip of the Si needle-like structure is coated with In14. Since the tip of the needle-shaped electrode is protected by metal, there is an advantage that the field emission characteristics are stable.

Further, in the present invention, it is not necessary to use an expensive silicon substrate as a substrate, and a glass substrate which is supplied inexpensively in a liquid crystal display or the like can be used, and the cost can be reduced.

[0030]

As described above, according to the present invention,
The effect of being able to stably form a needle-shaped electrode (tip) without using a microfabrication technology that is difficult to realize, such as the order of 10 Å, and stable tunneling characteristics can be obtained. It greatly contributes to the improvement.

[Brief description of drawings]

FIG. 1 is a diagram illustrating the principle of the present invention.

FIG. 2 is an explanatory diagram of a first embodiment of the present invention.

FIG. 3 is an explanatory diagram of a second embodiment of the present invention.

FIG. 4 is an explanatory diagram of a third embodiment of the present invention.

[Explanation of symbols]

In the figure, 1 substrate 2 metal oxide conductor, 3 Si needle structure 4 metal 5 needle electrode 11 Si substrate 12 In oxide conductor (ITO film) 13 Si needle structure 14 In 15 needle electrode 16 SiO ₂ film 17 Opening 18 Reducing atmosphere containing hydrogen 19 ITO alteration layer (In) 20 Electrode 21 Insulating layer (SiO ₂ , SiN, etc.) 22 Spacer 23 Grid electrode 24 Phosphor 25 Counter electrode

Claims (8)

[Claims] 1. A needle-shaped electrode having at least a silicon needle-shaped structure on a metal oxide conductor on a substrate, and a metal coating the tip of the silicon needle-shaped structure. 2. The needle electrode according to claim 1, wherein the substrate is a glass or silicon substrate. 3. The needle electrode according to claim 1, wherein the metal oxide contains at least one metal oxide of indium, tin, and zinc. 4. The metal is indium, tin, zinc, gold,
The needle-shaped electrode according to claim 1, which is made of at least one metal of silver or platinum. 5. The needle electrode according to claim 1, wherein the metal is formed by reducing the metal oxide conductor. 6. An acicular electrode having at least a silicon acicular structure on a metal oxide conductor on a substrate. 7. A method comprising forming at least a silicon needle-like structure on a metal oxide conductor on a substrate, coating the metal at the tip of the silicon needle-like structure, and then removing the metal. A method for manufacturing a characteristic needle-shaped electrode. 8. A structure having a plurality of metal oxide conductors having needle-shaped electrodes on a substrate and a plurality of grid electrodes via spacers, and a counter electrode on a counter substrate is covered with a phosphor. 6. The needle-shaped electrode according to any one of claims 1 to 5, wherein in the field emission flat panel display, the tip of the silicon needle-shaped structure forming the needle-shaped electrode is coated with a metal.