JPH11265652A - Vacuum microelement - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain an improvement in heat radiating property and low voltage drive in a vacuum microelement having an amorphous carbon thin film as an emitter. SOLUTION: A Mo metal layer (metal thin film) with a protruding part which is an emitter, a Si layer 103 and a DLC layer 104 consisting of an amorphous carbon such as diamond-like carbon or amorphous carbon are successively laminated on a quartz glass 101. A gate insulating film 105 and gate electrode having opening parts in the protruding part are successively laminated on the DLC layer 103.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vacuum micro device having a field emission cold cathode.

[0002]

2. Description of the Related Art In recent years, field-emission vacuum microdevices have been actively used due to their high-speed response, the possibility of improving radiation and high temperature resistance, and the possibility of high-definition, self-luminous display. R & D is ongoing.

As an emitter material, a material having a small electron affinity capable of emitting electrons in a low electric field is used. recent years,
It has been found that the electron affinity of diamond is close to zero (for example, J. Van et al., J. Vac. Sci. Technol. B, 10, 4, (1992)
Various methods have been proposed for forming a vacuum microelement using diamond as an emitter material. Also, an amorphous carbon-based thin film that can be formed at a lower temperature than diamond and that can be easily doped has been developed as an emitter material.

Amorphous carbon-based thin films include diamond-like carbon (DLC), amorphous carbon (a-
C). Hereafter, the amorphous carbon-based thin film
It is described. When DLC is used for the emitter, a Si substrate is processed by a thin film process to form conical projections. Next, DLC is formed on the surface of the projection.

In this structure, when a large current flows through the element, S
There is a problem that it is difficult to suppress the heat generation of the emitter due to the small heat radiation effect of i. Also, there is a problem that it is difficult to lower the voltage due to the resistance of Si even when performing electron emission in a low electric field.

[0006]

As described above, the conventional vacuum micro device using DLC has a problem that the emitter has a high resistance and it is difficult to reduce the voltage. An object of the present invention is to provide a vacuum micro device which can be driven at a low voltage by reducing the resistance of the emitter even when an amorphous carbon-based thin film is used as the emitter.

[0007]

Means for Solving the Problems [Configuration] The present invention is configured as follows to achieve the above object. The gist of the present invention resides in that the emitter has a three-layer structure.
That is, a DLC thin film is used as a first layer, an Si thin film as a second layer, and a metal thin film as a third layer, which is the outermost layer. (1) The present invention (claim 1) provides a vacuum micro-element comprising an emitter for emitting electrons and a gate electrode for controlling emission of electrons from the emitter, wherein the emitter is provided on the outermost surface layer. It is characterized by comprising an amorphous carbon thin film formed, a silicon thin film and a metal thin film sequentially formed below the amorphous carbon thin film.

[0008] The thickness of the silicon thin film is 500 nm or less, and the specific resistance of the silicon thin film is 10 ^-2 Ωcm or less. [Operation] The present invention has the following operation / effect by the above configuration.

According to the present invention, the heat radiation effect can be improved and the resistance can be reduced by the metal thin film, and the low field emission can be realized by the contact between the DLC thin film and the low-resistance Si thin film.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a cross-sectional view showing a configuration of a vacuum micro device according to one embodiment of the present invention.

On a quartz glass (insulating substrate) 101, a Mo metal layer (metal thin film) 102 having a projection and serving as an emitter,
Si layer 103 and DLC layer 10 made of amorphous carbon such as diamond-like carbon or amorphous carbon
4 are sequentially stacked. Then, a gate insulating film 105 having an opening in a convex portion and a gate electrode 106 are sequentially laminated on the DLC layer 103.

In this embodiment, since the emitter has a structure in which the Mo metal layer 102, the Si layer 103, and the DLC layer 104 are stacked, electron emission occurs in a low electric field. Further, the Mo metal layer 102 can reduce the resistance of the entire emitter and improve the heat radiation effect.

Next, a manufacturing process of the vacuum micro device will be described. FIG. 2 is a diagram showing a method for manufacturing a vacuum micro device according to one embodiment of the present invention. First, as shown in FIG.
1 is formed with a concave portion 202 having a sharpened bottom. As a method for forming such a concave portion 202, a Si
A method utilizing anisotropic etching of a single crystal substrate may be used.

That is, first, S in the (100) crystal orientation
A thermally oxidized SiO layer having a thickness of about 0.1 μm
_Two layers are formed, and a resist is further applied by spin coating. Next, exposure and development are performed, and the SiO ₂ thermal oxide film is etched with a mixed solution of NH ₄ F and HF. After removing the resist, an inverse pyramid-shaped concave portion 202 is formed in the Si substrate 201 by performing anisotropic etching using a KOH aqueous solution.

Next, as shown in FIG. 2B, the gate insulating film 105 is formed by thermally oxidizing the Si substrate 201.
To form By forming the gate insulating film 105 by thermal oxidation, the inverted pyramid-shaped concave portion 202 is sharpened. For this reason, the sharpening of the concave portion causes the electric field to be more concentrated at the tip portion of the emitter formed later, so that the electron emission can be performed at a low voltage. In the present embodiment, the gate insulating film 1
05 was formed with a thickness of 0.4 μm. Although the gate insulating film 105 can be formed by a CVD method or the like, the thermal oxide film is dense and the thickness control and the like are easy.

Then, a first DLC layer (carbon thin film) 104 of the emitter is formed on the gate insulating film 105. In this embodiment, the DLC layer 104 is formed by using a microwave CVD method. Further, as a raw material gas, an H ₂ flow rate of 100 sccm and a methane (CH ₄ ) flow rate of 0.
5sccm mixed gas, microwave power 1k
W, pressure 6 Torr, substrate temperature 500 ° C.
A DLC layer 104 having a thickness of 0.3 μm was formed.

On the DLC layer 104, a Si layer (Si thin film) 103 serving as a second layer of the emitter is formed to a thickness of 0.5 μm by a sputtering method. The specific resistance of the Si layer 103 was 0.01 Ωcm in this embodiment. Then, a molybdenum (Mo) metal layer (metal thin film) 102 serving as a third layer of the emitter is formed to a thickness of 3 μm by a sputtering method.

On the other hand, as a structural substrate serving as a second substrate,
A 1 mm thick quartz glass substrate (1 mm thick) 101 having a 0.3 μm thick Al layer 203 coated on the back surface is prepared. Then, as shown in FIG.
01 and the Si substrate 201 are connected to the third layer of the emitter, Mo.
Adhesion is performed with the metal layer 102 interposed therebetween. For this bonding,
For example, an electrostatic bonding method can be used.

Next, as shown in FIG. 2D, the AL layer 203 on the back surface of the glass substrate 101 is made of HNO ₃ .CH ₃ CO _3.
After removal with OH / HF mixture,
Only the single crystal substrate 201 is selectively etched to expose the gate insulating film 105.

Then, as shown in FIG. 2E, a 0.5 μm-thick W layer is deposited on the gate insulating film 105 to form a gate electrode 106. Next, FIG.
As shown in FIG.
The resist 204 is formed to such an extent that the tip of the convex portion of the emitter covered with is slightly hidden.

Next, as shown in FIG. 2 (g), dry etching is performed by oxygen plasma to etch the resist 204 so that the tip of the gate electrode 106 along the pyramid-shaped projections appears to some extent.

Next, as shown in FIG. 2 (h), the gate electrode 106 is etched so that the tip of the gate insulating film 105 along the pyramid-shaped projections appears to some extent. Then, the tip of the pyramid-shaped convex portion, in this case, the DLC layer 104 of the first layer which is the emitter layer appears to some extent,
After removing the gate insulating film 105 with a mixed solution of NH ₄ F and HF, the resist 204 is removed to complete the vacuum micro device.

When the film thickness of the Si layer 103 of the vacuum micro device formed through the above-described steps was changed, as shown in Table 1, when the film thickness reached 800 nm, S
Peeling of the i-layer 103 occurred. Therefore, the Si layer 103
Is preferably selected to be 500 nm or less.

[0024]

[Table 1]

It should be noted that the present invention is not limited to the above embodiment, but can be implemented in various modifications without departing from the spirit of the present invention. For example, the DLC may be an n-type or p-type film. In the case of the n-type, it is possible to introduce N ₂ gas as a dopant. Further, the material is not limited to N ₂ gas, and any material that can be a nitrogen source can be used. For example, materials such as urea, ethylenediamine, and dimethylamine can be used. Further, the carbon source is not limited to methane gas, but may be an organic solvent containing carbon, for example, acetone, ethanol, methanol, or the like.

In this embodiment, the microwave CVD method is used for forming the DLC. However, the present invention is not limited to this method, and various film forming methods such as a hot filament method and an RF glow discharge method can be considered.

In addition, molybdenum (Mo) can be used for the gate electrode in addition to tungsten (W). Further, the material used for the gate electrode is not limited to the metal thin film, and a part of the first Si substrate 101 can be used. An example is shown below. A p ⁺ layer serving as a gate electrode layer is formed on an n ⁻ Si substrate having a (100) crystal orientation by an ion doping method. An inverted pyramid-shaped concave portion is formed on the Si substrate on the p ⁺ layer side. Next, a thermal oxide film serving as a gate insulating film is formed to a thickness of about 0.4 μm. Next, a DLC, a Si thin film, and a metal thin film which are to be an emitter layer are sequentially formed on the thermal oxide film. On the other hand, a quartz glass substrate (1 mm thick) having a 0.3 μm-thick AL layer coated on the back surface is prepared as a structural substrate serving as a second substrate, and the glass substrate and the Si substrate are combined with a third layer of an emitter. Adhesion is performed through a certain Mo metal layer. After bonding, the AL layer is removed, and then the Si substrate is subjected to electrochemical etching using a KOH aqueous solution or the like. By using this electrochemical etching method, only the n ^- Si layer is removed, and only the p ⁺ Si layer serving as the gate layer remains. Then p ⁺ S
By removing the SiO ₂ gate insulating layer exposed from the i-gate layer, the first layer DLC as the emitter layer is exposed, and the vacuum micro device is completed.

Next, a flat panel type image display device using the vacuum micro device according to the above embodiment will be described. As shown in FIG. 3, the flat panel type image display device of this embodiment uses the above-described method to form a glass substrate 101 (vacuum micro-element) on the surface of which an emitter layer 301 on which a large number of pyramid-shaped emitters of a vacuum micro-element are arranged is formed. An element unit 300) and a glass face plate 311 on which a transparent electrode (anode electrode) layer 312 composed of a phosphor layer 313 and ITO are sequentially formed, are arranged at predetermined intervals, and are opposed to each other.
These form a vacuum housing. That is, the vacuum micro element unit 300 is used as a part of a vacuum housing. In addition, the present invention can be variously modified and implemented without departing from the gist thereof.

[0029]

As described above, according to the present invention, by forming the emitter into a three-layer structure of a metal thin film, a Si thin film, and a carbon thin film, low field emission is possible even under a large current. It is possible to provide a vacuum micro element capable of suppressing heat generation from itself by the heat radiation effect of the third metal layer.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of a vacuum micro device according to a first embodiment of the present invention.

FIG. 2 is a process cross-sectional view showing a manufacturing process of the vacuum micro device of FIG.

FIG. 3 is a diagram showing an example in which the vacuum micro device of the present invention is applied to a flat panel display.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 101 ... Quartz glass 102 ... Mo metal layer (metal thin film) 103 ... Si layer 104 ... DLC layer 105 ... Gate insulating film 106 ... Gate electrode 201 ... Si (100) single crystal substrate 202 ... Concave 203 ... AL layer 204 ... Resist

Claims (2)

[Claims] 1. A vacuum micro device comprising: an emitter for emitting electrons; and a gate electrode for controlling emission of electrons from the emitter, wherein the emitter is an amorphous carbon formed on an outermost surface layer. A vacuum micro device comprising: a thin film; a silicon thin film and a metal thin film sequentially formed below the amorphous carbon thin film. 2. The vacuum micro device according to claim 1, wherein said Si thin film has a thickness of 500 nm or less.