JP2007115564A - Method of manufacturing cold electron emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of producing a cold electron emitting element capable of forming a Spindt-type emitter of which the cost can be reduced. <P>SOLUTION: An emitter electrode 2 is formed on a substrate 1, and an amorphous silicon layer 3 is formed in a predetermined area on the emitter electrode 2. An insulation layer 5 is formed on the emitter electrode 2 so that its surface may be a flat surface continuous with the amorphous silicon layer 3, and a conductive layer 6 and an etching mask layer 7 are overlaid on the insulation layer 5 and the amorphous silicon layer 3 in order. The conductive layer 6 and the etching mask layer 7 are etched to expose the surface of the amorphous silicon layer 3. The exposed layer 3 is etched isotropically and the neighborhood of the surface of the amorphous silicon layer 3 is transformed. The transformed part, the etching mask layer 7, and conductive layer 6 on the amorphous silicon layer 3 are removed, and the amorphous silicon layer 3 is transformed into an approximately conic emitter 10. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a cold electron emission device having a Spindt-type emitter.

Cold electron-emitting devices having Spindt-type emitters are widely used for displays and magnetic measurements.
A cold electron emission device having a Spindt-type emitter utilizes a field emission phenomenon. That is, when the intensity of the electric field applied to the substance is increased, the cold electron-emitting device gradually reduces the energy barrier width on the substance surface according to the intensity, and when the electric field intensity exceeds a predetermined value, Makes use of the phenomenon that the tunneling effect can break through the energy barrier and thus cold electrons are emitted from the material. In this case, since the electric field concentrates on the Spindt-type emitter that emits cold electrons according to Poisson's equation, cold electrons can be efficiently emitted at a relatively low voltage.

The structure of a cold electron emission device having such a Spindt-type emitter is shown in FIG.
FIG. 8 is a perspective view showing a general structure of a cold electron emission device having a Spindt-type emitter.

As shown in FIG. 8, a cold electron emission device 120 having a Spindt-type emitter has an emitter electrode 102 formed on a substrate 101, and an insulating layer 103 and a gate electrode 104 are formed on the emitter electrode 102 in a predetermined manner. The openings 105 are sequentially stacked. In addition, a substantially conical Spindt emitter 106 is formed in the opening 105 in contact with the emitter electrode 102.
The sharper the tip of the Spindt-type emitter 106, the more the electric field is concentrated on the tip. Therefore, cold electrons can be efficiently emitted at a lower voltage.

Patent Documents 1 and 2 describe a method for forming such a substantially conical Spindt-type emitter.
The method of forming a Spindt emitter described in Patent Document 1 uses a single crystal silicon wafer as a substrate, and anisotropically etches the vicinity of the surface of the single crystal silicon wafer into a conical shape. How to get.
The method for forming a Spindt-type emitter described in Patent Document 2 is a method for obtaining a Spindt-type emitter by obliquely depositing a conductive material from above the gate electrode toward the emitter electrode.
JP-A-4-94033 JP-A-6-96664

However, since the Spindt-type emitter forming method described in Patent Document 1 uses an expensive single crystal silicon wafer, improvement in cost reduction of the cold electron-emitting device is desired.
In addition, the spint-type emitter formation method described in Patent Document 2 performs the oblique deposition while rotating the substrate when the conductive material is obliquely deposited, so that the mechanism of the deposition apparatus becomes complicated. , Troubles such as large equipment costs are required and productivity deteriorates. Therefore, the cold electron-emitting device manufactured by the Spindt-type emitter forming method described in Patent Document 2 is expensive.

  Accordingly, the problem to be solved by the present invention is to provide a method for manufacturing a cold electron emission device capable of forming a Spindt-type emitter capable of reducing the cost.

In order to solve the above problems, the present invention has the following means.
An emitter electrode forming step of forming an emitter electrode (2) on the substrate (1), and an amorphous silicon layer forming step of forming an amorphous silicon layer (3) in a predetermined range on the formed emitter electrode (2); An insulating layer (5) is formed on the emitter electrode (2) excluding the amorphous silicon layer (3) so that the surface of the amorphous silicon layer (3) and the surface thereof are continuous and flat. A conductive layer (6) is formed on each surface of the insulating layer (5) and the amorphous silicon layer (3), and an etching mask layer (7) is formed on the conductive layer (6). And a predetermined range of the etching mask layer (7) and the conductive layer (6) are sequentially etched in a ring shape so that the surface of the amorphous silicon layer (3) is exposed. A first etching step, a second etching step for isotropically etching the amorphous silicon layer (3) exposed in the first etching step, and altering at least the surface vicinity of the amorphous silicon layer (3) Altering step of changing to an altered portion, removing the altered portion, the etching mask layer (7), and the conductive layer (6) on the amorphous silicon layer (3), and removing the amorphous silicon layer (3) from the An emitter forming step of forming a substantially conical emitter (10) whose bottom surface is in contact with the emitter electrode (2).

  According to the present invention, the step of forming the emitter electrode 2 on the substrate 1, the step of forming the amorphous silicon layer 3 in a predetermined range on the emitter electrode 2, and the emitter leaving the predetermined range on the emitter electrode 2 A step of forming the insulating layer 5 on the electrode 2 so that the surface of the amorphous silicon layer 3 and the surface thereof are continuous and flat, and the conductive layer 6 and etching on the surfaces of the insulating layer 5 and the amorphous silicon layer 3. A step of sequentially laminating the mask layer 7, a step of sequentially etching a predetermined range of the etching mask layer 7 and the conductive layer 6 in a ring shape so that the surface of the amorphous silicon layer 3 is exposed, and the exposed amorphous silicon layer 3 Isotropic etching, at least a portion near the surface of the amorphous silicon layer 3 is altered to form an altered portion, an altered portion, A step of removing the conductive layer 6 on the masking mask layer 7 and the amorphous silicon layer 3 and forming the amorphous silicon layer 3 into a substantially conical emitter 10 whose bottom surface is in contact with the emitter electrode 2. As a result, a cold electron-emitting device having a Spindt-type emitter capable of reducing the cost can be produced.

The preferred embodiments of the present invention will be described with reference to FIGS.
Examples of the method for manufacturing a cold electron-emitting device according to the present invention will be described below as first to seventh steps.
FIGS. 1-7 is typical sectional drawing for demonstrating the 1st process-the 7th process in the Example of the manufacturing method of the cold electron emission element of this invention. 7A is a perspective view, and FIG. 7B is a schematic cross-sectional view. Each figure and each process correspond to each other.

<Example>
(First step) [See FIG. 1]
For example, Nb (niobium) is deposited on the surface of the substrate 1 so as to have a thickness of about 0.1 μm by using a vacuum deposition method. The formed Nb becomes the emitter electrode 2.
In the embodiment, an inexpensive glass plate was used as the substrate 1 instead of an expensive single crystal silicon wafer. A commercially available glass plate can be used.
Here, the vacuum film forming method indicates a sputtering method, a vapor deposition method, or the like, and in the examples, the sputtering method is used.

(Second step) [See FIG. 2]
An n-type amorphous silicon film is formed on the surface of the emitter electrode 2 so as to have a thickness of about 0.5 μm by using a vacuum film forming method.
In Examples, a plasma CVD (Chemical Vapor Deposition) method was used as the vacuum film forming method.
Next, the formed n-type amorphous silicon is selectively etched by photolithography to form a cylindrical n-type amorphous silicon layer 3 having a diameter of about 1 μm.
In this embodiment, dry etching using SF ₆ (sulfur hexafluoride) was used as the etching method.

(Third step) [See FIG. 3]
On the surfaces of the emitter electrode 2 and the n-type amorphous silicon layer 3, SiO ₂ (silicon dioxide) is formed so as to have a thickness of about 0.5 μm by using a vacuum film forming method. In the examples, the plasma CVD method was used as the vacuum film forming method.
Next, the surface vicinity of the deposited SiO ₂ and n-type amorphous silicon layer 3 is polished by, for example, chemical mechanical polishing (CMP), and the surface of the polished SiO ₂ and n-type amorphous silicon layer 3 is polished. Is a continuous flat surface and each thickness is about 0.3 μm. The polished SiO ₂ becomes the insulating layer 5.

(4th process) [Refer FIG. 4]
A conductive layer 6 is formed on the surfaces of the n-type amorphous silicon layer 3 and the insulating layer 5 by, for example, sputtering so that Nb (niobium) has a thickness of about 0.2 μm. A SiO ₂ layer 7 is formed on the surface of the layer 6 by depositing SiO ₂ to a thickness of about 0.2 μm, for example, by plasma CVD.
Next, by selectively etching the conductive layer 6 and the SiO ₂ layer 7 using a photolithographic method, a ring-shaped opening 8 is formed on the n-type amorphous silicon layer 3, and n in the opening 8 is formed. The surface of the mold amorphous silicon layer 3 is exposed.
In the example, the ring-shaped opening 8 is formed so that the outer shape of the n-type amorphous silicon layer 3 and the outer shape of the opening 8 are substantially coincident and the width w of the opening 8 is about 0.3 μm.
The SiO ₂ layer 7 after the opening 8 is formed serves as an etching mask 9.

(Fifth step) [Refer to FIG. 5]
The exposed n-type amorphous silicon layer 3 is isotropically dry-etched so as to have a shape close to a conical shape.
In the example, this dry etching was performed by reactive ion etching using SF ₆ as an etching gas, a degree of vacuum of 13.3 Pa, and an RF power of 160 W.
Further, in this dry etching, the insulating layer 5 is hardly etched.

(Sixth step) [Refer to FIG. 6]
O ₂ (oxygen) plasma treatment is performed to oxidize the vicinity of the surface of the n-type amorphous silicon layer 3. Moreover, the exposed surface vicinity portion of the conductive layer 6 is also oxidized by this O ₂ plasma treatment.
In FIG. 6, a portion oxidized by the O ₂ plasma treatment (sometimes referred to as an altered portion) is indicated by a hatched portion for easy understanding.
Further, in the embodiment, the altered portion is formed by altering the surface vicinity of the n-type amorphous silicon layer 3 by oxidation, but the present invention is not limited to this. For example, the altered portion may be formed by nitriding or the like instead of oxidation.

(Seventh step) [Refer to FIG. 7]
For example, wet etching using a buffered hydrofluoric acid solution is performed to remove the above-described altered portion. Further, by this wet etching, the etching mask 9 and the conductive layer 6 on the n-type amorphous silicon layer 3 are removed, and a substantially conical Spindt-type emitter 10 having a sharp tip is obtained. In addition, the conductive layer 6 after the wet etching becomes the gate electrode 12.
Note that the vicinity of the inner wall of the insulating layer 5 is also etched by this wet etching.

The cold electron-emitting device 20 in the embodiment is obtained by the first to seventh steps described above.
In this cold electron emitter 20, since the tip of the Spindt-type emitter 10 is pointed, the electric field tends to concentrate on the tip, so that cold electrons can be efficiently emitted at a lower voltage.
In addition, as described in the embodiments, according to the method for manufacturing a cold electron-emitting device of the present invention, a Spindt-type emitter can be formed without using a single crystal silicon wafer and without performing oblique deposition. Therefore, the cost of the cold electron emission device can be reduced.
Further, according to the method for manufacturing a cold electron emission device of the present invention, since a glass plate, for example, can be used for the substrate, it is possible to simultaneously form a plurality of cold electron emission devices on a large area glass plate, This is advantageous for reducing the cost of the cold electron-emitting device.

  The embodiment of the present invention is not limited to the configuration and procedure described above, and it goes without saying that modifications may be made without departing from the scope of the present invention.

It is typical sectional drawing for demonstrating the 1st process in the Example of the manufacturing method of the cold electron emission element of this invention. It is typical sectional drawing for demonstrating the 2nd process in the Example of the manufacturing method of the cold electron emission element of this invention. It is typical sectional drawing for demonstrating the 3rd process in the Example of the manufacturing method of the cold electron emission element of this invention. It is typical sectional drawing for demonstrating the 4th process in the Example of the manufacturing method of the cold electron emission element of this invention. It is typical sectional drawing for demonstrating the 5th process in the Example of the manufacturing method of the cold electron emission element of this invention. It is typical sectional drawing for demonstrating the 6th process in the Example of the manufacturing method of the cold electron emission element of this invention. It is the perspective view and typical sectional drawing for demonstrating the 7th process in the Example of the manufacturing method of the cold electron emission element of this invention. It is a perspective view for demonstrating the general structure of a cold electron emission element.

Explanation of symbols

1 substrate, 2 emitter electrode, 3 n-type amorphous silicon layer, 5 insulating layer, 6 conductive layer, 7 SiO ₂ layer, 8 opening, 9 etching mask, 10 emitter, 12 gate electrode, 20 cold electron-emitting device, w width

Claims (1)

An emitter electrode forming step of forming an emitter electrode on the substrate;
An amorphous silicon layer forming step of forming an amorphous silicon layer in a predetermined range on the formed emitter electrode;
An insulating layer forming step of forming an insulating layer on the emitter electrode excluding the amorphous silicon layer so that the surface of the amorphous silicon layer and the surface thereof are continuous flat surfaces;
A laminating step of forming a conductive layer on each surface of the insulating layer and the amorphous silicon layer, and forming an etching mask layer on the conductive layer;
A first etching step of sequentially etching a predetermined range of the etching mask layer and the conductive layer in a ring shape so that the surface of the amorphous silicon layer is exposed;
A second etching step for isotropically etching the amorphous silicon layer exposed in the first etching step;
An alteration process in which at least the vicinity of the surface of the amorphous silicon layer is altered to be an altered portion;
An emitter forming step of removing the altered portion, the etching mask layer, and the conductive layer on the amorphous silicon layer, and using the amorphous silicon layer as a substantially conical emitter whose bottom surface is in contact with the emitter electrode; ,
A method for manufacturing a cold electron-emitting device, comprising:

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