JP2002279887A - Electron emission element and image-forming device using same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve breakdown voltage of an electron emission element which can emit electron stably and with high efficiency and to improve degree of freedom in designing film thickness of a porous silicone layer. SOLUTION: It is an electron emission element which emits electron into the atmosphere by electron emitting phenomenon from a semiconductor. The surface 1a of a substrate 1 is processed to form a convex portion 11 which is framed in by an insulating thin film 3 with an opening 6 arranged in a selected part of it. The porous silicone layer 4 is formed by oxidization from the opening 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an electron-emitting device used as a charger of an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art Generally, a corotron charger and a scorotron charger are used in an electrophotographic image forming apparatus such as a plain paper copying apparatus, a facsimile, and a printer using an electrophotographic technique. These chargers use a corona discharge to charge the photoconductor in a non-contact manner, have excellent charging stability, and have been the mainstream of the charging method. However, the corona charger system is often generated amount of ozone and NOx, it has recently been studied contact charging method for charging the photosensitive member by contacting it by applying a voltage to the contact charger to the photosensitive member.

For example, Japanese Patent Application Laid-Open No. 5-88507 describes a roller charging system.
The 552 JP describes a blade charging method, in Japanese Patent Laid-Open 2-62563 Patent Publication describes a brush charging method. These contact charging systems can charge the photoconductor at a lower voltage than the corona charging system in which the photoconductor is charged in a non-contact manner, and the amount of ozone generated is 1 / of the corona charging system.
There is an advantage that it is reduced to about 100 to 1/500.

[0004]

However, in the contact charging system, problems such as scratches and stains due to contact with the member to be charged may occur. Further, when a pinhole is present on the surface of the member to be charged, the electric field concentrates on the pinhole, so that a defect such as white spots or black streaks occurs in an image.

Accordingly, the present applicant has already proposed a charging device using an electron-emitting device made of a semiconductor having a porous silicon layer free from such a problem, and an electrophotographic device using the same. (For example, Japanese Patent Application 2000-0
See 76511. ).

However, the thickness of the porous silicon layer has a large effect on the electron emission efficiency, and therefore, it is necessary to design an ideal anodization depth. Furthermore, in order to obtain a constant device current (Ips), the device voltage (Vp
In order to apply s), it is necessary to ensure the breakdown voltage of the device, and depending on the shape of the electron-emitting device, a problem may occur and a free design may not be expected.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to improve the breakdown voltage of a charge-emitting device capable of stably and efficiently emitting electrons and improve the degree of freedom in designing the thickness of a porous silicon layer.

[0008]

To solve the problems According to an aspect of, the invention is claimed in claim 1, an electron-emitting device to emit electrons into the atmosphere by an electron emission phenomenon from the semiconductor substrate surface comprises a convex portion The convex portion is surrounded by an insulating thin film, and the insulating thin film has a structure in which an opening is provided in a selected portion of the convex portion. An electron-emitting device characterized in that a porous silicon layer is formed by oxidation of the porous silicon layer.

[0009] According to a second aspect of the invention, the porous silicon layer, an electron-emitting device according to claim 1, characterized in that it is formed by anodic oxidation of the silicon or polysilicon of the opening surface is there.

According to a third aspect of the present invention, the substrate has a silicon surface processed into a convex shape, or the silicon substrate having a polysilicon deposited on the surface has the polysilicon processed into a convex shape; 3. The electron-emitting device according to claim 2, wherein a substrate in which a back electrode and polysilicon are deposited on an insulating substrate, wherein the polysilicon is processed into a convex shape is used.

According to a fourth aspect of the present invention, the thickness of the porous silicon layer is a, and the distance between the edge of the opening and the edge of the projection is the distance of the porous silicon layer covered with the insulating thin film. b1, if the level difference of the convex portion was set to c, a> b
The electron-emitting device according to any one of claims 1 to 3, wherein 1, a ≦ c is satisfied.

According to a fifth aspect of the present invention, the thickness of the porous silicon layer is a, and the distance of the porous silicon layer covered with the insulating thin film from the edge of the opening to the edge of the projection is b1, when the step of the projection is c, b1 =
4. The electron-emitting device according to claim 1, wherein a × sin45 ° and a ≦ c are satisfied. 5.

According to a sixth aspect of the present invention, the thickness of the porous silicon layer is a, and the distance between the edge of the opening and the edge of the projection is the distance of the porous silicon layer covered with the insulating thin film. b1, the side wall of the projection and the surface 1a of the substrate 1
When θd is the angle formed by θd, a ≧ b1 and θd = 60
The electron-emitting device according to any one of claims 1 to 4, wherein the angle?

The invention according to claim 7 is the electron-emitting device according to any one of claims 1 to 6, wherein the insulating thin film is made of a polymer resin.

The invention according to claim 8 is the electron-emitting device according to any one of claims 1 to 6, wherein the insulating thin film is any one of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and a tantalum oxide film.

According to a ninth aspect of the present invention, there is provided an image forming apparatus using the electron-emitting device according to the first to eighth aspects as a charger.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the drawings using examples.

[0018]

Embodiment 1 FIG. 1 is an explanatory diagram for explaining an example of an electron-emitting device according to an embodiment of the present invention.

First, as shown in FIG.
For example, a back surface electrode 2 is formed on a back surface of a substrate 1 formed of low-resistance silicon (Si). On the surface 1a side of the substrate 1, there is provided a convex portion 11 which is processed into a convex shape and has a step of a convex portion indicated by reference numeral c. The surface 1a and the convex portion 11 is masked with an insulating thin film 3,
The insulating thin film 3 has an opening 6 at a selected portion. Since the opening 6 is a window for anodic oxidation (window for anodic oxidation), it is manufactured by an appropriate design.

The silicon is oxidized through the opening 6 to form a porous silicon layer 4 having an optimum depth (thickness a) as shown in FIG. Next, FIG.
(C), the to the opening 6 is formed thin film electrode 5 the electron-emitting device is formed.

As such oxidation, rapid thermal oxidation (R
Oxidation by TO (Rapid Thermal Oxidation) or a chemical method is exemplified. Anodization using the back electrode 2 as a positive electrode is exemplified as a preferable method. By oxidizing in this manner, a porous silicon layer 4 having a fine structure in which a semiconductor layer and an insulator layer are stacked is formed.

Anodization is performed by using, for example, HF as an electrolytic solution.
Using a (hydrogen fluoride) / ethanol mixture, the platinum electrode is used as the negative electrode, the back electrode 2 is used as the positive electrode, and the silicon surface is irradiated with light from the opening 6 at a constant current.

Here, since anodization exhibits isotropic properties,
In addition to proceeding in the film thickness direction, anodization is also formed in a direction (surface direction) extending toward the surface direction of the lower surface of the insulating thin film 3. Thus, the anodization proceeds in the surface direction by the same distance as the depth (film thickness a) at which the anodization proceeds.

Here, as shown in FIG. 8, if the surface of the silicon substrate (substrate 1) is flat (unless the convex portion 11 is formed), the thickness a of the porous silicon layer 4 and the insulating property The distance anodized in contact with the thin film 3 (hereinafter referred to as the surface distance b
Hereinafter) is substantially equal (a = b). Here, in FIG. 8 and the following description, the terminal at the interface between the porous silicon layer 4 and the insulating thin film 3 generated by the anodization is expressed as a porous silicon layer end 33. b is defined as the distance b from the opening end 31 to the porous silicon layer end 33.

When the electron-emitting device shown in FIG. 7 is formed by attaching the thin-film electrode 5 to the structure shown in FIG.
In some cases, the breakdown voltage between the thin film electrode 5 and the surface direction is lower than the breakdown voltage in the film thickness direction.
It is considered that this is because the crystallinity of the silicon surface is discontinuous, and the discontinuous portion reacts differently with other portions during the anodizing treatment to change the film quality.

Here, as shown in FIG.
When the distance from the opening edge 31 to the protrusion edge 32 at which the upper wall 11a is insulated (hereinafter referred to as the upper wall distance b1) is set smaller than the optimum film thickness a (a> b1), the porous silicon Since the distance a1 to the layer end 33 is substantially equal to the film thickness a, the anodization proceeds from the opening end 31 around the convex edge 32 and proceeds along the side wall 11b. In addition, the distance from the convex edge 32 to the end 33 of the porous silicon layer (hereinafter referred to as a side wall distance c1) is a step of the convex (the convex edge 3).
If it is set smaller than (distance from 2 to the surface 1a) c, the porous silicon layer end 33 is formed along the side wall 11b. As a result, in FIG.
Is defined as the distance from the surface to the end of the porous silicon layer 33, the sum of the upper wall distance b1 and the side wall distance c1 (b =
b1 + c1), which is longer than the film thickness a.

In this case, in the electron-emitting device having the projection 11 shown in FIG. 1 or FIG. 2, the surface distance b of the porous silicon layer 4 formed under the insulating thin film 3 is reduced as shown in FIG. And the withstand voltage between the substrate 1 and the thin film electrode 5 is increased.

That is, the thickness a of the porous silicon layer 4
Each of the top wall distance b1 and the convex portion step c, a> b1, a
By satisfying ≦ c, improvement in breakdown voltage of the electron-emitting device is expected. Further, by setting as described above, it is possible to improve the breakdown voltage of the charge-emitting device capable of stably and efficiently emitting electrons and improve the degree of freedom in designing the thickness of the porous silicon layer.

According to the charging device having such an electron-emitting device, for example, Japanese Patent Application No. 2000-076511.
As in the charging device described in the specification and the electrophotographic device using the same, it is possible to perform charging without generating any discharge products such as ozone, and to charge an image recording device such as a copying machine, a printer, and a facsimile. And an image recording apparatus having a charger and a charger.

The electron emission mechanism of this electron-emitting device is shown in FIGS. As shown in FIG. 5, electrons near the Fermi level in the semiconductor in the porous silicon layer penetrate the potential barrier by the tunnel phenomenon and are injected into the insulator layer. This is high in resistance and has a large potential gradient, and is accelerated there and injected into the conductor of the thin film electrode to become hot electrons. Since this potential gradient contributes to the energy of electron emission, it is necessary that the thickness of the insulator layer is equal to or less than a predetermined value and the applied voltage is equal to or more than a predetermined value.

Generally, the thickness of the insulator layer needs to be about several μm or less, and the applied voltage needs to be about 10 V or more. Of these hot electrons generated inside the device, those having energy equal to or higher than the work function Φ of the thin film electrode 5 tunnel through this electrode and are emitted with a predetermined kinetic energy to the outside of the device. This thin-film electrode needs to be formed in a thickness that does not prevent electrons from tunneling, and is generally several tens nm or less.

As shown in FIG. 6, in silicon (semiconductor material), a plurality of microstructures composed of a silicon (Si) layer as a semiconductor layer and a silicon oxide layer as an insulator layer are formed. In this case, the inside of the fine structure to electrons multiple tunnels are believed readily electrons elongation electron drift length is emitted to the outside hot electrons of. This phenomenon is, as represented by porous silicon, by forming a porous semiconductor layer (porous silicon layer 4) in the order of nm on the surface thereof, and the electron emission characteristics are dramatically increased by such multi-step acceleration of electrons. It is said to improve. [Shape of convex portion] In the above embodiments, the details of the shape of the convex portion were not described. However, by optimally designing the shape of the convex portion, it is possible to improve the withstand voltage in the surface direction. Become.

[0033] In FIG. 2, the thickness of the porous silicon layer 4 a, the distance from the open end 31 until the porous silicon layer end 33 a1, porous silicon layer end from the opening end 31 33
B (surface distance) from the opening end 31 to the convex edge 32, b1 the upper wall distance from the opening end 31 to the convex edge 32, c the level difference of the convex (the distance from the convex edge 32 to the surface 1a), and c
, The angle (erosion angle) between the straight line from the opening end 31 to the porous silicon layer end 33 and the upper wall surface 11a of the projection 11 is θ, and the projection 11 If the angle (standing angle) between the side wall 11b and the surface 1a of the substrate 1 is θd, the film thickness a, the distance a1,
Surface distance b, the upper wall distance b1, protrusion step c, the side wall a distance c
1. The erosion angle θ satisfies the following conditions.

A = a1 a> b1 a ≦ c b = b1 + c1 θ = cos ⁻¹ × a1 / b1 = cos ⁻¹ × a / b1 c1 = sin θ × a1 = sin θ × a At this time, the surface distance b and the film thickness b / a = (b1 +
c1) / a is of greatest is the case erosion angle θ is 45 °. That is, when the optimum thickness a of the porous silicon layer 4 is set, a ≦ c is satisfied, and the erosion angle is 45 ° (b1 = a × sin 45 °), the surface distance b (= b1 + c1) is reduced
Is about 1.4 times as large as the film thickness a, and the breakdown voltage also becomes maximum.

Next, as shown in FIG. 3, when the upper wall distance b1 is fixed, the standing angle θd is changed from θd1 (obtuse angle) to θd.
2 (right angle), shake to Shitadi3 (obtuse), that the porous silicon layer 4 is in contact with the insulating film 3 (porous silicon layer end 3
3) are 331 to 3 according to the standing angles θd1 to θd3.
33, the side wall distance c1 is changed from c11 to c.
It increased to 13. That is, when the standing angle θd is an acute angle (θd
More becomes 3) increases the length of the side wall distance c33, it can be seen that it is easy to ensure a correspondingly pressure-resistant.

[0036] Here, when the stand angle at which θd to 60 ° as shown in FIG. 4, the distance a1 (= thickness a) from the open end 31 until the porous silicon layer end 33, top wall distance b1, the side walls It is possible to set equilateral triangles having the same distance c1. In this case, the thickness a of the porous silicon layer 4 and the surface distance b (= b
1 + c1) the ratio b / a = (b1 + c1 of) / a becomes possible to secure a 2, and a sufficient breakdown voltage.

The protrusions 1 on the substrate 1 in such a standing angle at which θd
To fabricate a 1, it is possible to produce by using the anisotropic etching of the dry etching (RIE, or the like). For example, a mixed gas such as SF ₆ + CCl ₄ (carbon tetrachloride) is used as an etching gas, and by changing the gas ratio, the erected angle θd can be processed to an acute angle or an obtuse angle. S
A mixed gas of F ₆ : CCl ₄ = 27: 3 (volume ratio), RF
When the etching is performed at a power of 300 W, the standing angle θd becomes almost vertical, but as the flow rate of CCl ₄ is reduced, the standing angle θd becomes an acute angle. Thus, the standing angle θd can be processed to an arbitrary angle by selecting the gas flow ratio.

Thus, the optimum thickness a of the porous silicon layer 4, the upper wall distance b1, and the standing angle θd are a ≧ b1, θ
By satisfying d = 60 ° ~ approximately 90 °, the surface distance b
Can be taken long enough, and the pressure resistance can be secured accordingly.

[0039]

Embodiment 2 In this embodiment 2, a substrate 1 (silicon substrate / polysilicon substrate) made of silicon having a polysilicon layer on the surface side is used. The polysilicon layer of the substrate 1 is processed into a convex shape, and the convex portions 11 are formed on the insulating thin film 3.
The opening 6 is provided in a selected portion of the insulating thin film 3. Since this opening 6 serves as a window for anodic oxidation, it is manufactured by an appropriate design.

The polysilicon layer (projection 11) is anodized and oxidized through the opening 6 opened in the insulating thin film 3,
The porous polysilicon layer 4 is formed on the projection 11. Here, since the back surface of the substrate 1 serves as an electrode, it is necessary to reduce the resistivity. However, the resistivity of the polysilicon to be the porous polysilicon layer 4 depends on the current-voltage value during anodization. Therefore, it is necessary to use an appropriate resistance value.

According to the second embodiment, by using a substrate having a silicon substrate / polysilicon structure, the substrate 1 has a resistivity suitable for each of them, and the efficiency of the charge-emitting device can be improved. Also in the charge-emitting device having such a configuration, the provision of the protrusions ensures the withstand voltage between the substrate 1 and the thin-film electrode 5, so that a highly efficient charge-emitting device can be realized.

[0042]

[Embodiment 3] In Embodiment 3, an insulating substrate / back electrode /
The surface of the substrate (polysilicon surface) composed of polysilicon is processed into a convex shape, and the convex portion is surrounded by the insulating thin film 3, and the insulating thin film 3 is provided with an opening 6 in a selected portion. It has the structure which is. Since this opening 6 serves as a window for anodic oxidation, it is manufactured by an appropriate design.

The polysilicon portion is anodized and oxidized through an opening 6 opened in the insulating thin film 3 to form a porous polysilicon layer 4.

By adopting such a configuration, it is possible to increase the area, and for example, it is possible to integrally fabricate A4 size and A3 size.

Also in the electron-emitting device having such a structure, the provision of the projections ensures the breakdown voltage between the back electrode and the thin-film electrode, so that a highly efficient electron-emitting device can be realized.

[0046]

Embodiment 4 This embodiment is an example in which the insulating thin film 3 is formed of a polymer resin. The properties required for the insulating thin film 3 are preferably those that are insoluble in acids and organic solvents, have high adhesion to silicon, have high insulation breakdown voltage, and have little deterioration over time.

Examples of such a polymer resin include polyimide resin having photosensitivity such as Photo Nice (trade name: Toray). The photosensitive polyimide resin is excellent in mass productivity because it can be patterned by a photolithography process. Also, polyimide resin in which is also used as a passivation film of a semiconductor chip,
Since the permeation of water and the like can be prevented, deterioration of the element can be prevented.

[0048] Hereinafter, an example of a manufacturing method.

1. A protrusion is formed on a silicon substrate.

2. A window including an opening 6 is opened at a selected portion of the convex portion 11 by applying a polymer resin and forming the insulating thin film 3 around the resin.

3. Anodization and oxidation are performed through the window to form a porous silicon layer 4.

4. The opening 6 to the thin-film electrode formed.

5. A back electrode 2 is formed on the back surface of the substrate.

[0054] Although 1-5 is a step of the silicon substrate in the porous silicon layer 4, in the case of large area, 5.
The other steps can be performed in the same manner, except for the step of forming the back electrode.

[0055] Thus, when the insulating thin film 3, a polymer resin, since the coating process can be used spinner coating or spray coating, the angle of the bottom surface and the side wall of the convex portion as shown in FIG. 4 (upright angle) can be one acute angle to form a good insulating film 3 having coverage.

[0056]

Embodiment 5 Embodiment 5 is an example in which the insulating thin film 3 is any one of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and a tantalum oxide film.

When the polymer resin is used as the insulating thin film 3, since the temperature applied to the insulating thin film 3 is at most about 400 ° C., the oxidation after the anodizing step should be performed only by the chemical method. Can not. Other rapid thermal oxidation as an oxidizing method (RTO: Rapid Thermal Oxidation)
This rapid thermal oxidation is performed at a temperature of about 900 ° C. to 1000 ° C.

[0058] insulating thin film 3, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a such an insulating thin film 3 that can withstand high temperatures for having either of the film of tantalum oxide film. In addition, since any of these insulating thin films 3 can be formed by sputtering, even if the erected angle θd of the bottom surface and the side wall of the projection is acute as shown in FIG. It becomes the thin film 3.

The electron-emitting device formed as described above can be applied to a charging device of an image forming apparatus such as an electrophotographic apparatus. Further, this charging device is smaller than a charger such as a corotron charger, a scorotron charger, a roller charger, or a brush charger (in particular, the film thickness can be reduced).
Therefore, by using such a charging device for charging the photosensitive member, the size of the electrophotographic apparatus itself can be reduced.

Further, since the charging efficiency is higher than that of other chargers, the power source can be reduced, so that the cost can be reduced. Further, since ozone and NOx are not generated, not only does not have a bad influence on the human body, but also a naturally friendly electrophotographic apparatus can be provided.

[0061]

According to the first aspect of the present invention, the silicon surface is processed into a convex shape, the convex portion is surrounded by an insulating thin film, and the insulating thin film has an opening at a selected portion of the convex portion. Since the porous silicon layer is formed by anodic oxidation from the opening, the pressure resistance in the surface direction of the porous silicon layer can be ensured and the degree of freedom in design can be improved. .

According to the second aspect of the present invention, the porous silicon layer according to the first aspect can be formed by anodic oxidation of silicon or polysilicon on the surface of the opening.

According to the third aspect of the present invention, in the substrate according to the second aspect, the silicon surface is processed into a convex shape or the polysilicon has a convex shape in a silicon substrate having polysilicon deposited on the surface. Processed or
Alternatively, a substrate in which a back electrode and polysilicon are deposited on an insulating substrate and the polysilicon is processed into a convex shape can be used.

According to the fourth aspect of the invention, the thickness of the porous silicon layer is a, and the distance of the porous silicon layer covered with the insulating thin film from the edge of the opening to the edge of the projection is b1. , A> b1, a ≦ c, where c is the step of the convex portion
By satisfying the above requirements, the withstand voltage in the surface direction of the porous silicon layer can be secured and the degree of freedom in design can be improved.

According to the fifth aspect of the present invention, the thickness of the porous silicon layer is a, and the distance of the porous silicon layer covered with the insulating thin film from the edge of the opening to the edge of the projection is b1. , if the level difference of the convex portion was set to c, b1 = a × sin
With the electron-emitting device according to any one of claims 1 to 3, satisfying 45 ° and a ≦ c, the withstand voltage in the surface direction of the porous silicon layer can be secured, and the degree of freedom in design can be improved.

According to the invention of claim 6, the thickness of the porous silicon layer is a, and the distance of the porous silicon layer covered with the insulating thin film from the edge of the opening to the edge of the projection is b1. When the angle between the bottom surface and the side wall of the convex portion is θd, a
5. The electron-emitting device according to claim 1, which satisfies ≧ b1, θd = 60 ° to approximately 90 °, thereby ensuring a withstand voltage in the surface direction of the porous silicon layer and a degree of freedom in design. Can be improved.

[0067] According to the invention of claim 7, wherein the insulating thin film for an electron-emitting device according to claim 1 to claim 6, wherein a polymer resin, suitable for mass production with excellent anti-deterioration of the element there.

According to the eighth aspect of the present invention, the insulating thin film is any one of a silicon oxide film, a silicon nitride film, a silicon oxynitride film, and a tantalum oxide film. because it can improve the heat resistance was that it is possible to increase the selection finger oxidation techniques.

According to the ninth aspect of the present invention, the first to the fifth aspects are described.
By the electron-emitting device according to claim 8, wherein the image forming apparatus using a charging device, it is possible to provide an image forming apparatus naturally friendly Ozone, NOx is not generated with possible to realize downsizing of the apparatus.

[Brief description of the drawings]

FIGS. 1A to 1C are diagrams illustrating a configuration of an electron-emitting device according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view illustrating a configuration of an electron-emitting device according to an embodiment of the present invention.

FIG. 3 is a partially enlarged view illustrating a porous silicon layer of the electron-emitting device according to the embodiment of the present invention.

FIG. 4 is a partially enlarged view illustrating a porous silicon layer of the electron-emitting device according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating an electron emission mechanism of the electron emission element according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating an electron emission mechanism of the electron emission element according to the embodiment of the present invention.

FIG. 7 is a diagram illustrating a configuration of a comparative electron-emitting device.

8 is a partial enlarged view illustrating a porous silicon layer of the electron-emitting device of FIG.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Substrate (silicon substrate) 1a Front surface 2 Back electrode 3 Insulating thin film 4 Porous silicon layer 5 Thin film electrode 6 Opening (window for anodic oxidation) 11 Convex 11b Side wall 31 Open end 32 Convex edge 33 Porous silicon layer end a (= a1) thickness b surface distance b1 top wall distance c protrusion step c1 sidewall distance θ erosion angle θd elevation angle at which

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Hiroshi Kondo 1-3-6 Nakamagome, Ota-ku, Tokyo F-term in Ricoh Co., Ltd. (reference) 2H200 FA07 HA11 HA28 HB14 HB45 MA04 MA08

Claims (9)

[Claims] 1. A is an electron-emitting device to emit electrons into the atmosphere by an electron emission phenomenon from the semiconductor, the surface of the substrate is processed into a convex shape with a convex portion, convex portion surrounded by an insulating thin film The insulating thin film has a structure in which an opening is provided in a selected portion of the projection, and a porous silicon layer is formed by oxidation from the opening. Electron emitting device. 2. The electron-emitting device according to claim 1, wherein the porous silicon layer is formed by anodic oxidation of silicon or polysilicon on the surface of the opening. 3. The substrate according to claim 1, wherein the silicon surface is processed into a convex shape, the polysilicon is processed into a convex shape in a silicon substrate having polysilicon deposited on the surface, or a back surface is formed on an insulating substrate. 3. The electron-emitting device according to claim 2, wherein a substrate on which an electrode and polysilicon are deposited, wherein said polysilicon is processed into a convex shape. 4. The thickness of the porous silicon layer is a, the distance of the porous silicon layer covered with the insulating thin film from the edge of the opening to the edge of the projection is b1, and the thickness of the projection is If the step has a c, a> b1, the electron-emitting device according to any one of claims 1 to 3 are met a ≦ c. 5. The thickness of the porous silicon layer is a, the distance of the porous silicon layer covered with the insulating thin film from the edge of the opening to the edge of the projection is b1, and the distance of the projection is When the step is c, b1 = a × sin45 °, a ≦
4. The electron-emitting device according to claim 1, wherein c is satisfied. 6. The thickness of the porous silicon layer a, the distance of the porous silicon layer in which the covered with an insulating film from the edge of the opening to an edge of the convex portion b1, the protrusions If the angle between the surface 1a of the the side walls substrate 1 was θd, a ≧ b1, electron-emitting device according to any one of claims 1 to 4 meet the θd = 60 ° ~ approximately 90 ° . 7. The electron-emitting device according to claim 1, wherein said insulating thin film is made of a polymer resin. 8. The electron-emitting device according to claim 1, wherein said insulating thin film is a silicon oxide film, a silicon nitride film, a silicon oxynitride film or a tantalum oxide film. 9. An image forming apparatus using the electron-emitting device according to claim 1 as a charger.