Patent Application
20090111350
1. Field of the invention
The present invention relates to a manufacturing method of an electron-emitting device, the electron-emitting device, an electron source having the electron-emitting device, and an image display apparatus having the electron source.
2. Description of the Related Art
There is a field emission type (FE type) and a surface conduction type or the like in the electron-emitting device.
In the FE type electron-emitting device, by applying a voltage between a cathode electrode (and an electron-emitting film arranged on the cathode electrode) and a gate electrode, an electron is pulled out from the cathode electrode (or the electron-emitting film) into vacuum. Therefore, an operation electric field largely depends on a work function of a cathode electrode (an electron-emitting film) to be used and its shape or the like. Generally, it is necessary to select the cathode electrode (the electron-emitting film) having a small work function.
Diamond, of which surface is terminated with hydrogen, is typical as a material having a negative electron affinity, and an electron-emitting device using a diamond surface having a negative electron affinity as an electron-emitting surface is disclosed in a specification of U.S. Pat. No. 5,283,501, a specification of U.S. Pat. No. 5,180,951, and V. V. Zhinov, J. Liu et al, “Environmental effect on the electron emission from diamond surfaces”, J. Vac. Sci. Technol., B16 (3), May/June 1998, pp. 1188 to 1193.
In addition, as a method for terminating a surface of diamond with hydrogen, a method using a plasma of hydrogen and a plasma of a compound containing hydrogen is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 2006-134724. Then, a method for carrying out hydrogen termination by using electron cyclotron resonance (ECR) plasma is disclosed in Japanese Patent Application Laid-Open (JP-A) No. 10-283914. In addition, in the case of growing diamond by a plasma CVD, it is considered that a neutral radical CH3. (“.” means radical) is largely involved in growth of diamond in the process of the growth of diamond.
However, it is difficult to manufacture diamond on a large area with a uniform film thickness, so that it is difficult to manufacture an electron-emitting device uniformly on a large area. Further, the emitted electrons are diffused because a surface roughness is large, so that it is difficult to display a high-definition image.
In addition, in Japanese Patent Application Laid-Open (JP-A) No. 10-081971, a method is disclosed, which forms a film made of SiO2 by complementing a charged particle in an ECR plasma with a mesh and selecting only a neutral particle in an apparatus using an ECR plasma.
The present invention has been made to solve the foregoing problems and an object of which is to provide an electron-emitting device, which can emit an electron with a small electron beam diameter in a low electric field.
In addition, a further object of the present invention is to provide an electron-emitting device of a field emission type, which can perform a high-efficient emission of an electron with a low voltage and of which manufacturing process is simple, an electron source, and an image display apparatus.
A manufacturing method of an electron-emitting device according to the present invention is characterized by having a step of preparing a base substrate provided with an insulating or semi-conducting layer and a step of exposing the layer to an atmosphere which contains neutral radical containing hydrogen.
In addition, an electron-emitting device according to the present invention is characterized by being manufactured by the manufacturing method of the electron-emitting device according to the present invention.
In addition, an electron source according to the present invention is characterized by having a plurality of the electron-emitting devices according to the present invention.
In addition, an image display apparatus according to the present invention is characterized by having the electron source according to the present invention and a light-emitting member, which emits light due to irradiation of electrons.
According to the present invention, it is possible to provide an electron-emitting device, which can emit an electron in a low electric field. Further, it is possible to provide an electron-emitting device capable of emitting an electron, of which a beam diameter is small, with a high efficiency in a low electric field, and the electron-emitting device can be manufactured by a simple process.
In addition, if the electron-emitting device according to the present invention is applied to the electron source and the image display apparatus, it is possible to realize an electron source and an image display apparatus, which are excellent in capability.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
With reference to the drawings, a preferable embodiment of this invention will be described with an example in detail below. However, a scope of this invention is not limited to a measurement, a material, a shape, and its relative arrangement or the like of a constituent part described in this embodiment unless there is a description in particular.
In
In
As shown in
Hereinafter, a manufacturing method of an electron-emitting film according to the present embodiment will be described with reference to
At first, a cathode electrode 102 is laminated on a substrate 101, of which surface is sufficiently cleaned. The substrate 101 includes a quartz glass, a glass having a reduced content of impurity such as Na, a Soda-lime glass, a laminated body having SiO2 laminated on a silicone substrate by a sputtering method or the like, and an insulating substrate made of a ceramics such as alumina, for example.
Generally, the cathode electrode 102 has a conductive property and is formed by a general vacuum film formation technique such as an evaporation method and a sputtering method, and a photolithography technique. For example, a material of the cathode electrode 102 is a metal such as Be, Mg, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni, Cr, Au, Pt, and Pd, or an alloy material. The thickness of the cathode electrode 102 is determined in the range of several ten nm to several mm, and preferably, the thickness of the cathode electrode 102 is selected in the range of several hundred nm to several μm.
Next, an insulating or semi-conducting layer is formed on the surface of the cathode electrode. This layer (film) is generally referred to as an electron-emitting film 103. The electron-emitting film 103 is formed by a general vacuum film formation technique such as an evaporation method and a sputtering method, and a photolithography technique. In addition, as other method, by dispersing metal particles in a polymer, it is possible to form the electron-emitting film 103. It is preferable that the electron-emitting film 103 is a film containing carbon as a main component, and specifically, it is preferable that the electron-emitting film 103 is a film composed of a carbon, a carbon composition, or a layer thereof containing dispersed metal particle. The size of the dispersed metal particle is determined in the range of several nm to several hundred nm, and preferably, the size is selected in the range of several nm to several ten nm. In addition, it is preferable that the density of the metal particle in the electron-emitting film is in the range of not less than 1×1014/cm3 not more than 1×1019/cm3. As a material of the metal particle, for example, a metal such as Be, Mg, Mn, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni, Cr, Co, Fe, Ni, Au, Pt, and Pd or an alloy material may be considered. A carbon material may be appropriately selected from the group consisting of, for example, a graphite, a fullerene, a carbon nano tube, a diamond-like carbon, an amorphous carbon, a hydrogenated amorphous carbon, a carbon having diamond dispersed therein, a carbon composition, and mixtures thereof. Preferably, the carbon material may be a material having a low work function such as a diamond thin film and a diamond-like carbon or the like. The film thickness of the electron-emitting film 103 is determined in the range of several nm to several μm, and preferably, the film thickness of the electron-emitting film 103 is selected in the range of several nm to several hundred nm. Hereinafter, the object manufactured up to step 2 will be referred to as a base substrate.
Next, the surface of the electron-emitting film is terminated with hydrogen.
The bias grid has a conductive property and is formed in a mesh-like structure. The size of the opening of this mesh is determined in the range of 1 μm to 10 cm, and preferably, in the range of 10 μm to 10 mm. Under such a condition, by selectively removing a charged particle in plasma, the density of the neutral radical in the atmosphere can be kept stable. Compared with a density of the charged particle, the density of the neutral radical is more than 1,000 times. In addition, a plasma source can be appropriately selected from the group consisting of high frequency plasma, remote plasma, and microwave plasma or the like.
Further, a potential of a bias grid (a grid bias) may be equipotential or negative to an earth. A range of the potential is determined in the range of 0 to −500 V, and preferably, the potential is selected in the range of 0 to −200 V. In addition, a surface potential of a sample (a substrate bias) is determined by a direct current power source B. The surface potential of the sample may be equipotential or negative to a grid bias, a range of the potential is determined in the range of 0 to 1,000 V, and preferably, the potential is selected in the range of 0 to 500 V.
Further, the processing gas may be a mixture gas made of plural kinds of gases. The processing pressure is determined in the range such that plasma can be maintained, and preferably, the processing pressure is determined in the range of 0.05 to 10 Pa.
Further, the base substrate may be heated by the substrate heater 411.
Hereinafter, with reference to
At first, a cathode electrode 202 is laminated on a substrate 201, of which surface is sufficiently cleaned. The substrate 201 is a quartz glass, a glass having a contained amount of impurity such as Na reduced, a Soda-lime glass, a laminated body having SiO2 laminated on a silicone substrate by a sputtering method or the like, and an insulating substrate made of a ceramics such as alumina, for example.
Generally, the cathode electrode 202 has a conductive property and is formed by a general vacuum film formation technique such as an evaporation method and a sputtering method, and a photolithography technique. For example, a material of the cathode electrode 202 is a metal such as Be, Mg, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni, Cr, Au, Pt, and Pd, or an alloy material. The thickness of the cathode electrode 202 is determined in the range of several ten nm to several mm, and preferably, the thickness of the cathode electrode 202 is selected in the range of several hundred nm to several μm.
Next, an insulating or semi-conducting layer is formed on the surface of the cathode electrode. This layer (film) is generally referred to as an electron-emitting film 203. The electron-emitting film 203 is formed by a general vacuum film formation technique such as an evaporation method and a sputtering method, and a photolithography technique. In addition, as other method, by dispersing metal particles in a polymer, it is possible to form the electron-emitting film 103. It is preferable that the electron-emitting film 203 is a film containing carbon as a main component, and specifically, it is preferable that the electron-emitting film 203 is a film composed of a carbon, a carbon composition, or a layer thereof containing dispersed metal particle. The size of the dispersed metal particle is determined in the range of several nm to several hundred nm, and preferably, the size is selected in the range of several nm to several ten nm. In addition, it is preferable that the density of the metal particle in the electron-emitting film is in the range of not less than 1×1014/cm3 not more than 1×1019/cm3. As a material of the metal particle, for example, a metal such as Be, Mg, Mn, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni, Cr, Co, Fe, Ni, Au, Pt and Pd or an alloy material may be considered. A carbon material may be appropriately selected from the group consisting of, for example, a graphite, a fullerene, a carbon nano tube, a diamond-like carbon, an amorphous carbon, a hydrogenated amorphous carbon, a carbon having diamond dispersed therein, a carbon composition, and mixture thereof. Preferably, the carbon material may be a material having a low work function such as a diamond thin film and a diamond-like carbon or the like. The film thickness of the electron-emitting film 203 is determined in the range of several nm to several μm, and preferably, the film thickness of the electron-emitting film 203 is determined in the range of several nm to several hundred nm. Hereinafter, the object manufactured up to step 2 will be referred to as a base substrate.
Next, an insulating layer 204 is accumulated. The insulating layer 204 is formed by a general vacuum film formation technique such as a sputtering method, a CVD method, and a vacuum evaporation method. The thickness of the insulating layer 204 is determined in the range of several nm to several μm and preferably is selected in the range of several ten nm to several hundred nm. It is desirable that the material of the insulating layer 204 is a material with high voltage tightness, which can withstand a high electric field, for example, SiO2, SiN, Al2O3, CaF, and an undoped diamond.
Then, a gate electrode 205 is accumulated. The gate electrode 205 has a conductive property same as the cathode electrode 202, and the gate electrode 205 is formed by a general vacuum film formation technique such as an evaporation method and a sputtering method, and a photolithography technique. The material of the gate electrode 205 is appropriately selected from the group consisting of a metal, an alloy material, a carbide, a boride, a nitride, a semiconductor, and an organic polymer material. As a metal, for example, Be, Mg, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni, Cr, Au, Pt, and Pd may be used. As a carbide, for example, TiC, ZrC, HfC, TaC, SiC, and WC may be used. As a boride, for example, HfB2, ZrB2, LaB6, CeB6, YB4, and GdB4 may be used. As a nitride, for example, TiN, ZrN, and HfN may be used. As a semiconductor, Si, and Ge or the like may be used. The thickness of the gate electrode 205 is determined in the range of several nm to several ten μm, and preferably, the thickness of the gate electrode 205 is determined in the range of several ten nm to several μm.
Next, a mask pattern 206 is formed by a photolithography technique.
Then, using the mask pattern 206, the gate electrode 205 and the insulating layer 204 are partially removed by dry etching.
Next, the insulating layer 204 is partially removed by wet etching. As a liquid to be used for wet etching, a liquid such that a rate of etching for the insulating layer 204 is higher than the rate of etching for the gate electrode 205 and the electron-emitting film 203 is preferable, and a liquid, whereby the electron-emitting film 203 is not deteriorated, is desirable.
Next, the surface of the electron-emitting film is terminated with hydrogen.
The electron-emitting device, which has been manufactured in this way, is set within a vacuum container 304 as shown in
The bias grid has a conductive property and is formed in a mesh-like structure. The size of the opening of this mesh is determined in the range of 1 μm to 10 cm, and preferably, in the range of 10 μm to 10 mm. Under such a condition, by selectively removing a charged particle in plasma, the density of neutral radical in the atmosphere can be kept stable. Compared with a density of the charged particle, the density of the neutral radical is more than 1,000 times. In addition, a plasma source can be appropriately selected from the group consisting of high frequency plasma, remote plasma, and microwave plasma or the like.
Further, a potential of a bias grid (a grid bias) may be equipotential or negative to an earth. A range of the potential is determined in the range of 0 to −500 V, and preferably, is selected in the range of 0 to −200 V. In addition, a surface potential of a sample (a substrate bias) is determined by a direct current power source B. The surface potential of the sample may be equipotential or negative to a grid bias. A range of the potential is determined in the range of 0 to 1,000 V, and preferably, the potential is selected in the range of 0 to 500 V.
Further, the processing gas may be a mixture gas made of plural kinds of gases. The processing pressure is determined in such a range that plasma can be maintained, and preferably, in the range of 0.05 to 10 Pa.
Further, the base substrate may be heated by the substrate heater 411.
Next, an example that the above-described electron-emitting device is applied to the electron source and the image display apparatus will be described.
Various arrangements of the electron-emitting device are employed. As an example, a plurality of the electron-emitting devices are arranged in an X direction and a Y direction in matrix. One electrodes of the plurality of electron-emitting devices in the same line are connected to a wire in the X direction in common, and other electrodes of the electron-emitting device in the same row are connected to a wire in the Y direction in common. This is referred to as a simple matrix arrangement.
Hereinafter, an electron source of a simple matrix arrangement, which is obtained by arranging the above-described plurality of electron-emitting devices, will be described with reference to
The X-directional wiring 502 is formed by m pieces of wires, namely, Dx1, Dx2, . . . , and Dxm, and the X-directional wiring 502 can be made of a conductive metal or the like, which is formed by using a vacuum evaporation method, a printing method, and a sputtering method or the like. The material, the film thickness, and the width of the wiring are appropriately designed. The Y-directional wiring 503 is formed by n pieces of wires, namely, Dy1, Dy2, . . . , and Dyn, and the Y-directional wiring 503 is formed in the same way as the X-directional wiring 502. An inter-layer insulating layer (not illustrated) is provided between these m pieces of X-directional wirings 502 and n pieces of Y-directional wiring 503, and the both wirings are electrically separated (both of m and n are positive integers).
The inter-layer insulating layer (not illustrated) is composed of SiO2 or the like, which is formed by using a vacuum evaporation method, a printing method, and a sputtering method or the like. For example, the inter-layer insulating layer is formed in a desired shape, on the whole surface or a partial surface of the electron source base substrate 501, on which the X-directional wirings 502 are formed. Particularly, the material, the film thickness, and the manufacturing method of the inter-layer insulating layer are appropriately designed so as to endure a potential difference in a cross portion between the X-directional wiring 502 and the Y-directional wiring 503. The X-directional wiring 502 and the Y-directional wiring 503 are pulled out as an external terminal, respectively.
The electron-emitting device 504 is provided with a pair of electrodes (a gate electrode and a cathode electrode). According to the example shown in
The constituent elements of the materials to form the X-directional wiring 502 and the Y-directional wiring 503, the material to form the wire connection, and the material to form a pair of device electrodes may be partially or entirely the same or may be different, respectively. These materials may be appropriately selected from the group consisting of the materials of the above-described device electrodes, for example. In the case that the material to form the device electrode and the wiring material are the same, the wiring connected to the device electrode may be made into an device electrode.
A scanning signal applying means (not illustrated) is connected to the X-directional wiring 502. The scanning signal applying means may apply a scanning signal to the electron-emitting device 504, which is connected to the selected X-directional wiring. On the other hand, a modulation signal generation means (not illustrated) is connected to the Y-directional wiring 503. The modulation signal generation means may apply a modulation signal, which is modulated in accordance with an input signal, to each row of the electron-emitting device 504. A driving voltage to be applied to each electron-emitting device may be supplied as a difference voltage between the scanning signal and the modulation signal to be applied to this device.
In the above-described configuration, by using a simple matrix wiring, each device is selected and each device can be individually driven. An image display apparatus, which is configured by using the electron source, will be described with reference to
As shown in
The above-described image display apparatus may apply a voltage to each electron-emitting device 615 via container external terminals Dox1 to Doxm and Doy1 to Doyn. Each electron-emitting device 615 may emit an electron in accordance with the applied voltage.
By applying a high voltage to the metal back 605 or a transparent electrode (not illustrated) via a high voltage terminal 614, the emitted electron is accelerated.
The accelerated electron may crash into the phosphor film 604. Thereby, the phosphor film 604 emits light and an image is formed.
The image display apparatus according to the present embodiment can be also used as an image display apparatus or the like as an optical printer that is configured by using a photosensitive drum or the like other than a display apparatus for TV broadcasting and a display apparatus of a teleconference system and a computer or the like.
Hereinafter, a step of manufacturing an electron-emitting film according to the present example will be described in detail with reference to
At first, a quartz glass as the substrate 101 is sufficiently cleaned, and by a sputtering method, a film of Pt being a thickness of 200 nm as the cathode electrode 102 is formed on the substrate 101.
By using a co-sputtering method, a diamond-like carbon film containing Pt is formed as the electron-emitting film 103 on the cathode electrode 102. The film thickness is about 30 nm, and a Pt density is about 20%.
The surface termination processing is carried out under the following conditions to form the hydrogen terminated surface 104.
With respect to this electron-emitting film, an electron emission characteristic is measured. The anode electrode is arranged so as to be parallel and flat to the electron-emitting film. The electron emission characteristic is measured with interval between the electron-emitting film and the anode electrode being 100 μm. As a result of evaluation of the property, it is possible to obtain an electron emission current of about 10 mA/cm2 in an electric filed of 55 V/μm.
Hereinafter, a step of manufacturing an electron-emitting film according to the present example will be described in detail with reference to
At first, a quartz glass as the substrate 101 is sufficiently cleaned, and by a sputtering method, a film of Pt being a thickness of 200 nm as the cathode electrode 102 is formed on the substrate 101.
By using a co-sputtering method, a diamond-like carbon film containing Co is formed as the electron-emitting film 103 on the cathode electrode 102. The film thickness is about 30 nm, and a Co density is about 20%.
The surface termination processing is carried out under the following conditions to form the hydrogen terminated surface 104.
With respect to this electron-emitting film, an electron emission characteristic is measured. The anode electrode is arranged so as to be parallel and flat to the electron-emitting film. The electron emission characteristic is measured with interval between the electron-emitting film and the anode electrode being 100 μm. As a result of evaluation of the property, it is possible to obtain an electron emission current of about 10 mA/cm2 in an electric filed of 40 V/μm.
Hereinafter, a step of manufacturing an electron-emitting film according to the present example will be described in detail with reference to
At first, a quartz glass as the substrate 101 is sufficiently cleaned, and by a sputtering method, a film of Pt of a thickness 200 nm as the cathode electrode 102 is formed on the substrate 101.
By using a filament CVD method, a carbon film is formed on the cathode electrode 102. After that, injecting Co of 1 atm % into a diamond-like carbon film by using an ion injection method, an electron-emitting film is formed. The film thickness is about 30 nm.
The surface termination processing is carried out under the following conditions to form the hydrogen terminated surface 104.
With respect to this electron-emitting film, an electron emission characteristic is measured. The anode electrode is arranged so as to be parallel and flat to the electron-emitting film. The electron emission characteristic is measured with interval between the electron-emitting film and the anode electrode being 100 μm. As a result of evaluation of the property, it is possible to obtain an electron emission current of about 12 mA/cm2 in an electric filed of 40 V/μm.
Hereinafter, a step of manufacturing an electron-emitting device according to the present example will be described in detail with reference to
At first, a quartz glass as the substrate 201 is sufficiently cleaned, and by a sputtering method, a film of Pt being a thickness of 200 nm as the cathode electrode 202 is formed on the substrate 201.
By using a co-sputtering method, a diamond-like carbon film containing Co is formed as the electron-emitting film 203 on the cathode electrode 202. The film thickness is about 30 nm, and a Co density is about 25%.
Next, in order to form the insulating layer 204, by a plasma CVD method using SiH4 and N2O as a raw material gas, a film of SiO2 is formed about 1,000 nm.
Next, a film of Pt as the gate electrode 205 is formed on the insulating layer 204 by using a sputtering method so as to be a thickness of 100 nm.
Next, exposing and developing a spin coating and a photoresist pattern of a positive-type photoresist (OFPR5000/manufactured by Tokyo Ohka Kogyo Co., Ltd.) by a photolithography, a mask pattern 206 is formed. An opening diameter of a resist is determined to be 5 μm.
Next, Pt is etched under such a condition that an etching gas is Ar gas, an etching power is 200 W, and an etching pressure is 1 Pa. Then, under such a condition that an etching gas is a mixture gas of CF4 and H2, an etching power is 150 W, and an etching pressure is 1.5 Pa, a dry etching is carried out and this etching is stopped in approximately a center portion of the insulating layer 204.
Next, removing the remained mask pattern by a removing liquid (manufactured by Tokyo Ohka Kogyo Co., Ltd.), and then, soaking a device in BHF, SiO2 on the upper surface of the electron-emitting film is wet-etched. Then, the device is cleaned with water for 10 minutes.
The surface termination processing is carried out under the following conditions and a hydrogen terminated surface 207 is formed so as to complete the electron-emitting device.
As shown in
Further, without limiting on the conditions of the example, based on the base substrate obtained according to the first to third examples, an electron-emitting device may be manufactured. The condition may be appropriately changed.
An image display apparatus using the electron-emitting device according to the fourth example is manufactured. The wiring is made by connecting the X-directional wiring to the cathode electrode 202 and connecting the Y-directional wiring to the gate electrode 205, respectively, as shown in
Inputting a pulse signal of 18 V as an input signal, a high-definition image can be formed.
As described above, according to the embodiment, by terminating the surface of the electron-emitting film and the surface of the electron-emitting film of the electron-emitting device with hydrogen, emission of an electron with a small electron beam diameter can be made in a low electric field. Further, it is possible to obtain an electron-emitting device, which can make an efficient emission of electron at a low voltage and of which manufacturing process is simple. In addition, if the electron-emitting device according to the present invention is applied to the electron source and the image display apparatus, it is possible to realize an electron source and the image display apparatus with an excellent capability.
While the present invention has been described with reference to exemplary embodiment, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
This application claims the benefit of Japanese Patent Application No. 2007-276269, filed on Oct. 24, 2007, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2007-276269 | Oct 2007 | JP | national |
