Patent Application
20110062852
1. Field of the Invention
The present invention relates to an electron beam apparatus which is used for a flat panel display and has an electron-emitting device that emits an electron provided therein.
2. Description of the Related Art
Conventionally, there is an electron-emitting device which makes a large number of electrons to be emitted from a cathode, collide against a facing gate and be scattered therein, and then takes out the electron. A surface conduction type electron-emitting device and a stacked type electron-emitting device are known as a device which emits an electron in such a form, and Japanese Patent Application Laid-Open No. 2000-251643 discloses a high-efficiency electron-emitting device in which a gap of an electron-emitting portion is 5 nm or less. In addition, Japanese Patent Application Laid-Open No. 2001-229809 discloses a stacked type electron-emitting device, in which conditions of enabling electron emission with high efficiency are given by functions of the thickness of a gate material, driving voltage and the thickness of an insulating layer. Furthermore, Japanese Patent Application Laid-Open No. 2001-167693 discloses a stacked type electron-emitting device having a structure in which a recess portion is provided in an insulating layer in the vicinity of the electron-emitting portion.
Japanese Patent Application Laid-Open No. 2000-251643 discloses a device which makes a plurality of electron-emitting points exist in the formed gap, and thereby can provide an electron-emitting device which inhibits electric discharge in an electron-emitting portion, and can stably work for a long period of time. However, the above electron-emitting devices do not solve a problem sufficiently that an amount of electron to be emitted from each of points of the electron-emitting points increases and decreases along with a driving period of time of driving a device, even though the technologies could inhibit the electric discharge in the electron-emitting portion. In addition, the above electron-emitting devices showed a phenomenon of increasing and decreasing the number of the electron-emitting points existing in the gap along with the driving period of time of the electron-emitting device.
The same phenomenon as the above described phenomenon has been found also in the device disclosed in Japanese Patent Application Laid-Open No. 2001-229809, and a stable electron-emitting device has been desired.
Furthermore, the device disclosed in Japanese Patent Application Laid-Open No. 2001-167693 shows an excellent electron-emitting efficiency, but its characteristics have been required to be further enhanced.
The present invention has been designed at solving the above described problems of a conventional technology, and is directed at providing an electron beam apparatus having an electron-emitting device provided therein, which has a simple structure, shows high electron-emitting efficiency and stably works.
A first aspect of the present invention is an electron beam apparatus comprising: an insulating member having a recess portion on a surface thereof; a gate disposed on the surface of the insulating member; a cathode disposed on the surface of the insulating member, and having a protruding portion protruding from an edge of the recess portion toward the gate in opposition to the gate; and an anode disposed in opposition to the protruding portion so that the gate is disposed between the anode and the protruding portion, wherein a length of the protruding portion in a direction along the edge of the recess portion is shorter than a length of a portion of the gate opposing the protruding portion in the direction along the edge of the recess portion.
The electron beam apparatus according to the present invention can include the aspects in which a plurality of cathodes are disposed corresponding to the gate; the gate has a humped portion in opposition to the protruding portion, and the humped portion is shorter, in the direction along the edge of the recess portion, than the protruding portion; and the gate is covered with an insulating layer at a portion opposing to the recess.
A second aspect of an electron beam apparatus according to the present invention is an image display apparatus having an electron beam apparatus according to the present invention, and a light emitting member disposed on the anode.
According to the present invention, it is possible to selectively form a portion (strong portion) which has an increased electric-field strength in an electron-emitting device, and as a result, it is possible to easily control the position of electron-emitting points in a preferred embodiment.
The electron beam apparatus also can prevent emitted electrons from forming a leak current after having collided against the surface of the gate by covering the surface of the gate to be exposed to a recess portion of an insulating member with an insulating layer, and further can enhance its electron-emitting efficiency.
Furthermore, when having a plurality of cathodes with respect to the gate, the electron beam apparatus according to the present invention can control a shape of an electron beam to be emitted toward an anode, and provides a further stable electron-emitting action.
Still furthermore, the electron beam apparatus can make an emitted electron selectively collide against the humped portion, by providing the humped portion shorter than a width of the protruding portion of the cathode on the gate, and simultaneously can make a colliding portion of the emitted electron centralized on a side face of the humped portion. As a result, the electron after having collided against the side face flies to the anode without further colliding against other parts, so that the electron-emitting efficiency is further enhanced.
Therefore, the present invention realizes an electron beam apparatus provided with an electron-emitting device which has high electron-emitting efficiency and has a stable emitting action.
Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings.
Exemplary embodiments according to the present invention will now be illustratively described in detail below with reference to the drawings. However, a dimension, a material, a shape, a relative arrangement and the like of components which are described in this embodiment do not limit the scope of this invention only into those, unless otherwise specified.
The present invention was extensively investigated so that, it is possible to selectively form a portion (strong portion) which has an increased electric-field strength in an electron-emitting device, and as a result, in a preferred embodiment, an electron-emitting portion can control a position of an electron-emitting point with a simple structure and can stably work.
Firstly, a structure of an electron-emitting device which can stably emit an electron according to the present invention will now be described below with reference to exemplary embodiments.
An electron beam apparatus according to the present invention includes an electron-emitting device which emits an electron, and an anode which an electron emitted from the electron-emitting device reaches.
An electron-emitting device according to the present invention includes an insulating member having a recess portion on a surface thereof, and a gate and a cathode disposed on the surface of the insulating member. The cathode has a protruding portion protruding from an edge of the recess portion toward the gate, and the protruding portion is positioned so as to oppose to the gate. Furthermore, a length of the protruding portion in a direction along the edge of the recess portion is formed so as to be shorter than a length of a portion of the gate opposing to the protruding portion in the direction along the edge of the recess portion. The anode is disposed in opposition to the protruding portion so that the gate is disposed between the anode and the protruding portion.
In
In an electron-emitting device according to the present invention, the gate 5 is formed on the surface of the insulating member 3 (upper face in this example), as is illustrated in
In
Here, an electron-emitting efficiency η is generally given by efficiency η=Ie/(If+Ie), by using the current If which is detected when a voltage is applied to the device and the current Ie which is taken out into the vacuum.
A state of the convergence of an electric field occurring when voltage Vf has been applied to a device according to the present invention as is illustrated in
The electric flux line 13 curves towards a protruding portion which has been formed in the recess portion 7 as is illustrated in
Moreover, the protruding portion has a shape of protruding toward the inner part of the recess portion 7 from the edge of the recess portion 7, as is illustrated in (h) of
Next,
An electron emission in a device due to the convergence of the electric field which was described above according to the present invention will now be sequentially described below with reference to
Here, T1 represents the thickness of a gate 5, T2 represents the thickness of an insulating layer 3b (=height of recess portion 7), and T3 represents the thickness of an insulating layer 3a (=height from surface of substrate 1 to edge of recess portion 7).
When a voltage Vf is applied to a device in
The strength and weakness of the electric field are determined by how much the electric flux line projected from the gate 5 of the electric field converge on the protruding portion of the cathode 6. As a result of the above investigation, it was found that the electric field to be formed at the point A or the point C in the cathode 6 becomes larger, as T5 which is a width of the gate 5 is wider than T4 which is a width of the cathode 6. Desirable sizes are those which satisfy T5/T4>approximately 1.5, for instance. When a plurality of the cathodes 6 are provided with respect to the gate 5, which will be described later, a distance between each of cathodes can be at least twice or more than that of T2 from the viewpoint of the convergence of an electric field, and the distance can be larger than T3.
In the above, it was described that electric fields in the maximum electric field points A and C were different from an electric field in a point B other than those points. As a result of a detailed investigation for the difference, it is found that the difference changes according to a distance between a gate 5 and a cathode 6 (size of gap 8). This distance dependency will now be described below with reference to
The electric flux lines of the cathode 6 in
This relationship is shown in a graph of
In
As is clear from the numeric values in Table 1, it was found that when the distance (d) was approximately 3 nm, a difference of electric-field strengths between the points A and C and the point B (difference of electric-field strengths between points D and F and point E in
An electron-emitting position in the preferred embodiment when a difference between the strengths of electric fields is formed in a protruding portion of the above described one cathode 6 will now be described below.
When a voltage is applied in between the cathode 6 and the gate 5 under the condition of keeping a distance (d) between the cathode 6 and the gate 5 at an appropriate distance as is illustrated in
The distance (d) and an amount of emitted electrons were examined in detail by using FEEM (which is a method of optically measuring an amount of emitted electrons with the use of commercial PEEM (photoelectron microscope) device while enlarging an electron-emitting portion with the use of electron lens). As a result, the electron-emitting portion could be clearly formed in the end part in the width direction of the protruding portion by setting the distance (d) at approximately 6 nm or more. As a result of the analysis, it was found that a difference between amounts of electrons emitted from the center and from the end part could be one order of magnitude or more. However, when the electron-emitting portion is formed in a shorter distance (d) less than 6 nm, the electron-emitting portion is formed in the vicinity of the center as well. Furthermore, when the electron-emitting portion is formed at a point having a distance (d) of approximately 3 nm, the electron-emitting points were observed at random in the width direction of the protruding portion, and a position of emitting electrons could not be clearly discriminated.
From these experimental results, a lower limit of the distance (d) as a preferred condition in which the electron-emitting point can be formed in the end part in the width direction of the protruding portion needs to be approximately 6 nm or more, and can be 10 nm or more.
As was described above, it was found that the following requirements were necessary in order to stably converge an electric field on the end part in the width direction of the protruding portion of the cathode 6.
(1) A width of the gate 5 is wider than that of the cathode 6.
(2) The cathode 6 has a protruding portion which protrudes in a recess portion 7, and the head of the protruding portion is formed in a side which is closer to the gate 5 than the edge of the recess portion 7.
As a result, in the preferred embodiment, it is possible to achieve, with a simple structure, the position control of the electron-emitting points in the electron-emitting device. In addition, it is confirmed as will be described later that an electron-emitting device having a structure in which the gate 5 has a humped portion thereon shows an effect of enhancing the efficiency even when the distance (d) is 6 nm or less. The detail will be described later.
Next, a trajectory of an electron which has been emitted in the above described manner will now be described below.
(Description of Scattering in Electron Emission)
In
As was described above, many of electrons which have been scattered in the gate 5 repeat elastic scattering (multiple scattering) several times in the gate 5, but cannot scatter in the upper side of the gate 5, and jump out to the anode side.
As was described above, it is apparent that such a structure as to reduce scattering frequency (falling frequency) of the electron in the gate 5 can realize an enhancement of the efficiency.
A scattering frequency and a distance will now be described below with reference to
The potential of the present device includes a potential in a gate side (high potential) and a potential in a cathode side (low potential) while sandwiching a gap 8 in between a cathode 6 and a gate 5. In the figure, S1, S2 and S3 represent each of region lengths which are determined by each of the potentials in the device, and are different from the simple thickness of an electrode, the thickness of an insulating layer and the like.
When a voltage Vf is applied in between the cathode 6 and the gate 5 of the device according to the present invention, electrons are emitted from the head of the protruding portion of the cathode 6 toward the opposing gate 5 having a high potential, and the electrons are isotropically scattered on the tip part of the gate 5. Many of electrons emitted from the tip part of the gate 5 repeat elastic scattering once to several times in the gate 5, similarly in a conventional device.
In the present invention, a space potential distribution formed by a driving voltage in between an anode 20 and the device is different from that in a conventional one, so that some of emitted electrons reach the upper part of the gate 5 without being scattered in the gate 5 and directly reach the anode 20. The electron which has not been scattered in the gate 5 in this way is important for the improvement of electron emission efficiency.
In the case of the present invention, the electron emission efficiency is mainly determined by a distance S1. Furthermore, an electron which has not been scattered exists when S1 is set at a length shorter than the maximum flight distance in a first scattering.
A scattering behavior in the present structure was examined in detail. As a result, it became apparent that a region which can enhance the electron emission efficiency exists as a function of a work function φwk of a material used for the gate 5 and a driving voltage Vf, and as a function of distances S1 and S3, that is to say, due to an effect of a shape in the vicinity of electron-emitting portion.
As a result of an analytic investigation, the following formula (I) concerning S1max (T1 in
S1max=A×exp {B×(Vf−φwk)/Vf} (1)
B=8.7, wherein S1 and S3 represent a distance (nm), φwk represents a value of a work function of the gate 5 (where the unit is eV), Vf represents a driving voltage (V), (A) represents a function of S3 and (B) represents a constant.
It was found that S1 is the important parameter relating to scattering for the electron emission efficiency as was described above, and that an effect of remarkably enhancing the efficiency can be obtained by setting S1 in a range of Formula (1).
Here, a feature of a protruding shape in a recess portion 7 and a desirable form thereof will now be described below.
When a tip part of the protruding portion is enlarged, a protruding shape represented by a curvature radius (r) exists on the tip part. The strength of the electric field on the tip part of the protruding portion varies depending on the curvature radius (r). As the curvature radius (r) is smaller, an electric flux line converges more, and consequently a higher electric field can be formed on the tip part of the protruding portion. Accordingly, when the electric field of the tip part of the protruding portion is kept constant, that is to say, when a driving electric field is kept constant, a distance (d) becomes large when the curvature radius (r) is relatively small, and the distance (d) becomes small, when the curvature radius (r) is relatively large. The difference of the distance (d) appears as a difference of scatter frequency, so that a device structure having a smaller curvature radius (r) and a larger distance (d) can show higher electron emission efficiency. The relationship will now be described below with reference to
Here, the horizontal axis shows a curvature radius (r) of a tip part of a protruding portion, and a vertical axis shows a distance (d) between a cathode 6 and a gate 5.
Incidentally, the curve in
This means, in other words, that when the curvature radius (r) is small, the electron emission efficiency increases due to the shape effect of the tip part of the protruding portion of the cathode 6, and accordingly S1 in the above described Formula (I) can be set at a large value on conditions that the electron emission efficiency is constant. This fact means that the structure of the gate 5 can be made to be strong. Accordingly, such a stable device as to be endurable to a drive for a long period of time can be provided.
By the way, there is a case where the protruding portion of the cathode 6 is formed into such a shape as to enter into the recess portion 7 with a distance (x), as is illustrated in
A method for manufacturing the above described electron-emitting device according to the present invention will now be described below with reference to
A substrate 1 is an insulative substrate for mechanically supporting a device, and is quartz glass, a glass containing a reduced amount of impurities such as Na, soda-lime glass or a silicon substrate. The substrate 1 needs to have functions of not only a high mechanical strength but also resistances to dry etching or wet etching and an alkaline solution such as a developer and an acid solution; and when being used as an integrated product like a display panel, can have a small difference of thermal expansion between itself and a film-forming material or another member to be stacked thereon. The substrate 1 can also be a material which hardly causes the diffusion of an alkali element and the like from the inner part of the glass due to heat treatment.
At first, an insulating layer 73 to be an insulating layer 3a, an insulating layer 74 to be an insulating layer 3b and an electroconductive layer 75 to be a gate 5 are stacked on the substrate 1, as is illustrated in
An electroconductive layer 75 is formed with a general vacuum film-forming technology such as a vapor deposition method and a sputtering method. The electroconductive layer 75 can be a material which has high thermal conductivity in addition to electroconductivity and has a high melting point. The material includes, for instance: a metal such as Be, Mg, Ti, Zr, Hf, V, Nb, Ta, Mo, W, Al, Cu, Ni, Cr, Au, Pt, Pd or an alloy material thereof; and a carbide such as TiC, ZrC, HfC, TaC, SiC and WC. The material also includes: a boride such as HfB2, ZrB2, CeB6, YB4 and GdB4; a nitride such as TiN, ZrN, HfN and TaN; a semiconductor such as Si and Ge; an organic polymer material; and further carbon and a carbon compound of dispersed amorphous carbon, graphite, diamond like carbon and diamond. The material for the electroconductive layer 75 is appropriately selected from these materials.
The thickness of the electroconductive layer 75 is set at a range of 5 nm to 500 nm, and can be selected from the range of 50 nm to 500 nm.
Next, after the above layer has been stacked, a resist pattern is formed on the electroconductive layer 75 with a photolithographic technology, and then the electroconductive layer 75, the insulating layer 74 and the insulating layer 73 are sequentially processed with an etching technique, as is illustrated in
A method to be generally employed for such an etching process is an RIE (Reactive Ion Etching) which can precisely etch a material by irradiating the material with a plasma that has been converted from an etching gas. A processing gas to be selected at this time is a fluorine-based gas such as CF4, CHF3 and SF6, when a target member to be processed forms a fluoride. When the target member forms a chloride as Si and Al do, a chloride-based gas such as Cl2 and BCl3 is selected. In order to set a selection ratio of the above layers with respect to a resist, to secure the smoothness of a face to be etched, or to increase an etching speed, hydrogen, oxygen, argon gas or the like is added at any time.
Only a side face of the insulating layer 3b is partially removed on one side face of the stacked body by using an etching technique, and a recess portion 7 is formed as is illustrated in
The etching technique can employ a mixture solution of ammonium fluoride and hydrofluoric acid, which is referred to as a buffer hydrofluoric acid (BHF), if the insulating layer 3b is a material formed from SiO2, for instance. When the insulating layer 3b is a material formed from SixNy, the insulating layer 3b can be etched with the use of a phosphoric-acid-based hot etching solution.
The depth of the recess portion 7, that is to say, a distance between the side face of the insulating layer 3b and the side face of the insulating layer 3a and the gate 5 in the recess portion 7 deeply relates to a leakage current occurring after a device has been formed, and the more deeply the recess portion 7 is formed, the smaller the value of the leakage current is. However, when the recess portion 7 is too much deeply formed, a problem of the deformation of the gate 5 occurs, so that the recess portion 7 is formed so as to be approximately 30 nm to 200 nm deep.
Incidentally, the present embodiment showed a form in which the insulating member 3 is a stacked body of the insulating layer 3a and the insulating layer 3b, but the present invention is not limited to the form. The recess portion 7 may be formed by removing a part of one insulating layer.
Subsequently, a release layer 81 is formed on the surface of the gate 5, as is illustrated in
The cathode material 82 constituting a cathode 6 is deposited on the substrate 1 and the side face of the insulating member 3, as is illustrated in
The cathode material 82 may be a material which has electroconductivity and emits an electric field, and generally can be a material which has a high melting point of 2,000° C. or higher, has a work function of 5 eV or less, and hardly forms a chemical reaction layer thereon such as an oxide or can easily remove the reaction layer therefrom. Such materials include, for instance: a metal such as Hf, V, Nb, Ta, Mo, W, Au, Pt and Pd, or an alloy material thereof; a carbide such as TiC, ZrC, HfC, TaC, SiC and WC; and a boride such as HfB2, ZrB2, CeB6, YBa and GdB4. The materials also include a nitride such as TiN, ZrN, HfN and TaN; and carbon and a carbon compound of dispersed amorphous carbon, graphite, diamond like carbon and diamond.
A method for depositing the cathode material 82 to be employed is a general vacuum film-forming technology such as a vapor deposition method and a sputtering method, and can be an EB vapor deposition method.
As was described above, it is necessary in the present invention to form a cathode by controlling an angle of vapor deposition, a film-forming period of time, a temperature during film formation and a vacuum degree during film formation so that the cathode 6 can form the optimum shape for efficiently taking out electrons.
The cathode material 82 on the gate 5 is removed by removing the release layer 81 with an etching technique, as is illustrated in
Next, an electrode 2 is formed so as to make the cathode 6 electrically conductive (
The thickness of the electrode 2 is set in a range of 50 nm to 5 mm, and can be selected from a range of 50 nm to 5 μm.
The electrode 2 and the gate 5 may be made from the same material or different materials, and may be formed with the same forming method or different methods. However, the film thickness of the gate 5 is occasionally set in a thinner range than that of the electrode 2, so that the gate 5 can be formed from a material having lower resistance.
Next, an application form of the above described electron-emitting device will now be described below.
When a level of convergence of the electric field is controlled by providing a plurality of the cathodes 6A to 6D in this way, an electron preferentially emits from the end parts in the width direction of the protruding portion in each of the cathodes 6A to 6D. As a result, the electron beam source can be provided which has a more uniform shape of an electron beam than that in the case of having provided one cathode 6 as illustrated in
A method of manufacturing a device in the present example includes patterning a cathode material 82 so that the number of the cathode becomes plural, in a step of
On the other hand,
Characteristics of a device in the present example will now be briefly described below with reference to
In
A method for manufacturing a device in the present example includes skipping a step of preparing a release layer 81 in
An electron beam apparatus according to the present invention can obtain a synergistic effect by combining a structure in
The device in the present example also can preferentially emit, by controlling a level of convergence of the electric field, electrons from the end parts in the width direction of the protruding portions in each of the cathodes 6A to 6D similarly to the device in
In the above description on the electron-emitting device according to the present invention, an embodiment was shown in which an insulating member 3 is formed of insulating layers 3a and 3b, and the lower face of the gate 5 is exposed to a recess portion 7. In the present invention, an embodiment can be also applied in which a side of the gate 5 opposing to the protruding portion of the cathode 6 (surface exposed to recess portion 7 in the present example) is covered with an insulating layer 3c, as is illustrated in
In the structure in
An electron beam apparatus according to the present invention can combine structures in
An image display apparatus having an electron source which is obtained by arranging a plurality of electron-emitting devices according to the present invention will now be described below with reference to
In
The wires in the X-direction 32 of m lines include Dx1 and Dx2 to Dxm, and can be made by an electroconductive metal or the like, which has been formed by using a vacuum vapor deposition method, a printing method, a sputtering method and the like. A material, a film-thickness and a width of the wires are appropriately designed.
The wires in the Y-direction 33 include n lines of wires Dy1 and Dy2 to Dyn, and are formed similarly to the wires in the X-direction 32. An unshown interlayer insulating layer is provided in between m lines of the wires in the X-direction 32 and n lines of the wires in the Y-direction 33, and electrically separates the wires in both directions from each other (m and n are both positive integer number).
The unshown interlayer insulating layer is made by SiO2 or the like, which has been formed with the use of a vacuum vapor deposition method, a printing method, a sputtering method or the like. The unshown interlayer insulating layer is formed, for instance, on the whole surface or one part of the surface of the electron source substrate 31 having the wires in the X-direction 32 formed thereon to form a desired shape; and the film-thickness, the material and the manufacturing method are appropriately set so as to be resistant particularly to a potential difference in the intersections of the wires in the X-direction 32 and the wires in the Y-direction 33. The wires in the X-direction 32 and the wires in the Y-direction 33 are taken out as external terminals, respectively.
An electrode 2 is electrically connected with a gate 5 (
A material constituting wires 32 and wires 33, a materiel constituting the wire connection 35 and a material constituting the electrode 2 and the gate 5 may be made from a partially equal constituent element or a totally equal constituent element, or may be made from different constituent elements respectively.
An unshown scanning-signal-applying unit is connected to the wires in the X-direction 32, and applies a scanning signal for selecting a row of electron-emitting devices 34 which have been arrayed in an X-direction. On the other hand, an unshown modulation-signal-generating unit is connected to the wires in the Y-direction 33, and modulates each column of the electron-emitting devices 34 which have been arrayed in a Y-direction, according to an input signal.
A driving voltage to be applied to each of the electron-emitting devices is supplied in a form of a differential voltage between the scanning signal and the modulation signal to be applied to the device.
The image display apparatus having the above described configuration can select an individual device and independently drive the device by using a simple matrix wiring.
The image display apparatus which has been configured by using an electron source having such a simple matrix arrangement will now be described below with reference to
In
Furthermore, a supporting frame 42 is shown, and an envelope 47 includes the supporting frame 42, and the rear plate 41 and the face plate 46, which are attached to the supporting frame 42 through a frit glass or the like. The envelope is sealed with the frit glass by baking the frit glass in the atmosphere or nitrogen gas in a temperature range of 400 to 500° C. for 10 minutes or longer.
The envelope 47 includes the face plate 46, the supporting frame 42 and the rear plate 41, as was described above. Here, the rear plate 41 is provided mainly so as to reinforce the strength of the electron source substrate 31, so that when the electron source substrate 31 itself has a sufficient strength, an additional rear plate 41 can be eliminated.
Specifically, the envelope 47 may include the face plate 46, the supporting frame 42 and the electron source substrate 31, through directly sealing the supporting frame 42 with the electron source substrate 31. On the other hand, the envelope 47 can have a structure which has a sufficient strength against atmospheric pressure, by arranging an unshown support member referred to as a spacer in between the face plate 46 and the rear plate 41.
In such an image display apparatus, the phosphor is aligned and arranged in the upper part of each of the electron-emitting devices 34, while considering the trajectory of an emitted electron.
Next, a configuration example of a driving circuit for displaying a television picture based on a television signal of an NTSC system on a display panel which is structured by using an electron source having a simple matrix arrangement will now be described below with reference to
In
The display panel 61 is connected to an external electric circuit through terminals Dx1 to Dxm, terminals Dy1 to Dyn and a high-voltage terminal Hy. A scanning signal is applied to the terminals Dx1 to Dxm so as to drive electron sources which are provided in a display panel, that is to say, a group of electron-emitting devices which are arranged into a matrix form of m rows and n columns through wires, sequentially by one row (N devices). On the other hand, a modulation signal is applied to terminals Dy1 to Dyn so as to control an output electron beam of each device in one row of electron-emitting devices, which has been selected by the scanning signal.
A direct-current voltage source Va supplies the direct-current voltage, for instance, of 10 [kV] to a high pressure terminal Hv, which is an accelerating voltage for imparting sufficient energy for exciting the phosphor onto an electron beam to be emitted from the electron-emitting device.
As was described above, the emitted and accelerated electrons by the scanning signal, the modulating signal and application of the high voltage to the anode irradiate the phosphor, and realize an image display.
Incidentally, when such a display apparatus is formed by using the electron-emitting device according to the present invention, the structured display apparatus shows a uniform shape of an electron beam, and the provided display apparatus can consequently show adequate display characteristics.
An electron-emitting device having a structure illustrated in
A PD200 was used for a substrate 1, which is low-sodium glass that has been developed for a plasma display, and SiN (SixNy) was formed thereon as an insulating layer 73 with a sputtering method so as to have a thickness of 500 nm. Subsequently, an SiO2 layer having a thickness of 30 nm was formed as an insulating layer 74 through a sputtering method. A TaN film having a thickness of 30 nm was stacked on the insulating layer 74 as an electroconductive layer 75 through a sputtering method (
Subsequently, a resist pattern was formed on the electroconductive layer 75 with a photolithographic technology, and the electroconductive layer 75, the insulating layer 74 and the insulating layer 73 were sequentially processed through a dry etching technique to form a gate 5 and an insulating member 3 which is formed of insulating layers 3a and 3b (
A recess portion 7 was formed in the insulating member 3 (
A release layer 81 was formed (
Molybdenum (Mo) which was a cathode material 82 was deposited on the gate 5, the side face of the insulating member 3 and the surface of the substrate 1. In the present example, an EB vapor deposition method was used as a film-forming method. In the present forming method, the substrate 1 was set at the angle of 60 degrees with respect to a horizontal plane. Thereby, Mo was incident on the upper part of the gate 5 at 60 degrees, and was incident on a slope face of the insulating member 3 after having been subjected to the RIE process, at 40 degrees. Mo was formed so as to have the thickness of 30 nm on the slope face (
After the Mo film was formed, the Mo film on the gate 5 was peeled by removing an Ni release layer 81 which had been deposited on the gate 5 with the use of an etchant containing iodine and potassium iodide.
Subsequently, a resist pattern was formed with a photolithographic technology so that a width T4 (
As a result of having analyzed the cross section with a TEM (transmission-type electron microscope), the shortest distance (d) between the cathode 6 and the gate 5 was 9 nm.
Next, an electrode 2 was formed by depositing Cu on the cathode with a sputtering method so as to have the thickness of 500 nm and patterning the Cu film.
After the device was formed through the above described method, the electron emission characteristics were evaluated by using a structure illustrated in
In addition, as a result of having observed the cross section of the protruding portion of the cathode 6 in the device of the present example with a TEM, the protruding portion showed the cross section having a shape as illustrated in
The electron-emitting device illustrated in
In the step of
After the Mo film was formed, the Mo film on the gate 5 was peeled by removing an Ni release layer 81 which had been deposited on the gate 5 with the use of an etchant containing iodine and potassium iodide.
Subsequently, a resist pattern was formed with a photolithographic technology so that a width T4 of the protruding portion on a cathode could be 3 μm and a distance between adjacent cathodes could be 3 μm. Afterwards, the cathodes of 17 lines were formed by processing the Mo film on the substrate 1 and the side face of the insulating member 3 with a dry etching technique. A processing gas used at this time was a CF4-based gas, because molybdenum employed as a cathode material 82 forms a fluoride.
As a result of having analyzed the cross section with a TEM, the shortest distance (d) between the cathode 6 and the gate 5 in
After an electrode 2 was formed with a similar method to that in Exemplary embodiment 1, the electron emission characteristics were evaluated by using a structure illustrated in
When considering from this characteristics, it is assumed that the electron emission current increased by only the number of the cathodes as a result of having prepared a plurality of cathodes.
In addition, an electron-emitting device was prepared in a similar manufacturing process, in which a width of the protruding portion of the cathode and a distance between adjacent cathodes were set at 0.5 μm respectively and the number of the cathodes was increased to 100 lines. Then, the device showed approximately 6 times more amount of emitted electrons.
The electron-emitting device illustrated in
SiO2 was deposited so as to have the thickness of 40 nm as an insulating layer 74 with a sputtering method, and TaN was deposited so as to have the thickness of 40 nm as an electroconductive layer 75 with a sputtering method.
An insulating layer 73, the insulating layer 74 and the electroconductive layer 75 were dry-etched by an RIE process in a similar way to that in Exemplary embodiment 1. The side face of an insulating member 3 and a gate 5 after having been etched was formed so as to have the angle of 80 degrees with respect to a substrate 1. Subsequently, a recess portion 7 was formed in the insulating member 3, by etching only the side face of an insulating layer 3b so as to form the recess portion with a depth of approximately 100 nm through an etching technique with the use of BHF.
In the step of
Subsequently, a resist pattern was formed with a photolithographic technology so that a width T4 of the protruding portion on a cathode 6 could be 70 μm and a width T7 of the humped portion 90 on the gate 5 could be smaller than T4. Here, T7 was controlled by controlling a taper shape of a resist pattern. Afterwards, the cathode 6 and the humped portion 90 were formed, by processing the Mo film on the substrate 1, the side face of the insulating member 3 and the gate 5 with a dry etching technique. A processing gas used at this time was a CF4-based gas, because molybdenum employed as a cathode material 82 forms a fluoride.
The width T7 of the obtained humped portion 90 was 30 nm smaller than the width T4 of the protruding portion of the cathode 6.
As a result of having analyzed the cross section with a TEM, the shortest distance (d) between the cathode 6 and the gate 5 in
Subsequently, after an electrode 2 was formed with a similar method to that in Exemplary embodiment 1, the electron emission characteristics were evaluated by using a structure illustrated in
The electron-emitting device illustrated in
Molybdenum (Mo) which was a cathode material 82 was deposited also on a gate 5, similarly to the method in Exemplary embodiment 3. In the present example, a sputtering vapor deposition method was employed as a film-forming method, and a substrate 1 was set at such an angle as to be horizontal with respect to a sputter target. Argon plasma was generated at a vacuum degree of 0.1 Pa so that sputter particles were incident on the surface of the substrate 1 at a limited angle, and the substrate 1 was set so that the distance between the substrate 1 and the Mo target could be 60 nm or less (mean free path at 0.1 Pa). Furthermore, the Mo film was formed at the vapor deposition speed of 10 nm/min so that the thickness of the Mo film could be 20 nm on the side face of a stacked body.
After the Mo film was formed, a resist pattern was formed with a photolithographic technology so that the width T4 of the protruding portion on a cathode and the width T7 of the humped portion could be 3 μm and that a distance between adjacent cathodes and a distance between adjacent protruding portions could be 3 μm.
Afterwards, the cathodes of 17 lines and the humped portions of 17 lines corresponding to the above cathodes were formed by processing the Mo film with a dry etching technique. A processing gas used at this time was a CF4-based gas, because molybdenum employed as a cathode material 82 forms a fluoride. The width T7 of the obtained humped portion was approximately 10 nm to 30 nm smaller than the width T4 of the protruding portion of the cathode.
As a result of having analyzed the cross section with a TEM, the shortest distance (d) between the cathode and the gate 5 in
Subsequently, after an electrode 2 was formed with a similar method to that in Exemplary embodiment 1, the electron emission characteristics were evaluated by using a structure illustrated in
In addition, an image display apparatus in
While the present invention has been described with reference to exemplary embodiments, 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. 2008-102009, filed Apr. 10, 2008, which is hereby incorporated by reference herein in its entirety.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2008-102009 | Apr 2008 | JP | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 12421794 | Apr 2009 | US |
| Child | 12946561 | US |
