JP2002190248A - Field emission type electron source device for cathode- ray tube and method for making the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a field emission electron source device that can display a highly bright and refined image and has high reliability at a low cost. SOLUTION: This field emission electron source device is equipped with a substrate, an insulating layer having a plurality of openings formed on the substrate, withdrawable electrodes formed on the insulating layer and a cathode formed in each of the openings in the substrate, wherein the insulating characteristic of the entire insulating layer is controlled by the use of an insulating layer of multilayer structure that has a relative dielectric constant different from the other layers.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a field emission type electron source device used for a cathode ray tube (CRT) used for a color television or a high definition monitor, an electron beam exposure device utilizing a converged electron beam, and the like.

[0002]

2. Description of the Related Art Conventionally, CRT displays have been widely used for color televisions and high-definition monitors. recent years,
With the introduction of thin displays such as liquid crystal displays and plasma displays, the flat display market is rapidly expanding, but CRT displays are still dominant in terms of price and performance as home TV applications of about 32 inches in size. .

With the full-scale introduction of digital terrestrial broadcasting, it is expected that the display technology for televisions will change significantly. In the conversion of televisions to digital systems, further improvement in resolution performance is particularly demanded for displays. However, there is a possibility that the television technology that has been widely used until now cannot sufficiently meet this demand.

[0004] The resolution performance of a CRT television is strongly related to the performance of an electron gun used as a heart for displaying images. Therefore, various attempts have been made to improve the resolution performance by increasing the current density of the cathode used in the electron gun to reduce the effective cathode area. In the case of a so-called hot cathode using an oxide as a cathode material, it is necessary to increase the current density to about 6 to 10 times that of the current state for digital broadcasting, but it is difficult to cope with this. In the hot cathode method, a heater for heating the cathode to a high temperature of about 800 ° C. to emit electrons is required, and a standby power of about several watts is always required even when the electron gun is not used. It has a fatal drawback in terms of power saving.

[0005] Therefore, improvement of an electron gun using a cold cathode, that is, a field emission type cathode is expected. The field emission cathode originally has a feature of high current density, and has been practically used in some products such as an electron beam microscope. When a field emission cathode is used, a heater for heating is not required at all, so that power consumption can be reduced, and waste of standby power can be eliminated. Another advantage is that the electron gun can be activated instantaneously.

A proposal for using a field emission cathode in an electron gun is as follows.
It has been made since ancient times. For example, JP-A-48-9046
Japanese Patent Application Laid-Open No. 7-212,199 proposes a color picture tube using a field emission cathode. FIG. 10 shows an integrated electron emitting section using a field emission cathode proposed in the publication. sapphire,
The conical cathodes 102 formed on a substrate 101 made of quartz or the like are insulated from each other by an insulating layer 103,
A red (R), green (G) or blue (B) luminance signal is added to each. These cathode projection groups 106 are made of tungsten, molybdenum, or the like. By applying a voltage of about +100 V to the cathode 102 to the extraction electrode 104, an electron flow can be extracted. Further, by using alumina for the insulating layer 103, the thickness can be made 1 to several μm, and the thickness of the integrated electron emitting section can be made about 100 μm.

In Japanese Patent Application Laid-Open No. 7-21903,
The control method of the field emission cathode proposed in the above publication is improved. As shown in FIG. 11, not only the three field emission cathode groups 201r, 201g and 201b can be controlled independently, but also the gate electrodes 203r, 203g and 203b corresponding to the cathode groups 201r, 201g and 201b are insulated from each other. , So that an independent control voltage can be applied to each. According to the publication, this configuration can provide a function of adjusting luminance unevenness between R, G, and B display colors caused by manufacturing variations between cathodes. It is stated that by applying luminance signals of opposite phases, the applied voltage applied to each can be halved.

In order to improve the display brightness and definition, it is considered that the cathode of the cathode ray tube will be required to operate at a high current density of 10 A / cm ² or more in the future. In the field emission cathode proposed in the gazette,
Operating the cathode at such a high current density for a long time,
The emission current gradually decreases.

Hereinafter, the problems of the above conventional example will be specifically described. In each of the above publications, a substantially conical projection electron source having a bottom diameter of about 1 μm or less and a tip radius of about 20 nm formed of a semiconductor or a metal such as molybdenum or tantalum is used as a cold cathode. . Further, an insulating layer having a single-layer structure and a gate electrode having an opening diameter of about 1 μm or less corresponding to each of the substantially conical projection electron sources formed on the insulating layer are used.

For operation at a high current density of 10 A / cm ² or more, it is necessary to apply a high voltage of 100 V or more to the gate electrode. When the cold cathode proposed in the above publication is operated under such a high voltage application condition, not only the tip portion but also a wide area around the tip portion reaches an electric field intensity at which electrons can be emitted. For this reason, under low operating voltage conditions, electrons are emitted only in the axial direction of the cone from a limited area near the tip of the cathode, but under high operating voltage conditions, the electron emission area becomes wider, 11
As shown in (b), electrons may be emitted in other directions, for example, toward the SiO ₂ insulating layer surrounding the periphery.

When some of the emitted electrons reach the insulating layer, the insulating layer is charged. If the electron emission operation by the application of such a high voltage is continued for a long time, the electric charge is accumulated and a negative electric field effect is caused. When the potential drops by about 10 V due to the accumulation of charges in the insulating layer, the electric field intensity at the tip of the conical projection electron source drops by about several percent. Since the relationship between the electric field intensity and the emission current is usually represented by an exponential function, even if the electric field intensity decreases by several%, the emission current decreases by about 30%. Therefore, when applied to an electron gun of a digital broadcasting television, a decrease in emission current causes a decrease in luminance, and a desired luminance cannot be maintained when used for a long time.

1 required for high brightness and high definition
As a method for achieving operation at a high current density of 0 A / cm ² or more, a method of improving the electron source density by reducing the size of the electron source array to, for example, half or less of the current size is promising. When the size of the electron source is reduced, the electron source density per unit area increases. Also, if the amount of current emitted from the whole is the same, the load of the amount of emission current per single electron source can be reduced by the increase in the density of the electron source.

[0013] However, miniaturization of the size of the electron source array is advantageous for the life characteristics of the electron source, but causes a new problem due to the accompanying thinning of the insulating layer. Chemical vapor deposition (CV), which has been widely used in the past,
In the case where the silicon oxide film formed by the method D) is used for the insulating layer, if the silicon oxide film is thin, there is a problem in electrical breakdown voltage. A voltage of about 100 V is normally applied to the extraction electrode in order to obtain a high emission current. For example, in a silicon oxide film having a thickness of 100 nm by a CVD method, when such a high voltage is applied, a leakage current is generated due to withstand voltage failure. May occur.

[0014]

SUMMARY OF THE INVENTION An object of the present invention is to provide an inexpensive field emission electron source device which can display a high-definition and high-definition image and has high reliability.

[0015]

A field emission electron source device for a cathode ray tube according to the present invention comprises a substrate, an insulating layer having a plurality of openings formed on the substrate, a lead electrode formed on the insulating layer, A cathode is provided in the opening on the substrate, the insulating layer is composed of a plurality of layers, and at least one of the plurality of layers has a relative dielectric constant different from other layers. By using a multi-layered insulating layer and using a material having a different dielectric constant from the other layers for the constituent layers, it is possible to control the insulating properties of the entire insulating layer, which is accompanied by miniaturization of the electron source array. It can easily cope with thinning of the insulating layer. If a material and a technique used in a semiconductor memory process are used, a highly reliable film can be formed.

When a substrate made of silicon single crystal is used,
Integration with a silicon functional device such as a MOSFET is facilitated, and functions such as stabilization control of device operation can be easily added. Further, processing utilizing characteristics of the silicon single crystal, such as crystal anisotropic etching, can be used.

When a silicon substrate is used, it is preferable to use a silicon oxide film obtained by thermally oxidizing the substrate surface as the lowermost layer of the insulating layer bonded to the substrate. This thermal oxide film is formed of a CV which is generally used as an insulating layer.
It is denser and has better insulating properties than the silicon oxide film formed by the method D. Further, the tip of the cathode to be formed by thermal oxidation is sharpened, and a substantially columnar cathode capable of operating at a low voltage can be obtained. In order to ensure insulating properties, it is useful to use a material having a higher dielectric constant than silicon oxide for the insulating layers other than the lowermost layer. When a CVD method or a sputtering method is used for forming each of the above layers, an insulating layer having excellent insulating properties can be obtained without being affected by steps of a base of a substrate.

Materials constituting each layer of the insulating layer include, for example, Si ₃ N ₄ , Ta ₂ O ₅ , SrTiO ₃ , SrBi ₂ Ta
_{2 O 9, (Ba x Sr} 1-x) TiO 3, Pb (Zr y T
i _1-y ) Use a high dielectric constant material such as O ₃ . Since these high dielectric constant materials have significantly higher pressure resistance than silicon oxide, they can be used for an insulating layer to suppress generation of leakage current due to poor voltage resistance. In particular, when a material having a relative dielectric constant of 7 or more is used, the effect of the high dielectric constant layer appears more clearly. In addition, sufficient insulation can be ensured even when the thickness of the insulating layer is reduced. When the uppermost layer of the insulating layer in contact with the extraction electrode is formed by plasma CVD at a high film formation rate, the efficiency of the processing time can be improved. In addition, when the insulating layer is formed by a vacuum evaporation method, an insulating layer having good insulating properties can be formed at low cost with a simple device.

Another field emission type electron source device for a cathode ray tube according to the present invention comprises a substrate, an insulating layer having a plurality of openings formed on the substrate, an extraction electrode formed on the insulating layer, and A cathode is provided in the opening, and a coating made of a material different from the material constituting the cathode is formed on the surface of the cathode. By providing this coating, it becomes possible to design the material of the electron emission surface independently of the process of processing the shape of the cathode. Therefore, it is possible to arbitrarily select the most suitable electron-emitting material for the operating conditions and operating environment. In order not to deteriorate the function of the cathode, the coating is preferably made of a metal having a work function of 4.8 eV or less, which is that of n-type silicon.

When a silicon substrate is used, it is preferable to use a material such as molybdenum, nickel, chromium, platinum, tungsten, cobalt, etc., which reacts with silicon in the substrate by heat treatment to convert to silicide. Since these silicides have an oxidation resistance function, it is possible to effectively prevent the electron emission performance of the cathode from deteriorating in a thermal process. In order not to lower the electron emission function,
It is preferable that the thickness of the coating be 20 nm or less.

According to still another aspect of the present invention, there is provided a field emission type electron source device for a cathode ray tube, a substrate, an insulating layer having a plurality of openings formed on the substrate, a lead electrode formed on the insulating layer,
And a cathode provided in an opening on the substrate, and a film made of a material different from a material constituting the cathode is formed on the surface of the extraction electrode. For example, it can be used as a protective film for preventing the extraction electrode from being damaged in a heat treatment in a later step. When the exposed surface of the extraction electrode is covered with a functional material, a desired function can be newly added in addition to the function of the extraction electrode.
When a lead electrode made of a silicon compound is used and a coating made of a refractory metal material that forms a silicide by heat treatment is formed on the surface thereof, a coating with high adhesion can be obtained.

As the refractory metal used for forming the metal silicide coating, molybdenum, tungsten, nickel,
Materials used in general semiconductor processes, such as chromium, tantalum, tungsten, and cobalt, may be mentioned. Since the processing of these materials is technically established, the coating can be formed with high yield. If a coating made of an insulating material is provided, even if minute foreign substances such as dust generated during the process adhere to the surface of the cathode, the insulating property between the cathode and the extraction electrode can be maintained.
The malfunction of the cathode operation can be prevented.

Still another aspect of the present invention is a field emission electron source device for a cathode ray tube, comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer;
And a cathode provided in the opening on the substrate, wherein the extraction electrode is thicker than the insulating layer. As a result, the effect of concentrating the electric field on the tip of the cathode is enhanced, and operation at a low voltage becomes possible when the amount of emitted electrons is the same.

According to still another aspect of the present invention, there is provided a field emission electron source device for a cathode ray tube, comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer;
And a cathode provided in the opening on the substrate, wherein the height of the cathode is larger than the thickness of the insulating layer and smaller than the sum of the thicknesses of the insulating layer and the extraction electrode. By making the tip of the cathode that emits electrons higher than the insulating layer on the periphery of the cathode, electrons emitted from the cathode can be prevented from reaching the insulating layer, and can be operated continuously for a long time. Reliability at the time of occurrence. In addition, there is also an effect of increasing the electric field strength at the tip of the cathode as compared with the conventional configuration, and operation at a low voltage becomes possible.

Further, in the case of using a cathode composed of a columnar portion having one end surface joined to the substrate and a conical portion having the other end surface as a bottom surface, the height of the columnar portion is larger than the thickness of the insulating layer. By making the extraction electrode surround the periphery of the conical portion, even when a high voltage is applied and electrons are emitted from the conical surface of the conical portion, the emitted electrons reach the insulating layer. Can be prevented, and the reliability in long-time continuous operation is further improved.

According to still another aspect of the present invention, there is provided a field emission type electron source device for a cathode ray tube, comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer;
And a cathode provided in the opening on the substrate, and the arrangement interval of the cathodes is 1.5 to 2.5 times the diameter of the opening. Conventionally, the arrangement interval of cathodes, which is about 5 to 10 times the diameter of the opening, is increased to 1.5 to 2.5 times, so that the cathodes are densely arranged without affecting the electron emission amount. Can be.

By using a substantially columnar cathode having a sharp tip as the above-mentioned cathode, a higher electric field concentration effect can be obtained as compared with a conventional cathode having a conical projection, and operation at a lower voltage is possible. Become.

A method of manufacturing a field emission type electron source device for a cathode ray tube according to the present invention comprises a substrate, an insulating layer having a plurality of openings formed on the substrate, a lead electrode formed on the insulating layer,
And a step of forming a cathode by etching the surface of a substrate made of a single crystal of silicon in the manufacture of a field emission type electron source device having a cathode provided in an opening on the substrate. Forming an insulating film and a conductive film on the surface of the substrate by sequentially laminating, forming a resist film on the surface of the conductive film on the substrate except for a predetermined region including a cathode, and dry etching. An etch back step of forming a lead electrode by removing the conductive film in the region, and removing the insulating film formed in the region by wet etching to form an insulating layer having an opening of a predetermined shape around the cathode. Forming.

After an insulating layer and a conductive film are sequentially formed on the entire surface of the substrate, a part of the conductive film is removed by a resist etch-back method. Unlike the conventional wet etching method, the conductive film is removed. Even if the material and thickness of the substrate change, uniform etching can be performed by adjusting the etching conditions, and the yield is improved.

Another method of manufacturing a field emission type electron source device for a cathode ray tube according to the present invention is the same as the above, except that a field emission type electron source device having a substrate, an insulating layer, an extraction electrode and a cathode is formed on a substrate. Forming a film made of a material different from the material constituting the cathode on the surface of the cathode formed in the above, and reacting the material of the film with the material of the cathode by heat treatment to convert it into a compound with the material of the cathode And According to this method, the cathode surface forming process which affects the electron emission characteristics is performed in the final step of forming the cathode, so that the cathode surface is less likely to be contaminated by the process, and has a good electron emission characteristic. It is possible to obtain a source device.

When a silicon substrate is used, it is preferable that the heat treatment is performed in a vacuum, and the material in the film is converted into silicide by the heat treatment. By performing the heat treatment step for silicidation in a vacuum, a favorable cathode can be formed by suppressing the oxidation of the cathode surface, so that favorable electron emission characteristics can be obtained. As a material of the film to be formed in advance, for example, molybdenum, nickel, cobalt, tungsten, platinum, or the like is used. When the coating is formed by a vacuum evaporation method, an extremely thin coating on the cathode surface can be formed with good control and without physical damage to the cathode tip. In addition, since the shape of the cathode tip can be favorably maintained without process damage, good electron emission characteristics can be obtained.

Similarly, it is useful to form a coating on the surface of the extraction electrode. For example, when a coating is formed on the surface of the cathode, the coating is also formed on the surface of the extraction electrode formed in advance with the insulating layer interposed on the substrate. The film formed here can be used as a protective film in heat treatment or as an insulating layer for preventing leakage current due to entry of foreign matter. It is preferable that the extraction electrode contains silicon, and a metal silicide coating having high adhesion to the extraction electrode and being thermally stable is formed on the surface of the extraction electrode, similarly to the coating formed on the cathode. For example, a metal such as molybdenum, tungsten, nickel, chromium, tantalum, tungsten, and cobalt is used. In the present invention, various substrates such as a silicon single crystal substrate and a GaAs substrate can be used unless otherwise limited. Further, other than the substantially columnar cathode, for example, a general cone-shaped cone-shaped cathode can be used. The field emission type electron source device of the present invention can be used for various applications such as a cathode ray tube, a high-luminance luminous tube for outdoor display, and a luminous tube for illumination.

[0033]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG. 1 shows a main part of a field emission type electron source device of this embodiment. On the surface of the substrate 1, an insulating layer 3 having a cylindrical space formed in an array and a substantially columnar cathode 2 having a circular cross-section disposed in the space of the insulating layer 3 are provided. I have. The tip of the cathode 2 is sharpened using a crystal anisotropic etching and a silicon thermal oxidation process. On the surface of the substrate 1, an insulating layer 3 having a two-layer structure including a first insulating layer 3a and a second insulating layer 3b laminated on the first insulating layer 3a is disposed with a cylindrical space surrounding the cathode 2 interposed therebetween. . On the upper surface of the insulating layer 3, a film-shaped lead electrode 4 is formed.

The thickness of the insulating layer 3 (that is, the first insulating layer 3
The sum of the thickness of a and the thickness of the second insulating layer 3b) is preferably about 500 nm in order to secure electrical insulation. When a silicon oxide film formed by, for example, a CVD method or the like is used for one of the insulating layers 3a and 3b, a material having a higher dielectric constant than silicon oxide is used for the other. The electric breakdown voltage characteristics can be improved as compared with the insulating layer formed. Since the relative dielectric constant of silicon oxide is about 3.8, a material having a relative dielectric constant of more than that, more preferably a material having a relative dielectric constant of more than 7, for example, Si
_{3 N 4, Ta 2 O 5} , SrTiO 3, SrBi 2 Ta 2 O 9,
_{(Ba x Sr 1-x)} TiO 3, Pb (Zr y Ti 1-y) O 3 the like.

The above-described cathode 2 and insulating layer 3 are formed, for example, as follows. First, as shown in FIG. 2A, the substrate 1 (10
A silicon oxide film 5 is formed on the 0) surface using a method such as a thermal oxidation method, and a photoresist 6 is applied on the silicon oxide film 5.

Next, as shown in FIG. 2B, a photoresist 6 applied on the silicon oxide film 5 is cured by photolithography to form a disk-shaped resist mask 6a having a diameter of about 0.5 μm. Form. Further, by performing anisotropic dry etching on the silicon oxide film 5, a silicon oxide mask 5a made of the silicon oxide film 5 located below the resist mask 6a is formed. After removing the resist mask 6a, the pillars 7 are formed on the surface of the substrate 1 by anisotropic dry etching using the silicon oxide mask 5a as shown in FIG.

Next, as shown in FIG. 2D, the column 7 is processed by wet etching using an etchant having a crystalline anisotropic property, for example, an aqueous solution of ethylenediamine and pyrocatechol. Form a drum-shaped portion 7a formed of a surface including the (331) surface and having a narrowed central portion. In this case, the diameter of the silicon oxide mask 5a is optimally designed in advance based on the azimuthal angle of the crystal, so that the diameter of the constricted central portion is about 0.1 μm and the drum-shaped portion 7 has a fine structure.
a can be formed uniformly and with good reproducibility.

Thereafter, as shown in FIG. 2E, a thin silicon oxide film 8 having a thickness of, for example, about 10 nm is formed by thermal oxidation in order to protect the constricted portion of the drum-shaped portion 7a. The substrate 1 is etched in the thickness direction by anisotropic dry etching using the silicon oxide mask 5a, and the columnar portions 7 are formed on the surface of the substrate 1 as shown in FIG.
b is formed. Next, as shown in FIG. 2G, a silicon oxide film 9 having a thickness of, for example, about 100 nm is formed on the surfaces of the columnar portions 7b and the substrate 1 by a thermal oxidation method. Due to these heat treatments, thermal oxidation also proceeds in the constricted portion of the drum-shaped portion 7a, and the drum-shaped portion 7b is divided into two in the constricted portion, and is processed into the shape of the cathode 2 to be obtained. The portion of the silicon oxide film 9 where the extraction electrode 4 is formed above is processed into the first insulating layer 3a in a later step. A silicon oxide film formed by a thermal oxidation method has higher film resistance than other methods such as a silicon oxide film formed by a vapor deposition method, and thus has a high insulation resistance.

Here, in the silicon thermal oxidation process for forming the silicon oxide film 9, the tip of the formed cathode 2 is sharpened. There is a close relationship between the temperature conditions of the thermal oxidation process and the radius of curvature of the tip of the cathode 2. That is, the internal stress generated at the interface between the substrate 1 and the thermal oxide film formed in the thermal oxidation process is caused by the tip of the cathode 2, that is, the drum-shaped portion 7.
a affects the sharpening of the top of the conical body formed by division. A temperature lower than the melting point of silicon oxide, for example 95
When thermal oxidation is performed at 0 ° C., stress is generated in the vicinity of the interface between the silicon oxide film 9 formed on the surface and the inside of the drum-shaped portion 7 b made of silicon. Can be formed. The lower the thermal oxidation temperature, that is, the lower the deposition rate of the thermal oxide film, the higher the internal stress, which is effective in sharpening the tip of the cathode. The radius of curvature at the tip is 2 nm by selecting the optimal conditions
It can be: Preferably, the heat treatment is performed at 950 ° C. or less and in a dry oxidation atmosphere. Under these conditions, 20
It takes about 2 hours of processing to form an oxide film of about 0 nm. The formation of a thicker film than this is not realistic in terms of productivity because the time required for the process is too long.

As shown in FIG. 3A, a silicon nitride film 1 is formed on the surface of the substrate 1 on which the cathode 2 is formed as described above.
0 and the conductive film 11 are sequentially formed by a vacuum evaporation method.
As the conductive film 11, another metal material such as niobium or a low-resistance polysilicon film is used.

Next, as shown in FIG.
A resist mask 12 is formed by using a positive resist on the periphery of the conductive film 11 excluding the portion where b is formed, that is, on the conductive film 11 excluding the portion where the opening is to be formed. Resist mask 12
Acts as a selective protection film in a resist etch-back process to be described later, so that the conductive film 11 formed above the drum-shaped portion 7b is desirably thinner than that formed in other regions. Next, as shown in FIG. 3C, a portion of the silicon nitride film 10 formed above the drum-shaped portion 7b and a portion of the conductive film 11 on the side wall thereof are selectively removed by reactive ion etching. I do. Thereby, the conductive film 11 is processed, and the extraction electrode 4 is formed. It is necessary to control the etching time so that the conductive film 11 formed other than above the drum-shaped portion 7b is not removed.

After the resist mask 12 is removed, the silicon nitride film 10 formed on the side wall and the upper part of the cathode 2 is selectively removed by wet etching using a phosphoric acid solution in an ultrasonic atmosphere, and further nitrided. The silicon oxide film 9 exposed by the selective removal of the silicon film 10 is selectively removed by wet etching using a buffered hydrofluoric acid solution to expose the cathode 2 as shown in FIG. Form a part. At this time, by optimizing the wet etching time, the diameter of the opening of the extraction electrode 4 can be made smaller than the diameter of the insulating layer 3 formed thereunder.

As in the present embodiment, when an insulating film to be processed into the first insulating layer 3a is formed simultaneously with a silicon thermal oxidation process for sharpening the tip of the cathode 2, the first insulating layer 3a is formed. A silicon oxide film having a thickness of about 200 nm is obtained. As described above, according to this embodiment, the insulating layer of the extraction electrode is formed of at least an insulating layer made of a silicon thermal oxide film that is advantageous for sharpening the cathode and an insulating layer made of a high dielectric constant material having excellent withstand voltage characteristics. Since it has a multilayer structure, it is possible to maintain field emission characteristics with excellent insulation resistance even when the insulating layer is made thinner due to miniaturization of a device. In addition, since the silicon thermal oxide film process is used to sharpen the cathode of the electron source at the same time as the formation of the insulating layer, the tip having a small tip curvature can be formed uniformly, resulting in stable and high-performance electron emission. Characteristics are obtained.

Embodiment 2 In this embodiment, an example of useful means for preventing deterioration of the cathode performance due to a heat treatment process for forming an array and prevention of deterioration of the cathode performance due to oxidation will be described. FIG. 4C shows a main part of the field emission type electron source device of this embodiment. A surface coating layer 12a is selectively formed on the surface of the cathode 2 and the surface of the extraction electrode 4 in a region where the cathode array is formed. It is not always necessary to form the surface coating layer 12a on the entire surface of the cathode 2, but it is sufficient that the surface coating layer 12a is formed on the front surface of the cathode 2, which is the electron emission region. Since the surface coating layer 12a covers the surface of the cathode 2, the electron emission characteristics of the cathode 2 are largely affected. Therefore, as the material of the surface coating layer 12a, a material having a low work function that can be expected to have good electron emission characteristics is desirable. In order not to deteriorate the microstructure at the tip of the cathode 2, it is desirable that the film be an extremely thin film having a thickness of 20 nm or less. In order to use it as an electron gun for CRT, CR
It is necessary that the material be excellent in process resistance so as not to degrade the initial characteristics as an electron source even after various heat treatment steps in the T manufacturing process. From such a viewpoint, as the material of the surface coating layer 12a, nickel, molybdenum, chromium, or the like, which is a metal material having a high melting point and reacting with silicon to convert to silicide, is used. By performing a predetermined heat treatment, these metal materials easily react with silicon in the substrate 1 and are converted into silicides.

Hereinafter, an example in which metal molybdenum is used will be described. Molybdenum is widely used as a micro cold cathode material. The work function is typically about 4.0 eV, and good electron emission characteristics can be obtained. However, when heat treatment is performed in an oxidizing atmosphere, the surface of metal molybdenum is easily oxidized, and the electron emission characteristics are significantly reduced. However, molybdenum silicide (Mo) produced by thermally reacting metallic molybdenum with silicon.
Si) is extremely stable with almost no oxidation even when a similar heat treatment is performed. Moreover, since the melting point of molybdenum silicide is as high as about 2800 ° C., the electron emission ability is extremely high, and its work function is about 4.5 eV, which is comparable to that of silicon.

Surface coating layer 12 of molybdenum silicide
a is formed, for example, as follows. First, an electron source structure including a lead electrode 4, an insulating layer 3, and a cathode 2 is formed on a substrate 1 made of a single crystal of silicon, and then, in a region where a cathode array is formed, as shown in FIG. Then, a resist mask 13 having an opening is selectively formed by photolithography. Note that the opening may be formed so as to be limited to at least a region of the cathode array where the electron emission operation is performed.

Thereafter, as shown in FIG.
A film 12 of molybdenum having a thickness of about 5 nm is formed on the entire surface of the substrate by a vacuum evaporation method. If the thickness of the film 12 to be formed is up to about 5 nm, the shape of the cathode 2 is hardly deteriorated, and the surface coverage is good. Thereafter, an unnecessary region of the resist mask 13 is removed using a resist stripper.
Remove and wash thoroughly. Next, the silicon substrate 1 is heat-treated for 1 hour in a vacuum atmosphere at 550 ° C., for example.
By this heat treatment, molybdenum constituting the coating 12 thermally reacts with silicon, which is the material of the cathode 2, to be converted into molybdenum silicide, and the surface coating layer 12a having high adhesion is obtained.

The composition of the surface of the surface coating layer 12a after the heat treatment was analyzed by Auger method, and it was found that a good film of molybdenum silicide containing silicon and molybdenum at a composition ratio of about 1: 1 was formed. confirmed. The work function of molybdenum silicide in the obtained surface coating layer 12a was about 4.6 eV, and it was confirmed that the work function was equal to or higher than that of silicon.

In order to investigate the effect of heat treatment, CRT
The change of electron emission performance was experimentally analyzed by exposing to the atmosphere of the glass sealing process in the manufacturing process. As a result, the electron source in which the surface of the cathode 2 is coated with molybdenum silicide has almost no decrease in the electron emission performance as compared with that before the heat treatment.
It was confirmed that the film has sufficient resistance to the heat treatment in the RT manufacturing process.

Embodiment 5 FIG. 5 shows a main part of a field emission type electron source device of this embodiment. In the field emission type electron source device of the present embodiment, a surface coating layer 12b similar to that of the second embodiment is provided on the surface of the extraction electrode 4. For example, the extraction electrode 4 is made of a conductive silicon compound such as polysilicon, which is doped with impurities to reduce the resistance, and the surface coating layer 12b covering the surface is made of molybdenum silicide. First, a molybdenum metal film is formed on the surface of the extraction electrode 4 by a vapor deposition method or the like, and the obtained film is subjected to a heat treatment to be silicided. Since the surface coating layer 12b made of molybdenum silicide obtained by the heat treatment is thermally stable, the extraction electrode 4 can be protected in a heat treatment in a later step. Therefore, the occurrence of defects in the manufacturing process can be reduced, and the manufacturing cost can be significantly reduced.

Next, an example in which the surface coating layer formed on the extraction electrode is made of an insulator will be described. The insulating surface coating layer is formed similarly to the conductive surface coating layer. For example, silicon oxide film, silicon nitride film, oxide film of other materials,
A material used in a general semiconductor process is used. Since the opening diameter of the extraction electrode is a submicron size, if foreign matter adheres to the opening of the extraction electrode in the manufacturing process, there is a possibility that the foreign matter is affected similarly to a general semiconductor device. If the adhered foreign matter is an insulator, it only causes a problem in the operation of the cathode in the region where the foreign matter is attached, and has relatively little effect on the entire cathode array. On the other hand, when the adhered foreign substance is a conductor, an electric path is formed between the cathode and the extraction electrode, so that a leak current flows between the cathode and the extraction electrode, and in some cases, a normal voltage is applied to the extraction electrode. May not be applied, causing a malfunction in the operation of the entire cathode array. Therefore, as shown in FIG. 5, by providing a surface coating layer 12b made of an insulator on the surface of the extraction electrode 4, various foreign substances can be formed in a post-process such as a semiconductor mounting process or a process of mounting an electron source as an electron gun. The cathode 2 and the extraction electrode 4
No leakage current is generated between the two because the insulation property between them is maintained. Therefore, the production yield can be significantly improved.

Embodiment 4 FIG. 6 shows a main part of a field emission type electron source device of this embodiment. In the field emission type electron source device of the present embodiment, as shown in FIG. 6, the height of the cathode 2 is set to be lower than the uppermost position of the surrounding extraction electrode 4 and higher than the lowermost surface. . With this design, the operation performance as an electron gun is dramatically improved.

Since the tip of the cathode 2, which is an electron emitting portion, is held higher than the lower surface of the extraction electrode 4 (ie, the upper surface of the insulating layer 3), electrons emitted in the horizontal direction in FIG. You will collide. FIG.
As shown by the arrow in FIG. 2B, in the conventional electron emitting portion, the electrons emitted from the cathode 102 collide with the insulating layer 105 and charge the insulating layer 105, so that the emission current of the cathode 102 decreases. However, according to the present embodiment, such charge does not occur, and stable operation can be achieved. Furthermore, when the height of the cathode 2 is made equal to the upper surface of the extraction electrode 4, the electric field intensity at the tip of the cathode 2 is increased by several% as compared with the case where the height is made equal to the lower surface. With this effect, the amount of electron emission can be increased by 10% or more even under the same voltage application condition.

On the other hand, even if the cathode 2 is made higher than the upper surface of the extraction electrode 4, the effect of preventing charge and the effect of increasing the electric field strength can be similarly obtained. However, such a configuration introduces another problem with the process. For example, in a metal wiring etching process or the like, the cathode 2 is placed in a plasma atmosphere.
May be exposed. Under such an atmosphere,
When the cathode 2 is higher than the upper surface of the extraction electrode 4, the tip of the cathode 2 is strongly affected by the plasma due to the antenna effect. As a result, even if the tip is sharply processed by thermal oxidation, the shape of the tip may be deteriorated due to the influence of the subsequent plasma etching process, and as a result, the electron emission characteristics may be reduced. . In the device manufacturing process, there is a possibility that the device surface is always in physical contact in steps such as film formation, etching, and cleaning. In a configuration in which the sharpened structure protrudes to the uppermost surface, there is a danger of receiving physical contact damage associated with these processing operations. Therefore, it is desirable that the height of the cathode 2 be lower than the upper surface of the extraction electrode 4 from the viewpoint of process yield.

Note that, similarly to the above embodiment, the columnar portion 2a
In the case where the cathode 2 composed of the conical portion 2b having the upper surface of the columnar portion 2a as the bottom surface is used, the cathode 2 is made lower than the upper surface and higher than the lower surface of the extraction electrode 4 as shown in FIG. It is more effective if the upper surface of 2a (that is, the bottom surface of the conical portion 2b) is higher than the lower surface of the extraction electrode 4.

Embodiment 5 In this embodiment, by controlling the ratio of the thickness of the insulating layer to the thickness of the extraction electrode, the electric field intensity at the tip of the cathode is increased, and more effective electron emission is realized. An example will be described.

The ratio between the thickness t of the insulating layer 3 and the thickness T of the extraction electrode 4 shown in FIG. 8 is designed to satisfy the relationship of T> t. For example, the height of the cathode 2 is 650 nm,
Assuming that the thickness of the insulating layer 3 is 300 nm and the thickness of the extraction electrode 4 is 350 nm, the height of the cathode 2 which is a standard configuration is 650 nm, the thickness of the insulating layer 3 is 450 nm, and the thickness of the extraction electrode 4 is When the same voltage is applied to the extraction electrode 4, the electric field intensity is increased by about 7% as compared with the case where the height is set to 200 nm. This is because, by increasing the thickness of the extraction electrode 4, equipotential lines of electric force lines are more concentrated on the cathode 2 side, and as a result, the electric field concentration effect near the tip of the cathode 2 is enhanced. This effect increases as the thickness of the extraction electrode 4 increases, that is, as the thickness of the insulating layer 3 decreases. However, if the thickness of the insulating layer 3 is too small, a withstand voltage failure occurs, so an optimal device design is required according to the operating conditions. For example, it is effective to use an insulating layer made of a material having a high insulating property and a high dielectric constant as in the first embodiment.

When the insulating layer 3 has a multilayer structure, at least one of which is a silicon oxide film formed by a vapor deposition method, the diameter of the opening of the extraction electrode 3 can be reduced to increase the amount of electron emission. . As a feature of the process by the vapor deposition method, the film formed tends to spread and become larger as the deposition proceeds. As in the present embodiment, the thickness of the insulating layer 3 formed by the vapor deposition method is reduced and the thickness of the extraction electrode 4 is increased by that amount, whereby the spread of the film in the horizontal direction can be suppressed. The diameter of the opening can be reduced. Actually, when the upper layer of the insulating layer 3 was a silicon oxide film formed by a vacuum evaporation method in the above configuration, it was confirmed that even when the cathode 2 having the same height was used, the opening diameter was reduced by about 20%. When this is converted into the amount of electron emission under the same applied voltage condition, the amount of electron emission increases several times as compared with the conventional example.

Embodiment 6 In this embodiment, an example will be described in which the electron emission characteristics are improved using the relationship between the distance between the cathodes and the diameter of the opening of the extraction electrode. It is assumed that 1.5D ≦ P ≦ 2.5D in the interval between the cathodes 2 indicated by P in FIG. 9 and the diameter of the opening of the extraction electrode 4 indicated by D. When the upper surface of the cathode 2 and the extraction electrode 4 are at the same height and the opening diameter D is fixed and the relative distance P of the cathode 2 is changed, the electric field strength at the tip of the cathode 2 becomes as shown in FIG. That is, when the interval between the cathodes is smaller than 1.5 times the aperture diameter, the electric field intensity at the tip of the cathode 2 sharply decreases. This is because the electric field from the extraction electrode 4 penetrates into the tip of the cathode 2, and the electric field concentration effect on the tip of the cathode 2 is weakened by the surrounding cathode 2. When the distance between the cathodes is 1.5 times or more the aperture diameter, the electric field intensity shows a tendency to be substantially saturated, and does not depend on the distance between the cathodes. Since it is desired to reduce the interval between the cathodes and increase the degree of integration of the cathodes 2, it is desirable to reduce the interval between the cathodes while taking into account the effect of the electric field strength.

Increasing the distance between the cathodes means that the degree of integration of the cathodes decreases. When the degree of integration of the cathode decreases, for example, when the cathode is used as an electron gun of a cathode ray tube, it is necessary to increase the load per electron source in order to obtain the same brightness and definition. In order to cope with higher brightness and higher definition, the interval between the cathodes is set to 2.
The limit is five times. That is, by setting the distance between the cathodes to 1.5 to 2.5 times the opening diameter of the extraction electrode, the current density can be improved without lowering the field emission characteristics of the field emission type electron source device.

[0062]

According to the present invention, a high-intensity, high-definition image can be displayed, and a highly reliable field emission electron source device can be provided at low cost.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view showing a main part of a field emission type electron source device according to one embodiment of the present invention.

FIG. 2 is a schematic longitudinal sectional view showing each step of a process for forming the cathode.

FIG. 3 is a schematic longitudinal sectional view showing each step of a process of forming the insulating layer and a lead electrode.

FIG. 4 is a schematic longitudinal sectional view showing each step of a process of forming a surface coating layer on a negative electrode surface in another example of the present invention.

FIG. 5 is a longitudinal sectional view showing a main part of a field emission type electron source device according to still another embodiment of the present invention.

FIG. 6 is a longitudinal sectional view showing a main part of a field emission type electron source device according to still another embodiment of the present invention.

FIG. 7 is a longitudinal sectional view showing a main part of a field emission type electron source device according to still another embodiment of the present invention.

FIG. 8 is a longitudinal sectional view showing a main part of a field emission type electron source device according to still another embodiment of the present invention.

FIG. 9 is a longitudinal sectional view showing a main part of a field emission type electron source device according to still another embodiment of the present invention.

FIG. 10 is a characteristic diagram showing a relationship between a cathode interval and an intensity of an electric field formed at a cathode tip.

FIG. 11 is a longitudinal sectional view showing a main part of a conventional field emission type electron source device.

FIG. 12 is a longitudinal sectional view showing a main part of another conventional field emission electron source device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 101 Substrate 2, 102 Cathode 2a Column part 2b Conical part 3, 103 Insulating layer 3a First insulating layer 3b Second insulating layer 4, 104 Leader electrode 5, 8, 9, 10 Silicon oxide film 5a Silicon oxide Mask 6 Photoresist 6a Resist mask 7 Column 7a Drum 7b Column 11 Conductive film 12 Coating 12a, 12b Surface coating layer 13 Resist mask 106 Cathode projection group 201r, 201g, 201b Field emission type cathode group 203r, 203g, 203b Gate electrode

Continuing from the front page (72) Inventor Shogo Kanamaru 1-1-4 Umezono, Tsukuba, Ibaraki Pref., National Institute of Advanced Industrial Science and Technology (72) Inventor Takashi Matsukawa 1-4-1, Umezono, Tsukuba, Ibaraki Pref. (72) Inventor Masayoshi Nagao 1-1-4 Umezono, Tsukuba City, Ibaraki Pref.Industrial Technology Institute (Electrical Technology Research Institute) (72) Keisuke Koga 1006 Odakadoma, Kadoma City, Osaka Matsushita Electric F-term (reference) in Sangyo Co., Ltd. 5C031 DD17

Claims (31)

[Claims] A substrate, an insulating layer having a plurality of openings formed on the substrate, a lead electrode formed on the insulating layer, and a cathode provided in the opening on the substrate. The insulating layer is composed of a plurality of layers,
At least one of the plurality of layers has a relative dielectric constant different from that of the other layers. 2. A field emission type electron source device for a cathode ray tube according to claim 1, wherein said substrate is made of a single crystal of silicon. 3. The field emission electron source device for a cathode ray tube according to claim 2, wherein a lowermost layer of said insulating layer which is bonded to said substrate is made of a thermal oxide film of silicon. 4. The field emission electron source device for a cathode ray tube according to claim 3, wherein layers other than the lowermost layer in the insulating layer are made of a material having a higher dielectric constant than silicon oxide. 5. A field emission electron source device for a cathode ray tube according to claim 1, wherein at least one of said insulating layers is formed by a chemical vapor deposition method or a sputtering method. 6. At least one of the insulating layers is formed of S
i ₃ N ₄ , Ta ₂ O ₅ , SrTiO ₃ , SrBi ₂ Ta ₂ O ₉ ,
_{(Ba x Sr 1-x)} TiO 3 and _{Pb (Zr y Ti 1-y} )
A cathode ray tube for a field-emission electron source according to claim 1, wherein comprising a one selected from the group consisting of O _3. 7. The field emission electron source device for a cathode ray tube according to claim 1, wherein an uppermost layer of the insulating layer joined to the extraction electrode is formed by a plasma CVD method or a vacuum evaporation method. 8. The field emission type electron source device for a cathode ray tube according to claim 1, wherein the cathode has a substantially columnar shape having a sharp tip. 9. A substrate made of a single crystal of silicon, an insulating layer having a plurality of openings formed on the substrate, a lead electrode formed on the insulating layer, and provided in the opening on the substrate. For a cathode ray tube comprising a plurality of layers including a layer made of a silicon oxide film obtained by thermally oxidizing the substrate and a layer made of a material having a higher relative dielectric constant than silicon oxide. Field emission type electron source device. 10. The field emission type electron source device for a cathode ray tube according to claim 9, wherein said cathode has a substantially columnar shape having a sharp tip. 11. The cathode and the substrate are formed by processing the same material substrate, and the tip of the cathode is sharpened when the substrate is thermally oxidized. The field emission type electron source device for a cathode ray tube according to the above. 12. A substrate, comprising: an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer; and a cathode provided in the opening on the substrate. A field emission type electron source device for a cathode ray tube, wherein the surface of the cathode is provided with a coating made of a material different from the material constituting the cathode. 13. The field emission electron source device for a cathode ray tube according to claim 12, wherein the coating is made of a material having a work function of 4.8 eV or less. 14. The field emission type electron source device for a cathode ray tube according to claim 12, wherein said substrate is made of a single crystal of silicon, and said coating is made of a metal silicide. 15. The method according to claim 15, wherein the metal is molybdenum, nickel,
The field emission type electron source device for a cathode ray tube according to claim 14, which is one kind selected from the group consisting of chromium, platinum, tungsten, and cobalt. 16. The field emission electron source device for a cathode ray tube according to claim 12, wherein the thickness of the coating is 20 nm or less. 17. A semiconductor device comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer; and a cathode provided in the opening on the substrate. A field emission type electron source device for a cathode ray tube, wherein the extraction electrode has on its surface a coating made of a material different from the material constituting the extraction electrode. 18. The field emission electron source device for a cathode ray tube according to claim 17, wherein the extraction electrode contains silicon, and the coating is made of a metal silicide. 19. The metal according to claim 1, wherein the metal is one selected from the group consisting of molybdenum, tungsten, nickel, chromium, tantalum, tungsten and cobalt.
8. A field emission electron source device for a cathode ray tube according to claim 7. 20. The method according to claim 1, wherein the coating is made of an insulating material.
8. A field emission electron source device for a cathode ray tube according to claim 7. 21. A semiconductor device comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer; and a cathode provided in the opening on the substrate. A field emission type electron source device for a cathode ray tube, wherein the extraction electrode is thicker than the insulating layer. 22. A semiconductor device comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer; and a cathode provided in the opening on the substrate. The height of the cathode is larger than the thickness of the insulating layer and smaller than the sum of the thicknesses of the insulating layer and the extraction electrode. 23. The cathode comprises a columnar portion having one end surface joined to the substrate, and a conical portion having the other end surface of the columnar portion as a bottom surface, wherein the height of the columnar portion is equal to the insulation height. 23. The field emission type electron source device for a cathode ray tube according to claim 22, wherein the thickness is larger than the thickness of the layer. 24. A semiconductor device comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer; and a cathode provided in the opening on the substrate. A field emission type electron source device for a cathode ray tube, wherein an arrangement interval of the cathodes is 1.5 to 2.5 times a diameter of an opening of the extraction electrode. 25. A substrate made of a silicon single crystal, an insulating layer having a plurality of openings formed on the substrate, a lead electrode formed on the insulating layer, and provided in the opening on the substrate. A method of manufacturing a field emission type electron source device for a cathode ray tube having a cathode formed by etching a surface of a substrate to form a projection, and forming the peak by processing the projection by anisotropic etching. And etching the surface of the substrate to process the protrusion into a columnar shape; forming a silicon oxide film on the surface of the flat portion of the substrate and the surface of the protrusion by thermal oxidation; and A step of sharpening the apex; a step of forming an insulating film made of a material having a higher dielectric constant than silicon oxide on the silicon oxide; Removing the i-film and the insulating film to form the silicon oxide film and the insulating film into an insulating layer and processing the projections into a cathode. . 26. A substrate formed of a silicon single crystal, an insulating layer having a plurality of openings formed on the substrate, a lead electrode formed on the insulating layer, and provided in the opening on the substrate. A method of manufacturing a field emission electron source device for a cathode ray tube, comprising: a cathode formed by processing a surface of a substrate to form a protruding cathode; and an insulating film on a surface of the substrate on which the cathode is formed. Forming a resist film on a surface of the conductive film on the substrate except for a predetermined region including the cathode; and forming the resist film on the surface of the conductive film on the substrate by dry etching. An etch-back step of removing a part of the conductive film to form an opening of the extraction electrode; removing an insulating film formed in the region by wet etching to form a predetermined shape around the cathode; Method of manufacturing a cathode ray tube for a field emission electron source apparatus and a step of forming an insulating layer having a mouth portion. 27. A semiconductor device comprising: a substrate; an insulating layer having a plurality of openings formed on the substrate; a lead electrode formed on the insulating layer; and a cathode provided in the opening on the substrate. A method of manufacturing a field emission electron source device for a cathode ray tube, comprising: forming a coating made of a material different from a material constituting the cathode on a surface of a cathode formed on a substrate; and heat treating the coating. Reacting the material with the material of the cathode to convert the material into a compound with the material of the cathode; and manufacturing a field emission electron source device for a cathode ray tube. 28. The cathode ray tube according to claim 27, wherein, in the step of forming the coating, a coating made of the same material as the coating is formed on the surface of a lead electrode formed in advance on the substrate with an insulating layer interposed therebetween. A method for manufacturing a field emission type electron source device. 29. The method according to claim 27, wherein the film is formed by a vacuum deposition method. 30. The method according to claim 27, wherein the substrate is made of a single crystal of silicon. 31. The method of manufacturing a field emission electron source device for a cathode ray tube according to claim 27, wherein the heat treatment is performed in a vacuum, and the material in the film is converted into a silicide by the treatment.