JP2005310724A - Field emission type electron source and manufacturing method for it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a field emission type electron source and a manufacturing method for it using a high-quality diamond with a sharp tip as a negative electrode for easily controlling respective emitters and hardly causing the breakage of the insulation or separation of an insulation layer and reduced in leak current. <P>SOLUTION: This field emission type electron source 2a is provided with the negative electrode 1a having an electron emission part 1 containing diamond as a material and having a projecting shape, a gate electrode 4, the insulation layer 3 separating the negative electrode 1a and the gate electrode 4 from each other, and an anode electrode 5. An intermediate layer 6 is formed in at least a part of the area between the negative electrode 1a and the insulation layer 3. The intermediate layer 6 has a plurality of layers 6a and 6b. The electron emission part 1 is doped with one or more kinds of elements selected from a group composed of boron, nitrogen, phosphorus, sulfur, lithium, and silicon as an impurity. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a field emission electron source, and more particularly to a field emission electron source having a diamond cathode.

  Conventionally, thermionic emission is often used to extract an electron beam, but a field emission electron source is sometimes used because a large current density is obtained with low power consumption. As such an electron source, for example, there is a Spindt-type cold cathode as found in Non-Patent Document 1. In this electron source structure, an insulating layer is formed on a cathode, and an extraction electrode is formed thereon. A voltage is applied to the extraction electrode to cause electrons to be emitted from the electron emission portion. For example, as shown in FIG. 20, there is a structure in which a cathode 100, an insulating layer 101, and an extraction electrode (gate electrode) 102 are sequentially stacked (Patent Document 2).

  In this manufacturing method, for example, in the case of the above-mentioned document, an extraction electrode having an opening is formed in advance on a substrate by using photolithography or the like, and a projection-like Mo or the like that becomes an electron emission portion is formed later. . As can be seen in Non-Patent Document 2, the electron emission part may be formed by an ion beam. As seen in Non-Patent Document 3, silicon oxide and a lead electrode are formed on a Si substrate on which irregularities are formed, a photoresist is applied so that only the tip of the protrusion is exposed, and Si serving as an electron emission portion is exposed by etching. ing.

As materials for electron sources, refractory metals such as tungsten and molybdenum have been used conventionally. However, in order to obtain a high-density electron beam current at a low voltage, it is desirable to use a low work function material such as LaB _6. In recent years, new materials have been developed, and diamond cathodes are attracting attention together with carbon nanotubes having a sharp structure with a high aspect ratio. Diamond, in particular, has unique properties such as negative electron affinity, chemical stability, and high thermal conductivity, and is considered promising among electron source materials.
Japanese Patent Laid-Open No. WO98 / 44529 JP-A-7-272618 Journal of Applied Physics 47 (1976) 5248 IEICE Technical Report Vol.103, No. 497 (2003) p.11 Japanese Journal of Applied Physics Vol.31, No.7B, L883 (1995) Applied Surface Science 146 (1999) 328 J. Vac. Sci. Technol. B, 14 (3), 1996, p1986-1989

  However, the carbon-based material has a problem of poor adhesion with an oxide generally used as an insulating layer. In particular, when the electron source is operated at a high current density and becomes a temperature environment of several hundred degrees or more, partial desorption starts in the form of CO molecules from the surface of the carbon-based material, and peeling of the oxide insulating layer is promoted. . Even when fluoride or the like is used as the insulating layer, the adhesion between the carbon-based material and the insulating layer is still not good.

  In addition, unlike the thermionic emission cathode, the field emission type cold cathode does not require heating, but heat is generated by the emitted high current density electrons. Therefore, due to the temperature change of the cold cathode due to heat generation, a stress having a magnitude corresponding to the difference in thermal expansion coefficient is applied between the cathode and the insulating layer. In fact, the temperature of the cold cathode can reach several hundred degrees or more. Particularly in recent years, the heat generation density has been increasing more and more with the miniaturization of the cold cathode. Therefore, there is a problem that peeling occurs between the cathode and the insulating layer depending on whether the adhesion between the cathode and the insulating layer is good or not, and the difference in thermal expansion coefficient between the two companies.

  Moreover, it has been difficult to apply the method of manufacturing a field emission electron source to a diamond cathode. For example, as disclosed in Non-Patent Document 4, when diamond grains are formed in the opening of the extraction electrode formed in advance, only diamond particles can be formed, and it is difficult to form diamonds having sharp tips. . In addition, since the crystal plane orientation is not determined in the form of particles, it is difficult to control doping. Further, in this method, when diamond is formed by using the microwave plasma CVD method, an eddy current is generated in the extraction electrode and the electrode is peeled off by heating, so that the microwave plasma CVD method cannot be used. Therefore, diamond is formed by the filament method, and it is difficult to form high-quality diamond.

  On the other hand, for example, Patent Document 2 discloses a method of forming an electrode in the vicinity of a tip on a diamond on which a protrusion shape has been formed. In this document, after depositing an insulating material and an electrode material on a boron-doped polycrystalline diamond protrusion, a resist is applied, and the electrode and the insulating material around the protrusion are removed by etching from the thin protrusion tip of the resist. Thus, an electrode is formed in the vicinity of the protrusion. However, in this method, the thickness of the insulating material is directly the distance between the tip of the protrusion and the electrode, and it is necessary to reduce the thickness of the insulating material in order to reduce the distance. However, if the film thickness is reduced, there is a problem that dielectric breakdown is likely to occur and the leakage current increases. Further, in this document, since the entire diamond is conductive, it is impossible to control individual emitters. Polycrystalline diamond has poor crystallinity and poor electrical characteristics, so it has been difficult to improve electrical emission characteristics.

  The present invention has been made to solve the above problems. That is, the present invention uses a high-quality diamond having a sharp tip as a cathode, can easily control individual emitters, does not easily cause dielectric breakdown or peeling of the insulating layer, and has a low leakage current, and its manufacture It aims to provide a method.

  In order to solve the above problems, a field emission electron source according to the present invention includes a cathode having a projecting electron emission portion containing diamond as a material, a gate electrode, an insulating layer separating the cathode and the gate electrode, and an anode electrode A field emission electron source comprising: an intermediate layer provided at least in part between the cathode and the insulating layer, the intermediate layer comprising a transition metal of group IVa to VIa or a carbide of silicon A group consisting of a carbide layer and a nitride layer made of a transition metal of group IVa to VIa, a nitride of aluminum or silicon, and the electron emission part is made of boron, nitrogen, phosphorus, sulfur, lithium and silicon One or more elements selected from the above are doped as impurities.

  The field emission electron source of the present invention is an electric field including a cathode having a projecting electron emission portion containing diamond as a material, a gate electrode, an insulating layer separating the cathode and the gate electrode, and an anode electrode. A radiation electron source comprising an intermediate layer provided at least in part between a cathode and an insulating layer, wherein the intermediate layer is at least one transition metal of zirconium, hafnium, vanadium, niobium, tantalum and chromium The electron emission portion is doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium, and silicon as impurities.

  In a field emission electron source having such a configuration, individual emitters can be easily controlled using high-quality diamond having a sharp tip as a cathode, dielectric breakdown and peeling of the insulating layer are unlikely to occur, and leakage current is small.

  As described above, the adhesion between the carbon-based material and the insulating layer is not good, but the IVa-VIa group transition metal or silicon layer, the carbide layer, and the nitride layer have good adhesion with the carbon-based material. . In particular, IVa to VIa group transition metals are chemically active and therefore have good adhesion to carbon-based materials, and IVa to VIa group transition metal carbides have better adhesion to carbon-based materials. Therefore, the adhesiveness between the above-described intermediate layer and the insulating layer is good, and peeling is hardly generated between the cathode and the insulating layer by inserting this intermediate layer. Moreover, the thermal conductivity of diamond, which is the material of the electron emission portion, is higher than that of other materials. Therefore, even if the field emission type electron source generates heat during operation, heat is efficiently radiated from the electron emission portion, so that peeling due to generation of thermal stress can be prevented.

  Examples of the IVa to VIa group transition metals include titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten. The transition metal of group IVa to VIa preferably has a high melting point. For example, Zr, Hf or Va, VIa group is more preferable in Ti group than Ti. However, Mo and W have properties such that when oxidized, the vapor pressure becomes high and becomes brittle, even in the VIa group, the Cr, Va, and IVa groups are more preferable.

  The intermediate layer preferably further includes a metal oxide layer on the insulating layer side, and the insulating layer preferably includes an oxide as a material. The intermediate layer preferably includes a nitride layer, and the insulating layer preferably includes nitride as a material. The intermediate layer preferably further includes a metal fluoride layer on the insulating layer side, and the insulating layer preferably includes fluoride as a material.

  In these cases, since the insulating layer and the intermediate layer contain the same element, the adhesion between the intermediate layer and the insulating layer is also improved. Moreover, when an intermediate | middle layer is two or more layers, it is preferable from the viewpoint of improving adhesiveness that the several layer which comprises an intermediate | middle layer contains the same transition metal or silicon | silicone. For example, when the insulating layer is made of an oxide, the intermediate layer is preferably made of a tantalum carbide layer and a tantalum oxide layer provided on the tantalum carbide layer.

  Further, it is preferable that the intermediate layer is in ohmic contact with the electron emission portion and functions as a wiring. Furthermore, it is preferable that the intermediate layer is separated into a wiring portion that is in ohmic contact with the electron emission portion and an adhesive portion that is not directly connected to the electron emission portion.

  Many of the intermediate layers have conductivity, and can be used as wiring, but cannot be electrically separated. In the XY wiring and the like used in the conventional FED, only the wiring has been installed between the substrate and the insulating layer. However, in the present invention, for example, from the viewpoint of further improving the adhesiveness, an adhesive portion that is arranged separately from the wiring portion and improves the adhesiveness with the insulating layer is provided. Since the intermediate layer is patterned in this manner, the area of the adhesion portion can be increased while allowing individual control of each electron emission portion, and adhesion can be maintained even if severe heat generation occurs. . In order to obtain better ohmic contact, the electron emission portion may be graphitized by implanting argon ions into the surface of the electron emission portion made of diamond.

  When these intermediate layers are not used as wiring, the thickness of the metal layer is desirably 10 nm or less. Even if the thickness is 10 nm or less, it is sufficient to increase the adhesion between the layers, and the insulating layer can be made thicker, so that good insulation can be maintained between the cathode and the gate electrode.

  Moreover, it is preferable that the thermal expansion coefficient of at least one layer constituting the intermediate layer is a value between the thermal expansion coefficients of the cathode and the insulating layer.

  Thereby, the difference in thermal expansion coefficient between the insulating layer and the intermediate layer and between the cathode and the intermediate layer is smaller than the difference in thermal expansion coefficient between the insulating layer and the cathode. Therefore, the stress applied with the temperature change of the field emission electron source is relaxed compared to the case where the insulating layer is provided directly on the cathode. For this reason, peeling is less likely to occur compared to a field emission electron source having no intermediate layer.

  The metal oxide layer is made of titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, scandium oxide, yttrium oxide, lanthanum oxide, zinc oxide, or aluminum oxide. It is preferable to consist of either.

  The nitride layer is preferably made of any one of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, molybdenum nitride, tungsten nitride, aluminum nitride, or silicon nitride.

  The insulating layer is made of any of silicon oxide, aluminum oxide, magnesium oxide, silicon nitride, silicon oxynitride, aluminum nitride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, or aluminum fluoride. It is preferable.

  Moreover, it is preferable that at least a part of the surface of the intermediate layer is made of a conductive material that does not dissolve in hydrofluoric acid.

  In this case, the intermediate layer can be prevented from being corroded by hydrofluoric acid. Specifically, for example, the surface of the intermediate layer is preferably covered with gold, platinum, molybdenum, silicon, or the like.

  For example, the intermediate layer in the case of making an ohmic contact is made of, for example, titanium or the like, depending on the type of impurities of diamond. Since titanium and the like are corroded by hydrofluoric acid, it is difficult to produce a field emission electron source.

  In addition, the intermediate layer has a wiring portion in ohmic contact with the electron emission portion, and at least a part of the wiring portion exposed from the insulating layer and electrically connecting the cathode and the outside is chemically stable. It is preferable that the metal film is covered.

  The chemically stable metal film is made of, for example, gold, platinum, molybdenum having a high melting point, tungsten, or the like. Further, the chemically stable metal film may be a laminate of Au / Pt, Au / Mo, Au / Ni, or the like.

  Moreover, the transition metal selected for the intermediate layer is generally susceptible to corrosion. However, regardless of the adhesion to the insulating layer, the portion that electrically connects the cathode and the outside does not need to be made of the same material as the intermediate layer. Considering the manufacturing process, if a stable metal film serving as a protective film is coated on the intermediate layer, it is possible to provide a field emission electron source that operates stably even for repeated use for a long time.

  The field emission electron source preferably further includes another insulating layer provided on the gate electrode and a focusing electrode provided on the other insulating layer.

  By this focusing electrode, the electrons emitted from the tip of the projection of the electron emitting portion proceed with good straightness without divergence.

  Moreover, it is preferable that an electron emission part contains a single crystal diamond as a material. In addition, the electron emission portion includes doping diamond formed by vapor phase synthesis on the substrate constituting the cathode as a material, and the substrate is synthesized by single crystal diamond synthesized at high temperature and high pressure or by vapor phase synthesis. It is preferable to contain non-doped diamond as a material.

  Here, the material of the substrate is not particularly limited and may be other than diamond, but is preferably Si or diamond. When the substrate material is diamond, the material may be polycrystalline diamond, but single crystal diamond is preferable from the viewpoints of doping control, crystal defects, electron emission characteristics, and the like. In particular, the material of the electron emission portion is preferably single crystal diamond. In this way, a well-doped diamond surface with few crystal defects can be obtained, so that a high-quality field emission electron source with a low voltage and a high current density can be obtained.

  Further, it is preferable that the condition of d <z and d <h is satisfied, where z is the height of the electron emission portion, d is the distance between the tip of the electron emission portion and the gate electrode, and h is the thickness of the insulating layer. Furthermore, it is preferable that z, d, and h satisfy the conditions of d <z / 2 and d <h / 2.

  The field emission electron source manufacturing method of the present invention is a method for manufacturing a field emission electron source including a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, and an anode electrode. A step of preparing a substrate, a step of forming a doped diamond doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities on the substrate; and etching A step of forming an electron emission portion from at least doping diamond, a step of forming an insulating layer on the cathode, a step of forming a gate electrode on the insulating layer, and a step of applying a resist on the gate electrode And a step of removing the gate electrode and the insulating layer around the electron emission portion by etching.

  The field emission electron source manufacturing method of the present invention is a method for manufacturing a field emission electron source including a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, and an anode electrode. A step of preparing a substrate, a step of forming a doped diamond doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities on the substrate; and etching A step of forming an electron emission portion from at least doped diamond, and a layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium on the substrate, a transition metal of group IVa to VIa Or a carbide layer made of silicon carbide, and transition metals of groups IVa to VIa, aluminum A step of forming an intermediate layer including at least one nitride layer of nitride of silicon or silicon, a step of forming an insulating layer on the cathode, a step of forming a gate electrode on the insulating layer, and a gate The method includes a step of applying a resist on the electrode and a step of removing the gate electrode and the insulating layer around the electron emission portion by etching.

  The field emission electron source manufacturing method of the present invention is a method for manufacturing a field emission electron source including a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, and an anode electrode. A step of preparing a substrate, a step of forming a doped diamond doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities on the substrate; and etching A step of forming an electron emission portion from at least doped diamond, and a layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium on the substrate, a transition metal of group IVa to VIa Or a carbide layer made of silicon carbide, and transition metals of groups IVa to VIa, aluminum A step of forming an intermediate layer including at least one nitride layer of nitride of silicon or silicon, a step of forming an insulating layer on the cathode, a step of forming a gate electrode on the insulating layer, and a gate Forming a separate insulating layer on the electrode, forming a focusing electrode on the other insulating layer, applying a resist on the focusing electrode, and focusing around the electron emission region by etching; Removing the electrode, the gate electrode, the insulating layer and another insulating layer.

  In the step of forming the intermediate layer, it is preferable to heat the metal film during or after the metal film is deposited on the substrate to form a metal carbide layer at the interface between the substrate and the metal film.

  In addition, in the step of forming the insulating layer, a series of steps of forming the insulating layer, applying a resist on the insulating layer, and removing the insulating layer around the electron emitting portion is performed a plurality of times, thereby increasing the height of the electron emitting portion. It is preferable that the insulating layer be formed so as to satisfy the conditions d <z and d <h, where z is the distance between the tip of the electron emission portion and the gate electrode and d is the thickness of the insulating layer.

  In the step of forming the insulating layer, it is preferable that the thickness of the insulating layer formed last is the maximum.

  The substrate is preferably a diamond substrate.

  Moreover, it is preferable that the substrate is a diamond substrate and includes a step of forming a protrusion shape on the diamond substrate by etching before the step of forming the doped diamond.

  Moreover, it is preferable that the substrate is a diamond substrate, and after forming the projection shape, an electron emission portion made of doped diamond is formed, and the subsequent projection shape forming step is not included.

  According to the present invention, an insulating layer and an electrode layer can be formed on diamond having excellent properties as an electron emission material, and high adhesion between the insulating layer and the cathode can be maintained even in high output operation. The gate electrode can be formed near the tip of the emitter with a longer life than the conventional diamond electron-emitting device, and excellent electron emission characteristics can be obtained.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

(First embodiment)
A first embodiment of the present invention will be described in connection with a manufacturing method. As shown in FIG. 4, first, a substrate 2 is prepared, and a doped diamond 1 doped with one or more elements selected from the group of boron, nitrogen, phosphorus, sulfur, lithium, and silicon as impurities is formed on the substrate 2. Form. On the doped diamond, for example, Al is deposited as a mask material, and a dot-like Al mask is formed by photolithography. Then, the doping diamond is etched by the RIE method, and at least the doping diamond 1 is formed into a protruding shape as shown in FIG. Thereafter, in order to change the surface termination of the projection-shaped diamond, surface hydrogenation treatment by microwave plasma or surface oxygenation treatment by atmospheric annealing may be performed.

  Next, as shown in FIG. 4B, silicon oxide is formed as the insulating layer 3, and the gate electrode 4 is formed on the insulating layer. A resist 20 is applied on the gate electrode (FIG. 4C). By optimizing the resist coating conditions, the resist immediately above the protrusion tip of the protrusion-shaped diamond is thinned, and the gate electrode and the insulating layer of the protrusion-shaped diamond portion are removed by etching (FIG. 4D). Thereafter, the resist is removed (FIG. 4E). Etching of the electrode and the insulating layer is preferably performed with hydrofluoric acid instead of dry etching. This is because diamond is chemically stable, and thus the sharpness of the tip of the diamond protrusion may be impaired by dry etching.

  With such a manufacturing method, as shown in FIG. 1, it is possible to obtain an electron source capable of controlling the electron emission by simply attaching the gate electrode 4 to the conductive diamond 1. Alternatively, in the middle of the method, at least the doped diamond is formed into a protruding shape by etching, and then an intermediate layer (the intermediate layer may be used as a cathode electrode) is formed on the substrate, and a resist is applied to the intermediate layer If a step of exposing at least the protrusion tip of the protrusion-shaped diamond is inserted, as shown in FIG. 2, the protrusion-shaped diamond electron emission portion 1 (the electron emission portion constitutes a cathode) and the electron emission portion 1 is a field emission electron source having an intermediate layer 6 formed between the protrusions except on the protrusion tips and on the protrusion side surfaces, the anode electrode 5 and the gate electrode 4 and insulatively separating the cathode and the gate electrode. Layer 3 is made of silicon oxide, and the electron emission portion is one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium, and silicon. It is possible to obtain a field emission electron source which is doped diamond as an impurity.

  By forming the intermediate layer in this way, carriers can be imparted to high-resistance diamond such as single phosphorus-doped or nitrogen-doped, and electron emission characteristics can be improved. This intermediate layer is preferably made of a conductive material whose surface is not soluble in hydrofluoric acid. In that case, even if the silicon oxide of the insulating layer is removed with hydrofluoric acid, the intermediate layer does not corrode. Since the vicinity of the protruding portion and the gate electrode is a three-dimensional shape and complicated, dry etching with too high vertical workability is rather not suitable, and wet etching such as hydrofluoric acid is desirable.

  The intermediate layer capable of making ohmic contact includes titanium and aluminum, although it depends on the impurities of diamond. Titanium, aluminum, and the like are corroded by hydrofluoric acid, so that gold, platinum, molybdenum, amorphous silicon, or the like can be stacked thereon. In order to obtain a better ohmic contact, the diamond surface may be graphitized by argon ion implantation or the like.

  Further, in the course of the manufacturing process, after applying a resist to expose at least the protrusion tip of the protrusion-shaped diamond from the intermediate layer, silicon oxide is formed as the first insulating layer 3, and the first insulating layer A gate electrode is formed thereon, silicon oxide is formed as a second insulating layer 7 on the gate electrode, a focusing electrode is formed on the second insulating layer, and a resist is applied on the focusing electrode. If the focusing electrode, the gate electrode, and the first and second insulating layers of the protruding diamond portion are removed by etching, the protruding electron emitting portion 1 and the electron emitting portion 1 are in ohmic contact as shown in FIG. A field emission type electron source including the intermediate layer 6 formed between the protrusions excluding the protrusion tips and on the protrusion side surfaces, the anode electrode 5, the gate electrode 4, and the focusing electrode 8 can be obtained. Electrons emitted from the projection tip of the electron emission portion by the focusing electrode proceed with good straightness without divergence.

  Here, the substrate is not particularly specified and may be other than diamond, but the substrate is preferably Si or diamond. In the case of a diamond substrate, polycrystal may be used, but single crystal diamond is preferable from the viewpoint of doping control, crystal defects, electron emission characteristics, and the like. In particular, the diamond protrusion is preferably a single crystal.

  Further, as shown in FIG. 5, if a projection 10 is formed on the diamond substrate 2 by etching and then a doped diamond 11 is grown, and after the etching of the doped diamond, the same steps as above are taken, as shown in FIG. Since the diamond 11 can be doped only in the vicinity of the tip of the diamond projection 10, the intermediate layer can control the electron emission of each emitter.

  Further, as shown in FIG. 6, after forming a projection 10 having a sharp tip by etching on the diamond substrate 2, a doping diamond 11 may be grown to create a pyramidal projection, for example. Thereby, it is possible to obtain a diamond emitter with better sharpness and less crystal defects on the surface as compared with etching. In this case, the protrusion shape forming step by etching of the doping diamond can be omitted.

  In this embodiment, the step of forming the insulating layer includes (1) film formation of the insulating layer, (2) application of the resist, and (3) a series of steps of removing the insulating layer of the protruding diamond portion. The insulating layer may be formed repeatedly. As shown in FIG. 7, when the insulating layer 3 is formed up to the same height as the protrusion-shaped diamond 1 at one time, when the insulating layer is etched, the protrusion-shaped electron emission portion is formed along with the vertical direction. The insulating layer is etched and spread in the lateral direction around the (emitter) by the same thickness, which leads to an increase in the diameter of the gate electrode. However, as shown in FIG. 8, the insulating layer 3 is not formed to the height of the protrusion-shaped diamond 1 at a time, but the insulating layer 3 is formed thinner than that, and the insulation around the emitter is formed each time the insulating layer is formed. By etching away the layer, the insulating film thickness can be increased while keeping the distance from the emitter to the edge of the insulating layer short. For example, in a simple calculation, when the insulating layer is formed in two steps, the distance between the tip of the emitter and the gate electrode is ½ that in the case where the insulating layer is formed once.

  In such a method, when the height of the projection of the electron emission portion is z, the distance between the tip of the projection and the gate electrode is d, and the thickness of the insulating layer between the diamond and the gate electrode is h, d <z and d < h, and the distance between the emitter and the gate electrode can be shortened while keeping the leakage current and withstand voltage high by increasing the thickness of the insulating layer as compared with the conventional electrode formation technology, thereby controlling the electron emission. The voltage can be kept low. Desirably, d <z / 2 and d <h / 2 in the electron source of this embodiment.

  In the step of performing the insulating layer a plurality of times, it is preferable that the last formed insulating film has the maximum thickness. This is because in the case where the insulating layer is formed a plurality of times, if all the film thicknesses are made constant, the recessed portion around the emitter is not filled, and the shape of the final gate electrode is deteriorated. By making the last insulating layer the thickest, the recess is completely filled, so that a gate electrode having a smooth edge can be formed.

  The diamond of this embodiment can be arbitrarily doped. Boron dope has a negative electron affinity on the hydrogen-terminated surface and provides excellent electron emission characteristics. Further, by performing n-type doping such as phosphorus and sulfur, electron emission of carriers is high and electron emission barrier is also small, so that more excellent electron emission is known. In the case of n-type diamond, there is a problem that carriers are compensated for at the p-type hydrogen termination, and therefore oxygen termination may be used. These may use a single impurity or may be doped at the same time. Arbitrary forms such as CVD and ion implantation can be used as the form of doping.

  The resist material used for etching the electrode and the insulating layer may be a material used in normal photolithography. At this time, exposure and development processes may be added after resist application to pattern electrodes such as gates.

  Desirably, the diamond is a single crystal. In the case of a single crystal, particularly when doping is performed by CVD, the amount of impurities mixed in can be controlled with high accuracy. On the other hand, the electron source may be made of polycrystalline diamond. Polycrystalline diamond makes it easier to obtain a sample with a larger area than single-crystal diamond, and boron-doped wafers have excellent conductivity. Further, the orientation can be controlled even in a polycrystal, and various cathodes can be used, for example, a phosphorous doped diamond is partially epitaxially grown on a (111) oriented polycrystal diamond.

(Example 1)
Boron-doped diamond was formed on a high-pressure synthetic Ib (100) single crystal diamond substrate using microwave plasma CVD. Hydrogen (H ₂ ) flow rate 200 sccm, methane / hydrogen (CH ₄ / H ₂ ) concentration 6.0%, diborane / methane (B ₂ H ₆ / CH ₄ ) concentration 167 ppm, pressure 5.3 kPa, substrate temperature 830 ° C. The film thickness was 5 μm. Next, an aluminum (Al) film was formed on the boron-doped diamond by sputtering, and dots having a diameter of 3 μm were formed by photolithography. This was etched by the RIE method to form a diamond having a protrusion shape. The reaction conditions were an oxygen flow rate of 50 sccm, a CF ₄ / O ₂ concentration of 2%, a pressure of 2 Pa, and an RF power of 250 W. The height of the formed protrusion is 3 μm. Next, a silicon oxide film having a thickness of 3 μm is formed by sputtering, and a Mo film having a thickness of 0.2 μm is formed thereon. A resist with a viscosity of 30 cp is spin-coated at 4000 rpm for 30 seconds, and Mo and silicon oxide around the protrusion are etched with aqua regia and buffered hydrofluoric acid from the tip of the protrusion where the resist becomes thin. The electrode thus formed was formed at a distance of 3.0 μm from the tip of the protrusion.

(Example 2)
Next, the same process as in Example 1 was performed until a protrusion having a height of 3 μm was formed by RIE, and then a silicon oxide having a thickness of 1.5 μm was formed by sputtering. A resist was spin-coated on this, and silicon oxide around the protrusions was removed by etching with buffered hydrofluoric acid. After removing the resist with an organic solvent, a second silicon oxide film having a thickness of 1.5 μm was formed, and an Mo film having a thickness of 0.2 μm was formed as an electrode. A resist was spin-coated on this, and Mo and silicon oxide at the tip of the protrusions where the resist became thin with aqua regia and buffered hydrofluoric acid were etched. As a result, the height z = 3 μm and the silicon oxide film thickness h = 3 μm and d = 3 μm in Example 1 are the same as z and h, but the gate is at a distance d = 1.5 μm where d is half. An electrode could be formed.

(Example 3)
In the same manner as in Example 1, after 2.5 μm of boron-doped diamond was formed by microwave plasma CVD and an emitter having a height of 3 μm was formed by RIE, Nb was 0.05 μm by sputtering as an intermediate layer on the emitter. A film was formed. This was spin-coated with a resist, and Nb at the tip of the emitter was removed with buffered hydrofluoric acid. Next, Pt was sputtered to 0.1 μm thereon, and similarly, a resist was spin-coated and Pt at the tip of the protrusion was removed with aqua regia to complete the intermediate layer. Next, 1 μm of a first silicon oxide was formed, a resist was spin-coated, and the silicon oxide around the protrusions was removed with buffered hydrofluoric acid. Next, after forming 1 μm of second silicon oxide, it was removed in the same manner, and further 1.5 μm of third silicon oxide was formed, and 0.1 μm of Mo was formed as a gate electrode. A resist was spin-coated thereon, and Mo and silicon oxide around the protrusions were removed with aqua regia and buffered hydrofluoric acid. According to the method of the present embodiment, a gate electrode that allows an electron emission by concentrating an electric field in the vicinity of the protrusion can be formed. Further, in Example 2, as shown in FIG. 9, there was a case where the edge of the gate electrode was distorted in a part of the gate electrode, because the depression around the emitter was not filled, but in this example, As shown in FIG. 10, all the gate electrodes had smooth edges.

Example 4
In the same manner as in Example 1, after 2.5 μm of boron-doped diamond was formed by microwave plasma CVD and an emitter having a height of 3 μm was formed by RIE, Ta was 0.05 μm by sputtering as an intermediate layer on the emitter. A film was formed. This was spin-coated with a resist, and Ta at the tip of the emitter was removed with buffered hydrofluoric acid. Next, Pt was formed thereon by sputtering with 0.1 μm, and similarly, a resist was spin-coated and Pt at the tip of the protrusion was removed with aqua regia to complete the intermediate layer. Next, 1 μm of a first silicon oxide was formed, a resist was spin-coated, and the silicon oxide around the protrusions was removed with buffered hydrofluoric acid. Next, 1 μm of second silicon oxide was formed, and then 0.1 μm of Mo was formed as a gate electrode. Further, 3 μm of third silicon oxide was formed, and 0.1 μm of Mo was formed as a focusing electrode. A resist was spin-coated thereon, and Mo and silicon oxide around the protrusions were removed alternately with aqua regia and buffered hydrofluoric acid. According to the method of the present embodiment, a gate electrode that emits electrons by concentrating the electric field in the vicinity of the protrusion and a focusing electrode that converges the emitted electrons can be formed, and an electron source with improved electron extraction efficiency can be obtained. I was able to.

(Example 5)
An Al film was formed by sputtering on a high-pressure synthetic Ib (100) single crystal diamond substrate, and dots having a diameter of 3 μm were formed by photolithography. This was etched by the RIE method to form a diamond having a protrusion shape. The reaction conditions were an oxygen flow rate of 50 sccm, a CF ₄ / O ₂ concentration of 2%, a pressure of 2 Pa, and an RF power of 250 W. The height of the formed protrusion is 3 μm. Next, phosphorus-doped diamond is formed using microwave plasma CVD. H ₂ flow rate is 200 sccm, CH ₄ / H ₂ concentration is 0.05%, PH ₃ / CH ₄ concentration is 10,000 ppm, pressure is 13.3 kPa, substrate temperature is 870 ° C., film thickness is 5 μm, and the side is surrounded by (111) plane A pyramidal protrusion was formed.

  Next, after forming an intermediate layer in the same manner as in Example 3, silicon oxide is divided into 1.5 μm portions each twice in the same manner as in Example 2 to form a total film thickness of 3 μm, and Mo is formed in a thickness of 0.2 μm. A resist with a viscosity of 30 cp is spin-coated at 4000 rpm for 30 seconds, and Mo and silicon oxide around the protrusion are etched with aqua regia and buffered hydrofluoric acid from the tip of the protrusion where the resist becomes thin. The electrode thus formed was formed at a distance of 1.5 μm from the tip of the protrusion.

  As described above, the insulating layer / electrode layer can be formed on diamond having excellent properties as an electron emission material by the method of the present embodiment, and closer to the emitter tip than the conventionally produced diamond electron emission element. A gate electrode can be formed, and excellent electron emission characteristics can be obtained. Such a field emission type electron source can improve the performance of microwave tubes such as traveling wave tubes and klystrons, high-frequency amplification elements, electron beam equipment such as SEMs and electron beam exposure machines, and light-emitting elements such as FEDs. it can.

  Further, the field emission electron source of the invention including this embodiment includes a projection-shaped electron emission portion, an intermediate layer formed between the projections and on the projection side surface except for the projection tip by ohmic contact with the electron emission portion, and an anode A field emission electron source having an electrode and a gate electrode, having an insulating layer separating the cathode and the gate electrode, and an electron emission portion selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon It is characterized by being doped with one or more elements as impurities.

  In addition, a field emission electron source according to another aspect of the invention including the present embodiment is formed on a protrusion-protruding electron emission portion, between the protrusions except for the protrusion tip, and on the protrusion side surfaces in ohmic contact with the electron emission portion. A field emission electron source having an intermediate layer, an anode electrode, a gate electrode, and a focusing electrode, and having an insulating layer separating the cathode and the gate electrode, and the electron emission portion is made of boron, nitrogen, phosphorus And doped with one or more elements selected from the group consisting of sulfur, lithium and silicon as impurities.

  It is preferable that at least the surface of the intermediate layer is made of a conductive material that does not dissolve in hydrofluoric acid. The electron emission part is preferably a single crystal, and the electron emission part is more preferably doped diamond formed on a substrate by a vapor phase synthesis method. The substrate is preferably single crystal diamond synthesized at high temperature and high pressure or non-doped diamond synthesized by a vapor phase synthesis method.

  Furthermore, d <z and d <h, where z is the height of the electron emission portion, d is the distance between the tip of the projection of the electron emission portion and the gate electrode, and h is the thickness of the silicon oxide that is the insulating layer. And z, d and h are more preferably d <z / 2 and d <h / 2.

  A method for manufacturing a field emission electron source according to the invention including the present embodiment is a method for manufacturing a field emission electron source including a protruding electron emission portion, an anode electrode, and a gate electrode. A step of forming a doped diamond doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon on the substrate, and at least a doped diamond by etching. A step of forming a protrusion shape, a step of forming an insulating layer, a step of forming a gate electrode on the insulating layer, a step of applying a resist on the gate electrode, and a gate electrode of a diamond portion having a protrusion shape by etching And a step of removing the insulating layer.

  Alternatively, it is a field emission electron source including a protrusion-shaped electron emission portion, an intermediate layer formed between the protrusion and the protrusion side surface except for the protrusion tip by ohmic contact with the electron emission portion, an anode electrode, and a gate electrode. A step of preparing a substrate, a step of forming a doped diamond doped with one or more elements selected from the group of boron, nitrogen, phosphorus, sulfur, lithium, and silicon as impurities on the substrate, and at least by etching A step of forming a doped diamond into a protrusion shape, a step of forming an intermediate layer on the substrate, a step of forming silicon oxide as an insulating layer, a step of forming a gate electrode on the insulating layer, A step of applying a resist to the substrate, and a step of removing the gate electrode and the insulating layer of the diamond-shaped protrusion by etching. A method of manufacturing a field emission electron source comprising.

  Alternatively, a field emission type including a projection-shaped electron emission portion, an intermediate layer formed between the projection and the side surface of the projection except for the tip of the projection by ohmic contact with the electron emission portion, an anode electrode, a gate electrode, and a focusing electrode An electron source, a step of preparing a substrate, and a step of forming a doped diamond doped with one or more elements selected from the group of boron, nitrogen, phosphorus, sulfur, lithium, and silicon as impurities on the substrate; A step of forming at least doping diamond by etching, a step of forming an intermediate layer on the substrate, a step of forming a first insulating layer, a step of forming a gate electrode on the insulating layer, Forming a second insulating layer on the gate electrode; forming a focusing electrode on the second insulating layer; and applying a resist on the focusing electrode That process and a method of manufacturing a field emission electron source comprising a step of removing the focusing electrode and the gate electrode and the first diamond portion of the projection shape by etching the second insulating layer.

  The substrate is preferably a diamond substrate, and the substrate is a diamond substrate, and preferably includes a step of forming a protrusion shape on the diamond substrate by etching before the step of forming the doped diamond. Further, it is preferable that the substrate is a diamond substrate, and after forming the protrusion shape, doping diamond is formed and the subsequent protrusion shape forming step is not included.

  In addition, it is preferable that the step of forming the insulating layer is performed a plurality of times as a series of steps of forming the insulating layer, applying a resist on the insulating layer, and removing the insulating layer of the protruding diamond portion. Furthermore, in the step of performing the insulating layer a plurality of times, it is preferable that the last formed insulating layer has a maximum thickness.

  Further, the step of forming the intermediate layer may include a step of applying a resist to expose at least the protrusion tip of the protrusion-shaped diamond from the intermediate layer. At this time, exposure may be performed to pattern the intermediate layer.

  According to the invention including the present embodiment described above, an insulating layer and an electrode layer can be formed on diamond having excellent properties as an electron emitting material, and the emitter tip can be formed more than a conventionally produced diamond electron emitting device. A gate electrode can be formed in the vicinity, and excellent electron emission characteristics can be obtained.

(Second Embodiment)
Hereinafter, preferred embodiments of a field emission cold cathode and a method for manufacturing the same will be described in detail with reference to the drawings.

  FIG. 11 is a cross-sectional view showing an embodiment of a field emission cold cathode. The field emission cold cathode 301 is of the Spindt type, and includes a cathode 310 (the cathode 310 may be used as a cathode electrode), a metal carbide layer 311, an insulating layer 15, and a gate electrode 16.

  The cathode 310 is made of a material whose main component is carbon and has conductivity. As the material of the cathode 310, for example, single crystal diamond, polycrystalline diamond, or the like can be used. For example, the cathode 310 can be made conductive by doping a material containing carbon as a main component. When diamond is used as the material of the cathode 310, any one or a combination of boron, nitrogen, phosphorus, sulfur, lithium, and the like can be used as the dopant. Alternatively, conductivity may be imparted to diamond by hydrogen-termination of the diamond surface regardless of doping. The cathode 310 has a structure in which a conical protrusion 310a (electron emitting portion) is formed in a partial region of the surface. The tip of the protrusion 310a has a sharp shape, and electrons are emitted from the tip from the electric field. On the other hand, the area | region where the protrusion part 310a is not formed among the surfaces of the cathode 310 has a flat shape.

  A metal carbide layer 311 is laminated on the flat portion of the cathode 310. A part of the metal carbide layer 311 is an opening 311 a, and the opening 311 a surrounds the protrusion 310 a of the cathode 310. The metal carbide layer 311 can be formed by sputtering, for example. The metal of the metal carbide layer 311 is a metal belonging to groups IVa to VIa. As the metal carbide layer 311, for example, titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide, tungsten carbide, or the like can be used.

  An insulating layer 15 is laminated on the metal carbide layer 311. A part of the insulating layer 15 is an opening 15a, and the opening 15a surrounds the protrusion 310a. The insulating layer 15 is for ensuring a potential difference between the cathode 310 and the gate electrode 16. The insulating layer 15 can be formed by, for example, a sputtering method or a CVD method. As the insulating layer 15, for example, silicon oxide, aluminum oxide, magnesium oxide, silicon nitride, silicon oxynitride, aluminum nitride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, aluminum fluoride, etc. Can be used.

  A gate electrode 16 is stacked on the insulating layer 15. A part of the gate electrode 16 is an opening 16a, and the tip of the protrusion 310a is located near the entrance of the opening 16a on the insulating layer 15 side. The gate electrode 16 is an electrode for applying a voltage between the cathode 310. This voltage generates an electric field at the tip of the protrusion 310a, and electrons are emitted from the tip. The gate electrode 16 can be formed by sputtering, for example. The gate electrode 16 is preferably made of, for example, a refractory metal such as molybdenum, tungsten, tantalum, or niobium, or a refractory silicide such as molybdenum silicide.

  In the field emission cold cathode 301 according to the present embodiment, a metal carbide layer 311 is provided between the cathode 310 and the insulating layer 15. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode 310 mainly composed of carbon and the metal carbide layer 311 is also good. Further, the metal of the metal carbide layer 311 is chemically active because it belongs to groups IVa to VIa, and the adhesion between the metal carbide layer 311 and the insulating layer 15 is good. From the above, as compared with the case where the insulating layer 15 is directly laminated on the cathode 310, peeling is caused between the cathode 310 and the insulating layer 15, that is, between the cathode 310 and the metal carbide layer 311 and between the metal carbide layer 311 and the insulating layer 15. Hard to occur. For this reason, the field emission type cold cathode 301 having high reliability and long operating life is realized.

  When titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide, or tungsten carbide is used as the metal carbide layer 311, the metal in these carbides is the insulating layer 15. In particular, the adhesion between the cathode 310 and the insulating layer 15 is less likely to occur. Although aluminum carbide can be used as the metal carbide layer 311, the aluminum carbide is decomposed by water or sublimated at 2000 ° C. in a vacuum, so that the metal carbide layer 311 may be separated from the cathode 310. There is sex. Therefore, as the material of the metal carbide layer 311, it is preferable to use the above materials such as titanium carbide.

  Further, when single crystal diamond or polycrystalline diamond is used as the cathode 310, these materials emit electrons with a particularly small electric field among carbon-based materials, so that the operating voltage of the field emission cold cathode 301 is lowered. Can do.

  When the insulating layer 15 is made of silicon oxide, aluminum oxide, magnesium oxide, silicon nitride, silicon oxynitride, aluminum nitride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, or aluminum fluoride These insulators are excellent in adhesion to the metal carbide layer 311, so that peeling between the cathode 310 and the insulating layer 15 is less likely to occur. In addition, since these insulators have high voltage resistance, they function as the insulating layer 15 suitably.

  FIG. 12 is a cross-sectional view showing another embodiment of a field emission cold cathode. The field emission type cold cathode 302 is a Spindt type as in FIG. 11 and has a structure in which the cathode 310, the metal carbide layer 21, the insulating layer 15, and the gate electrode 16 are sequentially laminated.

The metal carbide layer 21 is the same as the metal carbide layer 311 in FIG. 11 in that a part of the metal carbide layer 21 is an opening 21a. Further, the thermal expansion coefficient of the metal carbide layer 21 takes a value between the thermal expansion coefficient of the cathode 310 and the thermal expansion coefficient of the insulating layer 15. For example, as the cathode 310, the metal carbide layer 21, and the insulating layer 15, n-type conductive diamond doped with phosphorus, titanium carbide, and calcium fluoride can be used, respectively. In this case, the thermal expansion coefficients of diamond and calcium fluoride are 1 × 10 ⁻⁶ / ° C. and 20 × 10 ⁻⁶ / ° C., respectively, whereas the thermal expansion coefficient of titanium carbide is 7.4 × 10 ^−6. / ° C and values between them. The formation of the metal carbide layer 21 made of titanium carbide may be performed by sputtering titanium carbide on a portion other than the above-described diamond protrusion 310a, or by vapor deposition while heating titanium to 200 ° C. or higher. be able to.

  In the field emission cold cathode 302 according to the present embodiment, the metal carbide layer 21 is provided between the cathode 310 and the insulating layer 15. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode 310 mainly composed of carbon and the metal carbide layer 21 is also good. In addition, the thermal expansion coefficient of the metal carbide layer 21 takes a value between the thermal expansion coefficient of the cathode 310 and the thermal expansion coefficient of the insulating layer 15. Thereby, the difference in thermal expansion coefficient between the insulating layer 15 and the metal carbide layer 21 and between the cathode 310 and the metal carbide layer 21 is smaller than the difference in thermal expansion coefficient between the insulating layer 15 and the cathode 310. For this reason, the stress applied with the temperature change of the cold cathode between the insulating layer 15 and the metal carbide layer 21 and between the cathode 310 and the metal carbide layer 21 is caused when the insulating layer 15 is provided directly on the cathode 310. It becomes smaller than the stress applied between 15 and the cathode 310.

  As described above, the metal carbide layer 21 has good adhesion to the cathode 310 and relaxes the difference in thermal expansion coefficient between the cathode 310 and the insulating layer 15. As a result, as compared with the case where the insulating layer 15 is directly laminated on the cathode 310, between the cathode 310 and the insulating layer 15, that is, between the cathode 310 and the metal carbide layer 21 and between the metal carbide layer 21 and the insulating layer 15. Peeling hardly occurs. For this reason, the field emission type cold cathode 302 having high reliability and long operating life is realized.

  FIG. 13 is a cross-sectional view showing another embodiment of a field emission cold cathode. The field emission cold cathode 303 is of the Spindt type, and includes a cathode 310, a metal carbide layer 31, a metal layer 32, an insulating layer 15, and a gate electrode 16. A metal carbide layer 31 is stacked on the cathode 310, and a metal layer 32 is stacked on the metal carbide layer 31. An insulating layer 15 and a gate electrode 16 are sequentially stacked on the metal layer 32.

  A part of the metal carbide layer 31 is an opening 31a surrounding the protrusion 310a. As the metal carbide layer 31, the metal carbide belonging to groups IVa to VIa as in the metal carbide layer 311 in FIG. 11 or the thermal expansion coefficient of the cathode 310 and the insulating layer 15 as in the metal carbide layer 21 in FIG. Although it is preferable to use metal carbide having a value between, it is not essential to use these metal carbides.

  The metal layer 32 is a layer made of a thin film of a metal belonging to groups IVa to VIa, and a part of the metal layer 32 serves as an opening 32a surrounding the protrusion 310a. For example, as the cathode 310, the metal carbide layer 31, the metal layer 32, and the insulating layer 15, diamond, carbonization, ob, niobium, and calcium fluoride can be used, respectively.

  In the field emission cold cathode 303 according to this embodiment, a metal carbide layer 31 and a metal layer 32 are provided between the cathode 310 and the insulating layer 15 in this order from the cathode 310 side. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode 310 containing carbon as a main component and the metal carbide layer 31 is also good. Moreover, since the metal of the metal layer 32 is a metal belonging to groups IVa to VIa, it is chemically active. Thereby, both the adhesion between the metal layer 32 and the metal carbide layer 31 and the adhesion between the metal layer 32 and the insulating layer 15 are good. From the above, as compared with the case where the insulating layer 15 is directly laminated on the cathode 310, between the cathode 310 and the insulating layer 15, that is, between the cathode 310 and the metal carbide layer 31, between the metal carbide layer 31 and the metal layer 32, In addition, separation between the metal layer 32 and the insulating layer 15 hardly occurs. For this reason, the field emission type cold cathode 303 having high reliability and long operating life is realized.

  Further, by providing the metal layer 32, it can be used as a wiring on the cathode 310. When the metal layer 32 is not used as a wiring in this way, the thickness of the metal layer 32 is desirably 10 nm or less. Thus, even if the thickness of the metal layer 32 is 10 nm or less, it is sufficient to increase the adhesion between the layers. Further, since the insulating layer can be made thicker as the metal layer 32 is made thinner, good insulation between the cathode 310 and the gate electrode 16 can be maintained.

  Further, when niobium carbide is used as the metal carbide layer 31 and niobium is used as the metal layer 32, since these metals are the same, the adhesion between the metal carbide layer 31 and the metal layer 32 is improved.

  FIG. 14 is a cross-sectional view showing another embodiment of a field emission cold cathode. The field emission cold cathode 304 is of the Spindt type, and includes a cathode 310, a metal carbide layer 31, a metal oxide layer 44, an insulating layer 45, and the gate electrode 16. A metal carbide layer 31 is laminated on the cathode 310, and a metal oxide layer 44 is further laminated on the metal carbide layer 31. An insulating layer 45 and a gate electrode 16 are sequentially stacked on the metal oxide layer 44.

  A part of the metal oxide layer 44 serves as an opening 44a surrounding the protrusion 310a. The metal of the metal oxide layer 44 is the same as the metal of the metal carbide layer 31. For example, when niobium carbide is used as the metal carbide layer 31, niobium oxide is used as the metal oxide layer 44. In addition to niobium oxide, the metal oxide layer 44 includes titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, scandium oxide, yttrium oxide, lanthanum oxide, and oxide. Zinc, aluminum oxide and the like are used.

  The insulating layer 45 is made of an oxide insulator such as silicon oxide, and a part of the insulating layer 45 is an opening 45a surrounding the protruding portion 310a, as in the insulating layer 15 of FIG.

  In this field emission type cold cathode 304, a metal carbide layer 31 and a metal oxide layer 44 are provided between the cathode 310 and the insulating layer 45 in order from the cathode 310 side. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode 310 containing carbon as a main component and the metal carbide layer 31 is also good. The metal of the metal carbide layer 31 and the metal of the metal oxide layer 44 are the same. For this reason, the adhesion between the metal carbide layer 31 and the metal oxide layer 44 is good. Furthermore, since the insulator of the insulating layer 45 is an oxide, the adhesion between the metal oxide layer 44 and the insulating layer 45 which are also oxides is good. As described above, as compared with the case where the insulating layer 45 is directly laminated on the cathode 310, between the cathode 310 and the insulating layer 45, that is, between the cathode 310 and the metal carbide layer 31, and between the metal carbide layer 31 and the metal oxide layer 44. Peeling hardly occurs between the metal oxide layer 44 and the insulating layer 45. Therefore, a field emission cold cathode 304 having a high reliability and a long operation life is realized.

  Further, as the metal oxide layer 44, titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, scandium oxide, yttrium oxide, lanthanum oxide, zinc oxide, or oxide When aluminum is used, these metal oxides are particularly excellent in adhesion to both the metal carbide and the oxide insulator, and therefore between the metal carbide layer 31 and the metal oxide layer 44 and between the metal oxide layer 44 and the insulation. The adhesion between the layers 45 becomes better.

  FIG. 15 is a cross-sectional view showing another embodiment of a field emission cold cathode. The field emission cold cathode 305 is of the Spindt type and includes a cathode 310, a metal carbide layer 31, a metal nitride layer 54, an insulating layer 55, and the gate electrode 16. A metal carbide layer 31 is stacked on the cathode 310, and a metal nitride layer 54 is further stacked on the metal carbide layer 31. In addition, an insulating layer 55 and a gate electrode 16 are sequentially stacked on the metal nitride layer 54.

  A part of the metal nitride layer 54 is an opening 54a surrounding the protrusion 310a. The metal of the metal nitride layer 54 is the same as the metal of the metal carbide layer 31. For example, when titanium carbide is used as the metal carbide layer 31, titanium nitride is used as the metal nitride layer 54. In addition to titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, molybdenum nitride, tungsten nitride, aluminum nitride, or the like is used as the metal nitride layer 54.

  The insulating layer 55 is made of a nitride insulator such as silicon nitride, and a part of the insulating layer 55 is an opening 55a surrounding the protruding portion 310a as in the insulating layer 15 of FIG.

  In the field emission cold cathode 305, a metal carbide layer 31 and a metal nitride layer 54 are provided between the cathode 310 and the insulating layer 55 in order from the cathode 310 side. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode 310 containing carbon as a main component and the metal carbide layer 31 is also good. The metal of the metal carbide layer 31 and the metal of the metal nitride layer 54 are the same. For this reason, the adhesion between the metal carbide layer 31 and the metal nitride layer 54 is good. Furthermore, since the insulator of the insulating layer 55 is nitride, the adhesion between the metal nitride layer 54 and the insulating layer 55, which are also nitrides, is good. As described above, as compared with the case where the insulating layer 55 is directly laminated on the cathode 310, it is between the cathode 310 and the insulating layer 55, that is, between the cathode 310 and the metal carbide layer 31, and between the metal carbide layer 31 and the metal nitride layer 54. Peeling hardly occurs between the metal nitride layer 54 and the insulating layer 55. For this reason, the field emission type cold cathode 305 having high reliability and long operating life is realized.

  When titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, molybdenum nitride, tungsten nitride, or aluminum nitride is used as the metal nitride layer 54, these metal nitrides are In particular, since the adhesion between both the metal carbide and the nitride insulator is excellent, the adhesion between the metal carbide layer 31 and the metal nitride layer 54 and between the metal nitride layer 54 and the insulating layer 55 is improved.

  FIG. 16 is a cross-sectional view showing another embodiment of a field emission cold cathode. The field emission cold cathode 306 is of the Spindt type, and includes a cathode 310, a metal carbide layer 31, a metal layer 62, a metal oxide layer 64, an insulating layer 65, and a gate electrode 16. On the cathode 310, the metal carbide layer 31, the metal layer 62, the metal oxide layer 64, the insulating layer 65, and the gate electrode 16 are laminated in this order.

  Similarly to the metal layer 32 of FIG. 13, the metal layer 62 is a layer made of a thin film of a metal belonging to groups IVa to VIa, and a part of the metal layer 62 serves as an opening 62a surrounding the protrusion 310a. A part of the metal oxide layer 64 is an opening 64a surrounding the protrusion 310a. Unlike the metal oxide layer 44 of FIG. 14, the metal of the metal oxide layer 64 does not have to be the same as the metal of the metal carbide layer 31. In addition, the insulating layer 65 is made of an oxide insulator like the insulating layer 45 in FIG. 14, and a part of the insulating layer 65 is an opening 65a surrounding the protruding portion 310a. For example, titanium carbide, titanium, titanium oxide, and silicon oxide can be used as the metal carbide layer 31, the metal layer 62, the metal oxide layer 64, and the insulating layer 65, respectively.

  In the field emission cold cathode 306 according to this embodiment, a metal carbide layer 31, a metal layer 62, and a metal oxide layer 64 are provided in this order from the cathode 310 side between the cathode 310 and the insulating layer 65. . In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode 310 containing carbon as a main component and the metal carbide layer 31 is also good. Further, since the metal of the metal layer 62 is a metal belonging to groups IVa to VIa, it is chemically active, and the adhesion between the metal layer 62 and the metal carbide layer 31 and the adhesion between the metal layer 62 and the metal oxide layer 64 Both sexes are good. Furthermore, since the insulator of the insulating layer 65 is an oxide, the adhesion between the metal oxide layer 64 and the insulating layer 65, which are also oxides, is good. From the above, as compared with the case where the insulating layer 65 is directly laminated on the cathode 310, between the cathode 310 and the insulating layer 65, that is, between the cathode 310 and the metal carbide layer 31, between the metal carbide layer 31 and the metal layer 62, Separation hardly occurs between the metal layers 62 and between the metal oxide layers 64 and between the metal oxide layers 64 and between the insulating layers 65. For this reason, the field emission type cold cathode 306 having high reliability and long operating life is realized.

  Further, when zirconium carbide, zirconium, zirconium oxide, and silicon oxide are used as the metal carbide layer 31, the metal layer 62, the metal oxide layer 64, and the insulating layer 65, respectively, since zirconium is chemically active, the cathode When zirconium is directly formed thereon, for example, if a film is formed while heating, a zirconium carbide layer is naturally formed between the two. Similarly, when silicon oxide is directly formed on zirconium, a zirconium oxide layer is naturally formed between the two. For this reason, the process of forming an intermediate compound layer can be omitted.

  FIG. 17 is a cross-sectional view showing another embodiment of a field emission cold cathode. The field emission cold cathode 307 is of the Spindt type and includes a cathode 310, a metal carbide layer 31, a metal layer 62, a metal nitride layer 74, an insulating layer 75, and the gate electrode 16. On the cathode 310, the metal carbide layer 31, the metal layer 62, the metal nitride layer 74, the insulating layer 75, and the gate electrode 16 are laminated in this order.

  A part of the metal nitride layer 74 serves as an opening 74a surrounding the protrusion 310a. Unlike the metal nitride layer 54 of FIG. 15, the metal of the metal nitride layer 74 does not have to be the same as the metal of the metal carbide layer 31. In addition, the insulating layer 75 is made of a nitride insulator like the insulating layer 55 in FIG. 15, and a part of the insulating layer 75 is an opening 75a surrounding the protruding portion 310a.

  In the field emission cold cathode 307 according to the present embodiment, the metal carbide layer 31, the metal layer 62, and the metal nitride layer 74 are provided in this order from the cathode 310 side between the cathode 310 and the insulating layer 75. . In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode 310 containing carbon as a main component and the metal carbide layer 31 is also good. In addition, since the metal of the metal layer 62 is a metal belonging to groups IVa to VIa, it is chemically active, and the adhesion between the metal layer 62 and the metal carbide layer 31 and the adhesion between the metal layer 62 and the metal nitride layer 74. Both sexes are good. Furthermore, since the insulator of the insulating layer 75 is nitride, the adhesion between the metal nitride layer 74 and the insulating layer 75 which are also nitrides is good. As described above, as compared with the case where the insulating layer 75 is directly laminated on the cathode 310, between the cathode 310 and the insulating layer 75, that is, between the cathode 310 and the metal carbide layer 31, between the metal carbide layer 31 and the metal layer 62, Separation hardly occurs between the metal layers 62 and the metal nitride layers 74 and between the metal nitride layers 74 and the insulating layer 75. For this reason, the field emission type cold cathode 307 having high reliability and long operating life is realized.

  FIG. 18 is a cross-sectional view showing another embodiment of a field emission cold cathode. The field emission cold cathode 308 is of the Spindt type, and includes a cathode 310, a metal carbide layer 31, a metal layer 82, a metal oxide layer 64, an insulating layer 65, and the gate electrode 16. On the cathode 310, the metal carbide layer 31, the metal layer 82, the metal oxide layer 64, the insulating layer 65, and the gate electrode 16 are laminated in this order.

  A part of the metal layer 82 is an opening 82a surrounding the protrusion 310a. The metal layer 82 is formed by laminating thin films of two types of metals 83a and 83b belonging to groups IVa to VIa. For example, tantalum can be used as the metal 83a belonging to the IVa to VIa group on the metal carbide layer 31 side, and aluminum can be used as the metal 83b belonging to the IVa to VIa group on the metal oxide layer 64 side.

  In the field emission cold cathode 308 according to the present embodiment, a strong bonding surface is formed between the metals 83a and 83b belonging to groups IVa to VIa. In addition, since the metal layer 82 is formed by stacking two kinds of metals, different types of the two layers (here, the metal carbide layer 31 and the metal oxide layer 64) sandwiching the metal layer 82 are used. The metal will adhere. Therefore, for example, when the metal carbide layer 31 and the metal oxide layer 64 are tantalum carbide and aluminum oxide, respectively, tantalum is disposed on the metal carbide layer 31 side and aluminum is disposed on the metal oxide layer 64 side, whereby the metal layer The adhesion between the 82 and the metal carbide layer 31 and between the metal layer 82 and the metal oxide layer 64 can be improved. In the present embodiment, a metal nitride layer 74 and an insulating layer 75 may be used instead of the metal oxide layer 64 and the insulating layer 65, respectively.

  The field emission cold cathode is not limited to the above-described embodiment, and various modifications are possible. For example, in each embodiment, a Spindt-type cold cathode is shown, but a flat-type cold cathode may be used. FIG. 19 shows an example of a planar cold cathode having a structure in which a metal carbide layer 311, an insulating layer 15, and a gate electrode 16 similar to those in FIG. 11 are sequentially laminated on a cathode 90 having a flat entire surface. ing. Moreover, although the thing which consists of 1 type or 2 types of metals was shown as a metal layer, you may consist of 3 or more types of metals.

  The field emission cold cathode according to the invention including this embodiment includes a cathode mainly composed of carbon, a metal carbide layer provided on the cathode, an insulating layer provided on the metal carbide layer, and an insulating material. And a metal carbide layer containing a metal belonging to groups IVa to VIa.

  In this field emission type cold cathode, a metal carbide layer is provided between the cathode and the insulating layer. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode mainly composed of carbon and the metal carbide layer is also good. Moreover, since the metal of the metal carbide layer is a metal belonging to groups IVa to VIa, it is chemically active and the adhesion between the metal carbide layer and the insulating layer is good. As described above, peeling is less likely to occur between the cathode and the insulating layer as compared to the conventional field emission cold cathode. In the present invention, the term “between the cathode and the insulating layer” specifically means a cathode-metal carbide layer and a metal carbide layer-insulation layer.

  The field emission cold cathode according to the invention including this embodiment includes a cathode mainly composed of carbon, a metal carbide layer provided on the cathode, a metal layer provided on the metal carbide layer, and a metal layer. And a gate electrode provided on the insulating layer, and the metal layer may be made of a metal belonging to groups IVa to VIa.

  In this field emission cold cathode, a metal carbide layer and a metal layer are provided in this order from the cathode side between the cathode and the insulating layer. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode mainly composed of carbon and the metal carbide layer is also good. Further, the metal of the metal layer is chemically active because it belongs to groups IVa to VIa. Thereby, both the adhesion between the metal layer and the metal carbide layer and the adhesion between the metal layer and the insulating layer are good. As described above, peeling is less likely to occur between the cathode and the insulating layer as compared to the conventional field emission cold cathode. In the invention including this embodiment, the term “between the cathode and the insulating layer” specifically refers to the cathode-metal carbide layer, the metal carbide layer-metal layer, and the metal layer-insulation layer.

  The field emission cold cathode according to the invention including this embodiment includes a cathode composed mainly of carbon, a metal carbide layer provided on the cathode, a metal oxide layer provided on the metal carbide layer, and a metal. An insulating layer provided on the oxide layer, and a gate electrode provided on the insulating layer, wherein the metal carbide layer and the metal oxide layer contain the same metal, It may be characterized by comprising an oxide insulator.

  In this field emission cold cathode, a metal carbide layer and a metal oxide layer are provided in this order from the cathode side between the cathode and the insulating layer. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode mainly composed of carbon and the metal carbide layer is also good. The metal of the metal carbide layer and the metal of the metal oxide layer are the same. For this reason, the adhesiveness of a metal carbide layer and a metal oxide layer is good. Furthermore, since the insulator of the insulating layer is an oxide, the adhesion between the metal oxide layer, which is also an oxide, and the insulating layer is good. As described above, peeling is less likely to occur between the cathode and the insulating layer as compared to the conventional field emission cold cathode. In the invention including the present embodiment, between the cathode and the insulating layer is specifically between the cathode and the metal carbide layer, between the metal carbide layer and the metal oxide layer, and between the metal oxide layer and the insulating layer. It is.

  The field emission cold cathode according to the invention including this embodiment includes a cathode composed mainly of carbon, a metal carbide layer provided on the cathode, a metal nitride layer provided on the metal carbide layer, and a metal. An insulating layer provided on the nitride layer, and a gate electrode provided on the insulating layer, wherein the metal carbide layer and the metal nitride layer contain the same metal, It may be characterized by comprising a nitride insulator.

  In this field emission type cold cathode, a metal carbide layer and a metal nitride layer are provided in this order from the cathode side between the cathode and the insulating layer. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode mainly composed of carbon and the metal carbide layer is also good. The metal of the metal carbide layer and the metal of the metal nitride layer are the same. For this reason, the adhesion between the metal carbide layer and the metal nitride layer is good. Furthermore, since the insulator of the insulating layer is a nitride, the adhesion between the metal nitride layer, which is also a nitride, and the insulating layer is good. As described above, peeling is less likely to occur between the cathode and the insulating layer as compared to the conventional field emission cold cathode. In the invention including this embodiment, the space between the cathode and the insulating layer is specifically between the cathode and the metal carbide layer, the metal carbide layer and the metal nitride layer, and the metal nitride layer and the insulating layer. It is.

  The field emission cold cathode according to the invention including this embodiment includes a cathode mainly composed of carbon, a metal carbide layer provided on the cathode, a metal layer provided on the metal carbide layer, and a metal layer. A metal oxide layer, an insulating layer provided on the metal oxide layer, and a gate electrode provided on the insulating layer, wherein the metal layer is made of a metal belonging to groups IVa to VIa. The insulating layer may be made of an oxide insulator.

  In this field emission type cold cathode, a metal carbide layer, a metal layer, and a metal oxide layer are provided in this order from the cathode side between the cathode and the insulating layer. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode mainly composed of carbon and the metal carbide layer is also good. Further, since the metal of the metal layer is a metal belonging to groups IVa to VIa, it is chemically active, and both the adhesion between the metal layer and the metal carbide layer and the adhesion between the metal layer and the metal oxide layer are good. Furthermore, since the insulator of the insulating layer is an oxide, the adhesion between the metal oxide layer, which is also an oxide, and the insulating layer is good. As described above, peeling is less likely to occur between the cathode and the insulating layer as compared to the conventional field emission cold cathode. In addition, in the invention including this embodiment, between the cathode and the insulating layer, specifically, the cathode-metal carbide layer, the metal carbide layer-metal layer, the metal layer-metal oxide layer, and the metal oxide Interlayer-insulation layer.

  The field emission cold cathode according to the invention including this embodiment includes a cathode mainly composed of carbon, a metal carbide layer provided on the cathode, a metal layer provided on the metal carbide layer, and a metal layer. And an insulating layer made of aluminum oxide and a gate electrode provided on the insulating layer, and the metal layer may be made of a metal belonging to groups IVa to VIa.

  In this field emission cold cathode, a metal carbide layer and a metal layer are provided in this order from the cathode side between the cathode and the insulating layer. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode mainly composed of carbon and the metal carbide layer is also good. Further, the metal of the metal layer is chemically active because it belongs to groups IVa to VIa. Thereby, both the adhesion between the metal layer and the metal carbide layer and the adhesion between the metal layer and the insulating layer are good. As described above, peeling is less likely to occur between the cathode and the insulating layer as compared to the conventional field emission cold cathode.

  The field emission cold cathode according to the invention including this embodiment includes a cathode mainly composed of carbon, a metal carbide layer provided on the cathode, a metal layer provided on the metal carbide layer, and a metal layer. A metal nitride layer, an insulating layer provided on the metal nitride layer, and a gate electrode provided on the insulating layer, and the metal layer is made of a metal belonging to groups IVa to VIa. The insulating layer may be made of a nitride insulator.

  In this field emission cold cathode, a metal carbide layer, a metal layer, and a metal nitride layer are provided in this order from the cathode side between the cathode and the insulating layer. In this case, since the adhesion between the carbon-based material and the metal carbide is good, the adhesion between the cathode mainly composed of carbon and the metal carbide layer is also good. Further, since the metal of the metal layer is made of a metal belonging to groups IVa to VIa, it is chemically active, and both the adhesion between the metal layer and the metal carbide layer and the adhesion between the metal layer and the metal nitride layer are good. Furthermore, since the insulator of the insulating layer is a nitride, the adhesion between the metal nitride layer, which is also a nitride, and the insulating layer is good. As described above, peeling is less likely to occur between the cathode and the insulating layer as compared to the conventional field emission cold cathode. In addition, in the invention including this embodiment, between the cathode and the insulating layer, specifically, the cathode-metal carbide layer, the metal carbide layer-metal layer, the metal layer-metal nitride layer, and the metal nitride Interlayer-insulation layer.

  The field emission cold cathode according to the invention including this embodiment is provided between a cathode mainly composed of carbon, an insulating layer, a gate electrode provided on the insulating layer, and the cathode and the insulating layer. An intermediate layer composed of one or more layers selected from the group consisting of a metal carbide layer, a metal oxide layer, a metal nitride layer, and a metal layer, and heat of at least one of the layers constituting the intermediate layer The expansion coefficient may be a value between the thermal expansion coefficients of the cathode and the insulating layer.

  In this field emission type cold cathode, an intermediate layer is provided between the cathode and the insulating layer. The thermal expansion coefficient of at least one of the layers constituting the intermediate layer takes a value between the thermal expansion coefficient of the cathode and the thermal expansion coefficient of the insulating layer. Thereby, the difference in thermal expansion coefficient between the insulating layer and the intermediate layer and between the cathode and the intermediate layer is smaller than the difference in thermal expansion coefficient between the insulating layer and the cathode. For this reason, stress applied between the insulating layer and the intermediate layer and the temperature change of the cold cathode on each of the cathode and the intermediate layer is caused between the insulating layer and the cathode when the insulating layer is provided directly on the cathode. It becomes smaller than the stress applied to.

  As described above, the intermediate layer relaxes the difference in thermal expansion coefficient between the cathode and the insulating layer. As a result, peeling is less likely to occur between the cathode and the insulating layer as compared to conventional field emission cold cathodes. In addition, in the invention including this embodiment, between the cathode and the insulating layer is specifically between the cathode and the intermediate layer and between the metal carbide layer and the intermediate layer.

  The metal oxide layer is any of titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, scandium oxide, yttrium oxide, lanthanum oxide, zinc oxide, or aluminum oxide. It is preferable to consist of these.

  The metal nitride layer is preferably made of any one of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, molybdenum nitride, tungsten nitride, or aluminum nitride.

  The metal carbide layer is preferably made of any of titanium carbide, zirconium carbide, hafnium carbide, vanadium carbide, niobium carbide, tantalum carbide, chromium carbide, molybdenum carbide, or tungsten carbide.

  The cathode is preferably made of either single crystal diamond or polycrystalline diamond. In this case, electrons can be extracted with a particularly low operating voltage.

  The insulating layer may be made of any of silicon oxide, aluminum oxide, magnesium oxide, silicon nitride, silicon oxynitride, aluminum nitride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, or aluminum fluoride. Is preferred. In this case, an insulating layer having a particularly high withstand voltage is realized.

  In addition, the method of manufacturing a field emission cold cathode according to the invention including the present embodiment includes a step of preparing a cathode mainly composed of carbon, depositing a metal film on the cathode while heating, And a step of depositing an insulating layer on the metal film and forming a compound layer at the interface between the metal film and the insulating layer.

  According to this manufacturing method, when the metal film is formed on the cathode while heating, the metal carbide layer is formed at the interface between the cathode and the metal film. For this reason, the process of forming a metal carbide layer can be omitted. In addition, when an insulating layer is deposited on the metal film, a compound layer is formed at the interface between the metal film and the insulating layer. For this reason, the process of forming a compound layer can also be omitted.

  In the field emission type cold cathode, peeling is unlikely to occur between the cathode and the insulating layer, although a carbon-based material is used as the cathode material. Therefore, a field emission cold cathode having a long life and a method for manufacturing the same can be realized even with high power and high current density.

  Thermal electron emission has been conventionally used for extraction of an electron beam, but in recent years, field electron emission using a field emission type cold cathode has been increasingly used. According to the field emission type cold cathode, it is possible to take out an electron beam having a large current density with low power consumption.

  As a conventional field emission type cold cathode, for example, as shown in FIG. 20, there is a structure in which a cathode 100, an insulating layer 101, and an extraction electrode 102 (gate electrode) are sequentially laminated (Patent Document 2). In this field emission type cold cathode, electrons are emitted from the cathode by applying a voltage between the cathode and the extraction electrode.

By the way, refractory metals such as tungsten and molybdenum have been conventionally used as a material for the cathode. However, in order to obtain a high-density electron beam current at a low electron voltage, we are desirable to use a low work function material such as LaB _6. Among low work function materials, diamond having negative electron affinity is particularly promising as a cathode material. In addition, carbon-based materials such as carbon nanotubes having a sharp structure with a high aspect ratio are attracting attention as cathode materials.

  However, the carbon-based material has a problem of poor adhesion with an oxide generally used as an insulating layer. Even when nitride or fluoride is used as the insulating layer, the adhesion between the carbon-based material and the insulating layer is still not good.

  In addition, unlike the thermionic emission cathode, the field emission type cold cathode does not require heating, but heat is generated by the emitted high current density electrons. Therefore, due to the temperature change of the cold cathode due to heat generation, a stress having a magnitude corresponding to the difference in thermal expansion coefficient is applied between the cathode and the insulating layer. In fact, the temperature of the cold cathode can reach several hundred degrees or more. Particularly, in recent years, the heat generation density has been increasing with the miniaturization of the cold cathode. Therefore, there is a problem that peeling occurs between the cathode and the insulating layer depending on whether the adhesion between the cathode and the insulating layer is good or not and the difference in thermal expansion coefficient between them.

  The invention including this embodiment has been made in view of such circumstances, and even when a carbon-based material is used as a cathode material, an electric field in which separation between the cathode and the insulating layer hardly occurs. An object is to provide a radiation-type cold cathode and a method of manufacturing the same.

(Third embodiment)
FIG. 21 is a cross-sectional view schematically showing a field emission type electron source 2a of the third embodiment. The field emission electron source 2a includes a cathode 1a having a protruding electron emission portion 1 containing diamond as a material, a gate electrode 4, an insulating layer 3 separating the cathode 1a and the gate electrode 4, and an anode electrode 5. Prepare. An intermediate layer 6 is provided at least partially between the cathode 1 a and the insulating layer 3. The intermediate layer 6 includes a layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium, a carbide layer made of a transition metal of group IVa to VIa or a carbide of silicon, and a group IVa to VIa. And at least one nitride layer made of nitride of transition metal, aluminum or silicon. The electron emission portion 1 is doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities.

  In the present embodiment, as shown in FIG. 21, the intermediate layer 6 has a plurality of layers 6a and 6b. Layers 6a and 6b are independently of each other a layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium, a carbide layer made of a transition metal of group IVa to VIa or a carbide of silicon, And a nitride layer made of a transition metal of group IVa to VIa, a nitride of aluminum or silicon.

  In the field emission type electron source 2a having such a configuration, high quality diamond having a sharp tip is used as the cathode 1a, and individual emitters can be easily controlled, insulation breakdown and peeling of the insulating layer 3 are unlikely to occur, and leakage current is small. .

  The adhesion between the carbon-based material and the insulating layer is not good, but the layer made of a IVa to VIa group transition metal or silicon, the carbide layer, and the nitride layer have good adhesion with the carbon-based material. In particular, IVa to VIa group transition metals are chemically active and therefore have good adhesion to carbon-based materials, and IVa to VIa group transition metal carbides have better adhesion to carbon-based materials. Therefore, the adhesion between the above-described intermediate layer 6 and the insulating layer 3 is good, and peeling between the cathode 1a and the insulating layer 3 is less likely to occur when this intermediate layer 6 is inserted. In addition, the thermal conductivity of diamond, which is the material of the electron emission portion 1, is higher than that of other materials. Therefore, even if the field emission type electron source 2a generates heat during operation, heat is efficiently radiated from the electron emission portion 1, so that peeling due to generation of thermal stress can be prevented.

  Examples of the IVa to VIa group transition metals include titanium, zirconium, hafnium, vanadium, niobium, tantalum, chromium, molybdenum, and tungsten. In particular, the transition metal of group IVa to VIa is preferably a refractory metal such as tantalum or niobium.

  The intermediate layer 6 preferably further includes a metal oxide layer on the insulating layer 3 side, and the insulating layer 3 preferably includes an oxide as a material. Moreover, it is preferable that the intermediate layer 6 includes a nitride layer and the insulating layer 3 includes a nitride as a material. The intermediate layer 6 preferably further includes a metal fluoride layer on the insulating layer 3 side, and the insulating layer 3 preferably includes fluoride as a material.

  In these cases, since the insulating layer 3 and the intermediate layer 6 contain the same element, the adhesion between the intermediate layer 6 and the insulating layer 3 is also improved. Moreover, when the intermediate layer 6 is two or more layers, it is preferable that the several layers 6a and 6b which comprise the intermediate layer 6 contain the same transition metal or silicon from a viewpoint of improving adhesiveness. For example, when the insulating layer 3 is made of an oxide, the intermediate layer 6 is preferably made of a tantalum carbide layer 6a and a tantalum oxide layer 6b provided on the tantalum carbide layer 6a.

  FIG. 22A is a plan view schematically showing a field emission electron source 200a of another embodiment, and FIG. 22B is a cross-sectional view taken along the line XX in FIG. It is. The field emission electron source 200a includes a cathode 1a having a projecting electron emission portion 1 containing diamond as a material, a gate electrode 4, an insulating layer 3 separating the cathode 1a and the gate electrode 4, and an anode electrode 5. Prepare. An intermediate layer 6 is provided at least partially between the cathode 1 a and the insulating layer 3. The electron emission portion 1 is doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities.

  In the present embodiment, as shown in FIGS. 22A and 22B, the intermediate layer 6 is preferably in ohmic contact with the electron emission portion 1 and functions as a wiring. Furthermore, the intermediate layer 6 is preferably separated into a wiring portion 219 that is in ohmic contact with the electron emission portion 1 and an adhesive portion 218 that is not directly connected to the electron emission portion 1.

  The intermediate layer 6 is often conductive and can be used as a wiring, but it cannot be electrically separated. In the XY wiring or the like used in the conventional FED, only the wiring has been installed between the substrate 2 and the insulating layer 3. However, in the present invention, for example, from the viewpoint of improving the adhesion, an adhesive portion 218 that is disposed separately from the wiring portion 219 and improves the adhesion with the insulating layer 3 is provided. Since the intermediate layer 6 is patterned in this manner, the area of the bonding portion 218 can be increased while enabling individual control of each electron emitting portion 1, and adhesion is maintained even if severe heat generation occurs. I can do it. In order to obtain better ohmic contact, the electron emission portion 1 may be graphitized by implanting argon ions into the surface of the electron emission portion 1 made of diamond.

  The intermediate layer 6 includes a plurality of layers 6a and 6b. Layers 6a and 6b are independently of each other a layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium, a carbide layer made of a transition metal of group IVa to VIa or a carbide of silicon, And a nitride layer made of a transition metal of group IVa to VIa, a nitride of aluminum or silicon.

  In the field emission electron source 200a having such a configuration, high quality diamond having a sharp tip is used as the cathode 1a, individual emitters can be easily controlled, insulation breakdown and peeling of the insulating layer 3 are unlikely to occur, and leakage current is small. .

  Moreover, it is preferable that the thermal expansion coefficient of at least one layer of the layers 6 a and 6 b constituting the intermediate layer 6 is a value between the thermal expansion coefficients of the cathode 1 a and the insulating layer 3.

  Thereby, the difference in thermal expansion coefficient between the insulating layer 3 and the intermediate layer 6 and between the cathode 1a and the intermediate layer 6 is greater than the difference in thermal expansion coefficient between the insulating layer 3 and the cathode 1a. Get smaller. Therefore, the stress applied with the temperature change of the field emission electron sources 2a and 200a is relaxed compared to the case where the insulating layer 3 is provided directly on the cathode 1a. For this reason, peeling is less likely to occur compared to a field emission electron source having no intermediate layer.

  The metal oxide layer is made of titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, scandium oxide, yttrium oxide, lanthanum oxide, zinc oxide, or aluminum oxide. It is preferable to consist of either.

  The nitride layer is preferably made of any one of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, molybdenum nitride, tungsten nitride, aluminum nitride, or silicon nitride.

  The insulating layer is made of any of silicon oxide, aluminum oxide, magnesium oxide, silicon nitride, silicon oxynitride, aluminum nitride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, or aluminum fluoride. It is preferable.

  Moreover, it is preferable that at least a part of the surface of the intermediate layer 6 is made of a conductive material that does not dissolve in hydrofluoric acid. In this case, the intermediate layer 6 can be prevented from being corroded by hydrofluoric acid. Specifically, for example, the surface of the intermediate layer 6 is preferably covered with gold, platinum, molybdenum, silicon, or the like. For example, when the ohmic contact is made, the intermediate layer 6 is made of, for example, titanium or the like, although depending on the type of impurities of diamond. Since titanium and the like are corroded by hydrofluoric acid, it is difficult to produce a field emission electron source.

  In addition, the intermediate layer 6 has a wiring portion 219 that is in ohmic contact with the electron emission portion 1, and of the wiring portion 219, at least a portion 219 a that is exposed from the insulating layer 3 and electrically connects the cathode 1 a and the outside. It is preferable that a part is coated with a chemically stable metal film.

  The chemically stable metal film is made of, for example, gold, platinum, molybdenum having a high melting point, tungsten, or the like. Further, the chemically stable metal film may be a laminate of Au / Pt, Au / Mo, Au / Ni, or the like.

  Further, the transition metal selected for the intermediate layer 6 is generally easily corroded. However, regardless of the adhesion to the insulating layer 3, the portion that electrically connects the cathode 1 a and the outside need not be made of the same material as the intermediate layer 6. Considering the manufacturing process, it is possible to provide field emission electron sources 2a and 200a that operate stably for a long period of time when a stable metal film serving as a protective film is coated on the intermediate layer 6. I can do it.

  The field emission electron sources 2a and 200a preferably further include another insulating layer provided on the gate electrode 4 and a focusing electrode provided on another insulating layer. By this focusing electrode, the electrons emitted from the tip of the projection of the electron emission portion 1 proceed with good straightness without divergence.

  Moreover, it is preferable that the electron emission part 1 contains a single crystal diamond as a material. In addition, the electron emission portion 1 includes, as a material, doping diamond formed by vapor phase synthesis on the substrate 2 constituting the cathode 1a, and the substrate 2 is single crystal diamond synthesized at high temperature and high pressure, or vapor phase synthesis. It is preferable to include as a material non-doped diamond synthesized by the method.

  Here, the material of the substrate 2 is not particularly limited and may be other than diamond, but is preferably Si or diamond. When the material of the substrate 2 is diamond, the material may be polycrystalline diamond, but single crystal diamond is preferable from the viewpoint of control of doping, crystal defects, electron emission characteristics, and the like. In particular, the material of the electron emission portion 1 is preferably single crystal diamond. In this way, a diamond surface with good crystal doping with few crystal defects can be obtained, and therefore, high-quality field emission electron sources 2a and 200a with a low voltage and a high current density can be obtained.

  Further, the condition of d <z and d <h is satisfied, where the height of the electron emission portion 1 is z, the distance between the tip of the electron emission portion 1 and the gate electrode 4 is d, and the thickness of the insulating layer 3 is h. preferable. Furthermore, it is preferable that z, d, and h satisfy the conditions of d <z / 2 and d <h / 2.

  Next, the manufacturing method of the field emission type electron source of this embodiment is demonstrated. For example, the field emission electron source shown in FIG. 1 includes a cathode having a protruding electron emission portion 1 containing diamond as a material, a gate electrode 4, and an anode electrode 5. This field emission electron source is manufactured as follows, for example. A substrate 2 is prepared. On the substrate 2, a doped diamond is formed by doping one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities. The electron emission portion 1 is formed from at least the doping diamond by etching. An insulating layer 3 is formed on the cathode 1a. A gate electrode 4 is formed on the insulating layer 3. A resist is applied on the gate electrode 4. The gate electrode 4 and the insulating layer 3 around the electron emission portion 1 are removed by etching.

  Moreover, you may manufacture a field emission type electron source as follows. This field emission electron source is shown, for example, in FIG. A substrate 2 is prepared. On the substrate 2, a doped diamond is formed by doping one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities. An electron emission portion is formed at least from the doped diamond by etching. A layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium, a carbide layer made of a transition metal of group IVa to VIa or a carbide of silicon, and groups IVa to VIa. An intermediate layer 6 including at least one of the nitride layers made of nitride of transition metal, aluminum or silicon is formed. An insulating layer 3 is formed on the cathode 1a. A gate electrode 4 is formed on the insulating layer 3. A resist is applied on the gate electrode 4. The gate electrode 4 and the insulating layer 3 around the electron emission portion 1 are removed by etching.

  Moreover, you may manufacture a field emission type electron source as follows. This field emission electron source is shown, for example, in FIG. A substrate 2 is prepared. On the substrate 2, a doped diamond is formed by doping one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities. The electron emission portion 1 is formed from at least the doping diamond by etching. A layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium, a carbide layer made of a transition metal of group IVa to VIa or a carbide of silicon, and groups IVa to VIa. An intermediate layer 6 including at least one of the nitride layers made of nitride of transition metal, aluminum or silicon is formed. An insulating layer 3 is formed on the cathode 1a. A gate electrode 4 is formed on the insulating layer 3. Another insulating layer 7 is formed on the gate electrode 4. A focusing electrode 8 is formed on another insulating layer 7. A resist is applied on the focusing electrode 8. The focusing electrode 8, the gate electrode 4, the insulating layer 3, and the other insulating layer 7 around the electron emission portion 1 are removed by etching.

  In the step of forming the intermediate layer 6, it is preferable to heat the metal film during or after the metal film is deposited on the substrate 2 to form a metal carbide layer at the interface between the substrate and the metal film. Further, in the step of forming the insulating layer 3, a series of steps of forming the insulating layer 3, applying a resist on the insulating layer 3, and removing the insulating layer 3 around the electron emission portion 1 are performed a plurality of times. Assume that the height of the emitting portion 1 is z, the distance between the tip of the electron emitting portion 1 and the gate electrode 4 is d, and the thickness of the insulating layer 3 is h, so that the conditions of d <z and d <h are satisfied. Is preferably formed. Moreover, in the process of forming the insulating layer 3, it is preferable that the thickness of the last formed insulating layer 3 is the maximum.

  The substrate 2 is preferably a diamond substrate. It is preferable that the substrate 2 is a diamond substrate and includes a step of forming a protrusion shape on the diamond substrate by etching before the step of forming the doped diamond. It is preferable that the substrate 2 is a diamond substrate, and after forming the protrusion shape, the electron emission portion 1 made of doping diamond is formed, and the subsequent protrusion shape forming step is not included.

(Fourth embodiment)
A fourth embodiment of the present invention will be described in connection with a manufacturing method. As shown in FIG. 4, first, a substrate 2 is prepared, and a doped diamond 1 doped with one or more elements selected from the group of boron, nitrogen, phosphorus, sulfur, lithium, and silicon as impurities is formed on the substrate 2. Form. On the doped diamond, for example, Al is deposited as a mask material, and a dot-like Al mask is formed by photolithography. Then, the doping diamond is etched by the RIE method, and at least the doping diamond 1 is formed into a protruding shape as shown in FIG. Thereafter, in order to change the surface termination of the projection-shaped diamond, surface hydrogenation treatment by microwave plasma or surface oxygenation treatment by atmospheric annealing may be performed.

  Next, as shown in FIG. 4B, the insulating layer 3 is formed, and the gate electrode 4 is formed on the insulating layer 3. A resist 20 is applied on the gate electrode 4 (FIG. 4C). Here, silicon oxide was used as the insulating layer 3. By optimizing the resist coating conditions, the resist immediately above the protrusion tip of the protrusion-shaped diamond is thinned, and the gate electrode and the insulating layer of the protrusion-shaped diamond portion are removed by etching (FIG. 4D). Thereafter, the resist is removed (FIG. 4E). Since diamond is chemically stable, the insulating layer 3 is preferably etched by wet etching such as hydrofluoric acid instead of dry etching. This is because in the dry etching, the sharpness of the tip of the diamond protrusion may be impaired. The electrode layer may be patterned by dry etching.

  With such a manufacturing method, as shown in FIG. 1, it is possible to obtain an electron source capable of controlling the electron emission by simply attaching the gate electrode 4 to the conductive diamond 1. Alternatively, if at least the doped diamond is formed into a protrusion shape by etching in the middle of the method, and then a step of forming the intermediate layer 6 on the substrate and patterning it is inserted, as shown in FIG. A field emission electron source including a portion 1, the electron emission portion 1, an intermediate layer 6, an anode electrode 5, and a gate electrode 4, wherein the electron emission portion 1 is boron, nitrogen, phosphorus, sulfur, lithium A field emission electron source which is diamond doped with one or more elements selected from the group of silicon as impurities can be obtained.

  By forming the intermediate layer 6 in this way, it is possible to improve the adhesion between the cathode and the insulating layer 3 and to obtain a long-life electron source that does not peel off even during high output operation. In addition, when the intermediate layer 6 is used as a wiring, carriers can be imparted to high-resistance diamond such as single phosphorus-doped or nitrogen-doped, and electron emission characteristics can be improved. The intermediate layer 6 is preferably made of a conductive material whose at least part of the surface is insoluble in hydrofluoric acid. In that case, even if the insulating layer 3 is removed with hydrofluoric acid, the intermediate layer 6 is not corroded. Since the vicinity of the protruding portion and the gate electrode is a three-dimensional shape and complicated, dry etching with too high vertical workability is rather not suitable, and wet etching such as hydrofluoric acid is desirable.

  The intermediate layer 6 capable of making ohmic contact includes titanium, titanium carbide, and the like, although depending on the impurities of diamond. Since titanium and the like are corroded by hydrofluoric acid, gold, platinum, molybdenum, silicon, and the like can be stacked thereon. In order to obtain a better ohmic contact, the diamond surface may be graphitized by argon ion implantation or the like.

  When a carbide layer is used for the intermediate layer 6, a material that is carbide from the beginning, such as titanium carbide, may be formed by sputtering or the like. Further, a metal film may be formed while heating, or a carbide layer may be formed by heating after film formation at a low temperature.

  When the intermediate layer 6 functioning as a wiring is formed in this way, the wiring portion 219 connected to the electron emission portion 1 and drawn out of the insulating layer 3 as shown in FIG. It is also possible to separate the adhesive portion 218 that improves only the adhesion and form the insulating layer 3 thereon. In this way, the wiring portion 219 and the bonding portion 218 can be formed in a single process while maintaining the adhesion of the insulating layer 3 over a wide area, and the operation of each electron emission portion 1 can be controlled. Note that the gate electrode and the like are omitted in FIG.

  At this time, in particular, when the wiring portion 219 is attached on the projection-shaped diamond, a step of applying a resist to expose at least the projection tip of the cathode 1a and removing the wiring material at the projection tip by etching is added. Prior to etching, the resist may be patterned by exposure to separate the wiring portion 219 and the adhesive portion 218.

  Furthermore, in this structure, the wiring portion 219 exposed from the insulating layer 3 may be covered with a chemically stable metal film. In this way, the deterioration of the portion 219a that becomes a contact point with the external circuit in the wiring portion 219 is suppressed, and a stable operation can be obtained. Examples of chemically stable metal films include Au and Pt. Further, high melting point Mo, W, Ta, Nb or the like may be coated. Also, a laminated structure such as Au / Pt, Au / Mo, or Au / Ni may be used.

  In the course of the manufacturing process, after the intermediate layer 6 is formed, the first insulating layer 3 is formed, the gate electrode is formed on the first insulating layer, and the second insulating layer is formed on the gate electrode. A layer 7 is formed, a focusing electrode is formed on the second insulating layer, a resist is applied on the focusing electrode, and the focusing electrode, the gate electrode, and the first and second insulating layers of the protruding diamond portion are formed. If removed by etching, as shown in FIG. 3, a projection-shaped electron emission portion 1, an intermediate layer 6 formed between the projections and on the side surfaces of the projection except for the tip of the projection in ohmic contact with the electron emission portion 1, and the anode electrode 5 A field emission electron source including the gate electrode 4 and the focusing electrode 8 can be obtained. Electrons emitted from the projection tip of the electron emission portion by the focusing electrode proceed with good straightness without divergence.

  Here, the substrate is not particularly specified and may be other than diamond, but the substrate is preferably Si or diamond. In the case of a diamond substrate, polycrystal may be used, but single crystal diamond is preferable from the viewpoint of doping control, crystal defects, electron emission characteristics, and the like. In particular, the diamond protrusion is preferably a single crystal.

  Further, as shown in FIG. 5, if a projection 10 is formed on the diamond substrate 2 by etching and then a doped diamond 11 is grown, and after the etching of the doped diamond, the same steps as above are taken, as shown in FIG. Since the diamond 11 can be doped only in the vicinity of the tip of the diamond protrusion 10, it becomes possible to control the electron emission of each emitter by the cathode electrode.

  Further, as shown in FIG. 6, after forming a projection 10 having a sharp tip by etching on the diamond substrate 2, a doping diamond 11 may be grown to create a pyramidal projection, for example. Thereby, it is possible to obtain a diamond emitter with better sharpness and less crystal defects on the surface as compared with etching. In this case, the protrusion shape forming step by etching of the doping diamond can be omitted.

  In the present invention, the step of forming the insulating layer includes (1) film formation of the insulating layer, (2) application of the resist, and (3) a series of steps of removing the insulating layer of the protruding diamond portion a plurality of times. The insulating layer may be formed repeatedly. As shown in FIG. 7, when the insulating layer 3 is formed up to the same height as the protrusion-shaped diamond 1 at one time, when the insulating layer is etched, the protrusion-shaped electron emission portion is formed along with the vertical direction. The insulating layer is etched and spread in the lateral direction around the (emitter) by the same thickness, which leads to an increase in the diameter of the gate electrode. However, as shown in FIG. 8, the insulating layer 3 is not formed to the height of the protrusion-shaped diamond 1 at a time, but the insulating layer 3 is formed thinner than that, and the insulation around the emitter is formed each time the insulating layer is formed. By etching away the layer, the insulating film thickness can be increased while keeping the distance from the emitter to the edge of the insulating layer short. For example, in a simple calculation, when the insulating layer is formed in two steps, the distance between the tip of the emitter and the gate electrode is ½ that in the case where the insulating layer is formed once.

  In such a method, when the height of the projection of the electron emission portion is z, the distance between the tip of the projection and the gate electrode is d, and the thickness of the insulating layer between the diamond and the gate electrode is h, d <z and d < h, and the distance between the emitter and the gate electrode can be shortened while keeping the leakage current and withstand voltage high by increasing the thickness of the insulating layer as compared with the conventional electrode formation technology, thereby controlling the electron emission. The voltage can be kept low. Desirably, d <z / 2 and d <h / 2 in the electron source of the present invention.

  In the step of performing the insulating layer a plurality of times, it is preferable that the last formed insulating film has the maximum thickness. This is because in the case where the insulating layer is formed a plurality of times, if all the film thicknesses are made constant, the recessed portion around the emitter is not filled, and the shape of the final gate electrode is deteriorated. By making the last insulating layer the thickest, the recess is completely filled, so that a gate electrode having a smooth edge can be formed.

  The diamond of the present invention can be arbitrarily doped. Boron dope has a negative electron affinity on the hydrogen-terminated surface and provides excellent electron emission characteristics. Further, by performing n-type doping such as phosphorus and sulfur, electron emission of carriers is high and electron emission barrier is also small, so that more excellent electron emission is known. These may use a single impurity or may be doped at the same time. Arbitrary forms such as CVD and ion implantation can be used as the form of doping. In the case of n-type, the surface may be oxygen-terminated.

  The resist material used for etching the electrode and the insulating layer may be a material used in normal photolithography. At this time, exposure and development processes may be added after resist application to pattern electrodes such as gates. It is better to apply the resist so that the thickness of the resist film becomes thinner than the height of the projection of the cathode. In this case, etching starts easily from the tip of the protrusion with a wet etching solution, and an electrode having a good shape can be produced. When the resist film thickness is large, it is necessary to expose the protruding portion from the resist by dry etching or the like.

  Desirably, the diamond is a single crystal. In the case of a single crystal, particularly when doping is performed by CVD, the amount of impurities mixed in can be controlled with high accuracy. On the other hand, the electron source may be made of polycrystalline diamond. Polycrystalline diamond makes it easier to obtain a sample with a larger area than single-crystal diamond, and boron-doped wafers have excellent conductivity. Further, the orientation can be controlled even in a polycrystal, and various cathodes can be used, for example, a phosphorous doped diamond is partially epitaxially grown on a (111) oriented polycrystal diamond.

(Example 6)
Boron-doped diamond was formed on a high-pressure synthetic Ib (100) single crystal diamond substrate using microwave plasma CVD. Hydrogen (H ₂ ) flow rate 200 sccm, methane / hydrogen (CH ₄ / H ₂ ) concentration 6.0%, diborane / methane (B ₂ H ₆ / CH ₄ ) concentration 167 ppm, pressure 5.3 kPa, substrate temperature 830 ° C. The film thickness was 5 μm. Next, aluminum (Al) was formed on the boron-doped diamond by sputtering, and dots having a diameter of 3 μm were formed by photolithography. This was etched by the RIE method to form a diamond having a protrusion shape. The reaction conditions were an oxygen flow rate of 50 sccm, a CF ₄ / O ₂ concentration of 2%, a pressure of 2 Pa, and an RF power of 250 W. The height of the formed protrusion is 3 μm. Next, a silicon oxide film having a thickness of 3 μm is formed by sputtering, and a Mo film having a thickness of 0.2 μm is formed thereon. A resist with a viscosity of 30 cp is spin-coated at 4000 rpm for 30 seconds, and Mo and silicon oxide around the protrusion are etched with aqua regia and buffered hydrofluoric acid from the tip of the protrusion where the resist becomes thin. The electrode thus formed was formed at a distance of 3.0 μm from the tip of the protrusion.

(Example 7)
Next, the same process as in Example 6 was performed until a protrusion having a height of 3 μm was formed by RIE, and then silicon oxide having a thickness of 1.5 μm was formed by sputtering. A resist was spin-coated on this, and silicon oxide around the protrusions was removed by etching with buffered hydrofluoric acid. After removing the resist with an organic solvent, a second silicon oxide film having a thickness of 1.5 μm was formed, and an Mo film having a thickness of 0.2 μm was formed. A resist was spin-coated on this, and Mo and silicon oxide at the tip of the protrusions where the resist became thin with aqua regia and buffered hydrofluoric acid were etched. As a result, the height z = 3 μm of the projection of Example 6 and the silicon oxide film thickness h = 3 μm and d = 3 μm, while z and h are the same, but d is halved at a distance of d = 1.5 μm. An electrode could be formed.

(Example 8)
Similarly to Example 6, after forming boron-doped diamond by 2.5 μm by microwave plasma CVD and forming an emitter having a height of 3 μm by RIE method, 0.1 μm of tantalum is formed by sputtering as an intermediate layer on the emitter. A film was formed. A resist was spin-coated on this, and tantalum at the tip of the emitter was removed with buffered hydrofluoric acid. Next, annealing was performed at 300 ° C. in a vacuum to form a titanium carbide layer, thereby completing an intermediate layer capable of taking ohmic contact with the cathode. Next, 3 μm of silicon oxide for the first insulating layer was formed, and Mo of 0.1 μm was formed as a gate electrode. A resist was spin-coated thereon, and Mo and silicon oxide around the protrusions were removed with aqua regia and buffered hydrofluoric acid. According to the method of the present invention, it was possible to improve the adhesion between the cathode and the insulating layer, and to form a gate electrode that emits electrons by concentrating the electric field near the protrusion.

Example 9
Similarly to Example 6, after forming boron-doped diamond by 2.5 μm by microwave plasma CVD and forming an emitter having a height of 3 μm by RIE method, 0.1 μm of tantalum is formed by sputtering as an intermediate layer on the emitter. A film was formed. This was spin-coated with a resist and exposed to pattern so that the electron emission portions were individually wired, and the tantalum at the emitter tip and the separation portion was removed with buffered hydrofluoric acid. Next, annealing was performed at 300 ° C. in vacuum to form a tantalum carbide layer, thereby completing an intermediate layer capable of taking ohmic contact with the cathode. Next, 3 μm of silicon oxide for the first insulating layer was formed, and Mo of 0.1 μm was formed as a gate electrode. A resist was spin-coated thereon, and Mo and tantalum oxide around the protrusions were removed with aqua regia and buffered hydrofluoric acid. According to the method of the present invention, a field emission electron source having a gate electrode that improves the adhesion between the cathode and the insulating layer while concentrating the electric field in the vicinity of the protrusion while providing wiring for individually controlling the electron emission portion. I was able to form.

(Example 10)
Similarly to Example 6, after forming boron-doped diamond by 2.5 μm by microwave plasma CVD and forming an emitter having a height of 3 μm by RIE method, 0.1 μm of tantalum is formed by sputtering as an intermediate layer on the emitter. A film was formed. This was spin-coated with a resist and exposed to patterning so as to separate the wiring portion and the adhesion portion, and the tantalum at the emitter tip and the separation portion was removed with buffered hydrofluoric acid. Next, annealing was performed at 300 ° C. in vacuum to form a tantalum carbide layer, thereby completing an intermediate layer capable of taking ohmic contact with the cathode. Next, 3 μm of silicon oxide for the first insulating layer was formed, and Mo of 0.1 μm was formed as a gate electrode. A resist was spin-coated thereon, and Mo and silicon oxide around the protrusions were removed with aqua regia and buffered hydrofluoric acid. According to the method of the present invention, a gate electrode for individually controlling the electron emission portion and forming an adhesion portion improves adhesion between the cathode and the insulating layer, and concentrates an electric field near the protrusion to emit electrons. A field emission electron source with

(Example 11)
Similarly to Example 6, boron-doped diamond was formed to 2.5 μm by microwave plasma CVD, an emitter having a height of 3 μm was formed by RIE, and then niobium was formed to 0.05 μm by sputtering as an intermediate layer on the emitter. A film was formed. A resist was spin-coated thereon, and niobium at the tip of the emitter was removed with buffered hydrofluoric acid to complete the intermediate layer. Next, 1 μm of silicon oxide for the first insulating layer was formed, a resist was spin-coated, and the silicon oxide around the protrusions was removed with buffered hydrofluoric acid. Next, after forming 1 μm of second silicon oxide, it was removed in the same manner, and further 1.5 μm of third silicon oxide was formed, and 0.1 μm of Mo was formed as a gate electrode. A resist was spin-coated thereon, and Mo and silicon oxide around the protrusions were removed with aqua regia and buffered hydrofluoric acid. According to the method of the present invention, a gate electrode for electron emission by concentrating the electric field in the vicinity of the protrusion could be formed. Further, in Example 7, as shown in FIG. 9, there was a case where the edge of the gate electrode was distorted in a part of the gate electrode because the depression around the emitter was not filled, but in this example, As shown in FIG. 10, all the gate electrodes had smooth edges.

(Example 12)
As in Example 6, boron-doped diamond was formed to 2.5 μm by microwave plasma CVD, an emitter having a height of 3 μm was formed by RIE, and then chromium was deposited to 0.05 μm by sputtering as an intermediate layer on the emitter. A film was formed. This was spin-coated with a resist, and chromium at the tip of the emitter was removed with dilute sulfuric acid. Next, Pt is sputtered to 0.1 μm on this, and similarly, a resist is spin-coated and patterned by exposure, and the intermediate layer is completed by removing Pt at a distance of 10 μm or more from the protrusion and the tip of the protrusion with aqua regia. It was. Next, 1 μm of a first silicon oxide was formed, a resist was spin-coated, and the silicon oxide around the protrusions was removed with buffered hydrofluoric acid. Next, after forming 1 μm of second silicon oxide, it was removed in the same manner, and further 1.5 μm of third silicon oxide was formed, and 0.1 μm of Mo was formed as a gate electrode. A resist was spin-coated thereon, and Mo and silicon oxide around the protrusions were removed with aqua regia and buffered hydrofluoric acid. According to the method of the present invention, a gate electrode for electron emission by concentrating the electric field in the vicinity of the protrusion could be formed. Further, in Example 7, as shown in FIG. 9, there was a case where the edge of the gate electrode was distorted in a part of the gate electrode because the depression around the emitter was not filled, but in this example, As shown in FIG. 10, all the gate electrodes had smooth edges.

(Example 13)
Similarly to Example 6, boron-doped diamond was formed to 2.5 μm by microwave plasma CVD, an emitter having a height of 3 μm was formed by RIE, and then tantalum was 0.05 μm by sputtering as a cathode electrode on the emitter. A film was formed. This was spin-coated with a resist, and tantalum at the tip of the emitter was removed with buffered hydrofluoric acid to complete the intermediate layer. Next, 1 μm of a first silicon oxide was formed, a resist was spin-coated, and the silicon oxide around the protrusions was removed with buffered hydrofluoric acid. Next, 1 μm of second silicon oxide was formed, and then 0.1 μm of Mo was formed as a gate electrode. Further, 3 μm of third silicon oxide was formed, and 0.1 μm of Mo was formed as a focusing electrode. A resist was spin-coated thereon, and Mo and silicon oxide around the protrusions were removed alternately with aqua regia and buffered hydrofluoric acid. By the method of the present invention, it is possible to form a gate electrode that emits electrons by concentrating the electric field in the vicinity of the protrusion, and a focusing electrode that converges the emitted electrons, and a field emission electron source with improved electron extraction efficiency compared to the conventional method. I was able to get it.

(Example 14)
An Al film was formed by sputtering on a high-pressure synthetic Ib (100) single crystal diamond substrate, and dots having a diameter of 3 μm were formed by photolithography. This was etched by the RIE method to form a diamond having a protrusion shape. The reaction conditions were an oxygen flow rate of 50 sccm, a CF ₄ / O ₂ concentration of 2%, a pressure of 2 Pa, and an RF power of 250 W. The height of the formed protrusion is 3 μm. Next, phosphorus-doped diamond is formed using microwave plasma CVD. H ₂ flow rate is 200 sccm, CH ₄ / H ₂ concentration is 0.05%, PH ₃ / CH ₄ concentration is 10,000 ppm, pressure is 13.3 kPa, substrate temperature is 870 ° C., film thickness is 5 μm, and the side is surrounded by (111) plane A pyramidal protrusion was formed.

  Next, after the cathode electrode is formed in the same manner as in Example 8, silicon oxide is divided into 1.5 μm portions each twice in the same manner as in Example 7 to form a total film thickness of 3 μm, and Mo is formed in a thickness of 0.2 μm. A resist with a viscosity of 30 cp is spin-coated at 4000 rpm for 30 seconds, and Mo and silicon oxide around the protrusion are etched with aqua regia and buffered hydrofluoric acid from the tip of the protrusion where the resist becomes thin. The electrode thus formed was formed at a distance of 1.5 μm from the tip of the protrusion.

  As described above, an insulating layer / electrode layer can be formed on diamond having excellent properties as an electron emission material by the method of the present invention, and high adhesion between the insulating layer and the cathode can be achieved even in high output operation. The gate electrode can be formed in the vicinity of the tip of the emitter with a longer life than a conventionally produced diamond electron emission device, and excellent electron emission characteristics can be obtained. Such a field emission type electron source can improve the performance of microwave tubes such as traveling wave tubes and klystrons, high-frequency amplification elements, electron beam equipment such as SEMs and electron beam exposure machines, and light-emitting elements such as FEDs. it can.

The cross-sectional schematic diagram of the field emission type electron source created with the manufacturing method of 1st Embodiment is shown. The cross-sectional schematic diagram of the field emission type electron source of 1st Embodiment is shown. The cross-sectional schematic diagram of the other field emission type electron source of 1st Embodiment is shown. An example of the manufacturing process of 1st Embodiment is shown. The cross-sectional schematic diagram of the other field emission type electron source of 1st Embodiment is shown. The cross-sectional schematic diagram of the other field emission type electron source of 1st Embodiment is shown. An example of the etching process of the insulating layer of 1st Embodiment is shown. The other example of the etching process of the insulating layer of 1st Embodiment is shown. An example of the cross-sectional schematic diagram of the gate electrode of 1st Embodiment is shown. The other example of the cross-sectional schematic diagram of the gate electrode of 1st Embodiment is shown. It is sectional drawing which shows one Embodiment of a field emission type cold cathode. It is sectional drawing which shows other embodiment of a field emission type cold cathode. It is sectional drawing which shows other embodiment of a field emission type cold cathode. It is sectional drawing which shows other embodiment of a field emission type cold cathode. It is sectional drawing which shows other embodiment of a field emission type cold cathode. It is sectional drawing which shows other embodiment of a field emission type cold cathode. It is sectional drawing which shows other embodiment of a field emission type cold cathode. It is sectional drawing which shows other embodiment of a field emission type cold cathode. It is sectional drawing which shows one structural example of a planar cold cathode. It is sectional drawing which shows the conventional field emission type cold cathode. It is sectional drawing which shows typically the field emission type electron source of 3rd Embodiment. FIG. 22A is a plan view schematically showing a field emission electron source according to another embodiment, and FIG. 22B is a cross-sectional view taken along the line XX in FIG. is there.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Projection-shaped electron emission part, 2 ... Substrate, 3 ... Insulating layer, 4 ... Gate electrode, 5 ... Anode electrode, 6 ... Intermediate layer, 7 ... Another insulating layer, 8 ... Focusing electrode, 10 ... Projection-shaped diamond 11 ... Doping diamond, 20 ... Resist, 301-308 ... Field emission cold cathode, 310, 1a ... Cathode, 310a ... Projection, 311, 21, 31 ... Metal carbide layer, 15, 45, 55, 65, 75 ... Insulating layer, 16 ... Gate electrode, 32, 62, 82 ... Metal layer, 44, 64 ... Metal oxide layer, 54, 74 ... Metal nitride layer, 2a, 200a ... Field emission electron source, 218 ... Adhesive part 219 ... wiring part.

Claims (27)

A field emission electron source comprising a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, an insulating layer separating the cathode and the gate electrode, and an anode electrode,
An intermediate layer provided at least in part between the cathode and the insulating layer;
The intermediate layer includes at least one of a carbide layer made of a transition metal of Group IVa to VIa or a carbide of silicon, and a nitride layer made of a transition metal of Group IVa to VIa, aluminum or silicon,
The field emission electron source, wherein the electron emission portion is doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities. A field emission electron source comprising a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, an insulating layer separating the cathode and the gate electrode, and an anode electrode,
An intermediate layer provided at least in part between the cathode and the insulating layer;
The intermediate layer includes a layer made of at least one transition metal of zirconium, hafnium, vanadium, niobium, tantalum and chromium,
The field emission electron source, wherein the electron emission portion is doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon as impurities.   The field emission electron source according to claim 1 or 2, wherein the intermediate layer further includes a metal oxide layer on the insulating layer side, and the insulating layer includes an oxide as a material.   The field emission electron source according to claim 1, wherein the intermediate layer includes the nitride layer, and the insulating layer includes nitride as a material.   The field emission electron source according to claim 1 or 2, wherein the intermediate layer further includes a metal fluoride layer on the insulating layer side, and the insulating layer includes fluoride as a material.   The field emission electron source according to claim 1, wherein the intermediate layer is in ohmic contact with the electron emission portion and functions as a wiring.   7. The field emission according to claim 6, wherein the intermediate layer is separated into a wiring portion that is in ohmic contact with the electron emission portion and an adhesive portion that is not directly connected to the electron emission portion. Type electron source.   8. The thermal expansion coefficient of at least one layer among the layers constituting the intermediate layer is a value between the thermal expansion coefficients of the cathode and the insulating layer. Field emission electron source.   The metal oxide layer is any one of titanium oxide, zirconium oxide, hafnium oxide, vanadium oxide, niobium oxide, tantalum oxide, chromium oxide, molybdenum oxide, tungsten oxide, scandium oxide, yttrium oxide, lanthanum oxide, zinc oxide, or aluminum oxide. The field emission electron source according to claim 3, wherein   The nitride layer is made of any one of titanium nitride, zirconium nitride, hafnium nitride, vanadium nitride, niobium nitride, tantalum nitride, chromium nitride, molybdenum nitride, tungsten nitride, aluminum nitride, or silicon nitride. 5. The field emission electron source according to 4.   The insulating layer is made of any one of silicon oxide, aluminum oxide, magnesium oxide, silicon nitride, silicon oxynitride, aluminum nitride, magnesium fluoride, calcium fluoride, strontium fluoride, barium fluoride, or aluminum fluoride. The field emission type electron source according to any one of claims 1 to 10.   The field emission electron source according to any one of claims 1 to 11, wherein at least a part of the surface of the intermediate layer is made of a conductive material that is not soluble in hydrofluoric acid.   The intermediate layer has a wiring portion in ohmic contact with the electron emission portion, and at least a part of the wiring portion exposed from the insulating layer and electrically connecting the cathode and the outside is chemically The field emission electron source according to claim 6, wherein the field emission electron source is coated with a stable metal film.   14. The apparatus according to claim 1, further comprising: another insulating layer provided on the gate electrode; and a focusing electrode provided on the another insulating layer. Field emission electron source.   The field emission electron source according to any one of claims 1 to 14, wherein the electron emission portion includes single crystal diamond as a material.   The electron emission portion includes a doping diamond formed by vapor phase synthesis on the substrate constituting the cathode as a material, and the substrate is synthesized by single crystal diamond synthesized at high temperature and high pressure, or synthesized by vapor phase synthesis. The field emission electron source according to any one of claims 1 to 15, wherein the non-doped diamond is included as a material.   The height of the electron emission portion is z, the distance between the tip of the electron emission portion and the gate electrode is d, and the thickness of the insulating layer is h, and the conditions of d <z and d <h are satisfied. The field emission electron source according to any one of claims 1 to 16.   The field emission electron source according to claim 17, wherein the z, d, and h satisfy the conditions of d <z / 2 and d <h / 2. A method of manufacturing a field emission electron source comprising a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, and an anode electrode,
A step of preparing a substrate, a step of forming a doped diamond doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon on the substrate, and etching; A step of forming the electron-emitting portion from at least the doping diamond, a step of forming an insulating layer on the cathode, a step of forming the gate electrode on the insulating layer, and a resist on the gate electrode. A method of manufacturing a field emission electron source, comprising: a step of applying; and a step of removing the gate electrode and the insulating layer around the electron emission portion by etching. A method of manufacturing a field emission electron source comprising a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, and an anode electrode,
A step of preparing a substrate, a step of forming a doped diamond doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon on the substrate, and etching; A step of forming the electron emission portion from at least the doping diamond, and a layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium on the substrate, transitions of groups IVa to VIa Forming an intermediate layer including at least one of a carbide layer made of a metal or silicon carbide and a nitride layer made of a transition metal of group IVa to VIa, aluminum or silicon, and an insulating layer on the cathode And forming the gate electrode on the insulating layer And a step of applying a resist on the gate electrode, and a step of removing the gate electrode and the insulating layer around the electron emission portion by etching. . A method of manufacturing a field emission electron source comprising a cathode having a projection-shaped electron emission portion containing diamond as a material, a gate electrode, and an anode electrode,
A step of preparing a substrate, a step of forming a doped diamond doped with one or more elements selected from the group consisting of boron, nitrogen, phosphorus, sulfur, lithium and silicon on the substrate, and etching; A step of forming the electron emission portion from at least the doping diamond, and a layer made of at least one transition metal or silicon of zirconium, hafnium, vanadium, niobium, tantalum and chromium on the substrate, transitions of groups IVa to VIa Forming an intermediate layer including at least one of a carbide layer made of a metal or silicon carbide and a nitride layer made of a transition metal of group IVa to VIa, aluminum or silicon, and an insulating layer on the cathode And forming the gate electrode on the insulating layer A step of forming another insulating layer on the gate electrode, a step of forming a focusing electrode on the other insulating layer, a step of applying a resist on the focusing electrode, and etching. Removing the focusing electrode, the gate electrode, the insulating layer, and the another insulating layer around the electron emitting portion.   The step of forming the intermediate layer includes heating the metal film during or after depositing the metal film on the substrate to form a metal carbide layer at the interface between the substrate and the metal film. Item 22. The method for producing a field emission electron source according to Item 20 or 21. In the step of forming the insulating layer, the insulating layer is formed, a resist is applied on the insulating layer, and a series of steps of removing the insulating layer around the electron emission portion is performed a plurality of times,
The height of the electron emission part is z, the distance between the tip of the electron emission part and the gate electrode is d, and the thickness of the insulating layer is h, so that the insulation satisfies the conditions of d <z and d <h. The method for manufacturing a field emission electron source according to any one of claims 19 to 22, wherein a layer is formed.   24. The method of manufacturing a field emission electron source according to claim 23, wherein in the step of forming the insulating layer, the thickness of the last formed insulating layer is the maximum.   The method of manufacturing a field emission electron source according to any one of claims 19 to 22, wherein the substrate is a diamond substrate.   The field emission type according to claim 25, wherein the substrate is a diamond substrate, and includes a step of forming a protrusion shape on the diamond substrate by etching before the step of forming the doped diamond. Manufacturing method of electron source.   27. The electric field according to claim 26, wherein the substrate is a diamond substrate, and after forming the protrusion shape, the electron emission portion made of doped diamond is formed and does not include a subsequent protrusion shape forming step. A method for manufacturing a radiation electron source.

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