WO2023105899A1

WO2023105899A1 - Field emission element and method for producing same

Info

Publication number: WO2023105899A1
Application number: PCT/JP2022/037103
Authority: WO
Inventors: 昌善長尾; 博雅村田; 勝久村上
Original assignee: 国立研究開発法人産業技術総合研究所
Priority date: 2021-12-07
Filing date: 2022-10-04
Publication date: 2023-06-15
Also published as: JP2023084299A

Abstract

The present disclosure provides a field emission element 10 which is provided with: an emitter 12 that is formed on a substrate 11 and has an acute tip 12a; and a gate electrode 15 that is formed on the substrate, with insulating layers 13, 14 being interposed therebetween, and has an opening 15a from which the tip of the emitter is exposed. With respect to this field emission element 10, the gate electrode is formed of a polycrystalline multilayer graphene film. A method for producing a field emission element is also disclosed.

Description

Field emission device and manufacturing method thereof

The present invention relates to a field emission device that emits electrons from the tip of the emitter by applying a high voltage between the emitter and the gate electrode, and a manufacturing method thereof.

A field-emission electron source, which integrates an emitter with a conical shape perpendicular to the substrate and an extraction gate electrode for applying an electric field to emit electrons from the emitter, is used in display devices such as flat panel displays. , traveling wave tubes (ultra-high frequency tubes), etc.

A Spindt-type emitter is known as a field emission device (see, for example, Non-Patent Document 1). The inventor of the present application has disclosed a gate-electrode-integrated field emission device having a volcano-shaped extraction gate electrode (see Patent Document 1).

Field emission device arrays emit large currents when applied to traveling wave tubes and X-ray sources. When a large current is emitted, an unexpected discharge occurs between the emitter and gate electrode, and the discharge melts the emitter and gate electrode, causing a short circuit between the emitter and gate electrode, and the entire device stops functioning. A situation occurs.

In the field emission device, some of the electrons emitted from the emitter enter the gate electrode as an unexpected discharge, and as a result, gas is locally emitted from the gate electrode, and the gas emission is triggered. is also conceivable. A structure has been proposed in which, when a discharge occurs between an emitter and a gate electrode, an electrode as a fuse for power supply within a small block of a field emission device array is fused (see, for example, Patent Documents 2 and 3). ).

Japanese Patent No. 6635510 JP-A-4-284324 JP-A-5-144370

According to studies by the inventors of the present application, in field emission device arrays having the structures of Patent Documents 2 and 3, when discharge occurs between the emitter and the gate electrode in a small block, the fused electrode scatters, causing damage to the surrounding small blocks. It has been found that the field emission device array also causes an undesirable situation in which a short circuit occurs.

An object of the present invention is to provide a field emission device that avoids discharge between an emitter and a gate electrode, and suppresses adverse effects on other field emission devices even if discharge occurs.

According to one aspect of the present invention, an emitter having a sharp tip formed on a substrate, and a gate electrode having an opening exposing the tip of the emitter formed on the substrate with an insulating layer interposed therebetween. , wherein the gate electrode is composed of a polycrystalline multilayer graphene film.

According to the above aspect, since the gate electrode having the opening exposing the tip of the emitter is made of the multilayer graphene film, even if some of the electrons emitted from the emitter are incident on the gate electrode, abnormal discharge due to gas emission will occur. Even if the electrons enter the gate electrode and reach a high temperature, they do not melt and sublimate, so that defects such as short-circuiting between the emitter and the gate electrode do not occur. It is possible to provide a field emission device that suppresses adverse effects.

According to another aspect of the present invention, an emitter having a pointed tip formed on a substrate, and an opening exposing the tip of the emitter formed on the substrate with an insulating layer interposed therebetween, A method for manufacturing a field emission device comprising a gate electrode made of a multi-layered polycrystalline graphene film, the method comprising the steps of: forming a metal film at a position to be the gate electrode, and forming an amorphous carbon film thereon; and forming a polycrystalline multilayer graphene film in which the amorphous carbon film is crystallized at the position of the metal film by a layer exchange method in which the film and the amorphous carbon film are heated in a vacuum. provided.

According to the other aspect, the polycrystalline multilayer graphene film is formed as the gate electrode by using a layer exchange method between the metal film and the amorphous carbon film. The metal atoms of the metal film remain between the layers of the multilayer graphene film, and the orientation plane of the graphene in a part of the multilayer graphene film fluctuates from the direction parallel to the film surface of the multilayer graphene film. detachment can be suppressed.

1 is a cross-sectional view showing the configuration of a field emission device according to a first embodiment of the present invention; FIG. FIG. 2 is an explanatory diagram of a polycrystalline multilayer graphene film of a gate electrode; FIG. 4 is a process diagram (part 1) of the method for manufacturing the field emission device according to the first embodiment; FIG. 2 is a process diagram (part 2) of the method for manufacturing the field emission device according to the first embodiment; FIG. 4 is a cross-sectional view showing the configuration of a field emission device according to a second embodiment of the present invention; FIG. 11 is a process diagram (part 1) of the method for manufacturing the field emission device according to the second embodiment; FIG. 11 is a process diagram (part 2) of the method for manufacturing the field emission device according to the second embodiment; FIG. 10 is a cross-sectional view showing the configuration of a field emission device according to a third embodiment of the present invention; FIG. 5 is a cross-sectional view showing the configuration of a field emission device according to a fourth embodiment of the present invention;

Hereinafter, embodiments of the present invention will be described based on the drawings. Elements that are common among a plurality of drawings are denoted by the same reference numerals, and repeated detailed description of the elements is omitted.

[First embodiment]
FIG. 1 is a cross-sectional view showing the configuration of a field emission device according to the first embodiment of the present invention. Referring to FIG. 1, a field emission device 10 according to the present embodiment includes a substrate 11, an emitter 12 having a sharp tip 12a formed on the substrate 11, and an emitter 12 formed on the substrate 11 so as to surround the emitter 12. and a gate electrode 15 having an opening 15 a exposing the tip 12 a of the emitter 12 on the second insulating layer 14 . The field emission device 10 applies a high voltage, eg, 50 to 100 V, between the gate electrode 15 and the emitter 12 to extract electrons from the tip 12a of the emitter 12 and emit them to the outside.

The substrate 11 is a conductive substrate. The substrate 11 may be a substrate made of an insulating material, such as a glass substrate or a quartz substrate. In this case, an emitter electrode layer (not shown) made of a metal material is formed on the substrate 11 . The substrate 11 or emitter electrode layer is electrically connected to the emitter 12 .

The first insulating layer 13 is made of an insulating material, such as a silicon oxide film or an aluminum oxide film with a thickness of 500 nm. An opening 13 a communicating with the opening 15 a of the gate electrode 15 is formed in the first insulating layer 13 . The opening 13a is formed to be recessed from the emitter 12 more than the opening 15a.

The second insulating layer 14 is formed on the first insulating layer 13 and is made of an insulating material that is difficult for oxygen molecules and water molecules to permeate, such as a silicon nitride film. The second insulating layer 14 has a thickness of 30 nm, for example. The second insulating layer 14 prevents the oxygen molecules and water molecules released from the first insulating layer 13 from adversely affecting the formation of the multilayer graphene film of the gate electrode 15 on the second insulating layer 14 . Moreover, it is preferable to provide the second insulating layer 14 in terms of suppressing creeping discharge. When the first insulating layer 13 is a silicon thermally oxidized film, the second insulating layer 14 may be omitted because it does not adversely affect the formation of the multilayer graphene film. In the second insulating layer 14, an opening 14a communicating with the opening 13a and the opening 15a is formed.

The second insulating layer 14 preferably has a slight conductivity in that it can prevent discharge due to the charge-up of the field emission device 10, and preferably has an electrical resistance value of 1 GΩ to 10 GΩ.

The emitter 12 has a shape with a pointed tip 12a, for example, a conical or pyramidal shape. The emitter 12 is, for example, conical with a height of 800 nm and a diameter of 700 nm. The emitter 12 is made of metal material such as molybdenum, nickel, tungsten.

The gate electrode 15 is made of a polycrystalline multilayer graphene film. A multilayer graphene film is formed by stacking a plurality of two-dimensional sheet-like monolayer graphenes composed of a six-membered ring network of carbon atoms. The multilayer graphene film does not cause gas emission even if some of the electrons emitted from the emitter 12 are incident thereon, and can avoid abnormal discharge due to gas emission. The multilayer graphene film has an extremely high heat resistance with a sublimation point of 3500° C. or higher, and extremely high thermal conductivity. A defect such as a short circuit between 12 and gate electrode 15 does not occur.

FIG. 2 is an explanatory diagram of a polycrystalline multilayer graphene film of a gate electrode, where (a) is a plan view and (b) is a cross-sectional view. Referring to FIGS. 2A and 2B together with FIG. 1, the multilayer graphene film of the gate electrode 15 is made of polycrystal in which a large number of crystal grains 15b having grain boundaries 15c are formed. Each crystal grain 15b is formed by overlapping graphene 15d in multiple layers, and the orientation plane direction of each graphene 15d is substantially parallel to the film surface of the multilayer graphene film in the majority of the region 15e. This is the preferential orientation direction. As shown in FIG. 2B, the multilayer graphene film has a region 15f in which the orientation plane is inclined from the orientation plane of the surrounding region 15e forming the preferred orientation direction inside the crystal grain 15b or near the grain boundary. Some exist. That is, in the partial region 15f of the multilayer graphene film of the gate electrode 15, the orientation plane fluctuates from the direction parallel to the film surface of the multilayer graphene film. The region 15f in which the orientation surface fluctuates is about 1% in area ratio when the multilayer graphene film is viewed from above. In this way, the presence of the region 15f that fluctuates in the direction parallel to the film surface of the multilayer graphene film makes it difficult for the multilayer graphene film to peel off.

Since the orientation plane of the multilayer graphene film of the gate electrode 15 is partially swayed, the electrical resistivity in the orientation plane direction increases as the grain size of the crystal grains 15b decreases. On the other hand, the multi-layer graphene film is easy to peel when the grain size of the crystal grains 15b is large, and becomes difficult to peel when the grain size is small. Regarding the size of the crystal grains 15b, it is preferable that the average grain size is 300 nm to 3000 nm in terms of a good balance between the electrical resistivity and the difficulty of peeling. Especially preferred. The average grain size is measured using a transmission electron microscope (TEM), for example, on the multilayer graphene film. The exfoliated multilayer graphene film is placed on a TEM mesh, observed from a direction perpendicular to the orientation plane, and the particle diameter of the crystal grains 15b in a certain direction is measured. Find the diameter.

The multilayer graphene film of the gate electrode 15 contains metal atoms between graphene layers. A metal atom is an atom constituting a metal film used in the layer exchange method, and includes one metal selected from the group of Cr, Mn, Fe, Co, Ni, Ru, Ir, and Pt. This makes it difficult for the multilayer graphene film to peel off. This metal atom is preferably Ni because it has a low melting point and facilitates formation of a multilayer graphene film by a layer exchange method, as will be described later. It is particularly preferable to include 0.1% by weight to 1% by weight of the metal atoms in the multilayer graphene film in order to suppress exfoliation of the multilayer graphene film.

According to the present embodiment, since the gate electrode 15 having the opening 15a exposing the tip 12a of the emitter 12 is made of a multilayer graphene film, some of the electrons emitted from the emitter 12 are incident on the gate electrode 15. Even if the electrons enter the gate electrode 15 and reach a high temperature, they sublimate without melting, resulting in defects such as short-circuiting between the emitter 12 and the gate electrode 15. It is possible to provide the field emission device 10 that does not occur and that suppresses adverse effects on other field emission devices.

[Manufacturing Method of Field Emission Device According to First Embodiment]
3 and 4 are process diagrams of the method for manufacturing the field emission device according to the first embodiment. A method of manufacturing the field emission device 10 will be described with reference to FIGS. 3(a) to (d) and FIGS.

In the process of FIG. 3A, a first insulating film such as a silicon oxide film or an aluminum oxide film is formed on a conductive substrate 11 by a known film forming method such as a chemical vapor deposition (CVD) method or a sputtering method. Form layer 13A. When a substrate made of an insulating material, such as a silicon substrate, is used as the substrate 11, a metal film is formed as an emitter electrode layer on the silicon substrate by sputtering or vacuum deposition, and the first insulating layer 13A is formed thereon. . Alternatively, the silicon substrate may be made conductive by ion implantation or the like, and the first insulating layer 13A may be formed on the surface by thermal oxidation.

Next, a second insulating layer 14A is formed on the first insulating layer 13A by a known film forming method such as CVD or sputtering. The second insulating layer 14A is made of an insulating material that makes it difficult for oxygen molecules and water molecules from the first insulating layer 13 to permeate so as to eliminate adverse effects on the growth of the multilayer graphene film that serves as the gate electrode. The second insulating layer 14A is preferably a silicon nitride film that is difficult for oxygen molecules and water molecules to permeate. It is preferable that the thickness of the second insulating layer 14A is 20 nm or more because it is difficult for oxygen molecules and water molecules to pass therethrough. When the first insulating layer 13A is a silicon thermal oxide film, experiments have shown that a multilayer graphene film can be formed on the first insulating layer 13A by the method of the process of FIG. 3B without the second insulating layer 14A. Since it has been completed, the formation of the second insulating layer 14A may be omitted.

Next, a metal film 16A is formed on the second insulating layer 14A by a known film forming method such as sputtering or electron beam evaporation. The thickness of the metal film 16A is set to be the same as the thickness of the multilayer graphene film 15A formed by the layer exchange method in the step of FIG. 3B. The thickness of the metal film 16A may be set in consideration of electric field concentration and the like so that the finally formed field emission device 10 can easily emit electrons. The thickness of the metal film 16A is preferably 50 nm to 500 nm, more preferably 100 nm to 100 nm, from the viewpoint of film quality such as crystallinity, electrical resistivity, and thermal conductivity of the multilayer graphene film of the finally formed gate electrode 15. 200 nm is particularly preferred.

The metal film 16A is one metal selected from the group of Cr, Mn, Fe, Co, Ni, Ru, Ir and Pt. The layer exchange method and the elements of the metal film are disclosed in document Y. Nakajima et.al, ACS Appl. Mater. Interfaces 2018, 10, 41664-41669. The metal film 16A is preferably a Ni film because the formation temperature of the multilayer graphene film is low.

Next, an amorphous carbon film 18 is formed on the metal film 16A by a known film forming method such as CVD or sputtering. The thickness of the amorphous carbon film 18 is set to be the same as the thickness of the metal film 16A.

By forming an aluminum oxide film (not shown) having a thickness of about 2 nm between the metal film 16A and the amorphous carbon film 18, the film quality of the finally formed multilayer graphene film can be improved ( H. Murata et al., Scientific reports, (2019) 9, 4068).

Next, in the process of FIG. 3B, the substrate 11 on which the first insulating layer 13A, the second insulating layer 14A, the metal film 16A and the amorphous carbon film 18 are laminated in the process of FIG. 3A is heat-treated in a vacuum. , the multilayer graphene film 15A is formed by crystallizing the amorphous carbon film 18 at the position of the metal film 16A, the metal of the metal film 16A moves to the position of the amorphous carbon film 18, and the metal film 16B is formed. This process is called a layer exchange method. The heating conditions are appropriately selected according to the metal material of the metal film 16A, but are generally 800° C. for about one hour. When the metal of the metal film 16A was Ni, layer exchange occurred even under the heating condition of 500° C. for 1 hour.

In this step, metal atoms of the metal film 16A remain between the layers of the multilayer graphene film 15A. It is particularly preferable to include 0.1% by weight to 1% by weight of the metal atoms in the multilayer graphene film in order to suppress exfoliation of the multilayer graphene film. In addition, since the multilayer graphene film 15A has a region where the orientation surface fluctuates from the direction parallel to the film surface, the multilayer graphene film 15A that is difficult to peel off is formed.

Next, in the process of FIG. 3(c), the metal film 16B on the outermost surface is removed. The removing process is performed on the metal film 16B using an acidic chemical solution. If the metal film 16B is made of Ni, a nitric acid-based chemical solution may be used, and if the metal film 16B is made of another metal, aqua regia may be used. At this time, the chemical solution does not adversely affect the multilayer graphene film 15A, and the metal film 16B can be removed.

Next, a circular pattern with a diameter of about 1 μm is formed on the multilayer graphene film 15A by photolithography, and the underlying multilayer graphene film 15A, the second insulating layer 14A and the first insulating layer 13A are removed, and the substrate 11 is formed. An etching process is performed to expose the surface of , and a recess 17 consisting of openings 13a to 15a is formed. A reactive etching (RIE) method can be used for the etching process. In the etching by the RIE method, oxygen gas is used for the multilayer graphene film 15A, sulfur hexafluoride (SF ₆ ) gas is used when the second insulating layer 14A is a silicon nitride (SiN) film, and the first insulating layer 13A is etched. In the case of a silicon oxide (SiO ₂ ) film, mixed gas of tetrafluoromethane (CF ₄ ) and hydrogen (H ₂ ) gas, trifluoromethane (CHF ₃ ) gas, or the like is used. A known gas can be used for the RIE method depending on the material to be etched.

Next, an etching process is performed using a buffered hydrofluoric acid (BHF) solution to remove the second insulating layer 14A, the first insulating layer 13A, and the second insulating layer 14A in the lateral direction (in-plane direction). . Since the SiN film and the SiO ₂ film have different etching rates with respect to the BHF solution, as shown in FIG. structure.

Next, in the step of FIG. 3D, while rotating the substrate 11, a sacrificial layer material is vapor-deposited obliquely with respect to the substrate 11 to cover the surface of the multi-layer graphene film that will become the gate electrode 15 and the side wall of the opening 15a. A sacrificial layer 19 is formed. The angle of the oblique deposition is set so that the side walls of the opening 15a are sufficiently covered with the sacrificial layer material. The material of the sacrificial layer 19 is not particularly limited as long as it can be easily removed with an acid or alkaline chemical solution, and aluminum and magnesium oxide, for example, can be used.

Next, in the process of FIG. 4A, emitter material is deposited vertically on the substrate 11 by electron beam evaporation or ionized sputtering to form the conical emitter 12 on the surface of the substrate 11 within the recess 17 . Emitter material 12A is deposited on the surface of sacrificial layer 19 by this vapor deposition. The ionized sputtering method is performed, for example, by the method disclosed in Japanese Patent No. 6093968. In the ionized sputtering method, the choice of emitter materials _is wider than in the _electron beam evaporation method. Carbide, carbide semiconductors such as SiC and GeC (including those doped with impurities), conductive nitrides such as TiN, VN, CrN, ZrN, NbN, MoN, HfN, TaN, and WN, nitrides such as AlN and GaN semiconductors ₍ including _those doped with _impurities ), _Sr2RuO4 , _SrRuO3 , _RuO2 , _IrO2 , _Sr4Ru3O10 , _CaRuO3 , _BaRuO3 _, _LaNiO3 , _La3Ni2O7 _, _ReO3 , SrFeO ₃ , SrCoO ₃ , SrIrO ₃ , ZnO, InO ₂ , InGaZnO, and other conductive oxides can also be used.

In this step, stress is applied to the multi-layer graphene film of the gate electrode 15 via the sacrificial layer 18 due to the deposition of the emitter material, making it easier to peel off. However, in the multilayer graphene film 15A of the present embodiment, metal atoms remain between the layers in the previous step of FIG. Delamination of the multilayer graphene film itself can be suppressed by swaying from the direction parallel to .

Next, in the step of FIG. 4B, the sacrificial layer 19 is dissolved with an acid or alkaline chemical, the emitter material 12A deposited on the sacrificial layer 19 is removed, and the surface of the gate electrode 15 is exposed. When aluminum is used as the material of the sacrificial layer 19, an alkaline chemical solution such as sodium hydroxide can be used. As a result, only aluminum can be removed without dissolving the emitter 12 and the gate electrode 15 . When magnesium oxide is used as the material of the sacrificial layer 19, an acid that does not dissolve the material of the emitter 12, such as dilute acetic acid, can be used. The field emission device 10 is formed by the above steps.

According to the manufacturing method of the present embodiment, the polycrystalline multilayer graphene film 15A is formed as the gate electrode 15 by using the layer exchange method of the metal film 16A and the amorphous carbon film 18. The metal atoms of the metal film 16A remain between the layers of the multilayer graphene film, and the orientation plane of each crystal grain of the multilayer graphene film fluctuates from the direction parallel to the film surface of the multilayer graphene film, so that the multilayer graphene film itself is Peeling can be suppressed.

[Second embodiment]
FIG. 5 is a cross-sectional view showing the configuration of a field emission device according to the second embodiment of the invention. Referring to FIG. 5, the field emission device 50 according to the present embodiment includes a substrate 11, an emitter 52 formed on the substrate 11 and having a sharp tip 52a, and an emitter 52 formed on the substrate 11 so as to surround the emitter 52. and a gate electrode 55 having an opening 55 a exposing the tip 52 a of the emitter 52 on the second insulating layer 54 . Each component of the field emission device 50 is made of the same material as that of the field emission device 10 of the first embodiment, and detailed description thereof will be omitted. The field emission device 50 of this embodiment has a so-called volcano shape. The gate electrode 55 has a peripheral portion 55b of the opening 55a that extends along the surface of the tip portion 52a of the emitter 52 while being spaced apart, and has a shape in which the diameter of the opening 55a is smaller than that of the base portion 55c of the peripheral portion 55b. .

The gate electrode 55 is composed of a multilayer graphene film similar to that of the field emission device 10 of the first embodiment. The gate electrode 55 has a portion formed parallel to the substrate 11 (hereinafter also referred to as a parallel portion 55d) and a peripheral edge portion 55b extending obliquely upward at a base portion 55c. As for the orientation direction of the multilayer graphene film of the gate electrode 55, the parallel portion 55d is parallel to the substrate 11, and the peripheral edge portion 55b is parallel to the surface of the peripheral edge portion 55b and obliquely upward. The multilayer graphene film is formed by bending the orientation direction of the multilayer graphene film along the bent shape of the base portion 55c. In the vicinity of the opening 55a of the gate electrode 55, even if a discharge occurs between the gate electrode 55 and the emitter 52 and an overcurrent flows, the multi-layered graphene film will extend from the peripheral portion 55b of the gate electrode 55 to the peripheral parallel portion. Since the gate electrode 55 is oriented so that current can easily flow toward 55d, the gate electrode 55 is less likely to generate Joule heat and is less likely to reach a high temperature.

The height of the peripheral edge portion 55b of the gate electrode 55 is equal to or higher than that of the tip portion 52a of the emitter 52, for example, about 100 nm. Also, the spread of the emitted electron beam can be suppressed to some extent.

The second insulating layer 54 is formed to cover the bottom surface of the gate electrode 55 . It is preferable that the second insulating layer 54 is formed so as to cover the entire surface of the peripheral portion 55b of the gate electrode 55 facing the emitter 52 in that creeping discharge is suppressed by increasing the creeping distance of the insulator. .

The first insulating layer 53 is formed to cover the base of the emitter 52 and expose the tip 52a. Thereby, unnecessary electron emission caused by triple junction or the like can be suppressed.

According to the present embodiment, the same effects as those of the first embodiment are obtained, and furthermore, since it has a volcanic structure, even if discharge occurs between the gate electrode 55 and the emitter 52, the multilayer graphene film is oriented so that current can easily flow from the peripheral edge portion 55b of the gate electrode 55 to the peripheral parallel portion 55d. can.

[Manufacturing Method of Field Emission Device According to Second Embodiment]
6 and 7 are process diagrams of a method for manufacturing a field emission device according to the second embodiment. A method of manufacturing the field emission device 10 will be described with reference to FIGS.

In the process of FIG. 6( a ), a pointed emitter 52 is formed on the substrate 11 . Specifically, a method of etching a silicon substrate to form a sharp shape can be used. There is no particular limitation as long as the method can form a conical or pyramidal shape.

Next, in the process of FIG. 6(b), a first insulating layer 53A covering the surface of the substrate 11 and the emitter 52 is formed by the same method as in the first embodiment. For the first insulating layer 53A, the CVD method is preferably used to cover the entire emitter 52. For example, a silicon oxide film may be formed by the plasma-enhanced CVD method using tetraethoxysilane gas.

Next, a second insulating layer 54A, eg, a silicon nitride film, is formed to cover the surface of the first insulating layer 53A. A well-known film formation method such as a CVD method, a sputtering method, or the like can be used. It is preferred to use the method.

Next, a metal film 56A is formed on the second insulating layer 54A, and an amorphous carbon film 58 is further formed. The metal film 56A and the amorphous carbon film 58 are formed in the same manner as the metal film 16A and the amorphous carbon film 58 of the first embodiment, respectively.

Next, in the process of FIG. 6C, the substrate 11 on which the first insulating layer 53A, the second insulating layer 54A, the metal film 56A and the amorphous carbon film 58 are laminated in the process of FIG. 6B is heat-treated in a vacuum. is performed to form a multilayer graphene film 55A in which the amorphous carbon film 58 is crystallized at the position of the metal film 56A, the metal of the metal film 56A moves to the position of the amorphous carbon film 58, and the metal film 56B is formed. The process of FIG. 6(c) is performed in the same manner as the process of FIG. 3(b) of the first embodiment.

Next, in the process of FIG. 7(a), the removal of the outermost metal film 56B is performed in the same manner as in the process of FIG. 3(c) of the first embodiment.

Next, in the step of FIG. 7(b), the multilayer graphene film 55A and the second insulating layer 54A immediately above the tip of the emitter are removed. A so-called etch-back method can be used for this selective removal treatment. Specifically, a photoresist having a film thickness that covers the multilayer graphene film 55A and is flattened over the entire substrate 11 is applied. Next, the photoresist is uniformly etched with oxygen plasma, and the multilayer graphene film 55A is etched until the convex multilayer graphene film 55A directly above the tip 52a of the emitter 52 appears and the second insulating layer 54A is exposed. An opening 55a is formed. The height of the opening 55a of the gate electrode 55 is controlled by the etching time or the like.

Next, the second insulating layer 54A exposed in the opening 55a of the gate electrode 55 is etched to expose the first insulating layer 53A and form the opening 54a. When the second insulating layer 54A is a silicon nitride film, sulfur hexafluoride (SF ₆ ) gas, for example, can be used as the etching gas.

Next, in the step of FIG. 7(c), the first insulating layer 53A exposed from the

openings

54a and 55a is removed, and the tip 52a of the emitter 52 is exposed. A buffered hydrofluoric acid solution can be used in this removal treatment. Through the above steps, the field emission device 50 is formed.

According to the manufacturing method of this embodiment, the gate electrode 55 of the polycrystalline multilayer graphene film is formed by using the layer exchange method. The gate electrode 55 has a parallel portion 55 d parallel to the substrate 11 and a peripheral edge portion 55 b extending obliquely upward following the conical shape of the emitter 52 . Since the orientation direction of graphene in the multilayer graphene film is formed along the shape of the gate electrode 55, the orientation direction is changed at the base portion 55c. Thereby, the effect of the field emission device 50 described above is exhibited.

[Third embodiment]
FIG. 8 is a cross-sectional view showing the configuration of a field emission device according to the third embodiment of the invention. Referring to FIG. 8, the field emission device 80 according to the present embodiment includes a substrate 11, an emitter 52 formed on the substrate 11 and having a sharp tip 52a, and an emitter 52 formed on the substrate 11 so as to surround the emitter 52. a gate electrode 55 having an opening 55a exposing the tip 52a of the emitter 52 on the second insulating layer 54; the emitter 52 and the gate electrode 55 on the gate electrode 55; A third insulating layer 81 and a fourth insulating layer 82 formed to surround an opening 55a of the electrode 55, and a focusing electrode 83 having an opening 83a on the fourth insulating layer 82 to expose the emitter 52 and the gate electrode 55. and The field emission device 80 is a modification of the volcano-type field emission device 50 according to the second embodiment, and has a configuration in which the field emission device 50 is provided with a focusing electrode 83 .

The third insulating layer 81 is made of the same material as the first insulating layer 53 . The fourth insulating layer 82 is made of the same material as the second insulating layer 54 and is provided to prevent creeping discharge. This is to prevent the formation of a focal point (triple junction). A triple junction is a point where three things meet: a metal (a conductive substance), an insulator (a substance other than vacuum and air), and a vacuum. Originally unnecessary electron emission occurs due to field emission due to a strong electric field from the triple junction. The fourth insulating layer 82, like the second insulating layer 54, is preferably slightly more conductive than a perfectly insulating material.

The focusing electrode 83 is made of a conductive material, for example, a metal material such as niobium, and may use a multilayer graphene film. Since a potential between the potential applied to the gate electrode 55 and the potential applied to the emitter 52 is generally applied to the focusing electrode 83, the probability that electrons emitted from the emitter 52 flow in is low. No need.

[Manufacturing Method of Field Emission Device According to Third Embodiment]
6A to 6C and 7A are performed in the same manner as the field emission device 50 according to the second embodiment, and a second 3. An insulating layer 81, a fourth insulating layer and a focusing electrode 83 are formed. 7(b), the opening of the focusing electrode 83 and the opening of the fourth insulating layer 82 are formed using the etch-back method, and the third insulating layer 81 is etched from these openings with a BHF solution. is removed to form an opening. Then, the process of FIG.7(c) is performed. When the third insulating layer 81, the fourth insulating layer, and the focusing electrode 83 are formed on the multilayer graphene film 55A, the stress is applied to the multilayer graphene film and the film is easily peeled off. However, the orientation plane of each crystal grain of the multilayer graphene film 55A fluctuates from the direction parallel to the film surface of the multilayer graphene film, and the metal atoms of the metal film 56A remain between the layers of the multilayer graphene film 55A. As in the first and second embodiments, exfoliation of the multilayer graphene film can be suppressed.

[Fourth embodiment]
FIG. 9 is a cross-sectional view showing the structure of a field emission device according to the fourth embodiment of the invention. Referring to FIG. 9, the field emission device 90 according to the present embodiment is similar to the field emission device according to the third embodiment except that a fifth insulating layer 91 is provided between the gate electrode 55 and the third insulating layer 81. It has the same configuration as 80.

The fifth insulating layer 91 is an adhesion layer for enhancing adhesion between the multilayer graphene film of the gate electrode 55 and the third insulating layer 81 . The fifth insulating layer 91 is preferably made of a material that does not contain oxygen, such as silicon nitride. The fifth insulating layer 91 is formed, for example, by a reactive sputtering method using nitrogen gas and using pure silicon as a target.

Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and changes can be made within the scope of the present invention described in the claims. It is possible.

Reference Signs List

10, 50, 80, 90 field emission device 11

substrate

12, 52

emitter

13, 53 first insulating

layer

14, 54 second insulating

layer

15, 55

gate electrode

15A, 55A

multilayer graphene film

16A, 16B, 56A,

56B metal Films

18, 58 Amorphous carbon film 83 Focusing electrode 91 Fifth insulating layer

Claims

a pointed emitter formed on a substrate;
a gate electrode having an opening exposing a tip of the emitter formed on the substrate through an insulating layer;
The field emission device, wherein the gate electrode is composed of a polycrystalline multilayer graphene film.
The multilayer graphene film includes a plurality of crystal grains,
2. The field emission device according to claim 1, wherein the orientation direction of the multilayer graphene film is deviated from the preferential orientation direction in a partial region of the crystal grains.
The field emission device according to claim 2, wherein the crystal grains have an average grain size of 300 nm to 3000 nm when the multilayer graphene film is viewed from above.
The field emission device according to claim 2, wherein the multilayer graphene film contains 0.1% to 1% by weight of metal atoms.
The field emission device according to claim 1, wherein the multilayer graphene film contains 0.1% by weight to 1% by weight of metal atoms.
3. The gate electrode has a peripheral portion of the opening extending along the surface of the tip portion of the emitter while being spaced apart, and the opening having a shape with a smaller diameter than the base of the peripheral portion. 1. The field emission device according to 1.
The multilayer graphene film includes a plurality of crystal grains,
7. The field emission device according to claim 6, wherein the orientation direction of the multilayer graphene film is deviated from the preferential orientation direction in some regions of the crystal grains.
8. The field emission device according to claim 6, wherein said multilayer graphene film is formed so that the orientation direction of crystal grains corresponds to the shape of said gate electrode.
Convergence having another insulating layer on the gate electrode outside the opening of the gate electrode and another opening exposing the tip of the emitter and the tip of the gate electrode on the other insulating layer. 7. The field emission device of Claim 6, further comprising an electrode.
The multilayer graphene film includes a plurality of crystal grains,
10. The field emission device according to claim 9, wherein the orientation direction of the multilayer graphene film is deviated from the preferential orientation direction in some regions of the crystal grains.
11. The field emission device according to claim 10, further comprising an adhesion layer between said gate electrode and said other insulating layer.
The field emission device according to claim 9, further comprising an adhesion layer between said gate electrode and said other insulating layer.
A gate electrode made of a multi-layered polycrystalline graphene film, having an emitter formed on a substrate with a pointed tip, and an opening exposing the tip of the emitter formed on the substrate with an insulating layer interposed therebetween. and a method for manufacturing a field emission device,
forming a metal film at a position to be the gate electrode and an amorphous carbon film thereon;
and forming a polycrystalline multilayer graphene film in which the amorphous carbon film is crystallized at the position of the metal film by a layer exchange method in which the metal film and the amorphous carbon film are heated in a vacuum. Method.
forming a recess exposing the substrate in the multilayer graphene film and the insulating layer;
14. The method of claim 13, further comprising forming said emitter on said substrate within said recess.
forming the emitter on the substrate before forming the metal film;
14. The manufacturing method according to claim 13, further comprising, after forming the multilayer graphene film, forming the opening in the multilayer graphene film to expose the tip of the emitter.