JP2006351410A - Electron emitting element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron emitting element superior in electron emitting ability, its uniformity, and stability, and which is composed of a simple structure not having microstructure to require micro-fabrication and in which a diamond emitter is formed. <P>SOLUTION: In the electric field emission type electron emitting element in which an insulating layer 14 and a gate electrode 15 are sequentially laminated on the substrate 11, an opening part which reaches the substrate is installed at the gate electrode 15 and the insulating layer 14, and on the substrate 11 in the opening part, an emitter 12 is formed so that the emitter 12 will not contact the gate electrode 15, the emitter 12 is composed of diamond or diamond-shaped carbon, and the surface of the emitter 12 is terminated by electron donating groups 13. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a field emission type electron-emitting device (field emitter) that emits electrons by a strong electric field. More specifically, as an electron generation source or electron gun for an optical printer, an electron microscope, an electron beam exposure apparatus or the like, or as an ultra-compact illumination source for an illumination lamp, and more particularly, an array field emitter array constituting a flat display. The present invention relates to an electron-emitting device in which a diamond emitter useful as a surface electron source is formed.

  Conventionally, a cathode ray tube has been widely used as an electronic display device. However, the cathode ray tube consumes a large amount of energy in order to emit thermal electrons from the cathode of an electron gun, and requires a large volume in terms of structure. There were problems such as.

  For this reason, there is a demand for a flat display that can use cold electrons instead of thermal electrons to reduce energy consumption as a whole, and further downsize the device itself. Realization of high-speed response and high resolution is strongly demanded for the type display.

As a structure of a flat display using such cold electrons, a structure in which minute electron-emitting devices are arranged in an array in a flat plate cell of high vacuum is promising. As an electron-emitting device used for this purpose, a field-emission type electron-emitting device using a field emission phenomenon has attracted attention. In this field emission type electron-emitting device, when the strength of the electric field applied to the material is increased, the width of the energy barrier on the surface of the material is gradually reduced according to the strength, and a strong electric field having an electric field strength of 10 ⁷ V / cm or more is obtained. This makes use of the phenomenon that electrons in a substance can break through its energy barrier by the tunnel effect, and thus electrons are emitted from the substance. In this case, since the electric field follows Poisson's equation, if a portion where the electric field concentrates is formed on the member (emitter) that emits electrons, cold electrons can be efficiently emitted with a relatively low extraction voltage.

  As a general field emission type electron-emitting device, as shown in FIG. 3, a conical device having a sharp tip can be exemplified. In this element, a conductive layer 32, an insulating layer 33, and a gate electrode 34 are sequentially stacked on an insulating substrate 31, and an opening A reaching the conductive layer 32 is formed in the insulating layer 33 and the gate electrode 34. Has been. A conical emitter 35 having point-like protrusions is formed on the conductive layer 32 in the opening A so as not to contact at least the gate electrode 34.

  Among such conical emitters, Spindt-type emitters are widely known. An example of manufacturing an electron-emitting device including a Spindt-type emitter will be described with reference to FIGS.

First, as shown in FIG. 4A, an insulating layer 43 and a gate electrode 44 are sequentially formed on an insulating substrate 41 on which a conductive layer 42 has been formed in advance by sputtering or vacuum evaporation. Subsequently, using a photolithography method and a reactive ion etching (RIE) method, a circular hole (gate hole) is opened in part of the insulating layer 43 and the gate electrode 44 until the conductive layer 42 is exposed. Etch into. Next, as shown in FIG. 4B, a release layer 45 is formed only on the upper surface and side surfaces of the gate electrode 44 by oblique vapor deposition. As the material of the release layer 45, Al, MgO, or the like is often used. Subsequently, as shown in FIG. 4C, a metal material for the emitter 46 is deposited on the conductive layer 42 by normal anisotropic deposition from the perpendicular direction. At this time,
As the deposition progresses, the opening diameter of the gate hole is reduced, and at the same time, a conical emitter 46 is formed on the conductive layer 42 in a self-aligning manner. Deposition is performed until the gate hole is finally closed. As the material of the emitter, a metal such as Mo or Ni is used. Finally, as shown in FIG. 4D, the lift-off material 45 is removed by etching, and the gate electrode 44 is patterned as necessary. Thereby, an electron-emitting device having a Spindt-type emitter is obtained.

Known documents are described below.
CA Spindt: J. Appl. Phys., 39, 3504 (1968).

  On the other hand, silicon emitters using semiconductor integrated circuit manufacturing technology are also widely known.

  An example of manufacturing an electron-emitting device including a silicon emitter will be described with reference to FIGS. First, as shown in FIG. 5A, a single crystal silicon substrate 51 is thermally oxidized to form a silicon oxide layer on the surface, and the silicon oxide layer is patterned into a circular shape using a photolithography method, A circular silicon oxide layer 52 for etching mask is formed. This silicon oxide layer 52 also functions as a lift-off material as will be described later. The diameter of the silicon oxide layer 52 substantially corresponds to the gate diameter.

  Next, as shown in FIG. 5B, the silicon substrate 51 is etched by reactive ion etching (RIE) under a condition with a high side etch rate to form an emitter 53.

  Subsequently, as shown in FIG. 5C, an emitter tip sharpening silicon oxide layer 54 is formed on the surfaces of the silicon substrate 51 and the emitter 53 by thermal oxidation. Due to the stress generated when the silicon oxide layer 54 is formed, the tip of the emitter 53 inside the silicon oxide layer 54 is easily sharpened. Then, as shown in FIG. 5D, an insulating layer 55 and a gate electrode 56 are stacked by anisotropic vapor deposition. Finally, as shown in FIG. 5E, the etching mask silicon oxide layer 52 that also functions as a lift-off material is lifted off by etching, and the silicon oxide layer 54 on the surface of the emitter 53 is removed by etching. Then, the gate electrode 56 is patterned as necessary. Thereby, an electron-emitting device including a silicon emitter is obtained.

Known documents are described below.
K. Betsui: Tech. Dig. IVMC., (1991) p26.

  However, in the above-described Spindt-type emitter and silicon emitter, the metal or silicon, or a compound thereof, which is an emitter material, has a positive electron affinity (PEA), and therefore has a low electron emission ability, and the emitter portion. Concentration of the electric field on was essential. Therefore, in order to emit electrons from the surface of the emitter material, it is necessary to make the radius of curvature of the electron emission part as small as possible. As shown above, the emitter is subjected to ultrafine processing, and the tip shape of the emission part It was indispensable to have a conical shape with a radius of curvature of the tip of several nanometers or less.

  Furthermore, in order to be applied as a surface electron source for a display or the like, it is necessary to produce a large number of conical emitters obtained by performing the ultrafine processing as described above and arrange them on the array. However, because ultra-precision machining is required, structural defects are likely to occur, and it is not easy to produce a large area uniformly, resulting in a decrease in yield, and in addition, defect inspection is indispensable, resulting in an increase in manufacturing cost. was there.

On the other hand, as shown in FIG. 6, it has been proposed to make a disk-type emitter that does not have a conical shape and can be easily processed and has good uniform workability over a large area. In this disk-type emitter, an electric field concentrates on the ring-shaped peripheral edge Pe of the emitter 64, which is a boundary line between the emitter surface 64a and the emitter peripheral surface 64b, and electrons are emitted therefrom. In general, an emitter base layer 63 is formed between the emitter 64 and the emitter wiring layer 62 on the insulating substrate 61. It is desirable that the emitter underlayer 63 has a diameter smaller than the diameter of the emitter 64 so that the electric field can be easily concentrated on the peripheral edge Pe of the disk-shaped emitter. It is made of a material that is easier to etch than the emitter 64.

  An example of manufacturing an electron-emitting device having a disk-type emitter will be described with reference to FIGS.

  First, as shown in FIG. 7A, an emitter underlayer 73a and an emitter 74a material are sequentially formed on a glass substrate 71 on which an emitter wiring 72 has been formed in advance by sputtering or vacuum evaporation. Subsequently, as shown in FIG. 7B, a part of the material of the emitter base layer 73a and the emitter 74a is exposed using the photolithography method and the reactive ion etching method (RIE) until the emitter wiring 72 is exposed. Etching into a circular shape. Here, the photoresist used as the etching mask is left as the lift-off material 75.

  Next, as shown in FIG. 7C, the insulating layer 76 and the gate electrode 77 are deposited on the emitter wiring layer 72 by normal anisotropic deposition from the perpendicular direction. Finally, as shown in FIG. 7D, the lift-off material 75 is peeled off, and the gate electrode 77 is patterned as necessary. Thereby, an electron-emitting device having a disk-type emitter is obtained.

Known documents are described below.
Tech. Dig. 5th Int. Vac. Microelectronics Conf. (1992) p5-4).

  Since the disk-type emitter as described above does not need to be processed so that the emitter has a very sharp radius of curvature, the manufacturing method is very simple. However, the emitter material in the disk-type emitters disclosed so far is a metal, silicon, or a compound thereof, all of which exhibit the physical properties of PEA, have a low electron emission ability, and hence a high operating voltage. was there. Furthermore, it is very difficult to control the electron affinity (or work function) of an emitter made of metal, silicon, or a compound thereof because an oxide is easily generated on the surface in the atmosphere. Therefore, the electron emission characteristics vary between emitters or elements, and the thermal conductivity of the emitter material is low, so that element destruction due to Joule heat or the like also occurs.

  The present invention has been made in consideration of the above problems, and has an electron emission ability, uniformity, stability, and an electron having a diamond emitter formed of an easy structure that does not have a micro structure that requires micro processing. An object is to provide an emitting element.

  In order to solve the above problem, in the present invention, an insulating layer and a gate electrode are sequentially laminated on a base, an opening reaching the base is provided in the gate electrode and the insulating layer, and an emitter is formed on the base in the opening. Field emission type electron-emitting device formed so as not to contact the gate electrode, wherein the emitter is made of diamond or diamond-like carbon, and the surface of the emitter is terminated by an electron donating group An element is provided.

  As a result of detailed examination of the chemisorbed species and surface properties (work function, electron affinity, electrical conductivity, thermal conductivity) of the surface of diamond or diamond-like carbon, the present inventor found It was found from experimental facts that it has an electron affinity (NEA) and a very high electron emission ability.

  That is, it was found that the electron-donating group-terminated surface has an electric conductivity of several ohm centimeters or more, and has a thermal conductivity that is an order of magnitude higher than other materials of 10 W / cmK or more.

  Further, it was confirmed that such an electron donating group-terminated surface was not oxidized even in the atmosphere like other materials over time, and various physical properties did not change.

  From the experimental results as described above, diamond or diamond-like carbon having an electron-donating group-terminated surface, which shows an electron emission ability and thermal conductivity that are orders of magnitude higher than those of conventional metals, silicon and their compounds, is used as an emitter material. As a result, a high-performance and stable emitter can be obtained.

  The present invention also provides an electron-emitting device, wherein the electron donating group is any one of hydrogen, a hydrocarbon, and a hydroxyl group.

  In the present invention, the electron donating group is preferably hydrogen, hydrocarbon, or hydroxyl group.

  That is, since it can be easily generated on the surface of diamond or diamond-like carbon by plasma reaction or liquid layer reaction, it is easy to obtain a high-performance emitter simply because the electron donating group is hydrogen, hydrocarbon or hydroxyl group. Desirable from a viewpoint.

  Furthermore, in the present invention, there is provided an electron-emitting device characterized in that the emitter has any one of a columnar shape, a polygonal columnar shape, a truncated cone shape, and a polygonal truncated pyramid shape with the base on the base.

  In the present invention, it is desirable that the emitter has a shape of a cylinder, a polygonal column, a truncated cone or a polygonal frustum with the base on the base.

  In other words, when diamond or diamond-like carbon, which exhibits a very high electron emission capability, is used as the emitter material, the emitter tip tip structure does not need to be sharp or have a disk-like upper structure, and is very easy to manufacture. Even if it is an easy cylinder or truncated cone shape, sufficient characteristics can be obtained. Here, even if the emitter tip shape is a polygonal column or a polygonal frustum, the same effect can be obtained.

  According to the present invention, by using diamond or diamond-like carbon whose surface is terminated by an electron donating group as an emitter material, high electron emission can be achieved with an easy structure that does not require an ultrafine processing process and a simple manufacturing method. A uniform and stable electron-emitting device can be obtained.

  Therefore, even when applied to a flat panel display or the like, a high-speed, high-definition image can be obtained with low power consumption.

  The best mode for carrying out the invention will be described below.

  FIG. 1 is an explanatory view showing in cross section an example of a diamond emitter according to the electron-emitting device of the present invention. As shown in the figure, this diamond emitter has a structure in which a diamond emitter 12 is laminated on a substrate 11. The surface of diamond has a structure terminated with hydrogen (H) as an electron donating group 13. The structure of the diamond emitter is a cylinder. An insulating layer 14 and a gate electrode 15 are laminated so as to surround the diamond emitter.

  In the present invention, the substrate 11 is used as a support substrate for a diamond emitter. As such a substrate, a diamond substrate, a silicon substrate, a metal substrate, a glass substrate, a ceramic substrate, a quartz substrate, an SOI substrate, or the like can be used. When the substrate is an insulator, a metal thin film can be interposed as an electrode on the substrate.

  The diamond emitter 12 can be composed of diamond or diamond-like carbon made of single crystal, polycrystal, or nanocrystal. Further, a diamond film doped with impurities or diamond-like carbon can also be used.

  The shape of the emitter tip can be a cone, a truncated cone, a polygonal column, or a polygonal frustum in addition to a cylinder.

  Examples of the electron donating group 13 on the diamond surface include hydrogen, hydrocarbon, and hydroxyl group.

  The insulating layer 14 may be a metal oxide such as silicon oxide, silicon nitride, or aluminum oxide, or a nitride film as an insulating thin film.

  Examples of the material of the gate electrode 15 include refractory metals such as niobium, tantalum, titanium, molybdenum, and chromium.

  A manufacturing example of the electron-emitting device of the present invention will be specifically described with reference to FIG.

  FIG. 2 is a schematic explanatory view showing, in cross section, an example of the manufacturing process of the electron-emitting device of the present invention. First, as shown in FIG. 2A, a diamond film 22 'was formed on a silicon substrate 21 by a microwave plasma CVD method.

  The conditions for microwave plasma CVD are as follows.

Source gas: methane (50 sccm), hydrogen (450 sccm),
Substrate temperature: 820 ° C
Reaction pressure: 10.6 kPa
MW power: 2.5kW
Film thickness: 1 μm.

  Next, a silicon oxide film 23 was formed on the diamond film 22 'as a mask (hard mask) for etching, and then patterned to form a hard mask pattern. Subsequently, after applying a photoresist with a film thickness of 2 μm, a resist pattern (not shown) was formed by photolithography. Here, a circular pattern having a diameter of 7 μm was prepared.

  Next, as shown in FIG. 2B, the diamond film 22 'was etched into a predetermined shape by high frequency reactive ion etching (RIE) to form a cylindrical diamond emitter 22.

  Subsequently, as shown in FIG. 2C, the insulating layer material 24 'and the gate electrode material 25' were continuously deposited while leaving the hard mask as a lift-off material.

  Subsequently, as shown in FIG. 2D, the resist was removed by lift-off, and at the same time, the insulating layer material 24 ′ and the gate electrode material 25 ′ on the resist were removed to form the insulating layer 24 and the gate electrode 25.

  Finally, as shown in FIG. 2E, an electron-emitting device having a diamond emitter was obtained by hydrogen plasma treatment using high frequency or microwave. Plasma treatment conditions are as follows.

Source gas: Hydrogen (100 sccm)
Substrate temperature: room temperature Reaction pressure: 13.3 Pa
High frequency power: 300W
Time: 3 minutes.

  From the results of the micro-area XPS analysis, it was confirmed that oxygen was not adsorbed on the diamond emitter surface that had been subjected to the hydrogen plasma treatment (that it was a hydrogenated surface).

  When the produced diamond emitter was provided with a gap of 10 mm, an anode was installed and the electron emission characteristics were confirmed, electron emission was confirmed from the diamond emitter when a gate voltage of several volts or more was applied.

It is the model explanatory drawing which showed the example of the diamond emitter which concerns on the electron-emitting element of this invention in the cross section. It is the model explanatory drawing which showed the Example of the manufacturing process of the electron emission element of this invention in the cross section. It is an external view of the example of the conventional electron emission element. It is the model explanatory drawing which showed the example of the manufacturing process of the conventional electron emission element in the cross section. It is the model explanatory drawing which showed the other example of the manufacturing process of the conventional electron emission element in the cross section. It is an external view of the other example of the conventional electron emission element. It is the model explanatory drawing which showed the other example of the manufacturing process of the conventional electron emission element in the cross section.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Base 12 ... Diamond emitter 13 ... Electron donating group 14 ... Insulating layer 15 ... Gate electrode 21 ... Silicon substrate 22 ... Diamond emitter 22 '... Diamond film 23 ..Silicon oxide film 24 ... insulating layer 24 '... insulating material 25 ... gate electrode 25' ... electrode material 31 ... insulating substrate 32 ... conductive layer 33 ... insulating layer 34 ... Gate electrode 35 ... Emitter 41 ... Insulating substrate 42 ... Conductive layer 43 ... Insulating layer 44 ... Gate electrode 45 ... Release layer (lift-off material)
51 ... Single crystal silicon substrate 52 ... Silicon oxide layer 53 ... Emitter 54 ... Silicon oxide layer 55 ... Insulating layer 56 ... Gate electrode 61 ... Insulating substrate 62 ... Emitter wiring layer 63... Emitter ground layer 64... Emitter 64 a... Emitter surface 64 b... Emitter peripheral surface 65. Base layer 73a..Emitter base layer (before etching)
74... Emitter 74a .. Emitter (before etching)
75 ... Lift-off material 76 ... Insulating layer 77 ... Gate electrode

Claims (3)

  An insulating layer and a gate electrode are sequentially stacked on the base, an opening reaching the base is provided in the gate electrode and the insulating layer, and the emitter is formed on the base in the opening so as not to contact the gate electrode. A field emission type electron-emitting device, wherein the emitter is made of diamond or diamond-like carbon, and the surface of the emitter is terminated by an electron donating group.   The electron-emitting device according to claim 1, wherein the electron-donating group is any one of hydrogen, a hydrocarbon, and a hydroxyl group.   3. The electron-emitting device according to claim 1, wherein the emitter has any one of a cylindrical shape, a polygonal column shape, a truncated cone shape, and a polygonal frustum shape having a base on the base.

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