JP5013155B2 - Manufacturing method of diamond emitter array - Google Patents

Description

  The present invention relates to a diamond emitter array in which a diamond film is used as an emitter of a field emission type electron-emitting device that emits electrons by a strong electric field and the diamond emitters are arranged in an array, and a manufacturing method thereof. The present invention relates to a diamond emitter array in which a hydrogen termination surface of a film is an electron emission surface and a manufacturing method thereof.

  Conventionally, a cathode ray tube has been widely used as an electronic display device. However, since the cathode ray tube emits thermal electrons from the cathode of an electron gun, it consumes a large amount of energy and has a large structural volume. There was a problem such as need.

  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 substance is increased, the width of the energy barrier on the surface of the substance is gradually reduced according to the strength, and the electric field strength is 10 ⁷ V / cm or more. Then, the electrons in the material can break through the energy barrier by the tunnel effect, and therefore, the phenomenon that electrons are emitted from the material is utilized.

  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 type of such a field emission type electron-emitting device, a conical electron-emitting device having a pointed tip can be illustrated as shown in FIG. 4 (see, for example, Non-Patent Document 1). . In this element, a conductive layer 42, an insulating layer 43, and a gate electrode 44 are sequentially stacked on an insulating substrate 41, and an opening A is formed in the insulating layer 43 and the gate electrode 44, thereby forming a conductive layer. 42 is exposed. A conical emitter 45 having point-like protrusions is formed on the conductive layer 42 in the opening A so as not to contact at least the gate electrode 44. As such a conical emitter, a Spindt-type emitter is widely known.

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

  First, as shown in FIG. 5A, an insulating layer 53 and a gate electrode 54 are sequentially formed on an insulating substrate 51 on which a conductive layer 52 has been previously formed by a sputtering method, a vacuum evaporation method, or the like. Subsequently, a circular hole (gate hole) is opened in the insulating layer 53 and a part of the gate electrode 54 using the photolithography method and the reactive ion etching method (RIE) until the conductive layer 52 is exposed. Etch like so.

  Next, as shown in FIG. 5B, a release layer 55 is formed only on the upper surface and side surfaces of the gate electrode 54 by oblique deposition. As the material of the peeling layer 55, Al, MgO, or the like is often used.

  Subsequently, as shown in FIG. 5C, a metal material for the emitter 56 is vapor-deposited on the entire surface, that is, on the conductive layer 52 and the release layer 55 by normal anisotropic vapor deposition from the perpendicular direction. At this time, the conical emitter 56 is formed on the conductive layer 52 in a self-aligning manner as the opening diameter of the gate hole narrows as the deposition proceeds. Deposition is performed until the gate hole is finally closed. As the material of the emitter, Mo, Ni or the like is used.

  Finally, as shown in FIG. 5D, the release layer material 55 is removed by etching, and the gate electrode 54 is patterned as necessary. Thereby, an electron-emitting device having a Spindt-type emitter is obtained.

  On the other hand, silicon emitters manufactured by applying semiconductor integrated circuit manufacturing technology are also widely known. An example of manufacturing an electron-emitting device having such a silicon emitter will be described with reference to FIGS.

  First, as shown in FIG. 6A, a single crystal silicon substrate 61 is thermally oxidized to form a silicon oxide layer on the surface, and this silicon oxide layer is patterned into a circular shape by using a photolithography method. A circular etching mask silicon oxide layer 62 is formed. As will be described later, the silicon oxide layer 62 also functions as a lift-off material. The diameter of the silicon oxide layer 62 substantially corresponds to the gate diameter.

  Next, as shown in FIG. 6B, using the silicon oxide layer 62 as an etching mask, the silicon substrate 61 is etched by reactive ion etching (RIE) under a condition with a high side etch rate, and the emitter 63 is formed. Form.

  Subsequently, as shown in FIG. 6C, an emitter tip sharpening silicon oxide layer 64 is formed on the surfaces of the silicon substrate 61 and the emitter 63 by thermal oxidation. Due to the stress generated when the silicon oxide layer 64 is formed, the tip of the emitter 63 inside the silicon oxide layer 64 is easily sharpened.

  Then, as shown in FIG. 6D, an insulating layer 65 and a gate electrode 66 are stacked by anisotropic vapor deposition.

  Finally, as shown in FIG. 6E, the etching mask silicon oxide layer 62 that also functions as a lift-off material is lifted off by etching, and the silicon oxide layer 64 on the surface of the emitter 63 is removed by etching. Then, the gate electrode 66 is patterned as necessary. Thereby, the electron-emitting device provided with the silicon emitter is obtained.

  However, in the above-mentioned Spindt-type emitter and silicon emitter, the metal, 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. It was indispensable to concentrate the electric field on the part. 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 emitting portion as small as possible. As shown above, the emitter is finely processed to form the tip shape of the emitting portion. As a cone type, it was indispensable that the radius of curvature of its tip was several nanometers or less.

Furthermore, in order to apply as an electron source for a display or the like, it is necessary to produce a large number of emitters obtained by performing the fine processing as described above and arrange them in an array. However, since ultra-precision machining is required, structural defects are likely to occur, and it is not easy to produce a large area uniformly, and the yield is lowered, and defect inspection is indispensable, resulting in high manufacturing costs. There was a problem.
CA Spindt: J. Appl. Phys., 39, 3504 (1968) K. Betsui: Tech. Dig. IVMC., (1991) p26

The present invention has been made in consideration of the above-mentioned problems , and a diamond emitter array manufacturing method capable of forming a diamond emitter array having a simple structure that does not have a fine structure that requires microfabrication by a simple manufacturing process. The purpose is to provide.

  As a result of detailed examination of surface physical properties (work function, electron affinity) when hydrogen and oxygen are chemically adsorbed on the diamond film surface to obtain a hydrogen termination surface and an oxygen termination surface, Experiments have found that the work function is small and has a negative electron affinity (NEA), while the oxygen-terminated surface has a large work function and a positive electron affinity (PEA). Such physical properties can be considered to be based on the electron donating or electron withdrawing properties of hydrogen and oxygen chemisorbed on the diamond film surface. That is, the hydrogen termination portion on the surface of the diamond film has a very high electron emission capability and can emit electrons without requiring any high electric field.

  Therefore, the surface of the diamond film is separated into a part terminated with an electron donating group such as hydrogen and a part terminated with an electron withdrawing group such as oxygen, or an electron emitting group. It is possible to form a high performance portion and a low performance portion on the same plane with the same material. Further, since the pattern can be freely controlled and manufactured, a surface electron source capable of matrix driving can be formed by forming an array structure.

  The present invention has been made based on such findings.

That is, the first aspect of the present invention is a step of forming a diamond film on a substrate, and the entire surface of the diamond film is at least one selected from the group consisting of hydrocarbons, hydroxyl groups, methoxy groups, alcohols, and water vapor. Plasma treatment in a gas atmosphere, a step of making the entire surface of the diamond film a hydrogen termination surface , a step of providing a mask having a predetermined pattern on the hydrogen termination surface of the diamond film, and exposing the hydrogen termination surface from the mask Converting the portion into a halogen termination surface by heating in a gas atmosphere containing a halogen-based gas, leaving a hydrogen termination surface of a predetermined pattern in the portion covered with the mask, and removing the mask A method for manufacturing a diamond emitter array is provided.
According to a second aspect of the present invention, there is provided a step of forming a diamond film on a substrate, and a step of heating the entire surface of the diamond film in a gas atmosphere containing a halogen-based gas to thereby make the entire surface of the diamond film a halogen termination surface. A step of providing a mask having a predetermined pattern on the halogen termination surface of the diamond film, at least a portion of the halogen termination surface exposed from the mask is selected from the group consisting of hydrocarbons, hydroxyl groups, methoxy groups, alcohols, and water vapor Converting to a hydrogen termination surface by plasma treatment in one kind of gas atmosphere , leaving a hydrogen termination surface of a predetermined pattern in a portion covered with the mask, and removing the mask. A method for manufacturing a featured diamond emitter array is provided.

In the diamond emitter array manufactured by the method for manufacturing a diamond emitter array according to the first and second aspects of the present invention configured as described above, an electron donating group termination portion and an electron withdrawing group termination portion are formed on the surface of the diamond film. Are formed so as to be separated from each other. Unlike the conventional structure, the gate electrode is not required, and the emitter is not sharpened. Electrons can be emitted with a low extraction voltage. Therefore, a high performance diamond emitter array can be obtained at low cost. As a result, when applied to a flat panel display, a high-speed, high-definition image can be obtained with low power consumption.

  The hydrogen-terminated surface of diamond is known to exhibit conductivity, and by utilizing this property, the hydrogen-terminated portion of the diamond surface has not only high electron emission ability but also conductivity, It can also serve as wiring in the emitter array. Therefore, it is not necessary to provide a wiring with a good conductor such as a metal film as the emitter wiring.

In the method of manufacturing a diamond emitter array according to the first and second aspects of the present invention configured as described above, the surface of the diamond film is processed through a mask, and the processed surface is treated with an electron donating group or an electron withdrawing group. By a simple process of converting to an end surface, an electron donating group end surface, that is, an electron emission portion having a fine pattern of micron order or nano order can be formed very easily. Therefore, a high-performance diamond emitter array can be manufactured at low cost, and as a result, a flat panel display capable of obtaining high-speed and high-definition images with low power consumption can be manufactured.

  The electron-withdrawing group termination surface is an oxygen or halogen termination surface, and the surface to be treated is heated in a gas atmosphere containing an oxygen-based gas, immersed in an oxidizing solution, or in a gas atmosphere containing a halogen-based gas. It can be obtained by heating.

  The step of providing a mask can be performed by forming a resist pattern on the surface to be processed or placing a metal mask or a stencil mask on the surface to be processed. In the former method of forming a resist pattern, since the mask is in close contact with the diamond film, there is an advantage that a pattern with a clear boundary can be obtained, and in the method of placing the latter metal mask or stencil mask, There is an advantage that the process can be further simplified.

In the first and second aspects of the present invention, the predetermined pattern may be a stripe pattern.

  According to the present invention, by controlling the surface chemisorption structure by the treatment of the diamond film surface, that is, the electron donating group termination structure such as hydrogen exhibits high electron emission ability and conductivity, while oxygen such as oxygen The electron withdrawing group termination structure utilizes the structural control and physical properties unique to diamond materials that exhibit low electron emission ability and insulation, which makes it possible to obtain surfaces with different electron emission ability on the same material surface. By controlling the arrangement, an emitter array according to the application can be configured.

  Therefore, since it is not necessary to fabricate and control the microstructure, and to form the gate electrode and the wiring, the structure is simple, the element defect does not occur, and it can be manufactured by a simple process. A high-performance electron-emitting device and array using the NEA characteristics can be obtained. Also, when applied to a flat panel display, high-speed and high-definition images can be obtained with low power consumption.

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

  FIG. 1 is a cross-sectional view showing a diamond emitter array according to an embodiment of the present invention. As shown in FIG. 1, this diamond emitter array has a structure in which a diamond film 2 is laminated on a substrate 1. On the diamond film, an electron donating group terminal portion 1A and an electron donating group absent portion or an electron withdrawing terminal terminal portion 1B are formed separately.

  In the diamond emitter array according to one embodiment of the present invention, the substrate 1 is used as a support substrate for the diamond emitter array. As such a substrate, a diamond substrate, a silicon substrate, a metal substrate, a glass substrate, a ceramic substrate, a quartz substrate, or the like can be used.

  The diamond film 2 can be composed of diamond or diamond-like carbon made of single crystal, polycrystal, or nanocrystal. A diamond film doped with impurities can also be used.

  The electron donating group terminal portion 1A on the surface of the diamond film has a structure in which an electron donating group is chemisorbed, and has a high electron emission ability and high physical properties. Examples of the electron donating group include a hydrogen group, a hydrocarbon group, and a hydroxyl group. By chemically adsorbing these groups, a hydrogen-terminated surface with good electron emission ability and conductivity imparting performance can be obtained.

  Such a hydrogen termination surface can be obtained by subjecting the diamond film surface to plasma treatment in a gas atmosphere such as hydrogen, hydrocarbon, hydroxyl group, methoxy group, alcohols, and water vapor. The hydrocarbon is preferably methane, ethane or the like. Moreover, as alcohols, methanol and ethanol are preferable.

  The diamond film can be obtained by plasma CVD using hydrogen and hydrocarbon as a source gas. In this case, a hydrogen termination surface is formed to some extent on the surface. Therefore, in this case, it may not be necessary to perform special hydrogen termination on the diamond film.

  The electron donating group absent portion or the electron withdrawing group terminal portion 1B on the surface of the diamond film is a diamond surface having no terminal group, or has a structure in which an electron withdrawing group is chemisorbed and has a low electron emission ability. In addition, it exhibits physical properties with low conductivity. Examples of the electron-withdrawing group include oxygen and halogen. By chemically adsorbing these groups, an oxygen or halogen-terminated surface having electron-withdrawing ability and insulating property-providing performance can be obtained.

  Such an oxygen or halogen termination surface can be obtained by heating the surface of the diamond film in a gas atmosphere containing an oxygen-based gas or a halogen-based gas, or immersing it in an oxidizing or halogenating solution.

Examples of halogen include fluorine and chlorine. Further, oxygen, ozone, nitrogen oxides (N ₂ O, NO, NO ₂ ) and hydrogen peroxide (H ₂ O ₂ ) are used as oxygen-based gases, and CF ₄ , SF ₆ , Cl are used as halogen-based gases. ₂ can be mentioned. Examples of the oxidizing solution include nitric acid, hydrogen peroxide solution, hypochlorous acid, dichromic acid, and permanganic acid.

  When the hydrogen termination surface is formed in a predetermined pattern on the diamond film surface by the above processing method, the hydrogen termination surface is formed by processing the diamond film surface through a mask having a predetermined pattern. A case where an oxygen or halogen termination surface is formed by first forming a hydrogen termination surface on the entire surface and then processing through a mask of a predetermined pattern; In some cases, the hydrogen termination surface is formed by processing through a mask having the above pattern.

  In principle, the emitter array only needs to have an electron emission surface and a surface that does not emit electrons. Therefore, if the hydrogen termination surface exists in a pattern, it is not always necessary to form an oxygen or halogen termination surface. . However, as described above, the diamond film may already have a hydrogen termination surface on the entire surface depending on the film formation method. In this case, since desorption of hydrogen from the hydrogen termination surface is very difficult, it is necessary to partially convert an unnecessary hydrogen termination surface where electron emission is not desired to an oxygen or halogen termination surface by a substitution reaction. Alternatively, the entire surface of the diamond film needs to be an oxygen or halogen termination surface in advance.

  In either case, a resist pattern, a metal mask, or a stencil mask can be used as the mask. The resist may be an organic resist or an inorganic resist.

  Examples of manufacturing the diamond emitter of the present invention will be shown below to describe the present invention more specifically.

Example 1
In this embodiment, an example in which an oxygen or halogen termination surface is formed by processing through a mask having a predetermined pattern after a hydrogen termination surface is formed on the entire surface will be described with reference to FIG.

  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 of microwave plasma CVD are as follows.
Source gas: methane (50 sccm), hydrogen (450 sccm),
Substrate temperature: 820 ° C
Reaction pressure: 80 Torr
MW power: 2.5kW
Film thickness: 1 μm.

  After the diamond film 22 was formed, the surface of the diamond film 22 was immediately subjected to hydrogen plasma treatment using the same microwave plasma CVD apparatus. The conditions are as follows.

Source gas: Hydrogen (500 sccm),
Substrate temperature: 820 ° C
Reaction pressure: 80 Torr
MW power: 2.5kW
Time: 5 minutes.

  From the results of the micro-region XPS analysis, it was confirmed that oxygen was not adsorbed on the surface of the diamond film 22 subjected to the hydrogen plasma treatment.

  Subsequently, as shown in FIG. 2B, a photoresist was applied with a film thickness of 2 μm, and then a resist pattern 23 was formed by a photolithography method. Here, the line pitch is 100 μm and the width of the resist portion is 80 μm.

  Next, as shown in FIG. 2C, the surface of the exposed diamond film 22 was subjected to oxygen plasma treatment using high frequency. The plasma treatment conditions are as follows.

Source gas: oxygen (100 sccm),
Substrate temperature: room temperature Reaction pressure: 0.1 Torr
High frequency power: 300W
Time: 3 minutes.

  From the results of microscopic XPS analysis, it was confirmed that oxygen was adsorbed on the diamond surface subjected to the oxygen plasma treatment.

  Next, as shown in FIG.2 (d), the resist pattern 23 was peeled using the exclusive peeling liquid, and the diamond emitter array was obtained.

  An anode (not shown) was installed with a gap of 1 mm from the surface of the diamond emitter array thus fabricated, and a voltage was applied to the anode to confirm the electron emission characteristics. It was confirmed that the electrons were emitted only from the hydrogen termination portion by applying the voltage.

Example 2
In this embodiment, an example in which an oxygen or halogen termination surface is formed on the entire surface and then a hydrogen termination surface is formed by processing through a mask having a predetermined pattern will be described with reference to FIG.

  First, as shown in FIG. 3A, a diamond film 32 was formed on a silicon substrate 31 by a microwave plasma CVD method.

The conditions of microwave plasma CVD are as follows.
Source gas: methane (50 sccm), hydrogen (450 sccm),
Substrate temperature: 820 ° C
Reaction pressure: 80 Torr
MW power: 2.5kW
Film thickness: 1 μm.

  Subsequently, the surface of the diamond film 32 was subjected to oxygen plasma treatment using high frequency. The plasma treatment conditions are as follows.

Source gas: Oxygen (100 sccm)
Substrate temperature: room temperature Reaction pressure: 0.1 Torr
High frequency power: 300W
Time: 3 minutes.

  From the results of the micro-region XPS analysis, it was confirmed that oxygen was adsorbed on the surface of the diamond film 32 subjected to the oxygen plasma treatment.

  Subsequently, as shown in FIG. 3B, a photoresist was applied to a thickness of 2 μm, and then a resist pattern 33 was formed by photolithography. Here, the line pitch is 100 μm, and the width of the resist portion is 20 μm.

  Next, as shown in FIG. 3C, the exposed surface of the diamond film 32 was subjected to hydrogen plasma treatment using high frequency. The plasma treatment conditions are as follows.

Source gas: Hydrogen (100 sccm)
Substrate temperature: room temperature Reaction pressure: 0.1 Torr
High frequency power: 300W
Time: 3 minutes.

  It was confirmed from the results of microscopic XPS analysis that oxygen was not adsorbed on the diamond surface subjected to the hydrogen plasma treatment.

  Next, as shown in FIG. 3 (d), the resist was stripped using a dedicated stripping solution to obtain a diamond emitter array.

  An anode (not shown) was installed with a gap of 1 mm from the surface of the diamond emitter array thus prepared, and the electron emission characteristics were confirmed by applying a voltage to the anode. It was confirmed that electrons were emitted only from the hydrogen termination part.

  The diamond emitter array of the present invention is used 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 further to an array-like field constituting a flat display. It can be usefully applied as a surface electron source of an emitter array.

It is a schematic diagram showing a diamond emitter array according to an embodiment of the present invention. 6 is a cross-sectional view showing a manufacturing process of the diamond emitter array shown in Example 1. FIG. 6 is a cross-sectional view showing a manufacturing process of the diamond emitter array shown in Example 2. FIG. It is sectional drawing which shows the conventional electron emission element. It is sectional drawing which shows the manufacturing process of the electron emission element provided with the conventional Spindt type | mold emitter. It is sectional drawing which shows the manufacturing process of the electron emission element provided with the conventional silicon emitter.

Explanation of symbols

  1, 21, 31, 41, 51, 61 ... base, 2, 22, 32 ... diamond film, 23, 33 ... resist pattern, 42, 52, 62 ... conductive layer, 43, 53, 65 ... insulation Layers 44, 54, 66 ... gate electrodes, 62 ... silicon oxide layer for etching mask, 64 ... silicon oxide layer for sharpening the tip.

Claims (4)

Forming a diamond film on the substrate;
Plasma treatment of the entire surface of the diamond film in at least one gas atmosphere selected from the group consisting of hydrocarbons, hydroxyl groups, methoxy groups, alcohols, and water vapor makes the entire surface of the diamond film a hydrogen termination surface. The process of
Providing a mask having a predetermined pattern on the hydrogen termination surface of the diamond film;
The portions exposed from the mask of the hydrogen terminated surface, converted into the halogen termination surface by heating in a gas atmosphere containing a halogen gas, thereby leaving the hydrogen termination surface of the predetermined pattern portion covered by the mask And a step of removing the mask. A method of manufacturing a diamond emitter array, comprising: Forming a diamond film on the substrate;
Heating the entire surface of the diamond film in a gas atmosphere containing a halogen-based gas to make the entire surface of the diamond film a halogen termination surface;
Providing a mask having a predetermined pattern on the halogen termination surface of the diamond film;
The portion of the halogen termination surface exposed from the mask is converted to a hydrogen termination surface by plasma treatment in at least one gas atmosphere selected from the group consisting of hydrocarbons, hydroxyl groups, methoxy groups, alcohols, and water vapor. And a step of leaving a hydrogen termination surface of a predetermined pattern in a portion covered with the mask, and a step of removing the mask. 3. The diamond emitter array according to claim 1 , wherein the step of providing the mask comprises forming a resist pattern on the surface of the diamond film, or placing a metal mask or a stencil mask on the surface of the diamond film. Manufacturing method. The method for manufacturing a diamond emitter array according to claim 1 , wherein the predetermined pattern is a stripe pattern.

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