JP2010272504A - Electron source made of carbonaceous material and manufacturing method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a high-luminance electron source, using transition metal carbide and having superior mass productivity and being easy to obtain which is used in electron-beam apparatuses, vacuum tubes, and especially, in electron-optical apparatuses, such as, electron microscopes and electron lithographic apparatuses. <P>SOLUTION: Of the electron source used for an electron-optical equipment, such as, electron microscope and electron-beam lithographic apparatus, an electron-emitting section part consists of a surface-layer part and a base material part, of which the surface-layer part is of transition metal carbide, and the base material part is made of diamond single crystal. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is an electron source used in an electron beam and electron beam equipment such as an electron microscope and an electron beam exposure machine, a vacuum tube such as a traveling wave tube and a microwave tube, and a transition metal carbide is disposed on a surface layer portion of an electron emission portion. The present invention relates to a high-intensity electron source comprising a diamond base material.

  Since electrons have a negative charge and have a very small mass, an electron beam that is run with electrons aligned in one direction has the following characteristics. (1) The direction and convergence can be controlled by an electric field or a magnetic field. (2) A wide range of energy can be obtained by acceleration / deceleration by an electric field. (3) Since the wavelength is short, it can be narrowed down. Electron microscopes and electron beam exposure machines that make use of these characteristics are widely used.

At present, as cathodes often used for electron microscope applications, for example, according to Patent Documents 1 to 3, an inexpensive tungsten filament is used as a thermionic source, and a boron containing LaB ₆ or the like that can obtain a high-luminance electron beam. There is a chemical filament. Further, as a cathode having a higher brightness and a narrower energy width, sharpened tungsten, which is a field emission electron source utilizing a tunnel phenomenon due to a quantum effect, and ZrO / W, which is a thermal field emission electron source utilizing a Schottky effect due to an electric field. Is used.

  For these, an electron source with higher luminance is required, and for the practical application thereof, for example, research on an electron source using transition metal carbide as a material as described in Non-Patent Document 1 is being advanced. Yes. Alternatively, as disclosed in Patent Documents 4 and 5, transition metal carbides have been proposed to be used as a cathode of a cold cathode electron-emitting device having a substrate / insulating layer / gate structure or a cold cathode discharge lamp. Development is underway at each research institution as a next-generation electron source material.

Japanese Patent Publication No. 63-015633 Japanese Patent Laid-Open No. 03-129651 Japanese Patent Laid-Open No. 08-013733 JP 2005-18991 A JP 2005-85472 A

J. Vac. Sci. Techinol. B 26 (2), Mar / Apr 2008 p868-871

However, electron emission sources using transition metal carbides are widely used as LaB ₆ , tungsten, and ZrO / W electron sources in the field of electron sources used at least in electron beam equipment such as electron microscopes and electron beam exposure machines. It was not reached. Because it is necessary to use a single crystal that can specify the crystal orientation related to the work function in order to obtain a high-brightness electron source, a single crystal of transition metal carbide is manufactured because of its high melting point characteristics. This is because it is difficult to obtain and difficult to process.

  The above-mentioned problem is caused by forming transition metal carbide by processing a pure metal of a transition metal element such as Ti, Hf, or Zr into a needle shape like sharpened tungsten and then heating in a hydrocarbon gas atmosphere to perform carbonization treatment. It is conceivable to avoid this. However, since the surface after carbonization treatment is rough on the order of several tens of nanometers, it is necessary to control the surface roughness of the electron emission part with atomic order to ensure high convergence of the electron beam. There was a problem that could not be adopted.

  Therefore, the present invention has been made in view of such circumstances, and is excellent in mass productivity, which is used in electron beams, electron beam equipment, vacuum tubes, and particularly in electron optical equipment such as electron microscopes and electron beam drawing apparatuses. An object of the present invention is to provide a high-brightness electron source using a transition metal carbide which is easy to obtain.

As a result of intensive studies to solve the above problems, the inventors of the present invention have an electron emission portion composed of a surface layer portion and a base material portion, the surface layer portion is made of transition metal carbide, and the base material portion is made of a diamond single crystal. The inventors have found that the electron source is effective and have completed the present invention. The present invention has the following configuration.
(1) An electron source used in an electro-optical device, wherein an electron emission portion is composed of a surface layer portion and a base material portion, the surface layer portion is a transition metal carbide, and the base material portion is a diamond single crystal. An electron source characterized by
(2) The electron source according to (1) above, wherein the thickness of the surface layer portion is 20 nm or more.
(3) The electron as described in (1) or (2) above, wherein the transition metal / carbon atom ratio of the transition metal carbide from the surface of the surface layer part to a depth of 20 nm is 0.01 or more and 1 or less. source.
(4) The electron source according to (3) above, wherein a transition metal / carbon atom ratio of the transition metal carbide from the surface of the surface layer portion to a depth of 20 nm is 0.1 or more and 1 or less.
(5) The electron source according to any one of (1) to (4), wherein the transition metal is any one of Hf, Ti, Zr, Ta, or Nb.
(6) The transition metal carbide has a transition metal / carbon atom ratio of 1, and is any one of HfC, TiC, ZrC, TaC, or NbC. (1) to (5) The electron source in any one of.
(7) The electron source according to any one of (1) to (6) above, wherein the transition metal carbide in the surface layer portion is a single crystal.
(8) The surface of the transition metal carbide is treated by performing heat treatment at least once at a temperature of 50 ° C. or higher and 1600 ° C. or lower in a vacuum of 1 × 10 ⁻⁵ Pa or less in the electron source. The electron source according to any one of (1) to (7) above.
(9) Aging in which an electron emission current of 1 μA or more and 200 μA or less is drawn while heating the electron source in a vacuum of 1 × 10 ⁻⁶ Pa or less at a temperature of 100 ° C. or more and 1600 ° C. or less. The electron source according to any one of the above (1) to (8), wherein the electron source is implemented at least once or more and the surface of the transition metal carbide is a surface from which stable electron emission is obtained.
(10) The method for producing an electron source according to any one of (1) to (7) above, wherein a transition metal thin film is formed on the surface of a base material portion made of a diamond single crystal, and the transition metal is heated. And a method of forming a transition metal carbide on the surface of the base material portion by reacting diamond with diamond, and a step of removing unreacted transition metal.
(11) The method further includes a step of performing heat treatment for heating the surface of the transition metal carbide at a temperature of 50 ° C. or higher and 1600 ° C. or lower once in a vacuum of 1 × 10 ⁻⁵ Pa or lower. The manufacturing method of the electron source as described in said (10).
(12) The surface of the transition metal carbide is left in a state where an electron emission current of 1 μA or more and 200 μA or less is drawn while heating the surface of the transition metal carbide at a temperature of 100 ° C. or more and 1600 ° C. or less in a vacuum of 1 × 10 ⁻⁶ Pa or less. The method of manufacturing an electron source according to (10) or (11), further comprising a step of performing aging at least once.

  Since the electron source made of the carbon-based material of the present invention has such a structural feature, it is excellent in mass productivity and easy to obtain while realizing higher luminance than the conventional electron source.

  According to the present invention, it can be used for all devices using electron beams such as vacuum tubes, electron beam analyzers, accelerators, sterilizing electron beam irradiation devices, X-ray generators, resin irradiation devices, electron beam heating devices, An electron source made of a carbon-based material from which a high-intensity electron beam can be obtained is realized. Since the electron source comprising the carbon-based material of the present invention is excellent in mass productivity and easy to obtain, it is possible to obtain high-speed, Observation with high accuracy can be easily realized.

It is the schematic which shows an example of the electron source which concerns on this invention. It is an enlarged view of the chip | tip 11 in FIG. It is sectional drawing of the electron emission part in FIG. It is the schematic which shows another example of the electron source which concerns on this invention. It is the schematic which shows an example of the structure at the time of emitting an electron from the electron source of this invention.

  Hereinafter, with reference to the attached drawings, preferred embodiments of an electron source made of a carbon-based material according to the present invention will be described in detail. In the description of the drawings, the same reference numerals are assigned to the same elements, and duplicate descriptions are omitted. Further, the dimensional ratios in the drawings do not necessarily match those described.

  FIG. 1 is a plan view showing an embodiment of an electron source made of a carbon-based material according to the present invention. The electron source 10 supplies a chip 11, a support 12 for holding the chip 11, a base 13 for fixing the support 11, supplies emitted electrons to the chip 11 via the support 12, or supplies heating power to the chip 11. For this purpose, the power supply terminal 14 is used. As shown in the three-dimensional view of FIG. 2, the chip 11 includes a clamping part 21 and an electron emission part 22. As shown in FIG. 2, the electron emission portion 22 has a sharp protrusion 23 and is formed on the plane of the truncated pyramid portion 24. Field emission electrons are obtained by applying an electric field to the tip of the sharp projection 23.

  As shown in the cross-sectional view of FIG. 3, the electron emission portion 22 includes a surface layer portion 31 and a base material portion 32, where the surface layer portion 31 is made of a transition metal carbide and the base material portion 32 is made of a diamond single crystal. Diamond single crystals are classified into Ia type, Ib type, IIa type, IIb type, etc., depending on the type of impurities and defects mixed in, but any of them may be used. In addition, there are diamond single crystals that are naturally produced and those that are artificially manufactured. However, any diamond single crystal may be used without any problem and may be easily obtained by the operator. The size is a shape that fits in a rectangular parallelepiped space of 50 μm × 50 μm × 100 μm or more and 1 mm × 1 mm × 5 mm or less.

The thickness of the surface layer portion 31, that is, the transition metal carbide is preferably 20 nm or more and 1000 nm or less. The thickness of the transition metal carbide is evaluated by measuring the depth direction of AES (Auger Electron Spectroscopy), and a portion having a transition metal / carbon atom ratio of 0.01 or more is defined as a surface layer portion. If the thickness of the transition metal carbide is less than 20 nm, the electrical resistance of the transition metal carbide becomes extremely high, and as a result, the high luminance characteristics of the electron beam cannot be obtained. On the other hand, if it is thicker than 1000 nm, it takes time to form a transition metal thin film using a sputtering apparatus or an electron beam vapor deposition apparatus and heat treatment time, but on the other hand, there is almost no effect of improving luminance characteristics due to the increase in thickness. . By making the size of the diamond single crystal and the thickness of the transition metal carbide within the above-mentioned ranges, compatibility with conventional electron sources such as LaB ₆ and ZrO / W results. It becomes possible to mount the electron source of the present invention without modification.

  The transition metal carbide of the surface layer portion 31 is formed in a shape in which a diamond single crystal is processed into a columnar shape, a truncated pyramid is formed at an end portion, and a sharp projection is provided. A thin film of transition metal such as Ti, Zr, Ta, Nb is formed in the electron emission region, and heated in a vacuum or in an inert gas atmosphere at 400 ° C. or higher for 1 minute to 10 hours to form a diamond single crystal and a transition metal thin film. After forming a transition metal carbide having a desired thickness at the interface, an unreacted transition metal thin film is removed by an acid.

  The transition metal carbide having a depth of 20 nm from the surface of the surface layer portion 31 thus formed has an atomic ratio in which the transition metal / carbon atomic ratio is in the range of 0.01 to 1 depending on the type of transition metal, the processing temperature, and the processing time. Can take. In the electron emission, if this ratio is less than 0.01, almost carbon characteristics are obtained, and the work function becomes relatively large, so that the luminance is not obtained and is not suitable for the electron source of the present invention. A value greater than 1 is not a value obtained from the viewpoint of diffusion. If it is the said range, high-intensity is realizable compared with the conventional electron source. More preferably, the transition metal / carbon atom ratio is preferably 0.1 or more and 1 or less. If it is this range, since the characteristic of the ease of electron emission of transition metal carbide will become remarkable, sufficient high brightness | luminance can be implement | achieved compared with the conventional electron source.

  As the transition metal of the transition metal carbide, Hf, Ti, Zr, Ta, or Nb can be suitably used. These carbides have a relatively low work function and facilitate electron emission. When the transition metal / carbon atom ratio is 1, that is, when the transition metal carbide is HfC, TiC, ZrC, TaC or NbC, it can be used particularly preferably. Among these, the work function is particularly low and electron emission is easy.

  The transition metal carbide is preferably a single crystal. The transition metal carbide appearing on the surface after removing the unreacted transition metal thin film is often a single crystal, and in this case, the crystal orientation coincides with the diamond single crystal as the base material. Moreover, the surface roughness is the same as the base material part 32, and the surface roughness is not deteriorated by forming the transition metal carbide. By being a single crystal, an electron source with high luminance can be realized by selecting a crystal orientation having the lowest work function according to the material and making it coincide with the tip direction of the sharp protrusion 23.

  As described above, the transition metal carbide of the surface layer portion 31 is formed along the shape of the diamond base material. Therefore, the appearance shown in FIG. 2 is roughly a shape obtained by processing a diamond single crystal. This is a conventional electron source for making a diamond that is hard and difficult to process with high productivity and an electron source. There is no unique structure. The height of the sharp protrusion 23 is 10 μm or more, the tip curvature radius is 10 nm or more and 500 nm or less, and the surface roughness of the most advanced part is 1 nm or less.

  Portions other than the sharp projections 23 are produced by laser processing and polishing a diamond single crystal. Considering the ease of processing and concentration of the electric field at the sharpened protrusion, the truncated pyramid portion 24 has a truncated pyramid height of 0.1 mm to 0.5 mm and a truncated pyramid surface size within a range of 20 μm square to 100 μm square. Is preferred. The surface is mirror-finished by polishing, but at least the upper surface of the truncated pyramid is mirror-finished.

The sharp projection 23 is formed by forming a cylindrical etching mask on the upper surface of the truncated pyramid by photolithography and etching the upper surface of the truncated pyramid until the etching mask disappears by reactive ion etching (RIE). Etching is performed in a mixed gas atmosphere of oxygen and CF ₄ , the mask is set in the range of 1 μmφ to 10 μmφ in diameter and 0.1 μm to 10 μm in height, and the edge of the mask is carefully contoured to 10 nm or less. Photolithography is performed. As the mask material, metals such as Ti, Mo and W, and ceramics such as SiO ₂ and SiON can be used.

The surface roughness of the tip portion of the sharp projection 23 is related to the etching rate immediately before the etching mask disappears, and the slower the surface, the smoother the surface. As the etching progresses, the protrusion directly under the mask becomes higher and the mask thickness becomes thinner. However, depending on the etching conditions, the mask is also reduced in the radial direction, and in this case, the shape becomes tapered toward the tip of the protrusion. As such etching conditions, a pressure of 0.5 Pa to 50 Pa, a CF ₄ : oxygen gas mixing ratio of 1: 100 to 10: 1, and a high frequency power of 50 W to 500 W are selected. If it confirms that it reduced to about 2 micrometers, an etching rate shall be 0.1 micrometer / h or less. By doing so, the surface roughness of the electron emission portion at the tip of the sharp protrusion 23 is 1 nm or less, and the surface is smooth to the atomic level.

  As described above, chips other than sharp protrusions are processed by a technique with precision of micron order, such as laser processing and polishing, and the sharp protrusions are formed by etching masks and ion etching by photolithography capable of nano-order processing. Use a sharp projection processing method that combines. The shape of the sharp projection 23 is preferably tapered toward the tip so that the electric field is easily concentrated on the tip of the projection.

  From the viewpoint of reliability, it is desirable to use a metal having elasticity that does not lose the force to hold the chip 11 even at 1000 ° C. or higher. Specifically, an alloy containing molybdenum can be suitably used, but a refractory metal alone such as molybdenum, tungsten, or tantalum can also be used. The base 13 can be suitably made of an insulating ceramic such as alumina or steatite. A metal such as Kovar is used for the power supply terminal 14.

  The electron source made of the carbon-based material of the present invention has at least the above-described components. However, as shown in the cross-sectional view of FIG. 4, the column 12, the suppressor 40, the chip clamping screw 41 and the nut 42, pyrolytic carbon. The presence of components such as the spacer 43 is within the scope of the electron source of the present invention. The suppressor 40 is a metal part that covers other components and is provided with an opening so that the chip 11 protrudes, and has a function of suppressing emission of electrons from a part other than the chip 11. The chip fastening screw 41 and the nut 42 are for assisting the force with which the support 12 clamps the chip 11. The pyrolytic carbon spacer is sandwiched between the contact portions of the chip 11 and the support column 12 when the chip 11 needs to be heated.

FIG. 5 is a cross-sectional view showing an embodiment of a configuration for emitting electrons from an electron source according to the present invention. An aperture plate 50 is installed on the electron source 10, and an electron beam (emission electron) 51 is extracted by applying an extraction voltage, that is, a positive voltage to the chip 11 to the aperture plate 50. In the electron beam extraction configuration of FIG. 5, in order to extract desired electron source performance from the electron source 10, the diameter of the hole of the aperture plate 50 is 800 μm or less, the thickness is 600 μm or less, the tip of the chip 11 and the chip 11 of the aperture plate 50. The distance to the side surface is 50 μm to 2000 μm. By adopting such a configuration, the desired electron source performance is extracted when the degree of vacuum is 1.2 × 10 ⁻⁷ Pa or less, the temperature of the chip 11 is 1600 ° C. or less, and the extraction voltage is 3 kV to 10 kV. A converging beam can be obtained.

For example, after the electron source 10 according to the present invention is incorporated into an electron optical instrument such as an electron microscope having the above-described configuration, the temperature is set to 50 ° C. or higher and 1600 ° C. or lower in an ultrahigh vacuum of 1 × 10 ⁻⁵ Pa or lower. Then, the heat treatment of the transition metal carbide surface of the surface layer portion 31 is performed at least once. By doing so, the atomic arrangement in the vicinity of the surface of the transition metal carbide in the surface layer portion 31 and the bonding between the atoms are stabilized. As a result, more stable electron emission can be obtained as compared to before heat treatment. If the pressure during the heat treatment is greater than 1 × 10 ⁻⁵ Pa, the reaction between the residual gas in the vacuum and atoms in the vicinity of the surface of the transition metal carbide in the surface layer portion 31 becomes remarkable. Does not stabilize. On the other hand, if the temperature is less than 50 ° C., sufficient energy is not provided in the vicinity of the surface and the surface is not stabilized. On the other hand, when the temperature is 1600 ° C. or higher, the graphitization of the diamond single crystal of the base material portion 32 proceeds significantly, which is not suitable. More preferably, the heat treatment is preferably performed in an ultrahigh vacuum at a pressure of 1 × 10 ⁻⁶ Pa or less. Since there is almost no reaction between the residual gas in the vacuum and the atoms in the vicinity of the surface of the transition metal carbide in the surface layer portion 31, the vicinity of the surface of the surface layer portion 31 has a more stable atomic arrangement and bonds between atoms. Stable electron emission can be obtained.

The time for the heat treatment is 30 seconds or more and less than 1 hour, 1 hour or more and less than 10 hours, and further 10 hours or more and less than 72 hours. The time for one heat treatment refers to the time until the pressure increased by heating becomes equal to or lower than the base pressure before heating by vacuum evacuation by an ion pump or the like. Since the effect does not change, this time may be included.
When the surface layer portion 31 is heated, the temperature of surrounding components also rises. For example, when the components constituting the electron source 10 have been left in the atmosphere for a long time, the amount of gas released by heating is relatively small. In many cases, it takes a relatively long time such as 1 hour or more and less than 10 hours, and further 10 hours or more and less than 72 hours before the increased pressure becomes lower than the base pressure before heating. On the other hand, if the main heat treatment is performed immediately after the components constituting the electron source 10 are baked out and sufficiently degassed, the pressure becomes lower than the base pressure before heating in a relatively short time such as 30 seconds or more and less than 1 hour.

It is preferable to complete the heat treatment by performing the heat treatment a plurality of times and raising the temperature to a temperature at which the electron source is to be driven. Specifically, when the first heating is performed at a base pressure of 2 × 10 ⁻⁷ Pa, the pressure increases due to degassing. Therefore, the heating temperature is adjusted so as to be in a range of 1 × 10 ⁻⁵ Pa or less and left as it is. . After a while, the pressure returns to the base pressure or lower by vacuum evacuation by an ion pump or the like. Therefore, when it is further heated for the second time, the pressure rises again, and is left in the range of 1 × 10 ⁻⁵ Pa or less for a while. After a while, the pressure returns to the base pressure before the second heating, but the heating temperature is increased to a maximum of 1600 ° C. by performing this multiple times. The maximum heating temperature is not necessarily 1600 ° C., and may be up to the maximum temperature for driving the electron source.

After a heat treatment is performed a plurality of times to obtain a surface on which stable electron emission can be obtained, the surface is heated at a temperature of 100 ° C. or higher and 1600 ° C. or lower in a vacuum of 1 × 10 ⁻⁶ Pa or lower. The following aging is performed at least once in the state where the electron emission current is drawn. By doing so, as a result of stabilizing the atomic arrangement in the vicinity of the surface of the transition metal carbide in the surface layer portion 31 and the bonding between the atoms in a state suitable for electron emission, more stable electron emission can be obtained as compared to before aging. If the pressure at the time of aging is larger than 1 × 10 ⁻⁶ Pa, the number of times that the residual gas in the vacuum is ionized by the emitted electrons and collides with the surface atoms of the transition metal carbide in the surface layer portion 31 significantly increases. It is rough and sufficient aging effect cannot be obtained. On the other hand, if the temperature is lower than 100 ° C., sufficient aging effect cannot be obtained because sufficient energy for moving and stabilizing the atoms in the vicinity of the surface in a state suitable for electron emission is not given. On the other hand, when the temperature is 1600 ° C. or higher, the graphitization of the diamond single crystal of the base material portion 32 proceeds significantly, which is not suitable. More preferably, aging is preferably performed in an ultrahigh vacuum at a pressure of 2 × 10 ⁻⁷ Pa or less. As a result of significantly reducing the number of times the residual gas in the vacuum is ionized by the emitted electrons and collides with the surface atoms of the transition metal carbide in the surface layer portion 31, sufficiently stable electron emission is obtained. The aging treatment is preferably performed after the heat treatment, but only the aging treatment may be performed without performing the heat treatment.

The aging time is preferably 30 minutes or more and less than 10 hours per time. If it is less than 30 minutes, a sufficient aging effect cannot be obtained, and even if it is carried out for 10 hours or more, an aging effect corresponding to the time cannot be obtained. Aging is preferably performed a plurality of times by increasing the electron emission current stepwise at a constant temperature in a pressure range of 1 × 10 ⁻⁶ Pa or less in order to obtain high luminance and high stability electron emission. Specifically, for example, the first time is performed with an electron emission current of 1 μA or more and less than 5 μA for 1 hour, the second time is performed by raising the electron emission current to 5 μA or more and less than 20 μA for 1 hour, and the third time is an electron emission current. Is further increased to 20 μA or more and less than 60 μA for 2 hours to obtain high brightness and high stability. Higher luminance can be obtained by performing the electron emission current at 60 μA or more and less than 120 μA for the fourth time for 3 hours and the fifth time at 120 μA or more and 200 μA or less for 5 hours. The constant temperature is typically 700 ° C. or higher and 1600 ° C. or lower.

As described above, the transition metal carbide single crystal has a problem that it is difficult to manufacture, obtain, and process. In addition, as described above, it is difficult to control the surface roughness in the method of forming transition metal carbide by heating and carbonizing a pure metal of transition metal element in a hydrocarbon gas atmosphere. Not as widely used as the source.
In view of these problems, the present inventors have conducted extensive research. As a result of studying the ease of acquisition and processing, the inventors have come up with the idea of using a diamond single crystal as the substrate and using transition metal carbide obtained by reacting the diamond single crystal substrate and the transition metal thin film for the electron emission surface. Is. Then, the fabrication process for realizing it was examined.

Single crystal diamond of the size used for the tip of the electron source is readily available for jewelry and tools. In order to make it into a chip shape, laser processing and polishing processing are necessary as described above, but there is no problem since it has been widely used for jewelery and tool processing for a long time. The sharpening of the electron emitting portion needs to make full use of a technique combining photolithography and ion etching, but can be easily sharpened anywhere as long as the semiconductor device process can be performed.
If the transition metal thin film is coated using the diamond single crystal thus prepared as a base material and then annealed in vacuum or in an inert gas, the surface can be made into transition metal carbide. As a result of the study, it was concluded that it is excellent in mass productivity and can be easily obtained. Thus, as a result of the idea of using transition metal carbide obtained by reacting a base material of diamond single crystal and a transition metal thin film on the electron emission surface, an electron source made of an easily accessible carbon-based material was developed. It came to do. In addition, by finding a heat treatment method and an aging method suitable for a unique electron source structure, a surface with higher brightness and more stable electron emission has been obtained.

  The electron source made of the carbon-based material of the present invention will be described more specifically based on examples.

[Example 1]
An electron source a as shown in FIG. 1 was produced. The chip 11 was produced as follows.
First, a prismatic Ib type diamond single crystal having a size of 0.6 mm square × 2.5 mm was cut out with a laser processing machine. The crystal orientation was <110> in the longitudinal direction.
Next, the entire prism was mirror-polished by polishing and a truncated pyramid portion was formed at one end. The height of the truncated pyramid was 0.3 mm, and the truncated pyramid surface was 50 μm square. Then, a cylindrical etching mask made of SiO _{2 having a} diameter of 5 μmφ × 3 μm is formed at the center of the truncated pyramid surface using photolithography, and the etching mask disappears in a mixed gas atmosphere of oxygen and CF ₄ by reactive ion etching. Etching was performed to form a conical protrusion having a height of 30 μm and a tip curvature radius of 100 nm on the truncated pyramid.
The etching conditions were a pressure of 6 Pa, a CF ₄ : oxygen gas mixing ratio of 1:30, and a high frequency power of 450 W. After confirming that the diameter of the etching mask was 50 nm, the etching rate was reduced from 5 μm / h to 0.1 μm / h by reducing the high-frequency power and gas pressure during etching to 50 W and 1 Pa. Thus, the surface roughness of the electron emission portion at the tip of the sharp protrusion 23 was set to 0.9 nm.

Thus, after producing the base material part 32 which consists of a diamond single crystal, 1 micrometer of Hf was coated on the base material part 32 with the sputtering device. Then, after annealing at 400 ° C. for 60 minutes in a high vacuum at a pressure of 5 × 10 ⁻⁵ Pa, an acid treatment was performed to form a 30 nm thick HfC single crystal layer on the surface layer portion 31 of the base material portion 32. The transition metal / carbon atom ratio of this single crystal layer was 1. The thickness of the surface layer portion 31 was determined by analysis in the depth direction of AES, and the transition metal / carbon atom ratio was a value from the surface of the surface layer portion 31 to 20 nm.
The configuration of the electron source a other than the chip 11 is tungsten for the support column 12, alumina for the base 13, and Kovar for the power supply terminal 14.

Next, the produced electron source a was assembled in an electron gun chamber of an electron microscope with a configuration as shown in FIG. The aperture plate 50 had a hole diameter of 800 μm and a thickness of 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 50 on the chip 11 side was 2000 μm.
After confirming that the base pressure of the electron gun chamber was 1.2 × 10 ⁻⁸ Pa, the surface layer portion 31 was heat-treated. Heat treatment starts at a temperature of 300 ° C. in an ultra-high vacuum with a pressure of less than 5 × 10 ⁻⁶ Pa, maintains the temperature setting until the increased pressure is 1.2 × 10 ⁻⁸ Pa or less, and confirms that the pressure is below the base pressure. Then, the operation of raising the temperature again was repeated, and the process was completed when the heat treatment was performed at 1500 ° C. The temperature step during this time was repeated 13 times at about 100 ° C.
Further, it was confirmed that the base pressure of the electron gun chamber was 1.2 × 10 ⁻⁸ Pa, and the surface layer portion 31 was aged. Aging is carried out in an ultra-high vacuum under a pressure of less than 1 × 10 ⁻⁷ Pa at a temperature of 1500 ° C., 4 times in this order: electron emission current 1 μA for 1 hour, 10 μA for 1 hour, 50 μA for 2 hours, 150 μA for 3 hours. Finished.
As an evaluation, when the pressure was 1.2 × 10 ⁻⁸ Pa, the temperature of the chip 11 was 1500 ° C., and an extraction voltage of 8 kV was applied, an electron beam luminance of 5 × 10 ⁹ A / m ² sr was obtained. The beam stability (rms%) was 1%.

  The transition metal carbide forming process of the surface layer part 31 is summarized in Table 1, the heat treatment process is summarized in Table 2, the aging process is summarized in Table 3, and the evaluation process is summarized in Table 4.

[Example 2]
According to the conditions of the transition metal carbide forming process shown in Table 1, the electron source b, c, d, e is configured in the same manner as the electron source a of Example 1 except that the surface layer portion 31 is TiC, ZrC, TaC, or NbC. It was fabricated and assembled in the electron gun chamber of an electron microscope with the configuration shown in FIG. The aperture plate 50 had a hole diameter of 800 μm and a thickness of 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 50 on the chip 11 side was 2000 μm.
Subsequently, the heat treatment step shown in Table 2 and the aging step shown in Table 3 were advanced to obtain the results shown in the evaluation step of Table 4.
At a pressure of 1.2 × 10 ⁻⁸ Pa, when the beam was extracted by adjusting the chip temperature between 1500 to 1600 ° C. and the extraction voltage between ^{8 and} 10 kV, the electron beam brightness of 5 × 10 5 was obtained in all electron sources. ⁹ A / m ² sr or more was obtained.

[Example 3]
Electron sources f and g having the same configuration as that of the electron source a of Example 1 except that the surface layer portion 31 was changed to WC or MoC depending on the conditions of the transition metal carbide forming process shown in Table 1 and shown in FIG. Built into the electron gun chamber of an electron microscope with a simple structure. The aperture plate 50 had a hole diameter of 800 μm and a thickness of 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 50 on the chip 11 side was 2000 μm.
Subsequently, the heat treatment step shown in Table 2 and the aging step shown in Table 3 were advanced to obtain the results shown in the evaluation step of Table 4.
When the beam was extracted by adjusting the chip temperature and extraction voltage to predetermined values at a pressure of 1.2 × 10 ⁻⁸ Pa, an electron beam luminance of 5 × 10 ⁹ A / m ² sr or more was obtained. The beam stability (rms%) was 1%.

[Example 4]
Except for the electron sources h, i, j, and k depending on the conditions of the transition metal carbide forming process shown in Table 1, the configuration of the electron microscope of the electron microscope with the configuration shown in FIG. Built into the gun chamber. The aperture plate 50 had a hole diameter of 800 μm and a thickness of 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 50 on the chip 11 side was 2000 μm.
Subsequently, the heat treatment step shown in Table 2 and the aging step shown in Table 3 were advanced to obtain the results shown in the evaluation step of Table 4.

[Example 5]
All evaluations were performed in the same manner as the electron source a except that aging was not performed. A luminance of 5 × 10 ⁹ A / m ² sr was obtained, and the stability was 7%.

[Example 6]
The evaluation was the same as that for the electron source a except that no heat treatment was performed and the aging temperature was 100 ° C. and the pressure was 1 × 10 ⁻⁶ Pa. A luminance of 5 × 10 ⁹ A / m ² sr was obtained, and the stability was 15%.

[Example 7]
All evaluations were made in the same manner as the electron source a except that neither heat treatment nor aging was performed. A luminance of 5 × 10 ⁹ A / m ² sr was obtained, and the stability was 25%.

[Reference example]
An electron source A was produced in the same configuration as the electron source a in Example 1 except that the material of the chip 11 was all hafnium carbide, and was assembled in the electron gun chamber of the electron microscope with the configuration as shown in FIG. The aperture plate 50 had a hole diameter of 800 μm and a thickness of 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 50 on the chip 11 side was 2000 μm.
When the degree of vacuum was 1.2 × 10 ⁻⁸ Pa, the temperature of the chip 11 was 1500 ° C., and an extraction voltage of 8 kV was applied, an electron beam luminance of 5 × 10 ⁹ A / m ² sr was obtained, and the electron source a Similar performance was obtained.

DESCRIPTION OF SYMBOLS 10 Electron source 11 Chip 12 Support | pillar 13 Base 14 Feeding terminal 21 Clamping part 22 Electron emission part 23 Sharp protrusion 24 Pyramid part

31 Surface Layer 32 Base Material 40 Suppressor 41 Tip Tightening Screw 42 Tip Tightening Nut 43 Pyrolytic Carbon Spacer 50 Aperture Plate 51 Electron Beam (Emission Electron)

Claims (12)

  An electron source used in an electro-optical device, wherein an electron emission portion is composed of a surface layer portion and a base material portion, the surface layer portion is a transition metal carbide, and the base material portion is a diamond single crystal. Electron source.   The electron source according to claim 1, wherein a thickness of the surface layer portion is 20 nm or more.   The electron source according to claim 1 or 2, wherein a transition metal / carbon atom ratio of the transition metal carbide from the surface of the surface layer portion to a depth of 20 nm is 0.01 or more and 1 or less.   The electron source according to claim 3, wherein a transition metal / carbon atom ratio of the transition metal carbide from the surface of the surface layer portion to a depth of 20 nm is 0.1 or more and 1 or less.   5. The electron source according to claim 1, wherein the transition metal is any one of Hf, Ti, Zr, Ta, and Nb.   6. The transition metal carbide according to claim 1, wherein the transition metal carbide has a transition metal / carbon atom ratio of 1 and is any one of HfC, TiC, ZrC, TaC, or NbC. Electron source.   The electron source according to claim 1, wherein the transition metal carbide in the surface layer portion is a single crystal. The surface of the transition metal carbide is treated by performing heat treatment at least once or more at a temperature of 50 ° C. or higher and 1600 ° C. or lower in a vacuum of 1 × 10 ⁻⁵ Pa or less of the electron source. Item 8. The electron source according to any one of Items 1 to 7. At least one aging is performed in which the electron source is heated in a vacuum of 1 × 10 ⁻⁶ Pa or less at a temperature of 100 ° C. or higher and 1600 ° C. or lower and an electron emission current of 1 μA or higher and 200 μA or lower is drawn. The electron source according to any one of claims 1 to 8, wherein the electron source is implemented as described above, and the surface of the transition metal carbide is a surface from which stable electron emission is obtained. It is a manufacturing method of the electron source in any one of Claims 1-7,
Forming a transition metal thin film on the surface of the base material portion made of a diamond single crystal;
A step of reacting the transition metal and diamond by heating to form a transition metal carbide on the surface of the substrate part; and
And a step of removing an unreacted transition metal. The method further includes the step of performing heat treatment of heating the surface of the transition metal carbide to a temperature of 50 ° C. or higher and 1600 ° C. or lower in a vacuum of 1 × 10 ⁻⁵ Pa or lower at least once. 10. A method for producing an electron source according to 10. Aging in which the surface of the transition metal carbide is left in a state where an electron emission current of 1 μA or more and 200 μA or less is drawn while heating the surface of the transition metal carbide in a vacuum of 1 × 10 ⁻⁶ Pa or less at a temperature of 100 ° C. or more and 1600 ° C. or less. The method of manufacturing an electron source according to claim 10, further comprising a step of performing at least once.

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