JP2010020946A - Diamond electron source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a diamond electron source which is used for an electron beam, electron beam equipment, and a vacuum tube especially used for an electron microscope and an electron beam exposure equipment in which diamond is used, and which has high brightness and narrow energy width. <P>SOLUTION: This electron source is the diamond electron source and uses a columnar single crystal diamond, and constituted of an electron emitting part 11 and an energization heating part 12. The electron emitting part includes a sharp-pointed protrusion of height of 10 μm or more and a tip curvature radius of 5 μm or less only at one place at the end face of a column. Impurities most contained in the single crystal diamond of the electron discharge part are nitrogen of which the concentration is 1×10<SP>17</SP>cm<SP>-3</SP>or more, and in which resistance between room temperature (25°C) terminals of the energization heating part is 500 Ω or less. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an electron beam and electron beam equipment such as an electron microscope and an electron beam exposure machine, a diamond electron source used for a vacuum tube such as a traveling wave tube and a microwave tube.

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. As these cathode materials, there are, for example, an inexpensive W filament as a thermionic radiation source, and hexaboride such as LaB _{6 from which an} electron beam with high luminance can be obtained. Further, sharpening W using a tunnel phenomenon due to a quantum effect and ZrO / W utilizing a Schottky effect due to an electric field are used as a cathode having higher brightness and a narrow energy width.

However, the W filament is inexpensive, but its life is extremely short, about 100 hours. Therefore, when the filament breaks, replacement work such as opening the vacuum chamber to the atmosphere or adjusting the optical axis of the electron beam. There is a problem that must be done frequently. LaB ₆ has a long life of about 1000 hours as compared with W filament, but since it is used in a device that can obtain a relatively high-intensity beam, the replacement work is often performed by the device manufacturer, which is costly. There's a problem. There is also a problem in that the replacement cost is high for sharpened W that can provide higher luminance and ZrO / W that has a relatively long life of about one year.

  In the electron microscope, there is a demand for observing a nano-sized fine structure with high accuracy, such as a length measurement inspection in an LSI process, and in an electron beam exposure machine, development of an apparatus capable of drawing a thin line of less than 10 nm has progressed. Therefore, there is a demand for a cathode having higher luminance and a narrow energy width.

One material that meets these expectations is diamond. As described in Non-Patent Document 1 or Non-Patent Document 2, diamond has a negative electron affinity (NEA) state, or a small positive (PEA: Positive) value compared to a metal having a small work function. Electron Affinity) exists. Utilizing this very rare physical property enables high current density electron emission without the need for high heat exceeding 1400 ° C. like W filament, LaB ₆ , or ZrO / W, so that the energy width can be kept narrow. And a long life expectancy. Further, since there is a fine processing technique that can obtain a tip diameter of 10 nm as described in Non-Patent Document 3, there is no problem with increasing the brightness. Since diamond was found to have the above-mentioned electron affinity, electron sources such as Non-Patent Document 4 and Patent Document 1 have been proposed so far.

F. J. et al. Himpsel et al. Phys. Rev. B. , Vol. 20, Number 2 (1979) 624-627 J. et al. Ristein et al. , New Diamond and Frontier Carbon Technology, Vol. 10, no. 6, (2000) 363-382 Y. Nishibayashi et al. , SEI Technical Review, 57, (2004) 31-36. W. B. Choi et al. , J .; Vac. Sci. Technol. B14 (3), (1996) 2050-2055 Japanese Patent Laid-Open No. 4-67527

  However, when the electron source using the diamond is used in widely used electron microscopes and electron beam exposure machines, there are respective problems. That is, since a structure in which a plurality of electron emission points are arranged as described in Non-Patent Document 3 is a surface electron source, it is difficult to converge and form a fine beam, and it is easy to mount on an apparatus. is not. In the non-patent document 4, Mo having a sharp tip is coated with diamond and there is no problem in shape, but since it is polycrystalline, individual differences and variations in electrical characteristics are problematic. Since the structure proposed in Patent Document 1 is also a surface electron source, it is difficult to obtain a convergent beam, and it is not easy to mount it on an apparatus.

  Therefore, the present invention has been made in view of such circumstances, and is used for electron beams and electron beam equipment and vacuum tubes, in particular, electron microscopes and electron beam exposure machines. The aim is to provide a narrow diamond electron source.

In order to solve the above-mentioned problems, a diamond electron source according to the present invention is an electron source using columnar single crystal diamond, and is composed of an electron emission portion and a current heating portion, and the electron emission portion is an end face of the column. Has a single sharp protrusion with a height of 10 μm or more and a tip radius of curvature of 5 μm or less, and the impurity contained most in the single crystal diamond of the electron emission portion is nitrogen, and the nitrogen concentration is 1 × 10 ¹⁷ cm ⁻³ or more. The room temperature terminal resistance of the energization heating unit is 500Ω or less.
The present invention is a diamond electron source having a configuration as described below.

(1) An electron source using columnar single crystal diamond, which is composed of an electron emission portion and a current heating portion, and the electron emission portion is sharp with a height of 10 μm or more and a tip curvature radius of 5 μm or less on the end face of the column. The single-crystal diamond of the electron emission portion has a protrusion at only one location, and the most contained impurity is nitrogen, and the concentration of the nitrogen is 1 × 10 ¹⁷ cm ⁻³ or more. A diamond electron source having a room temperature (25 ° C.) terminal resistance of 500Ω or less.
(2) The diamond electron source according to (1), wherein the electron emission portion is an Ib type single crystal diamond.
(3) The energization heating unit has a diamond thin film containing the most phosphorus as an impurity and having a phosphorus concentration of 1 × 10 ¹⁶ cm ⁻³ or more on the surface of the single crystal diamond. The diamond electron source according to 1) or (2).
(4) The single-crystal diamond of the energization heating unit is single-crystal diamond containing the most boron as an impurity and having a boron concentration of 1 × 10 ¹⁸ cm ⁻³ or more. The diamond electron source according to any one of (3).
(5) The single crystal diamond of the energization heating unit has an ion implantation layer formed between the surface and a depth of 10 μm, according to any one of (1) to (3) Diamond electron source.
(6) Any one of (1) to (3), wherein the single crystal diamond of the energization heating portion has an electrically conductive layer formed by destroying a diamond crystal structure near the surface thereof. The diamond electron source described in 1.
(7) The diamond electron source according to any one of (1) to (3), wherein the single crystal diamond of the energization heating unit has a metal or semiconductor conductive thin film on a surface thereof.
(8) The diamond electron source according to any one of (1) to (7), wherein heat treatment is performed at a temperature of 700 ° C. or higher and 1400 ° C. or lower in a vacuum of 10 ⁻⁴ Pa or lower before use.

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, A diamond electron source having a large current and high brightness can be realized by emitting electrons stably. If the diamond electron source of the present invention is used, an electron microscope capable of high-magnification observation and an electron beam exposure machine capable of drawing fine patterns with high throughput can be realized.
Further, it is preferable to form a diamond thin film having a phosphorus concentration of 1 × 10 ¹⁶ cm ⁻³ or more on the surface of the single crystal diamond of the energization heating portion with phosphorus being the most abundant impurity. Since the phosphorus-doped diamond thin film is an n-type semiconductor, the electrons supplied from the power supply terminal can be smoothly transported to the diamond conduction band of the electron emission portion 11, and as a result, the electron emission becomes easier.

Since the diamond electron source of the present invention uses a single crystal, the shape controllability and impurity concentration controllability are good, and the performance variation during mass production is small. Further, since it is columnar and has only one sharp projection on the end face, it is highly compatible with electron sources such as ZrO / W and LaB ₆ used in electron microscopes and electron beam exposure apparatuses, and is easily spread. Since the resistance between the room temperature terminals of the energization heating part is as low as 500Ω or less, the entire electron source can be heated with a filament power source that heats ZrO / W, LaB _{6 and the} like, and the electron emission necessary for stabilizing the emission current by heating The moisture adhering to the part can be easily removed, and stable electron emission can be realized. The energization heating unit also serves to supply electrons to the electron emission unit, and a part of the electrons supplied by energization during the operation of the electron source flows to the electron emission unit. The energization heating unit and the electron emission unit are in an electrically connected state at least during heating. Nitrogen is the most abundant impurity in the single crystal diamond in the electron emission region, and the nitrogen concentration is 1 × 10 ¹⁷ cm ⁻³ or more, and when activated, the nitrogen is activated to generate a sufficient number of electrons in the conduction band of diamond. It is easy to emit electrons. Since the electron emission portion has a sharp protrusion having a height of 10 μm or more and a tip curvature radius of 5 μm or less, the electron beam can be easily drawn by applying an electric field to the tip.

  The electron emission portion of the diamond electron source of the present invention may be an Ib type single crystal diamond. The type Ib is a state in which most of the nitrogen atoms are substituted by carbon atoms, and is most easily activated when heated as a donor, so that more electrons are emitted to the conduction band, so that electron emission becomes easier.

  Hereinafter, preferred embodiments of a diamond electron source according to the present invention will be described in detail with reference to the accompanying drawings. 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 three-dimensional view showing an embodiment of a diamond electron source according to the present invention. The diamond electron source 10 uses columnar single crystal diamond as a material, and has 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 size within this range allows compatibility with conventional electron sources such as point electron sources such as LaB ₆ and ZrO / W, so that a diamond electron source can be used in a wide range of electron beam devices. .

  The diamond electron source 10 includes an electron emission unit 11 and an energization heating unit 12. The electron emission part 11 has one sharp protrusion. The height of the projection is preferably 10 μm or more and the radius of curvature of the tip is 5 μm or less. By applying an electric field to the tip, the electron beam can be easily extracted. The shape is preferably tapered toward the protrusion so that the electric field is easily concentrated on the tip of the protrusion. More preferably, the protrusion shape has a height of 15 μm or more and a tip curvature radius of 2 μm or less, which makes it possible to achieve a luminance higher than that of the conventional electron source ZrO / W.

Moreover, the impurity contained most in the single crystal diamond of the electron emission part 11 is nitrogen, and the nitrogen concentration is 1 × 10 ¹⁷ cm ⁻³ or more. This facilitates electron emission because nitrogen is activated during heating and emits a sufficient number of electrons to the conduction band of diamond. The nitrogen concentration is more preferably 2 × 10 ¹⁸ cm ⁻³ or more, which makes it possible to achieve a luminance exceeding that of the conventional electron source ZrO / W. The electron emission part 11 is an Ib type single crystal diamond, and can emit a large current. Type Ib is a state in which most of the nitrogen atoms are substituted by carbon atoms, and is a mixed state that is most easily activated as a donor during heating. Therefore, electron emission is easier because more electrons are emitted to the conduction band.

In the present invention, the electric heating unit 12 has a resistance between terminals of 500Ω or less at room temperature (25 ° C.).
As shown in the diamond electron source module 20 of FIG. 2, the inter-terminal resistance in the present invention is sandwiched between the power supply terminal 21 of the module 23 composed of components including the power supply terminal 21 and the ceramic base 22. This is the resistance between the power supply terminals 21 at the time. The power supply terminal 21 is made of a metal whose resistance is almost negligible, and in order to improve electrical contact with the diamond electron source 10, a relatively soft spacer such as graphite may be bitten. By having such a low inter-terminal resistance, the entire diamond electron source can be heated with a filament power source that heats ZrO / W, LaB _{6 and the} like of the electron beam apparatus. By heating, moisture attached to the electron emission portion necessary for stabilization of the emission current can be easily removed, and adhesion of molecules remaining in the vacuum to the protrusions of the electron emission portion 11 is also small. Therefore, stable electron emission can be realized. The operation is possible at a heating temperature of 400 ° C. or higher and 1450 ° C. or lower, more preferably 600 ° C. or higher and 1200 ° C. or lower. If the temperature is too low, a sufficient electron emission current cannot be obtained. If the temperature is too high, graphitization of the diamond surface proceeds and the life is shortened.

Next, although the concrete method for implement | achieving the room temperature terminal resistance of 500 ohms or less of the electricity heating part 12 is illustrated, this invention is not limited to these. The energization heating unit obtained by applying the following method can realize a large current and stable electron emission in an electron source using diamond.
(1) A method of forming a diamond thin film containing phosphorus as an impurity on the surface of single-crystal diamond in a current-heating section.
(2) A method in which single crystal diamond containing boron as an impurity is used as the single crystal diamond in the current heating section.
(3) A method of forming an ion implantation layer on the surface of the single crystal diamond of the energization heating unit.
(4) A method of forming an electrically conductive layer by destroying the crystal structure in the vicinity of the surface of the single crystal diamond in the energization heating section.
(5) A method of forming a metal or semiconductor conductive thin film on the surface of the single crystal diamond of the energization heating unit.
Below, each method of said (1)-(5) is demonstrated in detail.

<Method of forming a diamond thin film containing phosphorus as an impurity on the surface of single crystal diamond>
In this method, a diamond thin film containing the largest amount of phosphorus as an impurity and having a phosphorus concentration of 1 × 10 ¹⁶ cm ⁻³ or more is formed on the surface of the single crystal diamond of the energization heating unit 12 by microwave plasma CVD or DC plasma CVD. Form with. Since the phosphorus-doped diamond thin film is an n-type semiconductor, electrons supplied from the power supply terminal can be smoothly transported to the diamond conduction band of the electron emission portion 11, resulting in easier electron emission.

<Method of using single crystal diamond containing boron as an impurity as single crystal diamond>
In this method, the single crystal diamond of the energization heating unit 12 contains boron as an impurity most, and the boron concentration is 1 × 10 ¹⁸ cm ⁻³ or more.
The inter-terminal resistance becomes 10Ω or less at the operating temperature because boron is activated and lowered as the temperature rises. In this case, as shown in FIG. 3, the electron emission section 11 having a nitrogen concentration of 1 × 10 ¹⁷ cm ⁻³ or more and the energization heating section 12 having a boron concentration of 1 × 10 ¹⁸ cm ⁻³ or more are simultaneously provided as one. It exists in the columnar single crystal diamond 30. Such a diamond single crystal can be produced by, for example, a high-temperature high-pressure synthesis method. When a single crystal is synthesized by this method, it is possible to simultaneously grow a growth sector in which boron is mixed and a sector in which nitrogen is mixed with almost no boron mixed by selecting a synthesis condition. A desired diamond single crystal can be obtained by cutting out a columnar material so that two sectors can enter. Since there is no process for forming the energization heating unit 12, the yield can be increased.

<Method of forming an ion implantation layer on the surface of single crystal diamond>
In this method, the ion implantation layer 41 is formed between the surface of the single crystal diamond and a depth of 10 μm.
For example, as shown in FIG. 4, when the columnar single crystal diamond material 40 is a square column as viewed from the end surface on the energization heatable portion 12 side, the two surfaces sandwiched by the power supply terminal 21 and other surfaces are used. An ion implantation layer 41 is formed on at least one of the two surfaces to establish conduction between the power supply terminals 21. As the ion implantation conditions, the ion species are boron, sulfur, phosphorus, lithium, etc., the acceleration energy is preferably 10 keV to 10 MeV, and the dose amount is 1 × 10 ¹⁴ to 2 × 10 ¹⁶ cm ^−2. The degree of vacuum is 1 × 10 ⁻⁴ Pa or less, the temperature is 1000 to 1450 ° C., and the time is 10 to 60 minutes. Since stable resistance of the energization heating unit 12 can be obtained, variations in electron emission conditions between samples can be reduced.

<Method of forming an electrically conductive layer by destroying the crystal structure of the surface of the single crystal diamond in the energization heating section>
In this method, for example, as shown in FIG. 5, the diamond crystal structure in the vicinity of the surface of the single crystal diamond is broken to form the electrically conductive layer 51.
When the columnar single crystal diamond material 50 is a quadrangular prism as viewed from the end face on the energization heatable portion 12 side, the electric conductive layer 51 is formed by two surfaces sandwiched by the power supply terminal 21 and the other two surfaces. At least one of the surfaces is made conductive between the power supply terminals 21 by destroying the diamond crystal structure in the vicinity of the surface using an ion beam such as a focused ion beam processing apparatus. As ion beam irradiation conditions, gallium ion species, acceleration energy of 40 keV or less, and a dose of 1 × 10 ¹⁷ cm ⁻² or more can be suitably used. Since stable resistance of the energization heating unit 12 can be obtained, variations in electron emission conditions between samples can be reduced.

<Method of forming a conductive thin film of metal or semiconductor on the surface of single crystal diamond in the energization heating section>
In this method, as shown in FIG. 6, for example, a conductive thin film 61 of metal or semiconductor is formed on the surface of single crystal diamond.
When the columnar single crystal diamond material 60 is a quadrangular prism as viewed from the end face on the energization heatable portion 12 side, the conductive thin film 61 is formed by two surfaces sandwiched by the power supply terminal 21 and the other two surfaces. A metal thin film or a semiconductor thin film is formed on at least one of the surfaces, and conduction between the feeding terminals 21 is established. For metal thin films, heat-resistant metals such as titanium, tungsten, and molybdenum are preferably formed by sputtering or electron beam evaporation. For semiconductor thin films, silicon, silicon carbide, or the like having low resistance doped with impurities at a high concentration is used. It is good to form by CVD. Since stable resistance of the energization heating unit 12 can be obtained, variations in electron emission conditions between samples can be reduced.

The diamond electron source 10 is preferably heat-treated at a temperature of 700 ° C. or higher and 1400 ° C. or lower in a vacuum of 10 ⁻⁴ Pa or lower to realize more stable electron emission. Since the adsorbate on the surface is desorbed by this vacuum heat treatment and a more stable surface atomic structure is obtained, stable electron emission is realized. Therefore, if it is taken out from the vacuum before the operation, the performed vacuum heat treatment becomes invalid. As a heating method, it is preferable that current is supplied between the power supply terminals 21 in the state of the diamond electron source module 20 to conduct current heating. Moreover, as heating conditions, the temperature of 800 degreeC or more and 1100 degrees C or less is more preferable in the vacuum of 10 < ^-5 > Pa or less. This heat treatment is practical because a sufficient degassing rate is obtained and the surface does not graphitize even if left for a long time.

The present invention is characterized in that, as the single crystal diamond of the electron emission portion, the most contained impurity is nitrogen, and the single crystal diamond whose nitrogen concentration is 1 × 10 ¹⁷ cm ⁻³ or more is used.
Such a single crystal diamond is not attracting much attention as an electron source material because nitrogen is an n-type dopant for diamond, and its impurity level is as deep as 1.4 eV or more and is an insulator at room temperature. It was. However, as a result of earnest research by the present inventors, one single crystal diamond is divided into an electron emission portion and an electric heating portion, and the single crystal diamond having a low room temperature resistance of the electric heating portion is used, or the electric heating portion By applying a process that lowers the room temperature resistance, the entire diamond electron source can be heated by energization heating, electrically activates the nitrogen in the electron emission region, and draws electrons emitted from the conduction band by the electric field at the tip of the protrusion. Thus, an unprecedented electron source structure for obtaining electron emission has been found. As a result, nitrogen-doped single crystal diamond that can be artificially synthesized in large quantities at low cost can be used as an electron source, and a ZrO / W electron source or a LaB ₆ electron source mainly used in an electron beam apparatus, which could not be realized so far, Mass production of compatible diamond point electron sources is now possible.

The diamond electron source of the present invention will be described more specifically based on examples.
[Example 1]
First, a diamond electron source a1 as shown in FIG. 1 was produced. The size of the bottom surface is 0.6 mm square, the height is 2.5 mm, the shape is a truncated pyramid shape that tapers 2.2 mm from the bottom, and the size of the end surface is 30 μm square. The height of the protrusion was 30 μm and the radius of curvature at the tip was 0.5 μm. The upper part is an electron emission part and the lower part is an energization heating part with 2.0 mm above the bottom as a boundary. The most abundant impurity contained in the single crystal diamond in the electron emission portion is nitrogen and the nitrogen concentration is 3 × 10 ¹⁸ cm ⁻³ , and the most abundant impurity contained in the single crystal diamond in the current heating portion is boron and the boron concentration is The single crystal diamond material shown in FIG. 3 as 2 × 10 ¹⁹ cm ⁻³ was used. Then, the diamond electron source a1 was incorporated in a diamond electron source module as shown in FIG. The resistance between terminals at room temperature (25 ° C.) was 250Ω. When the electron beam was evaluated by incorporating the diamond electron source module into a conventional evaluation apparatus having a filament power source that can be heated by the electron source, the temperature of the diamond electron source was 1,000 ° C., the distance between the protrusion tip and the extraction electrode was 400 μm, and the extraction electrode aperture was At a diameter of 500 μmφ and an extraction voltage of 3.5 kV, an angular current density of 0.4 mA / sr was obtained.

The diamond electron source a2 was produced by changing the single-crystal diamond in the electron emission portion from the diamond electron source a1 to the Ib type. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained. Based on the diamond electron source a1, on the surface of the single crystal diamond of the energization heating part, the most abundant impurity is phosphorus, and a diamond thin film of 2 μm having a phosphorus concentration of 5 × 10 ¹⁹ cm ⁻³ is formed by microwave plasma CVD. Thus, a diamond electron source a3 was produced. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained.
The diamond electron sources a1 to a3 were incorporated in an evaluation apparatus, and the electron beam was evaluated after heating at a vacuum degree of 10 ⁻⁵ Pa or less and a temperature of 1050 ° C. for 20 hours. As a result, the beam stability for 10 hours was 1% rms, which was better than 5% rms when evaluated without vacuum heat treatment.

[Comparative Example 1]
From the diamond electron source a1, the shape of the protrusion was changed to a height of 9 μm, the diamond electron source a4 was changed, the nitrogen concentration was changed to 5 × 10 ¹⁶ cm ⁻³ , the diamond electron source a5 was changed to a boron concentration of 1 × 10 ¹⁷ A diamond electron source a6 was prepared by changing the resistance between terminals to 1 cm and changing to ³ cm- ³ . Although similarly evaluated, the diamond electron sources a4 and a5 were able to obtain only an angular current density lower than that of the conventional electron source ZrO / W electron source. The diamond electron source a6 could not be heated by the filament power source of the evaluation apparatus, and the electron beam could not be extracted.

[Example 2]
First, a diamond electron source b1 as shown in FIG. 1 was produced. The size of the bottom surface is 0.6 mm square, the height is 2.5 mm, the shape is a truncated pyramid shape that tapers 2.2 mm from the bottom, and the size of the end surface is 30 μm square. The height of the protrusion was 30 μm and the radius of curvature at the tip was 0.5 μm. The upper part is an electron emission part and the lower part is an energization heating part with 2.0 mm above the bottom as a boundary. The single crystal diamond in which the most contained impurity in the single crystal diamond in the electron emission portion is nitrogen and the nitrogen concentration is 3 × 10 ¹⁸ cm ⁻³ was used. In the current heating section, boron was ion-implanted and annealed at a depth of 2 μm from the single crystal diamond surface to form an ion-implanted layer as shown in FIG. Then, the diamond electron source b1 was incorporated in a diamond electron source module as shown in FIG. The resistance between terminals at room temperature (25 ° C.) was 50Ω. When the electron beam was evaluated by incorporating the diamond electron source module into a conventional evaluation apparatus having a filament power source that can be heated by the electron source, the temperature of the diamond electron source was 1,000 ° C., the distance between the protrusion tip and the extraction electrode was 400 μm, and the extraction electrode aperture was At a diameter of 500 μmφ and an extraction voltage of 3.5 kV, an angular current density of 0.4 mA / sr was obtained.

A diamond electron source b2 was produced by changing the single-crystal diamond in the electron emission portion from the diamond electron source b1 to the Ib type. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained. Based on the diamond electron source b1, a diamond thin film of 2 μm having a phosphorus concentration of 5 × 10 ¹⁹ cm ⁻³ is formed by microwave plasma CVD on the surface of the single-crystal diamond in the energization / heating section. Thus, a diamond electron source b3 was produced. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained.
The diamond electron sources b1 to b3 were incorporated in an evaluation apparatus, and the electron beam was evaluated after heating at a vacuum degree of 10 ⁻⁵ Pa or less and a temperature of 1050 ° C. for 20 hours. As a result, the beam stability for 10 hours was 1% rms, which was better than 5% rms when evaluated without vacuum heat treatment.

[Comparative Example 2]
From the diamond electron source b1, the shape of the protrusion is changed to a height of 9 μm, the diamond electron source b4 is changed, the nitrogen concentration is changed to 5 × 10 ¹⁶ cm ⁻³ , and the diamond electron source b5 is changed from the ion at the time of ion implantation layer formation. The diamond electron source b6 was produced by changing the inter-terminal resistance to 1 kΩ by reducing the implantation dose. Although similarly evaluated, the diamond electron sources b4 and b5 were able to obtain only an angular current density lower than the ZrO / W electron source of the conventional electron source. The diamond electron source b6 could not be heated by the filament power source of the evaluation apparatus, and the electron beam could not be extracted.

[Example 3]
First, a diamond electron source c1 as shown in FIG. 1 was produced. The size of the bottom surface is 0.6 mm square, the height is 2.5 mm, the shape is a truncated pyramid shape that tapers 2.2 mm from the bottom, and the size of the end surface is 30 μm square. The height of the protrusion was 30 μm and the radius of curvature at the tip was 0.5 μm. The upper part is an electron emission part and the lower part is an energization heating part with 2.0 mm above the bottom as a boundary. The single crystal diamond in which the most contained impurity in the single crystal diamond in the electron emission portion is nitrogen and the nitrogen concentration is 3 × 10 ¹⁸ cm ⁻³ was used. The energization heating unit is a focused ion beam processing apparatus, and is produced by destroying the crystal structure of the surface of a single crystal diamond under the conditions of ion species gallium, acceleration energy 30 kV, dose amount 1.5 × 10 ¹⁸ cm ⁻² . An electrically conductive layer as shown in FIG. Then, the diamond electron source c1 was incorporated in a diamond electron source module as shown in FIG. The resistance between terminals at room temperature (25 ° C.) was 10Ω. When the electron beam was evaluated by incorporating the diamond electron source module into a conventional evaluation apparatus having a filament power source that can be heated by the electron source, the temperature of the diamond electron source was 1,000 ° C., the distance between the protrusion tip and the extraction electrode was 400 μm, and the extraction electrode aperture was At a diameter of 500 μmφ and an extraction voltage of 3.5 kV, an angular current density of 0.4 mA / sr was obtained.

From the diamond electron source c1, the single crystal diamond of the electron emission portion was changed to the Ib type to produce a diamond electron source c2. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained. Based on the diamond electron source c1, a diamond thin film of 2 μm having a phosphorus concentration of 5 × 10 ¹⁹ cm ⁻³ is formed by microwave plasma CVD on the surface of the single-crystal diamond in the energization / heating section. Thus, a diamond electron source c3 was produced. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained.
The diamond electron sources c1 to c3 were incorporated in an evaluation apparatus, and the electron beam was evaluated after heating at a vacuum degree of 10 ⁻⁵ Pa or less and a temperature of 1050 ° C. for 20 hours. As a result, the beam stability for 10 hours was 1% rms, which was better than 5% rms when evaluated without vacuum heat treatment.

[Comparative Example 3]
From the diamond electron source c1, the shape of the protrusions was changed to a height of 9 μm, the diamond electron source c4 was changed, the nitrogen concentration was changed to 5 × 10 ¹⁶ cm ⁻³ , and the diamond electron source c5 was changed to a single crystal surface with a focused ion beam. The diamond electron source c6 was produced by changing the inter-terminal resistance to 1 kΩ by reducing the dose when roughening the film. Although similarly evaluated, the diamond electron sources c4 and c5 were able to obtain only an angular current density lower than that of the conventional electron source ZrO / W electron source. The diamond electron source c6 could not be heated by the filament power source of the evaluation apparatus, and the electron beam could not be extracted.

[Example 4]
First, a diamond electron source d1 as shown in FIG. 1 was produced. The size of the bottom surface is 0.6 mm square, the height is 2.5 mm, the shape is a truncated pyramid shape that tapers 2.2 mm from the bottom, and the size of the end surface is 30 μm square. The height of the protrusion was 30 μm and the radius of curvature at the tip was 0.5 μm. The upper part is an electron emission part and the lower part is an energization heating part with 2.0 mm above the bottom as a boundary. The single crystal diamond in which the most contained impurity in the single crystal diamond in the electron emission portion is nitrogen and the nitrogen concentration is 3 × 10 ¹⁸ cm ⁻³ was used. A conductive thin film as shown in FIG. 6 was formed in the energization heating portion by sputtering to form a titanium thin film of 100 nm and a tungsten thin film of 1000 nm thereon. Then, the diamond electron source d1 was incorporated in a diamond electron source module as shown in FIG. The resistance between terminals at room temperature (25 ° C.) was 5Ω. When the electron beam was evaluated by incorporating the diamond electron source module into a conventional evaluation apparatus having a filament power source that can be heated by the electron source, the temperature of the diamond electron source was 1,000 ° C., the distance between the protrusion tip and the extraction electrode was 400 μm, and the extraction electrode aperture was At a diameter of 500 μmφ and an extraction voltage of 3.5 kV, an angular current density of 0.4 mA / sr was obtained.

The diamond electron source d2 was produced by changing the single-crystal diamond in the electron emission portion from the diamond electron source d1 to the Ib type. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained. Based on the diamond electron source d1, on the surface of the single crystal diamond of the energization heating part, the most contained impurity is phosphorus, and a diamond thin film of 2 μm having a phosphorus concentration of 5 × 10 ¹⁹ cm ⁻³ is formed by microwave plasma CVD. Thus, a diamond electron source d3 was produced. When evaluated in the same manner, an angular current density of 0.5 mA / sr was obtained.
The diamond electron sources d1 to d3 were incorporated in an evaluation apparatus, and the electron beam was evaluated after heating for 20 hours at a vacuum degree of 10 ⁻⁵ Pa or less and a temperature of 1050 ° C. As a result, the beam stability for 10 hours was 1% rms, which was better than 5% rms when evaluated without vacuum heat treatment.

[Comparative Example 4]
From the diamond electron source d1, the shape of the protrusion was changed to 9 μm in height, the diamond electron source d4 was changed, the nitrogen concentration was changed to 5 × 10 ¹⁶ cm ⁻³ , and the diamond electron source d5 was sputtered to form a titanium / tungsten thin film. The diamond electron source d6 was produced by reducing the inter-terminal resistance to 1 kΩ by reducing the film thickness at the time of formation. Although similarly evaluated, the diamond electron sources d4 and d5 were able to obtain only an angular current density lower than that of the conventional electron source ZrO / W electron source. The diamond electron source d6 could not be heated by the filament power source of the evaluation apparatus, and the electron beam could not be extracted.

It is a figure which shows one Embodiment of the diamond electron source of this invention. It is a figure which shows a diamond electron source module. It is a figure which shows the diamond electron source which consists of an electron emission part of this invention, and an electricity heating part. It is a figure which shows the diamond electron source which formed the ion implantation layer in the electricity heating part of this invention. It is a figure which shows the diamond electron source which formed the electroconductive layer using the ion beam to the electricity heating part of this invention. It is a figure which shows the diamond electron source which formed the electroconductive thin film in the electricity heating part of this invention.

DESCRIPTION OF SYMBOLS 10 Diamond electron source 11 Electron emission part 12 Current heating part 20 Diamond electron source module 21 Feed terminal 22 Ceramic base 23 Module 30 Columnar single crystal diamond 40, 50, 60 Columnar single crystal diamond material 41 Ion implantation layer 51 Electrical conduction layer 61 Conductive thin film

Claims (8)

An electron source using a columnar single crystal diamond, which is composed of an electron emission portion and an energization heating portion, and the electron emission portion has a sharp protrusion having a height of 10 μm or more and a tip curvature radius of 5 μm or less on the end face of the column. The impurity contained only in one place and contained most in the single crystal diamond of the electron emission portion is nitrogen, and the concentration of the nitrogen is 1 × 10 ¹⁷ cm ⁻³ or more, and the room temperature ( 25 ° C.) Diamond electron source characterized in that resistance between terminals is 500Ω or less.   The diamond electron source according to claim 1, wherein the electron emission portion is an Ib type single crystal diamond. The current heating section has a diamond thin film containing the most phosphorus as an impurity and having a phosphorus concentration of 1 × 10 ¹⁶ cm ⁻³ or more on the surface of the single crystal diamond. The diamond electron source according to claim 2. The single crystal diamond of the energization heating part is a single crystal diamond containing the most boron as an impurity and having a boron concentration of 1 × 10 ¹⁸ cm ⁻³ or more. A diamond electron source according to any one of the above.   The diamond electron source according to any one of claims 1 to 3, wherein an ion-implanted layer is formed between the surface of the single-crystal diamond of the energization heating part and a depth of 10 µm.   4. The diamond electron according to claim 1, wherein the single crystal diamond of the energization heating portion has an electrically conductive layer formed by breaking a diamond crystal structure in the vicinity of the surface thereof. 5. source.   The diamond electron source according to any one of claims 1 to 3, wherein the single crystal diamond of the energization heating part has a metal or semiconductor conductive thin film on the surface thereof. The diamond electron source according to any one of claims 1 to 7, wherein the diamond electron source is heat-treated in a vacuum of 10 ^-4 Pa or less at a temperature of 700 ° C or higher and 1400 ° C or lower before use.

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