JP2010251087A - Cold-cathode field emission electron gun - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron gun capable of obtaining electron beams with high luminance and high stability used for an electron-beam equipment and a vacuum tube, especially, an electron microscope. <P>SOLUTION: The cold-cathode field emission electron gun used for an electronic optical equipment operates at 1,000°C or less, and as electron emission characteristics obtained, an emission current stability is less than 5%, and an angle current density is larger than 50 μA/sr. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention is an electron gun used for 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 an electron beam superior to a conventional tungsten cold cathode is obtained. The present invention relates to a cold cathode field emission electron gun.

  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.

Currently, as cathodes that are often used for electron microscope applications, according to Patent Documents 1 to 3, for example, a thermionic source is a low-cost tungsten filament, a boride made of LaB ₆ or the like from which a high-luminance electron beam can be obtained. There is a filament. Further, as a cathode having higher brightness and a narrower energy width, sharpened tungsten is used as a field emission electron source utilizing a tunnel phenomenon due to a quantum effect, and ZrO / W 2 is used as a thermal field emission electron source utilizing a Schottky effect due to an electric field. It has been.

  On the other hand, in an electron microscope, there is a demand for high-precision observation of nano-sized microstructures such as length measurement in an LSI process. Therefore, there is a demand for an electron gun that can obtain an electron beam with high brightness and a stable current. Yes.

The required electron beam luminance is 1 × 10 ⁹ A / m ² sr, and the electron beam current stability is less than 5%, which is realized by a beam extraction voltage of 3 kV to 10 kV. Here, the electron beam refers to an electron beam obtained on a sample stage in a sample chamber of an electron microscope. Stability is an index that indicates how much of the average current value obtained by averaging all sampling data after measuring the current for 24 hours or more at a sampling frequency of 10 Hz or more, and that all sampling data is included. It is defined as

  Comparing the electron beam performance obtained with an electron gun equipped with a conventional electron source for the required brightness and stability, tungsten filament, boride filament, and ZrO / W are stable at around 1%, but the brightness is small. The request could not be fulfilled. An electron gun equipped with sharpened tungsten did not satisfy the requirements because the stability was poor at 5% to 10%. That is, the conventional electron source cannot meet the user requirement of high brightness and high stability. Here, the electron gun is defined as including at least an extraction electrode aperture plate disposed at a certain distance from the electron source and the electron emission portion of the electron source as a constituent element.

Japanese Patent Publication No. 63-015633 Japanese Patent Laid-Open No. 03-129651 Japanese Patent Laid-Open No. 08-013733

  The present invention has been made in view of such circumstances, and provides an electron gun capable of obtaining an electron beam having high brightness and high stability, which is used in an electron beam and an electron beam apparatus and a vacuum tube, particularly an electron microscope. For the purpose.

  In order to solve the above-described problems, an electron gun according to the present invention is a cold cathode field emission electron gun used in an electro-optical device, which operates at 1000 ° C. or less, and has an emission current stability as an obtained electron emission characteristic. It is characterized in that the properties are less than 5% and the angular current density is greater than 50 μA / sr. Here, the emission current refers to the total electron emission current from the electron gun.

  Since the cold cathode field emission electron gun of the present invention has such a current stability and angular current density at a low operating temperature, it is particularly required for the brightness and stability required in the field of electron microscopes for length measurement inspection of semiconductor devices. Can be realized.

  Further, the electron gun of the present invention is a cold cathode field emission electron gun that operates at 1000 ° C. or lower, and the obtained electron emission characteristics include an emission current stability of less than 5% and an electron emission solid angle of 0. Emission current in the range of 0002 sr is greater than 5 nA.

  The cold cathode field emission electron gun of the present invention can realize such a current stability and a large current characteristic with a narrow solid angle at a low operating temperature. It can be suitably used in the electron microscope field.

  Alternatively, the electron gun of the present invention is a cold cathode field emission electron gun, which operates at 1000 ° C. or less, and as an electron emission characteristic obtained, emission current stability is less than 5% and energy dispersion is less than 0.4 eV. It is characterized by being.

  Since the cold cathode field emission electron gun of the present invention can realize such current stability and a narrow energy width at a low operating temperature, it has high brightness and high stability required in the field of electron microscopes for length measurement inspection of semiconductor devices. An electron beam can be obtained.

  Furthermore, the electron gun of the present invention is a cold cathode field emission electron gun, which operates at 1000 ° C. or less, and as an electron emission characteristic obtained, the angular current density is larger than 50 μA / sr and the energy dispersion is 0.4 eV. It is characterized by being less than.

  Since the cold cathode field emission electron gun of the present invention can realize such an angular current density and a narrow energy width at a low operating temperature, a high-brightness and highly stable electron beam can be obtained.

  The electron gun of the present invention is a cold cathode field emission electron gun, which operates at 1000 ° C. or less, and has an emission current within a range of a solid angle of electron emission of 0.0002 sr as 5 nA. It is large and has an energy dispersion of less than 0.4 eV.

  Since the cold cathode field emission electron gun of the present invention can realize a large current characteristic and a narrow energy width at a low operating temperature and in such a narrow solid angle, a high-brightness and highly stable electron beam can be obtained.

  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 cold cathode field emission electron gun capable of obtaining a high-luminance and highly stable electron beam is realized. In particular, if the cold cathode field emission electron gun of the present invention is used in an electron microscope for semiconductor device length measurement inspection, high-speed and high-precision observation that is impossible with a conventional electron gun can be realized.

It is a figure which shows an example of the electron source part of the cold cathode field emission electron gun by this invention. It is an enlarged view of the chip | tip 11 in FIG. It is the schematic which shows an example of a structure of the electron source part of the cold cathode field emission electron gun by this invention. It is a figure which shows an example of a structure at the time of making an electron emit from the cold cathode field emission electron gun by this invention.

  Hereinafter, preferred embodiments of a cold cathode field emission electron gun 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 plan view showing an embodiment of an electron source portion of a cold cathode field emission electron gun according to the present invention. The electron source 10 includes a chip 11 which is an electron emitting portion, a support 12 for holding the chip 11, a base 13 for fixing the support 11, and a power supply terminal 14 for supplying emitted electrons to the chip via the support 12. Consists of.

The tip 11 is preferably a diamond single crystal. The diamond single crystal is classified into Ia type, Ib type, IIa type, IIb type, and the like depending on the type of impurities and defects mixed therein, and any of them may be used. It is preferable that a boron-doped diamond epitaxial thin film or a phosphorus-doped diamond epitaxial thin film is formed on at least a part of the diamond single crystal of the chip 11 in order to contribute to improvement of the conductivity of the chip 11.
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. Due to the size within this range, compatibility with an electron gun equipped with a conventional electron source such as LaB ₆ or ZrO / W is achieved. As a result, the cold cathode electric field of the present invention is applied to an electron microscope in which these are used. An emission electron gun can be mounted.

  The chip 11 has a sharp projection 20 as shown in FIG. 2, and obtains field emission electrons by applying an electric field to the tip thereof. The sharp projection 20 is formed on the plane of the truncated pyramid 21, but has a unique structure that is not found in conventional electron sources because diamond that is difficult to process is used as the electron source. The sharp projection 20 has a conical shape, the apex angle is 30 ° or less, the height is 10 μm or more, the tip curvature radius is 0.05 μm or more and 1 μm or less, and the surface roughness of the most advanced part is 1 nm or less.

  Portions other than the sharp projections 20 are produced by laser processing and polishing a diamond single crystal. The pyramid 21 has a height of 0.1 to 0.5 mm and a size of the truncated pyramid surface within a range of 20 μm to 100 μm, considering the ease of processing and concentration of the electric field of the sharp projection. 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 20 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 carried out 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, W, and Al, and ceramics such as SiO ₂ and SiON can be used.

The surface roughness of the tip portion of the sharp projection 20 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 increases and the mask thickness decreases, but depending on the etching conditions, the mask also shrinks in the radial direction, and in this case, it becomes a conical shape that tapers toward the tip of the protrusion. . As such etching conditions, a pressure of 0.5 Pa to 20 Pa, a CF ₄ : oxygen gas mixing ratio of 1: 1000 to 1: 1, and a high frequency power of 50 W to 500 W are selected. If it is confirmed that the film has been reduced to about 2 μm, the etching rate is set to 0.1 μm / h or less. By doing so, a sharp pointed projection 20 is formed in a conical shape with an apex angle of 30 ° or less, and the surface roughness of the electron emission portion at the tip is finished to a smooth surface down to an atomic level of 1 nm or less.

  By satisfying the above chip configuration, desired electron gun performance can be obtained. As a result, beam performance required by the user can be obtained. The shape of the sharpened protrusion 20 is preferably a conical shape with an apex angle of 30 ° or less, which is a tapered shape toward the protrusion tip, as described above, so that the electric field is easily concentrated on the protrusion tip. Diamond can be suitably used because it has a low work function and is easy to emit electrons. Even a material other than diamond can be suitably used as long as it has a low work function and has an electron emission ease equal to or higher than that of diamond.

  In order to extract the same beam current from exactly the same material except that the work function is relatively large, it is necessary to make the extraction electrode closer to the material, increase the extraction voltage, etc. The conditions for extracting electrons become stricter than materials with a relatively small work function. If the extraction conditions are severe, there is a high possibility that the electron source is destroyed by discharge or the like, and it becomes difficult to pursue performances such as emission current stability, angular current density, and energy dispersion.

  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 portion of the cold cathode field emission electron gun of the present invention has at least the above-described components. As shown in the cross-sectional view of FIG. 3, the support 12, the suppressor 30, the chip clamping screws 31 and 32, the heat The presence of components such as cracked carbon spacer 33 is within the scope of the present invention. The suppressor 30 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 electron emission from a part other than the chip 11. The chip clamping screws 31 and 32 are for assisting the force with which the column 12 clamps the chip 11. The pyrolytic carbon spacer 33 is sandwiched between the contact portions of the chip 11 and the support column 12 when the chip 11 needs to be heated.

  FIG. 4 is a cross-sectional view showing an embodiment of a configuration when electrons are emitted from the cold cathode field emission electron gun according to the present invention. An aperture plate 40 is installed on the electron source 10, and an extraction voltage, that is, a positive voltage is applied to the chip 11 to the aperture plate 40, thereby extracting an electron beam (emission electron) 41.

In the electron beam extraction configuration of FIG. 4, in order to extract desired performance from the cold cathode field emission electron gun, the aperture plate 40 has a hole diameter of 800 μm or less and a thickness of 600 μm or less, and the tip of the tip 11 and the tip of the aperture plate 40. The distance to the surface on the 11th side is 50 μm to 2000 μm. By adopting such a configuration, a desired electron gun performance is obtained when the temperature of the chip 11 is 1000 ° C. or less and the extraction voltage is 3 kV to 10 kV in an environment with a vacuum degree of 1.2 × 10 ⁻⁷ Pa or less. The beam performance required by the user can be obtained.

  It is known that diamond has an excellent electron emission performance, but since it is difficult to process, an electron source shape and an electron gun configuration for extracting the maximum performance, that is, an electron beam extraction configuration has not been realized. However, as a result of diligent research by the present inventors, the electron source shape and electron gun configuration that draw out the maximum performance were found, and the ease of electron emission of diamond was fully utilized. The desired emission current stability, angular current density, and energy dispersion were obtained at a chip temperature of 1000 ° C. or lower, and the beam performance required by the user was obtained.

The cold cathode field emission electron gun of the present invention will be described more specifically based on examples.
[Example 1]
An electron source 1a was produced as an electron source portion of a cold cathode field emission electron gun as shown in FIG. The chip 11 was produced as follows.
First, an Ib type diamond single crystal was prepared. As a result of SIMS analysis of the diamond single crystal, it was found that 30 ppm of nitrogen was mixed in the diamond. This was cut out with a laser processing machine so as to be a prismatic Ib type diamond single crystal having a size of 0.6 mm square × 2.5 mm. The crystal orientation was <110> in the longitudinal direction. A phosphorus-doped epitaxial thin film was grown on a surface of 0.6 mm × 2.5 mm of this substrate by using a diamond vapor phase growth apparatus by 2 μm. 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 photolithography method is used to form a cylindrical etching mask made of Ti of 6 μmφ × 4 μm at the center of the truncated pyramid surface, 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 15 μm, a tip curvature radius of 0.3 μm, and a vertex angle of 15 ° on the truncated pyramid. Etching conditions were a pressure of 3 Pa, a CF ₄ : oxygen gas mixing ratio of 1:20, and a high frequency power of 200 W. After confirming that the diameter of the etching mask was 150 nm, the etching rate was reduced from 3 μm / h to 0.1 μm / h by reducing the high frequency power and gas pressure during etching to 50 W and 1 Pa. In this way, the surface roughness of the electron emission portion at the tip of the sharp projection 20 was set to 0.9 nm.
As the configuration of the electron source 1 a other than the chip 11, tungsten was used for the support 12, alumina was used for the base 13, and kovar was used for the power supply terminal 14.

  Next, the produced electron source 1a was assembled in an electron gun chamber of an electron microscope with an electron gun configuration as shown in FIG. The diameter of the hole of the aperture plate 40 was 800 μm, the thickness was 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 40 on the chip 11 side was 2000 μm.

When the degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 1000 ° C., and an extraction voltage of 7 kV was applied, an emission current stability of 3.0% and an angular current density of 70 μA / sr were obtained.
Next, when the temperature of the chip 11 was lowered to 25 ° C., the emission current stability was 3.8% and the angular current density was 55 μA / sr. During this time, the luminance changed from 1.4 × 10 ⁹ A / m ² sr to 1.1 × 10 ⁹ A / m ² sr.

[Comparative Example 1]
An electron source 1b was produced in the same manner as the electron source 1a except that the apex angle of the sharp projection 20 was 35 ° and the surface roughness of the electron emission portion at the tip was 1.5 nm. And it experimented by the same electron gun structure as Example 1 using the said electron source 1b.
The degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 1000 ° C., and an extraction voltage of 10 kV was applied, but the angular current density was as small as 40 μA / sr.
[Comparative Example 2]
In FIG. 4, all experiments were performed with the same electron gun configuration as in Example 1, except that the distance between the tip of the chip 11 and the surface of the aperture plate 40 on the chip 11 side was 3000 μm.
The degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 1000 ° C., and an extraction voltage of 10 kV was applied. However, the angular current density was as small as 35 μA / sr.

[Example 2]
An electron source 2a was produced as an electron source portion of a cold cathode field emission electron source as shown in FIG. The chip 11 was produced as follows.
First, a IIb type diamond single crystal was prepared. This diamond single crystal was analyzed by SIMS, and it was found that 100 ppm of boron was mixed in the diamond. This was cut out with a laser processing machine so as to be a prismatic IIb type diamond single crystal of size 0.6 mm square × 2.5 mm. 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 photolithography method is used to form a cylindrical etching mask made of Ti of 6 μmφ × 5 μm at the center of the truncated pyramid surface, and until 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 18 μm, a tip curvature radius of 0.2 μm, and a vertex angle of 15 ° on the truncated pyramid. Etching conditions were a pressure of 2 Pa, a CF ₄ : oxygen gas mixing ratio of 1:20, and a high frequency power of 250 W. After confirming that the diameter of the etching mask has reached 100 nm, the etching rate is reduced from 3.5 μm / h to 0.1 μm / h by reducing the high frequency power and gas pressure during etching to 50 W and 1 Pa. It was. In this way, the surface roughness of the electron emission portion at the tip of the sharp projection 20 was set to 0.9 nm.
As the configuration of the electron source 2 a other than the chip 11, tungsten was used for the support 12, alumina was used for the base 13, and kovar was used for the power supply terminal 14.

  Next, the produced electron source 2a was assembled in an electron gun chamber of an electron microscope with an electron gun configuration as shown in FIG. The diameter of the hole of the aperture plate 40 was 800 μm, the thickness was 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 40 on the chip 11 side was 2000 μm.

When the degree of vacuum is 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 is 1000 ° C., and the extraction voltage is 7 kV, the emission current stability is 3.2% and the solid angle of electron emission is within the range of 0.0002 sr. An emission current of 6.4 nA was obtained.
Next, when the temperature of the chip 11 was lowered to 25 ° C., the emission current stability was 4.1%, and the emission current within the range of the solid angle of electron emission of 0.0002 sr was 5.1 nA. During this time, the luminance changed from 1.5 × 10 ⁹ A / m ² sr to 1.2 × 10 ⁹ A / m ² sr.

[Comparative Example 3]
An electron source 2b similar to the electron source 2a was produced except that the apex angle of the sharp projection 20 was 35 ° and the surface roughness of the electron emission portion at the tip was 1.8 nm. And it experimented by the electron gun structure similar to Example 2 using the said electron source 2b.
Although the degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 1000 ° C., and an extraction voltage of 10 kV was applied, the emission current within the range of the solid angle of electron emission of 0.0002 sr was as small as 3.9 nA.
[Comparative Example 4]
In FIG. 4, all experiments were performed with the same electron gun configuration as in Example 2 except that the distance between the tip of the chip 11 and the surface of the aperture plate 40 on the chip 11 side was 3000 μm.
The degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 1000 ° C., and an extraction voltage of 10 kV was applied. However, the emission current in the range of the solid angle of electron emission of 0.0002 sr was as small as 3.5 nA. .

[Example 3]
An electron source 3a was produced as an electron source portion of a cold cathode field emission electron gun as shown in FIG. The chip 11 was produced as follows.
First, an Ib type diamond single crystal was prepared. As a result of SIMS analysis of the diamond single crystal, it was found that 20 ppm of nitrogen was mixed in the diamond. This was cut out with a laser processing machine so as to be a prismatic Ib type diamond single crystal having a size of 0.6 mm square × 2.5 mm. The crystal orientation was <110> in the longitudinal direction. A phosphorus-doped epitaxial thin film was grown on a surface of 0.6 mm × 2.5 mm of this substrate by using a diamond vapor phase growth apparatus by 2 μm. 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 photolithography method is used to form a cylindrical etching mask made of Ti of 6 μmφ × 4 μm at the center of the truncated pyramid surface, 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 20 μm, a tip curvature radius of 0.05 μm, and a vertex angle of 15 ° on the truncated pyramid. The etching conditions were a pressure of 3 Pa, a CF ₄ : oxygen gas mixture ratio of 1:30, and a high frequency power of 200 W. After confirming that the diameter of the etching mask has reached 50 nm, the etching rate is reduced from 3.5 μm / h to 0.1 μm / h by reducing the high frequency power and gas pressure during etching to 50 W and 1 Pa. It was. In this way, the surface roughness of the electron emission portion at the tip of the sharp projection 20 was set to 0.9 nm.
As the configuration of the electron source 3 a other than the chip 11, tungsten was used for the support 12, alumina was used for the base 13, and Kovar was used for the power supply terminal 14.

  Next, the produced electron source 3a was assembled in an electron gun chamber of an electron microscope with an electron gun configuration as shown in FIG. The diameter of the hole of the aperture plate 40 was 800 μm, the thickness was 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 40 on the chip 11 side was 2000 μm.

When the degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 1000 ° C., and an extraction voltage of 7 kV was applied, an emission current stability of 4.0% and an energy dispersion of 0.36 eV were obtained.
Next, when the temperature of the chip 11 was lowered to 25 ° C., the emission current stability was 4.2% and the energy dispersion was 0.26 eV. During this time, the luminance changed from 7.5 × 10 ⁹ A / m ² sr to 5.3 × 10 ⁹ A / m ² sr.

[Comparative Example 5]
In FIG. 1, the same electron source 3b as the electron source 3a was manufactured except that the radius of curvature of the tip of the chip 11 was set to 0.02 μm. And it experimented by the same electron gun structure as Example 3 using the said electron source 3b.
The degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 25 ° C., and an extraction voltage of 7 kV was applied, but the energy dispersion was as large as 0.45 eV.

[Example 4]
An electron source 4a was produced as an electron source portion of a cold cathode field emission electron gun as shown in FIG. The chip 11 was produced as follows.
First, a type IIa diamond single crystal was prepared. As a result of SIMS analysis of the diamond single crystal, it was found that both the amounts of nitrogen and boron mixed in the diamond were 1 ppm or less. This was cut out with a laser processing machine so as to be a prismatic IIa-type diamond single crystal having a size of 0.6 mm square × 2.5 mm. The crystal orientation was <110> in the longitudinal direction. A phosphorus-doped epitaxial thin film was grown on a surface of 0.6 mm × 2.5 mm of this substrate by using a diamond vapor phase growth apparatus by 2 μm. 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 Al of 6 μmφ × 4 μm is formed in 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 15 μm, a tip curvature radius of 0.05 μm, and a vertex angle of 15 ° on the truncated pyramid. Etching conditions were a pressure of ₄ Pa, a CF ₄ : oxygen gas mixing ratio of 1:25, and a high frequency power of 300 W. After confirming that the diameter of the etching mask was 50 nm, the etching rate was reduced from 3 μm / h to 0.1 μm / h by reducing the high frequency power and gas pressure during etching to 50 W and 1 Pa. In this way, the surface roughness of the electron emission portion at the tip of the sharp projection 20 was set to 0.9 nm.
As the configuration of the electron source 4 a other than the chip 11, tungsten was used for the support column 12, alumina was used for the base 13, and kovar was used for the power supply terminal 14.

  Next, the produced electron source 4a was assembled in an electron gun chamber of an electron microscope with an electron gun configuration as shown in FIG. The diameter of the hole of the aperture plate 40 was 800 μm, the thickness was 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 40 on the chip 11 side was 2000 μm.

When the degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 1000 ° C., and an extraction voltage of 7 kV was applied, an angular current density of 400 μA / sr and an energy dispersion of 0.38 eV were obtained.
Next, when the temperature of the chip 11 was lowered to 25 ° C., the angular current density was 250 μA / sr and the energy dispersion was 0.25 eV. During this time, the luminance changed from 7.8 × 10 ⁹ A / m ² sr to 1.5 × 10 ⁹ A / m ² sr.

[Comparative Example 6]
In FIG. 1, the same electron source 4b as the electron source 4a was produced except that the radius of curvature of the tip of the chip 11 was set to 0.02 μm. And it experimented by the same electron gun structure as Example 4 using the said electron source 4b.
The degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 25 ° C., and an extraction voltage of 7 kV was applied, but the energy dispersion was as large as 0.44 eV.

[Example 5]
An electron source 5a was manufactured as an electron source portion of a cold cathode field emission electron gun as shown in FIG. The chip 11 was produced as follows.
First, a diamond single crystal of Ib type in which boron was mixed in addition to nitrogen was prepared. When this diamond single crystal was analyzed by SIMS, it was found that the nitrogen concentration in the diamond was 30 ppm and the boron concentration was 100 ppm. This was cut out with a laser processing machine so as to be a prismatic Ib type diamond single crystal having a size of 0.6 mm square × 2.5 mm. The crystal orientation was <110> in the longitudinal direction. A phosphorus-doped epitaxial thin film was grown on a surface of 0.6 mm × 2.5 mm of this substrate by using a diamond vapor phase growth apparatus by 2 μm. 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 photolithography method is used to form a cylindrical etching mask made of Ti of 6 μmφ × 4 μm at the center of the truncated pyramid surface, 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 17 μm, a tip curvature radius of 0.05 μm, and a vertex angle of 15 ° on the truncated pyramid. Etching conditions were a pressure of 5 Pa, a CF ₄ : oxygen gas mixing ratio of 1:20, and a high frequency power of 250 W. After confirming that the diameter of the etching mask was 50 nm, the etching rate was reduced from 3 μm / h to 0.1 μm / h by reducing the high frequency power and gas pressure during etching to 50 W and 1 Pa. In this way, the surface roughness of the electron emission portion at the tip of the sharp projection 20 was set to 0.9 nm.
As the configuration of the electron source 5 a other than the chip 11, tungsten was used for the support 12, alumina was used for the base 13, and Kovar was used for the power supply terminal 14.

  Next, the produced electron source 5a was assembled in an electron gun chamber of an electron microscope with an electron gun configuration as shown in FIG. The diameter of the hole of the aperture plate 40 was 800 μm, the thickness was 600 μm, and the distance between the tip of the chip 11 and the surface of the aperture plate 40 on the chip 11 side was 2000 μm.

When the degree of vacuum is 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 is 1000 ° C., and an extraction voltage of 7 kV is applied, an emission current of 30 nA within an electron emission solid angle of 0.0002 sr and an energy dispersion of 0.39 eV are obtained. was gotten.
Next, when the temperature of the chip 11 was lowered to 25 ° C., an emission current of 23 nA and an energy distribution of 0.28 eV within a solid angle of electron emission of 0.0002 sr were obtained. During this time, the luminance changed from 8.1 × 10 ⁹ A / m ² sr to 1.6 × 10 ⁹ A / m ² sr.

[Comparative Example 7]
In FIG. 1, the same electron source 5b as the electron source 5a was produced except that the radius of curvature of the tip of the chip 11 was set to 0.02 μm. And it experimented by the same electron gun structure as Example 5 using the said electron source 5b.
The degree of vacuum was 1.2 × 10 ⁻⁷ Pa, the temperature of the chip 11 was 25 ° C., and an extraction voltage of 7 kV was applied, but the energy dispersion was as large as 0.46 eV.

10 Electron source 11 Chip 12 Prop 13 Base 14 Power supply terminal

20 Sharp Projection 21 Pyramidal Pedestal 30 Suppressor 31 Tip Tightening Screw 32 Tip Tightening Nut 33 Pyrolytic Carbon Spacer 40 Aperture Plate 41 Electron Beam (Emission Electron)

Claims (5)

  A cold cathode field emission electron gun used for an electro-optical device, which operates at 1000 ° C. or lower, and has an emission current stability of less than 5% and an angular current density of more than 50 μA / sr. An electron gun characterized by that.   A cold cathode field emission electron gun used in an electro-optical device, which operates at 1000 ° C. or lower, and has an emission current stability of less than 5% and an electron emission solid angle of 0.0002 sr. An electron gun having an emission current in the range greater than 5 nA.   A cold cathode field emission electron gun used for an electro-optical device, which operates at 1000 ° C. or lower, and has an electron emission characteristic obtained such that emission current stability is less than 5% and energy dispersion is less than 0.4 eV. An electron gun characterized by that.   A cold cathode field emission electron gun used for an electro-optical device, which operates at 1000 ° C. or lower, and has an electron emission characteristic obtained by having an angular current density of more than 50 μA / sr and an energy dispersion of less than 0.4 eV. An electron gun characterized by that.   A cold cathode field emission electron gun for use in an electro-optical device, which operates at 1000 ° C. or lower, and has an electron emission characteristic obtained such that an emission current in the range of a solid angle of electron emission of 0.0002 sr is larger than 5 nA An electron gun having an energy dispersion of less than 0.4 eV.

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