JP2009187923A - Method for manufacturing diamond electron source and diamond electron source - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a diamond electron source which forms with a sufficient controllability a spherical surface of a desirable top end shape for generating a large current/high focused electron beam and provide a diamond electron source. <P>SOLUTION: The method for manufacturing a diamond electron source which includes a top end portion as a diamond electron discharging point includes a process A in which a top end shape of the sharp top portion is rectified to a spherical surface by using a focused ion beam processing unit and a process B in which a process-damaged layer formed by the process A is removed by an acid solution. After the process A and the process B in the method for manufacturing the diamond electron source, the top end becomes a spherical surface of the diamond surface and as a result becomes an optimal diamond electron source for generating a large current/high focused electron beam and surpasses a conventional electron source in electron source performance such as an angle current density and luminance or the like. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a diamond electron source having a sharp portion as an electron emission portion and a diamond electron source, which are used in electron beam apparatuses such as an electron microscope, an electron beam exposure machine, and an X-ray generator. In particular, it is essential to produce a diamond electron source that can generate a high-intensity electron beam. It is related with the process of removing by diamond to make a diamond surface. In particular, the present invention relates to a diamond electron source obtained by performing the correction processing and the surface treatment.

  Diamond is considered to be a good electron-emitting material because it has a negative electron affinity (NEA) state or a small positive (PEA) state. Utilizing this property of diamond, many proposals have been made regarding an electron source using diamond or a method for manufacturing the same as disclosed in, for example, Japanese Patent Application Laid-Open No. 2007-042604.

  In an electron beam apparatus such as an electron microscope or an electron beam exposure machine, a high-current, high-brightness electron source is required as an apparatus used for nanoscale observation and microfabrication in the next-generation semiconductor process. Considering the application of diamond to these devices as an electron source, in order to realize generation of a higher current and higher focused electron beam than lanthanum hexaboride or zirconia tungsten of conventional electron sources, Shape is important.

  Since diamond is difficult to process, there is a problem that it is difficult to produce the shape of the electron emission portion. The conventional machining methods such as mechanical polishing and laser machining cannot be applied because it is difficult to obtain machining accuracy of the micron size or less required at the electron emission portion. Therefore, efforts have been made to overcome this problem. As a method for forming the sharpened portion, for example, dry etching as disclosed in Japanese Patent Application Laid-Open Nos. 2002-075171 and 2005-353449 is used. Microfabrication methods that have been proposed have been proposed.

However, it is difficult to realize a large current / high brightness electron source even by a processing method using dry etching. This is because dry etching cannot control the vertical and horizontal etching rates completely independently. For this reason, it is possible to produce a sharp point close to the target shape, but it is impossible to form a spherical surface having a desirable tip shape in order to generate a large current / highly focused electron beam with good controllability. As a result, the diamond electron source could not surpass conventional electron sources in terms of electron source performance such as angular current density and luminance.
Japanese Patent Laid-Open No. 2007-042604 Japanese Patent Application Laid-Open No. 2002-075171 JP 2005-353449 A

  The present invention has been made in view of such conventional circumstances, and relates to a diamond electron source used in an electron beam apparatus such as an electron microscope, an electron beam exposure machine, and an X-ray generator. The process of correcting the tip shape, which is the sharp electron emission point, necessary to generate an electron beam with high brightness, and removing the damaged layer after the correction process by surface treatment to change the surface of the electron emission point to diamond And a diamond electron source obtained through these steps.

  In order to solve the above-described problems, a method for manufacturing a diamond electron source having a sharp point as an electron emission point of diamond provided by the present invention has a spherical shape obtained by using a focused ion beam processing apparatus (FIB). It has the process A which correct | amends to a shape, and the process B which removes the work-affected layer formed by this process A with an acid aqueous solution. Optimum for generating a high-current, high-convergence electron beam as a result of the step A and step B being performed in the manufacturing process of the diamond electron source, resulting in a spherical shape with the electron emission point at the tip being the diamond surface. It becomes a new diamond electron source and can surpass conventional electron sources in terms of electron source performance such as angular current density and brightness.

  In the method for producing a diamond electron source of the present invention, the acid aqueous solution is preferably a heated mixed acid (mixed aqueous solution of nitric acid and sulfuric acid). By performing the step B with such an acid aqueous solution, the work-affected layer formed in the step A can be efficiently removed in a short time while maintaining the spherical shape.

  In addition, a method for manufacturing a diamond electron source having a sharp portion as an electron emission point of diamond provided by the present invention includes a step A of correcting the tip shape of the sharp portion into a spherical shape using a focused ion beam processing apparatus, And a step C of removing the work-affected layer formed in the step A with a high-temperature hydrogen atmosphere. Even when the step A and the step C are performed in the manufacturing process of the diamond electron source, a spherical shape in which the electron emission point at the sharpened portion is the diamond surface is obtained. As a result, it becomes an optimum diamond electron source for generating a large current / highly focused electron beam, and can surpass conventional electron sources in terms of electron source performance such as angular current density and luminance.

  In addition, a method for manufacturing a diamond electron source having a sharp portion as an electron emission point of diamond provided by the present invention includes a step A of correcting the tip shape of the sharp portion into a spherical shape using a focused ion beam processing apparatus, And a process D in which the work-affected layer formed in the process A is removed by heating in vacuum. By performing the process A and the process D in the manufacturing process of the diamond electron source, the tip of the diamond is made with a facility that is cheaper than the acid treatment apparatus including the acid draft used in the processes B and C and the high-temperature hydrogen atmosphere generation apparatus. The surface is a spherical shape. As a result, it becomes an optimum diamond electron source for generating a large current / highly focused electron beam, and can surpass conventional electron sources in terms of electron source performance such as angular current density and luminance.

  A diamond electron source having a sharp portion as an electron emission point of diamond provided by the present invention is a spherical surface having a height of the sharp portion of 10 μm or more and a tip shape having a curvature radius of 0.1 μm or more and 5 μm or less. The contour is less than 0.02 times the radius of curvature and the surface is diamond. In the manufacturing process of the diamond electron source, the tip shape thus controlled is obtained by performing any one of the step A and the step B, the step A and the step C, or the step A and the step D. It becomes a diamond electron source having a sharp point. It is the most suitable diamond electron source for generating a large current / highly focused electron beam and can surpass conventional electron sources in terms of electron source performance such as angular current density and brightness.

  According to the present invention, a function for processing an arbitrary fine three-dimensional shape of a focused ion beam processing apparatus (FIB), and a surface treatment for effectively removing a work-affected layer after processing by the focused ion beam processing apparatus, Can be applied to the manufacturing process of a diamond electron source to produce a diamond electron source having a spherical electron emission portion, which was difficult to obtain with the prior art, with a large current and high brightness. It is possible to provide a diamond electron source capable of generating a simple electron beam. Therefore, by mounting this diamond electron source on an electron beam apparatus, an electron microscope capable of high-magnification observation, an electron beam exposure machine capable of drawing a fine pattern with high throughput, and the like can be realized.

  Preferred embodiments of a method for producing a diamond electron source and a diamond electron source according to the present invention will be described in detail with reference to the drawings. In the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted. Further, the dimensional ratios in the drawings do not necessarily match those described. The present invention is not limited to the following embodiments, and modifications based on the technical idea of the present invention and other embodiments are included in the present invention.

  An embodiment of the present invention will be described with reference to FIGS. First, a diamond single crystal 10 is prepared in step (1). Although the present invention can be applied to polycrystalline diamond, it is preferable to use a diamond single crystal in order to stably produce a diamond electron source having a constant performance. A rectangular parallelepiped can be suitably used for the shape of the diamond single crystal. In particular, for the six faces constituting the rectangular parallelepiped, the six faces are either a single crystal that is a (100) plane (with an off angle of 7 ° or less), or four planes are (110) planes (with an off angle of 7 ° or less) and two planes are ( 100) plane (with an off angle of 7 ° or less), 2 planes with a (110) plane (within an off angle of 7 °), 2 planes with a (211) plane (with an off angle of 7 ° or less), and 2 planes with A single crystal having a (111) plane (with an off angle of 7 ° or less) is preferred.

The size of the diamond single crystal that can fit in a rectangular parallelepiped space of 50 μm × 50 μm × 100 μm or more and 1 mm × 1 mm × 5 mm or less can be suitably used from the viewpoint of mounting on an electron beam apparatus such as an electron microscope or an electron beam exposure machine. is there. If it is less than 50 μm × 50 μm × 100 μm, or larger than 1 mm × 1 mm × 5 mm, it becomes difficult to ensure compatibility with conventional electron sources such as lanthanum hexaboride and zirconia tungsten, and it is difficult to attach to the electron beam apparatus. is there. In order to obtain sufficient conductivity as an electron source, it is preferable that at least a part of the donor or acceptor impurity is contained in an amount of 1 × 10 ¹⁷ cm ⁻³ or more. P (phosphorus) is preferably used as the donor impurity, and B (boron) is preferably used as the acceptor impurity. Specifically, a high-temperature high-pressure synthetic diamond single crystal obtained by epitaxially growing a P-doped diamond thin film or a B-doped diamond thin film, a vapor-phase synthetic B-doped diamond single crystal, a high-temperature high-pressure synthetic B-containing diamond single crystal, etc. can be suitably used. It is.

  Next, in step (2), at least one end face of the diamond single crystal is polished to make the end face of the diamond single crystal 10 a smooth flat surface 11 as shown in FIG. The size of the smooth plane 11 is preferably 10 μm or more in order to form a sharpened portion having a sufficient size (height) as an electron source on the smooth plane 11 in a later step. Further, the smooth flat surface 11 preferably has a surface roughness Ra of 100 nm or less. When it is rougher than 100 nm, the surface of the electron emission point at the sharpened portion formed in the later step becomes rough, and sufficient luminance as a diamond electron source cannot be obtained.

  The smooth flat surface 11 may be formed on the entire surface of one end of the diamond single crystal 10 as shown in FIG. 1A, or the end face side surface is polished as shown in FIG. You may form in the taper sharp shape (substantially truncated pyramid shape) which has the smooth plane 11. FIG. By providing the smooth flat surface 11 at the top of such a tapered pointed shape, the electric field concentration on the sharpened portion finally obtained becomes larger, and a diamond electron source with higher luminance can be obtained.

Then, in step (3), as shown in FIG. 2, an etching mask 12 is formed on the smooth flat surface 11 to form a sharpened portion that is an electron emission portion by dry etching. The material of the etching mask 12 is preferably a material that can sharpen the diamond efficiently and with good shape by using the recession of the etching mask in the horizontal direction when dry etching the diamond. Specifically, an etching mask using an insulator such as SiO ₂ , SiON, SiO _x , Al ₂ O ₃ , or AlO _x or an iron-based metal such as Fe, Co, or Ni can be preferably used. Since the iron-based metal mask has a relatively high selection ratio with respect to diamond in dry etching, a higher sharp portion can be formed. As a result, a diamond electron source having better performance can be obtained. The etching mask 12 is preferably a circular thin film having a diameter of 1 μm to 10 μm. Other than this size, it is difficult to produce a sharp portion that can provide high luminance. The film thickness is preferably 1 μm or more in consideration of sharpening the diamond in consideration of the selection ratio using this as a mask. If the thickness is less than 1 μm, it is difficult to form sharp protrusions that are sufficiently high to obtain high brightness compared to conventional electron sources. For forming the etching mask 12, a thin film forming apparatus such as sputtering or CVD can be suitably used.

  Thereafter, in step (4), a part of the end face of the diamond single crystal 10 is sharpened by dry etching such as reactive ion etching (RIE) using the etching mask 12. Thereby, as shown in FIG. 3, the sharpened portion 13 can be formed at one end of the diamond single crystal 10. For the electron beam apparatus, it is preferable that the sharpened portion 13 has only one point in the diamond single crystal 10. Usually, since an electron beam apparatus such as an electron microscope or an electron beam drawing apparatus has an apparatus configuration using a single beam, only one pointed portion 13 which is an electron emission portion is sufficient. The sharpened portion 13 preferably has a conical shape with a height of 10 μm or more. By having such a tip shape, a diamond electron source having an electron source performance surpassing that of a conventional electron source can be obtained by a tip shape correction step (spherical shape processing step) and a surface treatment step of a later sharpened portion.

  Next, in step A, as shown in FIG. 4, the shape of the tip portion 14 of the sharpened portion 13 obtained as described above is corrected to a spherical shape using a focused ion beam processing apparatus. As the ion species of the processing beam, a Ga ion beam can be suitably used, but other Pt, Ni, or Ar ion beams can also be used. The energy of the processing beam is preferably 5 to 40 kV, and a practical diamond processing speed can be obtained within this range of energy. It is difficult to make the shape of the tip 14 into a spherical shape necessary for obtaining a high-current, high-luminance electron beam only by the dry etching in the step (4). This is because the etching mechanism for forming the sharpened portion 13 is complicated, and it is difficult to select the etching conditions and the mask shape, and there is variation between batches of the process. Therefore, if the tip portion 14 is corrected into a spherical shape using a focused ion beam processing apparatus capable of processing an arbitrary minute three-dimensional shape, the electron source performance surpasses that of the conventional electron source in the subsequent surface treatment process. A diamond electron source is obtained.

  Subsequently, in step B, as shown in FIG. 5, the work-affected layer 15 at the tip 14 corrected to a spherical shape is removed by dipping in the acid aqueous solution 16. When the energy of the processing beam is 5 to 40 kV, the work-affected layer 15 is from the outermost surface to a depth of about 40 nm. In the work-affected layer 15, the crystallinity of diamond is disturbed, and ion species of the work beam are mixed. Therefore, since the ease of electron emission of diamond is lost, it is removed with the acid aqueous solution 16. By applying this method, the tip portion 14 has a spherical shape that is a diamond surface. As a result, an optimum diamond electron source for generating a large current / highly focused electron beam can be produced.

  The acid aqueous solution 16 is more preferably a heated mixed acid (mixed aqueous solution of nitric acid and sulfuric acid). The process formed in step A by immersing the diamond in a mixed acid obtained by mixing 40% or more nitric acid aqueous solution and 80% or more sulfuric acid aqueous solution in a ratio of 1:20 to 2: 3 at 100 ° C. or more for 2 to 10 hours. The altered layer 15 can be efficiently removed in a short time while maintaining the spherical shape.

Alternatively, by applying the process C, as shown in FIG. 6, the work-affected layer 15 of the tip 14 corrected to a spherical shape can be removed by exposure to a high-temperature hydrogen atmosphere 17. The high-temperature hydrogen atmosphere 17 preferably has a gas pressure of 10 ⁻¹ Pa to 2.6 × 10 ⁴ Pa, and preferably has a gas temperature of 300 ° C. to 1000 ° C. using a hot filament or a heater. By applying this method, the tip portion 14 has a spherical shape that is a diamond surface. As a result, an optimum diamond electron source for generating a large current / highly focused electron beam can be produced.

Alternatively, by applying the process D, as shown in FIG. 7, the work-affected layer 15 of the distal end portion 14 corrected to a spherical shape can be removed by heating in a vacuum 18. The degree of vacuum of the vacuum 18 is preferably 10 ⁻⁴ Pa or less. Moreover, it is preferable that heating temperature shall be 600 to 1000 degreeC. By applying this technique, a spherical shape whose tip is a diamond surface is obtained with an equipment that is cheaper than an acid treatment apparatus including an acid draft used in steps B and C and a high-temperature hydrogen atmosphere generation apparatus. As a result, the diamond electron source is optimal for generating a large current / highly focused electron beam.

  In order to confirm the removal of the work-affected layer 15, Raman spectroscopic measurement may be performed before and after Steps B to D. If the Raman peak intensity of a small diamond that cannot be confirmed before the removal becomes as strong as a diamond single crystal for reference that is simultaneously measured, it can be confirmed that the work-affected layer 15 has been removed.

Through the above steps, as shown in FIG. 8, the height of the sharpened portion is 10 μm or more, the tip shape is a spherical surface with a radius of curvature of 0.1 μm or more and 5 μm or less, and the contour of the spherical surface has a curvature of 0.02 of the radius of curvature. A diamond electron source that is less than double and has a diamond surface can be produced. This is an optimum diamond electron source for generating a large current / highly focused electron beam and can surpass conventional electron sources in terms of electron source performance such as angular current density and luminance. An angular current density of 0.5 mA / sr or higher and a luminance of 5 × 10 ⁹ A / cm ² sr or higher can be obtained. On the other hand, it is difficult to exceed the performance of conventional electron sources with a diamond electron source that is outside the range of the above shape.

  From the outermost surface after processing with a focused ion beam to a depth of about 40 nm, the crystallinity of diamond is disturbed as described above, and a work-affected layer in which ion species of the processing beam are mixed is formed. For this reason, since the ease of electron emission inherent in diamond is lost, focused ion beam processing has been avoided as a method for processing electron emission points. However, while developing diamond electron sources for electron beam devices such as electron microscopes and electron beam lithography systems, in order to generate a high-current, high-intensity electron beam, the tip of the sharpened tip has a highly accurate spherical surface. It was found that focused ion beam machining was the best method for achieving this. Therefore, in order to sufficiently bring out the performance of the diamond electron source, it is essential to remove the work-affected layer that is always formed. Under such circumstances, as a result of intensive studies by the present inventors, as a method for removing the work-affected layer, a method using plasma in step B, a method using a high-temperature hydrogen atmosphere in step C, or a vacuum in step D The method of heating inside was found. Thus, a diamond electron source having an electron emission point from which a high current and high brightness electron beam can be obtained has been successfully produced, and the electron source performance such as angular current density and brightness has surpassed that of the conventional electron source.

  As described above, the method for manufacturing a diamond electron source according to the present invention has a large current by performing the correction processing step of the tip of the electron emission portion by the focused ion beam and the surface treatment step in the manufacturing step of the diamond electron source. -An optimum diamond electron source for generating a highly focused electron beam can be produced. In addition, since the diamond electron source according to the present invention has an electron emission point having a highly accurate spherical shape by the above process, the electron source performance such as angular current density and luminance can surpass the conventional electron source.

  The method for producing a diamond electron source and the diamond electron source of the present invention will be described more specifically based on examples.

A diamond electron source 1a was produced in the order of step (1), step (2), step (3), step (4), step A and step B. First, in step (1), two surfaces are (110) surfaces (within an off angle of 7 °), two surfaces are (211) surfaces (within an off angle of 7 °), and two surfaces are (111) surfaces (with an off angle of 7 °). And a P-doped epitaxial diamond thin film (P concentration, 1.7 × 10 ²⁰ cm ⁻³ ) on the (111) plane. The rectangular parallelepiped has a size of 0.6 × 0.6 × 2.5 mm. A diamond single crystal containing high-temperature and high-pressure synthetic B (B concentration 2.1 × 10 ¹⁹ cm ⁻³ ), which was vapor-phase grown, was prepared. The 0.6 × 0.6 mm surface was the (110) surface.

  Next, in step (2), the (110) surface of 0.6 × 0.6 mm is polished to obtain a smooth flat surface with a surface roughness Ra of 30 nm, and the end surface is further polished to a smooth top. A sharp truncated pyramid shape with a flat surface was formed. The smooth flat surface at the top was a 0.1 × 0.1 mm square. On this smooth plane, an Ni etching mask was formed in the middle of the square by sputtering in step (3). The size of the etching mask was 10 μm in diameter × 2 μm in thickness.

Then, in the step (4), using the Ni etching mask having a diameter of 10 μm × thickness of 2 μm, one sharp point was formed on the smooth square plane at the top of the diamond single crystal by dry etching. The etching conditions were RIE, high-frequency power of 300 W, pressure of 40 Pa, CF ₄ / O ₂ gas flow rate ratio of 2%, and etching time of 10 hours. The sharpened tip thus obtained was conical with a height of 30 μm.

  Next, in Step A, the shape of the tip of the conical sharpened portion obtained as described above was corrected to a spherical shape using a Ga focused ion beam. The energy of the Ga focused ion beam was 30 kV. Then, in step B, the work-affected layer generated in the correction process was removed with an acid aqueous solution. The acid aqueous solution used was a heated mixed acid (mixed aqueous solution of nitric acid and sulfuric acid), in which a 60% nitric acid aqueous solution and a 95% sulfuric acid aqueous solution were mixed at a ratio of 1: 3. Step B was carried out by heating the solution to 200 ° C. and immersing the diamond in it for 3 hours.

  After step B, it was confirmed by Raman spectroscopy and XPS that the surface state of the tip was diamond. The shape of the pointed portion of the diamond electron source thus obtained was observed with a scanning electron microscope. The height of the tip was 29 μm, the radius of curvature of the tip was 0.5 μm, and the spherical contour was 5.1 nm.

  The obtained diamond electron source was attached to an evaluation apparatus, and an electron beam was drawn out. A good result was obtained with an angular current density of 1.1 mA / sr at a beam extraction voltage of 4 kV and a beam acceleration voltage of 4 kV. When zirconia tungsten, which is a conventional electron source, was evaluated under the same evaluation conditions, the angular current density was 0.2 mA / sr.

A diamond electron source 2a was produced in the order of step (1), step (2), step (3), step (4), step A and step C. First, in step (1), two surfaces are (110) surfaces (within an off angle of 7 °), two surfaces are (211) surfaces (within an off angle of 7 °), and two surfaces are (111) surfaces (with an off angle of 7 °). And a P-doped epitaxial diamond thin film (P concentration, 1.7 × 10 ²⁰ cm ⁻³ ) on the (111) plane. The rectangular parallelepiped has a size of 0.6 × 0.6 × 2.5 mm. A diamond single crystal containing high-temperature and high-pressure synthetic B (B concentration 2.1 × 10 ¹⁹ cm ⁻³ ), which was vapor-phase grown, was prepared. The 0.6 × 0.6 mm surface was the (110) surface.

  Next, in step (2), the (110) surface of 0.6 × 0.6 mm is polished to obtain a smooth flat surface with a surface roughness Ra of 30 nm, and the end surface is further polished to a smooth top. A sharp truncated pyramid shape with a flat surface was formed. The smooth flat surface at the top was a 0.1 × 0.1 mm square. On this smooth plane, an Ni etching mask was formed in the middle of the square by sputtering in step (3). The size of the etching mask was 10 μm in diameter × 2 μm in thickness.

Then, in the step (4), using the Ni etching mask having a diameter of 10 μm × thickness of 2 μm, one sharp point was formed on the smooth square plane at the top of the diamond single crystal by dry etching. The etching conditions were RIE, high-frequency power of 300 W, pressure of 40 Pa, CF ₄ / O ₂ gas flow rate ratio of 2%, and etching time of 10 hours. The sharpened tip thus obtained was conical with a height of 30 μm.

Next, in Step A, the shape of the tip of the conical sharpened portion obtained as described above was corrected to a spherical shape using a Ga focused ion beam. The energy of the Ga focused ion beam was 30 kV. Then, in step C, the work-affected layer generated in the correction work was removed in a high-temperature hydrogen atmosphere. The pressure of hydrogen was 1.3 × 10 ³ Pa, the temperature was 500 ° C., and the time during which the work-affected layer was exposed to a high-temperature hydrogen atmosphere was 5 hours.

  After step C, the surface state of the tip was confirmed to be diamond by Raman spectroscopy and XPS measurement. The shape of the tip of the diamond electron source thus obtained was observed with a scanning electron microscope. The height of the sharpened portion was 29 μm, the radius of curvature of the tip was 0.5 μm, and the contour of the spherical surface was 6.2 nm.

  The obtained diamond electron source was attached to an evaluation apparatus to extract an electron beam. A good result was obtained with an angular current density of 1.1 mA / sr at a beam extraction voltage of 4 kV and a beam acceleration voltage of 4 kV. When zirconia tungsten, which is a conventional electron source, was evaluated under the same evaluation conditions, the angular current density was 0.2 mA / sr.

A diamond electron source 3a was produced in the order of step (1), step (2), step (3), step (4), step A and step D. First, in step (1), two surfaces are (110) surfaces (within an off angle of 7 °), two surfaces are (211) surfaces (within an off angle of 7 °), and two surfaces are (111) surfaces (with an off angle of 7 °). And a P-doped epitaxial diamond thin film (P concentration, 1.7 × 10 ²⁰ cm ⁻³ ) on the (111) plane. The rectangular parallelepiped has a size of 0.6 × 0.6 × 2.5 mm. A diamond single crystal containing high-temperature and high-pressure synthetic B (B concentration 2.1 × 10 ¹⁹ cm ⁻³ ), which was vapor-phase grown, was prepared. The 0.6 × 0.6 mm surface was the (110) surface.

  Next, in step (2), the (110) surface of 0.6 × 0.6 mm is polished to obtain a smooth flat surface with a surface roughness Ra of 30 nm, and the end surface is further polished to a smooth top. A sharp truncated pyramid shape with a flat surface was formed. The smooth flat surface at the top was a 0.1 × 0.1 mm square. On this smooth plane, an Ni etching mask was formed in the middle of the square by sputtering in step (3). The size of the etching mask was 10 μm in diameter × 2 μm in thickness.

Then, in the step (4), using the Ni etching mask having a diameter of 10 μm × thickness of 2 μm, one sharp point was formed on the smooth square plane at the top of the diamond single crystal by dry etching. The etching conditions were RIE, high-frequency power of 300 W, pressure of 40 Pa, CF ₄ / O ₂ gas flow rate ratio of 2%, and etching time of 10 hours. The sharpened tip thus obtained was conical with a height of 30 μm.

Next, in Step A, the shape of the tip of the conical sharpened portion obtained as described above was corrected to a spherical shape using a Ga focused ion beam. The energy of the Ga focused ion beam was 30 kV. After that, in step D, the work-affected layer generated in the correction work was removed by heating in vacuum. The degree of vacuum was 10 ⁻⁵ Pa and the heating temperature was 800 ° C. The heating time was 1 hour.

  After step D, the surface state of the tip was confirmed to be diamond by Raman spectroscopic measurement and XPS measurement. The shape of the tip of the diamond electron source thus obtained was observed with a scanning electron microscope. The height of the sharpened portion was 29 μm, the radius of curvature of the tip was 0.5 μm, and the contour of the spherical surface was 8.4 nm.

  The obtained diamond electron source was attached to an evaluation apparatus, and an electron beam was drawn out. Good results were obtained with an angular current density of 1.0 mA / sr at a beam extraction voltage of 4 kV and a beam acceleration voltage of 4 kV. When zirconia tungsten, which is a conventional electron source, was evaluated under the same evaluation conditions, the angular current density was 0.2 mA / sr.

  As described above, according to the present invention, the function of processing an arbitrary fine three-dimensional shape of the focused ion beam processing apparatus and the surface that effectively removes the work-affected layer after processing by the focused ion beam processing apparatus. A diamond electron source that has a spherical electron emission portion with a spherical tip that could not be obtained in the prior art by using this in combination with processing, and that can generate a large current and high-intensity electron beam. An electron source can be provided. Therefore, by mounting this diamond electron source on an electron beam apparatus, an electron microscope capable of high-magnification observation, an electron beam exposure machine capable of drawing a fine pattern with high throughput, and the like can be realized.

Conceptual diagram showing steps (1) and (2) Conceptual diagram showing process (3) Conceptual diagram showing process (4) Conceptual diagram showing process A Conceptual diagram showing process B Conceptual diagram showing process C Conceptual diagram showing process D The tip of the diamond electron source of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Diamond single crystal 11 Smooth plane 12 Etching mask 13 Sharp part 14 Tip part 15 Processed alteration layer 16 Acid aqueous solution 17 High temperature hydrogen atmosphere 18 Vacuum

Claims (5)

  A method of manufacturing a diamond electron source having a sharp point as an electron emission point of diamond, wherein the tip A of the sharp part is corrected to a spherical shape using a focused ion beam processing apparatus, and formed by the step A. And a process B for removing the work-affected layer with an acid aqueous solution.   The method for producing a diamond electron source according to claim 1, wherein the acid aqueous solution is a heated mixed acid.   A method of manufacturing a diamond electron source having a sharp point as an electron emission point of diamond, wherein the tip A of the sharp part is corrected to a spherical shape using a focused ion beam processing apparatus, and formed by the step A. And a step C of removing the work-affected layer in a high-temperature hydrogen atmosphere.   A method of manufacturing a diamond electron source having a sharp point as an electron emission point of diamond, wherein the tip A of the sharp part is corrected to a spherical shape using a focused ion beam processing apparatus, and formed by the step A. And a step D of removing the work-affected layer by heating in a vacuum.   A diamond electron source having a sharp portion as an electron emission point of diamond, the height of the sharp portion is 10 μm or more, and the tip shape is a spherical surface having a radius of curvature of 0.1 μm or more and 5 μm or less. A diamond electron source, characterized in that the surface is diamond with a radius of curvature of less than 0.02 times.

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