Electron source, electron gun, and charged particle beam device

Abstract

An electron source includes a suppression electrode having an opening at one end in a direction along a central axis and an electron emission material whose tip protrudes from the opening. The suppression electrode has a retreat portion at a position in the outer peripheral direction with respect to the opening, and the retreat portion retreats in the direction along the central axis to a position farther from the tip of the electron emission material than the opening. At least a part of the retreat portion has a structure configured to be within a diameter of 2810 μm or less from the center of the opening. Thus, an electron source, an electron gun, and a charged particle beam device such as an electron microscope using the electron gun are realized, in which mechanical differences in device performance due to axial deviation between the electron emission material and the suppression electrode are reduced.

Description

Technical Field

[0001] The present invention relates to an electron source that supplies an electron beam irradiated onto a specimen, an electron gun, and a charged particle beam apparatus using the electron gun. Background Art

[0002] A charged particle beam apparatus is an apparatus that irradiates a specimen with an electron beam emitted from an electron source and an electron gun, irradiates an X-ray target with the electron beam to emit X-rays, or irradiates a specimen with an ion beam emitted from an ion source to process the specimen, or generates an observation image using secondary electrons, transmitted electrons, reflected electrons, X-rays, etc. emitted from the specimen. Examples of charged particle beam apparatuses include electron microscopes, electron beam lithography apparatuses, X-ray microscopes, CTs, ion microscopes, etc.

[0003] In the above-mentioned charged particle beam apparatus, the generated image and its irradiation state are required to have high spatial resolution, repeated observation, good reproducibility in the case of irradiation, and the like.

[0004] For example, in an electron microscope, in order to achieve high spatial resolution, the brightness of the electron beam irradiated onto the specimen needs to be high. As an electron source that emits an electron beam with high brightness, a Schottky electron source (Schottky Emitter: hereinafter referred to as SE electron source) and a cold cathode field emission electron source (Cold Field Emitter: hereinafter referred to as CFE electron source) are widely used. An example of the structure of the SE electron source is described in Patent Document 1.

[0005] Furthermore, in recent years, the miniaturization and complication of semiconductor devices have been continuously developing, and electron microscopes are mostly used in the process management of their manufacturing processes. In an electron microscope that undertakes semiconductor measurement, in addition to the above-mentioned high-resolution performance, it is also required that the measurement results of the same size are obtained regardless of which device when observing the same specimen, that is, the mechanical difference in the measurement results between devices is small.

[0006] Prior Art Documents

[0007] Patent Documents

[0008] Patent Document 1: Japanese Patent Laid-Open No. 8-171879 Summary of the Invention

[0009] Problems to be Solved by the Invention

[0010] As described in Patent Document 1, the SE electron source includes a suppression electrode having an opening, and a single crystal wire (hereinafter referred to as a chip) that emits electrons from the front end as an electron emission material, and has a structure in which the front end (electron emission portion) of the chip protrudes from the opening of the suppression electrode. Further, an extraction electrode or the like is added to the SE electron source to form an electron gun (SE electron gun). In the SE electron gun, the chip is heated and an electric field is applied by the extraction electrode to emit electrons from the front end of the chip. The suppression electrode has the following function: applying a negative potential to the front end of the chip to suppress unnecessary thermoelectrons emitted from other than the front end of the chip.

[0011] In order to achieve this function, it is required that the central axes of the chip and the opening of the suppression electrode be aligned with high precision. Therefore, the chip and the opening of the suppression electrode are aligned and assembled in a coaxial manner mechanically and formed into an integrated electron source. This electron source is mounted on various devices such as electron microscopes and is used to emit electron beams.

[0012] Here, from the results of the inventors' research, it is known that for each individual electron source, the central axis of the chip and the central axis of the opening of the suppression electrode sometimes deviate by several micrometers to several tens of micrometers when the opening diameter of the suppression electrode is about 400 μm. If the central axes of the chip and the suppression electrode deviate, the electric field generated by the suppression electrode becomes a distribution in which the axis deviates from the chip, and an electric field in a direction (lateral direction) perpendicular to the central axis is generated in the space in front of the chip. The electron beam emitted from the front end of the chip is bent laterally by this electric field and passes outside the axis of the lens located downstream. As a result, off-axis aberration is generated in the lens, and the convergence diameter of the electron beam irradiated on the specimen becomes larger, resulting in poor resolution.

[0013] The larger the deviation amount of the axes of the chip and the suppression electrode, the larger the lateral electric field. Therefore, the electron beam is bent greatly and the off-axis aberration also becomes larger. The deviation amount of the axes of the chip and the suppression electrode varies for each individual electron source, so the size of the off-axis aberration also varies for each device equipped with the electron source, and the resolution differs. As a result, there arises a problem that the mechanical differences between devices such as electron microscopes become larger.

[0014] In addition, when the deviation amount of the axes of the chip and the suppression electrode is particularly large, the electron beam is bent greatly and thus cannot pass through the aperture or the opening of the electrode arranged downstream. In this case, the electron beam cannot reach the specimen, resulting in manufacturing defects in the electron source, electron gun, or electron microscope. This causes problems such as an increase in manufacturing cost and an increase in preparation time.

[0015] An object of the present invention is to provide an electron source, an electron gun, and a charged particle beam device such as an electron microscope using the electron gun, in which mechanical differences are reduced.

[0016] Means for Solving the Problem

[0017] An electron source according to an embodiment of the present invention is characterized by having: a suppression electrode having an opening at one end in a direction along a central axis; and an electron emission material whose front end protrudes from the opening. The suppression electrode further has a retreat portion at a position in the outer peripheral direction relative to the opening, and the retreat portion retreats in a direction along the central axis to a position farther from the front end of the electron emission material than the end of the suppression electrode. At least a part of the retreat portion is arranged within a diameter of 2810 μm from the center of the opening.

[0018] The effects of the invention are as follows.

[0019] According to the present invention, it is possible to provide an electron source, an electron gun, and a charged particle beam device such as an electron microscope using the electron gun with reduced mechanical differences. Other problems and new features will become clear from the description of this specification and the drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a diagram showing an outline of a scanning electron microscope according to Example 1.

[0021] Figure 2 It is a diagram illustrating the structure of an existing SE electron source.

[0022] Figure 3A It is a diagram illustrating the principle of electron beam bending in an existing SE electron source.

[0023] Figure 3B It is a diagram illustrating the principle of electron beam bending in an existing SE electron source.

[0024] Figure 4 It is a diagram illustrating the structure of the SE electron source according to Example 1.

[0025] Figure 5A It is a diagram illustrating the principle of the orbit of an electron beam in an existing SE electron source.

[0026] Figure 5B It is a diagram illustrating the principle of the orbit of an electron beam in an existing SE electron source.

[0027] Figure 5C It is a diagram illustrating the principle of the orbit of an electron beam in the SE electron source according to Example 1.

[0028] Figure 5D It is a diagram illustrating the principle of the orbit of an electron beam in the SE electron source according to Example 1.

[0029] Figure 6A It is a diagram showing the influence of the angle θ of the conical surface on the electron beam in the SE electron source according to Example 1.

[0030] Figure 6B It is a diagram showing the influence of the angle θ of the conical surface on the electron beam in the SE electron source of Example 1.

[0031] Figure 7A It is a diagram showing the influence of the deviation amount of the axis of the chip from the suppression electrode on the electron beam in the existing SE electron source.

[0032] Figure 7B It is a diagram showing the influence of the deviation amount of the axis of the chip from the suppression electrode on the electron beam in the SE electron source of Example 1.

[0033] Figure 7C It is a diagram showing the influence of the deviation amount of the axis of the chip from the suppression electrode on the electron beam in the existing type and the SE electron source of Example 1.

[0034] Figure 8A It is a diagram showing the relationship of the influence of L and θ on the electron beam in the SE electron source of Example 1.

[0035] Figure 8B It is a diagram showing the relationship of the influence of L and θ on the electron beam in the SE electron source of Example 1.

[0036] Figure 9 It is a diagram showing an example of the required suppression voltage in the SE electron source of Example 1.

[0037] Figure 10 It is a diagram showing the influence on the electron beam when the protruding length T of the chip is changed in the existing SE electron source.

[0038] Figure 11A It is a diagram showing the relationship of the influence of L and θ on the electron beam in the SE electron source of Example 2.

[0039] Figure 11B It is a diagram showing the relationship of the influence of L and θ on the electron beam in the SE electron source of Example 2.

[0040] Figure 12A It is a diagram showing the relationship of the influence of L and θ on the electron beam in the SE electron source of Example 2.

[0041] Figure 12B It is a diagram showing the relationship of the influence of L and θ on the electron beam in the SE electron source of Example 2.

[0042] Figure 13 It is a diagram showing the relationship of the influence of T and L on the electron beam in the SE electron source of Example 2.

[0043] Figure 14 It is a diagram explaining the structure of the SE electron source of Example 3.

[0044] Figure 15 This is a diagram showing the structure of the SE electron source of Example 4.

[0045] Figure 16 This is a diagram showing the structure of the SE electron source of Example 5.

[0046] Figure 17 This is a diagram showing the structure of the SE electron source of Example 6.

[0047] Figure 18 This is a diagram showing the structure of the SE electron source of Example 7. Detailed implementation manners

[0048] Hereinafter, various embodiments of an electron source, an electron gun, and a charged particle beam device such as an electron microscope of the present invention will be sequentially described with reference to the drawings. As a charged particle beam device, there is an electron microscope that irradiates an electron beam onto a specimen and detects secondary electrons, reflected electrons, or transmitted electrons emitted from the specimen to generate an observation image of the specimen. Hereinafter, as an example of the charged particle beam device, a scanning electron microscope among electron microscopes will be described, but the present invention is not limited thereto, and it can also be applied to other electron microscopes and charged particle beam devices.

[0049] Example 1

[0050] Figure 1 The overall schematic structure of the scanning electron microscope of Example 1 is shown. The scanning electron microscope irradiates the electron beam 115 emitted from the electron source 101 while scanning it onto the specimen 112, and uses the detector 114 to detect secondary electrons, reflected electrons, etc. emitted from the specimen 112 to generate an observation image of the specimen 112. The electron beam 115 focused on a minute point is scanned on the specimen 112, and the observation image is generated in association with the position irradiated by the electron beam 115 and the detection amount of secondary electrons, etc. In the figure, the emission direction of the electron beam 115 is set as the Z-axis, and the horizontal axis orthogonal to the Z-axis is set as the X-axis.

[0051] The scanning electron microscope includes a cylinder 125 and a specimen chamber 113. The inside of the cylinder 125 is divided into a first vacuum chamber 126, a second vacuum chamber 127, and a third vacuum chamber 128 from above. An aperture (not shown) through which the electron beam 115 passes is provided at the boundary of each vacuum chamber, and the inside of each vacuum chamber is maintained in a vacuum by differential pumping. Hereinafter, the device structures of each vacuum chamber will be described.

[0052] An electron source 101 is disposed inside the first vacuum chamber 126. The electron source 101 uses a SE electron source. The SE electron source 101 is held by an insulator 116 and is electrically insulated from the cylinder 125. An extraction electrode 102 is disposed opposite (downstream) below the SE electron source 101. An acceleration electrode 103 is disposed opposite below the extraction electrode 102. The electron gun 104 is composed of the SE electron source 101, the extraction electrode 102, and the acceleration electrode 103. An electron beam 115 is emitted from the SE electron source 101 and finally irradiated onto the specimen 112 to obtain an observation image. The detailed structure of the SE electron source 101 will be described below. The first vacuum chamber 126 is evacuated by an ion pump 120 and a non-evaporable getter pump 118 to a very high vacuum of about 10 －8 Pa, and more preferably to an extremely high vacuum of 10 －9 Pa or less.

[0053] A condenser lens 110 is disposed in the second vacuum chamber 127. The second vacuum chamber 127 is evacuated by an ion pump 121.

[0054] A detector 114 is disposed in the third vacuum chamber 128. An ion pump (not shown) is also disposed in the third vacuum chamber for evacuation.

[0055] An objective lens 111 and a specimen 112 are disposed in the specimen chamber 113. And, although not shown, a scanning deflector for scanning the electron beam 115 etc. are also disposed. The specimen chamber 113 is evacuated by a turbomolecular pump 109.

[0056] Next, the functions of the above-described respective structures and the process until the observation image is generated from the electron beam 115 emitted from the SE electron source 101 will be described.

[0057] Voltages are applied to the respective electrodes of the electron gun 104 using a power supply (not shown). An extraction voltage V1 that is positive with respect to the SE electron source 101 is applied to the extraction electrode 102 to emit the electron beam 115 from the SE electron source 101. The magnitude of the extraction voltage V1 is typically about 1 kV to 10 kV, and more preferably about 2 kV to 6 kV. An acceleration voltage V0 that is about 0.5 kV to 100 kV with respect to the SE electron source 101 is applied to the acceleration electrode 103 to accelerate the electron beam 115. An electrostatic lens is formed by the voltage difference between the extraction electrode 102 and the acceleration electrode 103.

[0058] A condenser lens 110 is disposed below the electron gun 104 to condense the electron beam 115 emitted from the electron gun 104 and adjust the current amount and opening angle of the electron beam 115. In addition, multiple condenser lenses may be provided, and they may also be disposed in other vacuum chambers. And, the part from the electron source 101 to the condenser lens 110 may be regarded as the electron gun 104.

[0059] Finally, the objective lens 111 disposed in the specimen chamber 113 further below condenses the electron beam 115 onto a minute point, and irradiates while scanning the specimen 112 with a scanning deflector (not shown). At this time, secondary electrons, reflected electrons, and X-rays that reflect the surface shape and material are emitted from the specimen 112. By detecting the secondary electrons, reflected electrons, and X-rays with the detector 114, an observation image of the specimen is obtained. Multiple detectors 114 may also be provided, and may be disposed in other vacuum chambers such as the specimen chamber 113.

[0060] Next, Figure 2 In the following, the structure of the existing SE electron source 201 used in a general scanning electron microscope is shown. The existing SE electron source 201 is configured to include a single crystal wire (hereinafter referred to as a chip) 202 as an electron emission material and a suppression electrode 203.

[0061] The chip 202 is a tungsten <100>-oriented single crystal wire with a diameter of about 0.12 mm. The tip of the chip 202 is sharpened, and the radius of curvature of the tip portion that emits electrons is about 1 μm or less. A part such as the middle section of the single crystal wire of the chip 202 is coated with zirconia. The chip 202 is welded to the filament 206. Both ends of the filament 206 are connected to two terminals 207. The two terminals 207 are held by insulators 208 and are electrically insulated from each other. The two terminals 207 extend in a direction coaxial with the SE chip 202 and are connected to a current source via a feed through (not shown).

[0062] In such a structure, a current is stably passed through the terminals 207 to heat the filament 206, thereby heating the chip 202 from 1500 K to 1900 K. At this temperature, the zirconia coated on the chip 202 diffuses and moves on the surface, covering the (100) crystal plane at the center of the tip of the chip 202 that becomes the electron source. When the (100) plane is covered with zirconia, the work function of this part decreases. Further, as described above, an extraction voltage V1 of about several kV is applied to the extraction electrode 102 ( Figure 1 as shown) disposed below the suppression electrode 203, so as to apply a strong extraction electric field of about 10 8 V / m in the central axis Z direction to the tip of the sharpened chip 202. As a result, the Schottky effect is generated and the work function is further reduced. As a result, thermoelectrons are emitted from the (100) plane at the tip of the heated chip 202, and the electron beam 115 is obtained.

[0063] As a typical shape, the suppression electrode 203 is a cup-shaped cylindrical metal or the like having a bottom surface (plane) 205. An opening 204 is disposed on the bottom surface (plane) 205. The suppression electrode 203 and the opening 204 are coaxially processed and the central axes coincide. This central axis is the Z axis that is the same as the emission direction of the electron beam 115. The chip 202 is disposed inside the opening 204, and the front end of the chip 202 is disposed so as to protrude from the opening 204 by a certain length T. The portion other than the front end of the chip 202 is covered by the suppression electrode 203.

[0064] The suppression electrode 203 is fitted with the insulator 208 and assembled and held. The suppression electrode 203 and the terminal 207 are electrically insulated by the insulator 208.

[0065] In this example, the plane 205 is a planar portion perpendicular to the central axis Z. The diameter of the plane 205 is typically about 4 mm to 10 mm. The diameter d of the opening 204 is typically about 0.2 mm to 1.2 mm, and more preferably about 0.4 mm. The side surface of the suppression electrode 203 typically has a cylindrical surface 210 parallel to the central axis Z of the suppression electrode 203, and a chamfered portion 209 is provided at the connecting portion of the plane 205 and the cylindrical surface 210.

[0066] As described above, the front end of the chip 202 is disposed so as to protrude from the opening 204 by the length T. The protruding length T of the front end of the chip 202 is typically about 0.15 mm to 0.35 mm, and more preferably about 0.25 mm.

[0067] A negative suppression voltage V of typically -0.1 kV to -1.2 kV, more preferably about -300 V to -600 V, is applied to the suppression electrode 203 with respect to the chip 202. S Using the electric field formed by the negative suppression voltage V S to suppress the emission of unwanted thermoelectrons that are to be emitted from portions other than the front end portion of the chip 202 such as the root of the chip 202 and the filament 206. As a result, it is possible to prevent deterioration of the high brightness performance and high resolution performance of the electron beam 115 caused by unwanted thermoelectrons.

[0068] In addition, the distance between the front end of the chip 202 and the Figure 1 extraction electrode 102 shown is typically about 0.15 mm to 1.5 mm. The distance between the front end of the chip 202 and the Figure 1 acceleration electrode 103 shown is typically about 1 mm to 50 mm.

[0069] Here, since the suppression electrode 203 and the insulator 208 are assembled by fitting, they are formed integrally in such a manner that the central axis of the chip 202 substantially coincides with the central axis of the opening 204 of the suppression electrode 203. However, in the processing and forming process, deviations occur due to the influence of mechanical tolerances, assembly errors, and strain caused by heat. Therefore, in reality, the central axis of the chip 202 and the central axis of the opening 204 sometimes deviate in the direction orthogonal to the Z-axis (such as the X-axis direction) at the opening 204 of the suppression electrode 203. The amount of deviation, that is, the deviation amount (hereinafter referred to as the axis deviation amount) Δ between the center of the opening 204 in the plane of the opening 204 and the chip 202 is several μm to several tens of μm in reality, and this axis deviation amount Δ varies for each individual electron source. In addition, since the central axis of the suppression electrode 203 and the central axis of the opening 204 are coaxially processed as described above, hereinafter, the axis deviation between the chip 202 and the opening 204 is sometimes referred to as the axis deviation between the chip 202 and the suppression electrode 203, which has the same meaning. Due to the occurrence of such an axis deviation Δ, there is an influence such as the bending of the electron beam 115. As a result, as will be described below, problems such as the occurrence of off-axis aberration due to the off-axis of the lens located downstream occur.

[0070] Next, with reference to FIG. 3, an outline of the principle of the bending of the electron beam 115 due to the axis deviation between the chip 202 and the opening 204 of the suppression electrode 203 will be described. In FIG. 3, the front end portion of the chip 202 is shown magnified in the SE electron source 101 mounted on the scanning electron microscope. In addition, the structures with the same reference numerals refer to the same structures as those described above, and the subsequent descriptions are omitted.

[0071] Figure 3A It is a schematic diagram in the ideal case where the axes of the chip 202 and the suppression electrode 203 coincide. In the case where the central axes coincide, as will be described below, only the Z-axis symmetric electric field distribution formed by the coaxial suppression electrode 203 acts on the electron beam 115 emitted from the front end of the chip 202. The electron beam 115 is only affected by the electric field in the traveling direction, that is, the Z direction, and advances straight along the Z direction without bending along the central axis. After that, the electron beam 115 advances on the central axis of the openings of the extraction electrode 102 and the acceleration electrode 103, so no off-axis aberration occurs.

[0072] Figure 3B It is a schematic diagram in the case where the suppression electrode 203 deviates from the chip 202. In addition, as shown by the axis deviation vector 302, the case where the suppression electrode 203 deviates to the right direction in the figure is shown. And the suppression electrode 203 shown by the dotted line shows the position in the case where no axis deviation occurs.

[0073] When the central axes of the chip 202 and the suppression electrode 203 are deviated, an electric field 301 in a direction (lateral direction) (X direction) perpendicular to the central axis is generated in the space in front of the emission direction of the electron beam 115 of the chip 202 as described below. The electron beam 115 emitted from the chip 202 is bent because it is subjected to a force not only in the Z-axis direction but also in the lateral direction by this electric field. After that, the electron beam 115 passes outside the axis of the electrostatic lens formed by the extraction electrode 102 and the acceleration electrode 103. As a result, the orbit of the electron beam 115 is disturbed due to off-axis aberration, and the convergence diameter when converging on the specimen 112 becomes larger, so that the resolution of the scanning electron microscope deteriorates. In addition, there are a condenser lens 110 and an objective lens 111 below the acceleration electrode 103. Since the electron beam 115 is bent, off-axis aberration is also generated in these lenses, deteriorating the resolution.

[0074] Since the axis deviation amount Δ of the electron source 101 varies for each individual, the magnitude of the bending of the electron beam 115 also varies for each individual. Therefore, for each scanning electron microscope equipped with an electron source, the off-axis aberration and the resolution are different, resulting in mechanical differences. If there are mechanical differences in the scanning electron microscope, for example, when measuring the size of a semiconductor pattern as a specimen and measuring the same-sized pattern using multiple electron microscopes, measurement results of different sizes corresponding to the mechanical differences of the scanning electron microscopes used for measurement are obtained, and the reliability, accuracy, and reproducibility of the measurement are reduced. The problem of this mechanical difference becomes a problem that is more likely to appear with the miniaturization of semiconductor patterns.

[0075] Furthermore, if the axis deviation Δ is large and the magnitude of the bending of the electron beam 115 is particularly large, it cannot pass through the openings of the extraction electrode 102 and the acceleration electrode 103, or other apertures (not shown), and cannot reach the specimen 112. In this case, it leads to manufacturing defects in the electron source, electron gun, or scanning electron microscope, increasing the manufacturing cost and preparation time.

[0076] To solve the above problems, in Embodiment 1, the shape of the suppression electrode 305 is made different from that of the existing suppression electrode 203.

[0077] Figure 4 The structure of the SE electron source 101 and the suppression electrode 305 of Embodiment 1 is shown. As Figure 4 shown, the suppression electrode 305 of Embodiment 1 is different from the existing suppression electrode 203 and has a conical surface (conical portion) 306 at a position near the central axis Z of the plane 205 which is its lower surface (bottom surface). The function of this conical surface 306 is that even when an axis deviation occurs between the chip 202 and the suppression electrode 305 as described below, the electron beam 115 will not bend.

[0078] The conical surface 306 forms an angle (cone angle) θ with a plane perpendicular to the central axis Z. A corner 307 is formed at the connecting portion of the conical surface 306 and the plane 205 (front end 213). The diameter when viewed from the position starting from the conical surface 306 (the position corresponding to the corner 307) along the central axis is designated as L. The diameter L is the diameter of the planar portion 205 (front end 213).

[0079] If the structure of the suppression electrode 305 is described in other expressions, it is as follows. The suppression electrode 305 has a central axis Z, and includes a front end 213 (plane 205) and a rear end 214 that are both ends in the direction along the central axis Z. At the front end 213 (plane 205), the chip 202 is disposed coaxially with the suppression electrode 305 with an opening 204 provided. Here, the front end portion of the chip 202 protrudes from the opening 204 and is disposed with the direction of emitting the electron beam 115 as the front, and the opposite direction as the rear. It is configured such that a conical portion 306 is provided at a position on the outer peripheral side of the front end 213 (plane 205) relative to the opening 204, and the conical portion 306 forms a surface (receding portion (surface)) 212 that recedes in the Z direction away from the front end of the chip 202 compared to the front end 213 (plane 205).

[0080] Compared with the existing suppression electrode 203, the suppression electrode 305 is an electrode that forms a receding portion 212 (conical surface 306) by receding the surface of the vicinity of the central axis Z within the plane of the plane 205, and the diameter of the planar portion 205 is smaller than the existing structure.

[0081] Since the conical surface 306 exists near the central axis Z, even when an axial deviation occurs between the chip 202 and the suppression electrode 305, the conical surface 306 acts on the electric field distribution formed by the suppression electrode 305, and as will be described below, the electron beam 115 will not bend. The above-mentioned diameter L and angle θ, which are parameters of the shape of the suppression electrode, have an appropriate design range as will be described below.

[0082] Similar to the existing SE electron source 201, the suppression electrode 305 is assembled and held by being fitted with the insulator 208.

[0083] The effects obtained from the structure of the suppression electrode of this Example 1 will be described. Figures 5A - 5D The explanatory diagram showing the following principle is shown: In the SE electron source 101 of Example 1, even when an axial deviation occurs between the chip 202 and the suppression electrode 305, the electron beam 115 will not bend. Figure 5A 、 Figure 5B The state in the case of using the existing type of suppression electrode 203 is shown, Figure 5C 、 Figure 5D The state in the case of using the suppression electrode 305 of Example 1 is shown. Moreover,Figure 5A and Figure 5C shows a situation where the chip 202 and the opening 204 have no axial deviation, Figure 5B and Figure 5D shows a situation where there is axial deviation.

[0084] First, Figure 5A is a schematic diagram showing the power lines in the case where there is no axial deviation in the existing SE electron source 201. The power lines are imaginary lines showing the direction of the electric field generated in space and show the direction of the force received by the electrons.

[0085] As described above, a voltage negative with respect to the chip 202 and the extraction electrode 102 is applied to the suppression electrode 203. As a result, a plurality of positive charges 401 are generated on the surface of the chip 202, and a plurality of negative charges 402 are generated on the surface of the suppression electrode 203. Therefore, power lines 403 are generated from the charge 401 toward the negative charge 402. In Figure 5A the state without axial deviation, the chip 202 and the suppression electrode 203 have a structure that is axially symmetric with respect to the central axis. In this case, there are no power lines crossing the central axis, and no lateral force is applied to the electron beam 115 emitted from the front end of the chip 202. Therefore, the electron beam 115 does not bend.

[0086] Figure 5B is a schematic diagram showing the additional power lines in the case where axial deviation has occurred in the existing SE electron source 201. The suppression electrode 203 is deviated from the chip 202 by an amount equivalent to adding charges in the Figure 5A state.

[0087] Let it be from the Figure 5A state to the Figure 5B state. The suppression electrode 203 is deviated in the direction shown by the axial deviation vector 302, that is, to the right direction in the figure, by a small amount (axial deviation amount Δ). In addition, Figure 5B the dashed line in shows the position of the suppression electrode 203 before axial deviation, and the solid line shows the position of the suppression electrode 203 after axial deviation. In addition, the axial deviation amount Δ is strictly defined as the deviation between the central axis of the opening 204 of the suppression electrode in the plane of the opening 204 and the central axis of the chip 202, but as approximately the same amount, it is simply shown as the displacement amount when the position of the opening end of the opening 204 changes (displaces) from the state before axial deviation to the state after axial deviation in FIG. 5 and the like.

[0088] In the opening 204, attention is focused on the spatial region 406 where the suppression electrode 203 approaches the chip 202. The case where the suppression electrode 203 moves in this spatial region is equivalent to the case where new negative charges 405 are added to this space due to axis deviation. And since the space on the left side of the spatial region 406 in the figure becomes the inside of the suppression electrode 203, no charges are generated. Therefore, positive charges 420 that cancel the negative charges 402 before axis deviation are also added. Furthermore, in the spatial region 406, the distance between the suppression electrode 203 and the chip 202 approaches. Therefore, the electrostatic capacitance increases, and the amount of negative charges in this space increases compared to before axis deviation. That is, the number of negative charges 405 is larger than the positive charges 420.

[0089] On the other hand, in the opening 204, attention is focused on the spatial region 407 where the suppression electrode 203 moves away from the chip 202. The disappearance of the suppression electrode 203 from this spatial region is equivalent to applying new positive charges 404 to this part to cancel the negative charges 421 before axis deviation. And since the right side of the spatial region 407 in the figure newly becomes the surface of the suppression electrode 203, negative charges 422 are added here. Furthermore, in the spatial region 407, the distance between the suppression electrode 203 and the chip 202 separates. Therefore, the electrostatic capacitance decreases, and the amount of negative charges in this space decreases compared to before axis deviation. That is, the number of positive charges 404 is larger than the negative charges 422.

[0090] In this way, the case where the suppression electrode 203 generates axis deviation is equivalent to adding Figure 5A the negative charges 405 and positive charges 420, and positive charges 404 and negative charges 422 shown in Figure 5B the charge distribution in the state without axis deviation shown.

[0091] Here, Figure 5B in, the positive charges 404 and negative charges 405 are exposed on the vacuum side surface of the suppression electrode 203 and have a relatively large amount of charge, forming the strongest electric field in the vacuum region. As a result, new electric field lines 408 connecting the two charges are generated in front of the chip 202. The electric field lines 408 are generated horizontally (in the X direction in the figure) across the central axis, applying a force to the electron beam emitted from the chip 202. As a result, the electron beam bends to the right in the figure. This is the principle of the bending of the electron beam due to the axis deviation of the suppression electrode 203.

[0092] Figure 5C is a schematic diagram showing the electric field lines in the case of no axis deviation in the SE electron source 101 of Embodiment 1. The SE electron source 101 of Embodiment 1 has a conical surface 306 near the axis on the lower surface of the suppression electrode 305. In the case of no axis deviation, compared with Figure 5AThe same, positive charge 401 and negative charge 402 are generated axially symmetrically, generating electric field lines 403. In this case, there are no electric field lines crossing the central axis either, so the electron beam 115 does not bend.

[0093] Figure 5D It is a schematic diagram showing the additional electric field lines in the case of an axial deviation by an axial deviation amount Δ to the right axis in the figure in the SE electron source 101 of Embodiment 1. In the SE electron source 101 of Embodiment 1, by providing the conical surface 306, charges are also generated on the conical surface, generating electric field lines 412 in the opposite direction to the electric field lines 408. As a result, the force that bends the electron beam is alleviated, and further a force that bends the electron beam back is generated. In addition, the dashed line in the figure shows the position of the suppression electrode 305 before the axial deviation, which is the same as the case shown, and the solid line shows the position of the suppression electrode 305 after the axial deviation. Figure 5C The same as the position of the suppression electrode 305 before the axial deviation shown, and the solid line shows the position of the suppression electrode 305 after the axial deviation.

[0094] Explain in more detail Figure 5D . In the SE electron source 101 of Embodiment 1, when an axial deviation occurs between the chip 202 and the suppression electrode 305, new positive charges 404 and negative charges 422, as well as new negative charges 405 and positive charges 420, are also generated in the opening 204, thus generating electric field lines 408.

[0095] Here, in the SE electron source 101 of Embodiment 1, equivalent charges are also generated on the conical surface 306 due to the axial deviation. Focus on the spatial region 413 where the conical surface 306 approaches the chip 202. The situation where the suppression electrode 305 in this space disappears is equivalent to the situation where a new positive charge 410 is added here to cancel the negative charge 402 before the axial deviation. And since the space on the right side of the spatial region 413 in the figure newly becomes the surface of the conical surface 306, a negative charge 423 is added here. Furthermore, in the spatial region 413, the conical surface 306 approaches the chip 202. As a result, the influence of the electric field caused by the chip 202 on the conical surface 306 increases, and the influence of the electric field caused by the extraction electrode 102 (not shown) on the conical surface 306 decreases. Since the voltage applied to the extraction electrode 102 is higher than that of the chip 202, the electric field of the conical surface 306 decreases. That is, the number of positive charges 410 becomes larger than that of the negative charge 423.

[0096] On the other hand, focus on the spatial region 414 where the conical surface 306 is away from the chip 202. The situation where the suppression electrode 305 is restricted from moving in this space is equivalent to the situation where new negative charges 411 are added here. And since the left side of the spatial region 414 becomes the inside of the suppression electrode 305, positive charges 424 that cancel out the negative charges before the axis deviation are added. Furthermore, in the spatial region 414, the conical surface 306 is away from the chip 202. As a result, the influence of the electric field caused by the chip 202 on the conical surface 306 decreases, and the influence of the electric field caused by the extraction electrode 102 (not shown) on the conical surface 306 increases. Since the voltage applied to the extraction electrode 102 is higher than that of the chip 202, the electric field of the conical surface 306 increases. That is, the number of negative charges 411 becomes larger than that of the positive charges 424.

[0097] Thus, on the surface of the conical surface 306, the positive charges 410 become more in the spatial region 413, and the negative charges 411 become more in the spatial region 414. As a result, new electric lines of force 412 connecting the two are generated. The electric lines of force 412 are in the opposite direction to the electric lines of force 408 generated by the opening 204. This can weaken the electric field generated at the opening 204, reduce the force generated by the electric lines of force 408, and make it difficult to bend the electron beam.

[0098] Moreover, the greater the amount of charge of the positive charges 410 and negative charges 411 generated on the conical surface 306, or the closer the distance between the positive charges 410 and negative charges 411, the stronger the electric field formed by the two, and the stronger the force brought by the electric lines of force 412. Therefore, by setting the amount of charge and the distance to appropriate values, it is also possible to bend back the electron beam that has been bent by the electric lines of force 408 using the electric lines of force 412 and return the electron beam to the central axis.

[0099] On the other hand, if the amount of charge is increased excessively or the distance is made too close, the force of the electric lines of force 412 becomes stronger than the force of the electric lines of force 408, and the electron beam bends to the left in the figure. When the force of the electric lines of force 412 is excessive, the degree of bending of the electron beam becomes larger compared to the case where the existing suppression electrode 203 has an axis deviation, and the influence of the axis deviation becomes larger compared to the prior art, and the problem becomes worse instead.

[0100] The amount of charge of the positive charges 410 and negative charges 411 generated on the conical surface 306, and the distance between the two charges are determined by Figure 4 the diameter L of the starting position of the conical surface 306 and the angle θ of the conical surface 306 as shown. The diameter L determines the distance between the positive and negative charges generated on the conical surface 306. The angle θ determines the degree of electric field concentration at the conical surface 306 and its corner 307, and determines the amount of charge generated at the conical surface 306 and the corner 307. Therefore, in order not to bend the electron beam even when an axis deviation occurs, it is necessary to design the diameter L and the angle θ within an appropriate range.

[0101] Here, the electric field formed by the charges generated on the surface weakens in inverse proportion to the distance between the positive and negative charges, that is, the distance between the surfaces. Therefore, in order to generate a sufficient electric field on the central axis using the conical surface 306, it is necessary to dispose the conical surface 306 near the central axis. That is, it is necessary to make the diameter L less than or equal to a certain distance. In addition, in the existing suppression electrode 203, although the chamfered portion 209 is provided, generally for the purpose of avoiding the electric field concentration at the corner of the suppression electrode 305, the diameter of the start position of the chamfered portion 209, that is, the diameter L of the plane 205, typically has a relatively large diameter of 4 mm or more. In such a case where the diameter L is large, no matter what structure is provided outside the plane 205, the electric field formed by this structure on the central axis is extremely small and will not affect the electron beam 115. Therefore, in the existing suppression electrode 203, no matter what shape and angle the chamfered portion 209 has, there is no influence. When the diameter of the plane 205 is large like this, the electric field in the lateral direction and the bending mode of the electron beam 115 are determined only by the electric field formed by the opening 204.

[0102] In addition, the principle that the above-mentioned electron beam 115 does not bend can also be achieved by setting a shape different from Figure 4 near the central axis. In Figure 5D the structure shown, essentially, a surface (receding portion (surface) 212) facing backward (upward in the figure) is provided at a position in the outer peripheral direction and near the central axis compared to the opening 204 of the suppression electrode 305, so that charges are generated here when the axis deviates, generating an electric field in the opposite direction. As a result, the electric field formed by the opening 204 is canceled, and further the electron beam is bent back, so that the electron beam 115 does not bend. In other words, taking the direction from the chip 202 toward the specimen as the front and the opposite direction as the rear, a surface (receding surface) (the conical portion 306 in Embodiment 1) that recedes more backward than the front surface (front end portion) 213 of the suppression electrode 305 is provided at a position in the outer peripheral direction and near the central axis Z of the suppression electrode 305, that is, a portion that is farther (away) from the front end of the chip 202 than the front end portion 213 in the central axis direction is used as a part of the receding portion 212. As a result, an electric field opposite to the direction of the electric field generated by the opening 204 when the axis deviates is generated in the vicinity of the central axis of this receding surface 212 (the conical portion 306 in Embodiment 1). As a result, the bending of the electron beam can be prevented.

[0103] As Figure 4Examples of the retracted surface other than the tapered portion 306 may also be stepped steps (corresponding to θ = 90 degrees (°)), spherical, elliptical and other curved surfaces, or surfaces formed by combining multiple tapered portions, steps, and curved surfaces. In addition, stepped steps can also be considered as tapered portions with a taper angle of 90°, and curved surfaces such as spheres and ellipses can also be considered as a type of tapered portion formed by continuously varying infinitesimal portions with different taper angles. The above-mentioned other shapes will be described as other embodiments below.

[0104] From here, the relationship between the shape parameters L, θ of the suppression electrode 305, the axis deviation amount Δ between the suppression electrode 305 and the chip 202, and the bending amount (displacement in the X direction in FIG. 5) of the orbit of the electron beam 115, and the appropriate design range of the shape parameters of the suppression electrode 305 will be described.

[0105] First, FIG. 6 shows an example of the influence of the angle θ of the conical surface 306 on the lateral bending (displacement in the X direction) of the electron beam 115 in the SE electron source 101 of Example 1.

[0106] Figure 6A is the result of calculating the electric field E in the direction perpendicular to the central axis Z (X direction, lateral direction) generated on the central axis Z when the angle θ of the conical surface 306 is changed from 0° to 14°. X Here, the central axis of the chip 202 is set as the Z axis, the direction perpendicular to it is set as the X axis, the front end surface of the chip 202 is set as Z = 0, and the sample side is set as Z > 0. As an example of the calculation conditions, the diameter L of the front end portion 213 (plane 205) of the suppression electrode 305, the protruding length T of the chip 202, the diameter d of the opening portion 204, and the axis deviation amount Δ between the chip 202 and the suppression electrode 305 are respectively set as L = 800 μm, T = 250 μm, d = 400 μm, Δ = 1 μm, the potential of the chip 202 is set as 0 V, and the extraction voltage V1 is set as 2 kV. And the suppression voltage V S is adjusted so that the electric field in the central axis direction (Z direction) applied to the front end of the chip 202 is equal in each shape. The lateral electric field E X is normalized by setting the absolute value of the maximum electric field at θ = 0° to 1. In addition, θ = 0° is the condition without the conical surface 306 and is the shape of the existing suppression electrode 203. And the above-mentioned calculation conditions are an example as described above. Regarding the case where various parameters (calculation conditions) change, the tendency of reducing the bending of the electron beam can also be examined as described below.

[0107] In the case of θ = 0°, the maximum electric field of E X = -1 is generated near the front end of the chip 202, and the electric field decreases as Z increases. Near Z = 800 μm, E XIs approximately 0. If θ is set to 2°, the electric field at the front end of the chip 202 decreases. If θ is increased to 6°, 10°, 14°, in addition to the gradual weakening of the electric field at the front end of the chip 202, an electric field on the + side is generated with the vicinity of Z = 200 μm as the vertex. Due to the positive / negative inversion of the electric field, the electric field on the + side acts to pull back the electron beam that has been bent once near the chip.

[0108] Figure 6B Is the calculation result of the orbit of the electron beam when the angle θ of the conical surface 306 is changed from 0° to 14°. It shows the position in the X direction (displacement amount or off-axis distance X) of the orbit of the electron beam with respect to the distance Z on the Z axis. The change rate (dX / dZ) of the vertical axis X with respect to the horizontal axis Z is the slope of the orbit of the electron beam. In addition, in the drawing, Z is marked up to 20 mm, showing up to near the accelerating electrode 103 located downstream. And, in the existing suppression electrode with θ = 0°, the off-axis distance X of the electron beam at Z = 20 mm is normalized with 1 for the vertical axis X. Parameters such as the shape of the suppression electrode 305 are the same as Figure 6A The same.

[0109] In the case of the existing suppression electrode with θ = 0°, the electron beam bends toward the + side and moves away from the central axis as Z increases. As θ increases, the slope (dX / dZ) of the electron beam decreases, and the off-axis amount X also decreases. If the slope (dX / dZ) of the electron beam at Z = 20 mm is compared with the prior art, the slopes for θ = 2°, 6°, 10° are 80%, 39%, 0.1% respectively. That is, in the case of θ = 10°, even if the chip 202 and the suppression electrode 305 have an axis deviation, the electron beam becomes a state where it hardly bends. Since the electron beam does not bend, the electron beam advances on the central axis and no off-axis aberration occurs in the electrostatic lens or other lenses. On the other hand, at θ = 14°, the force that bends the electron beam back becomes too strong, and the electron beam tilts toward the - side. If θ is further increased, the electron beam further tilts toward the - side, and the bending amount of the electron beam may deteriorate compared with the prior art. Thus, in order to reduce the bending of the electron beam compared with the prior art, θ needs to be within a certain range.

[0110] Next, using FIG. 7, an example of the influence in the case where the axis deviation amount Δ between the chip 202 and the suppression electrode 305 becomes large in the SE electron source 101 of the first embodiment will be described.

[0111] Figure 7A Shows the result of calculating the electric field E in the direction perpendicular to the central axis (X direction, lateral direction) generated on the central axis Z in the SE electron source 201 using the existing suppression electrode 203 when the axis deviation amount Δ is increased from 1 μm to 20 μm. X In addition, the lateral electric field E XThe absolute value of the maximum electric field when the axis is deviated by Δ = 1 μm is set to 1 for normalization.

[0112] E X increases approximately proportionally to the axis deviation amount Δ, and its distribution becomes a similar shape. The absolute values of the maximum of E when the axis deviation amounts Δ = 1 μm, 5 μm, 10 μm, and 20 μm are 1, 5, 10, and 20. Therefore, the lateral electric field E X becomes larger proportionally to the axis deviation amount Δ, and the electron beam is bent significantly. X

[0113] Figure 7B is the calculation result of the lateral electric field E when the axis deviation amount Δ increases under the condition of θ = 10° in the SE electron source 101 using the suppression electrode 305 of Example 1. In addition, the conditions used in other calculations are the same as those described in FIG. 6. X

[0114] Regarding the SE electron source 101 of Example 1, E X also increases proportionally to the axis deviation amount Δ, and its distribution becomes a similar shape. However, in the SE electron source 101 of Example 1, proportionally to the axis deviation amount Δ, the electric field on the + side with a vertex near Z = 200 μm also increases. As a result, even when the axis deviation amount Δ increases, the force that bends the electron beam back accordingly also increases, thus maintaining the state where the electron beam does not bend.

[0115] Figure 7C In, regarding the existing SE electron source 201 and the SE electron source 101 of Example 1, the axis deviation amount Δ is set as the horizontal axis, and the slope (dX / dZ) of the electron beam at the position of Z = 20 mm is set as the vertical axis for display. Figure 7C The shape of the suppression electrode 305 of Example 1 in Figure 7B is the same. In addition, regarding the slope (dX / dZ) of the electron beam on the vertical axis, in the SE electron source 201 using the existing suppression electrode 203, the slope at Z = 20 mm when the axis deviation amount Δ = 1 μm is set to 1 for normalization.

[0116] In the existing suppression electrode 203, the slope (dX / dZ) of the electron beam becomes larger proportionally to the axis deviation amount Δ. On the other hand, in the suppression electrode 305 of Example 1, even when the axis deviation amount Δ increases, the slope of the electron beam is approximately 0. In this way, even if the suppression electrode 305 of Example 1 generates an axis deviation, a state where the electron beam 115 does not bend can be achieved.

[0117] ​​Furthermore, in the prior art, a reference is set in the assembly process of the electron source for quality control so that the axial deviation between the chip 202 and the suppression electrode 203 is below a certain value. Moreover, among the manufactured electron sources, those with an axial deviation Δ that cannot be below a certain value are considered to be defective in manufacturing. On the other hand, when using the suppression electrode 305 of Example 1, since the electron beam 115 does not bend even if the axial deviation Δ is large, the reference for the assembly process can be significantly relaxed. This has the effects of reducing the manufacturing cost of the electron source, increasing the yield, and reducing the preparation time, etc.

[0118] Based on the above results, further research was conducted on the appropriate design of the shape of the suppression electrode 305 of Example 1.

[0119] Using FIG. 8, in the SE electron source 101 using the suppression electrode 305 of Example 1, the relationship between the appropriate L and θ is described. Figure 8A The results of calculating the slope (dX / dZ) of the electron beam 115 when Z = 20 mm with L and θ changed in the suppression electrode 305 of Example 1 are shown. The horizontal axis is set as L, and the vertical axis is set as θ, and the contour lines connecting the points that will result in the same slope of the electron beam are displayed. In addition, the slope of the electron beam is shown as a percentage compared to the slope of the electron beam of the existing SE electron source 201 using the existing suppression electrode 203. The lines of 90%, 50%, 0%, -50%, and -90% in the figure indicate that the slope of the electron beam is 90%, 50%, 0%, -50%, and -90% compared to the existing SE electron source 201. The meaning of "-" indicates that the slope of the electron beam is reversed compared to the prior art. Other conditions used in the calculation are the same as in FIG. 6.

[0120] In the SE electron source 101 of Example 1, in principle, the shorter L or the larger θ, the stronger the electric field formed by the conical surface 306. On the contrary, when L is too large or θ is too small, the electric field formed by the conical surface 306 becomes very weak, and the effect of reducing the slope of the electron beam is so small as to be negligible compared to the prior art. On the other hand, when L is too small or θ is too large, the electric field formed by the conical surface 306 becomes very large, and the slope of the electron beam becomes very large in the opposite direction compared to the prior art. In this case, the electron beam bends significantly in the opposite direction compared to the existing SE electron source 201. Therefore, it is necessary to design the diameter L and the angle θ within an appropriate range.

[0121] As an effect of the SE electron source 101 using the suppression electrode 305 of Example 1, if the case where the absolute value of the slope of the electron beam 115 is reduced by more than 10% compared to the prior art, that is, the absolute value of the slope is 90% or less of the existing value, is set as the threshold, then L and θ are preferably designed within the range surrounded by the Figure 8A shown lines of 90% to -90%.

[0122] More preferably, when the absolute value of the slope of the electron beam 115 is reduced by more than 50% compared with the prior art, that is, when the absolute value of the slope is 50% or less of the existing value, is taken as a threshold value, L and θ are preferably designed within the range surrounded by the line of 50% to -50% shown by Figure 8A Shown.

[0123] More preferably, in order to make the slope of the electron beam 115 0% of the existing value, that is, in order to make the electron beam not bend at all, it is preferably designed under the conditions on the 0% line shown by Figure 8A Shown.

[0124] The angle θ of the conical surface 306 is preferably at most 90°. When θ = 90°, the shape of the conical surface 306 is not conical but regarded as a stepped step. As Figure 8A Shown, under the condition of θ = 90°, when the slope of the electron beam is 90% of the existing value, L is about 2540 μm. In other cases of θ, the electric field formed by the conical surface 306 becomes weaker. Therefore, in order to obtain a slope of 90%, L needs to be smaller than this value. Therefore, at any angle, in order to obtain a slope of the electron beam of 90% or less, L needs to be 2540 μm or less. This becomes a reference when the conical surface 306 is arranged near the axis.

[0125] Similarly, under the condition of θ = 90°, when the slope of the electron beam is 50% of the existing value, L is about 1940 μm. Therefore, at any angle, in order to obtain a slope of the electron beam of 50% or less, L needs to be 1940 μm or less.

[0126] Similarly, under the condition of θ = 90°, when the slope of the electron beam is 0%, L is 1650 μm. Therefore, at any angle, in order to obtain a slope of the electron beam of 0%, L needs to be 1650 μm or less.

[0127] Figure 8B Is Figure 8A A graph with the vertical axis as logθ. In addition, the unit of θ is degree (°), and the unit of L is μm. The lines of 90%, 50%, 0%, -50%, and -90% are approximated by the following respective quadratic functions by setting the vertical axis as logθ.

[0128] The lines of 90%, 50%, 0%, -50%, and -90% are expressed as follows in sequence.

[0129] logθ = 2.40×10 －7 ×L 2 +3.18×10 －4 ×L - 4.08×10 －1

[0130] logθ = 3.80×10 －7 ×L 2 + 6.77×10 －5 ×L + 3.92×10 －1

[0131] logθ = 4.96×10 －7 ×L 2 -8.31×10 －5 ×L + 7.43×10 －1

[0132] logθ = 5.86×10 －7 ×L 2 -1.81×10 －4 ×L + 9.49×10 －1

[0133] logθ = 6.68×10 －7 ×L 2 -2.68×10 －4 ×L + 1.08

[0134] Therefore, for the SE electron source 101 of Example 1, another criterion is to design using L and θ within the range included in the above formula. For example, when reducing the slope of the electron beam from the existing 90% to -90%, use the formulas in the cases of the above 90% and -90% to satisfy the relationship of 2.40×10 －7 ×L 2 + 3.18×10 －4 ×L - 4.08×10 －1 ≤ logθ ≤ 6.68×10 －7 ×L 2 -2.68×10 －4 ×L + 1.08.

[0135] Here, Figure 8A and Figure 8B The appropriate ranges shown vary by about ±20% according to other conditions such as the protrusion length T of the chip, the diameter of the opening 204, the shape of the chip or extraction electrode, the suppression voltage, the extraction voltage, etc. And it is difficult to set a criterion by distinguishing each of these conditions. Therefore, it should be noted that the above ranges are not strict and there are cases where they vary with a certain likelihood.

[0136] As an example, this calculation is the result of the protrusion length T of the chip 202 being 250 μm. However, the influence of the lateral electric field 301 increases and decreases in inverse proportion to the protrusion length. As a result, the degree of electron beam bending changes, and the appropriate ranges of L and θ also change. If T is a value close to 250 μm, around 200 μm to 300 μm, then by designing approximately within the ranges of L and θ shown in FIG. 8, the slope of the electron beam can be reduced compared to the prior art. However, when the protrusion length T is outside this range, the appropriate L and θ are insufficient within the range of FIG. 8. The cases of different protrusion lengths as described above will be explained below.

[0137] This calculation is the result of the diameter of the opening 204 being 400 μm. However, as another example, when the diameter of the opening 204 is made larger, the influence of the electric field caused by the extraction electrode 102 on the opening 204 becomes stronger, and the amounts of positive charge 404 and negative charge 405 increase. As a result, the electron beam 115 bends more. At this time, in order to prevent the electron beam 115 from bending, it is necessary to increase the angle θ and decrease the diameter L compared to the range shown in FIG. 8. From the same calculation as above, it can be known that, for example, when the diameter of the opening 204 is 600 μm, the diameter L needs to be reduced by approximately 20%.

[0138] Next, the suppression voltage required for the SE electron source 101 using the suppression electrode 305 of Example 1 will be described. Figure 9 The results of calculating the suppression voltage required to make the electric field in the central axis direction (Z direction) applied to the front end of the chip 202 the same as that of the prior art when changing the diameter L under the condition of θ = 10° are shown. Other calculation conditions are the same as those in FIG. 6. In addition, the vertical axis is normalized by setting the suppression voltage applied to the SE electron source 201 using the existing suppression electrode 203 as 1.

[0139] The suppression electrode 305 of Example 1 has a retreat surface 212 such as a conical surface 306 near the central axis, so that the effect of suppressing the electric field in the central axis direction (Z direction) applied to the front end of the chip 202 as the original purpose of the suppression electrode 305 becomes weak. That is, the extraction and acceleration electric fields in the central axis direction applied to the front end of the chip 202 become stronger. In this case, the effect of suppressing unnecessary electrons as the function of the suppression electrode is reduced, and there is a problem of emitting more unnecessary electrons than the prior art. To take countermeasures, in Example 1, it is necessary to make the suppression voltage V S higher than that of the prior art to make the electric field in the central axis direction at the front end of the chip 202 the same as that of the prior art.

[0140] Figure 9The calculated result with L = 400 μm shows the condition where the starting position of the conical surface 306 coincides with the lower surface of the opening 204, referring to the shape without the plane 205. In this case, the required suppression voltage is 1.54, which must be increased by 54% compared to the prior art. This leads to issues such as an increase in power supply cost and an increased risk of surface discharge along the insulator 208. Also, since the opening 204 coincides with the starting position of the conical surface 306, the electric field concentrates at this point, increasing the risk of space discharge between the extraction electrode 102. In the case of causing the above-mentioned discharge, the tip of the chip 202 is melted and damaged, and the electron source becomes unusable. Usually, the protruding length T of the chip is adjusted and assembled under a stereomicroscope with the plane 205 as the reference plane. However, due to the absence of the plane 205, the adjustment of this protruding length becomes difficult, resulting in problems such as a decrease in yield and an increase in manufacturing cost.

[0141] As Figure 9 shown, making the diameter L larger than 400 μm, that is, increasing the diameter of the plane 205, can reduce the required suppression voltage. Also, the problems in the case without the above-mentioned plane 205 can be solved. In particular, Figure 9 the shown curve is convex downward and has the advantage that by slightly increasing L, the required suppression voltage can be significantly reduced.

[0142] As a reference for the size of L, if the case where the increase amount of the suppression voltage required in the case of L = 400 μm is 27% or less, which is half of 54%, that is, Figure 9 the case where it is set to 1.27 or less on the vertical axis is set as the threshold value, the L that achieves this threshold value is 720 μm or more. Therefore, making L 720 μm or more can reduce the increase in the required suppression voltage to less than half compared to the case without the plane 205. Thus, in a typical suppression electrode where the diameter d of the opening 204 is about 400 μm, a guideline is obtained to make L 720 μm or more.

[0143] More preferably, the case where the increase amount of the suppression voltage required in the case of L = 400 μm is 18% or less, which is one-third of 54% (the vertical axis is 1.18 or less), is set as the threshold value. The L that achieves this threshold value is 910 μm or more. Therefore, by making L 910 μm or more, the increase in the required suppression voltage can be reduced to less than one-third compared to the case without the plane 205.

[0144] If L is 2000 μm or more, the required suppression voltage is 1.01 or less, showing almost no change compared with the prior art. However, as described above, the electric field generated by the conical surface 306 decreases in inverse proportion to L. Therefore, increasing L to reduce the required suppression voltage and preventing the bending of the electron beam are in a trade-off relationship. In view of the overall device design, the designer determines the allowable value of the bending amount of the electron beam and the allowable value of the increase in the suppression voltage, and determines an appropriate L based on this. Then, θ is determined to reduce the bending of the electron beam within the desired range. Alternatively, the adjustment reference for the assembly error of the central axes of the chip 202 and the suppression electrode 305 is relaxed.

[0145] This calculation was performed for θ = 10°, but the same calculation was also performed for other angles θ, and the calculation results were similar to Figure 9 the results of the similar calculation. Therefore, in the case of other θ, by making the above-mentioned L 720 μm or more, the increase in the required suppression voltage can be made less than half compared with the case without the plane 205 at this θ. And by making L 910 μm or more, the increase in the required suppression voltage can be made less than one-third compared with the case without the plane 205 at this θ.

[0146] Example 2

[0147] In Example 1, the following structure was shown: Under the condition that the protruding length T of the chip 202 is about 200 μm to 300 μm, a conical surface 306 is provided on the suppression electrode 305 to prevent the electron beam from bending when the axis deviates. In Example 2, the suppression electrode 305 and the SE electron source 101 having the same structure as in Example 1 are used to illustrate the structure in the case where the protruding length T of the chip 202 is outside the above-mentioned range described in Example 1.

[0148] Figure 10 The lateral electric field E in the case where the protruding length T of the chip 202 is changed in the SE electron source 201 using the existing suppression electrode 203 is shown X . Figure 10 are the calculation results when changed to T = 150 μm, 250 μm, and 350 μm. The result of T = 250 μm corresponds to the result of θ = 0° shown in Figure 6A Example 1. And Z = 0 is set as the position of the front end surface of the chip 202 when T = 250 μm. Therefore, the front end surface of the chip 202 when T = 150 μm is Z = -100 μm, and the front end surface of the chip 202 when T = 350 μm is Z = 100 μm. The calculation conditions are that the diameter d of the opening 204 is set to 400 μm, the extraction voltage V1 is set to 2 kV. And the suppression voltage V SThe electric field adjusted to the central axis direction (Z direction) applied to the front end of the chip 202 is equal in each shape. The deviation amount Δ of the axis of the chip 202 and the suppression electrode 203 is 1 μm. The lateral electric field E as the vertical axis X is normalized by setting the absolute value of the maximum electric field at T = 250 μm to 1.

[0149] When T is changed, the lateral electric field formed by the opening 204 changes greatly. The peak value of the electric field at T = 250 μm is -1. In contrast, it is -3.4 at T = 150 μm and -0.33 at T = 350 μm. The reason is that Figure 5B the region shielding the power line 408 shown changes due to the protruding length T of the chip 202.

[0150] When the protruding length T of the chip 202 is shorter than 250 μm, the electric field also penetrates into the region without the chip 202, and the electron beam bends more. Therefore, in order to prevent the bending of the electron beam, it is necessary to enhance Figure 5D the reverse electric field 412 shown. To achieve this, it is necessary to make the diameter L of the conical surface 306 shorter or the angle θ larger.

[0151] When the protruding length T of the chip 202 is longer than 250 μm, the electric field in the region where the chip 202 moves is shielded, and the electron beam becomes more difficult to bend. Therefore, in the case of L and θ shown in Embodiment 1, the electron beam bends back excessively, and the slope of the electron beam may deteriorate compared to the prior art. Therefore, it is necessary to make L of the conical surface 306 longer or θ smaller.

[0152] Using FIG. 11, the relationship between appropriate L and θ when the protruding length T is set to 150 μm in the SE electron source 101 using the suppression electrode 305 of Embodiment 2 will be described. Figure 11A FIG. shows the result of calculating the slope of the electron beam obtained when L and θ are changed under the condition of T = 150 μm in the SE electron source 101 of Embodiment 2. In addition, the slope of the electron beam 115 is shown as a percentage compared to the slope of the electron beam 115 when T = 150 μm in the existing SE electron source 201. The conditions used in other calculations are the same as Figure 10 the same.

[0153] Figure 11A Compared with the lines in FIG. 8, for the lines of 90%, 50%, 0%, -50%, and -90% shown, L is shorter and θ is larger.

[0154] Under the condition of θ = 90°, the slope of the electron beam 115 is made 90% of the existing value, and L is approximately 2110 μm. In the case of other θ values, the electric field formed by the conical surface 306 becomes weaker. Therefore, in order to obtain a slope of 90%, L needs to be smaller than this value. Thus, at any angle, in order to obtain a slope of the electron beam below 90%, L needs to be 2110 μm or less.

[0155] Similarly, under the condition of θ = 90°, the slope of the electron beam 115 is made 50% of the existing value, and L is approximately 1450 μm. Therefore, at any angle, in order to obtain a slope of the electron beam below 50%, L needs to be 1450 μm or less.

[0156] Similarly, under the condition of θ = 90°, L is 1130 μm when the slope of the electron beam 115 is 0%. Therefore, at any angle, in order to obtain a slope of 0% of the electron beam, L needs to be 1130 μm or less.

[0157] Figure 11B is a graph with Figure 11A the vertical axis set to logθ. The unit of θ is degree (°), the unit of L is μm, and the lines of 90%, 50%, 0%, -50%, -90% are approximated by the following respective quadratic functions with the vertical axis set to logθ.

[0158] The lines of 90%, 50%, 0%, -50%, -90% are expressed as follows in sequence.

[0159] logθ = 2.69×10 －7 ×L 2 +3.64×10 －4 ×L - 2.21×10 －2

[0160] logθ = 4.62×10 －7 ×L 2 +1.70×10 －4 ×L + 0.74

[0161] logθ = 6.92×10 －7 ×L 2 -6.94×10 －6 ×L + 1.08

[0162] logθ = 9.88×10 －7 ×L 2 -2.25×10 －4 ×L + 1.31

[0163] logθ = 1.27×10 －6 ×L 2 -4.18×10－4 ×L + 1.45

[0164] Therefore, in the SE electron source 101 using the suppression electrode 305 of Embodiment 2, when the protrusion length T is 150 μm, one approach is to design using L and θ within the range enclosed by the above formula. For example, when reducing the slope of the electron beam from the existing 90% to -90%, use the formulas for the above 90% and -90% cases to satisfy 2.69×10 －7 ×L 2 + 3.64×10 －4 ×L - 2.21×10 －2 ≤ logθ ≤ 1.27×10 －6 ×L 2 - 4.18×10 －4 ×L + 1.45, and design in a way that satisfies this relationship.

[0165] Also, as will be described below, there is a proportional relationship between the protrusion length T and the allowable range of L. Therefore, the appropriate ranges of L and θ when T is between 150 μm and 250 μm are in the middle region of the ranges shown in FIGS. 8 and 11. In Embodiment 2, as a threshold, when T is less than 200 μm, use L and θ within the range shown in FIG. 11. If within this range, generally the slope of the electron beam can be reduced compared to the prior art even when T is less than 200 μm.

[0166] Next, with reference to FIG. 12, the relationship between the appropriate L and θ when the protrusion length T is set to 350 μm in the SE electron source 101 of Embodiment 2 will be described. Figure 12A The figure shows the results of calculating the slope of the electron beam obtained by changing L and θ under the condition of T = 350 μm in the SE electron source 101 using the suppression electrode 305 of Embodiment 2. In addition, the slope of the electron beam 115 is shown as a percentage compared to the slope of the electron beam 115 when T = 350 μm in the existing SE electron source 201. The conditions used in other calculations are the same as Figure 10 the same.

[0167] Figure 12A Compared with the lines of 90%, 50%, 0%, -50%, -90% shown, the L is longer and the θ is smaller for the lines in FIG. 8.

[0168] Under the condition of θ = 90°, the slope of the electron beam 115 is 90% of the existing value, and L is approximately 2810 μm. In the case of other θ values, the electric field formed by the conical surface 306 becomes weaker. Therefore, in order to obtain a slope of 90%, L needs to be smaller than this value. Thus, at any angle, in order to obtain a slope of the electron beam below 90%, L needs to be 2810 μm or less.

[0169] Similarly, under the condition of θ = 90°, the slope of the electron beam 115 is 50% of the existing value, and L is approximately 2270 μm. Therefore, at any angle, in order to obtain a slope of the electron beam below 50%, L needs to be 2270 μm or less.

[0170] Similarly, under the condition of θ = 90°, the slope of the electron beam 115 is 0%, and L is 1990 μm. Therefore, at any angle, in order to obtain a slope of 0% of the electron beam, L needs to be 1990 μm or less.

[0171] Figure 12B It is a graph with Figure 12A the vertical axis being logθ. The unit of θ is degree (°), the unit of L is μm, and the lines of 90%, 50%, 0%, -50%, -90% are approximated by the following quadratic functions with the vertical axis set as logθ.

[0172] The lines of 90%, 50%, 0%, -50%, -90% are expressed as follows in sequence.

[0173] logθ = 2.59×10 －7 ×L 2 +1.82×10 －4 ×L - 6.04×10 －1

[0174] logθ = 3.32×10 －7 ×L 2 +5.07×10 －5 ×L + 1.26×10 －1

[0175] logθ = 4.12×10 －7 ×L 2 -8.01×10 －5 ×L + 4.75×10 －1

[0176] logθ = 4.62×10 －7 ×L 2 -1.49×10 －4 ×L + 6.76×10 －1

[0177] logθ = 5.15×10 －7 ×L 2 -2.29×10 －4 ×L + 8.10×10 －1

[0178] Therefore, in the SE electron source 101 of Example 2, when the protrusion length T is 350 μm, one approach is to design using L and θ within the range enclosed by the above formula. For example, when reducing the slope of the electron beam from the existing 90% to -90%, use the formulas for the cases of 90% and -90% above to satisfy －7 ×L 2 +1.82×10 －4 ×L - 6.04×10 －1 ≤ logθ ≤ 5.15×10 －7 ×L 2 -2.29×10 －4 ×L + 8.10×10 －1 and design in a manner that satisfies the relationship.

[0179] The appropriate range of L and θ when T is between 250 μm and 350 μm is in the region intermediate to the ranges shown in FIGS. 8 and 12. In Example 2, as a threshold, when T is greater than 300 μm, use L and θ within the range shown in FIG. 12. If it is within this range, generally the slope of the electron beam can be reduced compared to the prior art even when T is greater than 300 μm.

[0180] Performing the above calculations, in the SE electron source 101 using the suppression electrode 305 of Example 2, the maximum value of L for the amount that allows the slope of the electron beam 115 when the protrusion length T is changed is obtained as follows. Figure 13 Shows the values of L for making the slope of the electron beam 90%, 50%, and 0% compared to the prior art under the condition of θ = 90° when the protrusion length T is from 150 μm to 350 μm.

[0181] In the case of other θ values other than θ = 90°, the electric field formed by the conical surface 306 becomes weaker, and L needs to be further shortened. Therefore, Figure 13 the L shown is the maximum L allowed to obtain the slope of the electron beam 115 for each percentage. Even for any percentage line, L and T have a linear relationship, and L also increases proportionally with T. Therefore, even for protrusion lengths other than the above calculations, the appropriate range can be known.

[0182] In the case where the protruding length is 350 μm, in order to achieve a slope less than 90% of the existing one, as shown in FIG. 12, it is necessary to make L less than or equal to 2810 μm at least. And if it is below this value of L, even when the protruding length is shorter than 350 μm, the slope of the electron beam can be made less than 90%. And, Figure 13 The T and L shown can be approximated by a substantially linear relationship. Therefore, in other words, if the relationship between L and T satisfies the linear approximation formula for the slope of the electron beam of 90%, that is, L ≤ 3.53T + 1607, the slope of the electron beam can be made less than 90%. Here, the units of L and T are μm.

[0183] Similarly, in the case where the protruding length is 350 μm, in order to achieve a slope less than 50% of the existing one, as shown in FIG. 12, it is necessary to make L less than or equal to 2270 μm at least. And if it is below this value of L, even when the protruding length is shorter than 350 μm, the slope of the electron beam can be made less than 50%. In other words, if the relationship between L and T satisfies the linear approximation formula for the slope of the electron beam of 50%, that is, L ≤ 4.10T + 861, the slope of the electron beam can be made less than 50%.

[0184] Furthermore, similarly, in the case where the protruding length is 350 μm, in order to achieve a slope of 0% of the existing one, as shown in FIG. 12, it is necessary to make L less than or equal to 1990 μm at least. And if it is below this value of L, even when the protruding length is shorter than 350 μm, the slope of the electron beam can be made 0%. In other words, if the relationship between L and T satisfies the linear approximation formula for the slope of the electron beam of 0%, that is, L ≤ 4.29T + 522, the slope of the electron beam can be made 0%.

[0185] Summarizing the above results, in order to reduce the inclination of the electron beam by at least 10%, that is, to reduce it to less than 90% of the original value, when the protruding length T = 350 μm, it is necessary to make the diameter L less than or equal to 2810 μm. Moreover, it can be seen that if it is below this value of L, even when the protruding length is shorter than 350 μm, the slope of the electron beam can be made less than 90%. And as described above, the protruding length T of the chip 202 typically mostly uses about 150 - 350 μm. Therefore, as a guideline, it is possible to make the diameter L of the plane 205 (front end 213) less than or equal to 2810 μm.

[0186] Example 3

[0187] In Example 2, the following structure was shown: under the condition that the protruding length T of the chip 202 is different, a conical surface 306 is provided on the suppression electrode 305 to prevent the electron beam from bending when the axis deviates. In Example 3, as an example of another retreat surface, a structure using a stepped step is adopted.

[0188] Figure 14 Shows the structure of the SE electron source 501 of Embodiment 3. In Embodiment 3, a stepped step 502 is provided on the lower surface of the suppression electrode 305. That is, the diameter of the front end 213 (plane 205) is set to L, and a stepped step 502 with θ = 90° at the corner 503 is provided near the central axis Z. The retreat portion 212 is formed by the corner 503, the step 502, and the plane portion 504. The stepped step 502 corresponds to the state where the cone angle θ of the cone portion 306 is set to θ = 90° in Embodiment 1 and Embodiment 2. As described above, the larger θ is, the stronger the electric field formed by the retreat surface of the retreat portion 212, that is, the cone portion 306, is when the axis deviates. Therefore, compared with the conical surface 306, it has the advantage that L can be increased by using the stepped step 502. In addition, the suppression electrode of Embodiment 3 can also be considered as a conical shape having a surface (step) 502 with a cone angle of 90° and a plane 504 with a cone angle of 0°.

[0189] Moreover, at the corner 503 of the stepped step 502 that is connected to the plane 205, the electric field is concentrated due to the extraction voltage, and there is a possibility of discharge. Therefore, the corner 503 can also be chamfered or rounded.

[0190] Embodiment 4

[0191] In Embodiment 3, as an example of other retreat surfaces provided on the suppression electrode 305, a structure using a stepped step was described. In Embodiment 4, as an example of other retreat surfaces, a structure using a wedge-shaped surface is adopted.

[0192] Figure 15 Shows the structure of the SE electron source 505 of Embodiment 4. In Embodiment 4, a wedge-shaped surface 506 is provided on the lower surface of the suppression electrode 305. The wedge-shaped surface 506 corresponds to the state where the cone angle θ of the cone portion 306 is set to θ > 90° in Embodiment 1 and Embodiment 2. In this structure, it is also possible to generate a reverse electric field when the axis deviates to suppress the bending of the electron beam. In particular, the electric field is concentrated at the vertex 507 of the wedge-shaped surface 506, and a large amount of charge is generated here, which can effectively suppress the bending of the electron beam 115. However, conversely, a larger electric field is applied to the vertex 507 than the corner 503 shown in Embodiment 3, and the possibility of discharge becomes further greater. Therefore, it is preferably θ ≤ 90°.

[0193] Embodiment 5

[0194] In Embodiment 4, as an example of other retreat surfaces provided on the suppression electrode 305, a structure using a wedge-shaped surface was described. In Embodiment 5, as an example of other retreat surfaces provided on the suppression electrode 305, a structure using a curved surface is adopted.

[0195] Figure 16 The structure of the SE electron source 510 of Example 5 is shown. In Example 5, a curved surface 511 is provided on the lower surface of the suppression electrode 305. That is, it becomes a structure having a curved portion 511 in the slanted portion of the cross section ( Figure 16 of the center axis Z passing through the suppression electrode 305). Hereinafter, the curved portion on this cross section will be simply referred to as the curved portion or the curved surface. According to another expression, the curved surface 511 can be expressed as a curved surface portion in which the angle (cone angle) formed with the plane perpendicular to the center axis continuously changes. Even if the retreat surface is a curved portion (curved surface), it is a surface that is farther from the front end of the chip 202 in the Z direction than the front end portion 213 (plane 205) of the suppression electrode, and thus retreats. As a result, when the axis deviates, positive charges 410 and negative charges 411 as shown in Figure 5D are generated on the curved surface 511, and the bending of the electron beam can be prevented by the same principle. The diameter L of the plane 205 in the case of Example 5 becomes the diameter at the position where the curved portion (curved surface) 511 starts.

[0196] The curved portion (curved surface) 511 may be a sphere, an ellipse, or any aspherical surface. As described above, the curved portion (curved surface) 511 can be regarded as a surface formed by combining an infinite number of cone portions having continuous minute angle changes. Therefore, when the diameter at an arbitrary position on the curved portion (curved surface) 511 is regarded as a new L' and the angle of the slope at that position is regarded as a new θ', by including at least one or more L' and θ' within the range shown in any of FIGS. 8 to 11 and FIG. 12, the effect of preventing the desired electron beam 115 from bending can be obtained. Since the curved portion (curved surface) 511 does not have a corner portion, it has the advantages of alleviating electric field concentration and reducing the risk of discharge.

[0197] Example 6

[0198] In Example 5, as an example of other retreat surfaces provided on the suppression electrode 305, a structure using a curved portion (curved surface) in the cross section was described. In Example 6, as an example of other retreat surfaces provided on the suppression electrode 305, a structure combining a plurality of conical surfaces and steps is formed.

[0199] Figure 17Shows the structure of the SE electron source 515 of Embodiment 6. In Embodiment 6, it is configured to provide a conical surface 516, a conical surface 517, and a stepped step 518 on the lower surface of the suppression electrode 305, and has portions with multiple different cone angles. Even when combining multiple conical surfaces, steps, and curved surfaces, by forming an inverse electric field on these surfaces when the axis is deviated, the bending of the electron beam 115 can be prevented. The inverse electric field is the sum of the electric fields formed by the conical surface 516, the conical surface 517, and the stepped step 518. If the starting positions of each surface are set as L1, L2, L3, and the slope angles are set as θ1, θ2, θ3, at least one or more combinations of L1 and θ1, L2 and θ2, L3 and θ3 are included within the range of L and θ shown in FIGS. 8 to 11 and FIG. 12, thereby enabling the effect of preventing the desired bending of the electron beam to be obtained. In addition, the combination of the conical surface and the step can be further increased in number, and the conical surface and the step can be replaced with a curved surface and a wedge-shaped surface.

[0200] Embodiment 7

[0201] In Embodiment 6, as an example of other recessed surfaces provided on the suppression electrode 305, a structure combining multiple conical surfaces and steps was described. In Embodiment 7, as an example of other recessed surfaces provided on the suppression electrode 305, a structure with a single conical surface is adopted.

[0202] Figure 18 Shows the structure of the SE electron source 520 of Embodiment 7. In Embodiment 7, a single conical surface 306 is provided on the lower surface of the suppression electrode 305. In the structure of this Embodiment 7, there is no Figure 4 shown flat surface 205. This corresponds to the state where L = d = 400 μm in Embodiments 1 and 2. Under this condition, by designing the relationship between L and θ and the relationship between L and T to satisfy the relationships described in Embodiments 1 and 2, a suppression electrode 305 capable of effectively suppressing the bending of the electron beam 115 can be obtained.

[0203] Since the processing of the lower surface of the suppression electrode 305 becomes simple, this structure has the advantage of being able to reduce the manufacturing cost. However, as described above, the electric field is concentrated at the front end 521 of the conical surface 306, and there is a risk of discharge. And, as described above, it becomes difficult to adjust the protruding length T of the chip 202 during assembly. In addition, as Figure 9 shown, the required suppression voltage increases. Therefore, within the range permitted by other design matters, it is preferably in the shape of providing a flat surface 205 as in Embodiment 1.

[0204] Above, the embodiments of the present invention have been specifically described, but the present invention is not limited to the above embodiments, and various modifications can be made without departing from its gist. For example, regarding FIGS. 6 to Figure 13The calculated results shown are for one example of the calculation conditions, but are not limited thereto. Moreover, the present invention has found an effect by making the shape of the suppression electrode 305 act on the electron beam 115. Therefore, the electron source 101 and the chip 202 in the embodiments of the present invention are not limited to the SE electron source described in the embodiments, and may also be electron sources, chips, and ion sources of different types such as CFE electron sources, thermionic electron sources, and photoexcited electron sources. Even for the above-mentioned electron sources, chips, and ion sources, the same effects can be obtained by mounting the same suppression electrode as in the embodiments of the present invention. Moreover, the material of the chip 202 is not limited to tungsten, and may also be other materials such as LaB6, CeB6, and carbon-based materials. Further, the electron source described in the embodiments of the present invention can also be used as an X-ray source that emits X-rays for target irradiation to an X-ray source. In addition to the above, the above embodiments have been described in detail with one example for easy understanding of the present invention, and are not limited to having the described structure. For example, as an example of an electron microscope, an example of a scanning electron microscope (SEM) has been described, but is not limited thereto, and can be applied to other various electron microscopes such as a transmission electron microscope (TEM) and a scanning transmission electron microscope (STEM), and charged particle beam devices. Regarding the signal generated from the specimen, it is not limited to the case of electrons (secondary electrons, reflected electrons, etc.), and characteristic X-rays can also be detected. Moreover, as a charged particle beam device, it can be applied not only to electron microscopes but also to electron beam lithography devices, X-ray microscopes, CTs, or ion microscopes that use electron beams. Further, a part of the structure of a certain embodiment can be replaced with the structure of another embodiment, or the structure of another embodiment can be added to the structure of a certain embodiment. Moreover, it is also possible to add, delete, or replace other structures to a part of the structure of each embodiment.

[0205] Symbol Explanation

[0206] 101 - SE electron source, 102 - extraction electrode, 103 - acceleration electrode, 104 - electron gun, 109 - turbomolecular pump, 110 - condenser lens, 111 - objective lens, 112 - specimen, 113 - specimen chamber, 114 - detector, 115 - electron beam, 116 - insulator, 118 - non-evaporable getter pump, 120 - ion pump, 121 - ion pump, 122 - ion pump, 125 - cylinder, 126 - first vacuum chamber, 127 - second vacuum chamber, 128 - third vacuum chamber, 201 - existing SE electron source, 202 - chip (single crystal wire as electron emission material), 203 - existing suppression electrode, 204 - opening, 205 - plane (bottom surface), 206 - filament, 207 - terminal, 208 - insulator, 209 - chamfered portion, 210 - cylindrical surface, 212 - rear portion (surface), 213 - front end, 214 - rear end, 301 - electric field, 302 - axis deviation vector, 305 - suppression electrode, 306 - conical surface (portion), 307 - corner, 401 - positive charge, 402 - negative charge, 403 - electric field line, 404 - positive charge, 405 - negative charge, 406 - spatial region, 407 - spatial region, 408 - electric field line, 410 - positive charge, 411 - negative charge, 412 - electric field line, 413 - spatial region, 414 - spatial region, 420 - negative charge, 421 - negative charge, 422 - negative charge, 423 - negative charge, 424 - positive charge, 501 - SE electron source, 502 - step, 503 - corner, 504 - plane, 505 - SE electron source, 506 - wedge-shaped surface, 507 - vertex, 510 - SE electron source, 511 - curved surface, 515 - SE electron source, 516 - conical surface, 517 - conical surface, 518 - step, 520 - SE electron source, 521 - front end.

Claims

1. An electron source, characterized in that, comprising: a suppression electrode having an opening at one end in the direction along the central axis; and an electron-emitting material, the front end of which protrudes from the opening, the suppression electrode further has a recessed portion at a position in the outer peripheral direction with respect to the opening, and the recessed portion retreats in the direction along the central axis to a position farther from the front end of the electron-emitting material than the end of the suppression electrode, at least a part of the recessed portion is arranged within a diameter of 2810 μm from the center of the opening, and the recessed portion has a tapered portion, and the angle formed by the tapered portion and the plane perpendicular to the central axis has at least two or more different angles.

2. The electron source according to claim 1, characterized in that the end of the suppression electrode is a plane perpendicular to the central axis.

3. The electron source according to claim 2, characterized in that the diameter of the plane is 720 μm or more.

4. The electron source according to claim 1, characterized in that the recessed portion has a part parallel to the central axis.

5. An electron source, characterized in that, comprising: a suppression electrode having an opening at one end in the direction along the central axis; and an electron-emitting material, the front end of which protrudes from the opening, the suppression electrode further has a recessed portion at a position in the outer peripheral direction with respect to the opening, and the recessed portion retreats in the direction along the central axis to a position farther from the front end of the electron-emitting material than the end of the suppression electrode, at least a part of the recessed portion is arranged within a diameter of 2810 μm from the center of the opening, the recessed portion has a tapered portion forming an angle θ with the plane perpendicular to the central axis, at least a part of the tapered portion is arranged within a diameter of L from the center of the opening, Let the unit of the above-mentioned diameter L be μm, and the unit of the above-mentioned angle θ be degree, i.e., °. The above-mentioned diameter L and the above-mentioned angle θ satisfy 2.40×10 －7 ×L 2 +3.18×10 －4 ×L-4.08×10 －1 ≤logθ≤6.68×10 －7 ×L 2 -2.68×10 －4 ×L + 1.08 relationship.

6. An electron source, characterized in that, comprising: a suppression electrode having an opening at one end in the direction along the central axis; and an electron-emitting material, the front end of which protrudes from the opening, the suppression electrode further has a recessed portion at a position in the outer peripheral direction with respect to the opening, and the recessed portion retreats in the direction along the central axis to a position farther from the front end of the electron-emitting material than the end of the suppression electrode, at least a part of the recessed portion is arranged within a diameter of 2810 μm from the center of the opening, at least a part of the recessed portion is arranged within a diameter of L from the center of the opening, the electron-emitting material protrudes from the opening by a length T, when the units of the diameter L and the length T are both set to μm, the diameter L and the length T satisfy the relationship L = 3.53T + 1607.

7. An electron source, characterized in that, comprising: a suppression electrode having an opening at one end in the direction along the central axis; and an electron-emitting material, the front end of which protrudes from the opening, the suppression electrode further has a recessed portion at a position in the outer peripheral direction with respect to the opening, and the recessed portion retreats in the direction along the central axis to a position farther from the front end of the electron-emitting material than the end of the suppression electrode, at least a part of the recessed portion is arranged within a diameter of 2810 μm from the center of the opening, The above-mentioned retreating portion has a tapered portion that forms an angle θ with a plane perpendicular to the above-mentioned central axis. At least a part of the above-mentioned tapered portion is arranged within a diameter L from the above-mentioned center of the above-mentioned opening. The length by which the above-mentioned electron-emitting material protrudes from the above-mentioned opening is less than 200 μm. Let the unit of the above-mentioned diameter L be μm, and the unit of the above-mentioned angle θ be degree, i.e., °. The above-mentioned diameter L and the above-mentioned angle θ satisfy 2.69×10 －7 ×L 2 +3.64×10 －4 ×L-2.21×10 －2 ≤logθ≤1.27×10 －6 ×L 2 -4.18×10 －4 ×L + 1.45 relationship.

8. An electron source, characterized in that, It has: A suppression electrode having an opening at one end in the direction along the central axis; and An electron-emitting material whose front end protrudes from the above-mentioned opening. The above-mentioned suppression electrode further has a retreating portion at a position in the outer peripheral direction relative to the above-mentioned opening, and this retreating portion retreats in the direction along the above-mentioned central axis to a position farther from the above-mentioned front end of the above-mentioned electron-emitting material than the above-mentioned end of the above-mentioned suppression electrode. At least a part of the above-mentioned retreating portion is arranged within a diameter of 2810 μm from the center of the above-mentioned opening. The above-mentioned retreating portion has a tapered portion that forms an angle θ with a plane perpendicular to the above-mentioned central axis. At least a part of the above-mentioned tapered portion is arranged within a diameter L from the above-mentioned center of the above-mentioned opening. The length by which the above-mentioned electron-emitting material protrudes from the above-mentioned opening is greater than 300 μm. Let the unit of the above-mentioned diameter L be μm, and the unit of the above-mentioned angle θ be degree, i.e., °. The above-mentioned diameter L and the above-mentioned angle θ satisfy 2.59×10 －7 ×L 2 +1.82×10 －4 ×L-6.04×10 －1 ≤logθ≤5.15×10 －7 ×L 2 -2.29×10 －4 ×L+8.10×10 －1 relationship.

9. An electron gun, characterized in that: It has an electron source according to any one of claims 1 to 8.

10. A charged particle beam device, characterized in that: It has an electron source according to any one of claims 1 to 8 or an electron gun according to claim 9.

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