JP4227646B2 - Electron beam source and electron beam application device - Google Patents

Description

  The present invention relates to an electron beam application apparatus such as an electron microscope and an electron beam source apparatus thereof.

  In order to obtain a high-resolution electron microscope, a high-luminance electron source is required. For this purpose, needle-shaped W metal field radiation (hereinafter abbreviated as W-FE) is used exclusively. I have been. An electron source using carbon nanotubes (hereinafter abbreviated as CNT) has been reported as a further increase in luminance. CNTs are bonded to the tip of a needle-like metal as an electron source, and the filament supporting the needle-like metal is energized and heated to clean the surface of the electron source, so-called flushing, and used as an electron source. In this case, the fact that the diameter of the virtual light source of electrons is smaller than that of W-FE is the cause of high brightness. Niels de Jong et al., Nature, Volume 420 (November 2002), pages 393-395, “High brightness from a multi-walled carbon nanotube”.

  Conventionally, when such a high-performance electron source is applied to an electron gun such as an electron microscope, the extraction electrode 22 and the anode electrode 23 as shown in FIG. 2A generally form a Butler lens. Here, the butler lens is a kind of electrostatic lens having a structure in which two circular electrode plates are arranged in parallel. The outer sides of the two discs are flat and the inner sides facing each other are gently from the outer periphery to the center. Say what is thinner. The two discs are provided with openings through which electron beams pass. A lens obtained by slightly deforming this shape so as to be easily processed is also called a butler lens or a butler type lens. Often used for electron guns.

  T. The paper by Kawasaki et al. From Microbeam Analysis, Volume 3 (1994) pp. 287-291, “Development and Application of a 350 kV Transmission Electro Micro Scopy Micro Microscope”. It is disclosed. FIG. 2B shows a schematic diagram of the electron gun shown in Kawasaki. In the electron gun described in this document, an extraction electrode for an electron beam emitted from the electron source 20 is also used as the upper magnetic pole 24, and the lower magnetic pole 25 has the same potential as the upper magnetic pole. In the electron gun described in Kawasaki, since the W-FE electron source 20 and a magnetic lens are used in combination, an increase in aberration can be suppressed and an electron beam current can be increased even if the electron beam capture angle is large.

High brightness electron beam from a multi-walled carbon nanotube / Nature 420 (November 2002) 393-395 T.A. Kawasaki, et al, Microbeam Analysis, Volume 3 (1994) pp. 287-291.

  In order to realize an electron gun with high brightness, it is necessary to use an electron source with a small virtual light source diameter. Further, in order to make full use of the performance of an electron source with a small virtual light source diameter, it is necessary to reduce the aberration of the electron gun itself as much as the virtual light source diameter of the electron source is reduced. However, in the conventional electron gun, the aberration of the electron gun itself is large, and when the virtual light source diameter of the electrons emitted from the electron source or the physical diameter of the tip of the electron source is about 100 nm or less, the virtual light source diameter of the electron beam source However, no matter how small, the effective light source diameter of the electron beam emitted from the electron gun does not decrease, and as a result, there is a problem that the luminance does not increase. This is a particularly serious problem in the butler lens structure of the conventional electron gun shown in FIG. 2A, and has been a major obstacle to utilizing the high luminance characteristics of the carbon nanotube and the field emission electron source having a very thin tip diameter.

  In addition, if the diameter of the electron source tip is physically reduced in order to reduce the virtual light source diameter of the electron, the deformation of the filament and the needle-shaped metal of the electron source due to the heat at the time of flushing becomes remarkable, and the light source Since the position moves, there is also a problem that the axial tonality is required every time.

On the other hand, as shown in FIG. 2B, in the case of using an electron gun aiming at high brightness by adding a coil 26 or a magnetic circuit, an electron optical system having a small focal length is necessary to reduce the aberration of the electron gun itself. However, in the electron gun structure by Kawasaki et al., It was difficult to generate a magnetic field strong enough to make use of a small light source diameter only in a minute space near the electron source. Further, in this case, there is a problem that the structure is complicated and the weight is increased, so that the structure is easily vibrated and the resolution is easily lowered.
Accordingly, an object of the present invention is to provide an electron gun with small aberration that can be used without degrading its performance even when combined with an electron source with a small virtual light source diameter.

  A magnetic field superimposed electron source in which the electron source is immersed in a magnetic field, a means for applying an electric field for extracting an electron beam from the electron source, and an upper magnetic pole serving as a means for applying a magnetic flux to the electron source; An electron gun with a small aberration is realized by providing a lower magnetic pole and applying a potential difference for generating an electric field between the upper magnetic pole and the lower magnetic pole.

  Due to the potential difference applied to the upper magnetic pole and the lower magnetic pole, an electron extraction electric field for the electron source is generated. Further, the aberration of the entire electron gun can be reduced by combining the upper and lower magnetic poles and the means for applying the extraction electric field (extraction electrode). This is because a magnetic field is generated by a component closest to the electron source, that is, an extraction electrode, whereby a strong magnetic field is obtained in a narrow region. As a result, an electron lens having a short focal length is formed in the vicinity of the electron gun. Because. In terms of electro-optics, the aberration is reduced when the focal length is shortened.

  As a magnetic field generation source, it is preferable to use a permanent magnet disposed in the same vacuum vessel as the electron source. Although it is possible to use a coil as the magnetic flux generation source, the use of a permanent magnet requires an extremely small volume to generate a magnetic flux of about 0.8 to 1.1 T, which is practical as an electron lens. There is. In order to apply a magnetic field to the electron source, the electron source and the magnetic field generating source are connected directly or via a magnetic pole made of a soft magnetic material. The shape of the permanent magnet is generally axisymmetric with the electron emission direction viewed from the electron source tip as the central axis. As a result, the magnetic polarization becomes axially symmetric as in the central axis direction or the radial direction, and an axial target magnetic field ideal as a low aberration electron lens can be obtained.

  The potential applied to the permanent magnet or the magnetic pole is the same as that of the electron source or the same as that of the extraction electrode. For this reason, since it is possible to form the magnetic pole and magnet which generate | occur | produce a magnetic field, and the electrode which generate | occur | produces the electric field which draws out an electron in the same small space, a strong magnetic field is obtained in a narrow area | region.

  The electron source combined with the electron gun of the present invention is preferably a light source with a virtual light source diameter as small as possible, and particularly when used in combination with a field emission electron source having a physical diameter of the tip of the electron source of 100 nm or less. The small feature of the present invention can be fully utilized, and an electron gun with higher performance than before can be realized.

According to the present invention, an electron source having a small light source diameter, such as a carbon nanotube or W-FE, can be used effectively, so that a high-performance electron gun can be formed. Furthermore, by using this, a high-performance electron beam application apparatus such as a higher-resolution electron microscope can be obtained.
Other objects, features and advantages of the present invention will become apparent from the following description of embodiments of the present invention with reference to the accompanying drawings.

FIG. 1A schematically shows one embodiment of the present invention. A magnetic circuit composed of a doughnut-shaped permanent magnet 3 is formed between the lower magnetic pole 2 and the upper magnetic pole 1, and basically has an axisymmetric structure. An electron source 4 is installed on the lower surface of the upper magnetic pole 1 on the central axis. The The upper magnetic pole 1 and the lower magnetic pole 2 are made of a permendur alloy. Are installed the lower magnetic pole 2 as a counter electrode for drawing electron beams, which are insulated upper magnetic pole 1 and electrically, the potential difference between the extraction voltages V ₁ to both applied through the insulator 5 . Due to this structure, the extraction electric field and the magnetic field are arranged very compactly in the vicinity of the electron source 4. Here, the electron source 4 includes a W needle 6 and a carbon nanotube 7 as shown in FIG. 1B. As shown in FIG. 1C, the bonding between the two is fixed to a vertical guide wall 8 provided at the tip of the W needle by a metal film 9 such as W. The tip portion 7 of the electron source 4 may have a needle shape, a rod shape, a conical shape, or a metal needle provided with a surface coating layer. Carbon nanotubes can be formed by CVD, discharge, or the like.

  The structure shown in FIG. 1C is generated by introducing a gas containing W atoms, specifically carbonyl tungsten, while irradiating a desired region with an electron beam or ion beam in an SEM (scanning electron microscope), and generating the decomposition. A method of depositing a W metal film is used. As long as the metal film has a melting point of 400 ° C. or higher, the same effect can be obtained by using other materials such as Al, Mo, Au. The permanent magnet is an alloy mainly composed of Sm and Co, and is magnetized so that the upper part and the lower part are polarized to one of the N pole and the S pole. When used at the saturation magnetic density of the material, the magnetization strength is stable for a long time, and in this case, it is about 1T. The insulator 5 is selected from a hard insulator material having a high melting point such as alumina.

  In an actual application apparatus, in order to use the electron source of FIG. 1A, after assembling, baking at about 400 ° C. is performed for about 1 to 20 hours while evacuating, and internal residual gas and adsorbate are evaporated and removed. . Next, flushing for cleaning the tip of the electron source is performed for a short time. In this embodiment, the emission current Ie from the electron source is increased and the tip is overheated by this Joule heat. The heating temperature is in the range of 500 ° C to 2000 ° C. This method has the advantage that deformation is suppressed to a minimum and no shaft adjustment is required because the portion of the electron source that is at a higher temperature is limited to the tip of the minute electron source as compared with the conventional filament heating flushing.

  Here, as shown in FIGS. 3A and 3B, the distance H12 between the upper magnetic pole and the lower magnetic pole on the central axis, the distance H24 between the tip of the electron source and the lower magnetic pole, and the opening diameter De of the lower magnetic pole are approximately as follows: It is desirable that

H12>H24> De / 2
This is because the lower magnetic pole also serves as the extraction electrode. For example, when the nonmagnetic extraction electrode 30 is attached as shown in FIG. 3B, the opening diameter is De. In this case, Mo, Ti, austenitic stainless steel or the like is used as the nonmagnetic material.

  The brightness of the electron beam obtained from the electron gun having the structure shown in FIGS. 1A to 1C is about 10 times higher than that of the conventional electron gun structure with the same emission current. This is because the electron lens having a short focal length is formed in the very vicinity of the electron source by this structure, so that the aberration of the electron gun can be suppressed to 3 nm or less. Therefore, by using this electron source device for an electron gun, high resolution and high-speed inspection of a microscope such as TEM and SEM can be achieved. The energy width of the electron beam varies depending on the electric field at the tip of the electron source, and the stronger the electric field, the wider the energy width. For this reason, there is a tendency that the energy width is widened when the emission current amount Ie is large, and therefore, there is a problem that the energy width is widened when the luminance is increased. Since the luminance can be achieved at a lower Ie, there is an advantage that the energy width can be narrowed. For example, in the conventional high-intensity electron gun, the energy range is 0.8 to 1 eV, but in the present invention, it can be monochromatic from 0.2 to 0.3 eV and from 1/4 to 1/3. This can contribute to high resolution of a microscope or the like because the chromatic aberration of the electron optical system can be reduced from ¼ to ３. Moreover, since an electron beam with uniform energy can be used in the analyzer, the energy resolution can be improved by applying it to the primary beam of electron energy loss spectroscopy, for example. Further, since the upper magnetic pole is arranged on the upper part of the electron source, the electron source is placed in the magnetic field, and the focal length can be shortened and the aberration of the electron optical system can be reduced.

  When there is a concern about loss of magnetic coupling in the insulator 5 in an application where the focal length of the electron gun is desired to be reduced, a magnetic material having a high electrical resistance such as iron oxide magnesium ferrite may be used. . In that case, since the electron source is placed in a stronger magnetic field, there is an advantage that the focal length of the electron gun is reduced.

  The Sm-Co magnet has an extremely high magnetic flux density of about 0.8 to 1.1 T and a high holding power, and has a Curie point of 700 ° C. or higher, which is higher than the vacuum baking temperature. be able to. Both end faces of the donut shape are polarized, and a magnetic field is generated on the central axis by using the upper magnetic pole 1 and the lower magnetic pole 2 to generate a large magnetic field in the vicinity of the electron source 4. As a result, a lens having a very small focal length is formed in the electron gun. Since the magnetic field strength can be from about 0.1 T to about 3 T, the size of the magnet and the shape of each magnetic pole may be selected in advance for each required magnetic field. The same effect can be obtained when the stoichiometric composition of the material used for the magnet is SmCo5, Sm2Co17, or a material close thereto. In the case of an application with a weak magnetic field of about 40% or less of the Sm-Co system, a cheaper one can be obtained by using an alnico magnet.

  In addition, since an alnico magnet has a small change in magnetic flux density due to a change in temperature, it is suitable for use in an environment where the temperature varies greatly. In this case, in order to reduce the focal length of the electron lens, since the alnico magnet has a small holding force, it is preferable to use a long shape between the magnetic poles. In applications where the baking temperature is sufficiently lower than 300 ° C., using a neodymium iron boron magnet, that is, Nd 2 Fe 14 B mainly, a magnetic field that is about 30% stronger than Sm—Co is obtained in addition to low cost. A gun with a shorter focal length can be obtained. As a magnetic material, a praseodymium magnet, a platinum magnet, an iron-chromium-cobalt magnet, or the like has a magnetic flux density, a holding power, and heat resistance suitable for the application, and the same effect can be obtained as long as it emits less gas in a vacuum.

  Since the magnetization accuracy of the permanent magnet is about 10%, and the magnetic flux density changes with temperature, an adjustment coil is provided to control a magnetic field with higher accuracy. It may be outside or inside the magnetic pole 2. Further, this coil may also be used as a heater. In that case, when used as a heater, the magnetic pole 2 is heated from 200 ° C. to 400 ° C. with a current of several A to 10 A. This can be used not only as a baking at the time of starting up the vacuum, but also as a means for finely adjusting the magnetic flux density according to the temperature. In this case, the clothing of the heater wire is preferably a highly heat-resistant material such as ceramics.

  Here, the insulator 5 is inserted in order to insulate the lower magnetic pole 2 from the magnet 3 and the upper magnetic pole 1, but both near the center of the upper magnetic pole connected to the electron source 4 and near the center hole of the lower magnetic pole. The same effect can be obtained if it has a structure in which an extraction voltage can be applied to. For example, the magnet 3 may be divided as shown in FIG. 8 and the insulator 5 may be inserted between them.

  9A, the rod-shaped permanent magnet 3 is placed on the central axis, and the magnetic field generated on the end face of the magnet magnetized in the longitudinal direction by the thin rod-shaped magnet is used to achieve high brightness as described above. The In FIG. 9A, the lower magnetic pole is fixed to the insulator 95 with a bolt 96, and the base magnetic pole 91 and the insulator 5 are sandwiched and fixed therebetween. The permanent magnet 3 is fixed together with the upper magnetic pole 1 in the magnet holder 92 by a magnet holder 94. The magnet presser has a screw formed on the outer periphery, and meshes with the female screw of the base magnetic pole 91. The magnet holder 92 is fixed to the base magnetic pole 91 by a countersunk screw 97. In this case, since there is no magnet on the inner wall of the lower magnetic pole, a coil 90 is formed by opening a hole as shown in FIG. 9B to increase the conductance of evacuation, or by placing a non-evaporable getter 93 and winding it outside as shown in FIG. 9A. It may be activated by energizing and heating to act as a vacuum pump. In this case, there is an advantage that a good state with few gas molecules is maintained for a long time around the electron source 4.

  In this embodiment, carbon nanotubes are used as the electron source. However, when the light source diameter or virtual light source diameter of the electron emission source is small and is about 3 nm or less, the present invention is applied to the electron source without impairing the small light source diameter. Since a line can be generated, the same effect is obtained. For example, a W needle having a tip diameter of 100 nm or less or a nanotip formed on the tip has the same effect because the light source diameter is small. The nanotip is formed by forming a protrusion of about several atoms at the tip of the needle by applying a positive voltage while heating the W-FE needle to obtain a field evaporation condition. In addition to W, a refractory metal such as Pt or Mo may be used. Also, the tip portion of the electron source can be sharpened to 100 nm or less by chemical or electrochemical etching.

The extraction voltage V ₁ during operation of the electron source is practically in the range of 100 V to 4 kV when the electron source is a carbon nanotube, and in the range of 2 kV to 5 kV when the tip diameter is 100 nm with a W needle. While observing the emission current Ie from the electron source, Ie is determined to be a desired value. This Ie is practically selected from the range of 10 nA to 500 μA for carbon nanotubes and from 10 nA to 30 μA for W needles. The upper magnetic pole 1 is at the same potential as the electron source 1 and is applied with an acceleration voltage Vo. Practically, Vo is selected from the range of -30 kV to -30 V for SEM (scanning electron microscope) and from the range of -30 kV to -1000 kV for TEM (transmission electron microscope).

  Further, the present invention may be applied to the case where the tip of the conventional W-FE electron source structure is thin as shown in FIG. Here, the W filament 21 is passed over the two through electrodes 101 fixed through the stem 100 made of an insulator, and an existing electron source in which the W-FE electron source 20 is fixed to the filament. It is. The tip diameter is about 100 nm or less. The magnetic circuit has a through hole at the center of the upper magnetic pole 1, and the electron source 20 is inserted into a region where the magnetic flux from the permanent magnet 3 is concentrated through this hole, and the upper magnetic pole 1 and the stem 100 are fixed by a joint 102.

The surface of the stem 100 is gold-plated and is electrically connected to one end of the through electrode 101. Therefore, the upper magnetic pole 1, the permanent magnet 3, and the electron source 20 are electrically connected and are at the same potential as the acceleration voltage Vo. As electrodes pull the lower magnetic pole 2, it is used to apply a drawer voltages V ₁ between the electron source 20. The structure shown in FIG. 10 has an advantage that it can be applied with a slight modification of a conventional electron gun structure such as SEM or TEM. In this case, as described above, a nanotip may be formed at the tip of the W needle.

Here, permendur is used as the soft magnetic material of the magnetic pole, but the same effect can be obtained by using other metal materials such as permalloy or pure iron depending on the required magnetic flux density.
As a simpler configuration, the brightness can be increased by placing a bar-shaped magnet 3 on the central axis as shown in FIGS. 11A and 11B and using a magnetic field generated on the end face of the magnet magnetized in the longitudinal direction by a thin bar-shaped magnet. Achieved. In this case, in order to directly install an electron source and maintain an elongated shape, an alnico magnet, an iron chrome cobalt magnet, or the like is more suitable than an Sm-Co system that is easily chipped. In the case of a material having a small holding force, the shape needs to be elongated. Therefore, practically, when the thickness is 0.1 mm, the length is 1 mm or more, more preferably about 5 mm to 10 mm. The electron source mounting position becomes easier to manufacture because the allowable range becomes wider as the diameter of the rod increases. In this case, since it is difficult to concentrate the electric field on the electron source if it is too thick, the diameter is practically about 5 mm or less. In this case, the length is about 20 mm or less in order to obtain an elongated shape.

  Further, even if the cylindrical permanent magnet 3 is magnetized so as to be polarized in the radial direction, the same effect can be obtained by concentrating the magnetic lines of force by the magnetic poles symmetrically with respect to the axis in the electron emission direction. For example, even in a structure in which the center and outer ring of the disk are polarized to S and N, if the upper magnetic pole 1 and the lower magnetic pole 2 are provided as shown in FIG. 11C, the same effect as the structure of FIG. In this case, there is an advantage that a magnet can be easily produced and can be produced at low cost.

In this embodiment, the magnetic flux of the magnetic circuit is generated by a permanent magnet, and the effect that it can be manufactured at a low cost is obvious as compared with the conventional example of FIG. 2B. That is, in the prior art, when using W-FE, since the atmosphere in the electron gun is used as an ultra-high vacuum region (pressure 10 ⁻⁸ Pa or less), baking at 200 ° C. to 400 ° C. is required as preparation. However, for this purpose, it is necessary to use an external coil coated with a high-temperature heat-resistant material, or it is necessary to make the external coil detachable. However, if the present invention is applied, if a permanent magnet for generating a magnetic field is selected such that the Curie point is sufficiently higher than the baking temperature, there is no need to take a special coating or removal structure.

FIG. 6 shows an outline of an example when applied to a scanning electron microscope.
In the assembly process of the electron gun, an error of about several tens of μm in the mounting position of the electron source 4 is inevitable. When the electron source 4 is deviated from the axis center of the electron optical system, the number of electron beams observed on the axis is deviated from the angle. Further, since the main component is shifted from the axis of the electron lens in the electron source, there arises a problem that the aberration increases. This is because, as a result of superimposing the magnetic field, the focal length is shortened and the accuracy of the electron source position is strict. As a method for solving this problem, there are a mechanical matching method and an electron optical system. In the case of mechanical alignment, for example, the position may be adjusted by placing the electron source 4 on the fine movement base 70 as shown in FIG.

  In this case, if a plurality of electron sources 4 are installed on the fine movement base 70 and the extraction electrode is a funnel type so that a strong electric field is applied only to the central portion, one of the plurality of electron sources 4 is selected. Therefore, there is an advantage that the electron source can be exchanged without opening the electron gun and can be used for a long time. On the other hand, as a method of correcting the axis deviation by the electron optical system, for example, there is a method of correcting the angle by the deflector 50 as shown in FIG. 5A. Although there are a pair of deflectors 50 on the paper surface, there are two pairs of correction directions because there are two axes of xy correction directions. The deflection method may be an electrostatic field or a magnetic field. Further, if two deflectors 50 are provided as shown in FIG. 5B, both the angle and the position of the electron beam 5 can be corrected. Therefore, an electron beam that has passed closer to the lens center of the electron gun can be used, and aberrations can be used. It is desirable in terms of reduction of

  In the scanning electron microscope of FIG. 6, the aberration of the electron source is suppressed by a two-stage deflector, excess electrons are blocked by the aperture 61, the electron beam 10 is converged by the objective lens 66, and the sample 67 is irradiated. The electron beam 10 is scanned on the surface of the sample 67 on the sample stage 68 by the scanning deflector 69, and the reflected electrons generated therefrom are bent by the upper reflected electron detector 29, and the secondary electrons are bent sideways by the ExB filter 64. Each is detected by the secondary electron detector 63, and an SEM image is obtained based on these. In order to reduce the chromatic aberration of the objective lens, the voltage Vb is applied to the booster electrode 65 and the retarding voltage Vr is applied to the sample 67 to increase the speed of electrons in the objective lens. The electron energy applied to the sample is | Vo | − | Vr |, which is used in the range of about 10 eV to 5 keV. The electron energy in the objective lens is | Vo | + | Vb |, and is used in the range of about 1 kV to 10 kV.

  The electron source of the present invention can reduce the aberration of the electron gun as compared with the conventional FE electron gun as shown in FIG. 2B, so that it can be used without impairing the small source size of the electron source. For example, when an electron source having a virtual source size of 3 nm is used and the reduction ratio of the entire electron lens is halved, the probe diameter on the sample can be 1.5 nm. As a result, since an electron source with a small source size can be used, a higher-resolution microscope observation can be performed.

  Further, since the electron beam with a wider radiation angle can be converged due to the magnetic field superimposed on the electron source 4, for example, even if the emission current is 0.1 μA, the probe current can be taken out at 10 pA or more, and the image can be obtained at a higher speed. It becomes possible to observe.

Further, since the chromatic aberration is dominant when the sample irradiation energy is about 3 kV or less, the electron beam becomes monochromatic as described above by using the electron source with the same luminance as the conventional one. Can be reduced to ¼, and a dramatic increase in resolution can be achieved. This SEM is suitable for observing organic substances that are easily damaged by an electron beam. For example, it is useful for observing fine processing resists and interlayer insulating materials and measuring lengths in LSI processes, or for observing proteins, living bodies, and cells.
While the above description has been made with reference to exemplary embodiments, it will be apparent to those skilled in the art that the invention is not limited thereto and that various changes and modifications can be made within the spirit of the invention and the scope of the appended claims.

The figure for demonstrating the structure of this invention. The figure for demonstrating the structure of this invention. The figure for demonstrating the structure of this invention. Explanatory drawing of a prior art. Explanatory drawing of a prior art. Explanatory drawing of one Example of this invention. Explanatory drawing of one Example of this invention. The characteristic view for demonstrating this invention. Explanatory drawing of the deflector concerning this invention. Explanatory drawing of the deflector concerning this invention. The figure which shows the whole structure of the apparatus concerning this invention. The figure which shows the partial modification of this invention. The figure which shows the other partial modification of this invention. The figure which shows the other Example of this invention. The figure which shows the other Example of this invention. The figure which shows the further another Example of this invention. The figure which shows the partial modification of this invention. The figure which shows the partial modification of this invention. The figure which shows the partial modification of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Upper magnetic pole 2 Lower magnetic pole 3 Permanent magnet 4 Electron source 5 Insulator 6 W needle 7 Carbon nanotube 8 Guide wall 9 Metal film 11 Anode 10 Electron beam 20 W-FE electron source 21 W filament 22 Extraction electrode 23 Anode 30 Extraction electrode 50 Deflector 60 Vacuum container 61 Aperture 62 Backscattered electron detector 63 Secondary electron detector 64 ExB
65 Booster electrode 66 Objective lens 67 Sample 68 Sample stage 90 Coil 91 Base magnetic pole 92 Magnet holder 93 Non-evaporating getter 94 Magnet presser 95 Insulating 96 bolt 97 Countersunk screw 100 Stem 101 Through electrode 102 Joint

Claims (5)

In a magnetic field superimposed electron source having a field emission electron source having a tip diameter of 100 nm or less and an extraction electrode, and the electron source is immersed in a magnetic field, the main source of the magnetic field is in the same vacuum container as the electron source. The permanent magnet has a substantially axisymmetric shape with the electron emission direction seen from the tip of the electron source as the central axis, and the magnetic polarization is axisymmetric as in the central axis direction or radial direction. A magnetic flux is provided by connecting to the electron source directly or via a magnetic pole made of a soft magnetic material, and the permanent magnet and the magnetic pole have the same potential as the electron source or the same as the extraction electrode, The permanent magnet has a hollow structure such as a donut shape, and the end of the permanent magnet on the electron emission direction side is magnetically coupled to the lower magnetic pole mainly composed of a soft magnetic material, and the other side of the permanent magnet is the soft magnet. It is magnetically coupled to the upper magnetic pole mainly composed of a ferromagnet, and the lower magnetic pole is the same as or in contact with the extraction electrode, and an electron source is connected to the center of the upper magnetic pole on the electron emission direction side. An electron source in which at least one insulator or high resistance is provided between the upper magnetic pole and the lower magnetic pole, the extraction electrode and the electron source are electrically insulated, and the extraction voltage V ₁ is applied between them. apparatus. The electron source device according to claim 1 ,
The electron source device in which the distance H12 between the upper magnetic pole and the extraction electrode in the vicinity of the central axis, the distance H24 between the tip of the electron source and the extraction electrode, and the opening diameter De of the extraction electrode are in the relationship of H12>H24> De / 2. In a magnetic field superimposed electron source having a field emission electron source having a tip diameter of 100 nm or less and an extraction electrode, and the electron source is immersed in a magnetic field, the main source of the magnetic field is in the same vacuum container as the electron source. The permanent magnet has a generally axisymmetric shape with the electron emission direction seen from the tip of the electron source as the central axis, and the magnetic polarization is axisymmetric as in the central axis direction or radial direction. A magnetic flux is provided by connecting to the electron source directly or via a magnetic pole made of a soft magnetic material, and the permanent magnet and the magnetic pole have the same potential as the electron source or the same as the extraction electrode, The electron source is fixed on a filament passed over two electrodes that penetrate the stem made of an insulator, and the permanent magnet has a hollow structure such as a donut shape. The other end of the permanent magnet is magnetically coupled to the upper magnetic pole whose main component is the soft magnetic material, and the lower magnetic pole is the same as the extraction electrode. The upper magnetic pole has a through hole, the upper magnetic pole and the stem are connected directly or via a joint, and at least one insulator or high resistance is provided between the upper magnetic pole and the lower magnetic pole. provided electrically insulates the extraction electrodes and the electron source, as adapted to use by applying a drawer voltages V ₁ therebetween, the electron source device. The electron source device according to any one of claims 1, 2 , and 3 ,
An electron source device in which at least one coil is installed in the vicinity of at least one magnetic pole and is energized. 5. The electron source device according to claim 1, further comprising at least a pair of electrostatic or magnetic deflectors each of x and y, means for placing an observation sample, and reflection An electron beam apparatus comprising: means for measuring at least one of electrons, secondary electrons, and absorbed current.

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